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Home My WebLink AboutSWP273218(2) 1 1 SEPA Environmental Review Application 1 Strander Boulevard Extension Project 1 City of Renton r September 2004 i 1 1 - 17 - 1 FLOOD HAZARD DATA i ................................................................................................................................................ The proposed project is a road construction project, therefore most of the 1 improvements will be at or above grade and all improvements will include storm E water management provisions and mitigation, as described in Section 6 of this application and in the Hydraulics Report provided in Section 21. 1 The Flood Insurance Rate Map (FIRM) for the project area are not updated to reflect current elevation conditions and do not contain the detail to use for engineering 1 design. In general, most of the project occurs below the 50-foot contour. The most current drawing of the floodplain areas available for this project is depicted on Figure 17-1, which shows the location of flood zones in relation to the project area. 1 For more details lease refer to the attached Flood plains Technical Discipline � P P P Report. 1 .................................................................................................................................................. 1 DEV CLOPM OF RENTON PLANNLNG 1 OCT 1 12004 1 Perteet inc. RE CEIVED 17-1 ' DRAFT FL DPLA 00 INS TECHNICAL DISCIPLINE REPORT Strander Boulevard Extension Project ' May 2004 Prepared For: City of Renton ' Department of Public Works Renton City Hall 1055 S. Grady Way Renton, WA 98055 Prepared By: Perteet Engineering, Inc. 2707 Colby Avenue, Suite 900 Everett, WA 98201 ' (425) 252-7700 DRAFT TABLE OF CONTENTS ' 1.0 INTRODUCTION......................................................................................................I 1.1 PROJECT ORGANIZATION AND SCOPE ........................................................................1 ' 1.2 STUDY AREA ............................................................................................................. 1 1.3 PROJECT BACKGROUND.............................................................................................5 1.4 PROJECT PURPOSE .....................................................................................................7 ' 1.5 PROJECT NEED...........................................................................................................7 2.0 DESCRIPTION OF ALTERNATIVES...................................................................9 ' 2.1 ALTERNATIVES CONSIDERED.....................................................................................9 3.0 METHODOLOGY AND COORDINATION........................................................15 3.1 EVALUATION CRITERIA ...........................................................................................15 3.2 APPROACH TO ANALYSES........................................................................................15 3.3 COORDINATION WITH AGENCIES AND JURISDICTIONS .............................................16 4.0 AFFECTED ENVIRONMENT...............................................................................17 4.1 TOPOGRAPHY AND HYDROGEOLOGY....................................................................... 17 4.2 HISTORY OF LAND USE............................................................................................ 18 4.3 FLOOD ZONE MAPPING............................................................................................19 4.4 MODELING RESULTS................................................................................................ 19 ' 4.5 PROPOSED ACTION EVALUATION FINDINGS AND PROJECT AREA-SPECIFIC ENVIRONMENTAL CONCERNS.........................................................................................21 5.0 IMPACT ANALYSIS ..............................................................................................22 5.1 NO ACTION ALTERNATIVE ......................................................................................22 5.2 ALTERNATIVE 1: CONSTRUCTION OF A ROADWAY OVERPASS CROSS-VALLEY LINK, ' RELOCATION OF THE UNION PACIFIC RAILROAD TRACK,AND MODIFICATION OF SW 27TH STREET TO FIVE LANES.........................................................................................22 5.3 ALTERNATIVE 2: CONSTRUCTION OF A ROADWAY UNDERPASS CROSS-VALLEY LINK,RELOCATION OF THE UNION PACIFIC RAILROAD TRACK,AND MODIFICATION OF SW 27TH STREET TO FIVE LANES ..................................................................................23 5.4 ALTERNATIVE 3: CONSTRUCTION OF A ROADWAY UNDERPASS CROSS-VALLEY LINK,UNION PACIFIC RAILROAD TRACK NOT RELOCATED,AND MODIFICATION OF SW 27TH STREET TO FIVE LANES.........................................................................................24 6.0 COMPARISON OF THE ALTERNATIVES........................................................24 ' 7.0 REFERENCES AND SOURCES 26 ........................................................................... Draft Floodplains Discipline Report i May 2004 Strander Boulevard Extension City of Renton DRAFT LIST OF TABLES TABLE 6.1: SUMMARY OF POTENTIAL IMPACTS FOR FLOODPLAINS...................................25 LIST OF FIGURES FIGURE 1.1: LOCATION MAP ...............................................................................................3 FIGURE 1.2: TYPICAL ROADWAY SECTION..........................................................................4 1 FIGURE 1.3: PROJECT SEGMENTS.........................................................................................6 FIGURE 2.1: PROPOSED ROADWAY LIMITS........................................................................10 FIGURE 4.1: FLOODPLAINS ................................................................................................20 r i r r r r r r r r r r r Draft Floodplains Discipline Report ii May 2004 Strander Boulevard Extension City of Renton DRAFT 1.0 INTRODUCTION 1.1 Project Organization and Scope This report has been prepared by Perteet Engineering, Inc. (Perteet) on behalf of the City of Renton to provide information regarding floodplain conditions in the vicinity of the proposed project area in the City of Tukwila and City of Renton, and to identify potential environmental issues that could affect the proposed action. It provides supporting information for the Environmental Assessment being prepared by Perteet for the proposed action. This report identifies and describes locations and quantities of fill below the 100-flood elevation by the Project. 