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SWP272328
TED Technical Information Report Bowen Scarff Renton Carco Renton, Washington 9705 Prepared for: Mr. Mike Scarff � Bowen Central al Avenue 1157 N Central Avenue &46 Kent, Washington 98032 1-800-5 77-1158 (206) 859-3624 fax 4 ,, Q�� Prepared by: Pacific Engineering Design, Inc. 130 Andover Park East, Suite 300 Seattle, Washington 98188 (206) 431-7970 (206) 431-7975 fax April 16, 1997 c,`� A. s�FyFP Revised June 12, 1997 0 O/S z a IE NA EMRES MAY 6, 1999 .a . ! . • . . PARTl PROACTOWNERAND FPAti1"'2''"P ,QJEC�LISCA[Ibt� ''i �PF OJEC1f;ENGINEEi#ti ' ti a w'r r M,; i N a r1� dE"SCF�IpTlb19: tt�s a .. r �,. �{;111....r is 11,�1,_,ta.s.:it. JnA o........w._• _ h:,iw.lf'r..: PART$.7YPEOFPERINRAPQLICATION,.u,;.��: ;;PARY,,d;07HEF1pERIVIi'f,S. ,„�;, z-�,,, �,;.t .;+.�:. 'r�,:• a :'P.AqI'6,`.SIrtECOMIIIIUNiTV'ANDDRhtiNAG ...p ....?�SIN'' • . urch+V.�ia�Y�'�"Y^,r a v. r1 S •G� 'e� t, � . .. . .. . . _.. .. ... . ._. rM.�n•m•k?v�•Nr...CG�13.r:.wh.,..•u.::>t:. ,.b..Au.eSS.ia'k:�' ' PARY 6,;,SITE CHARACI�IS'fICB-..4:�u.,..r:cx�:�x.:.w�.,`,;.•i.s:�::�'�+[,'�.;:,kfi��i� �3�i`••�:a,+a�'t�w.�.+�:.�it:;w :a,�.:�,�:-.;u .vr'"`ti ir:p♦y�v h v1dlY.[�ryry r' ��,it etr '�:, yf�,s`fes'.r ay'r l!} r , ,l "I.,'k i�o-...S n y'i ;.: t Nfl���yr��ILS '���i`�iM.i'WT•�CiLY:�=T,ylF��t.'�.h�,�I�ahWi�l.52 �r. a �h J t7y�� }r$1�;�:% '.%5 •S'�4� FFF Page 2 of 2 King County Building and Land Development Division TECHNICAL INFORMATION REPORT (TIR) WORKSHEET REFERENCE LIMITATIOWSITE CONSTRAINT Ch.4-Downstream Analysis -- - - - (] 7 F-I --- F-1 Additional Sheets Ahatched MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION FOLLOWING CONSTRUCTION (� Sedimentation Facilities Stabilize Exposed Surface ® Stabilized Construction Entrance Remove and Restore Temporary ESC Facilities ® Perimeter Runoff Control ( Clean and Remove All Silt and Debris Clearing and Grading Restrictions ® Ensure Operation of Permanent Facilities 0 Cover Practices Flag Limits of NGPES ® Construction Sequence Other Other Grass Lined Channel Tank ED Infiltration Method of Analysis ® Pipe System Vault-e.rsr 0 Depression S({tjpl Open Channel Energy Dissapalor Flow Dispersal Compensation/Mitigalion � Dry Pond ID Welland O Waiver of Eliminated Site Storage 0 Wet Pond ID Stream Regional Detention Brief Description of System Operation Ak-AfGrS n(le,AI)IS -M 17t01 - 012(t -M wfST t/kvl.T- T t/Nv�,-r -r-o b--NT'(Sel Qur/vrT�j S+ A t.r�- -fe �fScrfnr2G/£ Facility Related Site Limitations Additional Sheets Altatched Reference Facility Umltation rlGn� Drainage Easement I x� Cast in Place Vault =1 Other F-1 Access Easement Retaining Wall F--j Nativ6 Growth Protection Easement Rockery>4'High = Tract " Structural on Steep Slope Other 1 or a civil enginoor under my supervision have visited the site. Actual silo conditions ¢s observed were incorporated into this workshoot and the attatchmenls. To the bast of my knowledge the Information provided hero is accurate, 1,90 TABLE OF CONTENTS PAGE I . PROJECT OVERVIEW . . . . . . . . . . . . . . . . II . PRELIMINARY CONDITIONS SUMMARY . . . . . . . . IFI . OFF SITE ANALYSIS . . . . . . . . . . . . . . . . IV. RETENTION/DETENTION ANALYSIS . . . . . . . . . . V . CONVEYANCE SYSTEMS ANALYSIS . . . . . . . . . . . VI . SPECIAL REPORTS AND STUDIES . . . . . . . . . . . VII . BASIN AND COMMUNITY PLANNING AREAS . . . . . . . VIII . OTHER PERMITS . . . . . . . . . . . . . . . . . . IX. EROSION/SEDIMENTATION CONTROL DESIGN . . . . . . X. BOND QUANTITY WORK SHEET, RETENTION/DETENTION FACILITY SUMMARY SHEET AND SKETCH , AND DECLARATION OF COVENANT . . . . . . . . . . . . . XI . MAINTENANCE AND OPERATIONS MANUAL . . . . . . . . 1. Project Overview This project is located near the northwest quadrant of the 1-405 and SR-167 interchange (see vicinity map). The northerly property line abuts SW Grady Way, the westerly property line abuts Maple Avenue SW and the southerly property line abuts SW 13th Street. Good Chevrolet is located to the west, Sound Ford used cars to the south and a new Sound Mazda dealership to the east and north. The project area (including the alley and Right of Way vacations) is approximately 4.8 acres. A portion of adjacent property at the northwest corner of the site will remain unimproved. Also, a portion of the center of the site will temporarily remain as single family residences. These houses will eventually be removed and converted into additional parking for the project. Portions of SW 12th Street, SW Maple Avenue and SW 13th Street will be improved with curbs, gutters and some sidewalk. The site is very flat with a slight slope to the south and southwest. Most of the site has existing houses, garages trees and yard areas. There are recently installed sewer mains located in SW 12th Street, Maple Avenue SW and SW 13th Street. There is an existing water main located in SW 12 Street. There are existing storm lines located in SW 12th Street and Maple Avenue SW. The proposed development will be a Carco used car dealership and service building. Most of the site will be parking for the vehicles with minimal landscaping areas. SW 12th Street will be improved with curbs, gutters, sidewalk and landscaping. SW 13th Street will be vacated. Portions of SW 12th street will be vacated. Positions of Maple Avenue SW will be improved. The project will provide storm runoff control for most of the site. A portion of the site (Pierre Auto property) will drain to the Good Chevrolet detention vault. An underground wet-vault will be utilized for storage & runoff pre-treatment. sa ... 655 tNP —z�- DDMRlb[r 1"1 7lrenuih9lre I.L ______________aysoA[r �r Ar a sv - _. tulrls n sv '+ fWl v Sv 61, DM1ill KCA Av Sv Slx[U [� Z I i 6`:j IIHO12 V .__ ...._ p I hY 9N Y y .�E H Y Slf 'y�°i /•, 1. _w c.1�`5- w Ar Jam- 1 IE J YAII EY y R tl _ 1\Ir�CY X I.r n Lm i[ x AY � 4 pnC? a, AMUj �.._...'k.r+A(,1_ r ..� Ikxo�s . — P�— •9 He-'„ n_ -...� .q..—_ - g i4 - hh �e�, !`jr,:• •ci D roars y '1'X,..J• .• 1 Ix i��'a JIL•'im�.�:�' SJ3 Vpi ro.lisN„s . T. ��1� tOch s 9. .._ _.6 nidi.li �.«f}'n -,�''n i�Y n Vic§ „ A �., r.� S y ".,N. 16Ac? n-.__L'7 � •' �:F u �•r� n i�` r' �A� 1 HD5H3R � AY / IA•IS � . N lobo � asN � o •y.. �"'n. I // y- KS4,S�Ar o hill rAYrn It q3• N �1 t• UN rV .A tlw ��A�1• _ llT �r q AVj N ta n rl M.Y ....i•......__.._K�S N S N '• Wvl !r f (JJIp[ •. .a• : -..�.•.".. n• FRANr a r __11101 AV �3 ! 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N 7. 1 Sr .�` Il•px n O. ny._.1.Rrle_... 1[ Iaenl .Y•r N r, Gov- MART OAIAR ~ 2IIAL i1 11 AL 0., o.LSAc.�IL t0S.1 ALACI FIG COASS ,29 S1 R R. CO slurs l •� ,yc IT CO. (f) i ... S.F. Q.flO I i. I Sb Ac S IOAL, I ( �•S� - It 64 r....r —Zzo NO 7 R J�p tOtivO, WAY . I 64R 4 G ANY y is is �' w ` 1' 24 II, Z1 21 20 • 42 ¢11 Ji' a9 •� �• , Roe , 1�'�. Is e1 a3 44 4S fiISI4I7Il.l. ftNJS; f6171 � - u �Irr:1O fIIl S�!I SI w lSaS,I.S a�l�e . E s,9 I,6 OL• ,6 2 .S Id I9 R 1I 4 d rJ � t-: is Sr 44 Ss 019 ,, l 3 1s IS — " a5 35 � 71 dz l9 ., . • 6• •S' q i 7 1 r Jd jJ.0 I j0 19 W � (� 'Is` I •oI . a 43 13-ry. J _ 13 II Jc 10`6M S o u t .h R e n t ::'0 I ' o I a 5 jo 9 r'd-� Lr� iolaaT AcCE 55—� —"OVE PCROSSrN. •• . - .—.—.�.,.,� '. ):'=r—..OVE -CROSSING OSSIAIrl nCCfS Lrnu TE O S—� a ;; s; 20 , ,ws° s qo, I ; n t e r c h a n g is I_ _IJ IIIS 23 36 Oia� u �s��. - . . �2LIrL, MAP IKl - _... U N I i E L) STATES UN DEPARTMENT OF THE INTERIOR DEPART GEOLOGICAL SURVEY CORE 122*15' 'Zs' 47*30, 112*30" io nR�1fi NX 11-d JA 7' M, 7il 8 Jul La t-eld % .3 . ...... 30 ...Gro au 23 ..... ... 20' S157 _%N A Is W. rock �7130" .10 �Iz 1.Rest,..., 011 Is 26 -0 25 30 am 4 " 41 1 r ...... II. Preliminary Conditions Summary The site is very flat with a slight slope to the south and southwest. The surrounding roadways (SW Grady Way, Rainier Avenue South and the 405 on-ramp) are elevated above the average elevation of the site. The site does not appear to have any off-site drainage flowing onto the site. The closest storm connection point is an existing 18 inch storm line located along the west side of Maple Avenue SW. The USGS topography map, Soils map and Flood Insurance Rate Map have been included in this section. Ilt'1-l� I 'fi! I � ���� q� ,�.•�r 1. II l ,� ' t 111�.. •11 _ �, J I I �o•K ....." � d II i ..*,�'.41;---'� � 1 _ 1 —111 _ _ ail..•-:.. . . n.l, FI (. - .._.�_.. d: 11 '' 4.`._I+: �l'\, -,I, `, IIu` • �.1 I I II .�' ` , � 4t`li' � I1l'•,� 1`` ''7'� {�tl`+ { j ` I�``1�1' '�\ ��� * 'l /�\ �'.��� - t- IS 1 , 1 li■■ n r-�-o.. .f`��/+!•`, I ��� ,l •.14 I �I {I II 41 I -.I.���• J-; 1 _.\J�/ X.-LN j I MAP LENT OF AGRICULTURE ERVATION SERVICE A I 122' S' 47'30' A.A E. R.5 E. 1.SCArrtR rcrry .o.,ro..1.112'30" . tir rn —,cpSr,,,,o vA 775 ff I ' • ••1 •• •�• .r •. Ag .1 T `1 f r Blh River it __ A R o lS . I "uesta'�• '1 BrIJ' _ .r. '. D �[1{�411- Vida w'�o . 'TI. .. �• '� �' ^BaG',!a . L ' � = I S _ ! 