3617 UPLAND AVE Geotech Report 2025-03-28

GeoTest Services, Inc. April 15, 2021 3617 Upland Avenue, Everett,WA Project No. 21-0375 Proposed Garage The subsurface explorations that were performed in the area of the proposed garage encountered approximately 2 to 2.5 feet of loose topsoil and fill soils before encountering loose to medium-dense,weathered Transitional Beds. Due to the loose to medium-dense nature of the native, weathered Transitional Beds, GeoTest also recommends that the native subgrade be recompacted to a firm and unyielding condition.The proposed residence can then be constructed with conventional continuous or individual spread foundations bearing directly on the remedially compacted native subgrade, or on compacted structural fill placed atop these soils. Slabs-on- grade can be supported on the existing fill soils, provided that the existing subgrade is recompacted to a firm and unyielding condition. Further recommendations regarding the placement and compaction of structural fill can be found in the Fill and Compaction section of this report. The previously placed fill soils are not suitable for the conventional infiltration of stormwater. The native Transitional Beds encountered in the explorations are glacially consolidated and contain a high percentage of fines. GeoTest anticipates that perched groundwater seepage may be encountered atop the low permeability fill as well as native Transitional Beds depending on the time of year and after an extended period of heavy precipitation. Perched seepage was present in TP-2, and because of the extent of fines observed on site, it appears that the fill and native soils are not suitable for the conventional infiltration of stormwater.GeoTest recommends that approaches other than infiltration be considered to address stormwater management on this project. Site Preparation and Earthwork The portions of the site proposed for foundations should be prepared by removing topsoil, deleterious material, significant accumulations of organics, and loose fill soils (if present). GeoTest anticipates between 2 and 7 feet of stripping to expose suitable subgrade soils within previously placed fill or native soils within the vicinity of the proposed development. As discussed previously, we expect that the thicker depths of fill will be present in the area of the upslope portion of the proposed house footprint. Prior to placement of any foundation elements or structural fill, the exposed subgrade under all areas to be occupied by soil-supported floor slabs, spread, or continuous foundations should be recompacted to a firm and unyielding condition.Verification of compaction should be performed by qualified geotechnical personnel. The purpose of this effort is to identify loose or soft soil deposits so that, if feasible, the soil disturbed during site work can be recompacted. 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 6