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Home My WebLink AboutEX09_Supplemental_Geotechnical_Evaluation_Report_Pioneer_Engineers_240729_v1SUPPLEMENTAL GEOTECHNICAL REPORT PROPOSED 1828 RESIDENCE 1828 NE 20TH STREET RENTON, WASHINGTON For Yin Yin Leong c/o Ms. Tracy Hung 1828 NE 20th Street Renton, WA 98056 Prepared by Pioneer Engineers, Inc. P. O. Box 33628, Seattle, WA 98133 Phone: (206) 427-9118, Fax: (206) 306-2982 josephwu.pei@gmail.com April 15, 2024 Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 PIONEER ENGINEERS, INC. Geotechnical Engineering Earth Science Water Resources ___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ P. O. Box 33628Seattle, WA 98133 Phone: (206) 427-9118 Fax: (206) 306-2982 josephwu.pei@gmail.com April 15, 2024 Yin Yin Leong c/o Ms. Tracy Hung 1828 NE 20th Street Renton, WA 98056 Subject: Supplemental Geotechnical Report Proposed 1828 Residence 1828 NE 20th Street Renton, Washington Dear Ms. Hung: Per your and the civil engineer’s requests, Pioneer Engineers, Inc. (“PEI”) has conducted soil sampling in the proposed permeable pavement area for the development at the subject site in Renton, Washington. The sample is tested to obtain organic content (“OC”) and cation exchange capacity (“CEC”), where the approximate sampling location shown in Figure 1 - Site Exploration and Sampling Plan. Also presented in this report are geologic hazards and test results. Wellhead protection is addressed in PEI’s 12/30/2023 geotechnical evaluation report. Delineation of wetlands at the site performed by a wetland specialist is not included in this report. GEOLOGIC HAZARDS In accordance with RMC 4-3-050G(5), geologic hazards associated with the site include steep slope hazard, landslide hazard, erosion hazard, seismic hazard and coal mine hazard. Discussions, conclusions and recommendations are addressed in subtitled topics: Steep Slope and Landslide Hazards In accordance with RMC 4-3-050G(5a) and RMC 4-3-050G(5b), the site is located in a flat area with an overall ground slope less than 15 percent; therefore, it pertains to a classified low landslide (“LL”) hazard area. Steep slopes are susceptible to landslide hazards due to Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 April 15, 2024 Proposed 1828 Residence PEI Project No. G23A20S Page 2 PIONEER ENGINEERS, INC. steepness contributing to the mobilization (sliding) of a soil mass on a slope by gravitational force. As stated above, the site’s topographic condition makes it unable to meet the criteria of sensitive slopes or protected slopes, and thus it is not in an area of steep slope hazard. Erosion Hazard In accordance with RMC 4-3-050G(5c), the site is located in an area of low erosion hazard (“EL”) due to its overall site grade less than 15 percent. Based on the custom soil report from the interactive website of Natural Resources Conservation Service (“NRCS”) of USDA, the site is located in InC (Indianola loamy sand). InC is a dominant soil type on 5 to 15 percent slopes. During construction, the potential hazard can be further minimized by closely following the recommendations in Grading and Site Preparation of PEI’s 12/30/2023 geotechnical evaluation report and additional erosion control measures herein:  Construction will keep minimal disturbance to surface vegetation including trees, bushes and groundcover outside the clearing limits;  Standing water is not allowed to preside over the building area during construction;  Concentrated stormwater is forbidden from discharging onto a slope within the site;  Construction debris and yard waste are not dumped onto a slope;  Straw mulch should be placed over the bare ground to guard against erosion by surface runoff, prior to start of grading activities;  Grading activities are scheduled to start and complete in the official dry season;  All disturbed ground and disruption of surface vegetation due to construction activities are restored and re-planted with approved natural vegetation. With prudent implementations of the measures stated above, disturbance of ground can be minimized and related erosion hazard be mitigated to a lower level. Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 April 15, 2024 Proposed 1828 Residence PEI Project No. G23A20S Page 3 PIONEER ENGINEERS, INC. Seismic Hazard Seismic hazard is mostly caused by liquefaction during earthquake events in local areas. Liquefaction is a phenomenon when a loose saturated sand deposit subject to vibration, tends to compact and decrease in volume. If the sand deposit is unable to drain, the pore water pressure will build up in a soil mass to reach the effective overburden earth pressure at some depths. When these two pressures are equal, the sand deposit will completely lose its shear strength and bearing capacity to support structures. Consequently, the sand deposit reaches a "quick" condition, and liquefaction occurs. In accordance with RMC 4-3-050G(5d) and subsurface exploration, the site is underlain by competent native soils and stratified deposits of coarser particles in the lower soil profile, the risk of liquefaction to occur across the