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HomeMy WebLinkAboutPOLESTAR VILLAGE - PDP220010 - SUBMITTAL DOCUMENTS - ROUND 4 - DRAINAGE REPORTi PRELIMINARY DRAINAGE REPORT FOR POLESTAR VILLAGE Prepared For: POLESTAR GARDEN, INC PO BOX 211582 FORT COLLINS, COLORADO 80521 Michael Gornik (808) 443-9956 August 30th 2023 Project No. 39797.01 Prepared By: JR Engineering, LLC 2900 South College Avenue, Suite 3D Fort Collins, CO 80525 ii ii TABLE OF CONTENTS TABLE OF CONTENTS ......................................................................................................................... ii APPENDIX ..................................................................................................................................... iii Engineer’s Certification Block ........................................................................................................... iii GENERAL DESCRIPTION AND LOCATION ............................................................................................ 1 LOCATION ..................................................................................................................................... 1 DESCRIPTION OF PROPERTY .......................................................................................................... 1 MASTER DRAINAGE BASIN DESCRIPTION ....................................................................................... 1 FLOODPLAIN SUBMITTAL REQUIREMENTS ..................................................................................... 2 DRAINAGE BASINS AND SUB-BASINS ................................................................................................. 2 MAJOR BASINS AND SUB-BASINS ................................................................................................... 2 EXISTING SUB-BASIN DESCRIPTION ................................................................................................ 2 EXISTING OFFSITE DRAINAGE BASINS ............................................................................................ 2 EXISTING OFFSITE DRAINAGE DESCRIPTIONS ................................................................................. 3 PROPOSED SUB-BASINS DESCRIPTIONS ......................................................................................... 4 PROJECT DESCRIPTION ...................................................................................................................... 7 PROJECT DESCRIPTION .................................................................................................................. 7 PROPOSED DRAINAGE FACILITIES ...................................................................................................... 7 GENERAL CONCEPT ....................................................................................................................... 7 WATER QUALITY/ DETENTION FACILITIES ...................................................................................... 7 LOW IMPACT DEVELOPMENT ........................................................................................................ 8 DRAINAGE DESIGN CRITERIA ............................................................................................................. 9 REGULATIONS ............................................................................................................................... 9 FOUR STEP PROCESS TO PROTECT RECEIVING WATERS ................................................................. 9 DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS ........................................................... 10 HYDROLOGIC CRITERIA ................................................................................................................ 11 HYDRAULIC CRITERIA ................................................................................................................... 12 FLOODPLAIN REGULATIONS COMPLIANCE ................................................................................... 12 MODIFICATIONS OF CRITERIA ...................................................................................................... 12 EROSION CONTROL ..................................................................................................................... 13 CONCLUSIONS ................................................................................................................................. 13 COMPLIANCE WITH STANDARDS ................................................................................................. 13 DRAINAGE CONCEPT ................................................................................................................... 14 REFERENCES .................................................................................................................................... 15 iii iii APPENDIX Appendix A – Figures Appendix B – Hydrologic Calculations Appendix C – Hydraulic Calculations Appendix D – Water Quality Calculations Appendix E – Reference Appendix F – Maps Appendix G – LID Exhibit Engineer’s Certification Block I hereby attest that this report for the final drainage design for the Polestar Village was prepared by me or under my direct supervision, in accordance with the provisions of the Fort Collins Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others. Joseph Martin Frank, PE Registered Professional Engineer State of Colorado No. 53399 1 GENERAL DESCRIPTION AND LOCATION LOCATION The site is located in The Northwest Quarter of Section 16, Township 7 North, Range 69 West of the 6th P.M. in the City of Fort Collins, Larimer County, Colorado. More specifically, the site is a 20.55-acre property that is currently undeveloped. The site borders Mountaire Subdivision to the east, and to the south, the site borders the back of single-family residential lots facing West Elizabeth Ave. To the west, the site borders the Scenic Views retention pond and the Scenic Views Subdivision. To the north, the site borders single-family residential subdivisions, Locust Grove Filing No. 3, Locust Grove Filing No. 2 and the street Orchard Place. For additional information, refer to the site vicinity map within Appendix A of this report. DESCRIPTION OF PROPERTY The site generally drains west to east at a 2.5% to 1% slope. The site is located in the Canal Importation Basin, specifically north of West Elizabeth Street, east of South Overland Trail, and directly East of the Scenic Views Subdivision. The existing streets Orchard Place and West Plum Street dead end within the site. The Natural Resources Conservation Service (NRCS) soil survey shows that the majority are type C soils, which are characterized by a lower infiltration rate and corresponding higher runoff rates. The remaining soil on site are made up of Type B soils, which are characterized by a moderate infiltration rate and lower runoff rates. For additional information, refer to the NRCS soil map within Appendix A of this report. The existing site is currently used for Agricultural purposes and has an existing house, greenhouse, and field purposed for crops and areas with native grass. The existing irrigation ditch; i.e. the Pleasant Valley and Lake Canal is within the site, it borders the western boundary. The existing groundwater depths and boring locations are shown in Appendix E of this report. The depth from the bottom of the proposed pond to groundwater is approximately 6 to 9 feet, as shown in the Polestar Groundwater measurements spreadsheet in Appendix E of this report. An under-drain system will be designed at time of final design to lower the site’s groundwater elevations, and the proposed buildings on the site will not have basements. MASTER DRAINAGE BASIN DESCRIPTION The site is located in the Canal Importation basin. The 2022 Canal Importation Basin – Selected Plan Update plan by Jacobs Engineering report specifies that the site is to have a regional detention facility. For additional information on the drainage patterns and characteristics of the site, refer to the Drainage Basins and Sub-Basins section of this report. 2 FLOODPLAIN SUBMITTAL REQUIREMENTS The site is on FEMA FIRM panel 08069C0960F, dated 12/19/2006, as shown in Appendix A. The site lies within FEMA Zone X, areas which are determined to be outside the 0.2% annual chance floodplain. The site is not located within a FEMA regulated floodplain, as shown in Appendix A in the FEMA attachments. The site is located in the City of Fort Collins Canal Importation floodway and floodplain, as shown in Appendix A in the City of Fort Collins Flood map. JR Engineering has prepared a CLOMR for the Polestar site. Once the grading on the site is completed, a LOMR will be sumbitted to verify the site is in compliance with the CLOMR. No building permits for the residential structures in the existing effective floodway will be issued until the LOMR is approved. At time of Final Plan - FP a description will be provided describing how the development is within the applicable floodplain regulation (Chapter 10 of City Code); i.e elevations of the lowest floor above the regulatory flood protection elevation flood proofing, floodway regulation, erosion buffer zone regulation, no-rise, etc. The floodplain use permit will be submitted prior to the overlot grading. DRAINAGE BASINS AND SUB-BASINS MAJOR BASINS AND SUB-BASINS The Polestar Village site is 20.73 Acres; the site will be developed into a single-family, multi-family residential community with a community center and other amenities. The site will include future regional onsite and offsite detention. The site is located in the Canal Importation basin. EXISTING SUB-BASIN DESCRIPTION There are offsite areas that flow across the proposed development site. The existing drainage basins within the site flow from west to east. The existing corrected effective basin map is shown in Appendix E of this report. Basin EP 21.5, acres and 3.1% impervious. This basin is composed of native grassland, an existing shed, and includes a small portion includes residential lots from Locust Grove that drains directly onto the site and drains to a swale towards West Plum Street. EXISTING OFFSITE DRAINAGE BASINS Currently, the site collects offsite runoff at two different locations. The site is currently in the overflow path of the Scenic Views retention pond and receives direct runoff from Locust Grove Filing No. 3; which enters the site via curb and gutter from Locust Grove Drive. The Scenic Views retention facility receives 3 overflow runoff from the Pleasant Valley and Lake Canal, runoff from the Scenic Views multi-family Subdivision, the Colorado State Equine Horse center, and the Center of Disease Control facility. For additional information, refer to the existing drainage basin map in Appendix F of this report. EXISTING OFFSITE DRAINAGE DESCRIPTIONS The offsite flows are currently routed through the site. The existing offsite basins have been modeled in the Canal Importation Basin Selected Plan Update Conceptual Design Report –Plum Channel Flow Path by Jacobs Engineering Group; Dated June, 2022 and within the Canal Importation Basin Hydrologic Conversion from MODSWMM to EPA SWMM 5.1; Anderson Consulting Engineers, Inc, December 6, 2013, (Revised July 3rd 2014). JR Engineering has revised some of the basins in section 5.0 of the CLOMR to account for Polestar site. The basin map for the offsite areas is shown within the corrected effective SWMM drainage map within Appendix E for the revised hydrology update within the CLOMR. Basin 13 is 2.9 acres and 10% impervious. This basin is directly tributary to the privately owned Scenic Views retention facility. The Scenic Views Pond was designed by JR Engineering, LTD to be a temporary retention facility in 1998 as shown in Appendix E of this report. The temporary retention facility has not yet been converted into a detention facility. The retention pond is pumped into the Pleasant Valley and Lake Canal via existing submersible sumps pump, as shown in Appendix E of this report. The main pump has to be manually started, so the pond was modeled as a complete retention pond with no outflow, just an overflow path within the existing SWMM model. From the 1998 Scenic Views report, the manually operated pump system is designed to evacuate the pond within 24 hours after a large rainstorm event. This offsite basin is shown in the existing SWMM map shown within Appendix F of this report. 17W is 10.2 Acres and 45% impervious. This offsite basin is shown in the existing SWMM map, as shown within Appendix F of this report. For SWMM master planning purposes, Anderson used 45% impervious for single-family detached residential homes. This basin drains from Locust Grove Drive onto the Polestar site. In the proposed basin map in Appendix E, this basin is shown as OS1 and OS2 to delineate this area as two separate basins due to the crown in Locust Grove Drive. At the time of the Final design, the basin will be modeled with the rational method and will be split into basins OS1 and OS2 and will be captured by a series of inlets. 4 Basin 10, 64.4 Acres and 20% impervious. This basin is tributary to the Colorado State University Equine Reproduction Laboratory, located west of the site directly west of South Overland Trail. Runoff from this basin is released from the Equine Center pond and is then piped to the Scenic Views pond. This offsite basin is shown in the existing SWMM map shown within Appendix F of this report. Basin 11, 23.1 Acres and 70% impervious. This basin is tributary to the Scenic View’s subdivision. Runoff from this basin is detained in the Scenic Views pond. This offsite basin is shown in the existing SWMM map shown within Appendix F of this report. PROPOSED SUB-BASINS DESCRIPTIONS To model the proposed runoff going into the on-site detention facility the pond was modeled as a composite 21.5-acre basin in SWMM a with 50% impervious value. The Polestar SWMM model was slightly more conservative than the net preliminary basin area and impervious values to account for potential site changes, and the basin was delineated over a small portion of the Locust Grove subdivision that accounts for additional area. The proposed net area of the site is 20.73 acres at 47.9% impervious. The following is a description of the individual sub-basins for the composite basin. At time of Final, the drainage basins will be broken up and delineated in more detail, and runoff will be routed at corresponding design points with the rational method. The proposed site and pond drainage was modeled in a composite basin within SWMM, as part of the revised hydrology section of the CLOMR. Basin A1, 0.63 acres and 25.4% impervious this basin is composed of open space a proposed walk and a rain garden and an overflow structure that treats runoff and water quality from the Polestar Village site. Basin A2, 0.60 acres and 53.5% impervious this basin is composed of multi-family residential units, an alley, and onsite parking. The runoff from this basin will be conveyed via a paned alley to the curb and gutter on West Plum Street. Basin A3, 0.59 acres and 27.6% impervious this basin is composed of multi-family residential units, and a swale. The runoff from this basin will be conveyed via a swale and chase to West Plum Street. Basin A4, 2.13 acres and 51.1% impervious this basin is composed of multi-family residential units, paved walk and paved driveways paved parking spaces. The runoff from this basin goes to design point 4a at an on-grade inlet and drains on West Plum Street. 5 Basin A5, 1.85 acres and 59.4% impervious this basin is composed of a local residential street, paved walk, and paved driveways. The runoff from this basin goes to design point 5a and drains onto the West Plum Street. Basin A6, 0.97 acres and 70.5% impervious this basin is composed of a local street West Plum Street, paved walk and front-facing multi-family units. The runoff from this basin goes to a sump inlet at design point 6a. Basin A7, 0.88 acres and 60.5% impervious this basin is composed of a local Street West Plum, paved walk. The runoff from this basin goes to a sump inlet at design point 7a. Basin B1, 0.98 acres and 52.5% impervious this basin is composed of a residential alley, multi-family residential units, paved driveways and paved walk ways. The runoff from this basin drains to design point 1b and is treated for water quality within a rain garden, and then overflows into the detention facility. Basin B2, 0.56 acres and 65.8% impervious this basin is composed of open space and a side swale that runs adjacent to the property line. The runoff from this basin drains into a rain garden where it is treated for water quality and then the runoff outfalls into the on-site detention facility. Basin C1, 0.28 acres and 56.8% impervious this basin is composed of residential duplex units, paved walk, and a rain-garden. The runoff from this basin drains into a rain garden, where it is then released into the detention facility. Basin C2, 0.34 acres, and 29.3% impervious this basin is composed of paved walk, grass and multi-family units. The runoff from this basin drains into a type C inlet a design point 2C. Basin D1, 3.19 acres and 48.5% impervious this basin is composed a paved alley, and paved walk. The runoff from this basin drains into rain garden on the eastern border of this basin. Basin D2, 0.2 acres and 75.9% impervious this basin is comprised of a local residential street and paved walk. The runoff from this basin drains via chase curb and gutter and it is then treated for water quality within a rain garden within basin D1. 6 Basin D3, 0.19 acres and 76.2% impervious this basin is comprised of a local residential street and paved walk. The runoff from this basin drains via chase curb and gutter and it is then treated for water quality within a rain garden within Basin D4. Basin D4, 0.38 acres and 67.9% impervious this basin is comprised of alleys, multi-family residential units and paved walk. The runoff from this basin drains to a sump inlet at design point 4d. Basin E1, 2.20 acres and 41.4% impervious this basin consists of West Orchard Place and single family residential units. The runoff from this basin will drain to an on-grade inlet a design point 1e. Basin E2, 0.45 acres and 55.7% impervious this basin consists of a local residential road West Orchard Place, single family units and drains via curb and gutter to an on grade inlet a design point 2e. Basin E3, 0.45 acres and 55.7% impervious this basin consists of a local residential road West Orchard Place, single family units and drains via curb and gutter to an on grade inlet a design point 3e. Basin F1, 3.87 acres and 31.6% impervious this basin is composed of the onsite detention facility. O-1, 0.48 acres and 58% impervious this basin drains onto existing West Orchard Place and drains to an inlet and is treated for water quality and detained in the interim detention facility. O-2, 0.08 acres and 55% impervious, this basin drains onto West Orchard Place and is left untreated. This basin is a portion of a proposed single-family lot, proposed curb and gutter, and asphalt for Orchard Place. The runoff from this basin drains offsite onto the existing street Orchard Place. The runoff from this basin is difficult to capture with an inlet since it is next to a curb and gutter transition. Due to the small size of this basin, it is not anticipated to negatively affect the downstream drainage infrastructure. 