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HomeMy WebLinkAboutRS_Drainage Report_Goldsmith_200131_V1 Mitchell Preliminary Short Plat Level 1 Downstream Analysis and Preliminary Drainage Control Plan January 2020 Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx i TABLE OF CONTENTS 1.0 Project Overview .................................................................................................................. 1 2.0 Offsite Analysis .................................................................................................................... 4 Task 1. Define and Map Study Area Task 2. Information Review Task 3. Field Inspection Task 4. Drainage System Description and Problem Description 3.0 Preliminary Drainage Control Plan ..................................................................................... ..7 4.0 Flow Control and Water Quality Facility Analysis ................................................................. 8 Part A. Existing Site Hydrology Part B. Developed Site Hydrology Part C. Performance Standards Part D. Flow Control System Part E. Water Quality System FIGURES Figure 1 Vicinity Map Figure 2 Existing Site Aerial Photo Figure 3 USGS Soils Map Figure 4 Existing Conditions Map Figure 5 Downstream Map Figure 6 Preliminary Drainage Plan Figure 7 Critical Areas Map APPENDIX A. City of Renton Drainage Complaints Map B. Geotechnical Report by Mud Bay Geotechnical Services, LLC., December 19, 2019 Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 1 1.0 Project Overview Introduction This report provides design data and analysis for the improvements proposed for the Mitchell Short Plat. The site is approximately 39,891 SF (0.91 acres) and is located west of Meadow Ave N in the City of Renton, Washington, also known as Tax Parcel No. 3342700480, situated in the southeast and northwest quarters of Section 32, Township 24 North, Range 5 East, W.M. As required by the 2017 City of Renton Surface Water Design Manual (COR SWDM), this report includes a summary of the existing on-site and downstream conditions; proposed developed site conditions; and the proposed stormwater control plan. This report also gives specific details on how the project meets the minimum requirements specified in Section 1.2 of the 2017 COR SWDM. Project Description This project will provide the necessary site improvements required to serve the two single family lots proposed with this short plat. The existing residence will remain, and a new single-family residence will be constructed to the east of the existing building. Proposed improvements will include utilities, driveway improvements, site grading for the new home, and on-site stormwater management BMP’s. Refer to Figure 6 for the plat design and lot layout. Summary of Proposal This is a request for Preliminary Subdivision approval for two single family residential lots, public roads, public utilities (water, sewer, stormwater), on the existing parcel. Stormwater control facilities will be designed per the 2017 City of Renton Surface Water Design Manual requirements as identified above. The total project site is approximately 0.91 acres. Currently located on the site is a single family residence and its associated site improvements. Access to the site is provided via the existing driveway off Meadow Ave N. The existing residence will remain and a new single family residence will be constructed to the east of the existing residence. Proposed improvements will include utilities; on and off-site driveway improvements, and on-site stormwater managements BMPs. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 2 CORE REQUIREMENTS The following is a preliminary description of how the Mitchell project will meet the Core Requirements of the 2017 COR SWDM. Core Requirement #1 – Discharge at the Natural Location The proposed conditions will not alter the general downstream path. The proposed drainage improvements will continue to treat runoff within the property to the maximum extend feasible before discharging to the existing closed system within Meadow Ave N. Refer to the Offsite Analysis section (section 2) of this report for a description of the existing discharge point. Core Requirement #2 – Offsite Analysis A downstream drainage analysis has been completed and is included in this report. Core Requirement #3 – Flow Control No public conveyance system is proposed with this project. The project is located in a site requiring Peak Rate Flow Control Standard; however, based on the scope of the site improvements the project is exempt from providing flow control facilities. The increase in the peak developed condition runoff rate relative to the existing site condition is less than 0.15 cfs (based on continuous modeling with a 15 minute time step); therefore, based on the evaluation provided in Section 4, the project is exempt from requiring flow control. MGS Flood modeling was used to confirm compliance with the 2017 COR SWDM requirements. (Section 4) Core Requirement #4 – Conveyance System The design and analysis of the stormwater conveyance system for this project will comply with the requirements of the 2017 COR SWDM. Detailed design and analysis of the conveyance system would be completed if needed in future engineering plan submittals. Core Requirement #5 – Construction Stormwater Pollution Prevention The design of the construction stormwater pollution prevention (CSPP) plans for the proposed improvements will be per the requirements of the 2017 COR SWDM and included with future engineering plan submittals. Core Requirement #6 – Maintenance and Operation Proposed stormwater facilities will be privately owned or dedicated to the City of Renton by owner. Core Requirement #7 – Financial Guarantees and Liability This project will comply with all financial guarantees required by the City of Renton. Core Requirement #8 – Water Quality Facilities The project site is located in an area requiring Basic Water Quality Treatment. The Project proposes to treat stormwater runoff from the proposed road and driveways on-site. As detailed in section 4 of this TIR. Core Requirement #9 – On-site BMP’s Design and analysis of Flow Control BMP’s will be per requirements of the 2017 COR SWDM. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 3 SPECIAL REQUIREMENTS Special Requirement #1 – Other Adopted Area-Specific Requirements The site does not fall under any other known adopted area specific requirements. Special Requirement #2 – Flood Hazard Area Delineation This project development is adjacent to a zone X flood hazard area per FEMA Flood Maps. Special Requirement #3 – Flood Protection Facilities This project does not rely on an existing flood protection facility for protection against hazards posed by erosion or inundation or propose to modify or construct a new flood protection facility; therefore, flood protection facilities are not required. Special Requirement #4 – Source Control The proposed development does not require a commercial building or commercial site development permit; Therefore, water quality source control is not required. Special Requirement #5 – Oil Control This project does not have high use site characteristics; therefore, oil control BMP’s are not required. Special Requirement #6 – Aquifer Protection Area This project does not have high use site characteristics; therefore, oil control BMP’s are not required. 