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HomeMy WebLinkAboutLUA-06-077_MiscThe Landing City of Renton, WA oevEL~ CffY OF~~~N'NG JUN 222006 RECEIVED PRELIMINARY DRAINAGE REPORT Prepared for Fairfield Development Triad Job No. 05-071 The Landing -Preliminary Drainage Report The Landing PRELIMINARY DRAINAGE REPORT Prepared By: Sheri Murata, P.E. Reviewed By: Mark Reeves, P.E. June 22. 2006 Job #05·071 City of Renton, Washington Prepared For: Fairfield Development L.P. 5510 Morehouse Drive, Suite 200 San Diego, CA 92121 Issued June 22, 2006 ItRJAP. - The Landing -Preliminary Drainage Report Table of Contents 1 PROJECT OVERVIEW .................................................................................... 1-1 Appendix 1 ................................................................................................................................ 1-3 TlR Worksheet 2 PRELIMINARY CONDITIONS SUMMARy ...................................................... 2-1 3 OFFSITE ANALYSIS ....................................................................................... 3-1 3.1 Task 1: Study Area Definition and Maps ....................................................................... 3-1 3.2 Task 2: Resource Review ................................................................................................ 3-1 3.3 Task 3: Field Inspection .................................................................................................. 3-3 3.4 Task 4: Drainage System Description and Problem Screening .................................. 3-4 3.5 Task 5: Mitigation ............................................................................................................ 3-4 Appendix 3 ................................................................................................................................ 3-5 Site Map With Property Lines and Topography Map Assessor's Map Basin Reconnaissance Summary Report FFMA Map Excerptji-om Boeing Renton Preliminary Draft EIS L'xccrpt from City of lien/on Comprehensive Plan Sensilive Area Folio King County Soils Map Weiland fnventO/)i Afap 4 RETENTIONIDETENTION ANAL YSIS ............................................................ 4-1 4.1 SCSUHISBUH Method ..................................................................................................... 4-1 4.2 Existing Conditions ......................................................................................................... 4-1 4.3 Proposed Conditions ...................................................................................................... 4-2 4.4 Water Quality Treatment ................................................................................................. 4-2 4.5 Detention .......................................................................................................................... 4-3 Appendix 4 ................................................................................................................................ 4·4 Stormshed Results June 22, 2006 Job #05·071 !TRIAD . _\" 0(' J., T' , --- The Landing -Preliminary Drainage Report 1 PROJECT OVERVIEW The proposed project is the construction of 885 apartments (between Phase I, the south parcel and Phase 2, the north parcel), two parking garages with a total of 1,600 parking staJls, 15,000 SF of retail space and 6,000 SF for a clubhouse/leasing office on approximately 7.8 acres. The construction of a new street, N loth Street and the realignment of Logan Avenue N and Park Avenue N will be completed by the City. The site is bounded by Garden Avenue N on the east, Park Avenue N on the west, NE Park Dr on the north and N 10 th Street on the south. It is located in the City of Renton on the south end of Lake Washington. (Refer to the Vicinity Map located below). In general, the site lies within Section 8, Township 23 North, Range 4 East W.M. in King County, Washington. Vicinity Map Not to Scale The existing site consisted of an asphalt parking lot scattered with smaJl planter islands. The pavement has since been removed and the site has been cleared. To the east of the site is another existing parking lot, a concrete mixing plant, and Fry's Electronics. To the west of June 22, 2006 Job #05-071 1-1 The Landing -Preliminary Drainage Report the site is the Boeing Renton Facility. To the south are unoccupied Boeing properties and to the north is Gene Coulon Park. June 22, 2006 Job #05·071 /tIgN) ---1-2 Appendix 1 TIR Worksheet June 22. 2006 Job #05-071 The Landing -Preliminary Drainage Report ITRIAD I \"",:r"" 1-3 ---- King County Department of Development and Environmental Services TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Project Owner: FF Development L.P Address 5510 Morehouse Drive Suite 200 San Diego, CA 92121 Phone: (858)457-2123 Project Engineer: Mark Reeves, PE Company: Triad Associates AddresslPhone: 425-821-8448 Part 3 TYPE OF PERMIT APPLICATION D Subdivision D Short Subdivision D Grading [Sl Commercial [SlOther Multi-Family Part 5 SITE COMMUNITY AND DRAINAGE BASIN Community Drainage Basin Lower Cedar Drainage Basin I Part 6 SITE CHARACTERISTICS Part 2 PROJECT LOCATION AND DESCRIPTION Project Name: The Landing Location: Township .,2,.,3-'-'N'--____ _ Range '"5...!,E~ ____ _ Section 28 ______ _ Part 4 OTHER REVIEWS AND PERMITS D DFW HPA D Shoreline Management D COE 404 D Rockery D DOE Dam Safety D Structural Vaults D FEMA Floodplain D Other D COE Wetlands 0 River 0 Stream 0 Critical Stream Reach 0 Depressions/Swales 0 Lake 0 Steep Slopes Part 7 SOILS Soil Type Fill Postglacial Sand Postglacial Silt & Orgainic Deposits Alluvial Sand Slopes N/A N/A N/A N/A o Additional Sheets Attached Part 8 DEVELOPMENT LIMITATIONS REFERENCE ~ Ch. 3 -Offsite Analysis o o o o o o Additional Sheets Attached Part 9 ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION ~ Sedimentation Facilities ~ Stabilized Construction Entrance ~ Perimeter Runoff Control o Clearing and Grading Restrictions ~ Cover Practices [8] Construction Sequence o Other o Floodplain o Wetlands o Seeps/Springs o High Groundwater Table o Groundwater Recharge ~ Other None Erosion Potential Erosive Velocities N/A N/A N/A N/A N/A N/A N/A N/A LIMITATION / SITE CONSTRAINT MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION ~ Stabilize Exposed Surface ~ Remove and Restore Temporary ESC Facilities ~ Clean and Remove All Silt and Debris ~ Ensure Operation of Permanent Facilities ~ Flag Limits of SAO and open space preservation areas o Other Part 10 SURFACE WATER SYSTEM D Grass Lined Channel D Tank D Infiltration Method of Analysis IZJ Pipe System IZJ Vault D Depression SBUH D Open Channel D Energy Dissipater D Flow Dispersal Compensation I D Dry Pond D Wetland D Waiver Mitigation of Eliminated Site D Wet Pond D Stream D Regional Storage Detention Brief Description of System Operation A water quality vault will be used to treat the vehicle court Facility Related Site Limitations Reference Facility Limitation Part 11 STRUCTURAL ANALYSIS Part 12 EASEMENTSITRACTS D Cast in Place Vault D Drainage Easement D Retaining Wall D Access Easement D Rockery > 4' High D Native Growth Protection Easement D Structural on Steep Slope D Tract D Other D Other Part 13 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attachments. To the best of my knowledge the information provided here is accurate. ~ ~ '/2.I/O~ Signed/Date ,.....-I The Landing -Preliminary Drainage Report 2 PRELIMINARY CONDITIONS SUMMARY CORE REOUIREMENTS These core requirements are based on the 1990 King County Surface Water Design Manual and the City of Renton amendments. However, the water quality facility has been designed per the 2001 Department of Ecology Stormwater Management Manual for Western Washington. (2001 DOE Manual) Core Requirement I -Discharge at the Natural Location The proposed project will continue to utilize the site's current discharge point to Lake Washington via an existing 54" pipe in Garden Avenue to lohns Creek. Core Requirement 2 -Offsite Analysis A Levell downstream has been completed and is located in Section 3 Core Requirement 3 -Runoff Control No detention is required for this project since the receiving water is Lake Washington. More than 5,000 SF of replaced impervious area will be subject to vehicular traffic. A wet vault will be used for treatment, even though the replaced impervious area added is less than one acre (See Special Requirement #5: Special Water Quality Controls). Core Requirement 4 -Conveyance System All onsite storm drainage systems will be sized to convey the 25-year storm. It is assumed that the downstream pipes utilized by the project have adequate capacity. Core Requirement 5 -Temporary Erosion and Sediment Control Best Management Practices (BMPs) to minimize the transport of sediment to drainage facilities, water resources, and adjacent properties will be implemented for this project. Core Requirement 6 -Maintenance and Operation June 22. 2006 Job #05·071 2·1 The Landing -Preliminary Drainage Report The Water Quality vault will be on private property and therefore privately maintained. Core Requirement 7 -Bonds and Liability All drainage facilities will be constructed with the bond and liability requirements of the city of Renton. SPECIAL REQUIREMENTS No Special Requirements are required as part of this project. June 22, 2006 Job #05-071 2-2 The Landing -Preliminary Drainage Report 3 OFFSITE ANALYSIS 3.1 Task 1: Study Area Definition and Maps The project site is bounded by Garden Avenue N on the east, Park Avenue N on the west and N 10th Street (new street to be constructed) on the south. It is located in the City of Renton on the south end of Lake Washington. Currently the site is an asphalt parking lot with a few small planter islands which drains east to a 24-inch diameter pipe and then a 54-inch diameter pipe in Garden Avenue N. The pavement has since been removed and the site has been cleared. Runoff flows north crossing Park Avenue N. and continues along the east side of Lake Washington Blvd. It then flows west under Lake Washington Blvd and the railroad tracks into lohns Creek before flowing through Gene Coulon Park and into Lake Washington. This site lies within Basin V in Figure 3.2-2 from the Boeing Renton Comprehensive Plan Amendment EIS. Basin IV and portions of Basin VII mainly consisting of impervious surfaces also flow north into Johns Creek. 3.2 Task 2: Resource Review • Adopted Basin Plans and Finalized Drainage Studies This site is part of the Lower Cedar River Basin Plan which was last updated in January 2001. There are no areas of concern within the North Renton sub-basin of the project. • Basin Reconnaissance Summary Reports See Appendix 3.3 • Critical Drainage Area Maps This site is not within a critical drainage area. • Flood plain/floodway (FEMA) maps The site is within Zone C, which indicates areas of minimal flooding. June 22, 2006 Job #05·071 3·1 The Landing -Preliminary Drainage Report • Excerptfrom Boeing Renton Preliminary Draft EIS dated July 8,2003 Figure 3.2-2 shows the project site as part of Basin V draining to Garden Avenue N. and north to Johns Creek before discharging to Lake Washington • Excerptfrom the City of Renton Comprehensive Plan dated February 20, 1995, amended July 27, 1998 The City of Renton Comp Plan shows the site in the North Renton subbasin. • Sensitive Area Folio o Coal Mine Hazard The site is not within a Coal Mine Hazard o Erosion Hazard The site is not within an Erosion Hazard o Flood Hazard The site is not within a Flood Hazard o Seismic Hazard The site is within a Seismic Hazard zone and will be addressed during the final engineering for the site. o Landslide Hazard The site is not within a Landslide Hazard. • US Department of Agriculture, King County Soils The soils group is Ur, or Urban Land which means that the "soil has been modified by disturbance of the natural layers with additions of fill material several feet thick to accommodate large industrial and housing installations." (King County Soils Map) • Wetland Inventory Maps June 22. 