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HomeMy WebLinkAbout4065_TIRTechnical Information Report 1 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Storm Water Drainage Assessment Report Project Name: FYCD Cultural & Education Associates Project Address: 711 Monroe Ave N.E. Renton, Washington Parcel Numbers: 7809200075 Developer: Engineer: Ali Amirzehni P.E. Company: Consultant Engineer Address: 3952 112th Ave N.E., Bellevue, WA 98004 Phone Number: (206) 288-3122 Revised Report Date: October 11, 2019 10/11/2019 _______________________________ Engineer Stamp: Ali Amirzehni P.E., Consultant Engineer Zce.engineering@gmail.com, 206-288-3122 Technical Information Report 2 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Table of Contents Section 1: Project Overview Section 2: Conditions and Requirements Summary Section 3: Offsite Analysis Section 4: Flow Control, Low Impact Development (LID) and Water Quality Facility Analysis and Design Section 5: Conveyance System Analysis and Design Section 6: Special Reports and Studies Section 7: Other Permits Section 8: CSWPP Plan Analysis and Design SECTION 9 – BOND QUANTITIES, FACILITIES SUMMARIES, AND DECLARATION OF COVENANT SECTION 10 – OPERATIONS AND MAINTENANCE Appendix Soil Report Drainage Site Plan Erosion & Sediment Control Plan Maintenance Requirements Technical Information Report 3 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Section 1: Project Overview The site is located at 711 Monroe Avenue NE in Renton Washington. The site consists of a single lot with total area of about 13,532 square feet (0.31 acres). The western portion of the site is currently developed with a single-family residence. A driveway extends through the north portion of the property from the east and Monroe Ave NE. The reminder of the property is vegetated with grasses, shrubs, bushes, and trees. This project is proposing to demolish the existing single family residence and construct a new structure within the existing structure foot-print. The new structure will be converted to I Kuan Tao Cultural Center. Surface parking spaces will be provided within the front yard. Access to the site would be maintained off of Monroe Avenue NE. The site gently slopes downward toward the southwest and west with topographic relief of less than 8 feet. There is a moderate steep slope extending downward to the west in the area just west of the property. This area is well vegetated with low lying brushes and trees. The slope is up to 15’ height and has magnitudes of 30 percent. The site underlain by glacial till soil which typically has a very low permeability. The factored infiltration rate is 0.28 inches /hour according to the attached soil report prepared by COBALT Geoscience. This project proposes 4,674 sf of new plus replaced impervious surface, and Table 1 & 2 summarizes the impervious area calculation. Table 1. Summary of existing site conditions Table 2. Summary of proposed site conditions Surface Type Area Units Notes Roof (with eaves) 1,938 s.f. New Driveway 2,736 s.f. Existing Parking Area 1,962 s.f. To remain Total New & Replaced Imp Area * 4,674 s.f. Landscaped Area 8,878 s.f. Total Lot 13,552 s.f. Surface Type Area Units Notes Roof (with eaves) 1,720 s.f. Driveway & walkway 5,020 s.f. s Total Imp Area 6,740 sf Landscaped area 6,812 s.f. Total Lot 13,552 S.f. Technical Information Report 4 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Aerial Map Vicinity Map Technical Information Report 5 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Section 2: Conditions and Requirements Summary This project proposes to construct a cultural center with a 4,674 sf of new plus replaced impervious surface. As described in City of Renton Surface Water Design Manual, full drainage review is required. Technical Information Report 6 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Core Requirements 1-9 per 2017 City of Renton Surface Water Design Manual will apply. Core Requirements #1- Discharge at the Natural Location: The project will discharge to the natural downstream location. Downstream drainage patterns will not be altered. Core Requirement # 2-Offsite Analysis: Offsite Analysis is provided in Section 3. Core Requirement # 3 – Flow Control Facility: This project is proposing less than 5,000 sf of new impervious area and exempt from flow control facility. Refer to Section 4 of this report for a detailed discussion. Core Requirement # 4 – Conveyance system is discussed in section 5. Core Requirement # 5 – Erosion and Sediment Control: All erosion and sediment control measures shall be governed by the requirements of the City of Renton Surface Water Manual. The project provides the minimum ESC measures and discussed in Section 8. Core Requirement # 6 – Maintenance & Operation: Will be provided. Maintenance and operations of all drainage facilities located within the private residential property is the responsibility of the applicant or property owner. Maintenance guidelines are discussed in Section 10 of this report. Core Requirement # 7 – Financial Guarantees & Liability: A financial guarantee will be provided by the owner upon requested. Core Requirement #8- Water Quality: The project proposes less than 5,000 sf of new plus replaced PGIS and exempt from these requirements. Core Requirement #9- On Site BMP: The requirement for mitigation of target impervious surface is discussed in Section 4. Special Requirement #1: Other Adopted Requirements Based on available data at the time this report was prepared, there are no one Special Adopted Requirements for this project. Special Requirement #2: Flood hazard Area Based on the City of Renton COP map, This site is not located within a flood hazard area. Special Requirement #3: Flood Protection Facility N/A Special Requirement #4: Source Control N/A Special Requirement #5: Oil Control N/A Special Requirement #6: Aquifer protection Area Technical Information Report 7 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Based on the City of Renton COP map, This site is not located within an aquifer area. Section 3: Offsite Analysis Level 1 Downstream Analysis A field investigation was conducted on April 14, 2019. The weather was cloudy and dry. Stormwater from the site sheet flows from the property towards the Monroe Ave and discharges into the Monroe closed conveyance system via a catch basin located on Monroe Ave NE. The Closed conveyance system consists of series of catch basin and pipe conveyance system that runs east to west along the Monroe Ave NE Task 2 – Resource Review The City of Renton COP GIS map was utilized to review the City closed drainage system. No drainage complains was documented within one mile of the down-stream of flow path. •Wetlands Inventory: The project site is not located in or near a mapped wetland per the City of Renton COP map. •Landslide Area Maps: The project site is not located in or near a landside area per the City of Renton COP map. Task 3 – Field Inspection The Monroe Ave closed conveyance system consists of series of catch basin and pipe conveyance system. The system runs east to west and all the structures appears to be in fair condition. No sign of over-toping or flooding was observed. Task 4 – Drainage System Description and Problems Descriptions Based on this field inspection and resources review there appears to be no current significant erosion or capacity problems. Task 5 – Mitigation of Existing or Potential Problems There are no apparent erosion or capacity problems downstream of this project. 4,514752 City of Renton Print map Template This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere Notes None 04/14/2019 Legend 512 0 256 512 Feet Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Boundary Addresses Parcels Wellhead Protection Area Zones Zone 1 Zone 1 Modified Zone 2 Coalmines High Moderate Unclassified Erosion Hazard - High Floodway Special Flood Hazard Areas (100 year flood) Other Flood Areas (Zone X - 500 year flood) Channel Migration Zones (CMZ) as mapped by King County Moderate Hazard Area Potential Hazard Area Severe Hazard Area Landslide Very High High Moderate Unclassified Environment Designations Natural Shoreline High Intensity Shoreline Isolated High Intensity Shoreline Residential Urban Conservancy Jurisdictions Streams (Classified) <all other values> Type S Shoreline Type F Fish Type Np Non-Fish Type Ns Non-Fish Seasonal Unclassified Not Visited Wetlands Seismic