3214 BROADWAY Geotech Report 2022-10-25

American Property Development ES-0599.06 June 9, 2016 Page 6 Revised October 16, 2017 Structural Fill We anticipate structural fill placement will generally be required behind foundation walls and within utility trench excavations. Structural fill may also be necessary in slab-on-grade areas. Where structural fill is necessary below the proposed building foundations, a suitable crushed rock material should be used. In our opinion, clean crushed rock consisting of one-and-one-half inch to two-inch aggregate should be used below foundations where fill placement is necessary. Where structural fill is utilized outside of the foundation areas, a suitable granular soil with a moisture content that is at or near the optimum level should be used. The native silty sand soils can be considered for use as structural fill provided the soil is at or near the optimum level at the time of placement. The native soils have a moderate sensitivity to moisture, and will become unstable if exposed to excessive moisture. If the native soils cannot be successfully compacted, the use of an imported soil may be necessary. Imported soil intended for use as structural fill should consist of a well graded granular soil with a moisture content that is at or near the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well graded granular soil with a fines content of five percent or less defined as the percent passing the #200 sieve, based on the minus three-quarter-inch fraction. Structural fill is defined as compacted soil placed as wall backfill and in slab-on-grade, utility trench, and roadway areas. Soils placed in structural areas should be compacted to a relative compaction of 90 percent, based on the maximum dry density as determined by the Modified Proctor Method (ASTM D-1557-02) and placed in maximum twelve-inch lifts. In pavement areas, the upper twelve inches of the structural fill should be compacted to a relative compaction of at least 95 percent. As previously mentioned, structural fill below foundations should consist of a suitable crushed rock material. Erosion Control In general, control of off-site erosion for this project will likely be limited to construction entrances. Silt fencing should be installed as appropriate, and as needed along the site perimeter. Construction entrances should consist of quarry spalls underlain by a non-woven filter fabric. Quarry spall thickness will depend on subgrade stability at the entrance, but should typically be at least six inches. Shoring Recommendations We anticipate cuts of up to approximately 15 feet will be required to construct the below grade garage levels. Where sufficient space is available, a portion of the garage level excavations may be completed using open cuts. Temporary shoring or a combination of shoring and temporary slopes will be necessary where the building will be sited in close proximity to the property limits. Earth Solutions NW,LLC