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Home My WebLink AboutMASON STREET INFRASTRUCTURE PROJECT - FDP230016 - SUBMITTAL DOCUMENTS - ROUND 1 - Drainage Related Document NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: MASON STREET INFRASTRUCTURE FORT COLLINS | GREELEY 1 | 3 May 24, 2023 Stormwater Department City of Fort Collins 700 Wood Street Fort Collins, Colorado 80521 RE: PRELIMINARY DRAINAGE MEMORANDUM FOR MASON STREET INFRASTRUCTURE FORT COLLINS, COLORADO NE PROJECT NUMBER: 1971-001 Dear City Staff: This memo accompanies the submittal for the Mason Street Infrastructure Preliminary Development Plan (PDP). Specifically, this memo serves to document the overall drainage impacts associated with the proposed development. As each lot develops it will need to follow the Fort Collins Stormwater Criteria Manual and this Preliminary Drainage Memo. The proposed development site is comprised of two properties located east of N College Ave and north of Hickory Street. The overall site is roughly 13.45 acres in size. The site is situated around N Mason Street and Hibdon Court and will establish several lots for potential future development. The proposed development is comprised of three lots (Lot 1, Lot 2 & Lot 3), Mason Street widening and right of way dedication, and a single future development tract. The figure below shows the impacted properties. The subject properties are not located in a FEMA or City of Fort Collins regulatory floodplain. The site is currently zoned as Service Commercial District (C-S) and there are no structures on site. Figure 1: Aerial Photograph NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: MASON STREET INFRASTRUCTURE FORT COLLINS | GREELEY 2 | 3 The proposed development site is in the City of Fort Collins Dry Creek Master Drainage Basin. Detention requirements for this basin are to detain the difference between the 100-year development inflow rate and the historic 2-year release rate. In the Dry Creek Basin the 2-year historic release rate is 0.2 cfs/acre. With future development, the lots surrounding N Mason Street will be responsible for providing water quality treatment and Low impact development (LID) per the Fort Collins Stormwater Criteria Manual. This development will provide the interim condition for the Hickory Regional Detention Pond. The interim regional pond will be designed to maintain the existing detention pond volume (4 ac.ft.) as well as include any additional detention required for the future development of Lot 2 and areas included in the ‘A’ Basins. Detention and water quality treatment for all ‘B’ Basins will be determined with future development of Lot 3. The existing elevations in the area prevent an adequate slope through the regional pond in the interim. A series of dry wells will be installed to prevent stagnant water in the pond bottom. There