Hazard Areas Faults Water Service Areas Wastewater Service Areas Network Structures Inlet Manhole Utility Vault Unknown Structure Control Structures Pump Stations Discharge Points Water Quality Detention Facilities Pond Tank Technical Information Report 9 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington Section 4: Flow Control, Low Impact Development (LID) and Water Quality Analysis Flow Control Roof runoff This project is proposing less than 5,000 sf of new impervious area and exempt from flow control facility. Stormwater on-site BMPs elements are designed in-accordance to the 2017 City of Renton Surface Water Management Design Manual. To address the on-site BMPs requirements, implementing of full and basic dispersion trench BMP’s were considered first and determined to not feasible due to lack of native vegetation and required flow path and set required setbacks. Implementation of full and limited infiltration is not feasible due to soil type and shallow ground water table as described in the soil report prepared by Cobalt Geo dated May 14, 2018. The site is underlain by glacial till and infiltration is not recommended and/or potentially infeasible (see the attached drainage report). Rain garden BMP was also considered. Implementation of Rain garden is also not feasible due to soil type, land availability, conflict with utilities, and set back requirements. Perforated pipe connection BMP was selected for the roof runoff. All the downspouts will be tight lined and connected to the perforated pipe connection structure. The total new roof area is 1,938 sg, and 10’ of trench with perforated pipe will be provided with a connection to the City drainage system on Monroe Ave NE. Other hard surfaces: Implementation of dispersion, full and limited infiltration, permeable pavement is not feasible due to soil type and shallow ground water table as described in the soil report prepared by Cobalt Geo dated May 14, 2018. The site is underlain by glacial till soil and molting was also observed at depth of about 2 to 5 ft. Permeable pavement is not recommended and/or potentially infeasible (see the attached drainage soil report) A conveyance system will be provided to collect runoff from the parking lot area and connect to the Monroe Ave N. existing catch basin. The existing driveway drainage will not be altered and will continue to sheet flow and dissipate into the surrounding landscaped area. All new pervious area will receive soil amendment per the City Of Renton standard plan. Water Quality The project proposes less than 5,000 sf of new plus replaced PGIS and exempt from these requirements. Section 5: Conveyance System Analysis and Design Conveyance pipe connection to the Monroe Ave N catch basin Technical Information Report 10 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington 12” CPE (corrugated polyethylene pipe) @ min 1% slope will be ued. Pipe capacity and flow calculation: Roof = 1,938 sf New Driveway = 2,736 sf Existing Parking Area =1,962 sf Total impervious area= 6,636 sf (0.15 acre) 12” CPE (corrugated polyethylene pipe) capacity @ 1% slope: Q = 1.486/n * A * R2/3 * S ½ n = roughness coefficient =0.012 A = cross section of pipe = 3.14 (d/2)^2 = 3.14 (1 / 2)^2 = 0.78 R = wetted perimeter of pipe R^2/3 = (D/4)^2/3 = (1/4)^2/3 =0.39 S = slope 1% S^1/2 = 0.1 Q = ((1.486/0.012) * 0.78 * 0.39 * 0.1) = 3.76 cfs 12” pipe capacity @ 1% Site Flow calculation: C = Runoff Coefficient (weighted average) C=0.9 A= 6,636 ( 0.15 acres) IR = Peak Rainfall Intensity Pr = 3.4 inches (25-year, 24-hour runoff) ir = ar x Tc-br aR =2.66 bR = 0.65 Tc = Time of concentration (6.3 minutes minimum) ir = (3.4) x 1/(6.4)^.65 = 1.01 I= Pr x ir I25 = 3.4 x 1.01 = 3.43 A = Area in Acres = 0.1 acres Rational Method Flows: Q = CIRA = (0.9)(3.43 )(0.15 acres) = 0.46cfs < 3.76 cfs O.k. to use 12” pipe SECTION 6 – SPECIAL REPORTS Technical Information Report 11 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington N/A SECTION 7 – OTHER PERMITS N/A SECTION 8 – CSWPP ANALYSIS AND DESIGN ESC Plan Analysis and Design (Part A) All erosion and sediment control measures shall be governed by the requirements of the City of Renton Surface Water Manual. An Erosion and Sedimentation Control plan has been prepared to assist the contractor in complying with these requirements and designed to prevent sediment-laden run-off from leaving the site during construction. The Erosion and Sedimentation Control Design meets the 13 minimum requirements: 1. Clearing Limits – Areas to remain undisturbed shall be delineated with a high visibility plastic fence prior to any site clearing or grading. 