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20161005105257.pdfCITY COPY RAM Engineering Memorandum To: City of Edmonds Development Services Department Attn: JoAnne Zulauf 121 5th Avenue North Edmonds, WA 98020 From: Rob Long, PE RAM Engineering 16531 13th Ave W, Suite A108 Lynnwood WA 98037 Subject: Select SFR at 8711218`n St SW (Lot 1 of 2181n East SP) Plan Check #BLD 20160624 Date: July 19, 2016 Impervious Surface Area and Stormwater Detention Pipe Calculations RAM Job No. 15-032 _710116 This memo provides the proposed site impervious areas and stormwater detention pipe calculations for the construction of a new single family residence at 8711 218t" Street SW (future lot 1 of Select Homes 218th 2- Lot Short Plat, PLN20160015). In addition to the accommodating the initial house construction, the proposed detention tank has been sized to accommodate both lots of the proposed 2-lot short plat concurrently under permit review. The two lots will ultimately create and/or replace approximately 9,960 sf of impervious surface (Lot 1- 3,950 sf + Lot 2- 6,010 sf). To mitigate the development of the site, an underground detention tank system will be installed along the west boundary of the site to control the drainage runoff (flow control). All of the on -site impervious surfaces shall be collected and routed to the on -site detention tank. Project Impervious Area Summary: Lot 1 (#8711) Lot 2 (#8721) Total Building Rooftop, Covered Deck and Patio (roof line) 2,617 sf 3,289 sf 5,906 sf Uncovered Patio and Walks 60 sf 32 sf 92 sf Driveway (pollution generating) 1,273 sf _ 2,689 sf 3,962 sf Total Impervious 3,950 sf 6,010 sf 9,960 sf The stormwater control detention tank has been sized per Table 5-3 City of Edmonds Flow Control Requirements for Small Site Projects- Creek or Lake Basins in the Edmonds Stormwater Code Supplement (April 2010). Per Table 5-3, continuous hydrologic modeling with MGS (Puget East 36) precipitation data (WWHM 20012) shall be used to model the detention tank system. The detention tank system has been sized for the proposed 9,960 sf (0.229 ac.) of impervious surfaces using WWHM2012 continuous hydrologic modeling. RAM Engineering Per Table 5-3 in the Edmonds Stormwoter Code Supplement the following flow control standards are required for a Small Site project located within a creek basin: >SG00 sf Effective Imperious Area For d4teturion BNIIIS4 2-year = 0,07 cis/aae imptivious.. 