4518 SEAHURST AVE Geotech Report 2022-10-25

Naranjo JN 15186 May 18,2015 Page 3 CONCLUSIONS AND RECOMMENDATIONS GENERAL THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE CONTAINED IN THE REMAINDER OF THIS REPORT ANY PARTY RELYING ON THIS REPORT SHOULD READ THE ENTIRE DOCUMENT The test pits conducted for this study encountered native medium-dense sand at depths of 3 to 6 feet. Conventional footing foundations that bear on this competent material will provide adequate support to the residence. In our opinion the basement retaining wall at the east side of the residence will stabilize the uncontrolled fill to the east. The steep slope off-site to the north has a potential to experience shallow slope failures, as does any steep slope in the Puget Sound region. The proposed 30-foot building setback from the base of that slope should provide an adequate buffer from such shallow failures, Excavations more than 4 feet in height should have an inclination no steeper than 1:1 (H:V). Where excavations cannot be contained within the property and where permission from adjacent property owners to extend excavations into those properties cannot be obtained, excavation shoring would be required. We anticipate that shoring may be necessary for the northeast corner of the residence basement. Stacked concrete ecology blocks may be an appropriate shoring system. We are available to provide additional shoring recommendations after project plans have been more completely developed. In our opinion infiltration of stormwater into the sand that underlies the site is feasible. We can provide additional recommendations for infiltration once a preliminary infiltration design has been completed. The erosion control measures needed during the site development will depend heavily on the weather conditions that are encountered. We anticipate that a silt fence will be needed around the downslope sides of any cleared areas. Existing pavements, ground cover, and landscaping should be left in place wherever possible to minimize the amount of exposed soil. Rocked staging areas and construction access roads should be provided to reduce the amount of soil or mud carried off the property by trucks and equipment. Wherever possible, the access roads should follow the alignment of planned pavements. Trucks should not be allowed to drive off of the rock-covered areas. Cut slopes and soil stockpiles should be covered with plastic during wet weather. Following clearing or rough grading, it may be necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. On most construction projects, it is necessary to periodically maintain or modify temporary erosion control measures to address specific site and weather conditions. The drainage and/or waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from the surrounding soil, and can even be transmitted from slabs and foundation walls due to the concrete curing process. Water vapor also results from occupant uses, such as cooking and bathing. Excessive water vapor trapped within structures can result in a variety of undesirable GEOTECH CONSULTANTS,INC.