1.2 Study Area This project study area is located within the jurisdictions of both the City of Renton and the City of Tukwila in Section 19, Township 23 North, Range 5 East; Sections 24 and 25, Township 23 North, Range 4 East; Section 30, Township 23 North, Range 5 East(See Location Map, Figure 1.1). Renton is located at the south end of Lake Washington on the edge of metropolitan and rural King County. Its location between Seattle, Tacoma, and LBellevue places Renton in the center of a region that is the economic hub of the state. Renton encompasses approximately 16.7 square miles. Renton and Tukwila are at the crossroads of a regional transportation network where seven state and interstate highways converge and which is central to national and international air traffic. The stud area is sideways T-shape.e. It includes the area between the west side of the Y Y P Interurban Trail and the east side of the Burlington Northern Santa Fe (BNSF) railroad track. The study area is wider in the vicinity of Strander Boulevard because it is possible that the trail would be moved. The southern boundary is south of a railroad spur heading northwest from the Union Pacific Railroad (UPRR) mainline (the spur that crosses the Green River, not the short spur that serves adjacent businesses), which is about 1,700 feet south of Strander Boulevard. The spur would be the approximate takeoff point for a new UPRR mainline track that would replace the existing track. The new track would parallel the existing BNSF tracks. On the north end, the study area extends just past I-405 where the UPRR track begins to parallel the BNSF tracks. East of the BNSF tracks, the bulk of the proposed project construction in the primary study area would be confined to the Strander/27`h Avenue corridor, branching off at the points where the Boeing access roads and Sounder station access are to be located. From Oakesdale to East Valley Road, the expectation is to widen the existing roadway within the right-of-way limits. The new roadway would be five lanes with sidewalks and planter Draft Floodplains Discipline Report 1 May 2004 Strander Boulevard Extension City of Renton ' DRAFT strips on both sides (See Figure 1.2). The intent is to keep the project within City right- of-way. i 1 1 Draft Floodplains Discipline Report 2 May 2004 ' Strander Boulevard Extension City of Renton r Seattle Elliot Bay Lake Washington Bellevue O �F Mercer Island Burien'� , Puget Sound Tukwila► Renton V o f / u Sea11Tac 0 GO o 0 4 Project-Location Kent Des Moines 4 East Passage Auburn CV Federal Way �' D rTacoma RE N T O N City of Renton Figure 1 .1 Strander Boulevard Extension Perteet Engineering, Inc. Location Map Civil,Transportation and Survevin, rr � r r rr it a� rr rr ,� r� �r �■■� r rr r �r �r �■r � T m z oo � 5TRANDER BOULEVARD EXTENSION a TYPICAL ROADWAY SECTION c/) 0 v � 90, ROW (D 0 G' PLANTER 60 G' PLANTER < G' 51DEWALK 12 12' 12' 12' 12' 12' Q- THRU LANE THRU LANE TURN LANE THRU LANE THRU LANE 5HARED m U5E PATH x m 0 n WIDEN WITHIN THE ROW O WITH SHARED USE PATH ON 50UTH SIDE v -n C (D (D 0 tV DRAFT 1.3 Project Background This project began with the formation of the Project Stakeholder Committee composed of public agencies and private businesses. Members of the committee have some insight ' concerning the needs of this project, opportunities that this project could promote, and potential transit and commuter rail improvements it could provide for the Tukwila commuter rail station. The Project Team facilitated Project Stakeholder Committee meetings with affected agencies, such as WSDOT; City of Renton; City of Tukwila; King County; and private businesses, including Boeing, BNSF, and UPRR. Concurrently, the Project Team reviewed existing information regarding the corridor and the existing environment and infrastructure within the project corridor. The Project Team assembled information about to potential corridor concepts, existing and projected traffic that would be generated by the proposed corridor improvements, affected environment, and costs. The Project Stakeholder Committee, formed by the City of Renton, became a source of guidance and input with regard to the information assembled for the potential corridor concepts by the Project Team. The role of this committee was to review and comment on ' the major study tasks and to recommend preferred concepts. The committee met seven times during this phase of the project and provided the Project Team their endorsement to the Project Team's preliminary recommendation for each of the three proposed segments (See Figure 1.3): • Segment 1 —West Valley Highway to Oakesdale Avenue SW • Segment 2—Oakesdale Avenue SW to East Valley Highway • Segment 3 —added access to SR 167 via East Valley Road At the conclusion of the study, the City of Renton determined that construction of Segments 1 and 2 by themselves would provide a vital cross-valley route and have substantial utility independent of Segment 3. The Project Team prepared a statement of the problem based on a review of existing 1 traffic volumes,projected 20-year traffic volumes, economic growth projections from the cities of Renton and Tukwila, and committee member discussions. There were initially 13 potential concepts for Segment 1, 5 potential concepts for Segment 2, and 4 potential concepts for Segment 3. Each of these concepts was described in a conceptual level of detail. At this level of definition, the corridor improvements included sketches, key physical and operational features, functions, benefits, and potential impacts to the environment. r Draft Floodplains Discipline Report 5 May 2004 ' Strander Boulevard Extension City of Renton ~ VALLEY SW 7TH ST SN w i > S G NoY 1 ST T L - 6' INTERURBAN 2 AVE S d SW 16TH ST �y --- BLvo PKWY WI SEGMENT 1 Q ; I T SEGMENT 2 - o 0 o a a'c G B VD SW t STRANDER BLVD w > O W 3 co j SW 34TH ST } -- i co a SEGMENT 3 a Y / tr Q O a 0 Q , a <> SW 41TH ST 0 S T 180TH ' ST SE 43RD ST (S 180TH ST) r i ' RENT ON City of Renton Figure 1 .3 Strander Boulevard Extension Perteet Engineering,Inc. Project Segments Civil,Transportation and Surveying DRAFT The Project Team evaluated the concepts through a first-level screening, which was ' essentially a"fatal flaw" analysis. Concepts were recommended for elimination if they contained serious flaws, were likely to perform poorly, demonstrated an undesirable combination of performance and adverse impacts, or did not appear to meet the ' committee's committed goal for the project. Following the initial screening, a second screening was conducted on the concepts not eliminated. During the second-level screening, a more detailed evaluation was applied using additional criteria related to transportation performance, land use/social impacts, environmental impacts, and cost/feasibility. A final screening was conducted on the last remaining concepts using the same criteria as the second screening but with additional information collected, as well as the results of a traffic analysis on the effects of adding this east-west corridor between SW Grady Way and South 180th Street/SW 43rd Street. In addition,more detailed costs of the concepts were discussed and the potential for funding the concept and the overall ' financial viability of a concept were evaluated. During each of the evaluation screenings, the Project Stakeholder Committee was briefed on the evaluation. Upon endorsement by the Project Stakeholder Committee,the Project Team continued to the next level of evaluation. The final screening resulted in a preliminary recommendation for each segment by the ' Project Team. The Project Stakeholder Committee has concurred with this preliminary recommendation. ' 1.4 Project Purpose The purpose of this project is to improve travel speed, reliability, and access in the north Renton/south