'ry' r: t• r •t t A. Jil j i as.' / . . "' 1:;:..., ;• •_ 'A, -.. ; _ •.party .p P . •• -tit T '• ' ,., � PA �: � ; J G, Yr tLiV E..�= .0 :• i i? '.' C\6� .h :.^`il-,K�(wr AkF ��— W, Nq P1 ur P/'S`a� l� ; � � �i. L:,.• �l �i' � ;��J� ,x. Be0 coil Cie. se I •_]Y11Lty wa I .o. m Ur W • I =� e 1L:. •.I 30a ` 1 f Sew 8e ORYH `` 'J — ........... - .. , NR Vr �UrI '9• •Ag0 I Pu rrT U9 ll A' . aongacrel: T .l Pu P Vr y I W. OeD •'ui S©eCr M orTrack ��` fAeD •ry.✓•�•.'•v ;' tin I 27'30„ - �4 y;, url ur py 2 W Put, I �1 I i w 1 ' Sk o r� ) 25 0 ec1• IR.M 29 . .' I V ur„i 0 9203 Asc PY _ a If J• ` W. /h�P �.-.•.e.w.... ......,..,..,,.). +s^•.....:wi _�� �1��� �t �:y—•l �J,..� :-S3kp�`.�,N _..a. . ._ �...._...,tiro.'.�._.:::•. ...,..._... I .�- I _^ .3 O. I J �' :� �� ).�,� � ,�I� ]-". 1 K•1 r••. npn un+u •qx xv..•ns.m Iq. I I •F � 4'� C b2?.M,+ N- '" ..,• �.�. .. .�]' polo ' X3NOZ li Icr li 1 rJ 1 1 � f JtiCWtl I r+,....NIwuJ .d�'�', /ill ' _ i-• ..— ' Jr.a 61 ..'1'•.Y Ir O•J rrM I� .bV /. � �I �� oz .w n..m `••t. ....�.Nn. p1NpJ • i T � I /�V0 quill.•Ml w. !111 / F� 0 .0 \\ll xI.r.,l»...1•»r.,.. In r.n .I O H7 vv u MID NOI •tl w1•�pp: ` � 3 IMYII IM]rv. •w .'i•+l nuCpi P n i lNp! jl Y)I•00011 i)N10 3� 1 i Ntl)M1rpN IY)vQJ N11 r)YY lY.1pOp1I ® � � /j / I 0 X 3NOZ 1 X3NOZ � D '�••.�Y rl 1 1 n•wr•I M/ y.]MpI �� �• 't J / n rrr•w�••••rJ•.I N•wy w•.l N.INGZ ,��........r.w.•I IT INOJ I/ ' / •Z 'X' e r3NGJ i Nr)wrpNraa.++vpr' / � Y't• -- 3Y3NOZ r pu YONnv rylar 01111.OooV,mJ1+) n 'f' X3NOZ ON3031 CIO Jinn _ j III. Off•Site Analysis LEVEL ONE Runoff generally flows across this site in sheet fashion towards the south and southwest. There are three existing storm systems that collect and convey runoff towards the southwest of the site (see attached map). Runoff from the site and these existing systems collects into one type II manhole located near the Lind Avenue bridge and 1405. An area just south of 1-405 also drains to this manhole. Runoff flows from this manhole towards the west under the Lind Avenue bridge in a 30 inch concrete pipe. From there runoff flows southerly under 1-405 in another 30 inch concrete pipe to an open ditch. Runoff flows in this ditch westerly along the south side of 1405 to a pump station at Oaksdale Avenue SW and 1-405. This pump station appears to have been installed because Oaksdale Avenue SW was constructed under 1-405. From there runoff enters Springbrook Creek and flows northerly through the Black River and ultimately the Green River. !r1 ti la i I j - - i ;--�"r -�✓ SY'-- '=_-----:-_:.--- - -- fL_—o I �..— �•.•. J I = Vim'____ _ A v.. 'i'•• U't :c N. ;1 m77 F'C��'[Q i ��f�'f ;�. � i - •�1, \� %d•5 ' ' L _ ii.���•• R - x I� L �F: :_! n i �,"--.. .--•T DNTsI ,y!'Y- Ki -:F: "" ri r VaAG I6 � . SI ll k xitI aG -;l EGAiT�' '•:EN IFjtG-Ji1-�IQi'I+WipC W.9�L jUl10.'is A'I .3 qc .. "� �—• .__:7 rj M . ly,':_F9___-.S:_ 1 F • n� .Sr c_� .•t _ I I - ,�1-uul I \ N .� •_J 1 Y! yC 1 �� ��tc. ..Y—'-F'rn"7 � -� _ tea•:•:-a��0� r r.,lnin;dl�lr� 'I !\ �---"--f +� �.'� a {_ ", _� >< '1 I. � �F "ram • � �A�= �cz. f.r.•a .t r �•• � _. Dsi tip.�:Kl I-. a K�tt.L.i[ .... � � '- a ,':> �• - � 1.C t.i° n °I -.._-- -R �., � °G.E Mn w• r' ^G V\el �,^. Q("r 'i• r F s.G+W ..C 'r'I i rct� ly ---- 4 p :5.: i� u: S'S.RP'G �y�:,C`'� ` � I F-•.. F,I PLJP 1:i.S. r9 �1Yy I �: �`� � � SMi��r -L.v�.i 7.e� - _ �M j Y:3::n.lir _. 4i1i'°�LI F I• , �A �vG .:w. � A„: at- - . •.YJ'• - � :° I• _..',-'-.,t K:(.W .tl.vu:n.• • 'rr _ i=. •^psi' � .,1�•i c s �.r� s'•.. s. : 7rS I •M��rnKR ,. � d�� ` S r.r— Y ^•+• .N � f � I. - I �: I' _f. - THIS INv(n fCRi Inl MnAi IU. !CR Tr SICJIH TRAINAYC SYSTEM 12 SCIIEHATIC ot&Y. It WAS CUHPILCO rROTI MMERWS SWRCCS, IT IS THE REST JMrMHATlan AVAILASL( AT THIS TINE, Arlo SHULO Be 99(S r(R EEKRA,. WICAKC cAoty. AC CITY M REHTtW IL MT RCSA@HIIYLC HIT ERRMT M IWffT1pHS. VKH THIS IHCMMIIOH IS USCG rtlR CKINEERIr PURPOSEL 9CSILNCRS ARC TO rICLO vCRIrY THIS IKMHAj IOr4 IS • Jt": sw 3 7TH ST > Yuz•s S C-sla 2 y > N zvi y W W .t > zvz-. > LKE 1 Q 2LCZ-4 vI4 Q W tz- U it RC>- 1 Q LC 24 3 W Ett>• = Z W N 2lC3-2 W 1 2LE)-. 240-IL z,X3-2 . 4p.> > 2%c:1. / m" 2U3-9 2 tLtl•IR ELCS-9 / 2m3-L rn� O ELC)-E 1 ELU• Ylr]- z :w• J xlo->. Laa RIX4.9 RIO-( C• Lr>-I 21C.-10 U-1 2l rU..! zvC.-) E4c... ru._+ / Lit rva� RYIO W Etc. S Ytc.-b 21 4-9 or `•- Yra )..a r1b.-J zLc4-3 V1 YLRr zu.-a / 12 .-Y N YLCI-r eu.-r 1 •- 21 :lC.-3 W f �3 N zu.-1 > � � �- xu'• zaI-z I�l aL.-1 4n-I 2143a 21LSa I YL43-Y I-405 LLL LV3•. 2199•S � .. p' tlm- 24Y5•I W L1 r 1 zlc3-e —��— $lC3-IS YU]-I •I•Y>.l r.R]-1 'a'r nes-Ir 6TH ` - ♦ � :4oe-n ST au-L 1 ncaln ataLe a.I3-1 / X• 1.9 2l YA-II EI.YI-It 21.46-6 ' 14C6.6 %• (.1 II N lLC6Q __ 2LC6-1 $LfW-1Y $16-E _ - 21.06-0 I D< 24cL-. ztre-9 x1.Yc-R _ri,ow r, ztL l-10 - a1tL-1 AF IV. Retention - Detention Analysis The site has been designed to collect runoff from the entire Carco site. There is a small portion of the site (Pierre Auto) that will drain to the Good Chevrolet vault. Runoff will be collected via catch basins & roof drains and be routed to the wet-vault located at the westerly portion of the site. From there runoff will be routed via 12 inch storm pipe to the connection point (18 inch storm pipe) located in Maple Avenue SW. The detention system has been sized using the 1990 King County (1994 update) drainage manual. The facility has been sized to limit the discharge from this site to the 2, 10 and 100 year existing release rates. The developed 2, 10 and 100 year flows will be routed through a triple orifice discharge structure. The wet-vault will have dead storage to act as a bio-filter/pre treatment system. The wet-vault installation has been approved (in lieu of using bio-filtration or water quality swales) by the City of Renton. All of the storm calculations have been provided by using the "Water-Works" program. PACIFIC ENQINEEFiINa I]ESION INC. JOB (3CL,,rr7 S6M2r-f- 9 "O7 '- _ CIVIL ENGINEERING AND PLANNING CONSULTANTS SHEET NO. OF CALCULATED SV 7 L �i OATE AOtl- /7.,')7 I ....._ I rxiSZ>nLIJ Cor)'2 cins 1I t�TM n�4�A. d.g Ac . _1`r1L, vn.4Alip rS AC loo._.' 35 i rk.ISll)i1,1 )-kn0 ', usry ? ZO 'OL„rLl.t,lnh VnrTs (7l•Z. . 42c$S AGE 6klSmn� ScI S _ l/2 q,1 , C"4S5 `'n VMLV �L� U.�Gl1/_ .......... lzr�4S �SoJc ArLAI��� � 2S °7o ./ n�r2 /Cc�t I V"tt _._.Sc,� G2rn =_`1. `C,��I , r��zwccls. = 6 jAG .... G7 q2 . ._..... Ac 1, G2 , . .. i._ Tc ..... �CrA L`. . S Irr7 r�cn. ....... S om G.pOGs 500 lf+ ......Cn> nn�t, G1n $ .TTt�� .. I i ..._... - i ! -.' _ ,....... ......... .._.....,._... 4 _ �ryrLaPf;7 Cc>1�Tj1crls anti r«r g r c i ...... n� vlU S ' l /fin JSLAnr� S2..... 1M.(2ffz Vt.cl s .- CA-v /,q rT- I.,rJ� S 4,5� Ac G_rl 9b . ..... Tc ZG $pI ,r T LCty Ct T r�r7S4,'A*?rt 2CSS� . .. SLu�f' G,Do: ...... , ..._ �3G " Z..0)01MrrtT� _ ............. o rzrJ i i I 130 ANDOVER PARK EAST, SUITE 300 SEATTLE, WASHINGTON 98188 (206) 431-7970 FAX:431-7975 7/25/97 1 : 6 :15 pm Pacific Engineering Design Inc page 1 Bowen Scarff - Carco 9705 --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: A1/3 NAME: 1/3 Developed 2 year/ SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 80 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 0 . 67 inches AREA. . : 0 . 25 Acres 4 .55 Acres TIME INTERVAL. . . . : 10 .00 min CN. . . . .. 92 . 00 98 .00 TC. . . . .. 5 . 95 min 6 . 10 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 20 . 00 ns :0 . 1500 p2yr: 2 . 00 s :0 . 0050 impTcReach - Sheet L: 130 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 0200 impTcReach - Channel L: 750 . 00 kc:42 . 00 s : 0 . 0050 PEAR RATE : 0 . 51 cfs VOL: 0 . 18 Ac-ft TIME: 480 min BASIN ID: A10 NAME : Developed 10 year SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 80 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 2 . 90 inches AREA. . : 0 .25 Acres 4 .55 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 92 . 00 98 . 00 TC. . . . : 5 . 95 min 6 . 10 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 20 .00 ns : 0 . 1500 p2yr: 2 . 00 s :0 . 0050 impTcReach - Sheet L: 130 . 00 ns :0 . 0110 p2yr: 2 . 00 s:0. 0200 impTcReach - Channel L: 750 . 00 kc :42 . 00 s : 0 . 0050 PEAK RATE: 2 . 84 cfs VOL: 1 . 05 Ac-ft TIME: 480 min BASIN ID: A100 NAME: Developed 100 year SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 80 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPElA PERV IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 25 Acres 4 . 55 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 92 . 00 98 . 00 TC. . . . : 5 . 95 min 6 . 10 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 20. 00 ns:0 . 1500 p2yr: 2 . 00 s : 0 . 0050 impTcReach - Sheet L: 130 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 0200 impTcReach - Channel L: 750 . 00 kc :42 . 00 s: 0 . 0050 PEAK RATE: 3 . 