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HomeMy WebLinkAboutSWP272235(1) 1 STORM DRAINAGE REPORT 1 for SOUND MITSUBISHI SUBARU 1 USED CARS SOUTH GRADY WAY 1 RENI'ON, WA Prepared For: 1 SOUND MI T SUBI'SHT SUBARU Renton, WA 98055 1 1 F � z rC 1 0, tsTERo�� ph qiq IONAL l 1 EXPIRES 9/21j 1 1 Prepared By: WARNER ENGINEERING 1 5122 Olympic Drive NW, Suite B204 Gig Harbor, WA 98335 1 (206) 858-8577 October 11, 1995 1 Revised: January 5, 1906 Job Number: 023002 1 TABLE OF CONTENTS ' I. Project Overview H. Existing Conditions Summary III. Developed Conditions Summary ' IV. Discussion of Core Requirements tV. Discussion of Special Requirements VI. Conveyance System Analysis and Design ' VII. Water Quality Analysis and Design ' VIII. Appendices Appendix A - Vicinity Map Appendix B - SCS Soil Map ' Appendix C - Predeveloped Basin Map Appendix D - Postdeveloped Basin Map Appendix E - Isopluvial Maps: 2-, 10-, 100- Year ' Appendix F - Runoff Coefficients Appendix G- Waterworks program Calculations Pre-developed Data ' Post-developed Data Appendix H - Technical Information Report Worksheet ' IX. References 1 ' 2 t L PROJECT OVERVIEW ' This project is a new Mitsubishi Subaru used car dealership. The site is bounded on the north by SW Grady Way, and is east of the intersection of SW Grady Way and Rainier Ave. The project encompasses development of the entire 1 acre site. The work shall include the construction of a 960 SF modular building, and paving a parking and vehicle display area. See Appendix A for a vicinity map. ' IL EXISTING CONDITIONS SUMMARY tSOILS Soils on the site are identified by the SCS Soil Survey for King County' as Urban Land ' (U)- see Appendix B for SCS Soils information. The SCS description is as follows: Urban land(U) is soil that has been modified by disturbance of the natural layers with additions of fill material several feet thick to accommodate large industrial and housing installations. In the Green River Valley the fill ranges from about 3 to more than 12 feet in thickness, and from gravelly sandy loam to gravelly loam ' in texture. The erosion hazard is slight to moderate. No capability or woodland classification. tWe will assume that a hydrologic soil group C soil is present on the site. EXISTING DEVELOPMENT AND DRAINAGE ' The site currently is comprised of paved and gravel areas which are used for vehicle parking. The site is level with a very little vertical relief. Surface drainage on site is sheet flow to existing catch basins located near the northeast and southwest corners of the property. That flow enters the existing City storm system. See the Vicinity Map in ' Appendix A and the Predeveloped Basin Map in Appendix C. OFF-SITE AND DOWNSTREAM DRAINAGE ' There is no off-site drainage onto this site. See the Predeveloped Basin Map, Appendix C. ' Water leaving this site is picked up by two existing catch basins located along the east side of the property. That storm system flows east in an 8" pipe and then south in a 12" pipe which changes to a 24" pipe. It outlets to a ditch along the north side of I-405. At that ' point it continues west in the ditch. It re-enters a storm system which flows south under I-405. The system discharges to a ditch which flows south along the east side of Hwy. 167. It re-enters a storm system which flows west under Hwy. 167. That system flows ' south and then east along SW 19th Street. It continues flowing west to the pumping station