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SWP272710 (2)
i RE NOV 2 71995 ;sA s, Y_ CITY OF RENTON OAKESDALE AVENUE S.W. S.W. 16TH TO S.W. 31ST STREET e 4 �I K C.• WATERWAYS & r HYDROLOGICAL SYSTEMS TECHNICAL REPORT .. Prepared for 3 �f, M PLANNING/BUILDING/PUBLIC WORKS DEPARTMENT ti 200 Mill Avenue South Renton, WA 98055 a r ro, yy REVIEW DRAFT ,r NOVEMBER 21, 1995 �X F r n� "wZ y$. y �rR s, 4.y a �I S n•� k 1� Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report ' Table of Contents 1. INTRODUCTION.........................................................................................................1 ' 1.1 Purpose....................................................................................................................................................... 1 ' 1.2 Project Description.................................................................................................................................... 1 1.2.1 No-Action Alternative........................................................................................................................... 1 ' 1.2.2 Alternative A........................................................................................................................................ 1 1.2.3 Alternative C........................................................................................................................................2 2. STUDIES AND COORDINATION................................................................................2 3. AFFECTED ENVIRONMENT......................................................................................3 ' 3.1 Surface Water and Flooding......................................................................................................................3 3.1.1 Surface Water....................................................................................................................................... 3 ' 3.1.2 Flooding...............................................................................................................................................4 3.2 Groundwater..............................................................................................................................................4 3.3 Site Drainage Systems................................................................................................................................4 3.4 Utilities.......................................................................................................................................................5 ' 3.4.1 Storm Sewer (Figure 6)........................................................................................................................ 5 ' 3.4.2 Sanitary Sewer (Figure 7)....................................................................................................................6 3.4.3 Domestic Water Supply (Figure 8).......................................................................................................6 ' 3.4.4 Electrical Power (Figure 9)..................................................................................................................7 3.4.5 Natural Gas (Figure 10)....................................................................................................................... 7 I:\15203\reports\eis\htdrtech.doc 11/21/95: 1:38 PM iv City of Renton Oakesdale Avenue S.W. ' 4. IMPACTS.....................................................................................................................7 4.1 Surface Water and Flooding......................................................................................................................7 4.1.1 Surface Water.......................................................................................................................................7 ' 4.1.2 Flooding...............................................................................................................................................7 4.2 Groundwater..............................................................................................................................................8 4.3 Site Drainage Systems................................................................................................................................8 4.3.1 No-Action Alternative...........................................................................................................................9 , 4.3.2 Alternative A........................................................................................................................................9 4.3.3 Alternative C...................................................................................................................................... 12 4.4 Utility Conflicts........................................................................................................................................ 13 4.4.1 Storm Sewer (Figure 6)...................................................................................................................... 13 4.4.2 Sanitary Sewer (Figure 7 ........................................................... 13 4.4.3 Domestic Water Supply (Figure 8)..................................................................................................... 13 , 4.4.4 Electrical Power (Figure 9)................................................................................................................ 13 4.4.5 Natural Gas (Figure 10)..................................................................................................................... 13 , 4.5 Impacts of Construction........................................................................................................................... 13 ' 4.6 Cumulative Impacts................................................................................................................................. 14 ' 5. MITIGATION..............................................................................................................14 ' 6. REFERENCES..........................................................................................................27 ' v Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report List of Figures Figure1 Vicinity Map.............................................................................................................................I ' Figure 2 Project Alternatives.................................................................................................................16 Figure3 FEMA Floodways................................................................................................................... 17 ' Figure 4 Drainage Subareas -Alternative A........................................................................................... 18 ' Figure 5 Drainage Subareas -Alternative C...........................................................................................19 Figure 6 Storm Drainage Systems .........................................................................................................20 Figure7 Sanitary Sewers ......................................................................................................................21 Figure8 Water Supply..........................................................................................................................22 Figure9 Electrical Power......................................................................................................................23 Figure10 Natural Gas...........................................................................................................................24 Figure 11 Alternative A Fill &Excavation Areas....................................................................................25 ' Figure 12 Alternative C Fill&Excavation Areas....................................................................................26 List of Tables ' Table 1 Existing Drainage Subareas........................................................................................................6 Table 2 100-Year Floodway Storage Impact(Cubic Yards of Displacement)............................................8 Table 3 Impervious Surface Impacts (Acres)............................................................................ 