2.0 Off-Site Analysis The following is a Level 1 downstream analysis, performed in accordance with the 2017 City of Renton SWDM. A site visit was conducted by Goldsmith Engineering on January 7, 2020 to investigate the onsite drainage systems, confirm downstream drainage paths, and evaluate upstream tributary areas to the project site. The weather during the site visit was cloudy and wet with a temperature of approximately 45 degrees Fahrenheit. Task 1 – Define and Map Study Area The topographical field survey was supplemented by City of Renton GIS drainage information, aerial mapping, and information obtained by field investigation to further define and map the study area in order to prepare the offsite analysis. Task 2 – Information Review As mentioned earlier, the City of Renton drainage maps show the project area within the May Creek Basin. Based on the City of Renton GIS mapping data, there are no critical areas located on or adjacent to the subject site. This on-site and adjacent evaluation includes streams, wetlands, floodplains, steep slopes, landslide hazard areas, and seismic hazard areas. Per the COR GIS data and the site visit, there are no drainage problems within the downstream system. According to the Washington State Department of Ecology Flood Hazard Maps, the project area is not located within a Floodway or 100-year Floodplain. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 4 Task 3 – Field Inspection The project area slopes northeast with slopes ranging from 5% to 15%. There is an existing single family home to remain and a new single-family residence is proposed east of the existing residence. The rest of the property is covered by grass, and scattered bushes and trees. Task 4 – Drainage System Description and Problem Descriptions The downstream drainage path was determined based on City of Renton GIS storm drainage maps, site survey, and information gathered during a site visit. Refer to Figure 5 – Downstream Drainage Map. As previously stated, runoff from the site flows northeast towards Meadow Ave N. The proposed drainage improvements will treat stormwater runoff on-site to the maximum extend feasible before discharging stormwater to the existing closed system within Meadow Ave N. 1. Runoff is discharged from the site. 2. Stormwater sheetflows north along Meadow Ave N. 3. Runoff is collected by the public stormwater system within Meadow Ave N and piped north via a 10-inch closed system. 4. Stormwater keeps traveling north via a 12-inch pipe. 5. Runoff discharges to an existing catch basin and travels north along Meadow Ave N. through an 18-inch pipe system. 6. Stormwater travels west along N 40th St via an 18-inch closed pipe system. 7. Stormwater travels northwest starting at the intersection of Lake Washington Blvd N and N 40th St. through a concrete culvert 8. Runoff continues flow southwest through a 30-inch pipe 9. Stormwater eventually out falls to Lake Washington. Task 5 – Mitigation of Existing or Potential Problems As indicated previously, there are no existing problems on-site or downstream of the site. The design of a stormwater control plan meeting the City of Renton requirements, including recommended BMPs will mitigate any potential problems related to the development of the subject site. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 5 OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE -1 Surface Water Design Manual, Core Requirement #2 Basin: Lake Washington Watershed Sub-basin Name: East Lake Washington Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope (estimated) Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident 1 Site Boundary Property line N/A 0 None None N/A 2 Sheet Flow Sheet Flow to Closed Storm System 0.5 to 12% 0 to 90 ft None None No signs of major sediment, ponding, or flooding 3 Conveyance System Existing 10-inch pipe 0.5 to 12% 90 to 125 ft None Under Capacity No capacity problems were observed during site visit 4 Conveyance System Existing 12-inch pipe 0.5 to 7% 125 to 265 ft None Under Capacity No capacity problems were observed during site visit 5 Conveyance System Existing 18-inch pipe 0.5 to 7% 265 to 1,000 ft None Under Capacity No capacity problems were observed during site visit 6 Conveyance System Existing 18-inch pipe 0.5 to 7% 1,000 to 2,100 ft None Under Capacity No capacity problems were observed during site visit 7 Conveyance System Existing concrete culvert 0.5 to 7% 2,100 to 2,200 ft None Under Capacity No capacity problems were observed during site visit 8 Conveyance System Existing 30-inch pipe 0.5 to 7% 2,200 to 2,440 ft None Under Capacity No capacity problems were observed during site visit 9 Lake Lake Washington N/A +/-2,440 ft None Sedimentation, flooding No signs of major sediment, ponding, or flooding Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 6 3.0 Preliminary Drainage Control Plan The stormwater control plan for the site encompasses all available information about the site and its downstream drainage system. This includes site topography, geology, detailed field investigations, and drainage complaints and observations. Flow control and water quality treatment BMPs have been evaluated. Preliminary evaluation of proposed flow control and water quality facilities is provided in Section 4.0. A preliminary drainage plan is shown on Figure 6. FLOW CONTROL STANDARD This section is prepared in conformance with the requirements of the 2017 City of Renton Surface Water Design Manual (COR SWDM) guidelines for drainage review and for downstream analysis of a preliminary subdivision. The following describes the preliminary storm drainage design approach of the stormwater control facilities for the project. The project has been evaluated for flow control requirements. The proposed project was evaluated using the latest COR Surface Water Design Manual and the approved continuous model (MGS Flood) to compare the developed peak rates to the existing ones. According to Section 1.2.3 of the COR manual, the project Peak Rate Flow Control Standard is waived due to the evaluation of increase in peak rate flows. See section 4.0 of this report and MGS Flood calculations for more information. WATER QUALITY STANDARD The Basic Water Quality treatment for the proposed development is to be provided through the proposed permeable pavement. The proposed permeable surface will include a treatment liner layer to treat for water quality and will be designed in accordance with recommendations from the geotechnical engineer and section 6.2.4 of the COR SWDM. 4.0 Flow Control and Water Quality Facility Analysis The following is the preliminary analysis and design of the proposed stormwater flow control and water quality facility for the Mitchell preliminary plat. These facilities have been designed to ensure that any adverse impacts from the proposed development on downstream systems are prevented. Part A. Existing Site Hydrology The parcel is currently developed and is vegetated with grasses, bushes, and scattered trees. The existing residence will remain and a new single-family residence will be constructed to the east of the existing residence. General site topography of the property generally slopes towards the northeast. The project site consists of moderate slopes ranging from 5 to 15 percent, eventually being collected by the closed piped system within Meadow Ave N. Greenes Creek flows to the north and is located west of the property. As mentioned, in task 4 of Section 2 of this report, stormwater runoff flows north through a series of existing pipes before discharging into Lake Washington. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 7 Image 1 – Existing property looking west from Meadow Ave N. Per the Flow Control Applications Map provided by the City of Renton, the project is located within a Peak Rate Flow Control Standard area. The 2017 COR SWDM requires projects located in this area to match the developed peak discharge rates to existing site conditions for the 2, 10, and 100- year return periods. These assumptions have been used for calculating allowable release rates and flow durations for the existing stormwater control facilities. Existing site hydrology has been modeled using the approved continuous model (MGS Flood). NCRS soils mapping indicates that the site is underlain by Indianola loamy sand (InD). SCS Group A outwash soils (See Figure 3). Per the Geotechnical Report, the soils observed in the test pits are considered suitable for foundation support and for infiltration of site stormwater. See Appendix B for more information. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 8 Part B. Developed Site Hydrology The stormwater design has been developed to mitigate changes in stormwater runoff from the proposed short plat. Per Section 1.2.3 of the 2017 COR SWDM. The project has been evaluated for flow control requirements. The projects is located in a peak rate flow control standard area. The project has been found to be exempt from requiring a flow control facility. Per Section 1.2.3.A, Peak Rate Flow Control Standard Areas: Exceptions 1, the stormwater control facility requirement is waived for any threshold discharge area in which the target surfaces subject to this requirement will generate no more than a 0.15-cfs increase (when modeled using 15 minute time steps) in the existing site conditions 100-year peak flow (modeled using same time step unit used to calculate the developed flow). Runoff modeling for this project has been completed using the hydrologic modeling software MGS Flood as required by the 2017 COR SWDM. As specified by the design manual, changes in the runoff rates are required to be evaluated against the existing site conditions. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 9 Part C. Performance Standards Flow Control BMPs The project has implemented on-site flow control BMPs to the largest extend feasible for the project target surfaces using the list approach per the 2017 COR SWDM. The project site was evaluated per current code requirements using an approved continuous model. Water Quality Standard Proposed water quality facilities were designed to mitigate for future development of this site. The basic water quality facilities were examined using the current City of Renton Surface Water Design Manual to meet basic water quality treatment. Part D. Flow Control System As previously stated, this project is exempt from flow control because the difference between the 100-yr developed peak rates and the existing 100-yr peak rates are below the 0.15 cfs threshold as indicated in section 1.2.3 of the City of Renton Surface Water Design Manual. The developed 100- yr peak rate calculated is 0.246 cfs and the existing 100-yr peak rate flow is 0.231 cfs (using 15 min time steps). The difference in rates is equal to 0.015 cfs, proving to be less than the 0.15 cfs threshold; therefore, flow control requirements are waived. See MGs Flood calculations at the end of this report for more information. Part E. Water Quality System As noted above, basic water quality treatment for the site is provided by the proposed permeable pavement. The driveway surface area is the only area that requires water quality treatment for the project and will be treated on-site via a treatment liner, designed by Section 6.2.4 of the COR SWDM. Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 10 ————————————————————————————————— MGS FLOOD FLOW CONTROL PROJECT REPORT Program Version: MGSFlood 4.50 Program License Number: 201810008 Project Simulation Performed on: 01/31/2020 2:33 PM Report Generation Date: 01/31/2020 2:34 PM ————————————————————————————————— Input File Name: Flow Control & WQ.fld Project Name: Mitchell Short Plat Analysis Title: Flow Control & WQ Comments: Total Site = 39,891 SF (0.916 ac) ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 15 Full Period of Record Available used for Routing Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.921 0.922 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.921 0.922 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 ---------- Subbasin : Existing Lot ---------- -------Area (Acres) -------- Outwash Grass 0.741 Impervious 0.175 ---------------------------------------------- Subbasin Total 0.916 Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 11 ---------- Subbasin : ROW ---------- -------Area (Acres) -------- Impervious 0.005 ---------------------------------------------- Subbasin Total 0.005 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 ---------- Subbasin : Lot 1 ---------- -------Area (Acres) -------- Outwash Grass 0.346 Impervious 0.084 ---------------------------------------------- Subbasin Total 0.430 ---------- Subbasin : Lot 2 ---------- -------Area (Acres) -------- Outwash Grass 0.233 Impervious 0.092 ---------------------------------------------- Subbasin Total 0.325 ---------- Subbasin : ROW ---------- -------Area (Acres) -------- Outwash Grass 0.019 Impervious 0.005 ---------------------------------------------- Subbasin Total 0.023 ---------- Subbasin : Access Tract ---------- -------Area (Acres) -------- Outwash Grass 0.101 Impervious 0.043 ---------------------------------------------- Subbasin Total 0.144 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 12 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 2 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 4 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Existing Lot 245.975 Subbasin: ROW 0.000 Link: New Copy Lnk1 0.000 _____________________________________ Total: 245.975 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Lot 1 114.855 Subbasin: Lot 2 77.344 Subbasin: ROW 6.141 Subbasin: Access Tract 33.527 Link: New Copy Lnk2 0.000 _____________________________________ Total: 231.867 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 1.557 ac-ft/year, Post Developed: 1.468 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 Mitchell Preliminary Short Plat January 2020 Level 1 Downstream Analysis and Preliminary Drainage Control Plan r19133 Mitchell Technical Information Report 2020-01.docx 13 ********** Link: New Copy Lnk1 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 81.26 Inflow Volume Including PPT-Evap (ac-ft): 81.26 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 81.26 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk2 ********** Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 100.65 Inflow Volume Including PPT-Evap (ac-ft): 100.65 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 100.65 Secondary Outflow To Downstream System (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Copy Lnk1 Scenario Postdeveloped Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 6.947E-02 2-Year 8.582E-02 5-Year 9.141E-02 5-Year 0.110 10-Year 0.118 10-Year 0.144 25-Year 0.155 25-Year 0.181 50-Year 0.186 50-Year 0.231 100-Year 0.231 100-Year 0.246 200-Year 0.257 200-Year 0.275 500-Year 0.290 500-Year 0.313 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals 0.231 – 0.246 = 0.015 CFS Figures Vicinity Map 3625 Meadow Ave N, City of Renton, WA 98056 Tax Parcel 3342700480 FIGURE 1 North Not to Scale Site Pictom etr y, King C ou n ty, Ki ng Cou nty FIGUR E 2 - SITE AERIAL Date: 10/14/2019 Notes:±The i nfor ma tion inclu ded on thi s map has been c om pil ed by King Cou nty s taff from a vari ety of so urc es a n d is subject to c ha n ge w ith out n otice. King C ountymakes n o r epr e sentations o r w ar ra ntie s, express o r i mp li ed , as to acc ur a cy, co m pl ete ness, tim e line ss, or ri g hts to the use of s uc h i nform a tion . T hi s doc um e n t i snot intended for us e as a su rvey pr odu ct. King C ounty shall not be l iabl e for an y gene r al , spec ia l, in dire ct, inci de n ta l, or conse que ntia l dam a ges i nclu d in g,but n ot li mi ted to, lost reve n ues o r l os t p r ofi ts resulting fro m the use or mi suse of the i nfor ma tion contained on this m ap. An y s al e of this m ap or in form atio n onthis map is prohibited ex cept by wr itten pe r mis sion of King Cou n ty. United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for King County Area, Washington Mitchell Property Natural Resources Conservation Service October 14, 2019 9 Custom Soil Resource Report Soil Map 52637305263740526375052637605263770526378052637905263800526381052638205263730526374052637505263760526377052637805263790526380052638105263820560170 560180 560190 560200 560210 560220 560230 560240 560250 560260 560270 560280 560290 560300 560310 560170 560180 560190 560200 560210 560220 560230 560240 560250 560260 560270 560280 560290 560300 560310 47° 31' 30'' N 122° 12' 2'' W47° 31' 30'' N122° 11' 55'' W47° 31' 26'' N 122° 12' 2'' W47° 31' 26'' N 122° 11' 