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HomeMy WebLinkAboutDrainage Reports - 07/14/2016City of'Ft .Cd1i ed Plans Approved By Date INITQ N-R CONSU LTI N.G GROUP February 17, 2016 Mr. Wes Lamarque Fort Collins Utilities — Stormwater 700 Wood Street Fort Collins, CO 80522 Re: FCHA Villages on Redwood Final Storm Drainage Report Amendment Dear Wes, Please ,accept the following letter on behalf of the Fort Collins Housing Authority (FCHA) as an amendment to the "Final Drainage Report for Village on Redwood" prepared by Interwest Consulting Group, dated December 11, 2015. The purpose of this amendment is to document the revised drainage aspects in response to the amended Low Impact Development (LID) ordinance (Ordinance No. 007, 2016) and to demonstrate ability to comply with the City's current stormwater requirements. INTRODUCTION All ,site descriptions within the original report are consistent with this amendment. No site, buildings, walks, etc are proposed to be adjusted with this amendment. Under the current LID ordinance, proposed project sites are required to: Treat at least 75% of any newly developed or redeveloped area using one or a combination of LID techniques, or Treat at least 50% of any newly developed or redeveloped area using one or a combination of LID techniques when 25% of private drivable surfaces are permeable. In response to the current LID requirements, FCHA has requested that we revise the storm drainage design to satisfy the LID requirements by other techniques without permeable pavers. As -you may recall, we developed and presented preliminaryoptions and calculations for LID alternatives. The exhibits and calculations attached have been further detailed in reference to the approach we discussed to satisfied the current LID requirements. LOW IMPACT DEVELOPMENT TECHNIQUES With the removal of permeable pavers, the LID requirements are proposed to be satisfied by treating storm runoff by two (2) rain gardens. All runoff from Basins DI, D2, and 153 will be treated through a 1,200 sq-ft rain garden located within site's central green area. The rain garden within the detention pond is proposed to be expanded to 550 sq-ft to treat.all of Basin D4. All LID calculations were prepared in reference to Lot 1 only. Tract A is not proposed to have any development activity and was described by Basin D7. A small portion of Lot 1, in the southwest corner, is within Basin D7 and does not contain any paved driving surfaces. It is assumed that the roof areas would be treated by the grass buffer and existing 1218 W. ASH, STE. A, WINDSOR, COLORADO 60550 TEL. 970.674.3300 - FAX 970.674.3303 IRTRRMR6T CONSULTING GROUP February 17, 2016 Mr. Wes Lamarque Fort Collins Utilities - Stormwater 700 Wood Street Fort Collins, CO 80522 Re: FCHA Villages on Redwood Final Storm Drainage Report Amendment Dear Wes, Please accept the following letter on behalf of the Fort Collins Housing Authority (FCHA) as an amendment to the "Final Drainage Report for Village on Redwood" prepared by Interwest Consulting Group, dated December 11, 2015. The purpose of this amendment is to document the revised drainage aspects in response to the amended Low Impact Development (LID) ordinance (Ordinance No. 007, 2016) and