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Home My WebLink AboutSR_ERC_Report_wExhibits_WSADA Parking Lot_180730.pdfCity of Renton Department of Community & Economic Development Environmental Review Committee Report WSADA PARKING LOT LUA18-000384, ECF Report of July 23, 2018 Page 3 of 4 ERC REPORT 18-000384 native alluvial flood plain deposits compromised of fine and silty silt and sand mixed with gravel. Groundwater seepage was encountered at a depth of four to four and a half feet below existing grade. Due to the completion of the borings only a few weeks after the rainy season, Migizi Group, Inc does not anticipate that the groundwater would rise higher than the level observed in the test pits. According to the City of Renton Critical Areas Maps, the project site is located in a seismic hazard area. The submitted geotechnical report concluded that the project site is located in an area of high liquefaction potential. The geotechnical report would be required to be submitted with the construction permit application for the parking lot and compliance with the report would be reviewed at that time. The applicant has indicated the project would result in approximately 10,875 sq. ft. of new impervious area. Overall the project would not increase the imperious coverage on-site. Mitigation Measures: No further mitigation required. Nexus: Not applicable 2. Water Impacts: The applicant submitted a Technical Information Report (TIR) prepared by Sitts & Hills Engineers, Inc, dated May of 2018 and revised in June of 2018 (Exhibit 7). Based on the updated TIR, the project contains greater than 2,000 sq. ft. of new impervious surface and therefore a Full Drainage Review is required pursuant to the 2017 City of Renton Surface Water Design Manual (RSWDW). Based on the City’s flow control map, this site falls within the Peak Rate Flow Control Standard matching Existing Site Conditions. The project site is located within the Black River Drainage basin. A Full Drainage Review was included in the report. All nine core requirements and the six special requirements were discussed in the report. The project does not propose a flow control facility since the increase of peak flow rate during a potential 100-year rain event is less than 0.15 cubic feet per second (cfs). The project is required to provide enhanced basic water quality treatment prior to discharge. The applicant has proposed the use of two Filterra units in order to provide the required treatment. On-site BMPs will be required to help mitigate the new runoff created by the proposed improvements. The applicant has proposed limited infiltration in order to meet Core Requirement #9 for on - site BMPs. The final drainage report submitted at the time of construction permit application should address the implementation of on-site BMPs. Mitigation Measures: No further mitigation required. Nexus: Not applicable 3. Trees and Vegetation Impacts: The applicant submitted an arborist report prepared by Sitts and Hill Engineers, Inc. The applicant has proposed the removal of two (2) non-significant trees on the site, including a 6-inch caliper Hawthorn and a 3-inch caliper Alder located on the east side of the site. In addition, sparse native grasses and non -native shrubs including blackberry and butterfly bush are proposed for removal as part of the grading process. As part of the landscaping proposed for the perimeter and island landscaping associated with the parking lot, the applicant has proposed the installation variety of native shrubs and native ground cover plants. In addition, the applicant has proposed the installation of nine (9) 2-inch caliper shade trees. Mitigation Measures: No further mitigation required. Nexus: Not applicable 4. Transportation Impacts: The applicant submitted a parking and traffic analysis prepared by Heath & Associates, Inc. Due to the purpose of the parking lot – to provide overflow parking for mid-day trainings at the WSADA building – the report states that little to no increase in trips within the AM and PM is expected. Development Engineering 30 City of Renton Department of Community & Economic Development Environmental Review Committee Report WSADA PARKING LOT LUA18-000384, ECF Report of July 23, 2018 Page 4 of 4 ERC REPORT 18-000384 staff have reviewed the report and concur with the applicants assertion that traffic impacts would not be significant within the AM and PM peak times. Mitigation Measures: No further mitigation required. Nexus: Not applicable E. Comments of Reviewing Departments The proposal has been circulated to City Department and Division Reviewers. Where applicable, their comments have been incorporated into the text of this report and/or listed under Exhibit 8 “Plan Review Comments to Applicant.”  Copies of all Review Comments are contained in the Official File and may be attached to this report. The Environmental Determination decision will become final if the decision is not appealed within the 14-day appeal period (RCW 43.21.C.075(3); WAC 197-11-680). Environmental Determination Appeal Process: Appeals of the environmental determination must be filed in writing together with the required fee to: Hearing Examiner, City of Renton, 1055 South Grady Way, Renton, WA 98057, on or before 5:00 p.m. on August 17th, 2087. RMC 4-8-110 governs appeals to the Hearing Examiner and additional information regarding the appeal process may be obtained from the City Clerk’s Office, Renton City Hall – 7th Floor, (425) 430-6510. 30 CITY OF RENTON DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT STAFF REPORT TO THE ENVIRONMENTAL REVIEW COMMITTEE EXHIBITS Project Name: Washington State Auto Dealers Association Parking Lot Project Number: LUA18-000384, ECF, SPR-A Date of Meeting July 30th, 2018 Staff Contact Alex Morganroth Associate Planner Project Contact/Applicant Vicki Giles Fabre WSADA Property LLC 621 SW Grady Way Renton, WA 98057 Project Location 621 SW Grady Way Renton, WA 98057 The following exhibits are included with the ERC Report: Exhibit 1: Environmental Review Committee (ERC) Report Exhibit 2: Neighborhood Detail Map Exhibit 3: Site Plan Exhibit 4: Plan Set (Sheets S503-1, C601-2) Exhibit 5: Construction Mitigation Description Exhibit 6: Geotechnical Report prepared by Migizi Group, Inc (dated May 18, 2018) Exhibit 7: Technical Information Report (TIR) prepared by Sitts & Hills Engineers, Inc (dated May of 2018 and revised in June of 2018) Exhibit 8: Advisory notes to Applicant SW Grady WaySW Grady WaySW Grady WayRaymond Ave SWSW 12th StSW 12th StSW 12th StLind Ave SWSeneca Ave SWSW 13th StLind Ave SWLind Ave SWSW 10th StSW 10th StRECEIVED06/27/2018amorganrothPLANNING DIVISIONExhibit 2 TPN 3340404805 S.W. 12TH S T . R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ SURFACING AND DIMENSION PLAN RECEIVED 06/27/2018 amorganroth PLANNING DIVISION Exhibit 3 ENGINEERS, INC. SITTS & HILL DEALERS ASSOCIATION WASHINGTON STATE AUTO R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ COVER SHEET Exhibit 4 TPN 3340404805 S.W. 12TH S T . R Call 811 two business days before you dig LEGEND HORIZONTAL DATUM VERTICAL DATUM SITE DATA NOTES LEGAL DESRIPTION REFERENCES IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ TOPOGRAPHIC SURVEY TPN 3340404805 S.W. 12TH S T . R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ DEMOLITION, EROSION AND SEDIMENTATION CONTROL DETAILS R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ DEMOLITION, EROSION AND SEDIMENTATION CONTROL DETAILS R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ DEMOLITION, EROSION AND SEDIMENTATION CONTROL DETAILS TPN 3340404805 S.W. 12TH S T . R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ SURFACING AND DIMENSION PLAN R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ SURFACING AND DIMENSION NOTES R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ SURFACING AND DIMENSION DETAILS TPN 3340404805 S.W. 12TH S T . NORTH GRADING AND DRAINAGE PLAN LEGEND PROPOSED FEATURES- GENERAL NOTES KEY NOTES R Call 811 two business days before you dig ALLEY S.W. 12TH ST R E E T GRADING AND DRAINAGE PLAN IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ GRADING AND DRAINAGE NOTES R Call 811 two business days before you dig DATE:CHECKED:DRAWN:############P:\17600\17668\DRAWINGS\17668-C3.2.DWG 6/14/2018 6:46 PMThe design and information shown on this drawing is provided as a service to the project owner, engineer and contractor by CONTECH Engineered Solutions LLC or one of its affiliated companies ("CONTECH"). Neither this drawing, nor any part thereof, may be used, reproduced or modified in any manner without the prior written consent of CONTECH. Failure to comply is done at the user's own risk and CONTECH expressly disclaims any liability or responsibility for such use. If discrepancies between the supplied information upon which the drawing is based and actual field conditions are encountered as site work progresses, these discrepancies must be reported to CONTECH immediately for re-evaluation of the design. CONTECH accepts no liability for designs based on missing, incomplete or inaccurate information supplied by others. FILENAME:800-338-1122 513-645-7000 513-645-7993 FAX 9025 Centre Pointe Dr., Suite 400, West Chester, OH 45069 www.ContechES.com FILTERRA THROAT OPENING DETAILS FILTERRA THROAT OPENING DTL PRECAST TOP SLAB TYP 4" MIN. OPENING 4" MIN. OPENING CROWNED FLUME REVERSE FLUME - SLOPED TOWARDS FILTERRA THROAT CURB DOWEL PRECAST TOP SLAB CAST-IN-PLACE FLUME AND GUTTER (SLOPED TOWARD THROAT) PRECAST VAULT WALLCAST-IN-PLACE FLUME AND GUTTER (CROWNED AND SLOPED TOWARD FILTERRA THROATS) THROAT OPENING TYP SECTION VIEWS OF TYPICAL FLUME APPLICATIONS SEE ABOVE FOR DETAILS NOT SHOWN 4" MIN. OPENING THROAT OPENING TYP DOWELPRECAST VAULT WALL PRECAST TOP SLABSTANDARD 90° NOSING (OTHER NOSING AVAILABLE UPON REQUEST) CAST-IN-PLACE GUTTER AND THROAT OPENING (BY CONTRACTOR PER LOCAL STANDARDS)#4 DOWEL BARS @ 12" O.C. BY CONTECH TO BE BENT AS NECESSARY BY CONTRACTOR PRIOR TO INSTALLATION OF CAST-IN-PLACE GUTTER THROAT PROTECTION DEVICE DO NOT REMOVE - LEAVE IN PLACE UNTIL SITE IS STABILIZED AND FILTERRA IS ACTIVATED PRECAST VAULT WALL SECTION VIEW STANDARD THROAT OPENING 4"-6" CLEAR THROAT OPENING IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/ GRADING AND DRAINAGE DETAILS TPN 3340404805 S.W. 12TH S T . R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/RAY M O N D J. JOH N S O NN O. 4 4 9 E X P. 0 3 / 2 0 /1 9L A N D S C A P E A R C H I T E C TLANDSCAPE PLAN R Call 811 two business days before you dig LANDSCAPING NOTES IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/RAY M O N D J. JOH N S O NN O. 4 4 9 E X P. 0 3 / 2 0 /1 9L A N D S C A P E A R C H I T E C TLANDSCAPE NOTES R Call 811 two business days before you dig IN COMPLIANCE WITH CITY OF RENTON STANDARDSAAANNNNNNN WSADA PARKING LOT A-NNNNNNN PHONE: (253) 474-9449 | FAX: (253) 474-0153 4815 CENTER STREET | TACOMA, WA. 98409 SITTS & HILL ENGINEERS, INC. CIVIL STRUCTURAL SURVEYING http://www.sittshill.com/RAY M O N D J. JOH N S O NN O. 4 4 9 E X P. 0 3 / 2 0 /1 9L A N D S C A P E A R C H I T E C TTREE RETENTION PLAN SITTS & HILL ENGINEERS, INC. Professional Engineers and Planners BRENT K. LESLIE, P.E. 4815 Center Street, Tacoma, WA 98409 KATHY A. HARGRAVE, P.E. www.sitts-hill-engineers.com LARRY G. LINDELL, P.E. (253) 474-9449 MICHAEL A. McEVILLY, P.L.S. Civil, Structural and Surveying May 22nd, 2018 WASHINGTON STATE AUTO DEALERS ASSOCIATION (WSADA) 621 Southwest Grady Way Renton, Washington 98057 To: City of Renton Subject: Construction Mitigation Description Renton Parking Lot for WSADA This project proposes construction dates per permit approval, in anticipation for construction in August 2018 to September 2018. The proposed construction hours of operation for this parking lot are to be 6AM-4PM Monday through Friday. Proposed hauling/transportation routes shall be limited to accessing and leaving the site via the designated construction entrance on 12th Street Southwest. Completed hauling and transportation routes shall be made by the contractor. The project proposes to minimize dust by sweeping the adjacent streets (alley and 12th Street Southwest) at the end of each business day or as necessary. Traffic and transportation impacts will be mitigated by allowing construction to occur and end earlier than typical business hours. Erosion shall be mitigated via implementing BMPs such as silt fencing and catch basin protection. Noise shall be minimized by limiting construction to the hours of construction. Thank you again for giving us the opportunity to present our proposal for engineering services for the Washington State Auto Dealers Association parking lot improvements. Sincerely, SITTS & HILL ENGINEERS, INC. Kathy A. Hargrave, P.E. Principal P:\17600\17668\Applications and Permits\2018-05-22 Construction Mitigation Description.docx RECEIVED 06/27/2018 amorganroth PLANNING DIVISION Exhibit 5 Geotechnical Engineering Report Washington State Auto Dealers Association 621 SW Grady Way Renton, Washington 98057 May 18, 2018 prepared for: Sitts & Hill Engineers, Inc. Attention: Kathy Hargrave 4815 Center Street Tacoma, Washington 98409 prepared by: Migizi Group, Inc. PO Box 44840 Tacoma, Washington 98448 (253) 537-9400 MGI Project P1258-T18 Exhibit 6 i TABLE OF CONTENTS Page No. 1.0 SITE AND PROJECT DESCRIPTION............................................................................................... 1 2.0 EXPLORATORY METHODS ............................................................................................................. 2 2.1 Test Pit Procedures ................................................................................................................ 2 3.0 SITE CONDITIONS ............................................................................................................................ 3 3.1 Surface Conditions ................................................................................................................. 