Tukwila area. This would be accomplished by adding a new roadway segment from Strander Boulevard to SW 271h Street and roadway improvements along SW 27`h Street. This would result in a cross-valley link between West Valley Highway (SR 181) and East Valley Road via Strander Boulevard in Tukwila and SW 271h Street in Renton. ' 1.5 Project Need The proposed project would meet several needs important to both Renton and Tukwila. The project would: • Decrease travel time and increase reliability • Relieve congestion • Provide access to the future Sound Transit Tukwila Station • Improve freeway operation • Encourage transit-oriented development • Promote freight mobility and economic development Draft Floodplains Discipline Report 7 May 2004 Strander Boulevard Extension City of Renton DRAFT 1.5.1 The Need to Decrease Travel Time and Increase Reliability ' The absence of a direct route to and from the project area between West Valley Highway and SR 167 results in extra travel time for freight shippers, transit vehicles, and general- purpose vehicles. A grade-separated route crossing the UPRR and BNSF tracks would both decrease travel times and increase the certainty that vehicles would not be delayed by trains traveling through the area. ' 1.5.2 The Need to Relieve Congestion ' In order for traffic from Strander Boulevard to cross the UPRR and BNSF tracks and connect with East Valley Road, vehicles must either travel approximately .6 miles north on West Valley Highway to SW Grady Way and then east or go more than a mile south to SE 1801h Street/SW 43 d Street before going east. In either case, the circuitous route causes unnecessary congestion that would be alleviated by a direct cross-valley connection. ' 1.5.3 The Need to Provide Access to the Future Sound Transit Tukwila Station The Boeing Longacres site currently facilitates one of south King County's highest proportions of vanpool users at a temporary Sound Transit station. The temporary station will eventually develop into the Sound Transit Tukwila Station and will become an important intermodal center for the South King County area. Current routes from the temporary facility to the freeway system are convoluted and congested. Improved access to this commuter rail station will encourage transit use, and help to relieve traffic congestion in the region. Improved access would result in shorter commute times for high-occupancy vehicle (HOV)users, and keep the use of alternative modes of transportation high. 1.5.4 The Need to Improve Freeway Operation p P ' Due to high traffic volumes, it is difficult for HOV and freight traffic on 1-405, SW Grady Way, and SW 43rd Street to access important employment and industrial centers in the Green/Duwamish River valley. Bus movements across congested SR 167 traffic ' lanes between the inside HOV lanes and on- and off-ramps at the outside lanes increase travel times for HOVs and contribute to general purpose traffic congestion. By providing an additional cross-valley link, the proposed project would take some traffic off of I-405 and SR 167. 1.5.5 The Need to Encourage Transit-Oriented Development If the UPRR tracks are relocated to more closely parallel the BNSF tracks through the ' project area, additional land could be made available for economic development in Tukwila adjacent to the planned Sound Transit Tukwila commuter rail station. The location would be ideal for Transit Oriented Development (TOD) and would reinforce Draft Floodplains Discipline Report 8 May 2004 ' Strander Boulevard Extension City of Renton ' DRAFT opportunities for development and growth within the Boeing Longacres site and surrounding areas. ' 1.5.6 The Need to Promote Freight Mobility and Economic Development Fast, reliable freight access to industrial areas in the Green/Duwamish River Valley is crucial to economic development in the area; without such access, businesses could suffer and may choose to relocate. The extension of Strander Boulevard from West Valley Highway(SR 181) to SW 271h Street would improve access to SR 167,thus providing an alternative to the existing freight routes in the area. In addition to reducing travel time, the new facility may also reduce congestion in the area by drawing vehicles from other ' truck routes, thus reducing the overall congestion level in the area. Additional access to the fixture development of the Boeing Longacres site is equally important to the economic development currently projected and being planned. Without improved local and through ' access,the rate at which new and existing businesses choose to locate or expand here is likely to be significantly reduced. ' 2.0 DESCRIPTION OF ALTERNATIVES 2.1 Alternatives Considered Three action alternatives and a No Action alternative are evaluated in this report. The alternatives focus on a cross-valley link between West Valley Highway (SR 181) and East Valley Road(see Figure 2.1)that would begin at the signalized intersection of Strander Boulevard and West Valle Highway on the west and would terminate at the unsignalized intersection of SW 27t Street and East Valley Road on the east, a distance of 6,500 feet. At present, West Valley Highway to Oakesdale Avenue SW is an unimproved area with no roadway that directly connects Strander Boulevard with the area to the east. From Oakesdale Avenue SW to East Valley Road,there is an existing roadway approximately 3600 feet long. The project alternatives focus on strategies to cross the unimproved area, especially railroad tracks owned and operated by Union Pacific Railroad and Burlington Northern and Santa Fe Railway. r2.1.1 No Action Alternative The No Action alternative would keep the project corridor as it currently exists. No new roadways would be constructed or improved in the corridor. The purpose and need for the project would not be met by the No Action alternative. Draft Floodplains Discipline Report 9 May 2004 ' Strander Boulevard Extension City of Renton SEC. 19, T 23N, R 5E, W.M. S C. 25, T_23N R45E, W.M. I j - - _. 8 LANGSTON RD z S 133Rp ST S 132N ST �� S AIRPORT TON PIS ID 'Y 4 ELF CITY LIMITS w,-- mac" Q' S S 14aTu Sf r --� x rn _ GALLEY SW 7TH ST 3 So 7 s SPRINGBR OK STTH y\ TRAIL > $g S \ tee, GRA�YD r zo 151Si vt w ST ?