87 cfs VOL: 1 .45 Ac-ft TIME: 480 min 7/25/97 1 : 6 : 15 pm Pacific Engineering Design Inc page 2 Bowen Scarff - Carco 9705 ----------------------------------------------------------------- BASIN SUMMARY ,/ BASIN ID: A2 NAME: Developed 2 year V SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 .80 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 2 . 00 inches AREA. . : 0 . 25 Acres 4 . 55 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 92 . 00 98 . 60 TC. . . . : 5 . 95 min 6 . 10 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 20 . 00 ns : 0 . 1500 p2yr: 2 . 00 8 :0 . 0050 impTcReach - Sheet L: 130 . 00 ns :0 .0110 p2yr: 2 . 00 s : 0 . 0200 impTcReach - Channel L: 750 . 00 kc:42 .00 s : 0 . 0050 PEAK RATE: 1 . 9 f V L: 0 . 70 Ac-ft TIME: 480 min ID: a10 NAME: Existing 10 year SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 80 Acres BASEFLOWS: 0 an fs RAINFALL TYPE. . . . : TYPElA V PRECIPITATION. . . . : 2 . 90 inches AREA. . : 3 . 18 res 1 : 6 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 9 9 0 TC. . . . : 33 . 83 min 5 . 00 min ABSTRACTION COEFF: 0 .20 TcReach - Sheet L: 200 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 0065 PEAK RATE: 2 . 03 cfs VOL: 0 . 91 Ac-ft TIME: 480 min BASIN ID: a100 NAME: Existing 100 year SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 80 Acres BASEFLOWS: 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA r92O IMP PRECIPITATION. . . . : 3 . 90 inches AREA. . : cres 1 . 62 cres TIME INTERVAL. . . . : 10 . 00 min CN. . . . ; 8TC. . . . : in 5 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 200 . 00 ns : 0 . 1500 p2yr: 2 . 00 s:0 . 0065 PEAK RATE: 2 . 90 cfs VOL: 1 .30 Ac-ft TIME: 480 min BASIN ID: a2 NAME : Existing 2 year SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 80 Acres BASEFLOWS:t830min 0 cfs RAINFALL TYPE. . . . : TYPElA PRECIPITATION. . . . : 2 . 00 inches AREA. . : Acres 1 . 6 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 0TC. . . . : 5 . 00 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 200 . 00 ns: 0 . 1500 p2yr: 2 . 00 "s : 0 . 0065' PEAK RATE: 1 . 26 cfs VOL: 0 . 57 Ac-ft TIME: 4-80' min 7/8/97 2 : 10 :31 pm Pacific Engineering Design Inc page 1 Bowen Scarff - Carco 9705 --------------------------------------------------------------------- BASIN SUMMARY BASIN ID: A1/3 NAME : 1/3 Developed 2 year SBUH METHODOLOGY TOTAL AREA. . . . . . . : 4 . 80 Acres BASEFLOWS : 0 . 00 cfs RAINFALL TYPE. . . . : TYPEIA PERV IMP PRECIPITATION. . . . : 0 . 67 inches AREA. . : 0 . 25 Acres 4 . 55 Acres TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 92 . 00 98 . 00 TC. . . . : 5 . 95 min 6 . 10 min ABSTRACTION COEFF: 0 . 20 TcReach - Sheet L: 20 . 00 ns : 0 . 1500 p2yr: 2 . 00 s : 0 . 0050 impTcReach - Sheet L: 130 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 0200 impTcReach - Channel L: 750 . 00 kc:42 . 00 s : 0 . 0050 PEAK RATE: 0 . 51 cfs VOL: 0 . 18 Ac-ft TIME: 480 min 7/30/97 8 : 9 :51 am Pacific Engineering Design Inc page 1 Bowen Scarff - Carco 9705 ---------------------------------------------------------- HYDROGRAPH SUMMARY PEAK TIME VOLUME HYD RUNOFF OF OF Contrib NUM RATE PEAK HYDRO Area cfs min. cf\AcFt Acres 1 1 .262 480 24714 cf 4 . 80 rx15T z `tt 2 2 . 035 480 39552 cf 4 . 80 10 VR" btu+O I At tr-S 3 2 . 902 480 56428 cf 4 . 80 a 100 W"-&) 2. 4 1 . 906 '� 480 30429 cf 4 . 80 nfV z y2\ 7Ccf 5 2 . 841/ 480 45953 cf 4 . 80 10 ) �k 6 3 . 872 v 480 63280 cf 4 . 80 100 111 8 0 . 506 480 8010 cf 4 . 80 113 off, z 7 z o� 18 1 . 263 500 30429 c£ 4 . 80 uhwT owT r--v-. V ^r^ 5t04lj b��•�s 19 2 . 035 500 45953 cf 4 . 80 't". 20 3 . 377 500 63280 cf 4 . 80 Wl" eL. Aj,e t.7c 7/25/97 1 : 6 :15 pm Pacific Engineering Design Inc page 4 Bowen Scarff - Carco 9705 STORAGE STRUCTURE LIST RECTANGULAR VAULT ID No. V1 Description: Vault Length: 115 . 00 ft . Width: 17 . 00 ft . voids : 1 . 000 S).fL(tn0,f� 'Ar4,& I IS�x 17 ' VAu,— I °1 G)L (OnL7 1.3 70 gkc. -r) %uA—« (1 bZ SE 21 -7 3 S^� 1/3 Ofv zti2 _ %o)o cr C T"I ee 0 7/30/97 8 : 9 :51 am Pacific Engineering Design Inc page 3 Bowen Scarff - Carco 9705 DISCHARGE STRUCTURE LIST INLET CONTROL CULVERT ID No . Description: Diameter (ft) : 0 . 00 Entrance type : 4 Length (ft) 0 . 00 Invert Elev 0 . 00 Slope (ft/ft) : 0 . 0000 No. of Clvrts : 1 Mannings n 0 . 0120 Max Ponding el : 0 . 00 Stg-Dis Increment 0 . 10 COMBINATION DISCHARGE ID No. C1 Description: Combo Structure : 01 Structure : Structure : R1 Structure : Structure : MULTIPLE ORIFICE ID No. 01 Description: Orifice Outlet Elev: 19 . 00 Elev: 17 . 00 ft Orifice Diameter: 6 . 6445 in. Elev: 20 . 20 ft Orifice 2 Diameter: 4 . 5000 in. RISER DISCHARGE ID No. R1 Description: Riser Riser Diameter (in) : 12 . 00 elev: 21 .20 ft Weir Coefficient . . . : 9 . 739 height : 21 . 50 ft Orif Coefficient . . . : 3 . 782 increm: 0 . 10 ft 7/30/97 8 : 9 : 52 am Pacific Engineering Design Inc page 4 Bowen Scarff - Carco 9705 --------------------------------------------------------------------- LEVEL POOL TABLE SUMMARY MATCH INFLOW -STO- -DIS- <-PEAK, STORAGE <--------DESCRIPTION---------> (cfa) (cfa) --id- --id- <-STAGE> id VOL (cf) ............................................................................. ex2yr - dev2yr ............... 1. 1.91 V1 01 20.11 18 2171.75 cf exl0yr - dev10yr ............. 2.0 2.84 vl 01 20.80 19 3524.99 cf ex100yr - dev100yr ........... 2.90 3.87 Vl Cl 21.41 2 7D3.70 w� --y,- ) CL , d r�l - 2- 476' 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 HYDROLOGIC HYDROLOGIC SOIL GROUP GROUP' SOIL GROUP GROUP, Alderwood C Orcas Peat D Arents, Alderwood Material C Oridia D Arents, Everett Material B Ovall C Beausite C Pilchuck C Bellingham D Puget D Brlscot D Puyallup B Buckley D Ragnar B Coastal Beaches Variable Renton D Eadmont Silt Loam D River ash Variable Edgewick C Salal C Everett A/B `3ammamish D Indianola A Seattle D Kitsap C Shacar D Klaus C Si Silt C Mixed Alluvial Land Variable Snohomish D Neilton 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 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. C. (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 line to line textures. These soils have a slow rate of water transmission. D. (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 19M, Exhibit A-1. Revisions made fromSCS, Soil Interpretation Record. Form #5, September 19U. 3.5.2-2 11/92 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TABLE3.51B SCS \VESTERNWASHINGTON 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 or older second growth 42 64 76 81 Wood or forest land: young second growth or brush 55 72 81 86 Orchard: with cover crop 81 88 92 94 Open spaces, lawns, parks, golf courses, cemeteries, landscaping. good condition: grass cover on 75% or more of the area 68 80 66 90 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 87 89 Impervious surfaces, pavement, roofs, etc. 98 98 98 98 Open water bodies: lakes, wetlands, ponds, etc. 100 100 100 100 Single Family Residential (2) Dwelling Unh/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 11192 KING COUNTY. W AS HINGTON. SURFACE WATER DESIGN MANUAL FIGURE;3.5.1C 2-YEAR 24-IIOUR ISOPLUVIALS 4.. r11• 2.Q i ' �"•. "� F Otis• t I IN cwv f t 11 i � p N 4j11 1� •�' �r-�• V � � t-. Vv - 2-YEAR24-HOUR PRECIPITATION }- Y ISOPLUVIALS OF 2-YEAR 24-HOUR -35 TOTAL PRECIPITATION IN INCHES ry � 0 1 2 3 4 S 6 7 3 &111-$ N - � 1, 300,000 `_= 3.5.1-8 yr- 1/90 KING COUNTY. WASHINGTON. SURFACE WATER DESIGN MANUAL FIGURE3.5.1E 10-YEAR24-IIOURISOPLUVIALS �j22 i• -_ W it - - _ - •izD - _ ., 24 2S 2.7 29 3.0 u v Ile ♦ �. L . a SIT. `f� L .♦ :6— 10-YEAR 24-HOUR PRECIPITATION / P•3.4- ' ISOPLUVIALS OF 10-YEAR 24-HOUR TOTAL PRECIPITATION IN INCHES O 1 2 3 4 5 6 7 81,111, 2:300.000 3.5.1-10 ��j 1/90 0 KING COUNTY, W ASHINGTON• S U RFA CE WATER DESIGN MANUAL I•TGURE 3.S.111 100-YEAR 24.IIOUR ISOPLUVIALS 3.8 3 i- - . KNI 1 col JR ....r n. �r •` `-� � � s is � � . 100 `)-YEAR 24-HOUR PRECIPITATION 6 - 3.4 ---ISOPLUVIALS OF 100-YEAR 24-HOUR TOTAL PRECIPITATION IN INCHES p• "� - 0 1 2 3 4 S 6 7 8 Allies ~ 3.5.1-13 13300,000 1 90 V. Conveyance Systems Analyy� Pipe calculations have been included in this section. = PACIFIC ENGINEERING DESIGN INC. — CIVIL ENGINEERING AND PLANNING CONSULTANTS 130 ANDOVER PARK EAST-STE 300 SEATT'_E. WASHINGTON SS156 LOCATION INCRE— RUN—OFF TIME DF CAN RAINFALL RUN—OFF PIPE SLOPE CAPACITY LEN FLOW / REMARKSo MENTAL COEFFIC. _Lr, I AC CENTRATION INTENSITY _4_ DIA. AT DESIGN TIME N ; AREA A TC I (I AC I J 1 g SYSTEM FROM TO ACRES MINUTES NCHES/HR C.F.S. WCHES FT FT C.F.S. IFEET MIN. U.S.W.B. CHART N0. REMARKS' STORM FREQUENCY, NAME OF PROJECT _ PIPE COEFFiCEHT, ' CALCULATIONS BY, J08 NO. DATE SHEET-Cf_SHEETS PACIFIC ENGINEERING DESIGN INC. CIVIL ENGINEERING ANO PLANNING CONSULTANTS 130 ANDOVER PARK EAS7-STE 300 SEAT LE. WASHINGTON SE1 SS LOCATION INCRE- RUN-OFF TIME OFCON RAINFALL RLN-OFF PIPE SLOPE ICAPACITY LEN FLOW / REMARKS+ MENSAL COEFFIC. £ AC CENTRATION INTENSfTY _2- DIA. AT DESIGN TIME N ; AREA ,�, ,� - TC I (I AC I) �C, SYSTEM ' FROM TO ACRES MINUTES INCHES/HR C.F.S. INCHES FT FT C.F.S. FEET MIN, REMARKS+ U.S.W.B. CHART NO. _ STORM FREQUENCY, ' NAME OF PROJECT _ PIPE COEFFICENT, CALCULATIONS BY, 408 NO. DATE SHEET-Cfr-SHEETS PACIFIC ENGINEERING DESIGN INC. CIVIL ENGINEERING AND PLANNING CONSULTANTS 13O ANDOVER PARK EAST-STE 300 SEATTLE, WASHINGTON Set SS LOCATION INCRE— RUN—OFF TIME OF CON RAINFALL RUN—OFF PIPE SLOPE jCAPACrrY LENJ FLOW / REMARKSI MENTAL COEFFIC. AQ I AC CENTRATION INTENSffY 0 DIA. AT DESIGN TIME N ; AREA, ..C.. TC I (IACI ) 4 SYSTEM FROM TO ACRES MINUTES INCHES/HR C.F.S. INCHES FT/FT C.F.S. FEET MIN. U.S.W.B. CHART N0. REMARKS, STORM FREQUENCY, NAME OF PROJECT PIPE COEFFICENT, - - CALCULATIONS BYs JOB NO. DATE SHEET-CF-SHEETS V. Special Reports and Studiec The soils report prepared by Geotech has been included in this section. G E O T E C H February 17, 1997 CONSULTANTS, INC. 13236 N.E.20th St.