55'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 30 60 120 180 Feet 0 10 20 40 60 Meters Map Scale: 1:690 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: King County Area, Washington Survey Area Data: Version 15, Sep 16, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 1, 2019—Jul 25, 2019 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report 10 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI InC Indianola loamy sand, 5 to 15 percent slopes 1.2 100.0% Totals for Area of Interest 1.2 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. Custom Soil Resource Report 11 N88°40'46"W370.80N1°40'34"E 107.645018450185501865018750188 501895019050228503615036250363503645042450425504265042750429504305043150432N1°53'21"E107.65TAX PARCEL #33427004803625 MEADOW AVENUE NRENTON, WA 98056OWNER: TERESA K. MITCHELLTAX PARCEL #33427004843701 MEADOW AVENUE NRENTON, WA 98056OWNER: DONALD R. & DENICE DUNDASTAX PARCEL #33427004861409 N 37TH STREETRENTON, WA 98056OWNER: THEO A. & KIMBERLY A. BROWNETAX PARCEL #33427004821403 N 37TH STREETRENTON, WA 98056OWNER: ERIKA D. & MATTHEW E. JONESTAX PARCEL #3342700468(NO SITE ADDRESS)OWNER: RHONDA S. &WILLIAM J. COOKETAX PARCEL #33427004853714 PARK AVENUE NRENTON, WA 98056OWNER: RHONDA S. & WILLIAM J. COOKETAX PARCEL #33427004783708 PARK AVENUE NRENTON, WA 98056OWNER: ROY T. & SIRI M. DALYTAX PARCEL #33427004793702 PARK AVENUE NRENTON, WA 98056OWNER: LAURA L. &PAUL O. CLARKTAX PARCEL #33427004753603 MEADOW AVENUE NRENTON, WA 98056OWNER: KENNETH JOHNSTONN88°40'44"W 370.40TAX PARCEL #33427004733605 MEADOW AVE NRENTON, WA 98056OWNER: SEAMLENG TAINGTAX PARCEL #33427004723609 MEADOW AVE NRENTON, WA 98056OWNER: SYLVIA B. MATTHEWSTAX PARCEL #33427004813615 MEADOW AVE NRENTON, WA 98056OWNER: ANN PATRICIA KILLIANTAX PARCEL #33427004763619 MEADOW AVE NRENTON, WA 98056OWNER: MEGAN KUSSKEXSOHUOHUOHUOHUOHUOHUOHUOHUOHUOHUOHUOHUXXXXXXXXXXXXXX X X X X X X OHUOHUOHUOHUOHUOHUOHU OHU OHU OHU OHU OHU OHU OHU OHU SS SS SS SS SS SS SS SS SS SSXXXXXXXXXXGGGGGWWWWWWWWWWWWW G G G G G G G G G W W W W W W W W W W SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS S S S S S SSEEVERTICAL DATUM: NAVD 1988 PER CITY OF RENTON SURVEY CONTROL.MASTER BENCHMARK: CITY OF RENTON CONTROL POINT NUMBER 1836: FOUND 5 INCH DIAMETER CONCRETEMONUMENT WITH 1/8 INCH BRASS PLUG, DOWN 0.5 FEET IN A CASE AT THE INTERSECTION OF BURNETTEAVENUE NORTH AND NORTH 30TH STREET. ELEVATION WAS VERIFIED BY CHECKS TO THE ABOVE NOTEDCITY OF RENTON CONTROL POINT NUMBER 1886 AND OBSERVATIONS USING THE WASHINGTON STATEREFERENCE NETWORK. ORTHOMETRIC ELEVATION = 120.03 FEET, NAVD 1988, PER CITY OF RENTON.SITE BM#1: GOLDSMITH CONTROL POINT TMS-1, SET REBAR AND CAP ON SOUTH EDGE OF GRAVEL DRIVEWAYTO HOUSE #3625, 1.4 FEET WESTERLY OF THE WEST EDGE OF PAVEMENT OF MEADOW AVENUE NORTH.ELEVATION = 161.65 FEET (NAVD 1988).SITE BM#2: GOLDSMITH CONTROL POINT TMS-2, SET MAG NAIL 0.2 FEET EASTERLY OF THE WESTERLY EDGEOF PAVEMENT ON THE WEST SIDE OF MEADOW AVENUE NORTH AND 12 FEET NORTHERLY OF THESOUTHEAST CORNER OF THE PROPERTY CORNER FOR THIS SURVEY. ELEVATION = 165.92 FEET (NAVD 1988).SITE BM#3: GOLDSMITH CONTROL POINT TMS-3, SET REBAR AND CAP IN FRONT YARD, 5.1 FEET NORTHERLYOF THE 3 BLOCK HIGH CONCRETE WALL, AND 50 FEET EASTERLY OF THE WEST END OF SAID WALL.ELEVATION = 180.79 FEET (NAVD 1988).TREES TABLES0SCALE:4010201" = 20'60SMEADOW AVENUE N. (106TH AVENUE SE)LEGENDARBARBORAWNAWNINGBGBUILDINGBMBENCHMARKCONCCONCRETECORCORNERDIDUCTILE IRONELEVELEVATIONEMELECTRIC METERFNCFENCEINTINTERSECTIONIPIRON PIPEIPFIRON PIPE FOUNDMBMAILBOXMPMETAL POLEPEPOLYETHYLENEPVRPAVERSRBFREBAR FOUND (NO CAP) RCFREBAR & CAP FOUNDRETRETAINING WALLRPEROOF PEAK ELEVATIONSMHSANITARY SEWER MANHOLETMS-GOLDSMITH SURVEY CONTROLTSFTRANSFORMERUGUNDERGROUNDUPUTILITY POLEVERTVERTICALWMWATER METERFENCE LINEOVERHEAD UTILITIES LINEGAS LINESANITARY SEWER LINEWATER LINEXXOHUGSSSWDRAWN:APPROVED:PLOTTED:DESIGNED:L:\2019\19133\3 DEVELOPMENT\CAD\HOST DRAWINGS\PRELIMINARY SHORT PLAT\19133X02.DWG2020/01/17 08:47ClatorreSHEETSE 1/4, NW 1/4 SECTION 32, TOWNSHIP 24 N, RANGE 5 E, W.M.CITY OF RENTON, KING COUNTY, WASHINGTONTERRY MITCHELLJOB NO. 191333625 MEADOW AVE. N., CITY OF RENTON KING COUNTY, WASHINGTONHGGEXH5H.dwt BGOLDS 10/21/14 08:42S:\DWTs\Shared Printers\TitleBlocks\HGG Standard\HGGEXH5H.dwt FORMITCHELL PRELIMINARY SHORT PLATERMLDNKnow what'sbelow.before you dig.CallREXISTING CONDITIONS19133X02.dwg clator 01/17/20 08:46L:\2019\19133\3 DEVELOPMENT\CAD\HOST DRAWINGS\Preliminary Short Plat\19133X02.dwg 4,514752 City of Renton Downstream Map 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 01/02/2020 Legend 512 0 256 512 Feet Information Technology - GIS RentonMapSupport@Rentonwa.gov Network Structures Access Riser Inlet Manhole Utility Vault Clean Out Unknown Control Structures Pump Stations Discharge Points Water Quality Detention Facilities Pond Tank Vault Bioswale Wetland Other Stormwater Mains Culverts Open Drains Facility Outlines Private Network Structures Access Riser Inlet Manhole Clean Out Utility Vault Unknown Private Control Structures Private Pump Stations Private Discharge Points Private Water Quality Private Detention Facilities Tank, No Stormwater Wetland, No; Natural Wetland, No Filter Strip, No Infiltration Trench, No Vault, No Pond, No; Pond, Unknown Bioswale, No Stormtech Chamber, No Other, No Private Pipes Private Culverts Private Open Drains Private Facility Outlines Drainage Complaints Known Drainage Issues Renton King County Streets Points of Interest Parks Waterbodies Extent2010 50190502285042450425504265042750429504305043150432SLOT 2LOT 114,163 SF18,740 SF6,288 SFTRACT A(ACCESS & UTILITY)MEADOW AVENUE NDRAWN:APPROVED:PLOTTED:DESIGNED:L:\2019\19133\3 DEVELOPMENT\CAD\HOST DRAWINGS\PRELIMINARY SHORT PLAT\19133P01.DWG2020/01/31 14:42ClatorreSHEETSE 1/4, NW 1/4 SECTION 32, TOWNSHIP 24 N, RANGE 5 E, W.M.CITY OF RENTON, KING COUNTY, WASHINGTONCLTCLTKJGTERRY MITCHELLJOB NO. 191333625 MEADOW AVE. N., CITY OF RENTON KING COUNTY, WASHINGTONHGGEXH5H.dwt BGOLDS 10/21/14 08:42S:\DWTs\Shared Printers\TitleBlocks\HGG Standard\HGGEXH5H.dwt FORMITCHELL PRELIMINARY SHORT PLATKnow what'sbelow.before you dig.CallRPRELIMINARY GRADING, DRAINAGE AND UTILITY PLAN6.5' ROW DEDICATION700 SFEXISTING HOME TOREMAINPROPOSED 6" SANITARYSEWER SERVICEEXISTING UTILITY POLETO BE RELOCATED25'20'A A WATER METER, TYP.BSBLR25.0'PROPOSED MAJOR 10' CONTOUR430PROPOSED SANITARY SEWER PIPELEGENDSDPROPOSED SIDEWALKPROPOSED PERMEABLE PAVERDRIVEWAYPROPOSED CB TYPE IIPROPOSED SANITARY SEWER MHPROPOSED CB TYPE IPROPOSED STORM PIPEPROPOSED MINOR 2' CONTOUR428PROPOSED BSBL060401020SCALE: 1" = 20'CONNECT TO EX.SANITARY SEWERRELOCATE EX.WATER METER28' ACCESS TRACTSECTION A-AROAD A ACCESS DRIVEWAYN.T.S.10'DRIVINGLANE10'DRIVINGLANE±2%8'PLANTERSTRIP±2%N88°40'44"W 174.3N88°40'46"W 174.30N1°53'21"E 107.65 N1°40'34"E 79.6 N1°40'34"E 107.6 N88°40'44"W 190.020' 4,514752 Figure 7 - Critical Areas Map 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 10/14/2019 Legend 512 0 256 512 Feet Information Technology - GIS RentonMapSupport@Rentonwa.gov 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 Streets Points of Interest Parks Waterbodies Extent2010 4,514752 City of Renton Drainage Complaints 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 01/02/2020 Legend 512 0 256 512 Feet Information Technology - GIS RentonMapSupport@Rentonwa.gov Network Structures Access Riser Inlet Manhole Utility Vault Clean Out Unknown Control Structures Pump Stations Discharge Points Water Quality Detention Facilities Pond Tank Vault Bioswale Wetland Other Stormwater Mains Culverts Open Drains Facility Outlines Drainage Complaints Known Drainage Issues Renton King County Streets Points of Interest Parks Waterbodies Extent2010 Appendix B Geotechnical Report by Mud Bay Geotechnical Services, LLC. December 19, 2019 Mud Bay Geotechnical Services, LLC• 2724 Langridge Loop NW • Olympia, WA 98502 360-481-9784 • cheathman@mudbaygeotech.com December 29, 2019 Job:1172-KIN Page 1 Terry Mitchell 3625 Meadow Ave N, Renton WA 98056 Renton, WA 98056 Subject: 