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Home My WebLink AboutDrainage Reports - 12/07/2020 Drainage Memo October 1, 2020 Project: 609 South College Avenue Project No. 564-005 Attn: Stormwater Staff City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, CO 80521 Stormwater Staff: This letter serves to document the proposed drainage impacts of the addition to the existing building proposed at 609 South College Avenue in Fort Collins, Colorado. Project Overview The project proposes to add an addition to the rear (west side) of the existing building adding ~800 sf. Construction activities will also include the removal of the existing garage. A concrete patio area, concrete walks, and alley parking will also be added as a part of these improvements, as well as a rain garden similar to what was used at the Music District to provide LID treatment to the site. A dedicated fire service and a single-phase transformer will also be added as part of this project. Existing Site The existing site is relatively flat (0% - 1%) in the front and rear yards, and functions as an “A” Lot, with drainage generally draining from back to front along the side lot lines. In addition to the existing home, the lot consists of a garage, a concrete driveway, concrete entry walk, and concrete walks around the entire home. The remainder of the site is Kentucky Bluegrass lawn, with small landscaping beds and mature trees. The total existing impervious area for the lot is 2,781 sf. Proposed Site The proposed site will generally maintain the existing site drainage. Drainage from the rear yard, patio area, and roof will be directed overland via concrete pan along the southern lot line to a rain garden that will provide LID treatment. In the event of a large storm, water will exit out to College Avenue through a proposed sidewalk chase. The parking area will maintain the existing drainage pattern and flow west to Dalzell Alley. Existing grades outside of our improvements will remain unchanged, including along the north side of the existing house where no improvements are proposed. The total proposed impervious area for the lot is 4,725 sf. Of the existing impervious area, 1,505 sf is unmodified, resulting in 3,220 sf of new and modified impervious area. The proposed change in imperviousness will add an estimated 0.46 cfs to College Avenue and 0.1 cfs to Dalzell Alley in a 100-yr event. Water then flow through gutter to an existing single combo inlet located at Myrtle Street and College Avenue. The existing inlet located at Myrtle Street and College Avenue is undersized and is inundated in a 100-yr event, so the small additional flows will not affect the existing drainage paths. No adverse effects to adjacent properties are anticipated due to the increased imperviousness of the site. Detention Since the impervious area increase is than the 5,000 sf allowed in the Old Town Master Drainage Basin, no detention is required for the site. Floodplain The property is not located in a FEMA regulated flood hazard zone. The project site is, however, located partially within the City of Fort Collins regulated West Myrtle Street floodplain, which is part of a larger basin study, the Old Town Basin, as shown in Figure 1, below. A LOMA (Letter of Map Amendment) was approved on October 1, 2020. Based on existing ground elevations which show that the existing structure is elevated above current 100-year Base Flood Elevation Current floodplain mapping of the area has been recently revised by the City of Fort Collins. The original Old Town Basin study was entitled, “Old Town Basin Master Drainage Plan”, which was conducted by Anderson Consulting Engineers in May of 2002. We have been in discussion City Staff, and have been directed by Staff to utilize current draft information as best available data. The question of inadvertent detention has been discussed, and initially, it was thought that compensatory storage may be necessary with any fill placed within the development site. However, per correspondence with City Staff, this area is not within the inadvertent detention ponding area, which was referred to as the “College and Mulberry Pond”. Per City Staff, based on recent updated 2D modeling, the Base Flood Elevation (BFE) for this site is 4995.50 (NAVD 88). Figure 1 – Current City of Fort Collins Floodplain Mapping (Source: FCMaps, http://gisweb.fcgov.com) Control