10-year = 0.14 r f `aae 414Vcrt'iouas, rrtrtl 100-year = 0.3 3 d's,41a:r insperr°iow, For irrrrltrat'iou 13MPS: -yeas, - 0,07 r:fqacre irrrpenliorus„ f0-yegtr = 015 eisjacr°e irrrpeuVitraus, and 100-Year— 0.45 cfslacre impetviotus. Nety and uru ffee Shuplified Sizing Approach or coairrimlouns hydrologic modeling with N,IGS precipit,rrivau thfa" 2-Year Allowable Release Rate = 0.07 cfs/acre-impervious x 0.229 acres = 0.016 cfs 10-Year Allowable Release Rate = 0.14 cfs/acre-impervious x 0.229 acres = 0.032 cfs 100-Year Allowable Release Rate = 0.33 cfs/acre-impervious x 0.229 acres = 0.076 cfs The developed runoff rates and storage calculations were performed using the DOE 2012 Western Washington Hydrology Model (WWHM2012) continuous runoff model. The required detention system and release rates for the developed conditions are as follows: Proposed Detention Tank: 82 ft - 60" Diameter Pipe with 11116" (0.6875") orifice. Release Rates: Storm Event Mitigated Allowable 2-year = 0,016 cfs 0.016 cfs 10-year = 0.031 cfs 0.032 cfs 100-year = 0.066 cfs 0.076 cfs See WWHM2012 printout on the following pages. M Engineering 1653113`hAve W,Suite A108 Lynnwood WA 98037 (425)678-6960 RAMengineeringinc corn RAM Engineering WWHM2012 Input/Output Data: . . . . .... . ... .. .. .. . . .... ..... . %, 0.- L Khhgwt d K, Subbosin "smo:* f D.VW.. Ryma M. M- 6-nd". Flows To: Area in Boom %.*Md Available Pervious Acres Ava4able Iff, Ir Wto07141 r . . ......... ... ....... ------- ----- I F- 'qNW NIP! 4"gy ...... ........ j ... rfa . ....... . - - -------- - Q fa . . .. .. . ............ . ... ......... . . .. ...... .. .... .. -------- - - . . .. ......................... .. c .... .. . . . ------ - - .. . .. ........ E,1'611'1�""'��,'�'11�11 ud 71 ib ..... ....... .. N— told A- 8- rrAeh AUN T-4 I KC 991,9 . ... ... Facili. .......... . ... ..... tyType t**,, Outlet I Outlet 2 1 Ownromonet Connection Aw*W-t FW,,* WOTO"I, Emp,dk. k4fd b F 001yDimensions olR Typo owm jjq n,, 77 ,,y Ovation 04fics nimneleff 11 u Nmbou (11n) ro —15w-j 11, 116 Fe i 3 T.*. V.L—M- H..d 1. 01 931 Show Tank Table [6(1- f Intifial Sinno (M ............ Tide Gale I Time Senes I Demond Detempne OutlelArthTide Gage F Use ride Gale Tide Gem Eluvabon Nergaw Elevown M Waratons x 10 n K M 7J H 05 � 2 5 I eel @a W, M4941P 14" 1 SYAGE MW*od J, pri C tg WbA r C— r pdi 1110V 1'rql*"y Fjoww'st oeol 2 Y :r 0.0161 0.0240 10 Ya:r e.0310 25 Y. r - C .0424 " Year 0.0531 100 Y.&r 0.0660 AXWO41 P..k, 1902 0.0169 1903 0.0140 1904 0.01:: 1:05 0101, 1906 0.0127 1907 0.0205 1900 010154 1 2 :oil9 01015 1 1 0.0108 1911 0.0144 1912 0:0199 1913 0.0145 1:14 0.017 1915 0.0120 1916 O139 191.1 A0 .015 1916 0.0160 1919 0.0134 1920 0:0141 1921 0.0140 1922 0.016, 1923 0.0160 1 9 24 0.0134 1925 0.012E 1926 0.0150 1927 0.0151 1928 0.0144 1929 0 AM RAM Engineering 16531 13" Ave W, Suite A108 Lynnwood WA 98037 (425) 678-6960 RAMengineeringinc,corn RAM Engineering WWEM2012 PROJECT REPORT Project Name: 15-032 Short Plat Site Name: Site Address: City Report Date: 7/19/2016 MGS Regoin Puget East Data Start 1901/10/1 Data End : 2058/09/30 DOT Data Number: 03 Version Date: 2016/02/25 Version : 4.2.12 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC.....1............. ....n___ _.