3625 Meadow Ave N Renton, WA 98056 Site Development Geotechnical Recommendations Dear Ms. Mitchell, This report presents the results of our geotechnical investigation and contains geotechnical recommendations for the project taking place at 3625 Meadow Ave N, Renton WA. The analyses, conclusions, and recommendations in this report are based on three boring (designated as BH-1-19, BH-2-19, and BH-3-19) completed specifically for this project, published geologic information for the site and vicinity, USDA textural analysis of retained samples, and our experience with similar geologic materials. The conditions observed in the bore holes are assumed to be representative of the subsurface conditions throughout the project area. If during construction, subsurface conditions differ from those described in the explorations, we should be advised immediately so we may reevaluate the recommendations. Location and Description The parcel number 3342700480 is located at 3526 Meadow Ave N in Renton, WA. The site location and vicinity for the property are presented in Figure 1. The scope of the project, as we understand it, is to develop the site with a new access road covering 0.097 acres of the 0.91-acre parcel, in addition to construction a shop on the southern boundary of the parcel. Proposed development can be viewed on the provided Site Plan, attached to this report as Figure 2. It is anticipated the structure will be supported on shallow strip footing foundations and shallow pier foundations. Mud Bay Geotechnical Services, LLC• 2724 Langridge Loop NW • Olympia, WA 98502 360-481-9784 • cheathman@mudbaygeotech.com The site currently accommodates one single-family residence, a detached 2-car garage, a small section of asphalt drive, and a gravel access road. Surface conditions on the parcel consists of manicured and landscaped lawn, with the entirety of the site having a gentle grade projecting down-slope to the west and north west. Discussions with the client suggest the site is well draining, with little to no standing water being present following rain events. Several fruit and small native trees exist in the current front-yard. A retaining wall ranging in height from 2 to 4 feet spans the southern boundary of the neighboring parcel and appears to be in good condition. Site Soils and Geology As part of this project, we reviewed geologic data from the Washington State Department of Natural Resources available at the 1:100,000 scale and prepared a site-specific geology map, attached as Figure 3 to this report. The project vicinity geologic map indicates the project site is directly underlain by Pleistocene continental glacial drift, and the site vicinity consists generally of Pleistocene continental glacial till and Quaternary alluvium. Conditions observed at the site are generally consistent with the mapped geology. Along with the site geology, soil data was also reviewed and is represented in attached Figure 4, USDA Soil Map. The soil in this area was mapped by the United States Department of Agriculture, USDA, as Indianola loamy sand, 5 to 15 percent slopes. The USDA describes Indianola loamy sand as being "somewhat excessively drained" and forming often in sandy glacial drift deposits. Consistency across field classification, mapped soils, and soil descriptions all indicate the soil conditions at the site are consistent with the USDA mapping. See the Subsurface Exploration section below for a detailed soil characterization. It should be noted the percent slopes associated with these soils is an approximation and does not necessarily reflect the true surface topography. Subsurface Exploration As part of the geotechnical investigation, three shallow hand augured borings were completed. The borings were completed using a Humboldt Manufacturing model H-4414QC hand auger with a 4-inch diameter bucket tube sampler. In situ testing was performed at selected depths using a Humboldt Manufacturing model H-4202A dynamic cone penetrometer to estimate the density of the soil. The dynamic cone penetrometer uses a 15-lb steel mass falling a height of 20-inches onto an anvil to penetrate a 1.5-inch diameter 45-degree cone tip seated into the bottom of the hole. The number of blows is recorded to achieve at total of ¾ inches of penetration into the soil. This recorded blow count is correlated to the Standard Penetration Test (SPT) field N-value blow count determined in accordance with ASTM D1586, which is the standard in situ test method for determining relative density of cohesionless soils and the consistency of cohesive soils. Hand auger samples were removed from the bottom of the hole after the dynamic cone penetration testing was performed in order to observe the soil material at the approximate depth the test was performed. The soil samples were classified visually in the field in general accordance with ASTM D2488, the Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). Once transported back to the office, the samples were re-examined, and the field classifications were modified accordingly. We then selected representative samples for a suite of laboratory tests. The overall soil-testing program included moisture content analyses, Atterberg limits, and Mud Bay Geotechnical Services, LLC• 2724 Langridge Loop NW • Olympia, WA 98502 360-481-9784 • cheathman@mudbaygeotech.com particle-size analyses. The results of the laboratory tests are presented in Appendix B. Summary logs of the borings are included in Appendix A. Note the soil descriptions and interfaces shown on the log are interpretive, and actual changes may be gradual. Upon completion, the holes were backfilled to the original ground surface using excavated material from the spoil piles. Soil and Groundwater Conditions Three hand augured borings (designated BH-1-19, BH-2-19, and BH-3-19), were performed to a depth of 72 inches, 84 inches, and 72 inches, respectively, below the current ground surface in order to explore the subsurface conditions at the site location. The approximate locations of the borings have been included as Figure 5 attached to this report, Site Exploration Map. The subsurface conditions observed in all three of the borings consisted of very loose to loose, moist, brown, silty sand (SM) to a depth of 72 to 84 inches. It was noted that groundwater, likely a result of localized seepage, was present in boring BH-2-19. Boring BH-1-19 and BH-3-19 had moist soils throughout the entire depth. Shallow Foundation Support Shallow strip footings will be used to support the new addition and above ground structure loads. Based on the conditions observed in the boring, we recommend locating the bottom of the new footings on the native soil deposits at a minimum depth of approximately 1.5 feet below the existing ground surface. If the footings are placed on the native material at or below a depth of 1.5 feet, then the subgrade at that elevation should be cleared and grubbed and the exposed native subgrade soils should be compacted in place. The subgrade should be inspected for any pockets of loose material. Loose material should be removed and replaced with a minimum of 6-inches of crushed surfacing base coarse (CSBC). The CSBC should be placed in layers no greater than 6-inches and compacted to at least 95 percent of the maximum dry density. Prior to placement of the CSBC, we recommend placing a construction geosynthetic directly on the native subgrade within the footprint of all strip footings, piers, and slabs-on-grade. The geosynthetic used should meet the requirements of a construction geotextile for soil separation in accordance with Section 9-33.1 of the WSDOT Standard Specifications. Footings bearing on a subgrade prepared as described above can be designed using a maximum allowable bearing pressure of 1,200 psf. We recommend a minimum footing width of 18 inches be used in the design. The maximum allowable bearing pressure may be increased by up to one-third for short-term transient loading conditions such as wind and seismic loading. We anticipate that total