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CC - Storm Drainage Calcs Of THE LAN D GROUP Southridge Subdivision Phase 5 Meridian, Idaho ACHD Storm Drain Management & Engineering Drainage Report Developer Challenger Development, Inc. Engineer The Land Group, Inc. N 462 East Shore Drive, Suite 100 o�cJ10 T E� G Eagle, Idaho 83616 c3 G�S Contact: Jason Densmer, PE Ph: 208.939.4041 09 1 RTE OF TLG Project No. 117036 f�`SON DES� 01/13/2021 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 - thelandgroupinc.com Southridge Subdivision Phase 5 Meridian, ID Storm Water Management Report Report Purpose This report addresses the storm drainage systems for the proposed Southridge Subdivision Phase 5, located at the extension of S. Grand Fork Way south of Overland Road, between Linder Rd and Ten Mile, within the City of Meridian, Idaho. Stormwater management systems are included within the work that will serve the Phase 5. Prior construction of the Overland Road Re-alignment and S. Grand Fork Rd extension (separate, prior projects) contemplated the future improvements which are now part of the Southridge Subdivision Phase 5 and provided storm drainage capacity within the systems constructed by these projects to accommodate the Southridge Subdivision Phase 5 area. Site Description The general location of the project is described above.The site is adjacent to and west of the Southridge Subdivision Phase 1 and northwesterly of Southridge Subdivision Phase 3. The project also connects to the aforementioned S. Grand Fork Rd. extension to the northwest. The topography of the site is gently sloping, generally sloping from south to north. Southridge Subdivision Phase 5 comprises an area of approximately 10.22-acres. Storm Drainage Routing &Treatment: Generally, collection, routing and treatment of storm drainage from the project is as follows: 1. Roadways slope to gutters along the road edges 2. Gutters transport collected drainage to catch basins. 3. Stormwater flows through the catch basins into a storm drain piping network which transports the stormwater to existing piping within the Overland Road improved area. 4. Within the Overland Road,the piping network conveys storm water to treatment structures which ultimately discharge the treated stormwater to a detention pond. 5. The detention ponds provide temporary storm water holding volumes to allow sufficient time for the incoming flows to be attenuated and discharged at a pre-development rate. 6. The attenuated flows discharge to off-site drainage systems which are currently open ditches. Master Drainage Plan The Overland Road Re-alignment project prepared a detailed drainage study of the roadway area and the upland areas, including the area proposed for Southridge Subdivision Phase 5. (Note—the Overland Road study identified these areas as "Phase 4"). The Overland Road Realignment—Storm Water System Design Report (dated Aug.4, 2008) is attached to this report as Attachment A and incorporated by reference. 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 • thelandgroupinc.com Southridge Subdivision Phase 5 Meridian, ID Storm Water Management Report Conformance to Master Drainage Plan In the time since the Overland Road Realignment Project was prepared, the design of lots and roadways within this Phase area has been revised. These changes have had minor impacts to the anticipated stormwater flows from this area contemplated by the Master Drainage Plan. An exhibit showing the drainage basins of the proposed Phase 5 area and roadway extension and the resulting stormwater flows, calculated using the current ACHD methodology are included as Attachments B and C. Conclusion The development of Southridge Subdivision Phase 5 will not contribute more storm water to the existing Overland road system than was anticipated by the Master Drainage Plan. The master drainage study for this area anticipated a flow of 42.09 cfs.The Phase 5 and roadway extension improvements will contribute a total of 12.51 cfs.Therefore,this area will be adequately served by the existing system's capacity. 