Results shown on 'Detailed Summary' tab

Transcription

1 Fill in site's Pre Development parameters on 'Pre' tab (Site Area, Drainage Area, Impervious Area, CNpre, tc) Prior to using BSD or BMP practices, fill in site's Post Development parameters on 'Post' tab (Impervious Area, CNpre, tc) Instruction Flow Chart Pre-Devel. Peak flows Post-Devel. Peak flows, Post Storage Volumes Results shown on 'Detailed Summary' tab Will the site incorporate BSD or BMP YES NO Use storage volumes and peak flows from the 'Post' tab for final pond design. Using BSD Practices Only Use 'BSD_Credits' tab if site preserves 1) Natural Conservation Areas, 2) Stream Buffers, 3) Vegetated Channels 4) Infiltration Zones and/or 5) Env. sensitive large lot subdivisions Using BMP Practices New WQv' Did the Site use practices 1), 2) YES Use 'CN_BSD' tab to calculate site's new CN'post to be used for site runoff reduction calculations NO New CN'post Use the same CNpost from the 'Post' tab and input this value in the 'Post_BSD' tab. Use CN'post from the 'CN_BSD' tab and input this value in the 'Post_BSD' tab. New WQv' New WQv' New Storage Vs Use storage volumes and peak flows from the 'Post_BSD' tab for final pond design. Use storage volumes and peak flows from the 'Post_BSD' tab for final pond Site to also include upland BMPs? NO YES Size BMPs using either the City's 6 separate Design Aid sheets or other calculation method to determine BMP's storage volume (Vs) Use 'BMP_Credits' tab to input storage volumes BMP practice detains New WQv" Did the Site use BSD practices, Bioretention, Infiltration Trench, Porous Surfaces, Dry Swale, and/or Rain Garden/Cistern? YES NO Did the site use BSD practices AND adjust the CN (CN'post)? YES NO Use same CN'post from 'Post_BSD' tab; input value in 'Post_BSD+BMP' tab. Use same CNpost from 'Post' tab; input value in 'Post_BSD+BMP' tab. New WQv" Use storage volumes and peak flows from 'Post_BSD+BMP' tab for final pond design. Use 'CN_BMP' tab to calculate site's new CN"post for site runoff reduction calculations New CN"post Use CN"post from 'CN_BMP' tab ; input value in 'Post_BSD+BMP' tab. New WQv" New Storage Vs Use storage volumes and peak flows from 'Post_BSD+BMP' tab for final pond design.

2 Detailed Summary Site Hydrology Drainage Imperv. Area [ac] Area [ac] CN tc Pre-Development Post-Development yr 1yr [cfs] 2yr [cfs] 10yr [cfs] 25yr [cfs] Qpw [cfs] [cfs] Pre-Development N/A Post-Development WQv [cf] CPv [cf] 2yr [cf] 10yr [cf] 25yr [cf] 100yr [cf] Pre-Development Post-Development 62, ,308 77, , , ,860 Better Site Design Credited Practice Natural Area Conservation Stream Buffer Vegetated Channel Overland Flow Filtration/Infiltration Zones Environmentally Sensitive Large Lot Total V stored with BSD practices New Water WQv' WQv Credit [cf] - 11,491 8,208 20, ,038 21,340 Applicable BSD Credits to Adjust Site's CN: Conservation Areas Stream Buffers Infiltration Zones Adjustment to Runoff Reduction Volume (BSD) 11,491 cf 8,208 cf 821 cf 20,519 cf Adjusted CN post ' 77 Drainage Imperv. Area [ac] Area [ac] CN tc [hrs] Post-Development Post-Dev. with BSD Qpw [cfs] 1yr [cfs] 2yr [cfs] 10yr [cfs] 25yr [cfs] 100yr [cfs] Post-Development N/A Post-Dev. with BSD WQv [cf] CPv [cf] 2yr [cf] 10yr [cf] 25yr [cf] 100yr [cf] Post-Development 62, ,308 77, , , ,860 Post-Dev. with BSD 21, ,506 71, , , ,672 Page 1

