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Home My WebLink AboutReports - Drainage - 04/30/2025 FINAL DRAINAGE REPORT Prospect Plaza Redevelopment Fort Collins, Colorado Prepared for: CSU STRATA 2537 Research Boulevard, Suite 200 Fort Collins, Colorado 80523 (970) 491-2933 Prepared by: Sunny Civil 706 S College Avenue, Suite 203 Fort Collins, Colorado 80524 (970) 694-1389 April 30th, 2025 Project Number: 024-015 TABLE OF CONTENTS I. INTRODUCTION .......................................................................................................... 1 a) SITE LOCATION & ZONING ........................................................................................................... 1 b) EXISTING SITE CONDITIONS ........................................................................................................ 2 II. EXISTING DRAINAGE ................................................................................................ 3 a) EXISTING DRAINAGE PATTERNS & PREVIOUS STUDIES ........................................................ 3 III. PROPOSED DRAINAGE ........................................................................................... 4 a) PROPOSED PROJECT DESCRIPTION ......................................................................................... 4 b) MAJOR BASINS .............................................................................................................................. 4 c) SITE DRAINAGE ............................................................................................................................. 5 IV. DRAINAGE FACILITY DESIGN ................................................................................. 8 a) CRITERIA ........................................................................................................................................ 8 b) RUNOFF .......................................................................................................................................... 8 c) STORM SEWER .............................................................................................................................. 8 d) FACILITY DESIGN ........................................................................................................................... 9 e) FLOODPLAIN IMPACTS ............................................................................................................... 12 V. CONCLUSION .......................................................................................................... 13 a) IMPACT OF PROPOSED IMPROVEMENTS ................................................................................ 13 b) CODE COMPLIANCE .................................................................................................................... 13 VI. REFERENCES ........................................................................................................ 13 APPENDICES APPENDIX A…………………...……....MAPS & HYDROLOGIC CALCULATIONS APPENDIX B……………………………...…….…...HYDRAULIC CALCULATIONS APPENDIX C…………………….……………….…REFERENCED INFORMATION APPENDIX D…………………….…………………….…..……FLOODPLAIN MEMO LIST OF TABLES AND FIGURES FIGURE 1. VICINITY MAP……………………………………………………...……..1 TABLE 1. EXISTING BASIN CHARACTERISTICS….…………………..…………3 TABLE 2. IMPERVIOUSNESS SUMMARY……….……………..……..……….…..4 TABLE 3. PROPOSED BASIN CHARACTERISTICS….………………..…………7 TABLE 4. RAIN GARDEN SUMMARY…………….….…………………..…..……10 TABLE 5. RAIN GARDEN OUTFLOWS…………….…………….……..…………11 Page 1 of 13 www.sunnycivil.com I. INTRODUCTION a) SITE LOCATION & ZONING The project site is located at 304 and 318 West Prospect Road in Fort Collins, Colorado 80526, being a portion of the Southeast Quarter of Section 14, Township 7 North, Range 69 West of the 6th P.M., City of Fort Collins, County of Larimer, State of Colorado. The site is bordered by West Lake Street on the north, West Prospect Road on the south, and by Colorado State University (CSU) properties on the west and east. The Vicinity Map for the site showing all adjacent roadways can be seen below, as well as within Appendix A. Figure 1. VICINITY MAP Page 2 of 13 www.sunnycivil.com b) EXISTING SITE CONDITIONS The existing site area is currently comprised of three (3) individual parcels: Parcel 97144-08-016 (304 West Prospect Road) is comprised primarily of the southern and western portions of the overall site. This parcel includes a multi-tenant commercial building along Prospect Road, as well as the existing parking area on the western edge of the site. Parcel 97144-08-943 (318 West Prospect Road) is comprised primarily of the northern and eastern portions of the overall site. This parcel includes the multi-unit apartment complex and its adjacent parking areas and drive aisles. Parcel 97144-08-920 (323 West Lake Street) is located in the northwest corner of the overall site. This parcel includes a looped drive aisle which serves as a bus stop and bus turnaround for the CSU transit system. Arthur Ditch, a large irrigation canal that stretches across Fort Collins from the Cache la Poudre River to Spring Creek, passes through the limits of the site. The reinforced concrete box culvert is located near the western property boundary and runs the length of the site. The Arthur Ditch culvert is located within its own parcel (Parcel 97144-08-913). Additionally, an existing City of Fort Collins electrical duct banks runs along the eastern property boundary. There is a vast network of existing utilities that serve the existing commercial and residential buildings. The commercial building utilizes water and wastewater services from West Prospect Road, while the residential buildings are served from West Lake Street to the north. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Custom Soil Resource Report for the site, the project area is comprised entirely of Altvan-Satanta loams and is designed as Hydrological Soil B. The USDA NRCS soil report for the site can be seen within Appendix C. Per FEMA’s National Flood Hazard Layer (NFHL) FIRMette Map Panel 08069C0979H, dated May 2nd, 2012, the entirety of the site is located within Zone X, Area of Minimal Flood Hazard. The FEMA FIRMette Panel for the site can be seen within Appendix C. However, West Lake Street to the north, Centre Avenue to the west, and even the approximate northern third of the property are all located within the Colorado State University 100-year storm event floodplain. The impact of the proposed redevelopment to this existing floodplain is discussed in further detail within Section IVe of this report. Page 3 of 13 www.sunnycivil.com II. EXISTING DRAINAGE a) EXISTING DRAINAGE PATTERNS & PREVIOUS STUDIES According to the City of Fort Collins (COFC) Stormwater Master Planning, the site is located within the Spring Creek Drainage Basin. Spring Creek is located approximately 1,000 feet to the south of the property. Stormwater from the site is primarily conveyed to Spring Creek via Arthur Ditch and existing public storm sewer infrastructure. The site is also located within the CSU South Campus drainage basin, which has had numerous stormwater quality improvement facilities installed throughout the region. The CSU South Campus Stormwater Permanent SCM’s map, which depicts all of these South Campus facilities, is included within Appendix C of this report. Per this map, the only Stormwater Control Measure (SCM) located within the property is a Constructed Wetland (CW), which is denoted as S-11 by the CSU South Campus Stormwater Permanent SCM’s map. CW S-11 is located within the interior of the looped bus stop drive aisle. The existing site has been divided into two (2) drainage basins, which can be seen on the EXISTING DRAINAGE BASIN MAP located within Appendix A of the report. These basins have been delineated based off of the existing drainage patterns in the area. Brief summaries of each of the existing drainage basins are as follows: Existing Basin EX1 is comprised of the area to the north of the multi-tenant commercial building, which encompasses the existing multi-unit apartment complex, the bus stop, and all adjacent parking and pavement area. Runoff generated within the basin will flow north into West Lake Street, where it will be collected by the existing public storm sewer infrastructure. Once collected, stormwater will be routed south via the existing Arthurs Ditch that runs along the western edge of the property. Existing Basin EX2 is comprised of the area to the south of the multi-tenant commercial building, which encompasses the parking and pavement area along West Prospect Road. Additionally, the multi-tenant commercial building is split equally between Existing Basin EX1 and Existing Basin EX2 via various downspouts around the building. Runoff generated within the basin will flow directly into West Prospect Road to the south, where it will be collected by the existing downstream public storm sewer infrastructure to the east of the site. Table 1 below summarizes each of the existing drainage basins. TABLE 1. EXISTING BASIN CHARACTERISTICS Basin Area (acres) Composite Imperviousness (%) EX1 4.17 94.5 EX2 0.36 96.3 Page 4 of 13 www.sunnycivil.com III. PROPOSED DRAINAGE a) PROPOSED PROJECT DESCRIPTION The proposed redevelopment of the site will include the demolition of the existing multi- tenant commercial building, the multi-unit apartment complex, and the existing bus stop. In their place, a new multi-story, multi-unit student housing complex will be constructed. The proposed complex will also include a small commercial area and a muti-level parking garage. A new recessed bus stop area will be added along West Lake Street. Two access drives are proposed on the west and east sides of the complex, with both stretching from West Prospect Road to West Lake Street. The western roadway will serve as the primary driveway and emergency access, while the eastern roadway will serve as a pedestrian and cyclist connection, as well as an emergency aerial access for the fire department. A summary of the site’s overall composite imperviousness in the pre-redevelopment condition and the post-redevelopment condition is detailed below in Table 2. TABLE 2. IMPERVIOUSNESS SUMMARY CONDITION COMPOSITE IMPERVIOUSNESS (%) Pre-Redevelopment 94.60 Post-Redevelopment 73.69 As the overall imperviousness of the proposed redevelopment will be less than that of the existing site, full-spectrum stormwater detention is not required. However, the Prospect Plaza redevelopment will aim to implement Low-Impact Development (LID) water quality treatment measures via various bioretention areas, otherwise known as rain gardens. These rain gardens, in conjunction with a proposed storm sewer pipe network, will be strategically located and designed throughout the site in order to capture a minimum of 75% of the stormwater runoff that is to be generated by the proposed impervious areas. Once captured, the rain garden’s engineered media and vegetation facilitate filtration, adsorption, absorption, and biological processes that retain stormwater pollutants and enhance infiltration capabilities. b) MAJOR BASINS There are four (4) rain gardens proposed throughout the redevelopment. A description of each rain garden, and its corresponding tributary area, is as follows: Major Basin RG1 represents the tributary area of Rain Garden 1, which is located in the northwest corner of the site. RG1 will treat stormwater runoff generated within the western roadway and parking stalls, as well as a small portion of the roof area. Page 5 of 13 www.sunnycivil.com Major Basin RG2 represents the tributary area of Rain Garden 2, which is located in the northeast corner of the site. RG2 will treat stormwater runoff generated within portions of the northern courtyard, the central courtyard, and the majority of the northern half of the proposed roof area. Major Basin RG3 represents the tributary area of Rain Garden 3, which is located within the southwest courtyard. RG3 will treat stormwater runoff generated within the parking garage, the southwest courtyard, and the southwest portion of the proposed roof area. Major Basin RG4 represents the tributary area of Rain Garden 4, which is located within the southeast courtyard. RG4 will treat stormwater runoff generated within the southeast courtyard and the southeast portion of the proposed roof area. Each major basin has been primarily utilized for the design and analysis of the proposed rain gardens, which are discussed in further detail below in Section IV of this report. The delineation of the major basins can be seen on the PROPOSED MAJOR BASIN MAP within Appendix A of this report. c) SITE DRAINAGE Each of the previously discussed major basins have been divided into numerous sub- basins based off the localized drainage patterns for the proposed redevelopment. The proposed drainage basins can be seen on the PROPOSED DRAINAGE BASIN MAP located within Appendix