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Home My WebLink AboutTHE GROVE AT FORT COLLINS - PDP - 16-10B - REPORTS - DRAINAGE REPORT (3)Preliminary Drainage and Erosion Control Report for at Fort Collins, Colorado June 1, 2011 Prepared for: Campus Crest at Fort Collins, LLC 2100 Rexford Road, Suite 414 Charlotte, North Carolina 28211 Prepared by: 200 South College Avenue, Suite 100 Fort Collins, Colorado 80524 Phone: 970.221.4158 Fax: 970.221.4159 www.northernengineering.com Project Number: 502-001  This Preliminary Drainage Report is consciously provided as a PDF. Please consider the environment before printing this document in its entirety. When a hard copy is absolutely necessary, we recommend double-sided printing. June 1, 2011 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Preliminary Drainage and Erosion Control Report THE GROVE at Fort Collins Dear Staff: Northern Engineering is pleased to re-submit this Preliminary Drainage and Erosion Control Report for your review. This report accompanies the 06.01.11 Project Development Plan (PDP) submittal for the proposed Grove at Fort Collins multi-family (student housing) development. Staff Project Review comments dated 04.22.11 have been addressed with this Preliminary Drainage and Erosion Control Report. The subsequent Final Drainage and Erosion Control Report will continue to prove that surface and subsurface waters from this site will not adversely affect any adjacent properties. This report has been prepared in accordance to City of Fort Collins Storm Drainage Design Criteria and Construction Standards (SDDCCS), and serves to document the stormwater impacts associated with the proposed Grove student housing project. We understand that review by the City is to assure general compliance with standardized criteria contained in the SDDCCS. If you should have any questions as you review this report, please feel free to contact us. Sincerely, NORTHERN ENGINEERING SERVICES, INC. Aaron T. Cvar, PE Senior Engineer Nicholas W. Haws, PE Andrew G. Reese Project Manager Project Engineer Preliminary Drainage and Erosion Control Report TABLE OF CONTENTS 1.0 Scope ............................................................................................................ 1 2.0 Design Criteria and References ......................................................................... 1 3.0 Site Location and Description ........................................................................... 1 4.0 Existing Condition ........................................................................................... 2 5.0 Irrigation Facilities ........................................................................................... 5 6.0 Floodplain Encroachment ................................................................................. 8 7.0 Wetlands ..................................................................................................... 10 8.0 Proposed Development .................................................................................. 12 9.0 Proposed Drainage Plan ................................................................................. 12 10.0 Outfall ......................................................................................................... 14 11.0 Stormwater Quantity Detention ....................................................................... 16 12.0 Stormwater Quality Mitigation ........................................................................ 16 13.0 Erosion and Sediment Control ........................................................................ 18 14.0 Conclusions .................................................................................................. 19 References ............................................................................................................. 20 APPENDICES: APPENDIX A – Rational Method Developed Runoff Calculations APPENDIX B – Water Quality Calculations APPENDIX C – Previous Drainage Memos and Correspondence APPENDIX D – Floodplain Information APPENDIX E – Street Capacity Calculations APPENDIX F – Inlet and Curb Cut Calculations APPENDIX G – Storm Line and Culvert Calculations APPENDIX H – Prorated Culvert and Prorated WQ Pond Sizing Calculations APPENDIX I – Erosion Control Cost Estimates and Riprap/Erosion Calculations APPENDIX J – Supplemental Subsurface Water Investigation (by Applegate Group) APPENDIX K – Geotechnical / Soils Information (by Earth Engineering Company) APPENDIX L – Wetlands / Environmental Information (by Cedar Creek Associates) MAP POCKET: DR1 – Preliminary Drainage Exhibit FLOOD – Floodplain Exhibit Preliminary Drainage and Erosion Control Report 1 1.0 Scope This Preliminary Drainage and Erosion Control Report has been prepared for the proposed Grove at Fort Collins student housing community, and is intended to document the associated stormwater impacts. Major drainage items to be addressed at this point are: Historic drainage patterns and quantities of flow Proposed overall drainage patterns and quantities of flow Confirmation of existing facilities’ ability to convey and detain peak runoff from developed site Proposed stormwater infrastructure design concepts Proposed water quality concepts Confirmation that the proposed development will have no adverse drainage impacts In accordance with typical City process and development review standards, the items described above are taken to approximately a 50% level of design and analysis. This is to ensure that the proposed horizontal Site Plan and land use can indeed work. Final drainage design does not occur until after the project receives public hearing approval on the Project Development Plan (PDP). The remaining technical engineering details are typically resolved directly between City Staff, the Applicant, and other pertinent review agencies. This is not unique to the Grove, but rather standard procedure for all proposed development projects in the City of Fort Collins. 2.0 Design Criteria and References Drainage criteria outlined in the City of Fort Collins Storm Drainage Design Criteria and Construction Standards (SDDCCS) has been referenced in this study. The Rational Method has been used to estimate the peak discharge rates for the minor and major storm events. The minor and major rainfall events are considered to be the 2-yr and 100-yr storms, respectively. Runoff coefficients and rainfall values utilized in the Rational Method computations are consistent with the SDDCCS. The Urban Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria Manual, Volume III has been used for water quality design. Additionally, multiple previous studies and reports have been referenced in the preparation of this document (see page 18 for a full listing). 3.0 Site Location and Description The project site is located near the center of Section 23, Township 7 North, Range 69 West of the 6th Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. The site is bounded on the south by the Larimer Canal No. 2, on the west by Care Housing at Windtrail Park, on the east by Centre Avenue, and by the Sundering and Windtrail neighborhoods to the north. The Gardens on Spring Creek is located immediately northeast of the property (note, the street stub constructed due south of the Gardens on Spring Creek currently known as Rolland Moore Drive is expected to be re- named as Botanic Place once the new Rolland Moore Drive is constructed and accepted). The land is currently, and will continue to be, owned by the Colorado State University Research Foundation (CSURF). The developer of the Grove has entered into a long-term ground lease with CSURF. Existing ground cover is predominately a grass hayfield, with portions of non-native grassland along the northern and eastern boundaries. Abandoned local irrigation ditches and control structures exist along the southern property boundary, remnant of times when the land was an active hayfield. Jurisdictional wetlands exist along the northern property line. (Refer to the Ecological Characterization Study and Waters of the U.S. Delineation documents prepared by Cedar Creek Associates for additional information related to the wetlands). Preliminary Drainage and Erosion Control Report 2 Existing Project Site According to the NRCS Soil Survey, the site consists of loams and clay loam, which fall into Hydrologic Soil Groups B and C. More site-specific exploration found an overburden layer of brown and reddish brown sandy lean clay soils. Numerous soils bores and monitoring wells have been drilled on the subject property, and subsurface exploration reports have been prepared by both Earth Engineering Company (EEC) and Applegate Group. Copies of said reports can be found in Appendices J and K of this document. 4.0 Existing Condition 4.1 Historic Site Drainage The total area being subdivided is roughly 31.3 acres in size and currently consists of undeveloped pasture land. The site slopes generally from southwest to northeast at slopes ranging from 6% to 12% near the southern site boundary, and 1% to 5% heading further north. Runoff currently sheet flows to the north towards Spring Creek. The majority of flow is intercepted by a major drainageway designed with Windtrail P.U.D. This outfall channel was intentionally constructed as a wetland with the primary purpose of conveying developed flows from neighborhoods to the north and west along the backyards of Sundering Townhomes, as well as Windtrail Townhomes and Windtrail detached residences. Variances were granted with the Windtrail P.U.D. to intentionally create wet, flat, natural appearing drainage areas and man-made wetlands. This area is expected to hold water at times and have drainage back-ups by design. Preliminary Drainage and Erosion Control Report 3 The ability for the Windtrail outfall swale to sufficiently convey stormwater is dependent upon adequate maintenance of the wetland drainage facilities. The outfall swale falls within a drainage easement, and according to the plans approved with Windtrail P.U.D., the homeowners association shall be responsible for maintenance of the drainageway. Said easement and corresponding maintenance obligations carries forward, regardless of future ownership changes or development plans on the property. The Grove at Fort Collins subdivision plat preserves the pertinent drainage easements of record to allow continued maintenance activities by the responsible parties. A portion of the site also drains towards the triple 24” RCP culverts installed with the Centre for Advanced Technology (CAT) 22nd Filing under the roadway stub near the service entrance drive to the Gardens on Spring Creek. The culverts were designed to accept a 100-yr off-site flow of 57.6 cfs from the CSURF (Grove) parcel to the south. Said culverts discharge into the Horticulture Center Outfall Channel. This outfall channel, constructed with CAT-22, will now serve as the outfall for all off the developed runoff from the Grove student housing community. 4.2 Groundwater The project site lies in a region containing rather shallow groundwater. The areas with the smallest depth to water (DTW) tend to lie along the Windtrail P.U.D. Outfall Swale. Not only does this area along the northern subdivision boundary contain much of the shallowest groundwater, but it also appears to be the least influenced by seasonal changes due to fluctuating water levels in surrounding irrigation ditches. Portions of the neighborhoods to the north and northwest of the Grove currently battle shallow groundwater on a consistent basis. There are reports from residents of soggy crawlspaces and nearly constant sump pump discharges. However, such problems are rather sporadic. While one homeowner may have a routinely running basement sump pump, the neighbor next door or across the street may be completely dry and have a sump pump that has never kicked on. This appears to indicate that there are localized factors on a micro-level, in addition regional conditions, that influence the groundwater on properties in this area. The difficulties that Windtrail, Sundering, and other neighborhoods presently experience with shallow groundwater seemingly have very little to do with conditions of property to be platted as The Grove at Fort Collins. Rather, it is believed that groundwater along Spring Creek has much more to do with regional geologic and subsurface hydrologic parameters. While the subject property does have the ability to influence the local DTW, anything proposed within the Grove subdivision boundary would have nominal affects to the surrounding neighborhoods and area-wide groundwater levels. According to borings and other analysis performed by EEC, Applegate, and Miller Groundwater, the DTW not only varies seasonally, but also differs horizontally across the site. As previously mentioned, the areas with the shallowest groundwater tend to fall within the wetlands and floodplain adjacent to Windtrail P.U.D. Therefore, the proposed site development and buildings are placed to avoid the locations with the worst DTW. Additionally, underdrains will be installed to further protect the buildings and roadways from potentially shallow groundwater. Preliminary Drainage and Erosion Control Report 4 Details of the underdrain system will be included with the Final Utility Plans to be submitted after PDP approval. However, a preliminary layout can be found in the Preliminary Utility Plans prepared by Northern Engineering. The “subdivision-wide” underdrain system generally follows the public street network, and has been designed in accordance with Section 5.6 of the Larimer County Urban Area Street Standards (LCUASS). This underdrain system will outfall into the Grove’s water quality control structure, downstream of the orifice plate, thereby routing groundwater discharge into the CAT-22 outfall channel. The underdrain outfall elevation is expected to be around 4995.3- ft, whereas the 100-yr water surface elevation at this location is approximately 4994.9-ft. Additional recommendations and design parameters can be found in the Supplemental Subsurface Water Investigation by Applegate Group (Appendix J). Not only does said report further expound on the technical details of the underdrains and DTW levels, but it also contains preliminary modeling results to approximate the affects of the proposed site grading and subsurface drainage system. It can be concluded that the proposed Grove development will have a negligible impact to the historic groundwater condition along Spring Creek. The groundwater levels will neither lower enough to adversely impact the existing wetlands nor raise enough to negatively affect surrounding homes. Furthermore, permanently installed monitoring wells will allow for ongoing groundwater measurements to assess any fluctuations in DTW. These monitoring wells and groundwater readings will also aid in tracking the subsurface hydrology along the existing wetland channel. A narrative describing Cedar Creek Associates’ proposed monitoring plan can be found in Appendix L. Please see Section 5.0, below, for groundwater related to the Larimer Canal No. 2. 4.3 Off-Site Drainage In addition to the on-site project area, six (6) off-site basins have also been delineated. Basins 0S1 – OS4 are south of the site boundary, and generally drain to the north. While the Larimer County Canal No. 2 runs west to east through these basins, it is assumed to be full for the purposes of stormwater analysis and drainage basin delineation. Basins OS5 and OS6 consist of the existing Rolland Moore Drive stub (to be re-named) that will drain through new facilities to be constructed with the Grove prior to reaching the Horticulture Center Outfall Channel. Historic flows for the off-site basins have been computed and will be utilized, where appropriate, in the final design of the Grove drainage improvements. All off-site flow patterns and quantities will continue in their historic manner with the proposed student housing development. No provisions have been made for the future development of any off-site basins outside the limits of the Grove subdivision plat. There are also historic flows that enter the site from off-site basins to the north and west of the project boundary. However, since these flows travel directly to and/or through the Windtrail P.U.D. outfall swale along the northern property line, no explicit computations are necessary. The limits of development and other improvements associated with the Grove project will not be affected by, nor have an effect on, the historic Windtrail drainageway. Not only will the existing drainage easements be preserved with this development, but the entirety of Outlot A will be dedicated as a drainage easement with The Grove at Fort Collins subdivision plat. Therefore, the ability for the Windtrail HOA to fulfill their current channel maintenance obligations will not be impeded by this project. Preliminary Drainage and Erosion Control Report 5 4.4 Major Drainage Basin The site lies entirely within the Spring Creek Major Drainage Basin. More specifically, the Grove resides within Basin 130 of the Spring Creek Master Drainage Plan. Two regional stormwater studies have recently been conducted within the major drainage basin. The first is an analysis that primarily deals with the conveyance and detention for the areas that drain to the Burlington Northern Railroad (BNRR) pond south of the Fort Collins Hilton. Development boundaries and percentage of impervious areas for the proposed Grove student housing community have been shared with the parties involved in the study and modeling update. Please refer to the “Alternative Analysis for the Design of the Mason Street Outfall” report by Ayres Associates dated November 2010 for additional information. The second regional stormwater effort currently underway is a proposed Physical Map Revision (PMR) to the Spring Creek floodplain. This includes updates to both the MODSWMM hydrology as well as the HEC-RAS hydraulic modeling. Pertinent drainage parameters have been shared between City Staff, their consultants, and the Grove engineers. As a result, it is neither appropriate nor required that the Applicant for the Grove conduct any further modeling. The practical and preferred approach is to ensure consistent data and enable a more thorough and accurate effort by those already conducting larger-scale studies. The Grove student housing development remains consistent with the governing master drainage studies. 5.0 Irrigation Facilities All existing on-site irrigation facilities are assumed to be abandoned, and will be removed within the limits of work. The Larimer County Canal No. 2 roughly parallels the southern property boundary. The ditch is elevated in this area and has relatively steep banks. The proposed Grove subdivision boundary lies approximately 20’ – 40’ north of the top of ditch. Alternatively, the boundary line is intended to follow the toe of slope along the elevated portion of the Larimer Canal No. 2. This is to protect the structural integrity of the ditch, as well as to allow plenty of room for ditch access and maintenance activities. Another consideration regarding the ditch that runs along the southern property line is the potential for seepage. It is a known fact that the Larimer Canal No. 2 seeps in the area near Care Housing at Windtrail Park. The horizontal separation of the Grove property boundary, as well as the additional buffer provided by Outlot B, offers a certain level of protection for the buildings and roadway. However, The Grove at Fort Collins will install an underdrain system to safeguard the structural integrity of the foundations and subgrade. The potential for the Larimer Canal No. 2 to overtop in major rainfall events is no different than any other irrigation ditch elsewhere in Fort Collins, and is not a consideration or concern in selecting this site for development. Neither the subdivision boundary nor the limits of development for the proposed Grove student housing community impact existing ditch company rights-of-way, easements, integrity, or ability to access and maintain ditch company facilities. Nonetheless, the Larimer County Canal No. 2 Irrigating Company has been notified of the proposed project and copies of the applicable development plan documents have been provided for their review. Additionally, the final construction plans for the Grove will be routed to the ditch company for their approval and signature to confirm that there are no adverse impacts to their facilities. Preliminary Drainage and Erosion Control Report 6 The proposed Grove Project Development Plan has been discussed with Ditch Company representatives on multiple occasions since this project was first envisioned. Concerns of seepage, slope stability, large tree intrusion, access, and maintenance have been the main topics of conversation to date. The Ditch Company has issued multiple letters on the matter. Copies of said correspondence can be found in Appendix C. In order to address the concerns related to potential seepage and slope stability, additional testing and analysis is underway by Applegate Group, Miller Groundwater and Earth Engineering Company (EEC) to further resolve these issues. The supplementary data will provide a more accurate understanding of how much of an effect, if any, the May to July irrigation flows in the Larimer No. 2 canal have on downhill groundwater and slope stability. Of particular interest is the issue of a “connected” versus a “disconnected” water table. This will help determine whether or not the development’s grading and drainage changes could affect existing seepage rates from the ditch, and if so, to what extent. Brief memos further describing the additional testing efforts can be found in Appendix J (Applegate) and Appendix K (EEC). Development adjacent to the canal must be done with great care. The fact that the student housing buildings will not have basements or crawlspaces is one significant advantage. Cuts made along the canal, slope stability measures and retaining wall construction shall follow the strict recommendations of EEC. Slopes previously proposed at 2:1 or 3:1 in proximity to the ditch have been revised such that all design slopes are 4:1 or less. Additionally, a free-draining mechanically stabilized earth (MSE) retaining wall with modular concrete block facing will be constructed behind Buildings 3, 4, and 5. Underdrains (“toe drains”) shall be installed per the specifications of Applegate Group. While the toe drains will be slotted PVC between the canal and the Grove buildings, the outfall line may or may not be slotted. Depending on the outcome of the ditch realignment, as well as the final results from the May to July 2011 piezometer monitoring, the lower segments of the toe drain outfall line may separated from the LCUASS underdrain system and constructed as solid PVC to eliminate any potential for future transfer of groundwater to intended locations. As alluded to above, CSURF and the Ditch Company have agreed in concept to relocate the Larimer No. 2 Canal further south on land also owned by CSURF. The final details and terms of the agreement are currently being resolved between the land owner and Ditch Company. The proposed ditch realignment is shown for reference only on The Grove at Fort Collins PDP drawings dated 06.01.11. The ditch relocation will help achieve numerous objectives benefitting multiple parties. First of all, the newly cut and compacted channel section will have significantly less seepage than the existing ditch. Obviously the Ditch Company and its shareholders will benefit from the decreased seepage. Additionally, if the water table is indeed found to be influenced by seepage from the ditch, then downhill land owners and single-family residents