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HomeMy WebLinkAboutSWP272896 JAEGER ENGINEERING 9419 S. 204 PI..ACE - KENT, WASHINGTON 98031 54, PHONE (253) 850-0934 FAx (253) 8SO-0155 March 20, 2000 DRAINAGE REPORT CHOW 5 LOT SHORT PLAT 3303 TALBOT ROAD S. RENTON, WA. PREPARED FOR: Owner: Oswaldo Chow P.O. Box 27470 Seattle, Wa. 98125-2470 (206) 361-8478 �o �t y � 2oa�� PREPARED BY: 3 James J. Jaeger, P.E. TABLE OF CONTENTS Page I. Project Overview II. Preliminary Conditions Summary III. Off-Site Analysis IV. Flow Control and Water Quality Facility Design V. Conveyance System Design VI. Special Reports and Studies V11. Basin and Community Planning Areas V I I I. Other Permits IX. Erosion Control Analysis and Design 1 r I. OVERVIEW The proposed project is a 5 lot short plat located along the west side of Talbot Road S. just south of the intersection with S. 32nd St. The site address is 3303 Talbot Rd. S. The existing lot is a 1 .04 acre parcel that has an existing house with a long gravel driveway. The proposed short plat would divide the existing lot to create 5 new single family residential lots. The existing house would be demolished and removed. The existing lot is generally covered with lawn and sparse trees, mostly located in the southwest corner. The lot slopes down from the east to the west, away from Talbot Rd. S. at a slope of 8% until just west of the existing house. Then, there is a 10 high slope of 30% that levels out onto a gradual 40 ft. wide bench. After the bench, the property slopes down to a large wetland area at slopes ranging from 45% to 55%. This large wetland area is the wetland that sits between the toe of Talbot Hill and Hwy. 167. The existing frontage road, Talbot Rd. S., is an asphalt paved road with gravel shoulders along both sides. There is a section of vertical curb and gutter north of the site along the east side of the road that was constructed as part of the Plat of Winsper. Talbot Road is an arterial road at this location. There is sanitary sewer and water within Talbot Road as well as all private utilities. There is also a public san. sewer main and easement that runs through the west portion of the property above the steep slope down to the wetland area. The existing access to the lot is currently from Talbot Rd. S. The proposed access will also be from this location but will be improved to a 20 ft. wide paved private road with a "hammerhead" turn-around for emergency vehicles. The road will be on the south side of the short plat. There are no drainage improvements on the existing site. However, there is a drainage ditch just north of the north property line that runs from the east to the west. There is also a minor drainage ditch west of the house that runs to the southwest and down the slopes to the wetland. The majority of the site sheet flows to the west and down the hill towards the wetland area. There are ditches and pipes along the east side of Talbot Rd. S. The west shoulder ditch drains into the existing ditch north of the property. R Page 1 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PROJECTPART I OWNER AND PART 2 PROJECT • • PROJECT ^^ . • Project Owner 0S�QO_._0At,o'..0 _ Project Name AddressP-9� 2����-� Q ��0.. q1?1 Location Phone 3 Township._ 23_ Project Engineer .� -_ Range name S-_- �o��-t[� Section — - 30 Company t�/le�e.�-1xtQ -- --- �r _ __ Project Size J -C) `F AC Address Phone 9 L9_S _ PL-/ t. a Upstream Drainage Basin Size -____ _ __._AC PART 3 TYPE OF • OTHER LJ Subdivision C] DOF/G[IPA Shoreline Management Short Subdivision L] COE 404 >1 Rockery (•31 C_) Grading I___] DOE Dam Safety Structural Vaults [_I Commercial I J FEMA Floodplain I__ J Other (_ I Other -------------_-- _-_ -------.-- I -J COE Wetlands I I HPA COMMUNITYPART 5 SITE r DRAINAGE Community (--- --- Drainage Basin PART 6 SITE CHARACTERISTICS LI River ----_— -- _-- [. I Floodplain U Stream — - -.. _ ------ <_ Wetlands U Critical Stream Reach [ l Seeps/Springs C_J Depressions/Swales [ J I ligh Groundwater Table L:J Lake _-__ _ ____ A� _ L_--J Groundwater Recharge k�SteepSlopes - W� S -� �►�,Q I J Other _ [_J Lakeside/Erosion Hazard PART 7 SOILS it Type Slopes Erosi?n Poteptial Erosive Velocities -°-°c� ---- --- 1 -- - Modur - _ S.--FP -------- (_] Additional Sheets Attatched 1/90 Page 2 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PART 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT Chi-_Downstream Analysis- Additional Sheets Aftatched PART 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION Sedimentation Facilities Stabilize Exposed Surface Stabilized Construction Entrance ary FSC Facilities Remove and Restore Temporary Perimeter Runoff Control Clean and Remove All Silt and Debris Clearing and Grading Restrictions Ensure Operation of Permanent Facilities Cover Practices >6 Flag Limits of NG PES ,K— Construction Sequence Other Other PART 10 SURFACE WATER SYSTEM Grass Lined Channel El Tank U Infiltration Method of Analysis Pipe System 1-1 Vault E:j Depression ----------1_-E-- BQ-t-A Open Channel Ej Energy Dissapator >j:f Flow Dispersal Compensation/Mitigation Dry Pond Weiland Waiver of Eliminated Site Storage N3 Wet Pond IF Stream F�l Regional Detention . Brief Description of System Operation cbitv) """T, fD I CDa -,-L t At ;C)rsj�--b�- Jv3 -112�1-ZIA Facility Related Site Limitations VII Additional Sheets Attatched Reference Facility Limitation PART 11 STRUCTURAL ANALYSIS PARt 12 F-ASEMEN-tsrrRACTS (May require special structural review) >� Drainage Easement EJ Cast in Place Vault Other Access Easement Li Retaining Wall Native Growth Protection Easement Lj Rockery>41-ligh Tract Structural on Steep Slope Other PART 14 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were Incorporated Into this worksheet and the attatchments. 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Fred No Emilio Pltro(ti A ----- ® mislrl !.1)Aa W rr 1 E61 l�sl-06JAc Q n ' N � Leland _ Y 1 S r11 2 or S.Nllson w0 N W �U LLL"Y6al' U AC � ■- W V J I� Mil- QNILIL- - • ; ( er�7[�ate•1/�< I /Q,.'I I r O �'� 7° . o a } r t11 Ae J/ GI` -J ' IT " A 4 [1 r t S H Q nfvf��1 14 11 N tR 04-81 Z 4 n i u�„1 �© o/s nc/-I ,r p� IS F Q +I'r[��11� Q (31 Mward V y 4/_ 1 et J W Hawkins 16 (''1)1� 1 _FF7 1 � '1 II� LI lI71 OSr Ac� " S. 174TN ST.a enerlel l 11,11ms. (2) ° �" _1rs5A df a u O ), � lel r� H Cfin CIA- j,a,�•1 (��z 'e+c ='terry t „S S S 6r Ac iR ns-72 (31 a $ . ry L'L-313111 ,S,,1 Snm rel,neer n, --- 4SAcl ©IA` V A L L E M E 0 1 C A L Q. 1 11 e r 6 S m fl 4) T E tl e1 $ T2 A l0 (AI e0 { r C E N R �'l MORrH CANGUS INO,NG 311[ /LAN I�,' fit rnrE Noe MAp re rarpl.e.an DMclAl Reco4 'v L_ _.... wrwe,rar•rlr.r F.e•swr.r,F..,ryw • � wal w„o.r,.nN�«prn«w ti.a,.a l 6 2 N D eu _ ATLAS OF SEATTLE A■Rs er p FRw sromns L7 Nws[1A,ra(A p :�mow'�.:."�«L��..�.:».:,.,. AulA0A0-+-+-t-�-"• ::•,...'::�-'�.•'::`•.......,.:.:�.,�......r. . loe.uan.rts•. a_ .,,..w.....�.nr.•-+ KAOII MAP COM►ANY.INC.S2ATTl6 W■I1A111000IlAM �- 1AI1(Or eure(A rl _ SCA(('I INCH.200 FEET KROLL ��P PORTION OF NE 1/4 OF SE 1/4 OF SECTION 30, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M. mom=wAL CO111101.oP 6 Rmlldl(M.O-6)/'91) f11011i PLAT r.A SHORT PLAT/SUBDIVISION PLAN E EVA RM URA`CM OF MD"M(•"°-66) Fu,PC MCMU EBTS-OTY as OETITO�I`mII1.OL W9af7115 ^N.WVI E t OF 1 3 4_ EASRW 20*M708&Top pf 1 S/t BRASS OW +O N I CO VE WMAE71T a CASE M OdTU_.*:m 4 j TALBOT f ,OPOO E.IOISE 1 702.1 SS'WMBA y. s of 11E CEMTORIE s i MTN STRUT. !'J. EIZ+. 99.A78, ROAD DETAIL ,�,';, ""9 nOBTN«C ,66756SB96 EAS DU s 2,9�,,,.. BRASS o « S 3 ST. rOawpiT P��« E o< J .LBCi fOAO. ]pPC4TE 0 SEe T ro EMJIOE CIF mw INC 1 3/6-BORIS CAP SHORT PLAT LEGEND . � t -T-— I.a.aEs-N.153f So n ---------7 a _ PROPOSED.,Aam 6 L07S 5 a CAC K� .vOP SED 4REA OT.. 7.730 Sc n �% x✓ %2aoo' LOT 2: 6.00 50 r !�+ LOT 1 6.424 SO�• Lo.•: : So e \ LOT R&J.=o21 so n AREA EmST.BIMMOM L005 SOF_ AREA 3FE KE«B T' A fl snr PE71C4.hTAGE OF LAND M ST4EET' tD.K r3M*G:5 OESM71AL-6 Ou/AC(e-6) .rAmot EN06EE.KMG M19 SOL,70.T' PXE o.-Ow"0. :.J)650-093- "-cam, FAX r0 (253)660-M63 r � r 'hE'7at�aalW ,Ec-via\ ' '' r.-ucarMEr,noFnls �� ��� � �� �� Nc 'a3Lc i J,( K R/A OF TK BE I/40s SEC>0 ''` LINE '9uTH BEARING sor w-toam 25.0: N0:SO_'0'E� Z. s ru d OEBBS ' \ 1 ''$ , w ouILET sefll -3 45 N99'?^_'49'v l _ �1p"G` ' 1 ma ASMA( � ass NB9.27a9'y t `\,►� i I` 1 LZPT.L ^--__ - ----_ R��,...,�yyBM ' 1i11 1D '.4— �.� =0' - Y M COUL9'��iN M/ LOT 3 i - \�� \LOT 2 R 1 . \ \ a-_..- I 1(6.430 u.)t )� !1 \\ \� f•,a i1\ •Ir I 1 I �r'!I 1 I ! ��"rr' +Vi LEGEND \\ 26s.: uD6AIprT AS IROTFD EY 6 u.SIO'f, �-+� G�i/ `\c7 a w - •A-+.e W gown-.6:. �1 F. • FfOFC11P'aaaK,e ,w amt cp \�,�,. �;, +..�-' �' - '�- - 'S ( 1 ji W ,�; \ _ As wTE7 i �:-Slt►1 .w[6s/[96[zs• aaao )I ..