at Oaksdale Ave SW. The pumped water is discharged to a system which outlets to Springbrook Creek. Springbrook Creek flows northwest to the Green River. ' 3 M. DEVELOPED CONDITIONS SUMMARY ' ON-SITEDEVELOPMENTAND DRAINAGE ' The new dealership building will be a modular type structure of approximately 960 square feet and be located along the south property line Vehicle parking and display areas will comprise the remainder of the site. Storm drainage for the site will be as follows: ' The site will be graded to sheet flow to three catch basins. The system will discharge to the water quality oil/water separator and is then released to the existing catch basin and 8" ' line at the northwest comer of the site. The increase in run-off from the Pre-developed r Y condition to the Developed condition is less that 0.5 cfs, therefore no detention is proposed for this site. ' Water quality for those areas subject to vehicular traffic will be by use of a coalescing plate oil/water separator. Due to the small area on the siteand the extremely flat C � topography, a biofiltration swale is not possible. See the Postdeveloped Basin Map, Appendix D. ' OFF-SITE IMPROVEMENTS AND DRAINAGE No off-site improvements are proposed. The existing 8" line has capacity for the increased flow of 0.06 cfs for the 100-year storm event ' IV. DISCUSSION OF CORE REQUIREMENTS ' Core Requirement #1 - Discharge at the Natural Location As discussed in EXISTING CONDITIONS SUMMARY above, the site drainage ' currently drains to the existing catch basins located along the east property line. The proposed storm system will connect to this same storm system. ' Core Requirement 92 - Off-Site Analysis_ No offsite drainage enters the site. See Appendix C- Predeveloped Basin Map. A Level ' One Downstream Analysis is described in the Existing Conditions Summary. There are no known drainage problems in this system. ' Core Requirement#3 -Runoff Control ' This site is exempt from On-site Peak Rate Runoff Control because the increase in the peak runoff is less than 0.5 cfs more than the peak runoff rate for the existing site conditions. ' 4 ' Core Requirement#4 - Conveyance System ' The project storm system will convey the site 100 year design storm. Core Requirement#5 - Erosion/Sedimentation Control Plan ' An Erosion and sedimentation plan has been developed for this site as outlined in the King ' County Surface Water Design Manual. CB inlet protection and CB inlet sediment trap will be installed. ' Core Requirement #6 - Maintenance and Operation Maintenance and operation of all of the stormwater system on this site will be the ' responsibility of the Renton Mitsubishi Subaru Dealership. Core Requirement 47 - Bonds and Liability ' Bonds and liability insurance will be provided by the Renton Mitsubishi Subaru Dealership. V. DISCUSSION OF SPECIAL REQUIREMENTS Special Requirement 91 - Critical Drainage Areas The City has not indicated that this site is in a critical drainage basin. ' Special Requirement #2 - Compliance With Existing Master Drainage Plan There is no existing known Master Drainage Plan that includes this site. ' Special Requirement #3 - Conditions Requiring a Master Drainage Plan ' This project site does not trigger any of the thresholds that require a Master Drainage Plan. ' Special Requirement #4 - Adopted Basin or Community Plans The site is not in any known adopted basin or community plans. Special Requirement#5 - Special Water