2. Cover Measures – Disturbed Site areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection – Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. Traffic Area Stabilization – A stabilized construction entrance will be located at the point of ingress/egress. 5. Sediment Retention – Due to the size of the project and the nature of the proposed improvements, no sedimentation retention facility is proposed. 6. Surface Water Control – If necessary, surface water control will be provided by interceptor swales. 7. Dewatering Control – Will be provided as needed. 8. Dust Control – Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. 9. Flow Control – Due to the size of the project, no flow control is proposed. 10. Control Pollutants – Demolition of existing structures and disposition of the demolished material and other waste will be in accordance to the 2016 KCSWDM Section D.2.2. 11. Protect Existing and Proposed Flow Control BMPs – N/A. No flow control is proposed for this project. 12. Maintain BMPs – BMP’s shall be maintained throughout the project. 13. Manage the Project – ESC Lead will manage site development activities relative to ESC concerns to assure the success of protective ESC and SWPPS design and implementation. CSWPP Plans Design (Part B) Project does not require a CSWPPP since it proposes to disturb less than 1 acre of land. SECTION 9 – BOND QUANTITIES, FACILITIES SUMMARIES, AND DECLARATION OF COVENANT STORMWATER FACILITY SUMMARY SHEET Will be provided by the owner as needed. DECLARATION OF COVENANT Will be provided by the owner as needed. BOND QUANTITY WORKSHEET Bond worksheets will be provided by the applicant. Technical Information Report 12 I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington SECTION 10 – OPERATIONS AND MAINTENANCE This project will install an on-site perforated pipe connection BMP, and a conveyance system with a connection to the Monroe Ave conveyance system. The catch basin within the properties is the responsibility of the applicant or property owner. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 12/12/2016 2017 City of Renton Surface Water Design Manual A-10 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Sediment accumulation Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and is structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate.No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sedimentaccumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-11 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place.Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. TOPOGRAPHIC & BOUNDARY SURVEY TOPOGRAPHIC & BOUNDARY SURVEYBASIS OF BEARINGSLEGAL DESCRIPTIONVERTICAL DATUMSURVEYOR'S NOTESLEGENDVICINITY MAPN.T.S.REFERENCESI-KUAN TAO FYCD CULTURAL & EDU. ASSO.N.T.S.CONTROL MAP Cobalt Geosciences, LLC P.O. Box 82243 Kenmore, Washington 98028 www.cobaltgeo.com (206) 331-1097 May 14, 2018 Ms. Julie Chen greenhousetex@comcast.net RE: Stormwater Feasibility Evaluation Proposed Development Expansion 711 Monroe Avenue NE Renton, Washington Dear Ms. Chen, In accordance with your authorization, Cobalt Geosciences, LLC has prepared this letter to discuss the results of our stormwater feasibility evaluation at the referenced site. The purpose of our evaluation was to evaluate the shallow subsurface soil conditions and provide options for stormwater management. Site and Project Description The site is located at 711 Monroe Avenue NE in Renton, Washington. The site consists of one rectangular shaped parcel with a total area of about 13.552 square feet. The western portion of the site is currently developed with a single-family residence used as a business. A driveway extends through the north portion of the property from the east and Monroe Avenue NE. The remainder of the property is vegetated