__ 50 year PREDEVELOPED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use acre C, Lawn, Mod .23 Pervious Total 0.23 Impervious Land Use_ acre Impervious Total 0 Basin Total 0.23 Element Flows To: Surface MITIGATED LAND USE Name : Basin 1 Bypass: No GroundWater: No Pervious Land Use Pervious Total Imoervious Land Use ROOF TOPS FLAT DRIVEWAYS FLAT SIDEWALKS FLAT Impervious Total Basin Total Element Flows To: Surface Tank 1 Interflow acre 0 acre 0.136 0.091 0.002 0.229 0.229 Interflow Tank 1 Name : Tank 1 Tank Name: Tank 1 Dimensions Depth: 5 ft. Tank Type Circular Diameter 5 ft. Length : 82 ft. Dischar e Structure Riser Height: 4.9 ft. Riser Diameter: 6 in. Orifice 1 Diameter: 0.6875 in Element Flows To: Groundwater Groundwater Elevation: 2 ft. 1'MA Engineering 1.6531 1.3"' Arne 7W, Suite A1.08 11..yniriwcmod'WA 98037 (425) 678..6960 R/\Mc:rgVrueerfiuigiricxc rn ___W_ Engineering �� ������-���� ����Outlet 1 Outlet 2 Tank Hydraulic Table 100.06 e.002 0.000 0.000 n,nmm 100.11, 0.002 m-omo 0.010* 0.000 1100.z7 0.003 0,00e 0.000 0.000 200.22 o,uo$ 0.000 0-000 0.000 100.28 0.004 0.000 0.000 01000 100.33 0.00" 0.001 @.000 0.000 100,39, 0.005 0.m01 01000 m.umo 1,00.44 $.005 0,001 y.00m 0.080 I*m.ao u.oms 0.001 m.We0 u.00m zmo.56 n.&05 0.002! 0.00$ 0.000 zoV.$z 0^0m8 m.Vmu 0,000 m.00m 100'67 u.ome 0.002 0.000 o.Goo 100.72 #.una 0.003 0.000 0.000 zmo,ru 0.006 0.003 o.oum Moo z$m.ma o.00v o^ooa o.o00 0.000 :1 Da.my 0.097 m.*ow 0.000 n.moo zom.$u m.on7 0-0** u.oOo m.omn 101.00 e.DWI 0.005 0.000 a.000 z*z,V+ 0.007 0,005 0,000 a,umu 101.z3, 0,007 0.006 0.000 *.000 101^17 0.008 0.006 u.o*o 0.000 101.22 0.008 0.007 0.0011) 0.000 101.28 0.908 o.mu7 m.*nu 0.000 101.33 0.008 0.00 0.000 0.000 1,01,39 0,008 0,00* o.00m 0.008 101.$4 0.008 0.008 �O.m*m u.O�om 301.50 0.008 0.009 0.000 Moo 101.5e 0.$08 o^mme 0.000 o.m*o 101.61 0,008 0.010 o.moCI 0.m0m 101,67 o^omu 0,010 o^Aoo e.ouo 101.72 0.008 0.011 0.000 0.000 101.7e 0.009 0.011 0.000 0.000 101.83 0.009 0.012 0.000 0.000 101.89 0.009 0.012 0.000 0.000 101.94 0.009 0.013 0.000 0.000 102.00 0.009 0.013 0.000 0.000 102.06 0.009 o.uz« 0.003 0.000 102.11 0.009 u.oz« 0.004 0.000 102.17 0.009 0.015 0.005 0.000 102.22 0.009 0.015 0.006 0.000 102.28 o.un* 0.016 0.006 0.000 102.33 0.009 0.016 0.007 0.000 102.39 0.009 0.017 0.008 0.000 zoo.o« 0.009 0.018 0.008 0.000 102.50 0.009 0.018 0.009 0.000 102.56 0.009 0.019 0.009 0.000 102.61 0.009 0.019 0.010 0.000 102.67 0.009 0.020 0.010 0.000 102.72 0.009 0.020 0.010 0.000 102.78 0.009 0.021 0.011 0.000 102.83 0.009 0.021 0.011 0.000 102.e9 0.009 u.o:u 0.012 0.000 102.94 0.009 0.022 0.012 0.000 103.00 0.009 0.023 0.012 0.000 zoz.u* 0.009 0.023 0.013 0.000 103.11 o.00* 0.024 0.013 0.000 103.1'7 0.009 0.024 0.013 0.000 103.22 0.009 0.025 0.014 0.000 103.28 0.008 0.025 0.014 0.000 103.33 0.006 0.026 o.oz« 0.000 103.39 0.008 0.026 0.015 0.000 ms.