2006 Job #05·071 3-2 The Landing -Preliminary Drainage Report There are no wetlands in or near the project site. 3.3 Task 3: Field Inspection There were no problems encountered during the resource review. A site visit was completed on September 19,2005. The skies were partly sunny with an approximate temperature of70 degrees Fahrenheit. There were no obvious signs of problems such as flooding or erosion during the site visit. Silt and vegetation was observed in culverts prior to discharge into the park area which could limit capacity. However, Table 3.3.1 below summarizes drainage problems observed by City staff and Boeing employees. Table 3.3.1 Drainage Problems I D<'OWLg Guard Shack Creek Culvert have been in "full" In the past there have also been reports of flooding in Gene Coulon Park from Johns Creek. The existing site conditions consist of an asphalt parking lot with scattered planter islands throughout the area. The site is relatively flat with slopes no greater than I %. The subsurface conditions consist of 5-15 feet of fill, which is underlain by highly variable, discontinuous layers of soft and loose alluvial and lacustrine soils extending to depths of 40- 110 feet below ground surface. Beneath the soft and loose soils is a dense to very dense sand. The existing site drains east to Garden Avenue N. and flows north where it enters a series of open channels, culverts, and stilling ponds. Table 3.3.2 gives the approximate culvert diameters along the drainage path from upstream to downstream before entering Gene Coulon Park. June 22. 2006 Job #05·071 3-3 The Landing -Preliminary Drainage Report Table 3.3.2 Approximate Culvert/Pipe Sizes Garden Ave N North 72" -----~.-.------------_.,"_. Crossing Lake Washington Blvd West 4 -48" ---------------------1-----I -84" Crossing the Railroad West I -72" 2 -24" Crossing driveway off Lake Washington Blvd North 3 _60,,2 before Gene Coulon Park South EnlTance of Gene Coulon Park North 3 -60,,2 I Culvets were ll.Q! measured, Just approximated from a dlstance 2 These Culvcts are partially filled with silt and should be cleaned out. Once the flows enter Johns Creek it flows in for approximately 1,000 feet in a shallow, five foot wide channel before discharging to the south end of Lake Washington. 3.4 Task 4: Drainage System Description and Problem Screening There are no problems or increased flooding anticipated because there isn't a significant increase in runoff between existing and proposed conditions since the existing site consists mainly of asphalt. Also, some of the existing problems were also eliminated by the 72-inch diameter pipe installed in Garden Avenue N. All on-site conveyance will also be sized for the 25-year storm. 3.5 Task 5: Mitigation The only mitigation proposed for this project is a wet vault for water quality treatment. June 22. 2006 Job #05-071 :>-4 The Landing -Preliminary Drainage Report Appendix 3 Site Map w/Property Lines and Topography Map Assessor's !vIal' Basin Reconnaissance Summary Report FEMAMap Excerpt ;rom Racing Renton Preliminary Draji EIS Excerpt;rom City of Renton Comprehensive Plan Sensitive Area Folio King County Soils Map Wetland Inventory lilap June 22, 2006 Job #05-071 !TRIAD , ", o{ , ,T r < 3-5 U<jg-'<rolId -"",_ . r·""~4 .~" *'_ ).3MinS OIHd~£)OdOl z ~o, 'N\I1d 3JJS £IMOM8 £IM0N\l13~HS3>/\I1 £INI308 SII3N.LII'Id lS3J\1i'o'H -..... ------- ~ ~ --... .\ ,;;;-"""" ~ L -, ~ •• ., • , , ~ ,\ \ \, \\\\\j-,,-, I. ~~ \-'I--\-\: \ \ ,\\,I.\'" .-{-,of' \' " \ \ \ \ ' . \ ... . \ \/ \ \ \ \ , \\ '., ~\.X\ \' ",," \\ \ \ .. \ \ \ \ ," '\ \" " \ ' . \ \ \, '. I, i " • j 4 ~ ~ • ® KING COUNT"( DEPARTMENT of ASSESSMENTS ,., /'", ./ . ; , -."1 ,'if I:;: " , ',.,. .'''"'- -----" + q: -. .', NW08-23-05 ~C 27 Scal. 1"1200 11-m 100'1 .... "-". , •• 3' \ "~ ,,' "\ \ " \ " 1 " \' ,- RECONNAISSANCE REPORT NO. 13 LOWER CEDAR CREEK BASIN JUNE 1987 Natural Resources and Parks Division and Surface Water Management Division King County, Washington Departmeot of Public Worts Don LaBelle, Director King Couoty &ecutive Tim Hill King Couoty Couocil Audrey Gruger, District 1 Cynthia Sullivan, District 2 Bill Reams, District 3 Lois North, District 4 Ron Sims, District S Bruce Laing, District 6 Paul Barden, District 7 Bob Grieve, District 8 Gary Grant, District 9 I'IlrIr;s, PIanniog and Resources Joe Nagel, Director Surface Water Managemeot Division Joseph J. Simmler, Division Manager Jim Kramer, Assistant Division Manager Dave Clark, Manager, River & Water Narum Resources and Parts Division Russ Cahill, Division Manager Bill JoDy, Acting Division Manager Derek Poon, Chief, Resources Planning Section Bill Eckel, Manager, Basin Planning Program Resource Sect ion Larry Gibbons, Manager, Project Management and Design Section Cootn"buting Staff Doug Chin, Sr. Engineer Randall Parsons, Sr. Engineer Andy Levesque, Sr. Engineer Bruce Barker, Engineer Amy Stonkus, Engineer Ray Steiger, Engineer Pete Ringen, Engineer Consulting Staff Don Spencer, Associate" Geologist, Earth Consultants, Inc. John Bethel, Soil Scientist, Earth Consultants, Inc. P:CR Contributing Staff Ray Heller, Project Manager & Team Leader Matthew Clark, Project Manager Robert R. Fuerstenberg, Biologist & Team Leader Matthew J. Bruengo, Geologist Lee Benda, Geologist Derek Booth, Geologist Dyanne Sheldon, Wetlands Biologist Cindy Baker, Earth Scientist Di Johnson, Planning Support Technician Robert Radek, Planning Support Technician Randal Bays, Planning Support Technician Fred Bentler, Planning Support Technician Mark Hudson, Planning Support Technician Sharon Clausen, Planning Support Technician David Truax, Planning Support Technician Brian Vanderburg, Planning Support Technician Carolyn M. Byerly, Technical Writer Susanna Hornig, TeChnical Writer Virginia Newman, Graphic Artist Marcia McNulty, Typesetter Mildred Miller, Typesetter Jaki Reed, Typesetter Lela ura, Orfice Technician Marty Cox, Office Technician I I " I I TABLE OF CONTENTS I. SUMMARY II. INTRODUCTION m. FINDINGS IN LOWER CEDAR RIVER BASIN A. Overview of Basin B. Effects of Urbanization c Specific Problems 1. Drainage and nODding problems 2. Damage to property 3. Destruction of habitat IV. RECOMMENDATIONS FOR ACTION V. A. Reduce landslide hazards B. Reduce erosion and nODding C Prevent future erosion and nooding with appropriate analysis, planning, and policy development D. Stop present (and prevent future) damage to habitat by addressing specific problems in stream systems MAP APPENDICES: APPENDIX A: Estimated Costs APPENDIX B: Capital Improvement Project Ranking APPEDDIX C: Detailed Findings and Recommendations 1 1 2 2 4 5 5 6 6 7 7 7 8 8 11 A·I B·l Col I. SUMMARY The Lower Cedar River Basin, in southwest King County, is unique in its development pat- terns and the associated environmental problems that appear throughout the basin. Except for the city of Renton and areas on the Cedar River Valley floor, most of the development in the basin has occurred on the upland plateaus. Most of this development is recent and primarily residential. In addition, the plateau is the site of numerous sand and gravel mining operations and, in the southern uplands, an abandoned coal mine. Peat is also being mined nonh of Otler Lake. In some areas livestock are being raised on small farms; there are no major crop-related agricultural activities in the basin. The effeclS of development are most apparent where storm drainage is routed over the valley walls. ImpetVious surfaces 00 the plateau have mc:re-d the rate and volume of IItorm runoff, ...suIting in substantial erosioo, &iltation, and flooding below. In addi- tion, erosioo and &iltation have damaged or destroyed habitat in many tnbutaries, threatening the survival of fiSh. Habitat and water quality throughout the basin are also threatened by the filling of wetlands and the presence of \arp,e amounts of domestic tIash in some streams. The reconnaissance team noted that the Peterson Creek system has so far remained in its natural, nearly pristine condition. Maintaining this quality should be a high priority in future basin planning capital project programs. Recommendations in the Lower Cedar River Basin include 1) designing and c:oostructing appropriately sized RID and other drainage facilities; 2) establishiDg stricter land use policies regarding floodplains, wetlands, and gravel mining; 3) conducting more detailed and compreheosiYe bydraulic/bydrologic analyses of proposed developments; and 4) praenting damage to the Datura! drainage system_ The field team also recommends S) restoring the habitat of se....ral tributaries (e.g., cleaning gravels, revegetating stream banks, and diversifying streambeds for spawning and rearing) as well as 6) protecting the nearly prisIine quality of Peter.soo Cn:et. D. lNfRODUCTION: History and Goal<; of the Program P:LC In 1985 the King County Council approved funding for the Planning Division (now called the Natural Resources and Parks Division), in coordination with the Surface Water Management Division, to conduct a reconnaissance of 29 major drainage basins located in King County. The effon began with an initial investigation of three basins -. Evans, Soos, and Hylebos Creeks --in order to determine existing and potential surface water problems and to recommend action to mitigate and prevent these problems. These initial investiga- tions used available data and new field observations to examine geology, hydrology, and habitat conditions in each basin. Findings from these three basins led the King County Council to adopt Resolution 6018 in April 1986, calling for reconnaissance to be completed on the remaining 26 basins. The Basin Reconnaissance Program, which was subsequently established, is now an important ele- ment of surface water management. The goals of the program are to provide useful data with regard to 1) critical problems needing immediate solutions, 2) basin characteristics for use in the preparation of detailed basin management plans, and 3) capital costs associated with the early resolution of drainage and problems. The reconnaissance reports are intended to provide an evaluation of present drainage con- ditions in the County in order to transmit information to policymakers to aid them in developing more detailed regulatory measures and specific capital improvement plans. They are not intended to ascribe in any conclusive manner the causes of drainage or erosion 1 Lo" .. er Cedar River Basin (continued) problems; instead, they are to be used as initial surveys from which choices for subsequent detailed engineering and other professional environmental analyses may be made. Due to the limited amount of time available for the field work in each basin, the reports must be viewed as descriptive environmental narratives rather than as final engineering conClusions. Recommendations contained in each report provide a description of potential mitigative measures for each particular basin; these measures might provide maximum environmental protection through capital project construction or development approval conditions. The appropriate extent of such measures will be decided on a case-by-case basis by County offi- eials responsible for reviewing applications for permit approvals and for choosing among competing projects for public construction. Nothing in the reports is intended to substitute for a more thorough environmental and engineering analysis possible on a site-specific basis for any proposal. m. fINDINGS IN WWER CEDAR