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Report Submittal E?c -r*4ic&FolaNrpry tl R. �► ie"LPL Darko Simic AKS Engineering & Forestry Building Division DEC 3 2018 12965 SW Herman Rd. City of Tigard Suite 100 13125 SW Hall Blvd CITY Y OF k. AR Tualatin, OR 97062 Tigard, OR 97223 BUILDING DIVISION darkos@aks-eng.corn tigardbuildingpermits@tigard-or.gov 503-563-6151 503-718-2439 `` Brightwood 12/3/2018 6460 Grading Permit 00047 For Review and Comment Delivered by AKS Engineering DATED DESCRIPTION: ACTION: 1 10/8/2018 GeoReport DATED DESCRIPTION: ACTION: 1 10/5/2018 Final Stormwater Report DATED DESCRIPTION: ACTION: 1 10/4/2018 Check no 33725 in amt $325 F - DATED DESCRIPTION: ACTION: 1 3 11/29/2018 Grading Sub 1 - 1 Original, 2 Copies DATED DESCRIPTION: ACTION: 1 10/3/2018 Grading Permit Application DATED DESCRIPTION: ACTION: 1 7/12/2018 Plan Review Fee Email DATED DESCRIPTION: ACTION: 1 11/30/2018 Fire Flow Test Results DATED DESCRIPTION: ACTION: 1 12/3/2018 8 Cents to make up short check t Page 1 of l W Brightwood Subdivision • Tigard, Oregon „ Final Stormwater rx Report } � I Date: October 2018 OFFICE COPY Client: Venture Properties, LLC. 4230 SW Galewood Street, Suite 100 Lake Oswego, OR 97035 Engineering Contact: Darko Simic, PE DarkoS@aks-eng.com Engineering Firm: AKS Engineering & Forestry, LLC AKS Job Number: 6460 \ D .0.to PROffs,„ CD OREGON�b AIMS( tr ,a 12 OgRK0 S\‘I‘\G ENGINEERING&FORESTRY 12965 SW Herman Road,Suite 100 Tualatin,OR 97062 P: (503) 563-6151 www.aks-eng.com Table of Contents 1.0 Purpose of Report 1 2.0 Project Location/Description 1 3.0 Regulatory Design Criteria 1 3.1 STORMWATER QUANTITY 1 3.2 STORMWATER QUALITY 1 4.0 Design Methodology 2 5.0 Design Parameters 2 5.1 DESIGN STORMS 2 5.2 PRE-DEVELOPED SITE CONDITIONS 2 5.2.1 Site Topography 2 5.2.2 Land Use 2 5.3 SOIL TYPE 2 5.4 POST-DEVELOPED SITE CONDITIONS 2 5.4.1 Site Topography 2 5.4.2 Land Use 3 5.4.3 Post-Developed Input Parameters 3 5.4.4 Description of Off-Site Contributing Basins 3 6.0 Stormwater Analyses 3 6.1 PROPOSED STORMWATER CONDUIT SIZING AND INLET SPACING 3 6.2 PROPOSED STORMWATER QUALITY CONTROL FACILITY 3 6.2.1 PROPOSED LIDA PLANTERS SIZING CALCULATIONS 3 6.3 DOWNSTREAM ANALYSIS 4 6.4 PROPOSED STORMWATER QUANTITY CONTROL FACILITY DESIGN 4 Tables Table 5-1: Rainfall Intensities 2 Table 5-2: Hydrologic Soil Group Ratings 2 Table 6-1: LIDA Planter Sizing 3 Table 6-2: Pre and Post Developed Flows 4 Figures FIGURE1 VICINITY MAP FIGURE 2 PRE-DEVELOPED BASIN DELINEATION FIGURE 3 POST-DEVELOPED BASIN DELINEATION FIGURE4 WATER QUALITY TREATMENT MAP Appendices APPENDIX A HYDROCAD REPORTS FOR PRE-DEVELOPED CONDITION STORM EVENTS APPENDIX B HYDROCAD REPORTS FOR POST-DEVELOPED CONDITION STORM EVENTS APPENDIX C STORMWATER QUALITY CALCULATIONS APPENDIX D USDA-NRCS SOIL RESOURCE REPORT APPENDIX E TR55 RUNOFF CURVE NUMBERS Final Stormwater Report BRIGHTWOOD SUBDIVISION TIGARD,OREGON 1.0 Purpose of Report This report analyzes the effects of the proposed development regarding the existing and proposed stormwater conveyance system.Evaluation of the stormwater system includes documentation of criteria,methodology,and informational sources.The results of the final hydraulicanalysis are also presented. 2.0 Project Location/Description The proposed residential subdivision will be located at the property identified as 11375 SW North Dakota Street,Tigard,OR 97224. The 1.98 acre parcel(Washington County Tax Lot 600, 1S 1 34DB), is situated north of SW North Dakota Street and connects with SW 114th Place and SW Ellison Lane. The Brightwood subdivision will includethe creation of an 8-lot residential subdivision forsingle-family detached homes.Site improvements will include the construction of public streets and a stormwater facility located within Tract A.Underground utilities will include a stormwater collection and conveyance system. 3.0 Regulatory Design Criteria 3.1 STORMWATER QUANTITY Per Clean Water Services(CWS)Design and Construction Standards Man ual forSanitary Sewer and Surface Water Management(R&O 17-05), Section 4.03 Water Quantity Control Requirements,on-site detention is required when any of the following conditions exist: 1. There is an identified downstream deficiency and the District or City determines that detention rather than conveyance system enlargement is the more effective solution. 2. There is an identified regional detention site within the boundary of the development. 3. Water quantity facilities are required by District-adopted watershed management plans or adopted subbasin master plans. Per CWS standards and City of Tigard requirements,the proposed project will provide stormwater quantity management due the site's ultimate discharge point intothe Fanno Creek basin.The proposed stormwaterfacility will detain post-developed stormwaterflows for the 2 through 25-year storm events to the pre-developed stormwaterflows. 3.2 STORMWATER QUALITY Stormwater quality managementforthis project will be provided by an extended dry detention basin located within Tract A, and LIDA street side planter located on SW North Dakota Street.The stormwater facility and planter have been designed per Clean WaterServices Design and Construction Standards for Sanitary Sewer and Surface Water Management(R&O 17-05). Ass6460 Brightwood Subdivision October 2018 Final Stormwater Report Page 1 WININIMMIMMONAW 4.0 Design Methodology The Santa Barbara Urban Hydrograph(SBUH)Method was used to analyze stormwater runoff from the site. This method utilizes the SCS Type 1A 24-hour design storm. HydroCAD 10.0 computersoftware aided in the analysis. Representative CN numbers were obtained from the USDA-NCRS Technical Release 55 and are included in Appendix E. 5.0 Design Parameters 5.1 DESIGN STORMS PerCWS requirements,the following rainfall intensities and durations were used in analyzing the existing and proposed stormwater facilities: Table 5-1: Rai.fall Intensities Recurrence Total Precipitation Interval (Years) Depth(Inches) WQ 0.36 2 2.50 10 3.45 25 3.90 5.2 PRE-DEVELOPED SITE CONDITIONS 5.2.1 Site Topography Existing on-sitegrades vary from±2.5%to±8%, with a high point at±227 feet located at the northwest property corner and a low point of±219 feet nearthe center of the east property line.The site slopes from west to east and is split into two watersheds,which drain towardsthe northeast and southeast. 5.2.2 Land Use The existing site consists of a single family detached house with a gravel driveway and remainder of the site consists of woodland/grass conditions. 