8920 EVERGREEN WAY THE RESERVE 2025-07-25

Zipper Geo Associates. LLC Reserve at Everett Project No.1117.01 May 1,2013 is our opinion that the native soils encountered on the site are suitable for reuse as general structural fill from a compositional standpoint provided the soil is placed and compacted in accordance with the compaction recommendations presented in this report. Based on laboratory testing, soils within the upper 2 to 5 feet of existing site grades (excluding forest duff and topsoil)are expected to consist of weathered Glacial Till considerably above optimum moisture content for compaction. Soils encountered below the weathered glacial till are expected to be somewhat above optimum moisture content as well. Reuse of site soils for structural fill will only be feasible during extended periods of dry weather. Even during dry weather,some drying of site soils may be required for reuse as structural fill. Drying of over-optimum moisture soils may be achieved by scarifying or windrowing surficial materials during extended periods of dry weather. If encountered, soils which are dry of optimum may be moistened through the application of water and thorough blending to facilitate a uniform moisture distribution in the soil prior to compaction. We recommend that site soils used as structural fill have less than 4 percent organics by weight and have no woody debris greater than %2 inch in diameter. We recommend that all pieces of organic material greater than%2 inch in diameter be picked out of the fill before it is compacted.Any organic-rich soil derived from earthwork activities should be utilized in landscape areas or wasted off site. Imported Structural Fill: Imported structural fill may be required for raising site grades or for other reasons. The appropriate type of imported structural fill will depend on weather conditions. During extended periods of dry weather, we recommend imported fill, at a minimum, meet the requirements of Common Borrow as specified in Section 9-03.14(3) of the 2012 Washington State Department of Transportation,Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT Standard Specifications). During wet weather, higher-quality structural fill might be required, as Common Borrow may contain sufficient fines to be moisture sensitive. During wet weather we recommend that imported structural fill meet the requirements of Gravel Borrow as specified in Section 9-03.14(1) of the WSDOT Standard Specifications. Retaining Wall Backfill: Cast-in-place concrete foundation retaining walls should include a drainage fill zone extending at least two feet back from the back face of wall for the entire wall height. The drainage fill should meet the requirements of Gravel Backfill for Walls as specified in Section 9-03.12(2) of the WSDOT Standard Specifications. Specific recommendations for backfill of other types of retaining walls such as rockeries or segmental block walls are presented in subsequent sections of this report. Pavement Subgrades: Any structural fill used within the upper one foot below pavement sections should have a minimum California Bearing Ratio (CBR) of 15 when compacted to a minimum of 95 percent of the modified Proctor maximum dry density. A CBR value of 15 is representative of the soils encountered at the site and has been used to develop our pavement section recommendations. Page 9