to demonstrate; ability to comply with the City's current stormwater requirements. INTRODUCTION All site descriptions within the original report are consistent with this amendment. No site, buildings, walks, etc are proposed to be adjusted with this amendment. Under the current LID ordinance, proposed project sites are required to: Treat at least 75% of any newly developed or redeveloped area using one or a combination of LID techniques, or Treat at least 50% of any newly developed or redeveloped area using one or a combination of LID techniques when 25% of private drivable surfaces are permeable. In response to the current LID requirements, FCHA has requested that we revise the storm drainage design to satisfy the LID requirements by other techniques without permeable pavers. As you may recall, we developed and presented preliminary options and calculations for LID alternatives. The exhibits and calculations attached have been further detailed in reference to the approach we discussed to satisfied the current LID requirements. LOW IMPACT DEVELOPMENT TECHNIQUES With the removal of permeable pavers, the LID requirements are proposed to be satisfied by treating storm runoff by two (2) rain gardens. All runoff from Basins DI, D2, and D3 will be treated through a 1,260 sq-ft rein garden located within site's central green area. The rain garden within the detention pond is proposed to be expanded to 550 sq-ft to treat all of Basin D4. All LID calculations were prepared in reference to Lot 1 only. Tract A is not proposed to have any development activity and was described by Basin D7. A small portion of Lot 1, in the southwest corner, is within Basin D7 and does not contain any paved driving surfaces. It is assumed that the roof areas would be treated by the grass buffer and existing 1218 W. ASH, m. A, WINbsOR„COLORADO 80550 TEL. 970.674.3300 - FAX 970.674.3303 FCHA Villages on Redwood Final Storm Drainage Report Amendment February 17, 2016 Page 2 of 2 constructed wetland west of the proposed residential units. The proposed LID provides stormwater treatment to 75.6% of the developed site and satisfies the LID ordinance requirements. The rain gardens are designed to directly spill into the detention areas for events beyond the capacity of the rain garden. The rain garden are designed with full MItration sections, without underdrains, and have a maximum depth of 12 inches. All calculations are attached for reference. DETENTION VOLUMES With the removal of the permeable pavers, near is an increase in % impervious, requiring additional detention volume. The basins draining to the detention pond originally estimated the site to be 46.7% impervious (including the pavers). Removing the pavers causes an estimate increase of 3.2% impervious for an overall 49.9%o'impervious. This increase in impervious area requires an additional 0.023 acre-ft of detention storage. The previous design provided 0.0402 acre-ft of detention storage and this revision provides 0.0425 acre-ft. This was achieved by providing addition detention storage within the site's central green area All calculations are attached for reference. Thank you in advance for your consideration and if you have any questions or comments please contact me at (970) 347-8917. AP Attachments — EXISTING STORMWATER DETENTION POND TREE BRIE I I l RLE7WOIP I� 1 \II _ /EFII0TX4 -4110FIVIm" D7 it mlT mrsrRUCnpI IEMfE. W/ WT RNC PEST PRMERTY I (sEE EPRF6 WAI TRACTA D5 OR ARM ME Obi ,ililfIrdMA r ■ FIR l `all ♦ e �aS", Ja O $ION O M 1. THECITY STORMWATEA DEPARTMENT EROSIONCdJI«OLWSRECTOR MUST BE NOTREO AT LUST M HOURS 5 THE PROPFRKMVSi BE WATERED AND MNNTAWEOATALLTMES mIgWGCIXiSTRUCTgN ACTN'TES SO 70 PRIIXi TOANYCCNSIRUCipN ON T16.JTE PREVENT WINOCAUEED EROSION KL LAND MI FFJBBWG ACTNTDE55«.LLL BE MMEOMTELY DISCONTIW,£OYMEN 2 ALL NEWIREL omm MUST BE MBTM I Pn IMROR TO.IN, .Vp OBTUpBWG ACTMTY6POCI4RWC, BTREI FUGfT'f DUSTIMPACTS ADJA C ENT PROPEPTES AS CETERMIED BY THE CNY ENGI.NEERI VG DE PARTMENT GgApNG.ETC)IIIREOLWEp ER05gN CONTTm.MEA9Re5 BE INSTALIIDAT T«EANIMP(M1EiYEW 6 ALL TENFORARY 6TRTICTURJI EROSON CONTROL MEA,AME5 MD BE RESPECTED AND REPAIRED OR THE CONSTihICT)ONgO1JENCEAS IHUCATEDIN TPEAPPROVEDPR0ER 5C1E.➢IAE. CCN5Tf6KiNJN fiANS. RECONSTRUCTED AS NECESSARI APTEF GCN INNOFF EVENT AND EVERY 14 DAY S W ORDER TO A5516E ANO EROSION CONTROLREPORT, CONTINUEp PE{6ORMAKEOF TIEIR INIENDEO FUNCT10N.gLL gETNfED SEGMENTS. PARTICULARLYTNO5EQ1 3, PPEi115TURBANCE VEGETATION SNNL BE('ROTECITDANO TETNNEO WIEREJEi Po551BLE pEMOVAL OR NSTUR WEOF VE E%ISTNG GETATIONSHALL BE LIMPED TOTE AREA REOUIRED FOR IMMMIATE PAVED gOADWAY $UpFAC3. E«ALLBE REMOYFDANOm5fV5EOGE W ANANNFR AND LOCATION $OASNOT TO CAUSE THEIR RELEASE INTO ANT ORNNAGEWAY. CONSTRUCTION OPEPATpNS. AND MR THE RHOFEBT%tACT PERI000F THE 7, NO SOIL STOCNRL£ SHALL FEED TEN 1101 FEET IN HEIGHT. NJ. SOL STOE:i,L 55«ALL BE pr<,M TEO EREW 4. ALL SOILS E%NSED WRING LAND d5T1RBING ACTVNVISTR!PPINGGPAOWG. UTILITf INSTLL1ATpN5, -IMKPIUNG. FIWNG. ETC,) SHALL BE RE➢T IN A ROUGHENED CONDITION BY RIMING OR gSKWG ALONG LAND SEDIMENTT EEORT BYSURFACE ROUGHENING, WAT EKING AND PERIMETER SILT FENCWG. ANY SOLL MOCK 11-F REMNNWG AFPER SO DAYS SHALL BE SEEDED AND MULCHED CON.UNR MLLCH,VEGETATION, OR EITHER PERMANENT EROSION CONROI- 0 NSTNIED. NO 51 IN 6. CITYORGNANCE RtOHIINTSTMETRACgNG.DROPPING. 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CHECKED BY: 6bnwm MIRY m CHECKED BY: TNI4Eq� m PROF NO. 121T11200 CHECKED SY: PnMRMRquM pp CHECKED BY: EnvM. raM PYc r D.R.5 OF 22 CHECKED BY: oAx � k i 2 \ LL wz #*7� !US !|2 7 m �f | | | | ■ . . ! .��...� ! � £|- ! )|||!|||!!!|!| k ' �<��<f<{<■�«- ��,�-,-�-��° . . .. . �� J� ■®#klmkE§■ER# f &=,r;rE®■,�§! }\ ............. )� §2!!f/§,elK■; � ■!!■,-� $al;� J¥�,��};}°�w#■§ }��),■■■�,2!}y2 J} §!m§■!§§§§!§§ Ji2k}§|!)EK5?P #ƒ� |f §eR FCHA - Villages on Redwood Low Impact Development Design Engineer: T.Alva Design Firm: Interwest Consulting Group Project Number: 1237-112-00 Date: February 17, 2016 DESIGN CRITERIA Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, January 2010 City of Fort Collins - Ordinance No. 007, 2016 - Treat at least 75% of any newly developed or redeveloped area using one or a combination of LID techniques, or - Treat at least 50% of any newly developed or redeveloped area using one or a combination of LID techniques when.25%, of private driveable surfaces are permeable. Low Impact Development Summary Pavement Area Summary Total Paved Area: 49,417 sqft Permeable Paver Area: 0 sqft Percent Pavement Area as Developed Area Summary Total Site Area: Proposed Area of Pavers: Additional Area Treated by Pavers: Total Area Treated by Pavers: Area to be Treated by Rain Garden: Percent Site Area Treated by LID:. 