5.3 SOIL TYPE The soils beneath the project site and the associated drainage basins are classified as Aloha silt and Quatama loam according to the USDA Soil Survey for Washington County.The fol lowi ng table outlines the HydrologicSoil Group rating for the soil type: Table 5-2: Hydrologic Soil Group Ratings NRCS Map Unit Hydrologic Soil Identification NRCS Soil Classification Group Rating 1 Aloha siltloam C/D 37B Quatama loam,3 to 7 percent slopes C 5.4 POST-DEVELOPED SITE CONDITIONS 5.4.1 Site Topography The onsite slopes will be modified with cuts and fills to accommodate the construction of the public streets and a stormwaterfacility.Additionally,sloped residential building pads will be constructed adjacentto the public right-of-way.Majority of the proposed site will be routed towards the northeast basin with a small undetained amount flowing towards the southeast. I( 6460 Brightwood Subdivision October2018 ^� Final Stormwater Report Page 2 5.4.2 Land Use The site land-use will consist of single-familyresidential with the construction ofa new 8-lot subdivision with associated streets,sidewalk and underground utilities. 5.4.3 Post-Developed Input Parameters Appendices A,B,and C provide the HydroCAD reports and input parameters that were generated forthe analyzed storm events with respect to the drainage basins contributingto the subdivision.These reports include all the parameters(e.g.,impervious/pervious areas,time of concentration,etc.)used to model the site hydrology. 5.4.4 Description of Off-Site Contributing Basins No major off-site contributory basins drain onto the subject site.The surrounding subdivisions/properties drain toward and use their existing storm drainage systems and facilities. 6.0 Stormwater Analyses 6.1 PROPOSED STORMWATER CONDUITSIZING AND INLET SPACING The proposed on-site curb inlets have been spaced perCWS requirements to properly convey stormwater runoff.The proposed storm system pipes have been sized using Manning's equation to convey the peak flows from the 25-year storm event. 6.2 PROPOSED STORMWATER QUALITY CONTROL FACILITY An extended dry basin has been designed per Clean Water Services Design and Construction Standards for Sanitary Sewer and Surface Water Management(R&O 07-20) to provide water quality treatment for the proposed site.The extended dry basin is sized to treat impervious area runoff created by the proposed project. The Water Quality Volume will be routed through the proposed extended dry basin which will provide water quality treatment per CWS standards. Any additional stormwater runoff volume beyond the 25- year detention volume will be routed through the extended dry basin to an overflow structure and discharged into the existing storm drain manhole flowing to the east.Detailed calculations and checks against CWS criteria are included in the Appendices. A portion of the project site to the south will be situated at grades and elevations which will not allow stormwater runoff to be directed and discharged into the proposed extended dry basin.A small portion of impervious sidewalk and roadway area from SW North Dakota Street will sheet flow and be conveyed to the existing drainage inletto the east.This untreatable area will be addressed by providingtreatment in the form of LIDAflowthrough planter providingstormwaterqualitytreatment. 6.2.1 PROPOSED LIDA PLANTERS SIZING CALCULATIONS The proposed LIDA flow through planter was sized in accordance with CWS section 4.05.6B. Table 6-1: LIDA Planter Sizing LIDA Planter# Surface Area to Be Required Planter Area Planter Dimensions (LF) Treated(SF) (6%of SF To Be Treated) Planter Area(SF) 1 826 50 4.5(W)'X 12(L) = 54 SF Ags6460 Brightwood Subdivision October 2018 Final Stormwater Report Page 3 6.3 DOWNSTREAM ANALYSIS PerCWS standards and City of Tigard requirements,the proposed project will provide stormwater quantity management due the site's ultimate discharge point into the Fanno Creek. The proposed site will direct majority of stormwaterflow towards the extended dry basin discharging into the existing SW Ellson storm system. From the extended dry basin stormwaterflowwill be conveyed to an underground detention pipe and ultimately to the northeast open channel system via a closed conduit system.The extended dry basin has been sized to detain the post-developed stormwater flows from the 2 through 25-yearstorm events draining towards the existingSW Ellson Lane detention pipes to the pre-developed stormwater flows. A small portion of the proposed site will direct stormwaterflows towards the LIDA planter located on SW North Dakota Street.The stormwater will then be treated by the planter and discharged into the existing system on SW North Dakota. 6.4 PROPOSED STORM WATER QUANTITY CONTROL FACILITY DESIGN The proposed project provides stormwater quantity management by utilizing an extended dry basin designed perCWS standards.The following table outlines the results of the detention pond outflow which limits the post-development peak flows to less than pre-deveiopment peak flows for each storm event. Table 6-2: Pre and Post Developed Flows Recurrence Peak Pre-Development Peak Post-Development Peak Flow Increase or Interval (Years) Flows (cfs) Flows (cfs) (Decrease)—(cfs) 2 0.19 0.11 (0.08) 10 0.43 0.25 (0.18) 25 0.56 0.38 (0.18) The extended dry basin has been designed perCWS requirements with 1-foot freeboard,during the 25- year storm event,and a permanent pool storage depth of 0.4 feet. The proposed extended dry basin has sufficient capacity to detain the required post-developed site flows to the pre-developed site flows and meets the requirements established by Clean WaterService's Design and Construction forSanitarySewer and Surface Water Management Manual(R&O 07-20). As6460 Brightwood Subdivision October2018 Final Stormwater Report Page 4 , 0 ' ', CSC 9 ° NWy210 °ooa° e :: , i • Atill ---1‘ - t, 4IP mai API OP& 11a111■ IT Wi ■■I. a1 h• i NNr♦ ilk_ C ■11010 v. vim __ 411fr * ---•;T:,.....,_,;.-___ ___D„..z.__ e m Mint um MI 11 m r sw COTTIIOVWOOD L J "�■ ---4 _ � _ V 2\ PROJECT SITE -" SV/MA AIITI ST /ELLSON / __i 1 - 3 f-- SW NORTH DAKOTA ST _ 1111 4' _ _ __E- -_—_---_/,r----—- 1111 poo BURLCREST DR _ ___ ll ______ _ _______ ____ __ .111,0 Own I I I MI 1 1-1 1\ mow 0,0 00 fe iimm ... NNE so 4.1 El _____ ��♦III 111\_. ''♦''I - } '■. .■■T` _____, ay AIM MIR 1 1 C- ipdbh 1 k kEJiiU7 mignin .1. N DATE: 10-02-2018 BRIGHTWOOD SUBDIVISION: VICINITY MAP FIGURE SCALE: 1"= 500 FEET 1 _ ■ AKS ENGINEERING & FORESTRY, LLC DRWN: SPD 12965 SW HERMAN RD, STE 100 AK CHKD: DS 500 0 20•0 40•o TUALATIN, OR 97062 AKS JOB: P:503.563.6151 F:503.563.6152 aks—eng.com 6460 \ TAX LOT 800 ___ _ _ / TAX LOT 1200 . -..*. \ . , I\ TAX MAP 1S.1.34DB SW 114TH PLACE TAX MAP 1S.1.34DB _ - !, \ i. ,. ' 1 , . _ . . , _.i. - . . , . - - -.. . II - — — L.