is an existing outfall pipe at the southeast corner of the site that will be maintained with the interim regional pond. Runoff will be restricted and released just upstream of the existing site outfall to minimize the impact to downstream infrastructure. The release rate was determined based on the acreage of the proposed site. This is a conservative interim flowrate which does not take into account offsite basins. See the table below for a summary of the Hickory Regional Detention Pond. The site does receive notable runoff from adjacent properties which are detained in an existing detention pond onsite. The interim Hickory Pond will incorporate the existing detention volume and release rate in the interim condition. Additional analysis of these offsite flows will be performed with the Ultimate Hickory Regional Detention Pond and designed by the City of Fort Collins. Major Basin A Major Basin A encompasses the west side of N Mason Street and has a size of 11.28 acres. This basin includes the interim Hickory Regional Detention Pond (Lot 1) and area for future development (Lot 2). Basins A2-5 assume a future impervious value for Lot 2. Further analysis and adjustments will be provided with the future development of Lot 2. In the Interim condition, detention and standard water quality will be provided in the Interim Hickory Regional Detention Pond. Low Impact Development (LID) treatment will be required with the future development of Lot 2. Major Basin B Major Basin B encompasses the east side of N Mason Street and has a size of 2.16 acres. This basin includes a portion of the adjacent road and an area for future development (Lot 3). Basin B will follow the historic drainage paths east of Mason Street. A majority of the existing basin sheet flows to the adjacent property to the east. Runoff from Hibdon Court and a portion of N Mason Street is conveyed through a series of existing storm drains and roadside ditches to the site outfall location in the southeast corner of the site. Detention location and volume will be determined with the future development of Lot 3. Low Impact Development and water quality treatment will be required with the future development of Lot 3. NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: MASON STREET INFRASTRUCTURE FORT COLLINS | GREELEY 3 | 3 Interim Hickory Regional Detention Pond Summary Description Required Provided Notes Detention Pond 1.394 ac. ft. 19.23 ac. ft. Detention Volume required for ‘A’ Basins Water Quality Treatment 5478 ac. ft. 5,478 ac. ft. Standard water quality treatment for Major Basin A Required Release Rate 2.26 cfs 2.26 cfs Release rate per Dry Creek Basin Criteria (11.28ac*0.2cfs/ac) Notes: Table 1: Detention Pond Summary In summary, this Preliminary Drainage Memo addresses any potential stormwater changes associated with the proposed Mason Street Infrastructure