3 3.2 Soil Conditions ....................................................................................................................... 3 3.3 Groundwater Conditions ...................................................................................................... 3 3.4 Seismic Conditions ................................................................................................................. 4 3.5 Liquefaction Potential ............................................................................................................ 4 4.0 CONCLUSIONS AND RECOMMENDATIONS ............................................................................ 4 4.1 Site Preparation ...................................................................................................................... 5 4.2 Asphalt Pavement .................................................................................................................. 7 4.3 Structural Fill .......................................................................................................................... 8 5.0 RECOMMENDED ADDITIONAL SERVICES ................................................................................ 9 6.0 CLOSURE ........................................................................................................................................... 10 List of Tables Table 1. Approximate Locations and Depths of Explorations ............................................................................. 2 List of Figures Figure 1. Topographic and Location Map Figure 2. Site and Exploration Plan APPENDIX A Soil Classification Chart and Key to Test Data .................................................................................................. A-1 Logs of Test Pits TP-1 through TP-3 .......................................................................................................... A-2…A-4 Page 1 of 10 MIGIZI GROUP, INC. PO Box 44840 PHONE (253) 537-9400 Tacoma, Washington 98448 FAX (253) 537-9401 May 18, 2018 Sitts & Hill Engineers, Inc. 4815 Center Street Tacoma, Washington 98409 Attention: Kathy Hargrave Subject: Geotechnical Engineering Report Washington State Auto Dealers Association 621 SW Grady Way Renton, Washington 98057 MGI Project P1258-T18 Dear Ms. Hargrave: Migizi Group, Inc. (MGI) is pleased to submit this report describing the results of our geotechnical engineering evaluation for a proposed asphalt parking lot expansion to be located in a vacant lot immediately south of the existing parking lot for the Washington State Auto Dealers Association (WSADA) building in Renton, Washington. A previous Geotechnical Letter Report was prepared for the existing facilities by E3RA, Inc. dated April 4, 2012. This report has been prepared for the exclusive use of Sitts & Hill Engineers, Inc., and their consultants, for specific application to this project, in accordance with generally accepted geotechnical engineering practice. 1.0 SITE AND PROJECT DESCRIPTION The project site is located along the south side of SW Grady Way in a commercial area just north of I-405 in Renton, Washington, as shown on the enclosed Topographic and Location Map (Figure 1). The project area is rectangularly-shaped, encompassing a total area of 0.33-acres. The site is undeveloped and lies in the ancestral floodplain of the Black and Green Rivers before the partial draining of Lake Washington in 1916. The site is bordered by SW 12th St to the south, asphalt parking lots to the north and east, and Bell Electronics to the west. It is our understanding that the project area will be stripped, paved, and connected to the existing WSADA parking area to the north. The new parking lot will be at or near existing grade. Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 2 of 10 2.0 EXPLORATORY METHODS We explored surface and subsurface conditions at the project site on April 27, 2018. Our exploration and evaluation program comprised the following elements: • Surface reconnaissance of the site; • Three test pit explorations (designated TP-1, TP-2, and TP-3) advanced on April 27, 2018; and • A review of published geologic and seismologic maps and literature. Table 1 summarizes the approximate functional locations and termination depths of our subsurface explorations, and Figure 2 depicts their approximate relative locations. The following sections describe the procedures used for excavation of the test pits. TABLE 1 APPROXIMATE LOCATIONS AND DEPTHS OF EXPLORATIONS Exploration Functional Location Termination Depth (feet) TP-1 TP-2 TP-3 Roughly central to the western third of the property Roughly the middle-most point of the property Roughly central to the eastern third of the property 10 3 10 The specific numbers and locations of our explorations were selected in relation to the existing site features, under the constraints of surface access, underground utility conflicts, and budget considerations. It should be realized that the explorations performed and utilized for this evaluation reveal subsurface conditions only at discrete locations across the project site and that actual conditions in other areas could vary. Furthermore, the nature and extent of any such variations would not become evident until additional explorations are performed or until construction activities have begun. If significant variations are observed at that time, we may need to modify our conclusions and recommendations contained in this report to reflect the actual site conditions. 2.1 Test Pit Procedures Our exploratory test pits were excavated with a rubber-tracked mini-excavator operated by an excavation contractor under subcontract to MGI. An engineering geologist from our firm observed the test pit excavations, collected soil samples, and logged the subsurface conditions. The enclosed test pit logs indicate the vertical sequence of soils and materials encountered in our test pits, based on our field classifications. Where a soil contact was observed to be gradational or undulating, our logs indicate the average contact depth. We estimated the relative density and consistency of the in-situ soils by means of the excavation characteristics and the stability of the test pit sidewalls. Our logs also indicate the approximate depths of any sidewall caving or groundwater seepage observed in the test pits. The soils were classified visually in general accordance with the system described in Figure A-1, which includes a key to the exploration logs. Summary logs of our explorations are included as Figure A-2 through A-4. Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 3 of 10 3.0 SITE CONDITIONS The following sections present our observations, measurements, findings, and interpretations regarding surface, soil, groundwater, and infiltration conditions. 