3 Detailed Summary Better Site Design & Structural BMPs Credited Practices in CoC BMP Manual WQv Credit [cf] Bioretention Area 6,186 Infiltration Trench 8,102 Grass Filter Strip 1,000 Dry Swale - Pervious Surfaces - Credited Practices for Other Accepted Structural BMPs WQv Credit [cf] Wetlands - Wet Swale - Gravity Separator - Commercial SW Controls - Multi-Purpose Dention Area - Underground Detention - Rain Garden/Cistern - Total V stored with BSD practices 15,288 New Water WQv" 6,051 Applicable BSD Credits to Adjust Site's CN: Conservation Areas 11,491 cf Stream Buffers 8,208 cf Infiltration Zones 821 cf Applicable BMP Credits to Adjust Site's CN: Bioretention 6,186 cf Infiltration Trench 8,102 cf Porous Surfaces - cf Dry Swale - cf Rain Garden/Cistern - cf Runoff Reduction Vol. Adjustment 34,807 cf (BSD + BMP) Adjusted CN" post 76 Total Drainage Area [acres] Imperviou s Area [acres] Post-Development Post-Dev. with BSD Post-Dev. with BSD & BMPs Qpw [cfs] 1yr [cfs] 2yr [cfs] 10yr [cfs] 25yr [cfs] 100yr [cfs] Post-Development N/A Post-Dev. with BSD Post-Dev. with BSD & BMPs CN tc WQv [cf] CPv [cf] 2yr [cf] 10yr [cf] 25yr [cf] 100yr [cf] Post-Development 62, ,308 77, , , ,860 Post-Dev. with BSD 21, ,506 71, , , ,672 Post-Dev. with BSD & BMPs 6, ,861 66, , , ,561 Page 2

4 Pre-Development Site Information Site Area 38 acres data input cells Total Drainage Area 38 acres calculation cells Impervious Area 0 acres constant values Peak Flow CN pre 65 tc 0.32 hours S Ia Storm Precipitation (P), [inches] (Richland Co., Type II) Runoff (Q), [inches] Ia/P qu [csm/in] Peak Discharge (Qp pre), [cfs] 1-year storm year storm year storm year storm year storm Equations S = 1000/CN - 10 Ia = 0.2S log (qu) = C 0 + C 1 *log tc + C 2 (log tc) 2 Q = (9-0.2*S)^2 / (P+0.8*S) Qp= qu*a*q C0,C1,C2 coefficients depend on SCS type rainfall (Type II on sheet 'qu_pre')

5 Post-Development Without Better Site Design and Without Upland BMPs Site Information Water Quality Volume, WQv Site Area 38 ac Impervious Area, I 36.3 % Total Drainage Area 38 ac R Impervious Area 13.8 ac WQv ac-ft CN post 78 WQv 62,378 cf tc 0.17 hrs S R = *I Ia WQv = 1.2 * R * A / 12 Channel Protection Volume, CPv 25-Year Storage Volume 1-year precip inches 25-yr precip inches Runoff, Q inches Runoff, Q inches Ia/P Ia/P qu csm/in qu csm/in Peak flow, Qp post 68.1 cfs Qp post = qi cfs qu/qi Qp pre = qo 99.0 cfs Vs/Vr qo/qi 0.50 CPv 2.88 ac-ft Vs/Vr CPv 125,308 cf Vr ac-ft Vs, 25-yr 3.45 ac-ft Q = (P-0.2*S)^2 / (P+0.8*S) Vs, 25-yr 150,386 cf log (qu) = C 0 + C 1 *log tc + C 2 (log tc) 2 Qp= qu*a*q Q = (P-0.2*S)^2 / (P+0.8*S) qu/qi: Must detain for 24 hr, see 'qu_qi' tab log (qu) = C 0 + C 1 *log tc + C 2 (log tc) 2 Vs/Vr = (qu/qi)+1.64(qu/qi)^ (qu/qi)^3 Qp= qu*a*q CPv = (Vs/Vr)*Q*A/12 Vr = Q (A/640) 53.33, where A = Sq. miles qo= predevelopment peak flow for 25-yr Vs/Vr = (Qo/Qi)+1.64(Qo/Qi)^ (Qo/Qi)^3 Vs = Vr (Vs/Vr) Storm Precip. Qp Q [inches] Ia/P qu [csm/in] pre (qo), Qp post (qi), [inches] [cfs] [cfs] 2-year storm year storm year storm qo/qi Vs/Vr Vr [ac.ft] Vs [ac.ft] Vs [cf] 2-year storm , year storm , year storm ,860 Q = (P-0.2*S)^2 / (P+0.8*S) log (qu) = C 0 + C 1 *log tc + C 2 (log tc) 2 Qp= qu*a*q Vr = Q (A/640) 53.33, where A = Sq. miles qo= predevelopment peak flow for 2-yr, 10-yr and 100-yr Vs/Vr = (Qo/Qi)+1.64(Qo/Qi)^ (Qo/Qi)^3 Vs = Vr (Vs/Vr)