RIVER BASIN P:LC The field reconnaissance of Lower Cedar River Basin was conducted in January 1987 by Robert R. Fuerstenberg, biologist; Bruce L Barker, engineer; and Lee Benda, geologist. Their findings and recommendations are presented here. A Overview of Lower Cedar River Basin The lower Cedar River Basin is located in southwest King County and is 27 square miles in area. It extends southeast from the mouth of the Cedar River on Lake WaShington to approximately river mile 14.0. The boundary to the northeaSI is marked by a ridgetop connecting the city of Renton to Webster and Franklin Lakes; the boundary to Ihe southwest runs along Petrovilsky Road to Lake Youngs. Renton is the only incorporated area in the basin. Olher population centers include Fairwood, Maplewood Heights, and Maple Valley. Excepl for the city of Renton, most of the residential concentrations are located on Ihe upland plaleaus overlooking Ihe Cedar River Valley. These upland developments are recent compared to the smaller established communities on the valley noor. The basin lies within portions of three King County planning areas: Newcastle in Ihe northeast (which includes Renton), Tahoma-Raven Heights in the east, and Soos Creek (the largest of the three) in the west. Rural areas exist on the valley floor on both sides of the Lo""r Cedar River, from approximately river mile 5.50 to 13.00. These are limited to pastureland for horses, cows, and some sheep and several small "u-pick" fruit and vegetable farms. Similar areas are located on the southern uplands above the reach from river mile 5.50 to 7.00 and in the Lake Desire-Otter Lake area. The plateau is also the site of sand and gravel mining operations and, in the southern uplands, of the abandoned Fire King Coal Mine. Peat deposits exist west of Lake Desire and north and south of Otter L1ke, and peat mining is being carried out north of OUer Lake. Present zoning allo",,'5 for urban and suburban densities throughout much of the basin, particularly on the upland plateaus and in the Cedar River Valley from its mouth to appoximately river mile 6.50. Population projections for the year 2000 in the three plannign areas containing the Lower Cedar Basin are over 311,000, an increase of 47 2 I I I I I I P:LC Lower Cedar River Basin (continued) percent from the present. Most of this growth will occur in the Soos Creek Planning Area. Dominant geological and geomorphic features. The geology of the Lower Cedar River Basin is diverse. Geological formations exposed along the valley include sedimentary rocks, undifferentiated older glacial drift, extensive ground moraine deposits, recent alluvium along the Cedar River, and landslide deposits along the river and its tribu- taries. The sedimentary rocks, composed of moderately dipping sandstones, con- glomerates, mudstones, and shales, are exposed locally along the cliffs of the Cedar River Valley near the mouth of the Cedar River. In addition, the Renton formation, composed of sandstones, mudstones, and shales with periodic deposits of coal, is also exposed along the lower portion of the Lower Cedar River Valley. Undifferentiated glacial deposits found here are composed of three or more till sheets, glacio-fluvial sand and gravel, glaciO-lacustrine clay, and sand, and non-glacial sand, clay and thin peat. These lie over the sedimentary rock formations and are best exposed in cross-section along the cliffs of the main valley and major tributaries. The morphology of the Lower Cedar River Basin is dominated by the valley formed by the Cedar River. Valley walls are Sleep cliffs formed by landslides in glacial sedi- ments. A once extensive and meandering River, which created a wide valley floor as it cut its way westward, the Cedar today is diked for most of its length through the lower valley. A narrow but extensive band of landslide deposits exists along the steep cliffs of the main river and its major tributaries. The landslide deposits consist of deformed blocks of glacial sediments and colluvium derived from slides or mass flowage, such as landslides and debris flows. Rec .. nt alluvial deposits fill the valley and major tributaries. Small, composite, alluvial debris fans exist at the mouths of the largest tributaries. Closed depressions, principally in the uplands, have lacustrine and peat deposits. The Lower Cedar River Valley has a high potential for erosion due 10 steep slopes and the existence of a clay layer that promotes soil failures. In addition, the confined nature of tributary channels between steep hillslopes promotes bank erosion during high flows. Numerous recent landslides are evident along cliffs of many of the steep tributaries and along the main stem of the Cedar River. These have been accelerated by the removal of vegetation and the routing of concentrated storm flows over steep slopes in areas where development has occurred. Hydrologic aDd bydraulic cbaracteristics. The Cedar River Basin is composed of a complex drainage network conSisting of the Cedar River and 17 tributaries. The larger tributaries begin in lakes or wetlands on the bluffs and flow through relatively flat, stable channels to the edge of the Cedar River Valley, then plunge down to the valley floor through steep, erodible ravines. Tributaries of this type such as Tributary 0304 (with headwaters at Wetland 3111) and Tributary 0328 (which begins at Lake Desire), are found on the south side of the Cedar River. Another type of tributary collects surface nlnoff from urbanized areas, past\lfeland, and wooded areas. Tributaries 0302, 0307, and 0312 are examples of this type of tributary. They are intermittent (depending on rainfall), shorter in length, flow through shallower channels that are steeper at the bluffs and transport more material during times of 3 P:LC Lower Cedar River Basin (continued) high flows. Some of the worst problems located during field investigation (see Appendix C for a full listing) occur on this type of tributary. Catchments 5, 6, and 12 have very infiltrative soils. Urban developments hvae utilized RID poinds to effectively infiltrate all urban runoff before it reaches the valley hillslopes. The infiltrated runoff then reappears as springs. Two large lakes (Desire and Otter), together with four smaller ones (Shady, Peterson, Webster, and Francis) lie in the southeast third of the basin. Numerous large wetland areas exist in this section as well. The field team identified 10 potential wetland sites that had not been previously identified in the Sensitive Areas Map Folio (SAMF). The system of lakes and wetlands in this area effectively buffers the high flows draining to these tributaries. Habitat cbanlcteri&tic:s. With few exceptions, usable fish habitat exists only in peren- nial streams (i.e., Trib. 0302, 0304, 0305, 0328, and possibly 0308). In other streams (e.g., Trib. 0303 and 0310), steep gradients preclude fish use. Steep gradients also reduce fish use in the perennial systems (except for Trib. 0328). Habitat is in various stages of degradation in these systems; pools are being filled and gravels and debris shift regularly. In Tributary 0328 (Peterson Creek), however, habitat diversity is extensive, and the channel is not seriously degraded. At this location the field team obselVed at least three species of salmonoids. In general, the most diverse and least disturbed habitat in a tributary system occurs in the large wetland areas in the southeast third of the basin. Usable habitat for anadromous fish is found in the low-gradient portions of streams where channels cross the Cedar River Valley floor. In these reaches, however, only spawning habitat is likely to be available, as the pools and woody debris necessary for successlul rearing either do not exist or are quite limited. Excellent spawning and rearing areas exist where pools and riffles are extensive, instream cover and bank vegetation are intact, and diversity of habitat types is abundant. B. FIfects 0{ Urbanization in the Basin Flooding. erosion, and the degradation of habitat associated with development in the Lower Cedar River Basin are most apparent where development has eliminated vege- tation along the edges of the valley and where stormwster has been routed down channels and swales. The removal of vegetation, such as trees, above and below the edges of valley walls, as well as the discharging of stormwater over the valley wall, has resulted in tension cracks and landslides that are endangering some houses. The sedi- ments from these failures are depositing in streams and on valley floors and damaging fish habitat and private property. Discharging stormwater from increased impervious areas into steep tributary channels and swales is seriously destabilizing channels and valley walls; this in turn results in channel downcutting. bank erosion, and landslides. The sediments from these problems often degrade fish habitat and settle out on pri- vate property along the valley floor. Two serious instances of development-related erosion occurred during the November 1986 storm: 1) culverts rerouting the stream were plugged, causing the formation of a new channel that destroyed portions of roads on Tributary 0314; and 2) new, uncom- 4 I I I I I I I P:LC Lower Cedar River Basin (continued) pacted fill adjacent to new residences near collection point 5 was washed partly away during the storm, causing landsliding and gullying. Future problems will be similar to these, as commercial and residential developments increase flow rates and volumes by decreasing natural storage and infiltration. This is expected to occur if wetlands on the upper plateau are encroached upon or lost (e.g., on Trib. 0304 at RM 2.30 and on Trib. 0304A at Rm 1.60). The preservation of wetlands and streambank vegetation and the attenuation of storm flows are essential in this basin. c. Specific Problems Identified The steep valley sideslopes through which streams pass and the often dense upland development result in a number of similar problems that repeat themselves throughout the Lower Cedar River Basin. The most significant of these are outlined and discussed below. 1. Drainage and flooding problems are often tbe result of several conditions: a. Undersized culverts and inadequate entrance structures. The most notable area is on Tributary 0306 at river mile .30, where a culvert here was blocked by debris carried downstream by the stream and caused erosion and flooding of Faitwood Golf Course. The blockage was compounded by the fact that the culvert was undersized; the problem will worsen as flows increase from upstream development. b. Serious instream erosion and subsequent downstream sedimentation. These have been caused by three main factors: 1) runoff from residential developments on the bluffs above the valley, 2) compacted pastureland due to livestock, and 3) runoff from impeJVious areas Originating at gravel pits. These problems will continue and worsen until mitigative measures are taken. (See Appendix C for specific examples.) Co Undersized recbanoelized streams. Tributaries on the valley floor are too small to carry the increased flows originating in developed residential areas along the top of the bluffs. For example, Tributary 0302 at river mile .25, the channel along Maplewood Golf Course, overtops and floods during storms. d. e. Construction in wetland and floodplain areas, Many of the wetlands on the south side of the Cedar River are peat bogs, and roads built through them continue to settle each year, increasing the amount of flooding on the road. For example, the road crossing with Tributary 0328B north of Lake Desire will experience more severe flooding as the road settles. Discbarging of stormwater at tbe top of steep banks. At river mile 2.20 on the Cedar River, a trailer park (constructed on the edge of the cliff) discharges its drainage down the valley wall. Increased flows erode the steep valley, depositing sediments on the valley floor, blocking channels and causing flooding. These problems will eventually stabilize, but only after a large qllantity of soil has been eroded. 