1:\15203\reports\eis\htdrtech.doc 11121/95: 3:35 PM vi City of Renton Oakesdale Avenue S.W. ' 1 t 1 1 Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report ' 1 . Introduction sw Sun� �d Gre m �• Purpose T...... Oakesd Ra in Project This reports describes area hydrology 0g " s Q ' and impacts of construction and Tukwi Q operation of proposed alternatives for :s Oakesdale Avenue S.W. in the city of ��"�erei� a� Ren on Renton, Washington. This report is the technical document to support the Draft •J.._En ,67 Pro"ect Environmental Impact Statement. Strands sn,d swA,st Hydraulic design concepts presented in a this report will be developed in additional detail in the project design report and in swNtn t project final design. Water quality is not ....___._ P N discussed in this technical report. P SW 41st St O160th St gw ' 1.2 Project Description ent The City of Renton is proposing the 181 '67 phased construction of a new roadway 1# �� ' 1J4 112 link for Oakesdale Avenue S.W. The Mies 1 N one-mile long section of proposed road ' would connect to existing Oakesdale Avenue S.W. on the north at S.W. 16th Figure 1 Vicinity Map Street, and existing Oakesdale Avenue ' S.W. on the south at S.W. 31st Street. The City is anticipating a first phase of construction for a segment between S.W. 16th Street and S.W. 27th Street. The second construction phase, anticipated after year 2010, would extend south from S.W. 27th Street to S.W. 31st Street. North of S.W 16th Street, existing Oakesdale Avenue S.W. connects to a local arterial, Grady Way, and then to Monster Road and the regional arterial, Martin Luther King Junior Way (SR-900). Existing Oakesdale Avenue S.W. sou f its current cul-de-sac to us at S.W 31st Street is a five lane arterial to the Renton city limit at S.43rd Street. The route con iu s south into the ' City of Kent as 80th Avenue South to South 196th Street. Figure 1 shows the project vicinity and Figure 2 shows Oakesdale Avenue S.W. b3biqalternatives selected for environmental evaluation. 1.2.1 No-Action Alternative ' Under the No Action Alternative, Oakesdale Avenue S.W. would not be completed between S.W 16th and 31st Streets. The City of Renton would determine access and circulation requirements for properties abutting the proposed Oakesdale Avenue S.W. alignment. ' 1.2.2 Alternative A c This alignment is based on a location shown inpaster plan developed for the Boeing Company Longacres ' Office Park (Jones & Stokes Associates 1994). South of S.W. 16th Street, the alignment curves to the 1:115203\reports\eislhtdrtech.doc 11121/95: 1:38 PM 2 City of Renton Oakesdale Avenue S.W. ' southwest, crosses Springbrook Creek, and enters the Boeing Company Customer Service Training Center (CSTC) property. The alignment coincides with a section of CSTC circulation road, then curves to the ' southeast and leaves the CSTC area on a southerly bearing. The Phase 1 alignment terminates at S.W 27th Street while the Phase 2 alignment continues south from S.W. 27th Street, to the southern limits of the Boeing Longacres property. Between the CSTC development and S.W. 27th Street, the roadway could ' provide driveway access to future parking areas and building service roads located on presently undeveloped property to the east and west. Actual access points would be determined in future review of development proposals. At the southern limit of the Boeing property, the alignment shifts 45 feet to the east ' in order to meet existing Oakesdale Avenue S.W. at the S.W. 31st Street alignment. 1.2.3 Alternative C , This alternative's Phase 1 alignment continues south-southeast through Group Health Cooperative property east of Springbrook creek before crossing Springbrook Creek, continuing due south through CSTC property and south on the boundary between the Boeing Company Lonagacres Office Park site and ' Winmar Inc. property east of the former Longacres practice track. At the Seattle Water Department right- of-way,the alignment curves to the west and south to rejoin the Alternative A alignment north of S.W. 27th Street. The Phase 2 alignment is the same as Alternative A. I E 2. Studies and Coordination ftlAr, As described in Revised Code of Washington(RCW) 90.58,the State requires a permit for any "substantial fs r development" within 200 feet of its shorelines. Greek:--Subantial-deve,lepri3ent pririitsF are issued bat-the-.local_ cdictions and...�eyiewedT hv_�he �� �`ft. �MII r P� Washington State Department-of Ecotogy-(EcotoU). Aesirl, Vu air c,P.*e �., 4)e. ' As required by the Federal Flood Disaster Protection Act fofP19F73, all l?9al�uri�ic ionshha* regulations t/ovd regarding the construction, filling, grading, and alteratio�i e Trr adopted-specificProj t b alternatives would affee floodwayg 4X-c Ihan effort to continue the Soils Conservation Service (SCS) work that began in the IXOs, the f Rento-T-is-.dev_eloping current and future hydrology and hydraulic modeling for SprinybreakTreek. This SCS effort invoTv`es-several jurisdictions including the City of Kent, City o£-Tvcwila, King County, the King County Drainage Di King and the Green River fJwd-�ontrol Zone District. The City of , Renton is updating previous drainage plans ti5' with"the State Environmental Protection Act(SEPA) and to be consistent with current environmefifal concerns: - The_East Side Green River Watershed (ESGRW) Plan is an ongoing process which will require coordination between the-Oakesdale Avenue S.W. ' design and the City ofRenton through final design. Oakesdale Avenue S.W. drainage analyses ribed in this report_reflect current (October 1995) Renton models and proposed improvements for Springbrook T-lte-��t3�of Renton mod 1 fo and th,�t the existinu 100-ve�r_fr�P. ncc,_ _ lewer-thah--that depicted on the Federal"Emergency Management Agency(FEMA)-mapping----•"FNs-is a ' resrrlt--of-several contributing factors including channel-improvements, regional development;correeted- pump station capacity,.and use of a more_advanced modeling program. Continued modeling efforts are 3 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report underway for selection of future channel improvements that are expected to further lower the water surface ' ele�ie:3s: 5 ie�iq� of {4-e >.� Springbrook Creek is designated as 1(streams with flows greater than 2Q cu��wwic feet per second) Shor forth of S.W. 43rd Street. ��"` ° requires a.Shorel ne Substantial`Development Permit ' issued by the City of Renton, but Ecology has the power to deny a permit that has been approved by the City (R. J5askt4,941j. Both alternatives for Oakesdale Avenue S.W. propose new Springbrook Creek bridge crossings which therefore influence shorelines of the state. The City has' coordinated these ' Oakesdale Avenue S.W. improvements with Ecology. 1",7 ' The Washington State Department of Fish and Wildlife administers the Flydr ulic4I' -92LM AN p V=n=69r&Oiects within or affecting the ordinary high water mark or waters�o` [he Ifa e. "f'hi i wpf w. requires SEPA compliance. Both alternatives for Oakesdale Avenue S.W. propose new Springbrook Creek bridge crossings which would include construction within the ordinary high water channel area. The City ' r S has-coordinates these Oakesdale Avenue S.W. improvements with the Washington State Department of Fish and Wildlife. ' The-project.