A of the report. Also included within Appendix A of this report is the ROOFTOP OVERFLOW ROUTING MAP. Runoff that is to be generated by the proposed roof areas, as well as the parking garage, is routed differently depending on which storm event that is occurring. During low intensity rainfall events, runoff is to be captured by the primary roof drain systems. During high intensity rainfall events, runoff is routed through the overflow roof drains systems. Per the International Building Code (IBC), the primary roof drains systems have been designed to convey the first inch of rainfall that occurs. Any rainfall in excess of this initial amount will be directed to the overflow systems. The ROOFTOP OVERFLOW ROUTING MAP depicts where stormwater runoff will be directed during the 100-year storm event via the overflow systems. Brief summaries of each of the proposed drainage basins, including where generated runoff is to be directed, are as follows. Basin 1A is comprised of a small portion of the proposed roof area located at the northwest corner of the parking garage. During low intensity rainfall events, the primary roof drain system will direct any generated runoff to RG1 via the proposed storm sewer network. During high intensity rainfall events, the overflow roof drain systems will direct stormwater into the western roadway. Basin 1B is comprised primarily of the western access drive and parking stalls, as well as a small portion of the northern courtyard area. Runoff generated within this basin will be directed north via the proposed curb and gutter before entering RG1 though an opening in the curb. Page 6 of 13 www.sunnycivil.com Basin 2A is comprised of the northeastern portion of the proposed roof area. During low intensity rainfall events, the primary roof drain system will direct any generated runoff to RG2 via the proposed storm sewer network. During high intensity rainfall events, the various overflow roof drain systems will direct stormwater into the eastern access path, the northern courtyard, and the central courtyard. Basin 2B is comprised of the northwestern portion of the proposed roof area. During low intensity rainfall events, the primary roof drain system will direct any generated runoff to RG2 via the proposed storm sewer network. During high intensity rainfall events, the various overflow roof drain systems will direct stormwater into the northern courtyard. Basin 2C is comprised of the central courtyard area. Runoff generated within this basin will be collected by various area inlets located throughout the courtyard. These inlets will direct stormwater into the proposed storm sewer network, where the runoff will be routed to RG2. Basin 2D is comprised of RG2 itself and the courtyard area surrounding it. Runoff generated within the basin will flow directly into the rain garden via overland flow. Basin 3A is comprised of the proposed parking garage. During low intensity rainfall events, the primary roof drain system will direct any generated runoff to RG3 via the proposed storm sewer network. During high intensity rainfall events, generated runoff will overflow into the western roadway. Basin 3B is comprised of the southwest portion of the proposed roof area. During low intensity rainfall events, the primary roof drain system will direct any generated runoff to RG3 via the proposed storm sewer network. During high intensity rainfall events, the various overflow roof drain systems will direct stormwater either into the western roadway, towards West Prospect Road to the south, or towards the southeastern courtyard. Basin 3C is comprised of RG3 itself and the courtyard area surrounding it. Runoff generated within the basin will flow directly into the rain garden via overland flow. Basin 4A is comprised of the southeast portion of the proposed roof area. During low intensity rainfall events, the primary roof drain system will direct any generated runoff to RG4 via the proposed storm sewer network. During high intensity rainfall events, the various overflow roof drain systems will direct stormwater either into the eastern access path or towards West Prospect Road to the south. Basin 4B is comprised of RG4 itself and the courtyard area surrounding it. Runoff generated within the basin will flow directly into the rain garden via overland flow. The PROPOSED DRAINAGE BASIN MAP also details three (3) additional offsite basins, which represent areas that are not able to be routed to the proposed rain gardens. Instead, each of the offsite basins will direct stormwater runoff directly into the public roadways. A quick description of each of the offsite basins is as follows: Basin OS1 is comprised primarily of the lawn and sidewalk area along Prospect Road. This area is downhill of the southern rain gardens and would require major impacts to the public roadways in order to re-direct stormwater runoff back towards any proposed LID measures. Page 7 of 13 www.sunnycivil.com Basin OS2 is comprised primarily of the eastern emergency access path and portions of the northern courtyard. If this area were to be routed to a proposed rain garden, the resulting garden would be much larger and much deeper than what is allowable or functional. However, unlike the western access drive located within Basin 1A, the emergency access does not receive regular vehicular traffic. Therefore, the western drive was considered more of a treatment priority. Additionally, 75% of the proposed impervious area will still be receiving treatment even with Basin OS2 being directed offsite. Basin OS3 is comprised primarily of the pavement area above Arthur’s Ditch, which runs along the site’s western property line. Re-directing stormwater runoff generated within area towards a proposed LID measure would require large re-designs of the ditch itself. Table 3 below summarizes each of the proposed sub-basins and offsite basins that have been detailed above. TABLE 3. PROPOSED BASIN CHARACTERISTICS Basin Area (acres) Imperviousness (%) 1A 0.153 90.00 1B 0.633 86.2 2A 0.707 90.00 2B 0.261 90.00 2C 0.276 28.44 2D 0.135 13.96 3A 0.615 100.0 3B 0.347 90.00 3C 0.085 3.53 4A 0.177 90.00 4B 0.102 5.73 OS1 0.152 71.82 OS2 0.821 58.74 OS3 0.068 100.0 Page 8 of 13 www.sunnycivil.com IV. DRAINAGE FACILITY DESIGN a) CRITERIA The designs and analyzes presented and performed within this report have been prepared in accordance with the standards presented within the latest versions of the City of Fort Collins Stormwater Criteria Manual (FCSCM, denoted as “CRITERIA” within this report). b) RUNOFF Per the CRITERIA, hydrological calculations for the site have been prepared with the Rational Method. The results of these computations are included within Appendix A of this report. Erosion control will be provided for both the high and low flow conditions throughout the site. Temporary BMPs and erosion control measures will be placed throughout the site until the final landscaping and pavement has been installed. c) STORM SEWER The proposed storm sewer network has been designed primarily per the CRITERIA. Design and modeling techniques, as well as key parameters and characteristics for each component of the storm sewer system and drainage infrastructure, are discussed below. There are numerous storm sewer inlets of varying purpose, type, and design criteria located through the proposed redevelopment. These varying types of inlets are discussed below. There are two existing COFC Single Curb Inlets within West Lake Street located east of the existing bus stop loop. The inlet in the north flowline, the inlet in the south flowline, and the pipe between the two will be replaced and upsized within the proposed redevelopment of the site. Additionally, the south flowline inlet will be shifted south approximately 12 feet to the new gutter location. Each inlet will be replaced with a COFC Double Curb Inlet in order to provide a proposed interception capacity that is greater than the existing interception capacity. This analysis has been performed through utilization of the MHFD-Inlet, Version 5.03 (August 2023) spreadsheet. The results of this spreadsheet are included within Appendix B of this report. There is an existing Type 13 valley grate inlet within the West Prospect Road northern flowline located at the southwest corner of the site and directly above the Arthur Ditch reinforced concrete culvert. In the proposed condition, this inlet would be located within the western roadway’s access. In order to accommodate this change, the top of the inlet structure is to be replaced with a curb-less Type 13 valley grate inlet. However, due to the removal of curb at this inlet, the interception capacity of this inlet has been greatly decreased. An additional Type 13 combination curb inlet is proposed approximately 25 feet upstream of this inlet in order to provide additional interception capacity. These two proposed inlets have been design in conjunction in order to provide a proposed bypass flowrate that is less than the bypass flowrate within the existing condition. This analysis has been performed through utilization of the MHFD-Inlet, Version 5.03 (August 2023) spreadsheet. The results of this spreadsheet are included within Appendix B of this report. Page 9 of 13 www.sunnycivil.com There are numerous area inlets located within the central courtyard. These inlets are to be comprised of either Advanced Drainage Systems (ADS) Nyloplast drain basins or inline drains. Whether a drain basin or an inline drain, each inlet will be equipped with a ductile iron dome grate. These grates and inlets have been designed to convey the runoff from the incoming 100-year storm event into the proposed storm sewer network. Due to the building configuration enclosing this courtyard, the emergency overflow route for these inlets is limited to the breezeway at the southeast corner of the courtyard. As this breezeway is not adequate for emergency overflow during extreme storm events, these inlets have been greater oversized. · These inlets have been designed to convey the 100-year storm event while still providing one (1) foot of freeboard between the minimum opening elevation and the ponded water elevation. These inlets can be up to 70% to 95% clogged before this one (1) foot of freeboard is impeded. · Assuming the inlets are completely clogged, the swales and low areas within the courtyard will be able to store double the incoming 100-year storm event runoff volume while still providing 0.51 feet (~7 inches) between the ponded water elevation and the minimum opening elevation. The CENTRAL COURTYARD INLET & STORM SIZING EXHIBIT is included within Appendix B of this report. This exhibit depicts the ponding depths within the central courtyard, the capacity of each inlet and inlet grate, and the allowable clogging percentage for each of the proposed inlets. Additionally, each of the proposed rain gardens is to be equipped with an overflow riser, which are also to be comprised of ADS Nyloplast drain basins. The functionality of these risers, and the flow they are to collect, is discussed in further detail in Section IVd below. The proposed storm sewer pipes have been designed to convey the runoff rate each network will encounter during the 100-year storm event. However, due to the parking garage and roof drainage systems, the majority of the runoff generated by these areas will not be directed towards the proposed storm sewer networks. The amount of runoff entering the proposed storm sewer networks via the rain gardens is discussed in further detail in Section IVd below. The storm sewer pipes have been sized using Storm and Sanitary Analysis Extension for Autodesk® Civil 3D® 2025. The utilization of this modeling software ensures each pipe was sized adequately enough such that the hydraulic grade lines (HGLs) generated within the storm network during the 100-year recurrence interval major storm event would remain below finished grade. The results of this model are included within Appendix B of this report. Any proposed culverts, swales, and sidewalk chases have been modeled, sized, and evaluated within Hydraflow Express Extension for Autodesk® Civil 3D® 2025. The results of these models are included within Appendix B of this report. d) FACILITY DESIGN The proposed redevelopment of the site includes four (4) rain gardens. Each of the rain gardens has been designed to attenuate the water quality capture volume (WQCV) generated by their corresponding tributary areas. WQCV’s have been calculated via the criteria presented within Chapter 7 of the CRITERIA. The results of these calculations can be seen within Appendix B of this report. Page 10 of 13 www.sunnycivil.com Table 4 below summarizes the required WQCV for each rain garden, as well as the provided volume within each rain garden. TABLE 4. RAIN GARDEN SUMMARY RAIN GARDEN ID REQUIRED WQCV (CU. FT.) PROVIDED VOLUME WITHIN RG (CU. FT.) WQCV WSEL RG1 1031.73 1047.49 5000.92 