5 P:LC Lower Cedar River Basin (continued) 2 Damage to property is being caused by tluee faetors: a. Landslides and potential landslides. Landslides are accelerated by the removal of vegetation on steep slopes in preparation for residential construction and/or by the routing of storm flows over hillslopes. For example, a large landslide has already occurred in the front yard of a resi- dence on the Cedar River at river mile 7.80. b. SedimentatioD (from landslides). Sedimentation and channel and bank ero- sion are damaging private property along the valley floor (Trib. 0299 and 0310). Co F1oodiog during storms. Aooding has been brought on by the effects of development and associated changes to the natural drainage systems in the basin. (See "B" above.) 3. Destruction of babitat is being caused by four cooditioos: a. Sedimentation of pools and riffles and cementing of gravels. These problems, the result of severe erosion and the transport of bedload material, have been caused by upland developments in the basin and the presence of associated impervious surfaces, which increase the rate and quantity of surface runoff. Sedimentation and cementing of gravels in streambeds destroy natural spawning and rearing habitat. On Tributary 0307 at river mile .40 and Tributary 0305 at river miles .95, 1.20, and 1.70, recent high flows have eroded the streambed at least one foot, contributing to a serious siltation problem downstream. Heavy bedlo.1d transport is evi- dent in all systems of the basin except Tributary 0328. In Tributary 0303 at river mile .25, fine sediments are accumulating in gravels that may be used by resident fish. In Tributary 0304 between river miles .95 and 1.20, pools are being filled by sands and gravels and rearing habitat is being rapidly lost. b. Cbaooeli7Jltion of &beam beds. Loss of habitat through channelization has occurred in all the major streams of the basin, but most noticeably in those reaches that cross the valley floor. These reaches lack habitat diversity, reducing fish use for spawning and rearing. Channelization has damaged or destroyed. habitat in several reaches that were once heavily used by fish; these include Tributary 0302 between river mile .30 and 40, Tributary 0304 between river miles .O? and .18, Tributary 0305 between river mile .20 and .75, and Tributary 0328 from river mile 1.10 to 1.40. These systems cannot afford a further reduction of habitat and still remain viable fishery resour· ees. c. The aa:umulatioD of trash in stream beds. This problem occurs in close proximity to residential areas. Trash degrades water quality and is visually unpleasant. Tires, appliances, furniture, and other trash have been thrown into Tributary 0302 at river miles 1.00 and 1.10 and in Tributary 0303 at river mile .35. 6 . , .. i; Lower Cedar River Basin (continued) d Wetland encroacbment. Encroachment destroys habitat and eliminates natural water filtration and storage for surface runoff. Examples of this problem were observed on Tributary 0304 at river mile 2.30, Tributary 0308 at ,80, and Tributary 0304A at river mile 1,80, Many wetlands have already been completely lost through filling, for example On Tributary 0306A at river mile .55. Suspected violations were forwarded to Building and Land Development for enforcement. IV. RECOMMENDATIONS FOR ACTION P:LC The primary recommendations for action in the Lower Cedar River Basin addresses current severe problems related to erosion, habitat destruction, and nooding. Prevention of these problems will be accomplished by controlling locations and densities of new development and providing adequate RID facilities for stormwater. A Reduce landslide bazards by: 1. Including sensitiv1: areas not previously mapped on Ibe Sensitiv1: Areas Map Folio (SAMF). See Appendix C for a full listing of sensitive areas. 2 Establisbing building setbacks along cliffs and native grov.1h protection easements along steep ravines, 3. Discouraging or eliminating tbe routing of stormwater OYer cliffs, unless adequate tightline systems can be constructed to convey flows in a safe, nonerosive manner to the bottom of cliffs. 4. Decreasing peak nows by constructing larger RID facilities to lessen the landslide and erosion occurrence along tributary slopes. B. Reduce erosion and nooding in !be basin by improving surface water management: 1. Direct tbe Facilities Management Section of !be Surface Water Management Division to evaluate existing storm-detentioo and cooveyaoce facilities to deter· mine whether they are properly sized to meet current standards. Evaluation should begin with all single.orifice RID facilities. 2 Consider areas otber tban wetlands as regional storm-detention Cacilities. Tributary 0300 at river mile .42 is the site for a proposed dam, for example, 3. Utilize existing lower quafity wetlands (tbose rated olber Iban #1) as regional storm.<fetention facilities. Wetlands 3102 and 3142 could provide more live storage, for example. 4. 5. Review channel and culvert capacity Cor conveying existing and future runoCf, and establish floodplain areas in regions of slight gradient for existing and future nmoff conditions, Promote the infiltration of surface water through Ibe use of retention facilities and open channels instead of pipes where the soil and slope conditions permit. Collection points 5, 6, and 12 on plateaus have such soil conditions. 7 P:LC Lower Cedar River Basin (continued) C. Prewnt future problems of eroo;ion and Hooding with appropriate analysis, planning. and policy dC\'elopment related to surface water management: 1. Conduct a detailed, IXlIIlprebensive hydraulic/hydrologic analysis of any proposed developments to determine impacts on the drainage courses downstream. This is especially critical for areas on the' upper bluffs and plateau, which drain over steep, sensitive banks above the Cedar River. 2. Conduct a study of the impact o( locating mrdtratioa ponds utilized near the edge of the bluffs to determine their effect on seepage (aces on the lower face of the bluffs. This might be accomplished with a computer.based numerical model of the groundwater flow. 3. Require the tigbt1ioiog of storm drainage down steep or sensitive slopes when they cannot be directed away from the slopes. This is done by piping the flow down the slope and discharging it at the bottom with adequate energy dissipation. Many of the intermittent tributaries flowing down the banks should be tightlined as urban development increases flow to them. 4. Coosttuct new RID ponds with [dler berms 10 improve waler quality and reduce nne sedimenl loads. New RID ponds should have two cells with gravel.berm £i1ters and vegetated swales at the inlet and outlet. Consider Tributaries 0304, 0304A, 0302, and 0303 as sites for this type o( facility in order enhance water quality. S. Maintain natural vegetation on streambanks and HoodplaiDs. This is especially important for relatively flat channels flowing on the plateau before they reach the steep bluffs because these channels and their floodplains will attenuate flows during times of heavy runoff. 6. Maintain buffer areas around _tIaDdS. Many of the tributaries on the south side of the Cedar River headwater at wetlands. These wetlands act as natural storage areas during storms. 7. Reevaluale King County policy reg;anling permitting for gmveJ mining on steep, sensitive slopes. 8. Include the city of Rention in future inlerlocal agreements for planning and capi. tal imprOVement projects where city and county interests overlap. D. Eliminate present damage to habitat and preyent future damage by addressing specifIC problems in the stream systems. The following activities should be coordinated among King County, the Muckleshoot Indian Tribe, and State Departments of Fisheries and Game: 1. Reduce damaging storm flows with greater detention volume and lower release rates at upstrenm developments. 2. Implement restoration projects on Tributaries 0304 (river mile .00 •. 20), Tributary 0305 (river mile .20 •. 80), Tributary 0303 (river mile .25-.35), and Tributary 0328 (river mile 1.10 -1.40): 8 · , · , , . · , , . I I I I P:LC a. Lower Cedar River Basin (continued) 00 Tnbutary 0304: Clean streambed gravels, add habitat and bed-control weirs, and plant bank vegetation for shade. b. 00 Tributary 0305: Construct a new channel and move stream from road· side channel to its new location on adjacent lands. Implement a full restoration project to provide channel meanders, habitat structures, pool/rime enhancement, streambed gravel replacement, and revegetation. Co d. 00 Tn"butary 0303: Move stream from present channel to a location further north, away from the roadside. If relocation is not possible, these minimum steps should be taken: Add habitat structure to existing channel with root masses, denectors, boulder clusters, and other features; revegetate channel banks with shrubs and small trees; enhance stream crossings with bottomless pipe arches. 00 Tn"butary 0328 (peterson Creek): Add habitat structure by replacing the straight, shortened channel with a more natural, meandering one; place habitat structures (such as root masses, denectors, cover logs, and boulder clusters) throughout the channel; and revegetate banks with shrubs common to adjacent riparian zones (salmonberry, ninebark, or dogwood, for example). 3. Proted lbe Peterson Creek system (Tn"b. 0328) in its present, near·pristine state. This will include not only the restoration outlined in section A above, but also the adoption of land use management regulations to prevent future habitat destruction: a Proted all existing wetlands within tbe subcatchmeots of Peterson Creek. Employ wetland buffers at least 100 feet wide without exception. b. Restrict d.,..,lopmenl in tbe critical headwater area (drainage, habitat, water quality) bouuded by Lake Desire, Otter Lake, and Peterson Lake to rural densities. c. Designate and proted streamside managemenl zones of at least 100 feet from the ordinary high·water mark (OHWM) along the main stem of the creek. Use 25 feet from the OHWM on tributaries. d. Preserve Ooodplains and tbeir forests for dynamic retention of sediments and water. e. f. g. Restrict ""getation removal in stJeamside/wetland management zones. Size RID facilities 10 store lbe lOO-year stonn at a two·to·five.year release rate. Use lbe Iwo-ceU type of pond with a forebay, a gravel filter, and a vegetated swale outflow where feasible. Regulate more c101!ely all septic tank and drain·fleld instaUations, as well as maintenance schedules, particularly in the Lake Desire, Otter Lake, and Peterson Lake drainage areas. 9 4. P:LC Lower Cedar River Basin ( continued) b. Work with !be Stale Departmenl or Ecology 10 establisb minimum stream- now requirements for Peterson Creek and Lake Desire tributary. Develop and promote public education and involvement programs for basin awareness. Work with schools, environmental groups, and the civic and business communities to conduct educational and restoration programs. 10 - APPENDIX A ESTIMATED COSTS: PROPOSED CAPITAL IMPROVEMENT PROJECTS LOWER CEDAR CREEK BASIN • Indicates project was identified by Surface Water Management office prior to reconnaissance. NOTE: All projects are located on map included in this report. Project Numher 3105' 3109' P:LC.APA Collect. Point 10 10 Project Descript ion Enhance 2200' of Trit>. 