7 PROJECT DESCRIPTION PROJECT DESCRIPTION Polestar Village is a residential multi-family development that will consist of a community center, wellness center, alleys, local, and collector roadways. The Polestar Village site will hold regional detention and water quality for the site. In the future, after the site is fully developed, the Canal Importation basin offsite improvements will be built with additional volume from the Jacobs Canal Importation basin Selected Plan updated June 2022. JR Engineering has designated approximately 3 acres of the site for regional detention. The proposed and future detention facility volume requirements were done by modeling the site in EPA SWMM as part of the revised hydrology portion of the CLOMR, as shown within Appendix E. The future onsite regional detention facility is shown in Appendix F of this report. PROPOSED DRAINAGE FACILITIES GENERAL CONCEPT The proposed improvements to the Polestar Village site will result in the developed condition being treated and detained for water quality. Low-impact development best management practices are proposed to improve the quality of runoff and aid in reducing peak flows. Specifically, rain gardens are proposed near the central portion of the site to treat and provide water quality for the majority of the development. Runoff from the site is captured in inlets located in the alleys and grate inlet along the curb and gutter. Runoff is conveyed in storm sewers, along curb and gutter, and via surface flow to rain gardens. Secondly, surface overflow paths will be provided, such that the 100-year storm flows remain at least 1.0 to 1.5 feet below the finished floor elevation at the time of the final drainage report. WATER QUALITY/ DETENTION FACILITIES The majority of the water quality is treated within the onsite rain gardens. The remaining water quality within the site will be treated in the water quality and detention facility. A small portion of the site 0.08 acres of a type A lot, will be left untreated due to the lot draining to the existing West Orchard R.O.W and pavement adjacent to the lot frontage. Additionally, a portion of the berm and access road to the detention pond will drain off-site and into the Plum Channel drainage way. This is not anticipated to have any negative impact on downstream drainage infrastructure, and the total water quality is being treated for 99% of the Polestar site’s modified impervious area. For additional information, the LID water quality treatment exhibit is shown in Appendix G of this report. 8 LOW IMPACT DEVELOPMENT A minimum of 75 percent of new impervious surface area is treated by a Low-Impact Development (LID) best management practice (BMP) in accordance with City criteria. An illustrative LID/ Surface Map is provided in Appendix G, and the sizing of the LID methods is provided in Appendix D. 9 DRAINAGE DESIGN CRITERIA REGULATIONS This report was prepared to meet or exceed the City of Fort Collins stormwater criteria. The City of Fort Collins Stormwater Criteria Manual (dated 2018)(FCSCM) and the Urban Drainage Flood Control District’s (UDFCD) Drainage Criteria Manual (USDCM) Volumes 1, 2 and 3 were referenced as guidelines for this design. FOUR STEP PROCESS TO PROTECT RECEIVING WATERS The City of Fort Collins requires the Four Step Process to protect receiving waters. The four step process incorporates reducing runoff volume, treating water quality capture volume, stabilizing streams, and implementing long-term source controls. Volume reduction is an important part of the Four Step Process and is fundamental to effective stormwater management. Per City criteria, a minimum of 75 percent of new impervious surface area must be treated by a Low-Impact Development (LID) best management practice (BMP). The site incorporates rain gardens to provide water quality. The rain gardens will need to be cleaned and maintained to allow for long-term protection of the receiving waters. The proposed LID BMPs will have the effect of slowing runoff through the site lot and increasing infiltration and rainfall interception by encouraging infiltration and careful selection of vegetative cover. The improvements will decrease the runoff coefficient from the site and are expected to have no adverse impact on the timing, quantity, or quality of stormwater runoff. Overall water quality will be improved by the development. The majority of the new impervious area is treated by the proposed raingarden in the northwestern portion of the site as illustrated in the LID/Surface Map is provided in Appendix G. Refer to Appendix G for additional information on water quality treatment methods throughout the site. 10 DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS The site is part of the Canal Importation - Basin Selected Plan Updates Alternatives Analysis Report, by Jacobs Engineering Group and is currently in the process of conceptual design. The site was previously analyzed in the Canal Importation Basin Hydrologic Conversion from MODSWMM to EPA SWMM 5.1; Anderson Consulting Engineers, Inc, December 6, 2013, (Revised July 3rd 2014). Jacobs Engineering group is currently modifying the Anderson model for the City of Fort Collins Capital Improvement plan for the Canal Importation basin. JR Engineering will evaluate the floodplain for the site, and JR Engineering is in the process of preparing a CLOMR to show that the improvements to the site are not within the floodplain. The CLOMR will show changes to the existing floodway via an approved CLOMR. The improvements for the planned regional Happy Hearts detention facility will take place in the future after the site is developed into Polestar Village. The Polestar Community will not impact the downstream development, and onsite detention will be provided within the site, but the homes downstream of the site will remain within the floodplain until the improvements to the offsite and onsite facilities are put in place as recommended in the Canal Importation - Basin Selected Plan Updates, by Jacobs. The following items are a list of the subject improvements. Conversion of Scenic Views retention pond to a detention pond. Addition of a pipe outfall from the Scenic views detention pond to the Happy Heart Farms i.e Polestar detention pond. Increasing the volume of the onsite detention pond per the proposed outfall. Construction of the planned outfall from the regional detention facility Currently, in the 100-year event the Pleasant Valley and Lake Canal overflows and spills into the Scenic Views pond. The Scenic Views pond has a manually operated pumped outfall to the Pleasant Valley and Lake Canal. In the 100-year event, water overtops the Scenic Views pond and goes on the Polestar site, creating a floodplain as shown in the existing drainage map within Appendix F. In the proposed condition, the floodplain will go onto the onsite rain garden, overtop W. Plum Street and then the floodplain will be contained within the proposed detention facility. However, due to the shallow gravity outfall and limited volume the ultimate detention facility, as shown in Appendix E cannot be built due to the lack of a deep gravity outfall. The interim condition provides a drainage easement, an energy dissipation structure, a concrete pan and will convey runoff as shown in the exhibit in Appendix E. 11 The onsite detention requirement for the site is the runoff difference between the 100-year developed inflow rate and the 2-year historic runoff is 4.88 Acre-ft. For additional information on the detention pond volume calculation, please refer to the referenced CLOMR provided hydrology portion provided in Appendix F. Jacobs calculated the ultimate volume (Happy Heart Detention Pond) within the Canal Importation - Basin Selected Plan Updates dated June 2022 as 8.3 Acre-ft. The total ultimate detention volume was calculated by adding the Happy Heart Detention pond of volume 8.3 Acre-ft with the required interim (onsite) detention volume 4.88 Acre-ft for the Polestar site for a total volume of 13.18 Acre-ft. JR Engineering has verified that the proposed pond layout can be graded in the future to detain over 13.18 Acre-ft as shown in the Future regional detention map provided in Appendix F. JR Engineering has prepared three SWMM models for the Polestar site within the City of Fort Collins Canal Importation Basin: the Corrected Effective Model, the Proposed Model, and the Ultimate Model. The City of Fort Collins has requested that JR Engineering incorporate the Polestar Drainage model into the City master Canal Importation Drainage Plan SWMM mode. This was completed within the revised hydrology portion of the CLOMR, as shown within Appendix E. HYDROLOGIC CRITERIA Weighted percent imperviousness were calculated for each basin using the Fort Collins Stormwater Criteria Manual Table 3.2-2 for each basin. EPA SWMM was used to model the runoff for the site since the corresponding tributary area of the site is over 20 acres, and there are multiple detention basins upstream of the site that are in series with one another. The City of Fort Collins area has rainfall depths associated with the table below as shown in Chapter 5 of the Fort Collins Stormwater Criteria Manual. The corresponding site and tributary area were modeled in SWMM for the 2-year storm and the 100- year storm. 12 HYDRAULIC CRITERIA At time of the Final Plan (FP) StormCAD will be utilized to determine the hydraulic capacity of the storm sewer system on site. Additionally, hydraulic calculations for items such as; street capacity, inlet capacity, swales, channels and will be provided within the Final Drainage Report. FLOODPLAIN REGULATIONS COMPLIANCE As previously stated, the site lies within FEMA Zone X, areas which are determined to be outside the 0.2% annual chance floodplain. The site is not located within a FEMA-regulated floodplain, as shown in Appendix A in the FEMA attachments. The site is located in the City of Fort Collins Floodplain and there is a floodway within the site, as shown in Appendix A in the City of Fort Collins Flood map. All development will be in compliance with Chapter 10 of the City of Fort Collins Code. MODIFICATIONS OF CRITERIA JR is proposing modifications for the spillway in Scenic Views Pond to increase emergency overflow capacity, decrease the overall breadth of the floodplain and reduce the emergency overflow depth from 13 1.9 ft to 1.75 ft, as shown in the attached variance letter from the CLOMR in Appendix E. The proposed improvement will stop the overflow from overtopping the spillway by making the spillway longer. In addition, the new proposed configuration will provide 6” of freeboard for the Scenic Views pond. The proposed Polestar/Happy Heart Farms Spillway is intended to prevent the flow from the emergency spillway from being directed towards existing structures and homes downstream. Both proposed spillways exceed the required depth of six inches, but the variance is necessary to achieve the desired outcomes. For additional information, refer to Appendix E for the variance request letter is being review in conjunction with the CLOMR. EROSION CONTROL A statement of compliance with Erosion Control Criteria and all Erosion Control Materials will be provided with the Final Drainage Report. CONCLUSIONS COMPLIANCE WITH STANDARDS The hydrologic and water quality calculations were performed using the required methods as outlined in the City of Fort Collins Stormwater Criteria Manual. The drainage plan and stormwater management measures proposed within the Polestar site are complaint with all applicable State and Federal regulations governing stormwater discharge. The drainage design conforms to the Jacobs’ Master Canal Importation Basin plan by providing area designed for detention in the ultimate gravity pond outfall configuration. The site conforms to the revised Hydrology of documented Polestar Floodplain Modeling Report by JR Engineering dated June of 2023. The floodplain compliance requirements for the site have been detailed in the CLOMR (Conditional Letter of Map Revision) for various parameters, including elevation, flood proofing, critical facilities, tie-in of upstream and downstream WSEL (Water Surface Elevation), and structures. 14 DRAINAGE CONCEPT The proposed concept for the Polestar Village Development involves surface flows and piping of developed conditions and offsite flow through the interim detention facility. The site includes LID water quality facilities with rain gardens. Runoff for the site will be treated in an interim detention facility onsite. The proposed development will affect the drainageway termed “Plum Street Flow Path” which is located in the northwestern portion of the Canal Importation Basin. Onsite detention is provided for the Polestar site, but the homes downstream of the site will remain with the floodplain until the improvements to the offsite and onsite facilities are put in place as recommended in the Canal importation – Basin Selected Plan Updates Analysis Report, by Jacobs dated June 2022. 15 REFERENCES Fort Collins Stormwater Criteria Manual; City of Fort Collins, Colorado, December 2018. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3); Urban Drainage and Flood Control District, June 2001. Canal Importation Basin Hydrologic Conversion from MODSWMM to EPA SWMM 5.1; Anderson Consulting Engineers, Inc, December 6, 20213, (Revised July 3rd 2014) Canal Importation basin Selected Plan Update, Jacobs Engineering Group,Dated June 2023 Preliminary Geotechnical Investigation Polestar Village; CTL Thompson, Dated November 2021 Floodplain Modeling Report for Polestar Village; JR Engineering, Dated June 2022 16 APPENDIX A – FIGURES A Westrian Company Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 5/17/2022 Page 1 of 44491400449150044916004491700449180044919004492000449210044922004492300449240044914004491500449160044917004491800449190044920004492100449220044923004492400488700488800488900489000489100489200489300489400 488700 488800 488900 489000 489100 489200 489300 489400 40° 34' 59'' N 105° 8' 2'' W40° 34' 59'' N105° 7' 27'' W40° 34' 23'' N 105° 8' 2'' W40° 34' 23'' N 105° 7' 27'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 250 500 1000 1500 Feet 0 50 100 200 300 Meters Map Scale: 1:5,390 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 16, Sep 2, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 5/17/2022 Page 2 of 4 Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 3 Altvan-Satanta loams, 0 to 3 percent slopes B 68.4 43.1% 4 Altvan-Satanta loams, 3 to 9 percent slopes B 38.2 24.1% 37 Fort Collins loam, 5 to 9 percent slopes C 0.0 0.0% 48 Heldt clay loam, 0 to 3 percent slopes C 9.2 5.8% 64 Loveland clay loam, 0 to 1 percent slopes C 15.9 10.0% 74 Nunn clay loam, 1 to 3 percent slopes C 2.2 1.4% 76 Nunn clay loam, wet, 1 to 3 percent slopes C 11.8 7.5% 95 Satanta loam, 1 to 3 percent slopes C 12.9 8.1% Totals for Area of Interest 158.5 100.0% Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 5/17/2022 Page 3 of 4 Description 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. 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: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. 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. 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 (A/D, 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. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 5/17/2022 Page 4 of 4 ROCKY RDW ELIZABETH ST KIMBALL RD ORCHARD PL W PL U M ST ARANCIA DRLOUISE LNTIERRA LNCUERTO LNRADCLIFF CIR Printed: 07/14/2021. All floodplain boundaries are approximate. This information is based on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of Fort Collins Master Drainageway Plans. This letter does not imply that the referenced property will or will not be free from flooding or damage. A property not in the Special Flood Hazard Area or in a City Designated Floodplain may be damaged by a flood greater than that predicted on the map or from a local drainage problem not shown on the map. This map does not create liability on the part of the City, or any officer or employee thereof, for any damage that results from reliance on this information. City Flood Risk Map Moderate Risk May include:- Areas of FEMA 500-year floodplain (FEMA Zone X-shaded).- Areas of FEMA or City 100-year floodplain (sheet flow) with average depths of less than 1 foot.- Areas protected by levees from the 100-year flood.Low Risk Areas outside of FEMA and City mapped 100-year and 500-year floodplains. Local drainage problems may still exist. City Flood Fringe - May Include:- Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AO, and AH)- Areas of City 100-year floodplain including ponding areas and sheet flow areas with average depths of 1-3 feet.There is a 1% annual chance that these areas will be flooded. High Risk City Floodway - Area of 100-year floodplain with greatest depths and fastest velocities. 0 140 280 420 56070Feet Fort Collins Utilities Floodplain Administration (970) 416-2632 Page 1 of 7 City of Fort Collins Floodplain Review Checklist Development Review Submittals Instructions: Complete this checklist by marking all boxes that have been adequately completed. Put an “NA” next to any items that are not applicable to this particular submittal. Any boxes that are left blank and do not have an “NA” marked next to them are considered incomplete. Date of Review: Reviewer’s Name: Plat Map The following required items are on the plat: ☐ 100-year floodplain boundary ☐ City ☐ FEMA ☐ Floodway boundary ☐ City ☐ FEMA ☐ These items match the FIRM. (FEMA Basin) ☐ These items match the Master Plan. (City Basin) Site Plan The following required items are on the site plan: ☐ 100-year floodplain boundary- FEMA and City ☐ 500-year floodplain boundary (if proposed structure is a “critical facility” and a 500-year floodplain is mapped) ☐ Floodway boundary ☐ Erosion buffer zones ☐ Restrictions related to use (ie. critical facility or no residential use of lower floor if floodproofed mixed use structure) Drainage and/or Grading Plan (or a separate Floodplain Sheet if it is too cluttered on Drainage and Grading Plan) The following required items are on the drainage and/or grading plan: ☐ 100-year floodplain boundary- FEMA and City ☐ 500-year floodplain boundary (if proposed structure is a “critical facility” and a 500-year floodplain is mapped) ☐ Floodway boundary Fort Collins Utilities Floodplain Administration (970) 416-2632 Page 2 of 7 ☐ Erosion buffer zones ☐ Cross-section locations ☐ BFE lines ☐ Lowest floor elevation of structures (bottom of basement or crawl space is considered the lowest floor) ☐ The floodplain and floodway boundaries are in the correct location and labeled properly. ☐ The cross-section and BFE lines are in the correct location and labeled properly. ☐ Elevations are referenced to the 1988 datum: ☐ Floodway regulations have been met. ☐ No fill in the floodway unless a hydraulic analysis shows “no-rise”. ☐ No manufactured homes, except in an existing park, can be placed in the floodway. ☐ No changing a nonconforming non-residential or mixed use structure to a residential structure. ☐ Landscaping meets requirements for no encroachment in the floodway without a hydraulic analysis to show “no-rise”. ☐ No storage of materials or equipment. ☐ A note is on the plans about the above floodway restrictions. ☐ Critical facilities regulations have been met: ☐ 100-year –no at-risk population, essential service, government service or hazardous material critical facilities ☐ 500-year Poudre –no at-risk population or essential service, critical facilities ☐ Any pedestrian bridges in the floodway that are not able to pass the 100-year flow are designed to be “break-away”. ☐ Fences in the floodway will not block conveyance. Example: split-rail fence cabled together to not float, flap at bottom of privacy fence to allow water through (flap at BFE or above). ☐ Any items in the floodway that can float (Example: picnic tables, bike racks, etc.) are noted as being anchored. ☐ Erosion Buffer Zone requirements have been met: ☐ Design of any allowed development minimizes disturbance to channel bed and banks. Fort Collins Utilities Floodplain Administration (970) 416-2632 Page 3 of 7 ☐ No structures allowed. ☐ No additions to existing structures allowed. ☐ Any fencing is split-rail design and break-away, but cabled. Must be oriented parallel to general flow direction. ☐ No detention or water quality ponds. ☐ No bike or pedestrian paths or trails except as required to cross streams or waterways. ☐ Road, bicycle and pedestrian bridges must span erosion buffer zone. ☐ No fill. ☐ No outdoor storage of non-residential materials or equipment. ☐ No driveways or parking areas. ☐ No irrigated vegetation and non-native trees, grasses, or shrubs. ☐ No utilities except as necessary to cross streams or waterways. ☐ No grading or excavation except as required for permitted activities in erosion buffer zone. ☐ No construction traffic except as required for permitted activities in erosion buffer zone. ☐ Any construction in the erosion buffer zone shows that it will not impact the channel stability. ☐ A note is on the plans about the above erosion buffer zone restrictions. ☐ Any necessary floodplain modeling has been submitted and approved. All modeling must follow the City’s floodplain modeling guidelines. Special Poudre River Regulations ☐ Poudre River Floodway Regulations have been met. ☐ No construction of new residential, non-residential