2201 100TH ST SW AD SYSTEMS 2022-03-07

GeoTest Services, Inc. April 25,2017 2201 100th Street Southwest, Everett,WA Job No. 17-0186 CONCLUSIONS AND RECOMMENDATIONS It is our opinion that subsurface conditions at the site are suitable for the proposed construction of the proposed buildings, provided that the recommendations contained in our geotechnical engineering report are incorporated into the project design. As discussed previously, the borings generally encountered native, loose to medium-dense, silty sand (weathered till) either directly below the existing asphalt, or below the existing base fill as encountered in B-1. The weathered till overlies dense to very dense, glacial till. We recommend that the loose fill soils be removed from the building footprint down to the native, weathered or unweathered glacial till soils. The new building can be constructed with conventional continuous or individual spread foundations bearing either directly on the weathered on unweathered till soils, or on compacted structural fill placed atop these soils. Dense, unweathered till encountered at depth is unlikely to require much preparation. However, if foundations will be supported on the near-surface weathered till, the surface should be compacted to a firm and unyielding condition with a smooth-drum roller or other appropriate piece of construction equipment. Further recommendations regarding the placement and compaction of structural fill can be found in a subsequent section of this report. Mottling was observed in the test pits atop the dense to very dense, native soils. This is a possible indicator of perched groundwater conditions. Thus, it would not appear that the native soils would be suitable for infiltration. Depending on final grades, it may also be necessary to construct an interceptor drain, or French drain, on the northern, upslope side of the subject property in order to help divert surface water away from the new building. As preliminary grading plans had not been completed at the time that this report was written, we can provide additional recommendations regarding site drainage upon request. Site Preparation and Earthwork The portions of the site to be occupied by proposed foundations and floor slabs should be prepared by removing any existing topsoil, deleterious material and significant accumulations of organics from the area to be developed. Prior to the placement of any foundation elements or structural fill, the exposed subgrade under all areas to be occupied by soil-supported floor slabs and spread or continuous foundations should be recompacted to a firm and unyielding condition and proof rolled with a loaded dump truck, large self-propelled vibrating roller, or similar piece of equipment applicable to the size of the excavation. The purpose of this effort is to identify possible loose or soft soil deposits and recompact, if feasible, the soil disturbed during site excavation activities. Proof rolling should be carefully observed by qualified geotechnical personnel. Areas exhibiting significant deflection, pumping, or over-saturation that cannot be readily compacted should be overexcavated to firm soil. Overexcavated areas should be backfilled with compacted granular material placed in accordance with subsequent recommendations for structural fill. During periods of wet weather, proof rolling could damage the exposed subgrade. Under these conditions, qualified geotechnical personnel should observe subgrade conditions to determine if proof rolling is feasible. Page 4 of 13