-mustcomply with local government flood plain_management relations administered by the City of Renton. Personal contacts with the Renton Storm Water Utility(January 1995)have resulted in the use of two flood plain studies. The more conservative, adopted FEMA 100-year event floodway would be ' used to compute compensatory floodway storage requirements. Any fill/embankment volume within the FEMA floodway would be equally compensated by excavation to ensure that there is no net loss of floodway storage. The City of Renton's more detailed and current East Side Green River Watershed model ' backwater profiles would be the basis for all other designs concerning Springbrook Creek. Wetlands are another significant factor along the Oakesdale Avenue S.W. corridor. The Springbrook Creek basin includes many low lands and pooling areas which influence the corridor. Sip" both the, City and, U-� Eor -of--Engineers reirie-w—and-appraved.-wetland--mitigation--designs, A Jurisdictional Wetland Determination report has bee r pared by $!igrp iro and Associ-a7�tes (draft March 1995). This--report t' S r el if 't,�s ''f q�-�gtats J�,+eers. � l � � (c. .� !¢ . ... � � �,.l %e ` s�,,:r � r�-t ury,S ✓1" a"V of e g -of W �p uposed.�ve laiid it sets e h o€t'lie eot idor Water qua'tity unpaets are not addressed in this technical report. - a eq �®r eA.,. ion-404-oF�, Vz� ter s isc ar the �"et'"'JS. Unit soeiatefl wetlands;- ape f Fwigitteers am4+PA. Dort f this 'e-----�-- .;".�. �S ter Quality Ce�rty,fication,that state and federal �/ ' /$ ✓r•,( �o.n Yir -1 .c. .e/r��. OPrw. I' .1,. x. /SyN fA water quality standards would not be violated flee Ecology S._I'S /S ' Lam/'/IF7 Cil+/un 1 3. Affected Environment c.ng�r�csr w,+i, - Mkt c Ste( 3.1 Surface Water and Flooding Gs c4d.*,,ti,sr.e ly 3.1.1 Surface Water Oat "veiuw-S,W,,.4mpravPmPnts- contained k-Creekuilmteily-sahare ro c ' Co*on-River drainage,-basin. The terrain^is generally flat with wetland areas along much of the project r� f i,e pro 1 r� 4✓ee� I:\15203Veports\eis\htdrtech.doc I J 1121/95: 1:38 PM 4 City of Renton Oakesdale Avenue S.W. , length. The alle s been the subject of an ongoing channel improvement program to resolve flooding roblemsas cY, •W ,,. „�VIS s��e�,..a.,...,., ) p ��. [J to tatPc e„n rtme .�.�gLle>xltla�rc_.S.Qil,.� CS Ia reen IUTd-f tme-system-wi&-flood gates--at the,Black, River cetrfltxerree - etrgl�-this pre=venired-Willey-fleeding-from.Grom-River backwater,flooding still occurred because flood waters-.could not be discharged. This condition-was-improved-mi the 1960s-and•497As•by-tvvu projmtg:---`f re'MUward , recluees-flood-levels at the..confluence-and the-- straction of theAlack Rivetattar?;chi C1 rge from,Springbrook--ereek-during-E'rnrerr River fiewd stages: AAditional-_-f ct-proteetion was-achieved through nereased ehannel-storage-eapaeity-ffen}-tom .BRP-g-to , Grady Way and box culverts at the Grady Way and Intersftte-40-5-or_o�..., Springbrook Creek is aracter�ed as ��$ poo habitat suitabilit�6entributing land use/of primarily commercial/industria ,/ phy —alfild M.—anty d'""Eir,0455w- d"-*t0h6&___=WA0 ' ch2sinaldove!3M=nts, mid beex►-the sti�h}ert_a£ tt mew p�'tsJects v� �icaa�e-F t �y� t e-of4 3e-$ULS-c 'veb step-ar '-we—e-ad" imtim-vaRcl The section of channel-fromthc-BRF Ria-S:W.-I,6th-StreethmHeen engineered to as as a-Riae€€storage-area, and-the City of Renton.is continuing designs for further-channel ' wii ening-to extend the channel's storage capacity up to S.W. 43rd Street. Study area habitat is presented in the Wildlife, Vegetation, and Fisheries Technical Report(draft September 1995). ( af- rA.c lam/ S1 91111e, V-cn. /J�CCinP�Cr� i-�Mfi S�/_ij� /�Q�C �P Il L' 7 k,-a In-4� in r� ✓��AA, V?/y /if/[# once /e ln�vs � ✓�/ies�►fj�l �u/ Gylici-t�f r./a� / 3.1.2 Floodi g �.,/ The Federal Emergency Management Agency (FEMA) has �- defined m inco orate much of the project area. Figure 3 shows the FEMA-desi ated/c , Aye , recurrent-floodinginclude s ct om.e€-S W a3ud�S#e@t--west of Sprftb�cae yJ -�as€V -Read north of S.W 43rd-Street, and S.W-41stStrect.. A-nalysis--af--conditions_contri4uteug_-to-floo&ng.4R-W. Beck 1991) concluded that Springbrook Creek high-water-surface elevations•resulW�in-redueed-eappoeity--in , stnnn.drainage-systms. The City of Renton-is in the process of determining floodway elevations in the project area. Initial results ' indicate that 100-year flood levels are lower than FEMA-published values as result of channel capacity wemg�ai�-Creeic-f B- �"I"I`ie�iTy`bf Renton-is plaming fu kamlel-ia�pravementsse -�strea�}o€S.W-.46&S;tfeet. ' 3.2 Groundwater Groundwater flows in the project vicinity were reported in the Lonagacres Office Park EIS and technical reports (Jones & Stokes Associates 1994) Additional groundwater measurements were made in early 1995 in several of the boring made for soils investigations (Woodward Clyde 1995). The Oakesc Ay corridor ' area does not contain a principal sole source aquifer. The City of Renton obtains Cedar RiN; yI cquifer water from five wells about one-mile northeast of the project area. The closest private well is about 0.4 miles east of the site. ' 3.3 9Pi#,6 Drainage gars ails o,a,5J acX The existing site varies through the Oakesdale Avenue S.W. corridor. Most of the Longacres Park soil borings indicate that the upper soil layers consist of sandy silts, but there is no mention of Soil Conservation Service (SCS) hydrologic soil group in the geotechnical report texts (Woodward- Clyde ' 5 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report 1995; Geo Engineers, 1991). For theprelifnmary design, group D soils were assumed since this is 4/ -L 541cf 4WA ' �nsistent with designs on the Longacr+ite. 4,6p 516-4 wtJ-.ffWA,'a2 „rur- sous ^i c 7 APE p Is, Tv �l 9Enr, wf0 Htar, Saw �n��crt,raslr/row ;p� There are several existing drainage systems in the project area. These include culverts between existing ,4c.0 �?� ' IS wetlands and storm sewer systems from existing roadways or adjacent developments. Existing City,e �ystems include drainage for the existing Oakesdale Avenue S.W. v�.north of S.W. 34th Street, a��,,,r 51 cross culvert under Longacres Parkwa� and storm sewer systems for S.W. 27th Street and the S.W. 16th 61zbu+I ' Oil Stree . The Boeing Company CSTC and proposed Longacres Office k"A--1---" 15 Park sites include drainage f tore�,tt}},,at convey runoff in an easterly direction toward Springbrook Creek. t� Systems on thekonga6res^ ite in`cIufle one 12-inch pipe at the south end of the old practice track and two aISO ' �P 12-inch pipes crossing at the north end. These pipes discharge into drainage ditches within the practice track which drain via a 36-inch corrrugated e pi (C P) into S ringbrook Creek. On the CSTC site, U r° �m ryes f� n s , 4 4 + v \t—a 48-inch culvk. fee " br �. Suet. 7�iis culvert includes a cpntfei structure at (19 1fs 111t inlet f bArwetland/detption pond sys em. -�. c..nAn1 S�a/ro..wtef /� !GS('': �'iow. � CSTc�, 11 tt �nGCrl�l+a'� J¢O�•►•w�t�-�Sy'' 4 P-P vC�•c. Pc1 �f✓ ��SEE �r Detailed stormwater design has not been developed for the Boeing Longacres Office«}.,Park. retailed -for erties_. #iS Savfi�,, wdt'4akesdale Avenue&.W:-,align nts-worth}oecur atthc-tmc ufcnvirannnmtRl -ether.deuelopm� V fff•speeificpna ects. �.�►rkt r 1 F-¢ /'I�+- e e-w-� d F mod. Figures 4 and 5 show the drainage areasaffected-by project alternatives. marble 1�hIowJ(the 'impervious and pervious surface areas within each surface drainage area. System�A/B onWii re S4 AM/N on Figure 5 are identical. 