Quality Controls ' There is less than I acre of new impervious area subject to vehicular traffic. This project provides a water quality oil/water separator system that is designed per Department of Ecology Stormwater Management Manual for the Puget Sound. ' 5 1 Special Requirement #6 - Coalescing Plate Oil/Water Separators ' This site is will have less than 5000 square feet that is subject to petroleum storage, high vehicle usage, or heavy equipment use and is therefore exempt from a coalescing plate ' oil/water separator. Special Requirement#7 - Closed Depression ' There are no closed depressions on the project site. Special Requirement #8 - Use of Lakes, Wetlands or Closed Depressions for Peak Runoff Control ' The project will not use a lake, wetland or closed depression for peak runoff control. Special Requirement #9 - Delineation of 100 Year Floodplain The project falls within 100 year floodplain zone AH. According to the Federal Emergency Management Agency Community Map Numbers 53033C0328D and ' 53033C0329D dated September 29, 1989 portions of the surveyed property are inundated by the 100-year flood. Flood depth of 1 to 3 feet (usually areas of ponding). ' Special Requirement #10 - Flood Protection Facilities for Type 1 and 2 Streams This project does not abut a Type 1 or 2 stream and we do not propose to construct a ' new, or modify an existing, flood protection facility. This site is therefore exempt from this requirement. Special Requirement 411 - Geotechnical Analysis and Report ' A geotechnical analysis and report is not required for this project. Special Requirement #12 - Soils Analysis and Report ' A geotechnical analysis and report is not required for this project. ' Special Requirement 913 - Aquifer Recharge and Protection Areas This site is not in an aquifer recharge or protection area. 1 ' 6 1 VI. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ' See Appendix G. Summarized below are the design data ' Constants Pz =2 in. Soil Type C P,o = 2.9 in. CN= 86.0 grass P100= 3.9 in. CN= 89.0 gravel CN=98.0 impervious ' Existing conditions ' Q100= 0.77 cfs AP,, = 0.54 ac T, = 10 min. = 0.52 ac 1 Developed conditions ' Q100=0.83 cfs �= 0.12 ac T�= 10 min. =0.94 ac Maximum flow rate= Q,00,= 0.83 cfs All pipes on site are 8" ADS N-12 at 0.50% which have a capacity of 0.94 cfs. Therefore the conveyance system is sized to adequately handle the 100-year storm event. ' The existing 8" storm line has a capacity of 0.94 cfs at 0.50% and calculations show that the peak flow for the 100-year storm event is 0.83 cfs. Therefore this line is adequately sized. VII. WATER QUALITY ANALYSIS AND DESIGN ' A. The coalescing plate oil/water separator is sized for the 100-year storm event. ' Q100 =0.83 cfs= 372.50 gpm Use Pipe Inc. Model 612-SA or equal, with a capacity at 0.50 gpm/sf= 400 gpm. 7 V. APPENDICES ' Appendix A - Vicinity Map Appendix B - SCS Soil Map Appendix C - Predeveloped Basin Map ' Appendix D -Postdeveloped Basin Map Appendix E - Isopluvial Maps: 2-, 10-, 100- Year Appendix F -Runoff Coefficients Appendix G- Waterworks program Calculations Pre-developed Data ' Post-developed Data Appendix H- Technical Information Report Worksheet 8 APPENDIX A 4 x nE}• 2LGYi ZW]-i 2L£]-]1 2LN3-3 21ta-16 i ELG3-16 PW]-5 F� 21"3-' •r 3-B lLG3-I1 2 G3-9� Ella- 2LG3-1 21©-1 2LW-1) 2LG3-10 2p3-] 1 2W3- nW.2 2LG3- n 3 ' GRADY n53 3 2LE3-3 . n G3_10 2LG3-12 2w-f - E 6. nG3-14 nm0 bA3-1 / 2LX•-17 2LG3-5 - SITE 2U4-12 2LG3-15 2w3-4 2V4-16 1-13 au" � � zu•-u eiGa-u 21.D•-) � zu4a 2W4-12 nH4.15 2U4-4 24W-I3 2W4-) 1 D - D4 1 nG4 l nG.