would benefit as well. Future construction north of the canal would presumably be safer and more cost effective as a result. The proposed ditch realignment will offer additional horizontal separation from the active canal and The Grove at Fort Collins development plan. This again is an improvement for the Ditch Company, not only to gain distance, but to get away from the steep slope that currently exists downhill of the present alignment. Concerns of slope stability effectively go away from their perspective. Preliminary Drainage and Erosion Control Report 7 The canal is currently lined with numerous large cottonwood trees, many of which protrude into the ditch embankment and are nearing the end of their maximum lifetime. These trees pose major concerns to the Ditch Company in terms of water loss, as well as safety and liability. In fact, the Superintendent for the Larimer Canal No. 2 has gone on record to say that if the ditch remains in its present alignment, that he will have to remove multiple significant trees along the channel. The trees in question offer substantial habitat value to the wildlife corridor, as well as contributing to the aesthetic landscape of the area. Realigning the ditch will allow the existing trees to remain as-is. The intent is to restore the abandoned channel section to a more natural condition; therefore, a reclamation plan has been prepared to specify the planting of additional trees, shrubs, and native grasses. The new canal route will provide an additional wildlife corridor, essentially creating a refuge in the middle. The end result will offer a substantially improved natural habitat from what would occur to the wildlife corridor if the Ditch Company were to remove the large trees and keep the single channel where it is. The 04.04.11 memo from Senior Wildlife Biologist, T. Michael Phelan, further describes the benefits of realigning the ditch from a habitat perspective. As of the date of this report, the contact information of record for the Larimer County Canal No. 2 Irrigating Company is as follows: John Moen - Superintendent 970.482.3309 (970.218.0726 – mobile) John Strachan - President 970.223.5231 Gene Fischer - Attorney 970.482.4710 Preliminary Drainage and Erosion Control Report 8 6.0 Floodplain Encroachment The majority of Outlot A falls within the Spring Creek floodplain. Both 100-yr floodway (dark blue) and flood fringe zones (cyan) run along the northern property line. There is no erosion buffer zone associated with Spring Creek. Spring Creek is a regulatory FEMA floodplain. A copy of FIRM Panel 0987F with an effective date of 12.19.06 can be found in Appendix D. Please note, a Physical Map Revision (PMR) is currently being reviewed by FEMA for the Spring Creek floodplain. The placement of fill and the construction of new residential dwellings (including mixed-use development) is allowed in the Spring Creek 100-yr flood fringe. The City of Fort Collins has prepared a Quick Guide for all floodplain regulations other than the Poudre River. This document helps to clearly depict and explain the code allowance to fill in the flood fringe. A copy of this Quick Guide is included in Appendix D for reference. No floodplain modeling is required as part of this proposed development, as it will result in no change to the FEMA regulatory mapped flood hazard zones. However, a City of Fort Collins Floodplain Use Permit, along with ancillary support documents, will be required for each structure (Buildings 10 and 11) and each site construction element (stormwater swale and pond, paths, parking lots, streets, utilities, etc.) in the floodplain. Furthermore, FEMA Elevation Certificates shall be completed and approved before the Certificates of Occupancy are issued for Building 10 and Building 11. Preliminary Drainage and Erosion Control Report 9 A portion of the 100-yr flood fringe encroaches slightly into Tract A, Lot 1 and Lot 3. No structures are proposed within the floodplain on either Tract A or Lot 3. The only structures proposed within the (12.19.06) 100-yr floodplain are portions of Building 10 and Building 11, located on Lot 1. Both buildings are multi-family residential structures with identical floor plans. There will be no basements or crawl spaces associated with any structure within the Grove student housing community. All building foundations will be slab-on-grade with thickened perimeter footings (see schematic detail on Floodplain Exhibit and Sheet G5). All construction within the floodplain shall be in compliance with Chapter 10 of the City of Fort Collins Municipal Code. Specifically, the Lowest Floor and all HVAC equipment shall be elevated above the Regulatory Flood Protection Elevation. Buildings 10 and 11 are explicitly prohibited from being converted to a critical facility, as defined by Chapter 10 of the City Code. The controlling Base Flood Elevation (BFE) for Building 10 is 5004.31 feet (NAVD 88), and for Building 11 is 5002.81 feet (NAVD 88). Since the City of Fort Collins (and thus, the proposed Grove student housing development) is on the “original” 1929 (unadjusted) vertical datum, 3.0 feet was subtracted to convert the BFE’s to the project datum. Therefore, the resulting BFE affecting Building 10 is 5001.31, feet NGVD 29 (unadjusted), and Building 11 is 4999.81 feet, NGVD 29 (unadjusted). The Regulatory Flood Protection Elevation is eighteen (18) inches above the Spring Creek BFE. The consequent Regulatory Flood Protection Elevation for Building 10 is 5002.81 feet, NGVD 29 (unadjusted) or 5005.81 feet, NAVD 88 and the Regulatory Flood Protection Elevation for Building 11 is 5001.31 feet, NGVD 29 (unadjusted) or 5004.31 feet, NAVD 88. Regulatory Flood Protection Elevations Preliminary Drainage and Erosion Control Report 10 7.0 Wetlands As previously mentioned, an Army Corps of Engineers (ACOE) jurisdictional wetland currently exists along the northern property line. The wetland roughly follows the floodplain passing through Outlot A. A descriptive project history, including more than twenty (20) site plan alternatives, has been prepared by Ripley Design, Inc. to document the extensive effort that has been taken to create a plan that meets the City’s codes and objectives, while minimizing the impact to the existing wetlands. The proposed Grove PDP preserves 100% of the existing on-site ACOE jurisdictional wetlands. ACOE Wetland Delineation Map An existing clay tile underdrain is shown on the Windtrail P.U.D. Outfall Swale drawings, which roughly parallels the existing wetlands. Another underdrain line appears to have been installed parallel to the southern boundary of Sundering Townhomes as part of the Care Housing detention pond outfall. Since there will be no disturbance within the main wetland channel, it is not anticipated that the aforementioned drain tiles will be affected by the Grove. A very small (0.015-acre) pocket of non-jurisdictional wetlands exists near the northern corner of Building 11. Although this loss could be argued as nominal and inconsequential, the Applicant will be mitigating this area nonetheless through substantial buffer habitat enhancements, additional planting, and structural diversity augmentation within Outlot A. Preliminary Drainage and Erosion Control Report 11 Since this project will not be disturbing any jurisdictional wetlands, no 404 permit or other specific approval is necessary from the Army Corps of Engineers. However, the Applicant still intends to inform the ACOE of the proposed development plan and measures taken to protect the wetlands. Additionally, the Grove will conduct a monitoring program for a minimum of three (3) years after construction. The monitoring plan will include visual observations and recording of wetland vegetation, soils, and groundwater levels. Pre-construction monitoring has already begun as of April 2011. A copy of the proposed monitoring plan, as well as results to date, can be found in Appendix L. Results of the ongoing monitoring program will be provided to the City of Fort Collins Natural Resources Department. Obviously it is desired to have no adverse changes to the existing wetlands as a result of the development. However, the monitoring plan will ensure that objective data is available for accurate evaluation. Should there be any issues of concern, the Grove and the City will work together to make certain that the development adheres to its intent and promise to have no negative impacts to the existing wetlands. As previously mentioned, the existing wetlands were created (man-made) with the Windtrail P.U.D. subdivision, and receive substantial surface water runoff from surrounding neighborhoods and upstream development. This is considered to be a significant source of irrigation to the existing wetlands. Since the delivery of such surface water is not impacted by the Grove, it is doubtful that there will be a material reduction in wetland vegetation as a result of this development. Preliminary Drainage and Erosion Control Report 12 8.0 Proposed Development The proposed development will include construction of a 12-building, 218-unit student housing apartment community, including a clubhouse, pool, and other outdoor amenities capable of supporting 612 residents. Additionally, Rolland Moore Drive will be extended from its current terminus east of Shields Street towards a new intersection at Centre Avenue across from the southern entrance to the Natural Resources Research Center. Two new streets, “PUBLIC LOCAL STREET” and “PUBLIC COMMERCIAL STREET”, along with supporting earthwork, utility infrastructure, and stormwater improvements are also a part of the proposed Grove development. Site Plan 9.0 Proposed Drainage Plan 9.1 Drainage Basins The developed site has been broken into six (6) major drainage basins. The major basins have been further divided, where appropriate, into fifteen (15) total sub-basins. Basins A – D generally consist of the areas currently being developed as The Grove at Fort Collins student housing community, whereas Basin X is reserved for the future development of CSURF’s Tract A, and Basin CH is a small area at the west end of Rolland Moore Drive near the Care Housing subdivision. Basin A consists of public roadways, private parking lots and drive aisles, as well as buildings and landscape areas. Sub-basin A4 is comprised of Building 1 and the adjacent Lot 1, Block 1 parking area. This sub-basin drains into Storm Line 1, which travels east in Outlot A and north/northeast through sub-basins A3 and A2 into Swale 1. This swale then conveys flow east in Outlot A toward the water quality pond located in sub-basin A1. Preliminary Drainage and Erosion Control Report 13 Basin B is comprised of public roadway, private parking lots and drive aisles, as well as buildings and landscape areas. Sub-basins B1 and B2 drain to sump inlets in Rolland Moore Drive located west of Buildings 5 and 7. An RCP storm drain will convey runoff from the inlets into Storm Line 1, which ultimately discharges into the main water quality pond near the west end of the Rolland Moore Drive (to be renamed) street stub. Basin C consists of roadway, parking lot and drive aisles, as well as buildings, amenities and landscape areas. Sub-basins C1 and C2 drain to sump inlets in “PUBLIC LOCAL STREET” located northeast of Building 10. Sub-basin C3 drains to a sump inlet south of Buildings 10 and 11. Sub- basin C4 drains to a sump inlet in the private parking lot southeast of Building 9, which discharges into Swale 1 via Storm Line 2. Storm Line 3 will convey runoff from sub-basins C1-C3 into Swale 1. All of Basin C ultimately passes through Swale 1 prior to reaching the main water quality pond northeast of Building 11. Basin D is predominantly composed of public roadway along with portions of the clubhouse, Building 11, and adjacent landscaping. This basin drains to sump inlets located immediately south of the west end of the Rolland Moore Drive (to be renamed) street stub. Storm Line 4 will convey runoff from the inlets directly into the water quality pond on the west side of “PUBLIC COMMERCIAL STREET”. Basin X is currently comprised of undeveloped grassland owned by CSURF (Tract A). However, Basin X is subject to future development in accordance with the ODP of record (E zoning district). While the development of this parcel is not a part of The Grove at Fort Collins student housing project, certain assumptions have been made in the drainage computations contained within this report. A 90% impervious value has been assumed for Basin X. This basin drains north towards the intersection of “PUBLIC COMMERCIAL STREET” and the Rolland Moore Drive (to be renamed) street stub. Flared-end-sections will convey flows through Storm Line 4 under “PUBLIC COMMERICAL STREET” into the Grove’s water quality pond. Both the storm line and water quality pond have been “up-sized” to accommodate the fully developed future flows from Basin X. (At Final Design, Appendix H will document the proportionate size increase necessary to allow Tract A to develop without any on-site detention or water quality.) Basin CH is comprised of the public right-of-way of Rolland Moore Drive (RMD), as well as the adjacent vegetated area that sheet flows into the roadway. This basin represents a very small area at the western-most end of RMD. Runoff from Basin CH drains west to existing sump inlets installed with Care Housing at Windtrail Park. While this area leaves the Grove subdivision boundary “undetained,” runoff does receive quantity and quality mitigation through the existing drainage system. The Care Housing design assumed a small off-site area would drain from the east to the existing sump inlets. The area corresponds to the high point in Rolland Moore Drive roughly 50’± east of the current end of pavement. The Grove roadway plan (thus, corresponding tributary area) matches the design assumptions made with the Care Housing project; therefore, no further analysis or improvements are necessary for the runoff from Basin CH. Likewise, Basin CH has been excluded from the on-site “developed” stormwater computations since this area drains to a different outfall. Preliminary Drainage and Erosion Control Report 14 9.2 Developed Drainage Concept The Windtrail P.U.D. Outfall Swale currently drains a good portion of the site. The downstream end of this swale is located immediately east of 602 Gilgalad Way, which is also the limiting ‘pinch point’ of the outfall channel. The swale has a 100-yr design flow of approximately 130.7 cfs, with a maximum allowable capacity of 139.8 cfs. The swale was “over-sized” specifically to accommodate future developed flow from the land currently being platted as the Grove (then known as the CSURF/McCoy Land Swap). Therefore, previous Windtrail P.U.D. drainage designs would appear to provide sufficient capacity to drain a substantial portion of the Grove development. However, current homeowners in the neighborhoods north of Outlot A have expressed noted concerns with both surface and subsurface waters. Some of the issues regarding the backup of stormwater could be a result of the original design intent to achieve flat areas, subtle ponding, and created wetlands. Others could be a result of insufficient channel maintenance, over-irrigation, and sump pump discharge. Regardless of the factors currently causing water troubles for the Sundering and Windtrail neighborhoods, it is the strong desire and intent of the Applicant of the Grove to not exacerbate these problems in any way. Rather than sending developed runoff towards the Windtrail P.U.D. Outfall Swale, as it was originally intended, the Grove will design and install a completely separate outfall. Additionally, groundwater flows intercepted by the underdrain system will also be discharged away from existing homes in an effort to further ensure there are no adverse affects from the Grove development. A much better outfall for this project is the Horticulture Center Outfall Channel, which was constructed with the CAT-22 Gardens on Spring Creek improvements. 10.0 Outfall The CAT-22 Horticulture Center Outfall Channel currently flows behind the Gardens on Spring Creek. A concrete trail separates this outfall channel from the Windtrail P.U.D. outfall swale. The CAT-22 channel conveys flow from the current terminus of the Rolland Moore Drive stub (to be renamed) north towards Spring Creek. Dual 1.5’ x 6’ box culverts allow stormwater to pass under the Sherwood Lateral prior to reaching Spring Creek. The outfall channel was originally designed to convey 57.6 cfs from The Grove at Fort Collins project area in the 100-yr event. The 100-yr peak flow expected at this design point from the proposed student housing and future CSURF development is roughly 92.9 cfs. However, that does not necessarily imply that the outfall channel is insufficient to accommodate the developed runoff from the Grove. A simplified analysis of both the channel section itself, as well as the box culverts, estimated a 100-yr capacity in excess of 132 cfs. These cursory computations were calculated both with and without an assumed 34 cfs groundwater baseflow (extremely conservative). In all scenarios, the outfall could easily accept the fully developed 100-yr peak discharge from the Grove without overtopping. However, the Horticulture Center Outfall Channel cannot be fully evaluated with such simple analyses, as this channel is heavily influenced by the tailwater conditions in Spring Creek. Such correlation was witnessed as recently as this past fall of 2010 when there had been a build-up of debris immediately downstream of the outfall channel. The backwater effects caused the box culverts under the Sherwood Lateral to be nearly submerged. Fortunately, the City Stormwater Utility has since cleared the blockage in Spring Creek to provide unobstructed drainage. Nevertheless, this occurrence does prove the close correlation between the CAT-22 outfall channel and the water level in Spring Creek. Preliminary Drainage and Erosion Control Report 15 This relationship was first documented by Anderson Consulting Engineers (ACE) in their 2002 “Hydraulic Analysis of the Horticulture Center Outfall Channel.” A HEC-RAS model was developed for the outfall channel, and 100-yr stormwater elevations were computed at both the peak time in Spring Creek as well as the peak of the local basin tributary to the storm drain feeding the outfall channel. The 2002 ACE report was based upon older Spring Creek drainage models. Northern Engineering has since obtained the most current modeling data from the City of Fort Collins, and has re-run the analysis on the Horticulture Center Outfall Channel. Additionally, the 2002 ACE report had assumed a time of concentration of 37 minutes for the CSURF basin upstream of the triple culverts. The new results reflect the latest modeling data as well as an actual time of concentration for the Grove of 26 minutes. The channel proves to have sufficient capacity to accept the 100-yr peak discharge of 92.9 cfs from The Grove at Fort Collins. Additional information on this analysis can be found in Appendix C. Even if one were to consider a catastrophic, worst-case scenario, such as the culverts being clogged or a rainfall event exceeding the 100-yr design storm, the emergency spill path would be to the east/northeast. Such an emergency overflow would likely occur via shallow overland flow traveling across City-owned property towards Spring Creek. It is practically impossible for any water from the Horticulture Center Outfall Channel to ever reach the neighboring homes in Windtrail under any circumstance. This is all the more reason to utilize the Horticulture Center Outfall Channel rather than the Windtrail P.U.D. outfall swale for the Grove’s developed runoff. It also should be noted that it is accepted design practice for culverts to be submerged at depths one-and-a-half-times their height during major rain events. Not only is the CAT-22 channel an appropriate stormwater outfall, but it currently serves to relieve groundwater in the area as well. In fact, a perennial baseflow can be observed trickling in the bottom of this channel even in the dead of winter. The underdrain system to be installed with the Grove will also outfall directly into this channel rather than routing through the Windtrail wetland drainage. The underdrain outfall will connect into the outlet structure of the water quality pond, downstream of the orifice plate. The underdrain outfall will also have an invert elevation higher than the triple culverts draining the outlet structure. These measures will help minimize the potential for stormwater to backup into the underdrain system. While routine rain events are unlikely to cause backwater in the underdrains, the potential does exist for the aforementioned tailwater effects to impact the drains running in “PUBLIC LOCAL STREET” and “PUBLIC COMMERCIAL STREET”. Therefore, an inline backflow preventer will be installed on the underdrain outfall line just upstream of the outlet structure to ensure the roadway subgrade is not compromised. The peak discharge of the underdrain outfall is expected to only be around 1.53 cfs (15 gpm, or 0.03 cfs, from groundwater and 1.5 cfs from the rain gardens), and has a negligible impact on the outfall channel (see Appendix J for further details on the underdrain system). Nonetheless, the floor of the concrete outlet structure will be designed to prohibit groundwater discharge from trickling to the south and saturating the area in front of the water quality plate. Preliminary Drainage and Erosion Control Report 16 11.0 Stormwater Quantity Detention The effective Spring Creek Master Drainage Plan assumes a set area and impervious value for Basin 130. As such, stormwater quantity detention is not required if development patterns are at or below the assumed basin parameters. The actual impervious value for the developed area within the Grove subdivision boundary (including future CSURF development of Tract A) is just over 62%. Therefore, it is prudent to run the applicable modeling to ensure that on-site detention is not required and that downstream conveyance is sufficient. Fortunately, such additional analysis has been conducted to be absolutely certain that the proposed Grove development will not have any adverse drainage impacts to downstream properties. Further examination was given to Basin 130 in the City’s MODSWMM for the Spring Creek Master Drainage Plan. Ayres Associates recently completed a large-scale study and analysis of the stormwater system in this portion of the Spring Creek basin. The November 2010 “Alternative Analysis for the Design of the Mason Street Outfall” assumed a developed area of 24 acres with a percent impervious value of 90% associated with the proposed Grove project. These parameters were modeled with the larger Spring Creek Master Plan, and the output resulted in no rise in water surface elevation to Pond 303 (aka, BNRR Pond). Therefore, it is further proven that the proposed Grove student housing development and future CSURF development of Tract A can free release without any on-site quantity detention. In fact, the Grove’s actual developed area and percent impervious values are closer to 22 acres and 62%, respectively, so there should be more than enough capacity in the downstream regional pond. 12.0 Stormwater Quality Mitigation Regardless of whether or not on-site quantity detention is required, mitigation to address the stormwater quality of developed runoff is necessary. Water quality treatment for the Grove student housing community will primarily be achieved in the water quality pond located at the east/southeast corner of Outlot A. This pond will be designed as a standard dry extended detention basin (EDB), per City of Fort Collins guidelines. The