«o 0.008 0.027 0.015 0.000 103.50 0.008 0.0e7 0.015 0.000 103.56 0.008 0.028 0.016 0.000 103.61 0.008 0.028 0.016 0.000 103.67 0.008 0.029 0.016 0.000 103.72 0.008 0.029 0.016 0.000 103.'78 0.008 0.030 0.017 0.000 103.83 0.008 0.030 0.017 0.000 1.03.89 0.007 0.030 0.017 0.000 zna-e« 0.007 0.031 0.017 u,uno zu«.ou 0.007 0.031 0.018 0.000 zn«.oa 0.007 0.032 0.01e o.00u 104.1.1. 0.007 0.032 0.018 0.000 1.04.1.7 0.007 0.032 0.018 o.uuu zo«.uo 0.006 0.033 0.019 0.000 1.04,28 0.006 0.033 0.019 0.000 104,33 0.006 o.us« 0.019 0,000 zu«.ae 0.006 0.034 0.019 0,000 1.04.44 0.005 0.034 0.020 u.000 zo«.so 0.005 0.035 0.020 0,000 104.56 0.005 0.035 0.020 0.000 104.*1 0.005 0.035 0.020 0.000 104.e7 0.004 0.035 0.020 0.000 104.72 o.uu« 0.036 0.021 0.000 104.7e 0.003 0.036 0.021 0.000 m*.uo 0.003 0.036 0.021 0.000 104.89 0.002 0.036 0.021 0.000 104.94 0.002 0.036 0.071 0.000 105.00 0.000 0.037 0.182 0.000 105.06 0.000 0.000 0.299 0.000 umaLrozo aoonLro Stream Protection Duration Preuevel"neu L=na""e z"t=z° for poo w1 Total Pervious uxe=.o.uey Total Impervious Area:O Mitigated Landu""T"tal" for POC #1 Total pe=vi""o a=ea.o Total Impervious Area:0.229 Flow Frequency m"t"=n Periods for pr"ue=l"neu, poo Return Period Flow(cfs) s year 0.002732 zo year 0.00334 us year o.00«000 so year o.00«a«a zoo year 0.005185 sz=w Frequency Return Period" for Mitigated. POC #1 Return Period Flow(cfs) s year 0.02167 zo year 0.023947 os year 0.0267e2 so year 0.028827 zoo year 0.030875 Stream Protection Duration Annual Peaks for rreu°vel"peu and Mitigated. roc #z Year Predeveloped Mitigated 1950 0.002 0.022 1e51 0.002 0.019 1952 0.001 0.017 1*53 0.001 o.oz* 1954 0.003 0.022 zyss 0.003 0.023 sss 0.002 0.013 zysr 0.003 0.017 �ysu o.nuc 0.028 1e5e 0,002 0.018 1.ee0 0.002 0.016 1.961 n.u02 0.029 �y*u u.noz 0.017 1*63 n.ouu 0.023 1e64 0.002 0.015 zuao 0.002 0.014 zyss 0.001 0.015 1967 0,003 0.029 1.e*8 m.00a 0.020 zese 0.001. 0.023 RAM En&eeiring 1as3z1amAve W,suue«z08 1-yrinwood mmyn03n <425)e78 6960 nmweng�neennnccom zem 0.001 m.uzs 1.e71 *.00u 0.021. 1.e72 0.002 0.027 1.e73 0.001 n.u1e 1974 0.002 u.o21. zyrs 0.001 0.01.9 1.976 0.001. o.ozr zyn o.onz 0.014 1*78 8.001 0,01.3 1979 9.002 0.023 1.e80 o.000 0.014 �yaz u.ouz 0.015 zeou 0.002 0.016 1.ee3 $'uuc 0.019 zye« m,00u *.018 1.e85 m,000 0.021 1.966 0.006 0.022 zeor o.00u 0.019 zyou 0.002 0.017 zyoy 0.001 0.018 zyeu 0.002 0.014 1991. 