-B nX4-16 3 S l_ 2 4-9 2W4-5 2LW-3 3p14-7 D7-3 2U4-10 2U4_11 2U4-3 -/ zLG4-2 S RENTHN VILLAGE PL 21E.-2 ' 2U4-6 SS �1_7 fYu-2 2 E.-5 ELE4-3 I 2U4-B ELW-9 = tj4-1 21G4-1���^ 2LX4-1- UE4-6 ��- 2LE•-4 -...�...� 2U4-2 \ LSIt zus-n 2u4-1 I_405 _ 2LG3-11 f3 ziXS-6 N W W W } )-' O ELM-2 l zus-E F=-- 3 x �\ qi duo- Gs- ELES-3 ° S v, 15 H I .. - y ST 2 t-7 nL l 21 6 2LD6-13 ST X-1 Inm-1 zL 1 S-S PLE3 1 2LD6-12 2LD6-13 , ' x <` UJ -2l 5 -nu-9 1 Y D6-6 2LG6d� 1 21G6- 2LD6-2 26E6-8 '1 3•+ S 16 H T n" �GG-5 2LD6-1cy I LieLfb-2 E6R •� W mm-5 21X6-6 y ¢ 6 2LE6-3 L UU-1 2L -4 � flE6-9 U. 2UI-3 YLE6-ID 2LG64 S 7TH MI-5 - 2LG6-0 2LH6-3 fW6- y F- ' ti 2Ln-1 •l N ; oc O S I TH S 21X]-s 2Lf]-6 ' J V) •1 N _ _ _...r Q 2U7-1 2LG)-6 U]-2 no 2u)-3 -4 S zL zinc ELG)- ELMI-1 N 2Ln-S �/• 2LG]-1 ' VICINITY MAP 2LG6-3— ¢ %�0TH P I No 7 r 1 ' AE} 111 \\\Un• . 1 l i .d APPENDIX B ' •� t ! Y AD;;`i T 'g' 77. gC llth11el t , •1 Jr ubstav ^ gM' I EvD Ur ue xe> .BeD' ,, ' r.' � 'N•'� 1 aseb3/f ° I - F Park Pc W I 0�,?S 't l Vi ti� d0 • • • Px1 9 Rh• a W G I BeD ,BeC. : '?•..' ,�� �• , 1 c 9a St RA ROA rU •.•`1 / -S:" Fc a ' p. , fr C. ' lac Wo - ' •'� , -' ' : Ur ". _Y o a nC _—_ —_ —_ Ur P �13 PROJECT Ngl -���--_ — qg( ' Pu 1 , I _ tltltl...111 xa BeC y Gol�ourse SITE - � AmC xxxSa� No ` a Ur i ♦' PA1 rely; I • S• r InC BM v• 4 OjI 30�:- \�r Sew se DRTH ■ , �' - ' ryp • '� -• 6ubsta AmC W W 2 Q " N6 Ur Ur •' :( :120 i•. �O .\.ABD _ 20. u . . I _ .1 .• r ... _M•16 9 .•i , •y r I l Pu t u. !' n �. �� IiLongacre5 '= I Pu I Pu •'. e . 515° I'dl pSBeCI v Ur. ••��III Y I wo BeD tii n 105 11 i�F� Ur �� I Ur 'u• J'I (AgO 1 o i Track a 1 _■IU ua 29 - I ... .g 273 r0ff Ur C ' NB I AUK s rv0ir W M A66 S° T. n i Pu n Sk I I Wo M I ' Pu I � (�. u I � •• 0 =;, IBM 29 25 nl .- f 169 �203 AfiC V Ur� o PY - n o • Sk o e I. I I�i ^ Wo -r s A • -. a- _ I �U� �i I` Tu L 1 r InC I A68 I' (D s a So 'L7 AgD AmB 171 �----- _ MI 114 ' + ry Pu Wo I3Mp 94•p a61 r A � 1111 i •• ._ • 1r�C A Py - Z --• C>. ..t . Ngpy p` Ng _B I 2 3 a IBM 3 . A ABC n . 1 �u f y� 1AgB ,r 3 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL ' (2) CN values can be area weighted when they apply to pervious areas of similar CN's (within 20 CN points). However, high CN areas should not be combined with low CN areas (unless the low CN areas are less than 15% of the subbasin). In this case, separate hydrographs should be ' generated and summed to form one hydrograph. FIGURE 3.5.2A HYDROLOGIC SOIL GROUP OF THE SOILS INKING COUNTY 1 HYDROLOGIC ' HYDROLOGIC SOIL GROUP GROUP* FArents, OUP GROUP* C Orcas Peat D ' od C Oridia D Alderv+ood Material B Ovafl C Everett Material C pilchuck C D Puget D gam D Puyallup B B B D Ragnar Buckle y Variable Renton D Coastal Beaches D Riverwash Variable ' Earlmont dgewick D Everett Silt Loam C Salal C Everett ALB `Sammamish A Seattle D Indianola C Shacar D ' K aus C Si Silt C Klaus Variable D iable Snohomish Mixed Alluvial Land A Sultan C - Newbe B Tukwila D Newberg C Urban Variable ' Nooksack D Woodinville D Normal Sandy Loam ► ' HYDROLOGIC SOIL GROUP CLASSIFICATIONS ' A. (Low runoff potential). Soils having high infiltration rates, even when thoroughly wetted, and consisting chiefly of deep,well-to-excessively drained sands or gravels. These soils have a high rate of water transmission. ' B. (Moderately low runoff potential). Soils