RG2 1327.21 1437.68 5001.23 RG3 1430.17 1466.62 5006.48 RG4 227.30 227.88 5006.495 Per the CRITERIA, the depth of the WQCV within each rain garden must not exceed twelve (12) inches. Each of the defined rain garden areas are twelve (12) inches in depth and will not be exceeded by the WQCV. However, all of the rain gardens have additional storage volume available within their courtyards and surrounding areas. This additional volume will be utilized during large storm events to help convey stormwater. The conveyance of additional stormwater volumes is discussed in more detail later on in the section. The WQCV within each rain garden is to be drained within a minimum of 12 hours, as they are designated as LID systems. The bottom of each rain garden is to be equipped with a minimum thirty (30) inch deep engineered media of varying layers. The bottom layer of media is to contain an underdrain, which is to be comprised of a four (4) inch diameter perforated PVC pipe. These underdrains will direct collected infiltrated stormwater to the proposed downstream storm sewer infrastructure. Stormwater exiting through the underdrain will first pass through each pond’s respective overflow riser structure, which is to be comprised of an ADS Nyloplast drain basin. As each rain garden is to be drained within a minimum of 12 hours, these structures are to include an internal outlet weir wall. These weir walls are to contain a singular orifice, which has been sized to ensure the proper drain time for each rain garden. The design of these orifices is included within Appendix B of this report. As a LID system, each rain garden has only been designed to accommodate its respective WQCV. During storm events that generate a volume greater than the WQCV, stormwater will either be collected by an overflow riser or spill directly into the adjacent public roadways, without creating adverse impacts to the nearby buildings or infrastructure, via the overflow spillways. · The elevation of the riser is to be set at the WQCV water surface elevation (WSEL). Therefore, once volumes within each rain garden start to exceed the WQCV, runoff will begin to enter the proposed storm sewer networks through their respective risers. Runoff will continue to enter the riser until the WSEL within the pond exceeds the elevation of the invert of the overflow spillway. The sizing of each of the rain garden’s overflow riser is included within Appendix B of this report. Page 11 of 13 www.sunnycivil.com · Once the WSEL within the pond exceeds the elevation of the invert of the overflow spillway, runoff will begin to flow into the adjacent roadways via the proposed overflow spillways. The spillway for each pond has been designed to convey the incoming 100-year storm event runoff rate while maintaining one (1) foot of freeboard between the overflow WSEL and the nearest minimum opening elevation. An analysis of each pond overflow spillway is included within Appendix B of this report. RG3 and RG4, the two southern rain gardens, each have respective exceptions to the previous statements: · Due to grading constraints set by the adjacent existing roadway, the RG3 overflow spillway is unable to provide adequate freeboard between its resulting WSEL and the nearest minimum opening elevation. Therefore, the overflow riser has been upsized so that it may convey the entirety of the incoming 100-year storm event runoff rate. · Due to the additional runoff that is to be collected by the RG3 overflow riser, the proposed storm sewer network does not have the capacity to take runoff that would have entered through the RG4 overflow riser. Therefore, the RG4 overflow riser is to be equipped with a solid cover instead of a dome grate and will not accept any overflow. This will cause all volumes greater than the WQCV to be directed over the RG4 overflow spillway. Table 5 below summarizes the amount of runoff that each rain garden will contribute to the proposed storm networks during the 100-year storm event. Table 5. RAIN GARDEN OUTFLOWS RAIN GARDEN ID ORIFICE FLOWRATE (CFS) OVERFLOW RISER FLOWRATE (CFS) TOTAL FLOWRATE (CFS) RG1 0.021 2.50 2.521 RG2 0.027 4.90 4.927 RG3 0.027 3.41 3.437 RG4 0.004 -- 0.004 Page 12 of 13 www.sunnycivil.com e) FLOODPLAIN IMPACTS As mentioned in Section Ib of this report, the northern portion of the site is located within 100-year storm event floodplain, as mapped by CSU’s PCSWMM floodplain model. Flooding is the deepest within West Lake Street and extends south into the site. In order to accommodate the proposed redevelopment, the floodplain boundary within the site will be adjusted while maintaining the existing flood volume on-site. The proposed redevelopment will accommodate this floodplain volume within open space in the north portion of the site and within the proposed driveways on the west and east sides of the building. Additionally, the northwest portion of the building will not have a ground level and will instead be elevated on structural columns. The finished floor elevation of the residential portion of the proposed building is set at least 2 feet above the base flood elevation (BFE), and the commercial portion is set at least 1 foot above the BFE. An update to CSU’s floodplain model has been completed to ensure that the BFE used for the proposed redevelopment is accurate. The results of this update to existing CSU PCSWMM floodplain model are included within this report as Appendix D. The floodplain memo included within Appendix D also details floodwater located within West Prospect Road. The proposed doorways located between RG3 and RG4 have been elevated in order to provide additional freeboard between these openings and the water surface elevation within the roadway. Page 13 of 13 www.sunnycivil.com V. CONCLUSION a) IMPACT OF PROPOSED IMPROVEMENTS The drainage design for the Prospect Plaza redevelopment that is documented within this report presents a design that will effectively convey the proposed stormwater while providing water quality treatment. Storm inlets and pipes have been sized, at a minimum, to convey the runoff that is to be generated within the 100-year storm event. Some inlets have been oversized to ensure ponded stormwater will not impact the proposed building. Stormwater treatment and LID implementation will be provided within the four (4) proposed rain gardens. Each of the rain gardens will drain their respective WQCV in a minimum of 12 hours. Volumes greater than the WQCV will either enter the proposed storm sewer network via the overflow risers or flow to the existing public roadways via the overflow spillways. While located within the floodplain, the site has been designed in order to accommodate these floodwater volumes. Per the floodplain memo included within Appendix D of this report, the BFE in the post-redevelopment condition will be 0.01 feet lower than the BFE in the pre-redevelopment condition. b) CODE COMPLIANCE The proposed redevelopment of the site is in compliance with all state, county, and city regulations, standards, and criteria. VI. REFERENCES i. Urban Storm Drainage Criteria Manual, Volume 1, Mile High Flood District, partially updated March 2024 and as periodically amended ii. Urban Storm Drainage Criteria Manual, Volume 2, Mile High Flood District, revised January 2016 and as periodically amended iii. Urban Storm Drainage Criteria Manual, Volume 3, Mile High Flood District, partially updated March 2024 and as periodically amended APPENDIX A SUNNY CIVILProspect Plaza Redevelopment Vicinity Map PROJECT SITE PROSPECT RD LAKE ST CE N T E R A V E IRRCONTROL IRRCONTROL IRRCONTROL F.O.VAULT WV WV D G HYDWV GAS EL E C ELEC C.O. G C.O. ELEC W C.O. C C ELEC ELEC ELECD ELEC G E F.O.CS ELECELEC GAS D X X X X X X X X X X X X X X X X X T T T T T T T T T X X ELEC G D ELECCABLE CABLE G ELEC CABLE WW FO CABLE ELEC WV S H2O C CABLECABLE CC C CABLE G G G G G G E E ELEC E E ELEC E E ELEC E E ELEC CABLE CABLEG G E E ELEC CABLEG G CABLE CABLE M ELECBRKR CABLE ST ST ST ST ST S WAT WA T 1 STORY BRICK AND WOOD BUILDING FFE = 5008.42 BUS STOP DO NOT ENTER DO NOT ENTER STOP 2.5 STORY BRICK APARTMENTS FFE = 5007.37 2.5 STORY BRICK APARTMENTS FFE = 5007.24 2.5 STORY BRICK APARTMENTS FFE = 5007.05 2.5 STORY BRICK APARTMENTS FFE = 5006.46 2.5 STORY BRICK APARTMENTS FFE = 5006.14 2.5 STORY BRICK APARTMENTS FFE = 5006.22 2.5 STORY BRICK APARTMENTS FFE = 5006.39 2.5 STORY BRICK APARTMENTS FFE = 5006.64 2.5 STORY BRICK APARTMENTS FFE = 5006.91 2.5 STORY BRICK APARTMENTS FFE = 5007.08 2.5 STORY BRICK APARTMENTS FFE = 5007.43 GATE GATE SPEED BUMP BIKE RACK BI K E R A C K BI K E R A C K S BOULDERS BOULDERS 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 171.0' 50 . 4 ' 171.0' 50 . 4 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' 80.0' 39 . 3 ' SPEED BUMP S S S S S S D S G G G G G G G G G G G G G E E E W W W W W W W W W ± ± 03/19/2025DATE: EMDRAWN BY: 024-015PROJECT NO: PR O S P E C T P L A Z A R E D E V E L O P M E N T RE V I S I O N S # DA T E DE S C R I P T I O N SU N N Y C I V I L SHEET CO N C E P T U A L P L A N S C:\ U s e r s \ M a t t B a r r \ S u n n y C i v i l D r o p b o x \ P r o j e c t s \ 0 2 4 - 0 1 5 P r o s p e c t P l a z a \ 4 0 - D e s i g n \ R e p o r t s \ D r a i n a g e \ C A D \ X B A S N _ 0 2 4 0 1 5 . d w g 3/1 4 / 2 0 2 5 9 : 5 0 A M Ma t t B a r r CALL 811 72 HOURS PRIOR TO DIGGING, GRADING, OR EXCAVATING FOR THE MARKING OF UNDERGROUND, MEMBER UTILITIES. SUNNY CIVIL HAS USED THE BEST AVAILABLE INFORMATION TO PLOT UNDERGROUND UTILITIES SHOWN ON THIS PLAN. THE CONTRACTOR IS RESPONSIBLE FOR FIELD VERIFICATION OF UTILITY LOCATIONS AND DEPTHS PRIOR TO COSTRUCTION. PRELIMINARY 1 N EX I S T I N G D R A I N A G E B A S I N M A P SS SS SS SS SS SS SS SS SS SS SS SS WV WV D G HYDWV GAS EL E C ELEC C.O. G C.O. ELEC W C.O. C C ELEC ELEC ELECD ELEC G GAS D X X X X X X X X X X X X X X X X X ELEC D WV ST ST BUS STOP NO THRU TRAFFIC NO PARKING PARKING BY PERMIT ONLY STOP VISITORS PARKING GATE GATE SPEED BUMP S S S S S D E E E E E ECTVCTVCTV T VIS I T O R VIS I T O R VIS I T O R VA N VIS I T O R VA N T E ELEC F.O. FO ± ± ± ± ± ± ± ± 03/19/2025DATE: EMDRAWN BY: 024-015PROJECT NO: PR O S P E C T P L A Z A R E D E V E L O P M E N T RE V I S I O N S # DA T E DE S C R I P T I O N SU N N Y C I V I L SHEET CO N C E P T U A L P L A N S C:\ U s e r s \ M a t t B a r r \ S u n n y C i v i l D r o p b o x \ P r o j e c t s \ 0 2 4 - 0 1 5 P r o s p e c t P l a z a \ 4 0 - D e s i g n \ R e p o r t s \ D r a i n a g e \ C A D \ P M A J B A S N _ 0 2 4 0 1 5 . d w g 4/2 9 / 2 0 2 5 6 : 2 6 P M Ma t t B a r r CALL 811 72 HOURS PRIOR TO DIGGING, GRADING, OR EXCAVATING FOR THE MARKING OF UNDERGROUND, MEMBER UTILITIES. SUNNY CIVIL HAS USED THE BEST AVAILABLE INFORMATION TO PLOT UNDERGROUND UTILITIES SHOWN ON THIS PLAN. THE CONTRACTOR IS RESPONSIBLE FOR FIELD VERIFICATION OF UTILITY LOCATIONS AND DEPTHS PRIOR TO COSTRUCTION. PRELIMINARY 1 N PR O P O S E D M A J O R D R A I N A G E B A S I N M A P SS SS SS SS SS SS SS SS SS SS SS SS WV WV D G HYDWV GAS EL E C ELEC C.O. G C.O. ELEC W C.O. C C ELEC ELEC ELECD ELEC G GAS D X X X X X X X X X X X X X X X X X ELEC D WV ST ST BUS STOP NO THRU TRAFFIC NO PARKING PARKING BY PERMIT ONLY STOP VISITORS PARKING GATE GATE SPEED BUMP S S S S S D E E E E E ECTVCTVCTV T VIS I T O R VIS I T O R VIS I T O R VA N VIS I T O R VA N T E ELEC F.O. FO ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 03/19/2025DATE: EMDRAWN BY: 024-015PROJECT NO: PR O S P E C T P L A Z A R E D E V E L O P M E N T RE V I S I O N S # DA T E DE S C R I P T I O N SU N N Y C I V I L SHEET CO N C E P T U A L P L A N S C:\ U s e r s \ M a t t B a r r \ S u n n y C i v i l D r o p b o x \ P r o j e c t s \ 0 2 4 - 0 1 5 P r o s p e c t P l a z a \ 4 0 - D e s i g n \ R e p o r t s \ D r a i n a g e \ C A D \ P B A S N _ 0 2 4 0 1 5 . d w g 4/2 9 / 2 0 2 5 6 : 3 1 P M Ma t t B a r r CALL 811 72 HOURS PRIOR TO DIGGING, GRADING, OR EXCAVATING FOR THE MARKING OF UNDERGROUND, MEMBER UTILITIES. SUNNY CIVIL HAS USED THE BEST AVAILABLE INFORMATION TO PLOT UNDERGROUND UTILITIES SHOWN ON THIS PLAN. THE CONTRACTOR IS RESPONSIBLE FOR FIELD VERIFICATION OF UTILITY LOCATIONS AND DEPTHS PRIOR TO COSTRUCTION. PRELIMINARY 1 N PR O P O S E D D R A I N A G E B A S I N M A P SS SS SS SS SS SS SS SS SS SS SS SS WV WV D G HYDWV GAS EL E C ELEC C.O. G C.O. ELEC W C.O. C C ELEC ELEC ELECD ELEC G GAS D X X X X X X X X X X X X X X X X X ELEC D WV ST ST BUS STOP NO THRU TRAFFIC NO PARKING PARKING BY PERMIT ONLY STOP VISITORS PARKING GATE GATE SPEED BUMP S S S S S D E E E E E ECTVCTVCTV T VIS I T O R VIS I T O R VIS I T O R VA N VIS I T O R VA N T E ELEC F.O. FO ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 03/19/2025DATE: EMDRAWN BY: 024-015PROJECT NO: PR O S P E C T P L A Z A R E D E V E L O P M E N T RE V I S I O N S # DA T E DE S C R I P T I O N SU N N Y C I V I L SHEET CO N C E P T U A L P L A N S C:\ U s e r s \ M a t t B a r r \ S u n n y C i