1903 W MUKILTEO BLVD Geotech Report 2022-10-25

' Dr. Hong Li JN 12084 May 10, 2012 Page 2 The upper approximately one-half of the slope is steeper than the lower half, and we observed a zone of seepage popping out of the upper, steeper, portion of the slope. SUBSURFACE The subsurface conditions were explored by drilling one test boring on the Li property, at the approximate location shown on the Site Exploration Plan, Plate 2. Our exploration program was based on the proposed construction, anticipated subsurface conditions and those encountered during exploration, and the scope of work outlined in our proposal. We also conducted two borings on the adjacent eastern Scriven property at the same time. The borings were drilled on April 9, 2012 using a small track-mounted, hollow-stem auger drill. Samples were taken at 5-foot intervals with a standard penetration sampler. This split-spoon sampler, which has a 2-inch outside diameter, is driven into the soil with a 140-pound hammer falling 30 inches. The number of blows required to advance the sampler a given distance is an indication of the soil density or consistency. A geotechnical engineer from our staff observed the drilling process, logged the test borings, and obtained representative samples of the soil encountered. The Test Boring Logs are attached as Plate 3. Soil Conditions The soil beneath the surface of the Li property consisted of a thin layer of fill soil over native sand, silty sand, and sandy silt with occasional gravels. The native soil beneath the fill was similar in composition to what we found on the Scriven property. The sand was loose beneath the fill to a depth of approximately 16 feet, and was medium-dense beneath that. This soil has not been glacially compressed. The sand became silty and dense below about 20 feet beneath the ground surface. This dense silty sand to sandy silt was encountered to the maximum depth reached by our explorations of 31.5 feet. Groundwater Conditions Groundwater seepage was observed at varying depths throughout the test boring conducted on the Li property. Groundwater was encountered at approximately 16 feet, perched atop the denser soils beneath about 18 feet. Significant groundwater was also encountered beneath about 30 feet below the existing ground surface. The test borings were conducted following a wet spring, but were left open for only a short time period. Therefore, the seepage levels on the logs represent the location of transient water seepage and may not indicate the static groundwater level. Groundwater levels encountered during drilling can be deceptive, because seepage into the boring can be blocked or slowed by the auger itself. Groundwater was also observed exiting the face of the slope in various locations, and at multiple locations exiting the toe of the slope, along the railroad tracks. It should be noted that groundwater levels vary seasonally with rainfall and other factors. We anticipate that groundwater could be found in more permeable soil layers and between the near-surface weathered soil and the underlying denser soil. The stratification lines on the logs represent the approximate boundaries between soil types at the exploration locations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration locations. The logs provide specific subsurface information GEOTECH CONSULTANTS. INC.