1921 W MUKILTEO BLVD 2018-01-02 MF Import

Preliminary Geotechnical Engineering Evaluation ' 1919 Mukilteo Boulevard October 20, 2005 NGA File No. 718805 Page 13 IAll wall backfill should be well compacted as outlined in the Structural Fill subsection of this report. Care should be taken to prevent the buildup of excess lateral soil pressures, due to over -compaction of the wall backfill. This can be accomplished by placing wall backfill in eight -inch loose lifts and compacting it with small, hand -operated compactors within a distance behind the wall equal to at least one-half the height of the wall. The thickness of the loose lifts should be lessened to accommodate the lower compactive energy of the hand -operated equipment. The recommended level of compaction should still be maintained. �I Permanent drainage systems should be installed for retaining walls. Recommendations for these systems are found in the Subsurface Drainage subsection of this report. We recommend that we be retained to IIevaluate the proposed wall drain backfill material and drainage systems. II Pavement Subgrade A Pavement subgrade preparation, and structural fill placement where required, should be completed as Iirecommended in the Site Preparation and Grading and Structural Fill subsections of this report. The pavement subgrade should be proof -rolled with a heavy, rubber -tired piece of equipment, to identify soft or yielding areas that require repair. We should be retained to observe the proof -rolling and recommend repairs prior to placement of the asphalt or hard surfaces. Site Drainage Surface Drainage: Final site grades should allow for drainage away from the top of the steep slope and �I away from the planned residence. We suggest that the finished ground be sloped at a minimum gradient of three percent for a distance of at least 10 feet away from the building and top of slope. Runoff �I generated on this site should be collected and routed into a permanent discharge system. This should include all downspouts and runoff generated on all hard surfaces and yards areas. Under no !I circumstances should water be allowed to flow uncontrolled over the slope. Water should not be allowed to stand in any area where footings, slabs, rockeries, or pavements are to be constructed. Subsurface Drainage: If groundwater is encountered during construction, we recommend that the contractor slope the bottom of the excavation and collect the water into ditches and small sump pits where ' the water can be pumped out of the excavation and routed into a permanent storm drain. I I NELSON GEOTECHNICAL ASSOCIATES, !NC.