v i l D r o p b o x \ P r o j e c t s \ 0 2 4 - 0 1 5 P r o s p e c t P l a z a \ 4 0 - D e s i g n \ R e p o r t s \ D r a i n a g e \ C A D \ P R O O F _ 0 2 4 0 1 5 . d w g 4/2 9 / 2 0 2 5 6 : 2 7 P M Ma t t B a r r CALL 811 72 HOURS PRIOR TO DIGGING, GRADING, OR EXCAVATING FOR THE MARKING OF UNDERGROUND, MEMBER UTILITIES. SUNNY CIVIL HAS USED THE BEST AVAILABLE INFORMATION TO PLOT UNDERGROUND UTILITIES SHOWN ON THIS PLAN. THE CONTRACTOR IS RESPONSIBLE FOR FIELD VERIFICATION OF UTILITY LOCATIONS AND DEPTHS PRIOR TO COSTRUCTION. PRELIMINARY 1 N RO O F T O P O V E R F L O W R O U T I N G M A P Project Name:Prospect Plaza Redevelopment Project Number :024-015 Client:Tetrad/STRATA Asphalt, Concrete Rooftop Gravel Lawns, Clayey, <2%C C*Cf (acres) (acres) (acres) (acres) (acres)2, 5, 10 100 (%) EX1 Existing Site - North N/A 3.109 0.893 0.069 0.103 4.174 0.92 1.00 94.45% EX2 Existing Site - South N/A 0.257 0.099 - 0.004 0.360 0.94 1.00 96.26% 3.367 0.992 0.069 0.107 4.534 0.93 1.00 94.60% Asphalt, Concrete Rooftop Gravel Lawns, Clayey, <2%C C*Cf (acres) (acres) (acres) (acres) (acres)2, 5, 10 100 (%) 1A Western Rooftop Area RG1 - 0.153 - - 0.153 0.95 1.00 90.00% 1B Western Drive Aisle RG1 0.528 0.017 - 0.087 0.633 0.85 1.00 86.20% 2A Eastern Rooftop Area RG2 - 0.707 - - 0.707 0.95 1.00 90.00% 2B Northern Rooftop Area RG2 - 0.261 - - 0.261 0.95 1.00 90.00% 2C Centeral Courtyard RG2 0.075 - - 0.202 0.276 0.40 0.50 28.44% 2D Northeast Raingarden RG2 0.017 - - 0.119 0.135 0.29 0.36 13.96% 3A Parking Garage RG3 0.615 - - - 0.615 0.95 1.00 100.00% 3B Southwest Rooftop Area RG3 - 0.347 - - 0.347 0.95 1.00 90.00% 3C Southwest Raingarden RG3 0.000 0.001 - 0.083 0.085 0.21 0.27 3.53% 4A Southeast Rooftop Area RG4 - 0.177 - - 0.177 0.95 1.00 90.00% 4B Southeast Raingarden RG4 0.004 - - 0.099 0.102 0.23 0.29 5.73% Asphalt, Concrete Rooftop Gravel Lawns, Clayey, <2%C C*Cf (acres) (acres) (acres) (acres) (acres)2, 5, 10 100 (%) RG1 NW RG N/A 0.528 0.170 - 0.087 0.786 0.87 1.00 86.94% RG2 NE RG N/A 0.091 0.968 - 0.321 1.380 0.78 0.97 70.21% RG3 SW RG N/A 0.615 0.348 - 0.083 1.047 0.89 1.00 88.86% RG4 SE RG N/A 0.004 0.177 - 0.099 0.280 0.69 0.86 59.12% 1.239 1.664 - 0.590 3.493 0.82 0.98 78.68% OS1 Offsite to South N/A 0.106 0.003 - 0.044 0.152 0.74 0.92 71.82% OS2 Offsite to North N/A 0.475 - - 0.346 0.821 0.63 0.79 58.74% OS3 Arthurs Ditch N/A - - - 0.068 0.068 0.20 0.25 2.00% 0.582 0.003 - 0.457 1.041 0.62 0.78 56.96% 1.820 1.666 - 1.047 4.534 0.78 0.93 73.69% TOTAL (TREATED) TOTAL (UNTREATED) PROPOSED TOTAL TOTAL AREA Basin Description Major Basin Routing Surface Type TOTAL AREA Basin Name EXISTING BASINS DEVELOPED BASINS MASTER BASINS Surface Type EXISTING TOTAL Percent Impervious Runoff Coefficients Runoff Coefficients Percent Impervious Surface Type TOTAL AREA Basin Name Basin Description Major Basin Routing Major Basin RoutingBasin Description RATIONAL METHOD CALCULATIONS: COMPOSITE RUNOFF COEFFICIENT & PERCENT IMPERVIOUS Runoff Coefficients Percent ImperviousBasin Name MWB 4/24/2025 Prepared By: Date: 0.301 in A = 0.786 acres V = 0.0237 ac-ft 1031.73 cu. ft RG1 i = a = DRAIN TIME WQCV = 86.94% CITY OF FORT COLLINS (COFC) CALCULATION FOR: WATER QUALITY CAPTURE VOLUME (WQCV) 12 hr 0.80 Date: Prepared By: Client: Project Number : Project Name: Tetrad/STRATA 024-015 Prospect Plaza Redevelopment MWB 4/24/2025 MAJOR BASIN 0.221 in A = 1.380 acres V = 0.0305 ac-ft 1327.21 cu. ft CITY OF FORT COLLINS (COFC) CALCULATION FOR: WATER QUALITY CAPTURE VOLUME (WQCV) Project Name:Prospect Plaza Redevelopment Date: 4/24/2025 Project Number : 024-015 Prepared By: MWB Client: Tetrad/STRATA MAJOR BASIN RG2 DRAIN TIME 12 hr a = 0.80 i = 70.21% WQCV = 0.314 in A = 1.047 acres V = 0.0328 ac-ft 1430.17 cu. ft CITY OF FORT COLLINS (COFC) CALCULATION FOR: WATER QUALITY CAPTURE VOLUME (WQCV) Project Name:Prospect Plaza Redevelopment Date: 4/24/2025 Project Number : 024-015 Prepared By: MWB Client: Tetrad/STRATA MAJOR BASIN RG3 DRAIN TIME 12 hr a = 0.80 i = 88.86% WQCV = 0.187 in A = 0.280 acres V = 0.0052 ac-ft 227.30 cu. ft CITY OF FORT COLLINS (COFC) CALCULATION FOR: WATER QUALITY CAPTURE VOLUME (WQCV) Project Name:Prospect Plaza Redevelopment Date: 4/24/2025 Project Number : 024-015 Prepared By: MWB Client: Tetrad/STRATA MAJOR BASIN RG4 DRAIN TIME 12 hr a = 0.80 i = 59.12% WQCV = 1031.73 CF will be met at an elevation of:5000.92 1327.21 CF will be met at an elevation of:5001.23 1430.17 CF will be met at an elevation of:5006.48 227.30 CF will be met at an elevation of:5006.50 Prepared By: MWB Project Name:Prospect Plaza Redevelopment Date: 4/24/2025 Project Number :024-015 The required WQCV of: WATER SURFACE ELEVATION LEVELS: FOR RG WQCV RG2 The required WQCV of: RG4 The required WQCV of: The required WQCV of: RG3 RG1 Client:Tetrad/STRATA Top of RG3: 5,006.50, 1466.62 5,007.60, 4403.76 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5,005.50 5,005.92 5,006.34 5,006.76 5,007.18 5,007.60 Vo l u m e ( C F ) Elevation Top of RG1: 5,001.00, 1147.49 5,001.20, 1454.48 0 200 400 600 800 1000 1200 1400 1600 5,000.00 5,000.20 5,000.40 5,000.60 5,000.80 5,001.00 5,001.20 Vo l u m e ( C F ) Elevation Top of RG2: 5,001.30, 1437.68 5,001.90, 2716.9 0 500 1000 1500 2000 2500 3000 5,000.3 5,000.6 5,000.9 5,001.3 5,001.6 5,001.9 Vo l u m e ( C F ) Elevation Top of RG4: 5,006.50, 227.88 5,006.80, 460.15 0 50 100 150 200 250 300 350 400 450 500 5,005.50 5,005.76 5,006.02 5,006.28 5,006.54 5,006.80 Vo l u m e ( C F ) Elevation Project Name:Prospect Plaza Redevelopment Project Number :024-015 Client:Tetrad/STRATA Tc Final Tc C C*Cf Equation 5-3 Equation 5-3 2, 5, 10 100 L (ft) S (%) Ti (min) L (ft) S (%) V2 (ft/s) Tt (min) Tc (min)Length Tc (min) Tc (min) EX1 Existing Site - North 0.92 1.00 No 130.00 1.21% 2.00 400.00 1.20% Paved Areas 20 2.2 3.04 5.04 530 12.94 5.04 EX2 Existing Site - South 0.94 1.00 Yes 20.00 2.00% 0.67 2500.00 1.50% Paved Areas 20 2.4 17.01 17.68 2520 24.00 5.00 Tc Final Tc C C*Cf Equation 5-3 Equation 5-3 2, 5, 10 100 L (ft) S (%) Ti (min) L (ft) S (%) V2 (ft/s) Tt (min) Tc (min)Length Tc (min) Tc (min) 1A Western Rooftop Area 0.95 1.00 Yes 90.50 2.36% 1.34 445.00 0.80% Paved Areas 20 1.8 4.15 5.49 536 12.98 5.00 1B Western Drive Aisle 0.85 1.00 No 95.00 2.48% 1.35 450.00 0.85% Paved Areas 20 1.8 4.06 5.41 545 13.03 5.41 2A Eastern Rooftop Area 0.95 1.00 Yes 20.00 2.00% 0.67 2500.00 1.50% Tillage/Field 5 0.6 68.04 68.71 2520 24.00 5.00 2B Northern Rooftop Area 0.95 1.00 Yes 21.00 102.00% 0.19 2501.00 101.50% Tillage/Field 5 5.0 8.27 8.46 2522 24.01 5.00 2C Centeral Courtyard 0.40 0.50 No 75.00 2.20% 7.45 5.00 2.00% Short Pasture & Lawns 7 1.0 0.08 7.54 80 10.44 7.54 2D Northeast Raingarden 0.29 0.36 No 86.00 5.19% 7.41 24.00 13.50% Short Pasture & Lawns 7 2.6 0.16 7.56 110 10.61 7.56 3A Parking Garage 0.95 1.00 Yes 20.00 2.00% 0.67 2500.00 1.50% Tillage/Field 5 0.6 68.04 68.71 2520 24.00 5.00 3B Southwest Rooftop Area 0.95 1.00 Yes 20.00 2.00% 0.67 2500.00 1.50% Tillage/Field 5 0.6 68.04 68.71 2520 24.00 5.00 3C Southwest Raingarden 0.21 0.27 No 17.00 4.80% 3.83 4.00 25.00% Short Pasture & Lawns 7 3.5 0.02 5.00 21 10.12 5.00 4A Southeast Rooftop Area 0.95 1.00 Yes 20.00 2.00% 0.67 2500.00 1.50% Tillage/Field 5 0.6 68.04 68.71 2520 24.00 5.00 4B Southeast Raingarden 0.23 0.29 No 63.00 1.30% 11.08 4.00 25.00% Short Pasture & Lawns 7 3.5 0.02 11.10 67 10.37 10.37 OS1 Offsite to South 0.74 0.92 Yes 20.00 2.00% 1.20 2500.00 1.50% Paved Areas 20 2.4 17.01 18.21 2520 24.00 5.00 OS2 Offsite to North 0.63 0.79 No 45.00 3.35% 2.34 485.00 0.81% Paved Areas 20 1.8 4.58 6.93 523 12.91 6.93 OS3 Arthurs Ditch 0.20 0.25 Yes 20.00 2.00% 5.66 2500.00 1.50% Paved Areas 20 2.4 17.01 22.67 2520 24.00 5.00 (1.49/n)*R^(2/3) (1.49/n)*R^(2/3) DEVELOPED BASINS Basin Name Basin Description Basin Characteristics Small, Urban Basin? Overland Flow Channelized Flow Tc Equation 3.3-2 Equation 5-4 & 5-5 RATIONAL METHOD CALCULATIONS: COMPOSITE CALCULATED TIME OF CONCENTRATION Date: 4/24/2025 Prepared By: MWB EXISTING BASINS Basin DescriptionBasin Name Basin Characteristics Small, Urban Basin? Equation 5-4 & 5-5 Channelized Flow Equation 3.3-2 Overland Flow Equation 3.3-5 Tc Equation 3.3-5 Project Name:Prospect Plaza Redevelopment Project Number :024-015 Client:Tetrad/STRATA Area C C*Cf Tc I2 I10 I100 Q2 Q10 Q100 (acres)2, 5, 10 100 (min) (in/hr) (in/hr) (in/hr) (cfs) (cfs) (cfs) EX1 Existing Site - North 4.174 0.92 1.00 5.0 2.65 4.51 9.18 10.22 17.41 38.32 EX2 Existing Site - South 0.360 0.94 1.00 5.0 2.85 4.87 9.95 0.97 1.65 3.58 Area C C*Cf Tc I2 I10 I100 Q2 Q10 Q100 (acres)2, 5, 10 100 (min) (in/hr) (in/hr) (in/hr) (cfs) (cfs) (cfs) 1A Western Rooftop Area 0.153 0.95 1.00 5.0 2.85 4.87 9.95 0.41 0.71 1.53 1B Western Drive Aisle 0.633 0.85 1.00 5.4 2.60 4.43 9.01 1.39 2.37 5.70 2A Eastern Rooftop Area 0.707 0.95 1.00 5.0 2.85 4.87 9.95 1.91 3.27 7.03 2B Northern Rooftop Area 0.261 0.95 1.00 5.0 2.85 4.87 9.95 0.71 1.21 2.60 2C Centeral Courtyard 0.276 0.40 0.50 7.5 2.36 4.02 8.19 0.26 0.45 1.14 2D Northeast Raingarden 0.135 0.29 0.36 7.6 2.36 4.02 8.19 0.09 0.16 0.40 3A Parking Garage 0.615 0.95 1.00 5.0 2.85 4.87 9.95 1.67 2.85 6.12 3B Southwest Rooftop Area 0.347 0.95 1.00 5.0 2.85 4.87 9.95 0.94 1.61 3.45 3C Southwest Raingarden 0.085 0.21 0.27 5.0 2.85 4.87 9.95 0.05 0.09 0.22 4A Southeast Rooftop Area 0.177 0.95 1.00 5.0 2.85 4.87 9.95 0.48 0.82 1.76 4B Southeast Raingarden 0.102 0.23 0.29 10.4 2.13 3.64 7.41 0.05 0.09 0.22 OS1 Offsite to South 0.152 0.74 0.92 5.0 2.85 4.87 9.95 0.32 0.55 1.39 OS2 Offsite to North 0.821 0.63 0.79 6.9 2.42 4.13 8.40 1.26 2.15 5.47 OS3 Arthurs Ditch 0.068 0.20 0.25 5.0 2.85 4.87 9.95 0.04 0.07 0.17 Basin Characteristics Intensity Runoff Basin Characteristics Intensity Runoff DEVELOPED BASINS Basin Name Basin Description Basin Name Basin Description EXISTING BASINS RATIONAL METHOD CALCULATIONS: BASIN RUNOFF CALCULATIONS Date: 4/24/2025 Prepared By: MWB Project Name:Prospect Plaza Redevelopment Project Number :024-015 Client:Tetrad/STRATA Area Q2 Q10 Q100 Area Q2 Q10 Q100 (acres) (cfs) (cfs) (cfs) (acres) (cfs) (cfs) (cfs) 204 gpm 0.55 cfs 843 gpm RG2 (via 2D) 0.085 0.00 0.12 0.57 2.26 cfs RG2 (via 2C) 0.125 0.00 0.18 0.85 OS2 0.497 0.00 0.71 3.36 461.00 gpm RG1 (via 1B) 0.128 0.00 0.00 0.67 1.23 cfs OS2 0.134 0.00 0.00 0.70 800 gpm 2.14 cfs 391 gpm RG1 (via 1B) 0.091 0.00 0.15 0.63 1.05 cfs RG4 (via 4B) 0.133 0.00 0.21 0.92 OS1 0.124 0.00 0.20 0.86 199 gpm OS1 0.071 0.00 0.11 0.49 0.53 cfs OS2 0.107 0.00 0.17 0.74 Q2 Q10 Q100 (cfs) (cfs) (cfs) RG1 1.94 3.93 12.50 RG2 3.84 4.40 6.45 RG3 3.24 3.27 3.41 RG4 0.58 0.83 1.67 OS1 0.32 0.86 2.74 OS2 1.26 3.04 10.27 OS3 0.04 0.07 0.17 4/29/2025 MWB 0.276 0.085Southwest Raingarden3C 3.453B 6.12 0.40 1.14 0.707Eastern Rooftop Area2A Northern Rooftop Area2B 5.701.390.633Western Drive Aisle 3.271.91 Centeral Courtyard2C 1B 2D Northeast Raingarden 0.135 Basin Characteristics Runoff Basin Name Basin Description 1.530.153Western Rooftop Area1A 0.710.41 4A 0.220.102Southeast Raingarden4B 0.05 0.09 2.851.67 0.347 1.76 0.22 0.177Southeast Rooftop Area Southwest Rooftop Area 0.615Parking Garage3A 0.700.00 N/A N/A RG2 0.00RG1 N/A Routing Routing 0.153 0.615 RG2 IBC Flowrates 0.16 Roof Drains 0.170.070.04 DEVELOPED BASINS 0.820.48 RG1 (via 1B) RG1 (via 1B) 0.160.09 0.450.26 1.210.71 0.05 0.09 1.610.94 2.37 2.600.261 RG3 RG3 Contributing Basins Basin Characteristics MASTER BASINS OS3 OS2, % of 2A overflow, % of 2B overflow, % of 4A overflow OS1, % of 3B overflow, % of 4A overflow % of 3A overflow, 4A roof drains, 4B OS1 5.472.151.260.821Offsite to NorthOS2 0.068Arthurs DitchOS3 2A roof drains, % of 2A overflow, 2B roof drains, 2C, 2D 3A roof drains, 3B roof drains, 3C 1A roof drains and overflow, 1B, % of 2B overflow, 3A overflow, % of 3B overflow Runoff Basin Name N/A Overflow Drains RATIONAL METHOD CALCULATIONS: RUNOFF ROUTING N/A N/A N/A N/A N/A N/A N/A N/A 1.390.550.320.152Offsite to South N/A N/A N/A RG4 N/A 0.98 3.98 7.03 APPENDIX B Project: Inlet ID: Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =18.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.020 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.020 Height of Curb at Gutter Flow Line HCURB =6.00 inches Distance from Curb Face to Street Crown TCROWN =22.0 ft Gutter Width W =2.00 ft Street Transverse Slope SX =0.042 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.000 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.013 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =22.0 22.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 6.0 inches Check boxes are not applicable in SUMP conditions MINOR STORM Allowable Capacity is not applicable to Sump Condition Minor Storm Major Storm MAJOR STORM Allowable Capacity is not applicable to Sump Condition Qallow =SUMP SUMP cfs Design Information (Input)MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a' from above)alocal =2.00 2.00 inches Number of Unit Inlets (Grate or Curb Opening)No =1 1 Water Depth at Flowline (outside of local depression)Ponding Depth =6.0 6.