0305 from Cedar River to Elliot Bridge. Secure easements to wetland located in Cascade Park and construct a berm at the outlet. Replace existing catch hasins with control structures. Project should he justified hy a hasin study. Wetland rated #2. (This wetland will require further biological evaluation before RID design and co.nstruction.) Problem Addressed Mitigates flooding of King County park land. Detter utilizes wetland's storage capacity to address peak flows from surrounding urban area. A·I E~timated Costs and Comments $115,000 (NOTE: This project was proposed by Surface Water Management, is in the design phase, and will be mnstructed by 1989.) $186,000 Project Number 3111 (Wetland 3136) 3112 (Wetland 3142) 3114' (Wetland 3150) 3115 P:LC.APA Collect. Point 19 18 Proiect Description Secure easements to outlet to Francis Lake and 1100' of channel from lake to SE l84th St. Construct a weir to raise lake levell', and enhance 1100' of Trih. 0317. Should he justified hy a basin plan. Wetland rated # I. (This wetland will require further hiological evaluation hefore RID design and construction.) Secure easement for outlet to wetland and replace existing weir with a concrete-slotted weir. Should be jlL~tified by a basin plan. Wetland rated #2. (This wetland will require further biOlogical evaluation hefore RID design and construction. Secure casement to Wetland 3150 and construct a containment berm and control structure at the outlet. Project should he jlL~tified by a ba<in plan. Wetland rated #2. (This wetland will require further hiological evaluation before RID design and construciton.) Install detention pond and 1,000' of tightline. Project is indepen- dently justifiable. Problem Addressed Will provide additional storage to mitigate anticipated future incrca.~d flows. Will provide additional storage for anticipated future peak flows. Addres.'IC.~ anticipated increases in flow caused hy development. Mitigatc.~ «.'Verc erosion and flooding during times of high flows. A-2 Estimated Costs and Comments $175,000 S117,000 $134,000 $361,000 ~ Project Number JIl6 3117 3118 3119 3120 P:LCAPA Collect. Point 21 16 10 4 15 Proiect Dc.""ription Raise existing road emhankment 24'. Project should be indepen- dently justifiable. (Refer to Roads Division.) Install 1,400' of tightline, a sediment trap, and 700' of channel from Jones Rd. to Cedar River. Project is independently justi- fiable. Install 300' of 36" culvert, a new inlet structure, manhole, and catch basin. Project is independently justifiable. Construct a detention dam and control structure in a deep channelized section of Trib. Q300. Project is independently justifiable. Construct a sedimcntation pond and 1,000' of channel from Jones Rd. to Cedar River. Project is indepen- dently justifiable. Prohlem Addressed Miti:;.,tes seasonal Oooding of Lake Desire Dr. SE caused by road bed settling in the peat bog. Mitigates severe erosion, sediments deposited on County roads, and Oooding during times of high flows. Will prevent blockage of culvert and the accompanying flooding and erosion of Fairwood Golf Course and mobile home park below. Project location is ideal because it addres.""s flows from a large residential area before they reach the steep, sensitive area next to the Cedar River. Mitigatcs flooding of residence and sediment deposition on Jones Rd. A·3 - Estimated Costs and Comments $73,000 $501,000 $87,000 $159,000 $163,000 Project Collect. Estimated Costs Number Point Project Description Problem Addressed and Comments 3121 7 Secure easement to wetland and con· Addresses increased nows in Trib. $371,000 (Wetland struct a containment hcrm and concrcle 0304 and 0304A from residential 3102) weir at outlet. Project should be developments. justified by a basin plan. Wetland rated #2. Biological assessment is needed to assure that this project does not decrease habitat value.'\. 3122 11 Purcha.<;e existing ponds on Fairwood Mitigate.~ nooding and erosion $342,000 Golf Course and expand to provide downstream. greater now detention. Project is independently ju.'IIifiable. P:LC.APA A-4 - - APPENDIX B CAPITAL IMPROVEMENT PROJECT RANKING LOWER CEDAR RIVER BASIN Prior to the Lower Cedar River Basin field reconnaissance, 12 projects had been identified and rated using the CIP selection criteria developed by Ihe Surface Water Management (SWM) and Natural Resources and Parks Divisions. Following the reconnaissance, 13 projects remain proposed for this area. They include eight new, previously unidentified and unrated projects. These displace seven previously selected projects, which were eliminated based on the consensus of the recon- naissance team. Projects were eliminated for several reasons: two sites were annexed by the city of Renton, two projects were found to be unnecessary, two sites were categorized as #1 wetlands (and are· ineligible), and one project was determined to be infeasible. The previous SWM capital improvement project list for the Lower Cedar River Basin had an esti- mated cost of $2,710,000, while the revised list increases to an estimated cost of $2,784,000. This 3 perce ill increase in estimated capital costs is due to the addition of projects after the reconnaissance. The following table summarizes the scores and costs for the CIPs proposed for the Lower Cedar River Basin. These projects were rated according to previously established SWM Program Citizen Advisory Committee criteria. The projects ranked below are those for which the first rating question, ELEMENT 1: "GO/NO GO," could be answered affirmatively. Projects with scores of 100 or higher can be considered now for merging into the "Jive" CIP list. RANK PROJECT NO. SCORE COST 1 3122 103 $342,000 2 3118 90 87,000 3 3120 75 163,000 4 3109' 67 186,000 5 3121 65 371,000 6 3117 60 501,000 7 3115 60 361,000 8 3116 55 73,000 9 3114' 28 134,000 10 3111' 25 175,000 11 3112' 17 117,000 12 3119' 15 159,000 13 3105 12 115,000 TOTAL $2,784,000 , Projects propose" prior to the Reconnaissance Program P:LCAPB B-1 • All items listed here are located on final display maps APPENDIX C DETAILED FINDINGS AND RECOMMENDATIONS LOWER CEDAR RIVER BASIN in the offices of SUrface Water Management, Building and Land Devetopment, and Basin Planning. Trib. & Collect. Existing Anticipated Item* River Mile Point Category Prop. Proj. Conditions and Problems ~itions and Problems 1 5 Geology Gullying and landslides in Continued erosion. uncompacted fill in new development near edge of steep hillslope. 2 18 Geology Small landslide has fonned None (natural failure). debris flow (11/86). Sedimentation in yard of residence. 3 0299 4 Geology Landslide.. in sedimentary Natural failure. RM 2.6 rock in cutbanks adjacent to railroad. 4 0299 16 Geology Drainage from residential Increa<ing erosion. RM 9.65 area is resulting in gullying in swale. P: LC.APC C·I - Recommendations Recompact fill, revegetate, and drain adequately. None. None. Provide adequate RID to attenuate flows. Trib. & Collect. Existing Anticipated Item River Mile Point Category Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 5 0299 18 Geology Horse farm in uplands has Continued high erosion and Develop RID at horse farm RM 12.1 created extensive imper. sedimentation. to altenuate peak flows. vious surfaces, resulting See Project 3115. in channel scour, bank erosion, landslides, and sedimentation at mouth of basin. Residence overcome with sediment. 6 13 Geology Landslide terrain for sale Site of future mass erosion. Prohibit development here. by realtors. High risk for Notify Building and Land landslides, flooding (from Development. Add area to sprin~). SAMF. 7 7 Geology Large«ale landsides Natural process. None. adjacent to Cedar River due to sprin~ and cutting of toeslopes by streams. Appears to be natural. 8 2 Geology Gullying in valley wall, Unknown. None. possibly from natural sprin~. 9 14 Geology Landslide debris flow from Existing tension cracks Revegetate hillslope with residence on SE 147th Pl., indicate future instability. trees and shrubs. Renton. P: LC.APC C-2 =-=-~=-=- Item 10 11 12 13 14 15 Trib. & Collect. River Mile Point 0299.1A RM .08 0300 RM .00-.40 0300 0300 RM 1.40 0302 RM .50 21 4 4 4 6 0302 6 RM .80-1.00 P: LC.APC Category Prop. Proi. Hydrology 3116 Geology Hydrology 3119 Hydrology 3109 Geology Geology Existing Conditions and Problems Frequent flooding of county road caused by low road embankment. Extensive channel and bank erosion and numerous landslides due to development-related stormwater. Development-related peak flows have caused sig- nificant bank erosion. Collection point 4 has been nearly completely urbanized. Channel downcutting and bank erosion. Bank erosion (medium den- sity) at meanders and obstructions. C-3 Anticipated Conditions and Problems Road located on top of peat bog and will continue to settle, aggravating flooding problem. Problems will continue. Increased erosion on hillslopes below. Degradation of Trib. 0300 from RM .42 downstream. This section is very' steep and susceptible to erosion. Will continue at same level or increase. Increasing erosion with increasing flow from devel- opments. Recommendations Elevate the road 3-4' by filling on top of the present road embankment. Also stabilize embankment. Provide adequate RID in uplands. (See Project 3119.) Construct detention dam in deep. channelized reach of Trib. 0300. Construct berm and standard control structure at outlet to Wetland 3120 in Cascade Park. Control storm flows from uplands. Provide adequate RID in uplands as area develops. Trib. & Collect. Existing Anticipated Item River Mile Point Category Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 16 0302 6 Geology Gully erosion from broken None. Culvert has been None. culverts. repaired. 17 0302 6 Geology Severe gully erosion Continued erosion. TighUine flows to RM .60-.80 creating small valleys main stem. from daylight culverts. 18 0302 6 Habitat Stream channeled along While fish now use this Add habitat diversity RM.35 golf course road. No reach, lack of habitat will (e.g., structures, overhead overhead cover. No habi-eventually reduce popula-vegetation). Gain· tat diversity. tions. easement to restore mean- ders, if possible. 19 0302 6 Hydrology Tributary drains down Problem will worsen as Construct detention dam RM .45 steep bluffs on north development upstream upstream of golf course. side of Cedar River, continues. carrying debris and flooding Maplewood Golf Course. 20 0302 6 Habitat Water supply dam. Full As impoundment fills, storm-Dredge pond and maintain RM.50 barier to upstream water will flood over bank. it as sediment catch. migration. Impoundment Structure may fail. is filling with sediment. 21 0302 6 Habitat Severe gullying from right Will continue to erode until -Tightline downslope. RM .90 bank corregated metal reaches till layer. -Add velocity attenuator at pipe. Heavy sediment stream. delivery to stream. P: LC.APC C-4 Trib. & Collect. Item River Mile Point 22 23 24 25 26 0302 RM 1.00 0302 RM 1.10 0303 0303 RM .25 0303 RM .35 P: LC.APC 6 6 6 6 6 Category Prop. Proj. Habitat Habitat Geology Habitat Habitat Existing Conditions and Prohlems Trash in stream (auto, tires, appliances). Trash in stream. Water quality problem, unsightly. Extensive bank erosion in upper portions of t ribu- tary. Habitat suitable for resi- dent fish. Sediment accu- mulating. Trash and litter in channel affecting water quality, causing erosion. COs ------------~ Anticipated Conditions and Problems Area adjacent to corridor, will continue to collect trash and debris. Further worsening of water quality, sedimentation, erosion. Area adjacent to corridor, will continue to collect trash and debris. Further worsening of water quality. None. Sediments will eventually cover gravels. Habitat will become unsuitable for fish use. Further decreases in water quality. Recommendations Remove trash. Distribute educational materials to streamside residents. Cite violators. if problem persists. Remove trash. Distribute educational materials to streamside residents. Cite violators. if problem persists. Increase RID volumes, slow release rate to non erosive levels. Control stormwater volumes and discharge rates from developments. Manually dean gravels when necessary. Remove trash and litter. Distribute educational materials to streamside residents. -Cite violators. if problem persists. Trib. & Collect. Existing Anticipated Item River Mile Point Catel!OIV ProP. Proi. Conditions and Problems Conditions and Problems Recommendations 27 0304 7 Habitat Landslides contributing Sediment will continue to Maintain riparian corridor RM.4O sediment to channel. Heavy enter system until landslide with setbacks at least SO' deposition in pools, at stabilizes. from tops of banks. obstructions, even in riffles. 