251,435 sqft 0 sqft 0 sqft 0 sqft 178,311 sqft 190,155 sqft 75.6% 11 Design Procedure Form: Rain Garden (RG) 11 Designer: Company: Date: Project: Location: J. Claeys Interwast Consulting Group February 17. 2016 Villages st Redwood Basins D1-D3 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, I, I, = 50.0 (100 % 1 all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = IJ100) = 0.500 C) Water Quality Capture Volume (WQCV) fora 12-hour Drain Time WQCV = 0.17 watershed inches ( WQCV= 0.8' (0.91' ic- 1 A9' 1'. 0.78' 1) D) Contributing Watershed Area (Including rain garden area) Area - 130,104 sq ft E) Water Quality Capture Volume (WQCV) Design Volume Vwacv- cub Vol = (WQCV 112)' Area F) For Watersheds Outside of the Denver Region, Depth of ds = 0.43 In Average Runoff Producing Storm G) For Watersheds Oulaide of the Denver Region, Vwocv cares= 41;7f18d1 .cult Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume Vexvuase= cu ft (Only 8 a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum) Dwocv= 12 in B) Rain Garden Side Slopes (Z= 4 min., horiz. disc per unit vertical) Z = 4.O1) ft / ft (Use "0" 8 rain garden has vertical walls) C) Mlmimum Flat Surface Area Av„ = 1193 sq ft D) Actual Flat Surface Area A,.1= 1202 sq It E) Area at Design Depth (Top Surface Area) Arm = 1856 sq ft F) Rain Garden Total Volume Vr 1,529 cu It (V*-((Arm'Ax )/2)'Depth) 3. Growing Media Choose One p Is- Rain Garden Growing Media ® Other (Explain): City of Fort Collins Standard Rain Garden Section 4. Underdrain System A) Are underdralns provided? Oahe Orla O YES (10 No B) Underdrain system orifice diameter for 12 hour drain time I) Distance From Lowest Elevation of the Storage Y. N/A ft Volume to the Career of the OrKce Iq Volume to Drain in 12 Hours V0112= MIA cu ft IN) Orifice Diameter, 3/8" Minimum On = NIA in 1237-112-00 UD-BMP_V3.03 (Basins D1-D3).xlsm, RG 2/1612016. 2:57 PM Design Procedure Form: Rain Garden(RG) Sheet 2 of 2 Designer: J. Cleary. Company: Interwest Consulting Group Date: February 17, 2016 Project: Villages at Redwood Location: Basins 01-03 5. Impermeable Geomembrane Liner and Gectextile Separator Fabric Choose One — Q YES A) Is an impermeable Ilner provided due to proximity Q NO of structures or groundwater contamination? b. Inlet / Outlet Control r Choose One Q Sheet Flow. No Energy Disslpadan Repulrwi A) Inlet Control Q Concentrated Flow. Energy Dissipation Proviced Oxose One 7. Vegetation Seed (Plan for heguent weed control) Q plantings �0 p Sand Waco or other High Inaltrabun Sod S. Irrigation Chose One Q YES A) Will the rain garden be inigated? ONO Notes: 1237-112-00 UD-SMP_v3.03 (Basins D1-D3).xlsm, RG 2/16/2016, 2:57 PM Design Procedure Form: Rain Garden(RG) Sheet 1 of 2 Designer: J. Claeys Company: Interwest Consulting Group Data: February 17, 2016 ProJact: Villages at Redwood Location: Basin D4 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, 1„ 1„ = 65.8 % (100% d all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (I = 1,/100) = 0.868 C) Water