water quality capture volume (WQCV) will help remove sediment and other pollutants from developed runoff. Criteria for a 40-hour drain time treating the 80th percentile runoff event, as outlined in the Urban Storm Drainage Criteria Manual, Volume 3 – Best Management Practices (BMPs) by the Urban Drainage and Flood Control District has been used to design the WQCV. The required water quality volume is approximately 0.54 ac-ft, and over 0.64 ac-ft is provided. Technically speaking, the EDB will fully satisfy the minimum water quality requirements for the Grove development. However, this project is going above and beyond the minimum requirements. Nearly every drop of developed runoff will pass over or through some sort of vegetated surface prior to leaving the project boundary. Swale 1 is intended to function as a bio-swale, thereby offering additional water quality enhancement upstream of the water quality pond. Additionally, the CAT- 22 outfall channel itself is designed as a water quality grassed swale. Therefore, there will be multiple BMPs in series between the developed runoff from the Grove and the receiving waters of Spring Creek. Preliminary Drainage and Erosion Control Report 17 One more water quality concept worth noting is the pursuit of rain garden planters within the curb extensions of Rolland Moore Drive. These roadside planters will serve to treat the stormwater from the public right-of-way. Gutter flows will be routed through the curb extension areas to create ecological rain gardens. An area-wide underdrain system will already be employed, and the same drains will extend under the rain garden areas for subsurface drainage relief. Representative ideas for the curb extensions are illustrated below. Please note, these concepts remain very preliminary at this time. Therefore, final design configuration, plantings, etc. may vary from the sample photographs. Curb Extension / Rain Garden Concepts Photos courtesy of www.portlandonline.com Implementing these curb extension planters will have multiple benefits, the most obvious of which is the water quality treatment. However, there will also be the opportunity for the rain gardens to serve as a pilot project and case study for the region. Unfortunately, current Fort Collins street standards do not allow for such low-impact stormwater strategies; thus, a formal variance request has been submitted to the Engineering Department to allow them within the public right-of-way. The City of Fort Collins Engineering/Streets Department had initially expressed concerns regarding the long-term viability, and potential replacement, of such facilities. Admittedly, the ongoing operation and maintenance of the curb extension areas are unknown at this time since there is little data or precedence in our region for such facilities. Fortunately, subsequent meetings have helped to expose and formulate remedies to the major concerns. The concepts depicted above were discussed at two Utility Coordination Meetings (04.14.10 and 01.20.11), and received no objections from the providers. A design charrette was also held on 10.26.10 to specifically address the pavement management concerns, opportunities, and constraints. As a result, final design details are expected to meet the needs of all stakeholders. Nonetheless, it is possible that there may be additional refinement during the final design phase. Additionally, the City of Fort Collins Stormwater Utility will be providing the necessary assurance for the rain gardens. As a thought-partner in these concepts, City Stormwater Staff has agreed to help champion these efforts and truly create 21st Century Utilities. The curb extension planters fall very much inline with the current trends in Green Streets and sustainable infrastructure. In fact, such techniques coincide perfectly with the Plan Fort Collins objectives to innovate, sustain, and connect. Rolland Moore Drive has the potential to become a showcase example of a multi-functioning street. Furthermore, the Urban Water Center at Colorado State University has expressed interest in another partnership project with the City of Fort Collins to install sampling stations and monitor the above- described rain gardens. Preliminary Drainage and Erosion Control Report 18 13.0 Erosion and Sediment Control An Erosion and Sediment Control Plan (along with associated details) will be included with the final construction drawings. It should be noted, however, that any such Erosion and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs depicted, and additional or different BMPs from those included may be necessary during construction, or as required by the authorities having jurisdiction. It shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed or modified in conjunction with construction activities. It is imperative to appropriately reflect the current site conditions at all times. The Erosion and Sediment Control Plan will address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices from the UDFCD and the City of Fort Collins Erosion Control Reference Manual for Construction Sites will be utilized. Expected measures include: silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways, and inlet protection at existing and proposed storm inlets and culverts. Special care and attention shall be given to the wetland drainageway in Outlot A. Vehicle tracking control pads, spill containment and clean-up procedures, designated concrete washout areas, and job site restrooms shall also be provided by the Contractor. Preliminary Drainage and Erosion Control Report 19 14.0 Conclusions This Preliminary Drainage and Erosion Control Report has taken into consideration the comments and concerns raised with the previous development plan proposed for the subject property. The new analysis and updated Site Plan mitigate most, if not all, of the previous concerns. In addition to comments raised by City of Fort Collins Stormwater Staff, the Applicant also acknowledges receipt of Memorandums from the Windtrail and Sundering Townhomes Homeowners Associations dated 10.15.10 and 04.25.11, respectively; as well as concerns expressed by Mr. Terence H. Podmore, Ph.D. to the Ditch Company (Gene Fischer) on 01.27.11 and to the Fort Collins City Council on 04.19.11. All relevant engineering concerns voiced in said citizen comments have been diligently addressed. The proposed Grove at Fort Collins student housing development conforms to all governing drainage criteria and regulations. The proposed stormwater system will adequately treat the developed runoff for water quality before leaving the site. Regional conveyance and attenuation of peak discharge is provided off-site, and can safely accommodate full development of the subdivision. No adverse stormwater impacts are expected as a result of this project. The Grove will have a completely separate drainage system from Windtrail P.U.D.; thereby ensuring adjacent homeowners will not be affected by the Grove’s developed runoff. The proposed development complies with Chapter 10 of the City of Fort Collins Municipal Code – “Flood Prevention and Protection.” Final drainage improvements will be designed in accordance with applicable City of Fort Collins and UDFCD criteria. Extensive site analysis and alternative plan investigations have been conducted over the course of 2+ years. The resulting development plan best accommodates the multiple environmental and stormwater constraints of the site, while providing a great asset to the community. The Grove at Fort Collins will offer students a place to live that is close to campus and the Mason Corridor BRT, thereby lessening the vehicular impacts to local roadways and the environment. It also helps to consolidate students into an appropriate location (per vested ODPs, Master Plans, and compliant with City zoning and Land Use Code), and may relieve the stress on overburdened rental houses in single-family residential neighborhoods throughout the City. From a progressive stormwater management perspective, the rain gardens proposed along Rolland Moore Drive offer another opportunity to achieve the City’s vision for a 21st Century Utility. This collaborative effort is a true occasion to innovate, sustain, and connect. The Grove aligns with Plan Fort Collins objectives, moves towards multi-functioning (green) streets, helps create sustainable infrastructure, and promotes a high performing community. Preliminary Drainage and Erosion Control Report 20 References 1. Addendum to the Final Drainage Report for the Windtrail P.U.D., Townhomes Site, March 1, 1995, Lidstone & Anderson, Inc. (LA Project No. COTST18.8). 2. Alternative Analysis for the Design of the Mason Street Outfall, November 2010, Ayres Associates. 3. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities, November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services. 4. Ecological Characterization Study Report (ESCR) Update for The Grove 11/29/10 Concept Plan, November 30, 2010, Cedar Creek Associates. 5. Erosion Control Reference Manual for Construction Sites, January 1991, City of Fort Collins. 6. Flood Insurance Rate Map (FIRM) Panel 0987F, Effective Date December 19, 2006, Federal Emergency Management Agency (FEMA). 7. Fort Collins Municipal Code (Chapter 10 – Flood Prevention and Protection), 1987, Colorado Code Publishing Company, Fort Collins, Colorado. 8. Hydraulic Analysis of the Horticulture Center Outfall Channel, September 4, 2002, Anderson Consulting Engineers, Inc. 9. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007 10. Monitor Well Installation and Slope Stability Assessment Status, September 7, 2010, Earth Engineering Company (EEC Project No. 09-01-032). 11. Project Development Drainage and Erosion Control Report, Center for Advanced Technologies 22nd Filing “Community Horticultural Center,” January 2003, EDAW Inc. (Job No. 7F082.20). 12. Revised Subsurface Exploration Report, The Grove at Fort Collins, Fort Collins, Colorado, December 7, 2010, Earth Engineering Company, Inc. (EEC Project No. 09-01-032). 13. Slope Stability Assessment, The Grove at Fort Collins, Fort Collins, Colorado, October 7, 2010, Earth Engineering Company, Inc., EEC Project No. 09-01-032). 14. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 15. Storm Drainage Design Criteria and Construction Standards, City of Fort Collins, Colorado, Updated April 1999. 16. Supplemental Subsurface Water Investigation – The Grove at Fort Collins, December 8, 2010, Applegate Group (AG File No. 10-132). 17. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District, Wright-McLaughlin Engineers, Denver, Colorado, Updated June 2001. APPENDIX A RATIONAL METHOD DEVELOPED RUNOFF CALCULATIONS Preliminary Drainage and Erosion Control Report CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project: The Grove Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: A. Reese Asphalt ……....……………...……….....…...……………….…………………………………..0.95 100 Date: Concrete …….......……………….….……….………………..….………………………………… 0.95 90 Gravel ……….…………………….….…………………………..……………………………….0.. 50 40 Roofs …….…….………………..……………….…………………………………………….. 0.95 90 Pavers…………………………...………………..…………………………………………….. 0.40 22 Lawns and Landscaping Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0 Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0 2-year Cf = 1.00 100-year Cf = 1.25 Basin ID Basin Area (s.f.) Basin Area (ac) Area of Asphalt (ac) Area of Concrete (ac) Area of Roofs (ac) Area of Gravel (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Coefficient Composite % Imperv. A1 41,376 0.95 0.00 0.00 0.00 0.00 0.95 0.25 0.25 0.31 0.0 A2 25,167 0.58 0.41 0.05 0.06 0.00 0.06 0.88 0.88 1.00 87.6 A3 19,588 0.45 0.00 0.00 0.00 0.00 0.45 0.25 0.25 0.31 0.0 A4 58,269 1.34 0.46 0.10 0.22 0.00 0.56 0.66 0.66 0.82 56.0 B1 72,453 1.66 0.68 0.33 0.14 0.00 0.51 0.74 0.74 0.92 66.8 B2 291,955 6.70 1.42 0.70 0.92 0.00 3.66 0.57 0.57 0.71 43.0 C1 27,895 0.64 0.29 0.23 0.00 0.00 0.12 0.82 0.82 1.00 77.8 C2 60,895 1.40 0.28 0.18 0.36 0.00 0.58 0.66 0.66 0.83 55.0 C3 89,792 2.06 0.78 0.32 0.37 0.00 0.59 0.75 0.75 0.94 68.0 C4 53,675 1.23 0.48 0.24 0.15 0.00 0.36 0.74 0.74 0.93 67.5 Preliminary Drainage and Erosion Control Report Overland Flow, Time of Concentration: Project: The Grove Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S½ Velocity (Swale Flow), V = 15·S½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Is Length >500' ? C*Cf (2-yr Cf=1.00) C*Cf (10-yr Cf=1.00) C*Cf (100-yr Cf=1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) 2-yr Preliminary Drainage and Erosion Control Report Overland Flow, Time of Concentration: Project: The Grove Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S½ Velocity (Swale Flow), V = 15·S½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) A1 A1-A4, B1, B2, C1-C4, D1, D2, X 5 5 5 1071 0.5 1.41 12.6 909 1.3 1.71 8.9 26 26 26 COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Additional Gutter Flow Additional Swale Flow Design Point Preliminary Drainage and Erosion Control Report Rational Method Equation: Project: The Grove Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: A1 A1 0.95 11 11 11 0.25 0.25 0.31 2.13 3.63 7.42 0.5 0.9 2.2 A2 A2 0.58 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 1.4 2.5 5.7 A3 A3 0.45 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.3 0.5 1.4 A4 A4 1.34 5 5 5 0.66 0.66 0.82 2.85 4.87 9.95 2.5 4.3 11.0 B1 B1 1.66 10 10 9 0.74 0.74 0.92 2.26 3.86 8.03 2.8 4.7 12.3 B2 B2 6.70 10 10 10 0.57 0.57 0.71 2.26 3.86 7.88 8.6 14.7 37.5 C1 C1 0.64 5 5 5 0.82 0.82 1.00 2.85 4.87 9.95 1.5 2.6 6.4 C2 C2 1.40 5 5 5 0.66 0.66 0.83 2.85 4.87 9.95 2.6 4.5 11.5 C3 C3 2.06 5 5 5 0.75 0.75 0.94 2.85 4.87 9.95 4.4 7.5 19.2 C4 C4 1.23 5 5 5 0.74 0.74 0.93 2.85 4.87 9.95 2.6 4.5 11.4 D1 D1 0.93 5 5 5 0.79 0.79 0.99 2.85 4.87 9.95 2.1 3.6 9.2 D2 D2 0.75 5 5 5 0.78 0.78 0.98 2.85 4.87 9.95 1.7 2.9 7.4 X X 3.84 20 20 19 0.88 0.88 1.00 1.63 2.78 5.84 5.5 9.4 22.4 CH1 CH1 0.04 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.1 0.2 0.4 CH2 CH2 0.16 5 5 5 0.41 0.41 0.51 2.85 4.87 9.95 0.2 0.3 0.8 OS1 OS1 1.00 10 10 9 0.25 0.25 0.31 2.26 3.86 8.03 0.6 1.0 2.5 OS2 OS2 1.74 14 14 13 0.25 0.25 0.31 1.92 3.29 6.92 0.8 1.4 3.8 OS3 OS3 15.42 75 75 71 0.25 0.25 0.31 0.69 1.19 2.58 2.7 4.6 12.4 OS4 OS4 0.66 12 12 12 0.88 0.88 1.00 2.05 3.50 7.29 1.2 2.0 4.8 OS5 OS5 0.23 5 5 5 0.86 0.86 1.00 2.85 4.87 9.95 0.6 1.0 2.3 OS6 OS6 0.29 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.7 1.1 2.9 Area, A (acres) Intensity, i2 (in/hr) 100-yr Tc (min) DEVELOPED RUNOFF COMPUTATIONS C100 Design Point Flow, Q100 (cfs) Flow, Q2 (cfs) 10-yr Tc (min) 2-yr Tc (min) C2 Flow, Q10 (cfs) Intensity, i100 (in/hr) Basin(s) A. Reese Preliminary Drainage and Erosion Control Report Rational Method Equation: Project: The Grove Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: A1 A1-A4, B1, B2, C1-C4, D1, D2, X 22.54 26 26 26 0.68 0.68 0.85 59.65 1.40 2.39 4.87 21.6 36.8 93.7 C100 Intensity, i2 (in/hr) Intensity, i10 (in/hr) Intensity, i100 (in/hr) COMBINED RUNOFF COMPUTATIONS A. Reese April 6, 2011 Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 Design Point Basin(s) Area, A (acres) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) Composite % Imperv. C2 C 10 Q C f C i A D:\Projects\502-001\Drainage\Hydrology\PDP\502-001_Rational-Calcs.xlsx\Combined Runoff Preliminary Drainage and Erosion Control Report DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) A1 A1 0.95 0.25 0.31 11.3 11.1 0.5 2.2 A2 A2 0.58 0.88 1.00 5.0 5.0 1.4 5.7 A3 A3 0.45 0.25 0.31 5.0 5.0 0.3 1.4 A4 A4 1.34 0.66 0.82 5.0 5.0 2.5 11.0 B1 B1 1.66 0.74 0.92 9.7 9.4 2.8 12.3 B2 B2 6.70 0.57 0.71 10.0 9.7 8.6 37.5 C1 C1 0.64 0.82 1.00 5.3 5.1 1.5 6.4 C2 C2 1.40 0.66 0.83 5.0 5.0 2.6 11.5 C3 C3 2.06 0.75 0.94 5.0 5.0 4.4 19.2 C4 C4 1.23 0.74 0.93 5.0 5.0 2.6 11.4 CH1 CH1 0.04 0.80 1.00 5.0 5.0 0.1 0.4 CH2 CH2 0.16 0.41 0.51 5.0 5.0 0.2 0.8 OS1 OS1 1.00 0.25 0.31 9.9 9.2 0.6 2.5 OS2 OS2 1.74 0.25 0.31 14.1 13.1 0.8 3.8 OS3 OS3 0.66 0.88 1.00 12.3 11.8 1.2 4.8 OS6 OS6 0.29 0.80 1.00 5.0 5.0 0.7 2.9 A1 A1-A4, B1, B2, C1-C4, D1, D2, X 23 0.68 0.85 26.5 26.5 21.6 93.7 D:\Projects\502-001\Drainage\Hydrology\PDP\502-001_Rational-Calcs.xlsx\Summary Table APPENDIX B WATER QUALITY CALCULATIONS Project Tittle Date: Project Number Calcs By: Client Pond Designation 1 WQCV = Watershed inches of Runoff (inches) 59.65% a = Runoff Volume Reduction (constant) i = Total imperviouness Ratio (i = Iwq/100) 0.235 in A = 22.54 ac V = 0.53 ac-ft V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) 1.2 = 20% Additional Volume (Sediment Accumulation) Drain Time a = i = WQCV = Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event The Grove April 6, 2011 502-001 A. Reese Campus Crest Water Quality Pond 0.235 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 WQCV (watershed inches) Total Imperviousness Ratio (i = Iwq /100) Water Quality Capture Volume 6 hr 12 hr 24 hr 40 hr WQCV a 0.91 i 3 1 . 19 i 2 0 . 78 i WQCV a 0.91 i 3 1 . 19 i 2 0 . 78 i * * 1 . 2 12 V WQCV A ¸ ADDITIONAL INFORMATION TO FOLLOW AT FINAL DESIGN APPENDIX C PREVIOUS DRAINAGE MEMOS AND CORRESPONDENCE C.1 – Horticulture Center Outfall Channel Modeling C.1.a – Narrative C.1.b – MODSWMM: Spring Creek 100-yr PMR C.1.c – HEC-RAS: Truncated Spring Creek C.1.d – HEC-RAS: Horticulture Center Channel C.2 – Simplified Horticulture Center Outfall Analysis C.3 – BNRR Pond Capacity Confirmation C.4 – Ditch Company LetterV APPENDIX C.1 HORTICULTURE CENTER OUTFALL CHANNEL MODELING C.1.a – Narrative C.1.b – MODSWMM: Spring Creek 100-yr PMR C.1.c – HEC-RAS: Truncated Spring Creek C.1.d – HEC-RAS: Horticulture Center Channel APPENDIX C.1.a HORTICULTURE CENTER OUTFALL CHANNEL MODELING Narrative Preliminary Drainage and Erosion Control Report Horticulture Center Outfall Channel Analysis The Horticulture Center Channel conveys developed flows from the proposed Grove at Fort Collins project area into Spring Creek. The channel accepts stormwater from the outlet structure of the on-site water quality pond through (3) 24-inch culverts under the existing street stub (Rolland Moore Drive, to be renamed) and flows north between a spur of the Spring Creek bike trail and the Horticulture Center (also referred to as “The Gardens on Spring Creek”). Per Rational Method hydrologic calculations contained in Appendix A, the time of concentration for the developed site is 26 minutes. Based on the MODSWMM for the Spring Creek PMR, the flow in Spring Creek at this time stage is 165.7 cfs (see Appendix C.1.b). This flow rate was then modeled in a truncated version of the HEC-RAS model completed for the Spring Creek PMR (see Appendix C.1.c). From the HEC-RAS model, a water surface elevation in Spring Creek at the outfall point for the Horticulture Center Channel of 4992.12 was obtained. Utilizing this as a starting water surface, a HEC-RAS model of the Horticulture Center Channel was run to determine water surface elevations in the channel. Based on Rational Method hydrologic calculations for the developed site, peak 100-yr discharge from the site is 92.9 cfs. Thus, the Horticulture Center Channel has been analyzed for a 100-year flow rate of 92.9 cfs occurring at time 0:26. Results of the updated HEC-RAS analysis of the Horticulture Center Channel are provided in Appendix C.1.d. The output shows that the channel has in excess of 2-feet of freeboard with a peak 100-yr discharge of 92.9 cfs from the proposed Grove at Fort Collins development. APPENDIX C.1.b HORTICULTURE CENTER OUTFALL CHANNEL MODELING MODSWMM: Spring Creek 100-yr PMR APPENDIX C.1.c HORTICULTURE CENTER OUTFALL CHANNEL MODELING HEC-RAS: Truncated Spring Creek APPENDIX C.1.d HORTICULTURE CENTER OUTFALL CHANNEL MODELING HEC-RAS: Horticulture Center Channel 1 2 3 4 5 NOTE: BASE MAP INFORMATION OBTAINED FROM "HYDRAULIC ANALYSIS OF THE HORTICULTURE CENTER OUTFALL CHANNEL", PREPARED BY ANDERSON CONSULTING ENGINEERS, INC., SEPTEMBER 4, 2002 HEC-RAS Version 4.0.0 March 2008 U.S. Army Corps of Engineers Hydrologic Engineering Center 609 Second Street Davis, California X X XXXXXX XXXX XXXX XX XXXX X X X X X X X X X X X X X X X X X X X XXXXXXX XXXX X XXX XXXX XXXXXX XXXX X X X X X X X X X X X X X X X X X X X X X XXXXXX XXXX X X X X XXXXX PROJECT DATA Project Title: Horticulture Center Channel Project File : 502_001.prj Run Date and Time: 4/1/2011 1:30:41 PM Project in English units FLOW DATA Flow Title: Flow 01 Flow File : d:\Projects\502-001\Drainage\Modeling\hec-ras-hort ctr channel\502_001.f01 Flow Data (cfs) River Reach RS PF 1 Hort Ctr Channel1 5 92.9 Boundary Conditions River Reach Profile Upstream Downstream Hort Ctr Channel1 PF 1 Known WS = 4992.12 GEOMETRY DATA Geometry Title: geom1 Geometry File : d:\Projects\502-001\Drainage\Modeling\hec-ras-hort ctr channel\502_001.g01 CROSS SECTION RIVER: Hort Ctr Channel REACH: 1 RS: 5 INPUT Description: Station Elevation Data num= 4 Sta Elev Sta Elev Sta Elev Sta Elev 0 4998 15.5 4992.85 25.5 4992.85 41 4998 Manning's n Values num= 3 Sta n Val Sta n Val Sta n Val 0 .04 15.5 .04 25.5 .04 Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan. 15.5 25.5 122 122 122 .1 .3 CROSS SECTION OUTPUT Profile #PF 1 E.G. Elev (ft) 4995.06 Element Left OB Channel Right OB Vel Head (ft) 0.13 Wt. n-Val. 0.040 0.040 0.040 W.S. Elev (ft) 4994.93 Reach Len. (ft) 122.00 122.00 122.00 Crit W.S. (ft) Flow Area (sq ft) 6.49 20.76 6.49 E.G. Slope (ft/ft) 0.002876 Area (sq ft) 6.49 20.76 6.49 Q Total (cfs) 92.90 Flow (cfs) 12.79 67.31 12.79 Top Width (ft) 22.50 Top Width (ft) 6.25 10.00 6.25 Vel Total (ft/s) 2.75 Avg. Vel. (ft/s) 1.97 3.24 1.97 Max Chl Dpth (ft) 2.08 Hydr. Depth (ft) 1.04 2.08 1.04 Conv. Total (cfs) 1732.3 Conv. (cfs) 238.6 1255.2 238.6 Length Wtd. (ft) 122.00 Wetted Per. (ft) 6.58 10.00 6.58 Min Ch El (ft) 4992.85 Shear (lb/sq ft) 0.18 0.37 0.18 Alpha 1.15 Stream Power (lb/ft s) 0.35 1.21 0.35 Frctn Loss (ft) 0.47 Cum Volume (acre-ft) 0.06 0.19 0.06 C & E Loss (ft) 0.01 Cum SA (acres) 0.05 0.09 0.05 CROSS SECTION RIVER: Hort Ctr Channel REACH: 1 RS: 4 INPUT Description: Station Elevation Data num= 4 Sta Elev Sta Elev Sta Elev Sta Elev 0 4997 15 4992 19 4992 34 4997 Manning's n Values num= 3 Sta n Val Sta n Val Sta n Val 0 .04 15 .04 19 .04 Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan. 15 19 126 126 126 .1 .3 CROSS SECTION OUTPUT Profile #PF 1 E.G. Elev (ft) 4994.58 Element Left OB Channel Right OB Vel Head (ft) 0.24 Wt. n-Val. 0.040 0.040 0.040 W.S. Elev (ft) 4994.34 Reach Len. (ft) 126.00 126.00 126.00 Crit W.S. (ft) Flow Area (sq ft) 8.23 9.37 8.23 E.G. Slope (ft/ft) 0.005348 Area (sq ft) 8.23 9.37 8.23 Q Total (cfs) 92.90 Flow (cfs) 24.00 44.91 24.00 Top Width (ft) 18.06 Top Width (ft) 7.03 4.00 7.03 Vel Total (ft/s) 3.60 Avg. Vel. (ft/s) 2.91 4.79 2.91 Max Chl Dpth (ft) 2.34 Hydr. Depth (ft) 1.17 2.34 1.17 Conv. Total (cfs) 1270.3 Conv. (cfs) 328.1 614.1 328.1 Length Wtd. (ft) 126.00 Wetted Per. (ft) 7.41 4.00 7.41 Min Ch El (ft) 4992.00 Shear (lb/sq ft) 0.37 0.78 0.37 Alpha 1.20 Stream Power (lb/ft s) 1.08 3.75 1.08 Frctn Loss (ft) 0.88 Cum Volume (acre-ft) 0.04 0.15 0.04 C & E Loss (ft) 0.01 Cum SA (acres) 0.04 0.07 0.04 CROSS SECTION RIVER: Hort Ctr Channel REACH: 1 RS: 3 INPUT Description: Station Elevation Data num= 6 Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev 0 4997 18 4991 20 4991 32 4995 95 4996 162 4997 Manning's n Values num= 3 Sta n Val Sta n Val Sta n Val 0 .04 18 .04 20 .04 Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan. 18 20 186 186 186 .1 .3 CROSS SECTION OUTPUT Profile #PF 1 E.G. Elev (ft) 4993.69 Element Left OB Channel Right OB Vel Head (ft) 0.36 Wt. n-Val. 0.040 0.040 0.040 W.S. Elev (ft) 4993.33 Reach Len. (ft) 186.00 186.00 186.00 Crit W.S. (ft) Flow Area (sq ft) 8.14 4.66 8.14 E.G. Slope (ft/ft) 0.009541 Area (sq ft) 8.14 4.66 8.14 Q Total (cfs) 92.90 Flow (cfs) 31.59 29.72 31.59 Top Width (ft) 15.98 Top Width (ft) 6.99 2.00 6.99 Vel Total (ft/s) 4.43 Avg. Vel. (ft/s) 3.88 6.38 3.88 Max Chl Dpth (ft) 2.33 Hydr. Depth (ft) 1.17 2.33 1.17 Conv. Total (cfs) 951.1 Conv. (cfs) 323.4 304.3 323.4 Length Wtd. (ft) 186.00 Wetted Per. (ft) 7.37 2.00 7.37 Min Ch El (ft) 4991.00 Shear (lb/sq ft) 0.66 1.39 0.66 Alpha 1.18 Stream Power (lb/ft s) 2.55 8.85 2.55 Frctn Loss (ft) 0.25 Cum Volume (acre-ft) 0.02 0.13 0.02 C & E Loss (ft) 0.09 Cum SA (acres) 0.02 0.06 0.02 Warning: The conveyance ratio (upstream conveyance divided by downstream conveyance) is less than 0.7 or greater than 1.4. This may indicate the need for additional cross sections. CROSS SECTION RIVER: Hort Ctr Channel REACH: 1 RS: 2 INPUT Description: Station Elevation Data num= 6 Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev 0 4997 17.2 4997 17.25 4989.5 29.25 4989.5 29.3 4997 46.25 4997 Manning's n Values num= 3 Sta n Val Sta n Val Sta n Val 0 .04 17.25 .04 29.25 .04 Bank Sta: Left Right Lengths: Left Channel Right Coeff Contr. Expan. 