having moderate infiltration rates when thoroughly wetted, and consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. ' 0. (Moderately high runoff potential). Soils having slow infiltration rates when thoroughly wetted, and consisting chiefly of soils with a layer that impedes downward movement of water, or soils with moderately fine to fine textures. These soils have a slow rate of water transmission. ' 0. (High runoff potential). Soils having very slow infiltration rates when thoroughly wetted and consisting; chiefly of clay soils with a high swelling potential, soils with a permanent high water table, soils with a hardpan or clay layer at or near the surface, and shallow soils over nearly impervious material. These soils have a very slow rate of water transmission. ' From SCS, TR-55, Second Edition,June 19W, Exhibit A-1. Revisions made from SCS, Soil Interpretation Record, Form #5, September 1988. 11/92 3.5.2-2 a_ Q U ii x N77'28'26"E z 0 I 144.07' m z w 1 CATCH BASIN RIM EL. 21 .23' w Q I IE 8" CONC W 19.5' p IE 8" CONC E 19.4' W / TRAFFIC SIGNAL BOX W CATCH BASIN I tKLu ry ry 0 RIM EL. 22.28Cc y 5. . . IE 8" CONC E 20.8' I h d SD rl�. 10RN'. ry . aJ_Iry^ 0 5D " STOR►" ti ry BANTER `a\ FOUND NAIL • 8 ry� . IN CAP CORNER �ry ryry. r 0 i GRAVEL . y . . . . . :� ^� ryL . . . ti . 1 . . . . rye. .CUR . r LIGHT STANDARD CCESS.EASEMENT. ECORpING,'NO;.. . .� . . . . . . . . - 0�. . . ASPHALT. . . . . . .�. . . . . . . . . . . . . . . . . . . . . . 891 1 1 70364 AND . . ryy: - . . `l . .�� oPARCEL "C �Q. . cL. . h . . . . . . . I cr I RECORDING .Nq:0 ^> �l ^i Ica a .89111.7036 :'.'.'. ry _ —`y� . . . . . . . w I� p I GRAVEL Z z LIGHT STANDARD -y tK W 1 NQN.=EXCLUSIVE m PARKING EASEMENT RECORDING . La Q ' .FLOOD-ZONE"AH �ry .. .-. NO.. 8911170364 •�� 0 z lb & PARCEL SEE NOTE 9 ry : . : . ry5 h RECORDING .. . LIGHT STANDARD 'NO. 8911170362 o I/ 0 /I rytK m SEATTLE CITY LIGHT I TRANSMISSION LINE °� EASEMENT RECORDING NO.'S 7210300117 & 7210270580 y . hb l tON I SANITARY SEWER MAN I / RIM . EL 23:83" V °Lh. IE 18"?--W 100' GRAVEL . a IE '18"? SE 10.3- . . . LADDER :ON NW WALL . . . . . . . . . . . . . . . . . . _. . -- . . . . . . . . . . .. . . . . . . . . . . 84 W. W . . . . . . . . . .'W. . . . . . . . 5 y . . . . . 5. . . . . . . . . . . . . . . . y . . . . . . . . . . . . . . . . r1"?�. .'. .`L . . . .'. . . �1 . . . . . . . ".'.'.'.iy . . . . . . l . . .f .. . . . . r. . . . . . . . . . —' . . . . . . . . . . . . . . . . . . . . . . .� . . . . . . . . . . . . . . . . . . . . . . 'l . . . . . . . . . Pj ��. .. .� . . . . . . . . . . . . . . . . . y ry Q 'ss �S . . : ... .. ss. . . . . . tip: : . . .'_ . . . �� rye. — —. —. CATCH CONCRETE.. . . . - . . CURBS . . .. . . . . . . . . . . . . . . . ..'. . RIM EL . . . (FULL f P p . . . . . S p SD o " 5 . . . . . . . . — .' . — . _ LIGHT \ �b TRAFI �-10' WIDE SANITARY Xe . . c93. '. . . . . . . . . . . 4p41 £EWER EASEMENT. . . . . . . . . . . s,.s \ . . . e . . . 1�ECORDING NO . . . . . . . . . . . . . . . . . S.'- . . . . !y . . . . . . . . . . . . . . . . . . . .'.'.'. . . . . . . . . 663'1804. '. ASPHALT \ T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ m�� _ = _ I _ m _ \� 2 9 N 89'2 5± E ��, Im/ � M r n � o a x 10 LF-8"O @0.50% 2 o CB 1 , TYPE2 N77'28 26 E Z x. Z # CONNECT TO EX. CATCH BASIN Li Oil /WATER 144 07' tt� n 3 5 RIM=23.90 IE.=19.5 8" SW o f IE.=19.55 (8"NE,SW) w OVERFLOW EL. = 21 .90 O V CURB RAMP T5M ON C J _R CATCH BASIN FIC SIGNAL. BOX g EL 22.99' j w :U RIM EL. 22.28 ^ �� is CONC E 2-A.