- 1 I z z r 1.11".11111-1",_, limir-3,1117r--minor-um.r 7. , _ ttlillrei!ili!iliPpili! ic , . , ...—_.7____. ,,, , ch. -low-Imo--war Amu ----•olir ...., .. 1—, 11P9 \-- Alt" 4 ....*.Q. 1 1 44A I P I I I I Ig r al e I M,.. . , :.Ai ltiF EirgAMMIll.*4_11 i i., •.:. - . ..-,,,,7 . • . * IV /- --.— ---__ '. \ ----- Of /,440,----- ---, ., Ar ' 'ri ' -r- 1111 1 1 t ...4, -___ , „--- ,. , __ -4--1-S- , _ \-- ,_ _ - -- 4 ,. . -4,E /7u 41: 1 I II 22, ' ,;) I Cii ‘ I r — nr-----i --, I r-----7- 5-- ----1 r -- 7 - - 7 r .... , 0 . , tio I / t_ , , . I I ,-- , , . , I._ m .... ..1 1 TAX LOT 2638 I 11" ' ' ii3R il I ' TAX MAP 1S.1.34AC 1 , 5S 5S 5S 1 2 1 S , 1 4S . - -16SI Ar A _1 i i i I I 1 i 3s) 1 1--:, - Li / _ __ - : I . 8 _ i 7 5 1 - - w , 01 L 6 4 ..... L. . .1 L. . 1 L .... -.1 Oil IMIIE IMMO TAX LOT 2637 1 , ifi , ,,, TAX MAP 1S.1.34AC CC I \ I 1111 . //' r 2,2:1 -.\--- 2R ,i46,s, ,till 1 -- - - 4 ., I 1 S / A-- TR i TA I 4.., ... . .1 ''' - / u) I -, I - ,, ' IL . I : i ,/--- 20 ip STORMWA -1!•=•101omk .\---- _-7-----215 Fr' • I t JP --/ --\ i i '' ; , nn----1 rp I \ :A. .M1 _ b A 21.0,z - a ...... \ I I • r77-7\-- - -77.77777-7"1 --- IF '1 lilt r\\\\\\\\\\ \\1 (\, ,,, . / 1•\ \ \ \ \ \ \I --.......; ; 1 GRAVEL .1 TAX LOT 12600 .1 TAX LOT 2636 71 TAX MAP 1S.1.34DB 41 p,:. ...,, ; TAX LOT 12700 - I ' \ TAX LOT 12800 TAX MAP 1S1.34AC il TAX MAP 1S.1.34DB Z TAX MAP 1S.1.34DB ' ii ,, .. , is: :-.,''...-*,/ ---- ----, , ...: ....* ....„ (/) '• . --'''c \ 'i)k.-1 - - ....1 0 ...I r I ,,,,, '----- ___ ,, u 1 i V*A. . , 1 1 1 I -1-- I I ,' 1 - ',-- ' _----- Cn I 1 ! ,, 1 ''1 J -- i — - I/ 1 ,' i DATE: 10-02-2018 0 z FIGURE POST-DEVELOPED BASIN DELINEATION SCALE: 1"-= 40 FEET BRIGHTWOOD SUBDIVISION 3 • AKS ENGINEERING St FORESTRY, LLC AK IN D RH:::0B SPDDs M 12965 SW HERMAN RD, STE 100 c 40 0 16 24 32 40 TUALATIN, OR 97062 P:503.563.6151 F:503.563.6152 aks—eng.com 6460 SW 114TH PLACE TAX LOT 800 d. \ TAX MAP 1S.1.34DB ��� � _ : 1 a - - _ ► ,� ` . l ' • � TAX LOT 1200 7 TAX MAP 1S.1.34DB _ — 2 _ . ,.. ., _ _ _ _ 1 I sit, sm SN O s — s� O 4 i li I;h:;I r L._I \ I * N. 1, ../ v - ../ I v 1, .v Itoo :: ,-/ 1 - h`- I - r-7/ \--\ ///// w I V1 y I W II I i1 ID � _ ; TAX LOT 2638 00 TAX MAP 1 S.1.34AC H 1 I 4 3 1 • 0 I I .I 1 8 Q 7 6 5 I1 0 HI * cc 1 1 TAX LOT 2637 ZI i I c TAX MAP 1S.1.34AC , 2 1 I LIDA PLANTER 1 TR 'tR — ' STORMWA •?-11 •1041.5 A 1 , I I . 1 z 1 r I I Y I , I TAX LOT 12600 8 I I I TAX MAP 15.1.34DB W ;� TAX LOT 2636 1 � TAX LOT 12700 -J Z I TAX LOT 12800 TAX MAP 1 S.1.34AC TAX MAP 1S.1.34DB 'J Q 1 ` \' TAX MAP 1S.1.34DB WJ ` I I. 1 7 I POST-DEVELOPED IMPERVIOUS AREA TABLE C) z PROPOSED IMPERVIOUS AREA RECEIVING TREATMENT BY 33,877 SF EXTENDED DRY BASIN FACILITY SCALE: 1"= 40 FEET PROPOSED IMPERVIOUS AREA TO BE TREATED BY LIDA 826 SF PLANTER 1 TOTAL SITE IMPERVIOUS AREA CREATED AND TREATED 34,703 SF 40 0 16 24 32 40 DATE: 10-02-2018 FIGURE WATER QUALITY TREATMENT MAP BRIGHTWOOD SUBDIVISION 4 AKS ENGINEERING & FORESTRY, LLC DRwN: SPD 12965 SW HERMAN RD, STE 100 AK CHKD: DS TUALATIN, OR 97062 AKS JOB: P:503.563.6151 F:503.563.6152 aks—eng.com 6460 5 <2OS > 10 Pre-Devel ped-Onsite Pre-Developed-Onsi 1L Pre-Develo ed Flow (N) �_____ f TOTAL < t 30S) Pre-Developed Site Pre-Developed-Onsite Total (S) -----\_.- Subcat Reach Pon Link Routing Diagram for 6460 Pre-Developed -----\\___ Prepared by AKS ENGINEERING HydroCAD®10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC 6460 Pre-Developed Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.452 80 >75% Grass cover, Good, HSG D (30S) 0.041 91 Gravel surface, HSG D (30S) 0.000 98 Paved parking, HSG D (20S) 0.022 98 Unconnected roofs, HSG D (20S, 30S) 0.475 72 Woods/grass comb., Good, HSG C (10S) 0.992 79 Woods/grass comb., Good, HSG D (20S) 1.982 78 TOTAL AREA 6460 Pre-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment 10S: Pre-Developed-Onsite Runoff Area=20,703 sf 0.00% Impervious Runoff Depth>1.13" Flow Length=195' Slope=0.0300 '/' Tc=23.4 min CN=72/0 Runoff=0.09 cfs 0.045 af Subcatchment2OS: Pre-Developed-Onsite Runoff Area=43,622 sf 0.97% Impervious Runoff Depth>1.58" Flow Length=270' Slope=0.0260 '/' Tc=32.2 min CN=79/98 Runoff=0.29 cfs 0.132 af Subcatchment 305: Pre-Developed-Onsite Runoff Area=22,025 sf 2.51% Impervious Runoff Depth>1.75" Flow Length=190' Slope=0.0180 '/' Tc=28.1 min CN=81/98 Runoff=0.18 cfs 0.074 af Link 1 L: Pre-Developed Flow(N) Inflow=0.38 cfs 0.177 af Primary=0.38 cfs 0.177 af Link TOTAL: Pre-Developed Site Total Inflow=0.56 cfs 0.251 af Primary=0.56 cfs 0.251 af Total Runoff Area = 1.982 ac Runoff Volume = 0.251 af Average Runoff Depth = 1.52" 98.87% Pervious = 1.960 ac 1.13% Impervious = 0.022 ac 6460 Pre-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment 10S: Pre-Developed-Onsite Runoff = 0.09 cfs @ 8.07 hrs, Volume= 0.045 af, Depth> 1.13" Runoff by SBUH method, Split Pervious/lmperv., Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 20,703 72 Woods/grass comb., Good, HSG C 20,703 72 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 23.4 195 0.0300 0.14 Sheet Flow, Grass: Dense n= 0.240 P2= 2.50" Subcatchment 10S: Pre-Developed-Onsite Hydrograph 0.105? 0 Runoff 013' 0.09cfs 0009 ' 4 Typie-IA=24=hr- 0.085 - 25-YEAR Rainfall=3 90" 0.08 0.075 ' E Runoff-Area=20;703-sf- 0065�' �j Runoff-Volume=0.045-af- 0.06�'r ---- Runoff Depth>t113r= �0.055;'r 0.053' LL 0.0453, ��IIjI Flow Length=195' 0.035 , 0.03PI Tc-23.4-min- 7 0.025, 0.02=', %� C�1=72/0-- 0.015=' . ._' 0.01-3' 0.005 / — — — 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 6460 Pre-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 20S: Pre-Developed-Onsite Runoff = 0.29 cfs @ 8.09 hrs, Volume= 0.132 af, Depth> 1.58" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 43,198 79 Woods/grass comb., Good, HSG D 12 98 Paved parking, HSG D 412 98 Unconnected roofs, HSG D 43,622 79 Weighted Average 43,198 79 99.03% Pervious Area 424 98 0.97% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 32.2 270 0.0260 0.14 Sheet Flow, Grass: Dense n= 0.240 P2= 2.50" Subcatchment 20S: Pre-Developed-Onsite Hydrograph 0.32 p Runoff 0.3 0.29 cfs 0.26 _ ►I� Type IA 24-hr 0.26� /� 25-YEAR-Rainfall=3.901-1-- 0.24 Runoff-Area=43,622-sf 0.22 ,0.2- ♦ Runoff Volume=0.132:af 0.18 _ ,% �� Runoff Depth '1.58 0.16� c 0.14� / jFlow Length=270'- 0.12 r Slope=0.0260 0.08„ • 0.06- CN=79/98 0.04 0 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) W 6460 Pre-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 30S: Pre-Developed-Onsite (S) Runoff = 0.18 cfs @ 8.06 hrs, Volume= 0.074 af, Depth> 1.75" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 553 98 Unconnected roofs, HSG D * 1,782 91 Gravel surface, HSG D 19,690 80 >75% Grass cover, Good, HSG D 22,025 81 Weighted Average 21,472 81 97.49% Pervious Area 553 98 2.51% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 28.1 190 0.0180 0.11 Sheet Flow, Grass: Dense n= 0.240 P2= 2.50" Subcatchment 30S: Pre-Developed-Onsite (S) Hydrograph 0.19 0.18 cfs RW01f 0.18-?0.17, Type LA- - -T e 24 h-r . - 0.16= 4. 