3.1 Surface Conditions As previously indicated, the project site consists of a rectangularly-shaped, 0.33-acre commercial property situated near the intersection of I-405 and WA-167 in Renton. The property lies in the ancestral floodplain of the Black and Green Rivers before the partial draining of Lake Washington in 1916. The site is undeveloped and topographically flat, with the exception of a dry, empty pit in the southeastern corner of the property approximately 4 feet deep and 20 feet in length. Site vegetation is limited to sparse grass and spiky bushes lining the edges of the property, in addition to a line of deciduous and evergreen trees on the eastern boundary near an existing parking lot. No hydrologic features were observed on site, such as seeps, springs, ponds and streams. 3.2 Soil Conditions We observed subgrade conditions in three test pits across the property. These explorations revealed structural fill and construction-related debris such as concrete, asphalt, and brick in a dense condition down to approximately 2½ to 4½ feet below the surface. This material overlies dense native alluvial flood plain deposits comprised of fine sand, silty sand, silt and gravel. Native soils were all poorly consolidated and oversaturated. While excavating TP-2, a block of concrete prevented further excavation beyond 3 feet deep and the test pit was terminated. In the Geologic Map of the Renton Quadrangle, King County, Washington, as prepared by the Department of the Interior United States Geological Survey (USGS) (1965), the project site is mapped as containing Qaw, or Quaternary Alluvium associated with the flood plains of the White and Green Rivers. The upper part of these deposits are mostly clayey silt and fine sand, locally peaty, being 10 to 20 feet thick near Kent, thickening to 30 to 40 feet near Tukwila. The lower part of these deposits are mostly medium and coarse sand and can reach thicknesses of up to 75 feet. The National Cooperative Soil Survey (NCSS) for the King County Area classifies soils onsite as Ur-Urban Land, surrounded by minor soil units of sand and silt loam. This soil series reportedly formed along alluvial flood plains and is comprised of sandy loam, silt loam, silty clay loam and sand. Our subsurface explorations generally correspond with the site classifications prepared by the USGS and NCSS. The enclosed exploration logs (Appendix A) provide a detailed description of the soil strata encountered in our subsurface explorations. 3.3 Groundwater Conditions We encountered groundwater seepage in two of our three subsurface explorations, at a depth of 4 to 4½ feet below existing grade. Given the fact that our explorations were performed just outside of Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 4 of 10 what is generally considered the rainy season (November 1 to March 31), we do not anticipate that groundwater will rise much higher than that which we observed. Groundwater levels will fluctuate with localized geology and precipitation. 3.4 Seismic Conditions Based on our analysis of subsurface exploration logs and our review of published geologic maps, we interpret the onsite soil conditions to generally correspond with site class E, as defined by Table 30.2-1 in ASCE 7, per the 2015 International Building Code (IBC). Using 2015 IBC information on the USGS Design Summary Report website, Risk Category I/II/III seismic parameters for the site are as follows: Ss = 1.442 g SMS = 1.298 g SDS = 0.865 g S1 = 0.538 g SM1 = 1.292 g SD1 = 0.862 g Using the 2015 IBC information, MCER Response Spectrum Graph on the USGS Design Summary Report website, Risk Category I/II/III, Sa at a period of 0.2 seconds is 1.30 g and Sa at a period of 1.0 seconds is 1.30 g. The Design Response Spectrum Graph from the same website, using the same IBC information and Risk Category, Sa at a period of 0.2 seconds is 0.86 g and Sa at a period of 1.0 seconds is 0.86 g. 3.5 Liquefaction Potential Liquefaction is a sudden increase in pore water pressure and a sudden loss of soil shear strength caused by shear strains, as could result from an earthquake. Research has shown that saturated, loose, fine to medium sands with a fines (silt and clay) content less than about 20 percent are most susceptible to liquefaction. Poorly consolidated soils encountered below the water table (a depth of 4 to 4½ feet) present a moderate to severe risk for soil liquefaction. Recommendations for pavement section design and construction contained within this report helps mitigate some of this risk, but the risk for soil liquefaction and resultant post-construction settlement should still be considered moderate across the project area in the instance of a large-scale seismic event. 4.0 CONCLUSIONS AND RECOMMENDATIONS It is our understanding that the project area will be stripped, paved, and connected to the existing WSADA parking area to the north. The new parking lot will be at or near existing grade. We offer these recommendations: • Feasibility: Based on our field explorations, research, and evaluations, the proposed pavements appear feasible from a geotechnical standpoint. • Pavement Sections: We recommend a conventional pavement section comprised of an asphalt concrete pavement over a crushed rock base course over a properly prepared (compacted) subgrade or a granular subbase. Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 5 of 10 All soil subgrades should be thoroughly compacted, then proof-rolled with a loaded dump truck or heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling operation should be over excavated to an additional maximum depth of 12 inches and replaced with a suitable structural fill material. The following sections of this report present our specific geotechnical conclusions and recommendations concerning site preparation, spread footings, slab-on-grade floors, asphalt pavement, and structural fill. The Washington State Department of Transportation (WSDOT) Standard Specifications and Standard Plans cited herein refer to WSDOT publications M41-10, Standard Specifications for Road, Bridge, and Municipal Construction, and M21-01, Standard Plans for Road, Bridge, and Municipal Construction, respectively. 4.1 Site Preparation Preparation of the project site should involve erosion control, temporary drainage, clearing, stripping, excavations, cutting, subgrade compaction, and filling. Erosion Control: Before new construction begins, an appropriate erosion control system should be installed. This system should collect and filter all surface water runoff through silt fencing. We anticipate a system of berms and drainage ditches around construction areas will provide an adequate collection system. Silt fencing fabric should meet the requirements of WSDOT Standard Specification 9-33.2 Table 3. In addition, silt fencing should embed a minimum of 6 inches below existing grade. An erosion control system requires occasional observation and maintenance. Specifically, holes in the filter and areas where the filter has shifted above ground surface should be replaced or repaired as soon as they are identified. Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or near-surface water within the construction zones before stripping begins. Because the selection of an appropriate drainage system will depend on the water quantity, season, weather conditions, construction sequence, and contractor's methods, final decisions regarding drainage systems are best made in the field at the time of construction. Based on our current understanding of the construction plans, surface and subsurface conditions, we anticipate that curbs, berms, or ditches placed around the work areas will adequately intercept surface water runoff. Clearing and Stripping: After surface and near-surface water sources have been controlled, sod, topsoil, and root-rich soil should be stripped from the site. The proposed work area is currently paved and no stripping will be necessary. Site Excavations: Based on our explorations, we expect that excavations will encounter loose/soft to medium dense/stiff silty, sandy alluvial soils which can be easily excavated using standard excavation equipment. Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 6 of 10 Dewatering: We encountered groundwater seepage in two of three of our explorations at a depth of 4 to 4½ feet below existing grade. Given the fact that our explorations were performed just outside of what is generally considered the rainy season (November 1 to March 31), we do not anticipate that groundwater will rise much higher than that which we observed. If groundwater is encountered in shallower excavations, we anticipate that an internal system of ditches, sumpholes, and pumps will be adequate to temporarily dewater most excavations. For deeper excavations well below the water table, expensive dewatering equipment, such as well points, may need to be utilized in order to adequately dewater excavations. Temporary Cut Slopes: All temporary soil slopes associated with site cutting or excavations should be adequately inclined to prevent sloughing and collapse. Temporary cut slopes in site soils should be no steeper than 1½H:1V, and should conform to Washington Industrial Safety and Health Act (WISHA) regulations. Subgrade Compaction: Exposed subgrades for the foundations of the planned additions should be compacted to a firm, unyielding state before new concrete or fill soils are placed. Any localized zones of looser granular soils observed within a subgrade should be compacted to a density commensurate with the surrounding soils. In contrast, any organic, soft, or pumping soils observed within a subgrade should be overexcavated and replaced with a suitable structural fill material. Site Filling: Our conclusions regarding the reuse of onsite soils and our comments regarding wet- weather filling are presented subsequently. Regardless of soil type, all fill should be placed and compacted according to our recommendations presented in the Structural Fill section of this report. Specifically, building pad fill soil should be compacted to a uniform density of at least 95 percent (based on ASTM:D-1557). Onsite Soils: We offer the following evaluation of these onsite soils in relation to potential use as structural fill: • Fill: The fill that overlies the site contains construction debris and some organic material, so is not reusable as structural fill. If areas of debris and organic-free fill are encountered during the construction process and are thought to be reusable, we recommend that MGI evaluate their potential for reuse. • Alluvial Silt and Silty Sand: The alluvial silty sand that underlies the site is very moisture sensitive and will be difficult or impossible to reuse during most weather conditions. The majority of this soil type is currently above the optimum moisture content and will not compact adequately unless extensively aerated. • Alluvial Fine to Medium Sand with Gravel: Where encountered, and if properly segregated from its siltier counterpart, the clean native fine sands are a possible source of structural fill. This material type is relatively impervious to moisture content variations and can be reused in most weather conditions. Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 7 of 10 Permanent Slopes: All permanent cut slopes and fill slopes should be adequately inclined to reduce long-term raveling, sloughing, and erosion. We generally recommend that no permanent slopes be steeper than 2H:1V. For all soil types, the use of flatter slopes (such as 2½H:1V) would further reduce long-term erosion and facilitate revegetation. Slope Protection: We recommend that a permanent berm, swale, or curb be constructed along the top edge of all permanent slopes to intercept surface flow. Also, a hardy vegetative groundcover should be established as soon as feasible, to further protect the slopes from runoff water erosion. Alternatively, permanent slopes could be armored with quarry spalls or a geosynthetic erosion mat. 4.2 Asphalt Pavement Since asphalt pavements will be used across much of the project site, we offer the following comments and recommendations for pavement design and construction. Subgrade Preparation: We recommend a conventional pavement section comprised of an asphalt concrete pavement over a crushed rock base course over a properly prepared (compacted) subgrade or a granular subbase. All soil subgrades should be thoroughly compacted, then proof-rolled with a loaded dump truck or heavy compactor. Any localized zones of yielding subgrade disclosed during this proof-rolling operation should be over excavated to an additional maximum depth of 12 inches and replaced with a suitable structural fill material. All structural fill should be compacted according to our recommendations given in the Structural Fill section. Specifically, the upper 2 feet of soils underlying pavement section should be compacted to at least 95 percent (based on ASTM D-1557), and all soils below 2 feet should be compacted to at least 90 percent. Pavement Materials: For the base course, we recommend using imported crushed rock, such as "Crushed Surfacing Top Course” per WSDOT Standard Specification 9-03.9(3). If a subbase course is needed, we recommend using imported, clean, well-graded sand and gravel such as “Ballast” or “Gravel Borrow” per WSDOT Standard Specifications 9-03.9(1) and 9-03.14, respectively. Conventional Asphalt Sections: A conventional pavement section typically comprises an asphalt concrete pavement over a crushed rock base course. We recommend using the following conventional pavement sections: Minimum Thickness Section Automobile Parking Areas Driveways and Areas Subject to Truck Traffic Asphalt Concrete Pavement 2 inches 3 inches Crushed Rock Base 4 inches 6 inches Compaction and Observation: All subbase and base course material should be compacted to at least 95 percent of the Modified Proctor maximum dry density (ASTM D-1557), and all asphalt concrete should be compacted to at least 92 percent of the Rice value (ASTM D-2041). We recommend that an MGI representative be retained to