7 >µ ✓ its UN �/G cf ..o,,.o S A lug f-mr 3.4 Utilities p_+u ,/ ,� ' Utilities are based on those presented in the Longacres Office Park Draft Environmental Impact Statement (Jones & Stokes Associates 1994), various design drawings provided by the City, and field surveys ' conducted in February and March 1995. Utilities crossings that could conflict with proposed storm sewer systems are described in this section. ' 3.4.1 Storm Sewer (F1 ur 6) ; F +� ,'S r w n (4,4 t Ther ark five existing storm s wer syste at influence the project area. An existing 48-inch culvert connects the City of Renton wetlan F, G Shapiro and Associates 1993 and 1995 . e Boein ' Company Longacres Office Park site inc u es drainage features at coucey--runoff in an easterly direction qr f toward Springbrook Creek and primarily influence Alternative Aese systems include one 12-inch pipe �s at the south end of the old practice track and two 12-inch pipes crossing at the north end. The south pipe sstt�w�'"r �y►S conveys flow intercepted by a catchbasin on the west side of the former practice track. There is a 48-inch s � ' culvert crossing.20- feet north of S.W. 19th Street. This culvert includes a control structure at the m et .for Boeing CSTC wetland/detention pond system. o� rJ� M s►�e�" City of Renton storm sewer systems also exist in the project area. One system outlets to wetland F at the ' /�^ tiCAIrs' existing Oakesdale Avenue S.W. cul-de-sac (south end of the project). A S.W. 27th Street system begins Ii*Poc.-s ' at the future Oakesdale Avenue S.W. intersection and conveys runoff to the east. Also, a S.W. 16th Street system outfalls into Springbrook Creek from the east. These public storm sewer systems are the only systems to be modified by the project. All changes ensure that existing conditions are not significantly ' altered. I:\15203\reports\eis\htdrtech.doc 1121/95: 1:38 PM 6 City of Renton Oakesdale Avenue S.W. ' Table 1 Existing Drainage Subareas Area(Acres) ' Subarea Figure Imp. Perv. Total Existing Condition A & B 4 2.21 2.27 4.48 Wetla4ponds between S.W. 31st and 27th Streets. Asphalt ' (M & N) and gravel roadways, dense brush and trees. Sheet flows generally to the southeast to a low area. C 4 0.48 1.73 2.21 Gravel roadway and parking, grass, dense brush and trees. ' Sheet flows along a gentle slope northeast along a depression followi ti%P-.1 channel alignment. R a )f D & E 4 1.11 4.44 5.55 D- Gravel roadway and grass. Sheet flows travel along a flat path into the adjacent tributary to Springbrook Creek. E-Area includes gravel and asphalt roadways and grass. ' Sheet flows travel along a gentle sloping path into the adjacent constructed wetland. F 5 0.00 0.94 0.94 Areas include grass and dense brush and trees. Sheet flows ' travel along a circuitous flat path to outfall into Springbrook Creek. P 5 0.24 2.86 3.10 Gravel roadway and parking, grass, dense brush and trees. ' Sheet flows along a gentle slope northeast along a depression following,,,�P-1 channel alignment. R 5 0.00 3.54 3.54 Areas include"grass, brush, and trees. Sheet flows travel along a gentle sloping path into the adjacent constructed , wetland, or along a flat path into the adjacent tributary to Springbrook Creek. S 5 0.00 2.09 2.09 Areas include grass and dense brush and trees. Sheet flows ' travel along a circuitous flat path to outfall into Springbrook Creek. Source: HNTB,1995. 6�.vl G a.,-e Uh 3.4.2 Sanitary Sewer (Figure 7) d' °-$� - T�ijiS Metro has recently constructed a 108-inch diameter reliever trunk that pafallels a 72-inch diameter trunk in the proposed Oakesdale Avenue S.W. right-of-way and existing Longacres Parkway on Boeing Company property. The as-built drawings show control density fill waterstops which protect the ground water from ' an induced flow along the gravel backfill. These appear at even intervals along the 108-inch pipe. An existing 12-inch pipe connects to the 72-inch pipe at Alternative A station 36+00. This pipe was not located by the survey, but Metro as-built plans show this pipe to be very deep. �S 3.4.3 Domestic Water Supply (Figure 8) `'^"k_A H.'. /'G-1A ,oS There are two water suppl f aet res in the Oakesdale Avenue S.W. corridor. A City of Renton municipals ' 12-inch line follows a M rr'aiiWi alignment from S.W. 27th Street to S.W. 16th Street. This system includes I ' ' fire hydrants and service connections to adjacent properties. atom The City of Seattle Water Department maintains the 60-inch Cedar River Pipeline (No. 4) crossing the ' Oakesdale Avenue S.W. corridor. This water line is an obstruction to subsurface storm water conveyance. 7 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report 3.4.4 Electrical Power (Figure 9) Puget Sound Power&Lighting(PSP&L)has several lines in the project area. There is one 115kV line that runs the length of the Oakesdale Avenue S.W. corridor and three lines that cross. One line crosses with the large Cedar River water pipeline. Two lines cross in the vicinity of the Washington Thoroughbred Breeders Association building. D e Ian-es 3.4.5 NoUtr'f�tsr/(Figure 10) fic.,�"`has two�iipanes that cross the alignments approximately 550 feet north of S.W. 27th Street. These include a 14-inch and a 12-inch pipeline. WA fq'f 4. Impacts 4.1 Surface Water and Flooding Each of the proposed alternatives include two bridge crossings . The south bridge site is common to both Alternatives A and C. The bridge stru9ture,for this site would be designed to avoid . r n 1 e' W-LZ t4-- or minimize impacts to the City of Renton wetland7re "J .n'f`Thi'sbridge woufcf be .independent-of S brook-Cree . Standing water is common in this location but S /01-K Pig g Springbrook Creek � a✓e.� �s - out-of-bank flowrates and headlosses are negligible at the south bridge. deR'...f The north bride on either the Alternative A or C alignment,bridge, would cross the Boeing constructed wetlands ' and Springbrook Creek. None of the structure types would require bridge column or pier construction within the ordinary high water level,�p to two bridge columns/piers would be located within the 1 Op-year rn.ja, 8-1J,-7 flood-a-c alongSpringbrook Creek and a third column/ ier would be located in the 100- ear flo �`=P y oclPa�ea in ' the constructed wetland on Boeing CSTC property south of Springbrook Creeak.��5h the xce�tion o/fjthe��� columns/piers, there would be no encroachment within the 100-year flood elevation. Boh aternaies have a high angle of skew between the roadway and channel centerlines. iers/columns would not be parallel to the creek and could constrict channel flows, c4..1e43 No-e-4 ip"h• c ke,f Ae 4A" Springbrook Creek ehw=n storage vo�lume has a direct influence on the attenuation of steRijjunoff through the valley. Storage loss could result in higher peak runoff rates and more flooding during the 100- ' year frequency design storm. These extreme flood conditions are also sensitive lobmodifications to sub-drainage areas. When#ha storm ��tr r ,1 sewer, no r convey the flood water�,a overland flow chi tic become5impor o mair #laws CM M.- d Ow 5. e s r �. . 11t't'N&rc� annel-va�y.ybake^ dale Avenue S.W. would be built on low embankments which would alter h these existing sheet flow p tt-rns. This `"ws restrict the overland flows or alter the existing pattern" toward an alternate path. S ,L' V ant, Nod ' V-'zheck� In ar aS at /G pf C? currently contribute runoff to th r5iadway corridor, future development of adjacent properties would be required to restrict 10-year frequency design storm runoff to that of the existing conditions. Runoff from e-Adat ,�h � � C_tnr,�z�to✓� 44 ItV �owha�/tlx,. o•�at,f F�.�s f-T -cal rd� 1:1152o3\reports\eis\htdrtech.doc 11/21/95: 1:38PM 8 City of Renton Oakesdale Avenue S.W. ' cYowr�ctr� larger (less frequent) storm events must be accommodated by l .,. nverl flnw patterns. ' a M,nr,nUm The south bridge structure( 1migs And C)would l�e�designed to provid one foot clearance over the < �rn .woc 100-year flood elevation �br►dge structures ove"t�'Springbrook Creek would be designed to provide a minimum of/3 foot clearance over the 100-year flood elevation. GS J eA-4 the "—CC� , � �Od?.