with grasses, bushes, shrubs, and sparse deciduous and evergreen trees. The site slopes gently downward toward the southwest and west with topographic relief of less than 8 feet. There is a moderately steep slope extending downward to the west in the area just west of the property. This area is well vegetated with low- lying brush and variable diameter trees. The slope is up to 15 feet in height and has magnitudes of 30 percent. The property is bordered to the north and west by single-family residences, to the south by a commercial development, and to the east by Monroe Avenue NE. The project includes construction of a second story to the existing residence as well as expanded parking areas in the area between the building and Monroe Avenue NE. Stormwater management may include permeable pavements, infiltration systems, rain gardens, or other shallow best management practices (BMPs) from the King County Surface Water Design Manual. Area Geology The Geologic Map of King County indicates that the site is underlain by Vashon Glacial Till. Vashon Glacial Till is typically characterized by an unsorted, non-stratified mixture of clay, silt, sand, gravel, cobbles and boulders in variable quantities. These materials are typically dense and relatively impermeable. The poor sorting reflects the mixing of the materials as these sediments were overridden and incorporated by the glacial ice. May 14, 2018 Page 2 of 3 Stormwater Feasibility Evaluation www.cobaltgeo.com (206) 331-1097 Soil & Groundwater Conditions As part of our evaluation, we excavated two hand borings up to 6 feet below grade. Both hand borings encountered approximately 5 to 8 inches of topsoil and grass underlain by approximately 2 to 2.5 feet of loose to medium dense, silty-fine to fine grained sand with gravel (Weathered Glacial Till). This layer was underlain by medium dense to dense, silty-fine to medium grained sand with gravel (Glacial Till), which continued to the termination depths of the hand borings. Soil mottling was observed in both hand borings from about 2 to 5 feet below existing grades. Soil mottling (iron oxide staining) typically indicates the fluctuation level of seasonally perched groundwater. We also reviewed available exploration logs from nearby site locations, including across the street to the east. The soils described in these boring and test pit logs were consistent with those encountered in the hand borings. Stormwater Management Feasibility The site is underlain by glacial till which typically has a very low permeability. We conducted an EPA Falling Head infiltration test in HB-1 at a depth of 3 feet below grade. The factored infiltration rate was 0.28 inches/hour. The Washington State Department of Ecology (DOE) states that infiltration in soils with permeability of less than 0.3 inches/hour is not recommended and/or potentially infeasible. It is our opinion that infiltration of stormwater runoff is not feasible due to the underlying soil and groundwater conditions. The measured infiltration rates were less than 0.3 inches/hour in the upper 4 feet. Infiltration rates in underlying unweathered glacial till are typically less than 0.1 inches/hour. Groundwater and infiltrating surface waters are likely to migrate laterally to the southwest, potentially daylighting along the moderately steep slope west of the site. Depending on the volume of runoff from the new parking areas and roof area, the following stormwater management BMPs may be feasible: x Dispersion trenches with limited flowpaths (roof area) x Sheet flow (parking lots) x Rain gardens x Detention systems (R tanks or vaults) x Permeable pavements for flow control x Direct connection to City stormwater infrastructure We recommend that all systems be located east of the existing building to reduce the potential for impacts to the slope area west of the property. Based on our observations, a combination of permeable pavements, rain gardens, and detention with overflow to City infrastructure appear feasible. It may be necessary to utilize one or more of the above BMPs for stormwater management. Once the Civil designer has calculated volumes of runoff and has developed preliminary BMPs options, we can provide additional