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Home My WebLink AboutDrainage Reports - 10/06/2016AThis Drainage Report is consdousty provided as a PDF. Please consider the environment before printing this document in Its entirety. When a hard COPY is absolutety necessary, we recommend double -sided printing. eemer t t City of Fort Collins Approved Plans Approved by: Date: ' 0 B Prepared for: Maxiiimo Development Group 706 S. College Avenue, Suite 201 Fort Collins, CO 8024 Prepared by:. NORTHERN ENGINEERING 301 North Howes Street, Butte 100 Fort Collins, Colorado 80521 Phone: 970.221.4158 Fen 970.221.4159 www.northemengineedn.com Project Number: 1033-001 NorthernEnallneerina.com // 970.221.4158 I NORTHERN ENGINEERING September 21, 2016 City.of.Fort-Collins_.. - 110 Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Final Drainage Report for The Slab Dear Staff: Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report for your review. This report accompanies the Final Development Review submittal for the proposed The Slab. Comments from the Final Review Letter dated June 1, 2016 have been addressed. Written responses thereto can be found in the comprehensive response to comments letter on file with Current Planning. This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM), and serves to document the stormwater impacts associated with the proposed The Slab project. We understand that review by the City is to assure general compliance with standardized criteria contained in the FCSCM. If you should have any questions as you review this report, please feel free to contact us. Sincerely, NORTHERN ENGINEERING SERVICES, INC. Nicholas W. Haws, PE LEED Project Manager pp 9.21. G �ONAL�� JCoZSnowdon Project Engineer 11 1 E I I I 1 J J t 301 N. Howes Street, Suite 100, Fort Collins, CO 80521 1 970.221.4158 1 www.northernengineering.com i ' INORTHERN ENGINEERING The Slab TABLE OF CONTENTS ' I. GENERAL LOCATION AND DESCRIPTION................................................................... 1 A. Location.......................................................................................................................................1 B. Description of Property ......................................................................:.........................................2 1 C. Floodplain....................................................................................................................................3 II. DRAINAGE BASINS AND SUB-BASINS....................................................................... 5 ' A. Major Basin Description...............................................................................................................5 B. Sub -Basin Description..................................................................................................................5 III. DRAINAGE DESIGN CRITERIA...................................................:...............................6 A. Regulations.................................................................................................................................6 ' B. Four Step Process........................................................................................................................6 C. Development Criteria Reference and Constraints..........................:..............................................7 ' D. Hydrological Criteria....................................................................................................................8 E. Hydraulic Criteria.........................................................................................................................8 ' F. Floodplain Regulations Compliance..............................................................................................8 G. Modifications of Criteria..............................................................................................................8 ' IV. DRAINAGE FACILITY DESIGN....................................................................................9 A. General Concept..........................................................................................................................9 B. Specific Details...........................................................................................................................10 ' V. CONCLUSIONS......................................................................................................13 A. Compliance with Standards........................................................................................................13 ' B. Drainage Concept......................................................................................................................13 References....................................................................................................................... 14 APPENDICES: APPENDIX A — Hydrologic Computations ' APPENDIX B — Hydraulic Computations B.1 — Storm Sewers B.2 — Inlets B.3 — Detention Facilities ' APPENDIX C — Water Quality Design Computations APPENDIX D — Select Information from Previous Analysis APPENDIX E — NRCS Soils Report ' APPENDIX F — Conceptual Analysis of Future Drainage within Lot 2 APPENDIX G — Erosion Control Report ' final Drainage Report ■� I NORTHERN , ENGINEERING The Slab LIST OF TABLES AND FIGURES: Figure1 — Aerial Photograph................................................................................................ 2 Figure 2— Proposed Site Plan................................................................................................ 3 Figure 3 — Existing FEMA Floodplains.................................................................................... 4 ' Figure 4 — Existing City Floodplains...................................................... :................................ 4 Table 1 — Low Impact Development Summary Table................................................................ 7 ' Table 2 — Northern Pond Summary Table............................................................................. 11 Table 3 — Southern Pond Summary Table............................................................................. 12 Table 4 — Future Southern Pond Summary Table................................................................... 12 MAP POCKET: C8.00 - Drainage Exhibit Sheet 1 — Historic Drainage Exhibit (by DMW Civil Engineers) Final Drainage Report NORTHERN ENGINEERING The Slab 1 I. I 1 1 GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map 2. The Slab project is located in the southwest quarter of Section 14, Township 7 North, Range 69 West of the 6"' Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. 3. The project site is located west of South Whitcomb Street on the north side of West Prospect Road. 4. Currently the existing lot does not have any stormwater or water quality facilities. The project was previously designed and the slab of the proposed building was constructed. The entire site was overlot graded, but no other improvements were constructed. The site now consists of native vegetation. The area north of the existing slab drains towards the northeast corner of the site. The area south of the slab drains south into Prospect Road. The project is currently bordered to the north by a multi -family building, west by a single family residence, east by a single-family residence and south by Prospect Road. Final Drainage Report i NORTHERN ENGINEERING The Slab I B. Description of Property 1. The Slab is approximately 1.436 net acres. Figure 1 — Aerial Photograph 2. The Slab consists of one property, but some improvements required for this development are planned to occur within the properties to the north and east. The lot has an existing basement and first concrete floor of the previously designed multi- family building. The remaining area consists of native vegetation. The area planned to be used for an emergency access consists of native vegetation. The area planned to be used for some detention consists of a manicured front yard. 3. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Altvan- Satanta loam, which falls into Hydrologic Soil Groups B. 4. The proposed development will include the reuse of the existing structure. The proposed site plans to mimic the previously approved construction plans and concepts. The access to the site will come from Prospect Road west of the existing building leading to a parking area located north of the existing building. The project will utilize underground chambers to achieve LID requirements for the overall site. There is a proposed detention pond located at the northeast corner and another detention and water quality pond located east of the proposed site. An emergency access road is proposed to connect to W. Lake Street. A modified section is being proposed to, not only reduce flow, but supply water quality and detention. Final Drainage Report 2 ' NORTHERN ENRINEERINB 11 1 Figure 2— Proposed Site Plan ' 5. No irrigation facilities or major drainageways are within the property limits. 6. The project site is within the High Density Mixed -Use Neighborhood District (HMN) Zoning District. The proposed use is permitted within the zone district. C. Floodplain ' 1. The subject property is not located in a FEMA or City regulatory floodplain. 2. The FEMA Panel 08069CO979H illustrates the proximity of the project site to the nearest FEMA delineated regulatory floodplain. It is noted that the vertical datum utilized for site survey work is the City of Fort Collins Benchmark #28-92 ' Elevation = 5010.65 (NAVD 88) — Project Datum Elevation = 5007.48 (Fort Collins NVGD 29 — Unadjusted) Final Drainage Report .� NORTHERN ENGINEERING Il elf. ��.■I1�I _ _ \\\ II1I Figure 3 — Existing FEMA Floodplains Figure 4 — Existing City Floodplains Final Drainage Report 4 NORTHERN ENGINEERING The Slab ' II. DRAINAGE BASINS AND SUB -BASINS A. Major Basin Description ' 1. The Slab is located within the Old Town Basin, which is located primarily in Old Town Fort Collins. ' B. Sub -Basin Description 1. This property and project were previously analyzed in August, 2007 by DMW Civil Engineers. To honor the historic drainage patterns, the historic analysis from that report will be preserved throughout this analysis. Within that analysis, the site was divided into three on -site historic basins (El-3) and one off -site historic basin (E01). Basin El consisted of the northern half of the site and routed stormwater via overland ' flow to the northeast corner of the site. E2 consisted of the southern portion of the site and routed stormwater via overland flow to the southern property line. Basin E3 consisted of the area within Prospect Road public right-of-way and routed stormwater ' via gutter flow to the east. Off -Site Basin E01 consist entirely of the off -site emergency access easement and routes stormwater via overland flow north to Lake Street. A more detailed description of the projects proposed drainage patterns follows in Section IV.A.4., below. 2. There is a portion of the single family residence neighboring the project to the west that drains onto this property. The area is 0.370 acres and consists mostly of the backyard between the house and the garage, as well as a portion of both the house and garage. Drainage is routed via overland flow and sheet flows across the western boundary of the project. The proposed design will preserve this route and plans to ' pass the flow through the project. This basin has been delineated as Basin OWl and discharges 0.66 cfs and 1.2 cfs for the 2-year & 100-year event, respectively. 1 A full-size copy of the previously approved Drainage Plan by DMW Civil Engineers and the proposed Drainage Exhibit can be found in the Map Pocket at the end of this report. ' Final Drainage Report 5 NORTHERN , ENGINEERING The Slab III. DRAINAGE DESIGN CRITERIA , A. Regulations ' There are no optional provisions outside of the FCSCM proposed with The Slab project. B. Four Step Process The overall stormwater management strategy employed with The Slab project utilizes the "Four Step Process" to minimize adverse impacts of urbanization on receiving waters. The ' following is a description of how the proposed development has incorporated each step. Step 1 — Employ Runoff Reduction Practices Several techniques have been utilized with the proposed development to facilitate the ' reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the current use by implementing multiple Low -Impact Development (LID) strategies including: ' w Selecting a site that has been previously developed and currently consists of an existing building pad located in middle of the property. w Providing vegetated open areas along the south and east portion of the site to reduce , the overall impervious area and to minimize directly connected impervious areas (MDCIA). N1I Routing flows, to the extent feasible, through drain rock to increase time of concentration, promote infiltration and provide initial water quality. NB Providing underground detention area to increase time of concentration promote infiltration and provide water quality. , NB Routing runoff from the proposed roofs into either a bio-swale or underground vaults to promote infiltration, biological uptake, and evapotranspiration. Step 2 — Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow Release The efforts taken in Step 1 will facilitate the reduction of runoff; however, this ' development will still generate stormwater runoff that will require additional BMPs and water quality. Stormwater generated from the northern portion of the site will be routed into underground StormTech chambers designated as isolator rows, which are designed to provide water quality. All of the roof area draining to the north will be collected in roof ' leaders and discharged directly into the underground chambers. The area that is draining off -site to the north will be treated by use of a TrueGrid system with drain rock subsection and a 15' deep dry well. Stormwater generated from the southern portion of the site will ' be routed through either a bio-swale or into StormTech isolator rows designed to provide water quality. ' Below is a table that summarizes the Low impact Development practices being utilized within this project to not only reduce the amount of runoff generated from the site through infiltration, but also treat the runoff prior to releasing it from the site. , Final Drainage Report 6 ■V NORTHERN ENGINEERING J I Area Percent of Site Area of Run-on Area Run-on Area Design ND Area of Percent Basin ID Basin Area TreatrnentType Treated by Treated by LID Asphalt for Paver Ratio 13:1 PointSystem Pavers Pavers OD stem stem PerWn Section Max B!o-Swale nl Ni 0230 ac Yes 0.230ac 13% 0.000 ac 0.083 ac. N/A 0 N/A Off -Site StormTech n2 N2&N3 0.780 ac Yes 0.780ac 45% 0.000 ac 0.4S8 ac N/A 0 N/A Chambers sl SS 0.100 ac Extended Detention No N/A 096 0.000 ac. 0.000 ac. N/A 0 N/A s2 S2 0210 ac Blo-Swale Yes 0.210 ac 12% 0.000 ac 0.000 ac N/A 0 N/A S s3 S3 & S4 0.150 ac Yes 0.1s0 ac 9% 0.000 ac 0.048 ac N/A 0 N/A Chambers Chambers TrueGrid Infiltration on ONS 0.250 ac Yes 0.250 ac 15% 0.0D0 ac 0.0D0 ac N/A 0 N/A Section Total 1.720 at. S.fi20 ac 94% 0.000 ac 0.589 ac 0.00% Table 1— Low Impact Development Summary Table ' Step 3 — Stabilize Drainageways As stated in Section 1.B.5, above, there are no major drainageways in or near the subject site. While this step may not seem applicable to The Slab, the proposed project indirectly helps achieve stabilized drainageways nonetheless. Once again, site selection has a positive effect on stream stabilization. By repurposing an already developed, under-utilized site, combined with LID, the likelihood of bed and bank erosion is greatly reduced. ' Furthermore, this project will pay one-time stormwater development fees, as well as ongoing monthly stormwater utility fees, both of which help achieve Citywide drainageway stability. ' Step 4 — Implement Site Specific and Other Source Control Bill This step typically applies to industrial and commercial developments and is not applicable for this project. C. Development Criteria Reference and Constraints ' 1. A drainage study was prepared for this property by DMW Civil Engineers, dated August 27, 2007, but only the building foundation was constructed. That report will be utilized throughout this analysis. 