°6.a.n�y '>. t OEKTOKr'RE Y •\ i'31• •E•�-� L •J:uT EA.sO.ENi T _ J Y.PI TREE SET�a W s J\ war` - �� (2o w7b.0_ �rM 49 r m Br SIT - r, L$15a66/j: �E j 1 f SET REPO t CAP i sI 1 - dn— : � OKSnILiT•� 1 1� \as lac I� - ~ "' ••� ��f ( r 4 1.f SEE ROAD DETAIL � ...... ' I N •mrnu..om 78EE\ (2'i';(l r� ' R/ .1 ,I � .s�l_-_ )jr .Fna Ta¢ `C. VTLT PRE t `all t / `f f-6W_ . ■ • GAS IRETETR I ••�4���a!!..J Eat( -�++ ,-i; SM.T.fY 1EMM r.IfR«E 30 30 M_- Oz I CURVE TABLE � _ �l b�•-•i 0�'XE GRAPHIC SCALE C::RVE ILENGT IRADrilS: DELTA s M mw — c: 34:6j 22.001Mar!r VICINITY MAP CE-W!T cz: 5011 zoc, 91^.r09" ,ikoeo 6oac tr. u: e=• ,r[I.MASS R PL ""'c9rc OSWALDO CHOW MMMUP.O. BOX 27a70 s s CERYYKAIF \�P . SEATTLE WA_ 96125 a M"ADF AMM ma_w _ t9_AT w 86.v COBKM1,v� e of KT6 A w -W F K u.XR HALLlh' dC ASSOCIATE{ INC .. At Ag-«ft.—IV_Ar n.a_17 1w KaRRSr ar ..D�6o. oX+arwloc BE p It B a PROA� SHORT PIATISUBD MION PLAN � Lend Surveyors -- CPS Consultants we Out P NY 1 IN er A XURMOV b o W imesT a 09 0M Char ((� 31218 Pecilic Hwy. So. Suite 'N' CHOW SHORT PLAT nnaFs.I.E « .ILT-ramwn ,s 96-s9 Q� Federal Way NA 98003 233-941-SIO/ 1-800-311-5317 arw n EC F-,IW 9603 D� sKE �i0 �1ldT 4 tSa50 .PPtWICD OPN j,1./[ A_1y9y I Ati/ 9603t �= , II. CORE DRAINAGE REQUIREMENTS 1 . Discharge at Natural Location: The site will continue to discharge'at the natural location. This location is the western property line and the wetland that is west of the site. 2. Off-Site Analysis: An upstream and downstream drainage analysis has been performed and is detailed in section III of this report. 3. Runoff Control: This project is exempt from peak rate runoff control because the 100 year peak developed runoff is less than 0.5 CFS greater than the peak pre- developed runoff rate. The actual difference is 0.29 CFS. 4. Conveyance System: There are no existing drainage improvements on the site. The proposed sife will have some piping and ditches. All will be sized to handle the 100 year storm. A biofiltration swale will be constructed just prior to a dispersal trench that will spread out the flow prior to discharge above the slopes. The downspouts for the new houses will be piped into the drainage system with individual lot piped connections. 5. Erosion and Sedimentation Control Plan: An erosion control plan will be prepared for this site. Grading activities will not be extensive, but there will be some minor grading for the new private road. Silt fencing, rock pad construction access, soil cover and dust control will be part of the erosion control measures. 6. Maintenance and Operation: The maintenance of the drainage system and private road will be joint responsibility of the homeowners on an equal basis. The mutual agreement will be recorded on the final short plat mylar. 7. Bonds and Liability: Any required bonds and insurance will be provided prior to any construction activities. SPECIAL DRAINAGE REQUIREMENTS There are 12 special drainage requirements that may apply to any project. In this case, none of them are applicable to this project. r III. OFFSITE DRAINAGE A. UPSTREAM DRAINAGE The upstream drainage contribution to this site is negligible. The only up- gradient property is along the east property line, and this is the Talbot Road S. frontage. Talbot Road has a ditch along the west shoulder that discharges into an outlet ditch just north of this site. This outlet ditch intercepts all of the street flow from the north prior to entering the site. The site will get some minor runoff from Talbot Rd. along the frontage. B. DOWNSTREAM DRAINAGE The existing runoff from this property sheet flows to the west across the existing lawn area. There are no storm drainage improvements on this site, except for a small drainage ditch that was constructed southwest of the existing house. This small ditch picks up the drainage around the existing house and directs it to the southwest and down the slope to the Idrge wetland area. The majority of the site sheet flows to the west and down the slope to the large category 1 wetland that is at the base of the slope to the west. This wetland is approx. 150 ff. west of the site and located on the series of lots that are adjacent to and east of the Hwy. 167 freeway. This wetland extends for a long distancE: along the east side of the freeway. There are several pipes that run under the freeway from the east to the west. none of these pipes seem to drain the large wetland area, but may receive some overflow from the wetland. The pipe across the freeway that is nearest the subject site is pipe no. 26,F6-8 This pipe outlets into a large ditch recently constructed along the west side of the freeway and eventually feeds into the drainage system along the East Valley Hwy. This drainage system in turn eventually runs into a tributary to Springbrook Creek. There are no local piping systems downstream from the site. The major drainage feature is the large wetland area east of the 1-167 freeway. This wetland shows no sign of flooding or instability. The only question concerning this downstream system is the flow down the steep slopes above the wetland area. A concentrated flow may cause erosion on the slope. However, this project is not large enough to warrant the installation of a "Driscopipe" outfall system. I recommend that a flow spreader or dispersal trench be constructed above the slope, at least 25 ft. away from the top of the slope, to create a sheet flow effect down the slope. C-3 o ra W 3-] ~ z3.W-6 6a A mo-4 ; 26.r3-2 � 26�G3-3 � 11 2E G]-6 6,G3-7 ' 0 26,G3- � O Y6l]-1 Q N H z6.w s 26H3-2 S 1 � L ST 6H.-2 H. 2 �.-1 26,C4-2 24H4-° 26H, 5 cs-, f/1 _ 6,14 9 14-7 Y4 4-326�r4-s 26,G4-1 S 2 TH 6H4-] 26f4-12 6.H4-14 .c 6.1 9 �{ 2444-2 4H1-4 G4 7 - 6H.-1 ,1 S\ Y6.r4-4 - S BT PL 2 4-13 S C 414-6 6H4-I2 n 26J4-6 O 26.H4 10 2 14-5 V 26.f4-7 ;u 26H4 9 S Y4r.-3 24G,-6 = 6.H -7 26f4-° _ 26,W- / • 4H, .14 2414-1 4H4-0 S 14-3 26H4- 26.r4-9 24G4-4 S 2414-2 ti,r+-z 2614-11 9 24r4-10 2644-5 241S-7 26.HS- 6Jf3-s 4H.-16 26H 7 z6rs-e ME3-4 6j4-1 _ 6i13- MIS-6 '4C5-5 �• ��� T`' 2415-3 4E7- 24rs-3 - 4c5- 26NS-4 24r3-6 24w5-3 S 3 !4C3-6 / •• Y4I7-S Y + 2415 J _ 6H3-9 26.H5-1 s 3 ST N T Y4f5-3 6 S-7 2413-7 _4 2413-3 4HS° Y��2 Y4: Y6rS-Y 24G7-] Mrs-1 m 24r6-° m Y6.r6-5 26,rs-7 k� W'-2 26I6-1 26,H6-2 � 24H6-6 I S T26.ci-3 26.H6-7 26.C7-s 26.146-3 26H6-° MU-4 i-26X 7-6 Y4C7-3 24H7-6 1 26 N7-7 S 172ND ST to � �•... 24N,_1 f --- i I --, 26,C7-2 Y6,r7-2 Q 1 _ ?6'H 7-4 _ Li -` Si 36TH; ST ? W ' r IV. DETENTION ANALYSIS AND DESIGN A. PREDEVELOPED DRAINAGE The drainage from the existing site sheet flows to the west and down the existing slope to the wetland area to the west. There are no drainage improvements on the site. The area used to perform the drainage calculations does not include the area along the steep slopes on the west edge of the property. This area will remain in a sensitive area and will be undeveloped. This reduces the project area from 1 .04 acres to 0.88 acres. The existing drainage analysis was performed using the "Waterworks" hydrology software and its summary tables and charts are attached for reference. The methods outlined in the King County Surface Water Design Manual were used as guidelines. Following this page are the data sheets used for the computer input data. The computer summary sheets for peak flow and time of concentration calculations are also attached. Below is a brief description of the existing drainage characteristics: Time of concentration: 21 .03 minutes 2 year peak flow: 0.09 CFS 10 year peak flow: 0.22 CFS 100 year peak flow: 0.38 CFS project area: 0.88 acres pervious area: 0.77 acres curve number: 81 impervious area: 0.1 1 acres curve number: 92.88 B. DEVELOPED DRAINAGE The developed project will not include detention storage due to the minimal peak flow exemption allowed by the drainage code. The site will include a biofiltration swale because it has over 5000 SF of impervious surface subject to vehicular traffic. The swale will be designed for the 2 year developed storm event. ui 76) S s �� �1 -� 1 '37'v�.a ClS' Q�2 M O� +aa l�S C t,2 "a"'ter`c'.1`�►(� ' "D If ` 0 0 QAJ bLL Na-3 r4 Q-j --r� -A n C ss no 1f,\-h2d 2 'mod 11'0 r jS C3 h _�a w nPa+�'1"�acrl (? Oar-4� 1 G as I h a r,a cs s S ', �U•f-J� S21�gv.lc�rl ���tYJ '� s Tz 2 Q?6 (57� -W) 2 Jaeger Engineering CHOW SHORT PLAT DRAINAGE CALCULATIONS PREDEVELOPED HYDROGRAPH SUMMARIES ------------- BASIN SUMMARY BASIN ID: A10 NAME: PREDEVELOPED, 10 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0 . 77 Acres TIME INTERVAL. . . . . 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 21 . 03 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 11 Acres CN. . . . : 92 . 