{� ./,i n� 'N w ('/" ,G �v./a ,F�oud ,^^s! hC Gn y P�n34�� �j �Q e�.G6 tla�hi►. Preliminary estimates es of fill locations and quantities in the VEMA 100-year flood plan and below the 100- year flood level are 8,300 cubic yard for Alternative A and 12,300 cubic yards for Alternative C. Table 2 compares floodw&ll impacts. Figures 11 and 12 illustrate the location of fill and dredge activities for 6F each of the alternatives. 'Cir„. Table 2 100-Yea*loodl ay Storage Impact(Cubic Yards of Displacement) A r Alt. A Alt. C 100-yeaAooS4 fill (impact) 8,300 12,300 Stormwater detention/treatment/conveyance -3,940 -3,940 ' Longacres Parkway removal -4,200 -4,200 Storage deficit 160 4,160 ' 4.2 Groundwater e�r our ' Increased impervious area wouk Jmact subsurface hydrolo and reduce groundwater recharge. This would occur through two mechanisms: new impervious areas would replace existing gravel and prairie ground cover and roadway embankment would consolidate supporting soils. Alternative A is anticipated to add 7.6 acres of impervious surface to 3.8 acres existing in its alignment. Alternative C would add 7.9 ' acres of impervious surface to the 2.5 acres existing in its alignment. 4.3 Site Drainage Systems ' The flat topography and the moderately slow permeability of the project area suggest that localized surface drainage would be a major design consid ration. Introducing impervious surfaces te-a-prarticatm-urea-has ' the impact of increasing the runoff rate�re ative to that of the existing conditions. e exceeds- inundated: Flooding; erosiea,�accretion-(ground--build-rip)-v mid be-the-rests}t--E-vm-4Uinu atie pfeNi €er ' (i.e. runoff is-controlled..by.engineered,drainage-€eatures},-water--that✓vveald-uortna113c be.absorb►ed.iato-the.- ground.is-conveyed-away from-the'`affedtdd'tiiea. Possible effects , include sharper, higher peak storm discharge SN this is not mi �� -t�►e 001 s 4 c quilib ium Would be Offiet as Peak r o� � 9 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report Operational impacts include those caused by the indirect effects of the constructed project. Improvements ' to the Oakesdale Avenue S.W. corridor would contribute to the overall development of the project area by proving the missing transportation link necessary for development of the adjacent properties. Development would further increase the conversion of absorptive ground to impervious surfaces. 4.3.1 No-Action Alternative The No-Action Alternative would not impact the existing drainage systems. 4.3.2 Alternative A 4 Need ,o �,,,,,, +'�, � f4a4 ai`eaa; The jurisdictional wetland determination(based on field visits in January 1995) notes several wetland areas that would be within the boundaries of this alternative. Wetlands A and B are located to the east of the old practice track outside the influence of this alternative. Wetlands C and D are located on the east side of the ' alignment in City of Renton property between the old practice track and S.W. 27th Street. These wetlands would be influenced bv proppsy stormwater treatment areas. Wetlands E and F are on the east side of the alignment 4 -City'oi�iwen �5p t a'nc roserve between S.W. 27th Street and a existing Oakesdale Avenue S.W. cul-de-sac. Road y embai orient areas would reduce the size of a Ian each end of the ' proposed bridge structure. Wetland G is on the west side of the alignment between tl&5�w I oug wm&-3ite-and the existing Oakesdale Avenue S.W. cul-de-sac. This wetland would increase in size ' where existing Longacres Parkway is removed in conjunction with the Oakesdale Avenue S.W. improvements. S°.51 f44&5t 4gA.I.S w1 .*_4, ' Additional wetlands thin the Boeing Longacres site were identified by their jurisdictional wetland a� determination in November and December 19,9_1,_.((Sb_apirn 19931 Two general wetland areas were identified: one comprising wetlands U, R, W, and 7 in ide to cold r e track; and the secoT�d wetland S to btM a a e i M o t�w.A .nr4 ' S the south of S.W. 27th Street GGQ�e* �&A nof'at ve). �nry wetYrana S9'is subject to impacts from the Oakesdale Avenue S.W. project. As for wetland G, its size would increase where existing Longacres 0 Parkway is removed in conjunction with the Oakesdale Avenue S.W. improvements. d y►V ssc 6- "�-' ?-.fP ' Future development of the project corridor will convert most of the affected area into impervious area with reduced time of concentration. Table 3 summarizes impervious surface impacts for both Alternatives A and C. Storm sewer systems will collect all impervious areas including sidewalks, roadways, and a grass ' strip behind the curb in some areas. Fill slopes outside the sidewalk will bn grass slopes with storm runoff flowing to adjacent properties. This bypass flow area will be i i a detention/retention pond design to ensure that the total impact is mitigated. For most systems, the time of concentration equals ' the King CountWninimum of 6.3 minutes.r, Alternative A divides the roadway corridor drainage into six separate systems. These systems relate to each sag (low point) in the vertical alignment which is located to prevent conflicts with the existing underground utilities. ' The future storm sewer systems are described as follows. System A: Oakesdale Avenue S.W. from the existing cul-de-sac (S.W 31st Street Alignment) to the ' high point of the future bridge over wetland F. The new pavement area would replace wetland(standing water)area, so there would be no increase in impervious area within this system. The new outfall would discharge to wetland F. The existing Oakesdale Avenue ux�Pr yc►q��� f r�.N,,,..�.d r aes�-,�.f�br. 1:1152031reporisleis111d,1ec1.doc 11/21/95: 1:38 PM 10 City of Renton Oakesdale Avenue S.W. ' Table 3 Impervious Surface Impacts(Acres) Existing Build Change ' Drainage System Imp. Perv. Total Imp. Perv. Total Imp. ' Alternative A A & B 2.21 2.27 4.48 3.81 0.67 4.48 1.60 C 0.48 1.73 2.21 1.95 0.26 2.21 1.47 ' D & E 1.11 4.44 5.55 4.83 0.72 5.55 3.72 F 0.00 0.94 0.94 0.77 0.17 0.94 0.77 ' Totals 3.80 9.38 13.18 11.36 1.82 13.18 7.56 Alternative C ' M & N 2.21 2.27 4.48 3.81 0.67 4.48 1.60 P 0.24 2.86 3.10 2.12 0.98 3.10 1.88 ' R 0.00 3.54 3.54 2.80 0.74 3.54 2.80 S 0.00 2.09 2.09 1.61 0.48 2.09 1.61 Totals 2.45 10.76 13.21 10.34 2.87 13.21 7.89 ' Imp. impervious surface area Gt/C t�-e ,in f�J4A r 'IrC(n 496(tS c(lrvb5/ or c. Perv. pervious surface area S.W. system would be F .-net-mvdifi' Gyf erg 4, a,A�� ��e,� fi�C r/yo v.s V�b��r System B: Oakesdale Avenue S.W. from the high point of the future bridge over wetland F to the first crest (high point) north of S.W. 27th Stet. To the south of S.W. 27th Street, the new ' pavement area replaces wetland areaAso tifie�ncrease infimpervious area occurs within the north part of the system. The new outfall would outlet under S.W. 27th Street to wetland F. (.� f 4o b System C: Oakesdale Avenue S.W. from the Sw pipeline crossings (first crest north of S.W. 27th Street) to the 60-inch, Seattle Water Department waterline crossing. The new outfall ' would discharp to Springbrook Creek. /0c-5;Gr)tic. ah.q k mo r yU a 'hf f ✓�-u F w.e..