(Northup Way).Suite 16 JN 97020 Bellevue.ll'A 98005 (206)747.5618 FAX 747-8561 Barry D. Leahy P.O. Box 489 Medina, Washington 98004 Subject: Geotechnical Engineering Study Proposed Renton Auto Mall Between Southwest Grady Way and Southwest 13th Street Renton, Washington Dear Mr. Leahy: We are pleased to present this geotechnical engineering report for the proposed auto mall to be constructed in Renton, Washington. The scope of our work consisted of exploring site surface and subsurface conditions, and then developing this report to provide recommendations for general earthwork and design criteria for foundations, retaining walls, and pavements. You authorized our work by accepting our proposal, P-4112, dated January 13, 1997. The subsurface conditions of the proposed building site were explored with two test borings that encountered medium-dense to dense, gravelly sands. These competent soils were overlain by very loose fill and river deposits in the southern boring. Because the southern portion of the building will lie over the old Black River channel, we recommend that deep foundations be used to support the building and the floor slab in order to achieve the best building performance. The pavement sections will need to be underlain by imported structural fill where the near-surface soils are found to be loose or unstable. The excavated subgrade should be evaluated following completion of demolition of the existing structures. The near-surface soils will be silty and moisture-sensitive throughout much of the project site. The moisture sensitivity of the on-site soils will make wet weather grading more difficult and costly. The attached report contains a discussion of the study and our recommendations. Please contact us, if there are any questions regarding this report or if we can be of further assistance during the design and construction phases of this project. Respectfully submitted, GEOTECH CONSULTANTS, INC. Marc R. McGinnis, P.E. Associate ant -d GEOTECHNICAL ENGINEERING STUDY Proposed Renton Auto Mall Between Southwest Grady Way and Southwest 13th Street Renton, Washington This report presents the findings and recommendations of our geotechnical engineering study for the site of the proposed auto mall to be constructed in Renton. The Vicinity Map, Plate 1, illustrates the general location of the site. We were provided with a Preliminary Site Plan that was developed by Barry Wigington, Architect. This plan, which is dated December 6, 1996, illustrates the site boundaries, the location of the proposed building, and the paved inventory display areas. No information regarding existing topography or proposed final grading was provided. Based on the plan, and on discussions with you, we anticipate that a large building containing space for display and servicing of used automobiles will be located between Southwest 12th Street and Southwest 13th Street. Paved areas for outside display of automobiles will cover the remainder of the site. SITE CONDITIONS Surface The site is a large, irregularly shaped parcel that consists of 64 residential lots. Not all of these lots will be developed at this time. The property extends between Southwest Grady Way and Southwest 13th Street, with Maple Avenue Southwest defining the western boundary of the site. At the time of our field work, the property was developed with a total of 15 houses and several outbuildings. Pastures and yards surround the existing buildings. The relatively level site is approximately 3 to 4 feet lower in elevation than Southwest Grady Way. The area around the site is developed with many new office and retail buildings. Several automobile dealerships have also recently been constructed nearby. Subsurface The subsurface conditions of the proposed building area were explored by drilling two test borings at the approximate locations shown on the Site Exploration Plan, Plate 2. The field exploration program was based upon the proposed construction and required design criteria, the site topography and access, the subsurface conditions revealed during drilling, the scope of work outlined in our proposal, and the time and budget constraints. The borings were drilled on January 23, 1997 using a truck-mounted, hollow-stem auger drill. Samples were taken at 5-foot intervals with a standard penetration sampler. This split-spoon sampler, which has a 2-inch outside diameter, is driven into the soil with a 140-pound hammer falling 30 inches. The number of blows required to advance the sampler a given distance is an indication of the soil density or consistency. A geotechnical engineer from our staff observed the drilling process, logged the test borings, and obtained representative samples of the soil encountered. The Test Boring Logs are attached as Plates 3 through 6. GEOTECH CONSULTANTS,INC. Barry D. Leahy JN 97020 February 17, 1997 Page 2 Both borings encountered native, medium-dense, gravelly sands that became dense below a depth of approximately 20 feet. These coarse-grained soils have been deposited by the Cedar River to form a large delta in the Renton Valley. Some thin layers of silt and silty sand were found within the gravelly sands. Below a depth of about 55 feet, the sands became loose to medium-dense again. Boring 2 revealed about 10 feet of very loose silt and some possible fill overlying the first section of medium-dense to dense, gravelly sands. Our review of the Liquefaction Susceptibility of the Renton Quadrangle (Palmer, et. al, 1994) indicates that a portion of the abandoned Black River channel curves through the proposed area for the southern half of the building. The very loose soils found in the upper portion of Boring 2 appear to be deposits within the old river channel. The meandering river covered approximately one-half of the site between Southwest 12th Street and Southwest 13th Street, and the eastern, approximate one-fourth of the site between Southwest Grady Way and Southwest 12th Street. The final logs represent our interpretations of the field logs and laboratory tests. The stratification lines on the logs represent the approximate boundaries between soil types at the exploration locations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration locations. The logs provide specific subsurface information only at the locations tested. If a transition in soil type occurred between samples in the borings, the depth of the transition was interpreted. The relative densities and moisture descriptions indicated on the test boring logs are interpretive descriptions based on the conditions observed during drilling. Groundwater Groundwater seepage was observed at a depth of 8.5 to 10.5 feet. The groundwater seepage observed in the test borings appears to represent the approximate level of the static water table in the Renton Valley. It should be noted that the borings were conducted following a fairly wet winter and that groundwater levels vary seasonally with rainfall and other factors. CONCLUSIONS AND RECOMMENDATIONS General Based on the results of our test borings, it appears that the proposed site development is feasible from a geotechnical engineering standpoint. Because of the presence of at least 10 feet of very loose, highly compressible deposits below the southern portion of the proposed building, the use of conventional foundations will not be possible. Deep foundations extending into the medium-dense to dense sands should be used to support the building loads. Driven timber piles or augercast concrete piers will likely be the most economical types of deep foundations for this project site. For the best long-term performance, the floor slab for at least the portion of the building over the very loose to loose deposits in the old Black River Channel should be structurally supported on deep foundations. It could be difficult to use a conventional on-grade slab for even the remainder of the building, as the old channel curves through the building. Test