6 Better Site Design (BSD) Credits - <FORMAT 1> Better Site Design Practice Stormwater Credits Summary Practice Description Site's New Water Quality Undisturbed natural areas are conserved on a site, Natural area conservation thereby retaining their pre-development hydrologic WQv' 21,339 cu.ft and water quality characteristics. Stormwater runoff is treated by directing sheet flow Stream buffers runoff through a naturally vegetated or forested buffer as overland flow. Use of vegetated channels Vegetated channels are used to provide stormwater treatment. Overland flow filtration/infiltration zones Overland flow filtration/infiltration zones are incorporated into the site design to receive runoff from rooftops and other small impervious areas. Environmentally sensitive large lot subdivisions A group of site design techniques are applied to low and very low density residential development. Natural Area Conservation Credits Site Drainage Area, A 38 ac Impervious Area, I 13.8 ac Natural Conservation Area 7 ac New Drainage Area, A' 31 ac R ac-ft 62,378 ac-ft 1.17 ac-ft 50,887 cf 18.4 % reduction in water quality volume Stream Buffer Credits Site Drainage Area, A 38 ac Impervious Area, I 13.8 ac Area Draining to Buffer 5 ac New Drainage Area, A' 33 ac R ac-ft 62,378 cf 1.24 ac-ft 54,170 cf 13.2 % reduction in water quality volume Vegetated Channel Credits Site Drainage Area, A 38 ac Impervious Area, I 13.8 ac Area Draining to Buffer 12.5 ac New Drainage Area, A' 25.5 ac R ac-ft 62,378 ac-ft 0.96 ac-ft 41,859 cf 32.9 % reduction in water quality volume Overland Flow Filtration/Groundwater Recharge Zone Credits Site Drainage Area, A 38 ac Impervious Area, I 13.8 ac Disconnected Impervious Area 0.5 ac New Drainage Area, A' 37.5 ac R ac-ft 62,378 ac-ft 1.41 ac-ft 61,557 cf 1.3 % reduction in water quality volume Environmentally Sensitive Large Lot Subdivision Credits Criteria: potential list of design criteria listed in the Design Manual (or GSMM) Criteria: potential list of design criteria listed in the Design Manual (or GSMM) Criteria: potential list of design criteria listed in the Design Manual (or GSMM) Criteria: potential list of design criteria listed in the Design Manual (or GSMM) Criteria: This crredit could be excluded due to lack of potential use 62,378 potential list of design criteria listed in the Design Manual (or GSMM) 62, % reduction in water quality volume