88 TcReach - Sheet L: 280 . 00 ns : 0 . 2400 p2yr: 2 . 00 s : 0 . 1070 PEAK RATE: 0 . 22 cfs VOL: 0 . 10 Ac-ft TIME: 480 min BASIN ID: A100 NAME : PREDEVELOPED, 100 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 77 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 21 . 03 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 11 Acres CN. . . . . 92 . 88 TcReach - Sheet L: 280 . 00 ns : 0 . 2400 p2yr: 2 . 00 s : 0 . 1070 PEAK RATE : 0 . 38 cfs VOL: 0 . 16 Ac-ft TIME : 480 min BASIN ID: A2 NAME : PREDEVELOPED, 2 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 00 inches AREA. . : 0 . 77 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 21 . 03 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 11 Acres CN. . . . . 92 . 88 TcReach - Sheet L: 280 . 00 ns : 0 . 2400 p2yr: 2 . 00 s : 0 . 1070 PEAK RATE : 0 . 09 cfs VOL: 0 . 05 Ac-ft TIME: 480 min File Basin Hydrograph Storage Discharge Level pool 3eee5eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ; eeeeeeeeee ; ° ° SHEET FLOW CALCULATOR - INITIAL 300 FEET ° ° 0 0 0 0 °DES°Mannings Sheet Flow. . . . . : 0 . 2400 ° ° °ARE°Flow Length (ft) . . . . . . . . . 280 . 00 °HOICES ° °RAI02 yr 24 hr rainfall (in) : 2 . 00 ° ° °TIM°Land Slope (ft/ft) . . . . . . : 0 . 1070 ° ° °TIM° COMPUTED TRAVEL TIME (min) :(Z�D ° ° °RAI° TYPICAL MANNINGS VALUES FOR INITIAL 300 FT °A ° 0 0 °ABS° °BAS°Smooth Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 011 ° ° °STO°Fallow Fields of Loose Soil Surface . . . . . . . . . . . . . . . 0 . 05 °Y ° ° °Cultivated Soil with residue cover (s<=0 . 2 ft/ft) : 0 . 06 ° °PER°Cultivated Soil with residue cover (s>0 . 2 ft/ft) . : 0 . 17 ° ° °ARE°Short prairie grass and lawns . . . . . . . . . . . . . . . . . . . . . 0 . 15 ° ° °CN °Dense grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 24 ° ° ° °Bermuda grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 41 ° ° ° °Range (natural) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 13 ° 0 °PEA°Woods or forest with light underbrush. . . . . . . . . . . . : 0 .40 ° ° °PEA°Woods or forest with dense underbrush. . . . . . . . . . . . : 0 . 80 ° ° °TOT° 0 0 00F10Key: QUIT FSKey: CLEAR °ete ° Pgeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeefit ° �eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef r B. DEVELOPED DRAINAGE The developed project will not include detention storage due to the minimal peak flow exemption allowed by the drainage code. The site will include a biofiltration swale because it has over 5000 SF of impervious surface subject to vehicular traffic. The swale will be designed for the 2 year developed storm event. Similar to the existing condition, the SBUH hydrograph method was used to determine the peak flows for the various storm events. The computer data sheets for the developed flows follow this page as well as the work sheets and the time of concentration calculations. A brief summary of the developed drainage characteristics are: time of concentration: 8.37 minutes 2 year peak flow: 0.27 CFS 10 year peak flow: 0.46 CFS 100 year peak flow: 0.67 CFS total area: 0.88 acres pervious area: 0.49 acres curve number: 86 impervious area: 0.39 acres curve number: 98 C. HYDROLOGIC ANALYSIS The site is exempt from the peak rate runoff control due to the negligible peak rate runoff rate increase exemption. This is specified in section 1 .2.3 5 of the drainage manual. The developed peak 100 year runoff flow is 0.67 CFS. The 100 year pre-developed flow is 0.38 CFS. This is a 0.29 CFS difference, which is much less than the 0.5 CFS maximum allowed for this exemption. D. DETENTION ANALYSIS AND DESIGN Detention Storage is not required for this project as stated above. DEN E L•d PE D D12)p� A . R Ck � Pws e ct s\+-e- (Z�a-wvq— ct-'s . 4y- C A)Q\ t-.�v 'Sot 1 S o-�r e.� A�Id�Q�wOa� SAX I P_ S �`�c�t�to?-( c. I O V 5 4-to L3Q-3 CIS 2 PQry 10 V S 0, bC6 4q G. T m E- ©P Corte c-E+sT p f, Tm oti, : c- Cr--��h c a I D,s��- '• L, _ �_SZ�' E'cA wPS QS_xt� nc>r'rt�) 71Cn L d-P L o' - S S G2 -- (o 4- I z 'F I ow o-C"Ss Mw V►, T = 3 .3-7 m,�,. (.sue- � Ia C�"A C-e"Of e-r- D. TsoPLU VrP -s 11 P2 = 2 .0 �n z, PIo= ` .cl , n 3 ROO = 3, 9 �n S2� a- e CFZ hy60ro$*-4 3 QI 00 �Y`n M Q Jaeger Engineering CHOW SHORT PLAT DRAINAGE CALCULATIONS DEVELOPED HYDROGRAPH SUMMARIES BASIN SUMMARY BASIN ID: B10 NAME: DEVELOPED, 10 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0 . 49 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 8 . 37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 39 Acres CN. . . . . 98 . 00 TcReach - Sheet L: 150 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1200 PEAK RATE: 0 .46 cfs VOL: 0 . 15 Ac-ft TIME: 480 min BASIN ID: B100 NAME : DEVELOPED, 100 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 .49 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 8 . 37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 39 Acres CN. . . . . 98 . 00 TcReach - Sheet L: 150 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1200 PEAK RATE : 0 . 67 cfs VOL: 0 . 22 Ac-ft TIME: 480 min BASIN ID: B2 NAME: DEVELOPED, 2 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 00 inches AREA. . : 0 .49 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 8 . 37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 39 Acres CN. . . . ., 98 . 00 TcReach - Sheet L : 150 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1200 PEAK RATE : 0 . 27 cfs VOL: 0 . 09 Ac-ft TIME: 480 min File Basin Hydrograph Storage Discharge Level pool 3eee5eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ;eeeeeeeeee ; ° � 0 SHEET FLOW CALCULATOR - INITIAL 300 FEET ° 0 ° 0 0 0 °DESOMannings Sheet Flow. . . . . . 0 . 1500 0 ° °ARE°Flow Length (ft) . . . . . . . . : 150 . 00 0HOICES 0 ORAI02 yr 24 hr rainfall (in) : 2 . 00 ° 0 °TIM°Land Slope (ft/ft) . . . . . . . 0 . 1200 0 ° °TIM° COMPUTED TRAVEL TIME (min) : 37 0 0 °RAI° - TYPICAL MANNINGS VALUES FOR INITIAL 300 FT °A ° 0ABS° 0 0 °BAS°Smooth Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 011 ° 0 °STO°Fallow Fields of Loose Soil Surface . . . . . . . . . . . . . . : 0 . 05 0Y 0 0 °Cultivated Soil with residue cover (s<=0 . 2 ft/ft) : 0 . 06 ° 0 °PER°Cultivated Soil with residue cover (s>0 . 2 ft/ft) . : 0 . 17 0 0 °ARE°Short prairie grass and lawns . . . . . . . . . . . . . . . . . . . . . 0 . 15 0 0 °CN °Dense grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 24 0 ° 0 OBermuda grass . . . . . . 0 .41 0 0 O ORange (natural) . . . . 0 . 13 0 0 °PEA°Woods or forest with light underbrush. . . . . . . . . . . . : 0 . 40 0 0 °PEA°Woods or forest with dense underbrush. . . . . . . . . . . . : 0 . 80 0 0 °TOT° 0 ° 00F10Key: QUIT FSKey: CLEAR °ete ° Pgeeeeee.eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeefit 0 aeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef E. BIOFILTRATION Biofiltration will be provided for the site and designed for the 2 year developed storm event. The tributary area used to calculate the Biofiltration swale flow is the flow from the new road and from 4 of the 5 new houses and driveways. The westernmost lot has a drainage connection directly to the catch basin at the outlet of the bioswale. The bioswale will be located along the top of the slope along the west side of the property. A biofiltration swale was designed for this site using the criteria established in the 1990 King County Drainage Manual. TI-)e design flow was determined using the hydrograph as described above (see attached summary) and is 0.16 CFS. The specified design parameters from the Manual include the design slope of 2.0%, the "n" factor of 0.35, the depth of 4" and the side slopes of 3:1 . Using Manning's equation, the required bottom width is 1 .22 ft. The swale length is 50 ft., so a width adjustment is necessary. The adjustment calculations show a required bottom width of 4.88 ft. The swale hydrology was also checked for the developed 100 year flaw. This flow was determined to be 0.67 CFS. Using the actual swale slope of 1 .0% , an"n" factor of 0.03 and the 6 ft. bottom width; the 100 year flow would cause a flow depth of 0.10 ft. The total swale depth is 1 .0 ft. leaving a 0.90 ft. freeboard for the 100 year event. The velocity during the 100 year storm will be 1 .04 FPS. 16DkOS Jaeger Engineering 1 - CHOW SHORT PLAT DRAINAGE CALCULATIONS DEVELOPED 2 YR. DRAINAGE FOR BIOSWALE BASIN SUMMARY BASIN ID: C2 NAME: DEVELOPED, BIOSWALE, 2 YR. SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 34 Acres BASEFLOWS: 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 00 inches AREA. . : 0. 00 Acres TIME INTERVAL. . . . : 10_.QO min CN. . . . : 86. 00 TIME OF CONC. . . . . : --8.37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 .20 AREA. . : 0 . 