0.002 0.016 1.992 0.001 0.015 1.e93 0.001 0.016 1.9e4 0.001 0.013 zyys 0.002 0.017 zeya 0.004 0.017 zeer 0.007 0.022 zyyu 10.001 0.024 1.e99 0.002 0.014 u000 �.uoz 0.023 cnoz 0.000 0.017 znoz 0.002 m.oz« cous 0.001 0.017 uou« 0.002 0.025 2005 0.002 0.020 zuoa m.00« 0.018 2007 0.003 0.019 uona D.uuo 0.020 200e 0.001 0.017 Stream Protection Duration Ranked Annual Peaks for eredevelopea and Mitigated Rank Predevelomed Mitigated z 0.0066 0.0295 c 0.0062 0.0287 s 0.0045 0.0280 « 0.0040 0.0266 5 0.0038 0.0252 a o.00a« 0.0236 7 0.0030 0.0234 o 0.0029 0.0232 e 0.0029 0.0231 m 0.0028 0.0229 1.1. 0.0026 0.0226 zz 0.0025 0.0224 1.3 0.0024 0.0219 z« u.00e« 0.0217 1.5 0.0024 0.0215 1-6 0.0022 0.0e11 �7 0.0022 0.0209 za 0.0021 0.0207 ze 0.0021 0.0204 zu 0.0021 0.020* 21. 0.00e1 0.0197 ou 0.0020 n.ozo« zz 0.0020 0.0191 c« o.ou:o 0.0191 25 0.0019 0.0190 oa o.00z* 0.0190 zr 0.0019 0.0189 om 0.0018 0.0187 ue 0.0018 0.017e au 0.0017 0.0178 sz 0.0017 0.0177 sc 0.0017 0.0176 ss 0.0017 u.00« RAIRVIII Engineering 1653113"' Ave W,suueAzou Lynnwood mm 98037 (425)*78 6960 nAmeng/naeringinc.cmn RRAM Engineering 34 0.0016 0.0172 35 0.0016 0.0172 36 0.0016 0.0171 37 0.0016 0.0171 38 0.0015 0.0171 39 0.0015 0.0169 40 0.0015 0.0169 1 0.0015 0.0167 42 0.0015 0.0167 43 0.0015 0.0165 44 0.0014 0.0160 45 0.0014 0.0159 46 0.0014 0.0156 47 0.0014 0.0156 48 0.0013 0.0154 49 0.0013 0.0151 50 0.0013 0.0149 51 0.0013 0.0149 52 0.0012 0.0146 53 0.0011 0.0144 54 0.0011 0.0142 55 0.0011 0.0140 56 0.0010 0.0139 57 0.0010 0.0138 58 0.0008 0.0136 59 0.0008 0.0133 60 0.0008 0.0131 61 0.0002 0.0129 Stream Pr. ....._ otection Duration POC #1 Facility FAILED duration standard for 1+ flows, Flow(cfs) Predev Kit Percentage Pass/Fail 0.0009 13901 167560 1205 fif"aul. 0.0009 12690 165228 1302 ei1 0.0010 11586 162961 1406 "aa:l. 0,0010 10602 160694 1515 a.11 0.0011 9636 158598 1645 VaGV 0,0011 8793 156502 1779 Fail 0.0011 8029 154299 1921 Cail 0.0012 7375 152160 2063 L"a:il.. 0.0012 6744 149978 2223 0.0012 6175 147775 2393 Fai: 0.0013 5666 145529 2568 UH' 1. 0.0013 5189 143198 2759 F"aai :l. 0.0014 4770 140867 2953 Taal.. 0.0014 4365 138386 3170 FralV 0.0014 3991 135947 3406 1"aa..11. 0.0015 3638 133488 3669 .1. 0.0015 3311 130793 3950 aai:l. 0.0015 3052 128076 4196 fa"ai:l. 0.0016 2821 125210 4438 ;aR:Ll 0.0016 2631 122622 4660 1"all 0.0017 2411 120312 4990 1"'Ailll. 0.0017 2227 118259 5310 Fain. 0.0017 2082 116312 5586 VaVl. 0.0018 1945 114387 5881 pail 0.0018 1825 112462 6162 Ntit.. 0.0019 1705 110623 6488 "axial. 0.0019 1585 108869 6868 FaIH 0.0019 1479 107030 7236 Faall. 0.0020 1373 105126 7656 F,tSL 0,0020 1268 103393 8154 L"ai;l 0.0020 1193 101618 8517 vd l 0.0021 1114 99822 8960 0.0021 1038 97982 9439 11r,al9 0.0022 985 96121 9758 li'a:L,l 0.0022 944 94325 9992 Taal 0.0022 902 92571 10262 0.0023 860 90646 10540 Waxial. 0.0023 816 88721 10872'ail 0.0023 773 86817 11231 v'ail 0.0024 739 84978 11499 0.0024 696 83160 11948 Wail 0.0025 663 81406 12278 axial. RAIRVRI Engineering 1653113`r'Ave W,SniteA108 Lynnwood WA 98037 (U9678,..0)60 RAIla vnp,in(,Qi, q,a iir;,r,oin 0.0025 632 79716 12613 'a:ll 0.0025 608 78197 1,2861. P,i i 1 0.0026 582 76636 1.31.67 Fal� 0.0026 560 75053 1.3402 VV] 0.0026 543 73599 13554 'ail 0.0027 525 72059 13725 0.0027 51.1 70690 1.3833 'a l 1 0.0028 497 69257 1.3935 vail 0.0028 481. 