observe the compaction of each course before any overlying Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 8 of 10 layer is placed. For the subbase and pavement course, compaction is best observed by means of frequent density testing. For the base course, methodology observations and hand-probing are more appropriate than density testing. Pavement Life and Maintenance: No asphalt pavement is maintenance-free. The above described pavement sections present our minimum recommendations for an average level of performance during a 20-year design life, therefore, an average level of maintenance will likely be required. Furthermore, a 20-year pavement life typically assumes that an overlay will be placed after about 10 years. Thicker asphalt and/or thicker base and subbase courses would offer better long-term performance but would cost more initially; thinner courses would be more susceptible to “alligator” cracking and other failure modes. As such, pavement design can be considered a compromise between a high initial cost and low maintenance costs versus a low initial cost and higher maintenance costs. 4.3 Structural Fill The term "structural fill" refers to any material placed under foundations, retaining walls, slab-on- grade floors, sidewalks, pavements, and other structures. Our comments, conclusions, and recommendations concerning structural fill are presented in the following paragraphs. Materials: Typical structural fill materials include clean sand, gravel, pea gravel, washed rock, crushed rock, well-graded mixtures of sand and gravel (commonly called "gravel borrow" or "pit- run"), and miscellaneous mixtures of silt, sand, and gravel. Recycled asphalt, concrete, and glass, which are derived from pulverizing the parent materials, are also potentially useful as structural fill in certain applications. Soils used for structural fill should not contain any organic matter or debris, nor any individual particles greater than about 6 inches in diameter. Fill Placement: Clean sand, gravel, crushed rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, and each lift should be thoroughly compacted with a mechanical compactor. Compaction Criteria: Using the Modified Proctor test (ASTM:D-1557) as a standard, we recommend that structural fill used for various onsite applications be compacted to the following minimum densities: Fill Application Minimum Compaction Asphalt pavement base Asphalt pavement subgrade (upper 2 feet) Asphalt pavement subgrade (below 2 feet) 95 percent 95 percent 90 percent Sitts & Hill Engineers, Inc. – WSADA, 621 SW Grady Way, Renton, WA May 18, 2018 Geotechnical Engineering Report P1258-T18 Migizi Group, Inc. Page 9 of 10 Subgrade Observation and Compaction Testing: Regardless of material or location, all structural fill should be placed over firm, unyielding subgrades prepared in accordance with the Site Preparation section of this report. The condition of all subgrades should be observed by geotechnical personnel before filling or construction begins. Also, fill soil compaction should be verified by means of in-place density tests performed during fill placement so that adequacy of soil compaction efforts may be evaluated as earthwork progresses. Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on their grain-size distribution and moisture content when they are placed. As the "fines" content (that soil fraction passing the U.S. No. 200 Sieve) increases, soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, unyielding condition when the moisture content is more than 2 percentage points above or below optimum. For fill placement during wet-weather site work, we recommend using "clean" fill, which refers to soils that have a fines content of 5 percent or less (by weight) based on the soil fraction passing the U.S. No. 4 Sieve. 5.0 RECOMMENDED ADDITIONAL SERVICES Because the future performance and integrity of the structural elements will depend largely on proper site preparation, drainage, fill placement, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. Subsequently, we recommend that MGI be retained to provide the following post-report services: • Review all construction plans and specifications to verify that our design criteria presented in this report have been properly integrated into the design; • Prepare a letter summarizing all review comments (if required); • Check all completed subgrades for footings and slab-on-grade floors before concrete is poured, in order to verify their bearing capacity; and • Prepare a post-construction letter summarizing all field observations, inspections, and test results (if required). APPROXIMATE SITE LOCATION P.O. Box 44840 Tacoma, WA 98448 Location Job Number Figure DateTitle 621 SW Grady Way Renton, Washington Topographic and Location Map 1 05/16/18 P1258-T18 APPENDIX A SOIL CLASSIFICATION CHART AND KEY TO TEST DATA LOGS OF TEST PITS CLAYEY GRAVELS, POORLY GRADED GRAVEL-SAND-CLAY MIXTURES SILTS AND CLAYSCOARSE GRAINED SOILSMore than Half > #200 sieveLIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 CLEAN GRAVELS WITH LITTLE OR NO FINES GRAVELS WITH OVER 15% FINES CLEAN SANDS WITH LITTLE OR NO FINES MORE THAN HALF COARSE FRACTION IS SMALLER THAN NO. 4 SIEVE MORE THAN HALF COARSE FRACTION IS LARGER THAN NO. 4 SIEVE INORGANIC SILTS, MICACEOUS OR DIATOMACIOUS FINE SANDY OR SILTY SOILS, ELASTIC SILTS ORGANIC CLAYS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY OH INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS, OR CLAYEY SILTS WITH SLIGHT PLASTICITY CH SILTY GRAVELS, POORLY GRADED GRAVEL-SAND-SILT MIXTURES SANDS SILTS AND CLAYS Figure A-1 INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS R-Value Sieve Analysis Swell Test Cyclic Triaxial Unconsolidated Undrained Triaxial Torvane Shear Unconfined Compression (Shear Strength, ksf) Wash Analysis (with % Passing No. 200 Sieve) Water Level at Time of Drilling Water Level after Drilling(with date measured) RV SA SW TC TX TV UC (1.2) WA (20) Modified California Split Spoon Pushed Shelby Tube Auger Cuttings Grab Sample Sample Attempt with No Recovery Chemical Analysis Consolidation Compaction Direct Shear Permeability Pocket Penetrometer CA CN CP DS PM PP PtHIGHLY ORGANIC SOILS TYPICAL NAMES GRAVELS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS WELL GRADED GRAVELS, GRAVEL-SAND MIXTURES MAJOR DIVISIONS PEAT AND OTHER HIGHLY ORGANIC SOILS WELL GRADED SANDS, GRAVELLY SANDS POORLY GRADED SANDS, GRAVELLY SANDS SILTY SANDS, POORLY GRADED SAND-SILT MIXTURES CLAYEY SANDS, POORLY GRADED SAND-CLAY MIXTURES POORLY GRADED GRAVELS, GRAVEL-SAND MIXTURES SOIL CLASSIFICATION CHART AND KEY TO TEST DATA GW GP GM GC SW SP SM SC ML FINE GRAINED SOILSMore than Half < #200 sieveLGD A NNNN02 GINT US LAB.GPJ 11/4/05INORGANIC CLAYS OF HIGH PLASTICITY, FAT CLAYS CL OL MH SANDS WITH OVER 15% FINES Migizi Group, Inc. GB S-1 GP- GM SM SP ML 0.5 2.5 4.0 10.0 (GP-GM) Gray/brown gravel with silt and sand (dense, moist) (Fill) (SM) Gray silty sand with gravel and