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 • thelandgroupinc.com Southridge Subdivision Phase 5 Meridian, ID Storm Water Management Report Appendix A Overland Road Realignment Stormwater System — Design Report 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 • thelandgroupinc.com alga OVEMAND ROAD REALIGNMENT STORM .AT SYSTEM—DEsiGN REPORT DENTELOPER JLJ Enterprises, Inc. 1560 Carol Street Meridian, Idaho 83642 ENGINEER The Land Group, Inc. 462 East Shore Drive Eagle, Idaho 83616 Ph: (208) 939-4041 Project No. 06361 August 4,2008 THE LAND GROU11, IN"€, STORM WATERYSTEmDESCRIPTION: This report provides storm water system details for the Overland Road realignment and the future Southridge Subdivision Phases 4 and 6 projects. As depicted on the accompanying Storm Water System Report exhibits, these areas occupy approximately 48.5 acres. Construction documents specific to the Overland Road Realignment have been prepared and show design details. The future Phase 4 and Phase 6 construction documents will be prepared as individual projects and submitted at a later time. Storm Drainage Routing&'Treatment: Generally, collection,routing and treatment of the storm drainage are as follows: 1. Roadways slope to gutters along the road edges. 2. The gutters transport collected drainage to catch basins. 3. The storm water flows through the catch basins into treatment structures. 4. Discharge from the treatment structures is delivered to retention facilities. Storm drainage on the site is disposed of utilizing several different methods. Area 1 consists of approximately 960 feet of Overland Road and all of the future Southridge Subdivision Phase 6 (excluding a commercial portion). Area 1 is routed overland via curb and gutter to catch basins and sand and grease traps which treat the water prior to discharging into an above ground retention pond Nvith a sand infiltration window. The catch basins and sand and grease traps have been sized to accommodate flows from the 100-year storm event. The retention pond has been sized to provide adequate storage volume for the 100-year storm event. Area 2 consists of approximately 750 feet of Overland Road. Area 2 is routed overland via curb and gutter to catch basins and a sand and grease trap which treats the water prior to discharging into an underground seepage bed. The sand and grease traps have been sized to accommodate flows from the 100-year storm event. The seepage bed has been sized to provide adequate storage volume for the 100-year storm event. Areas 3 through 9 and all of the future Southridge Subdivision Phase 4 (excluding commercial portions) are routed via curb and gutter, and underground pipe to a Contech treatment structure with an offline bypass weir (Vortech 16000 hydrodynamic separator). This treatment structure has been sized to treat flows from the "water quality" storm event equal to 1/3 of the 2-Year went (approximately 7 cfs) and provides an 80% removal efficiency for particle sizes 110 ,,,m and larger. After treatment, water is discharged into a retention/amenity pond, which has been sized to provide adequate storage volume for the 100-year storm. event. The pond has also been designed to discharge offsite at predevelopment rates. See Summary of Drainage Calculations for breakdown of flows. Peak Rate