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Home My WebLink AboutPROSPECT STATION - FDP - FDP130027 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE REPORT Prospect Station Prepared for: r4 Architects 117 E. Mountain Ave., Suite 205 Fort Collins, CO 80524 (970) 224-0630 Prepared by: Interwest Consulting Group 1218 West Ash, Suite C Windsor, Colorado 80550 (970) 674-3300 May 29, 2013 Job Number 1068-069-01 iii TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................ iii 1. GENERAL LOCATION AND DESCRIPTION ................................................................ 1 1.1 Location ........................................................................................................................... 1 1.2 Description of Property ................................................................................................. 1 1.3 Floodplain Submittal Requirements ............................................................................. 1 2. DRAINAGE BASINS AND SUB-BASINS .......................................................................... 2 2.1 Major Basin Description ................................................................................................ 2 2.2 Sub-basin Description .................................................................................................... 2 3. DRAINAGE DESIGN CRITERIA ...................................................................................... 2 3.1 Regulations ...................................................................................................................... 2 3.2 Directly Connected Impervious Area (DCIA) Discussion .......................................... 3 3.3 Development Criteria Reference and Constraints ...................................................... 4 3.4 Hydrological Criteria ..................................................................................................... 4 3.5 Hydraulic Criteria .......................................................................................................... 5 3.6 Floodplain Regulations Compliance ............................................................................. 5 3.7 Modifications of Criteria ............................................................................................... 5 4. DRAINAGE FACILITY DESIGN ....................................................................................... 6 4.1 General Concept ............................................................................................................. 6 4.2 Specific Details ................................................................................................................ 6 5. CONCLUSIONS .................................................................................................................... 7 5.1 Compliance with Standards .......................................................................................... 7 5.2 Drainage Concept ........................................................................................................... 8 6. REFERENCES ...................................................................................................................... 8 APPENDIX VICINITY MAP AND DRAINAGE PLAN .............................................................................. A HYDROLOGIC COMPUTATIONS .......................................................................................... B HYDRAULIC COMPUTATIONS .............................................................................................. C WATER QUALITY INFORMATION ...................................................................................... D EXCERPTS FROM REFERENCE REPORTS......................................................................... E 1 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location The Prospect Station development