2. There are no known drainage studies for any adjacent properties that will have any effect on The Slab project. ' 3. The subject property is essentially an "in -fill' development project as the property is surrounded by currently developed properties. As such, several constraints have been identified during the course of this analysis that will impact the proposed drainage ' system including: Existing elevations along the southern property line adjacent to the West Prospect Road will be maintained. Existing elevations along the north and west will also be maintained. Areas along the eastern property line will be modified through grading off -site within a drainage easement. Existing elevations and vegetation on the western and northern sides of the subject property will be preserved. As previously mentioned, overall drainage patterns of the existing site will be maintained. Final Drainage Report 7 .V NORTHERN ENGINEERING D. Hydrological Criteria 1. The City of Fort Collins Rainfall Intensity -Duration -Frequency Curves, as depicted in Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations associated with this development. Tabulated data contained in Table RA-7 has been utilized for Rational Method runoff calculations. 2. The Rational Method has been employed to compute stormwater runoff utilizing coefficients contained in Tables RO-11 and RO-12 of the FCSCM. 3. The Rational Formula -based Modified Federal Aviation Administration (FAA) procedure has been utilized for detention storage calculations. 4. Three separate design storms have been utilized to address distinct drainage scenarios. A fourth design storm has also been computed for comparison purposes. The first design storm considered is the 800' percentile rain event, which has been employed to design the project's water quality features. The second event analyzed is the "Minor," or "Initial" Storm, which has a 2-year recurrence interval. The third event considered is the "Major Storm," which has a 100-year recurrence interval. The fourth storm computed, for comparison purposes only, is the 10-year event. 5. No other assumptions or calculation methods have been used with this development that are not referenced by current City of Fort Collins criteria. E. Hydraulic Criteria 1. As previously noted, the subject property historically drains in two different directions, north to Lake Street or south to Prospect Road. The majority of the site drains stormwater via overland flow. 2. All drainage facilities proposed with The Slab project are designed in accordance with criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District's (UDFCD) Urban Storm Drainage Criteria Manual. 3. As stated in Section I.C.1, above, the subject property is not located within any regulatory floodplain. 4. The Slab project does not propose to modify any natural drainageways. F. Floodplain Regulations Compliance 1. As previously mentioned, all structures are located outside of any FEMA 100-year or City floodplain, and thus are not subject to any floodplain regulations. G. Modifications of Criteria The proposed Slab development is not requesting any modification to the standards, but will be requesting an exception to be granted by the Utilities Executive Director or his designee to Section 4.15(b). The project is proposing to use the parking area for additional detention volume with depths that exceed the 12-inch maximum. These depths will not exceed 18-inches in the parking area and the area exceeding the 12- inches of ponding will occur within less than twenty-five percent (25%) of the total parking spaces provided. Please see the full-size copy of the Proposed Drainage Exhibit within Map Pocket to see the extents of these ponding areas. A signed copy of the approved modification has been attached to this report. Final Drainage Report 8 (NORTHERN ENGINEERING C I I i 11 1 IV. DRAINAGE FACILITY DESIGN A. General Concept 1. The main objectives of The Slab drainage design are to maintain existing drainage patterns and ensure no adverse impacts to any adjacent properties. 2. The existing site does have off -site flows from the west that historically drain onto the property. The current routing of this runoff will remain as is and pass through the proposed project. 3. A list of tables and figures used within this report can be found in the Table of Contents at the front of the document. The tables and figures are located within the sections to which the content best applies. 4. The Slab project is composed of three major drainage basins, designated as Major Basins N, Major Basin S and Major Basin 0. Major Basin N is further subdivided into three (3) sub -basins, designated as Sub -Basins N1-N3. Major Basin S is further subdivided into four (4) sub -basins, designated as Sub -Basins S1-S4. Major Basin 0 is further subdivided into three (3) sub -basins, designated as Sub -Basins ON1, OW1, and OS1. The drainage patterns anticipated for Major Basins N, S and OS and associated sub -basins are further described below. Basin N Basin N consists of all of the on -site improvements being proposed north of the existing concrete building slab. The major basin was divided into three (3) sub -basins to better size the LID concepts proposed on the northern side of the property. Sub - Basin N 1 encompasses the furthest downstream reach of Major Basin N and consists of a portion of the parking area and the entire Northern Detention Pond. The runoff from this basin is routed via overland flow and discharges directly into the proposed detention pond through a curb cut located at the eastern edge of the proposed parking. Sub -Basin N2 encompasses the northern portion of the parking area and the northern half of the proposed building. Runoff from this sub -basin drains via overland flow and is intercepted by an inlet located within the parking island. The water quality event will be routed into the underground StormTech Chambers, which provide LID treatment, while all events exceeding that volume will be routed through a curb cut into Sub -Basin N1. Sub -Basin N3 encompasses the southern portion of the parking area and is composed primarily of asphalt. Runoff from this sub -basin drains via overland flow and is intercepted by an inlet located within the parking island. The water quality event will be routed into the underground StormTech Chambers, which provide LID treatment, while all events exceeding that volume will be routed through a curb cut into Sub -Basin N2. Basin S Basin S consists of all of the on -site improvements being proposed west, east, and south of the existing concrete building slab. The major basin was divided into four (4) sub -basins to better size the LID concepts proposed on the west, east and south sides of the property. Sub -Basin S1 encompasses the furthest downstream reach of Major Basin S and consists of east of the proposed building. The runoff from this basin is routed via overland flow across a grass buffer yard and discharges off -site where it is intercepted by an area inlet and discharged directly into the Southern Detention Pond. Basin S2 encompasses the southern portion of the building and the area surrounding Final Drainage Report 9 �s NORTHERN ENGINEERING the building to the south. This area consists of the proposed building and the surrounding landscape areas. The runoff from this area will be routed via overland flow and roof leaders into a bio- swale. The runoff conveyed through the bio-swale is intercepted by an area inlet and routed directly into the Southern Detention Pond. Sub -Basin S3 encompasses the western portion of the building and drive aisle and is primarily composed of hardscapes. The runoff from the roof will be routed via underground pipe into the underground StormTech Chambers. The runoff from the remaining area will be routed via overland flow to a curb cut and discharge directly into Sub -basin S4. Sub -Basin S4 encompasses the furthest upstream reach of Major Basin S and consists of western portion of the project. The runoff from this basin is routed via overland flow into a small depression located at the southwest corner of the property. Runoff from this basin is intercepted by a storm pipe and routed into the underground StormTech Chambers. The underground StormTech Chambers have been sized to handle the water quality event. All events exceeding this volume will bypass the chambers and be routed directly into the Southern Detention Pond. Basin 0 Basin 0 consists of all of the off -site improvements being proposed. The major basin was divided into three (3) sub -basins all draining undetained in three different directions. Sub -Basin OW1 encompasses the area along the western edge of the site that historically drains across the site from the west. This includes a portion of the existing single family residences, associated backyard and existing garage buildings. The stormwater is routed via overland flow and sheet flow onto the property along the western property line. This stormwater is planned to be routed through the site and released undetained at historic rates. Sub -Basin OS1 encompasses the existing public right-of-way within Prospect Road. Other than the proposed entrance and the master planned public sidewalk, no other improvements are proposed. The stormwater is routed via overland and gutter flow and is released off -site, undetained east on Prospect Road. Sub -Basin ON encompasses the emergency access drive located to the north of the site. The stormwater is routed via overland and swale flow. A portion of the runoff is planned to be detained within a TrueGrid and drain rock section and released partially through infiltration and partial through an underdrain system. Another portion of the runoff is planned to be captured through infiltration within the bio-swale and the use of a dry well. Emergency overflow is planned to over top and be routed through a sidewalk chase and into Lake Street. A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report. B. Specific Details 1. One of the main drainage problems associated with this project site is the deficiency of water quality present within the existing site. Currently the entire site drains overland and discharges directly into either Lake Street or Prospect Road without water quality. The proposed site will mitigate this issue by instituting the following water quality devices: N9 All of the runoff generated from the proposed building will either be routed through drainage rock surrounding underground StormTech Chambers, into an engineered bio-swale or over a grass buffer section. N9 Most of the improvements generated from the parking lot will be routed through a sub -surface drainage rock surrounding underground StormTech Chambers. Final Drainage Report 10 ' ■V (NORTHERN ENGINEERING The Slal ' NO All runoff generated from the emergency access drive will be routed either through a TrueGrid system and sub -surface drainage rock or through an engineered bio- ' swale. Low Impact Development Design will be implemented to break up the impervious areas and promote infiltration. ' The southern detention pond is designed with a water quality element and is designed to slowly release the minor storm into Prospect Road. ' 2. Since the site was partially developed since 2007, the release rate for the undeveloped land (pre -development) was established through using the previously approved quantities as reported by DMW Civil Engineers (Refer to Appendix D for supporting documentation). The historic 2-year peak runoff rate was established for the entire project area excluding the portion of public right-of-way that contains the front landscape area designated as Basin OS1 and excluding the off -site emergency access drive to the north. The total establishes the overall maximum allowable release rate, 1.1 cfs, from the on -site improvements, in which 0.8 cfs drains to the north into Lake Street and 0.3 cfs drains to the south into Prospect Road. These release rates ' were utilized in the FAA procedure detention storage computations (Refer to Appendix B for these calculations). ' 3. Within the original report, it was assumed that porous concrete would not change or generate more runoff than historic conditions. Since that time, it has been proven that porous concrete is not a viable solution and will in fact change the characteristic and quantity of runoff from historic conditions. Through subsurface exploration, it ' was determined that the soils in