of Discharge The peak rate of discharge was calculated per Section 8005 of the ACHD Development Policy Manual. The peak flows and resulting runoff volumes represent the maximums from a 100-year storm event at the time of concentration. Pipe flows have been checked using a computer program based on the Manning's formula. Tributary areas for each drainage basin are shown on the exhibits provided the Appendix. As shown on the exhibits, drainage calculations and facilities for some of the tributary areas have been sized to accommodate future phases of the Southridge Development, Primary Conveyance System The primary conveyance system (street gutters, catch basins, and pipes) have been sized to accommodate the maximum flow from the 25-Year Storm Event. See construction drawings for details and sizes. or ±»tom xo GR< «6 !«c Pre development Discharge Summary � ( 2 - my2a �±�»�22� Predevelopmen1 Discharge (TR55).1xt Graphical Peak Discharge method (TR-55) 06361 - overland Road Pre-development Discharge, Given Input Data: Description . . . . . . . . . . . . . . . . . . . . . Pre-Development Discharge Rainfall distribution . . . . . . . . . , . Type II Frequency , ^ , , . ^ . . . . . . . . . ~ . . ^ ^ , . . 100 years Rainfall , P (24-hours) . . . , . . . . . . 2.8000 in Drainage area ` . . . . . . . 0.2260 mi2 Runoff curve number, CN . . . . . . . . 75 Time of concentration, Tl ' . . . . . . 3.3500 hrs Pond and swamp Areas . . . . . . . . . . . , 0.0000 % of Area computed Results: Initial abstraction, Io . . . . . . . . ,. 0'6057 in . Ia/P . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2301 unit peak discharge, qu . , . , . . . . . 135.5934 csm/in Runoff, 0 . . . . . . . . . ' . . . . . . . . . . ' . . 0.0325 in Pond and swamp adjustment, Fp , , . 1.0000 Peak discharge, qp . . . . . . . , . . , . . . 25.5796 cfs Page 1 THE IAN[) GROUP, INC. Post-Development Discharge Summary ?03x THE LAND GROUP, MC Overland ® 0 July 17, 2008 Storm raina Calculations Drainage Area#1 (See exhibit for location) Area= 238,651 sf Area= 5.48 acres C= 0.88 Tc= 93 min. i= 2.70 in/hr Q= 13.02 cfs V(required)= 15,588 cf —includes additional 15%for sediment storage V(provided)= 16,017 cf Infiltration System Characteristics(Pond with Drainage Window): k= 8.0 in/hr Width= 60.0 ft Length= 14.6 ft A perc. = 877 sf < Design Percolation Area of Drainage Window Q perc. = 585 cf/hr Infiltration Volume Check V(90%)= 14,029 cf —90%of Design Storm Vperc= 14,029 cf —Total Percolation Volume in 24-hours Sand and Grease Tra s Characteristics: Baffle 12 18 24 Spacing(in.) Area{s.f 4M 6.00 8.00 [1000 Gal.] Area(s.f) 5.25 7.88 10.50 [1500 Gal.] Velocity Through Baffle: Type; 2-1500 Gal/1-1500. Sand and Grease Trap by Boise Vault and Pre Cast A b= 26.50 sf <--24"between baffles Q max. = 13.02 cfs —Max Q at 100-Year Storm Site Planning .Z ndrr-rye Architecture Ci Z ngineerzna -Goff Co rse Irri rrtion&Etzgineenq •Graphic Communication -Sr raying 462 E.Shone Drive,Ste 100,Eagle,Idaho 83616 •P 208.939.4041 F 208.939.4445 .mvty thelandgroupinc..eom THE,LAND GROUP, U.N(I Overland o ( ) July 17, 200 Storm mina Calculations Drainage Area#2(Sege exhibit for location) Area= 71,717 sf Area= 1.65 acres C = 0.90 Tc= 10.00 min. i = 3.20 in/hr Q= 4,74 cfs V= 4,368 cf {--Includes additional 15%for sediment storage Infiltration System Characteristics(Seepage ggd1: k= 8.0 in/hr Width= 12.0 ft Depth= 12,0 ft <—Minus 1-foot Freeboard Voids= 40% +—Void Volume of Media A perc. = 1,405 sf <—2/3 Depth x Perimeter Q perc. = 937 cf/hr V sb= 10,919 cf —Seepage Bed Volume Required(40%Voids) Len th= 75M ft -Seepage Bed Length Required _a Actual Volume Provide( 4,742 cf r Infiltration Volume Check: V(90%)= 3,931 cf � 90%of maximum runoff developed in 24-hours Vperc= 22,484 cf < Total Percolation Volume in 24-hours Seepage fed Recovery Tirne: Vs Max= 4,368 cf —Maximum Runoff Developed Q perc 937 cf per hr Sand and Grease Tra s Characteristics. Baffle 12 18 24 Spacing(in.) Area(s.0 4.00 6.00 8.00 [1000 Gal.] Area(s.f} 5.25 7.88 10.50 [1500 Gal,] Velocity Through Baffle: Type: 1-1500 Gal. Sand and Grease Trap by Boise Vault and Pre Cast A b= 10.50 sf <-24"between baffles Q max, = 4.74 cfs —Max Q at 25-Year Storm Site Plannzng Lanr/rs e Architect re Civil Engineering -Golf Course Irtzgation Engineering Graphas Com ernication Sufiv ing 462 E.Shore Drive,Ste. 100,Eagle,Idaho 83b 1 f •P 208.939.4041 F 208.939,4443 -wzviy thelandgroupine eom THE, LAND c R()UP YNC, Overland Road (PN 06361) July 21, 20 Storm r inCalculations Drainage Area#3(See exhibit for location) Area= 63,375 sf Area= 1.45 acres C= 0.90 Tc= 10 min. (ACHD minimum): Actual = 5 i(100-yr)= 3.20 inihr i (25-yr)= 2.30 in/hr Q(100-yr)_ 4.19 cfs Q (25-yr)= 3.01 cfs Drainage Area#4 fee exhibit for location) Area= 61,919 sf Area= 1.42 acres C= 0.90 Tc= 10 min. (ACHD minimum): Actual = 9 i(100-yr)= 3.20 inihr i (25-yr)= 2.30 in/hr Q(100-yr)= 4.09 cfs Q(25-yr)= 2.94 cfs Drainage Area#6(See exhibit for location) Area= 81,526 sf Area= 1.87 acres C= 0.90 Tc= 15 min. i(100-yr)= 2.60 inihr i (25-yr)= 1.85 inihr Q(100-yr)® 4.38 cfs Q(25-yr)= 3.12 cfs Drainage Area#6(See exhibit for location) Area= 74,755 sf Area= 1.72 acres C= 0.90 Tc= 25 min. i(100-yr) = 1.80 in/hr i(25-yr)= 1.40 inihr Q(100-yr)= 2.78 cfs Q(25-yr)= 2.16 cfs Drainage Area#7(See exhibit for location) Area= 20,191 sf Area= 0.46 acres C= 0.90 Tc= 25 min. i (100-yr)= 1.80 in/hr i(25-yr)= 1 A0 in/hr Q(100-yr)= 0.75 cfs Q(25-yr)= 0.58 cfs Site Planning L andsc e Architecture Civil Engineenug -Golf Course Irrigation&Engineering Graphic Commrnuation •Surveying 462 E.Shore Dave,Ste, 100,Eagle,fdaho 8361 G •P 208.939.404 9 F 2©8.939.4445 -i vry thelandgrrruj inc.tvm T111" LAND GROUP, INC, Overland o (PN 06361) July 17, 2008 Storm r ina Calculations Drainage Area#8(See exhibit for location) Area= 78,102 sf Area= 119 acres C= 0.90 Tc= 20 min. i (100-yr)= 2.20 inihr i(25-yr)= 1.50 inthr Q(100-yr)= 3.55 cfs Q(25-yr)= 2.42 cfs Drainage Area#9(See exhibit for location) Area= 78,151 sf Area= 1.79 acres C= 0.90 Tc= 11 min. i(100-yr)= 3.10 infhr i (25-yr)= 2.30 inlhr Q(100-yr)= 5.01 cfs Q(25-yr)= 3.71 cfs outhridge Phase 4(See exhibit for location) Area= 1,343,302 sf Area= 30.84 acres C= 0.65 Tc= 22 min. i (100-yr)= 2.10 inlhr i (25-yr) = 1.52 inlhr Q (100-yr)= 42.09 cfs Q(25-yr) = 30.47 cfs Pre-Development Summary(TR-55 Method): A {cfs} Tc (acres) (100-yr) (min.) 144.90 25.58 201.00 Post-Development Summary--Overland Road/Phase 4(Rational Method): Q(cfs) Q(cfs) Q(cfs) i(inlhr) i(inlhr) i(inlhr) A Tc (100-yr} (25-yr} (113 2-yr) c (100-yr} (25-yr} (2-yr} {acres} (min.) 57.38 44.97 6.72 0.75 1 1.85 1 A5 1 0.65 41.35 25 Overland Road/Phase 4 Pond Sizing: Allowed Predevelopment Discharge(cfs)= 18.00 Total Q(cfs)= 57.38 Area of Direct Runoff(Area 10)(sf)= 47,940 Direct Runoff Volume(cf) 3,995 Actual Volume Provided(cf) 66,987 or Site Planning LancZsca e Archztect rre Civil Engineering -Go�Coarse Irrigation 6-En,ine ng Gr rabic COrr?r72dlft8cati07d Sere ing 462 E.Shore Drive,Ste. 100,Eagle,Idaho 83616 -P 208.939.4041 F 208.939.4445 •xww.thelan(&roxrpinc corn Exhibits filename Path: g:\2006\06361\cad\overland_c3d\_06361—postdevelopmentsw.dwg Last Plotted By gate welt . Date Plotted: Thursday,July 17 2008 at 10:33 AM Platting Device: mito.pc3 Plotst}1e Table: tlg mono.stb MATCHLINE - SEE SD 01 FOR CONTINUATION 3 {.i 1 r f i"i a u rr VP t 9 c.r M n e Ail V ti RP w ue 01) 7 a �n *� F CD r.CD CD AREA NOT INCLUDED Nl lid •A1ki'` .. �r r , w l u q M1 A � " ..