17.25 29.25 102 102 102 .1 .3 CROSS SECTION OUTPUT Profile #PF 1 E.G. Elev (ft) 4993.35 Element Left OB Channel Right OB Vel Head (ft) 0.06 Wt. n-Val. 0.040 0.040 0.040 W.S. Elev (ft) 4993.29 Reach Len. (ft) 102.00 102.00 102.00 Crit W.S. (ft) 4990.73 Flow Area (sq ft) 0.05 45.42 0.05 E.G. Slope (ft/ft) 0.000514 Area (sq ft) 0.05 45.42 0.05 Q Total (cfs) 92.90 Flow (cfs) 0.00 92.90 0.00 Top Width (ft) 12.05 Top Width (ft) 0.03 12.00 0.03 Vel Total (ft/s) 2.04 Avg. Vel. (ft/s) 0.05 2.05 0.05 Max Chl Dpth (ft) 3.79 Hydr. Depth (ft) 1.89 3.79 1.89 Conv. Total (cfs) 4098.4 Conv. (cfs) 0.1 4098.2 0.1 Length Wtd. (ft) 102.00 Wetted Per. (ft) 3.79 12.00 3.79 Min Ch El (ft) 4989.50 Shear (lb/sq ft) 0.00 0.12 0.00 Alpha 1.00 Stream Power (lb/ft s) 0.00 0.25 0.00 Frctn Loss (ft) Cum Volume (acre-ft) 0.02 C & E Loss (ft) Cum SA (acres) 0.00 0.03 0.00 CULVERT RIVER: Hort Ctr Channel REACH: 1 RS: 1.5 INPUT Description: Distance from Upstream XS = 1 Deck/Roadway Width = 100 Weir Coefficient = 2.6 Upstream Deck/Roadway Coordinates num= 2 Sta Hi Cord Lo Cord Sta Hi Cord Lo Cord 0 4997 4997 46 4997 4997 Upstream Bridge Cross Section Data Station Elevation Data num= 6 Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev 0 4997 17.2 4997 17.25 4989.5 29.25 4989.5 29.3 4997 46.25 4997 Manning's n Values num= 3 Sta n Val Sta n Val Sta n Val 0 .04 17.25 .04 29.25 .04 Bank Sta: Left Right Coeff Contr. Expan. 17.25 29.25 .1 .3 Downstream Deck/Roadway Coordinates num= 2 Sta Hi Cord Lo Cord Sta Hi Cord Lo Cord 0 4997 4997 56 4997 4997 Downstream Bridge Cross Section Data Station Elevation Data num= 6 Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev 0 4997 24.2 4997 24.25 4989.25 36.25 4989.25 36.3 4997 40 4997 Manning's n Values num= 3 Sta n Val Sta n Val Sta n Val 0 .04 24.25 .04 36.25 .04 Bank Sta: Left Right Coeff Contr. Expan. 24.25 36.25 .1 .3 Upstream Embankment side slope = 0 horiz. to 1.0 vertical Downstream Embankment side slope = 0 horiz. to 1.0 vertical Maximum allowable submergence for weir flow = .98 Elevation at which weir flow begins = 4994 Energy head used in spillway design = Spillway height used in design = Weir crest shape = Broad Crested Number of Culverts = 1 Culvert Name Shape Rise Span Culvert #1 Box 1.5 6 FHWA Chart # 8 - flared wingwalls FHWA Scale # 1 - Wingwall flared 30 to 75 deg. Solution Criteria = Highest U.S. EG Culvert Upstrm Dist Length Top n Bottom n Depth Blocked Entrance Loss Coef Exit Loss Coef 1 100 .016 .016 0 .5 1 Number of Barrels = 2 Upstream Elevation = 4989.5 Centerline Stations Sta. Sta. 20.25 26.25 Downstream Elevation = 4989.25 Centerline Stations Sta. Sta. 27.25 33.25 CULVERT OUTPUT Profile #PF 1 Culv Group: Culvert #1 Q Culv Group (cfs) 92.90 Culv Full Len (ft) 100.00 # Barrels 2 Culv Vel US (ft/s) 5.16 Q Barrel (cfs) 46.45 Culv Vel DS (ft/s) 5.16 E.G. US. (ft) 4993.35 Culv Inv El Up (ft) 4989.50 W.S. US. (ft) 4993.29 Culv Inv El Dn (ft) 4989.25 E.G. DS (ft) 4992.23 Culv Frctn Ls (ft) 0.61 W.S. DS (ft) 4992.12 Culv Exit Loss (ft) 0.30 Delta EG (ft) 1.12 Culv Entr Loss (ft) 0.21 Delta WS (ft) 1.17 Q Weir (cfs) E.G. IC (ft) 4991.71 Weir Sta Lft (ft) E.G. OC (ft) 4993.35 Weir Sta Rgt (ft) Culvert Control Outlet Weir Submerg Culv WS Inlet (ft) 4991.00 Weir Max Depth (ft) Culv WS Outlet (ft) 4990.75 Weir Avg Depth (ft) Culv Nml Depth (ft) Weir Flow Area (sq ft) Culv Crt Depth (ft) 1.23 Min El Weir Flow (ft) 4997.01 CROSS SECTION RIVER: Hort Ctr Channel REACH: 1 RS: 1 INPUT Description: Station Elevation Data num= 6 Sta Elev Sta Elev Sta Elev Sta Elev Sta Elev 0 4997 24.2 4997 24.25 4989.25 36.25 4989.25 36.3 4997 40 4997 Manning's n Values num= 3 Sta n Val Sta n Val Sta n Val 0 .04 24.25 .04 36.25 .04 Bank Sta: Left Right Coeff Contr. Expan. 24.25 36.25 .1 .3 CROSS SECTION OUTPUT Profile #PF 1 E.G. Elev (ft) 4992.23 Element Left OB Channel Right OB Vel Head (ft) 0.11 Wt. n-Val. 0.040 0.040 0.040 W.S. Elev (ft) 4992.12 Reach Len. (ft) Crit W.S. (ft) 4990.48 Flow Area (sq ft) 0.03 34.44 0.03 E.G. Slope (ft/ft) 0.001293 Area (sq ft) 0.03 34.44 0.03 Q Total (cfs) 92.90 Flow (cfs) 0.00 92.90 0.00 Top Width (ft) 12.04 Top Width (ft) 0.02 12.00 0.02 Vel Total (ft/s) 2.69 Avg. Vel. (ft/s) 0.06 2.70 0.06 Max Chl Dpth (ft) 2.87 Hydr. Depth (ft) 1.44 2.87 1.44 Conv. Total (cfs) 2584.0 Conv. (cfs) 0.0 2583.9 0.0 Length Wtd. (ft) Wetted Per. (ft) 2.87 12.00 2.87 Min Ch El (ft) 4989.25 Shear (lb/sq ft) 0.00 0.23 0.00 Alpha 1.00 Stream Power (lb/ft s) 0.00 0.62 0.00 Frctn Loss (ft) Cum Volume (acre-ft) C & E Loss (ft) Cum SA (acres) SUMMARY OF MANNING'S N VALUES River:Hort Ctr Channel Reach River Sta. n1 n2 n3 1 5 .04 .04 .04 1 4 .04 .04 .04 1 3 .04 .04 .04 1 2 .04 .04 .04 1 1.5 Culvert 1 1 .04 .04 .04 SUMMARY OF REACH LENGTHS River: Hort Ctr Channel Reach River Sta. Left Channel Right 1 5 122 122 122 1 4 126 126 126 1 3 186 186 186 1 2 102 102 102 1 1.5 Culvert 1 1 SUMMARY OF CONTRACTION AND EXPANSION COEFFICIENTS River: Hort Ctr Channel Reach River Sta. Contr. Expan. 1 5 .1 .3 1 4 .1 .3 1 3 .1 .3 1 2 .1 .3 1 1.5 Culvert 1 1 .1 .3 Profile Output Table - Standard Table 1 Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) 1 5 PF 1 92.90 4992.85 4994.93 4995.06 0.002876 3.24 33.74 22.50 0.40 1 4 PF 1 92.90 4992.00 4994.34 4994.58 0.005348 4.79 25.84 18.06 0.55 1 3 PF 1 92.90 4991.00 4993.33 4993.69 0.009541 6.38 20.95 15.98 0.74 1 2 PF 1 92.90 4989.50 4993.29 4990.73 4993.35 0.000514 2.05 45.52 12.05 0.19 1 1.5 Culvert 1 1 PF 1 92.90 4989.25 4992.12 4990.48 4992.23 0.001293 2.70 34.49 12.04 0.28 Profile Output Table - Standard Table 2 Reach River Sta Profile E.G. Elev W.S. Elev Vel Head Frctn Loss C & E Loss Q Left Q Channel Q Right Top Width (ft) (ft) (ft) (ft) (ft) (cfs) (cfs) (cfs) (ft) 1 5 PF 1 4995.06 4994.93 0.13 0.47 0.01 12.79 67.31 12.79 22.50 1 4 PF 1 4994.58 4994.34 0.24 0.88 0.01 24.00 44.91 24.00 18.06 1 3 PF 1 4993.69 4993.33 0.36 0.25 0.09 31.59 29.72 31.59 15.98 1 2 PF 1 4993.35 4993.29 0.06 0.00 92.90 0.00 12.05 1 1.5 Culvert 1 1 PF 1 4992.23 4992.12 0.11 0.00 92.90 0.00 12.04 ERRORS WARNINGS AND NOTES Errors Warnings and Notes for Plan : 1 River: Hort Ctr Channel Reach: 1 RS: 3 Profile: PF 1 Warning:The conveyance ratio (upstream conveyance divided by downstream conveyance) is less than 0.7 or greater than 1.4. This may indicate the need for additional cross sections. APPENDIX C.2 SIMPLIFIED HORTICULTURE CENTER OUTFALL ANALYSIS APPENDIX C.3 BNRR POND CAPACITY CONFIRMATION Nick Haws From: Aaron Cvar Sent: Thursday, June 24, 2010 1:38 PM To: Nick Haws Subject: FW: CSU Drainage Report 7/15/2010 From: Michaelsen, Jaclyn [mailto:michaelsenj@AyresAssociates.com] Sent: Wednesday, June 23, 2010 4:13 PM To: Aaron Cvar Subject: CSU Drainage Report Aaron- The MSO report is titled “Alternative Analysis for the Design of the Mason Street Outfall” May 2010. The report states the following about The Grove: CSURF Development on Centre Avenue– The Grove CSURF owns a piece of property which lies west of Centre Avenue and south of Spring Creek. This property is currently under design for development and is known as The Grove. Model results show that The Grove can release into the BNRR pond un-detained without creating a rise in the BNRR Pond. It was assumed that the development would discharge into a channel that runs along the north side of the development. The engineers for The Grove need to insure that this channel has capacity to convey the developed site flows, along with the flows currently draining to the channel to the BNRR Pond. The modeling assumed that the development is 24 acres in size and will have a percent impervious value of 90%. If these assumptions change, The Grove engineers will need to update the hydrologic modeling to again insure that there is no rise in the BNRR pond Water quality for The Grove will be provided in a water quality pond on The Grove project site. Water quality will not be provided in the proposed water quality pond within the BNRR Pond. CSURF Development on Centre Avenue – The Grove CSURF owns a piece of property which lies west of Centre Avenue and south of Spring Creek. This property is currently under design for development. The basins that will be affected with this development are Spring Creek Basins 127 and 130. The following depicts the basin characteristics: Table 0.4. The Grove Effective Conditions Basin Parameters Basin 130 discharges to conveyance element 130 and Basin 127 discharges to node 726. Both basins ultimately discharge into the BNRR Pond. Parameters Basin 127 Basin 130 Area 41.8 acres 90.3 acres Width 4,557 ft 15,000 ft Percent Impervious 25% 50% Basin Slope 1.5% 2.0% Model Spring Creek Spring Creek CSURF Development on Centre Avenue – The Grove CSURF owns a piece of property which lies west of Centre Avenue and south of Spring Creek, which is known as The Grove. This property is currently under design for development. Due to the close proximity of the property to the BNRR floodway, CSURF staff asked Ayres to determine if the development could discharge into the BNRR Pond without causing a rise in water surface elevation. The property is located in COFC Spring Creek Basin 130. Basins 831 and 832 were added to the model to represent the proposed development and Basins 127 and 130 were adjusted to remove the area. Table 3.6 summarizes the new basin characteristics and basin adjustments. It was concluded that this development can discharge into the BNRR Pond without creating a rise beyond the Effective Condition water surface of 4995.04. The new development meets City requirements; it will not cause a rise in the BNRR Pond. If any significant changes are made during final design of the development, The Grove engineers will need to adjust the modeling to ensure that there is no rise in the BNRR Pond. Table 0.7. The Grove Development Basin Parameters for Proposed Project Conditions Basin 832 drains to conveyance element 831 which drains to conveyance element 130. Basin 831 drains to conveyance element 130. Conveyance element 130 drains to the BNRR Pond. Conveyance elements 130 and 831 represent a channel just north of the Grove. The Grove development needs to ensure that the channels (conveyance elements 130 and 831) can convey the flows from the development, as well as flows currently draining to the channel, to the BNRR pond. Sorry it took so long to get to you, I completely forgot. Let me know if there is anything else you need. Thanks- Jackie Parameters Original Basin 127 Original Basin 130 Adjusted Basin 127 Adjusted Basin 130 Basin 831 Basin 832 Area 41.8 acres 90.3 acres 70.0 acres 67.5 acres 11.4 acres 13.3 acres Width 4,557 ft 15,000 ft 4,557 ft 9,800 ft 1,700 ft 1,950 ft % Impervious 25% 50% 25.0% 50.0% 90.0% 90.0% Basin Slope 1.5% 2.0% 1.5% 2.0% 0.5% 0.5% Model Spring Creek Spring Creek Spring Creek Spring Creek Spring Creek Spring Creek 7/15/2010 APPENDIX C.4 DITCH COMPANY LETTER6 M.B.y'~13-?_QJJ FRI 04:27 PM Fischer Law Offices FAX NO, 19704824729 p, 01/01 nEP ARTM.ENT OF THE ARMY CORP.S Of ENGJ.N8£RS, OwuiA DISTRtCT D£NVIi:R REGULATORY OFFICii:, 9307 SOU'!'H WADSWOl'<TH BOTJ1,EVARD JJITTLBTON, COLORADO a012B-690l May 11, 2011 Mr. John Strachan The Larimer County Canal. No. 2 Irrigation Company . PO Box 506 Fort Collins, CO 80522 RE: To Relocate 1300 feet of the Larimer County Canal No.2 for Maintenance Purposes COI"I)S File No. NWO-2011-866-DEN Reference is made to the above-mentioned project located in the SW Y4 of Section 23, T7N, R69W, Larimer County, Colorado. This project has been reviewed ill accordance with Section 404 of the Clean Water Act LInder which the U.S. Army Corps of Engineers regulates the discharge of dredged and fill material and certain excavation activities in waters of the United Slates. Waters of the U.S. includes ephemeral, intermittent and perennial streams, their surface connected wetlands and adjacent wetlands and certain lakes, ponds, drainage ditches and irrigation ditches that have a nexus to interstate commerce. This letter is to inform you that the proposed work is the type ofactivity that is included in the Section 404(0 exemption found at 33 C.F.R. Part 323.4(a) (3) construction and maintenance of farm or . stock ponds or irrigation ditches and associated structures and the maintenance of, but not the construction of drainage ditches. Although a Department of the Army permit will not be required for this activity, this does not eliminate the requirements that other applicable fed eral , state, tribal, and local permits are obtained if needed. - Ifthere arc any questions call Mr. Terry McKee at 303-979-4120 and reference Corps File No. NWO-2011-866-J)EN. Sincerely, trn frtce Cc: Sarah Fowler. EPA January I 7, 2011 Mr. Steve Olt P.O. Box 580 Fort Collins, CO 80522 Re: #16- lOB The Grove at Fort Collins PDP-Type II 1)ear Mr. Olt, The Larimer No 2 would like to comment on The Grove at Fort Collins PDP-Type II. The Company is concerned about seepage From the ditch and the impact to The Grove in the case of an APPENDIX D FLOODPLAIN INFORMATION CENTRE AVE S SHIELDS ST SHIRE CT HILL POND RD W STUART ST G I L GALA D W A Y WALLENBERG DR R A I N T R E E D R WORTHINGTON CIR R E S E A RC H BLVD WATERS EDGE ROLLAND MOORE DR BRIDGEFIELD LN EVENSTAR CT WOR T HIN G TON A VE WINTERBERRY WAY SPRING CREEK LN MIRRORMERE CIR SUNDERING DR NORTHERLAND DR FEMA Floodplains - The Grove CITY OF FORT COLLINS © GEOGRAPHIC INFORMATION SYSTEM MAP PRODUCTS These map products and all underlying data are developed for use by the City of Fort Collins for its internal purposes only, and were not designed or intended for general use by members of the public. The City makes no representation or warranty as to its accuracy, timeliness, or completeness, and in particular, its accuracy in labeling or displaying dimensions, contours, property boundaries, or placement of location of any map features thereon. THE CITY OF FORT COLLINS MAKES NO WARRANTY OF MERCHANTABILITY OR WARRANTY FOR FITNESS OF USE FOR PARTICULAR PURPOSE, EXPRESSED OR IMPLIED, WITH RESPECT TO THESE MAP PRODUCTS OR THE UNDERLYING DATA. Any users of these map products, map applications, or data, accepts same AS IS, WITH ALL FAULTS, and assumes all responsibility of the use thereof, and further covenants and agrees to hold the City harmless from and against all damage, loss, or liability arising from any use of this map # City of Fort Collins Floodplain Review Checklist 50% Development Review Submittals Instructions: Complete this checklist by marking all boxes that have been adequately completed. Put an “NA” next to any items that are not applicable to this particular submittal. Any boxes that are left blank and do not have an “NA” marked next to them are considered incomplete. Date of Review:_____________ Reviewer’s Name:____________________________ Plat Map The following required items are on the plat: 100-year floodplain boundary City FEMA Floodway boundary City FEMA The benchmark number and elevation of benchmark These items match the FIRM. (FEMA Basin) These items match the Master Plan. (City Basin) The benchmark number and elevation match with those published in the City of Fort Collins benchmark system. Site Plan The following required items are on the site plan: 100-year floodplain boundary- FEMA and City 500-year floodplain boundary (if proposed structure is a “critical facility” and a 500-year floodplain is mapped) Floodway boundary Erosion buffer zones Restriction related to use (i.e. critical facility or no residential use of lower floor if floodproofed mixed-use structure) Drainage and/or Grading Plan (or a separate Floodplain Sheet if it is too cluttered on Drainage and Grading Plan) The following required items are on the drainage and/or grading plan: 100-year floodplain boundary- FEMA and City 500-year floodplain boundary (if proposed structure is a “critical facility” and a 500-year floodplain is mapped) Floodway boundary Erosion buffer zones Cross-section locations BFE lines Regulatory Flood Protection Elevation for individual lots or groups of lots if structures are to be built in the floodplain. The floodplain and floodway boundaries are in the correct location and labeled properly. The cross-section and BFE lines are in the correct location and labeled properly. Elevations are referred to the appropriate datum: FEMA basins – list in both NGVD 29 and NAVD 88 City basins – list only in NGVD 29 Floodway regulations have been met. No fill in the floodway unless a hydraulic analysis shows “no-rise”. No manufactured homes, except in an existing park, can be placed in the floodway. No changing a nonconforming non-residential or mixed use structure to a residential structure. Landscaping meets requirements for no encroachment in the floodway without a hydraulic analysis to show “no-rise”. No storage of materials or equipment. Critical facilities regulations have been met: 100 year – No life safety, emergency response, or hazardous material critical facilities 500 year Poudre – No life safety or emergency response critical facilities Any items in the floodway that can float (Example: picnic tables, bike racks, etc.) are noted as being anchored. Erosion Buffer Zone requirements have been met: Design of any allowed development minimizes disturbance to channel bed and banks. No structures allowed. No additions to existing structures allowed. Any fencing is split-rail design and break-away, but cabled. Must be oriented parallel to general flow direction. No detention or water quality ponds. No bike or pedestrian paths or trails except as required to cross streams or waterways. Road, bicycle and pedestrian bridges must span erosion buffer zone. No fill. No outdoor storage of non-residential materials or equipment. No driveways or parking areas. No irrigated vegetation and non-native trees, grasses, or shrubs. No utilities except as necessary to cross streams or waterways. No grading or excavation except as required for permitted activities in erosion buffer zone. No construction traffic except as required for permitted activities in erosion buffer zone. Any construction in the erosion buffer zone shows that it will not impact the channel stability. Any necessary floodplain modeling has been submitted and approved. All modeling must follow the City’s floodplain modeling guidelines. Special Poudre River Regulations Poudre River Floodway Regulations have been met. No construction of new residential, non-residential or mixed-use structures. No redevelopment of residential, non-residential or mixed-use structures. No additions to residential, non-residential or mixed-use structures. No fill unless hydraulic analysis shows “no-rise”. Poudre River floodplain regulations have been met No construction of new residential or mixed-use structures No additions to residential structures No additions to mixed-use structures if there is an expansion in the residential-use area of the structure. No floatable materials on non-residential sites Information Related to Structures in the Floodplain The regulatory flood protection elevation shown on the plans is at least 2 ft above the BFE for the Poudre River and at least 18” above the BFE for new development and redevelopment, 6” above the BFE for additions, substantial improvement and accessory structures for all other floodplains. A note is on the plans that the lowest floor (including basement or crawl space) and HVAC will be required to be elevated above the regulatory flood protection elevation. Non-residential structures can be floodproofed instead of elevated to the regulatory flood protection elevation. A typical drawing detail is included for each foundation type proposed (slab-on- grade, basement, crawl space) showing the elevation of the HVAC and lowest floor elevation (which includes bottom of the basement or crawl space) relative to the BFE. If garages are not going to be elevated to the regulatory flood protection elevation, then a note is included stating the following requirements: There shall be 1 square inch of venting for every 1 square foot of enclosed area. The bottom of the venting shall not be higher than 1 foot above grade. The venting shall be on at least two sides, preferably on upstream and downstream sides. (Does not have to be divided equally). For manufactured homes, a note is included stating that all submittal requirements on separate sheet titled “Installation of a Mobile Home Located in a Floodplain: Submittal Requirements” shall be met. A note is on the plans stating that a floodplain use permit will be required for each structure and each site construction element (detention ponds, bike paths, parking lots, utilities, etc.) in the floodplain. A note is on the plans stating that a FEMA elevation or floodproofing certificate will be completed and approved before the CO is issued for any structures in the floodplain. This is required even if property is only in a City floodplain. Drainage Report The site is described as being in the floodplain. Floodplain name and if the floodplain is a FEMA or City-designated is described. Any floodway or erosion buffer zones on the site are described. The FEMA FIRM panel # and date and/or the Master Plan information is cited. A copy of the FIRM panel with the site location marked is included in the report. If a floodplain modeling report has been submitted, that report is referenced. The reason for the floodplain modeling report is described. If a FEMA CLOMR or LOMR is going to be needed, the reason for the CLOMR or LOMR is described. If a FEMA LOMR is required after construction, this is stated in the report. The location of the structures relative to the floodplain is described. If there is both a FEMA and a City floodplain on the site, the location of the structures relative to both is described. The use of the structures is described. This is to determine if the structure is residential, non-residential, or mixed-use. Also, structures in all 100- year and Poudre River 500-year floodplains cannot be used as a critical facility. (See Chapter 10 of City Code for definitions.) The report describes how the development will be in compliance with the applicable floodplain regulations (Chapter 10 of City Code). (Examples: elevation of lowest floor above regulatory flood protection elevation, floodproofing, floodway regulations, erosion buffer zone regulations, no-rise, etc.) The type of foundation construction for the structures (i.e. slab-on-grade, crawl space, basement, etc.) is discussed in the report. The type of foundation matches with the details shown on the grading plan. The report states that the lowest floor (including basement or crawl space) and HVAC will be required to be elevated above the regulatory flood protection elevation. Non- residential structures can be floodproofed instead of elevated to the regulatory flood protection elevation. If garages are not going to be elevated to