project. Additional Water quality & LID treatment to meet the City requirements will be provided with the future development of Lots 2 & 3. All existing downstream drainage facilities are expected to not be impacted negatively by this development. The PDP complies with the governing City of Fort Collins Master Drainage Plans and Stormwater Criteria Manual. Sincerely, NORTHERN ENGINEERING SERVICES, INC. MASON RUEBEL, PE Project Engineer 1) LID Treatment for 'A' Basins will be determined with future development 2) Detention and water quality treatment for 'B' Basins will be determined with future development NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: N MASON STREET INFRASTRUCTURE FORT COLLINS | GREELEY APPENDIX APPENDIX A HYDROLOGIC COMPUTATIONS Runoff Coefficient1 Percent Impervious1 Project: Location: 0.95 100%Calc. By: 0.95 90%Date: 0.50 40% 0.20 2% 0.20 2% Basin ID Basin Area (sq.ft.) Basin Area (acres) Asphalt, Concrete (acres)Rooftop (acres) Gravel (acres) Undeveloped: Greenbelts, Agriculture (acres) Lawns, Clayey Soil, Flat Slope < 2% (acres) Percent Impervious C2*Cf Cf = 1.00 C5*Cf Cf = 1.00 C10*Cf Cf = 1.00 C100*Cf Cf = 1.25 A1 353,448 8.11 0.00 0.00 0.00 0.00 8.11 2% 0.20 0.20 0.20 0.25 A2 51,700 1.19 0.70 0.00 0.00 0.00 0.49 60% 0.64 0.64 0.64 0.80 A3 20,207 0.46 0.28 0.00 0.00 0.00 0.19 60% 0.65 0.65 0.65 0.81 A4 27,101 0.62 0.37 0.00 0.00 0.00 0.25 60% 0.64 0.64 0.64 0.80 A5 16,210 0.37 0.22 0.00 0.00 0.00 0.15 60% 0.64 0.64 0.64 0.81 A6 8,892 0.20 0.17 0.00 0.00 0.00 0.03 85% 0.84 0.84 0.84 1.00 A7 5,782 0.13 0.08 0.00 0.00 0.00 0.05 61% 0.65 0.65 0.65 0.81 A8 8,112 0.19 0.15 0.00 0.00 0.00 0.03 83% 0.82 0.82 0.82 1.00 B1 16,311 0.37 0.11 0.00 0.00 0.00 0.26 31% 0.42 0.42 0.42 0.53 B2 13,729 0.32 0.17 0.00 0.00 0.00 0.14 55% 0.61 0.61 0.61 0.76 B3 64,249 1.47 0.06 0.00 0.00 0.00 1.41 6% 0.23 0.23 0.23 0.29 A 491,452 11.28 1.97 0.00 0.00 0.00 9.31 19% 0.33 0.33 0.33 0.41 B 94,289 2.16 0.34 0.00 0.00 0.00 1.82 17% 0.32 0.32 0.32 0.40 Total 585,741 13.45 2.31 0.00 0.00 0.00 11.14 19% 0.33 0.33 0.33 0.41 DEVELOPED RUNOFF COEFFICIENT CALCULATIONS Asphalt, Concrete Rooftop Gravel Streets, Parking Lots, Roofs, Alleys, and Drives: Character of Surface:N Mason Street Infrastructure Fort Collins M. Ruebel May 16, 2023 Lawns and Landscaping: Combined Basins 2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins Stormwater Manual (FCSM). Lawns, Clayey Soil, Flat Slope < 2% USDA SOIL TYPE: C Undeveloped: Greenbelts, Agriculture Composite Runoff Coefficient2 1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM. Notes: 1) Basin A2, A3, A4, & A5 use an assumed impervious percentage for future development. ####### Where: Length (ft) Elev Up Elev Down Slope (%) Ti 2-Yr (min) Ti 10-Yr (min) Ti 100-Yr (min) Length (ft) Elev Up Elev Down Slope (%)Surface n Flow Area3 (sq.ft.) WP3 (ft)R (ft)V (ft/s) Tt (min) Max. Tc (min) Comp. Tc 2-Yr (min) Tc 2-Yr (min) Comp. Tc 10-Yr (min) Tc 10-Yr (min) Comp. Tc 100- Yr (min) Tc 100-Yr (min) a1 A1 300 1.00%29.15 29.15 27.53 1,063 0.10%Valley Pan 0.02 6.00 10.25 0.59 2.20 8.06 17.57 37.21 17.57 37.21 17.57 35.59 17.57 a2 A2 130 2.00%7.74 7.74 5.02 N/A Valley Pan 0.02 6.00 10.25 N/A N/A 0.00 10.72 7.74 7.74 7.74 7.74 5.02 5.02 a3 A3 100 2.00%6.75 6.75 4.35 N/A Valley Pan 0.02 6.00 10.25 N/A N/A 0.00 10.56 6.75 6.75 6.75 6.75 4.35 5.00 a4 A4 100 2.00%6.79 6.79 4.40 N/A Gutter 0.02 3.61 19.18 N/A N/A 0.00 10.56 6.79 6.79 6.79 6.79 4.40 5.00 a5 A5 100 3.00%5.91 5.91 3.82 100 1.00%Swale (4:1)0.02 4.00 8.25 0.48 6.13 0.27 11.11 6.18 6.18 6.18 6.18 4.09 5.00 a6 A6 21 2.20%1.74 1.74 0.66 182 0.50%Gutter 0.02 3.61 19.18 0.19 2.31 1.31 11.13 3.06 5.00 3.06 5.00 1.97 5.00 a7 A7 21 2.20%2.97 2.97 1.91 120 2.50%Gutter 0.02 3.61 19.18 0.19 5.16 0.39 10.78 3.36 5.00 3.36 5.00 2.29 5.00 a8 A8 21 2.20%1.86 1.86 0.66 190 2.00%Gutter 0.02 3.61 19.18 0.19 4.62 0.69 11.17 2.55 5.00 2.55 5.00 1.34 5.00 b1 B1 35 2.00%5.95 5.95 5.03 200 0.10%Swale (4:1)0.02 4.00 8.25 0.48 1.94 1.72 11.31 7.67 7.67 7.67 7.67 6.75 6.75 b2 B2 35 2.00% 4.34 4.34 3.01 200 0.50% Swale (8:1) 0.02 8.00 16.12 0.50 4.40 0.76 11.31 5.10 5.10 5.10 5.10 3.77 5.00 b3 B3 281 0.50%34.32 34.32 32.04 N/A Gutter 0.02 3.61 19.18 N/A N/A 0.00 11.56 34.32 11.56 34.32 11.56 32.04 11.56 Notes S = Longitudinal Slope, feet/feet R = Hydraulic Radius (feet) n = Roughness Coefficient V = Velocity (ft/sec) WP = Wetted Perimeter (ft) DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Location: Maximum Tc:Overland Flow, Time of Concentration: Channelized Flow, Velocity:Channelized Flow, Time of Concentration: N Mason Street Infrastructure Fort Collins M. Ruebel May 16, 2023 Project: Calculations By: Date: Design Point Basin ID Overland Flow Channelized Flow Time of Concentration (Equation 3.3-2 per Fort Collins StormwaterManual)1.87 1.1 ∗ 1.49 ∗ /∗(Equation 5-4 per Fort Collins StormwaterManual) 180 10 (Equation 3.3-5 per Fort Collins StormwaterManual) ∗ 60 (Equation 5-5 per Fort Collins 1) Add 4900 to all elevations. 2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min. 3) Assume a water depth of 6" and a typical curb and gutter per Larimer County Urban Street Standard Detail 701 for curb and gutter channelized flow. Assume a water depth of 1', fixed side slopes, and a triangular swale section for grass channelized flow. Assume a water depth of 1', 4:1 side slopes, and a 2' wide valley pan for channelized flow in a valley pan. Tc2 Tc10 Tc100 C2 C10 C100 I2 I10 I100 QWQ Q2 Q10 Q100 a1 A1 8.11 17.6 17.6 17.6 0.2 0.2 0.3 1.7 2.9 6.0 1.4 2.8 4.8 12.2 a2 A2 1.19 7.7 7.7 5.0 0.6 0.6 0.8 2.5 4.2 10.0 0.9 1.9 3.2 9.5 a3 A3 0.46 6.7 6.7 5.0 0.6 0.6 0.8 2.6 4.4 10.0 0.4 0.8 1.3 3.7 a4 A4 0.62 6.8 6.8 5.0 0.6 0.6 0.8 2.6 4.4 10.0 0.5 1.0 1.8 5.0 a5 