this area have an infiltration rate of 0.63 inches/hour. To reduce runoff leaving the site, Sub -Basin ON1 (10,820 sq. ft.) is proposed to be handle completely through infiltration, resulting in an overall release rate of 0.16 cfs. In establishing a 0.16 cfs release rate, Sub -basin will require 1,422 cu. ft. of detention that will be stored within the drain rock under the concrete path and TrueGrid section. The overall storage supplied within the drain rock section is ' 2,055 cu. ft. and will completely drain within 3.5 hours. Through the use of infiltration and the drain rock section, the previously approved design concept will be maintained. ' 4. The FAA method was used to size both of the ponds for quantity detention. Calculations for the northern pond, based on the characteristics of Basin N and an ' adjusted release rate of 0.8 cfs, indicate a detention volume of 0.23 acre-feet. No additional volume is required for water quality with each basin receiving treatment either before or after the detention pond. Below is a table summarizing the results for the northern detention pond. Required Water Water Quallty Required 100-year Total Required High Water Quality Storage Surface Detention Volume Detention Volume Surface Elevation Top of Pond ' Pond ID (ac-ft) Elevation (ft) (ac-ft) (ac-ft) (ft) Elevation (ft) North Pond 0.000 NA 0.23 0.23 5026.78 5027AO Table 2 — Northern Pond Summary Table 1 Final Drainage Report 11 NORTHERN ENGINEERING Calculations for the southern pond, based on the characteristics of Basin S and adjusted release rate of 0.3 cfs, indicate a detention volume of 0.1039 acre-feet. At this point, no additional water quality is required with only a small portion of Basin S (Sub -Basin SU not being treated prior to Pond S. This Sub -Basin S1 will need to be accounted for upon the development of Lot 2. With the understanding that Lot 2 will develop at some point, calculations have been performed based on a conceptual site layout and some design assumptions. Based on the assumed characteristics of the future developed Lot and Basin S of Lot 1, an overall detention volume of 0.1379 acre-feet will be required. This volume includes the Water Quality Capture Volume for both the future developed Lot 2 draining to this pond and Basin S1 located on Lot 1. Below are two tables summarizing the current requirements and the assumed future requirements. For a conceptual analysis of future drainage patterns of Lot 2, refer to Appendix F. Required Water Water Quality Required 100-year Total Required High Water Quality Storage Surface Detention Volume Detention Volume Surface Elevation Top of Pond Basin ID (ac-ft) Elevation (ft) (ac-ft) (ac-ft) (ft) Elevation (ft) South Pond 0.0 NA 0.1039 0.1039 0.00 5025.60 Table 3 — Southern Pond Summary Table Total Detention Volume Required Water Water Quality Required 100-year (ac-ft) High Water Quality Storage Surface Detention Volume (w/ 0.0317 ark Surface Elevation Top of Pond Basin ID (ao-ft) Elevation (ft) (ac-ft) from tot 2) (ft) Elevation (ft) South Pond with Future Development 0.0024 5022.657 0.1039 0.1379 5025.75 5026A0 Table 4 — Future Southern Pond Summary Table 5. The emergency spillway for the northern pond will be located on the eastern wall. In the event that emergency overflows occur, the drainage will flow into off -site bio-swale and into Lake Street. The emergency spillway for the southern pond will be located on the southern wall. In the event that emergency overflows occur, the drainage will flow directly into Prospect Road. Final Drainage Report 12 ■� NORTHERN ENGINEERING The Slab V. CONCLUSIONS ' A. Compliance with Standards 1. The drainage design proposed with The Slab project complies with the City of Fort ' Collins' Stormwater Criteria Manual. The project is requesting an exception to be granted by the Utilities Executive Director or his designee to Section 4.15(b). The project is proposing to use the parking area for additional detention volume with ' depths that exceed the 12-inch maximum. These depths will not exceed 18-inches within the parking area and the area exceeding 12-inches of ponding will occur within less that twenty-five percent (25%) of the total parking spaces provided. Please see the full-size copy of the Proposed Drainage Exhibit within Map Pocket to see the extents of these ponding areas. 2. The drainage design proposed with The Slab project complies with the City of Fort Collins' Master Drainage Plan for the Old Town Basin: 3. There are no regulatory floodplains associated with The Slab development. 4. The drainage plan and stormwater management measures proposed with The Slab '. development are compliant with all applicable State and Federal regulations governing stormwater discharge. ' B. Drainage Concept 1. The drainage design proposed with this project will effectively limit potential damage ' associated with its stormwater runoff. The Slab will detain for the pervious area converted to impervious areas by releasing all on -site areas to the 2-year existing rate during the developed 100-year storm. The off -site basin, Basin ON1, will be released entirely through infiltration further improving downstream drainageways. 2. The proposed Slab development will not impact the Master Drainage Plan recommendations for the Old Town major drainage basin. 1 Final Drainage Report 13 WINORTHERN ENGINEERING References 1. 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. 2. Final Drainage Report for Observatory Park Fort Collins Colorado, August 27, 2007, DMW Civil Engineers. 3. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code. 4. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007. 5. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 6. 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N N it m G) A Q) < r OD O1 A CD O N a T t0 N C O N O IV W A W N !D O >r N w xo m 1 0_ a w O O O W O mo r M O co O O O x o 3 y to? 0 v m 0 No Text 1 I 1 1 1 1 1 1 1 1 u i 1 1 i 1 Northern Eneineerina.rom // 970.221.91SR N C C_ O a C d N cM C � N N 0 tVC4 O O K r1 hlaapena..ce ! Arces 1 _ _ Rner ._ ! Z`J 6A,,M, QED Puon -- FLY ED Pa d - i FO Vv.a.r.n i i N nrth ernE nnin ee rinn.rnm /1 970.221.4158 N NORTHERN ENGINEERING DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Project Number 1033-002 Project Name The Slab Project Location Fort Collins, Colorado Pond No North Pond Input Variables Results Design Point n1 Design Storm 100-yr C = 1.00 = 5. Amin A = 0.99 99 acres Max Release Rate = 0.80 cfs Required Detention Volume �ac-ft Time (min) Ft Collins 100-yr Intensity n/hr Inflow Volume (n3) Outflow Adjustment Factor 48V (cfs) Outflow Volume 3 (ft) Storage Volume (�t3) 5 9.950 2943 1 1.00 0.80 240 2703 10 7.720 4567 0.75 0.60 360 4207 15 6.520 5786 0.67 0.53 480 5306 20 5.600 6626 0.63 0.50 600 6026 25 4.980 7365 0.60 0.48 720 6645 30 4.520 8022 0.58 0.47 840 7182 35 4.080 8448 0.57 0.46 960 7488 40 3.740 8850 0.56 0.45 1080 7770 45 3.460 9211 0.56 0.44 1200 8011 50 3.230 9554 0.55 0.44 1320 8234 55 3.030 9859 0.55 0.44 1440 9419 60 2.860 10152 0.54 0.43 1560 8592 65 2.720 10459 0.54 0.43 1680 8779 70 2.590 10726 0.54 0.43 1800 8926 75 2.480 11004 0.53 1 0.43 1920 9084 80 2.380 11264 0.53 0.43 2040 9224 85 2.290 11515 0.53 0.42 2160 9355 90 2.210 11767 0.53 0.42 2280 9487 95 2.130 11971 0.53 0.42 2400 9571 100 2.060 12187 0.53 0.42 2520 9667 105 2.000 12424 0.52 0.42 2640 9784 110 1.940 12625 0.52 0.42 2760 1 9865 115 1.890 12858 0.52 0.42 2880 9978 120 1.840 13063 0.52 0.42 3000 1 10063 'Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. 1033-001 North DetentionVolume FAAModified Method.xls r 1 1 I i 1 1 1 1 Page 1 of 1 ' NORTHERN C N G N E E R I N G ADDRESS: I PHONE: 970.221.4158 2W S. College Aw. Suite 10 INE93�: w w.nonhernenginennng.com Fort Collins. CO 80524 f0.X: 970.221.4159 ' Project Tltle Project Number The Slab 1033-002 0ato: Cala By: June 22, 2016 C. Snowdon Client M"Mmo Pond Deslgnatlon North Pond 5024.25 In WatEa•13Du yVol NA on Volurce 0.2310 ac-ft d Vol"0.2310 ac-ft 3 D - Depth between contours (ft.) A, - Surface Arent lower contour (fe) A, = Surface Area upper contour (fe) Elevation Surface Incremental I Incremental ITotal Vol. Total Vol. (ft) I Area fft 1 I Depth (ft) I Vol. ife) I if 1 I (ac-ft) 5024.60 1051.76 0.20 129.24 144.89 5024.80 1714.12 0.20 273.90 418.79 5025.00 2038.51 0.20 374.79 793.58 5025.20 2232.65 0.20 426.97 1220.55 5025.40 2312.72 0.20 454.51 1675.07 5025.60 2521.90 0.20 483.31 2158.39 5025.80 3303.87 0.20 580.82 2739.20 5026.00 4064.79 0.20 735.55 3474.75 5026,20 5829.13 0.20 984.11 4458.86 5026.40 8341.03 0.20 1409.54 5869.39 5026.60 11228.54 0.20 1949.82 7818.21 5026.80 14437.71 0.20 2559.91 10378.12 5027.00 17562.97 0.20 3194.96 13573.08 5027.20 20441.93 0.20 3796.84 17369.92 5027.40 23355.75 0.20 4376.53 21746.45 5027.60 25939.97 0.20 4927.31 26673.76 5027.80 28115.64 0.20 5404.10 32077.87 5028.00 31104.31 0.20 5919.48 37997.35 Overall Detention EMeNatlon Depth Vohttne WQN 100-yr Detention Overall Detention NA 5026.78 5026.78 NA 2.53 2.53 NA 0.2310 0.2310 0.0004 0.0033 0.0096 0.0182 0.0280 0.0385 0.0495 0.0629 0.0798 0.1024 0.1347 0,3116 0.3998 0.4992 0.6123 0.7364 0.8723 ■� NORTHERN ADDRESS. PNON& 970.221.4158 WEIIIi ENGINEERING 200 S. College Ave. Suite 10 v .northernenglneeringwm Fort Collins, CO 80524 FAX: 970.221.4159 Project Title The Slab Date: June 22, 2016 Project Number 1033-002 Calcs By: C. Snowdon Client Maxiilmo Pond Designation North Pond Q = Release Rate (cfs) C = Discharge Coefficients (unitless) A, = Area Allowed of Opening (ft') g = Gravity (32.2 ft/s') E„ = High Water Surface Elevation (ft) E, = Elevation of Outlet Invert (ft) E, = Elevation of Outlet Centroid (ft) Circular Orifice 4- 6/32 in. 13.83 sq-in 0.77 cfs Reetaneulai Orifice 4EPear Orifice Orifice He t(in.) 3 - 1/2 in. Orifice Width (in.) 4 in. 2) 13.83 sq-in 0.78 cfs Q= 0.80 cfs C = 0.65 E„ = 5026.80 ft Ei = 5024.25 ft Ec=5024.42ft Circular E,,= 5024.39 ft Rectangular 0.096042533 ft A' 13.830125 in` I 1 Required Water Water Quality Regulted WOyeer Total Required High Water QualityRoraae Surfece 0etentlon Volume Oetemlon Volume Surface Elevation TOP d Pond Pont! 10 lack) flevatlon (N) (ac-R) (.>ft) (t) El.tlon lltl North Pond OA00 NA On an SO M S AO 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 i Oetentlpn Pond Summary Repulred Water (1uallty$to lx`ft) OW Water Ouallty Surface El. Mlon lftl NA Required 106year Oetentlon Volume lac-h) Mn Total Ragdrtd 0: tbn Voume lac-R) O.n HIRH Water Surface Elevation (R) S 6.78 To, of Pond Elevation (ft) N27.40 1 I Stormwater Detention and Infiltration Design Data Sheet ' The Slab Northern Detention Pond ' Stormwater Facility Name: Fort Collins, Colorado Facility Location &Jurisdiction: User (Input) Watershed Characteristics Watershed Slope = Watershed Length -to -Width Ratio= Watershed Area = Watershed Imperviousness= Percentage Hydrologic Sall Group A = Percentage Hydrologic Soil Group B = Percentage Hydrologic Soil Groups C/D = 0.050 ft/ft L:W acres percent percent percent percent 1.40 1.01 78.D% 0.0% 100.0% 0.D% User Input: Detention Basin Characteristics WQCV Design Drain Time= 40.00 hours After completing and printing this worksheet to a pdf, go to: hqps.LLmaperture.digitaidatase"ices.com/g h/?viewer-cswdif, create a new stormwater facility, and attach the pdf of this worksheet to that record. Design Storm Return Period Two -Hour Rainfall Depth , Calculated Runoff Volume: OPTIONAL Override Runoff Volume Inflow Hydrograph Volume: Time to Drain 97%of Inflow Volume: Time to Drain 99%of Inflow Volume: Maximum Forcing Depth Maximum Fondled Area Maximum Volume Stared: User Defined Stage [ftl User Defined Area Ift-21 User Defined Stage [ft] User Defined Discharge 1cfs1 0.00 277 0.00 0.00 0.20 1,034 0.20 0.20 0.40 1,759 0.40 0.40 0.60 2,254 0.60 0.60 0.90 3,103 0.80 0.90 1.00 1 3,869 1.00 1 0.80 1.20 5,304 1.20 0.80 1.40 8,308 1.40 0.90 1.60 11,316 1.60 0.80 1.80 14,531 1.80 0.80 2.00 17,725 2.00 0.90 R-t.rl Nvdrnorwnh Readts WDCV 2Year 5Year 10 Year 25 Year 50 Year 100 Year 0.53 0.98 1.36 1.71 2.31 2.91 3.67 0.026 0.D52 0.092 0.120 0.172 0.223 0.290 0.026 0.061 0.091 0.120 0.171 0.222 0.289 1 2 2 2 3 4 5 2 2 2 3 3 4 5 0.39 0.73 0.97 1.19 1.46 1.64 1.84 0.039 0.064 0.086 0.120 0.210 0.275 0.347 0.009 0.026 1 0.044 0.067 1 0.110 0.155 1_ 0.216 I 1 1 i i I 1 cre-ft , ¢re-k acre-ft tours , tours t cres tcre-k SDI Design_Data_FC_Rainfall - Northern Detention Pond.xlsm, Design Data 6/22/2016, 2:47 1 I I 1 1 1 1 1 t1_Design_Data_FC Rainfall - Northern Detention Pond.xlsm, Design Data Stormwater Detention and Infiltration Design Data Sheet 6/22/2016, 2:47 PM J ■� (NORTHERN ENGINEERING DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Project Number 1033-002 Project Name The Slab Project Location Fort Collins, Colorado Pond No South Pond Input Variables Results Design Point s1 Design Storm 100-yr C = 0.88 Tc = 5.60 min A = 0.49 acres Max Release Rate = 0.30 cfs Required Detention Volume 4524 ft3 0.10 ac-ft Time (min) Ft Collins IntensityOrVolume n/hr Inflow (ft3) Outflow Adjustment Factor Qav (c) a Outflow Volume (ft) Storage Volume (ft3) 5 9.950 1274 1.00 0.30 90 1184 10 7.720 1977 0.78 0.23 140 1837 15 6.520 2504 0.69 0.21 185 2319 20 5.600 2868 0.64 0.19 230 2638 25 4.980 3188 0.61 0.18 275 2913 30 4.520 3472 0.59 0.18 320 3152 35 4.080 3657 0.58 0.17 365 3291 40 3.740 3831 0.57 0.17 410 3421 45 3.460 3987 0.56 0.17 455 3532 50 3.230 4136 0.56 0.17 500 3635 55 3.030 4268 0.55 0.17 545 3722 60 2.860 4394 0.55 0.16 590 3804 65 2.720 4527 0.54 0.16 635 3892 70 2.590 4643 0.54 0.16 680 3962 75 1 2.480 4763 0.54 0.16 725 4038 80 2.380 4876 0.54 0.16 770 4105 85 2.290 4985 0.53 0.16 815 4169 90 2.210 5093 0.53 0.16 860 4233 95 2.130 5182 0.53 0.16 905 4276 100 2.060 5275 0.53 0.16 950 4325 105 2.000 5378 0.53 0.16 995 4382 110 1.940 5465 0.53 0.16 1040 4424 115 1.890 5566 0.52 0.16 1085 4480 120 1.840 5654 0.52 0.16 1130 4524 'Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. 