�. r ,� ,.� , En p 4W M� ~••.. f f a � , r, x , „f e,. p � r ti ,., a� co rye. ,a v � t I h"L r �.. I } t a 6 " ti. t pt r r� d rl P , ttM .,,.. ' 'r t ii ; I 1 k I , Sheet Title: Project Name: 2 �9 Overland Re-Alignment 1 I Post-Development 4 . 1 q CD Construction Documents Tributary Ar s $ wMeridian, Idaho 9 � Rename Path: g:\2006\06351\cod\overland_c3d\_08391—postdevelopmentsw.dwg Lost Plotted By. gabs welt Date Plotted; Thursday,July 17 2008 at 10:33 AM Plotting Device: mita,pe3 Plotsty7e Table: fig mono.stb a- ^ °k. r 9 A CD td t S �3 N a ;. � f p r m 1 �.. N C \ i tt CD CD rn QD rt� ° r " \ e ^ � E d r � r t r P , aF+^ z� � r 4 �t v , iL a , ` r i Rv� ° 5, F rt i 1 h em MATCHLINE — SEE SD 02 FOR CONTINUATION ! a Q 2 Sheet Title: ° Project Nome: Overland Re-Alignment Post-Development C � �g TributaryConstr � � Nay 2 Ra $ Meridian, Idaho s Filename Path: 9:\2006\06361\cod\overland_c3d\_06361_predevelopmentsw.dwg Lost Plotted By gobs welz Dote Plotted: Thursday,July 17 2008 at 11:07 AM Plotting Device: mito.pc3 Poi style Table: tig monostb i 4 n t !i J { { j y � � ° i t 3 { t, t F5 � '"� A v 9 F { 7 ! f t ?a t{ r {1 'i tL' � t� + d � t <w �.r r fir' ,' { J 1 > XPW If Q art r t k �l l ';try'1 b�°bN rk�.m+nn m "uW 41'rt I{iT'Qrt A4+1&'M1NIG'4 dswik�`�' p y. { A / 1 A« glNtylM�'2s' WF� v 0 t� / i r a 3Pp� A 1 it CD a� y^ d 4 p tiutfi>aly a v CD , _ . s I �S 4 �.g. {{s , � t CD t o � k { 2- °'n' Sheet Title: � Project Name:Cn CD U ri C ConstructionDocuments eridian, Idaho g Southridge Subdivision Phase 5 Meridian, ID Storm Water Management Report Appendix B Drainage Basin Map 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 • thelandgroupinc.com DO _ A a CD Q - O N Co A co cnC ' o/ II o � � / Subbasin 9 C T T n Cn I € y Cn Cn / 7393 SF uasn 10 � -n Sbbi II \ Cn T T CY / Cn /�/�'% _ - - - - - - - - - - — - - - - - - - 23407 - - - — _ _ _ _ _ _ _ _ T T / — _ 18'GIRR = 18 GIRR — S F 3 GIRR — — — — — — — — — — — \ o / _ — — _ — — — — — — — — — — — — — — — — — — — — — 18"GIRR — / u basin 8 � � / _ - - - -� 19713 SF R / / --- ----------- ----- OS ti 0SIltz 24"SD 24"SD & 2 SD 24 SD I o �� / O \ \ --- -- -- ------- — -- _ _-------------- �1 LU sa ' ' — -- — ---- e / N \ /w =O Subbasin 7 ' Subbasin 11 I .— I I / 23156 SF ' / I wCD LO \ - - I I I mw 13 �V I � I y I Cc 4:-A I I II cc R:cn ` N H cz- (/ CQ CA-)/ cn , O O mime 30 cr, "' l� =r30 y 1LM ob / _ \ C'3 I — — — — 1 o co; IC i v / O O / Cn � ,,� v / v N / o / c\ / 6�, �/ �, � T O N \ \ I ,' `��� �� basil ;1 ' C' I \ \ \\ J I CL L-LCn f I / C' �-- cc ccf'n T l I - I 1 I III I I so I I l \\ Sp W � 8 I I I 6 „S Ili— P�qq� \\\ � p \ T I \, Cn CD Il / Southridge Subdivision No. 3 / ,cV SS I / I 01 Southridge Subdivision No. 1 THE LAND GROUP INCORPORATED 462 East Shore Drive, Suite 100 Eagle, Idaho 83616 Ph. 208.939.4041 Fax. 208.939.4445 www.thelandgroupinc.com 3 E Project No.: 117002 >u Date of Issuance: 07-27-2017 Designed by: TLG Checked by: TLG o N Drainage Map 0 60' 120' Sheet No.:� 60' App B HORIZONTAL SCALE: 1' = �10 Southridge Subdivision Phase 5 Meridian, ID Storm Water Management Report Appendix C Drainage Calculations 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 • thelandgroupinc.com ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. teps for Peak Discharge Rate using the Rational Method calculated for post-developm Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Southridge-S.Grand Fork Wy Extension&Future Phase 5 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) 1 Click to Show More Subbasins o Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 11 5 Area of Drainage Subbasin(SF