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) =3.00 3.00 feet Width of a Unit Grate Wo =1.73 1.73 feet Open Area Ratio for a Grate (typical values 0.15-0.90)Aratio =0.43 0.43 Clogging Factor for a Single Grate (typical value 0.50 - 0.70)Cf (G) =0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60)Cw (G) =3.30 3.30 Grate Orifice Coefficient (typical value 0.60 - 0.80)Co (G) =0.60 0.60 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) =3.00 3.00 feet Height of Vertical Curb Opening in Inches Hvert =6.50 6.50 inches Height of Curb Orifice Throat in Inches Hthroat =5.25 5.25 inches Angle of Throat Theta =0.00 0.00 degrees Side Width for Depression Pan (typically the gutter width of 2 feet)Wp =2.00 2.00 feet Clogging Factor for a Single Curb Opening (typical value 0.10)Cf (C) =0.10 0.10 Curb Opening Weir Coefficient (typical value 2.3-3.7)Cw (C) =3.70 3.70 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70)Co (C) =0.66 0.66 Low Head Performance Reduction (Calculated)MINOR MAJOR Depth for Grate Midwidth dGrate =0.52 0.52 ft Depth for Curb Opening Weir Equation dCurb =0.33 0.33 ft Grated Inlet Performance Reduction Factor for Long Inlets RFGrate =0.94 0.94 Curb Opening Performance Reduction Factor for Long Inlets RFCurb =N/A N/A Combination Inlet Performance Reduction Factor for Long Inlets RFCombination =0.94 0.94 MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition)Qa =5.09 5.09 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q Peak)Q PEAK REQUIRED =5.09 5.09 cfs CDOT/Denver 13 Combination INLET IN A SUMP OR SAG LOCATION MHFD-Inlet, Version 5.03 (August 2023) MHFD-Inlet, Version 5.03 (August 2023) ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Prospect Plaza Redevelopment 1A & 1B - EXISTING H-VertH-Curb W Lo (C) Lo (G) Wo WP CDOT/Denver 13 Combination Override Depths 1 In the existing condition, the existing inlet within W Lake St (Structure ID 1B) has the capacity to intercept 5.09cfs Comprised of COFC Single Curb Inlet. Modeled as a single CDOT Type 13 Combination inlet within the spreadsheet (closest available comparable) Project: Inlet ID: Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =6.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.020 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.012 Height of Curb at Gutter Flow Line HCURB =6.00 inches Distance from Curb Face to Street Crown TCROWN =35.0 ft Gutter Width W =2.00 ft Street Transverse Slope SX =0.033 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.000 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =35.0 35.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 6.0 inches Check boxes are not applicable in SUMP conditions MINOR STORM Allowable Capacity is not applicable to Sump Condition Minor Storm Major Storm MAJOR STORM Allowable Capacity is not applicable to Sump Condition Qallow =SUMP SUMP cfs Design Information (Input)MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a' from above)alocal =2.00 2.00 inches Number of Unit Inlets (Grate or Curb Opening)No =2 2 Water Depth at Flowline (outside of local depression)Ponding Depth =6.0 6.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) =3.00 3.00 feet Width of a Unit Grate Wo =1.73 1.73 feet Open Area Ratio for a Grate (typical values 0.15-0.90)Aratio =0.43 0.43 Clogging Factor for a Single Grate (typical value 0.50 - 0.70)Cf (G) =0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60)Cw (G) =3.30 3.30 Grate Orifice Coefficient (typical value 0.60 - 0.80)Co (G) =0.60 0.60 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) =3.00 3.00 feet Height of Vertical Curb Opening in Inches Hvert =6.50 6.50 inches Height of Curb Orifice Throat in Inches Hthroat =5.25 5.25 inches Angle of Throat Theta =0.00 0.00 degrees Side Width for Depression Pan (typically the gutter width of 2 feet)Wp =2.00 2.00 feet Clogging Factor for a Single Curb Opening (typical value 0.10)Cf (C) =0.10 0.10 Curb Opening Weir Coefficient (typical value 2.3-3.7)Cw (C) =3.70 3.70 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70)Co (C) =0.66 0.66 Low Head Performance Reduction (Calculated)MINOR MAJOR Depth for Grate Midwidth dGrate =0.52 0.52 ft Depth for Curb Opening Weir Equation dCurb =0.33 0.33 ft Grated Inlet Performance Reduction Factor for Long Inlets RFGrate =0.71 0.71 Curb Opening Performance Reduction Factor for Long Inlets RFCurb =N/A N/A Combination Inlet Performance Reduction Factor for Long Inlets RFCombination =0.71 0.71 MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition)Qa =6.59 6.59 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q Peak)Q PEAK REQUIRED =5.09 5.09 cfs CDOT/Denver 13 Combination INLET IN A SUMP OR SAG LOCATION MHFD-Inlet, Version 5.03 (August 2023) MHFD-Inlet, Version 5.03 (August 2023) ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Prospect Plaza Redevelopment 1A & 1B - PROPOSED H-VertH-Curb W Lo (C) Lo (G) Wo WP CDOT/Denver 13 Combination Override Depths 1 In the proposed condition, the proposed inlet within W Lake St (Structure ID 1B) has the capacity to intercept 6.59cfs, which is greater than the existing value (5.09cfs) To be comprised of COFC Double Curb Inlet. Modeled as two CDOT Type 13 Combination inlets within the spreadsheet (closest available comparable) Project: Inlet ID: Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =13.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.0006 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.012 Height of Curb at Gutter Flow Line HCURB =6.00 inches Distance from Curb Face to Street Crown TCROWN =25.0 ft Gutter Width W =2.00 ft Street Transverse Slope SX =0.040 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.0012 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =25.0 25.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 6.0 inches Allow Flow Depth at Street Crown (check box for yes, leave blank for no) MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow =4.19 4.19 cfs Design Information (Input)MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a')aLOCAL =2.0 2.0 inches Total Number of Units in the Inlet (Grate or Curb Opening)No =1 1 Length of a Single Unit Inlet (Grate or Curb Opening)Lo =3.00 3.00 ft Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo =1.73 1.73 ft Clogging Factor for a Single Unit Grate (typical min. value = 0.5)Cf (G) =0.50 0.50 Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1)Cf (C) =N/A N/A Street Hydraulics: WARNING: Q > ALLOWABLE Q FOR MINOR & MAJOR STORM MINOR MAJOR Total Inlet Interception Capacity Q =2.34 2.34 cfs Total Inlet Carry-Over Flow (flow bypassing inlet)Qb =2.96 2.96 cfs Capture Percentage = Qa/Qo C% =44 44 % WARNING: MINOR STORM max. allowable capacity is less than the design peak flow of 5.30 cfs on sheet 'Inlet Management' WARNING: MAJOR STORM max. allowable capacity is less than the design peak flow of 5.30 cfs on sheet 'Inlet Management' INLET ON A CONTINUOUS GRADE MHFD-Inlet, Version 5.03 (August 2023) CDOT/Denver 13 Valley Grate MHFD-Inlet, Version 5.03 (August 2023) ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Prospect Plaza Redevelopment 8A - EXISTING CDOT/Denver 13 Valley Grate 1 In the existing condition, the existing inlet within W Prospect Rd (Structure ID 9B) will bypass 2.96cfs to downstream infrastructure. Project: Inlet ID: Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =6.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.0006 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.012 Height of Curb at Gutter Flow Line HCURB =6.00 inches Distance from Curb Face to Street Crown TCROWN =25.0 ft Gutter Width W =2.00 ft Street Transverse Slope SX =0.0440 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.001 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =25.0 25.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 6.0 inches Allow Flow Depth at Street Crown (check box for yes, leave blank for no) MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow =4.2 4.2 cfs Design Information (Input)MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a')aLOCAL =2.0 2.0 inches Total Number of Units in the Inlet (Grate or Curb Opening)No =1 1 Length of a Single Unit Inlet (Grate or Curb Opening)Lo =3.00 3.00 ft Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo =1.73 1.73 ft Clogging Factor for a Single Unit Grate (typical min. value = 0.5)Cf (G) =0.50 0.50 Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1)Cf (C) =0.10 0.10 Street Hydraulics: WARNING: Q > ALLOWABLE Q FOR MINOR & MAJOR STORM MINOR MAJOR Total Inlet Interception Capacity Q =2.86 2.86 cfs Total Inlet Carry-Over Flow (flow bypassing inlet)Qb =2.44 2.44 cfs Capture Percentage = Qa/Qo C% =54 54 % WARNING: MINOR STORM max. allowable capacity is less than the design peak flow of 5.30 cfs on sheet 'Inlet Management' WARNING: MAJOR STORM max. allowable capacity is less than the design peak flow of 5.30 cfs on sheet 'Inlet Management' INLET ON A CONTINUOUS GRADE MHFD-Inlet, Version 5.03 (August 2023) CDOT/Denver 13 Combination MHFD-Inlet, Version 5.03 (August 2023) ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Prospect Plaza Redevelopment 8B - PROPOSED CDOT/Denver 13 Combination 1 The westernmost (upstream) of the two inlets within W Prospect Road (Structure ID 9A) will bypass 2.44cfs to the easternmost (downstream) of the two inlets. Project: Inlet ID: Gutter Geometry: Maximum Allowable Width for Spread Behind Curb TBACK =8.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb)SBACK =0.078 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020)nBACK =0.012 Height of Curb at Gutter Flow Line HCURB =0.00 inches Distance from Curb Face to Street Crown TCROWN =25.0 ft Gutter Width W =2.00 ft Street Transverse Slope SX =0.040 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft)SW =0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO =0.0012 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020)nSTREET =0.012 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX =25.0 25.0 ft Warning 02 Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX =6.0 6.0 inches Allow Flow Depth at Street Crown (check box for yes, leave blank for no) MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow =7.5 7.5 cfs Warning 02: Max Allowable Depth for Minor Storm is greater than the Curb Height. Design Information (Input)MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a')aLOCAL =2.0 2.0 inches Total Number of Units in the Inlet (Grate or Curb Opening)No =1 1 Length of a Single Unit Inlet (Grate or Curb Opening)Lo =3.00 3.00 ft Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo =1.73 1.73 ft Clogging Factor for a Single Unit Grate (typical min. value = 0.5)Cf (G) =0.50 0.50 Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1)Cf (C) =N/A N/A Street Hydraulics: OK - Q < Allowable Street Capacity'MINOR MAJOR Total Inlet Interception Capacity Q =0.75 0.78 cfs Total Inlet Carry-Over Flow (flow bypassing inlet)Qb =1.75 1.86 cfs Capture Percentage = Qa/Qo C% =30 30 % Minor storm max. allowable capacity GOOD - greater than the design peak flow of 2.50 cfs on sheet 'Inlet Management' Major storm max. allowable capacity GOOD - greater than the design peak flow of 2.65 cfs on sheet 'Inlet Management' INLET ON A CONTINUOUS GRADE MHFD-Inlet, Version 5.03 (August 2023) CDOT/Denver 13 Valley Grate MHFD-Inlet, Version 5.03 (August 2023) ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) Prospect Plaza Redevelopment 8A - PROPOSED CDOT/Denver 13 Valley Grate 1 In the proposed condition, the proposed inlets within W Prospect Rd (Structure ID 9A & 9B) will bypass 1.86cfs to downstream infrastructure, which is less than the value within the existing condition (2.96cfs) ⅊⅊ PROPOSED BUILDING FFE: 5008 50 0 4 50 0 4 50 0 5 50 0 5 -7.6% 5003 500 4 500 5 50 0 6 50 0 6 5006 500 7 50 0 8 50 0 8 50 0 7 50 0 8 5007 5008 5008 50 0 9 50 0 8 50 0 7 50 0 7 50 0 8 50 0 7 50 0 7 500 7 ± ± ± ± ± ± ± PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C2.5 CENTRAL COURTYARD INLET & STORM SIZING EXHIBIT FFE: 5008.00 FFE: 5008.00 Rational Method Volume Approximation: V100 = 2 (Q100 * Tc) Incoming 100-Year Flowrate (Q100): 1.15cfs from 2C + 0.85cfs from 2A (2C) = 2.00cfs Basin Tc: 7.54mins V100 = 1809.6 Cu. Ft. Tc Q100 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490© Nyloplast Inlet Capacity Charts June 2012 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 10" Dome Grate Inlet Capacity Chart Incoming 100-yr flowrate: 0.53cfs 100-yr flowrate pond depth: 0.15ft Inlet Sizing Structure ID: 6H-1 Inlet rims at 5006 FFE at 5008 1ft of head = 1ft of freeboard Capacity at 1ft of freeboard: 1.75cfs 0.53cfs / 1.75cfs = 70% clogged 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490© Nyloplast Inlet Capacity Charts June 2012 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 8" Dome Grate Inlet Capacity Chart Incoming 100-yr flowrate: 