points/benchmarks utilized with the survey completed for the project are as per the plan set for the project and are shown in Figure 2, below. Figure 2 – Current City of Fort Collins Floodplain Mapping (Source: Utility Plans for 609 South College Avenue, Northern Engineering) It is noted that some of the surrounding developments have used the NGVD 29 (unadjusted) datum. The conversion from NAVD 88 to NGVD 29 (unadjusted) datum in this area is -3.18-ft. City LOMA approved on October 1, 2020 removed existing structure and new addition from 100-year floodplain. Any portion of the site to be developed outside of the approved LOMA area must comply with all floodplain regulations outlined in Chapter 10 of City Code. A floodplain use permit is required for any site construction element (detention ponds, bike paths, parking lots, utilities, etc.) in the floodplain. Water Quality and LID Water Quality for the site is being provided by the Udall Natural Area. LID treatment requirements will be achieved by directing the concentrated flows from the roof and the patio through concrete pan on the south side of the site into a rain garden in the front of the house. The rain garden will contain Bioretention Soil and landscape. Water will infiltrate the soil, removing stormwater contaminates. Due to the limited area available for the rain garden, it is only sized to handle the required volume for the run-on area of new or modified impervious area (%75 of 3,220 sf = 2,415 sf), though a majority of the new, modified, and existing impervious area flows into the rain garden (3,464 sf). It is assumed that this will not be a problem as the water flowing to the rain garden is not expected to be heavily contaminated. As an extra measure of protection, a grouted cobble sediment basin will be added before the rain garden to further remove contaminates. A variance regarding rain garden sizing design is being requested. In the event of a large storm, a sidewalk chase will allow rain garden overflow to travel to College Avenue. An exhibit has been provided to illustrate the existing and proposed impervious areas. Please feel free to contact us if you have any questions. Northern Engineering Services, Inc. Benjamin Ruch, PE Project Engineer 10/01/2020 CHARACTER OF SURFACE: RunoffCoefficient1PercentageImpervious1Project:Streets, Parking Lots, Roofs, Alleys, and Drives:Calculations By:Asphalt …………………......................... ...............................................................................0.95100%Date:Concrete ……………….......................... ...............................................................................0.95100%Gravel (packed) ……….......................... ...............................................................................0.5040%Roofs…………………........................... ...............................................................................0.9590%Pavers………………….......................... ...............................................................................0.5040%Recycled Asphalt......................... ...............................................................................0.8080%Lawns and LandscapingPlaygrounds25%Sandy SoilFlat <2% …………........................... ...............................................................................0.102%Average 2% to 7%......................... ...............................................................................0.152%Steep >7% …………......................... ...............................................................................0.202%Clayey SoilFlat <2% …………........................... ...............................................................................0.202%Average 2% to 7%......................... ...............................................................................0.252%Steep >7% …………......................... ...............................................................................0.352%2-year Cf = 1.00 10-year Cf = 1.00USDA SOIL TYPE: CSub-Basin IDSub-Basin Area(sq. ft.)Sub-Basin Area(ac.)Area of Asphalt & Concrete(ac.)Area of Roofs(ac.)Area of Gravel(ac.)Area ofLandscaping(ac)2-yearComposite RunoffCoefficient10-yearComposite RunoffCoefficient100-yearComposite Runoff CoefficientComposite% Imperv.Existing A6,0850.1400.0140.0250.0000.1010.250.250.3128%Existing B4880.0110.0020.0000.0000.0090.250.250.3120%Existing