7 Better Site Design (BSD) Credits <FORMAT 2> Better Site Design Practice Stormwater Credits Summary Practice Description Undisturbed natural areas are conserved on a site, thereby retaining their predevelopment hydrologic and water quality Natural area conservation characteristics. Stream buffers Use of vegetated channels Overland flow filtration/infiltration zones Environmentally sensitive large lot subdivisions Stormwater runoff is treated by directing sheet flow runoff through a naturally vegetated or forested buffer as overland flow. Vegetated channels are used to provide stormwater treatment. Overland flow filtration/infiltration zones are incorporated into the site design to receive runoff from rooftops and other small impervious areas. A group of site design techniques are applied to low and very low density residential development. Natural Area Conservation Vegetated Channel Site Drainage Area, A 38 ac Site Drainage Area, A 38 ac Impervious Area, I 13.8 ac Impervious Area, I 13.8 ac Natural Conservation Area 7 ac Area Draining to Buffer 12.5 ac New Drainage Area, A' 31 ac New Drainage Area, A' 25.5 ac R R ac.ft ac.ft 62,378 cu.ft 62,378 cu.ft 1.17 ac.ft 0.96 ac.ft 50,887 cu.ft 41,859 cu.ft 18.4 % reduction in WQv 32.9 % reduction in WQv Stream Buffer Overland Flow/Groundwater Recharge Site Drainage Area, A 38 ac Site Drainage Area, A 38 ac Impervious Area, I 13.8 ac Impervious Area, I 13.8 ac Area Draining to Buffer 5 ac Disconnected Impervious Area 0.5 ac New Drainage Area, A' 33 ac New Drainage Area, A' 37.5 ac R R ac.ft ac.ft 62,378 cu.ft 62,378 cu.ft 1.24 ac.ft 1.41 ac.ft 54,170 cu.ft 61,557 cu.ft 13.2 % reduction in WQv 1.3 % reduction in WQv Environ. Sensitive Large Lot Subdivision Revised Water Quality Volume WQv' 21,339 cf This crredit could be excluded due to lack of potential use 62,378 62,378

8 Post-Development: Better Site Design Site Utilizing Better Site Design Credits, but No Upland BMPs Site Information Water Quality Volume, WQv' Drainage Area, A 38 ac Credited Areas 25 ac Impervious Area 13.8 ac New Drainage Area, A' 13 ac CN' post 77 Impervious Area, I 36.3 % tc 0.17 hrs R S s 62,378 cf Ia WQv': BSD credits ac-ft *Adjust CN via 'CN_BSD' tab WQv': BSD credits 21,339 cf Channel Protection Volume, CPv 25 Year Storage Volume P,1-year storm 3.36 inches P,25-year storm 6.40 inches Runoff, Q' inches Runoff, Q' inches Ia'/P Ia'/P qu' csm/in qu' csm/in Peak flow, Qp' post 64.9 cfs Qp' post = qi' cfs qu/qi' Qp pre = qo 99.0 cfs Vs'/Vr' qo/qi' 0.51 CPv' 2.74 ac-ft Vs'/Vr' CPv' 119,506 cf Vr' ac-ft Vs', 25-yr 3.30 ac-ft Vs', 25-yr 143,651 cf Storm Precip. [inches] Q' [inches] Ia'/P qu' [csm/in] Qp pre (qo), [cfs] Qp post' (qi'), [cfs] 2-year storm year storm year storm qo/qi' Vs'/Vr' Vr' [ac.ft] Vs' [ac.ft] Vs' [cf] 2-year storm 10-year storm 100-year storm , , ,672

9 Adjusted Curve Number, CN' Site Utilizing Better Site Design Credits, but No Upland BMPs IF Site Soils are homogeneous, then determine the adjusted CN with procedure below: Step 1: Determine the CN multiplier based on the site's imperviousness % Impervious Hydrologic Soil Group C A, B, C, or D Use Figure below to determine site's s CN multiplier: CN Multiplier Step 2: Calculate adjusted CN CNpost 78 Adjusted CN post ' 75 IF Site Soils are NOT homogeneous, determine adjusted d CN with procedure below: Applicable BSD Credits to Adjust Site's CN: Conservation Areas 11,491 cf Stream Buffers 8,208 cf Infiltration Zones 821 cf Site Data: Site Drainage Area 38 ac Adjustment to Runoff Reduction Volume 20,519 cf (BSD) CNpost 78 S 2.82 Calculate l Site Runoff with and without t BMPs and the adjusted d CN: Storm Event 1-yr 1yr 2-yr 2yr 10-yr 25-yr 100-yr P [inches] Qpost: no runoff red. credits [in] Qpost: runoff reduction credits [in] Adjusted d CN post ' Adjusted d CN post ' 77 p *to be conservative, use 100-yr CN post ' for Post_BSD calculations