A5 0.37 6.2 6.2 5.0 0.6 0.6 0.8 2.7 4.6 10.0 0.3 0.6 1.1 3.0 a6 A6 0.20 5.0 5.0 5.0 0.8 0.8 1.0 2.9 4.9 10.0 0.2 0.5 0.8 2.0 a7 A7 0.13 5.0 5.0 5.0 0.6 0.6 0.8 2.9 4.9 10.0 0.1 0.2 0.4 1.1 a8 A8 0.19 5.0 5.0 5.0 0.8 0.8 1.0 2.9 4.9 10.0 0.2 0.4 0.7 1.9 b1 B1 0.37 7.7 7.7 6.7 0.4 0.4 0.5 2.5 4.2 9.1 0.2 0.4 0.7 1.8 b2 B2 0.32 5.1 5.1 5.0 0.6 0.6 0.8 2.9 4.9 10.0 0.3 0.5 0.9 2.4 b3 B3 1.47 11.6 11.6 11.6 0.2 0.2 0.3 2.1 3.6 7.3 0.4 0.7 1.2 3.1 Fort Collins Project: Location: Calc. By: Flow (cfs) Intensity, I from Fig. 3.4.1 Fort Collins Stormwater Manual Rational Equation: Q = CiA (Equation 6-1 per MHFD) DEVELOPED DIRECT RUNOFF COMPUTATIONS Intensity N Mason Street Infrastructure M. Ruebel May 16, 2023 Design Point Basin Area (acres) Runoff CTc (Min) Date: NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: N MASON STREET INFRASTRUCTURE FORT COLLINS | GREELEY APPENDIX APPENDIX B DETENTION POND COMPUTATIONS Date:05/16/23 Pond No.: A1 100-yr WQCV 5478 ft3 0.41 Quantity Detention 45026 ft3 11.28 acres Total Volume 50504 ft3 2.26 cfs Total Volume 1.159 ac-ft Time Time Ft.Collins 100-yr Intensity Q100 Inflow (Runoff) Volume Outflow (Release) Volume Storage Detention Volume (mins) (secs) (in/hr) (cfs) (ft3) (ft 3) (ft 3) 5 300 9.95 46.0 13805 677 13128 10 600 7.72 35.7 21422 1354 20068 15 900 6.52 30.2 27138 2030 25108 20 1200 5.60 25.9 31079 2707 28371 25 1500 4.98 23.0 34547 3384 31163 30 1800 4.52 20.9 37627 4061 33567 35 2100 4.08 18.9 39625 4738 34888 40 2400 3.74 17.3 41512 5414 36098 45 2700 3.46 16.0 43205 6091 37114 50 3000 3.23 14.9 44814 6768 38046 55 3300 3.03 14.0 46243 7445 38799 60 3600 2.86 13.2 47617 8122 39495 65 3900 2.72 12.6 49060 8798 40261 70 4200 2.59 12.0 50309 9475 40833 75 4500 2.48 11.5 51613 10152 41461 80 4800 2.38 11.0 52834 10829 42005 85 5100 2.29 10.6 54013 11506 42507 90 5400 2.21 10.2 55192 12182 43010 95 5700 2.13 9.9 56150 12859 43290 100 6000 2.06 9.5 57163 13536 43627 105 6300 2.00 9.2 58272 14213 44060 110 6600 1.94 9.0 59216 14890 44326 115 6900 1.89 8.7 60312 15566 44746 120 7200 1.84 8.5 61269 16243 45026 Input Variables Results Design Point Required Detention Volume Design Storm Detention Pond Calculation | FAA Method Project: Project Location: Calculations By: Mason Street Infrastructure Fort Collins, Colorado M. Ruebel Detention Pond Developed "C" = Area (A)= Max Release Rate = 1 Project: Date: Pond No.: 4,976.00 5,478.00 cu. ft. 4,976.08 4,976.08 5,478.00 cu. ft.0.08 ft. 4,908.00 50,504 cu. ft. 4,976.73 Max. Elev. Min. Elev. cu. ft. acre ft cu. ft. acre ft 4,976.00 N/A 0 0.00 0.00 0.00 0.00 0.00 4,977.00 4,976.00 138,772 1.00 69,386.00 1.59 69,386.00 1.59 4,978.00 4,977.00 246,557 1.00 192,664.50 4.42 262,050.50 6.02 4,979.00 4,978.00 291,935 1.00 269,246.00 6.18 531,296.50 12.20 4,980.00 4,979.00 320,713 1.00 306,324.00 7.03 837,620.50 19.23 Elev at 100-yr Volume: Crest of