the regulatory flood protection elevation, then a note is included stating the following requirements: There shall be 1 square inch of venting for every 1 square foot of enclosed area. There bottom of the venting shall not be higher than 1 foot above grade. The venting shall be on at least two sides, preferably on upstream and downstream sides. (Does not have to be divided equally). If a non-residential structure is to be floodproofed, then a note is included stating that all requirements on separate sheet titled “Floodproofing Guidelines” shall be met. (Floodproofing guidelines can be obtained at http://fcgov.com/stormwater/pdf/fp- floodproofing.pdf) For manufactured homes, a note is included stating that all submittal requirements on separate sheet titled “Installation of a Mobile Home Located in a Floodplain: Submittal Requirements” shall be met. (Mobile Home guidelines can be obtained at http://fcgov.com/stormwater/pdf/fp-mobilhome.pdf) The report states that a floodplain use permit will be required for each structure and each site construction element (detention ponds, bike paths, parking lots, utilities, etc.) in the floodplain. A note is in the report stating that a FEMA elevation or floodproofing certificate will be completed and approved before the CO is issued. In the compliance section, Chapter 10 of City Code is listed. FEMA CLOMR Approval If a FEMA CLOMR is required, the necessary modeling has been submitted and approved by the City. Additional Comments: ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Updated 11/29/2007 Terms to Note Lowest Floor Elevation – Elevation of the lowest floor of the lowest enclosed area (including bottom of basement or crawlspace). This is not the same as finished floor. The lowest floor should be distinguished from finished floor on plans and reports. Regulatory Flood Protection Elevation – For all floodplains except the Poudre River, the regulatory flood protection elevation is eighteen (18) inches above the base flood elevation. For the Poudre River floodplain, the regulatory flood protection elevation is twenty-four (24) inches above the base flood elevation. If there is both a FEMA and a City BFE, the higher BFE should be used to determine the regulatory flood protection elevation. Additional floodplain terminology is defined in Chapter 10 of City Code. NOTE: Issues specific to individual sites may arise that result in additional requirements. These will be discussed during initial meetings with the applicant. CITY OF FORT COLLINS MEMORANDUM DATE: AUGUST 2008 TO: INTERESTED PARTIES NEEDING VERTICAL CONTROL IN THE CITY OF FORT COLLINS FROM: WALLACE MUSCOTT PLS, CITY SURVEYOR RE: UPDATED CITY OF FORT COLLINS VERTICAL CONTROL The City of Fort Collins Survey Department is pleased to make available to you the expanded listing of the City of Fort Collins Vertical Control Network. Generally the vertical control monuments are a 2" aluminum cap set in a solid concrete structure. The monuments are stamped “City of Fort Collins Benchmark” along with a distinctive identifying number. The elevations are given in feet to the nearest one hundredth of a foot (0.01'). The data was obtained using a Leica NA2002 Digital Level and Digital Level Rod. The field data was gathered using Leica software. The data was then transferred into Star*Lev Least Squares Level Net Adjustment software for adjustment. As a matter of common survey practice, please remember to always check between a least two vertical control monuments. If you discover an unresolved error in the published datum, or if a vertical control monument has been destroyed or is going to be disturbed, please call the City of Fort Collins Survey Department at (970) 221-6605. PLEASE READ The City of Fort Collins has been maintaining a vertical control network for many years. There are records of old vertical control dating back to the early 1950's. The City’s vertical control has always been based upon “original” NGVD 1929 datum. In 1984 NGS re-leveled and adjusted the vertical control along the front range including Fort Collins. In Fort Collins the adjustment amounted to the new datum being 0.34' higher. Because Fort Collins had vertical control and flood mapping in place prior to 1984, we have continued to use the “original” 1929 datum for our basis of vertical control. Therefore, the City’s elevations are 0.34' lower than the published datum on the remaining NGS benchmarks in the City. We have provided City of Fort Collins elevations on the NGS benchmarks along with descriptions of their location. The descriptions are from the NGS data sheets and are used with their permission. The City of Fort Collins is not responsible for errors in the “City of Fort Collins Vertical Control Network” and makes no warranty, expressed or implied, in the accuracy thereof, and shall not be responsible for damages or injuries suffered by and party as a result of any such errors, whether such damages or injuries are direct, indirect, incidental or consequential. Quick Guide City of Fort Collins Floodplain Regulations Quick Guide 03/09 2 Table of Odds for Different Events Floodplain Facts • Property in the 100-year floodplain has a 1 percent chance in any given year of being flooded. • Over a 30-year period, there is a 26 percent chance that a property in the 100-year floodplain will be flooded. For comparison, there is only a 5 percent chance that the building will catch fire during that same 30-year period. • Some properties have an even higher risk of flooding because they are in areas where smaller, more frequent floods cause damage. Purpose of Floodplain Regulations Event Odds 1 in 100 1 in 124 1 in 500 1 in 4,000 1 in 600,000 1 in 120,526,770 3 Types of Floodplains • In Fort Collins, floodplains are designated by the City as well as by the Federal Emergency Management Agency (FEMA). • The FEMA-basin floodplains cover only the major drainages. Changes in these floodplains must be approved by FEMA (p. 5). • The City-basin floodplains further identify the flood hazard. Some of the flooding in City-basin floodplains is from irrigation ditch spills or undersized storm sewers that result in overland flooding. Changes in these floodplains can be approved by the City (p. 5). • For floodplain regulation purposes, a floodplain property is either in a FEMA-basin floodplain, a City-basin floodplain or the Poudre River floodplain. Floodplain Name Poudre River Spring Creek Dry Creek Cooper Slough Boxelder Creek Fossil Creek Old Town Canal Importation McClellands Creek Mail Creek Foothills Channel West Vine FEMA-Basin X X X X Poudre River City-Basin X X X X X X X X Floodplain Designations 4 Floodway 5 6 Summary of Floodway Development Regulations Residential Development • New residential development is not allowed. • Fill is not allowed unless the applicant can show no-rise (Floodway Modifications, p. 5). • Residential additions are not allowed. • Remodels are allowed subject to the substantial improvement requirements (p. 14-15). • Manufactured homes are allowed only in existing manufactured home parks. • Redevelopment (rebuild) of an existing structure is allowed (p. 14-15). Must meet the freeboard requirements for redevelopments (p. 10). • Detached garages and sheds are allowed if the applicant can show no-rise (p. 17 and Floodway Modifications, p. 5). Non-Residential Development • New non-residential development is allowed if the applicant can show no- rise (Floodway Modifications, p. 5). Must meet the freeboard requirements (p. 10-11). • Fill is not allowed unless the applicant can show no-rise (Floodway Modifications, p. 5). • Non-residential additions are allowed if the applicant can show no-rise (Floodway Modifications, p. 6). Must meet the freeboard requirements (p. 10-11). • Remodels are allowed subject to the substantial improvement requirements (p. 14-16). • Mobile buildings (modular offices) are allowed only in existing mobile building developments. • Redevelopment (rebuild) of an existing structure is allowed (p. 14-16). Must meet the freeboard requirements for redevelopments (p. 10-11). • Attached garages, detached garages and sheds are allowed if the applicant can show no-rise (p. 17 and Floodway Modifications, p. 5). Mixed-Use Development • New mixed-use development is not allowed. • Fill is not allowed unless the applicant can show no-rise (Floodway Modifications, p. 5). • Residential additions are not allowed to a mixed-use structure. Non-residential additions are allowed to a mixed-use structure if the applicant can show no-rise (Floodway Modifications, p. 5). Must meet the freeboard requirements (p. 10-11). 7 • Critical facilities are not allowed (p. 18). • New basements are not allowed below the freeboard level (p. 10). An existing basement in a redeveloped or substantially improved structure is not allowed to remain (p. 10 and 14-15). • Critical facilities are not allowed (p. 18). • New basements are not allowed below the freeboard level (p. 10-11). An exist- ing basement in a redeveloped or sub-stantially improved structure can remain if floodproofed (p. 10-11 and 14-16). • New outside storage of equipment or materials is not allowed unless the applicant can show no rise (Floodway Modifications, p. 5). • Critical facilities are not allowed (p. 18). • New basements are not allowed below the freeboard level (p. 10-11). An existing basement in a redeveloped or substantially improved structure is not allowed to remain if it is in residential use (p. 10 and 14-15). An existing basement in a redeveloped or substantially improved structure is allowed to remain if it is in nonresidential use and floodproofed (p. 10-11 and 14-16). • New outside storage of equipment or materials is not allowed unless the applicant can show no rise (Floodway Modifications, p. 5) Summary of Floodway Development Regulations (continued) Residential Development Non-Residential Development Mixed-Use Development 8 Summary of Floodplain Fringe Development Regulations Residential Development • New residential development is allowed. Must meet the freeboard requirements (p. 10). • Fill is allowed. • Residential additions are allowed. Must meet the freeboard requirements (p. 10). • Remodels are allowed subject to the substantial improvement requirements (p. 14-15). • Manufactured homes are allowed only to replace an existing manufactured home or fill a vacant lot in an existing manufactured home park. • Redevelopment (rebuild) of an existing structure is allowed (p. 14-15). Must meet the freeboard requirements for redevelopments (p. 10). • Attached garages, detached garages and sheds are allowed (p. 17). • Critical facilities are not allowed (p. 18). Non-Residential Development • New non-residential development is allowed. Must meet the freeboard requirements (p. 10-11). • Fill is allowed. • Non-residential additions are allowed. Must meet the freeboard requirements (p. 10-11). • Remodels are allowed subject to the substantial improvement requirements (p. 14-16). • Mobile buidlings (modular offices) are allowed only to replace an existing mobile building or fill a vacant lot in an existing mobile building development. • Redevelopment (rebuild) of an existing structure is allowed (p. 14-16). Must meet the freeboard requirements for redevelopments (p. 10-11). • Attached garages, detached garages and sheds are allowed (p. 17). • Critical facilities are not allowed (p. 18). Mixed-Use Development • New mixed-use development is allowed. Must meet the freeboard requirements (p. 10-11). • Fill is allowed. • Mixed-use additions are allowed. Must meet the freeboard requirements (p. 10-11). • Remodels are allowed subject to the substantial improvement requirements (p. 14-16). • Redevelopment (rebuild) of an existing structure is allowed (p. 14-16). Must meet the freeboard requirements for redevelopments (p. 10-11). 9 Mixed-Use Development • New basements are not allowed below the freeboard level for residential portions of mixed-use structures (p. 10). An existing basement in a redeveloped or substantially improved structure is not allowed to remain if it is in residential use (p. 10 and 14-15). New basements are allowed for non-residential portions of mixed- use structures. Must meet freeboard requirements and be floodproofed (p. 10-11). An existing basement in a redeveloped or substantially improved structure is allowed to remain if it is in non-residential use and floodproofed (p. 10-11 and 14-16). Non-Residential Development • New basements are allowed. Must meet freeboard requirements and be floodproofed (p. 10-11). An existing basement below the freeboard level in a redeveloped or substantially improved structure can remain if floodproofed (p. 10-11 and 14-16). Residential Development • New basements are not allowed below the freeboard level (p. 10). An existing basement in a redeveloped or substantially improved structure is not allowed to remain (p. 10 and 14-15). Summary of Floodplain Fringe Development Regulations (continued) 10 Freeboard Example of new development residential elevation (See p. 12-13 for detailed foundation designs) Slab on grade foundation Crawl space foundation 11 Freeboard continued Example of residential addition 12 Determination of Lowest Floor Based on Type of Foundation Lowest floor Freeboard elevation Floor slab on grade Freeboard Vents Enclosure Lowest floor elevation Unfinished area no HVAC Vents Lowest floor Freeboard elevation Basement Basement slab Freeboard Can have HVAC in enclosed area Lowest floor elevation Enclosure 13 Determination of Lowest Floor Based on Type of Foundation continued Pump f Vent b Maximum 2 feet Freeboard a Velocity < 5 ft. per sec. c No more than 4 feet to top of foundation wall Crawl space e Duct Work d 14 Vertical (Pop-top) addition All remodel work, including vertical addition, counts toward substantial improvement Vertical (Pop-top) addition Remodel work on these floors counts toward substantial improvement Remodel work, including vertical addition, does not count toward substantial improvement 15 Substantial Improvement and Redevelopment elevated 6" or 18" Example of residential substantial improvement or redevelopment 16 Store Store Store Store Basement Store Store Basement Apartments Apartments Substantial Improvement and Redevelopment continued Example of non-residential and mixed-use substantial improvements or redevelopments 17 Use flood resistant materials to 6" above flood level Example of attached structure Example of detached structure Use flood resistant materials to 18" above flood level Garages, Sheds and Accessory Structures 18 Examples of critical facilities 19 20 21 22 Required Documentation and Submittals (Note: Some items may require a registered professional engineer.) 23 Example of Flood Risk Map APPENDIX E STREET CAPACITY CALCULATIONS RESERVED FOR FUTURE USE APPENDIX F INLET AND CURB CUT CALCULATIONS RESERVED FOR FUTURE USE APPENDIX G STORM LINE AND CULVERT CALCULATIONS RESERVED FOR FUTURE USE APPENDIX H PRORATED CULVERT AND PRORATED WQ POND SIZING CALCULATIONS RESERVED FOR FUTURE USE APPENDIX I EROSION CONTROL COST ESTIMATE AND RIPRAP/EROSION CALCULATIONS RESERVED FOR FUTURE USE APPENDIX J SUPPLEMENTAL SUBSURFACE WATER INVESTIGATION (BY APPLEGATE GROUP) Water Resource Advisors for the West 1499 W. 120th Avenue, Suite 200 118 W. 6th Street, Suite 100 Denver, CO 80234 Glenwood Springs, CO 81601 303‐452‐6611 www.applegategroup.com May 26, 2011 Mr. Terence Podmore, Ph.D. 733 Gilgalad Way Fort Collins, CO 80526 Dear Dr. Podmore: At the request of Campus Crest, we have reviewed the written comments you provided to the Fort Collins City Council on April 19, 2011, regarding the proposed development on the CSURF property located to the south of your neighborhood, the Windtrail on Spring Creek. In those comments you noted the history of high water table conditions in your neighborhood and you expressed general concerns that the proposed development could interfere with groundwater flow patterns in a way that may potentially worsen this condition and thereby impact the “health and safety” of your neighborhood. Considering that you have professional expertise in land drainage, we’d like to offer you the opportunity to provide specific examples of how adding subsurface drains to the CSURF property could raise groundwater levels under your neighborhood or otherwise pose risk to health and safety. We’d be happy to meet with you, or you could document your specific concerns in writing. We offer the following site monitoring and design information for your consideration. Groundwater Drainage Concerns The installation of a subsurface drainage system is, of course, generally expected to lower the water table at the subject property relative to historic conditions. If there were an effect at adjacent neighborhoods from this drainage, the effect would be to slightly lower the water table there as well (though we expect little lowering of the water table at those distances from the drains). The subsurface drain system will have an outfall located above the 4994.9 ft, 100-yr flood level and will discharge to an existing ditch located below the wetland that separates the CSURF and Windtrail properties (it is immediately west of The Gardens on Spring Creek). This ditch appears to have perennial baseflow and ultimately drains into Spring Creek. With surface discharge points properly located, it is difficult to imagine likely scenarios in which adding subsurface drains to the CSURF property could raise the existing high water table conditions in the Windtrail neighborhood. We are aware of one contingency in which the preliminary design of the drainage system could potentially create localized areas with more groundwater: If the seasonal seepage water collected near the irrigation canal (via slotted drain pipes installed along the base of the canal embankment, similar to a “toe drain”) were routed to the drain system’s discharge outlet via the main network of slotted drain pipes, and if a clog were encountered in the section of drains in the lower portion of the property, then it is plausible that Dr. Terence Podmore May 26, 2011 Page 2 of 2 the drains would “surcharge” at the clog location. The result might be an area where the water table near the clog would be higher than before. Regardless of whether such effects could extend to adjacent neighborhoods, this concern could be resolved by routing the toe drain water to the final discharge outlet in a closed pipe instead of through the drain pipe network. A small cutoff wall, similar in concept to an anti-seep collar, could also be installed across the conveyance pipe’s backfill trench, just below the toe drain, to address similar concerns about the trench backfill channeling groundwater into new areas. Regarding concerns about widespread drain clogging, in that circumstance the water table might return to “natural” pre-existing conditions, but such failure would not make the water table any higher than the existing pre-drain conditions. Other Water Concerns Our scope is primarily limited to evaluating the subsurface drainage system to be installed to address shallow water table conditions at the property. Earth Engineering Consultants (EEC) is providing geotechnical design and Northern Engineering is providing civil design, including design for collecting and discharging stormwater runoff so as to not impact adjacent areas. We are aware that you have raised concern about canal seepage causing “piping” and consequent slope failure along the irrigation ditch embankment. Slope stability concerns are being evaluated by EEC and are not within the scope of our drainage evaluation. It is our understanding that EEC is designing a drained retaining wall to address potential slope stability issues along the canal and that a monitoring and maintenance program for the retaining wall and toe drain will be implemented. We are actively monitoring seasonal groundwater rise at the irrigation canal to provide EEC with information about existing hydraulic gradients and gradients to be expected after development. We’d be happy to discuss that monitoring program with you. Again, we’d be happy to meet with you to discuss remaining drainage concerns you may have. Sincerely, Applegate Group, Inc. Tom Hatton, P.G. Calvin D. Miller, PE Applegate Group, Inc. Miller Groundwater Engineering, LLC TH/ta cc: AG File No. 10-132 N:\10132 Grove at Ft Collins\Disciplines (Technical)\WRPM\Letter to T. Podmore-5.26.11.docx Wade and Mr. Podmore, Please see the information below provided by Sherri Langenberger, Development Review Manager, in response to Mr. Podmore's questions regarding ground water: _____ Within older areas or existing subdivision within Fort Collins, the groundwater level (or existence of it) is not an item that is reviewed or examined by any City department. A building is required to have a foundation that is designed by a licensed engineer and it is left to that engineer to appropriately design the foundation based on their evaluation of the water table. For new developments being processed under the Land Use Code Section 3.3.3(C), it states: “Any lands that are subject to high groundwater (meaning groundwater at an elevation such that basement flooding is reasonably anticipated by the City Engineer to occur) shall not be platted for building lots with basements unless adequate provisions to prevent groundwater from entering basements have been designed and approved by the City Engineer.” All language and criteria within the Larimer County Urban Area Street Standards speaks to the impact on the improvements within the right-of- way or public easements. The standards are silent on the design or impact regarding improvements proposed on private property. Per the Larimer County Urban Area Street Standards Section 5.1.1.A., “A geotechnical report is required for street and related improvements within the right-of-way, public easements, or slope easements.” If the soils report shows that groundwater is encountered or predicted to be encountered within 5 feet of the original proposed surface, a subsurface water investigation report is required. This report is required to ensure mitigation of high groundwater effects upon public improvements within the right-of-way. _____ In addition, the comments made at the Council meeting included a suggestion that there are liability issues related to this scenario. Whether the actions by a private property owner or developer have caused damage to another property, and the related legal rights and responsibilities of those involved, would require case-by-case investigation and evaluation. The parties involved would need to obtain their own private legal counsel in this regard as the City does not establish or determine matters of private liability of this nature. In addition, the City generally does not consider its role as a land use regulator to make the City responsible for damages that private developers cause to others. Regards, Wendy Bricher Executive Administrative Assistant City Manager's Office (970)221-6506 1499 West 120th Avenue, Suite 200 (303) 452-6611 • Fax: (303) 452-2759 Denver, Colorado 80234 www.applegategroup.com Water Resource Advisors for the West Memorandum Date: 4 April 2011 AG Job No.: 10-132 To: Nick Haws From: Tom Hatton Subject: Progress on Ground Water Investiation Issues are being raised regarding the subject of canal seepage from the Larimer #2 Ditch and the possible impacts this may have on the site, specifically that the excavation on the site will increase the ground water gradient and thereby increase flow from the ditch and create slope instability. We are pursuing a data collection effort to investigate the ground water response to the surface water in the ditch. To this end we are proceeding with efforts to acquire the data. The ditch will start running in May; therefore it is necessary to have monitor wells installed by the end of March to facilitate background measurements. To date we have installed three additional monitor wells, one on the north side of the ditch and one on the south side (see Figure 1, MW-A and MW-B). These wells were installed on March 29, 2011. Within the next two weeks we will install three piezometers (small diameter monitor wells) in close proximity to the ditch, shown as wells P-1, P-2, and P-3 on Figure 1. During this field effort we plan to perform the following: Collect soils samples for use in the slope stability analysis, Perform laboratory permeability tests, Perform slug tests on MW-B and MW-3, Install data loggers on the monitor wells, piezometers and the canal The objective of this ground water monitoring is to determine if the existing water table is affected by the canal and, if so, the degree of connectivity. Cross Section near MW-3 (project easting 190,970 ft) 4980 4985 4990 4995 5000 5005 5010 5015 5020 5025 5030 5035 5040 5045 5050 5055 5060 -50 -25 0 25 50 75 100 125 150 175 200 225 250 275 300 Distance from Middle of Irrigation Canal (feet) Elevation (ft) Proposed Grade Existing Grade Bedrock (estimated) Proposed Drains MW-3 MW-4 DRAFT MW-3 MW-4 MW-A MW-B P-1 P-2 P-3 "Connected" Water Table "Disconnected" WT (vertical exaggeration 5:2) Figure 1. Conceptual cross-section and proposed monitoring locations near MW-3. Prepared for: Campus Crest Development, LLC Supplemental Subsurface Water Investigation The Grove at Fort Collins Larimer County, Colorado The Grove at Fort Collins Prepared by: Water Resource Advisors for the West 1499 W. 120th Ave., Suite 200 Denver, CO 80234 Phone: 303-452-6611 Fax: 303-452-2759 www.applegategroup.com December 8, 2010 AG File No. 10-132 TABLE OF CONTENTS Introduction .................................................................................................................................................. 