site is low. This adverse potential can be further mitigated when design of residential buildings is in compliance with the standards and specifications stated in 2021 International Building Code (“2021 IBC”). Based on the 2021 IBC, the site is located in a classified Site Class D. The 0.2-second and 1-second spectral response accelerations are presented for seismic design: Regional Earthquake Ground Motion for the 0.2-Second Spectral Response Acceleration, SS = 1.440 g Regional Earthquake Ground Motion for the 1-Second Spectral Response Acceleration, S1 = 0.494 g Regional Earthquake Ground Motion for the 0.2-Second Spectral Response Design Parameter, Site Class D SDS = 0.960 g Regional Earthquake Ground Motion for the 1-Second Spectral Response Design Parameter, Site Class D SD1 = 0.593 g Site Coefficient Fa as a Function of Site Class and Mapped Spectral Response Acceleration at a 0.2-second Period (Ss) Fa = 1.000 Site Coefficient Fv as a Function of Site Class and Mapped Spectral Response Acceleration at a 1-Second Period (S1) Fv = 1.800 The development closely following the above design parameters will enhance structural integrity and further lower the risk of foundation distress by liquefaction during major seismic events. Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 April 15, 2024 Proposed 1828 Residence PEI Project No. G23A20S Page 4 PIONEER ENGINEERS, INC. Coal Mine Hazard The site is not located in an area of known coal mine workings and predicted ground subside, and thus the coal mine hazard is low, in accordance with RMC 4-3-050G(5e). OC AND CEC The OC test was performed in general accordance with ASTM D2974, using moisture content method A burnt at 221°F and ash content method C burnt at 824°F. The result was recorded as percentage by weight. The CEC test was performed closely following the test method EPA 9081, where the soil sample is mixed with an excess of sodium acetate solution, resulting in an exchange of the added sodium cations for the matrix cations. Subsequently, the sample is washed with isopropyl alcohol. An ammonium acetate solution is then added to replace the adsorbed sodium with ammonium. The concentration of displaced sodium is determined by atomic absorption, emission spectroscopy, or an equivalent measure. The sampling depth was taken as per the civil engineer’s specification. Please refer to the summary of material properties in Appendix for the sample’s soil information. The results indicate that OC is 3.8 percent greater than the threshold of 1.0 percent, and CEC is 5.9 meg/100g exceeding the threshold of 5.0 meg/100g. Respectfully submitted, PIONEER ENGINEERS, INC. Joseph Wu, P.E. Engineering Consultant One figure and one appendix attached. Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 Scale: 1" = 80' 4/15/24G23A20S SITE EXPLORATION AND SAMPLING PLAN PROPOSED 1828 RESIDENCE 1828 NE 20TH STREET RENTON, WASHINGTON 1 TP-1TP-2 TP-3 TP-4 A-1 APPROX. SAMPLING LOCATION APPROX. TEST PIT LOCATION Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 APPENDIX OC and CEC PIONEER ENGINEERS, INC. Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 A-1-2,2.0 2.0 32.6 3.8 SM Very dark brown, silty SAND A-2-2,2.0 2.0 17.8 1.8 SM Olive-brown, silty SAND A-3-2,4.0 4.0 22.0 1.3 SM Olive-brown, silty SAND A-4-2,4.0 4.0 13.6 1.4 SM Olive-brown, silty SAND (f e e t ) TO P D E P T H SAMPLE DESCRIPTION Notes: AS T M S O I L MO I S T U R E CO N T E N T ( % ) OR G A N I C % F I N E S EX P L O R A T I O N DE S I G N A T I O N 1. This table summarizes information presented elsewhere in the report and should be used in conjunction with the report test, other graphs and tables, and the exploration logs. 2. The soil classifications in this table are based on ASTM D2487 and D2488 as applicable. MATERIAL PROPERTIES 1 PAGE: 1 of 1 SUMMARY OF LIMITS (%) ATTERBERG BO T T O M D E P T H CO N T E N T ( % ) % S A N D % G R A V E L PIPLLL CL A S S I F I C A T I O N (f e e t ) SP E C I F I C G R A V I T Y 2024-123 T100PROJECT NO.: INDEX MATSUM 2 2024-123 T100.GPJ 4/9/24 FIGURE: 1828 Residence MLT for PEI Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7 HWA GEOSCIENCES 21312 30TH DRIVE SE, STE 110 BOTHELL , WA 98021 4/5/2024 Soil PROJ 2024-123 A-1-2 S24-06454 Date Received: Grower: Sampled By: Field: Laboratory #: Test Results Customer Account #: Customer Sample ID: Other Tests: Cation Exchange meq/100gCEC 5.9 pH 1:1 E.C. 1:1 m.mhos/cm Est Sat Paste E.C. m.mhos/cm Effervescence Lbs/Acre Ammonium - N mg/kg %Organic Matter W.B.ENR: $16.00This is your Invoice #: List Cost:K. Bair, PhD, CReviewed by:S24-06454 Account #:188200 We make every effort to provide an accurate analysis of your sample. For reasonable cause we will repeat tests, but because of factors beyond our control in sampling procedures and the inherent variability of soil, our liability is limited to the price of the tests. Recommendations are to be used as general guides and should be modified for specific field conditions and situations. Note: "u" indicates that the element was analyzed for but not detected Figure 2 Docusign Envelope ID: 104DBDA6-11CD-4791-91FF-7DA2A96942C7