input. We should review the final plans as they become available. May 14, 2018 Page 3 of 3 Stormwater Feasibility Evaluation www.cobaltgeo.com (206) 331-1097 Erosion and Sediment Control Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to wetlands, streams, lakes, drainage systems, and adjacent properties. Erosion and sediment control measures should be implemented, and these measures should be in general accordance with local regulations. At a minimum, the following basic recommendations should be incorporated into the design of the erosion and sediment control features for the site: x Schedule the soil, foundation, utility, and other work requiring excavation or the disturbance of the site soils, to take place during the dry season (generally May through September). However, provided precautions are taken using Best Management Practices (BMP’s), grading activities can be completed during the wet season (generally October through April). x All site work should be completed and stabilized as quickly as possible. x Additional perimeter erosion and sediment control features may be required to reduce the possibility of sediment entering the surface water. This may include additional silt fences, silt fences with a higher Apparent Opening Size (AOS), construction of a berm, or other filtration systems. x Any runoff generated by dewatering discharge should be treated through construction of a sediment trap if there is sufficient space. If space is limited other filtration methods will need to be incorporated. Closure The information presented herein is based upon professional interpretation utilizing standard practices and a degree of conservatism deemed proper for this project. We emphasize that this report is valid for this project as outlined above and for the current site conditions, and should not be used for any other site Sincerely, Cobalt Geosciences, LLC Phil Haberman, PE, LG, LEG Principal PH/sc Proposed Parking Expansion 711 Monroe Avenue NE Renton, Washington SITE PLAN FIGURE 1 Cobalt Geosciences, LLCP.O. Box 82243Kenmore, WA 98028 (206) 331-1097 www.cobaltgeo.com cobaltgeo@gmail.com N HB-1 HB-1 HB-2 Log of Hand Boring HB-1 Date: May 2, 2018 Contractor: Method: Hand Auger Depth: 6’ Elevation: N/A Logged By: PH Checked By: SC Initial Groundwater: None Sample Type: Grab Final Groundwater: N/A Material Description SPT N-Value Moisture Content (%)PlasticLimit LiquidLimit 10 20 30 400 50 1 2 3 4 5 6 7 8 9 10 End of Hand Boring 6’ Vegetation/Topsoil Loose to medium dense, silty-fine to medium grained sandwith gravel and cobbles, dark yellowish brown to yellowish brown, moist. (Weathered Glacial Till) SM Medium dense to dense, silty-fine to medium grained sand, mottledyellowishbrowntograyishbrown,moist.(GlacialTill)SM Cobalt Geosciences, LLC P.O. Box 82243Kenmore, WA 98028(206) 331-1097www.cobaltgeo.com cobaltgeo@gmail.com Proposed Parking Expansion 711 Monroe Avenue NE Renton, Washington Hand Boring Log Log of Hand Boring HB-2 Date: May 2, 2018 Contractor: Method: Hand Auger Depth: 6’ Elevation: N/A Logged By: PH Checked By: SC Initial Groundwater: None Sample Type: Grab Final Groundwater: N/A Material Description SPT N-Value Moisture Content (%)PlasticLimit LiquidLimit 10 20 30 400 50 1 2 3 4 5 6 7 8 9 10 End of Hand Boring 6’ Vegetation/Topsoil Loose to medium dense, silty-fine to medium grained sandwith gravel and cobbles, dark yellowish brown to yellowish brown, moist. (Weathered Glacial Till) SM Medium dense to dense, silty-fine to medium grained sand,mottledyellowishbrowntograyishbrown,moist.(GlacialTill) SM Cobalt Geosciences, LLC P.O. Box 82243Kenmore, WA 98028(206) 331-1097www.cobaltgeo.com cobaltgeo@gmail.com Proposed Parking Expansion 711 Monroe Avenue NE Renton, Washington Hand Boring Log N.T.S. CONTROL MAP LANDSCAPING LANDSCAPING EXIST. CONC. PAVING TO BE REMAINED EXIST. CONC. PAVING TO BE REMAINED REGISTE R E D31169PROF E SSIONAL E N G INEERSTATE O F WASHIN GT ONALI A M I RZ E H NI LANDSCAPING LANDSCAPING EXIST. CONC. PAVING TO BE REMAINED EXIST. CONC. PAVING TO BE REMAINED REGISTE R E D31169PROF E SSIONAL E N G INEERSTAT E O F WASHIN GT ONALI A M I RZ E H NI REGISTE R E D31169PROF E SSIONAL E N G INEERSTATE O F WASHIN GT ONALI A M I RZ E H NI