34 Acres CN. . . . . 98 . 00 TcReach - Shee L-; 150.00 ns : 0 . 1500 p2yr: 2 .00 s: 0 . 1200--- PEAK RATE: 0. 16 cis) VOL: 0.05 Ac-ft TIME: 480 mini Ij � r bL) f Trapezoidal Channel Analysis & Design Open Channel - Uniform flow Worksheet Name: CHOW SHORT PLAT Comment: BIOFILTRATION SWALE - DESIGN 2Y. FLOW Solve For Bottom Width Given Input Data: Left Side Slope. . 3.00: 1 (H:V) Right Side Slope. 3 .00: 1 (H:V) Manning' s n. . . . . . 0. 350 Channel Slope. . . . 0. 0200 ft/ft Depth. . . . . . . . . . . . 0 33 ft Discharge. . . . . . . . 0. 16 cfs Computed Results: Bottom Width. . . . 2 4:p)s Velocity. . . . . . . . . 0. 22 Flow Area. . . . . . 0 . 73 sf Flow Top Width . . . 3. 20 ft Wetted Perimeter. 3. 31 ft Critical Depth. . . 0 .08 ft Critical Slope. . . 4 .5157 ft/ft Froude Number. . . . 0.08 (flow is Subcritical) fiirce � c• n SW o�Q_ Jp ?r�O can c� 52) pp USA O - ujid'e Open Channel Flow Module, Version 3 . 12 (c) 1990 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 R Trapezoidal Channel Analysis & Design Open Channel - Uniform flow Worksheet Name: CHOW SHORT PLAT Comment: BIOFILTRATION SWALE - ACTUAL 100 YEAR FLOW Solve For Depth Given Input Data: Bottom Width. . . . . 6. 00 ft Left Side Slope. . 3 .00: 1 (H:V) Right Side Slope. 3. 00: 1 (H:V) Manning' s n. . . . . . 0 . 030 Channel Slope. . . . 0 .01 t/ft Discharge. . . . . . . . . 67` cfs JOD----------------- Yr. {off Computed Results: Depth . . . . . . . . . 0110 ft P Velocity. . . . . . . . . 1 f Flow Area. . . . . . , . 0 . 64 sf Flow Top Width. . . 6 . 61 ft Wetted Perimeter. 6 . 64 ft Critical Depth. . . 0. 07 ft Critical Slope . . . 0 .0321 ft/ft Froude Number. . . . 0. 59 ( flow is Subcritical ) 10D •fir. lo,�� P v Vj Open Channel Flow Module, Version 3 . 12 ( c) 1990 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 V. CONVEYANCE SYSTEM The piping will be sized to accommodate the 100 year developed flows as identified in the previous section of the report. The calculated 100 year developed flow for the entire site is 0.67 CFS. The pipe segments with the least capacity within the entire conveyance system will be a 12" CPEP pipe at a slope of 0.5% and an 8" CPEP pipe with a slope of 1 .0%. These will be several pipe segments that are within the interior of the site. The capacity of these pipes is 2.73 CFS and 1 .33 CFS, respectively. Thus, all of the pipes within the conveyance system will be able to handle the 100 year developed flow for the entire project. As such, an analysis of each pipe segment is not necessary. VI. ADDITIONAL STUDIES OR REPORTS A wetland study has been prepared by Del Moral and Assoc. A geotechnical has been prepared by Bergquist Engineering Services that is dated 6/21/99. VII. BASIN AND COMMUNITY PLAN AREAS This site is within the City of Renton It is within the Lower Green River Drainage Basin and the Springbrook Creek sub-basin. VIII. OTHER PERMITS A demolition permit will be required for the removal of the existing house. IX. EROSION CONTROL SYSTEM The erosion control system was designed to minimize any contaminated site runoff from entering the wetlands or leaving the site. There is little possibility that runoff will enter a neighboring property since there is only one downslope property, and this is the large wetland at the edge of tlw! Freeway. It will be protected by an interceptor Swale and silt fencing. Measures will also be taken to minimize the potential for runoff and mud entering the public ROW along the frontage road. A sediment trap will be, provided and is shown on the erosion control plans, which will be the future biofiltration swale facility. The permanent outlet piping and driscopipe will be installed at this time as a means of conveying the flows to the wetland during the construction phase. Besides the silt fencing, the erosion control plans also show the clearing limits and the location for a rock pad construction access point. Temporary interceptor ditches are shown to channel any runoff into the sediment trap. Temporary catch basin protection will be provided for all new catch basins. There are no existing catch basins on the frontage roads. APPENDIX A CHARTS, TABLES, GRAPHS FROM KING COUNTY SWM -MANUAL KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL FIGURE 311A HYDROLOGIC SOIL GROUP OF THE SOILS INKING COUNTY HYDROLOGIC HYDROLOGIC. SOIL GROUP GROUP' SOIL GROUP GROUP* Alderwoo C Orcas Peat D rein s. Alderwood Material Oridia D Arents, Everett Material B Ovall C Beauslte C Pilchuck C Bellingham D Puget D Briscot D Puyallup B Buckley D Ragnar B Coastal Beaches Variable Renton D Eadmont Sat Loam D Riverwash Variable Edgewick C Sala[ C Everett A Sammamish D Indianola A Seattle D Kitsap C Shacar D luaus C SI Silt C Mbced Alluvial Land Variable Snohomish D Nepton A Sultan C Newberg B Tukwila D Nooksack C Urban Variable Normal Sandy Loam D Woodinville D HYDROLOGIC SOIL GROUP CLASSIFICATIONS A. (Low runoff potential). Soils having high Infiltration rates, even when thoroughly wetted, and consfding chiefly of deep, well-to-excessively drained sands or gravels. These sops have a high rate of water transmission. B. (Moderately low runoff potential). Sops having moderate Infiltration rates when thoroughly wetted, and consisting chiefly of moderately fine to moderately coarse textures. These sops have a moderate rate of water transmission. C. (Moderately high n=ff potential). Sops having slow infiltration rates when thoroughly wetted, and consisting chiefly of sops with a layer that Impedes downward movement of water, or sops with moderately fine to fine textures. These sots have a slow rate of water transmission. D. (High runoff potential). Sops having very slow infiltration rates when thoroughly wetted and consl8ft chiefly of day soils with a high swelling potential, sops with a permanent high water table. sops with a hardpan or day layef at or near the surface, and shallow sops aver nearly Impervkm material. These sols have a very slow rate of water transmission. • From SCS, TR-55, Second Edition,June 1988, Exhibit A-1. Revisions made from SCS, Sol Interpretation Record, Form 05. September 1988. .. r 3.5.2-2 __ 190 a - KING COUNTY, WAStlINGTON, SURFACE WATER DESIGN MANUAL TABLE 3.SIB SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type to 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 Meadow or pasture: 65 78 85 89 Wood or forest land: undisturbed 42 64 76 81 �� Wood or forest land: young second growth or brush 55 72 1 per110,15 Orchard: with cover crop 81 88 94 Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% or more of the area 68 80 90 fair condition: grass cover on 50% to 75% of the area 77 85 90 92 t�V-XjQ�, �~ Gravel roads and parking lots 76 85 9 9t I trt�QexV• Dirt roads and parking lots 72 82 8 Impervious surfaces, pavement, roofs, etc. 98 98 98 98 Open water bodies: lakes, wetlands, ponds, etc. 100 100 00 100 Single Family Residential (2) �v 1 rr.�ea-Y� Dwelling Unit/Gross Acre % Impervious (3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected 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 50 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. 3.5.2-3 I/90 [bill • ' ems.■ f f� ro IIFF oil KING COUNTY, W AS HINGTON. SURFACE WATER DESIGN MANUAL i FIGURE 3.3.1E 10-YEAR 24-11OUR ISOPLUVIALS 22 . 23 ,v 24 28 28 aoti - meow `_- 3r v, 10-YEAR 24-HOUR PRECIPITATION � 3.4r ISOPLUVIALS OF IG-YEAR 24-HOUR •\ '^� i TOTAL PRECIPITATION IN INCHES 0 1 2 3 4 0 b 7 •Mlles . .I-I 3' � 40 11300.000 3 S 0 3�J 1/90 1 1 • • �I..