-A' n `'�- . ._ Ow 0 3 EL RT NEW CURB ,. _ �__ _— n DRNER t, fiTpRM 'von, d�A1'IIER _I � -� c?REEr UrI{T 1 g�' M . . g TRAFFIC g ��u<< a. v r� :" ::.: : :::::::.: `tom I SIGNAL BOX 3 TYPE1 ti ti ". . .". . .. . . . '.'.'. :::: . :.: 2.9Q .•..?. : 28 LF .�... �. . . . . . . . . . . . . . V V Mai '} i.`. - O• .. ..-. �... . f. � ate. ...... • a�c� •-�� -4•:. :�: •.: \� ........ GUR S TANDARD �. . . .... .:::'•::::}:' ::•:::•:::'''•:? :' : :`'::: .:.;:.t:eP :... N .^ •• .. M �.:.. y,:... .: .?..... .. ......... ....... ...:..:':::':'.. . ......... :.. :. ........._ ='. :........... ....... .I MATCH EXISTIN u :...... :: { h, . � • ••:•... .I� GROUND r... .:::::1: :: ---::.::::o TANoARa ... :•:.;....:::°: :;; ::: p MATCH EXI`. ::: "::::...::: . : :::r Y ..:..... . ..... - - r �" GROUND ' 24.00 ::. :: ........: t r; ....:: .::. . ;EX: ...... :r 1. i n :. . . . {{ .. . :: f '. .. .. w cti1 f z .... ::' • 4V. 4 _f y : . 2410 ::f :° :.. . .. r .. GHT STANDARD . ......:..... :.._::::•:. ::.......... ... •: . J : :': : . : ::SEWER MANHOLE ..... te . ....r:. w ry W [3 0 .'.• .. .. :c:::•::•:•:•:•'•...... . :rl: �: :,: i W WAI I . . .. �. :.. MATCH EXISTI ....,... ........... . r :i: qG �, : ° :::: :........ ^� ..:: ::::: GROUND DF .... .. .. ::::::•:':::: .. ...::f:l.:':: ': ':::: •..... g Y:;:... :24.00t ' :. ASfa . 24.10 ti . ::.:::::::.. . ...: i 1 FOUND CORNE ::: :..:: EX:' 23.60':''::_::::: ::: .::. -, 23.6Q :::: :::: ..:.::. N ...:. ... ..........[.... .. . ............... r''. . a •.. 23 40.... N89 7�8 18 24.9 •.::. . 23 40 N^ 35 5 . . . a�.,. ....::: 23:50:: : ::::::' ... .: ` Ct�� I '.;.: :: .: , .. EX. CAI�JRASIN MATCH EDGE OF. EX -PAVEMENT R 2 5' � ' t S� RIM EL 23.05 . . . . . . .��. . . . ^... . . .. . . . >`. . . . . . . .(TYP '?Q�%8ASI DEBRIS) m:..• '.'.'SS. �.'.'.' '.'.R;2.5'.. . . . . . . . . . . . �. rid'.'. . . . . . 4. . . . . ,. f.:.::..::...:....... .... . . . . . . . . . . . . . . . . . . . . . . . . . . . .3". .5.. . . . . . . . . . . . . . . . . . . . . . . . . . . . EX. CATC CONCRETE.. . . . . . . .......... .... . . { RI�1 EL 23.03 4� . . . (FULL OF DEBRIS) F` oft 917 .:. . . . _ . . .•� . t'i �' G' - ' - i, _ �iviii SinrviiAR . 1Li RAFT IC SIGNAL BOX b ' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . �1, R=245.00' . . . . . . . . . . . . . . ,ASF'rv'�.;...,. . ..Y . . . . . T.'.'. rA . . . -� � �l tell . . . . . ......•. .297. t �. . . . N 89'28'13 E Ile \t � f Oi, , iEtrlop a „1 = Ww Ali all 1_ 1 d. TAWPM ...mot .� � . x 1. ?fir;.= ..�w1El�' �, r►� , _ ' • �'i�I�h�rllf�i�� yam'`' • r� :•a._� 'tom: ■ � �iis►rir`l�•`� LR � ��1� �� � - Mmso 9.0 a ILA sad �.eii � �/'jam r�•` , fe I ON MA Md All All ML I, IMP mot 10 IN IRWIN� aa�a.,�1►�j fir q �, • i� r KING COUNTY, WASHINGTON, SURFACE WATER DESIGN APPENDIXF TABLE.2B SCS WESTERN WASHINGTON RUNOFF CURVE NLMIBERS ' SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type I ' rainfall distribution, 24•hour storm duration. CURVE NUMBERS BY HYDROLOGIC SOIL GROUP ' LAND USE DESCRIPTION A B C D Cultivated land(1): winter condition 86 91 94 95 ' Mountain open areas: low growing brush and grasslands 74 82 89 92 65 78 85 89 Meadow or pasture: Wood or forest land: undisturbed or older second growth 42 64 76 81 Wood or forest land: young second growth or brush 55 72 BI 86 81 88 92 94 Orchard: with cover crop ' Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% O or