1 I i L 1 r IL F L i 1033-001_South_DetentionVolume_FAAModifed Method.xls Page 1 of 1 1 NOR T H ERN ENGINEERING ABORE35ege are. SUN 10 Fort Collins, CO 80524 ENE: 970.221AI58 wEBSITE: FAX: 970.221.4159 `w^0.n^rthernengmeenng.c^m Project Title The Slab Date: July 14, 2016 Project Number 1033-002 Calcs By: C. Snowdon Client Maxilimo Pond Designation South Pond .Vert Elevll k .022A8 Water Quality Valu 0.0000 ac-ft 1D0-yr Detention Vol u BI 0.1039 ac-ft 0.1039 ac-ft v_D"A+Az+ A /3 D = Depth between contours (ft.) At = Surface Area lower contour (ft) A, Surface Area upper contour (ft) South Pond Volume Elevation Surface Incremental Incremental Total Vol. Total Vol. (ft) Area fiT) Depth (tt) Vol. (tt') (to) ac-ft) 5022.40 31.57 -0.08 -0.84 -0.84 0.0000 5022.60 606.08 0.20 51.73 50.89 0.0032 5022.80 1262.80 0.20 182.92 233.80 0.0054 5023.00 1688.26 0.20 294.08 527.88 0.0121 5023.20 1728.79 0.20 341.70 869.58 0.0200 5023.40 1769.97 0.20 349.87 1219.45 0.0280 6023.60 3811.84 0.20 358.17 1577.62 0.0362 6023.80 1654.92 0.20 366.63 1944.25 0.0446 6024.00 1898.32 0.20 375.26 2319.50 0.0532 5024.20 1942.77 0.20 384.08 2703.58 0.0621 5024.40 1988.49 0.20 393.12 3096.70 0.0711 5024.60 2035.25 0.20 402.36 3499.07 0.0803 5024.80 2063.04 0.20 411.82 3910.69 0.0898 6026.00 2131.89 0.20 421.48 4332.37 0.0996 6026.20 2181,79 0.20 431.36 4763.73 0.1094 Elevation Depth Volume WQCV NA NA NA 1l10-Vr Detention 5025.09 2.61 0.3039 Overall Detention 5025.09 2.61 0.1039 NORTHERN PHONE: 970.221.4158 INESSM: ■y ENGINEERING 200gE5S: W 5. College Ave. 10 Fort Collins, C090524 24 FA%:970.221.4159 w northernenglneennglxom Project Title The Slab Date: July 14, 2016 Project Number 1033-002 Calcs By: C. Snowdon Client Maxliimo Pond Designation South Pond O = Release Rate (cfs) C = Discharge Coefficients (unitless) A. = Area Allowed of Opening (ft') g = Gravity (32.2 ft/s) Ei, = High Water Surface Elevation (ft) Ei = Elevation of Outlet Invert (ft) E, = Elevation of Outlet Centroid (ft) Circular Orifice Rectangular Orifice Iflce 2 - 1/16 in. Orifice Width (in.) 2 - 1/2 in. Area (in) 5.13 sq-in 0 0.30 cfs Cit 0.65 Eh = 5025.09 ft Ei = 5022.48 ft E,=5022.59ft Circular Ec = 5022.57 ft Rectangular A, = 0.035607415 ft z 5.127468 in I 1 I 1 t 1 1 C� 1 I Required Water Water Quality Required 100-year Total Required High Water Quality Storage Surface Detention Volume Detention Volume Surface Elevation Top of Pond Basin ID (ac-ft) Elevation (ft) (ac-ft) (ac-ft) (ft) Elevation (ft) South Pond 0.0 NA 0.1039 0.1039 0.00 5025.60 I Stormwater Detention and Infiltration Design Data Sheet ' The Slab Southern Detention Pond Stormwater Facility Name: Facility Location & Jurisdiction: Fort Collins, Colorado User (input) Watershed Characteristics Watershed Slope = 0.050 Watershed Length -to -Width Ratio= 2.00 Watershed Area = 0.47 Watershed Imperviousness= 64.0% Percentage Hydrologic Soil Group A = 0.0% Percentage Hydrologic Soil Group B = 100.0% Percentage Hydrologic Soil Groups C/D = 0.0% User Input: Detention Basin Characteristics WQCV Design Drain Time= 40.00 hours Aker completing and printing this worksheet to a pdf, go to: h[tpv./_ma _enure.digitaidatasemices.com/gvh/7viewer-cswdif, create a new stormwater facility, and attach the pdf of this worksheet to that record. Design Storm Return Period = Two -Hour Rainfall Depth = Calculated Runoff Volume OPTIONAL Override Runoff Volume = Inflow Hydrograph Volume = Time to Drain 97%of Inflow Volume = Time to Drain 99%of Inflow Volume = Maximum Pointing Depth = Maximum Ponded Area = Maximum Volume Stared = User Defined Stage Ift) User Defined Area Ift-2] User Defined Stage Iftl User Defined Discharge Iefs) 0.00 67 0.00 0.00 0.20 475 0.20 0.10 0.40 1,231 0.40 0.20 0.60 1,925 0.60 0.30 0.90 2,226 0.80 0.30 1.00 1 2,359 1.00 1 0.30 1,20 2,359 1.20 0.30 1.40 2,359 1.40 0.30 1.60 2,359 1.60 0.30 1.90 2,360 1.80 0.30 2.Do 2,360 2.00 0.30 2.20 2,360 2.20 0.30 2.40 2,360 2.40 0.30 nnutad Nuri-aranh naodre WQCV 2 Year 5 year 10 year 25 Year SO Year 100 Year 0.53 0,98 1.36 1.71 2.31 2.91 3.67 0.010 0.023 0.036 0.048 0.071 0.094 0,124 0.010 0.022 0.035 0.048 0.071 0.094 0.124 1 2 2 2 3 4 5 1 2 2 3 3 4 5 0.29 1 051 0.68 0.88 1.15 1.62 2.12 0.019 0.036 0.047 0.052 0.054 0.054 0.054 0.003 0.008 0.0161 0.026 0.046 0.066 0.093 I I n acre-ft acre-ft acre-ft lours , lours t acres ' acre-ft SDI_Design_Data_FC_Rainfall - Southern Detention Pond.xlsm, Design Data 6/22/2016, 2:4511 I Stormwater Detention and Infiltration Design Data Sheet 35 - _10WR IN - - 100YR OUT 3 —50YR IN ' - 50YR OUT —25YR IN ' 2S - ssrRour �IGYR IN 2 - - 10YR OUT ' —SYR IN • • • SYR OUT 1.5 2YR IN 2YR OUT �WOLV IN 1 _ ••• WON OUT —. — O 0.1 2.5 — — �100YR 2 -Sm 25YR ' -10YR -SYR F 1.5 -2YR - ' -WQCV ' 0.5 - 0 OS 1 ' `I_Design_Data_FC_Rainfall - Southern Detention Pond.xism, Design Data 1 TIME 1Nr1 DRAW TIME W1 10 10 100 6/22/2016 :' -I- PM NORTHERN ENGINEERING ADDRESS: PHDNE: 970.221.4158 WEBSITE: 200 S. College Ave. Suite 10 Fort Collins, C080524 FAX: 970.221.4159 www•wrthernengineering.com Project Title The Slab Project Number 1033-002 Client Maxiiimo Pond Designation South Pond with Future Development Date: July 14, 2016 Calcs By: C. Snowdon WQCVa0.9ti'-1.19i2+0.78iDrain Time 40hi a= 1 WQCV = Watershed inches of Runoff (inches) I = 60.00% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio It = Iwa/100) WQCV = 0.236 in Water Quality Capture Volume 0.5 0.45 WQCV— a(0.9It'-1.191-+0.78i) s 0.4 c 0.35 a 0.3 y 0.25 0.2 0.15 3 01 0.05 0 0 Total Imperviousness Ratio (i = I Wa/100) Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event V=�WV� 0.10 ac *A*1 l 12 i IV = 0.0024 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) I 1 1 1 1 H I 1 1 1 NORTHERN AOOMS: 2M S. College Ave. Sulk 10 E N G I N E E R I N G Fort Collins, 0080 4 Project Title The Slab Project Number 1033-O02 Client Maxlllmo Pond Designation South Pond with Future Development PHONE: 970.221.4158 I EaSITE: FAX: 970.227.4159 " .nortiwronglneorngixom Date: July 14, 2016 Calm By: C. Snowdon 51039a ft Water Quality 0.D024 ac-ft 100.yr Detention V 0.1039 a<-ft Total Pond Volume (w/ Addlti 0.1379 ac-ft 0.0317 ac-ft assumed for v=DMA+A,+ 3 D= Depth between contours (ft.) Ai = Surface Area lower contour (ft") Ar = Surface Area upper contour (feg) ElevM Su Dotal Vol. _ (ft) Area (ft) Depth (4) Val. (f!') @F') (ao-ft) 5022.40 31.57 0.17 1.79 1.79 0.0000 5022.60 606.08 0.20 51.73 53.52 0.0012 5022.80 1262.80 0.20 182.92 236.44 0.0 554 WQCV 5023.00 1688.26 0.20 294.08 530.51 0.0122 5023.20 1728.79 0.20 341.70 872.21 0.0200 5023.40 1769.97 0.20 349.87 1222.08 0.0281 5023.60 1911.84 0.20 358.17 1580.25 0.0363 5023.80 1854.52 0.20 366.63 1946.88 0.0447 5024.00 1899.12 0.20 375.26 2322.14 0.0533 5024.20 1942.77 0.20 394.08 2706.22 0.0621 5024.40 1988.49 0.20 393.12 3099.33 0.0712 5024.60 2035.25 0.20 402.36 3501.70 0.0804 5024.80 2083.04 0.20 411.82 3913.52 0.0898 5025.00 2131.89 0.20 421.48 4335.00 0.0995 5025.20 2181.79 0.20 431.36 4766.36 r 0,1094 100-yr Voi 5025.40 2232.90 0.20 441.46 5207.82 0,1196 5025.60 2285.54 0.20 451.83 5659.65 0.1299 5025,80 2339.80 0.20 462.52 6122.18 0.1405 Total Vol 5026.00 2395.94 0.20 473.55 6595.73 0.1514 5026.20 2453.81 0.20 484.95 7080.68 0.1626 5026.40 2513.56 0.20 496.73 7577.41 0.1740 Elevation Depth Voluele. WqN 5022.65 0.42 0.0024 100.yr Detention 5025.09 2.86 0.1039 Overall Detention 5025.75 3.52 0.1379 NORTHERN ADDRESS: PHONE: 970.221.4158 ■� E N G I N E E R I N G 200 S. College Ave. Swte 10 Fort Collins, CO 80524 FAX: 970.221.4159 =SITE' www.northilmongineenng.corn Project Title The Slab Date: July 14, 2016 Project Number 1033-002 Calcs By: C. Snowdon Client Maxliimo Q= Release Rate (cfs) C = Discharge Coefficients (unitless) A. = Area Allowed of Opening (ft') g = Gravity (32.2 ft/s') Er, = High Water Surface Elevation (ft) Ei = Elevation of Outlet Invert (ft) Ec = Elevation of Outlet Centroid (ft) Circular Orifice o.3g cg Rectangular Orifice Z- irn: of Q= 0.30 cts C = 0.65 E„ = 5025.09 ft Er = 5022.23 ft E, = 5022.34 ft Circular E,=5022.32ft Rectangular 0,034022168 ft A. = n, 4.899192 Total Detention Volume Required Water Water quality Required 100-year (ac-ft) High Water Quality Storage Surface Detention Volume (w/ 0.0317 ac-ft Surface Top of Pond Basin ID (ac-ft) Elevation (ft) (ac-ft) from Lot 2) Elevation (ft) Elevation (ft) South Pond with Future Development 0.0024 5022.654 0.1039 0.1379 5025.75 5026.40 1 1 1 1 1 I StormTech® (kuxrlroo • Retention •Wale, Quality A do ision of Mm IX 3 r-0 ON I GL (o, 820 xAyF14 �. O.Co3 "A' (d. / 3(i0O SEA g" OL. 0000l� �S a, Co. 0600 If, 44/'.,( to, S ZO T7 L D. I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1� 1 800-821-6710 • www.ads-pipe.com ■� NORTHERN ' ENGINEERING I t I 1 1 I I 1 DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Project Number 1033-002 Project Name The Slab Project Location Fort Collins, Colorado Pond No Emergency Access Drive Input Variables Results Design Point ON1 Design Storm 100-yr C = 0.61 Tc = 7.00 min A = 0.25 acres Max Release Rate = 0.16 cfs Required Detention Volume 1422 ft3 0.03 ac-ft Time (min) Ft Collins 100-yr Intensity nlhr Inflow Volume a (ft) Outflow Adjustment Factor Oa" (cfs) Outflow Volume 3 ft ( ) Storage Volume 3 (ft ) 5 9.950 455 1.00 0.16 47 408 10 7.720 706 0.85 0.13 80 626 15 6.520 895 0.73 0.12 104 791 20 5.600 1025 0.68 0.11 127 898 25 4.980 1139 0.64 0.10 151 988 30 4.520 1241 0.62 0.10 174 1066 35 4.080 1307 0.60 0.09 198 1109 40 3.740 1369 1 0.59 0.09 221 1147 45 3.460 1425 0.58 0.09 245 1180 50 3.230 1478 0.57 0.09 268 1209 55 3.030 1525 0.56 0.09 292 1233 60 2.860 1570 0.56 0.09 316 1255 65 2.720 1618 0.55 0.09 339 1279 70 2.590 1659 0.55 0.09 363 1296 75 2.480 1702 0.55 0.09 386 1316 80 2.380 1742 1 0.54 0.09 410 1332 85 2.290 1781 0.54 0.08 433 1348 90 2210 1820 0.54 0.08 457 1363 95 2.130 1852 0.54 0.08 480 1371 100 2.060 1885 0.54 0.08 504 1381 105 2.000 1922 0.53 0.08 528 1394 110 1.940 1953 0.53 0.08 551 1402 115 1..0 1989 0.53 0.08 575 1414 120 1.840 2020 0.53 0.08 598 1422 'Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. 1033-001 _Emergency Drive_DetentionVolume_FAAModified Method.xls ' Page 1 of 1 NORTHERN ENGINEERING Project Title Project Number Client Pond Designation The Slab 1033-002 ADDRESS: PHONE: 970.221.4158 WEBSITE: 200 S. College Ave. Suite 10 Fort Collins, CO 80524 FAX: 970.221.4159 www.northernengmeering.com Maxiiimo Emergency Access Drive WQCV = a 0.91i' — WQCV = Watershed inches of Runoff (inches) a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = IwQ/100) 0.5 _0.45 WQCV =a(0.91i'-1.19i'+0.78i) s 0.4 c 0.35 Date: June 22, 2016 Calcs By: C. Snowdon 1233.hr a = 0.8 00% 0.128 in 0 r O W OI V W ,D O O O O O O O C O O Total Imperviousness Ratio (i = 1w /100) Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event A= 0.25 ac V =( WQCV )• A' 1.2 12 V= 10.0032ac-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) 1 NORTHERN alJmloar muy wlap Ae.Bw¢10�� rllolE s2o.u1.41s! ' E N G N E C R N G E Iwllftcoll d 1a1691022J 415a ww.nnrrnrmnMni« o-,,; «,r, Project Title The Slab Date. June 22, 2016 Project Number 103 002 CJIa BY C.Sowden Ghent Maaillmo ' Pond Designation Emergency AC[em Drive InVert ElbvaBdf 5023ffi 11 ' Water"InI lty Volume 139 M. h. 100ryr Detention Volume 1639 w. R. Total Pond Volume 1639 w. h. TrueGrld Section Volume Surface Volume AdAMW Volume Elev;ton Surface Ame ft 0,08 517.34 Incremental DOPth (R) Incremental Vol. fl 100%Cepocl Total Vol. ffe) Total Vol. 40%C."ci IRS Surface Nes its Incremental Depth (0) Incremental Vol, k) Total Val. Rr)(it") Total Volume N/A 0.1 N/A 25.97 0 1Z46 0 N/A N/A N/A 0 0 6.984 N/A N/A N/A 0 6.984 -155.88 1.794.76 0.1 83.66 147.53 99D1 245.38 39.604 98.152 N/A N/A N/A N/A N/A N/A 0 0 39.604 98,152 0.1 2,433.99 3,026.56 0.1 0.1 211.44 273.03 456 729.49 182.4 N/A N/A N/A 0 182.4 291.396 N/A N/A N/A 0 291,396 2 3,347.72 2 3,667.69 0.1 0.1 318.71 350.77 1047.07 1397.72 418.828 N/A N/A N/A 0 418.828 559.088 N/A N/A N/A 0 559,088 1,987.79 0.1 382.77 1780.38 712.152 N/A N/A N/A 0 712.152 72 4,308.03 0.1 414.79 2195.07 878.028 N/A N/A N/A 0 878.029 4,628.42 4,948.96 0.1 0.1 446.82 478.87 2641.8 1056.72 N/A N/A N/A 0 1056.72 3120.58 1248.232 N/A N/A N/A 0 1248.232 5,051.14 5,051.92 0.1 0.1 500.01 505.15 3620.56 1448.232 N/A N/A N/A 0 1449.232 4125.73 1650.292 N/A N/A N/A 0 1650,292 .22 5,052.69 0.1 505.23 4630.96 1852.384 N/A N/A N/A 0 1852.394 '3028.32 5,053.47 0.1 505.31 5136.27 2054.508 NIA N/A NIA 0 2054.508 North ernEnain eerina.rom // 970.221.415A WINORTHERN ENGINEERING Project Name The Slab Project Number 1033-002 Basin ID Basin N1 \ IC BIC—RETENTION SAND MEDIA _J0OOpa OC" '.GOC. i i GRAVEL LAYER J MEETING COOT 04 COARSE AGGREGATE SPECIFICATION. Bio-Swale Width: 2.0 ft. Bio-Swale Length: 313 ft. Overall Basin Area: 9,989 sq. ft Impervious Area: 5,476 sq. ft '—GEOTE%TLE FABRIC PCF GRAVEL PERFORATED HOPE UNDERDRAIN Bio-Swale Surface Area 625.8 sq. ft 10:1 Impervious Runon Area 6,258.0 sq. ft ■� NORTHERN E N G I N E L R I NG ADDRESS: PHONE: 970221.4158 200 S. College Ave. Style 10 WERSRE: Fort Collins, CO 80524 FA%: 970.221.4159 iww.northernengineering.corr Project Title Lake Street Apartments Date: May 22, 2016 Project Number 1232-001 Calcs By: C. Snowdon Client Basins Basins N2 & N3 WQCV=a0.9li'-1.19i'+0.78i 12hr - =a-- 0.8 WQCV = Watershed inches of Runoff (inches)86.00% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = 1 ,q/100) MMMOPPMTO.296 in 0.5 0.45 ra WQCV=a(0.91i'-1.19i`+0.78i) 0.4 0.35 0.3a 0.296 -_ s `m 0.25 3 0.2 �0.15 3 0.1 0.05 0 , 0 0 0 0 0 0 0 0 0 0 O 1+ N W A N al J W io O' O O O O O O O O O O C Total Imperviousness Ratio (i = I,,,e/100) Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event V _ (WQCV 0.78 ac 12 � 0.0191 ac-ft 833 cu. ft. V = Water Quality Design Volume (ac-ft) WQCV= Water Quality Capture Volume (inches) A = Watershed Area (acres) I7/14/2(I16 ADS StwrnTech Design Tool TOOL StormTech 4 [iIT rtnn o! ii(III(Ir Chamber Model SC-160 'Outlet Control Structure Yes (Outlet) Project Name The Slab - Basin N2 & N3 Project Location Fort Collins ' Project Date 07115/2016 Engineer Northern Engineering ' Measurement Type Required Storage Volume Imperial 833 cubic ft. Stone Porosity 0% Stone Above Chamber Stone Foundation Depth 6 in. 6 in. Average Cover Over Chambers 14 in. Constraint LENGTH 'Design Design Constraint Dimension 120 ft. 1 1 1 Rests dt-z System Volume and Bed Size Installed Storage Volume 836 cubic ft. Storage Volume Per Chamber 6.85 cubic ft. Number Of Chambers Required 122 each Number Of End Caps Required 16 each Rows/Chambers 7 row(s) of 16 chamber(s) Leftover Rows/Chamber: 1 row(s) of 10 chamber(s) Maximum Length 120.06 ft. Maximum Width 19.27ft. Approx. Bed Size Required 2208 square ft. System Components Volume Of Excavation (Not Including 218 cubic yards Fill) Non -woven Filter Fabric Required 550 square yards Length Of Isolator Row 115.9 ft. Geogrid NA square yards Woven Isolator Row Fabric 103 square yards PAVEMENT LAYER DESIGNED BY SITE DESIGN ENGINEER) � 1 M w rota nits �eoul Nr+a�ie w. a'LIM)mm1 Ir la MIN 1050 mm) (00m) MN. MAX I 1 1 12 (OOD mm) 1 I 1 I DEPTH OF STONE TO BE OETERMNED BY SITE DESIGN 25' IT("mm) ENGINEERS It 50 mm) MIN' I635 mm) _ _ TYP NO SPACING REOUIREO SINGLE LAYER OF GEOGRID BXIMGG TO BE ' A MINIMUM OF 4-(100.) OF BETWEEN CHAMBERS INSTALLED BETWEEN NON WOVEN GEOTEXTILE FOUNDATION STONE CAN BE USED MEN AND BASE STONE MEN BETWEEN 4' AND r OF RACING GEOGRID BX124GG ON THE FOUNDATION STONE IS USED BOTTOM OF THE FOUNDATION STONE ® ADS StormTech 2015 ' http://stumtechcalc.azamebsites.nett 1M Project: The Slab - Basins N2 & N3 -4 Chamber Modal - SG180 StCWFTTISbI • Units- Imperial ai�x woe ra .I c�. Number of chambers - 122 Voids in the alone (porosity)- Base of STONE E - D.DD �% h � IbWe attinMr Srve �" Ulatbtwm Amount of Slone Above Chamhen - Above fi in Amount of Stone Belaw Chambers - 6 In StormTech SC-160 Curnulativa Height of Incremental Single Incremental Incremental Incremental Ch Cumulative System Chamber I Total Chamber I Stone & St Chamber Elevation inches cubic reel cubfe feet wblc leaf cubic feel eueic lest feet to 0 UIJ u.uu auu u uu aoo. it 23 0.00 0.00 0.00 0.00 836.14 1.92 22 0.00 0.00 0.00 0.00 836.14 1.83 21 0.00 0.00 0.00 D.DD 836.14 1.75 20 0.00 0.00 0.00 0.00 836.14 1.07 19 0.00 0.00 0.00 0.00 035.14 1.58 18 0.05 625 0.00 6.25 836.14 1.50 17 0.13 16.40 0.00 16.40 629.89 1.42 16 0.29 35.45 0.00 35.45 813AS 1.33 15 0." 