0.24cfs 100-yr flowrate pond depth: 0.11ft Inlet Sizing Structure ID: 6I-1 Inlet rims at 5006 FFE at 5008 1ft of head = 1ft of freeboard Capacity at 1ft of freeboard: 0.99cfs 0.24cfs / 0.99cfs = 76% clogged 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 15" Dome Grate Inlet Capacity Chart Inlet rims at 5006 FFE at 5008 1ft of head = 1ft of freeboard Capacity at 1ft of freeboard: 3.85cfs 0.19cfs / 3.85cfs = 95% clogged Incoming 100-yr flowrate: 0.19cfs 100-yr flowrate pond depth: 0.06ft Inlet Sizing Structure ID: 6J 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 12" Dome Grate Inlet Capacity Chart Incoming 100-yr flowrate: 0.35cfs 100-yr flowrate pond depth: 0.11ft Inlet Sizing Structure ID: 6L Inlet rims at 5006 FFE at 5008 1ft of head = 1ft of freeboard Capacity at 1ft of freeboard: 2.33cfs 0.35cfs / 2.33cfs = 85% clogged 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490© Nyloplast Inlet Capacity Charts June 2012 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 10" Dome Grate Inlet Capacity Chart Incoming 100-yr flowrate: 0.49cfs 100-yr flowrate pond depth: 0.145ft Inlet Sizing Structure ID: 6L-1 Inlet rims at 5006 FFE at 5008 1ft of head = 1ft of freeboard Capacity at 1ft of freeboard: 1.75cfs 0.49cfs / 1.75cfs = 72% clogged 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490© Nyloplast Inlet Capacity Charts June 2012 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 12" Dome Grate Inlet Capacity Chart Incoming 100-yr flowrate: 0.09cfs 100-yr flowrate pond depth: 0.04ft Inlet Sizing Structure ID: 6M Inlet rims at 5006 FFE at 5008 1ft of head = 1ft of freeboard Capacity at 1ft of freeboard: 2.33cfs 0.09cfs / 2.33cfs = 96% clogged 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 8" Dome Grate Inlet Capacity Chart Incoming 100-yr flowrate: 0.10cfs 100-yr flowrate pond depth: 0.06ft Inlet Sizing Structure ID: 6M-1 Inlet rims at 5006 FFE at 5008 1ft of head = 1ft of freeboard Capacity at 1ft of freeboard: 0.99cfs 0.10cfs / 0.99cfs = 90% clogged 5007.0 - 1ft of freeboard 5007.0 - 1ft of freeboard 5007.0 - 1ft of freeboard 5007.0 - 1ft of freeboard 5007.0 - 1ft of freeboard 5006.11 - Inlet 6L 100-year ponding depth 5006.06 - Inlet 6J 100-year ponding depth 5006.11 - Inlet 6I-1 100-year ponding depth 5006.15 - Inlet 6H-1 100-year ponding depth 5006.145 - Inlet 6L-1 100-year ponding depth 5006.06 - Inlet 6M-1 100-year ponding depth 5006.04 - Inlet 6M 100-year ponding depth 5007.41 - Ponding Depth at 2*V100 (3619.2 CF) 5007.41 - Ponding Depth at 2*V100 (3619.2 CF) 5007.41 - Ponding Depth at 2*V100 (3619.2 CF) 5007.41 - Ponding Depth at 2*V100 (3619.2 CF) 5007.41 - Ponding Depth at 2*V100 (3619.2 CF) Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Friday, Mar 14 2025 Basin 1B Flume & Sidewalk Chase Rectangular Bottom Width (ft) = 2.00 Total Depth (ft) = 0.50 Invert Elev (ft) = 5001.96 Slope (%) = 2.00 N-Value = 0.013 Calculations Compute by: Known Depth Known Depth (ft) = 0.50 Highlighted Depth (ft) = 0.50 Q (cfs) = 7.769 Area (sqft) = 1.00 Velocity (ft/s) = 7.77 Wetted Perim (ft) = 3.00 Crit Depth, Yc (ft) = 0.50 Top Width (ft) = 2.00 EGL (ft) = 1.44 0 .5 1 1.5 2 2.5 3 Elev (ft) Depth (ft)Section 5001.00 -0.96 5001.50 -0.46 5002.00 0.04 5002.50 0.54 5003.00 1.04 Reach (ft) The SW Chase will be able to convey 7.77cfs before overtopping the 6" depth The SW Chase will be inundated within floodwater during the 100-year storm event Per MHFD USDCM Vol. 3, Chapter 4: * Use a minimum orifice size of 3/8 inch to avoid clogging * ** For the release rate thru each orifice: (sq. in.) (sq. ft.) 0.5185 0.0036 0.6903 0.0048 0.6903 0.0048 0.1104 0.0008 (inches) (ft) (cfs) D12 Date: Final D12** RG1 4/5 1.40 0.021 For rough-edged orifice entrance conditions, a discharge coefficient of 0.4 should be used. Raw corresponds to calcualtion, rounded has been set to nearest available orifice size Basin ID A h Q 1.33 1.33 1.33 1.40 (inches) 3/8 1 1 RG2 RG4 3/8 1.33 0.004 RG3 1 1.33 0.027 1 1.33 0.027 4/5 For square-edged, uniform orifice entrance conditions, a discharge coefficient of 0.61 should be used. If the downstream jet or orifice is submerged, then the effective head is the difference in elevation between the upstream and downstream water surfaces. If the outlet from the detention basin is under free outfall, the effective head is measured from the centroid of the orifice to the upstream water surface elevation. RG4 RG3 RG2 RG1 Basin ID 1031.73 (cu. ft.) (ft) For each pond, value set as vertical difference between bottom of pond and the outlet elevation of upturned elbow 1327.21 V 227.30 1430.17 y* 0.38 0.95 0.91 0.80 (inches) Raw D12** 024-015 Project Name:Prospect Plaza Redevelopment ORIFICE SIZING: FOR RG WQCV Rain gardens must utilizes an orifice to ensure the WQCV drains in a minimum of 12 hours, the simplified orifice equation (Equation 4-2) can be used for orifice sizing. Client:Tetrad/STRATA Project Number :MWB 4/24/2025 Prepared By: 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 18" Dome Grate Inlet Capacity Chart RG1 Overflow Riser Structure ID: 1C WQCV WSEL: 5000.92 Spillway Invert: 5001.22 Available Head: 0.30ft Maximum Capacity: 2.5cfs Incoming 100-yr flowrate: 12.50cfs 2.5cfs will enter the RG1 overflow riser 10.0cfs will utilize the overflow spillway 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 18" Dome Grate Inlet Capacity Chart RG2 Overflow Riser Structure ID: 2A WQCV WSEL: 5001.23 Spillway Invert: 5001.99 Available Head: 0.76ft Maximum Capacity: 4.9cfs Incoming 100-yr flowrate: 6.45cfs 4.9cfs will enter the RG2 overflow riser 1.55cfs will utilize the overflow spillway 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 24" Dome Grate Inlet Capacity Chart WQCV WSEL: 5006.48 Spillway Invert: 5007.64 Available Head: 1.16ft RG3 Overflow Riser Structure ID: 3B Maximum Capacity: 9.6cfs Incoming 100-yr flowrate: 3.41cfs 3.41cfs will enter the RG3 overflow riser Required Head: 0.31ft Required Capacity: 3.41cfs SUNNY CIVILPROSPECT PLAZA SSA PIPE SIZING MODEL MODEL NOTES: - Underdrains have not been modeled as they do not have slope - Roof drains have been sized per the IBC flowrates STORM 1 (ROOF DRAIN) STORM 1 STORM 2 STORM 6 STORM 5 STORM 7 STORM 3 STORM 4 STORM 4 (ROOF DRAIN) STORM 3 (ROOF DRAIN) STORM 8 PROSPECT PLAZA REDEVELOPMENT STORM 6 (ROOF DRAIN) STORM 6 (ROOF DRAIN) STORM 6 (ROOF DRAIN) STORM 1 WILL BE INUNDATED WITH FLOODWATER DURING THE 100-YEAR STORM EVENT PROPOSED PIPE SIZES AND SLOPES ARE LIMITED BY THE EXISTING REGIONAL DOWNSTREAM STORM SEWER INFRASTRUCTURE STORM 2 WILL BE INUNDATED WITH FLOODWATER DURING THE 100-YEAR STORM EVENT PROPOSED PIPE SIZES AND SLOPES ARE LIMITED BY THE EXISTING REGIONAL DOWNSTREAM STORM SEWER INFRASTRUCTURE STORM 8 WILL BE SURCHARGED DURING THE 100-YEAR STORM EVENT PROPOSED PIPE SIZES AND SLOPES ARE LIMITED BY THE EXISTING REGIONAL DOWNSTREAM STORM SEWER INFRASTRUCTURE Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Monday, Apr 28 2025 RG1 OVERFLOW SPILLWAY User-defined Invert Elev (ft) = 5001.21 Slope (%) = 2.00 N-Value = 0.013 Calculations Compute by: Known Q Known Q (cfs) = 12.50 (Sta, El, n)-(Sta, El, n)... ( 85.18, 5001.87)-(102.05, 5001.69, 0.013)-(155.03, 5001.21, 0.013)-(161.96, 5001.25, 0.013)-(174.62, 5001.48, 0.013)-(187.40, 5001.76, 0.013) Highlighted Depth (ft) = 0.19 Q (cfs) = 12.50 Area (sqft) = 3.79 Velocity (ft/s) = 3.30 Wetted Perim (ft) = 36.15 Crit Depth, Yc (ft) = 0.25 Top Width (ft) = 36.15 EGL (ft) = 0.36 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 Elev (ft) Depth (ft)Section 5000.75 -0.46 5001.00 -0.21 5001.25 0.04 5001.50 0.29 5001.75 0.54 5002.00 0.79 Sta (ft) Incoming 100-year flowrate Resulting WSEL: 5001.40 Nearest Minimum Opening Elevation: 5006 (Coffee Shop Doors) Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Monday, Apr 28 2025 RG2 OVERFLOW SPILLWAY User-defined Invert Elev (ft) = 5001.99 Slope (%) = 2.00 N-Value = 0.013 Calculations Compute by: Known Q Known Q (cfs) = 6.45 (Sta, El, n)-(Sta, El, n)... ( 41.17, 5002.40)-(55.37, 5002.00, 0.013)-(63.36, 5001.99, 0.013)-(76.09, 5002.08, 0.013)-(93.09, 5002.30, 0.013)-(107.69, 5002.55, 0.013) Highlighted Depth (ft) = 0.13 Q (cfs) = 6.450 Area (sqft) = 2.40 Velocity (ft/s) = 2.69 Wetted Perim (ft) = 28.09 Crit Depth, Yc (ft) = 0.17 Top Width (ft) = 28.08 EGL (ft) = 0.24 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 Elev (ft) Depth (ft)Section 5001.00 -0.99 5001.50 -0.49 5002.00 0.01 5002.50 0.51 5003.00 1.01 Sta (ft) Incoming 100-year flowrate Resulting WSEL: 5002.12 Nearest Minimum Opening Elevation: 5006 (Coffee Shop Doors) Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Monday, Apr 28 2025 RG3 OVERFLOW SPILLWAY User-defined Invert Elev (ft) = 5007.64 Slope (%) = 0.70 N-Value = 0.013 Calculations Compute by: Known Q Known Q (cfs) = 3.41 (Sta, El, n)-(Sta, El, n)... ( 35.25, 5008.00)-(47.78, 5007.80, 0.013)-(76.45, 5007.64, 0.013)-(81.96, 5008.10, 0.013)-(87.42, 5008.20, 0.013) Highlighted Depth (ft) = 0.15 Q (cfs) = 3.410 Area (sqft) = 2.15 Velocity (ft/s) = 1.58 Wetted Perim (ft) = 28.72 Crit Depth, Yc (ft) = 0.16 Top Width (ft) = 28.71 EGL (ft) = 0.19 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 Elev (ft) Depth (ft)Section 5007.00 -0.64 5007.50 -0.14 5008.00 0.36 5008.50 0.86 5009.00 1.36 Sta (ft) Resulting WSEL: 5007.79 Nearest Minimum Opening Elevation: 5008.25 (SE Courtyard Doors) Incoming 100-year flowrate (3.41 cfs) exceeds spillway Since freeboard is not adequate, the overflow riser has been sized to take the 100-year incoming flowrate. Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Monday, Apr 28 2025 RG4 OVERFLOW SPILLWAY User-defined Invert Elev (ft) = 5006.85 Slope (%) = 0.70 N-Value = 0.013 Calculations Compute by: Known Q Known Q (cfs) = 1.67 (Sta, El, n)-(Sta, El, n)... ( 158.62, 5007.32)-(201.74, 5006.85, 0.013)-(206.71, 5006.92, 0.013)-(215.03, 5007.33, 0.013) Highlighted Depth (ft) = 0.12 Q (cfs) = 1.670 Area (sqft) = 1.11 Velocity (ft/s) = 1.50 Wetted Perim (ft) = 17.02 Crit Depth, Yc (ft) = 0.13 Top Width (ft) = 17.02 EGL (ft) = 0.16 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 Elev (ft) Depth (ft)Section 5006.00 -0.85 5006.50 -0.35 5007.00 0.15 5007.50 0.65 5008.00 1.15 Sta (ft) Resulting WSEL: 5006.97 Nearest Minimum Opening Elevation: 5008.25 (SW Courtyard Doors) 5008.00 (SE Building Corner Doors) Incoming 100-year flowrate APPENDIX C LAGOON NRRC E NRRC D NRRC C NRRC B PROPERTY 583 CHILL PLANT 590 582 CONTAINERS 706 557 705 139 563 550 704 703 702 566 565 NRRC A 701 431 577 BARNS 555 554HOSPITALVETERINARY TEACHING 578 567 568 553 425 PUMP HOUSE 423422 USDA 424 USFW HILTON (2 0 ) (2 1 ) (23 ) (2 5 ) (2 6 ) (2 9 ) (3 0 ) (2 7 ) (2 8 ) (2 2 ) 31 1 31 2 30 8 30 6 30 3 30 4 30 5 30 9 31 0 31 3 SURPLUS 136 137 BOOK STORAGE 318 (34)(24)(18)301307317 256 257 258 259 260 261 262 263 252 253 254 255 264 250 Lake Street Parking Garage (Bldg K) (Bldg J) (Bldg H) (Bldg H) (Bldg C)(Bldg U) (Bldg A) (Bldg A) (Bldg B) 548 TMI 539Bus Barn (Bldg K2) UNIVERSITY TENNISCOMPLEX710 AGGIE VILLAGE SOUTH (3 1 ) (3 2 ) (3 3 ) 31 4 31 5 31 6 UNIVERSITY TENNIS PAVILION 183 187 Gait Analysis Center Gail Holmes Equine Orthopaedic Research Center IrrigationPump Station GIFFORD BLDG 152 155 MOLECULAR AND BIOSCIENCESRADIOLOGICAL HEADHOUSE CROP RESEARCHU.S.D.A. 380 381 CENTERHORTICULTURE WALNUT240 242 241 COTTONWOOD LODGEPOLE 116 MEDICALCENTER 243GROUNDSBLDG 243 117 541 585 Equine Performance Analysis Facility 711 DIAGNOSTIC MEDICINE CENTER CRABTREE HALL 942ROLL A N D M O O R E D R I V E PEREN N I A L L A N E G 537 538 FM Storage Building RCS Shop 581 SALTSHED 2301 RESEARCHBLVD 2401 RESEARCHBLVD JFEH LIBRARY/ DEPOSITORY/ ANNEX SPRING C R E E K SHERWOOD AUT H U R S D I T C H AUTHURS D I T C H SPRING CREEK SP R I N G CR E E K LATER A L BR, S-17b BR, S-13 BR, S-13 BR, S-13 CW, S-11 BS, S-6 BR, S-15 EDP, S-10 BR, S-14 BR, S-7 BS, S-12 DP, S-4 BS, S-16 DP, S-1 BS, S-2 BR, S-9 BR, S-17a Colorado State University South Campus Stormwater Permanent SCM's N Legend BR BS CS Bioretention Bioswale Cobble Swale CW DP EDP Constructed Wetland Detention Pond Extended Detention Pond GR GS PA Green Roof Grass Swale Porous Asphalt PMP PRP RG Permeable Pavers Porous Pavers Rain Garden RGSF UGS Raingarden/Sand Filter Underground System Stormwater Open Swales & Ditches Stormwater Underground Rivers & Creeks Irrigation Ditch Open Irrigation Underground Box Culvert Storm Sewer Outlet Revision "B" - May 2010 Revision "C" - Feb 2011 Revision "D" - Feb 2012 Revision "E" - Dec 2013 Revision "F" - Sept 2016 Revision "G" - Jan 2018 Revision "H" - Dec 2021 Revision "I" - Jan 2022 National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOODHAZARD AREAS Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mile Zone X Future Conditions 1% Annual Chance Flood Hazard Zone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 1/28/2025 at 6:51 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location. 