�t. ��r-�un t System D: Oakesdale Avenue S.W. from north of the 60-inch waterline crossing to just south of S.W. ' 19th Street. The new outfall could discharge to an adjacent detention/water quality facility and to the Springbrook Creek tributary at the north end of the old practice track. Since the Boeing Longacres Office Park master plan shows that the tribut� would be filled for a ' future parking lot, an alternate for this di outfall ceuid-was warranted. A combined outfall with System E is recommended as discussed below. System E: Oakesdale Avenue S.W. from just south of S.W. 19th Street to the crest of the future ' bridge over Springbrook Creek and including the S.W. 19th corridor east to the Winmar property line (east of former Longacres practice track). The subsurface system crosses over a 48-inch ductile iron culvert that serves the CSTC constructed wetland/detention ' ' 11 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report facility. This culvert would force a shows ment of the storm sewer trunkline to less than 2 feet clear below the pavemeni,1 e new outfall would outlet to an adjacent detention/water quality facility and eventually to Springbrook Creek. The proposed Oakesdale Avenue S.W. bridge structure would pass directly over a wetland outlet control ' structure. Since there would be inadequate clearance for it to remain, this control structure must be removed and replaced prior to the proposed bridge construction. 15 LijO/'J G4'6)A. sy.t'e4-5 P A.-O £ 4'4�0 5e nr.c4�t syyhtir6 Zor O MJ )i- L I,�►�`' System DE: Thi#m4ed fts the recommended alternateAte4ysWa-D. The Metro 108-inch sewer trunk I ,f plans (as-built) show two 12-inch CMP culverts crossing the Oakesdale Avenue corridor at station 37+20. The new outfall would outlet to an adjacent detention/water 46/1' quality facility and eventually to Springbrook Creek in the S.W. 19th Street alignment. ' System F: Oakesdale Avenue S.W. from the crest of the future bridge over Springbrook Creek to the centerline of S.W. 16th Street.rlw.a runoff would outlet to an adjacent detention/water quality facility, lie existing6t 'Sfi`eet system can not be used fornoutfall to ' s Springbrook Creek. Any existing off-site sheet flow from the adjacent undeveloped land would be allowed tenter the biofiltration swale on its way to the creek. ' Systems A and B both outlet to existing wetland areas. depmssiens-,-the-etbility-e€the-existing ecosystem.relies-en-the vellr af-wate>r disehafging fio#hemr. fie ' increased-impervious area and consolidation of the supporting soils could combine to increase the overland runoff_.a&upset-the ility-oftha-wcdaud. A detailed review of System B shows that it would cross three separate wetland ecosystems. The storm sewer would intercept runoff that contributes to wetlands D, E, ' and F. Impacts from these systems woul be insignificant due to the buffering effects of the wetlands. °� t1°ws 6IJ eel=.ti s OF S APP-4faak C rwf System B also directly impacts wetland D as the southwest corner is reconfigured as a stormwater treatment area. testing pool volume/elevation relationship of this.closed-&pmssion. le ' Systems C and DE � si�caut ixupacx ea- tlas----Their primary influence would be diversion of existmgYlLongacre Park site drainage through new, separate outfalls to Springbrook Creek. �tJ,U The new impervious area replaces gravel and grassy areas and would have shorter conveyance times and("',,,- 5N' ' increased peak discharge to the creek. Existing sheet flow crosses the Alternative A from west to east in Sd rar the area between thegge pipeline and the 60-inch waterline. Since most of the new roadway is on embankment, these existing sheet flow patterns would be diverted to the new sag location in System C. To ' the north of the 60-inch waterline, existing sheet flows are intercepted and conveyed by one of two pipes that cross the alignment to the old practice track ditches. Proposed embankment would cover the inlet _F.1-e-5h-j of both of these pipes and impact adjacent property unless these pipes are extended. ys—S tern C would M' '- directly impact wetland C as the northwest corner is reconfigured as a new stormwater treatment area. Ne, rtm4/n "' Creek-thFough the Longacres site drainage..o-a•r=w'yatW -W-12tkkreet. '✓►w4f J;A' up�„ba�Coi System F would collect runoff from an area that would have the greatest change in hydrologic conditions. tu This existing Group Health Cooperative land is undeveloped and consists of dense trees with underbrush and long travel times due to pooling and no defined outlet swale or channel. The new impervious area '�Ofk ' would have a much shorter conveyance time and higher peak discharge impact to Springbrook Creek. I:\15203\reports\eis\htdrtech.doc 11/21/95: 1:38 PM l 12 City of Renton Oakesdale Avenue S.W. , 4.3.3 Alternative CMG The drainage system for JhA alternative would be generally the same as for Alternative A. The result is ' five separate systems r to eAch sag (low point) in the vertical alignment. These future storm sewer systems are described as follows. System M: Oakesdale-Avenue-S, ing cu - e- bridge over wetland F --The new pavement area-replaces--wettand-(stwidit%-water area so there is_no_increase in impervious area-within this- system. The-,new-outfa*-wouIdl outlet to ' wetland F. The existing Oakesdale Avenue S:W.systenrwt�ild'bZ-relZS�te'd-to,-ensare-that the existing restricted outlet conditions-are-not-modified. ^s SH.nf4fr. /-\. System N: O the first , crest--north-of S.W: 27tl�St .-.To the sc>u of�S:W:2 flr� treet;-the -pain -area replaces "impervious," wetland area, so the increase.M.impervious,area_saccurs within the , north part of the system. The new outfall would-outlet TmderS.W.-29ttr Stteet ttrvxtFm& F.. l" ,ry? i �J�tnt ✓ . System P: Oakesdale Avenue S.W. from thegas crossings to the first crest to just north of ' S.W. 23rd Street. The new outfall would outlet to Springbrook Creek. gL,I%A r I L4410 y frteEtW�4.1r? System 2 Oakesdale Avenue S.W. from just north of S.W. 23rd Street to the crest of the future ' bridge over Springbrook Creek. The new outfall would outlet to an adjacent detention/water quality facility and eventually to Springbrook Creek. System ljf Oakesdale Avenue S.W. from the crest of the future bridge over Springbrook Creek to the ' centerline of S.W. 16th Street. The runoff would outlet to an adjacent detention/water �t quality facility, the existing S.W. 16th Street system can not be used for outfall to ' (,OVA Springbrook Creek. Any existing off-site sheet flow from the adjacent undeveloped land S� would be allowed to enter the biofiltration Swale on its way to the creek. Systems M and N are very similar to their corresponding systems on Alternative A, Systems A and B. The two alternatives differ only slightly at the north limit of these s stems; impacts to the loyal flow patterns and wetlands are the same. 71-- 96 rR,,i 01 K f* Systems P and would primarily influence diversion of the old practice track drainage throug new, separate outfalls to Springbrook Creek. The new impervious area replaces grassy areas and increase peak discharge to the creek. Since most of the new roadway is on embankment, the alternative's diagonal path ' across the practice track would stop existing ditch flow patterns. Flows from this southeast corner of the practice track could be diverted along the east edge of the new alignment north to combine with flows from ' the existing 36-inch culvert. This would provide a relatively economic solution to the impact to adjacent property without significant impact to the Springbrook Creek system. System P would directly impact wetland C as the northwest come is reconfigured for a new stormwater treatment area. No significant impact is anticipated as System7iverts existing flows upstream to a new outfall on Springbrook Creek ' just north of the 36-inch culvert(near S.W. 21st Street). System R impacts'are very similar to the corresponding systems on Alternative A, System F. The size of ' effected area is significantly larger compared to that of System F. 13 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report 4.4 Utility Conflicts ' This section describes potential conflicts between existing drainage systems and project construction, and between project drainage systems and existing project area utilities. ' 4.4.1 Storm Sewer (Figure 6) ' The Boeing Company wetland control structure is set directly in line with the Alternative A alignment. The bridge structure will pass directly over this control structure but with inadequate clearance for it to remain. This structure must be removed and replaced prior to the proposed bridge construction. ' All project storm sewer improvements would be designed to maintain the integrity of the existing Renton systems in S.W. 16th Street, S.W, 27th Street, and Oakesdale Avenue S.W. south of the S.W(D3 lst Street cul-de-sac. 4.4.2 Sanitary Sewer (Figure 7) Metro 108-inch and 72-inch trunk sewers have been avoided by aligninp the storm sewer along the west side of Alternative A ane eaa sou o do e r e �V O3r 2§t're`e'V �. Waterstops on the 108-inch ar pipe may extend up to conflict with Alternative A or C storm sewers. The final design effort should ensure that the integrity of these waterstops is maintained. There should be no conflict where thhe-~proposed Alternative A storm sewer crosses the 12-inch connection ' to the 72-inch trunk. 