more of the area ' fair.condition: grass cover on 50% to 75% of the area 77 85 90 92 Gravel roads and parking lots 76 85 89 91 Dirt roads and parking lots 72 82 8998 Impervious surfaces, pavement, roofs, etc. 98 98 98 to ., Open water bodies: lakes, wetlands, ponds, etc. 100 100 0 100 Single Family Residential (2) ' Dwelling Unit/Gross Acre % Impervious (3) Separate curve number 1.0 DU/GA is shall be selected 1.5 DU/GA 20 2.0 DU/GA 25 for pervious and 2.5 DU/GA 30 impervious portion ' 3.0 DU/GA 34 of the site or basin 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DU/GA 5o 6.0 DU/GA 52 . 6.5 DU/GA 54 ' 7.0 DU/GA 56 Planned unit developments, % impervious condominiums, apartments, must be computed ' commercial business and industrial areas. (1) For a more detailed description of agricultural land use curve numbers refer to National Engineering ' Handbook, Section 4, Hydrology, Chapter 9, August 1972. (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. Ir 3.5.2-3 11/92 ' APPENDIX G 9/7/95 4 : 6: 9 pm Warner Engineering page 1 SOUND MITSUBISHI SUBARU USED CARS ' STORM DRAINAGE ANALYSIS PREPARED BY: C. LEVEY --------------------------------------------------------------------- --------------------------------------------------------------------- ' BASIN SUMMARY ' BASIN ID: POST NAME: 100-YEAR POSTDEVELOPED STORM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 1. 06 Acres BASEFLOWS: 0. 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP ' PRECIPITATION. . . . : 3 .90 inches AREA. . : 0. 12 Acres 0.94 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00 98.00 TC. . . . : 10 . 00 min 5. 00 min ' ABSTRACTION COEFF: 0.20 PEAK RATE: 0. 83 cfs VOL: 0. 31 Ac-ft TIME: 480 min ' BASIN ID: PRE NAME: 100-YEAR PREDEVELOPED STORM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 1. 06 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP ' PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0. 12 Acres 0.94 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00 93 .98 TC. . . . : 10. 00 min 5. 00 min ' ABSTRACTION COEFF: 0. 20 PEAK RATE: 0.77 cfs VOL: 0. 28 Ac-ft TIME: 480 min t 1 ' 1/5/96 12 : 5 : 14 am Warner Engineering page 1 ' SOUND MITSUBISHI SUBARU USED CARS STORM DRAINAGE ANALYSIS CHECKING DOWNSTREAM CAPACITY ----------------------------BASIN SUMMARY 1 ' BASIN ID: post-100 NAME: 100-yr Postdeveloped storm SBUH METHODOLOGY TOTAL AREA. . . . . . . : 1. 19 Acres BASEFLOWS: 0. 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP ' PRECIPITATION. . . . : 3 . 50 inches AREA. . : 0. 12 Acres 1. 07 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86. 00 98. 00 TC. . . . : 10. 00 min 5. 00 min ' ABSTRACTION COEFF: 0. 20 PEAK RATE: 0 . 83 cfs VOL: 0. 31 Ac-ft TIME: 480 min 1 t 10/2/95 1: 7 : 17 pm Warner Engineering page 1 SOUND MITSUBISHI USED CARS ' STORM DRAINAGE ANALYSIS PREPARED BY: C. M. MODJESKI ---------------------------------------- BASIN SUMMARY BASIN ID: post NAME: 6-MONTH DEVELOPED STORM SBUH METHODOLOGY TOTAL AREA. . . . . . . : 1. 06 Acres BASEFLOWS: 0. 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP ' PRECIPITATION. . . . : 0. 66 inches AREA. . : 0. 94 Acres 0. 12 Acres TIME INTERVAL. . . . : 10. 00 min CN. . . . : 98 . 00 86.00 TC. . . . : 5. 00 min 10. 00 min ' ABSTRACTION COEFF: 0 . 20 PEAK RATE: 0. 10 cfs VOL: 0. 