25-YEAR-Rai nfalt=3.90"-- 0.15 0.14-1 Runoff-Area=22,025-sf --0.12_ Run:offVolume=0.074 of w 0.11 Runoff Depth>'1. 5�. 0.09= -- Flow L-ength=-1-90'- 0.04� F CN=• • _ 0.03= 0.01= ( 5 6 7 8 9 10 11 1'2 13 14 15 16 17 18 19 20 Time (hours) 6460 Pre-Developed Type IA 24-hr 10-YEAR Rainfall=3.45" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment 10S: Pre-Developed-Onsite Runoff Area=20,703 sf 0.00% Impervious Runoff Depth>0.88" Flow Length=195' Slope=0.0300 '/' Tc=23.4 min CN=72/0 Runoff=0.07 cfs 0.035 af Subcatchment2OS: Pre-Developed-Onsite Runoff Area=43,622 sf 0.97% Impervious Runoff Depth>1.28" Flow Length=270' Slope=0.0260'/' Tc=32.2 min CN=79/98 Runoff=0.22 cfs 0.106 af Subcatchment30S: Pre-Developed-Onsite Runoff Area=22,025 sf 2.51% Impervious Runoff Depth>1.43" Flow Length=190' Slope=0.0180 '/' Tc=28.1 min CN=81/98 Runoff=0.14 cfs 0.060 af Link IL: Pre-Developed Flow(N) Inflow=0.29 cfs 0.141 af Primary=0.29 cfs 0.141 af Link TOTAL: Pre-Developed Site Total Inflow=0.43 cfs 0.201 af Primary=0.43 cfs 0.201 af Total Runoff Area = 1.982 ac Runoff Volume = 0.201 af Average Runoff Depth = 1.22" 98.87% Pervious = 1.960 ac 1.13% Impervious = 0.022 ac 1 6460 Pre-Developed Type IA 24-hr 2-YEAR Rainfall=2.50" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 sin 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment 10S: Pre-Developed-Onsite Runoff Area=20,703 sf 0.00% Impervious Runoff Depth>0.41" Flow Length=195' Slope=0.0300 '/' Tc=23.4 min CN=72/0 Runoff=0.02 cfs 0.016 af Subcatchment2OS: Pre-Developed-Onsite Runoff Area=43,622 sf 0.97% Impervious Runoff Depth>0.68" Flow Length=270' Slope=0.0260 '/' Tc=32.2 min CN=79/98 Runoff=0.10 cfs 0.057 af Subcatchment30S: Pre-Developed-Onsite Runoff Area=22,025 sf 2.51% Impervious Runoff Depth>0.80" Flow Length=190' Slope=0.0180'/' Tc=28.1 min CN=81/98 Runoff=0.07 cfs 0.034 af Link IL: Pre-Developed Flow(N) Inflow=0.12 cfs 0.073 af Primary=0.12 cfs 0.073 af Link TOTAL: Pre-Developed Site Total Inflow=0.19 cfs 0.107 af Primary=0.19 cfs 0.107 af Total Runoff Area = 1.982 ac Runoff Volume = 0.107 af Average Runoff Depth = 0.65" 98.87% Pervious = 1.960 ac 1.13% Impervious = 0.022 ac 6460 Pre-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment 10S: Pre-Developed-Onsite Runoff = 0.09 cfs @ 8.07 hrs, Volume= 0.045 af, Depth> 1.13" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 20,703 72 Woods/grass comb., Good, HSG C 20,703 72 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 23.4 195 0.0300 0.14 Sheet Flow, Grass: Dense n= 0.240 P2= 2.50" Subcatchment 10S: Pre-Developed-Onsite Hydrograph 0.1?' _ _- -.-- 0.09 cfs ®Runoff 0.095'' 009 "r Type 1A-24=hr- 0 085? 25=YEAR Rainfall=3.90"-- 0.075 "� Runoff-Area=20-703-sf O.065 Runoff_Volume=0.045-a#- 13-0.055 ' Runoff Depth>t113`v LL0.045? Flow-Length-t95'- 0.04 •'� J 0.035:2' 0.03 Y' -c=23.4 illi -- 0.025? 3"_ CN=72/0 - 0.01-3" 0.005y 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 6460 Pre-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 20S: Pre-Developed-Onsite Runoff = 0.29 cfs @ 8.09 hrs, Volume= 0.132 af, Depth> 1.58" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 43,198 79 Woods/grass comb., Good, HSG D 12 98 Paved parking, HSG D 412 98 Unconnected roofs, HSG D 43,622 79 Weighted Average 43,198 79 99.03% Pervious Area 424 98 0.97% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 32.2 270 0.0260 0.14 Sheet Flow, Grass: Dense n= 0.240 P2= 2.50" Subcatchment 20S: Pre-Developed-Onsite Hydrograph 0.32 0.3 0.29 cfs Runoff 0.28 __----_ 'ypeld4-hr. 0.26 2-5-YEAR Rainfall=3.90"- 0.24- 0.22 Runoff-Area=43;622-sf 0.2 Runoff Volume=Q.132 of 0.18 Runoff-Depth>1.58"-- 0.16 LL 0.14 Flow-Length=270" - 0.12 Slope=0.0260 '['__ 0.1 • 0.08 _ 0.06 CN=79/98 0.04 0.02 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 6460 Pre-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 30S: Pre-Developed-Onsite (S) Runoff = 0.18 cfs @ 8.06 hrs, Volume= 0.074 af, Depth> 1.75" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 553 98 Unconnected roofs, HSG D 1,782 91 Gravel surface, HSG D 19,690 80 >75% Grass cover, Good, HSG D 22,025 81 Weighted Average 21,472 81 97.49% Pervious Area 553 98 2.51% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 28.1 190 0.0180 0.11 Sheet Flow, Grass: Dense n= 0.240 P2= 2.50" Subcatchment 30S: Pre-Developed-Onsite (S) Hydrograph 0.19 0,18 cfs 0 Runoff 0.18-> 0.17- , Type 1A 24—hr 016✓ r 25-YEAR Rainfall=3.90"- 0.15%' 0.14-> ________ _ Runoff-Area=22;025-sf.- 0.13:", Runoff Volume=0;074 aT Runoff Depth>1:75"- r Flow Length='I94' 0.08-> ]� 0.07-> Slope=O.0_1 8 7 0.06 0.05 - I I I 0.04 0.03'' 0.02 0.01 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 6460 Pre-Developed Type IA 24-hr 10-YEAR Rainfall=3.45" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment 10S: Pre-Developed-Onsite Runoff Area=20,703 sf 0.00% Impervious Runoff Depth>0.88" Flow Length=195' Slope=0.0300 '/' Tc=23.4 min CN=72/0 Runoff=0.07 cfs 0.035 af Subcatchment20S: Pre-Developed-Onsite Runoff Area=43,622 sf 0.97% Impervious Runoff Depth>1.28" Flow Length=270' Slope=0.0260 '/' Tc=32.2 min CN=79/98 Runoff=0.22 cfs 0.106 af Subcatchment30S: Pre-Developed-Onsite Runoff Area=22,025 sf 2.51% Impervious Runoff Depth>1.43" Flow Length=190' Slope=0.0180 '/' Tc=28.1 min CN=81/98 Runoff=0.14 cfs 0.060 af Link 1 L: Pre-Developed Flow(N) Inflow=0.29 cfs 0.141 af Primary=0.29 cfs 0.141 af Link TOTAL: Pre-Developed Site Total Inflow=0.43 cfs 0.201 af Primary=0.43 cfs 0.201 af Total Runoff Area = 1.982 ac Runoff Volume = 0.201 af Average Runoff Depth = 1.22" 98.87% Pervious = 1.960 ac 1.13% Impervious = 0.022 ac • 6460 Pre-Developed Type IA 24-hr 2-YEAR Rainfall=2.50" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment 10S: Pre-Developed-Onsite Runoff Area=20,703 sf 0.00% Impervious Runoff Depth>0.41" Flow Length=195' Slope=0.0300 '/' Tc=23.4 min CN=72/0 Runoff=0.02 cfs 0.016 af Subcatchment20S: Pre-Developed-Onsite Runoff Area=43,622 sf 0.97% Impervious Runoff Depth>0.68" Flow Length=270' Slope=0.0260 '/' Tc=32.2 min CN=79/98 Runoff=0.10 cfs 0.057 af Subcatchment30S: Pre-Developed-Onsite Runoff Area=22,025 sf 2.51% Impervious Runoff Depth>0.80" Flow Length=190' Slope=0.0180 Tc=28.1 min CN=81/98 Runoff=0.07 cfs 0.034 af Link'IL: Pre-Developed Flow(N) Inflow=0.12 cfs 0.073 af Primary=0.12 cfs 0.073 af Link TOTAL: Pre-Developed Site Total Inflow=0.19 cfs 0.107 af Primary=0.19 cfs 0.107 af Total Runoff Area = 1.982 ac Runoff