1:6,000 105°5'15"W 40°34'19"N 105°4'37"W 40°33'51"N Basemap Imagery Source: USGS National Map 2023 United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Larimer County Area, ColoradoNatural Resources Conservation Service January 28, 2025 17 Custom Soil Resource Report Map—Hydrologic Soil Group 44 9 0 7 1 0 44 9 0 7 3 0 44 9 0 7 5 0 44 9 0 7 7 0 44 9 0 7 9 0 44 9 0 8 1 0 44 9 0 8 3 0 44 9 0 8 5 0 44 9 0 8 7 0 44 9 0 8 9 0 44 9 0 7 1 0 44 9 0 7 3 0 44 9 0 7 5 0 44 9 0 7 7 0 44 9 0 7 9 0 44 9 0 8 1 0 44 9 0 8 3 0 44 9 0 8 5 0 44 9 0 8 7 0 44 9 0 8 9 0 492970 492990 493010 493030 493050 493070 493090 493110 492970 492990 493010 493030 493050 493070 493090 493110 40° 34' 7'' N 10 5 ° 4 ' 5 9 ' ' W 40° 34' 7'' N 10 5 ° 4 ' 5 2 ' ' W 40° 34' 1'' N 10 5 ° 4 ' 5 9 ' ' W 40° 34' 1'' N 10 5 ° 4 ' 5 2 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 45 90 180 270Feet 0 10 20 40 60Meters Map Scale: 1:963 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. Table—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 4.7 100.0% Totals for Area of Interest 4.7 100.0% Rating Options—Hydrologic Soil Group Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Custom Soil Resource Report 19 SS SS SS SS SS SS SS SS SS SS SS SS WV WV D D G HYDWV GAS EL E C ELEC C.O. G C.O. ELEC W C.O. C ELEC ELEC ELEC ELEC G GAS D X X X X X X X X X X X X X X X X X ELEC D WV ST ST ST S S S S S D E E E E E ECTVCTVCTV T VIS I T O R VIS I T O R VIS I T O R VA N VIS I T O R VA N T E ELEC F.O. FO PARKING GARAGE PROPOSED BUILDING FFE: 5008 AR T H U R D I T C H W LAKE ST 5007 50 0 7 50 0 8 50 0 5 5003 50 0 4 50 0 6 5002 5003 5004 50 0 0 AR T H U R D I T C H W PROSPECT RD 50 0 5 50 0 5 50 0 5 50 0 4 50 0 4 50 0 4 500 5 5002 50 0 3 500 4 500 6 50 0 7 5008 500 6 500 7 5007 500 5 5003 500 4 50 0 6 5000 5001 5002 -2.8% -2.8% -1.7%-2.1% -1 . 4 % -2.0% 5005 500 2 500 3 5004 500 6 500 7 500 8 500 5 5003 5004 500 7 50 0 1 50 0 2 5003 -2.4 % COURTYARD OVERFLOW PATH 5006 500 7 5008 50 0 8 50 0 8 50 0 8 50 0 8 50 0 7 5002 50025002 -0 . 6 % -0 . 6 % 50 0 8 50 0 9 DETAILED GRADING, SEE SHEET C2.1 DETAILED GRADING, SEE SHEET C2.2 DETAILED GRADING, SEE SHEET C2.3 5006 5007 5008 5002 5002 5003 DETAILED GRADING, SEE SHEET C2.4 DETAILED GRADING, SEE SHEET C2.5 FL 3.70 FL 3.78 FL 4.34 FL 4.16 FL 4.33 FL 4.27 SW 4.31 SW 3.73 SW 3.81 SW 7.99 SW 7.95 SW 8.00 FL 5.16 FL 5.79 FL 7.35 FL 5.49 SW 8.00 SW 8.00 SW 8.00 SW 8.00 SW 7.91 FG 6.75 FG 6.65 FG 4.43 FG 4.37 SW 8.00 COFFEE SHOP FFE: 5006 FL 4.18 5000 5001 5002 FL 5.92 FL 5.06 PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C2.0 OVERALL GRADING PLAN N ’ ’ ” ’ ’ LEGAL DESCRIPTION: HORIZONTAL DATUM: VERTICAL DATUM: FLOODPLAIN: NOTES: LEGEND XXXX XXXX XXXX XXXX ELEC G GAS D VI S I T O R VI S I T O R VI S I T O R VA N VI S I T O R VA N E ELEC F.O. 5002 5003 5004 50 0 0 5002 50 0 3 5000 5001 5002 -2.9 % -3 . 0 % -3 1 . 1 % -1 . 3 % -3.1 % -2.5% -1.9% -1 . 7 % -1.5% -1 . 8 % -2.2% -7.6 % -1 . 9 % -3.7 % -1.8 % -5 . 0 % -2 . 0 % -2.5% -2 . 3 % -2 . 2 % -2 . 2 % -1 . 7 % -1.8 % -2 . 2 % -1 . 8 % -2 . 7 % -1 . 9 % -3 . 3 % 5005 5002 500 3 5004 5003 5000 5000 5001 5002 5003 5002 -1 . 0 % -7 . 3 % -4.6% -1. 7 % -7 . 0 % -2. 9 % -2.8% -1 . 5 % -2 . 0 % -1 . 9 % SW 2 . 8 4 SW 2 . 8 4 SW 3.30 SW 3.28 SW 3 . 9 0 SW 3 . 8 2 SW 4 . 2 8 SW 4 . 2 3 SW 6 . 3 0 SW 7 . 8 9 SW 6 . 3 5 SW 6 . 5 1 SW 2 . 5 4 SW 2 . 3 9 SW 2 . 6 6 SW 2 . 7 8 SW 2 . 2 4 SW 2 . 5 8 SW 2 . 4 1 SW 2 . 6 4 SW 2 . 9 8 SW 2.39 SW 2 . 8 6 SW 2.57 SW 2.61 SW 2.40 SW 2 . 1 1 SW 2.51 SW 2.48 SW 2 . 2 7 SW 2 . 2 2 SW 2 . 1 7 SW 2 . 0 4 SW 6.62 SW 8 . 0 0 SW 8 . 0 0 FFE 8 . 0 0 SW 7 . 7 2 SW 8 . 0 0 SW 7 . 7 7 SW 7 . 9 5 SW 7 . 8 9 BW 3 . 5 1 TW 6.29 BW 5 . 2 6 TW 7 . 7 0 FG 7 . 7 6 FG 8 . 0 0 FG 7 . 6 4 FG 7 . 4 3 FG 7 . 3 3 FFE 8 . 0 0 SW 6 . 6 9 SW 1 . 8 7 SW 1 . 6 4 SW 1 . 4 9 SW 6 . 0 0 SW 5 . 4 8 -1 . 9 % FG 3 . 1 3 SW 7 . 8 9 SW 7 . 7 1 SW 7 . 7 7 SW 7 . 9 5 SW 7 . 9 5 SW 2 . 7 9 SW 2.81 SW 2 . 3 2 SW 2 . 7 7 FG 2.34 FG 3 . 5 0 FG 3 . 5 2 FG 3 . 5 0 FG 2.40 FG 2 . 9 8 SW 1 . 9 7 FG 2 . 0 3 SW 1 . 4 9 -2. 2 % SW 2 . 5 4 -8 . 3 % -4.3% -1.8% -1 . 5 % SW 3 . 1 5 SW 3 . 1 3 SW 3 . 2 6 SW 3 . 1 2 FG 3 . 3 7 FG 3.03 SW 3 . 2 2 SW 3 . 3 5 SW 8 . 0 0 SW 3 . 2 0 FL 1. 7 1 FL 1. 8 0 FL 2.89 FL 2.63 FL 2.72 FL 2. 7 5 FL 3. 0 3 FL 1.96 FL 2.31 FL 1. 7 2 FL 1. 5 9 SW 2 . 2 0 SW 2.28 SW 2 . 0 4 SW 2 . 1 5 -8.3% SW 2 . 4 8 SW 1 . 1 9 SW 1 . 1 4SW 1 . 2 2 SW 1 . 7 0 SW 1 . 8 6 -4 . 2 % -7.8% -2. 0 % SW 2.48 SW 2.58 TP 1.25 FG 2.17FG 2 . 4 1 TP 1. 2 5 TP 1.25 TP 1.04 TP 1. 2 5 TP 1. 2 5 TP 1. 2 5 BP 99 . 9 2 BP 99 . 9 2 BP 9 9 . 9 2 BP 9 9 . 9 2 BP 99 . 9 2BP 99 . 9 2 SW 1 . 9 5 FG 2 . 9 6 FL 1. 5 4 FL 1. 2 5 FL 1. 0 9 FL 0. 6 1 FL 0. 5 3 FG 5 . 2 0 SW 3 . 1 4 RIM 2.18 ME 1. 2 1 ME 1. 3 4 ME 1. 6 3 ME 0. 8 7 -2.5% -2.5% -2.1% -1.7% -1.7% SW 2 . 7 3 SW 2 . 6 8 SW 2 . 6 7 FL 2.20 FL 2.25 ME 1. 7 4 ME 1. 5 9 ME 2.91 FG 2 . 0 6 -2. 9 % -2 . 3 % -1 . 9 % -1 . 9 % -2 . 3 % SW 7 . 9 1 SW 7 . 9 0 -1.7% -8.1% -2. 9 % -7 . 4 % FG 3 . 0 2 FL 3. 3 8 ME 2.43 ME 3.52 ME 4.11 ME 4.45 ME 4.57 FL 4. 0 9 BP 99.92 W LAKE ST ME 1. 7 7 ME 2. 3 9 -1 . 6 % BW 3.50 FG 1 . 6 2 FG 2. 0 0 FG 1.90 BP 99.92 BP 99.92 BP 99.92 BP 9 9 . 9 2 TP 1. 2 5 TP 1. 2 5 TP 1.25 SW 3 . 8 2 SW 3 . 7 3 -2. 0 % SW 7 . 9 7 -1. 9 % BW 3 . 3 1 FG 4 . 8 1 TW 5 . 5 1 SW 6 . 6 1 -2. 1 % FG 7 . 3 3 FG 7. 8 3 -3.5% -1.4% -2.3% TP 1.25 TP 1.25 SW 7 . 7 0 PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C2.1 DETAILED GRADING PLAN N ’ ’ ” ’ ’ LEGAL DESCRIPTION: HORIZONTAL DATUM: VERTICAL DATUM: FLOODPLAIN: NOTES: LEGEND XXXX XXXX XXXX XXXX ELEC X X X X X X X X X X X X X X X X ELEC FO W LAKE ST 5003 50 0 4 COFFEE SHOP FFE: 5006 5003 -6. 3 %-7.1 % -2 . 1 % -3. 0 % -2.7 % -8: 1 -1 . 5 % -3.5% -7 : 1 -1 . 9 % -1.5% -5 . 1 % -3.0 % -4 . 7 % -4 : 1 -4:1 -2.1% -1.7% -1.7% -2.3% -3.0% -4 . 3 % -4 . 3 % -0.6% -1. 2 % -12.0% 5005 500 4 50 0 6 50 0 6 5006 50 0 1 50 0 2 5002 5002 -0 . 7 % FG 3. 4 4 FG 3 . 7 2 TW 5.57 SW 4 . 1 5 SW 4 . 0 5 SW 4 . 5 3 SW 4 . 4 6 SW 4 . 5 0 SW 5.23 SW 5.90 SW 5.09 SW 1 . 9 9 SW 4 . 3 5 SW 2 . 1 1 SW 4 . 4 4SW 4 . 4 2 SW 4 . 3 9 SW 4 . 4 0 SW 5 . 9 0 SW 5 . 8 6 SW 4 . 3 0 SW 5 . 7 0 FG 5 . 3 3 SW 6 . 0 0 FFE 6 . 0 0 SW 5.93 SW 5 . 7 6 SW 5.93 FG 3 . 7 6 SW 4 . 4 6 SW 4 . 1 0 SW 2.40 RIM 2.99 RIM 3.16 SW 5 . 8 1 SW 5 . 7 2 SW 2.15 SW 2.54 SW 6 . 0 0 SW 1.76 SW 1 . 5 3 SW 2 . 0 8 SW 2 . 2 5 SW 2 . 6 0 FL 2. 0 3 SW 2 . 6 6 FL 2. 0 8 SW 7 . 9 1 SW 6 . 9 5 SW 7 . 5 0 SW 7 . 5 0 SW 6 . 8 2 SW 3 . 9 5 SW 3 . 8 8 SW 3 . 9 4 SW 7 . 9 3 FG 3 . 8 0 FG 3. 7 5 FFE 8 . 0 0 SW 2.29 SW 2.95 SW 3.31 FG 7 . 3 3 FG 7.33 FG 7. 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 8 3 FG 4 . 0 0 FG 2 . 7 0 FG 3 . 1 4 FG 3 . 4 2 FL 2.85 FL 2.64 FL 2.51 FL 2. 2 4 FG 6 . 6 3 FG 6. 5 3 FG 5. 1 6 FG 3 . 5 3 FG 1. 5 6 TP 1. 3 0 TP 1. 3 0 TP 1. 3 0 TP 1. 3 0 TP 1. 3 0 TP 1. 3 0 BP 0 . 3 0 TP 1 . 6 2 SW 6 . 8 1 SW 7 . 2 2 SW 7 . 1 9 BW 3 . 5 7 SW 6.15 SW 6 . 9 5 SW 7 . 4 4 SW 7 . 9 1 SW 8 . 0 0 SW 8 . 0 0 FFE 8 . 0 0 SW 7 . 4 2 -8 . 3 % -1 . 4 % -8.1% TP 1. 4 8 SW 3.22 BW 5 . 6 7 FL 1. 9 6 FL 1. 7 9 FL 1. 6 3 FL 1. 4 7 ME 1. 9 9 ME 1 . 8 6 ME 1. 2 8 -3 . 4 % -3 . 5 % -3 . 3 % SW 4 . 3 6 -2 . 3 % -1 . 7 % -3 . 9 % -8.8 % -7.0 % -2.3 % -3.6% -1.8% -1 . 5 % SW 7 . 9 3 SW 1 . 6 6 SW 3.79 SW 4 . 3 2 SW 4 . 2 4 -1.5 % SW 3.62 SW 5 . 7 0 SW 5 . 7 6 SW 2.70 SW 5.90 BP 0 . 3 0 BP 0. 3 0 BP 0 . 3 0 BP 0. 3 0 BP 0. 3 0 BP 0 . 3 0 SW 8 . 0 0 ME 1. 6 4 ME 2. 1 2 ME 2. 2 2 ME 2. 2 8 FL 2. 2 8 SW 2 . 8 0 ME 3 . 0 0 ME 2. 2 8 ME 2. 6 6 -1.9 % -2.0% -5.0%-1.7% -4 . 9 % -1.6% -1. 8 % SW 4 . 1 7 SW 3 . 9 4 -2.2 % -2 . 0 % SW 2 . 0 2 FL 3.14 FL 3.38 -0 . 7 % FFE 8 . 0 0 -1.0% FG 7 . 8 3 FG 3. 7 3 BW 4 . 9 2 TW 6 . 6 0 TW 7 . 1 7 -12 . 6 % -1 0 . 9 % SW 6.23 SW 6.55 SW 6.46 -1 4 . 9 % -9 . 6 % -9. 3 % -4 : 1 -4:1 -4. 0 % -2.1% FL 2. 1 2 FL 2. 1 8 FL 2. 3 2 FL 2. 3 9 SW 2 . 8 7 ME 2. 8 0 ME 2. 9 3 SW 2 . 2 1 -8.1%-8.1% ME 3.30 ME 3.20 ME 2.92 ME 2.77 PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C2.2 DETAILED GRADING PLAN N ’ ’ ” ’ ’ LEGAL DESCRIPTION: HORIZONTAL DATUM: VERTICAL DATUM: FLOODPLAIN: NOTES: LEGEND XXXX XXXX XXXX XXXX EL E C X X X X X X X X X X X X X X X X X X X X X X 50 0 5 50 0 5 500 5 500 4 -1.7% -1.9% -2.1% -2.0 % -2.0% -1.6 % -2.3% -1.5 % -1.7% -9.2% -39.6% -4.4 % -4. 5 % -1.9% -1.7% -1.7 % -1. 7 % -4 . 0 % 5007 50 0 7 50 0 7 50 0 7 500 7 50 0 8 50 0 8 50 0 8 500 8 50 0 8 5008 50 0 8 50 0 7 SW 6 . 9 8 SW 7 . 3 1 -1.4 % SW 7 . 3 2 SW 7 . 4 1 SW 7 . 3 5 SW 7 . 4 6 SW 7 . 0 0 SW 7.1 7 SW 7 . 1 8 SW 7 . 3 3 SW 7 . 3 0 SW 7.10 SW 7.09 SW 7 . 3 1 SW 7 . 8 5 SW 7 . 8 9 SW 8 . 0 0 SW 8 . 0 0 SW 7 . 8 5 SW 7 . 2 7 SW 7 . 0 0 SW 6.68 SW 6.93 SW 6 . 8 6 SW 7 . 5 3 SW 7 . 1 0 SW 7 . 2 5 SW 7 . 2 9 SW 7 . 4 2 SW 7 . 6 6 SW 7.79 SW 7 . 9 2 SW 8 . 0 0 FFE 8 . 0 0 SW 8 . 0 0 SW 7 . 8 8 SW 8 . 0 0 SW 7 . 9 1 SW 7 . 8 4 SW 7 . 9 5 FFE 8 . 0 0 SW 8 . 0 0 SW 7 . 9 0 SW 8 . 0 0 SW 8 . 0 0 FFE 8 . 0 0 SW 7 . 9 2 FL 7. 8 2 FFE 8 . 0 0 FG 7 . 1 3 FG 7. 0 3 FG 6 . 9 5 FG 7 . 8 9 FG 8 . 9 7 FG 8 . 9 9 SW 7.17 FG 8. 9 9 FG 7 . 2 2 FG 7 . 1 2 FG 7. 2 0 SW 7 . 0 8 FG 6 . 9 1 FG 6.72 FG 6.65FG 8 . 4 0 FG 8 . 4 9 SW 7.14 FG 6.78 FG 6 . 6 5 FG 7. 0 0 FL 6.60 FL 6.50 FL 6.40 FL 6.00 FL 6.00 FL 6.00 FL 6. 4 6 FL 6.21 FL 6.32 FG 8.72 FG 8.50 SW 7 . 4 6 FG 9.24 FG 9.24 SW 7.24 FG 7.00 FG 6.66 FL 6.00 FL 6.52 SW 8 . 0 0 FFE 8 . 0 0 FG 7 . 3 3 FG 7. 3 3 FG 7. 3 3 FG 7. 3 3 FG 7. 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 8 . 0 0 FG 7.33 FG 7. 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7. 3 3 FG 7 . 3 3 FG 7.33 FG 7 . 3 6 FG 7 . 3 3 FG 7 . 3 3 FG 8. 6 2 FG 8. 4 8 FG 7 . 3 3 FG 7.61 -10.3% -25.2 % -25.7% -3 . 7 % -4 . 9 % -1.5% -2.2% -1.7 % FG 7.22 FG 7 . 4 7 FG 7.30 FG 7.33 FG 7.42 FG 7.41 FG 7.29 FG 7.23 FG 7.18 FG 7.10-12.0% -18 . 1 % SW 7 . 8 2 SW 7 . 7 9 SW 7 . 6 4 SW 7 . 3 5 SW 7.32 -1.9 % FG 7 . 3 3 FG 8 . 7 8 FG 8 . 7 8 SW 6 . 8 7 FG 6. 8 3 FG 6 . 8 3 FG 7 . 3 3 SW 7 . 0 5 FL 7. 9 8 -1 . 5 % -1.6% 50 0 6 50 0 7 50 0 7 50 0 7 50 0 8 50 0 7 50 0 7 50 0 8 -0 . 7 % -1 . 1 % -0 . 8 % -1 . 1 % -1 . 1 % -0 . 7 % -0 . 7 % FL 7.08 FL 6.56 FL 6.00 FL 6.96 FL 7.24 FL 7.21 FL 6.59 FL 6. 8 3 FL 6.00 FL 7.25 FL 7.21 FL 6.92 FL 6.44 FL 6 . 0 9 FL 6 . 0 0 SW 6 . 8 8 -2.3% -2.3% -0.5%-4.4%-4.3% SW 6 . 8 7 -1 . 5 % -1 . 6 % -1 . 7 % -1 . 9 % -1.6% -1.6 % -0 . 7 % -1 . 2 % -4.9% -4.5% -4.7% -2 . 0 % SW 6.04 FL 5.48FG 6 . 7 3 FG 5.44FG 5 . 5 0 FG 5 . 0 6 FG 5.00 SW 5 . 0 2 SW 4.78 SW 5.18 FL 4.33 SW 6.13 SW 4.50 FG 4.57FG 4 . 6 3 ME 5.11 ME 4. 8 8 ME 4.64 ME 4.29 ME 3.94 ME 3.73 FL 5.13 FL 4.74 FL 4.11 FL 3.84 SW 6.05 PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C2.3 DETAILED GRADING PLAN N ’ ’ ” ’ ’ LEGAL DESCRIPTION: HORIZONTAL DATUM: VERTICAL DATUM: FLOODPLAIN: NOTES: LEGEND XXXX XXXX XXXX XXXX D D G D ST ST ST ST ST ST ST T T AR T H U R D I T C H W PROSPECT RD 50 0 7 5008 500 6 5007 -1.6% -6 . 2 % -5 . 4 % -6:1 -4:1 -1 . 7 % -1 . 9 % -2 . 0 % -2 . 0 % 500 8 -2.2% 5008 50 0 8 -1.8% -1.8% 5008 5008 5008 500 7 5008 -4 . 7 % -7 . 8 % -1 . 2 % -1 . 5 % 5007 5007 5008 -1 . 0 % -2 . 1 % -8.3% -1 . 0 % -1.8% -1.8 % -1.5% -1 . 7 % -2 . 0 % -7:1 FL 7. 3 8 SW 8 . 1 3 SW 8 . 1 8 FL 7.02 FL 6. 8 1 FL 6. 7 2 FL 6. 4 5 SW 8 . 0 8 SW 7 . 8 8 SW 7 . 8 7 SW 7 . 7 2 SW 7 . 8 1 SW 7 . 6 7 SW 7 . 6 4 SW 7 . 5 4 SW 8 . 0 6 FL 7. 3 3 FL 8.09 SW 7 . 9 9 FL 7. 3 4 SW 7 . 9 3 FL 8.08 FL 7. 2 4 FG 8. 3 9 FG 8 . 2 1 FG 8 . 0 0 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7. 3 3 FG 7. 3 3 FG 7. 3 3 FG 7. 3 3 FG 7 . 3 3 FG 7. 3 3 SW 8 . 2 0 TP 6.50 TP 6.50 TP 6.50 TP 6.50 BP 5.50 FG 7 . 9 8 FG 8. 1 1 FG 8 . 1 2 FG 8 . 1 0 FG 8. 1 0 FFE 8.25 SW 8 . 1 6 FG 7. 3 3 SW 8 . 0 9 FFE 8.00 FL 7. 3 6 SW 8 . 0 0 SW 8 . 2 0 ME 7. 4 6 ME 7. 4 5 ME 7. 3 6 ME 7. 2 0 ME 7. 0 5 SW 8.25SW 8.18 SW 8.18 SW 8.25 FL 7. 0 8 FL 6. 9 3 BP 5.50 BP 5.50 BP 5.50 BP 5. 5 0 TP 6 . 5 0 BP 5. 5 0 TP 6 . 5 0 FG 7 . 8 3 SW 8.13 SW 8 . 1 2 SW 8 . 1 4 SW 7 . 9 5 ME 7. 9 3 ME 7. 8 5 SW 7 . 9 9 SW 8 . 0 4 SW 8 . 0 5 SW 8 . 0 2 SW 8 . 0 3 FG 8 . 1 0 FG 8 . 1 1 FG 8 . 1 1 FG 8 . 0 8 PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C2.4 DETAILED GRADING PLAN N ’ ’ ” ’ ’ LEGAL DESCRIPTION: HORIZONTAL DATUM: VERTICAL DATUM: FLOODPLAIN: NOTES: LEGEND XXXX XXXX XXXX XXXX HYDWV X X X X X X X X X WV 5007 50 0 7 50 0 8 50 0 6 5007 50 0 6 -2.0% -2.0% -3.0% -2 . 7 % -1 . 8 % -1 . 3 % -1.5% -2. 2 % -1 . 9 % -1.2 % -1 . 0 % -2.8% 5006 500 7 50 0 8 -8.3%-2.0% -2 . 0 % W PROSPECT RD -7.2 % -8 . 0 % -2. 8 % -0 . 8 % -0 . 8 % 0. 8 % -0 . 8 % -1 1 . 1 % -2 . 4 % -2 . 3 % -1 . 9 % -3 . 0 % 50 0 6 5006 5006 5007 5007 50 0 7 50 0 8 -1.7% -5.0% -5 . 0 % -1.5% -1.3% -1.8% -1.8% -5.5%-1 . 3 % -1 . 9 % -1.3 %-1.8% -2.0% -2.8% SW 8 . 0 3 SW 7 . 2 0 SW 7 . 2 7 SW 6 . 7 8 SW 6 . 8 5 SW 6 . 9 9 SW 6 . 8 1 SW 6 . 2 3 SW 6 . 0 3 FL 6. 5 1 FL 6.40 FL 6. 2 5 FL 6.28 SW 6 . 3 3 FL 6. 0 3 FL 5. 6 5 FL 6. 0 5 FL 5. 8 4 FL 5. 3 7 FG 8 . 0 0 SW 8 . 2 5 SW 7 . 8 8 FG 7.33FG 7. 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7. 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7 . 3 3 FG 7.33 FG 7 . 3 3 FG 7. 3 3 FG 8 . 0 0 FG 8.00 FG 7. 0 0 FG 6. 9 8 FG 6 . 9 4 FG 6 . 5 8 FG 6 . 