9909 2ND AVE W 2018-08-01 - Laserfiche WebLink

December 13,2006 Project No.T-6001 Prior to use, Terra Associates,Inc. should examine and test all materials imported to the site for use as structural fill. Structdral fill should be placed in uniform loose layers r.ot exceeding 12 inches and compacted to a minimum of 95 percent of the soil's maximum dry density, as determined by American Society for Testing and Materials 111 (ASTM)Test Designation D-698 (Standard Proctor). The moisture content of the soil at the time of compaction should be within two percent of its optimum, as determined by this ASTM standard. In nonstructural areas, the degree of compaction can be reduced to 90 percent. All structural fill placed within rights-of-way must conform to materials and compaction specifications set forth by the applicable jurisdiction. 5.3 Excavations A1= excavations at the site associated with c-onfined spaces, such as utilit` trenches and retaining walls; must be completed in accordance with loc-al, state, or federal requiremen:s. Based on current Washington Industrial Safety Health Act (WISHA) regulations, the upper loose to medium dense soils, and any soils with groundwater seepage at the site would be classified as Type C soils. The site's dense to very dense silty sands and gravels exposed with no groundwater seepage would be classified as Type B soils. Accordingly, for temporary excavations less than 20 feet in depth, the side slopes in Type C and Type B soils should, respectively, be laid back at slope inclinations of 1.5:1 (Horizontal:Vertical)and 1:1 or flatter. If there is insufficient room to complete the excavations in this manner, or if excavations greater than 20 feet deep are planned, the contractor may need to use temporary shoring to support the excavations. Excavations that extend below a depth of approximately three feet will encounter light to moderate groundwater seepage from excavation sidewalls. Construction of utiiities and/or stornwater detention vaults at locations where significant groundwater is present will likely require implementation of a dewatering system in order to stabilize soil cuts and maintain relatively dry working conditions during construction. Based on our test pits, we expect that conventional dewatering procedures that include routing seepage water along trenches to sump areas will be adequate for maintaining relatively dry working conditions. This information is provided solely for the benefit of the owner and other design consultants, and should not be construed to imply that Terra Associates, Inc. assumes responsibility for job site safety. It is understood that job site safety is the sole responsibility of the project contractor. c.4 Foundations The structures may be supported on conventional spread footing foundations bearing on competent native soils or on structural fills placed ahove these native soils. Foundation subgrades should be prepared as recommended in Section 5.2 of this report. Page No. 6