� -- J P�___ INTRURBAN \ S AVE. S SW 16TH ST - — -- ` y i 7UkVIILA PKWY I LONGACRES AY PRgPO ED RO D AY LIMITS a c f 0 ----_--- �p '3 � SPRIN OOK <' a — TRAIL BLVp _ 3 S'RANDLR ` ' 27TH S c a STPANOER BNSF TRACKS( J UPRR T CK(1) ST w 2 �I 3 I _ w K j p Y rl � a o o S ai SW 41TH ST ''eTy Z ST S '80 T-i 5r a S "8CT4 -' SE ST a3RD ST 1 1 INTE RAN (s 160T sT) ' TRAIL \ RE N T O N City of Renton Figure 2.1 Strander Boulevard Extension Perteet Engineering,Inc. Proposed Roadway Limits Civil,Transportation and Surveying DRAFT 2.1.2 Alternative 1: Construction of a Roadway Overpass Cross-Valley Link, Relocation of the Union Pacific Railroad Track, and Modification of SW 27th Street to Five Lanes Alternative 1 would create a link between West Valley Highway (SR 181) and Oakesdale ' Avenue SW with a single overcrossing of both Union Pacific Railroad (UPRR) and Burlington Northern and Santa Fe Railway (BNSF)tracks. From Oakesdale Avenue SW to East Valley Road, SW 27th Street would be widened and include pedestrian facilities ' and landscaping. Alternative 1 would include five elements: • Relocation of the Union Pacific Railroad track ' • New roadway construction from West Valley Highway to Oakesdale Avenue SW • Improvements to SW 27th Street ' Modifications to the Interurban Trail • Modifications to South Longacres Way Relocation of the Union Pacific Railroad Track The UPRR track would be shifted to the east to parallel the existing two sets of BNSF ' track. To develop this alternative, a new railroad track would be constructed within a new 100-foot right-of-way adjacent to the BNSF right-of-way and then joined with the existing UPRR track at both ends of the project area. Approximately 5,500 feet of new track would be constructed at an elevation similar to that of the existing BNSF tracks. Construction would require placement of 125,000 cubic yards of earth and gravel for the new railroad bed. The new UPRR track would be located at the center of the new 100- ' foot right-of-way. Approximately the same amount of track and railroad bed would be removed from the existing UPRR location as will be constructed at the new UPRR track location. The railroad bed material would be disposed of at an approved location or reused as a construction fill material. Construction would be sequenced so that disruption of railroad service would be avoided or minimized. With this alternative, the new UPRR track can be constructed while service is continuing on the old track. When the new track is completed,UPRR train ' traffic would be moved to the new track,the existing UPRR track and railroad bed would be removed, and construction of the roadway overpass would begin. ' New Roadway Construction from West Valley Highway to Oakesdale Avenue SW A new roadway would be constructed from the intersection of West Valley Highway (SR 181) and Strander Boulevard to the intersection of Oakesdale Avenue SW and SW 27th Street. The roadway alignment would be an extension of Strander Boulevard and curve to match up with the existing alignment of SW 27th Street. Alternative 1 would feature an overpass that would be constructed over the two existing BNSF tracks and the new UPRR track. The overpass would provide vertical clearance of Draft Floodplains Discipline Report 11 May 2004 Strander Boulevard Extension City of Renton ' DRAFT 17 feet and include four travel lanes, a sidewalk on the north side, and a shared use path (combined bicycle/pedestrian path) on the south side for pedestrians and bicycles. ' From West Valley Highway to the overpass,the roadway would consist of five lanes (four thru lanes and a two-way left turn lane), landscaped strips, a sidewalk on the north ' side, and a shared use path on the south side. Bicycle facilities would be provided in either combined travel lanes/bicycle lanes or as a shared use path. The landscaped strips would be provided between the traveled way and the pedestrian facilities, and in some locations where a two-way left turn lane is not needed, a landscaped median would be provided. The overpass would not have the two-way left turn lane and planter strips. From the overpass east to Oakesdale Avenue SW, the same five-lane roadway, landscape strips, and pedestrian/bicycle facilities would be constructed. This section (including the roadway, pedestrian facilities and landscaped strips) would be 90 feet wide from back of sidewalk to back of sidewalk, staying, for the most part, within the appropriate existing ' City-owned right-of-way. The new roadway construction would result in three new intersections between West ' Valley Highway to Oakesdale Avenue SW. There would be one intersection at the future Sound Transit Tukwila Station access road, and two intersections that would result from access roads to the Boeing Longacres site. New traffic signals would be installed at each ' of these intersections. Improvements to SW 27th Street ' The existing section of roadway between Oakesdale Avenue SW and East Valley Road would be widened to match that of the new roadway segment to the west (five lanes, ' landscaping strips, and pedestrian/bicycle facilities on each side). The section would be 90 feet wide from back of sidewalk to back of sidewalk, staying, for the most part, within existing City-owned right-of-way. At some locations where there are space constraints or the need to avoid wetland impacts, the planter strip may be eliminated. Portions of the north side and south side of the proposed improvements may require a 3-to 8-foot block or rock wall at the back of the sidewalk to minimize impacts to the adjacent wetlands. A handrail would be required along the top of these wall sections. ' Modifications to the Interurban Trail The new roadway segment linking West Valley Highway and Oakesdale Avenue SW ' would cut across the Interurban Trail. As a result, it would be necessary to construct a new means of making the trail continuous. The least obtrusive and preferred route is to have an at-grade crossing at either West Valley Highway or at the future Tukwila Station ' access road intersection. On the north side and the south side of the roadway, trail users would be routed onto the new bicycle/pedestrian facilities along the roadway, directed toward the intersection, cross the intersection, and then be directed back to the existing trail. Draft Floodplains Discipline Report 12 May 2004 ' Strander Boulevard Extension City of Renton ' DRAFT Modifications to South Longacres Way ' South Longacres Way, which is approximately 1,700 feet north of the intersection of Strander Boulevard and West Valley Highway, is bridged by the UPRR track and the BNSF tracks. It currently provides access to the temporary Sound Transit commuter rail parking area. The existing railroad bridges over South Longacres Way are narrow and have clearances that are below the minimum requirements. As a result of this project, if ' South Longacres Way were to continue to remain open, improvements would have to be made to provide minimum vertical clearances. A new UPRR bridge structure would have to be built, improvements would need to be made to the BNSF bridge structure, and the ' vertical profile of South Longacres Way would have to be lowered. 