pits would be needed to define the limits of unsuitable soils in the slab areas. Also, some differential settlement would occur between on-grade slabs and those supported on deep foundations. We have had a discussion with personnel from McDowell Northwest Pile Driving, who have installed driven timber piles for many of the recently built commercial developments around the site, including the new Good Chevrolet OEOTECH CONSULTANTS,INC. Barry D. Leahy JN 97020 February 17, 1997 Page 3 facility immediately to the west. Based on this discussion, driven timber piles seem to be the most commonly used type of deep foundation in the vicinity. McDowell Northwest also indicated that timber piles for the Good Chevrolet facility extended to a depth of 25 to 35 feet before reaching refusal. Exterior slabs, such as sidewalks, will likely settle relative to the building. This will be most noticeable over the old river channel. The potential for a downset occurring at a transition between an exterior slab and a doorway can be reduced by reinforcing the transition zone with continuous steel bars. The near-surface soils will likely be soft throughout major portions of the site. This situation will impact grading and construction. The two test borings were conducted to explore the proposed building area, not the near-surface conditions around the proposed paved areas. Test pits could be conducted following demolition of the existing structures to better explore the density and composition of the soils within approximately 5 feet of the ground surface. In areas of soft soils, at least 12 inches of imported, gravelly structural fill must be placed under pavement sections that are expected to,perform adequately for both drive lanes and parking areas. Additional structural fill, and possibly a geofabric, would also be needed in areas of excessively poor subgrade conditions. Construction access roads through areas of soft soils will need to consist of 12 to 18 inches of quarry spalls over a geofabric. Placement of approximately 12 inches of imported gravelly fill in the building area would provide a fairly stable working pad for construction of grade beams, utilities, and the floor slabs. The deep foundation contractor should be consulted regarding specific requirements for preparation of a working pad to provide access for the pile driver or pier drill rig. The native, gravelly sands can be reused as structural fill if their moisture content is not too high at the time of placement. Reuse of the silty soils found in the southern boring will not be possible. They should not be used as backfill for utility trenches in structural areas, such as under pavements. However, these unsuitable soils could be reused for non-structural areas, such as landscaping. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan review would be additional work beyond the current scope of work for this study, and it may include revisions to our recommendations to accommodate site, development, and geotechnical constraints that become more evident during the review process. Driven Timber Piles The proposed structure may be supported on sound, pressure-treated timber piles that conform to the specifications outlined in the Uniform Building Code (UBC) for end-bearing piles. Timber piles should have a minimum tip diameter of 8 inches, and they should be placed no closer than three pile diameters, center-to-center. An allowable compressive pile capacity of 30 tons can be used for piles driven to refusal. Refusal is defined as 30 blows per foot for the last 1 foot of driving, when driven with a hammer that has a rated energy of 15,000 foot-pounds. The minimum penetration is 25 feet below the existing grade. GEOTECH CONSULTANTS.INC. Barry D. Leahy JN 97020 February 17, 1997 Page 4 The piles should be marked in 1-foot increments to facilitate the recording of blow counts during the driving process. The pile number should be clearly marked on the location stake. We recommend driving the piles with a steam, air, or diesel hammer with fixed leads. Because soil conditions can be variable, driving test piles before ordering the production piles can help in obtaining a more accurate estimate of pile lengths and in determining driving characteristics. The piles and hammer used for the testing should be the same type as those to be used in production driving. Geotech Consultants personnel should observe the installation of both the test piles and production piles on a full-time basis. We anticipate that timber piles that are driven to refusal will have total or differential settlements on the order of one-quarter inch. Lateral loads due to wind or seismic forces may be resisted by the piles and by passive pressure on the grade beams. We anticipate each vertical pile will have a lateral capacity of at least one ton. Additional lateral loads can be resisted by battered piles and passive earth pressures on the grade beams. Piles may be battered at an angle of 1:5 (Horizontal:Vertical) without a reduction of the vertical load capacity. The lateral capacity of a battered pile can be assumed to be equal to the horizontal component of the axial capacity. Passive earth pressures on the grade beams can be assumed to be equal to that pressure exerted by a fluid that has a density of 200 pounds per cubic foot (pcf). Augercast Concrete Piers Augercast piers are installed using continuous flight, hollow-stem auger equipment. Concrete grout must be pumped continuously through the auger as it is withdrawn. We recommend that augercast piers be installed by an experienced contractor who is familiar with the anticipated subsurface conditions. An allowable compressive capacity .of 30 tons can be attained by installing a 14-inch-diameter, augercast concrete pier at least 15 feet into the medium-dense to dense sands. The piers should extend a minimum length of 25 feet below the existing ground surface. For transient loading, such as wind or seismic loads, the allowable pier capacity may be increased by one-third. We can provide design criteria for different pier diameters and embedment lengths, if greater capacities are required. The minimum center-to-center pier spacing should be three times the pier diameter. We estimate that the total settlement of single piers installed as described above will be on the order of one-half inch. Most of this settlement should occur during the construction phase as the dead loads are applied. The remaining post-construction settlement would be realized as the live- loads are applied. We estimate that differential settlements over any portion of the structures should be less than about one-quarter inch. We recommend reinforcing each pier its entire length. This typically consists of a rebar cage extending a portion of the pier's length with a full-length center bar. Each pier can be assumed to have a point of fixity at 12 feet below the ground surface for the computation of lateral load resistance. The loose soils against the upper 10 feet of the piers can be assumed to exert a passive resistance equal to 100 pcf acting on the pier's diameter. Passive earth pressures on the grade beams will also provide some lateral resistance. If structural fill is placed against the outside of the grade beams, the design passive earth pressure from the fill can be assumed to be equal to that pressure exerted by an equivalent fluid with a density of 200 pcf. GEOTECII CONSULTANTS,INC. Barry D. Leahy JN 97020 February 17, 1997 Page 5 Seismic Considerations The site is located within Seismic Zone 3, as illustrated on Figure No. 16-2 of the 1994 Uniform Building Code (UBC). In accordance with Table 16-J of the 1994 UBC, the site soil profile is best represented by Profile Type S3. The loose, saturated sands are moderately susceptible to liquefaction in the event of a large earthquake. The use of deep foundations to support the structure protects against the potential hazard of excessive foundation settlement that could result from seismic liquefaction. Floor Slabs Floor slabs over the old river channel should be constructed as reinforced slabs to span between the grade beams that will interconnect the deep foundations. This reduces the potential for differential settlement that could result if portions of the floor were constructed to bear on grade. If on-grade slabs are used over the native, gravelly sands, the slabs should be reinforced with steel bars to reduce cracking due to differential settlement. All slabs beneath spaces occupied by persons should be underlain by a capillary break or drainage layer consisting of a minimum 4-inch thickness of coarse, free-draining, structural fill with a gradation similar to that discussed later in Permanent Foundation and Retaining Walls. A vapor barrier, such as a 6-mil plastic membrane, should be placed beneath the slab in these areas to reduce the