1 Site Investigation ........................................................................................................................................... 1 Ground Water Model .................................................................................................................................... 2 Water Rights and Wells ................................................................................................................................. 2 Underdrain Design ........................................................................................................................................ 3 Water Quality ................................................................................................................................................ 4 FIGURES Figure 1 ....................................................................................................................................... Vicinity Map Figure 2 ......................................................................................................... Monitoring Well Location Map Figure 3 ................................................................................................................... Ground Water Flow Map Figure 4 .................................................................................................... Pre-development Depth to Water Figure 5 ...................................................................................... Depth to Water with Grading and No Drain Figure 6 ........................................................................................... Depth to Water with Grading and Drain Figure 7 ...............................................................................................................................Cone of Influence APPENDICES Appendix A ................................................................ Subsurface Report From Monitoring Well Installation Appendix B ............................................................................. Subdrain Design and Suggested Cross Section Appendix C ...................................................................................... Description Of Ground Water Modeling Appendix D……………………………………………………………………………………………………….Water Quality Lab Results The Grove at Ft. Collins, Subsurface Investigation Report | Introduction 1 INTRODUCTION The Grove at Fort Collins is a proposed multi-family project located west of Centre Avenue between West Prospect Rd. and West Drake Rd., see Figure 1. The project area is bordered by Centre Avenue to the east, Larimer #2 Ditch to the south, Windtrail P.U.D. outfall swale to the North and an existing residential development to the west. The site drains from the southwest to the northeast and has historically been used for agricultural purposes. There is also an existing wetland which has been identified along the northern property boundary. The site encompasses approximately 31 acres and the project is proposed as residential student housing. Earth Engineering Company, Inc. (EEC) conducted a geotechnical investigation of the site in 2009. This investigation included 13 test hole borings. Their report of July 10, 2009 describes the subsurface and ground water conditions at the site. The borings encountered sandy lean clay soils and sand and gravel underlain by claystone bedrock. This report is intended to supplement the EEC report, specifically as applying to the ground water conditions. Applegate Group was retained by Campus Crest Development, LLC to design an underdrain system to lower the ground water in accordance with Section 5.6 of the Larimer County Urban Street Standards, Subsurface Water Investigation. This included drilling of 12 monitor wells, preparation of a ground water flow model, determination of the impact to the water table, design flows from the underdrain system, engineering details and recommended maintenance requirements. SITE INVESTIGATION During the drilling conducted by EEC in 2009, ground water was encountered in 10 of the 13 borings, ranging in depth from 2 to 12 feet below surface on May 11, 2009. On July 1, 2009, approximately 6 weeks following the drilling the water levels in all the borings ranged from 0 (surface) to 5.5 feet below surface. EEC and Applegate constructed 12 monitor wells on August 27, 2010. The locations of the wells are shown on Figure 2. The purpose of these monitor wells is to determine the present, and where feasible, the future water levels. Soils samples were collected and are presently being analyzed. Previous water levels were taken by EEC in May and July of 2009. The water levels taken on August 30, 2010, although at different locations than the previous borings, show depth to water varying from 2 to 14 feet below surface. This is similar to the May 2009 water levels, indicating that the ground water in the area rises during the period the ditch is flowing. The water levels are influenced by seasonal precipitation and the water flow in the Larimer #2 Ditch. Interviews with ditch company personnel indicate that the ditch comes on mid-May and off by mid-July. The water levels taken on July 10, 2009 reflect a rise from the previous levels taken in May, 2009. This would indicate that water levels are The Grove at Ft. Collins, Subsurface Investigation Report | Ground Water Model 2 generally highest during the period that the ditch is running. The ditch flow influences the ground water table under the site for approximately two to three months a year. Inflow from the drainage to the west is also a factor. Ground water flow is to the northeast as shown on Figure 3. Subsurface samples were logged during the monitor well installation. The logs are contained in Appendix A. The subsurface characteristics show that the predominant soil type is sandy lean clay. All but wells 11 and 12 contain sand and gravel ranging from clay with gravel to gravel lenses of 4-5 feet in thickness. These gravels are the predominant water bearing strata. GROUND WATER MODEL The site data was used to develop a ground water flow model (MODFLOW). This model is used to determine the effectiveness of the underdrain to maintain ground water levels a minimum of three feet below subgrade. A detailed description of the modeling procedure is included in Appendix C. Figure 4 shows the pre-development water level surface on July 10, 2009. This surface is considered to be representative of the highest, conservative, estimate of the ground water table. Figure 5 shows the same water level after the proposed grading. Figure 6 shows the depth to the ground water after grading and with the underdrain. As shown on Figure 7 the drawdown in the wetlands is one foot or less. The model is conservative in that it does not include surface water contributions. Therefore, the drawdown will be less than this one foot estimate. WATER RIGHTS AND WELLS The site has been previously irrigated; however discussions with the ditch company representatives revealed that there are no water rights from the Larimer #2 Ditch now used on the property. We also researched the well permit file at the State Engineer’s Office for wells in the area. No well permits were found within 600 feet of the site. The nearest permitted well is located approximately 1,200 feet east of the site. This well is registered to Colorado State University with Permit No. 15871 for irrigation use. The Grove at Ft. Collins, Subsurface Investigation Report | Underdrain Design 3 UNDERDRAIN DESIGN The intent of the underdrain design is to lower the site groundwater level to meet the Larimer County Urban Area Street Standards requirement for a three foot difference between street subgrade elevations and the maximum predicted water table. In order to have a drain system which is accessible for cleanout and maintenance, 10” slotted PVC pipe will be used throughout the design. Cleanouts will be located at the upstream end of each drain and at each bend exceeding 45 degrees. Ground water calculations estimate the maximum ground water flowrate that the drain will need to intercept is 15 gallons per minute (0.033 cubic feet per second). In addition, the underdrain will be intercepting flows from proposed rain gardens located along the north and south sides of Rolland Moore Drive that will infiltrate rainwater during storm events. The flows that the underdrain can expect to during a storm event are 0.5 cfs and 1 cfs for the north and south sides of the street, respectively. The proposed 10” PVC pipe has a capacity of approximately 1.533 cfs and a normal depth of 0.49’ with the largest anticipated flow of 1.033 cfs at a minimum slope of 0.5%; this is more than sufficient to carry both the anticipated maximum groundwater flows combined with the rain garden flows. The 10” slotted PVC pipe should be bedded in ASTM C33 concrete sand with a minimum clearance of one foot of sand on all sides of the pipe and including a filter fabric layer between the existing soil and the sand. Calculations, gradations and a suggested cross section design can be found in Appendix B. Multiple underdrain main lines are proposed to be located on site. There will be one drain line located at the base of the slope on the south side of the site between the proposed buildings and the existing ditch. The other lines will be located along the curblines of the proposed Rolland Moore Drive alignment and public and private streets. The Northern Engineering final utility plan will indicate the horizontal and vertical design of the subdrain. Figure 6 of this report shows that the proposed grading and underdrain should prove sufficient to reduce peak seasonal ground water to a minimum depth of 3 feet below subgrade at the required locations. The underdrain outfall will connect into the outlet structure of the water quality pond, downstream of the orifice plate. The underdrain outfall will also have an invert elevation higher than the triple culverts draining the outlet structure. These measures will help minimize the potential for stormwater to backup into the underdrain system. While the routine rain events are unlikely to cause backwater into the underdrains, the potential does exist for flood events, effects to impact the drains running in “LOCAL PRIVATE STREET” and “LOCAL PUBLIC STREET”. Therefore, an inline backflow preventer will be installed on the underdrain outfall line just upstream of the outlet structure to ensure the roadway subgrade is not compromised. The Grove at Ft. Collins, Subsurface Investigation Report | Water Quality 4 WATER QUALITY The ground water quality was sampled in monitor Well #11 (see Figure 2). The objective was to screen for “contamination or undesirable characteristics” per Section 5.6.2. Since the range of water constituents is wide ranging, we chose to test for the EPA Primary Standards as a screen for any unusual indicators. The lab testing results, shown in Appendix D show the list of the Primary parameters. Of the 16 parameters tested, 12 were below detectable limits. Four parameters were detected as follows: TDS = 410 Fluoride = 0.594 Nitrate = 0.08 Barium = 0.125 These four parameters are well below the EPA limits, indicating that the ground water does not have any unusual characteristics that would indicate further investigation. FIGURES Printed: February 6, 2008 by JMD G:\Templates\8.5 x 11 (Profile).mxd Project Site The Grove at Fort Collins Vicinity Map Figure: Of: 1 Date: 08/07/2010 1 Job #: 10-132 Phone:KCD (303) 452-6611 Drawn By: Fax: (303) 452-2759 e-mail: info@applegategroup.com Water Resource Advisors for the West 1499 West 120th Ave., Ste 200 Denver, CO 80234-2728 www.ApplegateGroup.com 1:24,000 0 1,000 2,000 Feet O 0.5 0.5 0.5 0.5 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 4 4 4 4 4 4 5 5 6 7 8 9 10 11 12 190200 190400 190600 190800 191000 191200 191400 191600 191800 192000 192200 192400 easting (feet) 120600 120800 121000 121200 121400 121600 northing (feet) Model P11D: Area of influence of underdrains as defined by drawdown in groundwater levels (in feet) Drains Figure 7. Cone of Influence APPENDIX A: SUBSURFACE REPORT MONITORING WELL INSTALLATION APPENDIX B: SUBDRAIN DESIGN AND SUGGESTED CROSS SECTION APPENDIX C: DESCRIPTION OF GROUND WATER MODELING A Brief Description of groundwater modeling performed for The Grove A preliminary groundwater model of the property was constructed (using MODFLOW- 2000) to assess drainage requirements and evaluate drain placement. A single-layer model with variable grid elevation and variable thickness was used. The model used a 10 ft grid spacing in the north-south direction and 20 ft in the east-west direction, with the grid spacing gradually increasing outside the property boundaries out to the model’s boundaries. The model boundaries were defined by Spring Creek and wetlands to the north and the irrigation ditch to the south. The east and west model boundaries were established at a distance from the development area, at locations corresponding to likely flow lines. The bottom of the model grid was based on the depth from ground surface to the claystone “bedrock” as indicated by drilling logs from 13 exploratory soil borings and 12 monitoring well borings. (The locations and elevations of these 25 borings are approximate at this time.) Although it is possible that the shallow portion of this claystone bedrock is weathered and has significant permeability, for this preliminary model the bedrock was assumed to be impermeable. For reference (i.e., depth to water from ground surface, location of potential seeps, etc.) the model was constructed with variable top elevations closely corresponding to the existing grade (in the first model) and then corresponding to the proposed grade in the later model. No site-specific estimates are currently available for the hydraulic conductivity of the site soils (sandy clays with a gravel interval observed in most borings) or for the leakage rate of the irrigation ditch. Based on experience with groundwater systems and the lack of constraining data for site hydraulic conductivity and ditch leakage, plus based on several trial-and-error iterations of model construction and visual observation of the ditch bottom holding standing water, the ditch was represented in this preliminary model to have a constant leakage rate (instead of represented as a constant head) equal to 1.5 – 2.0 inches per day with a nominal wetted width of 10 feet. A site-wide recharge rate of 1.0 in/yr was assigned to the model, which is a common regional estimate. Hydraulic conductivity was adjusted until the modeled water levels approximated observed levels. The water level observations from July 1, 2009 (in the exploratory borings) were used instead of the August 2010 monitoring well observations since it is thought the July 1, 2009 data may represent “high water” conditions with the ditch running. A close calibration was achieved with hydraulic conductivity equal to 8 ft/day. (A lower value equal to 1.0 ft/day was used near the ditch to roughly approximate vertical flow conditions and to simulate the higher heads along the ditch.) Hydraulic conductivity equal to 8 ft/day may be high for the sandy clays observed at the site, but might represent an effective hydraulic conductivity of the sandy clays and the gravel layer observed in the site but represented with only a single model layer. This value might also reflect (indirectly) that the weathered portion of the claystone bedrock exhibits non-negligible permeability and provides a flow path. Note that a lower hydraulic conductivity might be used, but that decision in turn would require less leakage from the ditch in order to match the spatial distribution of observed water levels. The model indicated that the July 1, 2009 water levels---presumed to be high-water conditions while the irrigation ditch was running---could potentially intersect the pre- developed and pre-drained grade at certain locations. This might indicate areas that seep when the ditch is running or possibly areas with a very shallow water table that in turn have elevated evapotranspiration (ET) rates. Initial simulations were conducted allowing the water table to lie above ground surface, but this was later addressed [in part] by assigning reasonable ET rates (0.10 to 0.20 in/day) with a shallow ET extinction depth set at 2.0 ft. After the initial model construction was calibrated to match the observed water levels, the proposed ground surface grade was assigned to the model to help evaluate spatially variable depth to water. The proposed subsurface drains were simulated using MODFLOW’s “Drain Package” with the specified drainage threshold heads set at the proposed elevations of the subsurface drains. The model was then used to compute depth to water both with and without the drain in operation and to estimate the area of influence of the drain. Inflow to the proposed drain configuration was estimated at approximately 15 gpm. It should be noted that this inflow rate is sensitive to the model’s unconstrained assumptions about hydraulic conductivity and ditch leakage. It should also be noted that this was a preliminary model which is subject to refinement or revision as additional data becomes available. Still, although the model is only a rough approximation of actual conditions, such a model is a useful guide for initial expectations and possible drainage requirements. APPENDIX D: WATER QUALITY LAB RESULTS TECHNOLOGY LABORATORY, INC. CENTRE PROFESSIONAL PARK 1012 Centre Avenue Fort Collins, Colorado 80526 (970) 490-1414 CERTIFICATE OF ANALYSIS Applegate Group, Inc. 1499 West 120th Ave Denver, CO 80234 Sampled: 10/01/10 Received: 10/01/10 Laboratory ID: A2601-01 Sample ID: Well # 11 Project No.: 10-132 Matrix: Water Number Parameter Result Units Method Analyzed CAS Date Total Dissolved Solids (TDS) 410 mg/L EPA-160.1 10/01/10 7439-97-6 Dissolved Mercury < 0.0002 mg/L EPA-245.1 10/07/10 16984-48-8 Fluoride 0.594 mg/L EPA-300.1 10/01/10 84145-82-4 Nitrate-N 0.08 mg/L EPA-300.1 10/01/10 14797-65-0 Nitrite-N < 0.05 mg/L EPA-300.1 10/01/10 57-12-5 Cyanide <0.02 mg/L EPA-335.2 10/13/10 7440-36-0 Dissolved Antimony < 0.006 mg/L EPA-6010B 10/12/10 7440-38-2 Dissolved Arsenic < 0.005 mg/L EPA-6010B 10/12/10 7440-39-3 Dissolved Barium 0.125 mg/L EPA-6010B 10/12/10 7440-41-7 Dissolved Beryllium < 0.0003 mg/L EPA-6010B 10/12/10 7440-43-9 Dissolved Cadmium < 0.001 mg/L EPA-6010B 10/12/10 7440-47-3 Dissolved Chromium < 0.004 mg/L EPA-6010B 10/12/10 7440-50-8 Dissolved Copper < 0.005 mg/L EPA-6010B 10/12/10 7439-92-1 Dissolved Lead < 0.003 mg/L EPA-6010B 10/12/10 7782-49-2 Dissolved Selenium <0.005 mg/L EPA-6010B 10/12/10 7440-28-0 Dissolved Thallium < 0.0005 mg/L EPA-6010B 10/12/10 The results contained in this report Page 1 of 2 relate only to those items tested. APPENDIX K GEOTECHNICAL / SOILS INFORMATION (BY EARTH ENGINEERING COMPANY) DRILLING AND EXPLORATION DRILLING & SAMPLING SYMBOLS: SS: Split Spoon - 13/8" I.D., 2" O.D., unless otherwise noted PS: Piston Sample ST: Thin-Walled Tube - 2" O.D., unless otherwise noted WS: Wash Sample R: Ring Barrel Sampler - 2.42" I.D., 3" O.D. unless otherwise noted PA: Power Auger FT: Fish Tail Bit HA: Hand Auger RB: Rock Bit DB: Diamond Bit = 4", N, B BS: Bulk Sample AS: Auger Sample PM: Pressure Meter HS: Hollow Stem Auger WB: Wash Bore Standard "N" Penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2-inch O.D. split spoon, except where noted. WATER LEVEL MEASUREMENT SYMBOLS: WL : Water Level WS : While Sampling WCI: Wet Cave in WD : While Drilling DCI: Dry Cave in BCR: Before Casing Removal AB : After Boring ACR: After Casting Removal Water levels indicated on the boring logs are the levels measured in the borings at the time indicated. In pervious soils, the indicated levels may reflect the location of ground water. In low permeability soils, the accurate determination of ground water levels is not possible with only short term observations. DESCRIPTIVE SOIL CLASSIFICATION Soil Classification is based on the Unified Soil Classification system and the ASTM Designations D-2488. Coarse Grained Soils have move than 50% of their dry weight retained on a #200 sieve; they are described as: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are described as : clays, if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse grained soils are defined on the basis of their relative in-place density and fine grained soils on the basis of their consistency. Example: Lean clay with sand, trace gravel, stiff (CL); silty sand, trace gravel, medium dense (SM). CONSISTENCY OF FINE-GRAINED SOILS Unconfined Compressive Strength, Qu, psf Consistency < 500 Very Soft 500 - 1,000 Soft 1,001 - 2,000 Medium 2,001 - 4,000 Stiff 4,001 - 8,000 Very Stiff 8,001 - 16,000 Very Hard RELATIVE DENSITY OF COARSE-GRAINED SOILS: N-Blows/ft Relative Density 0-3 Very Loose 4-9 Loose 10-29 Medium Dense 30-49 Dense 50-80 Very Dense 80 + Extremely Dense PHYSICAL PROPERTIES OF BEDROCK DEGREE OF WEATHERING: Slight Slight decomposition of parent material on joints. May be color change. Moderate Some decomposition and color change throughout. High Rock highly decomposed, may be extremely broken. HARDNESS AND DEGREE OF CEMENTATION: THE GROVE AT FORT COLLINS FORT COLLINS, COLORADO PROJECT NO: 09-01-032 DATE: MARCH 2011 LOG OF MONITORING WELL NO. 13 RIG TYPE: CME45 SHEET 1 OF 1 WATER DEPTH FOREMAN: SM START DATE 3/29/2011 WHILE DRILLING 25' AUGER TYPE: 4" CFA FINISH DATE 3/29/2011 24 HOUR N/A SPT HAMMER: AUTO SURFACE ELEV N/A 7/1/2009 N/A SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF _ _ SANDY TO VERY SANDY LEAN CLAY (CL) 2 brown _ _ silty 4 _ _ 6 _ _ 8 _ _ 10 _ _ 12 with sand lenses _ _ 14 _ _ 16 _ _ 18 _ _ 20 SAND AND GRAVEL (SP-GP) _ _ brown 22 with a slight amount of clay _ _ 24 _ _ HIGHLY WEATHERED CLAYSTONE 26 grey/brow/rust _ _ 27' BOTTOM OF