53.92 0.00 53.92 778.04 1.25 14 0.54 65.78 0.00 85.76 724.12 1.17 13 0.62 75.19 0.00 75.19 WAS 1.08 12 0.68 83.05 D.Do 83.05 583.15 1.D0 11 0.74 89.78 0.00 69.78 500.10 0.92 10 0.78 95.57 0.00 95.57 410.32 0.83 9 0.82 100.64 0.00 100.64 314.75 0.75 8 0.06 104.96 0.00 1D4.98 214.11 0.67 7 0.89 109.15 0.00 109.15 109.15 0.58 6 0.00 0.00 0.00 0.00 0.00 0.50 5 0.00 0.00 0.00 0.00 0.00 0.42 4 0.00 0.00 0.00 0.00 0.00 0.33 3 0.00 0.00 0.00 0.00 0.00 0.25 2 0.00 0.00 0.00 0.00 0.00 0.17 1 0.00 0.00 0.00 0.00 0.00 0.08 W I NORTHERN ENGINEERING Project Name The Slab Project Number 1033-002 Basin I Basin S2 w rBIC—RETENTION SAND MEDIA ..o..:o`,C"o"o` o' `GEOTEXT LE _oOCoo'Doo Oocol FABRIC "o0 0 DOOCoo So. —PEA GRAIL (RAVEL LAYERJ MEETING CDOT #4 COARSE AGGREGATE SPECIFICATION. Bio-Swale Width: 5.5 ft. Bio-Swale Length: 122 ft. Overall Basin Area: 9,211 sq. ft Impervious Area: 6,452 sq. ft PERFORATED RDPE UNDERDRAIN Bio-Swale Surface Area 671.0 sq. ft 10:1 Impervious Runon Area 6,710.0 sq. ft ■V NORTHERN ENGINEERING ADDRESS: PHONE: 970.221.4158 WEOSRE: 200 S. College Ave. Suite 10 Fort Collins. C080524 FAX: 970.221.4159 w .northerneogineering.com Project Title Lake Street Apartments Project Number 1232-001 Client Basins Basins S3 & S4 WQCV =a 0.91i`—1.19i2 +0.78i WQCV = Watershed inches of Runoff (inches) a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = 1,/100) 0 0 0 0 0 0 0 0 0 O N A Q1 J 0 0 0 0 0 0 M 0 0 0 Total Imperviousness Ratio (i = I,,,a/100) Date: June 22, 2016 Calcs By: C. Snowdon _ 12 hr a = 0.8 73.00% 0 0 .- ro io 0 0 0 0 Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event V — WQCV 1 A 0.15 ac 12 � V = 1 0.0030 ac-ft 129 cu. ft. V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) 1 7/14/2016 User Inputs ADS StormTech Design Tool StormTech• ❑ . �,,.nurR4lA• rwnry ... MIT Chamber Model SC-160 Outlet Control Structure Yes (Outlet) Project Name The Slab - Basin S3 & S4 Project Location Fort Collins Project Date 07/15/2016 Engineer Northern Engineering Measurement Type Imperial Required Storage Volume 129 cubic ft. Stone Porosity 0% Stone Above Chamber 6 in. Stone Foundation Depth 6 in. Average Cover Over Chambers 14 in. Design Constraint LENGTH Design Constraint Dimension 120 ft. Results Svstem Volume and Bed Size Installed Storage Volume 130 cubic ft. Storage Volume Per Chamber 6.85 cubic ft. Number Of Chambers Required 19 each Number Of End Caps Required 4 each Rows/Chambers 1 row(s) of 16 chamber(s) Leftover Rows/Chambers 1 row(s) of 3 chamber(s) Maximum Length 120.06 ft. Maximum Width 6.77 ft. Approx. Bed Size Required 573 square ft. System Components Volume Of Excavation (Not Including 57 cubic yards Fill) Non -woven Fitter Fabric Required 182 square yards Length Of Isolator Row 115.9 ft. Geogdd NA square yards Woven Isolator Row Fabric 103 square yards PAVEMENT LAYER (DESIGNED BY SITE DESIGN ENGINEER) � I 1 r(150.1 1A1e uuu, n..w.vmvn (omm�..m MIN I350 rmm1 (3.0 m) MN' MAX I 17 1000 mml I DESTONE BE DETERMINED 8Y9ITE DESIGN 12-P00 mm) ENGINEER B'ft 50 mm1 MIN' ADM mmI TYP NO SPACING REQUIRED SINGLE LAYER OF GEOGRIO aXI24GG TO BE ' A MINIMUM OF 4'1100 mm10F BETWEEN CHAMBERS INSTALLED BETWEEN NON MAVEN GEOTE%TILE FOUNDATION STONE CAN BE USED WHEN AND BASE STONE WHEN BETWEEN 4' AND T OF PLACING GEOGRID M124GG ON THE FOUNDATION STONE IS USED BOTTOM OF THE FOUNDATION STONE ® ADS StormTech 2015 ' http://sLormtechcalc.azurmebsitm.nett 1/1 Project: The Slab - Basins S3 & S4 1♦ 6 Chamber Model - StorMTech- SC-160 Units- I im 100 100 v.! .,�..rwpm Number of chambers - 19 voice in the stone (oamsity) - 0 Base of STONE Elevation - 0.00 N IMiwc rer"ner`" wane m t�euu�lroas Amount of Stone Above Chambers - 6 is Amount of Stone Below Chambers - 6 Ilk StormTech SC-160 Cumulative Sicl Height of Incremental Single IraremeMal Incremental Incremental Ch Cumulative System Chamber Total Chamber Slone I & St Chamber ElmaBoo inches cubic reerI cubic lee( foublic feet tcubk fast cubic feet 24 uDV VDU uuu 23 0.00 MID 0.00 0.00 130.22 192 22 0.00 0.00 0.00 0.00 130,22 1.83 21 0.00 0.00 0.00 0.00 130.22 1,75 20 0.00 0.00 0.00 0.00 130.22 1.67 19 0.00 0.00 0.00 0.00 130.22 1.58 18 0.05 0.97 0.00 0.97 130.22 1,50 17 0.13 2.55 0.00 2.55 129.25 1.42 16 0.29 5.52 0.00 5.52 126.69 1.33 15 0." 8.40 0.00 8,40 121.17 1.25 14 0.54 10.24 0.00 10.24 112.77 1,17 13 0.62 11.71 0.00 11,71 102.53 1.08 12 0.68 12.93 0.00 12.93 90.82 1.00 11 0.74 13.98 0.00 13.98 77.88 0.92 10 0.78 14.88 0.00 14.88 63.90 0.83 9 0.82 15.67 0.00 15.67 49,02 0.75 8 0.86 16.35 0.00 16.35 33.35 0.67 7 0.89 17.00 0.00 17-00 17.00 0.58 6 OM 0.00 0.00 0.00 0.00 0.50 5 0.00 0.00 0.00 0.00 0,00 0.42 4 0.00 0.00 0.00 0.00 0.00 0.33 3 0.00 0.00 0.00 0.00 0.00 0.25 2 0.00 0.00 0.00 0.00 0.00 0.17 1 0,00 0.00 0.00 0.00 0,00 0.08 NorthernEnaineerina.com 11 970.221.4158 1 T CIVIL ENGINEERS Jy I ' August 27, 2007 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 1435 WEST 29" STREET L'OVELAND, C0 80538 (970) 461-2661 FAX (970) 451-2665 WWW.DMWCIVILENGINEERS.COM ' Re: Final Drainage Report for Observatory Park Fort Collins, Colorado Dear Staff: DMW Civil Engineers is pleased to submit this drainage study for Observatory Park for your review. This report complies with technical criteria set forth in the City of Fort Collins' Storm Drainage Design Criteria and Construction Standards manual and the Urban Storm Drainage Criteria Manual, Volume 3, by the Urban Drainage and Flood Control District. We acknowledge that the City of Fort Collins' review of this study is only for general conformancewith submittal requirements, current design criteria and standard engineering principles and practices. If you should have any questions or comments as you review this report, please feel free to contact me at your convenience. INSincerely, DMW CIVIL ENGINEERS, INC. 11 » 9 3388v� Jade P. Miller, P.E. (CO #33885) Project Engineer unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydoes.fcgov.com r. 1 1 1 u 1 1 1 I Drainage Design Considerations Observatory Park August 27, 2007 DMW Civil Engineers, Inc. parking area. Stormwater runoff then travels through a curb opening and into Detention Pond 2. Stormwater runoff from the north half of the roof of the proposed building will be conveyed directly to Detention Pond 2 via a roof drain system and an 6" discharge pipe. The 100-yr WSEL for Detention Pond 2 causes ponding in the parking lot, there is more discussion on this in the detention portion of this report. The site -generated, peak 2 and 100-year flows from Basin 2 are 2.3 and 9.6 cfs, respectively. The peak 2 and 100-year inflows to Detention Pond 2 from Basins 0-2 and 2 are 1.6 and 7.5 cfs, respectively Basin 3 (0.17 acres) consists of parking area and landscaping to the west of the proposed building. Basin 3 drains overland to a low point in the southwest comer of the parking area. Runoff is conveyed through a curb cut and a grated inlet to a 12" storm sewer which conveys flows to Detention Pond 4. Calculations for the curb opening and storm pipe capacity are attached in Appendix B. The peak 2 and 100-year flows from Basin 3 are 0.3 and 1.5 cfs respectively. Basin 4 (0.28 acres) consists of the southern half of the proposed building roof and Detention Pond 4. Runoff from Basin 4 drains overland to a swale north of the proposed right-of-way and sidewalk which conveys flows to the east to a proposed grated storm inlet. Stormwater runoff from the south half of the roof of the proposed building will be conveyed to the proposed storm sewer via a roof drain system and an 6" discharge pipe. The proposed storm sewer discharges runoff into Detention Pond 4. The peak 2 and 100-year flows from Basin 4 are 0.5 and 2.4 cfs respectively. The peak 2 and 100-year flows into Detention Pond 4 from Basins 3 and 4 are 0.9 and 3.9 cfs respectively. . Basin 5 (0.31 acres) is comprised entirely of the northern portion of West Prospect Road and right-of-way that is adjacent to the site. Runoff from Basin 5 drains overland to the northern curb and gutter on Prospect. The peak 2 and 100-year flows from Basin are 0.5 and 2.1 cis respectively. It is not possible for stormwater runoff from this basin to enter Detention Pond 4 and is, therefore, being released undetained. 5.3 Detention Detention Pond 2 is located at the northeast corner of the Observatory Park site and will detain flows within landscaped as well as parking areas. The pond will utilize a single stage release consisting of a 12" diameter HDPE outlet pipe with an orifice plate with a 2.25" diameter hole. Detention Pond 2 provides 7686 cubic feet of volume to detain the peak 100-year developed discharge from the site and release it at the existing 2-year rate of 0.2 cfs. The allowable release rate for Detention Pond 2 was determined by taking the existing 2-year peak flow of 0.8 cfs and subtracting the 0.1 cfs and 0.5 cfs 100-year peak, undetained releases from Page 4 's unofficial copy was downloaded on Mar-02-2015 from the City of FortCollins Public Records Website: hap://citydocs.fcgov.com .___ � a:<___�. n_s__ _.:__._.___m_a_..____.__.__ ______._ _..i.:—.._o r._...i.ou_ _..i.xun.: __.nmw_ _ �.n�_..n_�.c+_u�__n�.oncn •_nn�_ I I 1 I 1 1 Drainage Design Considerations Observatory Park August 27, 2007 DMW Civil Engineers, Inc. Basins 1 and 01, respectively. The required water quality volume for this pond is 2091 cubic feet. The 100-yr water surface elevation is 5024.00. Detention pond calculations are included in Appendix C. Detention Pond 4 is located at the southeast comer of the Observatory Park site between West Prospect Road and the existing residence at 730 West Prospect Road. The pond will utilize a single stage release consisting of a 120 diameter HDPE outlet pipe with an orifice plate with a 2.75" diameter hole. Detention Pond 4 provides 3153 cubic feet of volume to detain the peak 100-year developed discharge from the site and release it at the existing 2-year rate of 0.3 cfs. The allowable release rate of Detention Pond 4 was based on the 2-year release rate of the existing onsite basins; runoff from Prospect Road is allowed to free release, without detention. The required water quality volume for this pond is 871 cubic feet. The 100-yr water surface elevation is 5021.40.. Detention pond calculations are included in Appendix C. 5.4 Erosion Control Plan and Criteria The erosion control plan presented here is intended to control rainfall erosion. The Erosion Control Reference Manual for Construction Sites (ECRM), City of Fort Collins, has been referenced for this erosion control plan. The proposed rainfall erosion control plan during construction will consist of temporary structural erosion control measures. Temporary sediment control consisting of silt fencing will surround areas of the proposed construction. A vehicle tracking area will be used during construction as well as a straw bale barrier at the northeast corner of the site: See the Grading and Erosion Control Plan for locations of proposed erosion control measures. In addition to silt fence, Detention Pond 2 and Detention Pond 4 will both be utilized as a sediment basin for additional sediment control during construction. All temporary structural sediment control measures shall be inspected and maintained as needed after every storm event. See the Grading and Erosion, Control Plan for locations of proposed sediment control measures. Erosion Control calculations are included in Appendix D. 5.5 Water Quality Structural Best Management Practices (BMPs) are proposed for the Observatory Park site to improve water quality of runoff as recommended by the Urban Storm Drainaae Criteria Manual. The detention ponds incorporate extended detention basins for water quality purposes. An extended detention basin (EDB) is a sedimentation basin which uses a much ' smaller outlet that extends the emptying time of the more frequently occurring runoff events to facilitate pollutant removal. Soluble pollutant removal can be somewhat ' Page 5 's unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com I 1 1 I 1 C 1 i I 1 11 1 I I I t No Text k� g w . � k § m ® �c 2k § o � � cc � o a c V cc � ■ ■ � � � 0 tn9Wino o0000 J% 0 § k .. ° � § / cc 0. k � « e (0a cc a. 