6 1 FG 6 . 6 2 FG 6 . 8 7 FG 6 . 8 2 FG 6 . 9 2 FFE 8 . 0 0 FFE 8.00 SW 6.83 SW 6.79SW 8.00 SW 8.00 SW 8 . 1 3 SW 8 . 1 8 SW 8 . 1 0 SW 7 . 2 7 SW 6 . 7 1 SW 6.74 SW 6 . 7 5 SW 7 . 3 3 FFE 8 . 2 5 SW 6 . 4 1 SW 6 . 5 9 SW 7 . 0 9 SW 6.92 SW 6.92SW 7 . 0 9 SW 8 . 0 0 SW 8 . 0 0 SW 7 . 2 7 SW 7 . 3 3 SW 6.77 SW 8 . 1 1 SW 8 . 1 0 TP 6. 5 0 TP 6.41 TP 6.51 TP 6. 5 0 BP 5 . 5 0 BP 5.50 BP 5.50 BP 5. 5 0 SW 8 . 0 6 SW 7 . 9 0 SW 7 . 9 0 SW 7 . 9 1 SW 7 . 9 1 SW 6 . 9 1 SW 6 . 9 1 ME 6. 7 2 ME 6 . 6 0 ME 6. 2 7 ME 5. 7 7 ME 5. 4 7 FG 7.11 FL 6. 6 0 FL 6. 4 8 FL 6. 1 5 ME 5.59 ME 5.58 ME 5.53 ME 5.44 ME 5. 3 4 FL 6.19 FL 5.95 FL 5. 7 9 SW 7 . 9 6 FG 7. 3 3 PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C2.5 DETAILED GRADING PLAN N ’ ’ ” ’ ’ LEGAL DESCRIPTION: HORIZONTAL DATUM: VERTICAL DATUM: FLOODPLAIN: NOTES: LEGEND XXXX XXXX XXXX XXXX SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS WV WV D G HYDWV GAS EL E C ELEC C.O. G C.O. ELEC W C.O. C C ELEC ELEC ELECD ELEC G GAS D E E E E E E E E E E E E E E E E E E E E E E E E E E X X X X X X X X X X X X X X X X X T T TCTVCTVCTV TCTV T T T T CTV CTV CTV CTV G G G G G G G G G G G G G G ELEC D WV ST ST ST WAT WAT WAT WAT WAT WAT WAT S S S S S D G G G G G G G G G G G G G W W W W W W W W W W W W W E E E W W W W W W W W W SS SS SS SS E E ETTTCTVCTVCTV T VIS I T O R VIS I T O R VIS I T O R VA N VIS I T O R VA N T E ELEC F.O. FO EM E R G E N C Y A C C E S S D R I V E W PROSPECT RD (ROW WIDTH VARIES) COURTYARDPARKING GARAGE PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.0 OVERALL STORM SEWER PLAN N LEGEND XXXX XXXX XXXX XXXX HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: NOTES: · · · · · · SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS WV WV C.O. ELEC C.O. C C ELEC ELEC ELECD ELEC G GAS D E E E E E E X X X X X T T T T T TCTVCTVCTVCTVCTVCTV TCTV T T T T T T CTV CTV CTV CTV CTV CTV ELEC EE WAT WAT WAT WAT WAT WAT WAT WAT WAT WAT WAT LAKE STREET (R.O.W. VARIES) S S S G G G G G G G G G G G G G G G G G E E E W W W W W W W W W W W W W SS SS SS SS SS SS E E E E ETTTTTCTVCTVCTVCTVCTV VIS I T O R VIS I T O R VI S I T O R VA N VIS I T O R VA N E ELEC F.O. FO W LAKE ST COFFEE SHOP FFE: 5006 STORM 1 PROFILE PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.1 STORM 1 - PLAN & PROFILE LEGEND XXXX XXXX XXXX XXXX N HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: NOTES: · · · · · · SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS WV WV C.O. ELEC C.O. C C ELEC ELEC ELECD ELEC G GAS D E E E E E E X X X X X T T T T T TCTVCTVCTVCTVCTVCTV TCT V T T T T T T CTV CTV CTV CTV CTV CTV ELEC EE WAT WAT WAT WAT WAT WAT WAT WAT WAT WAT WAT LAKE STREET (R.O.W. VARIES) S S S G G G G G G G G G G G G G G G G G E E E W W W W W W W W W W W W W SS SS SS SS SS SS E E E E ETTTTTCTVCTVCTVCTVCTV VIS I T O R VIS I T O R VIS I T O R VA N VI S I T O R VA N E ELEC F.O. FO W LAKE ST COFFEE SHOP FFE: 5006 STORM 2 PROFILE PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.2 STORM 2 - PLAN & PROFILE LEGEND XXXX XXXX XXXX XXXX N HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: NOTES: · · · · · · G HYDWV GAS E E E E E E E E E X X X X X X X G G G G G G G G G G G G G G G G G G G G G G D WV SS ST ST WEST PROSPECT ROAD (R.O.W. VARIES) S W W W W W W W W W W W W W W W W W W WST T T AR T H U R D I T C H W PROSPECT RD PROPOSED BUILDING FFE: 5008 PROPOSED BUILDING FFE: 5008 STORM 3 PROFILE PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.3 STORM 3 - PLAN & PROFILE LEGEND XXXX XXXX XXXX XXXX N HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: NOTES: · · · · · · SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS D G HYDWV E E E E E E E E E X X X X X X X G G G G G G G G G G G G G G G G G G G G G G D WV SS ST ST ST WEST PROSPECT ROAD (R.O.W. VARIES) S W W W W W W W W W W W W W W W W W W ST T T AR T H U R D I T C H W PROSPECT RD PROPOSED BUILDING FFE: 5008 PROPOSED BUILDING FFE: 5008 STORM 4 PROFILE PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.4 STORM 4 - PLAN & PROFILE LEGEND XXXX XXXX XXXX XXXX N HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: NOTES: · · · · · · SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS WV D D GELE C G GA S D E E E E E E E E T T CT V CT V TCTV T T T T CT V CT V CT V CT V G G G G G G G G G G G D WV ST WA T WA T WA T WA T WA T S D G G G G G G G W W W W W W W W W W W W W W W W E E E T T T CT V CT V CT V T VISITOR VISITOR VISITOR VAN VISITOR VAN T E EL E C F.O . PARKING GARAGE PROPOSED BUILDING FFE: 5008 ARTHUR DITCH W P R O S P E C T R D COFFEE SHOP FFE: 5006 STORM 5 PROFILE PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.5 STORM 5 - PLAN & PROFILE LEGEND XXXX XXXX XXXX XXXX N HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: NOTES: · · · · · · STORM 6 PROFILE E E E E E E E E E E E E E E E E E T T T T T T CT V CT V CT V CT V CT V CT V T T T CT V CT V CT V WA T WA T WA T WA T WA T WA T WA T WA T WA T G G G G G G G G G G FO PROPOSED BUILDING FFE: 5008 COFFEE SHOP FFE: 5006 PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.6 STORM 6 - PLAN & PROFILE LEGEND XXXX XXXX XXXX XXXX HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: N NOTES: · · · · · · PROPOSED BUILDING COFFEE SHOP FFE: 5006 STORM 8 PROFILESTORM 7 PROFILE SS SS SS SS SS SS SS SS D G G G G G G G G G G G G D ST ST ST ST W W W W W W ST T T W PROSPECT RD PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.7 STORM 7 & 8 - PLAN & PROFILE LEGEND XXXX XXXX XXXX XXXX N HORIZONTAL DATUM: VERTICAL DATUM: ’ ’ ” ’ ’ LEGAL DESCRIPTION: FLOODPLAIN: NOTES: · · · · · · PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.8 STORM SEWER DETAILS PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.9 STORM SEWER DETAILS PROSPECT PLAZA REDEVELOPMENT No.Description Date SHEET: DATE: PROJECT: 3575 RINGSBY CT. SUITE 411 DENVER, CO 80216 (720) 677-7766 AGENCY APPROVAL 1 SPAR (ROUND 1) 11-15-2024 2 SPAR REVISION 01-20-2025 04-30-2025 CONSULTANTS PROSPECT PLAZA REDEVELOPMENT SCALE: AS NOTED 3 FDP (ROUND 1) 03-18-2025 4 FDP (ROUND 2) 04-30-2025 C5.10 STORM SEWER DETAILS APPENDIX D www.jvajva.com M E M O TO: Megan Walter, PE, LEED AP Principal DATE: December 16, 2024 FIRM: Sunny Civil JOB NO. 241198.CIV ADDRESS: 706 S College Ave, #203 PROJECT: Prospect Plaza Floodplain Model Fort Collins, CO 80524 SUBJECT: SPAR Submittal - PCSWMM Model Results Megan, JVA Inc. (JVA) has completed the initial update to the Colorado State Universite (CSU) PCSWMM Floodplain model for the Prospect Plaza Development (Site) SPAR submittal. The update included the following information, where and when it was acquired. • CSU PCSWMM Model (December 2023 Version) provided by Susanne Cordery on behalf of Ashraf Fouad with CSU on 11/20/2024 o No changes to 100year rainfall pattern o No changes to any subcatchment except at and around the site as necessary o No changes to generated nodes, mesh, and connections from 1D to 2D networks except for the site boundary area • Prospect Plaza CAD Exchange_24.11.14 provided on 11/21/2024 by Sunny Civil (coordinate system aligned to NAD83 HARN State Plane Colorado North from Fort Collins Local Coordinate System using the ESRI WKT and CAD file with 2 lines provided by Northern Engineering) o ABLDG_024015 o LBASE_024015 o PBASE_024015 o Prospect Plaza CAD Exchange_xx.xx.xx.dwg o XBASE_024015 o XCONT_024015 • Existing and Proposed Land XML files provided on 12/3/2024 by Sunny Civil o EX Surface (TRANSFORMED).xml o PR Surface (TRANSFORMED).xml • Percent Impervious Values o City of Fort Collins Stormwater Criteria Manual Dated December 18, 2018 ☐ Boulder ☒ Fort Collins ☐ Winter Park ☐ Glenwood Springs ☐ Denver 1319 Spruce Street Boulder, CO 80302 303.444.1951 213 Linden Street Suite 200 Fort Collins, CO 80524 970.225.9099 PO Box 1860 47 Cooper Creek Way Suite 328 Winter Park, CO 80482 970.722.7677 817 Colorado Avenue Suite 301 Glenwood Springs, CO 81601 970.404.3100 1675 Larimer Street #550 Denver, CO 80202 303.444.1951 MEMO Prospect Plaza Floodplain Model Job No.: 241198.CIV December 16, 2024 Page 2 of 3 The subcatchment for the site was updated based on the proposed grading. The site was split into seven subcatchments based on the proposed grading. The area, percent impervious, slope, flow length and outfall location were included in the model. The percentage of impervious area was calculated based on the CAD files provided by Sunny Civil and are provided in Table 1. The slope was calculated using the proposed .XML. Figure 1 shows the proposed subcatchments and outfall locations. The proposed storm pipe network was not defined at the time of the model update and therefore the subcatchments were discharged to the ground surface towards the northern? portion of the subcatchment. Table 1. Prospect Plaza Delineated Subcatchments Areas, Calculated Percent Imperviousness, and Slopes. Subcatchment Name Paved Concrete Roof Landscaping ATotal (sf) ATotal (ac) Imp (%) Slope (%) PP_Basin_470 85,930 85,930 1.97 90% 0.5 PP_Basin_470.1 3,676 3,676 0.08 2% 2.5 PP_Basin_470.2 3,551 3,551 0.08 2% 2.5 PP_Basin_471 5,403 7,538 12,941 0.30 43% 4.6 PP_Basin_471.1 11,820 6,795 1,431 20,046 0.46 93% 0.8 PP_Basin_473 20,556 16,684 1,180 9,156 47,576 1.09 81% 1.2 PP_Basin_474 645 3,270 3,915 0.09 18% 4.5 The 2-dimensional (2D) surface and connected 1-dimensional (1D) network in the PCSWMM model calculates the water surface elevation and water depth during the proposed rainfall event modeled period of 6-hours. The sites proposed grading and building boundary were used to update the obstruction layer, boundary layer and surface cell elevations in the model, which creates the model 2D cells. The boundary resolution, input that defines the number of cells and how detailed the 2D surface model is, was increased to 15 from 30. Lower resolution creates a more detailed point grid in the boundary polygon that creates the 2D cells. To match how the current PCSWMM model is set up, the sites subcatchments were connected to the 2D nodes using bottom orifices and the connections were made at the upper end of the subcatchments to represent storm flows through the site. The building and parking garage subcatchment was directly connected to the storm inlet and network in West Lake Street. Model Results The model results are provided in Table 2 and shown in Figures 2 to 5. Figure 2 is maximum flooding area shown as maximum water depth for the entire site. Figures 3 and 4 are zoomed in areas of the site with maximum water surface elevation of the cells labeled on the figures, duplicate labels were avoided. Figure 5 compares the expanse of maximum flooding extent area for the existing December 2023 model (blue area) and the proposed model area (red area). The overlapping max flooding areas are depicted in purple. MEMO Prospect Plaza Floodplain Model Job No.: 241198.CIV December 16, 2024 Page 3 of 3 Table 2. Maximum Water Surface Elevation Proposed Site and Existing Model Results Site Location Prospect Plaza 100yr PCSWMM model Maximum Water Surface Elevation (ft) December 2023 Existing 100yr PCSWMM model Maximum Water Surface Elevation (ft) North of Building (West Lake Road) 5004.38 5004.39 Southwest Edge of Site at West Prospect Road 5007.75 5007.76 West along Parking Garage/Building 5006.83 5006.22 West Water Quality Pond Area 5007.81 NA East Water Quality Pond Area 5007.21 NA Courtyard Area 5007.78 NA East Parking Lot 5005.83 5004.39 East Neighboring Parking Lot 5004.87 5004.39 As can be seen in Figure 5, flooding on the east side of the site extends into the neighboring property further than existing conditions. The max water surface elevation on West Lake Street at the inlets to Arthur’s Ditch is 0.01 feet lower for the Prospect Plaza model than in the existing model. On the west side of the site the proposed grading incorporates curb and gutter that drains the site flows to the north within the site and away from the neighboring building. The proposed site plan does increase the maximum water surface elevation on the east side of the site by a minimal amount. Figure 6 shows the flooding area after 6 hours. The ponding water depth at the Arthur Ditch inlets and low spot in West Lake Street is decreasing and water stored on site is contained to the proposed ponds and drainage channels. Signed: Copies to: Laurie Laos, PE, CFM Senior Engineer, JVA Attachments: Figure 1 – Proposed Site Subcatchment Layout Figure 2 – Proposed Site Maximum Flooding Area Figure 3 – Proposed Site Maximum Water Surface Elevation North Figure 4 – Proposed Site Maximum Water Surface Elevation South Figure 5 – Proposed Site and Existing Model Maximum Flooding Area Figure 6 – Proposed Site Flooding Area After 6 Hours Storm Pipe Storm Pipe 5004.385004.38 Storm Pipe Figure 3 - Proposed Site Maximum Water Surface Elevation (North) 5007.81 Storm Pipe Figure 4 - Proposed Site Maximum Water Surface Elevation (South) Existing Max WSEL Proposed Max WSEL Figure 5 - Proposed Site and Existing Model Maximum Flooding Area Water Depth AFTER 6 HR