is located in Fort Collins. It is located in the Northeast Quarter of Section 23, Township 7 North, Range 69 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. Please refer to the vicinity map in Appendix A. The project site is located at the southwest corner of West Prospect Road and the Burlington Northern (BNSF) Railroad. The property is bounded by the vacated Tamasag Drive on the west, West Prospect Road on the north, the Mason Trail and BNSF on the east and Lot 9 and 11 of Griffin Plaza Subdivision on the south. The legal description of the site is Prospect Station Subdivision being a replat of Lot 10, Griffin Plaza Subdivision and a portion of vacated Tamasag Drive. 1.2 Description of Property The property consists of 0.84 acres of land with 0.1 acres being dedicated to West Prospect Road. The project will consists of a new building replacing the existing building and a new parking and drive configuration. The northerly 0.6 acres drains northeast to West Prospect Road and the remainder sheets south at a range of approximately 0.5% to 1.5%. The land is currently occupied by an existing building and parking areas. The majority of the ground cover is asphalt. There is no offsite flow contributing to the site. Spring Creek Floodway has been mapped by the City and is located just east of the project. There are no improvements that are proposed in the Floodway. 1.3 Floodplain Submittal Requirements Floodplain Submittal is not required. No work shall occur within the City’s floodway; therefore, a “City of Fort Collins Floodplain Review Checklist for 50% Submittals” has not been included with this report. 2 2. DRAINAGE BASINS AND SUB-BASINS 2.1 Major Basin Description The proposed development lies within the Old Town (a small part of the northern portion of the site) and Spring Creek (the remainder of the site) Master Drainage Basins. Today, the entire site locally drains to Spring Creek via inlets and pipe in Prospect Road and BNSF ROW and not to the Old Town Basin. The development has also been accounted for in the design of the Mason Street Outfall (MSO) pond (showing the entire site in Spring Creek Basin). The site is considered to be basin 804 of the Griffin Plaza in the Mason Street Outfall report and a part of Spring Creek Basin 126 in the Spring Creek Master Plan. Please refer to Appendix F for an explanation of the division of Spring Creek and Old Town basins. 2.2 Sub-basin Description The northern portion of the site that is included in the Old Town Master Drainage Basin drains to the north where it is intercepted by West Prospect Road and then piped back to Spring Creek. The remainder of the site (included in the Spring Creek Master Drainage Basin) drains south through adjacent Lots 9 and 11 of Griffin Plaza Subdivision. There are no offsite flows associated with this site however Lot 1 and 2 of Griffin Plaza Subdivision will continue to flow south. Flow will sheet to a curb opening and into a new swale in the existing drainage easement south of the site. 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations This report was prepared to meet or exceed the “City of Fort Collins Storm Drainage Design Criteria Manual” specifications. Where applicable, the criteria established in the “Urban Storm Drainage Criteria Manual” (UDFCD), developed by the Denver Regional Council of Governments, has been used. 3 3.2 Directly Connected Impervious Area (DCIA) Discussion Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process for receiving water protection that focuses on reducing runoff volumes, treating the water quality capture volume (WQCV), stabilizing drainageways and implementing long-term source controls. The Four Step Process applies to the management of smaller, frequently occurring events. Step 1: Employ Runoff Reduction Practices To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low Impact Development (LID) strategies, including Minimizing Directly Connected Impervious Areas (MDCIA). Runoff for the northern and eastern portions of the site will be routed through vegetated areas through sheet flow thereby reducing runoff from impervious surfaces over permeable areas to slow runoff and increase the time of concentration and promote infiltration. Runoff from the parking lot shall drain directly to two rain gardens thereby slowing runoff and also promoting infiltration. Runoff from building roofs shall drain directly to a sump manhole that incorporates the SNOUT® water quality system from Best Management Products, Inc. device. Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release Once runoff has been minimized, the remaining runoff shall be treated through the rain gardens and a sump manhole with SNOUT® water quality system from Best Management Products, Inc. device. Both the rain gardens and the device allow for settlement of sediments. Step 3: Stabilize Drainageways Natural Drainageways are subject to bed and bank erosion due to increases in frequency, duration, rate and volume of runoff during and following development. Because the site will drain to an existing storm system and water quality and detention pond, bank stabilization is unnecessary with this project. 4 Step 4: Implement Site Specific and Other Source Control BMPs Proactively controlling pollutants at their source by preventing pollution rather than removing contaminants once they have entered the stormwater system or receiving waters is important when protecting storm systems and receiving waters. This can be accomplished through site specific needs such as construction site runoff control, post- construction runoff control and pollution prevention / good housekeeping. It will be the responsibility of the contractor to develop a procedural best management practice for the site. 3.3 Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the City Stormwater Department. Because water quality capture volume from this site will not be provided for in the BNRR pond, water quality facilities are required for the new construction proposed on the site. Water quality will be met through the use of two rain gardens and a sump manhole with the SNOUT® water quality system from Best Management Products, Inc. device. Impervious area for the site has already been accounted for in the hydrology for Spring Creek and the MSO project, detention is not required for this development. Please refer to excerpts from the Mason Street Outfall report in Appendix E. 3.4 Hydrologic Criteria Runoff computations were prepared for the 10-year minor and 100-year major storm frequency utilizing the rational method. All hydrologic calculations associated with the basins are included in Appendix B of this report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub- basins. Standard Form 9 (SF-9) provides a summary of the design flows for all Sub- basins and Design Points associated with this site. Water quality volume was calculated in the Master Plan using the method recommended in the “Urban Storm Drainage Criteria Manual”. Rather than achieving this volume, we are requesting a variance to use 2 rain gardens and a SNOUT® system in series. All related information is located in Appendix D. 5 3.5 Hydraulic Criteria All hydraulic calculations are prepared in accordance with the City of Fort Collins Drainage Criteria and included in Appendix C of this report. 3.6 Floodplain Regulations Compliance Floodplain Regulations Compliance is not required. No work shall occur within the City’s floodway. 