7800 EVERGREEN WAY HYUNDAI Wetland Report 2025-08-05

areas and in utility trenches, but should not be used under the building floor slabs. For use as general structural fill across the site, the asphalt and concrete rubble should be crushed or otherwise ground up and should meet the gradation requirements for gravel borrow as described in Section 9-03.14(1) of the 2020 WSDOT Standard Specifications. If recycled asphalt and/or concrete will be used under pavement areas, we recommend that it meetthe gradation requirements for CSBC as described in Section 9-03.9(3) of the 202O WSDOT Standard Specifications. Recycled asphalt and concrete should not be used in landscape areas. 4.7.3.4, Fill Placement and Compaction Criteria Structural fill should be mechanically compacted to a firm, non -yielding condition. Structural fill should be placed in loose lifts not exceeding 12 inches in thickness when using heavy compaction equipment and not more than 6 inches when using hand -operated compaction equipment. The actual thickness will be dependent on the structural fill material used and the type and size of compaction equipment. Each lift should be moisture conditioned to within about 2 percent of the optimum moisture content to achieve proper compaction to the specified density before placing subsequent lifts. Compaction of structural fill should be in accordance with the ASTM D 1557 (modified proctor) test method. Structural fill should be compacted to the following criteria: 1. Structural fill placed below floor slabs and foundations should be compacted to 95 percent of the MDD. 2. Structural fill in new pavement and hardscape areas including utility trench backfill, should be compacted to at least 90 percent of the MDD, except that the upper 2 feet of fill below final subgrade should be compacted to at least 95 percent of the MDD, see Figure 4. 3. Structural fill placed as CSBC below pavements should be compacted to 95 percent of the MDD. 4. Subbase materials placed below CSBC should be compacted to 95 percent of the MDD. 5. Non-structural fill, such as fill placed in landscape areas, should be compacted to at least 90 percent of the MDD. 4.7.3.5 Weather Considerations Disturbance of near -surface soils should be expected if earthwork is completed during periods of wet weather. During dry weather, the soils will: (1) be less susceptible to disturbance, (2) provide better support for construction equipment, and (3) be more likely to meet the required compaction criteria. The wet weather season generally begins in October and continues through May in Western Washington, however, periods of wet weather may occur during any month of the year. For earthwork activities during wet weather, we recommend that the following steps be taken: ■ The ground surface in and around the work area should be sloped so that surface water is directed away from the work area. The ground surface should be graded so that areas of ponded water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and trenches. Measures should be implemented to remove surface water from the work area. ■ Earthwork activities should nottake place during periods of moderate to heavy precipitation. ■ Slopes with exposed soils should be covered with plastic sheeting. GEOENGINEER� December6, 2021 Page 10 File No. 24 59-003-00