� .,, '� �,•,,,,1 rig"' - `� Iglow gig P ff ski m 111 goo Is Rai LIN Will A W-11 Bn . . MO- - F i T JAEGER ENGINEERING 9419 S. 204 PLACE - KENT, WASHINGTON 98031 - PHONE (253) 850-0934 FAx (253) 850-0155 March 20, 2000 DRAINAGE REPORT CHOW 5 LOT SHORT PLAT 3303 TALBOT ROAD S. RENTON, WA. PREPARED FOR: Owner: Oswaldo Chow P.O. Box 27470 Seattle, Wa. 98125-2470 (206) 361-8478 1� OF �I c G7 y PREPARED BY: 20' 1700 S�pN EN� 20l �L 3L James J. Jaeger, P.E. wws in/ Zak 2 U 4h7/0 C) 1 t TABLE OF CONTENTS Page I. Project Overview II. Preliminary Conditions Summary III. Off-Site Analysis IV. Flow Control and Water Quality Facility Design V. Conveyance System Design VI. Special Reports and Studies VII. Basin and Community Planning Areas V I I I. Other Permits IX. Erosion Control Analysis and Design I. OVERVIEW The proposed project is a 5 lot short plat located along the west side of Talbot Road S. just south of the intersection with S. 32nd St. The site address is 3303 Talbot Rd. S. The existing lot is a 1 .04 acre parcel that has an existing house with a long gravel driveway. The proposed short plat would divide the existing lot to create 5 new single family residential lots. The existing house would be demolished and removed. The existing lot is generally covered with lawn and sparse trees, mostly located in the southwest corner. The lot slopes down from the east to the west, away from Talbot Rd. S. at a slope of 8% until just west of the existing house. Then, there is a 10 high slope of 30% that levels out onto a gradual 40 ft. wide bench. After the bench, the property slopes down to a large wetland area at slopes ranging from 45% to 55%. This large wetland area is the wetland that sits between the toe of Talbot Hill and Hwy. 167. The existing frontage road, Talbot Rd. S., is an asphalt paved road with gravel shoulders along both sides. There is a section of vertical curb and gutter north of the site along the east side of the road that was constructed as part of the Plat of Winsper. Talbot Road is an arterial road at this location. There is sanitary sewer and water within Talbot Road as well as all private utilities. There is also a public san. sewer main and easement that runs through the west portion of the property above the steep slope down to the wetland area. The existing access to the lot is currently from Talbot Rd. S. The proposed access will also be from this location but will be improved to a 20 ft. wide paved private road with a "hammerhead" turn-around for emergency vehicles. The road will be on the south side of the short plat. There are no drainage improvements on the existing site. However, there is a drainage ditch just north of the north property line that runs from the east to the west. There is also a minor drainage ditch west of the house that runs to the southwest and down the slopes to the wetland. The majority of the site sheet flows to the west and down the hill towards the wetland area. There are ditches and pipes along the east side of Talbot Rd. S. The west shoulder ditch drains into the existing ditch north of the property. Page 1 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PROJECTPART I OWNER AND PART 2 PROJECT • • PROJECT • 1 Project Owner 0 S QO ow Project Name —CA O�J_ S h a r+ ��ogt— AddressP.-(2C7 -70 `,ieaT1�0. � location Phone ?�t�lo _3 t o l - _ Township _ Z3 N -� - --�4 - -- ----- Project Engineer �O�N`!� Range Company Section 3 0 -- Project Size J �. 4- AC Address Phone 9L S �-�� 1 O --- � - 7- - Upstream Drainage Basin Size ___ _ PART 3 TYPE OF • OTHER L- ) Subdivision [_] DOF/G HPA L J Shoreline Management ,Short Subdivision U COE 404 >< Rockery C3 t �?K) C_] Grading LA DOE Dam Safety [_.__] Structural Vaults [_ Commercial [ ] FEMA Floodplain [__1 Other (- I Other ---__-___ -__-.-- [-_] COE Wetlands I _I HPA COMMUNITYPART 5 SITE DRAINAGE((�1 1 I' Community Drainage Basin c f Vn nab PART 6 SITE CHARACTERISTICS �) River _-------------- _ L 1 Floodplain U Stream Well, -- --- [_) Critical Stream Reach [ ] Seeps/Springs L_J Depressions/Swales [ ] F ligh Groundwater Table LA Lake _—_._.—_______ _____ [ J Groundwater Recharge Steep Slopes Wei Other Lakeside/Erosion Hazard PART 7 SOILS Soil Type Slopes Erosion Pote teal Erosive Velocities [] Additional Sheets Attatched Page 2 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET PART 8 DEVELOPMENT LIMITATIONS REFERENCE LIMITATION/SITE CONSTRAINT Ch. -_Downstream Analysis I—A F-1 F-1 F-1 Additional Sheets Attatched PART 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION Sedimentation Facilities Stabilize Exposed Surface Stabilized Construction Entrance Remove and Restore Temporary FSC Facilities Perimeter Runoff Control Clean and Remove All Silt and Debris Clearing and Grading Restrictions Ensure Operation of Permanent Facilities K— Cover Practices ><I Flag Limits of NGPES Construction Sequence Other Other PARTIO SURFACE WATER SYSTEM J-5—<z Grass Lined Channel LJ Tank � Infiltration Method of Analysis Pipe System Ll Vault E] Depression LJ Open Channel F—j "Energy Dissapator Flow Dispersal>- Compensation/Mitigation LA Dry Pond Welland LJ Waiver of Eliminated Site Storage I-A Wet Pond r 5 Stream FLI Regional Detention Brief Description of System Operation -W-J�D At — P Facility Related Site Limitations Additional Sheets Aitatched Reference Facility Limitation PART11 STRUCTURAL ANALYSIS PAAt 12 EASEWNTSIRACTS (May require special structural review) b;;� Drainage Easement LJ Cast in Place Vault Ej Other >f Access Easement Lj Retaining Wall I j Native Growth Protection Easement U Rockery>4'High -'] Tract EJ Structural on Steep Slope J Other PART 14 SIGNATURE OF PROFESSIONAL ENGINEER I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were Incorporated Into this worksheet and the attatchments. To the best of my knowledge the Information provided here Is accurate. 1/90 JJ�rU� t rn p l + Y . ' sr 111911 __---I_ Ste'I G 3� 'IY >v�tib ,fit t � �f - 3S AV 1115L1 —t4 t»�..I� e N li e) `. Hf x ��` d6c� 3S►t� 35 A N161w -•--) 1x 7 Q t► to s aNiii I6��1 l Et�3 3s nr ti£Zt �ili 1 ° _. � ..',�zii� �, 35.._..A aNZZt � ✓, siii is ev isizi !ra ^Y F ^r IS. s jS Fr 3s AY 3S AV~ IIOlT evo�<r iliozi Moll " 3S AV 1116 1 `V I L, A a �d�� t, •�'} "' �o~ 1 G; 75'ate S AV t'x i= �~ &� r" .r" Is . .}. 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Sk I 7. Ur '_-- o IA el • S AMC li /• I Tu Ag AgD �M , mg : •• So \• I _ •:� 6M 194AgE Am n .: . . • _• • AgC • � u Fig. 2. Soils Map for Subject property. (AgC=Alderwood gravely sandy loam, gentle slope;AgD =Alderwood gravely sandy loam, steep slope; SK= Seattle muck); lnC =heavily disturbed. -- -,(] U IKh J.M.It.-- .'r y S H ss \ o L AaA^N _ ___ _Ud _—_fa—_ A r [ » w. '•'rr > 1 j v f C W. R..... tO TAUT': r r i Sam r.NnA.r 6 HAA q`F �'' „ CL a` �S I is Ac _ - n •" S u A• K" „ ,. , rQA 111 H N .i r 44 IS � ... r D '!a•M I N.N.A. Hast..gs 1106finjs 'o • N w •�« 41 N w r Imo) ' rt S. 31 ST ~ St. .r.e LM Ac �Ifl l lhH Sao A, I�.1• jr N H M O �r » As 11 Y H u AS L Alt at" 10.. ___=9� .. 1'_IL_ _ 1 M, Z.IAC . Iho e i ( 14 ,7 a SArx IN1) D se Ac r Ner men 4dmere Y e `'� 111.'t' S1 i F� ____ rp f 16 s T f PL ♦ - ! Ac 17. ia A,f n . o.4LAc sent-n ` » T (©�r� � 0 SS Ar' As a A. S.. IA[•'1' • T /s. 1 rr • • N Pa• A Del.... Kohl xI +. N n Progressive Inveslmenl Co . 169j/1 � 108At41 \ , • �• 1 [' Srm OSAt Jai et 7Fadden,' _-_=°L" Wu Cnson f t i f f 1s n e r I . R.Mc Faddcn IA[. •� J. V Farrell _ 1� 10Q AI P.V Pe01 V. � rner Werner I John V Farrell '.r r m Alake—Ik. p ?SA. LKAOc.I„ o f�.71 - --__- -- Whitaker !r 7-'• •>, L.M Ac. __ _ b.'Napmishi •a JI a •�,d rfje+ se Il ttlEi s m Ac e 1 * 400+I oSOAc r•O rd MondfAl 3gAc. 6sf063AcJ CQ w; ? IAJ ti Leland k + 1 �• � Il t Ig S.Wilson •77C�^�]1qy,�r S z 51f -_fir f III o s eoi_ ,••1 i _ r i.h Ie K I _D k T, Jlar_ c ,1._A�777 r _ I ' • `j ; 1 W' l.N.c •, b�4 r r 0 'r a• _DYl_ i Ao a •• I .4f or�n�^/�A J _1QIl__ 1 tl I 4� ♦~ 'S_ 36TH �T a ..�.7 1.., a P.411-41 v4� �. + Ie © o ss A47 ua IS e = US (3) Howard t(� w Q Q l Q i i US I! W Hawkins f'1 16!� n 1 ram-, li e 24 fa s N E-.[JI[-il Ife` S. 1741 H ST.a Cnorles L 0—Ib1.. r.D. 12) o N s a 3 1 121 111 _ �1► c h 2 vn 3' 6 9 _.i m _LL� tlH3331111 �. � 2 is SIM, ae lle-tt UI ,S. -mn. I• y Sm1 reunher --- J •S T. a © V A L L E 1 M E D I C A L01 ?b _ a p 6 IA) ` )111 f s 12 A:141 41 41C E Fl T E R �Jr srtu_» o::J'• �'.0 Too NoerN C—.S '�mo1AIG Sn[ ►uN y L_ \\ rgr•'NdN.A.r.vw.••vo•arA..>w •, �rrN'ewo..r.rn.r..r..•�prw.N• a.w L 1 0 1 N 0 ---L eueaNA Q APPf=HOES[:I=] Nwsl NUNAIR p I '`-" S �-�.� w.`" .) ATLAS OF SEATTLE MN4o"-•-."r-++ ...r-ti...'w�wr....F4..'..`•�' .w 1.e.n•c.—.e. Ww INOIICOUGNIAN IAA of Nu11etA J1 "'^"•°'�•'�"''`'"' '^'�^' KKOII MA/COMPANY.INC.f1A!!l/ 1 SCAt[ 1INCH•t0IT IJET KROLL MAP 4-DO PORTION OF NE 114 OF SE 114 OF SECTION 30, TOWNSHIP 23 NORTH, RANGE 5 EAST, W.M. NOW MAT r 6EV.TOI o.Rr Ora. SHORT PLAT/SUBDIVISION PLAN �w� OF OF RERTa Or"OF OF RErTa(•„10-M) C Lc MCA` wwxd Ts-CRY,a a RDPM CMMM r0A9aAEra 129929a 70a1 TOP 1 34.BRASS DW" COUCRETE MGMU IT M CASE M CERTEMM OF T/ADOT ROAD.OPP09TE MOUSE R0.3021 15'ROtM L O<W CER?MJW OF i 168T STREET. !,.+J EIEVAT*O 99..7a' ROAD DETAIL a'$; ""° 18-" 0%3/'BRAS' S 32J D ST. 29920. M - ,J,:9R.i3 OF 9 rN-KT R roAAU T M USE M CTO M LrSE AA90T EgAO.IPK 2,00Vf'lAT TO MOUY M0. 21100' J (.�J 2a+9.GE+ATIOM-99.1TT SHORT PLAT LEGEND TOTAL AREA tW AC9[S .3,:352 S0 ——----- -� r� fo nROPoYD rnHn 0�tD3 S ]a, CALC PC•• RROPC,wz AREA _OT 7.T30 SO vT Mar De IOA07 - '� LOT 2 aaso SO E' LOT ILQ-SO A- \ Lot. 1.90 SO P• •.G \JJs�G \ AREA EMST IRRDrci 2009 SOP' V 1 AREA Y t-D M STOM A.ai,SOT'. MCEMTACE or LAW AR STREET aim , z3MG a RESbEMTI C-a DU/AC(4-9) E4GA4EER. W9 S EMOREEAR- c 9.,t i S SOl'4 20.�. 