1329 MADRONA AVE Geotech Report 2022-10-25

Subsurface Exploration,Geologic Hazard,and Janowicz Property Geotechnical Engineering Report Everett,Washington Preliminary Design Recommendations PRELIMINARY DESIGN RECOMMENDATIONS 8.0 INTRODUCTION Our exploration indicates that, from a geotechnical standpoint, the property is suitable for the proposed residential construction provided the recommendations contained herein are properly followed. The bearing stratum was relatively deep in our exploration borings and deep foundations bearing in very dense and hard, non-glacial sediments should be used for foundation support. Driveway pavement subgrades can be supported on the existing surface that has been proof-rolled and found to be in a firm and unyielding condition. . 9.0 SITE PREPARATION 9.1 Site Drainage • Prior to earthwork, the site should be provided with adequate, temporary drainage to prevent surface water accumulation on any part of the site. Timely and economical completion of the grading for this project will depend on adequate control of surface water, as well as any groundwater seepage that is encountered during construction. Groundwater seepage was observed at about 7 feet in exploratory boring EB-1 and about 9 feet in exploratory boring EB-2. Control of groundwater seepage should be anticipated during construction for excavations made anywhere onsite around or below these depths, such as might occur for a daylight basement. 9.2 Clearing,Stripping,and Grubbing Site preparation of planned building and driveway areas should include removal of all vegetation and organic topsoil, and any remaining roots should be grubbed. For planning purposes, an average stripping depth of 6 to 12 inches should be assumed. Volume estimates for stripped material should include a typical swell factor of approximately 25 percent relative to the in-place volume. Areas where loose surficial soils exist due to grubbing operations should be considered as fill to the depth of disturbance and treated as recommended below for structural fill placement. 9.3 Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction based on the local subsurface soil and moisture conditions encountered at that time and location. For estimating purposes,we anticipate that temporary, unsupported cut slopes in the colluvium or landslide deposits can be made at a maximum slope of 1H:1V (Horizontal:Vertical) to a maximum depth of 4 feet. Steeper or May 10,2018 ASSOCIATED EARTH SCIENCES,INC. NS/(d-170649E002-2-Projectsl20170649!KE'WP Page 11