Volume = 0.107 af Average Runoff Depth = 0.65" 98.87% Pervious = 1.960 ac 1.13% Impervious = 0.022 ac a X D S a 0 D 0 z v Appendix A: HydroCAD Reports for Pre-Developed Condition Storm Events (25-Year Storm Event Analysis) (10-Year Storm Event, Summary Only) (2-Year Storm Event, Summary Only) a 0 a 3 O 3 m ro �5.1 S (.:1:17S) 11 th 11. th 5R b 4R r> 3R < (3s) It 4' 1 " Lot 1,3 (4S) .1S` i Lot 4 Ellson Lots 5-8 Al> �P— — 2R 2S f Back of Lots Storm Facility 1 " Lot 2 0 1L Post-Deve ped Flow ( ) 7 I ( 6S ; ------------ TOTAL North Dakota Planter Post-Developed Site Total I Subcat Reach `Pon Link Routing Diagram for 6460 Post-Developed - Prepared by AKS ENGINEERING --�� HydroCAD®10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC 6460 Post-Developed Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (acres) (subcatchment-numbers) 0.380 74 >75% Grass cover, Good, HSG C (2.1 S, 6S) 0.805 80 >75% Grass cover, Good, HSG D (1 S, 4.1 S, 5.1S) 0.485 98 Impervious Area on Lot @2,640 sf/Lot (2S, 3S, 4S, 5S) 0.312 98 Impervious Surfaces (1S, 2.1S, 4.1S, 5.1S, 6S) 1.982 86 TOTAL AREA 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment 1S: Back of Lots Runoff Area=18,718 sf 0.96% Impervious Runoff Depth>1.97" Tc=5.0 min CN=80/98 Runoff=0.20 cfs 0.071 af Subcatchment2.1 S: Ellson Runoff Area=21,045 sf 31.51% Impervious Runoff Depth>2.19" Tc=5.0 min CN=74/98 Runoff=0.24 cfs 0.088 af Subcatchment2S: Lot 2 Runoff Area=2,640 sf 100.00% Impervious Runoff Depth>3.66" Tc=5.0 min CN=0/98 Runoff=0.06 cfs 0.018 af Subcatchment3S: Lot 1,3 Runoff Area=5,280 sf 100.00% Impervious Runoff Depth>3.66" Tc=5.0 min CN=0/98 Runoff=0.11 cfs 0.037 af Subcatchment4.1 S: 114th Runoff Area=11,049 sf 37.45% Impervious Runoff Depth>2.59" Tc=5.0 min CN=80/98 Runoff=0.16 cfs 0.055 af Subcatchment4S: Lot 4 Runoff Area=2,640 sf 100.00% Impervious Runoff Depth>3.66" Tc=5.0 min CN=0/98 Runoff=0.06 cfs 0.018 af Subcatchment5.1S: 114th Runoff Area=11,436 sf 15.77% Impervious Runoff Depth>2.22" Tc=5.0 min CN=80/98 Runoff=0.14 cfs 0.049 af Subcatchment5S: Lots 5-8 Runoff Area=10,560 sf 100.00% Impervious Runoff Depth>3.66" Tc=5.0 min CN=0/98 Runoff=0.22 cfs 0.074 af Subcatchment6S: North Dakota Planter Runoff Area=2,954 sf 27.96% Impervious Runoff Depth>2.12" Tc=5.0 min CN=74/98 Runoff=0.03 cfs 0.012 af Reach 3R: 12" Avg. Flow Depth=0.31' Max Vet=3.23 fps Inflow=0.68 cfs 0.233 af 12.0" Round Pipe n=0.013 L=138.9' S=0.0080 '/' Capacity=3.18 cfs Outflow=0.68 cfs 0.232 af Reach 4R: 12" Avg. Flow Depth=0.22' Max Vet=4.61 fps Inflow=0.57 cfs 0.196 af 12.0" Round Pipe n=0.013 L=125.5' S=0.0250 '/' Capacity=5.64 cfs Outflow=0.57 cfs 0.196 af Reach 5R: 12" Avg. Flow Depth=0.26' Max Vel=2.27 fps Inflow=0.36 cfs 0.123 af 12.0" Round Pipe n=0.013 L=198.5' S=0.0050 '/' Capacity=2.52 cfs Outflow=0.36 cfs 0.122 af Pond 1 P: Storm Facility Peak Elev=217.81' Storage=6,404 cf Inflow=1.18 cfs 0.410 af Outflow=0.37 cfs 0.269 af Pond 2R: 12" Peak Elev=217.82' Inflow=0.98 cfs 0.339 af Primary=0.98 cfs 0.339 af Secondary=0.00 cfs 0.000 af Outflow=0.98 cfs 0.339 af Link 1 L: Post-Developed Flow(N) Inflow=0.37 cfs 0.269 af Primary=0.37 cfs 0.269 af Link TOTAL: Post-Developed Site Total Inflow=0.38 cfs 0.281 af Primary=0.38 cfs 0.281 af 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 4 Total Runoff Area = 1.982 ac Runoff Volume = 0.422 of Average Runoff Depth = 2.56" 59.80% Pervious = 1.185 ac 40.20% Impervious = 0.797 ac 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 1S: Back of Lots Runoff = 0.20 cfs @ 7.98 hrs, Volume= 0.071 af, Depth> 1.97" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 18,538 80 >75% Grass cover, Good, HSG D 180 98 Impervious Surfaces 18,718 80 Weighted Average 18,538 80 99.04% Pervious Area 180 98 0.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 1 S: Back of Lots Hydrograph ■Runoff 0.21-='- 0.20 cfs Type 1A-24-hr- 0.18t 25=YEAR-Ra i nfafl=8:90"- 0.17 0.16-Y_ Runoff-Area=18-718 sf 0.14-:, Runoff Volume=0:0-71-af - 0.13' r - 0.12?' . Runoff Depth>1:97"-- 0.11 LL o Tc=5.0-min - 0.09-' 0.08 ;. CN=80/98- 0.07- 0.06#' 0.05- ,. 0.04 a _ 0.03 0.031 a 0.01 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment 2.1S: Elison Runoff = 0.24 cfs @ 7.96 hrs, Volume= 0.088 af, Depth> 2.19" Runoff by SBUH method, Split Pervious/lmperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 6,631 98 Impervious Surfaces 14,414 74 >75% Grass cover, Good, HSG C 21,045 82 Weighted Average 14,414 74 68.49% Pervious Area 6,631 98 31.51% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 2.1S: Elison Hydrograph 0.24 cfs . -________-- ■Runoff Type IA_24-hr 0.22 2.5-YEAR.RainfaU=3.9.0"--Runoff Area=21045 sf 0.18 ,,r Runoff Volume=0:088 af 0.14-~ Runoff Depth>2.19" 0.121' Tc=5.0 m i n 0.1i' CN=74/98 0.08 , 0.06� 0.04 0.02av 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 2S: Lot 2 Runoff = 0.06 cfs @ 7.90 hrs, Volume= 0.018 af, Depth> 3.66" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 2,640 98 Impervious Area on Lot @2,640 sf/Lot 2,640 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 2S: Lot 2 Hydrograph 0.06- 0.06 cfs III Runoff 0.055 Type_IA 24-hr 0 05 ___ ___25-YEAR Rainfall=3.90" 0.045 .runoff Area=2,64O af_ 0 04 Runoff_Volume=0.018,af_ 0.035- Runoff Depth>3.66" Tc=5.0 min 0.025-- C N=0/98 0.02? 0.015? 0.005? 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment 3S: Lot 1,3 Runoff = 0.11 cfs @ 7.90 hrs, Volume= 0.037 af, Depth> 3.66" Runoff by SBUH method, Split Pervious/lmperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description * 5,280 98 Impervious Area on Lot A2,640 sf/Lot 5,280 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 3S: Lot 1,3 Hydrograph 0.12 0.11 cfs 111 Runoff 0.115 0.105.' Type 1A-24=hr ''" 25=YEAR Rainfafr=3.90"-- 0.095:' `0.09 - Runoff Area=5,280-st- 0.085 i e 005 RunofFVotume=0:037-af 0.07 �r .065 Runoff Depth>3..66`_r_ 3 0.06 '` LL 0.055=' Tc=5.O-Min- 0.05?' /+ p 0.045-? r C, N=4/'98- 0.04k - 0.035 _ 0.03 0.025?- - 0.02- 0.015= - 0.01- A 0.005 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 4.1S: 114th Runoff = 0.16 cfs @ 7.94 hrs, Volume= 0.055 af, Depth> 2.59" Runoff by SBUH method, Split Pervious/lmperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 4,138 98 Impervious Surfaces 6,911 80 >75% Grass cover, Good, HSG D 11,049 87 Weighted Average 6,911 80 62.55% Pervious Area 4,138 98 37.45% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 4.1S: 114th Hydrograph 0.16 cfs II Runoff 015r" Type IA-24-hr - °.14 2.5-YEAR.Rainfall=3.90"-_ 0.12 _ _ Runoff Area=f-1;049-sf - Runoff Volume=0.055_af 0.1 Runoff Depth>2.59"- °.06 TC=5.0 min__ 0.o7 `r 0.061 CN=80/98 V 0.053 = 0.04 " 0.03 "�- 0.02 0.01 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment 4S: Lot 4 Runoff = 0.06 cfs @ 7.90 hrs, Volume= 0.018 af, Depth> 3.66" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 2,640 98 Impervious Area on Lot @2,640 sf/Lot 2,640 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 4S: Lot 4 Hydrograph 0.06. __-_ ________I 0.06cfs ■Runoff 0.055�, Type IA 24-hr 005 25-YEAR Rainfall=3.90" 0.045A Runoff.Area=2,640..sf-_ 0.04:1'r - ---- ------- - Runoff_Volume=0.018 af _ 7, 0.0353 Runoff Depth>3.66".. 