2.1.3 Alternative 2: Construction of a Roadway Underpass Cross-Valley Link, ' Relocation of the Union Pacific Railroad Track, and Modification of SW 27th Street to Five Lanes ' Alternative 2 would create a link between West Valley Highway and Oakesdale Avenue SW with a single underpass of both the UPRR and BNSF tracks. As described previously for Alternative 1, the UPRR track would be relocated to the east to parallel the existing BNSF tracks. The roadway would be the same as Alternative 1 and have the same five elements as Alternative 1, listed below: ' Relocation of the UPRR track • New roadway construction from West Valley Highway to Oakesdale Avenue SW ' Improvements to SW 27`h Street • Modifications to the Interurban Trail • Modifications to South Longacres Way ' Relocation o the Union Pacific Railroad Track .f This project element would be the same as for Alternative 1; however, construction sequencing would be different. Construction would be sequenced so that disruption of railroad service would be avoided or minimized. The construction of the new railroad track and the roadway underpass (see new roadway construction subsection below)would also be constructed simultaneously. When the new track is completed, train traffic from the western BNSF tracks would be temporarily shifted to the new track and construction of the underpass beneath the unused ' tracks would take place. After completion of the second section of the underpass,train traffic from the eastern BNSF track would be temporarily shifted to the western track, and the third section of the underpass would be constructed under the eastern BNSF ' track. When the underpass is completed, BNSF train traffic would be shifted back to their two original tracks, and UPRR train traffic would be relocated to the new track, and the existing UPRR track and railroad bed would then be removed. Draft Floodplains Discipline Report 13 May 2004 ' Strander Boulevard Extension City of Renton ' DRAFT New Roadway Construction from West Valley Highway to Oakesdale Avenue SW ' This project element would be the same as Alternative 1, except that an underpass of all three railroad tracks (the relocated track used by UPRR and the two BNSF tracks) would ' be constructed rather than an overpass. The underpass would provide 17 feet of clear distance between the roadway and the bottom of the bridge structure and would contain all of the same roadway elements as in Alternative 1. Other elements of Alternatives would be walls along the underpass and in other various locations and the construction of water quality treatment and detention facilities. The underpass section would include a pump system to remove the accumulated rainwater. Improvements to SW 27`h Street ' This project element would be the same as for Alternative 1. Modifications to the Interurban Trail This project element would be the same as for Alternative 1. Modifications to South Longacres Way ' This project element would be the same as for Alternative 1. 2.1.4 Alternative 3: Construction of a Roadway Underpass Cross-Valley Link, Union Pacific Railroad Track Not Relocated, and Modification of SW 271h Street to Five Lanes As with Alternative 2, Alternative 3 would create a link between West Valley Highway and Oakesdale Avenue SW with a single underpass of both the UPRR and BNSF tracks. Alternative 3 differs from Alternatives 1 and 2because the UPRR track would not be ' relocated to the east to parallel the existing BNSF tracks. For this alternative, the UPRR track would remain in their existing location. The roadway would be the same as that for Alternative 2 and would have most of the same elements as Alternative 2: • New roadway construction from West Valley Highway to Oakesdale Avenue SW • Improvements to SW 27'h Street • Modifications to the Interurban Trail • Modifications to South Longacres Way New Roadway Construction from West Valley Highway to Oakesdale Avenue SW Under Alternative 3, this project element would be the same as Alternative 2 except that the length of the underpass would be longer because of the different location of the railroad structures. The longer underpass would result in the purchase and modification to the existing parcels and businesses on the northeast and southeast corners of the intersection of Strander and West Valley Highway. Changes would have to be made to Draft Floodplains Discipline Report 14 May 2004 ' Strander Boulevard Extension City of Renton ' DRAFT these lots so that the driveways could match into the new roadway, which would be at a lower elevation than the existing roadway. All other elements of the project that would result from the Alternative 3 would be the same as Alternative 2. Improvements to SW 27th Street ' This project element would be the same as for Alternative 1. Modifications to the Interurban Trail This project element would be the same as for Alternative 1. Modifications to South Longacres Way With Alternative 3, there would be no required modifications to South Longacres Way because no changes would be made to the existing UPRR or BNSF tracks. 3.0 METHODOLOGY AND COORDINATION 3.1 Evaluation Criteria The impacts of the proposed action on floodplains were evaluated by determining the location and amount of fill below the maximum elevation of the 100-year flood and ' considering the ability of flood waters to pass along the route of any identified floodway. Identified areas of concern include: • Location and volumes of construction and fill that would be placed below the elevation of a 100-year flood ' • Location and volumes of construction and fill that might impede the passage of flood flows along floodways • Possible effects of mainstem river channel migration on the flood zone and proposed project area. 3.2 Approach to Analyses rThis study was performed in general accordance with the WSDOT Environmental Procedures Manual M31—I1 (WSDOT 2004). The study was accomplished by performing the following tasks: • The proposed project area was located in relation to the 100-year ' floodplain and floodway, as they are identified by the Federal Emergency Management Agency (FEMA) on NFIP Flood Insurance Rate Maps (FIRMS). • The flooding history of the Green/Duwamish River valley was researched. • The elevation of the 100-year flood was compared with proposed action construction work and elevations. • Areas of fill below the 100-year flood elevation were identified, and fill volumes calculated using cross-sections through the construction and fill areas. Draft Floodplains Discipline Report 15 May 2004 ' Strander Boulevard Extension City of Renton ' DRAFT • The crossing of Springbrook Creek, an identified floodway, was analyzed for flow passage. • Analyses by King County of channel migration hazard for large rivers were consulted. • Publicly available records were reviewed at local environmental agencies, ' as necessary, to obtain supplemental information regarding present and past environmental conditions. • Available geologic literature and topographic maps were reviewed to preliminarily identify surface drainage paths in the project study area. • Environmental conditions within the proposed study area were summarized. • Potential impacts to the proposed action due to the potential or known presence of floodplain encroachment were identified ' • Potential measures and options to mitigate potential impacts of floodplain encroachment to the proposed action were identified. 3.3 Coordination with Agencies and Jurisdictions r The City of Renton was consulted during the preparation of this report. In addition, ' FEMA NFIP FIRMs (dated May 1995) for King County and Incorporated Areas were reviewed for the proposed project area. FEMA and King County web sites were also consulted. . King County's "iMAP," an interactive map-making application that provides online access to an extensive library of geographic information, was reviewed? The information available in iMAP includes 100-year Floodplains and Floodways, which are a compilation of best available floodplain boundaries using FEMA preliminary and final ' FIRMs and King County flood boundary work maps. Channel Migration Hazard Areas have also been mapped by King County and were reviewed on the website. 