4uv,, f-+c t ur,�,�, cr(3 /al ccr..e�e y/ ,dr�-q,,t, t,t/�,�- 44n..0- C L`' ss iN Sc,,- 7-7 N? 4.4.3 Domestic Water Supply (Figure 8) ' The City of Renton 12-inch system could have conflicts with the storm sewer system which will require relocation of some water line segments. S ormw�ter runoff will cross the Seattle Water Department 60-inch r ru, ,, & ' system by gutter flow or by non-standard storm sewer pipes with less than 2-feet of clearance below the pavemene',' 'he 60-inch water pipeline will not be relocated by the proposed improvements ' 4.4.4 Electrical Power (Figure 9) NOW fr-, 1114 w e-,+ 17 1 The build alternative drainage systems will not directly affect the Puget Power overhead power lines. ' s 4.4.5 Gas pi4, al (Figure 10) U Neither of the two project alternatives will impact the �_y4s 12-inch and i -inch ' pipelines. 4.5 Impacts of Construction Temporary impacts would occur on the waterways and hydraulic systems during construction f Y Y Y $ o o the Oakesdale Avenue S.W. improvements. Existing drainage structures or flow pattern could be significantly ' altered by the contractor's operations. Constructing the roadway would require careful staging of earthwork, utility, and pavement to ensure that the waterways are protected from temporary impacts. Within the floodway, excavation volumes must equal or exceed fill volumes at all times. Existing sheet Nee- L � , SK,n. ��- UvMC I:\152031reports\eislhtdrtech.doc 1121/95: 1:38 PM ftr/l J XrUAre, wvtik IywK W��N G1�1 �iro Of�d�"�r'`r .AG6��tS'�INcl�w�6�G� 14 City of Renton Oakesdale Avenue S.W. ' flow patterns of adjacent properties should not be obstructed or impacted in any way. Modification of existing storm sewer and culvert features should be staged to ���f!a upstream impacts. ' Bridge construction would have the most direct influence on the existing waterways. Temporary stream diversions is preferable during construction of bents in Sprin brook Creek but may not be feasible due to ' the steep slopes and private runoff control structure, /� tv" ak GS�� ��u✓lc, mould 1 f�tc 4.6 Cumulative Impacts ' Completion of Oakesdale Avenue S.W. would provide access to abutting property, allowing development or redevelopment to occur on t* propertf 5Developme t would occur along the Phase 1 portion of the ' project (S.W 16th to 27th Streets). There would rW be 40YAIvelopment along the Phase 2 section which crosses between two wetlands, but the rate of development in the project area could be affected by improved access along the entire Oakesdale Avenue/80th Avenue South corridor. Project effects on project ' area development from a regional development perspective would generally be a redistribution of forecast growth, rather than an increase in projected growth. Changes in development rates or patterns would affect the amount of impervious ground cover, amount of groundwater recharge, and alterations in flow patterns and quantities. All development projects would be required to comply with federal, state and local requirements regulating 3k drainage andjloo4way impacts. 5. Mitigation Placement of fill and structures in the 100-year floodNyay would require replacement, one a one-to-one basis, of the lost flood storage. Approximately 4,000 cubic yards of storage would be replaced by the construction of detention ponds, biofiltration swales, and storm sewers (see Table 2). An additional 4,200 ' cubic yards of storage would be provided if existing Longacres Parkway embankment south of SW 27th U,, Street is removed. Another 160 cubic yards of storage would have to be provided for Alternative A and \k° 14,160 cubic yards would have to be provided for Alternative C. These quantities are based on current ' (May 1995) FEMA mapping and flood elevations. If results of recent hydrologic modeling modeling conducted by the City of Renton are adopted by FEMA,the 100-year flood elevation could bAgouin three feet lower than the current FEMA elevation and flood compensatory storage requirements would be substanha`�ly reduced. I 1110 AS a Jo ki The/King County Surface Water Design Manual (KCSWDM) 1301ated_into the City of Renton is very specific on the issue of stormwater retention/detention systems. der, ' the-City.-of Roaten--is-op�imievatwo-equi~vak�,nt--styOakzescWe Ave-,HO .mods 1 King4-n I � l.Jokt� <je. o�G2vwGe1 �ol.W�e/cer //' Q�en ba Smfi,f ��e✓ley �1EH.Oh4t�l H af 4m N� On-site flows would be conveyed to existing wetland areas or directly to Springbrook Creek after required L'mw yu.N� treatment. Storm runoff detention would be provided through storage pond and controlled ogtlet �y in . Land would be set aside and maintained as City of Renton stormwater treatment areas Existing bands of at - native growth vegetation would be preserved as a buffer adjacent to wetlands, seams, and ' , whenever possible,to mitigate the erosion potential. Impacts to surface drainage and infiltration and groundwater that are caused by the conversion of large ' areas of absorptive surface soils to impervious paved surfaFes may be mitigated by enhancing the absorptive capacity of the remaining unpaved groundrn/ regrading, construction of detention basins, introduction of special vegetation, and soil replacement. ' 15 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report 4LII orb" JMP-a- s to closed depressions, as expected at Wetland-Du st be-mitigated-as-speei�fie £ W o1S -V- Additional grading would reconstruct the existing stage/storage-relationshi o€-arty--�eleseff d S5t Some of this effort could be combined with mitigation of impacts to wetlands. The U.S. Environmental Protection Agency (EPA) has issued rules regarding the National Pollutant ��f.Y�.y ' Discharge Elimination System (NPDES). ThPwP rep ons ---:li�::dg control Qf c a:r atiu d � T--nr Q oc Sw uvui j o stormwater-pennit-for all point-diseharge-leeatiens-4n-the--city-:_-Whemdssued,-.ibis t would---control-runoff-from-aH-point--diseharge--_lacatiens-in-the_city. Also, an NPDES stormwater management permit for construction activities would be prepared for the project since more than two hectares-{five acres] of land would be disturbed. Construction practices and devices would be employed to mitigate the increased potential for erosion and sediment transport. These may include scheduling earthwork activities to avoid the rainy season, limiting topsoil exposure, and using sediment control devices such as silt fences, straw bales, and temporary sedimentation ponds. Newly constructed earthen ' embankments, roadway shoulders, drainage channels, and graded areas would be revegetated by seeding with erosion control mixtures. iNS r ,kvr tic,,,,. P6 /y. ' Peak rate runoff mitigation would be provided on all systems where increases are expected. This would be accomplished through earthen detention ponds set adjacent to the roadway corridor. A 200-foot biofiltration swale or equivalent will provide water quality treatment at each pond outlet. 