28 0304 8 Habitat Horses have access to Further decreases in water Encourage residents· to fence RM 2.10 stream, causing some bank quality, bank erosion likely. channel back l~' from ordinary deterioration and possibly high-water mark. affecting water quality. -Limit access to livestock to one or two points along stream. 29 0304 8 Hydrology Aooding caused by failing Problem will continue until -Problem referred to Main- RM 230 RID at 176th St. & 146th outlet structure is tenance section of Surface Ave SE. modiried. Water Management Division. 30 0304 8 Habitat Encroachment occurring Wetland likely to be Require encroaching fills RM 2.40 along all boundaries of reduced slowly until it is to be removed. this headwater wetland. completely destroyed. Loss -Establish specific buffer of storage, filtration, around this wetland. organic production, and Enforce sensitive areas wildlife habitat. ordinances and regula- tions. 31 0304 7 Geology Several gullies due to Problem will continue. Tightline drainage. RM.80 daylight culverts; a few have recent landslides. P: LC.APC C-6 Trib. & Collecl. Item River Mile ~ 32 33 34 36 37 0304 RM .00 0304 RM .20 0304 RM .62 0304 RM.80 0304A RM 1.30 P: LC.APC 7 7 7 7 7 Category Prop. Proj. Habitat Habitat Habitat Habitat Hydrology 3102 Existing Conditions and Problems Extensive riffle (to RM .15. Creek channeled. No woody debris, little bank vegetation. Steel head, coho spawners here. Debris jam may he a partial migration barrier. Debris jam. Bed drops 3' over jam and sediment, forming anadromous barrier. Water tumid; oily sheen and odor present. Storm drains empty directly into stream. Existing forested wetland provides detention for Trib. 0304A and 0304 in heavily developed area. C-7 Anticipated Conditions and Problems Gravels risk becoming cemented. Few resting areas for upstream migrating fish. Debris will continue to accumulate. Channel will likely divert or jam will fail, releasing accumulated sediment. Debris will continue to accumulate. Channel will likely divert or jam will fail, releasing accumulated sediment. Water quality will continue to decline as runoff and waste enter stream. Additional storage could be utilized by constructing berm and weir at outlet. This could be done to atlen- uate increased peak news as upstream area develops. Recommendations Enhance habitat by addi- tion of woody debris in stream. Revegetate bank. Enhance pool/riffle ratio. Selectively remove debris to allow fish passage. Stabilize large woody debris. Selectively remove debris to allow fish passage. Stabilize large woody debris. Educate residents about • how to maintain water quality. Mark storm drains with "Dump no oil" signs. Emphasize recycling of oil. Construct a proportional weir and berm at wetland outlet. Project could be used instead of Project 3107 to rpeserve the #1 rated wetland (where project would be built). Trib. & Collect. Existing Anticipated Hem River Mile Point Cate~ Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 38 0304A 18 Hydrology 3115 Runoff generated on top of Flooding will continue as -Constroct detention pond RM.4O bluffs on southwest side long as land use remains the at top of bluffs. of Cedar River is causing same on top of bluffs or -Tightline drainage down severe bank erosion, until mitigating measures bluffs, then channelize it nooding and debris nows are taken. Runoff origin-to an existing ditch onto several residences ates from highly compacted alongside SR 169. of valley noor. pastureland on uplands. -Prevent similar problems elsewhere with land use regulations, including provisions for preservation of vegetation buffers near tops of cliffs. 39 0305 10 Geology Extensive bank erosion, Susceptible to increases Attenuate high flows. partly due to subsurface with increasing storm now. clay layer and landslide topography. 40 0305 10 Geology Local severe bank Problem will continue. Existing rock-filled RM 1.10 erosion. gabions are denecting now. 41 0305 10 Geology Extensive channel down-Continued erosion. Attenuate high nows with RM 2.10-cutting and bank erosion. adequate RID. (RID 1.75 currently exists.) 42 0305 10 Geology Several gullies and asso-Erosion will continue. Tightline culverts. RM 2.15-ciated landslides due to 1.75 daylight culverts on steep slopes adjacent to chan- nels. P: I.C.APC C.g -.. -----• • • ---... Trill. & Collect. Existing Anticipated Item River Mile Point Category Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 43 0305 10 Habitat Madsen Creek in ditch along Potential for fuel entry in-Acquire 30' easement away RM .20 SE Jones Rd. Heavy silt; to creek. Further decreases from roadside. Construct road runoff; water quality in water quality can be ex-new stream channel. adversely affected. peeted. 44 0305 10 Habitat Creek in ditch along south Further decreases in water Acquire 30' easement away RM .35 side of SR 169. Heavy quality can be expected. from roadside. Construct inputs of oils, anti-Potential for autos to enter new stream channel. freezes, heavy metals, channel. Lack of habitat. organic pollutants likely. Sand, silt from roadside (of SR 169) enters also. 45 0305 RM .00-10 Hydrology 3105 Section of Trib. 0305, Flooding will continue. Construct and enhance 2200' of .40 RM .00-.40 is experiencing (See Appendix A, Project channel through undeveloped extensive flooding. 3105.) King County Park Land. 46 0305 10 Habitat Channelized along dri-Further siltation, water Acquire easement; move RM.50 veway; lacks habitat quality degradation can be creek from driveway diversity. Driveway sedi-anticipated. Lack of habitat 10-15'. Add meanders and ments enter channel, and precludes optimum salmonid habitat structures to oil placed on driveway use. increase diversity. enters stream. 47 0305 10 Habitat Channelized tributary Little salmonid use Add structures to increase RM .65 lacks habitat diversity, anticipated. Spawning and diversity in stream. cover for salmonids. rearing success limited Manually clean gravels by Gravels compacted. (unles., reach is restored). churning them. P: LC.APC C-9 Trib. & Collect. Existing Anticipated Item River Mile Point Category Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 48 0305 10 Habitat Good spawning riffles occur Increased nows may cause Control nows into system RM.90 here. 'n-3" gravels, few gravel bar movement. from developed areas fines, not compact. High Suitable gravels may be upstream. If necessary, nows are moving material, transported downstream to add bed controls to hold however. unusable areas for spawning gravels or "vee" strue· salmon ids. tures to recruit them. 49 0305 10 Habitat Severe bank CUlling and Further erosion/scouring can Control high nows by RM .95 erosion occurs here. l3ed be expected. Channel increasing upper basin R/D scouring evident. Reach deterioration will continue. facilities, lowering SUbject to high, ra pid Aows appear to be generated discharge rates to stream. nows. at developments. 50 0305 10 Habitat Much woody debris Debris jams will occur with Control upstream nows RM 1.20 movement and numerous greater frequency as nows with greater RID volume, debri.. jams. Reach is increase. Sediments will lower discharge rates. subject to high, rapid build up and channel will Selectively remove debris. nows. divert. 5] 0305 ]0 Habitat Channel erosion, bank Further channel deteriora--Increase RID capacity. RM 1.70 failures, downculling oc-lion may be expected. Silt, -Decrease discharge rates. curring. Reach subject to sand transport to mainstem high, rapid nows. will increase. 52 m06 10 Geology Failure of manhole during Not applicable. Repair manhole. RM.40 11/86 storm has resulted in gully erosion. P:LCAPC C-10 - - -- ---• • • • Trit>. & Collect. Existing Anticipated Item River Mile Point Category Prop. Proj. Conditions and Proolems Conditions and Problems Recommendations 53 0306 IO Geology Channel downcutring, hank Erosion will increase. Clay Further increase in runoff RM .20 erosion and several layer in valley makes area should be attenuated; this landslides, due both from sensitive to landslides. is a sensitive channel. increased storm flows and development along edge. 54 0306 IO Geology Undersized culvert in arti-Possible fill failure: Lake Enlarge the corregated RM .30 ficial fill in golf course ponded beh ind culvert in metal pipe and/or threatens to build lake and in 1981 and threatened construct adequate trash possibly overtop bank. the fill. rack. Breach flood possible. 55 0306 11 Habitat Channel subject to high, Further channel damage can Increase RID capacity, RM.25 damaging flows. Erosion be expected. Sediment decrease discharge rate. evident. transport downstream will continue. 56 0306 10 Geology Downculling, bank erosion Will continue or increase in Attenuate stonn flows. RM .30-.45 and landslide.o;. future. 57 0306 Hydrology 3118 Trib. 0306 connects with Problem will worsen as -Replace existing pipes RM .30 large tributary at manhole development upstream with larger diameter pipes here. Dcbris from 0306 continues. (if downstream analysis clogs this manhole, causing allows for increased flows). severe erosion of Fairwood Install new inlet struc- Golf Course. lures with trash racks. 58 0306A 11 Hydrology 3122 Existing small ponds on Area upstream is developing -Acquire easements for ponds RM 1.30 0306A are overtopped and quickly, thus worsening the and additional area around ponds receive considerable silt problem. and construct detention pond. during high flows. The Location is ideal for addressomg ponds are located on peak flows before they reach Fairwood Golf Course. the sensitive Cedar Reiver bluffs. P: LC.APC C-Il Trib. & Collect. Existing Anticipated Item River Mile Point Categorv ProP. Proi. Conditions and Problems Conditions and Problems Recommendations 59 0306A 11 Habitat Some usable habitat exists Further habitat deterioration -Increase RID capacities. RM .25 for resident salmonids. likely. Channel erosion will -Decrease discharge rates. Water quality is poor. increase. -Encourage use of 2-ce1l Channel subject to high detention ponds, swales. nows. -Prohibit filling of existing wetlands, ponds in upper basin. 60 0307 12 Geology Extensive bank erosion at Increased erosion will -Mitigate development- RM .10-.40 all meanders and obstruc-result with increased nows. related high nows. tions (trees, cars) due -Provide adequate RID. to increased nows from development. 61 0307 12 Geology Stream eroding toes of Increasing erosion with -Mitigate development RM .10-.60 slopes resulting in increasing nows. related high nows. landslide failures. -Provide adequate RID. 62 0307 12 Habitat Stream channel pushed to Erosion will worsen as -Increase RID capacity at RM.30 one side of ravine for stream nows increase. all delivery points. roadway. High energy May threaten road bank at -Reduce release rate below system. Much bank cutting, toe of slope. channel scour level. sediment transport, debris movement. 