or Acres) SF 47,973 46,630 43,572 30,430 17,928 28,823 26,199 19,713 7,393 23,407 23,156 Acres 7.24 6 Determine the Weighted Runoff Coefficient(C) 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.90 0.90 0.90 0.90 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avgl 0.67 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User calculate min 10 Min. Estimated Runoff Coefficients for Various Surfaces Type of Surface Runoff Coefficients"C' 8 Tc i 2.58 in/hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qpeak 12.51 cfs Urban neighborhoods 0.50-0.70 Residential 3 Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 16,759 ft Multi-family 0.60-0.75 V=Ci(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 10,474 ftI Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,Cemeteries 0.10-0.25Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin streets Asphalt 0.95 Basin Forebay V 1,676 ft' concrete 0.95 Primary Treatment/StorageBasin V 15,083 ft' Brick 0.95 Roofs 0.95 Subsurface Storage Gravel 0.75 Volume With 15%Sediment Factor V 19,273 ft' Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0.15 Average:2-6% 0.09 0.12 0.15 0.20 Steep:>6% 0.13 0.18 0.23 0.28 Adapted from ASCE G:\2017\117002\CAD\Calcs and Reports\ACHD_SD_CALCS_117002 7/27/2017,7:19 PM Version 9.0,December 2016 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Southridge-S.Grand Fork Wy Extension&Future Phase 5,Facility 2 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 23,156 Acres 0.53 6 Determine the Weighted Runoff Coefficient(C) 0.60 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted AvgJ 0.60 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate min o Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"C 8 Tc i 2.58 in/hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qp-k 0.82 cfs Urban neighborhoods 0.50-0.70 Residential 3 Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) V 1,102 ft Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vr, 689 ft' Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,Cemeteries 0.10-0.25Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets s Asphalt 0.95 Basin Forebay V 110 ft Concrete 0.95 Primary Treatme nt/Sto rage Basin V 992 ft' Brick 0.95 Roofs 0.95 Subsurface Storage Gravel 0.75 Volume With 15%Sediment Factor V 1,268 ft' Fields:Sandy soil Soil Type Slope A 6 c D Flat:0-2% 0.04 0.07 0.11 0.: Average:2-6% 0.09 0.12 0.15 0.. Steep:>6% 0.13 0.18 0.23 0.: Adapted from ASCE G:\2017\117002\CAD\Calcs and Reports\ACHD_SD_CALCS_117002.xlsm 8/28/2017,2:57 PM Version 9.0,December 2016 ACHD Calculation Sheet for Sizing Conveyance Swale NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the "Peak QV"tab User input in yellow cells. 1 Project Name Southridge-S.Grand Fork Wy Extension &Future Phase 5 2 Enter Design Inflow Q;,, 0.82 cfs 3 Enter Design Outflow Qo„t 0.82 cfs 4 Storage Volume Vstore 0 W VStore=(Qi n-Qout)x3600 5 Set Swale Bottom Width b 0.00 ft 6 Set Swale Depth y 1.00 ft 7 Swale Side Slopes H:1 H:1 3.00 8 Calculate cross-sectional area Axs 3.00 ft` 9 Find length for capacity L 0 ft 10 Time to Drain 0.0 hours 90%volume in 48-hours minimum OK For Conveyance Swales Only 11 Enter longitudinal slope SL 0.040 ft/ft 12 Enter Manning's n for swale n 0.025 13 Solve for depth of flow YFlow 0.29 ft 14 Solve for area flow Aflow 0.26 ft` 15 Find Wetted Perimeter P 0.62 ft P= b+2y(1+z2)1/2 16 Find Hydraulic Radius RH 0.42 ft RH = (by+zy2)/[b+2y(1+z2)1/2] 17 Find Velocity V 3.19 ft/s V=Q/A Is V<0.9 fps? - 18 Calculate Length 1,722 770 ft L=Vx540s (9 minx60 s/min) Residence time 9 min minimum G:\2017\117002\CAD\Calcs and Reports\ACHD_SD_CALCS_117002.xlsm 8/28/2017, 2:57 PM Version 9.0, December 2016