potential for transmission of water vapor through the floor slab. Permanent Foundation and Retaining Walls Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures imposed by the soil they retain. The following recommended design parameters are for walls that restrain level backfill: Parameter Design Value Active Earth Pressure' 35 pcf Soil Unit Weight 130 pcf Where: 1. pcf is pounds per cubic foot. 2. Active and passive earth pressures are computed using the equivalent fluid densities. For a restrained wall that cannot deflect at least 0.002 times its height, a uniform lateral pressure equal to 10 psf times the height of the wall should be added to the above active equivalent fluid pressure. GEOTECH CONSULTANTS,INC. Barry D. Leahy JN 97020 February 17, 1997 Page 6 The values given above are to be used to design permanent foundation and retaining walls only. We recommend a safety factor of at least 1.5 for overturning and sliding, when using the above values to design the walls. The design values given above do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharge slopes or loads, such as vehicles, will be placed behind the walls. If these conditions exist, those pressures should be added to the above lateral soil pressures. Also, if sloping backfill is desired behind the walls, we will need to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. The surcharge due to traffic loads behind a wall can typically be accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid density. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. The wall design criteria assume that the backfill will be well-compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should be accomplished with hand-operated equipment to prevent the walls from being overloaded by the higher soil forces that occur during compaction. Retaining Wall Backfill Backfill placed behind retaining or foundation walls should be coarse, free-draining, structural fill containing no organics. This backfill should contain no more than 5 percent silt or clay particles and have no gravel greater than 4 inches in diameter. The percentage of particles passing the No. 4 sieve should be between 25 and 70 percent. The purpose of these backfill requirements is to ensure that the design criteria for a retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively impermeable soil or topsoil, or the surface should be paved. The ground surface must also slope away from backfilled walls to reduce the potential for surface water to percolate into the backfill. The sub-section entitled General Earthwork and Structural Fill contains recommendations regarding the placement and compaction of structural fill behind retaining and foundation walls. The above recommendations are not intended to waterproof the below-grade walls. If some seepage through the walls or moist conditions are not acceptable, damp-proofing or waterproofing should be provided. This could include limiting cold-joints and wall penetrations, and possibly using bentonite panels or membranes on the outside of the walls. Applying a thin coat of asphalt emulsion is not considered waterproofing, but it will help to prevent moisture, generated from water vapor or capillary action, from seeping through the concrete. Excavations and Slopes - Excavation slopes should not exceed the limits specified in local, state, and national government safety regulations. Based upon Washington Administrative Code (WAC) 296, Part N, the soil type at the subject site would be generally be classified as Type C. Temporary cut slopes above the GEOTECH CONSULI?ANTS,INC. Barry D. Leahy JN 97020 February 17, 1997 Page 7 water table should not be excavated at an inclination steeper than 1.5:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. Dewatering and shoring will be needed for deep excavations that extend below the water table. The above-recommended temporary slope inclination is based on what has been successful at other sites with similar soil conditions. Temporary cuts are those that will remain unsupported for a relatively short duration to allow for the construction of foundations, retaining walls, or utilities. Temporary cut slopes should be protected with plastic sheeting during wet weather. The cut slopes should also be backfilled or retained as soon as possible to reduce the potential for instability. Please note that loose soil can cave suddenly and without warning. Utility contractors should be made especially aware of this potential danger. Fill slopes constructed of compacted granular fill should not be constructed with an inclination greater than 2:1 (H:V). To reduce the potential for shallow sloughing, fill must be compacted to the face of these slopes. This could be accomplished by overbuilding the compacted fill and then trimming it back to its final inclination. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. Also, all permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the surficial layer of soil. Drainage Considerations We recommend the use of footing drains at the base of footings, where (1) crawl spaces or basements will be below a structure, (2) a slab is below the outside grade, or (3) the outside grade does not slope downward from a building. Drains should also be placed at the base of all backfilled, earth-retaining walls. These drains should be surrounded by at least 6 inches of 1-inch- minus, washed rock and then wrapped in non-woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least as low as the bottom of the footing, and it should be sloped for drainage. Drainage should also be provided inside the footprint of a structure, where (1) a crawl space will slope or be lower than the surrounding ground surface, (2) an excavation encounters significant seepage, or (3) an excavation for a building will be close to the expected high groundwater elevations. We can provide recommendations for interior drains, should they become necessary, during excavation and foundation construction. All roof and surface water drains must be kept separate from the foundation drain system. A typical drain detail is attached to this report as Plate 7. For the best long-term performance, perforated PVC pipe is recommended for all subsurface drains. Groundwater was observed during our field work. If seepage is encountered in an excavation, it should be drained from the site by directing it through drainage ditches, perforated pipe, or French drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to buildings should slope away at least 2 percent, except where the area is paved. GEOTECH CONSULTANTS,INC. Barry D. Leahy JN 97020 February 17, 1997 Page 8 Pavement Areas All pavement sections may be supported on competent, native, gravelly sand or on at least 12 inches of imported, gravelly structural fill placed over soft soils. The excavated subgrade must be in a stable, non-yielding condition at the time of paving or placement of structural fill. Additional structural fill or fabric may be needed to stabilize excessively soft, wet, or unstable areas. We recommend using Supac 5NP, manufactured by Phillips Petroleum Company, or a non-woven fabric with equivalent strength and permeability characteristics. In most instances where unstable subgrade conditions are encountered, 12 inches of granular, structural fill will stabilize the subgrade, except for very soft areas where additional fill could be required. The subgrade should be evaluated by Geotech Consultants, Inc., after the site is stripped and cut to grade. Recommendations for the compaction of structural fill beneath pavements are given in a later sub- section entitled General Earthwork and Structural Fill. The performance of site pavements is directly related to the strength and stability of the underlying subgrade. The pavement for lightly loaded traffic and parking areas should consist of 2 inches of asphalt concrete (AC) over 4 inches of crushed rock base (CRB) or 3 inches of asphalt-treated base (ATB). We recommend providing heavily loaded areas with 3 inches of AC over 6 inches of CRB or 4 inches of ATB. Heavily loaded areas are typically main driveways, dumpster sites, or areas with truck traffic. The pavement section recommendations and guidelines presented in this report are based on our experience in the area and on what has been successful in similar situations. Some maintenance and repair of limited areas can be expected. To provide for a design without the need for any repair would be uneconomical. General Earthwork and Structural Fill All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. It is extremely important that the foundations for the existing structures are also removed. The stripped or removed materials should not be mixed with any materials to be used as structural fill, but they could be used in non-structural areas, such as landscape beds. Structural fill is defined as any fill placed under a building, behind permanent retaining or foundation walls, or in other areas where the underlying soil needs to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The optimum moisture content is that moisture content that results in the greatest compacted dry density. The moisture content of fill is very important and must be closely controlled during the filling and compaction process. The allowable thickness of the fill lift will depend on the material type selected, the compaction equipment used, and the number of passes made to compact the lift, T-he"loose lift thickness should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not compacted to specifications, it can be recompacted before another lift is placed. This eliminates the need to remove the fill to achieve the required compaction. The following table presents recommended relative compactions for structural fill: GEOTECH CONSULTANTS,INC. Barry D. Leahy JN 97020 February 17. 