1130 RAINIER AVE Geotech Report 2025-07-28

Everett Housing Authority JN 12080 May 16, 2012 Page 11 PAVEMENT AREAS The pavement section may be supported on competent, native soil, on structural fill, or on existing fill compacted to a 95 percent density. Because the site soils are silty and moisture sensitive, we recommend that the pavement subgrade must be in a stable, non-yielding condition at the time of paving. Granular structural fill or geotextile fabric may be needed to stabilize soft, wet, or unstable areas. To evaluate pavement subgrade strength, we recommend that a proof roll be completed with a loaded dump truck immediately before paving. In most instances where unstable subgrade conditions are encountered, an additional 12 inches of granular structural fill will stabilize the subgrade, except for very soft areas where additional fill could be required. The subgrade should be evaluated by Geotech Consultants, Inc., after the site is stripped and cut to grade. Recommendations for the compaction of structural fill beneath pavements are given in the section entitled General Earthwork and Structural Fill. The performance of site pavements is directly related to the strength and stability of the underlying subgrade. The pavement for lightly loaded traffic and parking areas should consist of 2 inches of asphalt concrete (AC)over 4 inches of crushed rock base (CRB)or 3 inches of asphalt-treated base (ATB). We recommend providing heavily loaded areas with 3 inches of AC over 6 inches of CRB or 4 inches of ATB. Heavily loaded areas are typically main driveways, dumpster sites, or areas with truck traffic. Increased maintenance and more frequent repairs should be expected if thinner pavement sections are used. Water from planter areas and other sources should not be allowed to infiltrate into the pavement subgrade. The pavement section recommendations and guidelines presented in this report are based on our experience in the area and on what has been successful in similar situations. As with any pavements, some maintenance and repair of limited areas can be expected as the pavement ages. Cracks in the pavement should be sealed as soon as possible after they become evident, in order to reduce the potential for degradation of the subgrade from infiltration of surface water. For the same reason, it is also prudent to seal the surface of the pavement after it has been in use for several years. To provide for a design without the need for any maintenance or repair would be uneconomical. GENERAL EARTHWORK AND STRUCTURAL FILL All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and other deleterious material. The stripped or removed materials should not be mixed with any materials to be used as structural fill, but they could be used in non-structural areas, such as landscape beds. Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building, behind permanent retaining or foundation walls, or in other areas where the underlying soil needs to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The optimum moisture content is that moisture content that results in the greatest compacted dry density. The moisture content of fill is very important and must be closely controlled during the filling and compaction process. The allowable thickness of the fill lift will depend on the material type selected, the compaction equipment used, and the number of passes made to compact the lift. The loose lift thickness should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not sufficiently compacted, it can be recompacted before another lift is placed. This eliminates the GEOTECH CONSULTANTS,INC.