0.03 LL i Tc=5.0 m i n 0.025. 0.02rf C N=0/98 0.015 0.01 0.005 `r~q 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 5.1S: 114th Runoff = 0.14 cfs @ 7.97 hrs, Volume= 0.049 af, Depth> 2.22" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description * 1,804 98 Impervious Surfaces 9,632 80 >75% Grass cover, Good, HSG D 11,436 83 Weighted Average 9,632 80 84.23% Pervious Area 1,804 98 15.77% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 5.1S: 114th Hydrograph 0.15 0.14 cfs ■Runoff 0.14% Type 0.13 -IA-24-hr-- 0.12= - _-_______. ___-25=YEAR Rai nfall=3:90"-- - 0.11 . . _ . . . _Runoff.Ar_ea=11,436.sf__ ____- Runoff Volume=0:049 of- , 0.09 0.08� Runoff Depth>2.22"- - LL 0.07� TC.=5.Q-min__ 0.06 -CN=80/98-- 0.05 ' 0.04y __. ___ 0.03. ' r 0.02 '' 0.01. -' 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) i 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 12 Summary for Subcatchment 5S: Lots 5-8 Runoff = 0.22 cfs @ 7.90 hrs, Volume= 0.074 af, Depth> 3.66" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 10,560 98 Impervious Area on Lot @2,640 sf/Lot 10,560 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 5S: Lots 5-8 Hydrograph 0.24"r r 0.22 cfs ®Runoff 0.23-? 00..22121 t Type IA-24=hr- = .- 0.2y _ 25=YEAR-Rai nfall=3:90"-- ` - 0.19 0.16 RunofArea=i0;560:st-_ 0.17•% 016f Runoff Volume=0.0Z4:aT= 0.15 r m u yyrr�++ 0.13 ;� Runoff De th-3.6Vr'-_ 0.124,r LL 0.11 Tc=5.-0 r niq_ 0.1? 0.09 t CN=a/J8--°8 0.07 0.0s 0.05 0.04 0.03 0.02 ' r • 0.01 - / 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment 6S: North Dakota Planter Runoff = 0.03 cfs @ 7.97 hrs, Volume= 0.012 af, Depth> 2.12" Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type IA 24-hr 25-YEAR Rainfall=3.90" Area (sf) CN Description 826 98 Impervious Surfaces 2,128 74 >75% Grass cover, Good, HSG C 2,954 81 Weighted Average 2,128 74 72.04% Pervious Area 826 98 27.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment 6S: North Dakota Planter Hydrograph 0.036=� 0.0341" 0.03 cfs II Runoff 0.032' Type IA-24eh.r_ _ r _ 0.03 25=YEAR Rainfall=3.9011- 0.028 " 0.026= Runoff Area=2,954 sf 0.024 0.022=g- Runoff Volume=0.012 af 0.023 Runoff Depth>2.42"-- 0.018'f LL 0.016�+� Tc=5.0 min.. 0.0,4 EN=74/98 .. 0.012 ,r 0.01-' 0.008 > 0.006 0.004 0.002 r 0 J 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 6460 Post-Developed Type IA 24-hr 25-YEAR Rainfall=3.90" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 17 Summary for Pond 1 P: Storm Facility Inflow Area = 1.914 ac, 40.63% Impervious, Inflow Depth > 2.57" for 25-YEAR event Inflow = 1.18 cfs @ 7.95 hrs, Volume= 0.410 af Outflow = 0.37 cfs @ 9.16 hrs, Volume= 0.269 af, Atten= 68%, Lag= 72.6 min Primary = 0.37 cfs @ 9.16 hrs, Volume= 0.269 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 217.81' @ 9.16 hrs Surf.Area= 3,348 sf Storage= 6,404 cf Flood Elev= 219.00' Surf.Area=4,248 sf Storage= 10,926 cf Plug-Flow detention time= 379.9 min calculated for 0.269 af(66% of inflow) Center-of-Mass det. time= 175.3 min ( 899.0 - 723.8 ) Volume Invert Avail.Storage Storage Description #1 215.10' 10,926 cf Custom Stage Data (Prismatic)Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 215.10 1,337 0 0 216.00 2,042 1,521 1,521 217.00 2,776 2,409 3,930 218.00 3,484 3,130 7,060 219.00 4,248 3,866 10,926 Device Routing Invert Outlet Devices #1 Primary 214.90' 12.0" Round Culvert L= 50.0' Ke= 0.500 Inlet/Outlet Invert= 214.90' /212.50' S= 0.0480 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf #2 Device 3 215.10' 2.0' long (Profile 17) Broad-Crested Rectangular Weir Head (feet) 0.49 0.98 1.48 1.97 2.46 2.95 Coef. (English) 2.84 3.13 3.26 3.30 3.31 3.31 #3 Device 1 215.10' 0.6" Vert. Orifice/Grate C= 0.620 #4 Device 1 217.65' 2.0' long (Profile 17) Broad-Crested Rectangular Weir Head (feet) 0.49 0.98 1.48 1.97 2.46 2.95 Coef. (English) 2.84 3.13 3.26 3.30 3.31 3.31 Primary OutFlow Max=0.37 cfs @ 9.16 hrs HW=217.81 TW=0.00' (Dynamic Tailwater) f_ AL- =Culvert (Passes 0.37 cfs of 5.87 cfs potential flow) Orifice/Grate (Orifice Controls 0.02 cfs @ 8.15 fps) 2=Broad-Crested Rectangular Weir(Passes 0.02 cfs of 29.50 cfs potential flow) 4=Broad-Crested Rectangular Weir(Weir Controls 0.36 cfs @ 1.13 fps) 6460 Post-Developed Type IA 24-hr 10-YEAR Rainfall=3.45" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method SubcatchmentlS: Back of Lots Runoff Area=18,718 sf 0.96% Impervious Runoff Depth>1.61" Tc=5.0 min CN=80/98 Runoff=0.16 cfs 0.058 af Subcatchment2.1S: Ellson Runoff Area=21,045 sf 31.51% Impervious Runoff Depth>1.83" Tc=5.0 min CN=74/98 Runoff=0.20 cfs 0.074 af Subcatchment2S: Lot 2 Runoff Area=2,640 sf 100.00% Impervious Runoff Depth>3.21" Tc=5.0 min CN=0/98 Runoff=0.05 cfs 0.016 af Subcatchment3S: Lot 1,3 Runoff Area=5,280 sf 100.00% Impervious Runoff Depth>3.21" Tc=5.0 min CN=0/98 Runoff=0.10 cfs 0.032 af Subcatchment 4.1 S: 114th Runoff Area=11,049 sf 37.45% Impervious Runoff Depth>2.20" Tc=5.0 min CN=80/98 Runoff=0.13 cfs 0.046 af Subcatchment4S: Lot 4 Runoff Area=2,640 sf 100.00% Impervious Runoff Depth>3.21" Tc=5.0 min CN=0/98 Runoff=0.05 cfs 0.016 af Subcatchment5.1S: 114th Runoff Area=11,436 sf 15.77% Impervious Runoff Depth>1.85" Tc=5.0 min CN=80/98 Runoff=0.11 cfs 0.040 af Subcatchment5S: Lots 5-8 Runoff Area=10,560 sf 100.00% Impervious Runoff Depth>3.21" Tc=5.0 min CN=0/98 Runoff=0.20 cfs 0.065 af Subcatchment6S: North Dakota Planter Runoff Area=2,954 sf 27.96% Impervious Runoff Depth>1.76" Tc=5.0 min CN=74/98 Runoff=0.03 cfs 0.010 af Reach 3R: 12" Avg. Flow Depth=0.29' Max Vet=3.09 fps Inflow=0.59 cfs 0.200 af 12.0" Round Pipe n=0.013 L=138.9' S=0.0080'/' Capacity=3.18 cfs Outflow=0.59 cfs 0.200 af Reach 4R: 12" Avg. Flow Depth=0.20' Max Vet=4.40 fps Inflow=0.49 cfs 0.168 af 12.0" Round Pipe n=0.013 L=125.5' S=0.0250 '/' Capacity=5.64 cfs Oufflow=0.49 cfs 0.168 af Reach 5R: 12" Avg. Flow Depth=0.24' Max Vel=2.17 fps Inflow=0.31 cfs 0.105 af 12.0" Round Pipe n=0.013 L=198.5' S=0.0050'/' Capacity=2.52 cfs Oufflow=0.31 cfs 0.105 af Pond 1 P: Storm Facility Peak Elev=217.77' Storage=6,265 cf Inflow=0.99 cfs 0.348 af Outflow=0.24 cfs 0.208 af Pond 2R: 12" Peak Elev=217.77' Inflow=0.83 cfs 0.290 af Primary=0.83 cfs 0.290 af Secondary=0.00 cfs 0.000 af Outflow=0.83 cfs 0.290 af Link IL: Post-Developed Flow(N) Inflow=0.24 cfs 0.208 af Primary=0.24 cfs 0.208 af Link TOTAL: Post-Developed Site Total Inflow=0.25 cfs 0.218 af Primary=0.25 cfs 0.218 af 6460 Post-Developed Type IA 24-hr 10-YEAR Rainfall=3.45" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 4 Total Runoff Area = 1.982 ac Runoff Volume = 0.358 of Average Runoff Depth = 2.17" 59.80% Pervious = 1.185 ac 40.20% Impervious = 0.797 ac AK fl. Appendix B: HydroCAD Reports for Post-Developed Condition Storm Events (25-Year Storm Event Analysis) (10-Year Storm Event, Summary Only) (2-Year Storm Event, Summary Only) O 7 3 ro 6460 Post-Developed Type IA 24-hr 2-YEAR Rainfall=2.50" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 3 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SBUH method, Split Pervious/Imperv. Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method SubcatchmentlS: Back of Lots Runoff Area=18,718 sf 0.96% Impervious Runoff Depth>0.90" Tc=5.0 min CN=80/98 Runoff=0.08 cfs 0.032 af Subcatchment2.1S: Ellson RunoffArea=21,045 sf 31.51% Impervious Runoff Depth>1.13" Tc=5.0 min CN=74/98 Runoff=0.12 cfs 0.045 af Subcatchment2S: Lot 2 Runoff Area=2,640 sf 100.00% Impervious Runoff Depth>2.27" Tc=5.0 min CN=0/98 Runoff=0.03 cfs 0.011 af Subcatchment3S: Lot 1,3 Runoff Area=5,280 sf 100.00% Impervious Runoff Depth>2.27" Tc=5.0 min CN=0/98 Runoff=0.07 cfs 0.023 af Subcatchment4.1 S: 114th Runoff Area=11,049 sf 37.45% Impervious Runoff Depth>1.40" Tc=5.0 min CN=80/98 Runoff=0.08 cfs 0.030 af Subcatchment4S: Lot 4 Runoff Area=2,640 sf 100.00% Impervious Runoff Depth>2.27" Tc=5.0 min CN=0/98 Runoff=0.03 cfs 0.011 af Subcatchment5.1S: 114th Runoff Area=11,436 sf 15.77% Impervious Runoff Depth>1.10" Tc=5.0 min CN=80/98 Runoff=0.06 cfs 0.024 af Subcatchment 5S: Lots 5-8 Runoff Area=10,560 sf 100.00% Impervious Runoff Depth>2.27" Tc=5.0 min CN=0/98 Runoff=0.14 cfs 0.046 af Subcatchment6S: North Dakota Planter Runoff Area=2,954 sf 27.96% Impervious Runoff Depth>1.07" Tc=5.0 min CN=74/98 Runoff=0.02 cfs 0.006 af Reach 3R: 12" Avg. Flow Depth=0.24' Max VeI=2.74 fps Inflow=0.39 cfs 0.134 af 12.0" Round Pipe n=0.013 L=138.9' S=0.0080 '/' Capacity=3.18 cfs Outflow=0.39 cfs 0.134 af Reach 4R: 12" Avg. Flow Depth=0.16' Max VeI=3.87 fps Inflow=0.32 cfs 0.111 of 12.0" Round Pipe n=0.013 L=125.5' S=0.0250 '/' Capacity=5.64 cfs Outflow=0.32 cfs 0.111 af Reach 5R: 12" Avg. Flow Depth=0.19' Max VeI=1.92 fps Inflow=0.20 cfs 0.070 af 12.0" Round Pipe n=0.013 L=198.5' S=0.0050'I' Capacity=2.52 cfs Outflow=0.20 cfs 0.070 af Pond 1P: Storm Facility Peak Elev=217.72' Storage=6,095 cf Inflow=0.61 cfs 0.223 af Outflow=0.11 cfs 0.084 af Pond 2R: 12" Peak Elev=217.72' Inflow=0.54 cfs 0.191 af Primary=0.54 cfs 0.191 of Secondary=0.00 cfs 0.000 af Outflow=0.54 cfs 0.191 af Link IL: Post-Developed Flow(N) Inflow=0.11 cfs 0.084 af Primary=0.11 cfs 0.084 af Link TOTAL: Post-Developed Site Total Inflow=0.11 cfs 0.090 af Primary=0.11 cfs 0.090 af . _ . 6460 Post-Developed Type IA 24-hr 2-YEAR Rainfall=2.50" Prepared by AKS ENGINEERING HydroCAD® 10.00-20 s/n 01338 ©2017 HydroCAD Software Solutions LLC Page 4 Total Runoff Area = 1.982 ac Runoff Volume = 0.229 of Average Runoff Depth = 1.39" 59.80% Pervious = 1.185 ac 40.20% Impervious = 0.797 ac A.cS ('1 Uq ar a) II) Appendix C: Stormwater Facility Water 74, Quality Calculations CU o' • STORMWATER QUALITY CALCULATIONS AMIN:10 Client: Venture Properties ENGINEERING&FORESTRY Project: Brightwood Subdivision AKS Job No.: 6460 Date: 10/1/2018 Done By: SD Checked By: DS IMPERVIOUS AREA Total Site Area: 1.98 acres Total Site Area: 86,249 square feet(sf) Number of Lots: 8 Impervious Area Per Lot: 2,640 sf Total Impervious Lot Area: 21,120 sf Road & Sidewalk Impervious Area: 12,757 sf Total Impervious Area: 33,877 sf WATER DESIGN QUALITY VOLUME (WQV) (Per CWS 4.05.6b-R&O 17-05) WQV= 0.36"X Area(ft) = 1016 cubic feet 12" per ft WATER QUALITY FLOW (WQF) (Per CWS 4.05.6b-R&O 07-20) WQF = WQV(sf) = 0.07 cfs 4"60"60 WATER QUALITY MANHOLE SUMP VOLUME CALCULATIONS (Per CWS 4.06.1 b-R&O 07-20) CWS Criteria: Sump Volume=20 cubic feet per 1.0 cfs of flow 25-year Flow through WQ Manhole = 0.98 cfs Calculated Manhole Sump Volume = 19.6 cubic feet Calculated Manhole Sump Depth (60" Dia. Manhole) = 1.0 ft < 5 feet maximum 1 of 2 EXTENDED DRY BASIN DESIGN & CALCULATIONS Hydraulic Design Criteria(Per CWS 4.06.2-R$O 17-05) Permanent Pool Depth: 0.4 ft Permanent Pool covers bottom of basin Design Detention Volume: 1.0 x Water Quality Volume (WQV) Water Quality Drawdown Time: 48 hours Maximum Depth of WQ Pool: 4 ft Avoid direct flow across WQ pond to avoid short circuiting Extended Dry Basin Sizing Design: Bottom Minimum Side Top of Pond Perm. Pool Pool Bottom Bottom of Slope Bottom Width Slopes Elev. Depth Area Pool Elev. (ft/ft) (ft) H:V (ft) (ft) (sf) (ft) 0.0 4 3.0 219 0.4 1337 215.1 Water Quality Flow Hydraulic Calculations: Max. Pool Calculated Pool Elev. at Orifice CL Calculated Calculated Q WQV Height Orifice Diameter Elev.,25-yr Pond WQV WQV Pool Event Depth (cfs) (ft) (ft) (in) (ft) (cubic feet) (ft) 0.01 215.8 215.12 0.58 217.81 1128 0.7 Check Against Design Criteria: Calculated Meet CWS Criteria? Minimum Freeboard: 1.2 feet Yes more than 1 foot Minimum Bottom Width: 4 feet Yes greater than 4 feet Maximum Pool Depth at WQV: 0.7 feet Yes less than 4 feet Detained Water Quality Volume: 1128 cubic feet Yes greater than 1016 cf 2 of 2 Aiss 9 i (p r fD !-° Appendix D: Relevant Information from Technical Release 55, Urban Hydrology for Small Watersheds (77 1I �V J � O0 1 � 51 .�r TR55 RUNOFF CURVE NUMBERS Chapter 2 Estimating Runoff Technical Release 55 Urban Hydrology for Small Watersheds Table 2-2a Runoff curve numbers for urban areas 11 immimmil Curve numbers for ----- Cover description -- hydrologic soil group Average percent Cover type and hydrologic condition impervious area Z A B C D Fully developed urban areas (vegetation established) Open space(lawns,parks,golf courses,cemeteries,etc.)W: Poor condition(grass cover<50%) 68 79 86 89 Fair condition(grass cover 50%to 75%) 49 69 79 84 Good condition(grass cover>75%) 39 61 r-7 1—g� Impervious areas: El El Paved parking lots,roofs,driveways,etc. (excluding right-of-way) 98 98 El Streets and roads: u L_! Paved;curbs and storm sewers(excluding right-of-way) 98 98 98 98 Paved;open ditches(including right-of-way) 83 89 92 93 Gravel(including right-of-way) 76 85 89 Dirt(including right-of-way) 72 82 87 Western desert urban areas: Natural desert landscaping(pervious areas only)Ai 63 77 85 88 Artificial desert landscaping(impervious weed barrier, desert shrub with 1-to 2-inch sand or gravel mulch and basin borders) 96 96 96 96 Urban districts: Commercial and business 85 89 92 94 95 Industrial 72 81 88 91 93 Residential districts by average lot size: 1/8 acre or less(town houses) 65 77 85 90 92 1/4 acre 38 61 75 83 87 1/3 acre 30 57 72 81 86 1/2 acre 25 54 70 80 85 1 acre 20 51 68 79 84 2 acres 12 46 65 77 82 Developing urban areas Newly graded areas (pervious areas only,no vegetation)5i 77 86 91 94 Idle lands(CN's are determined using cover types similar to those in table 2-2c). 