OS1,5940.0370.0030.0190.0000.0140.250.250.3157%1) Runoff coefficients are taken from the Fort Collins Stormwater Criteria Manaual, Table 4.1-3and Table 3.2-2.EXISTING COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS609 S. College AvenueB. RuchJuly 1, 2020100-year Cf = 1.25Composite Runoff Coefficient with Adjustment CHARACTER OF SURFACE: RunoffCoefficient1PercentageImpervious1Project:Streets, Parking Lots, Roofs, Alleys, and Drives:Calculations By:Asphalt …………………......................... .............................................................................0.95100%Date:Concrete ……………….......................... .............................................................................0.95100%Gravel (packed) ……….......................... .............................................................................0.5040%Roofs…………………........................... .............................................................................0.9590%Pavers………………….......................... .............................................................................0.5040%Recycled Asphalt......................... .............................................................................0.8080%Lawns and LandscapingPlaygrounds25%Sandy SoilFlat <2% …………........................... .............................................................................0.102%Average 2% to 7%......................... .............................................................................0.152%Steep >7% …………......................... .............................................................................0.202%Clayey SoilFlat <2% …………........................... .............................................................................0.202%Average 2% to 7%......................... .............................................................................0.252%Steep >7% …………......................... .............................................................................0.352%2-year Cf = 1.00 10-year Cf = 1.00USDA SOIL TYPE: CSub-Basin IDSub-Basin Area(sq. ft.)Sub-Basin Area(ac.)Area of Asphalt & Concrete(ac.)Area of Roofs(ac.)Area of Pavers(ac.)Area ofLandscaping(ac)2-yearComposite RunoffCoefficient10-yearComposite RunoffCoefficient100-yearComposite Runoff CoefficientComposite% Imperv.Proposed A6,2060.140.0380.0380.0050.0620.550.550.6953%Proposed B8240.020.0160.0000.0000.0030.550.550.6984%Proposed OS11,1390.030.0020.0120.0000.0130.600.600.7547%PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS609 S. College AvenueB. RuchJuly 1, 20201) Runoff coefficients are taken from the Fort Collins Stormwater Criteria Manaual, Table 4.1-3and Table 3.2-2.100-year Cf = 1.25Composite Runoff Coefficient with Adjustment Project:609 S. College AvenueCalculations By:Date:Is Length >500' ?C*Cf(2-yr Cf=1.00)C*Cf(10-yr Cf=1.00)C*Cf(100-yr Cf=1.25)Ti2-yr(min)Ti10-yr(min)Ti100-yr(min)Velocity,V(ft/s)Tt(min)2-yrTc(min)10-yrTc(min)100-yrTc(min)Existing A Existing A No0.25 0.25 0.3122.1 22.1 20.5 N/A N/A 22.1 22.1 20.5Existing BExisting BNo0.250.250.315.95.95.5N/AN/A5.95.95.5Existing OSExisting OSNo0.25 0.25 0.311.9 1.9 1.8 N/A N/A 5.0 5.0 5.0EXISTING TIMES OF CONCENTRATION COMPUTATIONSB. RuchJuly 1, 2020DesignPointSub-BasinOverland Flow Gutter/Swale Flow Time of ConcentrationVelocity (Gutter Flow), V = 20·S½Tt = L / 60VTc = Ti + Tt (Equation RO-2)Velocity (Swale Flow), V = 15·S½NOTE: C-value for overland flows over grassy surfaces; C = 0.25Overland Flow, Time of Concentration:Gutter/Swale Flow, Time of Concentration:(Equation RO-4)()31*1.187.1SLCfCTi-= Project:609 S. College AvenueCalculations By:Date:Is Length >500' ?C*Cf(2-yr Cf=1.00)C*Cf(10-yr Cf=1.00)C*Cf(100-yr Cf=1.25)Ti2-yr(min)Ti10-yr(min)Ti100-yr(min)Velocity,V(ft/s)Tt(min)2-yrTc(min)10-yrTc(min)100-yrTc(min)Proposed A Proposed A No0.25 0.25 0.3112.0 12.0 11.1 1.87 1.2 13.2 13.2 12.3Proposed BProposed BNo0.350.350.446.16.15.4N/AN/A6.16.15.4Proposed OS1Proposed OS1No0.00 0.00 0.002.6 2.6 2.6 N/A N/A 5.0 5.0 5.0Tt = L / 60VPROPOSED TIME OF CONCENTRATION COMPUTATIONSOverland Flow, Time of Concentration:B. RuchJuly 1, 2020Gutter/Swale Flow, Time of Concentration:Tc = Ti + Tt (Equation RO-2)Velocity (Gutter Flow), V = 20·S½Velocity (Swale Flow), V = 15·S½NOTE: C-value for overland flows over grassy surfaces; C = 0.25DesignPointSub-BasinOverland Flow