Pond Elev.: Volume at Grate: Grate Elevation: Storage and Water Quality Pond 1 Project Number: Project Location: Calculations By:1 Water Quality Depth: 100-yr Volume: STAGE STORAGE CURVE Contour Contour Surface Area (ft2) Depth (ft) Incremental Volume Cummalitive Volume Pond Stage Storage Curve 1971-001 Fort Collins, CO M. Ruebel Elev at WQ Volume: N Mason Street Infrastructure May 17, 2023 Pond Outlet and Volume Data Outlet Elevation:Water Quality Volume: 1 NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: N MASON STREET INFRASTRUCTURE FORT COLLINS | GREELEY APPENDIX APPENDIX C WATER QUALITY COMPUTATIONS Project: Calc. By: Date: 11.28 <-- INPUT from impervious calcs 19%<-- INPUT from impervious calcs 0.19 <-- CALCULATED 40 hours <-- from FCSM Figure 5.4-1 1.00 <-- from FCSM Figure 5.4-1 0.11 <-- MHFD Vol. 3 Equation 3-1 0.13 <-- FCSCM Equation 7-2 5,478 <-- Calculated from above 0.08 <-- INPUT from stage-storage table 1.18 <-- CALCULATED from Equation EDB-3 WQCV (watershed inches) = WATER QUALITY POND DESIGN CALCULATIONS Water Quality for Detention Pond N Mason Street Infrastructure M. Ruebel May 16, 2023 Required Storage & Outlet Works Basin Area (acres) = Basin Percent Imperviousness = Basin Imperviousness Ratio = Drain Time = Drain Time Coefficient = WQCV (ac-ft) = WQ Depth (ft) = Area Required Per Row, a (in 2) = WQCV (cu. ft.) = NORTHERNENGINEERING.COM | 970.221.4158 FORT COLLINS | GREELEY NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE MEMO: N MASON STREET INFRASTRUCTURE FORT COLLINS | GREELEY APPENDIX MAP POCKET DR1 – DRAINAGE EXHIBIT SELECF ESMVAULTELECVAULTCABLEVAULTELECVAULTELECVAULTELECCABLECABLEVAULTELECCELECELECELECCTVCTVCTVOHU OHU OHU OHU E E EEOHUEEXXXXXXCTVCTVCTVCTVCTVCTVCTVCTVCTVOHUOHU XXXXXXXXXXXXXXCTVCTVCTVCTV CTVCTVCTV CTVCTVGGGGGGGGCTVCTVGGSSSSSSSSSSSSSS SS SS SS SS SSH2OH2OARVH2OH2ODHYDSFESFESWWWWWWWWWWWWWWWWWWWXXXXXXXXXXXXXOHUOHUOHUOHUOHUXXXXXXXXWWWWWWWWWWWWWWWWWWWX X WWWWWSSSS SS SS SS SS SS SS DELECXXXXXX X X X X WWWXXXXXX X X X SS SS SS SS SS SS SS SS ST ST ST ST ST ST STSTSTSTSTSTST8" W8.11 ac.A10.46 ac.A31.19 ac.A20.32 ac.B20.37 ac.B1b1a10.13 ac.A7a70.20 ac.A60.19 ac.A81.47 ac.B3a6a8b2NCFS LLC300 HICKORY STREETFORT COLLINS, COQR INC.280 HICKORY STREETFORT COLLINS, COQR INC.200 HICKORY STREETFORT COLLINS, COR AND S HOLDINGS1235 N. COLLEGE AVENUEFORT COLLINS, COHAINES BRANDON KUHRT 1295N. COLLEGE AVENUE FORTCOLLINS, COGRATITUDE LLC1303 N. COLLEGE AVENUEFORT COLLINS, COHOYT JOHN R1307 N. COLLEGE AVENUEFORT COLLINS, CO1311 N. COLLEGE LLCHIBON CT.FORT COLLINS, CO1311 N. COLLEGE LLC1311 N. COLLEGE AVENUEFORT COLLINS, COWANKIER LANCE1401 N. COLLEGE AVENUEFORT COLLINS, COWOOD RONALD G/ JENNIFERL/ WILLARD E122 HIBDON COURTFORT COLLINS, COTHOMPSON PROPERTIES LLC1319 N. COLLEGE AVENUEFORT COLLINS, COD AND S MOTELS INC1405 N. COLLEGE AVENUEFORT COLLINS, CORICHEY ADDIE1601 N. COLLEGE