or mixed- use structures. ☐ No redevelopment of residential, non-residential or mixed-use structures. ☐ No additions to residential, non-residential or mixed-use structures. ☐ No fill unless hydraulic analysis shows “no-rise”. ☐ Poudre River floodplain regulations have been met ☐ No construction of new residential or mixed-use structures ☐ No additions to residential structures ☐ No additions to mixed-use structures if there is an expansion in the residential-use area of the structure. ☐ No floatable materials on non-residential sites ☐ Emergency Response and Preparedness Plan (ERPP) draft has been prepared. Fort Collins Utilities Floodplain Administration (970) 416-2632 Page 4 of 7 Information Related to Structures in the Floodplain ☐ For structures in the floodplain, a table is shown that lists the following: ☐ City BFE at upstream end of structure ☐ FEMA BFE at upstream end of structure (if different than City BFE) ☐ Regulatory flood protection elevation ☐ Lowest floor elevation (bottom of basement or crawl space is considered lowest floor) ☐ Floodproofing elevation for non-residential structures (if applicable) ☐ Garage slab elevation ☐ HVAC elevation ☐ The BFE at upstream end of structures are correct based on interpolation between the cross-sections. ☐ The regulatory flood protection elevation is correct. ☐ The lowest floor and HVAC are at or above the regulatory flood protection elevation. ☐ Elevations are referenced to the 1988 datum. ☐ A typical drawing detail is included for each foundation type proposed (slab-on- grade, basement, crawl space) showing the elevation of the HVAC and lowest floor elevation (which includes bottom of the basement or crawl space) relative to the BFE. ☐ If garage is not elevated to the regulatory flood protection elevation, then a drawing detail is included showing vent placement, size, and number. ☐ There is 1 square inch of venting for every 1 square foot of enclosed area. ☐ The bottom of the venting is not higher than 1 foot above grade. ☐ The venting is on at least two sides, preferably on upstream and downstream sides. (Does not have to be divided equally). ☐ If a non-residential structure is to be floodproofed, one of these conditions is met: ☐ All requirements on separate sheet titled “Floodproofing Guidelines” have been met. ☐ If floodproofing information is not submitted as part of the plans, then a note is on the plans stating that floodproofing information will be submitted at the time of the building permit application. ☐ For manufactured homes, all submittal requirements on separate sheet titled “Installation of a Mobile Home Located in a Floodplain: Submittal Requirements” have been met. Fort Collins Utilities Floodplain Administration (970) 416-2632 Page 5 of 7 ☐ If the floodplain use permit is not going to be submitted until the building permit is applied for, then a note is on the plans stating that the floodplain use permit will be submitted at the time of building permit application. ☐ A note is on the plans stating that a FEMA elevation or floodproofing certificate will be completed and approved before the CO is issued. This is required even if property is only in a City floodplain. Drainage Report ☐ The site is described as being in the floodplain. Floodplain name and if the floodplain is a FEMA or City-designated is described. Any floodway or erosion buffer zones on the site are described. ☐ The FEMA FIRM panel # and date and/or the Master Plan information is cited. ☐ A copy of the FIRM panel with the site location marked is included in the report. ☐ If a floodplain modeling report has been submitted, that report is referenced. The reason for the floodplain modeling report is described. ☐ If a FEMA CLOMR or LOMR has been approved for the site, the case number is referenced. The reason for the CLOMR or LOMR is described. ☐ If a FEMA LOMR is required after construction, this is stated in the report. ☐ The location of the structures relative to the floodplain is described. If there is both a FEMA and a City floodplain on the site, the location of the structures relative to both is described. ☐ The use of the structures is described. This is to determine if the structure is residential, non-residential, or mixed-use. Also, structures in all 100-year and Poudre River 500-year floodplains cannot be used as a critical facility. (See Chapter 10 of City Code for definitions.) ☐ If in the Poudre River 100-year floodplain, the requirement to complete an Emergency Response and Preparedness Plan (ERPP) is discussed and the requirement for annual training drills and an annual update in the first quarter of every year is discussed. ☐ The report describes how the development is in compliance with the applicable floodplain regulation (Chapter 10 of City Code). (Examples: elevation of lowest floor above regulatory flood protection elevation, floodproofing, floodway regulation, erosion buffer zone regulation, no-rise, etc.) Fort Collins Utilities Floodplain Administration (970) 416-2632 Page 6 of 7 ☐ The type of foundation construction for the structures (i.e. slab-on-grade, crawl space, basement, etc.) is discussed in the report. ☐ The type of foundation matches with the lowest floor elevations and grading plan. ☐ If any of the garages are not going to be elevated above the regulatory flood protection elevation, the hydraulic venting requirements are discussed. ☐ For structures in the floodplain, a table is included (same table as on the Drainage/Grading Plan) that lists the following: ☐ City BFE at upstream end of structure ☐ FEMA BFE at upstream end of structure (if different than City BFE) ☐ Regulatory flood protection elevation ☐ Lowest floor elevation (bottom of basement or crawl space is considered lowest floor) ☐ Floodproofing elevation for non-residential structures (if applicable) ☐ Garage slab elevation ☐ HVAC elevation ☐ Elevations are referenced to the NAVD 1988 datum. ☐ If the floodplain use permit is not going to be submitted until the building permit is applied for, then a note must be included in the report that states the permit will be submitted at the time of building permit application. ☐ If floodproofing information is not submitted as part of the plans, then a note must be in the report stating that floodproofing information will be submitted at the time of the building permit application. ☐ A note is in the report stating that a FEMA elevation or floodproofing certificate will be completed and approved before the CO is issued. ☐ In the compliance section, Chapter 10 of City Code is listed. Floodplain Use Permit ☐ Floodplain Use Permit has been submitted for each structure. ☐ Permit fee has been submitted. ☐ All information on permit matches the plans. ☐ All information on permit meets floodplain regulations. Fort Collins Utilities Floodplain Administration (970) 416-2632 Page 7 of 7 FEMA CLOMR Approval ☐ FEMA has approved any necessary CLOMRs. ☐ The City has received copies of all updates to the FEMA submittal. Additional Comments: Floodplain terminology is defined in Chapter 10 of City Code. NOTE: Issues specific to individual sites may arise that result in additional requirements. These will be discussed during initial meetings with the applicant. Please refer to Chapter 10 of City Code for specific floodplain regulations. 17 APPENDIX B – HYDROLOGIC CALCULATIONS Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.: Calculated By:ARJ Checked By:0 Date:4/7/23 A1 0.63 100%0.06 9.3%45%0.12 8.7%90%0.04 6.1%2%0.41 1.3%25.4% A2 0.60 100%0.19 31.2%45%0.00 0.0%90%0.14 21.4%2%0.27 0.9%53.5% A3 0.59 100%0.08 13.1%45%0.00 0.0%90%0.09 13.0%2%0.43 1.4%27.6% A4 2.13 100%0.68 31.8%45%0.00 0.0%90%0.43 18.4%2%1.02 1.0%51.1% A5 1.85 100%0.61 32.8%45%0.00 0.0%90%0.53 25.9%2%0.71 0.8%59.4% A6 0.97 100%0.60 61.7%45%0.09 4.3%90%0.04 3.9%2%0.23 0.5%70.5% A7 0.88 100%0.47 53.2%45%0.04 2.2%90%0.04 4.4%2%0.32 0.7%60.5% B1 0.98 100%0.29 29.4%45%0.00 0.0%90%0.24 22.2%2%0.45 0.9%52.5% B2 0.57 100%0.23 40.7%45%0.00 0.0%90%0.15 24.5%2%0.18 0.6%65.8% C1 0.28 100%0.03 10.3%45%0.00 0.0%90%0.14 45.7%2%0.11 0.8%56.8% C2 0.34 100%0.02 6.5%45%0.00 0.0%90%0.08 21.4%2%0.24 1.4%29.3% D1 3.19 100%1.12 35.1%45%0.00 0.0%90%0.44 12.4%2%1.63 1.0%48.5% D2 0.20 100%0.15 75.4%45%0.00 0.0%90%0.00 0.0%2%0.05 0.5%75.9% D3 0.19 100%0.15 75.7%45%0.00 0.0%90%0.00 0.0%2%0.05 0.5%76.2% D4 0.38 100%0.23 61.6%45%0.00 0.0%90%0.02 5.7%2%0.12 0.6%67.9% E1 2.20 100%0.40 18.3%45%1.10 22.6%90%0.00 0.0%2%0.70 0.6%41.4% E2 0.45 100%0.17 37.4%45%0.18 17.8%90%0.00 0.0%2%0.10 0.5%55.7% E3 0.45 100%0.15 33.9%45%0.22 21.7%90%0.00 0.0%2%0.08 0.4%55.9% F1 3.87 100%0.04 1.0%45%0.53 6.1%90%1.00 23.3%2%2.31 1.2%31.6% Onsite Basins 20.73 47.9% OS1 8.33 100%2.02 24.3%45%6.31 34.1%90%0.00 0.0%2%0.00 0.0%58.3% OS2 2.40 100%0.92 38.4%45%1.47 27.5%90%0.00 0.0%2%0.01 0.0%65.9% Locust Grove Filing No. 3 - Tributary to Pond 10.74 60.0% O-2 0.08 100%0.02 23.2%45%0.05 31.5%190%0.00 0.0%2%0.01 0.1%54.8% O-1 and O-2 Drains onto W. Orchard Place 39797.01 Weighted % Imp. Basins Total Weighted % Imp.Basin ID Total Area (ac)% Imp.Area (ac) Lawns % Imp. Area (ac)Weighted % Imp. Paved Roads and Walks Roofs Weighted % Imp. COMPOSITE % IMPERVIOUS CALCULATIONS % Imp. Area (ac) Single Family Lots % Imp.Area (ac)Weighted % Imp. X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 1 4/10/2023 18 APPENDIX C – HYDRAULIC CALCULATIONS 19 APPENDIX D – WATER QUALITY CALCULATIONS Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.:39797.01 Calculated By:ARJ Checked By:0 Date:4/7/23 Basin Area (ac)% Imp. A1 0.63 25.4% A2 0.60 53.5% A3 0.59 27.6% A4 2.13 51.1% A5 1.85 59.4% A6 0.97 70.5% A7 0.88 60.5% Total 7.64 52.9% WQCV Drain Time (hr):12 Coefficient, a (Figure 3.2):0.8 WQCV (in):0.17 WQCV (ac-ft):0.13 WQ Pond Tributary Areas #1 - Rain Garden X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 7 4/10/2023 Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.:39797.01 Calculated By:ARJ Checked By:0 Date:4/7/23 Basin Area (ac)% Imp. B1 0.98 25.4% B2 0.57 53.5% Total 1.55 35.7% WQCV Drain Time (hr):12 Coefficient, a (Figure 3.2):0.8 WQCV (in):0.13 WQCV (ac-ft):0.02 WQ Pond Tributary Areas # 2- Rain Garden X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 2 of 7 4/10/2023 Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.:39797.01 Calculated By:ARJ Checked By:0 Date:4/7/23 Basin Area (ac)% Imp. C1 0.28 56.8% C2 0.34 29.3% Total 0.62 41.5% WQCV Drain Time (hr):12 Coefficient, a (Figure 3.2):0.8 WQCV (in):0.15 WQCV (ac-ft):0.01 WQ Pond Tributary Areas # 3 - Rain Garden X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 3 of 7 4/10/2023 Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.:39797.01 Calculated By:ARJ Checked By:0 Date:4/7/23 Basin Area (ac)% Imp. D1 3.19 48.5% D2 0.20 75.9% Total 3.39 50.1% WQCV Drain Time (hr):12 Coefficient, a (Figure 3.2):0.8 WQCV (in):0.17 WQCV (ac-ft):0.06 WQ Pond Tributary Areas # 4 - Rain Garden X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 4 of 7 4/10/2023 Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.:39797.01 Calculated By:ARJ Checked By:0 Date:4/7/23 Basin Area (ac)% Imp. D3 0.19 76.2% D4 0.38 67.9% Total 0.57 70.8% WQCV Drain Time (hr):12 Coefficient, a (Figure 3.2):0.8 WQCV (in):0.22 WQCV (ac-ft):0.01 WQ Pond Tributary Areas # 5 - Rain Garden X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 5 of 7 4/10/2023 X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 6 of 7 4/10/2023 Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.:39797.01 Calculated By:ARJ Checked By:0 Date:4/7/23 Basin Area (ac)% Imp. F1 3.87 31.6% E1 2.20 41.4% E2 0.45 55.7% E3 0.45 55.9% Total 6.97 37.8% WQCV Drain Time (hr):40 Coefficient, a (Figure 3.2):1.0 WQCV (in):0.17 WQCV (ac-ft):0.12 WQ Pond Tributary Areas WATER QUALITY IN DETENTION POND This table shows the WQ on-site treated in the Polestar Detention pond. This calculation includes 20% contingency for sediment accumulationas shown in equaltion 7-2. PLEASE NOTE area on MHFD sheet was multiplied by 1.2 X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 7 of 7 4/10/2023 Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =52.9 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.529 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.17 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area)Area = 332,798 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 =0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region,VWQCV OTHER =4,755 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =11 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical)Z =4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =3521 sq ft D) Actual Flat Surface Area AActual =5093 sq ft E) Area at Design Depth (Top Surface Area)ATop =6271 sq ft F) Rain Garden Total Volume VT=5,209 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar #1 - Rain Garden; Basins A1-A7 UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO No. 1 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:51 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar #1 - Rain Garden; Basins A1-A7 Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO No. 1 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:51 AM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =35.7 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.357 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.13 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area)Area =67,518 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 =0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region,VWQCV OTHER =757 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =3 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical)Z =4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =482 sq ft D) Actual Flat Surface Area AActual =3542 sq ft E) Area at Design Depth (Top Surface Area)ATop =5651 sq ft F) Rain Garden Total Volume VT=1,149 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar #2 - Rain Garden; B1-B2 UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO No. 2 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:53 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar #2 - Rain Garden; B1-B2 Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO No. 2 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:53 AM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =41.5 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.415 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.15 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area)Area =27,007 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 =0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region,VWQCV OTHER =331 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =3 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical)Z =4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =224 sq ft D) Actual Flat Surface Area AActual =760 sq ft E) Area at Design Depth (Top Surface Area)ATop =1937 sq ft F) Rain Garden Total Volume VT=337 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar Village Rain Garden No. 3; Basins C1-C2 UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO No. 3 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:54 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar Village Rain Garden No. 3; Basins C1-C2 Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO No. 3 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:54 AM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =50.1 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.501 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.17 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area)Area = 147,668 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 =0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region,VWQCV OTHER =2,033 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =6 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical)Z =4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =1480 sq ft D) Actual Flat Surface Area AActual =2720 sq ft E) Area at Design Depth (Top Surface Area)ATop =5487 sq ft F) Rain Garden Total Volume VT=2,052 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 10, 2023 Polestar Village Rain Garden No. 4; Basins D1-D2 UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO No. 4 UD BMP _v3.07.xlsm, RG 4/10/2023, 9:34 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 10, 2023 Polestar Village Rain Garden No. 4; Basins D1-D2 Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO No. 4 UD BMP _v3.07.xlsm, RG 4/10/2023, 9:34 AM Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =70.8 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.708 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.22 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area)Area =24,829 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 =0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region,VWQCV OTHER =461 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =12 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical)Z =4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =352 sq ft D) Actual Flat Surface Area AActual =1323 sq ft E) Area at Design Depth (Top Surface Area)ATop =2710 sq ft F) Rain Garden Total Volume VT=2,016 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided?1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y =ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =cu ft iii) Orifice Diameter, 3/8" Minimum DO = in Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar Village Rain Garden No. 5; Basins D3-D4 UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO No. 5 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:57 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) ARJ JR Engineering April 7, 2023 Polestar Village Rain Garden No. 5; Basins D3-D4 Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO No. 5 UD BMP _v3.07.xlsm, RG 4/7/2023, 8:57 AM 20 APPENDIX E – REFERENCES Polestar Village - Floodplain Modeling Report September 2023 8 5.0 HYDROLOGY 5.1 Discharges and Model Frequencies EPA SWMM version 5.2 (build 5.2.1) was used to model the hydrology of the site. The frequency modeled was the 100-year event. The discharges are below in the Modified Simplified - Table B.1.1 Plum Channel Flow Path Discharge Profile. For additional information on the Modified -Table B.1.1 Plum Channel Flow Path Discharge Profile, refer to Appendix J.V. Modified Simplified - Table B.1.1 Plum Channel Flow Path Discharge Profile 5.2 Revised Hydrologic Analysis The Polestar site is within the City of Fort Collins Floodplain, and the City of Fort Collins has requested that JR Engineering incorporate the Polestar Drainage model into the City master Canal Importation Drainage Plan SWMM model. In addition, the City of Fort Collins is requesting that JR Engineering revise the CLOMR inputs to match the Hydrology for the site and the proposed improvements to the site. In 2013/2014 Anderson Consulting Engineers was contracted by the City of Fort Collins to convert the effective hydrologic model for the Canal importation basin from ModSWMM to EPA SWMM[1]. In 2014 Anderson, was hired by the City to Map the 100-year effective floodplain[2]. JR Engineering has incorporated the revised Hydrology in a standalone Appendix -Appendix J at the end of this report to be referenced in this report and the drainage report. JR Engineering has prepared three SWMM models, which include the Corrected Effective Model, the Proposed Model, and the Ultimate Model for the site. Please refer to detailed sections in this Revised Hydrology Analysis outlining each SWMM model, and accompanying SWMM maps for additional information. Polestar Village - Floodplain Modeling Report September 2023 9 The City of Fort Collins effective SWMM model[1] flows do not match flows modeled in the City’s effective HEC-RAS model[2]. The flow overtopping the Scenic Views pond (pond 313) is currently 241 cfs as modeled in the City of Fort Collins effective flood plain model[2]. This flow does not match the modeled flow in the City’s SWMM Model[1] of 156 cfs, as shown in the attached excerpt of the 2014 Anderson report in Appendix J.V. JR engineering has prepared four SWMM schematics maps to show the changes being made to 2014 Existing Model, the Corrected Effective Model, the Proposed Model, and the Ultimate Model for the site with the defined gravity outfall. The SWMM schematics are shown in Appendix J.111. SWMM output and input files are provided for each scenario for the 100-year event. The inputs for the basins modified for each scenario are shown in the Appendix J.II. All of the SWMM models were run on EPA STORM WATER MANAGEMENT MODEL - VERSION 5.2 (Build 5.2.1). 