04 Ac-ft TIME: 480 min 1 APPENDIX H Page 1 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT JIR) WORKSHEET PART I PROJECT OWNER AND PART 2 PROJECT LOCATION PROJECT ENGI NEER AND DESCRIPTION ' Project Owner RSGh 5n�dtr 9Yi Project Name Sc 5ubaru Address 750 lea i n n e r AV" e,tQyirks�_ Location ' Phone Township 2 3 N Project Engineer t;nMu Garner Range 5 E Company Warner Enaineertin Section Mtil 19 Project Size 1.0 AC ' Address Phone 122 DC . ' Or Nw S+e 82oy Upstream Drainage Basin Size iv one AC G15 NorberLUA 833 a -S 8- S -r? PART 4 OTHER PERMITS F-1 Subdivision • 0 DOF/G HPA 0 Shoreline Management Short Subdivision COE404 0 Rockery (] Grading DOE Dam Safety ED Structural Vaults Q'"Commerclal FEMAFloodplain O Other 0 Other COE Wetlands 0 HPA PART 5 SITE COMMUNITY AND DRAINAGE ' Community Ren-Fo n ' Drainage Basin Green t2;u�T -P-ART61- SITE CHARACTERISTICS EJ River _ O Floodplain 0 Stream E3 Wetlands C:1 Critical Stream Reach Q Seeps/Springs 0 Depressions/Swales Q High Groundwater Table = Lake = Groundwater Recharge Steep Slopes 0 Other Fla+ Si h4 In t i rh n r) o- ea ' Lakeside/Erosion Hazard PART 7 SOILS ' Soil Type Slopes Erosion Potential Erosive Velocities C>rn P_Ii kla} 5t;�h+ Fa Meducle Z �Ps Sandu ' �Urboa (.ands ' O Additional Sheets Altatched 1/90 Page 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PART 8 DEVELOPMENT LIMITATIONS y1� 1 i REFERENCE LIMITATION/SITECONSTRAINT t F-1 Ch.4-Downstream Analysis IJnne - ! 4e p✓. i -),cs CAS exe, p:Lfcii 0 a ' (] Add itional Sheets Attatched PARTS ESC REOUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION Sedimentation Facilities Stabilize Exposed Surface ' F-1 Stabilized Construction Entrance Remove and Restore Temporary ESC Facilities 0 Perimeter Runoff Control QK Clean and Remove All Silt and Debris ' I] Clearing and Grading Restrictions E�r Ensure Operation of Permanent Facilities ED Cover Practices (] Flag Limits of NGPES (� Construction Sequence Other ' (] Other h PART r SURFACE WATER SYSTEM J ' (] Grass Lined Channel (] Tank Infiltration Method of Analysis ET�r�Pipe System 0 Vault Depression SCS ' ED Open Channel Energy Dissapator Flow Dispersal Compensagon/Miligation 0 Dry Pond [] Welland I] Waiver of Eliminated Site Storage 0 Wet Pond (] Stream ID Regional Detention None ' Brief Description of System Operation Cni%ch bos�n5 Collet.} YldWS onto ao. rq Flows -'o wa�rer ual'.k� o;l�taa�v St�arohor ti,l�;ch dlscl�ar+4ri �e Cck., Skar�m su-,,}ern t„��I�s�r1- dc�}enh'.n Facility Related Site Limitations (] Additional Sheets Attatched Reference Facility Umftation PART 11 STRUCTURAL ANALYSIS PART 12 EASEMENTSiTFAr"I (May require special structural review) ' 0 Drainage Easeme tron wc��(*a Ica a (] Cast in Place Vault 0 Other Q Access Easeme ; 0 Retaining Wall Native Growth Prteca�� "d (] Rockery>4'High Tract � 7 0 Structural on Steep Slope Other �' ?� R16157� ^ 1PART 14 SIGNATURE OF PROFESSIONAL ENGINEER 1 or a civil engineer under my supervision have visited the site. Actual expi s 9/21/ ' site conditions as observed were incorporated into this worksheel and the 19�1attatchments. To the best of my knowledge the information provided here is accurate. s 7 f! 1/90 ' V1. REFERENCES ' 1. Soil Survey of King County Area. Washington. United States Department of Agriculture, Soil Conservation Service. November 1973. ' 2. Stormwater Management Manual for the Puget Sound Basin. Washington State Department of Ecology. February, 1992. 3. Waterworks. Software for Hydrology. Version 2.7. Engenious Systems, Inc. Seattle, Washington. 1 1 1 1 9 1 • � � � � 1� �� 7 1 •1 i � 1 1 � � 1