AVENUEFORT COLLINS, CO MASON STREET N MASON STREETHICKORY STREET20' WATERLINE ANDROW EASEMENTREC. NO. 850401136' UTILITYEASEMENTBK 1658 PG 7466' UTILITY EASEMENTPER PLAT OF BREWSUB. FIRST FILING10' UTILITY EASEMENTBK 1658 PG 74645' ROWBK 1743 PG 63210' UTILITYEASEMENTBK 1572 PG 32245' ROWBK 1743 PG 63210' UTILITYEASEMENTBK 1572 PG 32153.5' PERPETUAL EASEMENT FORELECTRIC POWER TRANSMISSION LINEBK 923 PG 282HIBDON COURT24' ACCESS EASEMENTREC. NO. 2014003629230' EASEMENT FOR ROAD PURPOSESBK 1143 PG 187(EXCEPTION PARCEL PIB FCIF25205400)20' RIGHT OF WAY EASEMENTBK 1114 PG 55530' UPRR TRACK EASEMENTBK 2027 PG 988REC. NO. 98091992REC. NO. 20060019203UNION PACIFIC RAILROADDRY WELL (TYP.)HICKORY REGIONALDETENTION PONDSWALE STORM DRAIN LINE A(INTERIM POND OUTFALL)STORM EXTENSION WATER QUALITY OUTLETSTRUCTURE WITHRESTRICTOR PLATE0.62 ac.A40.37 ac.A5a5LOT 1LOT 2LOT 3SWALE20' UTILITY EASEMENTPER VALLEY STEEL &WIRE SUBDIVISION PLAT6' UTILITY EASEMENTREC. NO. 2006-0068858REC. NO. 2006-0068859CURB CUT &SIDEWALK CHASEROW AGREEMENT WITH UNIONPACIFIC RAILROAD FOR THEPURPOSE OF IRRIGATION DITCH &IRRIGATION WATER UNSPECIFIEDWIDTH BK 813 PG 27 TO BEVACATED PER LANGUAGE FOUNDON PAGE 28 OF SAID DOCUMENTDR1DRAINAGE EXHIBIT9CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOUDIG, GRADE, OR EXCAVATE FOR THE MARKING OFUNDERGROUND MEMBER UTILITIES.CALL UTILITY NOTIFICATION CENTER OFCOLORADOKnow what'sbelow.before you dig.CallRNORTH( IN FEET )1 inch = ft.Feet0505050100150SheetThese drawings are instruments of service provided by Northern Engineering Services, Inc. and are not to be used for any type of construction unless signed and sealed by a Professional Engineer in the employ of Northern Engineering Services, Inc.NOT FOR CO N S T R U C T I O N REVIEW SE T of 9MASON STREET INFRASTRUCTURE PROPOSED CONTOURPROPOSED STORM SEWERPROPOSED SWALEEXISTING CONTOURPROPOSED CURB & GUTTERPROPERTY BOUNDARYPROPOSED INLETADESIGN POINTFLOW ARROWDRAINAGE BASIN LABELDRAINAGE BASIN BOUNDARYPROPOSED SWALE SECTION11NOTES:1.REFER TO THE PRELIMINARY DRAINAGE REPORT, DATED MAY 24, 2023 FORADDITIONAL INFORMATION.ALEGEND:FOR DRAINAGE REVIEW ONLYNOT FOR CONSTRUCTIONDEVELOPED DRAINAGE SUMMARYDesignPointBasin IDTotalArea(acres)C2C1002-Yr Tc(min)100-Yr Tc(min)Q2(cfs)Q100(cfs)a1A18.1140.200.2517.5717.572.8012.19a2A21.1870.640.807.747.741.889.48a3A30.4640.650.816.756.750.783.72a4A40.6220.640.806.796.791.044.97a5A50.3720.640.816.186.180.642.98a6A60.2040.841.005.005.000.492.03a7A70.1330.650.815.005.000.251.07a8A80.1860.821.005.005.000.431.85b1B10.3740.420.537.677.670.391.79b2B20.3150.610.765.105.100.542.37b3B31.4750.230.2911.5611.560.713.10Interim Hickory Regional Detention Pond VolumeContour Elev.Contour Surface Area (ft2)Cummalitive Volumecu. ft.acre ft498032071383762119.2P:\1971-001\Dwg\Sheets_Mason Street\Drainage\1971-001_DRNG_Mason Street.dwg, 5/24/2023 8:24:17 AM, 1:1