settlement will not exceed one inch, and differential settlement along an equivalent 50-foot length of footing will not exceed half of the total settlement. The settlement is expected to be elastic and will occur as the footings are loaded. We recommend footing subgrade preparation be evaluated by Mud Bay Geotechnical Services, LLC prior to placement of concrete. Foundation subgrade preparation should not be performed during periods of wet weather. We recommend staging the foundation subgrade ex cavation, compaction of native subgrade soils, and placement of CSBC to limit the time the foundation subgrade is exposed to weather. Mud Bay Geotechnical Services, LLC• 2724 Langridge Loop NW • Olympia, WA 98502 360-481-9784 • cheathman@mudbaygeotech.com Lateral Earth Pressures The portion of the new footings and stem walls below final grade should be designed to resist lateral earth pressures of the backfill placed behind the walls. For lateral load analysis, we recommend the geotechnical parameters in Table 1 be used for lateral design and analysis. Table 1 : Lateral Earth Pressure Parameters Parameter Design Value Backfill Unit Weight (γ) 135 pcf Wall Backfill Soil Friction Angle (φf) 37° Coefficient of Sliding (tan φf) 0.55 Active Earth Pressure (Ka) 0.23 (EFP 31.1 psf) At Rest Earth Pressure (K0) 0.40 (EFP 54.0 psf) Passive Earth Pressure (Kp) 4.02 (EFP 542.7 psf) The passive earth pressure coefficient and coefficient of sliding presented in Table 1 are ultimate values and should be reduced by a factor of safety equal to 1.5 for final design. The lateral earth pressure coefficients provided in Table 1 are based on the use of Gravel Backfill for Walls. Active earth pressures can be assumed for design, provided that the walls can yield laterally at least 0.001H (where H is the exposed wall height in feet). If the wall is not capable of yielding that amount, then at-rest earth pressures should be used. Seismic loading represented as a rectangular shaped dynamic uniform lateral surcharge equal to 8H psf should be applied, with the resultant acting at a height of 0.5H, where H is the height of the wall. This value, which was calculated using the Mononobe-Okabe method, is appropriate for yielding walls designed in accordance with the 2015 IBC. Drainage Considerations We recommend including a perimeter footing drain system, consisting of a 4 -inch diameter, perforated or slotted, rigid plastic pipe placed at the base of the wall footings. The drain should be embedded in a clean, free-draining sand and gravel meeting the requirements of Section 9- 03.12(4) of the WSDOT Standard Specifications for Gravel Backfill for Drains. The drains should be sloped slightly to drain to an appropriate discharge area. Appropriate water and weather proofing measures should be used in order to reduce the potential for leaks through the stem walls. Utilities Utilities may need to be temporarily or permanently relocated as part of the project. The utility subgrade (base of trench excavation) should be relatively firm prior to placing bedding materials. Subgrade that is observed to be soft, pumping, or containing abundant organics or refuse should be sub-excavated to firm subgrade soil or a maximum depth of 2 feet. Sub- excavated areas should be backfilled with structural fill. Mud Bay Geotechnical Services, LLC• 2724 Langridge Loop NW • Olympia, WA 98502 360-481-9784 • cheathman@mudbaygeotech.com Material placed directly below, around, and above utility pipes should consist of Gravel Backfill for Pipe Zone Bedding as described in Section 9-03.12(3) of the WSDOT Standard Specifications. The pipe bedding materials should be placed and compacted to a relatively firm condition in accordance with the manufacturer’s specifications. Bedding and cover should be a minimum of 6-inches thick. Earthwork Considerations Soils placed as fill beyond the limits of foundation subgrade, wall backfill, and pipe zone areas described previously should be considered structural fill. Structural fill should consist of material meeting the requirements of Common Borrow as described in Section 9 -03.14(3) of the WSDOT Standard Specifications. Based on the conditions observed in the boring, the onsite material that will be removed for construction meets the requirements for Common Borrow, provided that it can be moisture conditioned to achieve proper compaction. The onsite material contains a fines content great enough that it is considered to be moisture sensitive. This material may be difficult to compact if exposed to wet weather. Drying excessively wet soil will be easier during the drier time of the year. Structural fill should be placed and compacted in lifts no greater than 8 inches when using relatively large compaction equipment, such as a vibrating compaction equipment attached to an excavator or a drum roller. If small, hand-operated compaction equipment is used to compact the structural fill, fill lifts should not exceed 6 inches. Based on the small size of the project and difficult access, most likely small hand-operated equipment will be used. Structural fill should be placed and compacted to between 92 and 95 percent of the maximum dry density. All other fill material should be placed and compacted as described previously. Fill placed in softscape, landscape, or common areas that can accommodate some settlement should be compacted to a relatively firm and unyielding condition. Stormwater infiltration Design On site stormwater facilities will be used for stormwater treatment and flow control. The soils in the upper 4 to 6 feet were classified for USDA soil texture in order to estimate the long-term infiltration rate. Based on the conditions observed in the bor ings and laboratory testing for soil gradation, the soils at the site are classified as a sandy loam to loam soil. We recommend assuming a long-term infiltration rate of 1.0 inches per hour. Erosion Control Erosion control should be implanted during construction with the use of silt fences and construction fencing around the perimeter of the work area. Jute, coir, or turf reinforcement mat should be placed on the surface of all exposed ground surfaces with slopes greater than 15 percent, pinned a minimum of 30 inches below the surface. The erosion condition of slopes should be monitored periodically during construction for any signs of surface erosion or degradation. If significant erosion is observed, then it should be mitigated as soon as possible. To redu ce the potential for long term erosion from occurring, it is recommended the surface all bare ground are vegetated following construction with a combination of native plants and hydroseeding. Mud Bay Geotechnical Services, LLC• 2724 Langridge Loop NW • Olympia, WA 98502 360-481-9784 • cheathman@mudbaygeotech.com Recommended Additional Services Before construction begins, we recommend a copy of the draft plans and specifications prepared for the project be made available for review so that we can ensure that the geotechnical recommendations in this report are included in the Contract. Mud Bay Geotechnical Services, LLC is also available to provide geotechnical engineering and construction monitoring services throughout the remainder of the design and construction of the project. The integrity of the geotechnical elements of a project depend on proper site preparation and construction procedures. In addition, engineering decisions may need to be made in the field if conditions are encountered that differ from those described in this report. During the construction phase of the project, we recommend that Mud Bay Geotechnical Services, LLC be retained to review construction submittals, observe and evaluate subgrade for footings, structural fill placement and compaction, and provide recommendations for any other geotechnical considerations that may arise during construction. Intended Use and Limitations This report has been prepared to assist the client and their consultants in the engineering design and construction of the subject project. It should