concrete/asphalt/brick debris (dense, moist) (Fill) (SP) Blue/gray fine to medium sand with gravel (medium dense, moist) (Alluvium) (ML) Blue/gray silt (very soft, wet) (Alluvium) Moderate caving observed from 4 to 10 feet Moderate groundwater seepage observed at 4 feet The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot. Bottom of test pit at 10.0 feet. NOTES LOGGED BY ZLL EXCAVATION METHOD Rubber Tracked Mini Excavator EXCAVATION CONTRACTOR Paulman GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 4/27/18 COMPLETED 4/27/18 AT TIME OF EXCAVATION 4.00 ft Moderate seepage AT END OF EXCAVATION --- AFTER EXCAVATION --- TEST PIT SIZEGROUND ELEVATION SAMPLE TYPENUMBERDEPTH(ft)0.0 2.5 5.0 7.5 10.0 PAGE 1 OF 1 Figure A-2 TEST PIT NUMBER TP-1 CLIENT Sitts & Hill Engineers, Inc. PROJECT NUMBER P1258-T18 PROJECT NAME Washington State Auto Dealers Association PROJECT LOCATION 621 SW Grady Way, Renton, WA COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 5/16/18 11:29 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1258-T18\P1258-T18 TEST PITS.GPJMigizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 Fax: 253-537-9401 U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION GP- GM SM 0.8 3.0 (GP-GM) Gray/brown gravel with silt and sand (dense, moist) (Fill) (SM) Gray silty sand with gravel and concrete/asphalt/brick debris (dense, moist) (Fill) Refusal at a depth of 3 feet atop a large section of concrete No caving observed No groundwater seepage observed The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot. Bottom of test pit at 3.0 feet. NOTES LOGGED BY ZLL EXCAVATION METHOD Rubber Tracked Mini Excavator EXCAVATION CONTRACTOR Paulman GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 4/27/18 COMPLETED 4/27/18 AT TIME OF EXCAVATION --- AT END OF EXCAVATION --- AFTER EXCAVATION --- TEST PIT SIZEGROUND ELEVATION SAMPLE TYPENUMBERDEPTH(ft)0.0 2.5 PAGE 1 OF 1 Figure A-3 TEST PIT NUMBER TP-2 CLIENT Sitts & Hill Engineers, Inc. PROJECT NUMBER P1258-T18 PROJECT NAME Washington State Auto Dealers Association PROJECT LOCATION 621 SW Grady Way, Renton, WA COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 5/16/18 11:29 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1258-T18\P1258-T18 TEST PITS.GPJMigizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 Fax: 253-537-9401 U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION GP- GM SM SM ML 1.0 3.5 4.5 10.0 (GP-GM) Gray/brown gravel with silt and sand (dense, moist) (Fill) (SM) Gray silty sand with gravel and concrete/asphalt/brick debris (dense, moist) (Fill) (SM) Gray silty sand with gravel, wood, glass, plastic and other detritus (loose, wet) (Fill) (ML) Blue/gray mottled silt (very soft, wet) (Alluvium) Moderate caving observed from 4.5 to 10 feet Moderate groundwater seepage observed at 4.5 feet The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 0.5 foot. Bottom of test pit at 10.0 feet. NOTES LOGGED BY ZLL EXCAVATION METHOD Rubber Tracked Mini Excavator EXCAVATION CONTRACTOR Paulman GROUND WATER LEVELS: CHECKED BY JEB DATE STARTED 4/27/18 COMPLETED 4/27/18 AT TIME OF EXCAVATION 4.50 ft Moderate seepage AT END OF EXCAVATION --- AFTER EXCAVATION --- TEST PIT SIZEGROUND ELEVATION SAMPLE TYPENUMBERDEPTH(ft)0.0 2.5 5.0 7.5 10.0 PAGE 1 OF 1 Figure A-4 TEST PIT NUMBER TP-3 CLIENT Sitts & Hill Engineers, Inc. PROJECT NUMBER P1258-T18 PROJECT NAME Washington State Auto Dealers Association PROJECT LOCATION 621 SW Grady Way, Renton, WA COPY OF GENERAL BH / TP LOGS - FIGURE.GDT - 5/16/18 11:29 - C:\USERS\JESSICA\DESKTOP\TEST PITS AND BORINGS - GINT\P1258-T18\P1258-T18 TEST PITS.GPJMigizi Group, Inc. PO Box 44840 Tacoma, WA 98448 Telephone: 253-537-9400 Fax: 253-537-9401 U.S.C.S.GRAPHICLOGMATERIAL DESCRIPTION Washington State Auto Dealers Association (WSADA) Renton Parking Lot Technical Information Report Prepared for: Washington State Auto Dealers Association 621 SW Grady Way Renton, WA 98057 Contact: Vicki Giles Fabré Phone: (206) 433-6300 Prepared by: Sitts & Hill Engineers, Inc. 4815 Center Street Tacoma, Washington 98409 Contact: Kathy Hargrave, P.E. Phone: (253) 474-9449 May 2018 Revised June 2018 S&H Job Number 17,668 Exhibit 7 Full document available in Laserfiche Submittals Folder DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT Page 1 of 4 LUA18-000384 ADVISORY NOTES TO APPLICANT The following notes are supplemental information provided in conjunction with the administrative land use action. Because these notes are provided as information only, they are not subject to the appeal process for the land use action. Planning: (Contact: Alex Morganroth, 425-430-7219, amorganroth@rentonwa.gov) 1. RMC section 4-4-030.C.2 limits haul hours between 8:30 am to 3:30 pm, Monday through Friday unless otherwise approved by the Development Services Division. 2. Commercial, multi-family, new single family and other nonresidential construction activities shall be restricted to the hours between seven o’clock (7:00) a.m. and eight o’clock (8:00) p.m., Monday through Friday. Work on Saturdays shall be restricted to the hours between nine o’clock (9:00) a.m. and eight o’clock (8:00) p.m. No work shall be permitted on Sundays. 3. Within thirty (30) days of completion of grading work, the applicant shall hydroseed or plant an appropriate ground cover over any portion of the site that is graded or cleared of vegetation and where no further construction work will occur within ninety (90) days. Alternative measures such as mulch, sodding, or plastic covering as specified in the current King County Surface Water Management Design Manual as adopted by the City of Renton may be proposed bet ween the dates of November 1st and March 31st of each year. The Development Services Division’s approval of this work is required prior to final inspection and approval of the permit. 4. A National Permit Discharge Elimination System (NPDES) permit is required when more than one acre is being cleared. 5. The applicant may not fill, excavate, stack or store any equipment, dispose of any materials, supplies or fluids, operate any equipment, install impervious surfaces, or compact the earth in any way within the area defined by the drip line of any tree to be retained. 6. The applicant shall erect and maintain six foot (6') high chain link temporary construction fencing around the drip lines of all retained trees, or along the perimeter of a stand of retained trees. Placards shall be placed on fencing every fifty feet (50') indicating the words, “NO TRESPASSING – Protected Trees” or on each side of the fencing if less than fifty feet (50'). Site access to individually protected trees or groups of trees shall be fenced and signed. Individual trees shall be fenced on four (4) sides. In addition, the applicant shall provide supervision whenever equipment or trucks are moving near trees. 