3.3.1 Policies and Approvals Presidential Executive Order ' Presidential Executive Order 11988, Floodplain Management(May 24, 1977) directs federal agencies to avoid to the extent possible adverse impacts associated with ' floodplains and to avoid direct or indirect support of floodplain development. The Flood Control Zone Act ' The Flood Control Zone Act of 1935, as amended, (Title 86 RCW) is the primary statutory authority regulating state flood control jurisdictions, which include flood control districts, counties, and zone districts. The act also regulates flood control management, flood control contributions, cooperation with federal agencies on flood control, and state participation in flood control maintenance. The 1937 Act at RCW 86.09, Flood Control Districts, is the section of the act most relevant to WSDOT projects. Draft Floodplains Discipline Report 16 May 2004 Strander Boulevard Extension City of Renton DRAFT Memorandum of Agreement(MOA) on Work in State Waters Memorandum of Agreement (MOA) on Work in State Waters,June 2002. This interagency MOA is between Washington State Departments of Fish and Wildlife ' (WDFW), Ecology, Military (Emergency Management Division and Transportation); Washington State Association of Counties; and Association of Washington Cities. The MOA addresses construction work in state waters and establishes procedures to prevent habitat loss through damage by flooding and future land development and to restore fish and wildlife habitat loss resulting from past flooding, land development activities, or public transportation facilities. The MOA outlines permit requirements and WSDOT responsibilities to contact WDFW and Ecology during times of emergencies (and defines what constitutes an emergency). The MOA also includes methods for reducing flood hazard, both by project design and by retrofitting undersized or below standard ' stormwater conveyances. Water Quality Permits Shoreline permits are required for work in floodplains; a variety of water quality permits (such as Clean Water Act Sections 401 and 404, HPA) may also apply. Applications for a nationwide permit to work in the 100-year floodplain are required by Ecology to demonstrate that there will be no loss of flood storage or function. Also,prior to any work in the 100-year floodplain, notice must be given to the Army Corps of Engineers. Floodplain Development Permit In addition to the water quality permits, local city or county governments that are participating in the NFIP issue a floodplain development permit for any structure or activity that may adversely affect the flood regime of a stream within the flood zone. State law requires local entities to have a local floodplain ordinance that meets or exceeds NFIP requirements; cf RCW 86.16 and WAC 173-158. 4.0 AFFECTED ENVIRONMENT 4.1 Topography and Hydrogeology Several rivers originally flowed into the Green/Duwamish River valley. The Green and ' White rivers flowed out of the mountains to the east and from Mount Rainier, forming a confluence near what is now downtown Auburn. From there, the Green River traveled north and was met by the Black River(an outflow from Lake Washington) near what is now Tukwila. The combined rivers formed the Duwamish("many colors") River, which t flows north into Elliott Bay. South of the White/Green river confluence lay the Stuck River, which flowed into the Puyallup River and Commencement Bay in south Puget Sound. The Stuck and White rivers flowed so near to each other that during spring floods, the two rivers would Draft Floodplains Discipline Report 17 May 2004 ' Strander Boulevard Extension City of Renton DRAFT sometimes merge, spilling water far to the north and south. In 1906 one of the largest floods diverted most of the White River's water to the Stuck River, leaving the White ' River's northern channel dry. Subsequently, government engineers built a diversion dam that permanently diverted all of the water into the Stuck River and then into the Puyallup River. The natural hydrology was greatly altered by considerable other filling, diking, channelizing, and other activities, and by the Howard Hanson Dam (see Section 4.2). The East Side Green River Watershed, also known as the Black River Basin, encompasses 24 square miles and includes portions of the cities of Renton, Tukwila and Kent, as well as some land in unincorporated King County. The proposed project area includes the Green River and its floodplain and adjacent areas, mostly below the 50-foot contour. 4.2 History of Land Use Up until the middle of the 20th century,the Green/Duwamish River valley (originally the valley of the White River) was used almost exclusively for agriculture and animal husbandry, as well as isolated single-family residential use. When settlers first arrived in the Green River Valley in the 1850s, they found arable land, abundant salmon, and proximity to both Puget Sound and the mountain passes. The valley was a center for hop ' farming until an aphid infestation in 1890, after which the area was devoted mostly to dairy and berry farms. The land was very fertile, but farmers dealt continuously with the problem of annual flooding. Farmers built their buildings on small stilts or on slightly higher ground and learned to tie-up rowboats to their front porches in case of extreme flooding conditions. By the late 1950s, levees were constructed along much of the Green River. The Howard A. Hanson Dam, dedicated in 1962, brought flood relief to the Green River valley from major valley flood events. For the next few years, farming flourished in the valley because floods were no longer an issue. However, developers who had previously shunned the waterlogged valley saw that miles of flat, open land were available. In the 1960s, the Boeing Company built a vast aerospace plant a few miles north of downtown tKent, while other companies began building warehouses up and down the valley. Farmland acreage decreased as industry moved in. Jobs were created in the valley, and apartment houses and condominiums began sprouting up over the next few decades, as well as shopping centers, strip malls, and auto dealerships. By the end of the 20th century, farming was a mere side industry in the area. The dam project that was meant to be a boon for farmers turned out to have quite the opposite effect. While farms are still interspersed in the valley, many of those that remain are ' being encroached by asphalt, concrete, and steel. Busy highways and traffic jams have taken the place of flooded waterway logjams. While the major valley flooding has been controlled, portions of the East Side Green River Watershed, have experienced recurrent flooding problems. For example,there were five floods (January 9 and November 24, 1990; April 5, 1991; February 8-9, 1996; Draft Floodplains Discipline Report 18 May 2004 ' Strander Boulevard Extension City of Renton ' DRAFT Decemberl996—January 1997) in the 7 years preceding the 1997 watershed report(City of Renton, 1997).None of these flood events have affected any parts of the proposed ' project area. This area is the subject of continuing flood control planning. 