5.2.1 City Effective SWMM Model (2014 Anderson) -100yr Canal Importation Hydrology Update.inp When the City’s SWMM hydrology model is re-run in the current software version 5.2. The runoff overtopping the Scenic Views pond (Pond 313) is 0 cfs. Pond 313 floods, and there is no flow in the downstream link element of pond 313. This error (warning 10), is a result of a code change between different versions of SWMM past 2014. The 2014 Anderson SWMM model results show 156 cfs overtopping the Scenic Views Spillway. After a discussion with City Staff, the preferred way to model pond 313 was to set the invert of the pond at the spillway elevation, so there is no inadvertent detention or storage modeled in pond 313 and to avoid warning number 10. This change is reflected in the corrected effective SWMM model. 5.2.2 Corrected Effective Model -100yr CE Canal Importation Hydrology Update.inp The corrected model accounts for additional runoff that drains directly onto the site from the Locust Grove Filling No. 1 subdivision directly north of the site. This runoff (onto the Polestar site) was not accounted for in the previous model, and all of the runoff was assumed to drain directly onto Orchard Place to junction J17, as shown in the Existing SWMM Schematic. JR Engineering’s survey topo showed that this basin should be broken up to account for the additional runoff that travels down Locust Grove Drive and drains directly onto the Polestar site. As a result, Basin 17 was broken up into two corresponding basins (17E and 17W), as shown in the attached Corrected Effective SWMM Schematic in Appendix J.III. Basin 15 was also broken up into two basins to account for the existing Polestar Site (EP) and existing lots from the Mountaire Subdivision (15E), as shown in the attached SWMM Schematic in Appendix J.III. The following is a list of changes made from the existing City Effective SWMM Model (2014 Anderson)to the Corrected Effective Model. Polestar Village - Floodplain Modeling Report September 2023 10 Broke up basin 17 into basins 17E and 17W to reflect the existing drainage topography and account for the runoff from Locust Grove Drive that drains directly onto the Polestar Site. Broke basin 15 to basin EP1 and M15 to account for the drainage directly tributary to the Polestar site and separate runoff that is tributary to the Mountaire Subdivision. For the impervious calculations, a typical value used in the existing model of 45% was applied for single-family detached residential area. For the existing Polestar site, the percent impervious was determined with survey topo. These updates resulted in a combined modified imperviousness of 29% in the Corrected Effective Model, compared to 34% in the original effective SWMM modeling, since the effective model assumed a portion of the existing Polestar site was impervious and did not utilize survey information. The topography on the existing Polestar site is primary grass and the net composite percent impervious of the existing site is 3.7%. Removed Junction J113 and Conduit 113 to create positive drainage, to simplify the model, and to avoid modeling errors resulting from SWMM Warning 10. Edited the stage storage curve for Pond 313 curve name (313_AB*JR_Edit) to reflect the pond being 100% full up to the spillway elevation at the start of the 100 yr storm. The pond contours were revised using JR survey topo. Removed outlet offset from elements 110_overflow and 110_Pipe. Updated outlet offset from 4 ft to 5 ft for link stability for element 116. The rating table for 313 spillway overflow (313out_JR_Edit) was added, with the same formula as 313 out but includes additional head. See the SWMM model. Added a time series for the City of Fort Collins 2 year storm. The Downstream outfall of pond 315 contains a twin 24” RCP. The City’s effective model only modeled one pipe. JR Engineering added an additional conduit (C-1) to account for the additional pipe. Changed 315out to 315out_Spillway added a separate rating curve based on the spillway overflow based on the attached calculation from the Ayres Update Hydrologic Analysis for West Plum Street Basin, as shown in Appendix J.IV. Changed the name of 315out to 315out_culverts to represent the twin 24” culvert outfall for the Kimball pond. Added a rating curve for the culverts determined in MHFD-Culvert_v4.0 design workbook. Pond 315. Updated rating curve to support 0.14 ft of head to prevent flooding within model. See storage rating curve 315*JR_edit within SWMM. Updated max depth of pond 315 to be 5.1 ft. Junction J37 was added to divert flow for the culverts, with an invert of 4096.6 for the twin culverts invert. Polestar Village - Floodplain Modeling Report September 2023 11 Table 1: Comparison of Scenic View Pond Modeling - Effective vs Corrected Effective Note: Storage Element 313 is the Scenic Views Pond. 5.2.3 Proposed Model -100yr Proposed Polestar - Canal Importation Hydrology Update.inp The Proposed Model incorporates the improvements to the Polestar Site and the basins from the existing corrected effective model. Interim detention for the site is provided within node 23 (the proposed detention facility). The existing overflow spillway for Pond 313 (Scenic Views Pond) is currently undersized to handle the total inflow of approximately 350 cfs. The current spillway for pond 313 is 10 feet wide and 1.5 ft deep, and is set at an elevation of 5112.5 on the NGVD 29 datum. The total existing inflow exceeds the capacity of the spillway and spills over the pond embankment, which is acting as an overflow weir for 290 ft. The depth in the existing condition is approximately 2 feet. JR engineering, is proposing that the spillway be built at the same elevation as the NGVD 29 datum. JR Engineering’s Design documents are on the NAVD 88 datum (5112.5+3.07=5115.57). The spillway will be modified to convey flow at a greater depth than the City’s required depth of 0.5 feet and convey flow at a depth of 1.75 feet. JR Engineering has asked for a variance to this criterion, as shown in the Appendix J.VI, which includes an existing cross section of the Scenic Views Pond Spillway, a proposed cross section of the Scenic Views Pond Spillway, and the proposed Polestar Pond spillway. This modification will decrease the overall breadth of the floodplain, and it will serve as an interim improvement to the site. The updated Scenic Views overflow weir will contain the flows within the spillway section with 6 inches of freeboard and there will be no embankment overtopping in the 100-year event. The impacts on volume, HGL, and outflow from this change are shown in Table 2 below. The outlet structure rating table was developed using the (MHFD-Detention_v4-06 workbook design tool), as shown in Appendix J.II for an outlet structure with an restricted 42-inch pipe.The objective of the project’s detention facility is to detain the site’s runoff and improve downstream conditions as much as possible in the allocated pond footprint. The interim detention facility detains the site’s runoff and minimizes peak flow with additional supplemental volume, as shown in Tables 4 and 5. The onsite detention requirement for the site is the runoff difference between the 100-year developed inflow runoff rate and the 2-year historic runoff is 4.88 Acre-ft. The calculation for the onsite detention is shown in Appendix J.11. The following is a list of changes made from the Corrected Effective Model to the Proposed Model. Converted element 313out from an outlet element to a weir element. See attached exhibit for the Scenic Views Spillway pond in Appendix J.VI. Note the Jacobs Spillway is on NAVD88, and the existing spillway is on NGVD29.SWMM still Max. HGL, ft Max. HGL, ft NAVD 88 NAVD 88 313 151.26 3.47 156.14 5114.25 143.545 3.29 252.16 5114.4 City Effective SWMM Model (2014 Anderson)Corrected Effective Model Storage Element Max. Vol., 1000 ft3 Ac-ft Max. Outflow, cfs Max. Vol., 1000 ft3 Ac-ft Max. Outflow, cfs Polestar Village - Floodplain Modeling Report September 2023 12 models positive drainage. The SWMM model was left on NVGD29. The difference is 3.07ft (As referenced in the Anderson Report for the Plum Creek Channel[2]). Changed basin EP to P. Basin P is 50% impervious. Improvements to the Polestar site will not exceed 50%. Updated and converted junction 23 to a pond element for the Polestar Pond. Added stage storage curve for pond 23. See SWMM Pond_23. Added an additional junction below the outfall for pond 23 (junction J14). Re-named element 15 to be M-15. Changed element to a broad trapezoidal element to reflect improvements to the Plum Creek Channel (see SWMM model). The flow will be hydraulically modeled in HEC-RAS. Created two outfall elements for pond 23. One of the outfalls reflects the interim outfall (INTERIM_OUTLET), and the other outfall represents the spillway i.e., a weir sized for the Ultimate condition (SPILLWAY_OUTFALL). See attached variance exhibit for Polestar Spillway (Appendix J.VI). The hydraulics for the rating curve of the interim outlet (23_INTERIM_OUTLET) for a 42-inch pipe was determined using an MHFD spreadsheet. The weir coefficient for the Scenic View pond and Polestar pond were determined within OpenFlows FlowMaster based on a broad crested weir cross-section, as shown in sub Appendix J.VI – Spillway Variance Request. Table 2: Comparison of Scenic View Pond Modeling - Corrected Effective vs Proposed Note: Storage Element 313 is the Scenic Views Pond The objective of this project is to detain the site’s runoff and improve downstream conditions within the constraints of the allocated pond footprint and existing gravity outfall. The interim detention facility detains the site’s runoff. To compare flows leaving the site between each respective model, refer to Table 3 below. For information on the ultimate condition, refer to the section about the ultimate condition provided in section 5.2.4. In the 100 year event, 9.58 Acre-ft of detention is provided in the Happy Heart/Polestar interim detention pond. The peak release rate leaving the site is reduced to 174 cfs from the effective flow of 330 cfs. As a result of this project, there is less flow leaving the site and going down stream. Max. HGL, ft Max. HGL, ft NAVD 88 NAVD 88 313 143.545 3.29 252.16 5114.4 102.67 2.36 244.77 5113.88 Corrected Effective Model Proposed Model Storage Element Max. Vol., 1000 ft3 Ac-ft Max. Outflow, cfs Max.Vol, 1000 ft3 Ac-ft Max. Outflow, cfs Polestar Village - Floodplain Modeling Report September 2023 13 Table 3:Flow Comparison Downstream of the Happy Heart Pond Model Element Flow (CFS) Effective flows (2014 HEC-RAS Model) (EF)15 330 Effective Model (2014 SWMM Model) (E)15 200 Corrected Effective Model (CE) SWMM Model 15 305 Proposed Model (PR) SWMM Model M-15 174 Note: Flow rounded to the nearest integer. Flow comparison is for flow leaving the site. 5.2.4 Ultimate Model –100yr Ultimate Polestar Regional Detention.inp The Ultimate SWMM model incorporates improvements from the Canal Importation Basin Selected Plan Update Conceptual Design Report –Plum Channel Flow Path by Jacobs Engineering Group, Dated June 30th, 2022. The report outlines the ultimate improvements to the Plum Channel Flow Path. Jacobs Engineering Group has conceptually modified the Canal Importation model for the City of Fort Collins Capital Improvement plan[3]. The Polestar detention facility will be converted into a regional detention facility with a deep underground gravity outfall in Orchard Place. The changes that are being made to the site in the ultimate condition are summarized below. 1.Conversion of Scenic Views retention pond to a detention pond. 2.Addition of a pipe outfall from the Scenic Views detention pond to the Happy Heart Farms Pond, also known as the future Polestar regional detention pond. 3.Increasing the volume of the onsite Polestar detention pond per the proposed ultimate outfall 4.The planned future gravity outfall in Orchard Place JR Engineering has provided an ultimate SWMM schematic and a map from Jacobs of the site, as shown in Appendix J.III – SWMM Maps. The ultimate SWMM model was incorporated in the conceptual Jacobs model (Plum Detention.inp). The outlet structure- rating table was developed using the (MHFD-Detention_v4-06 workbook design tool) as shown in the Appendix J.II for an outlet structure with a restricted 30-inch pipe. It is important to note that the JR ultimate SWMM model does not replace the Jacobs model. The purpose of the ultimate model is to show the Polestar site can provide detention in the ultimate condition. The following is a list of changes made from the Proposed Model to the Ultimate Model. Started with the February 2022 Jacobs model. Brought in proposed elements into the SWMM model for the Polestar site as shown in the SWMM Map. Added basins P and 17W from the proposed model tributary to the storage node for pond 23. (See SWMM Map) Added basin 17E and 15W to the model. (See SWMM Map). Polestar Village - Floodplain Modeling Report September 2023 14 Updated the stage storage of the detention facility at storage node 23 to reflect the ultimate pond. See SWMM for stage storage. Used Jacobs outlet for 313out. Used the Jacobs pond grading for the stage storage for pond 313. See SWMM model. Defined two elements for the outfall of Pond 313. 313_SPILLWAY for the spillway and 313out for the ultimate gravity outfall. Set 313_SPILLWAY to reflect Proposed JR spillway (See SWMM Model). Updated the stage storage for the Polestar detention pond to reflect the ultimate regional detention facility. See SWMM model (Polestar_Ultimate_Pond). The hydraulics for the rating curve of the ultimate outlet (23_ULTIMATE_OUTLET) were determined using a MHFD spreadsheet to account for onsite WQ and a restrictor plate for a 30” Pipe. Made element 115_pipe and 16_pipe double barrel 24” RCP. From single barrel 24” concrete pipes to reflect the actual existing condition. Changed the name of 315out to 315_culverts to represent the twin 24” culvert outfall for the Kimball pond. Added a rating curve (315out_Culverts) for the culverts determined in MHFD-Culvert_v4.0 design workbook. Table 4: Comparison of Storage elements in the Proposed Model and the Ultimate Model Note: Storage Element 313 is the Scenic Views Pond. Storage Element 23 is the Polestar/Happy Heart Farms Pond. Max. HGL, ft Max. HGL, ft NAVD 88 NAVD 88 38.48 5107.14 9.44 53.62 5109.96 23 417.098 9.58 173.75 5108.89 585.81 13.45 313 102.67 2.36 244.77 5113.88 411.216 Proposed Model Ultimate Model Storage Element Max.Vol., 1000 ft3 Ac-ft Max. Outflow, cfs Max. Vol., 1000 ft3 Ac-ft Max. Outflow, cfs Polestar Village - Floodplain Modeling Report September 2023 15 5.3 Onsite and Ultimate Detention Calculations - Polestar/Happy Heart Farm Detention Pond The onsite detention requirement for the site is the runoff difference between the 100-year developed inflow rate and the 2-year historic runoff is 4.88 Acre-ft. The calculation for the onsite detention is shown in Appendix J.11. The proposed detention provided onsite within the interim condition is 6.75 Acre-ft up to the pond spillway elevation at 5107.76.Jacobs calculated the ultimate volume (Happy Heart Detention Pond) within the Canal Importation - Basin Selected Plan Updates dated February 2022 as 8.3 Acre-ft. The total ultimate detention volume was calculated by adding the Happy Heart Detention pond of volume 8.3 Acre-ft with the required interim (onsite) detention volume 4.88 Acre-ft for the Polestar site for a total volume of 13.18 Acre-ft. Table 5 summarizes the detention pond changes in Table 5. TABLE 5 - POLESTAR / HAPPY HEART FARM DETENTION SUMMARY Condition Required Volume (ACRE-FT) Provided Volume Graded To Spillway (Acre-Ft) Additional Volume Provided ( Acre-Ft) WQCV ( ACRE-FT) Total Peak Outflow Interim 4.88 6.75 1.87 1.2 176 Ultimate 13.18 14.89 1.71 1.2 38.48 For the ultimate condition, JR Engineering has provided a pond layout that exceeds the ultimate detention requirements, as specified in Table 4. In the ultimate model, the site is releasing at a lower rate of 38.48 cfs vs. the Jacobs release rate of 47.01 cfs. JR Engineering wants to be conservative and detain at least 13.18 acres of runoff (calculated from the Jacob Canal Importation report + Polestar site). The Jacobs Canal Importation model release rate is not explicitly stated in the report [3]. Table 6 shows the volume in the ultimate model (slightly higher than what is required) and the volume provided in the ultimate Jacobs model with each model’s respective release rates. TABLE 6: Jacobs Plum Model vs JR Ultimate SWMM Model Happy Heart Farms/Polestar Detention Pond Pond 23 SWMM Model Max Volume in SWMM Total Peak Outflow JR-ULTIMATE MODEL 13.45 Acre-ft 38.48 cfs JACOBS MODEL 8.3 Acre-ft 47.01 cfs Polestar Village - Floodplain Modeling Report September 2023 16 5.4 Hydrology Summary The revised hydrology takes into account more accurate data and information, such as an additional runoff source from the Locust Grove subdivision that currently drains directly on the existing Polestar site based on JR Engineer’s survey topography. The benefits of updating the hydrology were a critical component to delineating a site-specific basin for the Polestar site to calculate detention requirements, so the CLOMR is accurate and reflects the modeled flow leaving, the site to accurately map the floodplain. The corrective effective SWMM model shows that certain homeowners downstream of the site are currently experiencing adverse impacts from flows and runoff that is greater than what is currently mapped, as shown in Appendix J.V within the Modified Table B.1.1 Plum Channel Flow Path Discharge Profile. JR Engineering has prepared four SWMM schematics to show the changes being made to the site and provided input and output files for each scenario for the 100-year event. The existing 2014 Anderson SWMM model includes an error for the Scenic Views pond, pond 313 (warning 10), and the corrected effective model accounts for additional sub-basins not included in the previous model and fixes the error for pond 313 (warning 10). The proposed SWMM model includes the development’s modifications to the Polestar site, and the ultimate model includes the planned outfall for the Scenic Views pond (pond 313) and the outfall for the Polestar detention facility (pond 23). Polestar Village - Floodplain Modeling Report September 2023 27 9.0 REFERENCES [1] Canal Importation Basin Hydrologic Conversion from MODSWMM to EPA SWMM 5.1; Anderson Consulting Engineers, Inc, December 6, 2013, (Revised July 3rd 2014) [2] Canal Importation Basin Master Drainage Plan Hydraulic Evaluation and Mapping Update by Anderson Consulting Engineers, Inc., Dated July 2014. [3] Canal Importation Basin Selected Plan Update Conceptual Design Report –Plum Channel Flow Path by Jacobs Engineering Group; Dated June 30st 2022. [4]Fort Collins Stormwater Criteria Manual, December 2018. [5]Home Rule Charter and Code of the City of Fort Collins, Published by Order of the City Council, dated April 13th 2023. Appendix J – Hydrology Appendix J.I -Vicinity Map A Westrian Company Appendix J.II - Calculations and Exhibits Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.: Calculated By:ARJ Checked By:0 Date:2/7/23 Tributary Area Width L=A/W Slope % Imperv N-Imperv N-Perv Store Imperv.Dstore perv.Zero % imperv. Storage (max) Storage (min)Decay Rate Sub-basin 17 25.5 3968.00 279.93 1.00%45.0%0.016 0.1 0.1 0.3 25 0.51 0.5 6.48 15 30.0 4356.00 300.00 2.00%25.0%0.016 0.1 0.1 0.3 25 0.51 0.5 6.48 Note: Only these two basin in the existing Hydrology were modified. Note: City of Fort Collins 2018 Criteria Recommends 1 for Zero % imperv. In the existing SWMM model this was 25. Note: City of Fort Collins 2018 Criteria Recommends 0.25 for N-Perv. In the existing SWMM model this mas 0.1. Tributary Area Width L=A/W Slope % Imperv N-Imperv N-Perv Store Imperv.Dstore perv.Zero % imperv. Storage (max) Storage (min)Decay Rate Sub-basin EP 21.5 1205.33 777.00 1.64%3.7%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 17W 10.2 1481.04 300.00 0.60%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 17E 14.8 2148.96 300.00 1.33%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 15E 9.0 1306.80 300.00 1.19%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 Tributary Area Width L=A/W Slope % Imperv N-Imperv N-Perv Store Imperv.Dstore perv.Zero % imperv. Storage (max) Storage (min)Decay Rate Sub-basin P 21.5 1572.48 595.58 0.86%50.