Quality Capture Volume(WOCV)fora 12-hour Chun Time WOCV= 0.21 watershed inches i WQCV= 0.8' (0.91' 1°- 1.19' it a 0.78' 1) DI Contributing Watershed Area (Including rain garden area) Area = 48.207 sq it E) Water Duality Capture Volume (WOCV) Design Volume Vwocv = Cu It Val = (WQCV 112) - Area F) For Watersheds Outside of the Denver Region, Depth of ds = 0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region. VWcxv ones = 826.8 cu ft Water Quality Capture Volume (WOCV) Design Volume H) Lear Input of Water Quality Capture Volume (WQCV) Design Volume Vwrx:v uses = cu ft (Only if a different WQCV Design Volume Is desired) 2. Basin Geometry A)WQCV Depth (12-inch maximum) DWwv= 12 In B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 —ft/ft (Use'0' 8 rain garden has vertical wells) C) Mlmimum Flat Surface Area Ave = 551 sq ft Of Actual Flat Surface Area Arw„a = 556 sq ft E) Area at Design Depth (Top Surface Area) Arv, = 1063 aq If F) Rain Garden Total Volume Vr= 810 cu it (Vr ((A,. - A.vm.) / 2) „ Depth) 3. Growing Media r Ofaous 0. O 18" Rain Garden Growing Media ® Other (Explain): Garden Section City of Fort Collins Standard Rath 4. Undamraln System r Choose One 0 A) Are undendralns provided? Q NO 8) Undardraln system entries diameter for 12 hour drain Isms I) Distance From Lowest Elevation of the Storage y= WA ft Volume to the Center of the Odfice if) Volume to Drain in 12 Hours Vol,, = WA cu It !it) Orifice Diameter, 318„ Minimum Do= WA In 1237-112-00 UD-BMP_v3.03 (Basins D4).xlsm, FIG 2/16/2016. 2:58 PM Design Procedure Form: Rain Garden (RG) Sheet 2 of 2 Designer: J. Claeys Company: Intemest Consulting Group Date: February 17, 2016 Project: Villages at Redwood Location: Basin D4 5. Impermeable Geomembrane Leer and Geotextile Separator Fabric Choose One O YES A) Is an impermeable liner provided due to proximity NO of structures or groundwater contamination? 6. Inlet / Outlet Control Ir Choose One Q Sheet I'll". No EMrtJy D irsip bore Required A) Inlet Control Q Concentrated Flaw- Energy Doslpatim Provided Choose One i vegetation a Seed (Plan for frequent weed control) p Plantings Q Sand Grown or Other High Infiltration Sod 6. Irrigator, ChooseOne NO LQ A) Will the rain garden be irrgated? NO Notes: 1237-112-00 UD-BMP_v3.03 (Basins D4).xlsm, RG 211612016, 2:58 PM Village on Redwood 100-vr Detention Volume-: FAA Method Design Engineer: T. Alva Design Firm: Intenvest Consulting Project Number. 1237-112-00 Date: February 17, 2016 DESIGN CRITERIA. Urban Sion Drainage Criteria Manual, urban D2lnsge and Flood Control OlWcL June 2001 (devised ApHl 2008) City of Fort Collins-. Storm Water Criteria Manual Detention Volume Calculation Runoff Coefficient (C) - " "0.62 Frequency Factor,(Cr) 1.25 1 Required Detention Adjusted Runoff Coefficient (CC r) 0.78 fta acre-ft Area (A)! 