5 1 G O 9 t KEM'.RA 990i. --ow 40.!M31 950-093A •\ J'\..,\ 9i .F raAG.COt"r EAR NO (253)9-4-0.55 I , 74. �y' \ ' aEeAa,aad� 1 ([i.vi r\ r_•of a R[R,.A2 OP n a f 1' I NE -a3Lc v \e \\` '.1 E' / c./A or HE SE,/.v SEC so ' VINE e_E'dGTµ BEARING I '\ Ls►ssRa It mw ap � ...aam' eSAt'. wol'So'27E� -� - -L. - I M..1 1^ ' Pt oEs95 a' 20AC N89.20'•9'y4 \ -7- - - •, 1 27- - I , RO OUR- SEEM MET•ACK a _$ ) ma A594ALj _. A�g • V v89'27 9• I l LOT 5 `l a 1 w.Aa so rc ,eRss \\,.,\ ;, I T102,iF.1 alr ' SEiAR.I I OaZT' i •w CORC -5 ,X e99.2^.••9'L 1 \� .Dcsove/rB4O0g�) y sAr.wer LOT 3' i •!nr '" ? se sc; o \9C"2 i l�1( , ,EALLMi s -eA�• i .{..2.Sf)r _ ) `I �I\ V^ LOT 2 44 — I .1, LEGEND �, i *��\ YMLM ff AS ROR7 91 aS'.MGY•' .E' y `S:) (1t•52o SI: L if V '2• r^ _`, `� ` • I w �0 ,-w q v M 99Z0'A9'R ''r , --j-�7tZ . � CROR\i+CO9Q = 1PN07 CO�R\b�M M [�\ �.�,. i �\ \ .l �- �/�9{,_ • � AS WTp < \� SS7►1 y _1) --' R,IX[L�/ �,L U�LTT EASpENT ��� � f'.v�L'1_ wL�E1i- J i� �`} _ ••A•�''""'�I JMAPLE RC REj•LAP a°ij\ :- !26 SE aAa- M9f76r'1 War � 1 \ t b 11 � t CjjTt S`<�3 ocxnRl*T9fE I \\ \\\.\\\Sa'a �? )1 ( -s'.g,RE9.R a capsaso� 'n it r• �1 .� �_ !•i :t tt...:= .. ,' \l Ls 8 �.me r I t 7 Ca07 T9EE +r \ SEE ROAD DETAIL A! • ' • 1 conaw ma ✓ ^i X R i l r,•' r ljt !JI r i. I r7 ti .. Iqr am g_ssa`. � �awT TREE, ! ��'r�� /// i !i `° 4 \• i � EA. + , stir R.1E , .\` -\),�i/ �1 Ii �, .� I '.I - IN 'M &..!TART SEVER r.Awz 30 30 •L ` y'�. --eN`-'�--.•.';.�,, <) rar oR..rAwwE CURVE TABLE w. " �'Ra GRAPHIC SCALE :CliRv_ILENGT6,I RADIUS I DELTA i VICINITY MAP 'D-EPI K RISER 6 TE*Af-ER C: 34.101 22.00)e9'se•�!• • „_,,r,ar- _2 2SO!1 22001 9I'31091! , N.7.S. IN..,COX ca>rr OSWALDO CHOW P.O.90r 27470 FECORDOs CDFTFCAlr s rvis0E1T M HALLIN & ASSOCIATES INC. AlSEArML iiii 9 25 2a ACCM razn R9s_m o_ n_At_r na w—MM Amm".aARfr.ROE n r ar ucv tS` "�' SHOBr PLATISUBDMMON Prat►rrc A[016r a/ ,,,��,���,Q AAsr AmR9ooa5�R( \ Land SuneyOn -- CPS Consultants nAARr o nu).0 9Anfr amour a Ar Re Ammo ono oa 31218 Pacdic HM7.. So. Suite 'A' CHOW SHORT PLAT R, AILT-rEIOK A I9 94-M QQ Federal Nay NA 98003 253-941-540s 1-800-"1-5317 ar.~ soar 1O -i0�'iwc 9aosEaRc I — K3 aorr•9>trr Mn +x90 A9nR1teD aPM anE .-)a-aa .oM 9aosE of 1 II. CORE DRAINAGE REQUIREMENTS l . Discharge at Natural Location: The site will continue to discharge-at the natural location. This location is the western property line and the wetland that is west of the site. 2. Off-Site Analysis: An upstream and downstream drainage analysis has been performed and is detailed in section III of this report. 3. Runoff Control: This project is exempt from peak rate runoff control because the 100 year peak developed runoff is less than 0.5 CFS greater than the peak pre- developed runoff rate. The actual difference is 0.29 CFS. 4. Conveyance System: There are no existing drainage improvements on the site. The proposed sife will have some piping and ditches. All will be sized to handle the 100 year storm. A biofiltration swale will be constructed just prior to a dispersal trench that will spread out the flow prior to discharge above the slopes. The downspouts for the new houses will be piped into the drainage system with individual lot piped connections. 5. Erosion and Sedimentation Control Plan: An erosion control plan will be prepared for this site. Grading activities will not be extensive, but there will be some minor grading for the new private road. Silt fencing, rock pad construction access, soil cover and dust control will be part of the erosion control measures. 6. Maintenance and Operation: The maintenance of the drainage system and private road will be joint responsibility of the homeowners on an equal basis. The mutual agreement will be recorded on the final short plat mylar. 7. Bonds and Liability: Any required bonds and insurance will be provided prior to any construction activities. SPECIAL DRAINAGE REQUIREMENTS There are 12 special drainage requirements that may apply to any project. In this case, none of them are applicable to this project. III. OFFSITE DRAINAGE A. UPSTREAM DRAINAGE The upstream drainage contribution to this site is negligible. The only up- gradient property is along the east property line, and this is the Talbot Road S. frontage. Talbot Road has a ditch along the west shoulder that discharges into an outlet ditch just north of this site. This outlet ditch intercepts all of the street flow from the north prior to entering the site. The site will get some minor runoff from Talbot Rd. along the frontage. B. DOWNSTREAM DRAINAGE The existing runoff from this property sheet flows to the west across the existing lawn area. There are no storm drainage improvements on this site, except for a small drainage ditch that was constructed southwest of the existing house. This small ditch picks up the drainage around the existing house and directs it to the southwest and down the slope to the large wetland area. The majority of the site sheet flows to the west and down the slope to the large category 1 wetland that is at the base of the slope to the west. This wetland is approx. 150 ft. west of the site and located on the series of lots that are adjacent to and east of the Hwy. 167 freeway. This wetland extends for a long distance along the east side of the freeway. + There are several pipes that run under the freeway from the east to the west. none of these pipes seem to drain the large wetland area, but may receive some overflow from the wetland. The pipe across the freeway that is nearest the subject site is pipe no. 26,F6-8 This pipe outlets into a large ditch recently constructed along the west side of the freeway and eventually feeds into the drainage system along the East Valley Hwy. This drainage system in turn eventually runs into a tributary to Springbrook Creek. There are no local piping systems downstream from the site. The major drainage feature is the large wetland area east of the 1-167 freeway. This wetland shows no sign of flooding or instability. The only question concerning this downstream system is the flow down the steep slopes above the wetland area. A concentrated flow may cause erosion on the slope. However, this project is not large enough to warrant the installation <` of a "Driscopipe" outfall system. I recommend that a flow spreader or dispersal trench be constructed above the slope, at least 25 ft. away from the top of the slope, to create a sheet flow effect down the slope. ti o A Mr3-3. a � 29,G7-6 A A 24r3-4 26.r7-z I N � 11 1 26 W-3 2SG3-S 6,G3-7 4-00 O 2bG3- J C3 L6I]-1 Q H �-26.G3 S 5 '-2 ST 6.H4- N4-1 24C4_2 2bN4-6 2"4 S 6,14-8 ,14-7 26.G4-1 S 2 TH 6N4-7 I t4 .-7 2bn-3 6,H4-14 26I4-12 6.1 9 26.G4-2 .G4-7 6.H4-1 �-4 S� tor"-4 S BT PL 2 .-U 1 G 4t4-6 26f 4-6 <]. 26,H4 10 2 14-5 U 24r4-7 1^ 26J14 9 24N-3 `/ '{_' 2bW-6 = 6.M� 1. 01 2614-0 26,G4- ♦ 4w 24I4-t 4H4-B S 14-7 26H4- t4r4-9 26.G4-4 2414-2 2W 4-2 26f 4-11 9 J 24r4-10 26,G4-5 24IS-7 • 26.N7- 6'�-3 4M4-16 26 7 26.17-8 24C3-4 U4-1 6M 24IS-6 .. �• \ C n �� 24IS-5 'bC3-3 6.E5- - 4G5- 26N3-4 J J rs-6 26,H3-7 '- Mrs-6 '4C3-6 / 0-' t41S-S t4r3-4 J J�/1 • -2SN3- J z6.Ns-1 S 6J1S 9 3 ST T tors-7 6f3-7 24IS-7 _4 24IS-3 bMs a t6�s ft 26,: t6 S-t 24G3-7 t6.r3-1 ,�/ •• 24r6-i _ 26f6-6 �_( ...►� m t4r6-3 24r6-7 SA, m b i fi1N t4rG-4 fix6_3 tTF- d WS-2 26.F6-1 26.N6-2 � 24N6-6 S T 2"4-3 26,H6-7 24C7-3 24M6-B 26.W-3 24C7-4 t6,C 7-6 t4C7-3 24N7-6 1 �i4r7-6 --- 26M7-7S 172ND ST / I --1 26.C7-2 26.r 7-2 1 LiS� 136 TH IV. DETENTION ANALYSIS AND DESIGN A. PREDEVELOPED DRAINAGE The drainage from the existing site sheet flows to the west and down the existing slope to the wetland area to the west. There are no drainage improvements on the site. The area used to perform the drainage calculations does not include the area along the steep slopes on the west edge of the property. This area will remain in a sensitive area and will be undeveloped. This reduces the project area from 1 .04 acres to 0.88 acres. The existing drainage analysis was performed using the "Waterworks" hydrology software and its summary tables and charts are attached for reference. The methods outlined in the King County Surface Water Design Manual were used as guidelines. Following this page are the data sheets used for the computer input data. The computer summary sheets for peak flow and time of concentration calculations are also attached. Below is a brief description of the existing drainage characteristics: Time of concentration: 21 .03 minutes 2 year peak flow: 0.09 CFS 10 year peak flow: 0.22 CFS 100 year peak flow: 0.38 CFS project area: 0.88 acres pervious area: 0.77 acres curve number: 81 impervious area: 0.11 acres curve number: 92.88 B. DEVELOPED DRAINAGE The developed project will not include detention storage due to the minimal peak flow exemption allowed by the drainage code. The site will include a biofiltration swale because it has over 5000 SF of impervious surface subject to vehicular traffic. The swale will be designed for the 2 year developed storm event. 