4.3 Flood Zone Mapping The NFIP FIRMs for the proposed project area(King County Washington and Incorporated Areas) are dated May 1995. These and other FIRMs are designed for ' insurance purposes; as such, most are not accurate enough to rely on for engineering design or land use decision-making. The NFIP maps tend to underestimate both the extent and depth of inundation; some of the drawbacks of the FIRMs are listed below: LMany FIRMS do not have calculated base flood elevations. • Many are based on outdated hydrographic and channel cross-section data, and/or inadequate topographic data. • Many are based on inadequate topographic data. • The delineation of channel migration zones and the relationship between ' these zones and the 100-year floodplain are not well established on the FIRM maps. ' The most current Floodplain information that is available from the City of Renton is shown in Figure 4.1. The City of Renton is currently preparing an updated, more ' accurate delineation of the floodplain in the Springbrook Creek area. However, this work is in progress, and revised mapping is not available. The 1997 corrections to 100-year floodplain elevations were used in the cross-sectional analysis of the proposed action. ' Because floodplain maps only show inundation areas, King County has begun to map areas at risk from stream bank erosion. This mapping is part of the process of updating the critical areas information for the 10-year updates of its Comprehensive Plan under the state Growth Management Act. Channel migration hazard areas have been mapped in unincorporated areas of King County along major water courses including the Green River, Cedar River, White River, Skykomish River, and all three forks of the Snoqualmie River. 4.4 Modeling Results For the 1997 East Side Green River Watershed Project, the City of Renton developed ' hydrologic (Hydrologic Simulation Program—FORTRAN [HSPF]) and hydraulic (Full EQuations [FEQ]) computer models to analyze the existing drainage system and its response to current and future storm events and to evaluate flood control measures. FEQ is a complex computer program for flood management and hydraulic-structure evaluation that simulates the movement of a flood through streams that include hydraulic control structures. HSPF-generated hydrographs were imported into the FEQ model and then routed through the Green/Duwamish River valley's conveyance system. Draft Floodplains Discipline Report 19 May 2004 ' Strander Boulevard Extension City of Renton �� _w w No /VA j j //�.,%y;•.. �� :.. � �iJ II ' '///,,.jam ..�. ' ; lor X. lion �1 VAM I 1 41-A JIM 71 • • ROADWAY1 PROP sky 34th St SkV '= 1 - 3M St May ,e, KEY - . City Limits Wetlands - Flood . RENTON ' City of - • Figure Strander Boulevard • Perteet Engineering, Inc. Floodplains ' DRAFT ' High water surface elevation in Springbrook Creek is a major cause of flooding in its gJ tributary systems. This causes water to back-up in the tributaries and reduces their ' storage capacities and contributing to the ponding of excess water. Future increases in the creek's surface water elevation will increase the frequency of flooding events. The high surface elevations are due to a combination of restrictions at several roadway crossings plus inadequate stream channel capacity. Future land use in the East Side Green River Watershed will be based on the comprehensive land use plans of King County and the cities of Renton, Tukwila and Kent, as of 1996, and is projected to result in the conversion of approximately 590 acres ' of undeveloped lowland area to commercial and industrial uses. The total amount of impervious surface is projected to increase by 45 percent, from approximately 5,300 to 7,740 acres. The City of Renton's 1997 future land use condition analysis included the assumption, with a few exceptions, that there would be no constructed improvements to the existing Springbrook Creek system. The SW 27th Street crossing of Springbrook Creek was included as one of the output points for the 1997 modeling. Under the FEQ simulation of the 100-year event,the current elevation of the 100-year flood is 16.58 feet above mean sea level, using the North American Vertical Datum 1988 (NAVD88). The future 100-year flood elevation is 17.48 feet. 4.5 Proposed Action Evaluation Findings and Project Area-Specific Environmental Concerns ' The research for this report addressed the following identified floodplain concerns for the proposed project area: ' 4.5.1 Impacts on 100-Year Flood Storage Volume With the proposed action, impacts on flood storage capacity would occur along SW 27th ' Street in the proposed project area, in the vicinity of Springbrook Creek. Floodplain volume impacts were calculated as volume displaced, as a result of construction or project-related fill, below the elevation of the 100-year flood. Volumes were found via Eaglepoint, through the Site Design Module. The "Calculating Prismoidal Volume"Function was used with the Flood Plain Surface Model and Existing Surface ' Model. 4.5.2 Impacts on the Passage of Flood Flow along a FEMA Floodway ' The action would add lanes across Springbrook brook Creek, which is an identified proposed p FEMA floodway. In 1999, the City of Renton replaced two 128-inch-wide by 83-inch- high corrugated metal pipe arches with a new three-sided box culvert(I 0-feet-highby 30-feet-wide) at this location. The culvert was sized to pass the future 100-year flood ' 21 May 2004 Draft Floodplams Discipline Report y Strander Boulevard Extension City of Renton DRAFT ' volume, as modeled by HSPF using future land use conditions flows that were hydraulically routed through an FEQ model. The culvert itself was built broadly enough ' to accommodate extra lanes on SW 27th Street. Therefore,the proposed action would not impact the floodway. ' 4.5.3 Mainstem River Channel Migration The Green River is diked and bermed along the reaches above and below the proposed project area. No channel migration zone is mapped to the proposed project area, and the proposed action is not expected to impact channel migration. 5.0 IMPACT ANALYSIS 5.1 No Action Alternative 5.1.1 Direct Impacts There would be no direct floodplain impacts associated with the No Action alternative. 5.1.2 Indirect Impacts ' There would be no indirect floodplain impacts associated with the No Action alternative. 5.1.3 Cumulative Impacts There would be no cumulative floodplain impacts associated with the No Action alternative. 5.1.4 Mitigation Measures ' No mitigation measures for the No Action alternative would be necessary. 5.2 Alternative 1: Construction of a Roadway Overpass Cross-Valley Link, Relocation of the Union Pacific Railroad Track, and Modification of SW 27th Street to Five Lanes ' 5.2.1 Direct Impacts Impacts on 100-Year Flood Storage Volume Alternative 1 would place construction and associated fill below the 100-year flood elevation in the SW 27th Street area in the vicinity of Springbrook Creek. This fill would total approximately 107 cubic yards for current conditions and 375 cubic yards for future ' conditions, and if unmitigated, would reduce flood storage capacity by those amounts. ' Draft Flood plains Discipline Report 22 May 2004 P P P Y ' Strander Boulevard Extension City of Renton DRAFT Impacts on the Passage of Flood Flow Along a FEMA Floodway ' Alternative 1 would add lanes across Springbrook Creek, an identified FEMA floodway. In 1999,the City of Renton replaced two 128-inch-wide by 83-inch-high corrugated ' metal pipe arches with a new 3-sided box culvert (10 feet high by 30 feet wide) at this location. The culvert was sized to pass the 100-year flood volume, and built to accommodate extra lanes on SW 27th Street. Therefore, Alternative would not adversely ' impact floodway. 