7. This permit is shall comply with the Bald and Golden Eagle Protection Act. The permitted is responsible for adhering to the U.S. Fish and Wildlife Service National Bald Eagle Management Guidelines (2007) and /or your U.S. Fish and Wildlife Service permit. Development Engineering: (Contact: Rohini Nair, 425-430-7298, rnair@rentonwa.gov) 1. See Attached Development Engineering Memo dated July 13, 2018 Building: (Contact: Craig Burnell, 425-430-7290, cburnell@rentonwa.gov) 1. Recommendations of the geotechnical report must be followed as a condition of building permits. Exhibit 8 ADVISORY NOTES TO APPLICANT Page 2 of 4 LUA**-000*** DEPARTMENT OF COMMUNITY & ECONOMIC DEVELOPMENT M E M O R A N D U M DATE: 7/13/2018 TO: Alex Morganroth, Planner FROM: Rohini Nair, Civil Plan Reviewer SUBJECT: Utility and Transportation Comments for WSADA Paarking Lot Parcel 3340404805 LUA 18-000384 I have reviewed the application for the WSADA Paarking Lot parking lot Parcel ID 3340404805 and have the following comments: EXISTING CONDITIONS The site is approximately 0.33 acres in size and is rectangular in shape. The site is currently vacant without ant buildings. Water Water service is provided by City of Renton. The site is in the Valley service area in the 196 hydraulic pressure zone. There is an existing 8-inch City water main located in SW 12th Street (see Water plan no. W-2798). The approximate static water pressure is 73 psi at the elevation of 28 feet. The site is located outside of an Aquifer Protection Area. Sewer Wastewater service is provided by City of Renton. There is an existing 12-inch PVC gravity wastewater main located in alley north of the site (see City plan no. S-0145). Storm There is an existing 12–inch storm drainage conveyance in the alley north of the site (see City plan no. SW- 3657). The existing property does not contain stormwater facilities. There is no existing stormwater main within SW 12th Street. Streets SW 12th Street is a Collector Arterial with an existing right of way (ROW) width of 60 feet as measured using the King County Assessor’s Map. The existing pavement width is about 24 feet without curb, gutter and sidewalk. North of the site is a fully paved public alley with 16 feet ROW width. CODE REQUIREMENTS WATER 1. The information provided with the land use application of the proposed parking lot does not include any building or any water service requirements. 2. If landscape irrigation is proposed, a separate meter will be required for landscape irrigation per COR Standard Plan 320.1. A double check valve assembly (DCVA) is required behind the meter per COR Standard Plan 340.8. SEWER 1. The information provided with the land use application of the proposed parking lot does not include any building or any sewer service requirements. ADVISORY NOTES TO APPLICANT Page 3 of 4 LUA**-000*** SURFACE WATER 1. A geotechnical report, dated May 2018, completed by Migizi Group, Inc. for the site has been provided. Erosion control measures will need to be in place prior to starting construction activities on the site. Geotechnical recommendations need to be followed during construction. 2. A Preliminary Drainage Plan and Technical Information Report (TIR), revision date July 2018, was submitted by Sitts & Hill Engineers, Inc. for the Land Use review. Based on the City of Renton’s flow control map, the site falls within the Peak Rate Flow Control Standard area matching Existing Site Conditions and is within the Black River Drainage Basin. The development is subject to Full Drainage Review in accordance with the 2017 Renton Surface Water Design Manual (RSWDM). All nine core requirements and the six special requirements have been discussed in the Technical Information Report. 3. The project does not propose a flow control facility since the increase of peak flow rate during the 100 year event is less than 0.15 cfs. 4. The development is required to provide enhanced basic water quality treatment prior to discharge. The water quality treatment is proposed by the use of two Filterra units. 5. Limited infiltration is proposed to meet the requirements of Core Requirement #9 on-site BMPS. 6. Stormwater facilities and on-site BMPS shall be designed in accordance with the RSWDM that is current at the time of civil construction permit application. Final drainage plan and Technical Information Report (TIR) report are required to be provided with the construction permit application. 7. Surface water system development fee is $0.687 per square foot of new impervious surface, but not less than $1,718.00. This is payable prior to issuance of the construction permit. TRANSPORTATION 1. The proposed development fronts SW 12th Street (a Commercial and Industrial access street) on the south and a public alley on the north. The 4.5 feet wide dedication on SW 12th Street frontage shown in the plans is acceptable. Based on the $100,000 project cost information provided by the applicant, the project meets the frontage improvement exemption mentioned in RMC 4-6-060.D.1 which is the exemption for projects with valuation less than $150,000. Therefore, the applicant is not proposing the construction of frontage improvements on SW 12th Street. 2. The traffic memo for the project prepared by Heath & Associates mentioned that traffic impact analysis is not triggered by the project. 3. Refer to City code 4-4-080 regarding driveway regulations. a. The maximum width of any driveway shall not exceed 30-feet. b. Driveways shall be located a minimum of 5-feet from property lines. c. Maximum driveway slope is 8%. 4. Paving and trench restoration shall comply with the City’s Trench Restoration and Overlay Requirements. GENERAL COMMENTS 1. Adequate separation between utilities as well as other features shall be provided in accordance with code requirements. a. 7-ft minimum horizontal and 1-ft vertical separation between storm and other utilities is required with the exception of water lines which require 10-ft horizontal and 1.5-ft vertical. b. The stormwater line should be minimum 5 feet away from any other structure or wall or building. c. Trench of any utility should not be in the zone of influence of the retaining wall or of the building. 2. All civil construction permits for utility and street improvements will require separate plan submittals. All utility plans shall confirm to the Renton Drafting Standards. A licensed Civil Engineer shall prepare the civil plans. Please visit the Development Engineering Forms page for the most up-to-date plan submittal requirements: http://rentonwa.gov/business/default.aspx?id=42473 ADVISORY NOTES TO APPLICANT Page 4 of 4 LUA**-000*** 3. A landscaping plan shall be included with the civil plan submittal. Each plan shall be on separate sheets. 4. Fees quoted in this document reflect the fees applicable in the year 2018 only and will be assessed based on the fee that is current at the time of the permit application or issuance, as applicable to the permit type. Please visit www.rentonwa.gov for the current development fee schedule. 5. * An additional technology fee will be added to each fee marked with an asterisk (*).