not be used, in part or in whole for other purposes without contacting Mud Bay Geotechnical Services, LLC for a review of the applicability of such reuse. This report should be made available to prospective contractors for their information only and not as a warranty of ground conditions. The conclusions and recommendations contained in this report are based on Mud Bay Geotechnical Services, LLC understanding of the project at the time that the report was written and on-site conditions that existed at time of the field exploration. If significant changes to the nature, configuration, or scope of the project occur during the design process, we should be consulted to determine the impact of such changes on the recommendations and conclusions presented in this report. Site exploration and testing describes subsurface conditions only at the sites of subsurface exploration and at the intervals where samples are collected. These data are interpreted by Mud Bay Geotechnical Services, LLC rendering an opinion regarding the general subsurface conditions. Actual subsurface conditions can be discovered only during earthwork and construction operations. The distribution, continuity, thickness, and characteristics of identified (and unidentified) subsurface materials may vary considerably from that indicated by the subsurface data. While nothing can be done to prevent such variability, Mud Bay Geotechnical Services, LLC is prepared to work with the project team to reduce the impacts of variability on project design, construction, and performance. We appreciate the opportunity to serve your geotechnical needs on this project and look forward to working with you in the future. Please contact us at your earliest convenience if you have any questions or would like to discuss any of the contents of this report. Mud Bay Geotechnical Services, LLC• 2724 Langridge Loop NW • Olympia, WA 98502 360-481-9784 • cheathman@mudbaygeotech.com Sincerely, Chris Heathman, P.E. Mud Bay Geotechnical Services, LLC Figure 1: Site Map 3625 Meadow Ave N, Renton WA, 98056 Site Development Geotechnical Report JOB #:1172-KIN Date: Nov., 2019 Site Location Figure 2: Site Plan 3625 Meadow Ave N, Renton WA, 98056 Site Development Geotechnical Report JOB #:1172-KIN Date: Nov., 2019 LEGEND Figure 3: WA DNR Geologic Map 3625 Meadow Ave N, Renton WA, 98056 Site Development Geotechnical Report JOB #: 1172-KIN Date: Nov., 2019 Site Location 200 ft 100 m LEGEND Site Location Figure 4: USDA Soils Map 3625 Meadow Ave N, Renton WA, 98056 Site Development Geotechnical Report JOB #: 1172-KIN Date: Nov., 2019 BH-1-19 BH-2-19 Site Location Figure 5: Site Exploration Map 3625 Meadow Ave N, Renton WA, 98056 Site Development Geotechnical Report JOB #:1172-KIN Date: Nov., 2019 Sample Location BH-3-19 APPENDIX A – FINAL BORING LOGS Completed: Hammer Type: Backfilled: Hammer Weight: Hammer Drop: Groundwater Depth: Total Depth of Boring: Lithology Very loose, moist, brown, silty sand (SM) Very loose, moist, brown, silty sand (SM) Loose, moist, brown, silty sand (SM) Loose, moist, brown, silty sand (SM) Standard Penetration Slit Spoon Sampler (SPT) Blows/3/4"Density 0-4 Very Loose 5-10 Loose 11-24 Medium Dense 25-50 Dense >50 Vey Dense Project: Client: Boring No. 1 of 3: Site Development Terry Mitchell BH-1-19 Project Number:Drilling Contractor:Drill Rig Type: 1172-KIN n/a Hand Auger Address:DateStarted: Bit Type: Diameter: 3625 Meadow Ave N, Renton WA 98056 11/6/2019 n/a 4 inches Fluid: 11/6/2019 Steel n/a Logged By: Logan Krehbiel 11/6/2019 15lbs 20 inches Drill Crew: Elevation: Samantha Denham none Existing Surface 72"DepthSample TypeSample NumberBlow Counts (blows/3/4")Graphic LogDry Density (pcf)Moisture Content (%)Additional TestSoil Group Name: modifier, color, moisture, density/consistency, grain size, other descriptors Rock Description: modifierm color, hardness/degree of concentration, bedding and joint characteristics, solutions, void conditions. Bore Log Symbols Soil Density Modifiers Gravel, Sand, Non-Plastic Silt Elastic Silts and Clays California Sampler Blows/3/4" Consistency Shelby Tube 0-1 Very Soft CPP Sampler 2-4 Soft StabIlized Ground water 5-8 Medium Stiff 31-60 Hard 31-61 Very Hard Groundwater At time of Drilling 9-15 Stiff Bulk/ Bag Sample 16-30 Very Stiff 18"S-1 1 36"S-2 3 54"S-3 6 72"S-4 6 Completed: Hammer Type: Backfilled: Hammer Weight: Hammer Drop: Groundwater Depth: Total Depth of Boring: Lithology Very loose, moist, brown, silty sand (SM) Very loose, moist, brown, silty sand (SM) Loose, moist, brown, silty sand (SM) Sharp increase in moisture content @ 68". Very loose, moist, brown, silty sand (SM) Standard Penetration Slit Spoon Sampler (SPT) Blows/3/4"Density 0-4 Very Loose 5-10 Loose 11-24 Medium Dense 25-50 Dense >50 Vey Dense Project: Client: Boring No. 2 of 3: Site Development Terry Mitchell BH-2-19 Project Number:Drilling Contractor:Drill Rig Type: 1172-KIN n/a Hand Auger Address:DateStarted: Bit Type: Diameter: 3625 Meadow Ave N, Renton WA 98056 11/6/2019 n/a 4 inches Fluid: 11/6/2019 Steel n/a Logged By: Logan Krehbiel 11/6/2019 15lbs 20 inches Drill Crew: Elevation: Samantha Denham none Existing Surface 84"DepthSample TypeSample NumberBlow Counts (blows/3/4")Graphic LogDry Density (pcf)Moisture Content (%)Additional TestSoil Group Name: modifier, color, moisture, density/consistency, grain size, other descriptors Rock Description: modifierm color, hardness/degree of concentration, bedding and joint characteristics, solutions, void conditions. Bore Log Symbols Soil Density Modifiers Gravel, Sand, Non-Plastic Silt Elastic Silts and Clays California Sampler Blows/3/4" Consistency Shelby Tube 0-1 Very Soft CPP Sampler 2-4 Soft StabIlized Ground water 5-8 Medium Stiff 31-60 Hard 31-61 Very Hard Groundwater At time of Drilling 9-15 Stiff Bulk/ Bag Sample 16-30 Very Stiff 18"S-1 1 36"S-2 6 54"S-3 5 72"S-4 4 Completed: Hammer Type: Backfilled: Hammer Weight: Hammer Drop: Groundwater Depth: Total Depth of Boring: Lithology Very loose, moist, brown, silty sand (SM) Very loose, moist, brown, silty sand (SM) Loose, moist, brown, silty sand (SM) Loose, moist, brown, silty sand (SM) Standard Penetration Slit Spoon Sampler (SPT) Blows/3/4"Density 0-4 Very Loose 5-10 Loose 11-24 Medium Dense 25-50 Dense >50 Vey Dense Project: Client: Boring No. 3 of 3: Site Development Terry Mitchell BH-3-19 Project Number:Drilling Contractor:Drill Rig Type: 1172-KIN n/a Hand Auger Address:DateStarted: Bit Type: Diameter: 3625 Meadow Ave N, Renton WA 98056 11/6/2019 n/a 4 inches Fluid: 11/6/2019 Steel n/a Logged By: Logan Krehbiel 11/6/2019 15lbs 20 inches Drill Crew: Elevation: Samantha Denham none Existing Surface 72"DepthSample TypeSample NumberBlow Counts (blows/3/4")Graphic LogDry Density (pcf)Moisture Content (%)Additional TestSoil Group Name: modifier, color, moisture, density/consistency, grain size, other descriptors Rock Description: modifierm color, hardness/degree of concentration, bedding and joint characteristics, solutions, void conditions. Bore Log Symbols Soil Density Modifiers Gravel, Sand, Non-Plastic Silt Elastic Silts and Clays California Sampler Blows/3/4" Consistency Shelby Tube 0-1 Very Soft CPP Sampler 2-4 Soft StabIlized Ground water 5-8 Medium Stiff 31-60 Hard 31-61 Very Hard Groundwater At time of Drilling 9-15 Stiff Bulk/ Bag Sample 16-30 Very Stiff 18"S-1 1 36"S-2 3 54"S-3 5 72"S-4 6 APPENDIX B – LABORATORY TEST RESULTS Date Revised:Date Sampled: Test(s) Performed:Test(s) Performed: X X X Respectfully Submitted, NW Region Laboratory Manager Atterberg Limits Asphalt Extraction/Gradation Moisture Content Specific Gravity, Coarse Specific Gravity, Fine Hydrometer Analysis Proctor Sand Equivalent Fracture Count See Report WSDOT Degradation Bulk Density & Voids Corporate ~ 777 Chrysler Drive • Burlington, WA 98233 • Phone (360) 755-1990 • Fax (360) 755-1980 Regional Offices: Olympia ~ 360.534.9777 Bellingham ~ 360.647.6111 Silverdale ~ 360.698.6787 Tukwila ~ 206.241.1974 Visit our website: www.mtc-inc.net Meghan Blodgett-Carrillo If you have any