Gutter Flow Time of Concentration(Equation RO-4)()31*1.187.1SLCfCTi-= Project:Calculations By:Date:Existing AExisting A0.142222210.250.250.311.532.615.530.050.090.24Existing BExisting B0.016650.250.250.312.764.729.950.010.010.03Existing OSExisting OS0.045 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.03 0.04 0.11Rainfall Intensity:EXISTING RUNOFF COMPUTATIONSRational Method Equation:609 S. College AvenueB. RuchJuly 1, 2020Flow,Q100(cfs)Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8DesignPointSub-Basin(s)Area, A(acres)2-yrTc(min)10-yrTc(min)100-yr Tc(min)C2C10C100Intensity,i2(in/hr)Intensity,i10(in/hr)Intensity, i100(in/hr)Flow,Q2(cfs)Flow,Q10(cfs)()()()AiCCQf= Project:Calculations By:Date:Proposed AProposed A0.141313120.550.550.691.983.397.160.160.270.70Proposed BProposed B0.026650.550.550.692.674.569.950.030.050.13Proposed OS1Proposed OS10.035 5 5 0.60 0.60 0.75 2.85 4.87 9.95 0.04 0.08 0.20July 1, 2020Intensity,i10(in/hr)C10Area, A(acres)Intensity,i2(in/hr)100-yr Tc(min)B. Ruch609 S. College AvenuePROPOSED RUNOFF COMPUTATIONSC100DesignPointFlow,Q100(cfs)Flow,Q2(cfs)10-yrTc(min)2-yrTc(min)C2Flow,Q10(cfs)Intensity, i100(in/hr)Sub-Basin(s)Rational Method Equation:Rainfall Intensity:Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8()()()AiCCQf= GWCSEVAULTELECTELETVAULTELECCONTROLIRRVAULTELEC/ / / / / / / // / / / / / / // / / / / / / // / / / / / / // / / / / / / /X EEEWSSSSSSSS605 COLLEGE LTD605 S COLLEGE AVEFORT COLLINS, CO 805243003GATON III INCDBA CANINOS ITALIAN RESTAURANT613 S COLLEGE AVEFORT COLLINS, CO 805243003SOUTH COLLEGE AVENUE DALZELL ALLEY EXISTING 100-YR FLOODPLAIN(CITY OF FORT COLLINS)EX A0.140 acEX AEX OSEX BEX OS0.037 acEX B0.011 acHISTORIC DRAINAGE EXHIBITFORT COLLINS, CO609 S. COLLEGEENGINEERNGIEHTRONRNOCTOBER 1, 2020P:\564-005\DWG\DRNG\564-005_EXST DRNG.DWG( IN FEET )01 INCH = 20 FEET2020DRAINAGE SUMMARY TABLEDESIGNPOINTBASINIDTOTALAREA(acres)C2C1002-yrTc(min)100-yrTc(min)Q2(cfs)Q100(cfs)Existing AExisting A0.140.250.3122.120.50.050.24Existing BExisting B0.010.250.315.95.50.010.03Existing OSExisting OS0.040.250.315.05.00.030.11Proposed AProposed A0.140.550.6913.212.30.160.70Proposed BProposed B0.020.550.696.15.40.030.13Proposed OS1Proposed OS10.030.600.755.05.00.040.20 GWCSEVAULTELECTELETVAULTELECVAULTELEC/ / / / / / / // / / / / / / // / / / / / / // / / / / / / // / / / / / / /E E EX EEEWSSSSSSSSXXXXXXXXXXA0.142 acAOSBOS0.026 acB0.019 ac605 COLLEGE LTD605 S COLLEGE AVEFORT COLLINS, CO 805243003GATON III INCDBA CANINOS ITALIAN RESTAURANT613 S COLLEGE AVEFORT COLLINS, CO 805243003SOUTH COLLEGE AVENUE DALZELL ALLEY EXISTING 100-YR FLOODPLAIN(CITY OF FORT COLLINS)PROPOSED DRAINAGE EXHIBITFORT COLLINS, CO609 S. COLLEGEENGINEERNGIEHTRONRNOCTOBER 1, 2020P:\564-005\DWG\DRNG\564-005_DRNG.DWG( IN FEET )01 INCH = 20 FEET2020DRAINAGE SUMMARY TABLEDESIGNPOINTBASINIDTOTALAREA(acres)C2C1002-yrTc(min)100-yrTc(min)Q2(cfs)Q100(cfs)Existing AExisting A0.140.250.3122.120.50.050.24Existing BExisting B0.010.250.315.95.50.010.03Existing OSExisting OS0.040.250.315.05.00.030.11Proposed AProposed A0.140.550.6913.212.30.160.70Proposed BProposed B0.020.550.696.15.40.030.13Proposed OS1Proposed OS10.030.600.755.05.00.040.20 XS#:1205 4990.5ft NGVD 29XS#:1364 4990ft NGVD 29XS#:1699 4992.8ft NGVD 29XS#:1529 4992.5ft NGVD 29XS#:1882 4993.7ft NGVD 29XS#:1929 4992.3ft NGVD 29S COLLEGE AVEW MYRTLE ST DALZELL ALYE MYRTLE ST CORBIN ALY Printed: 11/07/2019. All floodplain boundaries are approximate. This information is based on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of Fort Collins Master Drainageway Plans. This letter does not imply that the referenced property will or will not be free from flooding or damage. A property not in the Special Flood Hazard Area or in a City Designated Floodplain may be damaged by a flood greater than that predicted on the map or from a local drainage problem not shown on the map. This map does not create liability on the part of the City, or any officer or employee thereof, for any damage that results from reliance on this information. City Flood Risk Map Moderate Risk May include: - Areas of FEMA 500-year floodplain (FEMA Zone X-shaded). - Areas of FEMA or City 100-year floodplain (sheet flow) with average depths of less than 1 foot. - Areas protected by levees from the 100-year flood. Low Risk Areas outside of FEMA and City mapped 100-year and 500-year floodplains. Local drainage problems may still exist. City Flood Fringe - May Include: - Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AO, and AH) - Areas of City 100-year floodplain including ponding areas and sheet flow areas with average depths of 1-3 feet. There is a 1% annual chance that these areas will be flooded. High Risk City Floodway - Area of 100-year floodplain with greatest depths and fastest velocities. 