BORING 28 _ _ 30 _ _ 32 _ _ 34 _ _ 36 _ _ 38 _ _ 40 _ _ 42 _ _ 44 _ _ 46 _ _ 48 _ _ 50 THE GROVE AT FORT COLLINS FORT COLLINS, COLORADO PROJECT NO: 09-01-032 DATE: MARCH 2011 LOG OF MONITORING WELL NO. 14 RIG TYPE: CME45 SHEET 1 OF 1 WATER DEPTH FOREMAN: SM START DATE 3/29/2011 WHILE DRILLING 24' AUGER TYPE: 4" CFA FINISH DATE 3/29/2011 24 HOUR N/A SPT HAMMER: AUTO SURFACE ELEV N/A 7/1/2009 N/A SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF _ _ SANDY LEAN CLAY (CL) 2 brown _ _ 4 SAND AND GRAVEL (CL) CS _ _ 21 reddish brown, medium dense 6 SANDY LEAN CLAY (CL) _ _ brown/reddish brown 8 stiff _ _ with sand and gravel lenses CS 10 9 _ _ SAND AND GRAVEL (SP-GP) 12 reddish brown _ _ medium dense 14 CS _ _ 25 16 SANDY LEAN CLAY (CL) _ _ brown 18 medium stiff _ _ with a slight amount of gravel CS 20 6 _ _ 22 _ _ SAND AND GRAVEL (SP-GP) 24 reddish brown CS _ _ 24 medium dense 26 _ _ SANDSTONE/CLAYSTONE 28 grey/tan/rust _ _ moderately hard CS 30 50/9" 30' BOTTOM OF BORING _ _ 32 _ _ 34 _ _ 36 _ _ 38 _ _ 40 _ _ 42 _ _ 44 _ _ 46 _ _ 48 _ _ 50 THE GROVE AT FORT COLLINS FORT COLLINS, COLORADO PROJECT NO: 09-01-032 DATE: MARCH 2011 LOG OF MONITORING WELL NO. 15 RIG TYPE: CME45 SHEET 1 OF 1 WATER DEPTH FOREMAN: SM START DATE 3/29/2011 WHILE DRILLING None AUGER TYPE: 4" CFA FINISH DATE 3/29/2011 24 HOUR N/A SPT HAMMER: AUTO SURFACE ELEV N/A 7/1/2009 N/A SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF _ _ SANDY LEAN CLAY (CL) 2 reddish brown _ _ medium stiff 4 silty with gravel CS _ _ 6 6 _ _ 8 _ _ CS 10 11 _ _ 12 _ _ 14 CS _ _ 15 16 _ _ 18 _ _ CS 20 21 SANDSTONE/CLAYSTONE _ _ grey/tan/rust 22 moderately hard _ _ 24 CS _ _ 50/6" 24.5' BOTTOM OF BORING 26 _ _ 28 _ _ 30 _ _ 32 _ _ 34 _ _ 36 _ _ 38 _ _ 40 _ _ 42 _ _ 44 _ _ 46 _ _ 48 _ _ 50 THE GROVE AT FORT COLLINS FORT COLLINS, COLORADO PROJECT NO: 09-01-032 DATE: APRIL 2011 LOG OF MONITORING WELL NO. 16 RIG TYPE: LIMITED ACCESS SHEET 1 OF 1 WATER DEPTH FOREMAN: SM START DATE 4/11/2011 WHILE DRILLING None AUGER TYPE: 4" CFA FINISH DATE 4/11/2011 24 HOUR N/A SPT HAMMER: MANUAL (70 LB) SURFACE ELEV N/A 7/1/2009 N/A SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF _ _ SANDY LEAN CLAY (CL) 2 reddish brown _ _ stiff 4 silty with calcareous deposits _ _ slight amount of gravel 6 _ _ CS 8 13 _ _ 10 _ _ SAND AND GRAVEL (SP-GP) CS 12 28 reddish brown, medium dense _ _ 14 SANDY LEAN CLAY (CL) _ _ reddish brown CS 16 35 very stiff _ _ with gravel 18 _ _ stiff CS 20 27 _ _ 22 22' BOTTOM OF BORING _ _ 24 _ _ 26 _ _ 28 _ _ 30 _ _ 32 _ _ 34 _ _ 36 _ _ 38 _ _ 40 _ _ 42 _ _ 44 _ _ 46 _ _ 48 _ _ 50 THE GROVE AT FORT COLLINS FORT COLLINS, COLORADO PROJECT NO: 09-01-032 DATE: APRIL 2011 LOG OF MONITORING WELL NO. 17 RIG TYPE: LIMITED ACCESS SHEET 1 OF 1 WATER DEPTH FOREMAN: SM START DATE 4/11/2011 WHILE DRILLING None AUGER TYPE: 4" CFA FINISH DATE 4/11/2011 24 HOUR N/A SPT HAMMER: MANUAL (70 LB) SURFACE ELEV N/A 7/1/2009 N/A SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF _ _ SANDY LEAN CLAY (CL) 2 reddish brown _ _ silty 4 _ _ 6 _ _ 8 _ _ 10 _ _ 12 SAND AND GRAVEL (SP-GP) _ _ reddish brown 14 _ _ 16 _ _ 17' BOTTOM OF BORING 18 _ _ 20 _ _ 22 _ _ 24 _ _ 26 _ _ 28 _ _ 30 _ _ 32 _ _ 34 _ _ 36 _ _ 38 _ _ 40 _ _ 42 _ _ 44 _ _ 46 _ _ 48 _ _ 50 THE GROVE AT FORT COLLINS FORT COLLINS, COLORADO PROJECT NO: 09-01-032 DATE: APRIL 2011 LOG OF MONITORING WELL NO. 18 RIG TYPE: LIMITED ACCESS SHEET 1 OF 1 WATER DEPTH FOREMAN: SM START DATE 4/11/2011 WHILE DRILLING None AUGER TYPE: 4" CFA FINISH DATE 4/11/2011 24 HOUR N/A SPT HAMMER: MANUAL (70 LB) SURFACE ELEV N/A 7/1/2009 N/A SOIL DESCRIPTION D N QU MC DD A-LIMITS -200 SWELL TYPE (FEET) (BLOWS/FT) (PSF) (%) (PCF) LL PI (%) PRESSURE % @ 500 PSF _ _ SANDY LEAN CLAY (CL) 2 reddish brown _ _ silty with a slight amount of gravel 4 _ _ 6 _ _ 8 _ _ 10 _ _ SAND AND GRAVEL (SP-GP), reddish brown 12 12' BOTTOM OF BORING _ _ 14 _ _ 16 _ _ 18 _ _ 20 _ _ 22 _ _ 24 _ _ 26 _ _ 28 _ _ 30 _ _ 32 _ _ 34 _ _ 36 _ _ 38 _ _ 40 _ _ 42 _ _ 44 _ _ 46 _ _ 48 _ _ 50 APPENDIX L WETLANDS / ENVIRONMENTAL INFORMATION (BY CEDAR CREEK ASSOCIATES) April 4, 2011 Linda Ripley VF Ripley Associates 401 W. Mountain Ave., Suite 200 Fort Collins, CO 80521 RE: The Grove ESCR Update #2 Regarding the Re-location of the Larimer No. 2 Canal Linda: This letter report is submitted to address questions the City of Fort Collins has asked relating to habitat changes along the current alignment of the Larimer No. 2 Canal once the ditch owner realigns the canal to the south as planned. Realignment of the ditch to the south of its existing alignment would be the only change in project area baseline conditions since submittal of the December 9, 2010 ECSR update for The Grove project area. Based on a proposal received from the Board of Directors of the Larimer No. 2 Canal, the existing ditch alignment along the southern edge of The Grove project area would be straightened and moved to the south because of concerns regarding ditch slope stability issues with the current alignment and the proposed Grove development. The abandoned ditch segment would remain in place and under ownership of the ditch company but would no longer carry irrigation water along most of its length adjacent to the south boundary of The Grove project area. The following text provides an assessment of how habitat values would change along the abandoned ditch segment. Projected Habitat Conditions for the Abandoned Segment of the Larimer No. 2 Canal The buffer between The Grove development and the abandoned segment of the Larimer No. 2 Canal would remain the same. The south edge of the proposed Grove development would maintain an average buffer width of greater than 50 feet from the Larimer No. 2 Canal, but there would be a buffer width of less than 50 feet along a few segments of the south edge of the development. A constant 50-foot buffer would create a buffer area of 88,849 square feet (2.04 acres). With the current proposal and an average buffer width of greater than 50 feet, a buffer area of 100,068 square feet (2.30 acres) would be created. Proposed buffer areas are depicted on the Site Plan provided in the PDP submittal package. Buffer segments with less than optimal buffer widths will be mitigated and other buffer segments will be enhanced by plantings of native shrubs and trees to create additional habitat and vegetation structural diversity as well as natural visual shielding between the proposed development and the interior portions of the buffers. Native shrub and tree cover is essentially lacking in the proposed buffer areas, and plantings of native woody species would provide considerable habitat enhancement for these areas beyond their existing conditions. In addition, plantings of native woody species to enhance habitat and provide visual shielding is consistent with the performance standards described under Section 3.4.1(E)(1) of the Land Use Code and would maintain the effectiveness of the buffer areas even where the buffer distance would be less than the City buffer zone standards. Details of native species to be planted as well as the locations, configurations, and density of native shrub and tree plantings are shown on the Landscape Plan provided in the PDP submittal package. The existing outer slopes of the ditch embankments and inner slopes down to approximately 3 to 4 feet from the bottom of the ditch are vegetated primarily by relatively dense stands of smooth brome (Bromopsis inermis1 ), an upland non-native grass species. Narrow (2 to 3-foot wide), non-continuous strips of reed canarygrass (Phalaroides arundinacea) and Emory sedge (Carex emoryii) are the wetland herbaceous species supported at the average high water line along the lower portion of the inner ditch embankments. Two small pockets of coyote willow (Salix exigua) also grow at one site along this wetland 1 Scientific nomenclature for vegetation follows: Weber, W. A. and R. C. Wittmann. 2001. Colorado Flora: Eastern Slope, third edition. University Press of Colorado, Boulder, Colorado. 488 pp. L. Ripley 4/4/11 Page 2 of 2 zone. Aside from the coyote willow, the only other woody species growing along the ditch embankments are 14 large eastern cottonwoods (Populus deltoides) and one green ash (Fraxinus pennsylvanica). The bottom of the ditch and lower 2 to 3 feet of the inner ditch embankments are relatively bare of any vegetation, probably the result of water inundation during the growing season and/or mechanical clearing from ditch maintenance activities. Once irrigation water is removed from the abandoned ditch segment, it is likely that the strips of reed canarygrass and Emory sedge would slowly be lost and be replaced by stands of smooth brome that would move down the embankment slope as soil conditions dry. It would also be expected that the two pockets of coyote willow would die off as soil moisture levels drop. Smooth brome cover would likely also spread down to the base of the inner ditch embankments. It is not anticipated that annual weeds would dominate vegetation cover on inner ditch embankments since they are not currently common along the upper portions of the ditch banks, and smooth brome should spread aggressively down the lower slopes once soil moisture levels are reduced. It is somewhat uncertain what vegetation will become established along the bare ditch bottom. Soils along the ditch bottom appear to be a mix of sands and clayey soils. Smooth brome would likely spread into the clay soil areas, but sandy soils are not favorable for smooth brome establishment. Sandy areas have low moisture holding capacity and may remain relatively bare of vegetation except for few annual weeds such as cheatgrass (Anisantha tectorum). Overall however, I would not expect the majority of the currently bare ditch areas to become dominated by weedy species. I discussed the possible fate of the 14 cottonwoods and one green ash along the abandoned portion of the ditch with Tim Buchanon, City Forester. Tim indicated the fate of these trees is somewhat uncertain, but since the trees have become established along the ditch and have adapted to increased soil moisture conditions from ditch seepage, it is likely they will slowly decline and may die off completely in 10 to 20 years. Most of these trees are near the end of their maximum lifetime and loss of a water source to their roots could speed up their expected decline. There is some potential that seepage from the new ditch alignment could be a sufficient water supply replacement to maintain the current vigor of some of the existing trees, but this is uncertain as well. Wildlife use of the abandoned ditch segment as movement corridor is not likely to change and may be improved without water flow. Mitigation plantings proposed by The Grove project for the buffer zone would increase vegetation diversity and cover along the north side of the ditch, and herbaceous vegetation cover would increase within the ditch once water flow is stopped. Lack of water flows in spring and summer would also improve the travel corridor for terrestrial species. As the mature trees age and die off, overall songbird diversity and use of the corridor may decline until trees planted in the buffer zone mature in stature. Linda, this concludes my second update for the ECSR for the Grove Project. Please let me know if you have any questions or require further assistance. Sincerely, INC. T. Michael Phelan Principal and Senior Wildlife Biologist November 30, 2010 Linda Ripley VF Ripley Associates 401 W. Mountain Ave., Suite 200 Fort Collins, CO 80521 RE: ESCR Update for The Grove 11/29/10 Concept Plan Linda: This letter report is submitted to address the recent changes in The Grove Concept Plan regarding environmental impacts and mitigation required by Section 3.4.1 of the City of Fort Collins Land Use Code. Baseline conditions of the project area have not changed since the submittal of the May 6, 2010 ECSR prepared for the project area. However, Section 5.0 of the May 6, 2010 ECSR needs to be revised based on the new Concept Plan. The following text provides an up-to-date assessment of project impacts and required mitigation based on the 11/29/10 Concept Plan for The Grove and should be used to replace Section 5.0 of the May 6, 2010 ECSR. 5.0 WILDLIFE AND NATURAL AREAS MITIGATION 5.1 Project Background and Impacts Development planning for the project area had a number of physical and infrastructure constraints to accommodate, and the current site plan has evolved over a period of several months involving interaction between the Project Applicant, Design Team, CSURF, City of Fort Collins (City) staff from various departments, and surrounding neighbors. A summary of the evolution of the site plan development process is attached to the Ripley Design, Inc. Planning Objectives letter provided with the PDP submittal. Development considerations and constraints affecting site plan design included, but are not limited to, the non-standard shape of the development parcel, the presence of wetlands on the north and Larimer Canal No. 2 to the south, the extension of Rolland Moore Drive to connect between Centre Avenue and Shields Street, FEMA floodway mapping, and project design objectives. The current site plan has attempted to minimize impacts to natural areas (wetlands in particular) and meet City natural area buffer standards, to the extent possible, given the identified development constraints. The following sections summarize natural areas impacts associated with the proposed Grove Project and mitigation measures developed by the design team and Cedar Creek Associates, Inc. to minimize impacts and enhance natural areas buffers to compensate for unavoidable adverse effects to natural areas. General mitigation recommendations provided in this section are based on existing habitat conditions and current City of Fort Collins guidelines provided in Section 3.4.1 of the Land Use Code Buffer Standards. As indicated in Section 4.0, the only special habitat features present are wetlands along the north property edge and mature eastern cottonwoods along the Larimer No. 2 Canal. Both the Larimer No. 2 Canal and the wetland drainage represent potential movement corridors for urban-adapted wildlife species. The City buffer zone standard for wildlife movement corridors is 50 feet, which would apply to the Larimer No. 2 Canal and the wetland drainage. This setback from the Larimer No. 2 Canal would also protect most of the mature eastern cottonwood trees growing along the canal. Because large cottonwood trees provide potential raptor nesting habitat, these trees should be surveyed again prior to any construction activities during the breeding, nesting, and nestling rearing periods to L. Ripley 11/30/10 Page 2 of 4 confirm the presence or absence of raptor nesting activity. If an active raptor nest is discovered, a buffer zone setback, as prescribed in Section 3.4.1 of the Fort Collins Land Use Code, should be maintained during the breeding, nesting, and nestling rearing period. The City buffer zone standard for wetlands, greater than 0.3 acre without significant waterfowl use, is 100 feet. This would apply to the wetlands along the northern property edge. A 100-foot setback along the north edge wetlands would also protect the potential wildlife movement corridor along this drainage. These buffer zone standards can be modified by the decision maker as long as overall project design meets the performance standards described under Section 3.4.1(E)(1) of the Land Use Code. Generally, a buffer standard less than 80 percent of the minimum distance specified under Section 3.4.1 (E) of the Land Use Code would require project review though Planning and Zoning Board Review as defined under Section 2.1.1 of the Land Use Code. Based on the current site plan, a 100-foot setback will not be maintained along some portions of the wetland drainage, and there would be an encroachment of a total of less than 0.1 acre of development into two wetland areas associated with the north drainage. The remainder of the north edge of the proposed development would maintain an overall average buffer width slightly less than 100 feet overall because of project design constraints. A 100-foot buffer would have created a buffer area of 5.22 acres. With the slightly reduced buffer, a buffer area of 5.02 acres would be created. The south edge of the site would maintain an average buffer width of greater than 50 feet from the Larimer No. 2 Canal, but there would be a buffer width of less than 50 feet along a few segments of the south edge of the development. A constant 50-foot buffer would have created a buffer area of 2.07 acres. With the current proposal and an average buffer width of greater than 50 feet, a buffer area of 2.29 acres would be created. Proposed buffer areas are depicted on PDP submittal Sheet S-2. Buffer segments with less than optimal buffer widths will be mitigated and other buffer segments will be enhanced by plantings of native shrubs and trees to create additional habitat and vegetation structural diversity as well as natural visual shielding between the proposed development and the interior portions of the buffers. Native shrub and tree cover is essentially lacking in the proposed buffer areas, and plantings of native woody species would provide considerable habitat enhancement for these areas beyond their existing conditions. In addition, plantings of native woody species to enhance habitat and provide visual shielding is consistent with the performance standards described under Section 3.4.1(E)(1) of the Land Use Code and would maintain the effectiveness of the buffer areas even where the buffer distance would be less than the City buffer zone standards. Details of native species to be planted as well as the locations, configurations, and density of native shrub and tree plantings are shown on the landscape site plan sheet (L-1) provided in the PDP submittal package. Trees Two mature cottonwood trees would be lost to development at the proposed intersection of realigned Rolland Moore Drive and Centre Avenue. One of these trees was determined to be hazardous and one was determined to be cotton bearing by the City Forester, and the City will not require mitigation for these two native trees. Additionally, two boxelder trees growing along the Larimer No. 2 Canal, determined to be hazardous by the City Forester, will be removed by development and not replaced with mitigation trees. Russian olive trees, classified as nuisance trees in the northern buffer zone, will also be removed without mitigation. The City will require mitigation tree planting for only one tree, a small mulberry (Morus sp.) that would be lost to development. Wetland Mitigation Development of the current site plan would result in the loss of less than 0.1 acre of wetland through the direct placement of fill. This is a significant reduction from the 0.49 acre of wetland impact that would have occurred with the former Concept Plan for The Grove. The areas of wetlands to be impacted are the lowest quality and least diverse wetland community, in terms of vegetation structural and species diversity, in comparison to the main body of wetlands along the northern property boundary. Wetlands to be impacted are characterized by a dense grass/forb community dominated primarily by reed canarygrass L. Ripley 11/30/10 Page 3 of 4 intermixed with lesser amounts of Baltic rush and Nebraska sedge. Reed canarygrass is considered and exotic and invasive wetland species. Any disturbance requiring the placement of fill in over 0.1 acre of jurisdictional wetlands in the project area will require 404 permit coordination with the U.S. Army Corps of Engineers. Since wetland impacts would be less than 0.1 acre, wetland disturbance would be covered under the U.S. Army Corps of Engineers’ existing Nationwide Permit, and the U.S. Army Corps of Engineers would not require any wetland mitigation for the project. Wetland mapping completed for project area by Cedar Creek Associates, Inc. (Cedar Creek) has been previously approved by the U.S. Army Corps of Engineers. Once the Concept Plan is finalized, Cedar Creek will submit a brief report to the U.S. Army Corps of Engineers confirming that wetland impacts would be less than 0.1 acre. The City will require mitigation for wetland loss, and Cedar Creek will prepare a formal wetland mitigation plan that will provide mitigation, management, monitoring, and site maintenance specifications to address the City’s requirements for mitigation of project development wetland losses. It is assumed the City will require wetland mitigation in a 1 for 1 replacement ratio of wetland area constructed to wetland area impacted. The site for the compensatory wetland will be selected based on the potential for adequate hydrologic support. Given the wetland mitigation area will be in an upland area immediately adjacent to the existing wetlands, it is believed that existing groundwater levels will serve as a sub-irrigation support source. This assumption is based on groundwater levels measured in observation wells (B-2, B-3 and B-4) in 2009 as a part of the drilling/monitoring activities conducted on site. These levels range from 2.0 to 3.0 feet 24 hours following drilling to 0.5 to 3.0 feet during July and November 2009. Further, a clay stone layer is present at a depth from 7.0 to 8.0 feet in wells B-3 and B-4, indicting a potential for perching groundwater inputs in the upper soil profile at the selected wetland mitigation site. In addition, this site could take advantage of any flood flows emanating from the unnamed drainage, should flooding occur. Surface drainage flows from the development will also be directed, in part, to the mitigation site and will provide an additional source of hydrologic support. Lastly, incident precipitation will also add, to a limited degree, to the hydrologic input to the mitigation site. Soil material will be excavated down to the depth necessary to access groundwater during the growing season at the proposed mitigation site. The exact excavation depth has yet to be determined. The site will then be over excavated by approximately 1.0 foot. Soils salvaged from the wetlands to be impacted will be spread over the mitigation site to a depth of approximately 1.0 foot bringing the finished grade to a design elevation reflecting a saturated, but not flooded, soil moisture regime. Soil samples will then be taken to determine the chemical and fertility status of the applied wetland soil and the sub-grade material underlying the applied wetland soils. Following the receipt of laboratory data, fertilizer will be added as per laboratory recommendations. The seedbed will then be prepared and the mitigation site seeded with a wetland seed mixture. If appropriate given soil chemistry constraints, willow cuttings will be planted around the compensatory mitigation site to enhance the wildlife habitat value of the mitigation feature. Given the overall mitigation approach, the form, values, and function of the impacted wetlands are anticipated to be re-established to higher quality levels than those currently supported at the wetland impact areas. Red Fox Dens Project development would result in the loss of all the fox burrows in and near the project area except for the one burrow complex closest to the Larimer No. 2 Canal (see Figure 2). Field surveys and observations by adjacent neighbors indicate fairly consistent fox use of the project area for hunting, breeding, and rearing of young. In order to avoid the potential loss of fox young from site development, it is recommended that construction in the project area occur outside of the parturition and early rearing period (March through May) unless surveys can demonstrate a lack of den occupation during the breeding season. Young are typically born in March through early April and remain in the den their first month of life1 . Once the young begin to venture out of the den, they are often moved to alternative den 1 Fitzgerald, J.P., C.A. Meaney, D.A. Armstrong. 