questions concerning the test results, the procedures used, or if we can be of any further assistance please call on us at the number below. Rice Density Loamy Sand Non-plastic Materials Testing & Consulting, Inc. Geotechnical Engineering • Special Inspection • Materials Testing • Environmental Consulting Test Results Olympia, WA 98502 Chris Heathman December 10, 2019 19S056-07 B19-1174 Project #: 1172 - KINAddress: As requested MTC, Inc. has performed the following test(s) on the sample referenced above. The testing was performed in accordance with current applicable AASHTO or ASTM standards as indicated below. The results obtained in our laboratory were as follows below or on the attached pages: Test Results Client: Sample #: Date: Project: Mud Bay Geotechnical Services, LLC. 2724 Langridge Loop NW Attn: Sulfate SoundnessSieve Analysis Not Reported Project:Date Received:4-Dec-19 Project #:Sampled By:Client Client:Date Tested:5-Dec-19 Source:Tested By:A. Eifrig Sample#:B19-1174 D(5) =0.010 mm % Gravel =1.0%Coeff. of Curvature, CC =1.31 Specifications D(10) =0.020 mm % Sand =60.5%Coeff. of Uniformity, CU =6.87 No Specs D(15) =0.029 mm % Silt & Clay =38.4%Fineness Modulus =0.74 Sample Meets Specs ?N/A D(30) =0.059 mm Liquid Limit =0.0%Plastic Limit =0.0% D(50) =0.107 mm Plasticity Index =0.0%Moisture %, as sampled =n/a D(60) =0.134 mm Sand Equivalent =n/a Req'd Sand Equivalent = D(90) =0.482 mm Fracture %, 1 Face =n/a Req'd Fracture %, 1 Face = Dust Ratio =3/7 Fracture %, 2+ Faces =n/a Req'd Fracture %, 2+ Faces = Actual Interpolated Cumulative Cumulative Sieve Size Percent Percent Specs Specs US Metric Passing Passing Max Min 12.00"300.00 100%100.0%0.0% 10.00"250.00 100%100.0%0.0% 8.00"200.00 100%100.0%0.0% 6.00"150.00 100%100.0%0.0% 4.00"100.00 100%100.0%0.0% 3.00"75.00 100%100.0%0.0% 2.50"63.00 100%100.0%0.0% 2.00"50.00 100%100%100.0%0.0% 1.75"45.00 100%100.0%0.0% 1.50"37.50 100%100.0%0.0% 1.25"31.50 100%100.0%0.0% 1.00"25.00 100%100%100.0%0.0% 3/4"19.00 100%100%100.0%0.0% 5/8"16.00 100%100.0%0.0% 1/2"12.50 100%100%100.0%0.0% 3/8"9.50 100%100%100.0%0.0% 1/4"6.30 99%100.0%0.0% #4 4.75 99%99%100.0%0.0% #8 2.36 99%100.0%0.0% #10 2.00 98%98%100.0%0.0% #16 1.18 94%100.0%0.0% #20 0.850 92%100.0%0.0% #30 0.600 91%100.0%0.0% #40 0.425 90%90%100.0%0.0% #50 0.300 79%100.0%0.0% #60 0.250 75%100.0%0.0% #80 0.180 68%100.0%0.0% #100 0.150 66%66%100.0%0.0% #140 0.106 50%100.0%0.0% #170 0.090 44%100.0%0.0% #200 0.075 38.4%38.4%100.0%0.0% Copyright Spears Engineering & Technical Services PS, 1996-98 Comments: Reviewed by: Meghan Blodgett-Carrillo Materials Testing & Consulting, Inc. Visit our website: www.mtc-inc.net All results apply only to actual locations and materials tested. As a mutual protection to clients, the public and ourselves, all reports are submitted as the confidential property of clients, and authorization for publication of statements, conclusions or extracts from or regarding our reports is reserved pending our written approval. Corporate ~ 777 Chrysler Drive • Burlington, WA 98233 • Phone (360) 755-1990 • Fax (360) 755-1980 Regional Offices: Olympia ~ 360.534.9777 Bellingham ~ 360.647.6111 Silverdale ~ 360.698.6787 Tukwila ~ 206.241.1974 Geotechnical Engineering • Special Inspection • Materials Testing • Environmental Consulting Sieve Report ASTM C-136, ASTM D-6913 19S056-07 Mud Bay Geotechnical Services, LLC. BH-3-19 S3 @ 54'' ASTM D-2487 Unified Soils Classification System ASTM D-2216, ASTM D-2419, ASTM D-4318, ASTM D-5821 SM, Silty Sand brown Sample Color: 1172 - KIN 8"6"4"2"3"1½"1¼"10"1"¾"5/8"½"3/8"¼"#4#8#10#16#20#30#40#50#60#80#100#140#170#2000% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 100.0% 0.0010.0100.1001.00010.000100.000% Passing% PassingParticle Size (mm) Grain Size Distribution Sieve Sizes Max Specs Min Specs Sieve Results Project:1172 - KIN Date Received:4-Dec-19 Project #:19S056-07 Sampled By:Client Client :Mud Bay Geotechnical Services, LLC.Date Tested:5-Dec-19 Sample Color Source:BH-3-19 S3 @ 54''Tested By:A. Eifrig Sample#:B19-1174 Assumed Sp Gr :2.70 Sample Weight:50.07 grams Hydroscopic Moist.:6.31%Sieve Percent Adj. Sample Wgt :47.10 grams Size Passing 3.0"100%75.000 mm Hydrometer 2.0"100%50.000 mm Reading Corrected Percent 1.5"100%37.500 mm Minutes Reading Passing 1.25"100%31.500 mm 2 7 14.5%0.0371 mm 1.0"100%25.000 mm 5 6.5 13.5%0.0235 mm 3/4"100%19.000 mm 15 5.5 11.4%0.0137 mm 5/8"100%16.000 mm 30 5 10.4%0.0097 mm 1/2"100%12.500 mm 60 4.5 9.3%0.0069 mm 3/8"100%9.500 mm 250 3 6.2%0.0034 mm 1/4"99%6.300 mm 1440 2.5 5.2%0.0014 mm #4 99%4.750 mm #10 98%2.000 mm % Gravel:1.0%Liquid Limit:0.0 %#20 92%0.850 mm % Sand:60.5%Plastic Limit:0.0 %#40 90%0.425 mm % Silt:30.8%Plasticity Index:0.0 %#100 66%0.150 mm % Clay:7.7%#200 38.4%0.075 mm Silts 37.8%0.074 mm 22.7%0.050 mm 12.7%0.020 mm Clays 7.7%0.005 mm 5.5%0.002 mm Colloids 3.7%0.001 mm Particle Size % Sand:77.0%2.0 - 0.05 mm % Silt:17.4%0.05 - 0.002 mm % Clay:5.6%< 0.002 mm Loamy Sand Comments: Reviewed by: Meghan Blodgett-Carrillo All results apply only to actual locations and materials tested. As a mutual protection to clients, the public and ourselves, all reports are submitted as the confidential property of clients, and authorization for publication of statements, conclusions or extracts from or regarding our reports is reserved pending our written approval. USDA Soil Textural Classification ASTM C-136 Soils Particle ASTM D-422, HYDROMETER ANALYSIS Sieve Analysis Grain Size Distribution Visit our website: www.mtc-inc.net Corporate ~ 777 Chrysler Drive • Burlington, WA 98233 • Phone (360) 755-1990 • Fax (360) 755-1980 Regional Offices: Olympia ~ 360.534.9777 Bellingham ~ 360.647.6111 Silverdale ~ 360.698.6787 Tukwila ~ 206.241.1974 Materials Testing & Consulting, Inc. Geotechnical Engineering • Special Inspection • Materials Testing • Environmental Consulting USDA Soil Textural Classification Hydrometer Report SM, Silty Sand Diameter brown Soils Particle Diameter ASTM D 2487 Soils Classification Project: Project #: Client:Sample Color Source: Sample #: #1 #2 #3 #4 #5 #6 Weight of Wet Soils + Pan: Weight of Dry Soils + Pan:Non-Plastic Weight of Pan: Weight of Dry Soils:Liquid Limit @ 25 Blows:N/A Weight of Moisture:Plastic Limit:N/A % Moisture:Plasticity Index, IP:N/A Number of Blows: #1 #2 #3 #4 #5 #6 Weight of Wet Soils + Pan: Weight of Dry Soils + Pan:Non-Plastic Weight of Pan: Weight of Dry Soils: Weight of Moisture: % Moisture: Copyright Spears Engineering & Technical Services PS, 1996-98 Comments: Reviewed by: Meghan Blodgett-Carrillo Geotechnical Engineering • Special Inspections • Materials Testing • Environmental Consulting Materials Testing & Consulting, Inc. Regional Offices: Olympia ~ 360.534.9777 Bellingham ~ 360.647.6111 Silverdale ~ 360.698.6787 Tukwila ~ 206.241.1974 6-Dec-19 BH-3-19 S3 @ 54'' Mud Bay Geotechnical Services, L A. Eifrig 4-Dec-19 Client ASTM D4318 - Liquid Limit, Plastic Limit and Plasticity Index of Soils 1172 - KIN Unified Soils Classification System, ASTM D-2487Date Received: B19-1174 Visit our website: www.mtc-inc.net Corporate ~ 777 Chrysler Drive • Burlington, WA 98233 • Phone (360) 755-1990 • Fax (360) 755-1980 Liquid Limit Determination threads. Non-plastic. Liquid limit cannot be determined as the material displays rapid dilation. Plastic limit cannot be established as the material does not roll down to 1/8" Sampled By: Date Tested: Tested By: Plastic Limit Determination All results apply only to actual locations and materials tested. As a mutual protection to clients, the public and ourselves, all reports are submitted as the confidential property of clients, and authorization for publication of statements, conclusions or extracts from or regarding our reports is reserved pending our written approval. 19S056-07 SM, Silty Sand brown 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 10 100% MoistureNumber of Blows, "N" Liquid Limit 0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % 0%10%20%30%40%50%60%70%80%90%100%110%Plasticity Index Liquid Limit Plasticity Chart MH or OH ML or OLCL-ML