63 0307 13 Hydrology Area on top of hluffs near Infiltration sites should Construct retention faci- RM.6O Trib. 0307 has excellent be used whenever possible. Iities for new develop- infiltrative capacity. These would provide ground-menu in area at these sites. water recharge. P: LCAPC C-12 - Trib. & Collect. Item River Mile Point 64 65 66 67 68 0309 RM .10 0310 RM.60 0310 RM .05 0310 RM 1.50 0310 RM .25 P: LC.APC 15 15 15 15 15 Categorv Prop. Proj. Habitat Geology Geology Geology Habitat 3120 Existing Conditions and Protolems Subject to heavy, rapid nows. Channel erosion, deposition bars migration. Sedimentation upstream from culvert due to debris and undersized culvert. New corregated metal pipe con- tinues to pass water through. Severe erosion below culvert, severe sedimen- tation in residence yard. Road drainage forming gully adjacent to road; road bed in danger. Corregated metal pipe is anadromous barrier. C-13 Anticipated Conditions and Problems Erosion, deposition will increase. Sediments will migrate downstream, creating a water quality problem. Continued sedimentation. Continued erosion and sedimentation. Continued erosion. Problem will continue. • • • Recommendations -Control storm nows upstream. • Control volume and discharge rates. See "Hydrologic and hydraulic characteristics" section in this report. -Install energy dissipator below corregated metal pi pe. Excavate channel through yard where original channel was located. Reroute drainage. Refer problem to Roads Maintenance. Reinstall corregated metal pipe at or below bed level. Trib. & Collect. Existing Anticipated Item River Mile Point Category Prop. Proj. Conditions and Prolllems Conditions and Problems Recommendations 69 0310 15 Hydrology 3120 Existing channel draining Frequency and severity of Construct detention pond RM .40 off bluffs on north side problem will worsen as on upstream side of Jones of Cedar River, causing development on bluffs Rd. to trap sediments, and flooding of residences and i ncrease.~. enhance 1,000' of creek debris flows onto Jones Rd. from Jones Rd. to Cedar during peak flows. River. 70 0310 15 Habitat Corregated metal pipe Problems will continue and Remove new and old pipes; RM.60 outlet approximately worsen as outfall velocities replace at lower level 9' above bed level. will scour bed and banks. with oversized pipe with Complete barrier to fish. Upstream has recent (11/86) trash rack. Old culverts at bed level deposition up to 4' deep. are plugged. 71 0311 13 Geology Gully erosion in drainage Continued accelerated ero-If possible, enlarge RID RM 1.70 swale due to outflow of sion. prior to its outlet in the wetland that partly seems wetland. to act as an RID facility. 72 0314A 16 Hydrology 3117 Severe erosion, flooding, Problem will be aggravated -Tightline drainage between RM.20 damage to County and as area above develops. detention ponds in gravel pit. private roads from -Construct detention pond increased runoff from next to Jones Rd. to trap gravel pit operations on sediments. hillside. -Construct channel from Jones Rd. to Cedar River. 73 0314N 16 Geology Inadequate RID, plugged Not applicable. See hydrology comment 03148 culvert caused by exten-aboVe. RM .10-.40 sive channel and bank erosion and landslides. Water has cut a new channel. P: LC.APC C-14 ------ Item 74 75 76 77 Trib. & Collect. River Mile Point 0317 RM 1.60 0320 RM 2.40 0318 RM .10 0382 RM .35 19 19 P: LCAPC Category Prop. Proj. Hydrology 3111 Hydrology 3114 Habitat Habitat Existing Condit ions and Prolliems Francis Lake is only hydraulic control for Trib. 0317. Existing forested wetland with large amount of un- utilized storage. Wetland currently detains flows on Trib. 0320. Salmonid parr in many pools. Large pools up to I. 75' deep. Some deposi- tion in pools, behind obstructions. Salmonid use apparent from carcasses. Sockeye, Chinook spawners. Some sedimentation occurring. C-IS Anticipated Condit ions and Problems Trib. 0317 flows through steep area downstream of lake. If area around Francis Lake develops, increased peak flows could cause severe damage to Trib. 0317 in the steep region. If surrounding area urban- izes, this would be a good site to altenuate peak flows. Decrease in water quality with increasing develop- ment. Loss of habitat. Decrease in fish use. System is mostly in natural condition. As development increases, higher flows and worse water quality can be expected. • • Recommendations Construct proportional weir at outlet. -Enhance 1,100' from • Francis Lake to SE 184th St. Construct containment berm and control structure at outlet of wetland (if bio- logical analysis permits). Establish and maintain adequate buffers, 100 from ordinary high-water mark or 25' from top fo slope break, wh ichever is greater. Maintain adequate stream corridor buffers. Reduce discharge rates to pre-development levels. Prevent clearing, grading within buffers. Trib. & Collect. Existing Anticipated Item River Mile Point Category Prop. Proj. Conditions and Problems Conditions and Problems Recommendations 78 0328 19 Geology Medium-density landslides None. Umit development in the RM .50 and high-density bank basin. erosion occurring due to natural causes. This indi- cates channel and valley sensitive to effects of development. (Sensitivity due to clay layer. Basin hosts some o( best (ish habitat in upper reaches.) 79 0328 19 Habitat Significant salmonid use Sedimentation (rom upstream Maintain leave strips RM .70 throughout. Sockeye reach possible. Adjacent adjacent to stream at spawners, carcasses present. development will likely least 100' (rom ordinary Coho, steelhead parr in reduce diversity and quality high-water mark. Restrict pools. Excellent habitat of habitat. use/development within this for spawning and rearing streamside management zone. (a redd site). Much diversity --most exemplary in basin. Channelized reach. Uniform May cause thermal problems Restore stream habitat 80 0328 19 Habitat channel, no habitat diver-as water temperatures rise. throughout: add structure, RM 1.10 sity. Heavy sand deposition. No useful habitat. diversity, bank vegetation, 1.40 Little overhead canopy or and canopy. Cost should be bank vegetation. borne by party(ies) who channelized this reach. 81 0328 19 Hydrology 3112 Lake Peterson is small, Lake provides good peak flow Replace weir at outlet RM 1.40 open-water wetland with a attenuation and will become with a higher weir in weir at outlet. more important as upstream order to gain additional tributary area develops. storage. P: LC.APC C-16 " II I NATIONAL FLOOD INSURANCE PROGRAM FLOOD INSURANCE RATE MAP (;ITY OF RENTON, WASHINGTON <SEE MAP INDE)( FOR PANELS NOT PRINTED) COMMUNITY·PANEL NUMBER 530088 0002 B EFFECTIVE DATE: MAY 5, 1981 federal emergency management agency federal insurance administration \ \ I~ I KEY TO MAP SOO·Year Flood Boundary---- lOO·Year Flood Boundary---- Zone Designations· With Date of Identification e.g., 12/2/74 lOa·Year Flood Boundary---- SOO·Year Flood Boundary---- Base Flood Elevation Line With Elevation In Feet •• ---5131-- Base Flood Elevation in feet Where Uniform Within Zone** <EL 9871 Elevation Reference Mark RM7 X oMl.5 River Mjle ··Referenced to the National Geodetic Vertical Datum of 1929 ·EXPlANATION OF ZONE DESIGNATIONS ZONE A AO AH A1-A30 A99 B o V V1-V30 EXPLANATION Areas of 1 aO·year flood; base flood elevations and flood hazard ("ctofS not determined, Areas of lOO·year shallow flooding where depths are between one (1) and three (3) feet; average depths of inundation are shown, but no flood hazard factors are determined. Areas of lOa-year shallow flooding where depths are between one (1) and three (3) feet; base flood elevations are shown, but no flood hazard factors are determined. Areas of laO-year flood; base flood elevations and flood hazard factors determined. Areas of lOO-year flood to be protected by flood protection system under construction; base flood elevations and flood hazard factors not determined. Areas between limits of the 10o-year flood and 500- year flood; or certain areas subject to laO-year flood- ing with average depths less than one (1) foot or where the contributing drainage area is less than one square milej Or areas protected by levees from the base flood_ Medium shadin Areas of minimal flooding. (No shading) Areas of undetermined, but possible, food hazards. Areas of 100-year coastal flood with velocity (wave action); base flood elevations and flood hazard factors not determined. Areas of 100-year coastal flood with velocity (wave action); base flood elevations and flood hazard factors determined. NOTES TO USER Certain areas not in the special flood hazard areas (zones A and V) may be protected by flood control structures. This map is for flood insurance purposes only; it does not neces- Sarily show all areas subject to flooding in the community or all planimetric features outside special flood hazard areas. For adjoining map panels, see separately printed Index To Map Panels. INITIAL IDENTIFICATION, JUNE 7,1974 I I I t====~ I i i i I I, N u w z 2 " ...• ~.~:-,-:'::7:.;,<;,<;, ------:'.0:= WIUIAMS AVE N <l' ---.,. ,. ~ W~!J-~ Ayf, N . :r VI ..... ,-.' :=:.-' ~.~~ ;::::=;-. _ .. ! .... __ ..:;:-:"-0 -;:----~----- BASIN 6 " .. :~-:;; .,: 'T-' , I , I ., ' "~-"; ." .1 ~=,' . ,_ ...... -.. ~.J -~ ;., d'l1 CEDAR RIVER ;<. . (i.~: ~1r: " ," ,"'" .~~;-- ",,-' -"!: ... ( .-.,. . -1 'I- ..... ,~: ~-,;~.;~ ~~'.-.\:--. ;;:~~;: BASIN 4 P~llY ~v(~ Z i.n ;! , -, , ___ :2-I:I ... I~ I " J' : ;1; '--~.' .. '-4 r i ~:-J '£f~~{"'!~k --:'1 . , " , GARDEN , . •. I_~~ =t ii. BASIN? ~. '-.. 'f-OO-.... ~~'"~ •• ;"1 • ',:~.'"' '-:1 "L.: -':'" :-1', . ,;:):!' •. - . ! ,-,-~. -~ -;1.' . ,., ....... ,;..::.~:-~~::.-..... "=!' ,~ '. , BASIN 5 as BASIN 1 -~ r \ ... "" , , < \ \ \ \ \ \ \ ... ~- BASIN 3 .J:'" ,: ..... .. ' " " . < . \-- " LEGEND IIAJOR ORAINAGE BASIN IIAJOR STmil DRAIN UNE flOOD PLAIN BOUNDARY ~ flOW OIR£Cll~ NO'TES: 1. SEE TAIU XX FOR SURfACE WAlER QUANlITIES FlO'll1NG TO EACH OOTF AU. FOR lIiE 6 PTH TO 100 'lEAR DES1GN STORII5. LAKE WA9iINGTOII crs as as .. -N o 200' 400' 800' I !, I JOHN'S . CREt:K ' -.---.-,~ / , -. SCAlE: 1"=400' " / / ~ lili :! Si CD r l! Q .. ~1!1 !;~ e 3 :::I «I .2''t: IL :::I 1/1 ! J ZIO LLI a::; ~ ..: ;::)= .... ~ Il1O \!) tit) < ~ .. ~ --- KENT I .. ': ::1 'i ~ OlY (E RENTON, 1991 ... -.J;t' .... , i!2')i7.-'-... . j-\, --=---~~~ j 1.11 ....... ll ~:iCi:?;.~ ....... \'l ~\ ) . I • . , ,:::: .;: r---··, "l.~ ;"'~r I r )' , ~ ____ J LoWm·CDM JmII '-'f'" IIt>llIt .... ~ I! , ,----: :~-~~,"'"-\ ')i '-r \ : ~ , ' -~ \ ..... ,; .f',.;." LU£ . '. '\::::"' r".11I1 UAt' \,j .-_"~.::l!:JC!:_ '!! J'!l!.:!':~.t:... '" I.AJfr 'rOI1.mt 1,·· : ____ -L_....:_~-_---,~--....; -.-.. i ........ ~ - I ...... ' -~ ~ ..;:: Figure 4-1 SURFACE WATER DRAINAGE BASNS Major Bosin Boundary t.4ojor Bosin Names Sub-Sosin Boundary Sub-Soundary Nomes City Limits Urban Growth Boundary _. -----.---,-,,-, -Spl'le,.e of In fluence o 5000 10000 ~ Note: For 9rophic presentation only. Focilities ort! not to scale. e LONG RANGE PLANNING O.DennisGn R.KacOnie, D.Visneski 2'" Warcb 1995 paYISSBpUn -SI!W!l All:) ----- alBJapOVII -I I pJBZBH 461H -ooot OOS\ 0 SV3~V a~VZVH 3NllAJ lV08 NO~ONIHSV'M 3)1Y1 ,OOOC=.1 oooe OOgl 0 SJ!W!1 All:) ----- SV3~V a~VZVH NOISO~3 NOlDNlHSV In lDIV1 -..n ~ ----- l~iiiiiiiiiiiiiiiiiiiiiii~1 ~ I 0009 000£ 0 SV3C1V OClVZVH 0001=1 / / ( \ \ \ \ / / \ \ \ '\ r--- / , -""-"-"-"---:------------~-""---" " ..... . -------------------- pJezeH 46!H • sp'w!l ;\J!O ----- SV3t1V OtlVZVH 81V\1S13S -- - 'PIH "-A • II!W!"J AI!:> -----'PH II PJDZDH "~!Iu!)