0 40 80 120 16020 Feet G WC SCEVAULTELECTELETVAULTELECCONTROLIRRVAULTELEC/ / / / / / / // / / / / / / // / / / / / / /G G SOUTH COLLEGE AVENUEDALZELL ALLEYXXXX X X G WC S E VAULT ELEC TELE T VAULT ELEC VAULT ELEC / / / / / / / // / / / / / / // / / / / / / /SOUTH COLLEGE AVENUEDALZELL ALLEYROOFTOPCONCRETEASPHALTPAVERSSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)1,92885300100%100%100%40%86TOTALS2,7812,781TOTAL=ROOFTOPCONCRETEASPHALTPAVERSSURFACEAREA (SF)% IMPERV.IMPERV.AREA (SF)2,1642,4820198100%100%100%40%TOTALS4,8444,725TOTAL=EXISTINGPROPOSED2,164791,92885302,4820P:\564-005\DWG\DRNG\564-005_IMPERVIOUS.DWG 609 S. COLLEGE AVE.FORT COLLINS COLORADO301 N. Howes Street, Suite 100Fort Collins, Colorado 80521ENGINEERNGIEHTRONRNPHONE: 970.221.4158www.northernengineering.comDESCRIPTIONEXISTING VS. PROPOSEDIMPERVIOUS AREADRAWN BYB. RuchDATEOctober 1, 2020PROJECT564-005SK-C1DRAWINGSCALE1"=30'CHANGE IN IMPERVIOUS AREA = 1,944 SF1,360 SF ROOF UNMODIFIED+ 145 SF WALK UNMODIFIED--------------------------------1,505 SF EXISTING IMPERVIOUS UNMODIFIED75% TREATMENT NEW AND MODIFIED IMPERV.= 75% (4,725 -1,505) = 2,415 SFWATER QUALITY PROVIDED BYUDALL NATURAL AREA. GEVAULTELECVAULTELEC/ / / / / / / // / / / / / / // / / / / / / // / / / / / / // / / / / / / /XOHUXXXXXXXXXX RAIN GARDEN REQUIRED VOLUME: 81 CU. FT. (TO TREAT NEW AND MODIFIED IMPERVIOUS AREA) PROVIDED VOLUME: 83 CU. FT. GROUTED COBBLE SEDIMENT BASIN w/ 2'x2' CONCRETE BOTTOM P:\564-005\DWG\DRNG\564-005_LID.DWG609 S. COLLEGE AVE. FORT COLLINS COLORADO 301 N. Howes Street, Suite 100 Fort Collins, Colorado 80521 E N G I N E E R N GI EHTRON R N PHONE: 970.221.4158 www.northernengineering.com DESCRIPTION LID TREATMENT EXHIBIT DRAWN BY B. RUCH DATE October 1, 2020 PROJECT 564-005 LID-1 DRAWINGSCALE 1"=20' ( IN FEET ) 1 inch = ft. Feet03030 30 LEGEND RAIN GARDEN TREATMENT AREA RAIN GARDEN UNTREATED AREA 609 S. College Ave. Project Summary Total Proposed Impervious Area 4,725 sf Existing Impervious Area 2,781 sf Unmodified Existing Impervious Area (Roof and Walks) 1,505 sf New Impervious Area 1,944 sf New and Modified Impervious Area 3,220 sf Target Treatment Percentage New and Modified Impervious Area 75% Minimum Area to be Treated by LID measures 2,415 sf Rain Garden Total Rain Garden Run on Area (Existing and New/Modified Impervious Area)**3,464 sf **Rain Garden only sized to treat required impervious area (2,415 sf). Total Treatment Area 2,415 sf New and Modified Impervious Area Treatment Percentage**75% Percent Total Project Immpervious Area Treated**73.3% **Rain Garden only sized to treat 75% new and modified impervious area (2,415 sf). ** WATER QUALITY FOR ENTIRE SITE PROVIDED BY UDALL NATURAL AREA Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia =100.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 1.000 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 2,415 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =81 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER =cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum)DWQCV =8 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin =48 sq ft D) Actual Flat Surface Area AActual =51 sq ft E) Area at Design Depth (Top Surface Area)ATop =199 sq ft F) Rain Garden Total Volume VT=83 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided? 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 Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 =N/A cu ft iii) Orifice Diameter, 3/8" Minimum DO =N/A in Design Procedure Form: Rain Garden (RG) Benjamin Ruch Northern Engineering August 24, 2020 609 S. College Fort Collins, CO UD-BMP (Version 3.06, November 2016) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO RG_UD-BMP_v3.06.xlsm, RG 8/24/2020, 6:12 AM Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) Benjamin Ruch Northern Engineering August 24, 2020 609 S. College Fort Collins, CO Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO RG_UD-BMP_v3.06.xlsm, RG 8/24/2020, 6:12 AM 10/01/2020