5.2.2 Indirect Impacts ' If unmitigated, the reduction of flood storage capacity under Alternative 1 would result in the additional backing-up of water in the upstream tributaries so Springbrook Creek, which would reduce their floodwater storage capacities and contribute to the ponding of excess water. This would contribute to additional ponding of excess water and contribute to a slightly higher flood elevation and frequency in these upstream areas. ' Mainstem Green River Channel Migration ' The Green River is diked and bermed along the reaches above and below the proposed project area.No channel migration zone is mapped to the area, and no impacts to or from channel migration are expected. ' 5.2.3 Cumulative Impacts ' Portions of the East Side Green River Watershed have had recurrent flooding problems. If unmitigated, the loss of some floodwater storage capacity would result in a slightly higher flood elevation and frequency in upstream tributaries of Springbrook Creek. ' 5.2.4 Mitigation Measures ' Under Alternative 1, a location(s) should be identified in the Springbrook Creek drainage upstream of the SW 27th Street crossing for the development of approximately 375 cubic ' yards of compensatory storage. The compensatory storage could be achieved by removing dirt below the floodplain elevation and transferring the volume to a receiving location above the floodplain elevation. One hundred seven cubic yards should be below ' elevation 16.58 feet, and an additional 268 cubic yards should be below 17.48 feet. 5.3 Alternative 2: Construction of a Roadway Underpass Cross-Valley Link, Relocation of the Union Pacific Railroad Track, and Modification of SW 27th Street to Five Lanes 5.3.1 Direct Impacts Impacts from Alternative 2 would be the same as described for Alternative 1. Draft Floodplains Discipline Report 23 May 2004 ' Strander Boulevard Extension City of Renton DRAFT 5.3.2 Indirect Impacts Impacts from Alternative 2 would be the same as described for Alternative 1. ' 5.3.3 Cumulative Impacts Impacts from Alternative 2 would be the same as described for Alternative 1. ' 5.3.4 Mitigation Measures ' Mitigation measures would be the same as described for Alternative 1. 5.4 Alternative 3: Construction of a Roadway Underpass Cross-Valley Link, Union Pacific Railroad Track Not Relocated, and Modification of SW 27th Street to Five Lanes 5.3.1 Direct Impacts Impacts from Alternative 3 would be the same as described for Alternative 1. ' 5.4.2 Indirect Impacts ' Impacts from Alternative 3 would be the same as described for Alternative 1. 5.4.3 Cumulative Impacts ' Impacts from Alternative 3 would be the same as described for Alternative 1. ' 5.4.4 Mitigation Measures Mitigation measures for Alternative 3 should be the same as described for Alternative 1. ' 6.0 COMPARISON OF THE ALTERNATIVES ' Alternatives 1, 2, and 3 all would result in the same impacts on floodplains. Draft Floodplains Discipline Report 24 May 2004 Strander Boulevard Extension City of Renton DRAFT ' t' Impacts for Flood plains Table 6.1: Summary of Potential pa s p ' Alternative Direct Impacts Indirect Impacts Cumulative Impacts No Action None None None ' Alternative 1: Improvements to SW Improvements to SW Improvements to SW Construction of a 27th Street 27th Street 27th Street Roadway Overpass Construction and If unmitigated, reduced Portions of the East ' Cross-Valley Link, associated fill will be flood storage capacity Side Green River Relocation of the placed below the 100- would result in some Watershed have had Union Pacific RR year flood elevation in additional backing-up recurrent flooding Track, and Modification the vicinity of of water in the problems. If ' of SW 27th Street to Sp g rin brook Creek. Five Lanes upstream tributaries unmitigated, the loss of This fill will total and ponding of excess some floodwater ' approximately 107 water. This would storage capacity would cubic yards for current contribute to a slightly result in a slightly conditions, and 375 higher flood elevation higher flood elevation ' cubic yards for future and frequency in these and frequency in conditions. If upstream areas. upstream tributaries of unmitigated, floodwater Springbrook Creek. ' storage capacity would be reduced accordingly. ccordin ly. Alternative 2: Impacts would be the Impacts would be the Impacts would be the Construction of a same as described for same as described for same as described for Roadway Underpass Alternative 1. Alternative 1. Alternative 1. ' Cross-Valley Link, Relocation of the Union Pacific RR ' Tracks, and Modification of SW 27th Street to Five ' Lanes Alternative 3: Impacts would be the Impacts would be the Impacts would be the Construction of a same as described for same as described for same as described for Roadway Underpass Alternative 1. Alternative 1. Alternative 1. Cross-Valley Link, Union Pacific RR Track not Relocated, and Modification of SW 27th Street to Five Lanes Draft Floodplains Discipline Report 25 May 2004 ' Strander Boulevard Extension City of Renton DRAFT 7.0 REFERENCES AND SOURCES ' Federal Emergency Management Agency(FEMA). 1995 (May).National Flood Insurance Program's Flood Insurance Rate Map (FIRM), King County Washington and ' Incorporated Areas. Federal Highway Administration(FHWA). 1987. Technical Advisory T6640.8A. King County. 2004. Best Available Science. Volume I. A review of science literature. King County Executive Report. Critical Areas, Stormwater, and Clearing and Grading ' Proposed Ordinances. Ch. 4. Channel Migration Zones. 2004. Channel Migration Hazard Areas mapping. 2004. iMAP (interactive map-making application) at: ' http://www.metrokc.gov/gis/mapportal/iMAP—main.htm. • Countywide aerial images (1998). • Floodplains-100-year layer. A compilation of best available floodplain ' boundaries. Sources for the data include FEMA preliminary and final flood insurance maps (FIRMs) and King County flood boundary work maps. • Floodway layer. A compilation of best available floodplain boundaries. ' Sources for the data include FEMA preliminary and final flood insurance maps (FIRMs) and King County flood boundary work maps. ' Renton, City of. 1997 (September). East Side Green River Watershed Project Final Plan and Environmental Impact Statement, Vol. I. Stein,Alan J. 2001. "White River Valley" and"Howard A. Hanson Dam," at Seattle/King Co.HistoryLink.org. ' Washington State Department of Ecology. 2004. Facility/Site Atlas (USGS topography, 1:24,000; aerial imagery 1:24,000, 1991-97). ' Washington State Department of Transportation. 2004. WSDOT Environmental Procedures Manual M31-11 (March 2004). Draft Floodplains Discipline Report 26 May 2004 Strander Boulevard Extension City of Renton