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 17W 10.2 1481.04 300.00 0.60%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 17E 14.8 2148.96 300.00 1.33%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 15E 9.0 1306.80 300.00 1.19%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 Tributary Area Width L=A/W Slope % Imperv N-Imperv N-Perv Store Imperv.Dstore perv.Zero % imperv. Storage (max) Storage (min)Decay Rate Sub-basin P 21.5 1572.48 595.58 0.86%50.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 17W 10.2 1481.04 300.00 0.60%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 17E 14.8 2148.96 300.00 1.33%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 15E 9.0 1306.80 300.00 1.19%45.0%0.016 0.25 0.1 0.3 1 0.51 0.5 6.48 SWMM INPUTS 39797.01 Basin inputs City of Fort Collins Default Inputs City of Fort Collins Horton inputs Existing SWMM INPUTS Basin inputs City of Fort Collins Default Inputs City of Fort Collins Horton inputs Proposed SWMM INPUTS 2014 SWMM - 100yr Canal Importation Hydrology Update Basin inputs City of Fort Collins Default Inputs City of Fort Collins Horton inputs Ultimate SWMM INPUTS Basin inputs City of Fort Collins Default Inputs City of Fort Collins Horton inputs X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 1 2/9/2023 REQUIRED POLESTAR DETENTION POND VOLUME The onsite detention for the site i.e. the required runoff difference between the 100 year developed inflow rate and the 2-year historic runoff is 4.88 Acre-ft. In the SWMM model. P - 100 year developed inflow 1.61*106 Gallons of total runoff EP - 2-year existing inflow 0.02*106 Gallons of total runoff (1.61*106 - 0.02*106) gallons (𝟎𝒆𝒓𝟑 𝟑.𝟑𝟑𝟎𝟑𝒆𝒂𝒍𝒍𝒏𝒏𝒓)* (𝟎𝒂𝒄𝒓𝒆 𝟑𝟑,𝟑𝟑𝟎𝒆𝒓𝟑) = 4.88 Acre-ft. P - Peak Runoff – 119.98 CFS EP - 2 Year Peak Runoff – 2.31 CFS 0 20 40 60 80 100 120 140 0:00:00 1:12:00 2:24:00 3:36:00 4:48:00 6:00:00 7:12:00 8:24:00Runoff - CFS Time Time vs. Runoff 2 Year Existing (Basin EP) 100 Year Developed (Basin P) Polestar Pond 100 year Drain Time The Polestar Detention Facility meets Colorado Revised Statute (CRS) §37-92-602 (8) by continuously releasing and/or infiltrating at least 97% of all of the runoff from a rainfall event that is less than or equal to a 5-year storm within 72 hours after the end of the event. The Pond continuously releases or infiltrates at least 99% of the runoff within 120 hours after the end of events greater than a 5-year storm. PRPOPOSED –WATER QAULITY FOR POLESTAR DETENTION POND Subdivision:Polestar Project Name:Polestar Location:Fort Collins Project No.:39797.01 Calculated By:ARJ Checked By:0 Date:8/7/23 Basin Area (ac)% Imp. F1 3.87 31.6% E1 2.20 41.4% E2 0.45 55.7% E3 0.45 55.9% Total 6.97 37.8% WQCV Drain Time (hr):40 Coefficient, a (Figure 3.2):1.0 WQCV (in):0.17 WQCV (ac-ft):0.12 WQ Pond Tributary Areas WATER QUALITY IN DETENTION POND This table shows the WQ on-site treated in the Polestar Detention pond. This calculation includes 20% contingency for sediment accumulationas shown in equaltion 7-2. PLEASE NOTE area on MHFD sheet was multiplied by 1.2 X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 1 8/7/2023 X:\3970000.all\3979701\Excel\Drainage\3979701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 1 8/7/2023 PROPOSED POLESTAR DETENTION POND A Westrian Company Project: Basin ID: Depth Increment =1.00 ft Watershed Information Top of Micropool --0.00 ------66 0.002 Selected BMP Type =EDB 5103 --0.19 ------382 0.009 43 0.001 Watershed Area =8.36 acres 5104 --1.19 ------20,275 0.465 10,371 0.238 Watershed Length =1,149 ft 5105 --2.19 ------59,591 1.368 50,303 1.155 Watershed Length to Centroid =689 ft 5106 --3.19 ------87,449 2.008 123,823 2.843 Watershed Slope =0.011 ft/ft 5107 --4.19 ------99,692 2.289 217,394 4.991 Watershed Imperviousness =37.80%percent 5108 --5.19 ------106,050 2.435 320,265 7.352 Percentage Hydrologic Soil Group A =0.0%percent 5109 --6.19 ------112,486 2.582 429,533 9.861 Percentage Hydrologic Soil Group B =34.0%percent 5110 --7.19 ------119,103 2.734 545,328 12.519 Percentage Hydrologic Soil Groups C/D =66.0%percent -------- Target WQCV Drain Time =40.0 hours -------- Location for 1-hr Rainfall Depths = User Input -------- -------- -------- Optional User Overrides -------- Water Quality Capture Volume (WQCV) =0.121 acre-feet acre-feet -------- Excess Urban Runoff Volume (EURV) =0.305 acre-feet acre-feet -------- 2-yr Runoff Volume (P1 = 0.82 in.) =0.183 acre-feet 0.82 inches -------- 5-yr Runoff Volume (P1 = 1.09 in.) =0.285 acre-feet inches -------- 10-yr Runoff Volume (P1 = 1.4 in.) =0.460 acre-feet 1.40 inches -------- 25-yr Runoff Volume (P1 = 1.69 in.) =0.702 acre-feet inches -------- 50-yr Runoff Volume (P1 = 1.99 in.) =0.908 acre-feet inches -------- 100-yr Runoff Volume (P1 = 2.86 in.) =1.565 acre-feet 2.86 inches -------- 500-yr Runoff Volume (P1 = 3.14 in.) =1.769 acre-feet inches -------- Approximate 2-yr Detention Volume =0.172 acre-feet -------- Approximate 5-yr Detention Volume =0.277 acre-feet -------- Approximate 10-yr Detention Volume =0.372 acre-feet -------- Approximate 25-yr Detention Volume =0.437 acre-feet -------- Approximate 50-yr Detention Volume =0.478 acre-feet -------- Approximate 100-yr Detention Volume =0.720 acre-feet -------- Set Zone 1 as WQCV -------- Define Zones and Basin Geometry -------- Zone 1 Volume (WQCV) =0.12 acre-feet -------- Zone 2 Volume (User Defined - Zone 1) =0.00 acre-feet -------- Zone 3 Volume (100-year - Zones 1 & 2) =0.60 acre-feet -------- Total Detention Basin Volume =0.72 acre-feet -------- Initial Surcharge Volume (ISV) =user ft 3 -------- Initial Surcharge Depth (ISD) =user ft -------- Total Available Detention Depth (Htotal) =user ft -------- Depth of Trickle Channel (HTC) =user ft -------- Slope of Trickle Channel (STC) =user ft/ft -------- Slopes of Main Basin Sides (Smain) =user H:V -------- Basin Length-to-Width Ratio (RL/W) =user -------- -------- Initial Surcharge Area (AISV) =user ft 2 -------- Surcharge Volume Length (LISV) =user ft -------- Surcharge Volume Width (WISV) =user ft -------- Depth of Basin Floor (HFLOOR) =user ft -------- Length of Basin Floor (LFLOOR) =user ft -------- Width of Basin Floor (WFLOOR) =user ft -------- Area of Basin Floor (AFLOOR) =user ft 2 -------- Volume of Basin Floor (VFLOOR) =user ft 3 -------- Depth of Main Basin (HMAIN) =user ft -------- Length of Main Basin (LMAIN) =user ft -------- Width of Main Basin (WMAIN) =user ft -------- Area of Main Basin (AMAIN) =user ft 2 -------- Volume of Main Basin (VMAIN) =user ft 3 -------- Calculated Total Basin Volume (Vtotal) =user acre-feet -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- DETENTION BASIN STAGE-STORAGE TABLE BUILDER Optional Override Area (ft 2) Length (ft) Optional Override Stage (ft) Stage (ft) Stage - Storage Description Area (ft 2) Width (ft) Polestar - Interim Detention Pond (PLEASE NOTE: THE AREA ON THIS MHFD SHEET WAS MULTIPLIED BY 1.2 TO ACCOUNT FOR SEDIMENTATION FOR WQCV) MHFD-Detention, Version 4.06 (July 2022) Volume (ft 3) Volume (ac-ft) Area (acre) After providing required inputs above including 1-hour rainfall depths, click 'Run CUHP' to generate runoff hydrographs using the embedded Colorado Urban Hydrograph Procedure. ExampleZone Configuration (Retention Pond) MHFD-Detention_v4-06 -Interim Pond.xlsm, Basin 8/7/2023, 11:17 AM 1 User Defined Stage-Area Booleans for Message 1 Equal Stage-Area Inputs Watershed L:W 1 CountA Watershed Lc:L Watershed Slope 0 Calc_S_TC Booleans for CUHP 1 CUHP Inputs Complete H_FLOOR 1 CUHP Results Calculated L_FLOOR_OTHER 0.00 ISV 0.00 ISV 0.00 Floor 0.00 Floor 0.90 Zone 1 (WQCV)0.90 Zone 1 (WQCV) 0.90 Zone 2 (User)0.90 Zone 1 (WQCV) 1.83 Zone 3 (100-year)1.83 Zone 3 (100-year) DETENTION BASIN STAGE-STORAGE TABLE BUILDER MHFD-Detention, Version 4.06 (July 2022) 0.000 3.130 6.260 9.390 12.520 0.000 0.685 1.370 2.055 2.740 0.00 2.00 4.00 6.00 8.00 Volume (ac-ft)Area (acres)Stage (ft.) Area (acres)Volume (ac-ft) 0 29800 59600 89400 119200 0 5 10 15 20 0.00 2.00 4.00 6.00 8.00 Area (sq.ft.)Length, Width (ft.)Stage (ft) Length (ft)Width (ft)Area (sq.ft.) MHFD-Detention_v4-06 -Interim Pond.xlsm, Basin 8/7/2023, 11:17 AM Project: Basin ID: Estimated Estimated Stage (ft)Volume (ac-ft)Outlet Type Zone 1 (WQCV)0.90 0.121 Orifice Plate Zone 2 (User)0.90 0.000 Orifice Plate Zone 3 (100-year)1.83 0.599 Weir&Pipe (Restrict) Total (all zones)0.720 User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP)Calculated Parameters for Underdrain Underdrain Orifice Invert Depth =N/A ft (distance below the filtration media surface)Underdrain Orifice Area =N/A ft2 Underdrain Orifice Diameter =N/A inches Underdrain Orifice Centroid =N/A feet User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP)Calculated Parameters for Plate Centroid of Lowest Orifice =0.00 ft (relative to basin bottom at Stage = 0 ft)WQ Orifice Area per Row =5.278E-03 ft2 Depth at top of Zone using Orifice Plate =0.90 ft (relative to basin bottom at Stage = 0 ft)Elliptical Half-Width =N/A feet Orifice Plate: Orifice Vertical Spacing =N/A inches Elliptical Slot Centroid =N/A feet Orifice Plate: Orifice Area per Row =0.76 sq. inches (diameter = 1 inch)Elliptical Slot Area =N/A ft2 User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest) Row 1 (required)Row 2 (optional)Row 3 (optional)Row 4 (optional) Row 5 (optional) Row 6 (optional) Row 7 (optional) Row 8 (optional) Stage of Orifice Centroid (ft)0.00 0.30 0.60 Orifice Area (sq. inches)0.76 0.76 0.76 Row 9 (optional)Row 10 (optional) Row 11 (optional) Row 12 (optional)Row 13 (optional)Row 14 (optional) Row 15 (optional) Row 16 (optional) Stage of Orifice Centroid (ft) Orifice Area (sq. inches) User Input: Vertical Orifice (Circular or Rectangular)Calculated Parameters for Vertical Orifice Not Selected Not Selected Not Selected Not Selected Invert of Vertical Orifice =N/A ft (relative to basin bottom at Stage = 0 ft)Vertical Orifice Area =N/A ft2 Depth at top of Zone using Vertical Orifice =N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Centroid =N/A feet Vertical Orifice Diameter =N/A inches User Input: Overflow Weir (Dropbox with Flat or Sloped Grate and Outlet Pipe OR Rectangular/Trapezoidal Weir and No Outlet Pipe)Calculated Parameters for Overflow Weir grate Zone 3 Weir Not Selected Zone 3 Weir Not Selected Overflow Weir Front Edge Height, Ho =1.00 N/A ft (relative to basin bottom at Stage = 0 ft)Height of Grate Upper Edge, Ht =5.00 N/A feet Overflow Weir Front Edge Length =5.00 N/A feet Overflow Weir Slope Length =16.49 N/A feet Overflow Weir Grate Slope =4.00 N/A H:V Grate Open Area / 100-yr Orifice Area =12.70 N/A Horiz. Length of Weir Sides =16.00 N/A feet Overflow Grate Open Area w/o Debris =57.39 N/A ft2 Overflow Grate Type =Type C Grate N/A Overflow Grate Open Area w/ Debris =57.39 N/A ft2 Debris Clogging % =0%N/A % User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice)Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate Zone 3 Restrictor Not Selected Zone 3 Restrictor Not Selected Depth to Invert of Outlet Pipe =0.07 N/A ft (distance below basin bottom at Stage = 0 ft)Outlet Orifice Area =4.52 N/A ft2 Outlet Pipe Diameter =42.00 N/A inches Outlet Orifice Centroid =0.96 N/A feet Restrictor Plate Height Above Pipe Invert =20.00 inches Half-Central Angle of Restrictor Plate on Pipe =1.52 N/A radians User Input: Emergency Spillway (Rectangular or Trapezoidal)Calculated Parameters for Spillway Spillway Invert Stage=4.98 ft (relative to basin bottom at Stage = 0 ft)Spillway Design Flow Depth=0.26 feet Spillway Crest Length =36.80 feet Stage at Top of Freeboard =6.65 feet Spillway End Slopes =2.50 H:V Basin Area at Top of Freeboard =2.65 acres Freeboard above Max Water Surface =1.41 feet Basin Volume at Top of Freeboard =11.06 acre-ft Max Ponding Depth of Target Storage Volume =1.79 feet Discharge at Top of Freeboard =312.07 cfs Routed Hydrograph Results Design Storm Return Period =WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year One-Hour Rainfall Depth (in) =N/A N/A 0.82 1.09 1.40 1.69 1.99 2.86 3.14 CUHP Runoff Volume (acre-ft) =0.121 0.305 0.183 0.285 0.460 0.702 0.908 1.565 1.769 Inflow Hydrograph Volume (acre-ft) =N/A N/A 0.183 0.285 0.460 0.702 0.908 1.565 1.769 CUHP Predevelopment Peak Q (cfs) =N/A N/A 0.1 0.3 1.4 3.6 5.0 9.6 11.0 OPTIONAL Override Predevelopment Peak Q (cfs) =N/A N/A Predevelopment Unit Peak Flow, q (cfs/acre) =N/A N/A 0.01 0.04 0.17 0.43 0.60 1.15 1.32 Peak Inflow Q (cfs) =N/A N/A 1.6 2.6 4.4 7.2 9.3 15.7 17.6 Peak Outflow Q (cfs) =0.1 1.8 0.1 0.6 1.6 3.2 4.6 9.1 10.5 Ratio Peak Outflow to Predevelopment Q =N/A N/A N/A 2.1 1.1 0.9 0.9 0.9 1.0 Structure Controlling Flow =Plate Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Max Velocity through Grate 1 (fps) =N/A 0.03 0.00 0.0 0.0 0.1 0.1 0.2 0.2 Max Velocity through Grate 2 (fps) =N/A N/A N/A N/A N/A N/A N/A N/A N/A Time to Drain 97% of Inflow Volume (hours) =38 46 48 49 46 43 41 34 32 Time to Drain 99% of Inflow Volume (hours) =40 51 52 53 52 50 49 46 45 Maximum Ponding Depth (ft) =0.90 1.32 1.02 1.16 1.29 1.44 1.53 1.79 1.85 Area at Maximum Ponding Depth (acres) =0.33 0.58 0.39 0.45 0.55 0.68 0.77 1.00 1.06 Maximum Volume Stored (acre-ft) =0.122 0.306 0.166 0.220 0.284 0.376 0.448 0.670 0.742 DETENTION BASIN OUTLET STRUCTURE DESIGN MHFD-Detention, Version 4.06 (July 2022) Polestar - Interim Detention Pond (PLEASE NOTE: THE AREA ON THIS MHFD SHEET WAS MULTIPLIED BY 1.2 TO ACCOUNT FOR SEDIMENTATION FOR WQCV) The user can override the default CUHP hydrographs and runoff volumes by entering new values in the Inflow Hydrographs table (Columns W through AF). Example Zone Configuration (Retention MHFD-Detention_v4-06 -Interim Pond.xlsm, Outlet Structure 8/10/2023, 11:46 AM COUNTA for Basin Tab =1 Ao Dia WQ Plate Type Vert Orifice 1Vert Orifice 2 Count_Underdrain =0 0.11(diameter = 3/8 inch)2 1 1 Count_WQPlate =1 0.14(diameter = 7/16 inch) Count_VertOrifice1 =0 0.18(diameter = 1/2 inch)Outlet Plate 1 Outlet Plate 2 Drain Time Message Boolean Count_VertOrifice2 =0 0.24(diameter = 9/16 inch)4 1 5yr, <72hr 0 Count_Weir1 =1 0.29(diameter = 5/8 inch)>5yr, <120hr 0 Count_Weir2 =0 0.36(diameter = 11/16 inch)Max Depth Row Count_OutletPipe1 =1 0.42(diameter = 3/4 inch)WQCV 91 Count_OutletPipe2 =0 0.50(diameter = 13/16 inch)2 Year 103 COUNTA_2 (Standard FSD Setup)=1 0.58(diameter = 7/8 inch)EURV 133 Hidden Parameters & Calculations 0.67(diameter = 15/16 inch)5 Year 117 MaxPondDepth_Error?FALSE 0.76 (diameter = 1 inch)10 Year 130 Spillway Depth Cd_Broad-Crested Weir 3.00 0.86(diameter = 1-1/16 inches)25 Year 145 0.26 WQ Plate Flow at 100yr depth =0.09 0.97(diameter = 1-1/8 inches)50 Year 154 CLOG #1=100%1.08(diameter = 1-3/16 inches)100 Year 180 1 Z1_Boolean n*Cdw #1 =0.32 1.20(diameter = 1-1/4 inches)500 Year 186 1 Z2_Boolean n*Cdo #1 =1.45 1.32(diameter = 1-5/16 inches)Zone3_Pulldown Message 1 Z3_Boolean Overflow Weir #1 Angle =0.245 1.45(diameter = 1-3/8 inches)1 Opening Message CLOG #2=N/A 1.59(diameter = 1-7/16 inches)Draintime Running n*Cdw #2 =N/A 1.73(diameter = 1-1/2 inches)Outlet Boolean Outlet Rank Total (1 to 4) n*Cdo #2 =N/A 1.88(diameter = 1-9/16 inches)Vertical Orifice 1 0 0 1 Overflow Weir #2 Angle =N/A 2.03(diameter = 1-5/8 inches)Vertical Orifice 2 0 0 Boolean Underdrain Q at 100yr depth =0.00 2.20(diameter = 1-11/16 inches)Overflow Weir 1 1 1 0 Max Depth VertOrifice1 Q at 100yr depth =0.00 2.36(diameter = 1-3/4 inches)Overflow Weir 2 0 0 0 500yr Depth VertOrifice2 Q at 100yr depth =0.00 2.54(diameter = 1-13/16 inches)Outlet Pipe 1 1 1 0 Freeboard 2.72(diameter = 1-7/8 inches)Outlet Pipe 2 0 0 1 Spillway Count_User_Hydrographs 0 2.90(diameter = 1-15/16 inches)0 Spillway Length CountA_3 (EURV & 100yr) =1 3.09(diameter = 2 inches)FALSE Time Interval CountA_4 (100yr Only) =1 3.29(use rectangular openings)Button Visibility Boolean COUNTA_5 (FSD Weir Only)=0 0 WQCV Underdrain COUNTA_6 (EURV Weir Only)=1 1 WQCV Plate 0 EURV-WQCV Plate Outlet1_Pulldown_Boolean 0 EURV-WQCV VertOriice Outlet2_Pulldown_Boolean 0 Outlet 90% Qpeak Outlet3_Pulldown_Boolean 0 Outlet Undetained 0 Weir Only 90% Qpeak 0 Five Year Ratio Plate 0 Five Year Ratio VertOrifice EURV_draintime_user Spillway Options Offset Overlapping S-A-V-D Chart Axis Default X-axis Left Y-Axis Right Y-Axis minimum bound 0.00 0 0 maximum bound 8.00 490,000 320 S-A-V-D Chart Axis Override X-axis Left Y-Axis Right Y-Axis minimum bound maximum bound DETENTION BASIN OUTLET STRUCTURE DESIGN MHFD-Detention, Version 4.06 (July 2022) 0 2 4 6 8 10 12 14 16 18 20 0.1 1FLOW [cfs]TIME [hr] 500YR IN 500YR OUT 100YR IN 100YR OUT 50YR IN 50YR OUT 25YR IN 25YR OUT 10YR IN 10YR OUT 5YR IN 5YR OUT 2YR IN 2YR OUT EURV IN EURV OUT WQCV IN WQCV OUT 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0.1 1 10PONDING DEPTH [ft]DRAIN TIME [hr] 500YR 100YR 50YR 25YR 10YR 5YR 2YR EURV WQCV 0 50 100 150 200 250 300 0 50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00AREA [ft^2], VOLUME [ft^3]PONDING DEPTH [ft] User Area [ft^2] Interpolated Area [ft^2] Summary Area [ft^2] Volume [ft^3] Summary Volume [ft^3] Outflow [cfs] Summary Outflow [cfs] MHFD-Detention_v4-06 -Interim Pond.xlsm, Outlet Structure 8/10/2023, 11:46 AM Outflow Hydrograph Workbook Filename: Inflow Hydrographs The user can override the calculated inflow hydrographs from this workbook with inflow hydrographs developed in a separate program. SOURCE CUHP CUHP CUHP CUHP CUHP CUHP CUHP CUHP CUHP Time Interval TIME WQCV [cfs] EURV [cfs] 2 Year [cfs] 5 Year [cfs] 10 Year [cfs] 25 Year [cfs] 50 Year [cfs] 100 Year [cfs] 500 Year [cfs] 5.00 min 0:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 0.07 0:15:00 0.00 0.00 0.05 0.16 0.27 0.19 0.27 0.42 0.49 0:20:00 0.00 0.00 0.41 0.63 0.86 0.57 0.73 1.18 1.39 0:25:00 0.00 0.00 1.07 1.73 2.84 1.52 2.00 3.90 4.71 0:30:00 0.00 0.00 1.53 2.43 4.11 4.86 6.48 10.88 12.42 0:35:00 0.00 0.00 1.64 2.60 4.36 6.47 8.43 14.38 16.27 0:40:00 0.00 0.00 1.64 2.55 4.28 7.17 9.25 15.55 17.53 0:45:00 0.00 0.00 1.54 2.43 4.06 7.11 9.15 15.67 17.64 0:50:00 0.00 0.00 1.45 2.31 3.80 6.95 8.93 15.25 17.17 0:55:00 0.00 0.00 1.37 2.18 3.57 6.50 8.38 14.58 16.42 1:00:00 0.00 0.00 1.30 2.05 3.35 6.07 7.85 13.93 15.68 1:05:00 0.00 0.00 1.24 1.96 3.18 5.68 7.36 13.36 15.05 1:10:00 0.00 0.00 1.17 1.87 3.04 5.25 6.82 12.33 13.91 1:15:00 0.00 0.00 1.10 1.77 2.91 4.86 6.32 11.35 12.82 1:20:00 0.00 0.00 1.03 1.65 2.71 4.44 5.77 10.21 11.53 1:25:00 0.00 0.00 0.96 1.52 2.48 4.03 5.23 9.12 10.30 1:30:00 0.00 0.00 0.89 1.41 2.25 3.62 4.68 8.10 9.14 1:35:00 0.00 0.00 0.83 1.31 2.05 3.22 4.16 7.16 8.08 1:40:00 0.00 0.00 0.79 1.22 1.91 2.89 3.73 6.41 7.25 1:45:00 0.00 0.00 0.76 1.14 1.80 2.64 3.41 5.84 6.60 1:50:00 0.00 0.00 0.73 1.08 1.70 2.44 3.14 5.34 6.04 1:55:00 0.00 0.00 0.69 1.02 1.60 2.26 2.91 4.89 5.53 2:00:00 0.00 0.00 0.64 0.95 1.48 2.09 2.69 4.48 5.07 2:05:00 0.00 0.00 0.57 0.85 1.32 1.87 2.40 3.98 4.50 2:10:00 0.00 0.00 0.51 0.75 1.16 1.65 2.12 3.50 3.95 2:15:00 0.00 0.00 0.45 0.66 1.01 1.45 1.85 3.04 3.43 2:20:00 0.00 0.00 0.39 0.57 0.87 1.25 1.59 2.62 2.95 2:25:00 0.00 0.00 0.34 0.48 0.73 1.06 1.35 2.20 2.48 2:30:00 0.00 0.00 0.29 0.41 0.61 0.88 1.11 1.80 2.02 2:35:00 0.00 0.00 0.24 0.33 0.49 0.70 0.88 1.42 1.59 2:40:00 0.00 0.00 0.19 0.26 0.38 0.54 0.67 1.06 1.19 2:45:00 0.00 0.00 0.15 0.21 0.30 0.39 0.49 0.78 0.88 2:50:00 0.00 0.00 0.12 0.17 0.25 0.30 0.37 0.59 0.67 2:55:00 0.00 0.00 0.10 0.14 0.21 0.23 0.29 0.45 0.51 3:00:00 0.00 0.00 0.09 0.12 0.17 0.18 0.23 0.34 0.39 3:05:00 0.00 0.00 0.07 0.10 0.14 0.14 0.18 0.26 0.30 3:10:00 0.00 0.00 0.06 0.08 0.12 0.11 0.14 0.20 0.23 3:15:00 0.00 0.00 0.05 0.07 0.10 0.09 0.11 0.15 0.17 3:20:00 0.00 0.00 0.04 0.06 0.08 0.07 0.09 0.12 0.13 3:25:00 0.00 0.00 0.04 0.05 0.06 0.06 0.07 0.09 0.11 3:30:00 0.00 0.00 0.03 0.04 0.05 0.05 0.06 0.07 0.08 3:35:00 0.00 0.00 0.02 0.03 0.04 0.04 0.05 0.06 0.07 3:40:00 0.00 0.00 0.02 0.02 0.03 0.03 0.03 0.05 0.05 3:45:00 0.00 0.00 0.01 0.02 0.02 0.02 0.03 0.03 0.04 3:50:00 0.00 0.00 0.01 0.01 0.02 0.02 0.02 0.02 0.03 3:55:00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02 4:00:00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 4:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:15:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:20:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:25:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:30:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:15:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:20:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:25:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:30:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 6:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 DETENTION BASIN OUTLET STRUCTURE DESIGN 10 100 0 50 100 150 200 250 300 OUTFLOW [cfs]MHFD-Detention_v4-06 -Interim Pond.xlsm, Outlet Structure 8/10/2023, 11:46 AM Summary Stage-Area-Volume-Discharge Relationships The user can create a summary S-A-V-D by entering the desired stage increments and the remainder of the table will populate automatically. The user should graphically compare the summary S-A-V-D table to the full S-A-V-D table in the chart to confirm it captures all key transition points. Stage Area Area Volume Volume Total Outflow [ft][ft 2][acres][ft 3][ac-ft][cfs] For best results, include the stages of all grade slope changes (e.g. ISV and Floor) from the S-A-V table on Sheet 'Basin'. Also include the inverts of all outlets (e.g. vertical orifice, overflow grate, and spillway, where applicable). DETENTION BASIN OUTLET STRUCTURE DESIGN Stage - Storage Description MHFD-Detention, Version 4.06 (July 2022) MHFD-Detention_v4-06 -Interim Pond.xlsm, Outlet Structure 8/10/2023, 11:46 AM ULTIMATE POLESTAR DETENTION POND A Westrian Company HAPPY HEART FARMS DETENTION POND BY JACOBS ENGINEERING GROUP CONCEPTUAL DESIGN PLAN & PROFILE CANAL IMPORTATION BASIN N Project: Basin ID: Depth Increment =1.00 ft Watershed Information Top of Micropool --0.00 ------32 0.001 Selected BMP Type =EDB 5099 --0.99 ------12,276 0.282 6,092 0.140 Watershed Area =8.36 acres 5100 --1.99 ------42,526 0.976 33,493 0.769 Watershed Length =1,149 ft 5101 --2.99 ------62,048 1.424 85,780 1.969 Watershed Length to Centroid =689 ft 5102 --3.99 ------69,405 1.593 151,506 3.478 Watershed Slope =0.011 ft/ft 5103 --4.99 ------75,067 1.723 223,742 5.136 Watershed Imperviousness =37.80%percent 5104 --5.99 ------80,847 1.856 301,699 6.926 Percentage Hydrologic Soil Group A =0.0%percent 5105 --6.99 ------86,761 1.992 385,503 8.850 Percentage Hydrologic Soil Group B =34.0%percent 5106 --7.99 ------93,012 2.135 475,390 10.913 Percentage Hydrologic Soil Groups C/D =66.0%percent 5107 --8.99 ------99,265 2.279 571,528 13.120 Target WQCV Drain Time =40.0 hours 5108 --9.99 ------105,638 2.425 673,979 15.472 Location for 1-hr Rainfall Depths = User Input 5109 --10.99 ------112,095 2.573 782,845 17.972 5110 --11.99 ------118,779 2.727 898,282 20.622 -------- Optional User Overrides -------- Water Quality Capture Volume (WQCV) =0.121 acre-feet acre-feet -------- Excess Urban Runoff Volume (EURV) =0.305 acre-feet acre-feet -------- 2-yr Runoff Volume (P1 = 0.82 in.) =0.183 acre-feet 0.82 inches -------- 5-yr Runoff Volume (P1 = 1.09 in.) =0.285 acre-feet inches -------- 10-yr Runoff Volume (P1 = 1.4 in.) =0.460 acre-feet 1.40 inches -------- 25-yr Runoff Volume (P1 = 1.69 in.) =0.702 acre-feet inches -------- 50-yr Runoff Volume (P1 = 1.99 in.) =0.908 acre-feet inches -------- 100-yr Runoff Volume (P1 = 2.86 in.) =1.565 acre-feet 2.86 inches -------- 500-yr Runoff Volume (P1 = 3.14 in.) =1.769 acre-feet inches -------- Approximate 2-yr Detention Volume =0.172 acre-feet -------- Approximate 5-yr Detention Volume =0.277 acre-feet -------- Approximate 10-yr Detention Volume =0.372 acre-feet -------- Approximate 25-yr Detention Volume =0.437 acre-feet -------- Approximate 50-yr Detention Volume =0.478 acre-feet -------- Approximate 100-yr Detention Volume =0.720 acre-feet -------- Set Zone 1 as WQCV -------- Define Zones and Basin Geometry -------- Zone 1 Volume (WQCV) =0.12 acre-feet -------- Zone 2 Volume (User Defined - Zone 1) =0.00 acre-feet -------- Zone 3 Volume (100-year - Zones 1 & 2) =0.60 acre-feet -------- Total Detention Basin Volume =0.72 acre-feet -------- Initial Surcharge Volume (ISV) =user ft 3 -------- Initial Surcharge Depth (ISD) =user ft -------- Total Available Detention Depth (Htotal) =user ft -------- Depth of Trickle Channel (HTC) =user ft -------- Slope of Trickle Channel (STC) =user ft/ft -------- Slopes of Main Basin Sides (Smain) =user H:V -------- Basin Length-to-Width Ratio (RL/W) =user -------- -------- Initial Surcharge Area (AISV) =user ft 2 -------- Surcharge Volume Length (LISV) =user ft -------- Surcharge Volume Width (WISV) =user ft -------- Depth of Basin Floor (HFLOOR) =user ft -------- Length of Basin Floor (LFLOOR) =user ft -------- Width of Basin Floor (WFLOOR) =user ft -------- Area of Basin Floor (AFLOOR) =user ft 2 -------- Volume of Basin Floor (VFLOOR) =user ft 3 -------- Depth of Main Basin (HMAIN) =user ft -------- Length of Main Basin (LMAIN) =user ft -------- Width of Main Basin (WMAIN) =user ft -------- Area of Main Basin (AMAIN) =user ft 2 -------- Volume of Main Basin (VMAIN) =user ft 3 -------- Calculated Total Basin Volume (Vtotal) =user acre-feet -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- DETENTION BASIN STAGE-STORAGE TABLE BUILDER Optional Override Area (ft 2) Length (ft) Optional Override Stage (ft) Stage (ft) Stage - Storage Description Area (ft 2) Width (ft) Polestar - Ultimate Detention Pond (PLEASE NOTE: THE AREA ON THS MHFD SHEET WAS MULTIPLIED BY 1.2 TO ACCOUNT FOR SEDIMENTATION FOR WQCV) MHFD-Detention, Version 4.06 (July 2022) Volume (ft 3) Volume (ac-ft) Area (acre) After providing required inputs above including 1-hour rainfall depths, click 'Run CUHP' to generate runoff hydrographs using the embedded Colorado Urban Hydrograph Procedure. ExampleZone Configuration (Retention Pond) MHFD-Detention_v4-06 - Ultimate Pond.xlsm, Basin 8/7/2023, 2:20 PM 1 User Defined Stage-Area Booleans for Message 1 Equal Stage-Area Inputs Watershed L:W 1 CountA Watershed Lc:L Watershed Slope 0 Calc_S_TC Booleans for CUHP 1 CUHP Inputs Complete H_FLOOR 1 CUHP Results Calculated L_FLOOR_OTHER 0.00 ISV 0.00 ISV 0.00 Floor 0.00 Floor 0.93 Zone 1 (WQCV)0.93 Zone 1 (WQCV) 0.93 Zone 2 (User)0.93 Zone 1 (WQCV) 1.94 Zone 3 (100-year)1.94 Zone 3 (100-year) DETENTION BASIN STAGE-STORAGE TABLE BUILDER MHFD-Detention, Version 4.06 (July 2022) 0.000 5.160 10.320 15.480 20.640 0.000 0.685 1.370 2.055 2.740 0.00 3.00 6.00 9.00 12.00 Volume (ac-ft)Area (acres)Stage (ft.) Area (acres)Volume (ac-ft) 0 29700 59400 89100 118800 0 5 10 15 20 0.00 3.00 6.00 9.00 12.00 Area (sq.ft.)Length, Width (ft.)Stage (ft) Length (ft)Width (ft)Area (sq.ft.) MHFD-Detention_v4-06 - Ultimate Pond.xlsm, Basin 8/7/2023, 2:20 PM Project: Basin ID: Estimated Estimated Stage (ft) Volume (ac-ft)Outlet Type Zone 1 (WQCV)0.93 0.121 Orifice Plate Zone 2 (User)0.93 0.000 Orifice Plate Zone 3 (100-year)1.94 0.599 Weir&Pipe (Restrict) Total (all zones)0.720 User Input: Orifice at Underdrain Outlet (typically used to drain WQCV in a Filtration BMP)Calculated Parameters for Underdrain Underdrain Orifice Invert Depth =N/A ft (distance below the filtration media surface)Underdrain Orifice Area =N/A ft2 Underdrain Orifice Diameter =N/A inches Underdrain Orifice Centroid =N/A feet User Input: Orifice Plate with one or more orifices or Elliptical Slot Weir (typically used to drain WQCV and/or EURV in a sedimentation BMP)Calculated Parameters for Plate Centroid of Lowest Orifice =0.00 ft (relative to basin bottom at Stage = 0 ft)WQ Orifice Area per Row =6.597E-03 ft2 Depth at top of Zone using Orifice Plate =1.00 ft (relative to basin bottom at Stage = 0 ft)Elliptical Half-Width =N/A feet Orifice Plate: Orifice Vertical Spacing =N/A inches Elliptical Slot Centroid =N/A feet Orifice Plate: Orifice Area per Row =0.95 sq. inches (diameter = 1-1/16 inches)Elliptical Slot Area =N/A ft2 User Input: Stage and Total Area of Each Orifice Row (numbered from lowest to highest) Row 1 (required)Row 2 (optional)Row 3 (optional)Row 4 (optional)Row 5 (optional) Row 6 (optional)Row 7 (optional)Row 8 (optional) Stage of Orifice Centroid (ft)0.00 0.33 0.67 Orifice Area (sq. inches)0.95 0.95 0.95 Row 9 (optional)Row 10 (optional)Row 11 (optional)Row 12 (optional)Row 13 (optional)Row 14 (optional) Row 15 (optional) Row 16 (optional) Stage of Orifice Centroid (ft) Orifice Area (sq. inches) User Input: Vertical Orifice (Circular or Rectangular)Calculated Parameters for Vertical Orifice Not Selected Not Selected Not Selected Not Selected Invert of Vertical Orifice =N/A ft (relative to basin bottom at Stage = 0 ft) Vertical Orifice Area =N/A ft2 Depth at top of Zone using Vertical Orifice =N/A ft (relative to basin bottom at Stage = 0 ft)Vertical Orifice Centroid =N/A feet Vertical Orifice Diameter =N/A inches User Input: Overflow Weir (Dropbox with Flat or Sloped Grate and Outlet Pipe OR Rectangular/Trapezoidal Weir and No Outlet Pipe)Calculated Parameters for Overflow Weir grate Zone 3 Weir Not Selected Zone 3 Weir Not Selected Overflow Weir Front Edge Height, Ho =1.00 N/A ft (relative to basin bottom at Stage = 0 ft)Height of Grate Upper Edge, Ht =4.00 N/A feet Overflow Weir Front Edge Length =5.00 N/A feet Overflow Weir Slope Length =12.37 N/A feet Overflow Weir Grate Slope =4.00 N/A H:V Grate Open Area / 100-yr Orifice Area =15.56 N/A Horiz. Length of Weir Sides =12.00 N/A feet Overflow Grate Open Area w/o Debris =43.05 N/A ft2 Overflow Grate Type =Type C Grate N/A Overflow Grate Open Area w/ Debris =43.05 N/A ft2 Debris Clogging % =0%N/A % User Input: Outlet Pipe w/ Flow Restriction Plate (Circular Orifice, Restrictor Plate, or Rectangular Orifice)Calculated Parameters for Outlet Pipe w/ Flow Restriction Plate Zone 3 Restrictor Not Selected Zone 3 Restrictor Not Selected Depth to Invert of Outlet Pipe =0.00 N/A ft (distance below basin bottom at Stage = 0 ft)Outlet Orifice Area =2.77 N/A ft2 Outlet Pipe Diameter =30.00 N/A inches Outlet Orifice Centroid =0.79 N/A feet Restrictor Plate Height Above Pipe Invert =16.50 inches Half-Central Angle of Restrictor Plate on Pipe =1.67 N/A radians User Input: Emergency Spillway (Rectangular or Trapezoidal)Calculated Parameters for Spillway Spillway Invert Stage=8.78 ft (relative to basin bottom at Stage = 0 ft)Spillway Design Flow Depth=0.26 feet Spillway Crest Length =36.80 feet Stage at Top of Freeboard =11.28 feet Spillway End Slopes =2.50 H:V Basin Area at Top of Freeboard =2.62 acres Freeboard above Max Water Surface =2.24 feet Basin Volume at Top of Freeboard =18.72 acre-ft Max Ponding Depth of Target Storage Volume =1.83 feet Discharge at Top of Freeboard =538.84 cfs Routed Hydrograph Results Design Storm Return Period =WQCV EURV 2 Year 5 Year 10 Year 25 Year 50 Year 100 Year 500 Year One-Hour Rainfall Depth (in) =N/A N/A 0.82 1.09 1.40 1.69 1.99 2.86 3.14 CUHP Runoff Volume (acre-ft) =0.121 0.305 0.183 0.285 0.460 0.702 0.908 1.565 1.769 Inflow Hydrograph Volume (acre-ft) =N/A N/A 0.183 0.285 0.460 0.702 0.908 1.565 1.769 CUHP Predevelopment Peak Q (cfs) =N/A N/A 0.1 0.3 1.4 3.6 5.0 9.6 11.0 OPTIONAL Override Predevelopment Peak Q (cfs) =N/A N/A Predevelopment Unit Peak Flow, q (cfs/acre) =N/A N/A 0.01 0.04 0.17 0.43 0.60 1.15 1.32 Peak Inflow Q (cfs) =N/A N/A 1.6 2.6 4.4 7.2 9.3 15.7 17.6 Peak Outflow Q (cfs) =0.1 2.5 0.2 0.8 1.8 3.6 5.0 9.9 11.5 Ratio Peak Outflow to Predevelopment Q =N/A N/A N/A 2.6 1.3 1.0 1.0 1.0 1.0 Structure Controlling Flow =Plate Overflow Weir 1 Overflow Weir 1 Overflow Weir 1Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Overflow Weir 1 Max Velocity through Grate 1 (fps) =N/A 0.06 0.00 0.0 0.0 0.1 0.1 0.2 0.3 Max Velocity through Grate 2 (fps) =N/A N/A N/A N/A N/A N/A N/A N/A N/A Time to Drain 97% of Inflow Volume (hours) =38 41 44 43 39 36 33 27 25 Time to Drain 99% of Inflow Volume (hours) =40 46 48 48 47 45 43 39 38 Maximum Ponding Depth (ft) =0.93 1.39 1.06 1.18 1.31 1.46 1.56 1.83 1.89 Area at Maximum Ponding Depth (acres) =0.26 0.56 0.32 0.41 0.50 0.61 0.68 0.86 0.91 Maximum Volume Stored (acre-ft) =0.123 0.308 0.158 0.202 0.261 0.349 0.413 0.613 0.675 The user can override the default CUHP hydrographs and runoff volumes by entering new values in the Inflow Hydrographs table (Columns W through AF). DETENTION BASIN OUTLET STRUCTURE DESIGN MHFD-Detention, Version 4.06 (July 2022) Polestar - Ultimate Detention Pond (PLEASE NOTE: THE AREA ON THS MHFD SHEET WAS MULTIPLIED BY 1.2 TO ACCOUNT FOR SEDIMENTATION FOR WQCV) Example Zone Configuration (Retention Pond) MHFD-Detention_v4-06 - Ultimate Pond.xlsm, Outlet Structure 8/7/2023, 2:21 PM COUNTA for Basin Tab =1 Ao Dia WQ Plate Type Vert Orifice 1Vert Orifice 2 Count_Underdrain =0 0.11(diameter = 3/8 inch)2 1 1 Count_WQPlate =1 0.14(diameter = 7/16 inch) Count_VertOrifice1 =0 0.18(diameter = 1/2 inch)Outlet Plate 1 Outlet Plate 2 Drain Time Message Boolean Count_VertOrifice2 =0 0.24(diameter = 9/16 inch)4 1 5yr, <72hr 0 Count_Weir1 =1 0.29(diameter = 5/8 inch)>5yr, <120hr 0 Count_Weir2 =0 0.36(diameter = 11/16 inch)Max Depth Row Count_OutletPipe1 =1 0.42(diameter = 3/4 inch)WQCV 94 Count_OutletPipe2 =0 0.50(diameter = 13/16 inch)2 Year 107 COUNTA_2 (Standard FSD Setup)=1 0.58(diameter = 7/8 inch)EURV 140 Hidden Parameters & Calculations 0.67(diameter = 15/16 inch)5 Year 119 MaxPondDepth_Error?FALSE 0.76 (diameter = 1 inch)10 Year 132 Spillway Depth Cd_Broad-Crested Weir 3.00 0.86(diameter = 1-1/16 inches)25 Year 147 0.26 WQ Plate Flow at 100yr depth =0.12 0.97(diameter = 1-1/8 inches)50 Year 157 CLOG #1=100%1.08(diameter = 1-3/16 inches)100 Year 184 1 Z1_Boolean n*Cdw #1 =0.32 1.20(diameter = 1-1/4 inches)500 Year 190 1 Z2_Boolean n*Cdo #1 =1.45 1.32(diameter = 1-5/16 inches)Zone3_Pulldown Message 1 Z3_Boolean Overflow Weir #1 Angle =0.245 1.45(diameter = 1-3/8 inches)1 Opening Message CLOG #2=N/A 1.59(diameter = 1-7/16 inches)Draintime Running n*Cdw #2 =N/A 1.73(diameter = 1-1/2 inches)Outlet Boolean Outlet Rank Total (1 to 4) n*Cdo #2 =N/A 1.88(diameter = 1-9/16 inches)Vertical Orifice 1 0 0 1 Overflow Weir #2 Angle =N/A 2.03(diameter = 1-5/8 inches)Vertical Orifice 2 0 0 Boolean Underdrain Q at 100yr depth =0.00 2.20(diameter = 1-11/16 inches)Overflow Weir 1 1 1 0 Max Depth VertOrifice1 Q at 100yr depth =0.00 2.36(diameter = 1-3/4 inches)Overflow Weir 2 0 0 0 500yr Depth VertOrifice2 Q at 100yr depth =0.00 2.54(diameter = 1-13/16 inches)Outlet Pipe 1 1 1 0 Freeboard 2.72(diameter = 1-7/8 inches)Outlet Pipe 2 0 0 1 Spillway Count_User_Hydrographs 0 2.90(diameter = 1-15/16 inches)0 Spillway Length CountA_3 (EURV & 100yr) =1 3.09(diameter = 2 inches)FALSE Time Interval CountA_4 (100yr Only) =1 3.29(use rectangular openings)Button Visibility Boolean COUNTA_5 (FSD Weir Only)=0 0 WQCV Underdrain COUNTA_6 (EURV Weir Only)=1 1 WQCV Plate 0 EURV-WQCV Plate Outlet1_Pulldown_Boolean 0 EURV-WQCV VertOriice Outlet2_Pulldown_Boolean 0 Outlet 90% Qpeak Outlet3_Pulldown_Boolean 0 Outlet Undetained 0 Weir Only 90% Qpeak 0 Five Year Ratio Plate 0 Five Year Ratio VertOrifice EURV_draintime_user Spillway Options Offset Overlapping S-A-V-D Chart Axis Default X-axis Left Y-Axis Right Y-Axis minimum bound 0.00 0 0 maximum bound 12.00 820,000 540 S-A-V-D Chart Axis Override X-axis Left Y-Axis Right Y-Axis minimum bound maximum bound MHFD-Detention, Version 4.06 (July 2022) DETENTION BASIN OUTLET STRUCTURE DESIGN 0 2 4 6 8 10 12 14 16 18 20 0.1 1FLOW [cfs]TIME [hr] 500YR IN 500YR OUT 100YR IN 100YR OUT 50YR IN 50YR OUT 25YR IN 25YR OUT 10YR IN 10YR OUT 5YR IN 5YR OUT 2YR IN 2YR OUT EURV IN EURV OUT WQCV IN WQCV OUT 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0.1 1 10PONDING DEPTH [ft]DRAIN TIME [hr] 500YR 100YR 50YR 25YR 10YR 5YR 2YR EURV WQCV 0 100 200 300 400 500 0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 800,000 0.00 2.00 4.00 6.00 8.00 10.00 12.00AREA [ft^2], VOLUME [ft^3]PONDING DEPTH [ft] User Area [ft^2] Interpolated Area [ft^2] Summary Area [ft^2] Volume [ft^3] Summary Volume [ft^3] Outflow [cfs] Summary Outflow [cfs] MHFD-Detention_v4-06 - Ultimate Pond.xlsm, Outlet Structure 8/7/2023, 2:21 PM Outflow Hydrograph Workbook Filename: Inflow Hydrographs The user can override the calculated inflow hydrographs from this workbook with inflow hydrographs developed in a separate program. SOURCE CUHP CUHP CUHP CUHP CUHP CUHP CUHP CUHP CUHP Time Interval TIME WQCV [cfs]EURV [cfs]2 Year [cfs] 5 Year [cfs] 10 Year [cfs] 25 Year [cfs] 50 Year [cfs] 100 Year [cfs] 500 Year [cfs] 5.00 min 0:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 0.07 0:15:00 0.00 0.00 0.05 0.16 0.27 0.19 0.27 0.42 0.49 0:20:00 0.00 0.00 0.41 0.63 0.86 0.57 0.73 1.18 1.39 0:25:00 0.00 0.00 1.07 1.73 2.84 1.52 2.00 3.90 4.71 0:30:00 0.00 0.00 1.53 2.43 4.11 4.86 6.48 10.88 12.42 0:35:00 0.00 0.00 1.64 2.60 4.36 6.47 8.43 14.38 16.27 0:40:00 0.00 0.00 1.64 2.55 4.28 7.17 9.25 15.55 17.53 0:45:00 0.00 0.00 1.54 2.43 4.06 7.11 9.15 15.67 17.64 0:50:00 0.00 0.00 1.45 2.31 3.80 6.95 8.93 15.25 17.17 0:55:00 0.00 0.00 1.37 2.18 3.57 6.50 8.38 14.58 16.42 1:00:00 0.00 0.00 1.30 2.05 3.35 6.07 7.85 13.93 15.68 1:05:00 0.00 0.00 1.24 1.96 3.18 5.68 7.36 13.36 15.05 1:10:00 0.00 0.00 1.17 1.87 3.04 5.25 6.82 12.33 13.91 1:15:00 0.00 0.00 1.10 1.77 2.91 4.86 6.32 11.35 12.82 1:20:00 0.00 0.00 1.03 1.65 2.71 4.44 5.77 10.21 11.53 1:25:00 0.00 0.00 0.96 1.52 2.48 4.03 5.23 9.12 10.30 1:30:00 0.00 0.00 0.89 1.41 2.25 3.62 4.68 8.10 9.14 1:35:00 0.00 0.00 0.83 1.31 2.05 3.22 4.16 7.16 8.08 1:40:00 0.00 0.00 0.79 1.22 1.91 2.89 3.73 6.41 7.25 1:45:00 0.00 0.00 0.76 1.14 1.80 2.64 3.41 5.84 6.60 1:50:00 0.00 0.00 0.73 1.08 1.70 2.44 3.14 5.34 6.04 1:55:00 0.00 0.00 0.69 1.02 1.60 2.26 2.91 4.89 5.53 2:00:00 0.00 0.00 0.64 0.95 1.48 2.09 2.69 4.48 5.07 2:05:00 0.00 0.00 0.57 0.85 1.32 1.87 2.40 3.98 4.50 2:10:00 0.00 0.00 0.51 0.75 1.16 1.65 2.12 3.50 3.95 2:15:00 0.00 0.00 0.45 0.66 1.01 1.45 1.85 3.04 3.43 2:20:00 0.00 0.00 0.39 0.57 0.87 1.25 1.59 2.62 2.95 2:25:00 0.00 0.00 0.34 0.48 0.73 1.06 1.35 2.20 2.48 2:30:00 0.00 0.00 0.29 0.41 0.61 0.88 1.11 1.80 2.02 2:35:00 0.00 0.00 0.24 0.33 0.49 0.70 0.88 1.42 1.59 2:40:00 0.00 0.00 0.19 0.26 0.38 0.54 0.67 1.06 1.19 2:45:00 0.00 0.00 0.15 0.21 0.30 0.39 0.49 0.78 0.88 2:50:00 0.00 0.00 0.12 0.17 0.25 0.30 0.37 0.59 0.67 2:55:00 0.00 0.00 0.10 0.14 0.21 0.23 0.29 0.45 0.51 3:00:00 0.00 0.00 0.09 0.12 0.17 0.18 0.23 0.34 0.39 3:05:00 0.00 0.00 0.07 0.10 0.14 0.14 0.18 0.26 0.30 3:10:00 0.00 0.00 0.06 0.08 0.12 0.11 0.14 0.20 0.23 3:15:00 0.00 0.00 0.05 0.07 0.10 0.09 0.11 0.15 0.17 3:20:00 0.00 0.00 0.04 0.06 0.08 0.07 0.09 0.12 0.13 3:25:00 0.00 0.00 0.04 0.05 0.06 0.06 0.07 0.09 0.11 3:30:00 0.00 0.00 0.03 0.04 0.05 0.05 0.06 0.07 0.08 3:35:00 0.00 0.00 0.02 0.03 0.04 0.04 0.05 0.06 0.07 3:40:00 0.00 0.00 0.02 0.02 0.03 0.03 0.03 0.05 0.05 3:45:00 0.00 0.00 0.01 0.02 0.02 0.02 0.03 0.03 0.04 3:50:00 0.00 0.00 0.01 0.01 0.02 0.02 0.02 0.02 0.03 3:55:00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.02 0.02 4:00:00 0.00 0.00 0.00 0.01 0.01 0.01 0.01 0.01 0.01 4:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:15:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:20:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:25:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:30:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:05:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:10:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:15:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:20:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:25:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:30:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:35:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:40:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:45:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:50:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5:55:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 6:00:00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 DETENTION BASIN OUTLET STRUCTURE DESIGN 10 100 0 100 200 300 400 500 12.00 OUTFLOW [cfs]MHFD-Detention_v4-06 - Ultimate Pond.xlsm, Outlet Structure 8/7/2023, 2:21 PM Summary Stage-Area-Volume-Discharge Relationships The user can create a summary S-A-V-D by entering the desired stage increments and the remainder of the table will populate automatically. The user should graphically compare the summary S-A-V-D table to the full S-A-V-D table in the chart to confirm it captures all key transition points. Stage Area Area Volume Volume Total Outflow [ft][ft 2][acres][ft 3][ac-ft][cfs] MHFD-Detention, Version 4.06 (July 2022) DETENTION BASIN OUTLET STRUCTURE DESIGN Stage - Storage Description For best results, include the stages of all grade slope changes (e.g. ISV and Floor) from the S-A-V table on Sheet 'Basin'. Also include the inverts of all outlets (e.g. vertical orifice, overflow grate, and spillway, where applicable). MHFD-Detention_v4-06 - Ultimate Pond.xlsm, Outlet Structure 8/7/2023, 2:21 PM Project Name:Polestar Subdivision:Polestar Project No.: Location:Fort Collins Calculated By:ARJ Checked By:0 Date:3/15/23 Head (ft)Discharge (cfs)Head (ft)Discharge (cfs) 0 0.00 0 0.00 0.5 0.03 0.5 0.04 0.9 0.06 0.93 0.07 1 0.06 1 0.08 1.5 4.08 1.5 4.10 2 14.13 2 14.16 2.5 27.55 2.5 17.44 3 31.55 3 19.82 3.5 35.11 3.5 21.94 4 38.33 4 23.88 4.5 41.30 4.5 25.67 5 44.07 5 27.34 5.5 46.68 5.5 28.92 6 49.15 6 30.41 6.5 51.50 6.5 31.84 7 53.75 7 33.20 7.15 54.41 7.5 34.51 SEE WQCV STAGE IN RED 8 35.77 8.5 36.99 9 38.17 9.5 39.32 10 40.43 SEE WQCV STAGE IN RED WQ orifice plate, 42" Pipe and Overflow Structure INTERIM_OUTLET ULTIMATE_OUTLET WQ orifice plate, 30" Pipe w/ Restrictor plate and Overflow Structure Stage Discharge 39797.01 NOTE:In the Jacobs SWMM model the outfall was modeled as a 30" unrestricted pipe. Appendix J.III - SWMM Maps %%%%%%%§§§§%%%%%%% %%%%%%%%%%%%%%%%%%%§%§§§§%%§§%§% %% %%%%%%%%%%%%%%%% %%%% %%%%%%%%%§%%%%§§%%%%%%%%%%%%§%%%%§§%§§%%%%%%%%%%§%%%%% % %%§%%%%§%%%%%%%%%%%%%§%%%%%%%%%%%%§%%%%%§§%%%%%%%!