3.7 Modifications of Criteria A variance for water quality mitigation requirements is being requested. The site will not meet the full water quality volume requirement but as much drainage as is physically possible from the site will be treated in two bio-retention facilities (rain gardens) and a sump manhole with SNOUT® water quality system from Best Management Products, Inc. The reason for this is that the site is a redeveloped Brownfield site and it is preferred to minimize exposure to leftover contaminants on-site after the cleanup occurred. The water will eventually reach the BNRR water quality pond via the storm system but will be pretreated on site. The entire site’s required water quality capture volume is 0.022 ac-ft and the BNRR pond has ample volume (but will technically be treated on site). Please refer to Appendix F for supporting information regarding water quality and the BNRR pond. Please refer to Appendix D for SNOUT® information. Following the Urban Drainage design procedure for sizing rain gardens, the required water quality capture volume for the proposed area to be treated (Basin A-1) is 455 cubic feet. The proposed rain gardens provide 256 cubic feet of volume, which is approximately 56% of the required water quality capture volume. We have maximized the area of the rain gardens with the existing constraints that are associated with the site. Please see the attached Urban Drainage Design Procedure form in Appendix D for more information. The rain gardens will be filled with a 12” rain garden growing media with granular material following the guidelines in Urban Drainage and the City of Fort Collins. The rain gardens will be lined with an impermeable geomembrane liner. Once the rain gardens are completely saturated, water will overtop into the two rain garden inlets then 6 be conveyed north and east to the existing storm sewer in West Prospect Road via a new 18-inch storm system. During extreme events or complete failure of the storm sewer system, water will overtop the rain gardens and flow south to a 8’ curb cut with a maximum ponding depth of 6 inches. 4. DRAINAGE FACILITY DESIGN 4.1 General Concept The majority of the proposed development will be collected and conveyed to the proposed storm drain system where it will be treated for water quality via rain gardens and a SNOUT® water quality system from Best Management Products, Inc. before being released into the existing storm system. 4.2 Specific Details A summary of the drainage patterns within each basin is provided in the following paragraphs. Please refer to Appendix A for the drainage plan. Basin A-1 is 0.39 acres and is calculated to have a 10-year discharge of 1.7 cfs and a 100- year discharge of 3.9 cfs. Flows from Basin A-1 are captured by the proposed rain gardens before being released into the existing storm system located in West Prospect Road. This system then releases flow into the BNRR pond. Basin A-2 is 0.11acres, contains the north half of the roof and is calculated to have a 10- year discharge of 0.5 cfs and a 100-year discharge of 1.1 cfs. Flows from Basin A-2 are captured by the proposed roof drains before being released into the existing storm system located in West Prospect Road. This system then releases flow into the BNRR pond. Basin A-3 is 0.05 acres, contains a portion of the southeast roof and is calculated to have a 10-year discharge of 0.2 cfs and a 100-year discharge of 0.5 cfs. Flows from Basin A-3 are captured by the proposed roof drains that direct flow to the manhole containing a sump and the SNOUT® water quality system from Best Management Products, Inc. before being released into the existing storm system located in West Prospect Road. This system then releases flow into the BNRR pond. 7 The areas of Basins A-1 through A-3 were not included in the Mason Street Outfall SWMM model; therefore, impact to the existing storm system was analyzed. The hydrograph for this area was added to the model which shows that the area peaks at the same time as the entire system which is unlikely. It seems that the model does not account for several thousand feet of pipe in the system. However, maximum flow in the system increases from 137.5 cfs to 141.8 cfs at the downstream 