1318 W MUKILTEO BLVD 2016-01-01 MF Import

Wrought Corporation August 11, 2006 CONCLUSIONS AND RECOMMENDATIONS C�T�.`I�:�_l� JN 06287 Page 3 THI•S SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY. MORE SPECIFlC 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 in the area of the residence encountered native sand that became medium- dense or denser at depths ranging from approximately 2 to 6 feet below the ground surtace. This soil is suitable to support the proposed building loads, although some overexcavation will likely be needed to reach the competent sand. The loose upper sand should not be relied upun to support the residence loads. Some compaction of the competent sand with vibratory equipment may be needed if it is disturbed during excavation. A significant geotechnical engineering consideration for the residence construction is the needed excavations. An approximate 10- to 11-foot-tall retaining wall is proposed on the southern edge of the property, while some areas of an approximate 10-foot-tall retaining wall are proposed at steps in the reside�ce. The upper loose soil should not be temporarily excavated steeper than 1.5:1 (Horizontal:Vertical), while the more competent sand can be excavated at a 1:1 (H:V) inclination. In the southern retaining wall area, we believe that an open excavation could potentially destabilize the existing retaining wall to the south. Therefore, we recorimend that the southern retaining wall be constructed as a shoring wall. To make open excavations along portions of the western side of the residence, the excavations will have to extend onto the neighboring property. A ternporary easement would have to be obtained from the neighboring property owner would be needed to do this. If an easement cannot be obtained, then temporary shoring would be needed. As noted earlier, the competent native sand was not revealed in the test holes excavated in the driveway area until a depth of about 8 feet. Because of this soil condition, and because the surface of the driveway will be situated up to 6 feet above existing ground, and because a rockery is located just below the driveway area, we recommend that the driveway be constructed as a "bridge" that is supported on drilled concrete piers. These piers will have to be designed for embedment well below the loose, upper sand. Details regarding the piers are given in a subsequent sectian of this report. 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. Rocked construction access roads should be extended into the site to reduce the amount of soil or mud carried off the property by trucks and equipment. Wherever possible, these roads should follow the alignment of planned pavements, and trucks should not be allowed to drive off of the rock-covered areas. Existing catch basins in, and immediately downslope of, the planned work areas should be protected with pre-manufactured silt socks. Cut slopes and scil stockpiles should be covered with plastic during wet weather. Following rough grading, it may be necessary to muich or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. 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 GEOTECH CONSULTANTS. INC.