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(!(#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*#*©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©L©LÄ2þ245ac.Ä2þ982ac.ÄþÄ2þ17.7ac.Ä2þ66.9ac.Ä2þ1065ac.Ä2þ5538ac.Ä2þ1530ac.Ä2þ9912ac.Ä2þ9533ac.Ä2þ5832ac.Ä2þ5494ac.Ä2þ6842ac.Ä2þ7230ac.Ä2þ5777ac.Ä2þ422.2ac.Ä2þ718.4ac.Ä2þ339.1ac.Ä2þ521.3ac.Ä2þ230.4ac.Ä2þ812.9ac.Ä2þ229.7ac.Ä2þ132.9ac.Ä2þ199.6ac.Ä2þ143.3ac.Ä2þ912.8ac.Ä2þ677.9ac.Ä2þ947.9ac.Ä2þ937.6ac.Ä2þ875.6ac.Ä2þ980.8ac.Ä2þ4414.5ac.Ä2þ1088.8ac.Ä2þ1217.8ac.Ä2þ2122.2ac.Ä2þ1725.5ac.Ä2þ5932.8ac.Ä2þ2028.6ac.Ä2þ5132.8ac.Ä2þ7204.6ac.Ä2þ4230.9ac.Ä2þ5030.6ac.Ä2þ2224.7ac.Ä2þ1613.7ac.Ä2þ1851.1ac.Ä2þ4331.2ac.Ä2þ5631.5ac.Ä2þ1123.1ac.Ä2þ8207.5ac.Ä2þ1167.7ac.Ä2þ5335.8ac.Ä2þ5730.9ac.Ä2þ5433.2ac.Ä2þ2246.4ac.Ä2þ5233.1ac.Ä2þ4955.4ac.Ä2þ1183.3ac.Ä2þ5191.6ac.Ä2þ5290.7ac.Ä2þ6611.8ac.Ä2þ5693.4ac.Ä2þ6926.2ac.Ä2þ7532.8ac.Ä2þ5792.8ac.Ä2þ5590.9ac.Ä2þ5090.9ac.Ä2þ5391.2ac.Ä2þ9713.4ac.Ä2þ5981.7ac.Ä2þ5888.9ac.Ä2þ7130.4ac.Ä2þ5201.7ac.Ä2þ5505.7ac.Ä2þ5702.3ac.Ä2þ7026.5ac.Ä2þ7313.5ac.Ä2þ5302.5ac.Ä2þ9610.3ac.Ä2þ5604.3ac.Ä2þ7413.9ac.Ä2þ5873.9ac.Ä2þ5807.2ac.þÄ2þ13951.2ac.Ä2þ14056.8ac.Ä2þ11124.6ac.Ä2þ11018.5ac.Ä2þ10914.7ac.Ä2þ11313.5ac.Ä2þ11211.1ac.Ä2þ11414.1ac.Ä2þ11520.1ac.Ä2þ11711.2ac.Ä2þ58915.6ac.Ä2þ19528.9ac.Ä2þ11924.6ac.Ä2þ97810.8ac.Ä2þ21923.8ac.Ä2þ12034.4ac.Ä2þ57810.3ac.Ä2þ59711.1ac.J9J8J5J4J3J2J1I8I7I5I4299399396395390378370368367366344324322319318317316315313310308304301802414410J94J93J75J74J34J22J21J17J10I17I13I12I10A31A30A28A27A26A25A24A23A22A21A19A17A15A14995879874873872871869863862861859856855854853852850311306303302300290276274272220205PP_4PP_3PP_2PP_1J945J944J878J720J719J715J714J713J712J711J709J598J593J589J587J583J580J579J577J573J570J569J563J559J550J549J543J539J533J529J520J519J513J433J424J423J418J190J167J148J123J121J120J118J117J116J115J113J110J108J105J103J102J101IB-3IB-1I6-4I6-3I6-2I6-1GC_2A16a529out519outJ543_US8 Outfall446 Spill445 Spill444 Spill442 Spill441 Spill428 Spill47 Outfall119 Storage720 Outfall719 Outfall715 Outfall714 Outfall713 Outfall712 Outfall549_outfall520 Outfall424 Outfall318 Outfall317 Outfall311_outfall299 OutfallGC3InletSkylineInlet2SkylineI17-1870378 OutfallSkylineEX-2278 OutfallI7-1Avery LowFlow 1, 2, 3Avery OutletJ523I12-1GC_5Overland TrailOverland TrailTaft Hill RoadLaporte AvenueElizabeth StreetMulberry StreetMulberry Street99 5 10176859 4 75731184288818711767114331037098741491587821287761719 3C11715A18 87148589113C2156018955 0 10159386207127135631 7 2105_pipe2 4 C20121583108569116944523b94518_pipe105_overflowPP_3472_pipe573104_pipe533a5433_pipe110_pipe103_overflowC3418587a577a167_pipeL8587b577bC23PP_4188_pipe2855 8 0 18_overflow102_pipeA28-85019022283A14110_overflowIBa16_pipeC 4 C22L1092L6-2A22540C8520719_pipeA 2 0 115_pipeGC_2288L17SHEET:1DATE:PROJECT NUMBER:CHECKED BY:DESIGNED BY:DRAWN BY:BNAMMCAMHCOFC2012.0107/01/2014³Legend!(Junction#*Outfall©LStorage%Conveyance ElementNon-Routing Element§OutletSubbasin0 400 800200FeetCITY OF FORT COLLINSCANAL IMPORTATION HYDROLOGIC CONVERSIONFROM MODSWMM TO EPA SWMM 5.0SUBBASIN AND ROUTING ELEMENTLOCATION MAP A Westrian Company A Westrian Company A Westrian Company A Westrian Company Appendix J.IV - Offsite Photos and Calculations POND 315 OUTFALL – DUEL 24” RCP EAST OF KIMBALL STEET ROCKY ROAD – DUEL 24“ STORM UTILITY MARKINGS - (ON WEST SIDE) POND 316 INFLOW PEAR STREET– (FACING WEST) Project: ID: 47187.82 X Design Information (Input): Circular Culvert:Barrel Diameter in Inches D =24 inches Inlet Edge Type (Choose from pull-down list)Grooved Edge Projecting OR: Box Culvert:Barrel Height (Rise) in Feet H (Rise) =ft Barrel Width (Span) in Feet W (Span) =ft Inlet Edge Type (Choose from pull-down list) 2.00 Number of Barrels # Barrels =2 Inlet Elevation at Culvert Invert 5094.40 Elev IN =5096.6 ft Outlet Elevation OR Slope 0.005 So =0.005 ft/ft Culvert Length L =440 ft Manning's Roughness n =0.013 Bend Loss Coefficient Kb =0 Exit Loss Coefficient Kx =1 1 Design Information (calculated): Entrance Loss Coefficient Ke =0.20 Friction Loss Coefficient Kf =5.43 Sum of All Loss Coefficients Ks =6.63 Minimum Energy Condition Coefficient KElow =-0.0028 Orifice Inlet Condition Coefficient Cd =0.67 Calculations of Culvert Capacity (output):Backwater calculations required to obtain Outlet Control Flowrate when HWo < 0.75 * Culvert Rise Headwater Tailwater Inlet Inlet Outlet Controlling Flow Surface Surface Control Control Control Culvert Control Elevation Elevation Equation Flowrate Flowrate Flowrate Used (ft)(ft)Used (cfs)(cfs)(cfs) 5096.60 5095.20 No Flow (WS < inlet)0.00 0.00 0.00 N/A 5096.85 5095.20 Min. Energy. Eqn.0.50 #N/A #N/A #N/A 5097.10 5095.20 Min. Energy. Eqn.2.32 #N/A #N/A #N/A 5097.35 5095.20 Min. Energy. Eqn.5.06 #N/A #N/A #N/A 5097.60 5095.20 Min. Energy. Eqn.8.68 #N/A #N/A #N/A 5097.85 5095.20 Regression Eqn.12.62 #N/A #N/A #N/A 5098.10 5095.20 Regression Eqn.17.28 27.88 17.28 INLET 5098.35 5095.20 Regression Eqn.22.62 29.43 22.62 INLET 5098.60 5095.20 Regression Eqn.27.94 30.91 27.94 INLET 5098.85 5095.20 Regression Eqn.32.94 32.33 32.33 OUTLET 5099.10 5095.20 Regression Eqn.37.42 33.69 33.69 OUTLET 5099.35 5095.20 Regression Eqn.41.46 35.00 35.00 OUTLET 5099.60 5095.20 Regression Eqn.45.10 36.28 36.28 OUTLET 5099.85 5095.20 Regression Eqn.48.44 37.51 37.51 OUTLET 5100.10 5095.20 Regression Eqn.51.54 38.71 38.71 OUTLET 5100.35 5095.20 Regression Eqn.54.44 39.88 39.88 OUTLET 5100.60 5095.20 Regression Eqn.57.22 41.02 41.02 OUTLET 5100.85 5095.20 Regression Eqn.59.82 42.12 42.12 OUTLET 5101.10 5095.20 Regression Eqn.62.30 43.21 43.21 OUTLET 5101.35 5095.20 Regression Eqn.64.70 44.26 44.26 OUTLET 5101.60 5095.20 Regression Eqn.67.04 45.30 45.30 OUTLET 5101.85 5095.20 Regression Eqn.69.30 46.31 46.31 OUTLET 5102.10 5095.20 Regression Eqn.71.48 47.30 47.30 OUTLET 5102.35 5095.20 Regression Eqn.73.62 48.28 48.28 OUTLET Processing Time:00.16 Seconds CULVERT SIZING (INLET vs. OUTLET CONTROL WITH TAILWATER EFFECTS) Kimball Detention (Pond 315 Culverts) MHFD-Culvert, Version 4.00 (May 2020) MHFD-Culvert_v4.0.xlsm, Culvert Rating 3/17/2023, 3:07 PM Project: ID: CULVERT SIZING (INLET vs. OUTLET CONTROL WITH TAILWATER EFFECTS) Kimball Detention (Pond 315 Culverts) MHFD-Culvert, Version 4.00 (May 2020) 5096.6 5097.6 5098.6 5099.6 5100.6 5101.6 5102.6 5103.6 0 20 40 60 80Stage (feet, elev)Discharge (cfs) STAGE-DISCHARGE CURVE FOR THE CULVERT Inlet Control Outlet Control Stage-Discharge MHFD-Culvert_v4.0.xlsm, Culvert Rating 3/17/2023, 3:07 PM Stage Discharge Project Name:Polestar Subdivision:Polestar Project No.:39797.01 Location:Fort Collins Calculated By:ARJ Checked By: Date:3/15/2023 Pond 315 - 24" Double Barrel Culvert Outlet Pond 315 - Weir Discharge Elevation Stage (ft)Discharge (cfs)Energy Equation Elevation Stage (ft)Weir Length (ft)Discharge (cfs)5096.60 0.00 0.00 No Flow (WS < inlet) 5100.40 0 0 0.00 5096.85 0.25 0.50 Min. Energy. Eqn. 5100.60 0.2 11.6 2.80 5097.10 0.50 2.32 Min. Energy. Eqn. 5100.80 0.4 15.3 10.45 5097.35 0.75 5.06 Min. Energy. Eqn. 5101.00 0.6 19.6 24.59 5097.60 1.00 8.68 Min. Energy. Eqn. 5101.20 0.8 24.3 46.95 5097.85 1.25 12.62 Regression Eqn. 5101.40 1 43.2 116.64 5098.10 1.50 17.28 INLET 5101.50 1.1 59.9 186.59 5098.35 1.75 22.62 INLET 5101.60 1.2 63.5 225.38 5098.60 2.00 27.94 INLET 5101.70 1.3 75.3 301.35 5098.85 2.25 32.33 OUTLET 5101.80 1.4 87 389.11 5099.10 2.50 33.69 OUTLET offset 3.8 feet from culvert invert at 5096.6 5099.35 2.75 35.00 OUTLET 5099.60 3.00 36.28 OUTLET 5099.85 3.25 37.51 OUTLET 5100.10 3.50 38.71 OUTLET 5100.35 3.75 39.88 OUTLET 5100.60 4.00 41.02 OUTLET 5100.85 4.25 42.12 OUTLET 5101.10 4.50 43.21 OUTLET 5101.35 4.75 44.26 OUTLET 5101.60 5.00 45.30 OUTLET 5101.85 5.25 46.31 OUTLET 5102.10 5.50 47.30 OUTLET 5102.35 5.75 48.28 OUTLET Q=C*L*H^1.5 C=2.7 L=Weir Length H=Height Pond 315 Outlet Pond - Double Barrel Culvert Outlet See Attached MHFD-Culvert_4.0 Spreadsheet Appendix J.V - Flow Comparison COFC2012.01_CI Basin Hydrologic Conversion_Report.docx 13 Anderson Consulting Engineers, Inc. FIGURE 3.1 Table B.1.1 Plum Channel Flow Path Discharge Profile100‐year/Result to be Mapped10‐year 2‐year5271 11324167 10 Upstream Study Limit4872 1533076 184277.999 115_pipe/115_overflow*214/14073 14 Upstream of Rocky Street Culvert4277 115_pipe/115_overflow*214/14073 14 Rocky Street Culvert Overtopping3993 16_pipe/16_overflow*234/16079 243816 16_pipe/16_overflow*234/16079 243544 11622170 132999.999 18_pipe/18_overflow*377/349117 46 Upstream of Gallup Road Culvert2999 18_overflow34992 23 Gallup Road Overtopping2661 18_pipe/18_overflow*377/349117 462570 118375116 461323 20424153 69938 220‐322444168 84 Upstream of Glenmoor Pond* Discharge based on the sum of pipe and overflow dischargesDischarge (cfs)HEC‐Ras Sation EPA SWMM Element Description Modified - Table B.1.1 Plum Channel Flow Path Discharge Profile Effective HEC-RAS hydraulics model/Result 100-year CE 100 year - Proposed Result Mapped by Anderson /Result Modeled /Result Modeled 5271 113 (313out in CE models)241 155 252 245 Upstream Study Limit 5190 NODE 23 ---------362 Pond Inflow 4872 (L)15 330 200 305 --- 4675 POND OUTFLOW J14 ---------174 Pond outflow 4277.999 C-1+115_pipe/115_overflow*214/140 167/139 290/242 187/140 Upstream of Rocky Road Culvert 4277 C-1+115_pipe/115_overflow*214/140 167/139 290/242 187/140 Rocky Road Culvert Overtopping 3993 C-1+16_pipe/16_overflow*234/160 193/160 313/253 201/142 3816 C-1+16_pipe/16_overflow*234/160 193/160 313/253 201/142 3544 (L)116 221 180 229 176 2999.999 18_pipe/18_overflow*377/349 354/327 285/258 285/257 Upstream of Gallup Road Culvert 2999 18_overflow 349 327 258 257 Gallup Road Overtopping 2661 18_pipe/18_overflow*377/349 354/327 285/258 285/257 2570 (L)118 375 352 284 281 1323 (L)20 424 406 356 356 938 (L)220-322 444 434 391 390 Upstream of Glenmoor Pond * Discharge based on the sum of pipe and overflow discharges Flow is presented as (total flow)/(Surface Flow) --- null value XXXX -New Station or Element Modeled Discharge (cfs) Effective HEC RAS - STATION EPA SWMM ELEMENT Effective SWMM hydrology model Location Appendix J.VI - Spillway Variance Request Stormwater Alternative Compliance/Variance Application City of Fort Collins Water Utilities Engineering Section A: Engineer/Owner Information Engineer Name____________________________________________Phone___________________________ Street Address_____________________________________________________________________________ City__________________________________________State________________________Zip_____________ Owner Name______________________________________________Phone___________________________ Street Address_____________________________________________________________________________ City__________________________________________State________________________Zip_____________ Section C: Alternative Compliance/Variance Information Section B: Proposed Project Information Legal description and/or address of property____________________________________________________ Project Name______________________________________________________________________________ Project/Application Number from Development Review (i.e. FDP123456)__________________________ Description of Project_______________________________________________________________________ __________________________________________________________________________________________ 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_______________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ State the requirement from which alternative compliance/variance is sought. (Please include applicable Drainage Criteria Manual volume, chapter and section.) What hardship prevents this site from meeting the requirement? What alternative is proposed for the site? Attach separate sheet if necessary Attach separate sheet if necessary  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 VARIANCE REQUEST Date:May 16th 2023 From:Joseph Frank, PE Subject:Scenic Views and Polestar Spillway Variance Request I am writing to request a variance from the 2018 Stormwater City of Fort Collins criteria regarding the spillway requirements for Scenic Views Pond and Polestar/Happy Heart Detention pond. Specifically, the variance is for: Chapter 8, Section 3.5– Spillway Max Flow Depth Emergency overflow depth shall be no more than six inches (6”) at the crest during the 100- year storm. The Scenic Views Pond and Polestar/Happy Heart Detention pond are located in the City of Fort Collins floodplain termed “Plum Street Flow Path” and have higher than average peak inflows. Scenic View Pond Spillway Existing condition for Scenic Views Pond: The existing spillway has a depth of 1.5 feet and width of 10 feet. The existing spillway elevation is at (5115.57 on the NAVD 88 datum) and (5112.5 on the NVGD 29 datum). The flow from the pond (349 cfs = peak pond inflow per corrected effective SWMM model) surpasses the capacity of the spillway, causing it to overflow and overtops the embankment at an approximate depth of 2.02 feet. The water then spills over the eastern portion of the retention pond for a distance of approximately 290 ft, see existing scenic views pond spillway section in Appendix A.1. Proposed condition: JR Engineering is proposing to modify the overflow spillway while maintaining the existing spillway elevation of 5115.57 as to not impact volume within the pond. The proposed spillway has a crest length of 51 feet and will result in an overflow depth 1.75 feet at 349 cfs, which exceeds the city's required depth of six inches. See the scenic views spillway improvement section in Appendix A.1. Justification for Variance: The proposed improvements are intended to increase the emergency overflow spillway capacity and improve the existing spillway by providing additional riprap protection. This modification will decrease the overall breadth of the floodplain, reduce the emergency overflow depth from 2.02 feet to 1.75 feet and serve as an improvement to the existing scenic views retention pond.The spillway variance is necessary to increase the emergency capacity and prevent overtopping of the existing embankment. Please refer to exhibits and calculations in Appendix A.1 for additional information.  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Polestar Detention Pond Spillway Proposed Polestar/Happy Heart Farms Spillway: The proposed spillway has a crest length of 36.8 feet and will result in an overflow depth 2.21 feet at 362 cfs (peak pond inflow per proposed SWMM model), which exceeds the city's required depth of six inches. This spillway is intended to remain in place when the ultimate regional pond is constructed which will result in an overflow depth of 1.61 feet at 221 cfs. See the Polestar detention facility spillway section in Appendix B.1. Justification for Variance: The request is to allow for the same approach as the Concept Canal Importation Master Plan by Jacobs and prevent the flow from the emergency spillway from being directed towards existing structures and homes downstream. By narrowing the spillway and allowing the overflow depth to exceed six inches the spillway will better direct flows between houses and towards the improvements in the drainage easement to the east of the Polestar development. Refer to exhibits and calculations in Appendix B.1 for additional information.  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Appendix A.1 A Westrian Company Scenic Views Pond Broad Crested Weir Project Description Crest LengthSolve For Input Data cfs348.61Discharge ft5,117.32Headwater Elevation ft5,115.57Crest Elevation ft0.00Tailwater Elevation GravelCrest Surface Type ft20.00Crest Breadth Results ft51.0Crest Length ft1.75Headwater Height Above Crest ft-5,115.57Tailwater Height Above Crest ft^(1/2)/s2.95Weir Coefficient 1.000Submergence Factor ft^(1/2)/s2.95Adjusted Weir Coefficient ft²89.3Flow Area ft/s3.90Velocity ft54.5Wetted Perimeter ft51.02Top Width Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2/9/2023 FlowMaster [10.03.00.03] Bentley Systems, Inc. Haestad Methods Solution CenterScenic Views Pond.fm8 EXISTING SCENIC VIEWS - SPILLWAYA Westrian Company SCENIC VIEWS - SPILLWAY IMPROVEMENTA Westrian Company  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Appendix B.1 Ultimate Polestar - Broad Crested Weir Project Description Headwater ElevationSolve For Input Data cfs221.20Discharge ft5,107.76Crest Elevation ft0.00Tailwater Elevation GravelCrest Surface Type ft25.00Crest Breadth ft36.8Crest Length Results ft5,109.37Headwater Elevation ft1.61Headwater Height Above Crest ft-5,107.76Tailwater Height Above Crest ft^(1/2)/s2.93Weir Coefficient 1.000Submergence Factor ft^(1/2)/s2.93Adjusted Weir Coefficient ft²59.4Flow Area ft/s3.73Velocity ft40.0Wetted Perimeter ft36.80Top Width Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 3/20/2023 FlowMaster [10.03.00.03] Bentley Systems, Inc. Haestad Methods Solution CenterPolestar Pond.fm8 POLESTAR DETENTION FACILITY - SPILLWAYA Westrian Company Polestar Interim Broad Crested Weir - 1 Project Description Headwater ElevationSolve For Input Data cfs361.80Discharge ft5,107.76Crest Elevation ft0.00Tailwater Elevation GravelCrest Surface Type ft25.00Crest Breadth ft36.8Crest Length Results ft5,109.97Headwater Elevation ft2.21Headwater Height Above Crest ft-5,107.76Tailwater Height Above Crest ft^(1/2)/s2.99Weir Coefficient 1.000Submergence Factor ft^(1/2)/s2.99Adjusted Weir Coefficient ft²81.3Flow Area ft/s4.45Velocity ft41.2Wetted Perimeter ft36.80Top Width Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 3/20/2023 FlowMaster [10.03.00.03] Bentley Systems, Inc. Haestad Methods Solution CenterPolestar Pond.fm8 Stormwater Alternative Compliance/Variance Application City of Fort Collins Water Utilities Engineering Section A: Engineer/Owner Information Engineer Name____________________________________________Phone___________________________ Street Address_____________________________________________________________________________ City__________________________________________State________________________Zip_____________ Owner Name______________________________________________Phone___________________________ Street Address_____________________________________________________________________________ City__________________________________________State________________________Zip_____________ Section C: Alternative Compliance/Variance Information Section B: Proposed Project Information Legal description and/or address of property____________________________________________________ Project Name______________________________________________________________________________ Project/Application Number from Development Review (i.e. FDP123456)__________________________ Description of Project_______________________________________________________________________ __________________________________________________________________________________________ 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_______________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ State the requirement from which alternative compliance/variance is sought. (Please include applicable Drainage Criteria Manual volume, chapter and section.) What hardship prevents this site from meeting the requirement? What alternative is proposed for the site? Attach separate sheet if necessary Attach separate sheet if necessary  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 VARIANCE REQUEST Date:May 16th 2023 From:Joseph Frank, PE Subject:Scenic Views and Polestar Spillway Variance Request I am writing to request a variance from the 2018 Stormwater City of Fort Collins criteria regarding the spillway requirements for Scenic Views Pond and Polestar/Happy Heart Detention pond. Specifically, the variance is for: Chapter 8, Section 3.5– Spillway Max Flow Depth Emergency overflow depth shall be no more than six inches (6”) at the crest during the 100- year storm. The Scenic Views Pond and Polestar/Happy Heart Detention pond are located in the City of Fort Collins floodplain termed “Plum Street Flow Path” and have higher than average peak inflows. Scenic View Pond Spillway Existing condition for Scenic Views Pond: The existing spillway has a depth of 1.5 feet and width of 10 feet. The existing spillway elevation is at (5115.57 on the NAVD 88 datum) and (5112.5 on the NVGD 29 datum). The flow from the pond (349 cfs = peak pond inflow per corrected effective SWMM model) surpasses the capacity of the spillway, causing it to overflow and overtops the embankment at an approximate depth of 2.02 feet. The water then spills over the eastern portion of the retention pond for a distance of approximately 290 ft, see existing scenic views pond spillway section in Appendix A.1. Proposed condition: JR Engineering is proposing to modify the overflow spillway while maintaining the existing spillway elevation of 5115.57 as to not impact volume within the pond. The proposed spillway has a crest length of 51 feet and will result in an overflow depth 1.75 feet at 349 cfs, which exceeds the city's required depth of six inches. See the scenic views spillway improvement section in Appendix A.1. Justification for Variance: The proposed improvements are intended to increase the emergency overflow spillway capacity and improve the existing spillway by providing additional riprap protection. This modification will decrease the overall breadth of the floodplain, reduce the emergency overflow depth from 2.02 feet to 1.75 feet and serve as an improvement to the existing scenic views retention pond.The spillway variance is necessary to increase the emergency capacity and prevent overtopping of the existing embankment. Please refer to exhibits and calculations in Appendix A.1 for additional information.  