60” RCP causing negligible change to the system. Please refer to Appendix C for the modified MSO SWMM analysis and comparison. Basin B is 0.18 acres and has a 10-year discharge of 0.5 cfs and 1.3 cfs. Flows from this basin will continue current conditions and sheet north to West Prospect Road where it will be conveyed east via curb and gutter to the existing storm inlet in West Prospect Road. This inlet is part of the existing storm system that discharges to the BNRR pond. Basin C is 0.10 acres and is calculated to have a 10-year discharge of 0.3 cfs and a 100- year discharge of 0.8 cfs. Flows from this basin will continue current conditions and sheet east to the ditch adjacent to the Mason Trail. The percent impervious weighted average of the entire site is 75% which is below the Mason Street Outfall assumption of 85%; therefore, detention is not required. 5. CONCLUSIONS 5.1 Compliance with Standards All computations that have been completed within this report are in compliance with the City of Fort Collins Storm Drainage Design Criteria Manual. 8 5.2 Drainage Concept The proposed drainage concepts presented in this report and on the construction plans adequately provides for stormwater quantity and quality treatment of proposed impervious areas. Conveyance elements have been designed to pass required flows and to minimize future maintenance. If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. 6. REFERENCES 1. City of Fort Collins, “Fort Collins Stormwater Criteria Manual Amendments to the Urban Drainage and Flood Control District Criteria Manual”, adopted December 2011. 2. Urban Drainage and Flood Control District, “Urban Storm Drainage Criteria Manual”, Volumes 1 and 2, dated June 2001, and Volume 3 dated November 2010. 3. Ayers Associates, “Alternative Analysis for the Design of the Mason Street Outfall”, dated November 2010. A APPENDIX A VICINITY MAP AND DRAINAGE PLAN Prospect Rd Tamasag Dr 3 4 493210 493210 493220 493220 493230 493230 493240 493240 493250 493250 493260 493260 493270 493270 493280 493280 493290 493290 493300 493300 493310 493310 493320 493320 493330 493330 4490630 4490630 4490640 4490640 4490650 4490650 4490660 4490660 4490670 4490670 4490680 4490680 4490690 4490690 4490700 4490700 4490710 4490710 0 30 60 120 180 Feet 0 5 10 20 30 Meters 40° 34' 1'' 105° 4' 43'' 40° 33' 59'' 105° 4' 43'' 40° 33' 59'' 40° 34' 1'' 105° 4' 48'' 105° 4' 48'' Map Scale: 1:611 if printed on A size (8.5" x 11") sheet. 0$3/(*(1' 0$3,1)250$7,21 $UHDRI,QWHUHVW $2, $UHDRI,QWHUHVW $2, 6RLOV 6RLO0DS8QLWV 6RLO5DWLQJV $ $' % %' & &' ' 1RWUDWHGRUQRWDYDLODEOH 3ROLWLFDO)HDWXUHV &LWLHV :DWHU)HDWXUHV 6WUHDPVDQG&DQDOV 7UDQVSRUWDWLRQ 5DLOV ,QWHUVWDWH+LJKZD\V 865RXWHV 0DMRU5RDGV /RFDO5RDGV 0DS6FDOHLISULQWHGRQ$VL]H î +\GURORJLF6RLO*URXS +\GURORJLF6RLO*URXS²6XPPDU\E\0DS8QLW²/DULPHU&RXQW\$UHD&RORUDGR &2 0DSXQLWV\PERO 0DSXQLWQDPH 5DWLQJ $FUHVLQ$2, 3HUFHQWRI$2, $OWYDQ6DWDQWDORDPVWR SHUFHQWVORSHV % $OWYDQ6DWDQWDORDPVWR SHUFHQWVORSHV % 7RWDOVIRU$UHDRI,QWHUHVW 'HVFULSWLRQ +\GURORJLFVRLOJURXSVDUHEDVHGRQHVWLPDWHVRIUXQRIISRWHQWLDO6RLOVDUH DVVLJQHGWRRQHRIIRXUJURXSVDFFRUGLQJWRWKHUDWHRIZDWHULQILOWUDWLRQZKHQWKH VRLOVDUHQRWSURWHFWHGE\YHJHWDWLRQDUHWKRURXJKO\ZHWDQGUHFHLYHSUHFLSLWDWLRQ IURPORQJGXUDWLRQVWRUPV 7KHVRLOVLQWKH8QLWHG6WDWHVDUHDVVLJQHGWRIRXUJURXSV $%&DQG' &RPSRQHQW3HUFHQW&XWRII1RQH6SHFLILHG 7LHEUHDN5XOH+LJKHU +\GURORJLF6RLO*URXS±/DULPHU&RXQW\$UHD&RORUDGR 3URVSHFW6WDWLRQ 1DWXUDO5HVRXUFHV &RQVHUYDWLRQ6HUYLFH :HE6RLO6XUYH\ 1DWLRQDO&RRSHUDWLYH6RLO6XUYH\ 3DJHRI B APPENDIX B HYDROLOGIC COMPUTATIONS SUMMARY DRAINAGE SUMMARY TABLE Design Tributary Area C (10) C (100) tc (10) tc (100) Q(10)tot Q(100)tot Sub-basin REMARKS Point (ac) (min) (min) (cfs) (cfs) A1 A-1 0.39 0.91 1.00 5.0 5.0 1.7 3.9 Area Draining to Rain Garden A2 A-2 0.11 0.96 1.00 5.0 5.0 0.5 1.1 Roof Area to Storm Sewer A3 A-3 0.05 0.86 1.00 5.0 5.0 0.2 0.5 Roof Area to Storm Sewer B B 0.18 0.58 0.73 5.0 