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O ci �C 000 0 a o MI. N 0 0 0 0 0 m O OOp O O O O m o m N OfAA00 8 CD C Qzm < � cna00v Q gr J V N N o o ` M IV A A O �1 OL n O A .a�OW3 j� 00000 0000c 0 0 0 0 0 y 00000 0000o pig N O O O O O 0 0 0 0 0 3 y 000 OFF, J gg O .. ft;� v v Cn to fo O "W — i►��$ m 0m�=1 m zl 7 0 m m m' a to n m F =T a m_ m fD H V N N N< n 0 W O o a CL 4 -4 m m ao O O t� C/ I 1 . r NorthernEnaineerina.com // 970.221.4158 T • • I N C O R P O R A T E D March 9, 2016 Maxiiimo Development Group 706 South College Avenue Fort Collins, Colorado 80524 Attn: Christian Bachelet Subject: Subsurface Investigation and Hydraulic Conductivity Testing 808 West Prospect Road Fort Collins, Colorado CTLIT Project Number: FC07161-125 CTLIThompson, Inc. has conducted a subsurface investigation and hydraulic conductivity testing at 808 West Prospect Road. The purpose of our investigation was to determine relevant soil and infiltration characteristics at the project location to inform possible construction of a dry well drain system. This letter presents the results of our investigation. Subsurface Investigation Our investigation included drilling three exploratory borings and six hydraulic conductivity test holes at the locations shown on Figure 1. Our exploratory borings were drilled to a depth of approximately 20 feet. Hydraulic conductivity test holes were drilled to depths between 71/2 and 15 feet as needed to test different soil layers. The hydraulic conductivity test holes were fitted with slotted PVC pipes to facilitate testing. A representative from our firm observed drilling, logged the soils encountered and collected samples. Samples were taken at 21/2 to 5 foot intervals by driving a 2.5-inch O.D. modified California sampler 12 inches. This method is similar to the standard penetration test and is typical of local practice. Summary logs of the borings, including results of field penetration testing, are shown on Figure 2. Samples were return to our laboratory and examined by the geotechnical engineer for this project. Laboratory tests were assigned, including moisture content, dry density, gradation and Atterberg limits tests to classify the soils. Results of laboratory tests are given on Figure 3 and summarized in Table 1. Subsurface Conditions Soils encountered in our borings consisted of 12 to 20 feet of sandy clay with layers of clayey sand overlying cleaner sands with occasional gravel. The upper 1 to 2 feet of material in all three borings was identified as probable fill. Groundwater was encountered in one boring during drilling at a depth of 19 feet, and was measured in two borings several days after drilling at depths of 18'/2 and 19 feet. I I I I 11 I IL J I 400 North Link Lane I Fort Collins, Colorado 80524 Telephone:970-206-9455 Fax:970-206-9441 11 1 I I I 1] 1 T Fines contents (percent passing No. 200 sieve) measured in laboratory varied from 53 to 78 percent for the upper clayey materials. Fines contents of about 15 percent were measured in the cleaner, underlying sands. Hydraulic Conductivity Testing Falling head, open hole conductivity tests were conducted at the six hydraulic conductivity test holes. Tests were conducted by adding water and measuring the change in water depth over consecutive time intervals. Results of our testing are presented in Table A below. TABLE A SUMMARY OF HYDRAULIC CONDUCTIVITY TEST RESULTS Bottom of Test Hole (ft) Hydraulic Conductivity (fUyr) Hydraulic Conductivity (cm/s) P-1 8 631 6 x 10 ` P-2 15 184 1.78 x 10-^ P-3 8 215 2.08 x 10 " P-4 15 463 4.47 x 10-4 P-5 71/2 175 1.69 x 10-1 P-6 15 69 6.66 x 10-5 We appreciate the opportunity to work with you on this project. Please do not hesitate to contact us with any other questions or concerns. Sincerely, CTLITHOajMPSON INC Brendan P. Moran, El Staff Geotechnical Engineer Spencer Schr Geotechnical MAXIIIMO DEVELOPMENT GROUP 2 808 WEST PROSPECT ROAD CTL I T PROJECT NO. FC07161-125 APPROXIMATE SCALE: 1" = 120' 0' _6�0' 120. LEGEND: INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING INDICATES APPROXIMATE LOCATION OF INFILTRATION TEST r MAXIIIMO DEVELOPMENT GROUP 808 WEST PROSPECT ROAD CTL I T PROJECT NO. FC07161-125 8 L lie 4 Prospect Road Locations of Exploratory Borings ' and Infiltration Tests FIGURE 1 , d 1 1 1 1 k CO) C 1 ii.nsF��gn w uwwawuw 8 X N N IJ N M o $5 g m f! N i� 0> oO > o No Text Cl I 1 I 1 1 11 p 1 v 0 0 CID o ____?_x m O mm 0 0 N w w o Go vw C) mC z �u �m 0 m z w N O A L r D �w rwi N �Qm W -n m zc� cn �N v Ln O cn w cn u, m<o m cnm �m mtioz o � (n 0 cn Cr) D Z Z r < < p < p < D D n D n (n 0 0 < 0-< < O-< O < cn { { 0 r r G) cn r A � v G � m o z < n USDA United States Department of Agriculture N RCS Natural Resources Conservation Service A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Larimer County Area, Colorado The Slab October 6, 2015 1 Preface ISoil surveys contain information that affects land use planning in survey areas. They ' highlight soil limitations that affect various land uses and provide information about, the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, ' conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. ' Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area ' planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nres.usda.govtwps/portal/ nres/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (http:// offices. sc.egov.usda.govAocator/app?agency=nres) or your NRCS State Soil Scientist (http://www.nres.usda.govtwps/portal/nres/detail/soils/contactus/? cid=nres142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil I Survey. Information about soils is updated periodically. Updated information is available 1 through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means I for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 i i i i i i i i i i i i Contents Preface....................................................................................................................2 How Soil Surveys Are Made..................................................................................5 SoilMap..................................................................................................................7 SoilMap................................................................................................................8 Legend..................................................................................................................9 MapUnit Legend................................................................................................10, Map Unit Descriptions........................................................................................10 Larimer County Area, Colorado......................................................................12 3—Altvan-Satanta loams, 0 to 3 percent slopes.........................................12 Soil Information for All Uses...............................................................................14 Soil Properties and Qualities..............................................................................14 Soil Qualities and Features.............................................................................14 Hydrologic Soil Group (The Slab)................................................................14 References............................................................................................................19 i 4 I I How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the ' surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. , Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, , soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is , related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil -vegetation -landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock , fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic ' classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil scientists classified and named the soils in the survey area, they compared the I Custom Soil Resource Report ' individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and ' research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have I similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is ' needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. ' The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil - landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil -landscape model is refined, a significantly smaller number of ' measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of ' ' characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field -observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable overlong periods of time, but they are not predictable from year to year. For example, soil ' scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. 1 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit; and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 7 a Custom Soil Resource Report Soil Map N 492270 4a22gp 492330 492330 492351 40° 39'TN $Rj — .. �T.r-( ♦�T. F'- Ti lv% 1 I 1 E - y r T fir! IL Vl, Far 1 ' 1 1 1 Iffi70 492M 492310 492330 s 49239C N MmSaft1:WVpk d mApaMalC(&Vx11') MM w Mks N 0 10 ZO 40 6f1 Feet 0 45 90 180 270 Map poje[llan: Web MnCahir Qm mardhatrs: WGSB4 Edge Ga: UTM Zm 13N WGS84 8 492370 492390 F, o- is. I I C I C O 1] 1 r O m C O) m y W y o p m N m � O m= C O y V W O q Q' m W (V J y L0 O e m m 0 U m� v� m 2y m m m 9 m 3 C JOG m my O L aDi o y c6E D mu c°+ A w W E W nh�o m D m E ev m rn J m m O` 3i 5 M= n a N Nq o m E O W m m GD L.. m N Vml fn p E m m N LJ (mpS M Tm C O 0 J U p V p Q j m 3 w E W W m o Z y D m Z a o Z U o N ^ E m Q $ m m E W O m W y C m J J Q m 3 m L _ N0. la co Q D mm NOmOW° LE =DD Q5E _m W C � m C. WW OOO mGmm LL 0To E9 LnGWm`m mm Z cm L om o' m 22 ` m m0 � my Qu m Dm c md m m3 nnaE Q ¢. J> E omi Q m o Ho Emm= 5 mm $� mma .0 mw m E oa a. i. cti-� oc m2 0 nm oD gcm oho. .y mm� m 6NA oommo o° z� rto''am c E'9 EF wm uNE m�''c L^2 nm Nv EQ' y t m c,m'_mo mm '°m °o m'o wnm tmomo �' `O �o sE W F 3 w E n m n. E v1 3 U E$ o a m f- £ co y rn a m m m m N c U y m t L n m m W � S � n m E° m O L a m m—' m c « 1'0 m z t O a m rr O W ` « A l 0 3 r m W J CL Q ¢ 0 m p o m m g m 5 °`° a � a « m m E E m 3 � d m c m n n m Z5O LL T m n c a o p12 Yj d c o 0 0°'m rn rn m p m m U U c7 c7 E i a K m m m iq in to 9 a m N n 1 I Custom Soil Resource Report Ci i 1 I C 1 1 Map Unit Legend urimer County Area, Colorado (C0044) r - .:-wh ✓Q'k.71.3isk,k ,"�.: fi, 1 4 9 S Map Unit Symbol Map Unit Nam ar Aeies In AOI `Y Percent of AO m 3 Altvan-Satanta loams, 0 to 3 1.9 100.0% percent slopes Totals for Area of Interest 1.9 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits forthe properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic Gasses. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness ' or accuracy of the data. The objective of mapping is not to delineate pure taxonomic Gasses but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. 10 Custom Soil Resource Report An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam; 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha - Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. 11 Custom Soil. Resource Report Larimer County Area, Colorado ' 3—Altvan-Satanta loams, 0 to 3 percent slopes ' Map Unit Setting National map unit symbol. jpw2 Elevation: 5,200 to 6,200 feet Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost -free period. 135 to 150 days Farmland classification: Prime farmland if irrigated ' Map Unit Composition Altvan and similar soils: 45 percent Satanta and similar soils: 30 percent ' Estimates are based on observations, descriptions, and trehsects of the mapunit. Description of Altvan Setting ^ Landform: Benches, terraces Landform position (three-dimensional): Side slope, tread Down -slope shape: Linear Across -slope shape: Linear Parent material: Mixed alluvium 1 Typical profile H1- 0 to 10 inches: loam H2 - 10 to 18 inches: clay loam, loam, sandy clay loam H2 - 10 to 18 inches: loam, fine sandy loam, silt loam H2 - 10 to 18 inches: gravelly sand, gravelly coarse sand, coarse sand H3 - 18 to 30 inches: H3 - 18 to 30 inches: H3 - 18 to 30 inches: H4 - 30 to 60 inches: H4 - 30 to 60 inches: H4 - 30 to 60 inches: Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding. None Calcium carbonate, maximum in profile: 10 percent Available water storage in profile: Very high (about 13.2 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonir igated): 3e Hydrologic Soil Group. B 1 12 Custom Soil Resource Report Description of Satanta Setting Landforrn: Terraces, structural benches Landform position (three-dimensional): Side slope, tread Down -slope shape: Linear Across -slope shape: Linear Parent material. Mixed alluvium and/or eolian deposits Typical profile H1 - 0 to 9 inches: loam H2 - 9 to 18 inches: loam, clay loam, sandy clay loam H2 - 9 to 18 inches: loam, clay loam, fine sandy loam H2 - 9 to 18 inches: H3 - 18 to 60 inches: H3 - 18 to 60 inches: H3 - 18 to 60 inches: Properties and qualities Slope: 0 to 1 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Available water storage in profile: Very high (about 27.4 inches) Interpretive groups Land capability classification (irrigated): 1 Land capability classification (nonirrigated): 3c Hydrologic Soil Group: B 13 I 1 1 1 Soil Information for All Uses 1 ' Soil Properties and Qualities The Soil Properties and Qualities section includes various soil properties and qualities 1 displayed as thematic maps with a summary table forthe soil map units in the selected area of interest. A single value or rating for each map unit is generated by aggregating the interpretive ratings of individual map unit components. This aggregation process 1 is defined for each property or quality. 1 Soil Qualities and Features Soil qualities are behavior and performance attributes that are not directly measured, but are inferred from observations of dynamic conditions and from soil properties. Example soil qualities include natural drainage, and frost action. Soil features are attributes that are not directly part of the soil. Example soil features include slope and depth to restrictive layer. These features can greatly impact the use and management 1 of the soil. Hydrologic Soil Group (The Slab) 1 Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long - duration storms. 1 The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: 1 Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly 1 wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. 1 Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. 1 1 14 Custom Soil Resource Report Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when ' thoroughly wet. These consist chiefly of clays that have a high shrink -swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have ' a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group WD, B/D, or C/D), the first letter is for , drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. I I I 15 1 Custom Soil Resource Report Map —Hydrologic Soil Group (The Slab) pN yy C ti 492270 492290 492310 492330 49M s Map Scale: 1:9469pFOed w A plrhalt(W x 11') Meet N -- — M'h!s 0 10 2D 40 60 Fee 0 46 90 180 270 Mep pOj8dLb : Nkb I W CNb Cana Coordinates: WG584 Edge Um: UTM ZOne 13N WGSB4 16 11 iQ' 30'TN %$T l I a S s E� am 3J' 1' N 492370 492390 s u { ) \ § 0 -j $ ■ � |!)) ) :a0zrn f{ƒ],$ 000,\ {� c ° ; . 