10 Best Management Practices (BMP) Credits Structural BMPs Designed for Site BMPs in City of Columbia's BMP Manual: Water Quality Volume Credited Practice Stored, WQv [cf] Bioretention Area 6,186 Infiltration Trench 8,102 Grass Filter Strip 1,000 Dry Swale Pervious Surfaces Retrieve WQ Volumes from BMP Design Aid Worksheet Other Accepted Structural BMPs: Water Quality Volume Credited Practice Stored, WQv [cf] Wetlands Wet Swale Gravity Separator Commercial SW Controls Multi-Purpose Dention Area Underground Detention Rain Garden/Cistern Provide Supporting Calcultions for WQ Volumes Site's Remaining Water Quality Volume (for a pond): WQv" 6,051 cu.ft

11 Post-Development: Structural BMPs Site Utilizing Better Site Design Credits and Upland BMPs Site Information Water Quality Volume, WQv" Total Drainage Area, A 38 ac s 62,378 cf Impervious Area 13.8 ac WQv', with BSD credits 21,339 ac-ft CN' post 76 WQv stored with BMPs 15,288 cf tc 0.17 hrs WQv", with all credits 6,051 cf S Ia *Adjust CN via 'CN_BMP' tab Channel Protection Volume, CPv 25 Year Storage Volume P,1-year storm 3.36 inches P,25-year storm 6.40 inches Runoff, Q' inches Runoff, Q' inches Ia'/P Ia'/P qu' csm/in qu' csm/in Peak flow, Qp' post 61.9 cfs Qp' post = qi' cfs qu/qi' Qp pre = qo 99.0 cfs Vs'/Vr' qo/qi' 0.53 CPv' 2.61 ac-ft Vs'/Vr' CPv' 113,861 cf Vr' ac-ft Vs', 25-yr 3.15 ac-ft Vs', 25-yr 137,045 cf Storm Precip. [in] Q' [in] Ia'/P qu' [csm/in] Qppre (qo) Qp'post [cfs] (qi) [cfs] 2-year storm year storm year storm year storm 10-year storm 100-year storm qo/qi' Vs'/Vr' Vr' [ac.ft] Vs' [ac.ft] Vs' [cu.ft] , , ,561

12 Adjusted Curve Number, CN" Site Utilizing Better Site Design Credits and Upland BMPs IF Site Soils are homogeneous, then determine the adjusted CN with procedure below: Step 1: Determine the CN multiplier based on the site's imperviousness % Impervious Hydrologic Soil Group 36.3 C A, B, C, or D Use Figure below to determine site's CN multiplier: Step 2: CN Multiplier Calculate adjusted CN CNpost Adjusted CN" post IF Site Soils are NOT homogeneous, determine adjusted CN with procedure below: Applicable BSD Credits to Adjust Site's CN: Conservation Areas Stream Buffers Infiltration Zones Applicable BMP Credits to Adjust Site's CN: Bioretention Infiltration Trench Porous Surfaces Dry Swale Rain Garden/Cistern Site Data: Site Drainage Area Adjustment to Runoff Reduction Volume (BSD) CNpost S 11,491 cf 8,208 cf 821 cf 6,186 cf 8,102 cf 1,000 cf - cf - cf 38 ac 35,807 cf Calculate Site Runoff with and without BMPs and the adjusted CN: Storm Event 1-yr 2-yr 10-yr 25-yr 100-yr P [inches] Qpost: no runoff red. credits [in] Qpost: runoff reduction credits [in] Adjusted CN post '' Adjusted CN" post 76 *to be conservative, use 100-yr CN"post for Post_BSD calculations