! n~~i 8",""P"W. SV3~V O~VZVH 3011S0NVl NO.LDNlHSV Nt. H)fV'l If drained, this soil is used for row crops. It c' s also used fOr pasture. Capability unit IIw-3; o woodland classification. I Urban Land I Urban land (Ur) is soil that has been modified by r4isturbance of the natural layers with additions of 'ill material several feet thick to accommodate large ndustrial and housing installations. In the Green iver Valley the fill ranges from about 3 to more shan 12 feet in thickness, and from gravelly sandy r oam to gravelly loam in texture. " The erosion hazard is slight to moderate. No apability or woodland classification. Woodinville Series The Woodinville series is made up of nearly level 'nd gently undulating, poorly drained soils that 'ormed lUlder grass and sedges, in alluvium, on stream ottoms. Slopes are 0 to 2 percent. The annual precipitation ranges from 35 to 55 inches, and the ~~an annual air temperature is about 50 0 F. The 'rost-free season is about 190 days. Elevation 'anges from about sea level to about 85 feet. In a representative profile, gray silt loam, ~llty clay loam, and layers of peaty muck extend to depth of about 38 inches. This is underlain by ',reenish-gray silt loam that extends to a depth of 60 inches and more. Woodinville soils are used for row crops, pasture, nd urban development. Woodinville silt loam (Wo) .--This soil is in elon- vated and blocky shaped areas that range from S to early 300-acres in size. It is nearly level and ently undulating. Slopes are less than 2 percent. Representative profile of Woodinville silt loam, .in pasture, 1,700 feet south and 400 feet west of :he north quarter corner of sec. 6. T. 2S N., R. 7 , . ~pl--O to 3 inches, gray (5Y 5/1) silt loam, grayish brown (IOYR 5/2) dry; common, fine. prominent. dark reddish-brown (5YR 3/4) and reddish-brown (5YR 5/4) mottles; moderate, medium. crumb structure; hard, friable, sticky. plastic; many fine roots; medium acid; clear, smooth boundary. 2 to 4 inches thick. I, Ap2--3 to 8 inches, gray (5Y 5/1) silty clay loam, light brownish gray (2.5Y 6/2) dry; many, fine prominent, dark reddish-brown (SYR 3/3 and 3/4) mottles and common, fine, prominent mottles of strong brown (7.SYR 5/6) and red- dish yellow (7.5YR 6/6) dry; moderate, fine and very fine. angular blocky structure; hard, friable, sticky, plastiC; common fine rootSj medium acid; abrupt, wavy boundary. 4 to 6 inches thick. B21g--8 to 38 inches, gray (5Y 5/1) silty clay loam, gray (SY 6/1) dry; common, fine, prominent, brown (7.5YR 4/4) mottles and medium, promi- nent mottles of brownish yellow (IOYR 6/6) dry; 2S percent of matrix is lenses of very dark brown (lOYR 2/2) and dark yellowish-brown (IOYR 3/4) peaty muck, brown (7.5YR 4/2) dry; massive; hard, firm, sticky, plastic~ few fine rootsj medium acid; clear, smooth boundary. 30 to 40 inches thick. B22g--38 to 60 inches, greenish-gray (SBG 5/1) silt loam, gray (5Y 6/1) dry; few, fine, prominent mottles of brownish yellow (IOYR 6/6) dry; massive; hard, very friable, slightly sticky, slightly plastic; strongly acid. The A horizon ranges from dark grayish brown to gray and from silt loam to silty clay loam. The B horizon ranges from gray and grayish brown to olive gray and greenish gray and from silty clay loam to silt loam. In places there are thin lenses of very fine sandy loam and loamy fine sand. Peaty lenses are common in the B horizon. These lenses are thin, and their combined thickness, between depths of 10 and 40 inches, does not exceed 10 inches. Soils included with this soil in mapping make up no more than 25 percent of the total acreage. Some areas are up to 15 percent Puget soils; some are up to 10 percent Snohomish soilsj and some areas are up to 10 percent Oridia, Briscot, Puyallup, Newberg, and Nooksack soils . Permeability is moderately slow. There is a sea- sonal high water table at or near the surface. In drained areas, the effective rooting depth is 60 inches or more. In undrained areas, rooting depth is restricted. The available water capacity is high. Runoff is slow, and the hazard of erosion is Slight. Stream overflow is a severe hazard unless flood protection is provided (pl. III, top). This soil is used for row crops, pasture, and urban development. Capability unit IIw-2; woodland group 3w2. 33 • .Iand 972 as part of Irtment of and the ation ,A' ~ ',,' ~ '7 " ~ ~, , '''./' ,-;:;,.t:. ':, , 8M, -.,:- " 4>- Co'~'" -""':W;; ?SiJ:m~~~~," ,,'It . '. ~ • • ,. ••• ~. 'f,. 'A. BM.~l~ _ ~.. '.' B::f ~', . ~ . N" .- c;> R. 4 E. R. 5 E. ?eWf"Oi ~rre Scale 1 :24 000 Th'$ mtp ;1. one of ;I set 0120. KING COUNTY AREA, WASHINGTON NO, 5 i j - 1/2 0 MILE + N The boundaries of the senSitive areas dis- played on these maps are approximate, Additional sensitive ueas that have no~ been mapped may be present on a devel· opment proposal site. Where differences occur between what Is Illustrated on these maps and the site conditions, the actual pre- sence or absence on the site of the sensitive area -as defined In the sensitive Area Ordinance -Is the legal control. NUmbered wetlands, eXt:spt those with an "a" or "b" designation are Included In the Kin, County Wetland. In~t!nton', The locations of wetlands designated "<I" have been verified on the site by ill variety of sources. wetlandS deSignated "b" are map- ped In the U.S. Fish ancl Wildlife Service National Wetland. IMento")'! but their loca- tions ha ... e not been field ve'l led. There may be gaps In the numbering se· quence within Individual drainage basins. Wetlands _ We!Iendo _ OpenWoIe, _ Baoln Boundarieo Sub-basin BoundarIes Duwamish \ 4 -, The Landing -Preliminary Drainage Report 4 RETENTIONIDETENTION ANALYSIS All hydrologic analysis and facility design is based on the 2001 Department of Ecology Stormwater Management Manual for Western Washington, instead of the 1990 King County Surface Water Manual as required per the Site Plan Review. 4.1 SCSUHISBUH Method The Santa Barbara Urban Hydrograph (SBUH) and Soils Conservation Service Unit Hydrograph (SCSUH) method are both based on an SCS Curve Number and use basic SCS equations for computing soil absorption and precipitation excess. The SBUH method however, directly computes a runoffhydrograph without the intermediate step of computing a unit hydro graph. Stormshed software was used for all runoff calculations. 4.2 Existing Conditions The existing conditions consist of a 7.8 acre asphalt parking lot with several planters scattered throughout the site. There is existing storm drains consisting of catch basins, pipe and a storm vault. The site is relatively flat with slopes no greater than I %. Table 4.2.1 shows the existing site conditions and Table 4.2.2 shows the existing 2-yr, 10-yr and 100-yr, 24-hour runoff rates. Table 4.2.1 Existing Landuse Table 4.2.2 Existing Runoff Rates June 22, 2006 Job #05-071 4-1 The Landing -Preliminary Drainage Report 4.3 Proposed Conditions The proposed project will construct a total of 885 apartments, 1,600 parking spaces, 15,000 SF of retail, and 6,000 SF for a clubhouse/leasing office. In between the northern and southern complex there will be a vehicle court, serving as the main access points to the parking garages and connect Garden Avenue N and Park Avenue N. Roadway improvements include realigning Park Avenue N and Logan Avenue N. and constructing a new street, N. 10tll Street which will connect Garden Avenue N. and Park Avenue N. Garden Avenue N will also potentially be widened by four feet. Table 4.3.1 shows the developed site conditions and Table 4.3.2 shows the developed 2-yr, 10-yr and 100-yr, 24-hour runoff rates. Table 4.2.1 Developed Site Conditions Table 4.2.2 Developed Runoff Rates 4.4 Water Quality Treatment The only area that will be treated is the vehicle court. The parking garage floors will drain to the sanitary sewer, so no storm water treatment is required. As part of the vehicle court, 0.43 ac of impervious area and 0.07 ac of pervious area will be added. A water quality vault will be used for treatment. The vault was sized based on the volume of the water quality design storm, which was computed by taking 72% of the 2-yr, 24-hour total precipitation. For this site: 2-yr, 24-hour Precipitation (from Figure 3.5.1 C) = 2.0 inches WQ Precipitation (6-mo, 24-hr) = 0.72 * 2.0 = 1.44 inches Water Quality Storm Volume = 2,061 CF June 22. 2006 Job #05-071 4-2 The Landing -Preliminary Drainage Report This facility has been sized as a large wetpond, so the welpool volume has been sized 1.5 times larger than the water quality storm. Required Water Quality Treatment Volume = 1.5 x 2,061 CF = 3,092 CF 84'x Tx Tvault will be used and provide 3,234 cfoftreatment with 1 'of sediment storage and 0.5' of freeboard. Please see Appendix 4.1 for Stormshed results. 4.5 Detention No detention is required for this project, since there will be direct discharge to Lake Washington. June 22, 2006 Job #05-071 4-3 Appendix 4 Stormshed Results June 22, 2006 Job #05-071 The Landing -Preliminary Drainage Report 4-4 Stormshed Results Ex Event Summary: BasinlD Peak Q Event (cis) Ex 3.38 Ex 5.05 Ex 6.89 Drainage Area: Ex Hyd Method: SBUH Hyd Peak Factor: 484.00 Storm Dur: 24.00 hrs Area Pervious 0.3900 ac Impervious 7.4300 ac Total 7.8200 ac Supporting Data: Pervious CN Data: Planters Impervious CN Data: Asphalt Pervious TC Data: Flow type: Description: Sheet Planter Sheet On Parking Lot Channel In Pipe Impervious TC Data: Flow type: Description: Sheet Across Parking Lot Channel Pipe Flow Dev Event Summary: BasinlD Peak Q Event (cis) Dev 3.16 Dev 4.94 Dev 6.94 Drainage Area: Dev Hyd Method: SBUH Hyd Peak Factor: 484.00 Storm Dur: 24.00 hrs Area Pervious 2.4000 ac Impervious 5.4300 ac Total 7.8300 ac Supporting Data: Pervious CN Data: Planters Impervious CN Data: Asphalt Pervious TC Data: 05-071 PeakT (hrs) 8.00 8.00 8.00 CN 90.00 98.00 90.00 98.00 Peak T (hrs) 7.83 7.83 7.83 CN 90.00 98.00 90.00 98.00 Peak Vol Area Method Raintype (ac-ft) ac ILoss 1.1341 7.82 SBUH/SCS TYPE1A 2 yr 1.7138 7.82 SBUHlSCS TYPE1A 10 yr 2.3611 7.82 SBUHlSCS TYPE1A l00yr Loss Method: SCS CN Number SCSAbs: 0.20 Intv: 10.00 min TC 0.10 hrs 0.08 hrs 0.3900 ac 7.4300 ac Length: Slope: Coeff: Travel Time 20.00 ft 2.00% 0.0600 1.60 min 110.00 ft 1.00% 0.0110 2.13 min 425.00 ft 0.50% 42.0000 2.39 min Length: Slope: Coeff: Travel Time 165.00 ft 1.00% 0.0110 2.95 min 355.00 ft 0.50% 42.0000 1.99 min Peak Vol Area Method Raintype (ac-ft) ac ILoss 1.0219 7.83 SBUH/SCS TYPE1A 2 yr 1.5866 7.83 SBUHISCS TYPE1A 10 yr 2.2241 7.83 SBUH/SCS TYPE1A 100 yr Loss Method: SCS CN Number SCSAbs: 0.20 Intv: 10.00 min TC 0.03 hrs 0.04 hrs 2.4000 ac 5.4300 ac E:\PROJECTS\05071\Engineering\Docs\Stonnshed Summary,doc '1 I , - , . , - Flow type: Description: Sheet Planter Channel In Pipe Impervious Te Data: Flow type: Description: Sheet Across Vehicle Court Channel Pipe Flow WQ Event Summary: BasinlD Peak Q Event (ets) WQ 0.05 Drainage Area: WQ Hyd Method: SBUH Hyd Peak Factor: 484.00 Storm Our: 24.00 hrs Area Pervious 0.0670 ac Impervious 0.4300 ac Total 0.4970 ac Supporting Data: Pervious eN Data: Planters Impervious eN Data: Asphalt Pervious Te Data: Flow type: Description: Sheet Planter Channel In Pipe Impervious Te Data: Flow type: Description: PeakT (hrs) 7.63 CN 90.00 98.00 90.00 98.00 Sheel Across Vehicle Court Channel Pipe Flow 270.00 ft 05-071 Length: Slope: Coeff: TravelTime 5.00 ft 2.00% 0.0600 0.54 min 270.00 ft 0.50% 42.0000 1.52 min Length: Slope: Coeff: Travel Time 60.00 ft 2.00% 0.0110 1.02 min 270.00 ft 0.50% 42.0000 1.52 min Peak Vol Area Method Raintype (ac-ft) ac fLoss 0.0177 0.50 SBUHISCS TYPE1A Smo Loss Method: SCSAbs: SCS CN Number 0.20 Intv: 10.00 min TC 0.03 hrs 0.04 hrs 0.0670 ac 0.4300 ac Lenglh: 5.00 ft 270.00 ft Slope: 2.00% 0.50% Length: Slope: 60.00 ft 2.00% 0.50% 42.0000 Coeff: 0.0600 42.0000 Coeff: 0.0110 1.52 min Travel Time 0.54 min 1.52 min Travel Time 1.02 min E: \PROJECTS\OS071 \Engi neeri ng\Docs\stormshed Summary. doc