00z f` ! M |/j;HOgOgggg§! ��■|�;f■■■■ Custom Soil Resource Report 1 1 1 1 1 1 1 Table —Hydrologic Soil Group (The Slab) U,rimer County Aa,.CooredoHydrologic Soil Group=sumry lre(C0644) _ Map unit symboTAJtvan-Satanta ap unit name ,Rating Acres in AOI percent of AOI. 3 loams, 0 percent slopes B 1.9 100.0% Totals for Area of Interest 1.9 100.0% Rating Options —Hydrologic Soil Group (The Slab) Aggregation Method., Dominant Condition Component Percent Cutoff., None Specified Tie -break Rule: Higher 18 a References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep -water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nres.usda.gov/wps/portal/nres/ detail/national/soils/?cid=nres 142p2_054262 Soil Survey Staff.1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook436. http:/twww.nres.usda.govtwps/portal/ nres/detail/national/soils/?cid=nres 142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http://www.nres.usda.govtwps/ portal/nres/detail/national/soils/?cid=n res 142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nres.usda.gov/wps/portal/nres/detail/soils/ home/?cid=n res 142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nres.usda.gov/wps/portal/nres/ detail/national/landuse/rangepasture/?cid=stet prdb 1043084 Custom Soil Resource Report 1 United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nres.usda.gov/wps/portal/ nres/detail/soils/scientists/?cid=nres142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http:/twww. nres. usda.govtwps/portal/nres/detail/national/soils/? cid=n res 142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrr-s.usda.gov/lntemet/FSE—DOCUMENTS/nrcsl42p2_052290.pdf ' 20 NorthernEnalneerina.com // 970.221.4158 NORTHERN ENGINEERING Drainage Letter Report Date: October 21, 2013 ' Project: Lot 2, Observatory Park Subdivision Project No. 1033-002 Fort Collins, Colorado ' Attn: Mr. Brian Hood Colorado State University Research Foundation ' 2537 Research Boulevard, Suite 200 Fort Collins, Colorado 80526 . Purpose This letter serves to provide adequate documentation of the existing and conceptual drainage patterns of Lot 2, Observatory Park Subdivision. Within this study, we will document the historic discharge locations and historic runoff rates for both the minor and major storm events. We will ' also document conceptual discharge locations, developed runoff rates and the detention required to restrict the developed release to the historic 2-year runoff rate. ' Project Location The drainage study area is located in the southwest Quarter of Section 14, Township 7 North, Range 69 West of the 6"' Principle Meridian, City of Fort Collins, County of Larimer, State of 1 Colorado, more specifically Lot 2, Observatory Park Subdivision. The project is located west of Whitcomb Street on the north side of Prospect Road and is currently addressed 714 and 730 West Prospect Road. ' Historic Drainage Patterns Currently there are two existing single family residences with a couple of out buildings. There is an ' existing gravel drive that runs between the two residences supplying access. There is currently a natural ridge line running through the middle of the lot from west to east. Lot 2 historically drains both north and south and historically discharges in both the southeast and northeast comers of the ' property; therefore two basins (Basin HN1 and HS1) were delineated to calculated existing stormwater generated from the site. The northern historic basin (Basin HN1) routes stormwater via overland flow and discharges at the northeast comer at a 2-year release rate of 0.29 cfs and a 100- year release rate of 1.29 cfs. The southern historic basin (Basin HSD routes stormwater via overland flow and discharges at the northeast comer at a 2-year release rate of 0.41 cfs and a 100- year release rate of 1.85 cfs. All existing stormwater is currently released from the site undetained and untreated. An exhibit illustrating the historic drainage patterns and associated calculations have been attached to this memo. ' 301 N. Howes Street, Suite 100, Fort Collins, CO 80521 I 970.221.4158 I www.northernengineering.com W I NORTHERN ENGINEERING Lot 2, Observatory Park Subdivision , Proposed Drainage Patterns A conceptual sketch of the site layout was received from CSU Research Foundation and is attached to this memo for reference. The conceptual layout includes the restoration of the two existing single family residences and the relocation of three additional single family residences to be placed on site. It also shows a shared drive access running down the middle of the site from south to north with associated sidewalks connecting the buildings to the access drive. With the current City of Fort Collins Standards, it is assumed that 25% of the overall access drive and parking area would be composed of permeable pavers. For this analysis it was assumed that the existing ridgeline running west to east would be maintained, creating two developed major basins (Basin S and Basin N) similar to historic the historic basins mentioned above. Basin N1 is assumed to drain stormwater via overland flow and discharge into a proposed detention pond located in the northeast comer of the site. Currently Lot 1 is being processed through the City to resurrect the previously approved design plans for a multi -family residences. Through this design, the increased runoff rate generated from the proposed improvements are to be detained at the southwest corner of Lot 2. It was assumed that a portion of the southern basin would drain to this pond subdividing the southern basin into two basins, (Sub -Basin S1 and S2). Sub -Basin S1 is assumed to drain stormwater via overland flow and discharge into the detention pond proposed for the improvements being proposed for Lot 1 and out fall into W. Prospect Road. Sub -Basin S2 is assumed to drain stormwater via overland flow and discharge into a conceptual detention pond located in the southeast corner of the site and is assumed to outfall into W. Prospect Road. Detention There were three conceptual ponds that were analyzed for this project. Conceptually, one would be located in the northeast corner, second would be located in the southwest comer and the third would be located in the southeast comer. The pond located in the northeast corner would capture the increased runoff from sub -basin N1 and would require 0.06 acre-feet of detention volume. An outfall for this pond is unknown at this time and therefore a conceptual grading analysis was not performed. The pond located in the southeast comer would capture the increase in runoff from sub - basin S2 and would require 0.0345 acre-feet of detention pond. In assuming the outfall to be the gutter of W. Prospect Road, a conceptual grading analysis was performed to better understand the capacity of a conceptual pond located in the southeast corner of Lot 2. Below is a table summarizing the results of the southeast detention pond. Required Water Water Quality Required 1100-year High Water Quality Storage Surface Detention Volume Total Detention Surface Top of Pond Basin ID (ac-ft) Elevation (ft) (ac-ft) Volume (ac-ft) Elevation (ft) Elevation (ft) Off -Site 0.005 5020.72 Q0300 0.0345 5021.89 S023.00 Southeast Pond Table 1- Southeast Detention Pond Summary The pond located in the southwest corner was analyzed to capture the increase in runoff from sub - basin S1 and the proposed increase in runoff from the improvements being proposed within Lot 1. The increase in runoff from sub -basin S1 would require 0.0345 acre-feet of detention volume. The increase in runoff from Lot 1 would require 0.1155 acre-feet of detention volume. For both Lot 1 and 2 to utilize this pond, the southwest pond would require a total detention volume of 0.1472 acre-feet. A grading plan is currently under review with the City for Lot 1 to adequately handle the overall detention volume. Below is a table summarizing the results of the detention pond. Conceptual Drainage Analysis 2 , NORTHERN ENGINEERING Lot 2, Observatory Park Subdivision Total Detention Required Water Water Quallty Required 100-year Volume (ac-ft) High Water Quality Storage Surface Detention Volume (w/ 0.1155 ac-ft Surface Top of Pond Basin ID (ac-ft) Elevation (ft) (ac-ft) from Lot 1) Elevation (ft) Elevation (ft) Off -Site 0.0042 Southeast Pond 5022.960 0.0275 0.1472 5025.72 5025.80 Table 2 — Southwest Detention Pond Summary Conclusion In concluding, the design of Lot 1 and current configuration of the southwest pond should be adequately sized to handle increased runoff from Lot 1 and the assumed drainage patterns of Lot 2. It has been assumed the historic ridge line will be remain. The southeast pond, through the use of walls, should have adequate space to supply the required detention for the southeastern portion of Lot 2. The northern pond should have adequate space to detention the required detention volume, but outfall has not been determined and therefore, a grading analysis was not performed. If you should have any questions as you review this report, please feel free to contact us. Sincerely, Northern Engineering Services Inc. Co Pnowdon` Project Engineer Conceptual Drainage Analysis 3 tl V X rt , V r ie 1 _ J ti. 4 , NorthernEngineerinq.com // 970.221.4158 II EXISTING SINGLE FAMILYi ,RESIDENCE f OWNER: COLORADO FARM HOUSE ASSOCIATION HN1 .2304 0.562 L TXLSTING GRAVEL DRIVE - EXISTING AUXILIARY Ar,.W BUILDING -EXISTING SINGLE FAMILY RESIDENCE J o r\\--7ixlSTING GP. �VdL DRIVE =I_1.-m4w4 W. PROSPECT ROAD 40 0 40 (IN FEET) 1 INCH = 40 FEET N 7th. 2015 f t. c o I I i n s c 0 NORTHERN ENGINEERING I I I I I I I I 11 / I I I I E) LO cli /00 �04% §§) fo ./ ear /j0 m c t�>1a �k ��t�6§§ 2 _ � a\ a��o o v �j\ f � 3 �a_2�mm U § �((!I tom Lai U $§3��A4$ LA. k M k 8 m CL k go @@] Au § 00 10 cm saaa^ o aa 2§. / � k k �2 600CA §§] k \k\ k 2 :.tj (�2 �$— � Soco 0 Lai 2�0 ° )(� % ' �22000 q8@ � (:E k:(;! © lbi k): %NK ■:({ -a 2 'A§(ii)i\�:a LL § §2 C3cl 6 � a No Text I I I I I I n � I I I I I I I ! ■!# m2 �_ � � JQ�f� c § . £®# N ,7! k)/ o0 &! iƒk[46. � 2 � S � | / 2 2 � Lu � , a \\ � ; }■;� � a:,�� R�� 7 00 ;\ s-- 3- ! ■I�k== 2 | j All K � | k - } Q , . � �� .� � �2 y .§ 0 � a I I I I I I I I I I I I I I I w I NorthernEnninaerina.com 11 970.221-4198 n,',' i 7th, 2015 Nu J OWNER: COLORADO FARM HOUSE ASSOCIATION F--, �-� mmir-owm PERMEABLE PAVERS SIDEWALKCHASE- W. PROSPECT ROAD 40 0 40 1 1 ( IN FEET) 1 INCH = 40 FEET NORTHERN ENGINEERING —fWA F D_ O, a= z Of 0 oI 0 0l z U) 0O m Z) NORTH DETENTIOP POND QV ' LU LU , Z Q 0 ' D_ W Z O ' SOUTHEAST ' DETENTION POND SIDEWALK CHASE ft.collins cl 1 11 1 rn e_e 3 t7 N A n n m w O N R r y sr O C �a S S R g W 3 l9 N 14 W 7 fT N fn N W V W 0 � $ T 3 06 :-- O O O O r+OINw to fn W W 01 0fn0 V CA M n O `� 8 O O C O C C 9 N O V V W N AA In W ..,X� y ' m 000 O O' OR(n0wrl) tO fn V O to W A :i S n C C V p Cp G C 70 a y v 00 N 00000C Ato WtO to O � V fT � ANO OD N to .n.. o fn W OfnOfnfn n N fQ/�� tY w N K O O O 00 W 3 00 Nw top 3 A y y 00000 �� a 0000 o a a m 3 O 0 O 0 O 0 O 0 O 0 � C C Z W A 000 OD 0 00 01 M V ;I� C o 3 : � W O1 O m fAn A tNO n 0 0o a fa o (_� ;cu y 00000 �P.tWo tAO NN O W .� u w m e C 000P.0 c 3 0 oN r to tAON N O 00i y 00000 (� O~ c3 0 43 c• O j y * �ACt to Atn O N ff 4 ,go m P NO.O tl O 0 � N � N O � fn m OD V OODD too 9 Z I I i I I I I I I I I I I I to Ca I E \i®I=00Ito . ) \'o'o • � _ �&! OX %&& 2 ,»3«gg -- z; 'a' k - ■ 0 k �E 2 $ » A 7- % § f ...;� § § § 00 | | ! � \ / �$I;Q; -m;MWIM ■ B�l�! � - -lcdLdui � o Lul f--§§§ � ■' ~°® k �a f « ) ��f900 , �wq;q; 00 k }k �� \/> £££ aa\ • \_ �$! ] % A � I � % � I I I I [] I � I ? © D 2 coo | 00 , ! � co co .4 ( !�. }00 ID N N f| /C2 2 /�� 0 � a rw7e� k � )!2 § 2 ° ini"bo 00w 0 . � I .m mz 0 }o .q mz �m oz I 8^ fM M a Q vv/1 N ul cn N Cn v O O O C ~ CD N ~ CO 00 E g � a w C1 00 C O O O � '++ Lo M N O a v 0 0 0 Z N Q Z tN to m Z 2z W C c �N n w d � w 0 m Ol O1 a � r D P .n SS NnrfhwrnF nninnarinn.rnm // OJn.JJ1A15A 1 NORTHERN ENGINEERING ' DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Project Number 1033-002 Project Name The Slab Project Location Fort Collins, Colorado Pond No Off -Site North Pond Input Variables Results Design Point nl Design Storm 100-yr C = 0.52 Tc = 10.00 min A = 0.56 acres Max Release Rate = 0.29 cfs Required Detention Volume 2727 ft 3 0.06 aC-ft Time (min) Ft Collins intensity n/hrry Inflow Volume (ft3) Outflow Adjustment Factor QS ( ) Outflow Volume 3 (n) Storage Volume (ft') 5 9.950 869 1.00 0.29 87 782 10 7.720 1349 1.00 0.29 174 1175 15 6.520 1709 0.83 0.24 218 1491 20 5.600 1957 0.75 0.22 261 1696 25 4.980 2175 0.70 0.20 305 1871 30 4.520 2369 0.67 0.19 348 2021 35 4.080 2495 0.64 0.19 392 2104 40 3.740 2614 0.63 0.18 435 2179 45 3.460 2720 0.61 0.18 479 2242 50 3.230 2822 0.60 0.17 522 2300 55 3.030 2912 0.59 0.17 566 2346 60 2.860 2998 0.58 0.17 609 2389 65 2.720 3089 0.58 0.17 653 2437 70 2.590 3168 0.57 0.17 696 2472 75 2.480 3250 1 0.57 0.16 740 2510 80 2.380 3327 0.56 0.16 783 2544 85 2.290 3401 0.56 0.16 827 2574 90 2.210 3475 0.56 0.16 870 2605 95 2.130 3535 0.55 0.16 914 2622 100 2.060 3599 0.55 0.16 957 2642 105 2.000 3669 0.55 0.16 1001 2669 110 1 1.940 3729 0.55 0.16 1044 2685 115 1.890 3798 0.54 0.16 1088 2710 120 1 1.940 3858 0.54 0.16 1131 2727 'Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. l- t 1 1 L 1 I 1 1 1033-001_Off-Site North_DetentionVolume_FAAModified Method.xls Page 1 of 1 1 NORTHERN ' �NGI VEER NC� 1 1 1 1 1 I DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Project Number 1033-002 Project Name The Slab Project Location Fort Collins, Colorado Pond No Off -Site Southwest Pond Input Variables Results Design Point s1 Design Storm 100-yr C = 0.40 Tc = 7.00 min A = 0.37 acres Max Release Rate = 0.20 cfs Required Detention Volume 1199 ft3 0.03 ac-ft Time (min) Ft Collins 100-yr Intensity n/hr Inflow Volume (ft3) Outflow Adjustment Factor Oar (cfs) Outflow 3 Volume (ft) Storage Volume (ft3) 5 9.950 442 1.00 0.20 60 382 10 7.720 686 0.85 0.17 102 584 15 6.520 868 0.73 0.15 132 736 20 5.600 995 0.68 0.14 162 833 25 4.980 1106 0.64 0.13 192 914 30 4.520 1204 0.62 0.12 222 982 35 4.080 1268 0.60 0.12 252 1016 40 3.740 1328 0.59 0.12 282 1046 45 3.460 1383 0.58 0.12 312 1071 50 3.230 1434 0.57 0.11 342 1092 55 3.030 1480 0.56 0.11 372 1108 60 2.860 1524 0.56 0.11 402 1122 65 2.720 1570 0.55 0A 1 432 1138 70 2.590 1610 0.55 0.11 462 1148 75 2.480 1652 0.55 0.11 492 1160 80 2.380 1691 0.54 0.11 522 1169 85 2.290 1728 0.54 0.11 552 1176 90 2.210 1766 0.54 0.11 582 1184 95 2.130 1797 0.54 0.11 612 1185 100 2.060 1829 0.54 0.11 642 1187 105 2.000 1865 0.53 0.11 672 1193 110 1 1.940 1895 0.53 0.11 702 1193 115 1.890 1930 0.53 0.11 732 1198 120 1.840 1 1961 0.53 1 0.11 762 1 1199 'Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. 