5.0 0.5 1.3 Area Draining to W. Prospect C C 0.10 0.61 0.77 5.0 5.0 0.3 0.8 Area Draining to East Page 6 Interwest Consulting Group LOCATION: Prospect Station PROJECT NO: 1068-069-01 COMPUTATIONS BY: es DATE: 3/25/2013 Recommended Runoff Coefficients from Table 3-3 of City of Fort Collins Design Criteria Recommended % Impervious from Urban Storm Drainage Criteria Manual Runoff % coefficient Impervious C Streets, parking lots (asphalt): 0.95 100 Sidewalks (concrete): 0.95 96 Roofs: 0.95 90 Landscape Areas: 0.25 0 SUBBASIN TOTAL TOTAL PAVED ROOF SIDEWALK LANDSCAPE RUNOFF % DESIGNATION AREA AREA AREA AREA AREA AREA COEFF. Impervious REMARKS (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C) A-1 0.39 17,015 9,320 6,703 0 993 0.91 90 Area Draining to Rain Garden A-2 0.11 4,938 0 4,938 0 208 0.96 90 Roof Area to Storm Sewer A-3 0.05 2,170 0 1,888 0 282 0.86 78 Roof Area to Storm Sewer B 0.18 7,747 0 0 3,686 4,061 0.58 46 Area Draining to W. Prospect C 0.10 4,496 0 0 2,344 2,152 0.61 50 Area Draining to East Total 0.83 36,366 9,320 13,529 6,030 7,695 0.73 75 Equations - Calculated C coefficients & % Impervious are area weighted C = Σ (Ci Ai) / At Ci = runoff coefficient for specific area, Ai Ai = areas of surface with runoff coefficient of Ci n = number of different surfaces to consider At = total area over which C is applicable; the sum of all Ai's 03-25-13 Flow.xls Interwest Consulting Group STANDARD FORM SF-2 TIME OF CONCENTRATION - 10 YR LOCATION: Prospect Station PROJECT NO: 1068-069-01 COMPUTATIONS BY: es DATE: ####### 10-yr storm Cf = 1.00 SUB-BASIN INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS DATA TIME (ti) (tt) (URBANIZED BASIN) tc DESIGN SUBBASIN(s) Area C Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 PONIT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) A1 A-1 0.39 0.91 20 2.0 1.3 136 0.5 0.016 1.4 1.60 2.9 156 10.9 5.0 A2 A-2 0.11 0.96 5 2.0 0.5 0 0.5 0.016 1.4 0.00 0.5 5 10.0 5.0 A3 A-3 0.05 0.86 5 2.0 0.8 0 0.5 0.016 1.4 0.00 0.8 5 10.0 5.0 B B 0.18 0.58 25 2.0 3.8 0 1.1 0.016 2.1 0.00 3.8 25 10.1 5.0 C C 0.10 0.61 25 2.0 3.6 0 3.0 0.030 1.9 0.00 3.6 25 10.1 5.0 EQUATIONS: tc = ti + tt ti = [1.87 (1.1 - CCf ) L0.5 ] / S 1/3 tt = L/Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 min. due to limits of IDF curves 03-25-13 Flow.xls Interwest Consulting Group STANDARD FORM SF-2 TIME OF CONCENTRATION - 100 YR LOCATION: Prospect Station PROJECT NO: 1068-069-01 COMPUTATIONS BY: es DATE: ####### 100-yr storm Cf = 1.25 SUB-BASIN INITIAL /OVERLAND TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS DATA TIME (ti) (tt) (URBANIZED BASIN) tc DESIGN SUBBASIN(s) Area C C*Cf Length Slope ti Length Slope n Vel. tt tc = Total L tc=(l/180)+10 PONIT (ac) (ft) (%) (min) (ft) (%) Manning (ft/s) (min) ti + tt (ft) (min) (min) (1) (2) (3) (4) (5) (6) (7) (8) rough. (9) (10) (11) (12) (13) (14) A1 A-1 0.39 0.91 1.00 20 2.0 0.7 136 0.5 0.016 1.4 1.60 2.3 156 10.9 5.0 A2 A-2 0.11 0.96 1.00 5 2.0 0.3 0 0.5 0.016 1.4 0.00 0.3 5 10.0 5.0 A3 A-3 0.05 0.86 1.00 5 2.0 0.3 0 0.5 0.016 1.4 0.00 0.3 5 10.0 5.0 B B 0.18 0.58 0.73 25 2.0 2.8 0 1.1 0.016 2.1 0.00 2.8 25 10.1 5.0 C C 0.10 0.61 0.77 25 2.0 2.5 0 3.0 0.030 1.9 0.00 2.5 25 10.1 5.0 EQUATIONS: tc = ti + tt ti = [1.87 (1.1 - CCf ) L0.5 ] / S 1/3 tt = L/Vel. Velocity from Manning's Equation with R=0.1 (corresponds to Figure 3-3 of City of Fort Collins Design Manual) final tc = minimum of ti + tt and urbanized basin check min. tc = 5 min. due to limits of IDF curves 03-25-13 Flow.xls Interwest Consulting Group RATIONAL METHOD PEAK RUNOFF (City of Fort Collins, 10-Yr Storm) LOCATION: Prospect Station PROJECT NO: 1068-069-01 COMPUTATIONS BY: es DATE: ######## 10 yr storm, Cf = 1.00 DIRECT RUNOFF CARRY OVER TOTAL REMARKS Design Tributary A C Cf tc i Q (10) from Q (10) Q(10)tot Sub-basin Design Point (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) A1 A-1 0.39 0.91 5.0 