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Polestar Detention Pond Spillway Proposed Polestar/Happy Heart Farms Spillway: The proposed spillway has a crest length of 36.8 feet and will result in an overflow depth 2.21 feet at 362 cfs (peak pond inflow per proposed SWMM model), which exceeds the city's required depth of six inches. This spillway is intended to remain in place when the ultimate regional pond is constructed which will result in an overflow depth of 1.61 feet at 221 cfs. See the Polestar detention facility spillway section in Appendix B.1. Justification for Variance: The request is to allow for the same approach as the Concept Canal Importation Master Plan by Jacobs and prevent the flow from the emergency spillway from being directed towards existing structures and homes downstream. By narrowing the spillway and allowing the overflow depth to exceed six inches the spillway will better direct flows between houses and towards the improvements in the drainage easement to the east of the Polestar development. Refer to exhibits and calculations in Appendix B.1 for additional information.  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Appendix A.1 A Westrian Company EXISTING SCENIC VIEWS - SPILLWAYA Westrian Company SCENIC VIEWS - SPILLWAY IMPROVEMENTA Westrian Company Scenic Views Pond Broad Crested Weir Project Description Crest LengthSolve For Input Data cfs348.61Discharge ft5,117.32Headwater Elevation ft5,115.57Crest Elevation ft0.00Tailwater Elevation GravelCrest Surface Type ft20.00Crest Breadth Results ft51.0Crest Length ft1.75Headwater Height Above Crest ft-5,115.57Tailwater Height Above Crest ft^(1/2)/s2.95Weir Coefficient 1.000Submergence Factor ft^(1/2)/s2.95Adjusted Weir Coefficient ft²89.3Flow Area ft/s3.90Velocity ft54.5Wetted Perimeter ft51.02Top Width Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2/9/2023 FlowMaster [10.03.00.03] Bentley Systems, Inc. Haestad Methods Solution CenterScenic Views Pond.fm8 Chapter 12 Storage September 2017 Urban Drainage and Flood Control District 12-33 Urban Storm Drainage Criteria Manual Volume 2 Figure 12-21. Embankment protection details and rock sizing chart (adapted from Arapahoe County)  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Appendix B.1 POLESTAR DETENTION FACILITY - SPILLWAYA Westrian Company Polestar Interim Broad Crested Weir - 1 Project Description Headwater ElevationSolve For Input Data cfs361.80Discharge ft5,107.79Crest Elevation ft0.00Tailwater Elevation GravelCrest Surface Type ft25.00Crest Breadth ft36.8Crest Length Results ft5,110.00Headwater Elevation ft2.21Headwater Height Above Crest ft-5,107.79Tailwater Height Above Crest ft^(1/2)/s2.99Weir Coefficient 1.000Submergence Factor ft^(1/2)/s2.99Adjusted Weir Coefficient ft²81.3Flow Area ft/s4.45Velocity ft41.2Wetted Perimeter ft36.80Top Width Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 8/23/2023 FlowMaster [10.03.00.03] Bentley Systems, Inc. Haestad Methods Solution CenterPolestar Pond.fm8 Ultimate Polestar - Broad Crested Weir Project Description Headwater ElevationSolve For Input Data cfs221.20Discharge ft5,107.79Crest Elevation ft0.00Tailwater Elevation GravelCrest Surface Type ft25.00Crest Breadth ft36.8Crest Length Results ft5,109.40Headwater Elevation ft1.61Headwater Height Above Crest ft-5,107.79Tailwater Height Above Crest ft^(1/2)/s2.93Weir Coefficient 1.000Submergence Factor ft^(1/2)/s2.93Adjusted Weir Coefficient ft²59.4Flow Area ft/s3.73Velocity ft40.0Wetted Perimeter ft36.80Top Width Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 8/23/2023 FlowMaster [10.03.00.03] Bentley Systems, Inc. Haestad Methods Solution CenterPolestar Pond.fm8 Chapter 12 Storage September 2017 Urban Drainage and Flood Control District 12-33 Urban Storm Drainage Criteria Manual Volume 2 Figure 12-21. Embankment protection details and rock sizing chart (adapted from Arapahoe County)  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Appendix C.1 1 Andrew Joyce From:Theodore Bender <tbender@fcgov.com> Sent:Monday, May 1, 2023 5:11 PM To:Joey Frank; Andrew Joyce; Kenneth Merritt Cc:Heidi Hansen; Dan Mogen; Matt Simpson; Ken Sampley Subject:Polestar Variance Response Attachments:Downstream Structures.jpg Hello JR Team, the correct minimum freeboard requirement at the spillway may not be the “6-inches” that we had been discussing, but -inches. This requirement is based on the need to provide 12-inches of freeboard from the (primary) 100- st bullet of the City 2018 Stormwater Criteria Manual). Typicall lower stage. The only outlet from the Scenic View Pond is the over ow spillway. did slow down our response. We understand the Polestar development project would improve the Scenic View spillway and we have taken this into We’ow this spillway. the north and south) the primary Scenic View spillway. This has been the main driver in our internal discussion to maintain safety for the future residents of this site. The result of our internal discussion is that City sta has agreed the 12-inches of freeboard, above the over ow WSEL, will not be required. Instead, we like to ask these structure directly below the Scenic Polestar Pond (Happy Heart/Eastern pond) The 6-inches of freeboard at this pond measured from the 100-yr WSE to the top of the pond embankment is approved. The main concern at this pond is that we not direct ow from the emergency spill towards any As we discussed in the past, we asked our master planning consultant to narrow up the conceptual design weir cross- The full master planned improvement at The proposed Polestar spillway weir dimensions are acceptable if the hydraulics show these exi are not impacted. As a part of the hydraulics phase of the CLOMR, please focus on this area and provide a gure to show these downstream structures will not be impacted.- and appropriately placed to provide con dence in the oodplain and oodway width in this area. If the CLOMR structures, we would ask that it be modi ed and remodeled. From the n is able to protect the area from excessive erosion. Scenic Views Pond (Western pond) City sta discussed the freeboard at the Scenic View Pond in detail. I understand from your email last week you no longer wish to pursue a variance request at this lo Please send us a spillway cross- eastern pond to show the 100- The 6-inches of freeboard suggested at this pond measured from the 100-yr WSE to the top of the pond embankment is 2 acceptable.-inches of freeboard from the highest adjacent BFE for the structures immediately east (downstream) of the Scenic View pond (image This BFE would be CLOMR. Because these structures will be placed downstream of the primary outlet to this pond, we feel this Our decision is grounded in public safety and the safety of the new residents downstream of this spillway. Scenic View Pond in your analysis. We will review this as we This is a complicated project in a high ood risk area. This project is more complicated than other CLOMR requests; this CLOMR proposal is to change both the hydrology and hydraulics for this site, while most CLOMRs only propose to change the hydraulics. Please reach out if you’d like to discuss. We are happy to chat further. -TRB Theodore R. Bender, PE, CFM Stormwater Engineering Manager Master Planning and Floodplain Management 700 Wood Street Fort Collins, CO 80522-0580 (970) 221-6503 tbender@fcgov.com  7200 South Alton Way Suite C400 Centennial, CO 80112 303-740-9393  Fax 303-921-7320  25188 Genesee Trail Road Suite 110 Golden, CO 80401 303-740-9393  Fax 303-921-7320  5475 Tech Center Drive Suite 235 Colorado Springs, CO 80919 719-593-2593  Fax 303-921-7320  2900 South College Avenue Suite 3D Fort Collins, CO 80525 970-491-9888  Fax 303-921-7320 Appendix D.1 CONCEPTUAL DESIGN PLAN & PROFILE CANAL IMPORTATION BASIN N SHEET 1SHEET 2SHEET 3Ä2þ245ac.Ä2þ982ac.Ä2þ903ac.Ä2þ507ac.Ä2þ17.7ac.Ä2þ66.9ac.Ä2þ1065ac.Ä2þ5538ac.Ä2þ1530ac.Ä2þ9912ac.Ä2þ9533ac.Ä2þ5832ac.Ä2þ5494ac.Ä2þ8918ac.Ä2þ6842ac.Ä2þ7230ac.Ä2þ8213ac.Ä2þ5777ac.Ä2þ9218ac.Ä2þ4115ac.Ä2þ4681ac.Ä2þ3424ac.Ä2þ422.2ac.Ä2þ718.4ac.Ä2þ339.1ac.Ä2þ521.3ac.Ä2þ230.4ac.Ä2þ812.9ac.Ä2þ229.7ac.Ä2þ132.9ac.Ä2þ199.6ac.Ä2þ143.3ac.Ä2þ912.8ac.Ä2þ677.9ac.Ä2þ947.9ac.Ä2þ937.6ac.Ä2þ875.6ac.Ä2þ980.8ac.Ä2þ367.2ac.Ä2þ397.3ac.Ä2þ336.7ac.Ä2þ373.1ac.Ä2þ382.3ac.Ä2þ408.8ac.Ä2þ52135ac.Ä2þ514.4ac.Ä2þ613.3ac.Ä2þ624.9ac.Ä2þ633.5ac.Ä2þ658.2ac.Ä2þ4414.5ac.Ä2þ1088.8ac.Ä2þ1217.8ac.Ä2þ2122.2ac.Ä2þ1725.5ac.Ä2þ5932.8ac.Ä2þ2028.6ac.Ä2þ5132.8ac.Ä2þ7204.6ac.Ä2þ4230.9ac.Ä2þ5030.6ac.Ä2þ2224.7ac.Ä2þ1613.7ac.Ä2þ1851.1ac.Ä2þ4331.2ac.Ä2þ5631.5ac.Ä2þ1123.1ac.Ä2þ8207.5ac.Ä2þ1167.7ac.Ä2þ5335.8ac.Ä2þ5730.9ac.Ä2þ5433.2ac.Ä2þ2246.4ac.Ä2þ5233.1ac.Ä2þ4955.4ac.Ä2þ1183.3ac.Ä2þ5191.6ac.Ä2þ5290.7ac.Ä2þ6611.8ac.Ä2þ5693.4ac.Ä2þ6926.2ac.Ä2þ7532.8ac.Ä2þ5792.8ac.Ä2þ5590.9ac.Ä2þ5090.9ac.Ä2þ5391.2ac.Ä2þ8110.3ac.Ä2þ9713.4ac.Ä2þ5981.7ac.Ä2þ5888.9ac.Ä2þ7130.4ac.Ä2þ5201.7ac.Ä2þ5505.7ac.Ä2þ5702.3ac.Ä2þ7026.5ac.Ä2þ8823.4ac.Ä2þ7313.5ac.Ä2þ5302.5ac.Ä2þ8319.6ac.Ä2þ9610.3ac.Ä2þ5604.3ac.Ä2þ7413.9ac.Ä2þ5873.9ac.Ä2þ8615.3ac.Ä2þ5807.2ac.Ä2þ5409.7ac.Ä2þ4732.9ac.Ä2þ7626.5ac.Ä2þ5082.1ac.Ä2þ5062.4ac.Ä2þ5073.7ac.Ä2þ3027.4ac.Ä2þ9112.6ac.Ä2þ1225.4ac.Ä2þ8518.5ac.Ä2þ1213.7ac.Ä2þ8458.4ac.Ä2þ2858.4ac.Ä2þ4245.1ac.Ä2þ4326.8ac.Ä2þ4912.8ac.Ä2þ1302.8ac.Ä2þ1311.5ac.Ä2þ3114.3ac.Ä2þ4849.8ac.Ä2þ1234.5ac.Ä2þ1246.2ac.Ä2þ1416.3ac.Ä2þ3511.7ac.Ä2þ2953.7ac.Ä2þ2621.8ac.Ä2þ4550.3ac.Ä2þ2797.1ac.Ä2þ3233.2ac.Ä2þ5433.7ac.Ä2þ2513.9ac.Ä2þ5510.9ac.Ä2þ5711.6ac.Ä2þ5613.1ac.Ä2þ1438.4ac.Ä2þ5955.2ac.Ä2þ5814.4ac.Ä2þ6058.4ac.Ä2þ6413.1ac.Ä2þ13951.2ac.Ä2þ14056.8ac.Ä2þ11124.6ac.Ä2þ11018.5ac.Ä2þ10914.7ac.Ä2þ11313.5ac.Ä2þ11211.1ac.Ä2þ11414.1ac.Ä2þ11520.1ac.Ä2þ11711.2ac.Ä2þ58915.6ac.Ä2þ19528.9ac.Ä2þ29510.6ac.Ä2þ11924.6ac.Ä2þ97810.8ac.Ä2þ21923.8ac.Ä2þ12034.4ac.Ä2þ57810.3ac.Ä2þ59711.1ac.Ä2þ13333.3ac.Ä2þ13214.5ac.Ä2þ13430.9ac.Ä2þ14211.5ac.Ä2þ13872.1ac.Ä2þ53155.4ac.Ä2þ135127.9ac.Overland TrailOverland TrailTaft Hill RoadLaporte AvenueElizabeth StreetMulberry StreetMulberry StreetProspect RoadDrake RoadTaft Hill RoadShields StreetProspect RoadShields StreetDrake RoadINDEXDATE:PROJECT NUMBER:CHECKED BY:DESIGNED BY:DRAWN BY:BNAMMCAMHCOFC2012.0107/01/2014³LegendSubbasinSheet BoundaryCITY OF FORT COLLINSCANAL IMPORTATION HYDROLOGIC CONVERSIONFROM MODSWMM TO EPA SWMM 5.0INDEX MAP0 800 1,600400Feet Civil ƒ Water Resources ƒ Environmental 375 East Horsetooth Road, Building 5, Fort Collins, CO 80525 Phone (970) 226-0120 / Fax (970) 226-0121 www.acewater.com Civil ƒ Water Resources ƒ Environmental 375 East Horsetooth Road, Building 5, Fort Collins, CO 80525 Phone (970) 226-0120 / Fax (970) 226-0121 www.acewater.com COFC2012.01_CI Basin Hydrologic Conversion_Report.docx 12 Anderson Consulting Engineers, Inc. Table 3.2 100-Year Peak Discharge Comparison Table. SWMM ID Discharge (cfs) Percent Change from Previous Study Location Mulberry Flow Path 304 114.9 6.4 Golf Course Pond 205 641.3 28.3 Taft Hill Road 3 463.3 57.1 U/S of Briarwood Road Plum Flow Path 850 50.6 -4.5 Skyline Drive 852 63.8 -17.1 Glenmoor Drive 220 434.6 -13.4 East edge of Taft Hill Road 853 407.0 -16.4 West edge of Taft Hill Road 118 352.2 -11.3 854 354.9 -25.9 Ponderosa Drive 855 192.6 10.1 Pear Street 315 193.3 49.8 Kimball Detention Pond 856 200.4 36.3 Kimball Road 113 154.5 51.5 Elizabeth Flow Path 445 10.5 101.9 Elizabeth/City Park Intersection 444 200.5 0.3 Elizabeth/City Park Intersection Clearview Flow Path 861 226.5 6.3 272 257.8 -25.1 862 334.5 -10.1 Clearview Ave. 276 390.5 -42.9 Clearview Ave. and Taft Hill Road 863 405.8 -40.1 879 426.0 -41.6 871 396.8 13.0 Canal Importation Flow Path 242 526.1 -2.4 Confluence w/ Spring Creek 244 521.9 -2.6 Shield Street 241 481.4 0.7 864 436.4 -6.6 Heatheridge Road 40 429.1 -7.5 27 718.7 44.3 Fairbrooke Pond 860 196.3 -3.3 867 256.7 -9.9 COFC2012.01_CI Basin Hydrologic Conversion_Report.docx 13 Anderson Consulting Engineers, Inc. FIGURE 3.1 COFC2012.01_CI Basin Hydrologic Conversion_Report.docx 2 Anderson Consulting Engineers, Inc. P-1 P-2 P-3 P-4 P-5 P-6 TH-1 TH-2 W. Elizabeth Street W. Plum Street Orchard Place Kimball RoadOVERLAND TRAILTAFT HILL RD.W. MULBERRY ST. W. ELIZABETH ST. SITE LEGEND: INDICATES APPROXIMATE LOCATION OF TEMPORARY PIEZOMETER INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING P-1 TH-1 J.R.ENGINEERING, LLC POLESTAR VILLAGE PRELIM CTL I T PROJECT NO. FC10101-115 FIGURE 1 Locations of Exploratory Borings VICINITY MAP FORT COLLINS, COLORADO NOT TO SCALE 300' APPROXIMATE SCALE: 1" = 300' 150'0' P-1 P-2 P-3 P-4 P-5 P-6 TH-1 TH-2 W. Elizabeth Street W. Plum Street Orchard Place Kimball Road(18.5) (4.5) (22)(10) (21.5) (3.5) (20.5) (22.5) [5097.8] [5106.7] [5089.8][5096.0] [5115.1] [5091.0] [5088.3] [5095.0] LEGEND: INDICATES APPROXIMATE LOCATION OF TEMPORARY PIEZOMETER INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING INDICATES ESTIMATED DEPTH TO GROUNDWATER IN FEET INDICATES ESTIMATED GROUND WATER SURFACE ELEVATION P-1 (10) TH-1 [5096] J.R.ENGINEERING, LLC POLESTAR VILLAGE PRELIM CTL I T PROJECT NO. FC10101-115 FIGURE 2 Groundwater Depth and Elevation 300' APPROXIMATE SCALE: 1" = 300' 150'0' P-1 P-2 P-3 P-4 P-5 P-6 TH-1 TH-2 W. Elizabeth Street W. Plum Street Orchard Place Kimball Road(7) [5109.3] (11) [5100.8] (5.5) [5100.5] (11) [5099.8] (12) [5103.5] (10.5) [5108.1] (8) [5103.2] (12) [5100.5] LEGEND: INDICATES APPROXIMATE LOCATION OF TEMPORARY PIEZOMETER INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING INDICATES ESTIMATED DEPTH TO BEDROCK IN FEET INDICATES ESTIMATED GROUND BEDROCK ELEVATION P-1 TH-1 J.R.ENGINEERING, LLC POLESTAR VILLAGE PRELIM CTL I T PROJECT NO. FC10101-115 FIGURE 3 Bedrock Depth and Elevation 300' APPROXIMATE SCALE: 1" = 300' 150'0' [5103.2] (8) 5,075 5,080 5,085 5,090 5,095 5,100 5,105 5,110 5,115 5,120 5,075 5,080 5,085 5,090 5,095 5,100 5,105 5,110 5,115 5,120 40/12 38/12 50/12 50/8 50/7 WC=14.1DD=121SW=4.4 WC=13.6DD=124SW=1.9 SS=0.170 P-1 El. 5116.3 39/12 42/12 50/10 50/9 50/9 WC=15.5DD=120SW=7.3 WC=13.1DD=124SW=2.8 WC=13.9DD=121-200=99UC=20,800 WC=14.3DD=124SW=2.1 P-2 El. 5111.8 14/12 44/12 39/12 32/12 50/9 WC=14.2DD=124SW=7.8 WC=15.3DD=118SW=4.5 P-3 El. 5106.0 50/10 20/12 50/8 50/11 50/7 WC=2.2-200=23SS=<0.01 WC=14.5DD=119SW=3.7 WC=13.3DD=126SW=3.9 WC=16.1DD=117SW=2.3 WC=14.8DD=125SW=3.3 P-4 El. 5110.8 25/12 35/12 50/9 50/9 50/8 WC=13.5DD=122SW=6.1 WC=13.9DD=121-200=100UC=17,250 WC=13.9DD=122SW=2.1 P-5 El. 5115.5 8/12 22/12 50/6 50/6 50/5 WC=17.0 -200=61 WC=13.1DD=120SW=0.0 LL=34 PI=18 P-6 El. 5118.6 11/12 50/12 50/12 50/9 50/7 WC=15.1 -200=44 WC=13.7DD=124SW=4.3SS=0.050 WC=15.3DD=120SW=2.0 LL=30 PI=14 TH-1 El. 5111.2 29/12 38/12 50/10 50/9 50/9 WC=14.8DD=122SW=3.1 WC=14.7DD=122 WC=14.6DD=124SW=3.3 WC=14.8DD=123SW=4.4 TH-2 El. 5112.5 ELEVATION - FEETFIGURE 4 DRIVE SAMPLE. THE SYMBOL 40/12 INDICATES 40 BLOWS OF A 140-POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES.ELEVATION - FEETWATER LEVEL MEASURED ON SEPTEMBER 24, 2021. SAND, CLAYEY, MOIST, MEDIUM DENSE TO DENSE, RED-BROWN (SC) 2. 3. FILL, GRAVEL, SAND, CLAY, SILT, MISC. DEBRIS, WHITE, PINK, GRAY, TAN THE BORINGS WERE DRILLED ON SEPTEMBER 22, 2021, USING 4-INCH DIAMETER CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG. 1. LEGEND: NOTES: CLAY, SANDY, MOIST, STIFF TO VERY STIFF, RED-BROWN, TAN (CL) WEATHERED CLAYSTONE, SANDY, MOIST, FIRM TO MEDIUM HARD, RED-BROWN, TAN, GRAY CLAYSTONE, SANDY, MOIST, MEDIUM HARD TO HARD, BROWN, GRAY, OLIVE WATER LEVEL MEASURED AT TIME OF DRILLING. BORING ELEVATIONS WERE SURVEYED BY A REPRESENTATIVE OF OUR FIRM REFERENCING THE TEMPORARY BENCHMARK SHOWN ON FIGURE 1. THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN THIS REPORT. 4. Summary Logs of Exploratory Borings WC DD SW -200 LL PI UC SS - - - - - - - - INDICATES MOISTURE CONTENT (%). INDICATES DRY DENSITY (PCF). INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%). INDICATES PASSING NO. 200 SIEVE (%). INDICATES LIQUID LIMIT. INDICATES PLASTICITY INDEX. INDICATES UNCONFINED COMPRESSIVE STRENGTH (PSF). INDICATES SOLUBLE SULFATE CONTENT (%). J.R. ENGINEERING, LLC POLESTAR VILLAGE PRELIM CTL | T PROJECT NO. FC10101-115 SW=3.8 J.R. ENGINEERING, LLC POLESTAR VILLAGE PRELIM CTL | T PROJECT NO. FC10101-115 Conceptual Underdrain Detail FIGURE 5 9/24/2021 10/18/2021 11/18/2021 12/15/2021 1/12/2022 2/15/2022 3/16/2022 4/12/2022 5/18/2022 6/14/2022 P-1 5116.3 5107.8 5107.8 5107.8 5107.3 5106.3 5106.8 5106.3 5106.8 5106.8 5106.8 P-2 5111.8 5089.8 5092.8 5095.3 5095.8 5095.8 5096.3 5096.8 5096.3 5096.3 5095.3 P-3 5106.0 5096.0 5097.0 5096.5 5096.5 5095.0 5095.5 5095.0 5095.5 5095.0 5093.5 P-4 5110.9 5088.4 5091.9 5096.9 5099.9 5100.9 5102.4 5102.4 5102.9 5102.9 5102.4 P-5 5115.5 5095.0 5104.0 5109.0 5109.5 5109.0 5109.0 5114.5 5109.3 5109.0 5109.0 P-6 5118.7 5115.2 5114.7 5112.7 5112.2 5111.2 5111.2 5112.2 5112.3 5113.7 5113.7 9/24/2021 10/18/2021 11/18/2021 12/15/2021 1/12/2022 2/15/2022 3/16/2022 4/12/2022 5/18/2022 6/14/2022 P-1 8.5 8.5 8.5 9 10 9.5 10 9.5 9.5 9.5 P-2 22 19 16.5 16 16 15.5 15 15.5 15.5 16.5 P-3 10 9 9.5 9.5 11 10.5 11 10.5 11 12.5 P-4 22.5 19 14 11 10 8.5 8.5 8 8 8.5 P-5 20.5 11.5 6.5 6 6.5 6.5 1 6.2 6.5 6.5 P-6 3.5 4 6 6.5 7.5 7.5 6.5 6.4 5 5 Ditch Running?Yes Covered in Snow No Yes Yes Yes Yes P-5 (3/16/22): Water ponding on the surface nearby. Piezometer #Groundwater Elevation (feet)Piezometer Elevation (feet) CTL Project No. FC10101-112 Polestar Village Groundwater Monitoring Piezometer #Groundwater Depth (feet) 21 APPENDIX F – MAPS Know what'sbelow.before you dig.CallRELIZABETH STPLUM STOVERLAND TR ORCHARD PLA Westrian Company LOCUST GROVE DRIVE A Westrian Company ELIZABETH STPLUM STOVERLAND TR ORCHARD PLKnow what'sbelow.before you dig.CallR······LOCUST GROVE DRIVEW. ORCHARD PLW PLUM ST Know what'sbelow.before you dig.CallRELIZABETH STPLUM STOVERLAND TR ORCHARD PLA Westrian CompanyPOLESTAR DEVELOPMENT - DRAINAGE OUTFALLDRAINAGE EASEMENT EXHIBITBBAACC Know what'sbelow.before you dig.CallRELIZABETH STPLUM STOVERLAND TR ORCHARD PLA Westrian CompanyW PLUM STW. ORCHARD PLLOCUST GROVE DRIVE LOCUST GROVE DRIVEW. ORCHARD PLW PLUM STPOLARIS ST 22 APPENDIX G –LID EXHIBIT Know what'sbelow.before you dig.CallRELIZABETH STPLUM STOVERLAND TR ORCHARD PLLID/WQ TREATMENTA Westrian Company W. ORCHARD PLLOCUST GROVE DRIVE W PLUM ST