67931. 14122 0.0028 464 06583 14349 0.0029 455 65257 14342 7ail 0.0029 443 63974 1,4441. ➢!'1a1 0.0029 430 62626 1.4564 11,'jl� 0.0030 420 61.236 14580 Fal 0.0030 41.2 5991.0 1.454.1, Va L 1 0.0031 401. 58520 14593 :'aiL 0.0031 395 57087 1.4452 V,: a i 1: 0.0031 387 55696 1.4391 FaD 0.0032 380 54328 1.4296 Pail 0.0032 371 53001. 1.4285 1 i 1 0.0032 364 5171.8 14208 Fait 0.0033 350 50478 1.4422 valV 0.0033 338 49237 1.4567 Vail 0.0034 325 48082 1.4794 FaLl 0.0034 316 46970 1.4863 i 1 0.0034 305 45879 .1.5042 i li 0.0035 295 44767 ' 15 1.7 5 Y,,a u 0.0035 289 43655 1.51.05 Va:Gl 0.0036 275 42564 1.5477 f'a:ll 0.0036 269 41430 15401. 0.0036 262 40382 1541.2 FaH 0.0037 249 39291 1.5779 F:aLL 0.0037 244 38222 1.5664 17,iil 0.0037 237 37174 1.5685 P,a16 0.0038 232 36168 1.5589 FaH 0.0038 224 35206 1571.6 I:'ail 0.0039 220 34265 1.5575 L',:iil 0.0039 217 33260 1.5327 Y,:,a a 0.0039 21.1. 32254 1.5286 w'i u 0.0040 208 31420 1.5105 Vail 0.0040 204 30500 1,4950 L'rail. 0.0040 202 2958.1. .1.4644 17a i L 0.0041 1.96 28704 1.4644 :a'a t 1 0.0041 194 27891. 1.4376 Ya'l 0.0042 1.87 27057 14468 llail 0.0042 1.83 26287 14364 17aiL 0.0042 1.77 25495 14403 17,il� 0.0043 1.73 24725 1.4291. ll,',i i Y 0.0043 169 24020 1.4213 Fail 0.0043 167 23292 .1,3947 0.0044 1.63 22544 1,3830 C,r11 0.0044 1.55 21.859 1.41.02 'a i 1 0.0045 153 2 :1.17 7 1.3841. V:P,a a 1 0.0045 145 20533 1.4160 Fail 0.0045 1.39 1.991.3 14325 :'a i L 0.0046 136 19278 14175 P'alV 0.0046 1.32 18685 1. 4 1. 55 'a j 1 0.0046 1.30 1.81.29 13945 Va i I E. .. . . .... . . ...... e development has an increase in flow durations :from 1/2 Predeveloped 2 year flow to the 2 year :flow or more than a 1.0% increase from the 2 year to the 50 yea:r. :flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. Per1nd and Imp1nd Changes No changes have been made. ying documentation are provided 'as -is' without warranty of any kind.. The entire Fh"1-s­program-"a and Fa"'"cc -omp a n - "-"- -- . ...... risk regarding the per. f.ormance and :results of this program is assumed by End User. Clear Creek Solutions Inc. and the gover. nine n t al licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying document ation . In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for .loss of business profits, loss of business information, business interruption, and the like) arising out of. the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized :representatives have been advised of the possibility of such RAM Engineering 1-653113 1h Ave W, Suite A108 Lynnwood WA 98037 (425) 678 6960 RAMengineeringinc.corn