12 -D...I._ a S S a1� q acoo� _Xa .a CAS S noI/\-a2� 2 � 110 : 'fyJ s no 1nxa�vA= ' -� tv1. �,a� s �,as sus �{- S YJ I�Y c7s M ACa� ;'Ad 2 s S<I 'S-b Jaeger Engineering CHOW SHORT PLAT.' DRAINAGE CALCULATIONS PREDEVELOPED HYDROGRAPH SUMMARIES BASIN SUMMARY BASIN ID: A10 NAME : PREDEVELOPED, 10 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0 . 77 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 21 . 03 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 11 Acres CN. . . . . 92 . 88 TcReach - Sheet L: 280 . 00 ns : 0 . 2400 p2yr: 2 . 00 s : 0 . 1070 PEAK RATE: 0 . 22 cfs VOL: 0 . 10 Ac-ft TIME : 480 min BASIN ID: A100 NAME : PREDEVELOPED, 100 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 77 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 21 . 03 min IMPERVIOUS AREA ABSTRACTION COEFF : 0 . 20 AREA. . : 0 . 11 Acres CN. . . . : 92 . 88 TcReach - Sheet L: 280 . 00 ns : 0 . 2400 p2yr: 2 . 00 s : 0 . 1070 PEAK RATE: 0 . 38 cfs VOL: 0 . 16 Ac-ft TIME : 480 min BASIN ID: A2 NAME: PREDEVELOPED, 2 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 00 inches AREA. . : 0 . 77 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 81 . 00 TIME OF CONC. . . . . : 21 . 03 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 11 Acres CN. . . . . 92 . 88 TcReach - Sheet L: 280 . 00 ns : 0 . 2400 p2yr: 2 . 00 s : 0 . 1070 PEAK RATE: 0 . 09 cfs VOL: 0 . 05 Ac-ft TIME: 480 min File Basin Hydrograph Storage Discharge Level pool 3eee5eeeeeeeeeeeeee�eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ; eeeeeeeeee ; ° ° SHEET FLOW CALCULATOR - INITIAL 300 FEET ° ° ° ° ° ° °DES°Mannings Sheet Flow. . . . . . 0 . 2400 ° ° °ARE°Flow Length (ft) . . . . . . . . . 280 . 00 °HOICES ° °RAI02 yr 24 hr rainfall (in) : 2 . 00 ° ° °TIM°Land Slope (ft/ft) . . . . . . : 0 . 1070 ° ° °TIM° COMPUTED TRAVEL TIME (min) :(Z�D ° ° °RAI° TYPICAL MANNINGS VALUES FOR INITIAL 300 FT °A ° ° ° °ABS° °BAS°Smooth Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 011 ° ° °STO°Fallow Fields of Loose Soil Surface . . . . . . . . . . . . . . . 0 . 05 °Y ° ° °Cultivated Soil with residue cover (s<=0 . 2 ft/ft) : 0 . 06 ° ° °PER°Cultivated Soil with residue cover (s>0 . 2 ft/ft) . : 0 . 17 0 ° °ARE°Short prairie grass and lawns . . . . . . . . . . . . . . . . . . . . . 0 . 15 ° ° °CN °Dense grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 24 ° ° ° °Bermuda grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 41 ° ° ° °Range (natural) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 13 ° ° °PEA°Woods or forest with light underbrush. . . . . . . . . . . . : 0 . 40 ° ° °PEA°Woods or forest with dense underbrush. . . . . . . . . . . . : 0 . 80 0 ° °TOT° ° ° 00F10Key: QUIT FSKey: CLEAR °ete ° Pgeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeefit ° aeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef PR L-OFGC I r`M F O F w�'4 C-t 1`-T B. DEVELOPED DRAINAGE The developed project will not include detention storage due to the minimal peak flow exemption allowed by the drainage code. The site will include a biofiltration swale because it has over 5000 SF of impervious surface subject to vehicular traffic. The swale will be designed for the 2 year developed storm event. Similar to the existing condition, the SBUH hydrograph method was used to determine the peak flows for the various storm events. The computer data sheets-for the developed flows follow this page as well as ttie work sheets and the time of concentration calculations. A brief summary of the developed drainage characteristics are: time of concentration: 8.37 minutes 2 year peak flow: 0.27 CFS 10 year peak flow: 0.46 CFS 100 year peak flow: 0.67 CFS total area: 0.88 acres pervious area: 0.49 acres curve number: 86 impervious area: 0.39 acres curve number: 98 C. HYDROLOGIC ANALYSIS The site is exempt from the peak rate runoff control due to the negligible peak rate runoff rate increase exemption. This is specified in section 1 .2.3- 5 of the drainage manual. The developed peak 100 year runoff flow is 0.67 CFS. The 100 year pre-developed flow is 0.38 CFS. This is a 0.29 CFS difference, which is much less than the 0.5 CFS maximum allowed for this exemption. D. DETENTION ANALYSIS AND DESIGN Detention Storage is not required for this project as stated above. D E>\1 E.Ld P& D Puy I r,a(c---E A.. ARC ( IN � Pros e c s area t-, vrmaE-P, 5 So S o--"—, l�X wo1 Sir I s� �-ram I� t c. l�3(p(�� + 35(2o)4 -63,P)= 4bf3q,) Ste• boo se s ca Zs-.nz�o 5-P. e,= 1 Z-SZ�D SF- �ho��se. l I b 6 SF Z PQ-rvloL) s C-- Tm E ©F Cori c-EN�T1(�,f oN: ►c_ uc sio-MI C-RI: L = i �' shee-fi low It> wpsfi a-c�= no r-44) 7ic k.Q- d-P Lo-�- S- 2. I Z `�'o I ow c-c-rosS I 1), Iso PLU r Kt-s S ay �-e Pz. = z .o \n . 3 . Roo = 3, 9 vn E . P F-CroW-S �P CF< Sew c� e 2• Q10 = E�, 4c� c.Fs h�yc�r-a�� 3 C ,a, = O (o 7 CFs �r�m a.. Jaeger Engineering CHOW SHORT PLAT DRAINAGE CALCULATIONS DEVELOPED HYDROGRAPH SUMMARIES BASIN SUMMARY BASIN ID: B10 NAME: DEVELOPED, 10 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0 .49 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 8 . 37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 39 Acres CN. . . . . 98 . 00 TcReach - Sheet L: 150 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1200 PEAK RATE: 0 .46 cfs VOL: 0 . 15 Ac-ft TIME : 480 min BASIN ID: B100 NAME : DEVELOPED, 100 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE . . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 .49 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 8 . 37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA.. . : 0 . 39 Acres CN. . . . . 98 . 00 TcReach - Sheet L: 150 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1200 PEAK RATE: 0 . 67 cfs VOL: 0 . 22 Ac-ft TIME: 480 min BASIN ID: B2 NAME: DEVELOPED, 2 YEAR SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 88 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 . 00 inches AREA. . : 0 .49 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 8 . 37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 39 Acres CN. . . . :. 98 . 00 TcReach - Sheet L: 150 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 1200 PEAK RATE: 0 . 27 cfs VOL: 0 . 09 Ac-ft TIME : 480 min File Basin Hydrograph Storage Discharge Level pool 3eee5eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ; eeeeeeeeee ; ° ° SHEET FLOW CALCULATOR - INITIAL 300 FEET ° ° ° ° ° ° °DES°Mannings Sheet Flow. . . . . . 0 . 1500 ° ° °ARE°Flow Length (ft) . . . . . . . . : 150 . 00 °HOICES ° °RAI02 yr 24 hr rainfall (in) : 2 . 00 ° ° °TIM°Land Slope (ft/ft) . . . . . . . 0 . 1200 ° ° °TIM° _ COMPUTED TRAVEL TIME (min) : 37 ° ° °RAI° TYPICAL MANNINGS VALUES FOR INITIAL 300 FT °A ° °ABS° ° ° °BAS°Smooth Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 011 ° ° °STO°Fallow Fields of Loose Soil Surface . . . . . . . . . . . . . . : 0 . 05 °Y ° ° °Cultivated Soil with residue cover (s<=0 . 2 ft/ft) : 0 . 06 ° ° °PER°Cultivated Soil with residue cover (s>0 . 2 ft/ft) . : 0 . 17 ° ° °ARE°Short prairie grass and lawns . . . . . . . . . . . . . . . . . . . . . 0 . 15 ° ° °CN °Dense grasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . 24 ° ° ° °Bermuda grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 .41 ° ° ° °Range (natural) . . . . 0 . 13 ° ° °PEA°Woods or forest with light underbrush. . . . . . . . . . . . : 0 .40 ° ° °PEA°Woods or forest with dense underbrush. . . . . . . . . . . . : 0 . 80 0 ° °TOT° ° ° 00F10Key: QUIT FSKey: CLEAR °ete ° Pgeeeeee,eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeefit ° �eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeef E. BIOFILTRATION Biofiltration will be provided for the site and designed for the 2 year developed storm event. The tributary area used to calculate the biofiltration swale flow is the flow from the new road and from 4 of the 5 new houses and driveways. The westernmost lot has a drainage connection directly to the catch basin at the outlet of the bioswale. The bioswale will be located along the top of the slope along the west side of the property. A biofiltration swale was designed for this site using the criteria established in the 1990 King County Drainage Manual. The design flow was determined using the hydrograph as described above (see attached summary) and is 0.16 CFS. The specified design parameters from the Manual include the design slope of 2.0%, the "n factor of 0.35, the depth of 4" and the side slopes of 3:1 . Using Manning's equation, the required bottom width is 1 .22 ft. The swale length is 50 ft., so a width adjustment is necessary. The adjustment calculations show a required bottom width of 4.88 ft. The swale hydrology was also checked for the developed 100 year flow. This flow was determined to be 0.67 CFS. Using the actual swale slope of 1 .0% , an"n" factor of 0.03 and the 6 ft. bottom width; the 100 year flow would cause a flow depth of 0.10 ft. The total swale depth is 1 .0 ft. leaving a 0.90 ft. freeboard for the 100 year event. The velocity during the 100 year storm will be 1 .04 FPS. 16DkOS Jaeger Engineering 1 CHOW SHORT PLAT DRAINAGE CALCULATIONS DEVELOPED 2 YR. DRAINAGE FOR BIOSWALE BASIN SUMMARY BASIN ID: C2 NAME: DEVELOPED, BIOSWALE, 2 YR. SBUH METHODOLOGY TOTAL AREA. . . . . . . : 0 . 