1 Average runoff condition,and Ia=0.2S. 2 The average percent impervious area shown was used to develop the composite CN's.Other assumptions are as follows:impervious areas are directly connected to the drainage system,impervious areas have a CN of 98,and pervious areas are considered equivalent to open space in good hydrologic condition.CN's for other combinations of conditions may be computed using figure 2-3 or 2-4. 3 CN's shown are equivalent to those of pasture.Composite CN's maybe computed for other combinations of open space cover type. 4 Composite CN's for natural desert landscaping should be computed using figures 2-3 or 2-4 based on the impervious area percentage (CN=98)and the pervious area CN.The pervious area CN's are assumed equivalent to desert shrub in poor hydrologic condition. 6 Composite CN's to use for the design of temporary measures during grading and construction should be computed using figure 2-3 or 2-4 based on the degree of development(impervious area percentage)and the CN's for the newly graded pervious areas. (210-VI-TR-55,Second Ed.,June 1986) 2-5 Chapter 2 Estimating Runoff Technical Release 55 Urban Hydrology for Small Watersheds Table 2-2c Runoff curve numbers for other agricultural lands II miiiiiiii Curve numbers for — --- — Cover description — — --- hydrologic soil group— Hydrologic Cover type condition A B C D Pasture,grassland,or range—continuous Poor 68 79 86 89 forage for grazing.2/ Fair 49 69 79 84 Good 39 61 74 80 Meadow—continuous grass,protected from — 30 58 71 78 grazing and generally mowed for hay. Brush—brush-weed-grass mixture with brush Poor 48 67 77 83 the major element.2 Fair 35 56 70 77 Good 30 V 48 65 73 Woods—grass combination(orchard Poor 57 73 82 86 or tree farm).li/ Fair 43 65 76 82 Good 32 58 r-9$ El Woods.2/ Poor 45 66 77 83 Fair 36 60 73 79 Good 30 4/ 55 70 77 Farmsteads—buildings,lanes,driveways, — 59 74 82 86 and surrounding lots. 1 Average runoff condition,and I.=0.2S. 2 Poor: <50%)ground cover or heavily grazed with no mulch. Fair: 50 to 75%ground cover and not heavily grazed. Good: >75%ground cover and lightly or only occasionally grazed. 3 Poor. <50%ground cover. Fair: 50 to 75%ground cover. Good: >75%ground cover. 4 Actual curve number is less than 30;use CN=30 for runoff computations. 5 CN's shown were computed for areas with 50%woods and 50%grass(pasture)cover.Other combinations of conditions may be computed from the CN's for woods and pasture. 6 Poor: Forest litter,small trees,and brush are destroyed by heavy grazing or regular burning. Fair: Woods are grazed but not burned,and some forest litter covers the soil. Good: Woods are protected from grazing,and litter and brush adequately cover the soil. (210-VI-TR-55,Second Ed.,June 1986) 2_7 1110 E. d r 3i Appendix E:pp x USDA-MRCS Soil Resource Report 3 Hydrologic Soil Group—Washington County,Oregon 3 v F v 518020 516053 516030 516110 516140 516170 516200 516230:7 45°26'27"N 45°26'27"N i Sw Cottonwood Ln i Q bS R I Xt , W i O a o g r Tr T y 3 Co r�a�o l !tt L! 3 hS c3dill Ird„tip i i�17�o L vfUod&i�thi;�uo g,ic,��lic,,, • 45°26'18"N ' 45°26'18"N 516020 516053 516080 516110 516140 516170 516200 516230 3 N 3 4 Map Scale:1:1,440 if printed on A portrait(8.5'x 11")sheet R Meters N 0 20 40 80 120 AFeet 0 50 10D 200 300 Map projedion:Web Merotnr Corner coordinates:WGS84 Edge tics:UTM Zone lON WGS84 sNatural Resources Web Soil Survey 3/12/2018 Conservation Service National Cooperative Soil Survey Page 1 of 4 mow Hydrologic Soil Group—Washington County,Oregon MAP LEGEND MAP INFORMATION Area of Interest(AOI) c The soil surveys that comprise your AOI were mapped at Area of Interest(AOI) C/D 1:20,000, Soils Soil Rating Polygons a D Warning:Soil Map may not be valid at this scale. 0 A p Not rated or not available Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil ND Water Features line placement.The maps do not show the small areas of B Streams and Canals contrasting soils that could have been shown at a more detailed Transportation scale. 0 B/D C Rails Please rely on the bar scale on each map sheet for map ,.y,. Interstate Highways measurements. C/D US Routes Source of Map: Natural Resources Conservation Service D Web Soil Survey URL: Major Roads Coordinate System: Web Mercator(EPSG:3857) 0 Not rated or not available Local Roads Maps from the Web Soil Survey are based on the Web Mercator Soil Rating Lines Background projection,which preserves direction and shape but distorts A Aerial Photography distance and area.A projection that preserves area,such as the ND Albers equal-area conic projection,should be used if more accurate calculations of distance or area are required. B This product is generated from the USDA-NRCS certified data as es.: B/D of the version date(s)listed below. . C Soil Survey Area: Washington County,Oregon Survey Area Data: Version 15,Sep 19,2017 . . C/D Soil map units are labeled(as space allows)for map scales D 1:50,000 or larger. . . Not rated or not available Date(s)aerial images were photographed. Aug 3,2014—Aug Soil Rating Points 23,2014 l3 A The orthophoto or other base map on which the soil lines were NDcompiled and digitized probably differs from the background imagery displayed on these maps.As a result,some minor Dy B shifting of map unit boundaries may be evident. F$ BID i-I1.a Natural Resources Web Soil Survey 3/12/2018 "r's® Conservation Service National Cooperative Soil Survey Page 2 of 4 , Hydrologic Soil Group—Washington County,Oregon Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Aloha silt loam C/D 5.8 66.1% 37B Quatama loam,3 to 7 C 3.01 33.9% percentp _ slopes i Totals for Area of Interest 8.8 100.0%I Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D)and three dual classes (ND, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential)when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential)when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (ND, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method:Dominant Condition (ADA Natural Resources Web Soil Survey 3/12/2018 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Sail Group—Washington County,Oregon Component Percent Cutoff:None Specified Tie-break Rule: Higher is Natural Resources Web Soil Survey 3/12/2018 Conservation Service National Cooperative Soil Survey Page 4 of 4