1997 Page 9 Minimum Location of Fill Placement Relative Compaction Beneath footings, slabs, 95% or walkways Behind retaining walls 90% Beneath pavements 95% for upper 12 inches of subgrade, 90% below that level Where: Minimum Relative Compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D 1557-78 (Modified Proctor). Ideally, structural fill that will be placed in wet weather should consist of a coarse, granular soil with a silt or clay content of no more than 5 percent. The percentage of particles passing the No. 200 sieve should be measured from that portion of soil passing the three-quarter-inch sieve. LIMITATIONS The analyses, conclusions, and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil encountered in the test borings is representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated soil conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking soil samples in test borings. Subsurface conditions can also vary between exploration locations. Such unexpected conditions frequently require making additional expenditures to attain a properly constructed project. It is recommended that the owner consider providing a contingency fund to accommodate such potential extra costs and risks. This is a standard recommendation for all projects. This report has been prepared for the exclusive use of Barry D. Leahy, the Scarffs, and their representatives for specific application to this project and site. Our recommendations and conclusions are based on observed site materials, and selective engineering analyses. Our conclusions and recommendations are professional opinions derived in accordance with current standards of practice within the scope of our services and within budget and time constraints. No warranty is expressed or implied. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. We recommend including this report, in its entirety, in the project contract documents so the contractor may be aware of our findings. GEOTECI I CONSULTANTS,INC. Barry D. Leahy JN 97020 February 17, 1997 Page 10 ADDITIONAL SERVICES Geotech Consultants, Inc. should be retained to provide geotechnical consultation, testing, and observation services during construction. This is to confirm that subsurface conditions are consistent with those indicated by our exploration, to evaluate whether earthwork and foundation construction activities comply with the general intent of the recommendations presented in this report, and to provide suggestions for design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. However, our work would not include the supervision or direction of the actual work of the contractor and its employees or agents. Also, job and site safety, and dimensional measurements, will be the responsibility of the contractor. The following plates are attached to complete this report: Plate 1 Vicinity Map Plate 2 Site Exploration Plan Plates 3 - 6 Test Boring Logs Plate 7 Footing Drain Detail We appreciate the opportunity to be of service on this project. If you have any questions, or if we may be of further service, please do not hesitate to contact us. Respectfully submitted, GEOTECH CONSULTANTS, INC. g• AfC �Q of wASy��rir / x N 2 W wa ��E SOON T F E z i7 47 EXPIRES 4 11 , Marc R. McGinnis, P.E. Associate James R. Finley, Jr., P.E. Principal MRM/JRF:ant cc: Lance Mueller & Associates - Mike Galbraith GEOTECII CONSULTANTS,INC. + T AV Ir SV 1-----.,-_-----_ - i to Tn... YS `� r�.lr�' w IlPill G N I MCLI. W :Y - ' "r ,q.Ir�. A� ;•01 i r1't}! E R4E \H an "° `Y 'W _ N` - _ C ' R5Ei do y r S IICG; AY SY SIRECA r z r°+rafr.• ,!ti r sJ,•.'� l +f r 1 �y 11 x AV SW ate• L ND V ti AY SY vy, n k•Yf { 1+� .! wu YI Wr i -!Y nv 011 19 1'AIU ! hr �S AY rS4 [la. 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PROPOSED I I BUILDING I B-2 o SW j3kb STREET S�r'O LEGEND: APPROXMATE BORING LOCATIONS. SITE EXPLORATION PLAN GEOTECH BETWEEN SW GRADY WAY CONSULTANTS & SW 13th STREET RENTON, WA JaD No.e Doe: Plole� 9A0 0 FEB 1997. 2 Go`arcs ��°Y,¢s�o°� BORING . 1 USCS Description Sod over: Brown, slightly silty SAND, fine- to medium-grained, moist,---- sP ; loose to medium-dense S41 5 I -becomes less silty, very gravelly, medium-dense 1 48 10 - -becomes saturated 2 42 ' grades to coarser grained sand and gravel S 15 P 3 26 Ni :Z' 20 4 22 �I -becomes gray, slightly silty, dense 25 5 54 s Sfl 30 GP 6 74 35 61 Brownish gray, gravelly, slightly silty to silty SAND, very moist, dense SP SM 40 'Pest boring 1 is continued on the next page. TEST BORING LOG GEOTECH BETWEEN SW GRADY WAY COYSUI,'r:W'fS,INC. & SW 13th STREET RENTON, WA Job No: Date: Logged by: Plate: 97020 FEB 1997 JHS BORING 1 CONTINUED USCS Description 8 76. _ - - yYY.} as 9 26 r 3 +�a so 10 37 I srez ss 11 33 x 60 12 12 ' ntt Gray, slightly sandy, clayey SILT, wet, medium-stiff 65 Test boring was terminated at 61.5 feet below grade on 1/23/97. Groundwater seepage was encountered at 9 feet during drilling. TEST BORING LOG GEOTECH BETWEEN SW GRADY WAY SW 13th STREET Coxsut,rnrv�rs,INC.tNc I RENTON, WA Job No: Date: Logged b�y: Plate: 97020 FEB 1997 JHS l 4 o�°����Qe, o}aSt400� BORING 2 4'o G° S° �� Q° USCS Description Sod Brown, silty SAND, fine-grained with occasional gravel, sM (possible fill) 5L grades to sandy SILT 1 8 IL Black,peaty SILT, very moist, medium-stiffto 2 32 Fs-p-j Brown, coarse-grained SAND and GRAVEL, saturated, GP , medium-dense r 15 3 14 I = Gray SAND, fine- to medium-grained, saturated, medium-dense Sp�- 4 20 ' nit Brown, low plasticity SILT with peaty inclusions and occasional SAND, very moist, medium-stiff 25 s I Gray SAND, fine- to medium-grained, saturated, medium-dense 5 48 InIX with brown silt lenses -becomes coarse-grained with gravel, dense 30 6 51 SP GPI_ 35 7 82 •aF4_EyP�.. 4o s Test boring 2 is continued on the next page. . TEST BORING LOG GEOTECH BETWEEN SW GRADY WAY AI# CONSULTANTS,INC. & SW 13th STREET 4, RENTON, WA Job No; ]Dfite: •- Logged by: Plate: 97020 FEB7997 JNS 5 i e` �11 BORING 2 CONTINUED Sad 4%, USCS Description 8 50/4" 3 " X 5 Y 9 49 ' sP GP 10 '? 10 50/4" I with traces of wood fibers Gray, silty SAND, fine- to medium-grained, wet, medium-dense is 11 24 I smt 20 12 31 25 Test boring was terminated at 61.5 feet below grade on 1/23/97. Groundwater seepage was encountered at 10 feet during drilling. 30 35 40 TEST BORING LOG GEOTECH BETWEEN SW GRADY WAY CONSUL'rANPS,INC. & SW 13th STREET RENTON, WA Job No: Date: Logged by: Plate: 97020 FEB 1997 JHS 6 Slope backlill away from foundation. TIGHTLINE ROOF DRAIN Do not connect to fooling drain. BACKF/L L See text for VAPOR BARRIER requirements, SLAB .�— WASHED ROCK ° " ^; `" — c FREE-DRAINING NONWOVEN GEOTEXT/LE SAND/GRAVEL FILTER FABRIC 4 PERFORATED HARD PVC PIPE Invert a/ least as low as fooling and/or crow/ space. Slope to drain. Place weepholes downward. FOOTING DRAIN DETAIL GEOTECH BETWEEN SW GRADY WAY CONSULTANTS & SW 13th STREET RENTON, WA J°D N°J ao/N Sto/e+ P/o/r 97020 FEB 1997 4 T.S. VII. Basin and Community Planning Areas N/A AH. Other Pea o1j s N/A IX. Erosion - Sedimentation Control Design The erosion control calculations have been included in this section. PACIFIC ENOINEERINQ �ESICN INC. JO8 aoWL ) 5"'Kl- CIVIL ENGINEERING AND PLANNING CONSULTANTS SHEET NO OF CALCULATED BY DATE S�QIM�n7 �pnr7 51ZIrtic�' }24 Gl Crc :z 3,8G CFs� � SA �$urcr'nGf r�v54� _Z,X GC.z /D',Q.o0 �16 .�2 . ZOS�o sr-/C�rs _...... , .... . Sit shy LR✓Srrt p, r� , `_ IQ .y v 2.03 Gres f� :3a Qsr� naT� = ISh '... 21552 .... SPILII,-A`y wt�=2� IpDy2 nry = 3, Sc7 GFS �- cQ'i0o/C3 :Z1 x ��3/z�) �.Z,4 x, �IZ) _.�O t .t .. Or nr.(LI6_ 021,rI6r 7s4 h 2 .:9 c3 1o..L k3GooT .... 3°ISsG � Z x3 'Sl IG6,9) > 32. �� ... a�6Sr0..2 ¢ .. .24 x o DO°7 1 ..3 � .... G2��rG� ...... 130 ANDOVER PARK EAST, SUITE 300 SEATTLE, WASHINGTON 98188 (206) 431-7970 FAX:431-7975 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL FIGURE 4.4.7J RISER rNFLO1V CURVES Weir Flow Orifice Flow ----_ 100 ;7 — 36 t — 33 44 30 c - — 27 o — w — — 24 — t U a 21 u � 18 ei a — 6 d — 15 10 - -. 