34 Acres BASEFLOWS : 0.00 cfs RAINFALL TYPE. . . . : USER1 PERVIOUS AREA PRECIPITATION. . . . : 2 .00 inches AREA. . : 0. 00 Acres TIME INTERVAL. . . . : 10.00 min CN. . . . : 86 . 00 TIME OF CONC. . . . . : 8 . 37 min IMPERVIOUS AREA ABSTRACTION COEFF: 0 . 20 AREA. . : 0 . 34 Acres CN. . . . . 98. 00 TcReach - Shee 150 .00 ns:0. 1500 p2yr: 2 . 00 s:0. 1200 :PEAK RATE 0. 16 cf-s) VOL: 0.05 Ac-ft TIME: 480 min Trapezoidal Channel Analysis & Design Open Channel - Uniform flow Worksheet Name: CHOW SHORT PLAT Comment: BIOFILTRATION SWALE - DESIGN 2Y. FLOW Solve For Bottom Width Given Input Data: Left Side Slope. . 3 .00: 1 (H:V) Right Side Slope. 3. 00: 1 (H:V) Manning' s n. . . . . . 0. 350 Channel Slope. . . . 0 . 0200 ft/ft Depth. . . . . . . . . . . . 0 33 ft Discharge. . . . . . . . CO. 16 cfs-) Computed Results: Bottom Width. . . . 1 2 ft Velocity. . . . . . . . . 0. 22 ps Flow Area. . . . . . . . 0. 73 sf Flow Top Width. . . 3.20 ft Wetted Perimeter. 3. 31 ft Critical Depth. . . 0 . 08 ft Critical Slope . . . 4 . 5157 ft/ft Froude Number. . . . 0 .08 ( flow is Subcritical) O l o•1�j � � �� SW Ole_ 2�c)Q zz �v pp w d'e Open Channel Flow Module, Version 3 . 12 (c) 1990 Haestad Methods, Inc. * 37 Brookside Rd. * Waterbury, Ct 06708 t Trapezoidal Channel Analysis & Design Open Channel - Uniform flow Worksheet Name: CHOW SHORT PLAT Comment: BIOFILTRATION SWALE - ACTUAL 100 YEAR FLOW Solve For Depth Given Input Data: Bottom Width. . . . . 6.00 ft Left Side Slope. . 3 .00: 1 (H:V) Right Side Slope. 3. 00: 1 (H:V) Manning' s n. . . . . . 0 . 030 Channel Slope. . . . 0.0100 t/ft Discharge. . . . . . . . . 67'cfs JpD Yr. {o� �f Computed Results: Depth. . . . . . . . . . . . 0 0 ft Velocity. . . . . . . . . 1 . 4 fpp Flow Area. . . . . . . . 0 . 64 sf Flow Top Width. . . 6 . 61 ft Wetted Perimeter. 6 . 64 ft Critical Depth. . . 0.07 ft Critical Slope . . . 0. 0321 ft/ft Froude Number. . . . 0. 59 ( flow is Subcritical ) 100 ir-. -PIou-k� P FPS- Open Channel - Flow Module, Version 3 . 12 (c) 1990 Haestad Methods, Inc. * 37 Brookside Rd * Waterbury, Ct 06708 V. CONVEYANCE SYSTEM The piping will be sized to accommodate the 100 year developed flows as identified in the previous section of the report. The calculated 100 year developed flow for the entire site is 0.67 CFS. The pipe segments with the least capacity within the entire conveyance system will be a 12" CPEP pipe at a slope of 0.5% and an 8" CPEP pipe with a slope of 1 .0%. These will be several pipe segments that are within the interior of the site. The capacity of these pipes is 2.73 CFS and 1 .33 CFS, respectively. Thus, all of the pipes within the conveyance system will be able to handle the 100 year developed flow for the entire project. As such, an analysis of each pipe segment is not necessary. VI. ADDITIONAL STUDIES OR REPORTS A wetland study has been prepared by Del Moral and Assoc. A geotechnical has been prepared by Bergquist Engineering Services that is dated 6/21/99. VII. BASIN AND COMMUNITY PLAN AREAS This site is within the City of Renton It is within the Lower Green River Drainage Basin and the Springbrook Creek sub-basin. Vill. OTHER PERMITS A demolition permit will be required for the removal of the existing house. IX. EROSION CONTROL SYSTEM The erosion control system was designed to minimize any contaminated site runoff from entering the wetlands or leaving the site. There is little possibility that runoff will enter a neighboring property since there is only one downslope property, and this is the large wetland at the edge of tht: Freeway. It will be protected by an interceptor swale and silt fencing. Measures will also be taken to minimize the potential for runoff and mud entering the public ROW along the frontage road. A sediment trap will be provided and is shown on the erosion control plans, which will be the future biofiltration swale facility. The permanent outlet piping and driscopipe will be installed at this time as a means of conveying the flows to the wetland during the construction phase. Besides the silt fencing, the erosion control plans also show the clearing limits and the location for a rock pad construction access point. Temporary interceptor ditches are shown to channel any runoff into the sediment trap. Temporary catch basin protection will be provided for all new catch basins. There are no existing catch basins on the frontage roads. APPENDIX A CHARTS, TABLES, GRAPHS FROM KING COUNTY SWM-MANUAL KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL FIGURE 3.S2A HYDROLOGIC SOIL GROUP OF THE SOILS INKING COUNTY HYDROLOGIC HYDROLOGIC. SOIL GROUP GROUP" SOIL GROUP GROUP* teiis. woo - Orcas Peat D Mderwood Material Oridia D Arents, Everett Material B Ovall C Beausite C Pilchuck C Bellingham D Puget D Briscot D Puyallup B Buckley D Ragnar B Coastal Beaches Variable Renton D Earimont Sot Loam D Riverwash Variable Edgewick C Salal C Everett A Sammamish D Indianola A Seattle D Kitsap C Shacar D luaus C Si Sot C Mixed Alluvial Land Variable Snohomish D Neliton A Sultan C Newberg B Tukwila D Nooksack C Urban Variable Normal Sandy Loam D Woodinville D HYDROLOGIC SOIL GROUP CLASSIFICATIONS A. (Low runoff potenti4. Soils having high Infiltration rates, even when thoroughly wetted, and consisting chiefly of deep, wed-to-excessively drained sands or gravels. These soils have a high rate of water transmission. B. (Moderately low runoff potential). Sops having moderate infiltration rates when thoroughly wetted, and consisting chiefly of moderately fine to moderately coarse textures. These sons have a moderate rate of water transmission. C. (Moderately high runoff potential). Solis having slow Infiltration rates when thoroughly wetted, and consisting chiefly of sags with a layer that Impedes downward movement of water, or sofls with moderately fine to fine textures. These soars have a slow rate of water transmission. D. (High runoff potential). Solis having very slow infiltration rates when thoroughly wetted and coraisft chiefly of day sods with a high swelling potential, sons with a permanent high water table, soils with a hardpan or day layer at or new the surface, and shallow soils over nearly Impervious material. These Bois have a very slow rate of water transmission. • From SCS. TR-55, Second Edition,June 19W. Exhibit A-1. Reviskxia made from SCS, Sol Interpretation Record, Form 05. September 198(L 3.5.2-2 1190 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TABLE 3.S.2B SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type 1A 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 Meadow or pasture: 65 78 85 89 Wood or forest land: undisturbed 42 64 76 81 Wood or forest land: young second growth or brush 55 72 1 PSI►OJS Orchard: with cover crop 81 88 94 Open spaces, lawns, parks, golf courses, cemeteries, landscaping. Y good condition: grass cover on 75% 1=t1t or more of the area 68 80 90 fair condition: grass cover on 50% to 75% of the area 77 85 90 92 T) '0 - -' f I V-%,j �^ Gravel roads and parking lots 76 85 9 91 1rr�PexV• Dirt roads and parking lots 72 82 q 8 Impervious surfaces, pavement, roofs, etc. 98 98 (98-Y 98 Open water bodies: lakes, wetlands, ponds, etc. 100 100 00 100 �^ LTV Single Family Residential (2) `mv� Dwelling Unit/Gross Acre % Impervious (3) 1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected 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 50 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. 3.5.2-3 1190 a .' •: 1l - AIR WAM Sm� �. M A�■ '�►�� �,, .fir+��lf �`g� �t►�.� 1 • � � ,{■ � Vow • , KING COUNTY. W AS HINGTON. SURFACE WATER DEIGN MANUAL i FIGURE 3.5.1E 10-YEAR 24-IIOUR ISOPLUVIALS Iva 222 1 ~ . 23 24 _ .I - 25 ?8 - d 29 a0 _ s, r. r wr 33 pa erwb" , �. it. w l 10-YEAR 24-HOUR PRECIPITATION ••• as so 3.4-"• ISOPLUVIALS OF 10-YEAR 24-HOUR \ "•� Ir TOTAL PRECIPITATION IN INCHES 30 0 0 1 2 ] 4 0 6 7 .Milo, f e 11300.000 3.5.1-10 �rL�J 1/90" 4 0 UIT SLIT, • M P l NO 0 0 a op 007 r � ► �p"!i NA `�' � �J ISM twFMWWA l2r,rp , �►. INCHES ""YA TOTAL PRECIPITATION IN � �