1994. Mammals of Colorado. Denver Museum of Natural History and University Press of Colorado, Niwot, Colorado. 467 pp L. Ripley 11/30/10 Page 4 of 4 sites by the adults, and nearby construction after this period is less likely to compromise their successful rearing. If the site is developed it is uncertain if red fox will continue to use the general area for hunting, breeding, and parturition. However, given the adaptability of red fox in urban areas, the maintenance of natural buffer zones along the wetland drainage and Larimer Canal No. 2, and the preservation of what appears to be the primary natal den adjacent to Larimer Canal No. 2, red fox may well continue to reside in the area, especially as long as the land between Larimer Canal No. 2 and the New Mercer Ditch remains undeveloped. Although continued fox use of the project area will provide wildlife viewing opportunities for existing residents and future residents of the Grove development, fox use of this area is not ideal from a wildlife management perspective and a fox health standpoint. Fox presence in what will become a more highly developed area increases the risk for vehicle/fox collisions as well as fox/human/human pet conflicts. In addition, foxes raised in this type of urban setting may become habituated to foraging in trash containers or relying on human handouts. Wild foxes can also be carriers for rabies and distemper, which may be passed on to unvaccinated pets. Because of this, the Colorado Division of Wildlife (CDOW) typically recommends that fox use of den sites in urban areas be discouraged during the non-breeding season to reduce potential conflicts with foxes and humans. The other advantage of discouraging fox use of den burrows during the non-breeding season is, that if efforts are successful, there would be no need to preclude construction activities at or near the burrow sites during the parturition and early rearing period (March through May). Based on informal conversations with the CDOW, it is recommended that the existing fox burrows be permanently closed and plugged with non-excavatable material during the fall/early winter period to discourage their use of the project area. Linda, this concludes my revisions for the ECSR for the Grove Project. Please let me know if you have any questions or require further assistance. Sincerely, INC. T. Michael Phelan Principal and Senior Wildlife Biologist Date/Moni- toring Site Depth to Groundwater (in.) Percent Vegetation Cover April 1 Well 4 79.0 90+ Well 8 56.0 90+ Well 9 56.0 90+ Well 10 62.0 70+ Well 11 45.5 95+ Well 12 53.5 100 VC-1 NA 80-85 VC-2 NA 90+ April 15 Well 4 79.0 NR Well 8 51.0 NR Well 9 48.5 NR Well 10 49.0 NR Well 11 36.5 NR Well 12 48.0 NR April 30 Well 4 78.5 90+ Well 8 52.0 90+ Well 9 47.0 90+ Well 10 49.0 75 Well 11 37.5 95+ Well 12 49.5 100 VC-1 NA 90 VC-2 NA 90+ May 14 Well 4 71.0 NR Well 8 48.0 NR Well 9 41.5 NR Well 10 41.5 NR Well 11 31.5 NR Well 12 44.0 NR May 30 Well 4 30.0 90+ Well 8 27.0 90+ Well 9 31.5 90+ Well 10 28.5 85 Well 11 17.0 95 Well 12 34.5 100 VC-1 NA 95 VC-2 NA 90 Tyla (98), Phar (2) Phar (80), Brin (10) Tyoa (10), Phar( 80) Tyla remains decumbent in plot Heavy to light rains last two weeks. Too early in some cases to ID grass species. Irrigation ditch running at near OHWM level. Juba, Juncus sp.,Carex, Pha Scpu (50), + mixed herb. Scpu (50), + mixed herb. Tyla (40), Brin et al. (45) THE GROVE AT FORT COLLINS PROJECT – CAMPUS CREST DEVELOPMENT, LLC UNDISTURBED WETLAND MONITORING PROGRAM January 11, 2011 Revised: January 12, 2011, January 19, 2011 Wetlands occurring along the drainage (Windtrail P.U.D. Outfall Swale) to the north of the mitigation area will be monitored to assess the effects, if any, resulting from proposed project development. Monitoring will occur on a semi-monthly basis during the growing season beginning on or about April 1 and ending on or about October 1 for a total of 12 yearly monitoring visits. Monitoring will begin on or about April 1, and terminate on or about October 1, 2011 to collect up to one year of baseline data prior to construction. Monitoring will then occur for a three- year period following the completion of construction of the groundwater diversion pipeline. Should construction of the pipeline terminate between April 1 and October 1, 2011, the post- construction three-year monitoring period will begin at the time of termination and end at a time to be negotiated with the City. During each monitoring visit, the depth to ground water will be measured in Applegate well numbers 4, 8, 9, 10, 11, and 12. (These wells are the most recently installed, immediately south of the southern border of the existing wetlands.) Ocular estimates of vegetation cover and composition (dominant species) in the existing undisturbed wetlands will be made once a month at seven to eight sites employing a plot size of 10 feet x 10 feet. Six of the sites will correspond to, and be offset into the wetlands from, the wells listed above. The remaining plot(s) will be located to the west of well #4. In addition, a photo will be taken of each plot once a month at the time of the vegetation analysis. The plots will be permanently marked in the field with metal fence posts, metal stakes, or similar to facilitate repeatable evaluations. The locations of the plots will be reviewed and approved by the City’s Environmental Planner prior to initiating the field sampling. Any of the wells noted above that are eliminated due to site grading will be reinstalled in an offset manner to the north to retain the ability to monitor the existing undisturbed wetlands. The results of each individual monitoring visit will be sent electronically to the City following the field evaluation. Results to be reported include the depths to groundwater in each monitoring well and a summary of the results of the vegetation cover and composition evaluation. A final monitoring report will be submitted to the City on or before December 31 of each monitoring year. The report will include a summary of the monitoring methodology, annual results in table format, a photo log, and a comparison with previous year’s monitoring data. Any negative impacts to the existing wetland vegetation community will be noted. Negative impacts would include changes in the existing hydrologic regime / wetland vegetation community leading to changes in vegetation density and plant community diversity that would signal a reduction in the size, functions and values of these wetlands. When assessing potential negative (or positive) impacts, the local affects of climate, precipitation, and land use will also be considered. Of particular note will be flows in the Larimer #2 Canal located above the proposed development. Negative impacts to the hydrologic regime/vegetation community composition, should such be determined to be permanent by an evaluation of the data, will be resolved by supplementing the existing wetlands with additional water. The groundwater diversion pipeline is engineered such that groundwater that it carries can be diverted to any portion of the wetland that experiences a negative impact. Campus Crest Development, LLC will secure a surety bond or set up an escrow account to ensure that the monitoring program will proceed to conclusion assuming a maximum total of four years of monitoring. MAP POCKET DR1 – PRELIMINARY DRAINAGE EXHIBIT FLOOD – FLOODPLAIN EXHIBIT S C GAS EL VAULT D D TELE EL VAULT D EL VAULT S S S GAS GAS S F E S F E S F E S F E S F E S F E S C EL EL VAULT S S S D EL VAULT EL VAULT EL VAULT CON IRR CON IRR CON IRR CON IRR CON IRR F E S F E S F E S F E S F E S F E S CON IRR S EL VAULT EL VAULT CON IRR CON IRR CON IRR S S UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD S C GAS S EL VAULT D D TELE EL VAULT D EL VAULT S S S GAS GAS S F E S F E S F E S F E S F E S F E S C EL MH MH EL VAULT MH MH S S S D MH EL VAULT EL VAULT EL VAULT CON IRR CON IRR CON IRR CON IRR CON IRR F E S F E S F E S F E S F E S F E S CON IRR S EL VAULT EL VAULT CON IRR CON IRR CON IRR S S F E S ST UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD GM EM EM GM GM GM GM GM EM EM EM EM GM EM GM EM GM EM GM EM EM GM GM EM STORM DRAIN ROLLAND MOORE DRIVE ROLLAND MOORE DRIVE ROLLAND MOORE DRIVE CENTRE AVENUE \A1;(3) STORM CULVERT EXISTING LARIMER CANAL NO.2 \pxq \pxq \pxqc;WINDTR \pxqc \pxqc;SU \pxqc;C \pxqc;CEN NORTHERLAND DRIVE SHADOWMERE COURT HILLPOND ROAD SHIRE COURT WINTERBERRY WAY SHIRE COURT CHETWOOD COURT GILGALAD WAY GILGALAD WAY \pxqc;T \pxqc;CSU WATER QUALITY POND 19906 19776 20028 20554 21070 21198 21468 21791 22164 FLOWS TO SPRING CREEK AND BNRR POND REFER TO TABLE FOR INFORMATION {\C98;50 4998 {\C98;50 5000 {\C98;50 5001 {\C98;50 5002 {\C 5005 {\C 5006 {\C98;5 5007 {\C98;5 5008 {\C98;50 5009 {\C98;50 5010 {\C98;5 5011 {\C98;50 5011 {\C9 5009 {\C 5009 {\C98;5 5008 {\C9 5010 {\C9 5011 ROLLAND MOORE DRIVE (TO BE RENAMED) PUBLIC COMMERCIAL STREET BLDG 3 BLDG 2 BLDG 1 BLDG 4 BLDG 5 BLDG 6 BLDG 7 TRACT A (CSURF) OUTLOT A BLOCK 1 LOT 1 BLOCK 3 LOT 1 BLOCK 3 OUTLOT B BLOCK 3 OUTLOT C BLOCK 3 LOT 3 BLOCK 1 LOT 2 BLOCK 1 LOT 1 BLOCK 2 BLDG 8 BLDG 9 CLUBHOUSE BLDG 12 STORM DRAIN STORM DRAIN REFER TO TABLE FOR INFORMATION PUBLIC LOCAL STREET OUTLOT A BLOCK 1 OUTLOT B BLOCK 1 BLDG 10 BLDG 11 20225 G G NORTH ( IN FEET ) 1 inch = ft. 100 0 100 Feet 100 200 300 REVIEW Date: No. Revisions: By: DESIGNED BY: DRAWN BY: SCALE: PROJ DATE:\P EXHIBIT 200 South College Avenue, Suite 100 Fort Collins, Colorado 80524 E N G I N E E R I N G N O R T H E RN PHONE: 970.221.4158 FAX: 970.221.4159 www.northernengineering.com These drawings are instruments of service provided by Northern Engineering Services, Inc. and are not to be used for any type of construction unless signed and sealed by a Professional Engineer in the employ of Northern Engineering Services, Inc. NOT FOR CONSTRUCTION FOR REVIEW ONLY 06/01/ at ft.collins co t h e FLOODPLAIN FLOODPLAIN EXHIBIT A. Reese A. Reese 1"=100' LEGEND: 5013 PROPOSED CONTOUR 93 EXISTING STORM SEWER PROPOSED STORM SEWER PROPOSED SWALE EXISTING CONTOUR PROPOSED 30" VERTICAL NOTES: PROPOSED STORM INLET PROPOSED CONCRETE CROSS PAN (TYP.) PEDESTRIAN CURB & GUTTER EXISTING WETLANDS PROPERTY BOUNDARY FOR STORMWATER REVIEW ONLY NOT FOR CONSTRUCTION \px LOWEST BASE \BASEHVACA1;18"\PMIN. \A1 MINIMUM DETAIL NTS FIELD SURVEY BY: BENCHMARKS: ORIG {\Fsimple FEMA REFERENCE: {\Fsimp FEMA CROSS-SECTION (CSL) 20554 FIRM PANEL 08069C0987F EXCERPT NTS SLAB-ON-GRADE FEMA BASE FLOOD ELEVATION (BFE) EXISTING 100-YR 5000 ELEVATION NAVD 88 {\fArial|b0 BUILDING 11 EL. NAVD 88 NGVD A 5002.81 FT 4999.81 FT B 5004.31 FT 5001.31 FT C 5011.93 FT 5008.93 FT REGU 5004.31 FT 5001.31 FT BUILDING 10 EL. NAVD 88 NGVD A 5004.31 FT 5001.31 FT B 5005.81 FT 5002.81 FT C 5012.20 FT 5009.20 FT REGU 5005.81 FT 5002.81 FT UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD UD GM EM EM GM GM GM GM GM EM EM EM EM GM EM GM EM GM EM GM EM EM GM GM EM F E S ST 1 1 \pxq \pxqc;W CEN \pxqc \pxqc;SU \pxqc;C \pxqc;CEN NORTHERLAND DRIVE SHADOWMERE COURT HILLPOND ROAD SHIRE COURT SHIRE COURT CHETWOOD COURT GILGALAD WAY \pxqc;T \pxqc;CSU \pxqc;CENT FLOWS TO SPRING CREEK AND BURLINGTON NORTHERN RAILROAD POND NEW MERCER DITCH WORTHINGTON CIRCLE ROLLAND MOORE DRIVE \A1;3 LARIMER CANAL NO.2 CENTRE AVENUE PUBLIC COMMERCIAL ST BLDG 3 BLDG 2 BLDG 1 BLDG 4 BLDG 5 BLDG 6 BLDG 7 TRACT A (CSURF) OUTLOT A LOT 1 BLOCK 3 LOT 1 BLOCK 3 OUTLOT B LOT 1 LOT 2 BLOCK 1 LOT 1 BLOCK 2 BLDG 8 BLDG 9 CLUB HOUSE BLDG 10 BLDG 11 OUTLOT B STORM LINE 3 PUBLIC LOCAL ST ROLLAND MOORE DR. (TO BE RENAMED) OUTLOT A OUTLOT A B2 6.70 ac OS3 15.42 ac OS1 1.00 ac OS2 1.74 ac OS4 0.66 ac OS5 0.23 ac A2 0.58 ac A1 0.95 ac A3 0.45 ac A4 1.34 ac B1 1.66 ac C1 0.64 ac C2 1.40 ac C3 2.06 ac C4 1.23 ac D1 0.93 ac D2 0.75 ac CH1 .05 ac CH2 0.16 ac X 3.84 ac A1 B2 B1 CH1 X A2 D2 OS3 OS2 os1 A3 C1 C2 C3 C4 A4 CH2 D1 OS6 0.29 ac OS5 OS6 OS4 WATER QUALITY POND STORM LINE 1 STORM LINE 2 \A1;STO\\A1;DRAINA A1;TR STORM LINE 4 NORTH ( IN FEET ) 1 inch = ft. 100 0 100 Feet 100 200 300 REVIEW Date: No. Revisions: By: DESIGNED BY: DRAWN BY: SCALE: PROJ DATE:\P Sheet Of 23 Sheets 200 South College Avenue, Suite 100 Fort Collins, Colorado 80524 E N G I N E E R I N G N O R T H E RN PHONE: 970.221.4158 FAX: 970.221.4159 www.northernengineering.com These drawings are instruments of service provided by Northern Engineering Services, Inc. and are not to be used for any type of construction unless signed and sealed by a Professional Engineer in the employ of Northern Engineering Services, Inc. NOT FOR CONSTRUCTION PRELIMINARY 06/01/ at ft.collins co t h e DR1 DRAINAGE EXHIBIT PRELIMINARY A. Reese A. Reese 1"=100' LEGEND: 4953 PROPOSED CONTOUR 93 PROPOSED STORM SEWER PROPOSED SWALE EXISTING CONTOUR PROPOSED CURB & GUTTER NOTES: PROPOSED INLET A DESIGN POINT FLOW ARROW DRAINAGE BASIN LABEL BASIN DESIGNATION BASIN AREA (AC) DRAINAGE BASIN BOUNDARY FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTION \pxi-3.75 SWALE SECTIONS S1:\A1;MIN. TW S2:1 1 \A1 SWALE SUMMARY TABLE SWALE ID MIN D MIN TW S1 S2 1 2 16 4 4 PROPOSED SWALE SECTION 1 1 B2 1.45 ac EXISTING WETLANDS EXISTING FEMA FLOODWAY EXISTING 100-YR FEMA DEVELOPED RUNOFF COMPUTATIONS Design Point Basin(s) Area, A (acres) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) C2 C10 C100 Intensity, i2 (in/hr) Intensity, i10 (in/hr) Intensity, i100 (in/hr) Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) A1 A1 0.95 11 11 11 0.25 0.25 0.31 2.13 3.63 7.42 0.5 0.9 2.2 A2 A2 0.58 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 1.4 2.5 5.7 A3 A3 0.45 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.3 0.5 1.4 A4 A4 1.34 5 5 5 0.66 0.66 0.82 2.85 4.87 9.95 2.5 4.3 11.0 B1 B1 1.66 10 10 9 0.74 0.74 0.92 2.26 3.86 8.03 2.8 4.7 12.3 B2 B2 6.70 10 10 10 0.57 0.57 0.71 2.26 3.86 7.88 8.6 14.7 37.5 C1 C1 0.64 5 5 5 0.82 0.82 1.00 2.85 4.87 9.95 1.5 2.6 6.4 C2 C2 1.40 5 5 5 0.66 0.66 0.83 2.85 4.87 9.95 2.6 4.5 11.5 C3 C3 2.06 5 5 5 0.75 0.75 0.94 2.85 4.87 9.95 4.4 7.5 19.2 C4 C4 1.23 5 5 5 0.74 0.74 0.93 2.85 4.87 9.95 2.6 4.5 11.4 D1 D1 0.93 5 5 5 0.79 0.79 0.99 2.85 4.87 9.95 2.1 3.6 9.2 D2 D2 0.75 5 5 5 0.78 0.78 0.98 2.85 4.87 9.95 1.7 2.9 7.4 X X 3.84 20 20 19 0.88 0.88 1.00 1.63 2.78 5.84 5.5 9.4 22.4 CH1 CH1 0.04 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.1 0.2 0.4 CH2 CH2 0.16 5 5 5 0.41 0.41 0.51 2.85 4.87 9.95 0.2 0.3 0.8 OS1 OS1 1.00 10 10 9 0.25 0.25 0.31 2.26 3.86 8.03 0.6 1.0 2.5 OS2 OS2 1.74 14 14 13 0.25 0.25 0.31 1.92 3.29 6.92 0.8 1.4 3.8 OS3 OS3 15.42 75 75 71 0.25 0.25 0.31 0.69 1.19 2.58 2.7 4.6 12.4 OS4 OS4 0.66 12 12 12 0.88 0.88 1.00 2.05 3.50 7.29 1.2 2.0 4.8 OS5 OS5 0.23 5 5 5 0.86 0.86 1.00 2.85 4.87 9.95 0.6 1.0 2.3 OS6 OS6 0.29 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.7 1.1 2.9 Date Date Date Date Da CHECKED APP BY: Date CHECKED BY: CHECKED BY: CHECKED BY: CHECKED BY: City Engineer Water & Wastewater Utility Stormwater Utility Parks & Recreation Traffic Engineer Environmental Planner City of Fort Collins, Colorado UTILITY PLAN APPROVAL CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES. CALL UTILITY NOTIFICATION CENTER OF COLORADO Know what'sbelow. Call before you dig. R FLOODPLAIN BOUNDARY Tyla (20), Brin (60) Site conditions essentially the same at each site as for April 1; plants decumbent at many sites; intermittent rain the previous week; still too early for many species ID. Vegetation evaluation and photos not required for mid- month field visit. Heavy rains earlier in week. No free H20 or saturated soils observed No free H20 or saturated soils Plants decumbent, senescent; no free H20 or saturated soils Site conditions essentially the same at each well site as for April 1 Vegetation monitoring required on the first monitoring visit each month NR NR TABLE 1: GROUNDWATER AND VEGETATION COMMUNITY MONITORING RESULTS -2011 Dominant Plant Species (% Cover) Comments Due to time of year and plant condition, it was difficult in some cases to identify plants to species level Plants decumbent, senescent; no free H20 or Mixed herbaceous saturated soils Scpu (75) Scpu (20), Mixed grasses (70 Tyla (40), Brin et al. (30) Tyla (40+), Brin (45+) Plants decumbent, senescent; no free H20 or saturated soils Plants senescent; no free H20 or saturated soils Soils saturated to surface, in part No free H20 or saturated soils NR NR NR Tyla (100) Phar (65), Brin (10) Phar (60), Tyla (10) NR (Not Required) Tyla (35+), Brin (45+) Tyla (98), Phar (2) Phar (70), Brin (10) Phar (60-65), Tyla (15) Mixed herbaceous Scpu (50) Scpu (40), Mixed species Tyla (35), Brin et al. (40) NR NR NR NR NR NR Earth Engineering Company Earth Engineering Company Earth Engineering Company Earth Engineering Company Earth Engineering Company Earth Engineering Company Limestone and Dolomite: Hard Difficult to scratch with knife. Moderately Can be scratched easily with knife. Hard Cannot be scratched with fingernail. Soft Can be scratched with fingernail. Shale, Siltstone and Claystone: Hard Can be scratched easily with knife, cannot be scratched with fingernail. Moderately Can be scratched with fingernail. Hard Soft Can be easily dented but not molded with fingers. Sandstone and Conglomerate: Well Capable of scratching a knife blade. Cemented Cemented Can be scratched with knife. Poorly Can be broken apart easily with fingers. Cemented • Attached garages, detached garages and sheds are allowed (p. 17). • Critical facilities are not allowed (p. 18). • Remodels are allowed subject to the substantial improvement requirements (p. 14-16). • Redevelopment (rebuild) of an existing structure is allowed (p. 14-16). Must meet the freeboard requirements for redevelopments (p. 10-11). • Detached garages and sheds are allowed if the applicant can show no-rise (p. 17 and Floodway Modifications, p. 5). 4 999 5001 5000 5029 5027 5024 5026 5004 5003 5002 5019 5005 5012 5016 5031 5011 5021 5013 5023 5008 5009 5014 5018 5020 5015 5010 5015 5027 5012 5012 5000 5016 5012 5014 5018 5011 5 013 5014 5005 5019 5021 5011 5013 5003 5013 5014 18198 19906 19392 19776 18809 24654 24053 22186 20390 22759 20028 20858 22577 21070 23338 20554 22354 21929 21468 21198 22375 21791 22164 S SHIELDS ST CENTRE AVE W LAKE ST W PROSPECT RD BAY RD SHEELY DR CENTER AVE S WHI TCOMB ST BIRKY PL W STUART ST JUNIPER LN HOBBIT ST BALSAM LN RESEARCH BLVD WALLENBERG DR BAY DR BENNETT RD WORTHINGTON CIR WATERS EDGE ROLLAND MOORE DR PROSPECT LN EVENSTAR CT SUMMER ST WIND TRL # 4999 5001 5000 5029 5027 5024 5026 5004 5003 5002 5019 5005 5012 5016 50 31 5011 5021 5013 5023 5008 5009 5014 5018 5020 5015 5010 5015 5027 5012 5012 5000 5016 5012 5014 5018 5011 5013 5014 5005 5019 5021 5011 5013 5003 5013 5014 18198 19906 19392 19776 18809 24654 24053 22186 20390 22759 20028 20858 22577 21070 23338 20554 22354 21929 21468 21198 22375 21791 22164 S SHIELDS ST CENTRE AVE W LAKE ST W PROSPECT RD BAY RD SHEELY DR CENTER AVE S WHITCOMB ST BIRKY PL W STUART ST JUNIPER LN HOBBIT ST BALSAM LN RESEARCH BLVD WALLENBERG DR BAY DR BENNETT RD WORTHINGTON CIR WATERS EDGE ROLLAND MOORE DR PROSPECT LN EVENSTAR CT SUMMER ST WIND TRL 0 300 600 1,200 Feet . Printed: 3/13/2009 product, in consideration of the City's having made this information available. Independent verification of all data contained herein should be obtained by any users of these products, or underlying data. The City disclaims, and shall not be held liable for any and all damage, loss, or liability, whether direct, indirect, or consequential, which arises or may arise from these map products or the use thereof by any person or entity. 0 145 290 580 870 1,160 1,450 1,740 Feet extreme event that causes a breech of the ditch. As superintendent for the Larimer No 2 Irrigating Company, I have experienced situations where drains cease to operate. This can cause property damage and is upsetting to the homeowners. Often they will direct their complaints to the [)itch Company. In my opinion, there are better solutions to this problem. For example, the ditch could he lined or relocated. I would like to further discuss this issue with you and the developer. Thank-you. Sincerely, John Moen Larimer No 2 Irrigating Company Superintendent Contact at 970-218-0726 cc Rosanna Harris ¹ · ¨ © § 40 hr April 6, 2011 Intensity, i10 (in/hr) Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 C10 Q C f C i A D:\Projects\502-001\Drainage\Hydrology\PDP\502-001_Rational-Calcs.xlsx\Direct-Runoff Basins Tc Calculated at Upstream Design Point A. Reese April 6, 2011 Time of Concentration (Equation RO-4) 3 1 1 . 87 1 . 1 * S Ti C Cf L D:\Projects\502-001\Drainage\Hydrology\PDP\502-001_Rational-Calcs.xlsx\Combined-Tc Tc (min) 10-yr Tc (min) 100-yr Tc (min) A1 A1 No 0.35 0.35 0.44 20 25.0 2.1 2.1 1.9 0 0.0 0.00 N/A 910 1.2 1.64 9.2 11 11 11 A2 A2 No 0.95 0.95 1.00 144 3.8 2.2 2.2 1.4 124 0.5 1.41 1.5 0 0.0 0.00 N/A 5 5 5 A3 A3 No 0.35 0.35 0.44 32 20.0 2.9 2.9 2.6 0 0.0 0.00 N/A 0 0.0 0.00 N/A 5 5 5 A4 A4 No 0.95 0.95 1.00 145 3.8 2.2 2.2 1.4 247 0.9 1.90 2.2 0 0.0 0.00 N/A 5 5 5 B1 B1 No 0.95 0.95 1.00 18 2.3 0.9 0.9 0.6 937 0.8 1.77 8.8 0 0.0 0.00 N/A 10 10 9 B2 B2 No 0.95 0.95 1.00 18 2.3 0.9 0.9 0.6 946 0.8 1.74 9.0 0 0.0 0.00 N/A 10 10 10 C1 C1 No 0.95 0.95 1.00 16 2.3 0.9 0.9 0.6 713 1.8 2.65 4.5 0 0.0 0.00 N/A 5 5 5 C2 C2 No 0.95 0.95 1.00 16 2.3 0.9 0.9 0.6 651 1.9 2.77 3.9 0 0.0 0.00 N/A 5 5 5 C3 C3 No 0.95 0.95 1.00 162 3.4 2.4 2.4 1.6 69 0.5 1.41 0.8 0 0.0 0.00 N/A 5 5 5 C4 C4 No 0.95 0.95 1.00 198 2.7 2.8 2.8 1.9 65 2.1 2.88 0.4 0 0.0 0.00 N/A 5 5 5 D1 D1 No 0.95 0.95 1.00 28 4.9 0.9 0.9 0.6 661 3.3 3.62 3.0 0 0.0 0.00 N/A 5 5 5 D2 D2 No 0.95 0.95 1.00 25 4.4 0.9 0.9 0.6 920 3.6 3.77 4.1 0 0.0 0.00 N/A 5 5 5 X X No 0.25 0.25 0.31 467 6.6 18.3 18.3 17.0 0 0.0 0.00 N/A 242 2.9 2.55 1.6 20 20 19 CH1 CH1 No 0.95 0.95 1.00 18 2.3 0.9 0.9 0.6 55 0.5 1.41 0.6 0 0.0 0.00 N/A 5 5 5 CH2 CH2 No 0.95 0.95 1.00 18 2.3 0.9 0.9 0.6 55 0.5 1.41 0.7 0 0.0 0.00 N/A 5 5 5 OS1 OS1 No 0.25 0.25 0.31 156 8.1 9.9 9.9 9.2 0 0.0 0.00 N/A 0 0.0 0.00 N/A 10 10 9 OS2 OS2 No 0.25 0.25 0.31 243 5.4 14.1 14.1 13.1 0 0.0 0.00 N/A 0 0.0 0.00 N/A 14 14 13 OS3 OS3 Yes 0.25 0.25 0.31 500 0.2 60.8 60.8 56.3 0 0.0 0.00 N/A 815 0.4 0.95 14.3 75 75 71 OS4 OS4 No 0.25 0.25 0.31 25 2.0 6.3 6.3 5.8 815 1.3 2.28 6.0 0 0.0 0.00 N/A 12 12 12 OS5 OS5 No 0.95 0.95 1.00 25 0.4 1.9 1.9 1.3 299 1.8 2.65 1.9 0 0.0 0.00 N/A 5 5 5 OS6 OS6 No 0.95 0.95 1.00 25 3.0 1.0 1.0 0.6 380 1.2 2.19 2.9 0 0.0 0.00 N/A 5 5 5 DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Gutter Flow Swale Flow Design Point Basin Overland Flow A. Reese April 6, 2011 Time of Concentration (Equation RO-4) 3 1 1 . 87 1 . 1 * S Ti C Cf L D:\Projects\502-001\Drainage\Hydrology\PDP\502-001_Rational-Calcs.xlsx\Tc-2-yr_&_100-yr D1 40,718 0.93 0.34 0.25 0.13 0.00 0.21 0.79 0.79 0.99 73.3 D2 32,884 0.75 0.40 0.17 0.00 0.00 0.18 0.78 0.78 0.98 73.9 X 167,347 3.84 3.46 0.00 0.00 0.00 0.39 0.88 0.88 1.00 90.0 Developed 982,013 22.54 9.01 2.56 2.37 0.00 8.60 0.68 0.68 0.85 59.7 CH1 1,849 0.04 0.02 0.01 0.00 0.00 0.01 0.80 0.80 1.00 75.1 CH2 7,125 0.16 0.03 0.01 0.00 0.00 0.13 0.41 0.41 0.51 21.9 OS1 43,398 1.00 0.00 0.00 0.00 0.00 1.00 0.25 0.25 0.31 0.0 OS2 75,899 1.74 0.00 0.00 0.00 0.00 1.74 0.25 0.25 0.31 0.0 OS3 671,617 15.42 0.00 0.00 0.00 0.00 15.42 0.25 0.25 0.31 0.0 OS4 28,715 0.66 0.46 0.13 0.00 0.00 0.07 0.88 0.88 1.00 87.5 OS5 9,951 0.23 0.15 0.05 0.00 0.00 0.03 0.86 0.86 1.00 85.4 OS6 12,693 0.29 0.17 0.06 0.00 0.00 0.06 0.80 0.80 1.00 76.9 TOTAL 851,247 19.54 0.83 0.26 0.00 0.00 18.45 0.29 0.29 0.36 5.44 DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I. 10-year Cf = 1.00 April 6, 2011 D:\Projects\502-001\Drainage\Hydrology\PDP\502-001_Rational-Calcs.xlsx\C-Values