1033-001_Off-Site Southwest_DetentionVolume_FAAModified Method.xls ' Page 1 of 1 NORTHERN ENGINEERING Project Title Project Number Client Pond Designation The Slab 232-035 ADDRESS: PHONE: 970,221.4159 J WEBSrrE: 200 S. College Ave. Suite 10 Fort Collins, C080524 FAv/ww,northernengincering.mm X: 970221.4159 CSU Research Foundation Off -Site Southwest Pond WQCV=a 0.91i'-1.19i'+0.78i WQCV = Watershed inches of Runoff (inches) a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = 1 ,o/100) 0.5 0.45 0.4 0,35 0.3 0.25 0.2 0.1 0.05 0 0 0 0 Date: October 21, 2015 Calcs By: C. Snowdon Drain Time 40 h i a= 1 i = 1 19.00% WQCV= 0.111 in Water Quality Capture Volume WQCV = aj 0.9li'—1.19i' + 0.78i) Total Imperviousness Ratio (i = I W,/100) Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event _ WQCV 0.38 ac V *A*1.2 12 MMr0 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) NORTHERN AooREss: PRONE: 970.221 41% wEes TE: ENGINEERING 200 g. Collage Ave. gwte In www,nurdrcrnengnreenng.com Fart Colons, C080524 FAX: 970,221,4158 Project Title The Slab Date: October 21, 2015 Project Number 232-035 Calm By: C Snowdon Client CSU Research Foundation Pond Designatlon Off -Site Southwest Pond 50275a Mf um, 0.0042 ac-ft 300-yr Detention Volume 0.0275 ac- k 7P.ndVolume(w/ 0.1155 0.1472 ac-ft ac-ft from Ya D-IA +A 2+ 4 // D = Depth between contours (ft.) Ar = Surface Area lower contour (ft') At = Surface Area upper contour (ft) OFF -Site Southwest Pond Volume Elevation Surface Incremental Incremental Total Vol. Total Vol. (ft) Area W) I Depth (ft) I Vol. (it) (fl) I (sc-ft) 5022.60 67.03 0,12 2,68 2,68 0.0001 5022.80 474.51 0.20 47.99 50.67 0.0012 5023.00 1230.74 0.20 164.63 215.30 r 0.0049 5023.20 1925.36 2226.46 0.20 0.20 313.03 414.82 528.33 943.15 0.0121 0.0217 5023.40 5023.60 2358.58 0.20 458.44 1401.59 r 0,0322 5023.80 2358.83 0.20 471.74 1873.33 0.0430 5024.00 2359.07 0.20 471.79 2345.12 0.0538 5024.20 2359.32 0.20 471.84 2816.96 0.0647 5024.40 2359.57 0.10 471.99 3298.85 0.0755 5024.60 2359.82 0.20 471.94 3761 0.0863 5024.80 2360.07 0.20 471.99 4232.78 0.0972 5025.00 2360.32 0.20 472.04 47D4.82 0.1080 5025.20 2360.57 0.20 472.09 5176,91 0.1188 5025.40 2360.92 0.20 472.14 5649.05 0.1297 5025.60 2361.07 0.20 472.19 1121.23 0.1405 5025.80 2361.33 0.20 472.24 6593.47 0.1514 Elevation Depth Volume WQCVJ 5022.96 0.48 0.0042 100-yr Detention 5023.51 1.03 0.0275 OverMl Detention 5025.72 3.24 0.1472 Total Vol r Perforatlon Sbdng Da (in.) In - Min 5, 1 n t 1/4 Area/Row 0.05 Required Area 0.049 sq-in Per Row No. of Rows 1 Total Outlet 0.05 sq. in. Area I 1 Total Detention Required Water Water Quality Required 100-year Volume (ac-ft) High Water Quality Storage Surface Detention Volume (w/ 0.1155 ac-ft Surface Elevation Top of Pond Basin ID (ac-ft) Elevation (ft) (ac-ft) from Lot 1) (ft) Elevation (ft) Off -Site Southwest 0.0042 5022.960 0.0275 0.1472 5025.72 5025.80 Pond 1 1 1 i 1 1 1 1 1 I 1 11 1 1 1 1 1 1 I 1 WEIiMI ENGIN r+rv--- Rirve DETENTION POND CALCULATION; MODIFIED FAA METHOD w! Ft Collins IDF Project Number 1033-002 Project Name The Slab Project Location Fort Collins, Colorado Pond No Off -Site Southeast Pond Input Variables Results Design Point s2 Design Storm 100-yr C = 0.61 Tc = 6.00 min A = 0.26 acres Max Release Rate = 0.21 cfs Required Detention Volume 13U7 ft3 0.03 ac-ft Time (min) Ft Collins 100-yr Intensity inlhr Inflow Volume a (ft) Outflow Adjustment Factor 48V cfs ( ) 3 Outflow Volume ft ( ) Storage Volume s (ft) 5 9.950 473 1.00 0.21 63 410 10 7.720 735 0.80 0.17 101 634 15 6.520 931 0.70 0.15 132 798 20 5.600 1066 0.65 0.14 164 902 25 4.980 1185 0.62 0.13 195 989 30 4.520 1290 0.60 0.13 227 1064 35 4.080 1359 0.59 0.12 258 1101 40 3.740 1424 0.58 0.12 290 1134 45 3.460 1482 0.57 0.12 321 1160 50 3.230 1537 0.56 0.12 353 1184 55 3.030 1586 0.55 0.12 384 1202 60 2.860 1633 0.55 0.12 416 1217 65 2.720 1682 0.55 0.11 447 1235 70 2.590 1725 0.54 0.11 479 1246 75 2.480 1770 0.54 0.11 510 1260 80 2.380 1812 0.54 0.11 542 1270 85 2.290 1852 0.54 0.11 573 1279 90 2.210 1893 0.53 0.11 605 1288 95 2.130 1926 0.53 0.11 636 1289 100 2.060 1960 0.53 0.11 668 1292 105 2.000 1998 0.53 0.11 699 1299 110 1.940 2031 0.53 1 .11 731 1300 115 1.890 2068 0.53 0.1 1 762 1306 120 1.840 2101 0.53 0.11 794 1307 'Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. 1033-001_Off-Site Southeast_DetentionVolume_FAAModified Method.xls ' Page 1 of 1 NORTHERN C ENGINEERING ADDRESS: PHONE: 970-221.4158 WEBSRE= 200 S. College Ave. Suite 10 Fort Collins, CO 80524 FAX: 970.221.4159 www.narthamengineering.com Project Title The Slab Date: October 21, 2015 Project Number 232-035 Calcs By: C. Snowdon Client CSU Research Foundation Pond Designation Off -Site Southeast Pond WQCV= 0.9 y3-1.19i'+0.78i40hi 777' WQCV = Watershed inches of Runoff (inches) 38.00% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = l ,q/100) WQCV = 0.174 in 0.5 0.45 ti 0.4 t c 0.35 u 0.3 z d 0.25 3 0.2 0.15 3 0.1 0.05 Water Quality Capture Volume WQCV=a(0.9k'-1.19/'+0.7&) 0 G O O G O O C O G O i, 0 w 0 in it n 0 o 0 0 0 0 0 0 o a o 0 0 0 0 Total Imperviousness Ratio (i = I,/100) Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event Y=AA = 0.26 ac 1 WQC'1.2 J/ V = 0.0045 ac-fIt V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) 1.2 = 20%Additional Volume (Sediment Accumulation) NORTHERN A°0RE'g' PHONE: s2o.zzl.dl g wEBSITE: E N GIN E E R I N G FortC College Are.10 Fort Calllns, CO g0524 2d .northernerlineenng.com FA%: 870.221.d159 Project Title The Slab Date: October 21, 2015 Project Number 232-035 Cale By: C. Snowdon Client CSU Research Foundation Pond Designation Off -Site Southeast Pond - .- 500.17 ft Water QuallryVol 0.0045 ac-ft 100-.yr Detention Vol 0.0300 ac-ft 0.0345 ac-ft Dia v_D'Ar+At+ A�" /3 (in.) n Min Sr J. D. Depth between contours (ft.) n At. Surface Area lower contour (ft) t 1/4 A, = Surface Area upper contour (ft') Area/Row 0.05 Off -Site Southeast Pond`Volum s Elevation Surface Incremental Incremental Total Vol. Total Vol. (ft) Area (;) Depth (ft) Vol. (ft) (ft) (ac-ft) 5020.20 4.86 0.03 0.05 0.05 0.0000 5020.40 236.86 0.20 18.38 18.43 0.0004 5020.60 651.62 0.20 85.42 103.85 0.0024 5020.80 985.44 0.20 162.56 266.41 0.0061 5021.00 1051.55 0.20 203.66 470.07 0.0108 5021.20 1099.14 0.20 215.05 685.12 0.0157 5021.40 1146.24 0.20 224.52 909.64 0.0209 5021.60 1192.71 0.20 233.98 1143.52 0.0263 5021.80 1238.47 0.20 243.10 1386.63 0.0318 5022.00 1283.51 0.20 152.18 1638.81 0.0376 5022.20 1327.89 0.20 261.13 1899.94 O.D436 5022.40 1371.83 0.10 269.96 2169.90 0.D498 5022.60 1415.74 0.20 278.75 2448.64 0.0562 5022.80 1460.54 0.20 287.62 2736.26 0.0628 5023.00 1510.03 0.20 297.04 3033.30 0.0696 Elevation Depth Volume WQCVJ 5020.72 0.55 0.0045 100-yr Deentionj 5021.73 1.56 0.0300 Overall Detentionj 5021.89 1.72 0.0345 , Required Water Water Quality Required 100-year High Water Quality Storage (ac- Surface Detention Volume Total Detention Surface Elevation Top of Pond Basin ID ft) Elevation (ft) (ac-ft) Volume (ac-ft) (ft) Elevation (ft) Off -Site Southeast 0.005 5020.72 0.0300 0.0345 5021.89 5023.00 ' Pond 1 1 FI N.,th.,.Fnoi...6n.,.. 11 970.221.415R ' NORTHERN EN GI NE EN I N 6 The Slab ' A comprehensive 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 shall address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices ' from the Volume 3, Chapter 7 — Construction BMPs will be utilized. Measures may include, but are not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and ' clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall also be provided by the Contractor. ' Grading and Erosion Control Notes can be found on Sheet CS2 of the Utility Plans. The Utility Plans at final design will also contain a full-size Erosion Control Plan as well as a separate sheet dedicated to Erosion Control Details. In addition to this report and the referenced plan sheets, the ' Contractor shall be aware of, and adhere to, the applicable requirements outlined in any existing Development Agreement(s) of record, as well as the Development Agreement, to be recorded prior to issuance of the Development Construction Permit. Also, the Site Contractor for this project will ' be required to secure a Stormwater Construction General Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division — Stormwater Program, before commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor ' shall develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and document the ongoing activities, inspections, and maintenance of construction BMPs. 1 1 Final Erosion Control Report EN 1 ' Stormwater Alternative ComplianceNariance Application ' City of Fort Collins Water Utilities Engineering Engineer Name Nick Haws _ Phone 970.568.5414 ' Street Address 301 N- Howes Street, Suite 100 City Fort Collins State CO Zip 80521 ' Owner Name Colorado State University Research Foundation Phone 970.491.2625 Street Address P.O- Box 483 City Fort Collins State CO Zip 80522 ' Project Name The Slab Project/Application Number from Development Review (i.e- FDP123456) FDP160022 ' Legal description and/or address of property Lot 1 and Lot 2, The Slab Property ' Description of Project- Multifamily with associated parking areas, sidewalks and drive aisles. Project primarily resides on Lot 1 and is approximately 1.4 acres in size. ' Existing Use (check one): residential non-residential mixed -use • vacant ground Proposed Use (check one): residential non-residential mixed -use other ' If non-residential or mixed use, describe in detail The project is proposed as a three-story multi- familiy building, primarily for student housing. Currently there are 61 dwelling units included. 1 State the requirement from which alternative compliance/variance is sought. (Please include applicable Drainage Criteria Manual volume, chapter and section.) Section 4.15(b) What hardship prevents this site from meeting the requirement? The project was previously designed and approved in 2007 (Observatory Park) allowing 18-inches of ponding with the proposed parking area. After approval, the foundation and slab for the first floor were constructed. Due to the constructed foundation, the existing design will need to be maintained and therefore, the same varience approved in 2007 is required again for the revised plans. Attach separate sheet it necessa.r What alternative is proposed for the site? The project is proposing to use the parking area for additional detention volume with depths that exceed the 12-inch maximum. These depths will not exceed 18-inches in the parking area, and the area exceeding 12-inches of ponding will occur within less than twenty-five percent (25%) of the total parking spaces provided. Signage is proposed to warn people that ponding may occur. Arlach sepaate sheet it ne:essary p.W 2 The owner agrees to comply with the provisions of the zoning ordinance, building code and all other applicable sections of the City Code, Land Use Code, City Plan and all other laws and ordinances affecting the construction and occupancy of the proposed building that are not directly approved by this variance. The owner understands that if this variance is approved, the structure and its occupants may be more susceptible to flood or runoff damage as well as other adverse drainage issues. Signature of owner. Date: 8 /S—/G I The engineer hereby certifies that the above information, along with the reference plans and project ' descriptions is correct. Signature of engineer: � Date: �7.1 $•1 6 I PE STAMP Date complete application submitted: 9 lr G Date of approval/denial: LLnVariance: approved❑ denied - Staff justification/notes/c/oonditions: 7-4 rx,. ,a S%� /CuRc(,X',' S Xya�r&Af /�.y..C�� Ak6IC sQ 1`/fvt Wf.,ch ShD J�ll M//1/M 4/ Y�%(fM1T ✓L61 Approved by: .r Entered in UtilityFile Database? t,- Ylyes no I I 1 i I 1 t 11 ■ I pmEHOAL NEW \ Lu Q w W \ --_ fn \� W COMMENT RDDE DATE ��_ ■ Z PARTNERI Y 2 F __\ II ■ ■ ® NORTH (MiQT) I YIN SO a LEGEND: PROPERTY BOUNDARY — — PROPOSED BASH BASH ONES m m m m m "SING STORM YHEH LINE PROPOSES UNDERORAIx —UD— PRLPOSED STORM MEN ESmxO INLET ERAIE ■ PROPOSED CONTOUR —65 E4rnxO CONTOUR---yOfY--- PROPOSE➢ SWAIE APPROXIMATE UNITS OF OEVELOPMExi Lfv PROPOSED INFLOW VERICAL CURB h MOTHER PROPOSED QUI NERTIM CURB.h BUFFER PROPOSED RIBBON DOW PROPOSED OVERLAND FLOW DIRECTION _TUTU 1 p 23 PROPOSED PFAMEABIF PAN.nO PROPOSED BIO-SNNE Z co r BA9x DELINEATOR oB1 MNW RUNOFT COEFFOENT . l g RUNOFF CC£FFICIEHi 6t BASIN ACREAGE W DESICH POINT 02 NOTES: O 1. ME MI TYPE AND LOCATION OF ALL NNOM UNDERGROUND Unun[5 ARE APPROXIMATE MEN WOW M NEW DRAMNCS. IF SWLL BE ME IESSIUNSIBILITY CE THE CONTRACTOR TO WRIFY ME E%ISTENCE CE ALL Z Z W UNOgPRgRq UTILITIES IN ME AREA OF ME BONN. BEFORE CO MENI HOF CONSTRUCTION . ME CONTRACTOR SHALL BE MSPM98LF FOR LOCATING ALL UNDERGROUND UTUPES AND SNAIL IS RESPONSIBLE FOR FOR &L MMOM UNDERGROUND UTILITIES. 6 2 PETER DRA THE DD DRMNACE REPORT Pq ME $1A0. DATED 9:PTEMBq 21.2ttl PT. T FTH ADI INFORMATION.REPORT 14 BENCHMARK/BASIS OF BEARING �6 MQECT DATUM NAWPd CII PCM COLMS BENCHMARK $6_ N2 SOUTHRFST CMF{R OF HEST PROSPECT ft. AND CgnE AYE. ON A WATER VµW MT. ELEVAPM.5010.65 CITY OF PORT COLLINS BENCHMARK 29-61 p p ARnOMMATE JCO FEET SOUTH OF REST PROSPECT W. AND SKEWS $T., ON THE NORTH END OF THE IWJ 6 WEST BRIDGE PAAA➢ET WAIL ELEVATION-b95.67 REARS NOR: THIS PLAN SET IS USING NA'NN FOR A wRTCµ EANM. SURROUNDING DEVELOPMENTS HAW USED HCA9B UHAD LISTED FOR NOR m WRTCAL DATUMS. �' CyCyCy IF NOW29 UNADJUSTED DATUM IS REWIRED FOR MY PURPOSE, THE E FOLLOMNC EQUATOR SHOULD RE UWO: NM20 UNADJUSRo • NAWN - 117'. iii U SOPS d I645 OF BASS OF BEARIMOS IS THE SOUN NNE OF LOT I AS BEARING NORTH SIR n' L' REST (ASSUMES BFN6H0). m w 2 m,LUTIEIrNOT" TOAIION FNHERDF COLORADO a m W C9 Q Q K IMyebelow. w Callenanyco". MNN.EM M MmMH.M M 9MmM City of Fort Collins, Colorado UTILITY PLAN APPROVAL APPROY®: �e CI@CREL BY:� NECKED BY: �I♦ CHECKED BY. vv e�cH'eato $IPI DIMC6BD BY: B C7.00 CHOOKID BY: BorimDmeDW PlemeC Of 16 Sheets