4.92 acres "1849476 - "0.4251 " Allowed Release Rate _ _6.96 ... _ cis 100-yr Accumulative Release Detained Detained Time Intensitv Qiw Runoff Volume Volume Volume Volume 5 9.95 3Z94 11,381.81 2,068.00 9,293.81 0.2134 10 7.72 29.44 17,661.82 4,176:00 13,495.82 0.3096 15 6.52 24.86 22,374.68 6,264.00 16,116.68 0.3699 20 5.60 21:35 25.623.36 8,352.00 17,271.36 0.3965 25 4.98 18.99 28,483.11 10'"0.00 18,043.11 0.4142 30 4.52 1723 31,022.57 12,628.00 18A94.57 OA246 35 4.08 15.56 32,669.78 14,616.00 18,053.78 0.4145 40 3.74 14.26 34,225:49 16,704.00 17,521.49 0.4022 45 3.46 13.19 35,621.05 18,792.00 16,829.05 0.3863 50 3.23 12.32 36,947.97 20,880.00 16,067.97 0.3689 65 3.03 11.55 38,126.19 22,968.60 15,158.19 0.3480 60 2.86 10.91 39,258.65 25,056.00 14,202.65 0.3260 65 2.72 10.37 40,446.30 27,144.00 13,304.30 0.3054 70 2.59 9.88 41,477.81 29,232.00 12,245.81 0.2811 75 2.48 9.46 42,553.08 31,320.00 11,233.08 0,2579 80 2.38 9.07 43,559.71 33,408.00 10,151.71 0.2331 85 2.29 8.73 44,532.03 36,496.00 9,036.03 0.2074 90 2.21 8.43 45,504.34 37,584.00 7,920.34 0.1818 95 2.13 8.12 46,293.63 39,672.00 6,621.63 0.1520 100 2.06 7.85 47,128.68 41,760.00 5,368.68 0.1232 106 2.00 7.63 4043.60 43,848.06 4,195.80 0.0963 110 1.94 7.40 48,821.65 45,936.00 2,885.65 0.0662 115 1.89 7.21 49,725.33 48,624.00 1,701.33 0.6391 120 1.84 7.02 50,514.62 50,112.00 402.62 0.0092 125 1.79 6.83 51,189.53 52.200.00 -1,01OA8 -0.0232 130 1.75 6.67 52,047.45 54,288.00 -2,240.55 -0.0514 135 1.71 6.52 62,813.86 56.376.00 -3,562.14 -0.0618 140 1.67 6.37 63,488.76 58.464.00 -4,975.24 -0.1142 146 1.63 6.22 M,072.15 60,552.00 -6,479.65 -0.1468 150 1.60 6.10. 54,907.26 62,640.00 -7,732.80 -0.1775 155 1.57 5.99 55,673.61 64,728.00 -9,054.39 -0.2079 166 1.54. 5.87 56,371.39 66,816.00 -10,444.61 -0.2398 165 1.51 5.76 57,000.54 68,904.00 -11,903.46 -0,2733 170 1.48 5.64 57,561.05 70,992.00 -13,430..9.5 -0.3083 175 1.45 5.53 58,052.93 73,080.00 -15,027.08 -0.3450 180 1.42 5.41 58,476.17 76,168.00 -16,691.83 -0.3832 185 1.40 5.34 59,254.02 77.M.00 -18,001.98 -0.4133 190 1.38 5.26 59,986.12 79,344.00 -19,357.88 -0.4444 195 1.36 5.19 60,672.46 81,432.00 -20,759.54 -0.4766 200 1.34 5.11 61,313.04 83,520.00 -22,206.96 -0.5098 206 1.32 5.03 61,907.87 85,608.00 -23,700.13 -0.5"1 210 1.30 4.96 62,456.94 87,696.60 -25,234.06 -0.5794 215 1.28 4.88 62,960.26 89,784.00 -26,823.74 -0.6158 220 1.26 4.80 63,417.82 91,872.00 -28,4M.18 -0.6532 225 1.24 473 63,829.62 93,960.00 -30,130.38 -0.6917 230 1.22 4.65 64,195.67 96,048.00 -31,852.33 -0.7312 235 1.21 4.61 65,053.59 98,136.00 -33,082.41 -0.7695 140 1.20 4.58 65,888.64 100,224.00 -34,335.36 -0.7882 Village on Redwood Critical Pond Elevations. Design Engineer. T.Alva Design Firm: Interwest Consulting Group Project Number: 1237-112-00 Date: February 17, 2016. DESIGN CRITERIA Urban Storm. Drainage Criteria. Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008) Stage Storage Volume (pond volume calculated using the prismoidaI formula): V _ (A, +AZ + VA,A, Depth 3 CONTOUR (Fn AREA AREA ACRE) t VOLUME' ACRE DEPTH (FT) CUMULATIVE VOLUME ACRE- 4962.33 0 1 0.000 1 0.000 0.00 0.000 4963.0 2019 0:046 0.010 0.67 0.010 4964.0_ _ 6600- . 0:152__ _ 0.094 --_-- ----1.67. � 0.104 4965.0 --- - -10636 6244 0.208 2.67 0:312- 4966.0 17563 0.403 0.320 3.67 0.632 Required 100-yr Detention Volume (Including WOCV) = 0.425 Acre -Ft Interpolates to an Elev. of 4965.35 ft DETENTION POND VOLUME VERSUS ELEVATION 4966.50 4966.00 4966.50 p 4965.00 4964.50 a 4964.00 - 4963.50 ry 4963.00 4962.50 4962.00 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 DETENTION -POND VOLUME (AC -FT) 1237-112-00 PondCalcs.xls - Pond Stage Storage Page 1 of 1 Ihterwest Consulting Group