10 0.1 -- 3s. 1.0 L 5 a 5 C 1 k 10.0 HEAD IN FEET (measured from crest of riser) SOURCE: USDA•SCS OMEn = 9.739 DHn 00RIFEE = 3.782 WWI O in cls. D and H in feel 4.4.E-10 Il�o KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL i o Design of emergency overflow spillways require the analysis of a broad-crested trapezoidal weir. The following weir section is required for the emergency overflow spillway: FICURE4.4.4A WEIR SECTION FOR EMERGENCY OVERFLOW SPILLWAY SMEP-l�Ee1G,V oJEe,pLoW � b IINH• I. � � �P�ap peY ablc.g.3.bq o The emergency overflow spillway weir section shall be designed to pass the 100-year, 24-hour design storm event for developed conditions as follows: For this weir, Om = C (2g)' 2(2/3LW2 + 6/15 Tan&H'rz) using C = 0.6 (discharge coefficient); Tan - 3 (for 3:1 slopes); = 72°: The equation becomes: Q,. - 3.21 (LH'n + To find width L. the equation is rearranged to use the computed Q,. (peak flow for the 100-year, 24- hour design storm) and trial values of H (0.2 feet minimum). L = (Q,w/(3.21H'/z)) - (2.41-1); 6 feet minimum Access/Maintenance: Pond access tracts and roads are required when ponds do not abut public right-of- way. Road(s) shall provide access to the control structure and along side(s) of the pond as necessary for vehicular maintenance. For ponds with bottom widths of 15 feet or more, the access road shall extend to the pond bottom and an access pad provided to facilitate cleaning. For ponds less than 15 feet In width, an access road must extend along one side. 0 Roads and pads shall meet the following criteria: - Maximum Grade: 15% to control structure, 20% Into pond. - Provide 40' minimum outside turning radius on the access road to the control structure and the turnaround to the pond bottom. - Fence gates shall be provided for access roads at straight sections of road. - Access roads shall be 15' in width on curves and 12' on straight sections. - Access pads shall be 15' in width and 25' in length. 0 Manhole and catch basin lids must be at either edge of an access road or pad and be at least three feet from a property line. o Access shall be limited by a double-posted gate if a fence Is required or by bollards. Bollards shall consist of two fixed bollards on each side of the access road and two removable boifards equally located between the fixed bollards. !^ o Access roads and pads shall be constructed by utilizing one of the following techniques: 4AA-2 1/90 KING COUNTY , WASHINGTON , SURFACE WATER DESIGN MANUAL Design and Installation Specifications i 1. See Figures 5.4.5.2A, 5.4.5.2B, and 5.4.5.2C for details. 2. If permanent runoff control facilities are part of the project, they should be used for sediment retention (see introduction to this section). Determining Pond Geometry 1. Obtain the discharge from the hydrologic calculations of the peak flow for the 2-year, 24- hour developed storm (Q ), The 10-year, 24-hour design storm shall be used if the project size, expected timing anyduration of construction, or downstream conditions warrant a higher level of protection. If no hydrologic analysis is required, the rational method may be used (Section 4.3.3). 2. Determine the required surface area at the top of the riser pipe with the equation: SA =2 x Q2/0.00096 or 2080 square feet per cfs of inflow See Section 5.4.5.1 for more information on the derivation of the surface area calculation. 3. The basic geometry of the pond can now be determined using the following design criteria: • Required surface area at top of riser. • Minimum 3.5' depth from top of riser to bottom of pond. • Maximum 3:1 interior side slopes and maximum 2:1 exterior slopes. The interior slopes can be increased to a maximum of 2:1 if fencing is provided at or above the maximum water surface. • One foot of freeboard between the top of the riser and the crest of the emergency spillway. (^ Flat-bottomed. • Minimum one foot deep spillway. • Length to width ratio between 3:1 and 6:1. Sizing of Discharge Mechanisms Principal Spillway Determine the required diameter for the principal spillway (riser pipe). The diameter shall be the minimum necessary to pass the pre-developed 10-year, 24-hour design storm (Qto). Use Figure 4.4.71 to determine this diameter ( h = one foot). Note that a permanent control structure may be used instead of a temporary riser. Emergency Overflow Spillway Determine the required size and design of the emergency overflow spillway for the 100-year, 24-hour developed design storm using the procedure in Section 4.4.4 (Emergency Overflow Spillway subsection). Dewatering Orifice Use the following steps to determine the size of the dewatering orifice: 1. Determine the size of the dewatering orifice(s) (minimum 1" diameter) using a modified version of the discharge equation for a vertical orifice and a basic equation for the area of a circular orifice. First, determine the required area of the orifice with the following equation: _ A.(2h)" A° 10.6x3600Tgo.s where: Ao = orifice area (square feet) As = pond surface area (square feet) h = head of water above orifice (height of riser in feet) 166 5.4.5.2-2 11194 KING COUNTY , WASHINGTON , SURFACE WATER DESIGN MANUAL T = dewatering time (24 hours) g . acceleration of gravity (32.2 feet/second2) 2. Convert the required surface area to the required diameter of the orifice: The orifice diameter (D) in inches is: D = 24 xA4 4 3. The vertical, perforated tubing connected to the dewatering orifice must be at least 2 inches larger in diameter than the orifice to improve flow characteristics. The size and number of performations in the tubing should be large enough so that the tubing does not restrict flow. The flow rate should be controlled by the orifice. Additional Design Specifications Pond Divider The pond shall be divided into two roughly equal volume cells by a permeable divider that will reduce turbulence while allowing movement of water between cells. The divider shall be at least one-half the height of the riser and a minimum of 1 foot below the top of the riser. Wire- backed, 2-3 feet high, extra strength filter fabric (Section 5.4.3.1) supported by treated 4'x4"s can be used as a divider. Alternatively, staked straw bales wrapped with filter fabric may be used. If the pond is more than 6 feet deep, a different mechanism must be proposed. A riprap embankment is one acceptable method of separation for deeper ponds. Other designs that satisfy the intent of this provision are allowed as long as the divider is permeable, structurally sound, and designed to prevent erosion under or around the barrier. Depth Gauge To aid in determining sediment depth, one-foot intervals shall be prominently marked on the riser. Embankment If an embankment of more than 6 feet is proposed, the pond must comply with the criteria for Berm Embankment/Slope Stabilization in Section 4.4.4. FIGURE 5.4.5.2A SEDIMENT POND PLAN VIEW KEY OmOER INTO SLOPE l0 PREVENT FLOW AROVNO SOCS THE POND LENGTH SHA1l BE D TD 6 WE$ 1NE UUNVU POND YROIN EVERGCNCY ONERFLOW JSPILLWAY O / POND ICIWIII INFIO W SLT FENCE OR EOUNµCNT DMOER RISER PIPE OISCI CE TO STABa11ED COINCYANCE. OUTLET OR LEVEL SPREADER NOTE: PO110 MAY BE FORMED BY BERM CA By PM1V1 OR COMPLETE E%CAVAiMN kd' 5.4.5.2-3 11194 KING COUNTY , WASHINGTON , SURFACE WATER DESIGN MANUAL FIGURE 5.4.5.2E SEDIMENT POND CROSS-SECTION I � RISER PIPE CREST Of 6• U.N. 'MOTH (PRINCIPAL SPILLWAY) EMERGENCY SPILLWAY OPEN AT TOP WITH TRASH RACK -11IWII DEVICE PCR FIC. A.K,KE 1_ EMBANKMENT COMPACTED 95%. �l MIN.DCWATCRINC O 1' _ :. I• PERVIOUS MATERIALS SUCH AS I J -------� GRAVEL OR CLCAH SANO SHALL 1 (SCE RISER DETAIL) T _ _ NOf BE USED. r � i ------------------- r i 'L—II II III TI OEWAIERINC i.Ll -"'-'I 11I-II III _I I- WIRC-BACKED SILL rCNCC. ORIFICE }II fLI1' II STAKED HAYBALES WRAPPED 111 I I II I I C J "- SRN FILTER rABRIC. OR DISCHARGE 70 STABILIZED COUNµCNT OMDCR CONCRETE BASE CONVEYANCE. OUTLET OR (SEE RISER OCTAL) LEVEL SPRCAOCR FIGURE 5.4.5.2C SEDIMENT POND RISER DETAIL POLYEIHYIENE CAP PROYIOC ADEQUATE SIRAPPINC PERFORATCO POLYETHYLENC DRANACC 1U61NC• DMMEIER - CORRUCATEO MIN• 0' LARGER LIAH - METAL RISER OEWAIERING ORIFICE. TUBING SHKL COMPLY _ WITH ASIL r6E7 AND 3.5' N. AASHTO M294. WAICRIICM DENATERNC ORIFICE, SCMCOULC _ COUPLNC TACK WELD TO STEEL STUD MIN. _ OUMCICR AS PER CALCULATIONS - ��I jlllll 1 C' UK AND WIRLICAY MY, METµ 5UKE5 CONCRETE BASE MNT rLOlATIOmBE 0 TO �+-]K R1511% DIA MIN.--rl Maintenance Standards 1. Sediment shall be removed from the pond when it reaches 1 foot in depth. 2. Any damage to the pond embankments or slopes shall be repaired. r �P 5.4.5.24 11/94 X. Bond Quantity Work Sheet Retention/Detention Facility Summary Sheet and Sketch and Declaration of Covenant These items have been included in this section.