1Lf' a 'Mirk �e�,,.� t6 /Asr P..�u��a�rt~ vy, P� ly, Garn✓.�r. . ' /vN'E miTec�r�oa 1'aA IAOA6r or- /?Pe6k 5;7euerVfk DeO 5/iZ/. 66/ w1C F�ws .�mn ^ncN S /.,, ouwn�o , s�P� 2sr� ' �`► it L1 C, /�.�,oc�,4 S S 134t I:\15203\reports\eis\htdrtech.doc 1121/95: 1.38 PM ..'" uNt.st s1N U6't �. ,- L�✓ t2� �4s �M ," -. CSTC Proposed k �-"� ��� � •� r,< � S,IN 21.st St" �.. Lollgaeres —At ice Park All, VUI S St �` > Q��RIM1C EL r qN,r q ca a y b q � r.' N � � t 'f k WOMMI t t tt73 `�,� i�, tick �,,i; ''r I i•f' S.e €s l �-i� ''Sfa j :-t2 a,�"Ccl+'-.yf,�-�d.''!� fifasr♦ :�'�.�, ,I.Ves l '7 �#�"-7:P •G r,� a ,•�� T i 1, ti �t $ v- � S1/V1 Gtll S1 ` 1 • SVV�116'tliSt , A' — � .�: e ■ . �; �'� �t..,��aa� 'fie A "� cc h'. s i F, _IProposed . � ��Longacres �� SiVU2�1st Sr m tlrt SVIl23rd Sty 1 : mumcm f._ QI��)�I�� • ®®X CD �. ..C .t isrial Plot r 9... 1 19 ' Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report At Ph, ti .:.���_ �s�+ .Y s}E�;F •'►�c 1�".,'-. rr� a 4'$.e.�rM3 w�•.�n p-a.�F{t..�c:� i.1••� ; d i g n- q sayE ps.1Sr++ jC F 3 Zxir_; f t 14, sk IN 1 r 14 1 1 r. `j�'i .a.aiMrw x _ c� � '..' Y JT 1 ' Figure 5 Drainage Subareas-Alternative C I\15203\reports\eis\htdrtech.doc 110/95: 3:33 PM 20 City of Renton Oakesdale Avenue S.W. , (NNY I S fV I S -1740u y oaf S NUS 3 / rYY . rd ��SI N .��r• 1 5E1 UW Office P�111( �a. • yp+y P x • sCVAvE5 Ga TNdS OF.N,.,A71 ArJ -,feW MMI J�N cEss A0X1, IV S,rMwc�r VU Figure 6 Storm Drainage Systems ' L� s'vGGfS� Sl�oui,..tr W1 rli 1015 19r5/(W-776YJ /S T�1 Cy,J rU L I Jill 7-1'k (=, �G >ieGolL�fh. I:\15203\reports\eis\htdrtech.doc 1121/95: 333 PM ' ,e "S:W 1r6d6tSita •+�*++ �r Y� StINffi1i61 a S1 --rl WiM MA ° '• ° Gl,oi,p H valth' ' oemg Alf, y. �..B � CSTC- 119 kp ( Proposed sAr-1sl St k• %LompiC Ies +, 1 Metro Renton° • Office Park s a' 11 South interceptor 72 ,..& 108" Y Metro TU4 w i I , Svv 23r 1 sl, I�nte'rce tor F10 ¢ U' 1 Q; 1211 1 a - Aerial Motog 194 • f �yjR ,�y�fVh 4 ` S'�1N�tt61 i 1 y ■ pp g` 1 ripM ■ Z Y4 ?T. 1� 14 s 1211 oeina- z CSTC � � > .. s a $1NMIr �y ■ x` • .� - 7- ffi. � .._ S�Ff.,y Cal S�� -1.� l #, Proposed Lonyacres { SVJ 21 ,l S! Office Park ? City Of Seattle Cedar River Pipeline No. 4 It (30-Foot Fee Owri`ershp) SW 231d Si, • r� 3°. i h + nc1 0 re Aerial Phologr3phy" ,90 / 1 • . . e a W a �« S, 14116�14 r PSP_+ ©. �� G'ioill i Mul 1r2kV Lineod : r > CSTC = PSP+'L t ; T5kV Line- JOS I Prtiposed '"t SW21st St Lonfacres i _ r 1 �� . ' yOffice Parr �r , �A� 9 1' / � b a �SW23rdSt � PSP+L Leased �... 115kV Line ffey (Sealtle.City Light Owned* i p P;SP+L Leased'' V § ,"` sv'rz-�th.s� ► 12kV Line Q �0 Aerial PNotogr y ,90 Lo .�'•:: �" �� - � -tl' IRS x`Y Gas Mta ism • S�►G```v VI/ashi'`ngto� mix-Mural G`as 52 $WsI3dit• ti IT T - CSTC aor a�`µ - '`, I.M. P pos SW 1,9h St 2.4 Proposed SIIV 2Yst St > Office RI-ui( SW 236d St Petro'Ieum ,PiAMITM pelfrre � v�."• f�_ i�1K'"fit-P1-Ilr-�.� 4o� � IwCy r ks. 4" Gas Main Washington Natural Gas s DetentnPond« f 1 « ��` Biofiltrtro SIt y�S, e� suuasti,vst �,uvsti, t r - Brid�ge Sit. 4. ,.Boemy CSTC e c cc SW 19.t11 St �® kesdale Ave,nu`e \ aI A�ignment'��A�l�' � PROWL Detention�.Pand & ` Biofiltration Syste�t � ' j°:,Proposed k U �a 8r E �SW21stS.t �` j, Longacres �.,� l.K ; ? 70 -e palk Detention d.,.�. 4 B.iofiltrafion. &' Conveyance Sys'tei '°C` 'S W 230 S i v E Detention Pond & - Removal of ," Biofiltration System B Longa°cres Pkwy-,,,,� Bridge Site 1 A �— Biofiltration System A Q JV, Y Q ! ,. 0 `"., -•^Ht.tn*t - Aerial Photogr r Y .9L A • A 1 -•• • of ,o 3 0,"1 � Deten nPoMOW ;I Aeo nd & '- ���°�� Bibfrltratroln�S4ys=t�e�rrf.R i'� .^ S,ILVy1.6tI,St fi.A Boemg CSTC � 7. }i d ¢_ . • Oa_kesdaleAvenue Alignment - � -- Detention-Pond� g Biofiltrat'.on Siystem ( _+. Propotied Long,CM., SW€21st St DetentionPond� Office: Nfj � �. u Biofiltration. , :+ Conveyance Sy"stern P` " r Y .z qq i q' to I I WI_),ik. c 1 Detention Pond& Removal of Q; Biofiltration System N Longacres Pkwy Bridge Site 1 A Biofiltration System M a �"" Avol Photography 21=98 27 Draft Environmental Impact Statement Waterways and Hydrological Systems Technical Report 6. References #iAk /S 3C-cck (�4--k aiw-'rix &V Geo Engineers. 1991. Report of Geotechnical Engineering Services, Boeing Longacres Park. January 23. ' Bellevue,WA. Prepared for BE&C Engineers. Seattle,WA. and for Boeing Support Services. Herrera Environmental Consultants, Inc. 1991. Water Quality Monitoring and Quality Assurance ' Project Plan for the Black River Water Quality Management Plan. October 10. Seattle, WA. Prepared for R.W. Beck and Associates and City of Renton, Department of Public Works. Renton, WA. ' Jones & Stokes Associates, Inc. 1991a. Wetland Inventory Work Plan for the Eastside Green River Watershed Management Plan/Black River Water Quality Management Plan. September 12. Renton, WA. Prepared for the City of Renton, Planning/Building/Public Works. Renton,WA. 1991b. Critical Area Inventory. June. Prepared in association with R.W. Beck and Associates. Seattle,WA. Prepared for City of Renton, Planning/Building/Public Work. Renton,WA. 1994. Draft Environmental Impact Statement for Longacres Office Park. Volume I & II. ' August. Bellevue,WA. Prepared for Boeing Commercial Airplane Group. Renton,WA. Northwest Hydraulic Consultants Inc. 1991. East Side Green River Watershed Hic Analysis. December. Kent, WA. Prepared for R.W. Beck and Associates and City of Renton, Department of Public Works. Renton,WA. Renton, City of. 1988a. wings for-Soils Conservation-Service-,P-L.aad-P,,q-C 1.988b. P-9 and Panther Creek Wet!an&s D* .Auo rib, 09 R imton,Deem tment of ' Public Works. Renton;W-A, 1994b. Traffic Counts ' R.W. Beck and Associates. 1991a. Current Conditions Document for East Side Green River Watershed Plan. October. Prepared in association with Northwest Hydraulic Consultants, Herrera ' Environmental Consultants, and Jones & Stokes Associates. Seattle, WA. Prepared for City of Renton, Storm Water Utility. Renton,WA. ' 1991b. Project Summary Document for East Side Green River Watershed Plan. December. Prepared in association with Northwest Hydraulic Consultants, Herrera Environmental Consultants, and Jones & Stokes Associates. Seattle, WA. Prepared for City of Renton, Storm Water Utility. ' Renton, WA. Shapiro and Associates, Inc. 1992. Environmental Report for the South Interceptor Parallel: Phases 1B and II. August. Seattle, WA. Prepared for Municipality of Metropolitan Seattle (Metro). Seattle, WA I:\15203Veports\eis\htdrtech.doc 11/21/95: 1:38 PM 28 City of Renton Oakesdale Avenue S.W. ' 1993. City of Renton Jurisdictional Wetland Determination for Longacres Office Park Project. Seattle , WA. July. Prepared for Boeing Commercial Airplane Group, Seattle, WA. and the City of ' Renton,WA. (Jones & Stokes, Appendix D). 1995. Draft Jurisdictional Wetland Determination for Oakesdale Avenue S.W. Seattle , WA. ' March. Prepared for The HNTB Companies. Bellevue,WA. Shannon & Wilson, Inc. 1992. Preliminary Wetland Delineation Van Woerden Avenue Southwest or Raymond Avenue S.W. October. Seattle,WA. Prepared for Winmar Company, Inc. Seattle,WA. ' URS Company. 1982. Advance Planning Study Report for Valley Parkway Southwest, S.W. 43rd Street to Empire Way South and Southwest 27th Street from East Valley Highway to West Valley , Highway. January. Seattle,WA. Prepared for City of Renton,WA. Woodward-Clyde. 1995. Geotechnical Predesign Report Oakesdale Avenue Extension Renton ' Washington. June 1995. Seattle,WA. Prepared for HNTB. Bellevue,WA. 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