4.87 1.7 1.7 A2 A-2 0.11 0.96 5.0 4.87 0.5 0.5 A3 A-3 0.05 0.86 5.0 4.87 0.2 0.2 B B 0.18 0.58 5.0 4.87 0.5 0.5 C C 0.10 0.61 5.0 4.87 0.3 0.3 Q = Cf C iA Q = peak discharge (cfs) C = runoff coefficient Cf = frequency adjustment factor i = rainfall intensity (in/hr) from City of Fort Collins IDF curve (4/16/99) A = drainage area (acres) i = 41.44 / (10+ tc)0.7974 03-25-13 Flow.xls Interwest Consulting Group RATIONAL METHOD PEAK RUNOFF (City of Fort Collins, 100-Yr Storm) LOCATION: Prospect Station PROJECT NO: 1068-069-01 COMPUTATIONS BY: es DATE: ######## 100 yr storm, Cf = 1.25 DIRECT RUNOFF CARRY OVER TOTAL REMARKS Des. Area A C Cf tc i Q (100) from Q (100) Q(100)tot Design Point Design. (ac) (min) (in/hr) (cfs) Point (cfs) (cfs) A1 A-1 0.39 1.00 5.0 9.95 3.9 3.9 A2 A-2 0.11 1.00 5.0 9.95 1.1 1.1 A3 A-3 0.05 1.00 5.0 9.95 0.5 0.5 B B 0.18 0.73 5.0 9.95 1.3 1.3 C C 0.10 0.77 5.0 9.95 0.8 0.8 Q = C iA Q = peak discharge (cfs) C = runoff coefficient i = rainfall intensity (in/hr) from City of Fort Collins IDF curve (4/16/99) A = drainage area (acres) i = 84.682 / (10+ tc)0.7975 03-25-13 Flow.xls C APPENDIX C HYDRAULIC CALCULATIONS Circular Area Inlet Capacity LOCATION: PROSPECT STATION PROJECT NO: 1068-069-01 COMPUTATIONS BY: ES SUBMITTED BY: INTERWEST CONSULTING GROUP DATE: 3/25/2013 Inlet Data: Weir Length 6.3 ft Open Area 1.4 ft^2 Solve for h using Orifice Equation Q = Co Ao sqrt(2gh) where Qo = flow through orifice (cfs) Co = orifice discharge coefficient g = gravitational acceleration = 32.2 ft/s Ao = effective area of the orifice (ft 2 ) h = head on the orifice (ft) Qo = 2.50 cfs 100-yr Event Ao = 0.68 ft 2 (Assume 50% clogged) Co = 0.65 Solve for h: 0.50 ft Q= 2.50 cfs Required Head d= 0.50 ft Available Head Prior to Overtopping 0.50 ft 24" ADS Area Inlet (A-1) Rectangular Area Inlet Capacity LOCATION: PROSPECT STATION PROJECT NO: 1068-069-01 COMPUTATIONS BY: ES SUBMITTED BY: INTERWEST CONSULTING GROUP DATE: 3/25/2013 Inlet Data: Weir Length 6.7 ft Open Area 2.2 ft^2 Solve for h using Orifice Equation Q = Co Ao sqrt(2gh) where Qo = flow through orifice (cfs) Co = orifice discharge coefficient g = gravitational acceleration = 32.2 ft/s Ao = effective area of the orifice (ft 2 ) h = head on the orifice (ft) Qo = 4.10 cfs 100-yr Event Ao = 1.12 ft 2 (Assume 50% clogged) Co = 0.65 Solve for h: 0.49 ft Solve for h using Weir Equation Q = CLH 3/2 where C = weir coefficient H = overflow height L = length of the weir Q = 4.10 cfs C = 3.00 L = 6.7 ft Solve for H: 0.35 ft ORIFICE CONTROLS Q= 4.10 cfs Required Head d= 0.49 ft Available Head Prior to Overtopping 0.50 ft City of Fort Collins Area Inlet Scenario: 100-yr Title: Prospect Station x:\...\design\stormcad\05-21-13 storm system.stm 05/21/13 09:09:53 AM Interwest Consulting Group © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Project Engineer: Interwest Consulting Group StormCAD v5.5 [5.5005] Page 1 of 1 P-5 P-4 P-3 P-2 P-1 O-1 I-1 J-1 I-2 I-3 J-2 Calculation Results Summary Title: Prospect Station x:\...\design\stormcad\05-21-13 storm system.stm 05/21/13 09:10:36 AM Interwest Consulting Group © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Project Engineer: Interwest Consulting Group StormCAD v5.5 [5.5005] Page 1 of 2 ================================================================= Scenario: 100-yr >>>> Info: Subsurface Network Rooted by: O-1 >>>> Info: Subsurface Analysis iterations: 1 >>>> Info: Convergence was achieved. CALCULATION SUMMARY FOR SURFACE NETWORKS ________________________________________________________________________________________________________ | Label | Inlet | Inlet | Total | Total | Capture | Gutter | Gutter | | | Type | | Intercepted | Bypassed | Efficiency | Spread | Depth | | | | | Flow | Flow | (%) | (ft) | (ft) | | | | | (cfs) | (cfs) | | | | |-------|---------------|----------------------|-------------|----------|------------|--------|--------| | I-3 | Generic Inlet | Generic Default 100% | 0.00 | 0.00 | 100.0 | 0.00 | 0.00 | | I-2 | Generic Inlet | Generic Default 100% | 0.00 | 0.00 | 100.0 | 0.00 | 0.00 | | I-1 | Generic Inlet | Generic Default 100% | 0.00 | 0.00 | 100.0 | 0.00 | 0.00 | -------------------------------------------------------------------------------------------------------- CALCULATION SUMMARY FOR SUBSURFACE NETWORK WITH ROOT: O-1 _______________________________________________________________________________________________ | Label | Number | Section | Section | Length | Total | Average | Hydraulic | Hydraulic | | | of | Size | Shape | (ft) | System | Velocity | Grade | Grade | | | Sections | | | | Flow | (ft/s) | Upstream | Downstream | | | | | | | (cfs) | | (ft) | (ft) | |-------|----------|---------|----------|--------|--------|----------|-----------|------------| | P-1 | 1 | 18 inch | Circular | 33.00 | 5.50 | 4.54 | 94.13 | 93.90 | | P-2 | 1 | 18 inch | Circular | 96.00 | 5.50 | 4.60 | 94.62 | 94.39 | | P-3 | 1 | 18 inch | Circular | 79.00 | 4.40 | 4.23 | 94.93 | 94.81 | | P-5 | 1 | 12 inch | Circular | 13.00 | 0.50 | 5.16 | 95.05 | 95.06 | | P-4 | 1 | 18 inch | Circular | 12.00 | 3.90 | 9.22 | 95.26 | 95.06 | ----------------------------------------------------------------------------------------------- ______________________________________________________ | Label | Total | Ground | Hydraulic | Hydraulic | | | System | Elevation | Grade | Grade | | | Flow | (ft) | Line In | Line Out | | | (cfs) | | (ft) | (ft) | |-------|--------|-----------|-----------|-----------| | O-1 | 5.50 | 96.60 | 93.00 | 93.00 | | J-1 | 5.50 | 97.20 | 94.39 | 94.13 | | I-1 | 5.50 | 98.50 | 94.81 | 94.62 | | J-2 | 4.40 | 98.10 | 95.06 | 94.93 | | I-3 | 0.50 | 98.60 | 95.05 | 95.05 | | I-2 | 3.90 | 98.60 | 95.26 | 95.26 | ------------------------------------------------------ Calculation Results Summary Title: Prospect Station x:\...\design\stormcad\05-21-13 storm system.stm 05/21/13 09:10:36 AM Interwest Consulting Group © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Project Engineer: Interwest Consulting Group StormCAD v5.5 [5.5005] Page 2 of 2 ================================================================= Completed: 05/21/2013 09:10:23 AM Profile Scenario: 100-yr Title: Prospect Station x:\...\design\stormcad\05-21-13 storm system.stm 05/21/13 09:10:57 AM Interwest Consulting Group © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Project Engineer: Interwest Consulting Group StormCAD v5.5 [5.5005] Page 1 of 1 Elevation (ft) Station (ft) Profile: Profile - 1 Scenario: 100-yr -3+00 -2+00 -1+00 0+00 85.00 90.00 95.00 100.00 Sump: 94.50 ft Rim: 98.10 ft Label: I-2 Sump: 89.50 ft Rim: 98.10 ft Label: J-2 Sump: 93.64 ft Rim: 98.50 ft Label: I-1 Sump: 93.16 ft Rim: 97.20 ft Label: J-1 Sump: 93.00 ft Rim: 96.60 ft Label: O-1 S: 0.041667 ft/ft Size: 18 inch L: 12.00 ft Dn. Invert: 94.00 ft Up. Invert: 94.50 ft Label: P-4 S: 0.004557 ft/ft Size: 18 inch L: 79.00 ft Dn. Invert: 93.64 ft Up. Invert: 94.00 ft Label: P-3 S: 0.005000 ft/ft Size: 18 inch L: 96.00 ft Dn. Invert: 93.16 ft Up. Invert: 93.64 ft Label: P-2 S: 0.004848 ft/ft Size: 18 inch L: 33.00 ft Dn. Invert: 93.00 ft Up. Invert: 93.16 ft Label: P-1 Profile Scenario: 100-yr Title: Prospect Station x:\...\design\stormcad\05-21-13 storm system.stm 05/21/13 09:11:21 AM Interwest Consulting Group © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Project Engineer: Interwest Consulting Group StormCAD v5.5 [5.5005] Page 1 of 1 Elevation (ft) Station (ft) Profile: Profile - 2 Scenario: 100-yr -1+00 0+00 85.00 90.00 95.00 100.00 Sump: 94.50 ft Rim: 98.10 ft Label: I-3 Sump: 89.50 ft Rim: 98.10 ft Label: J-2 S: 0.038462 ft/ft Size: 12 inch L: 13.00 ft Dn. Invert: 94.00 ft Up. Invert: 94.50 ft Label: P-5 PROSPECT STATION Table 1. Comparison of existing and proposed HGL. 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