6200 12TH DR SE Geotech Report 2022-10-25

Catholic Housing Services JN 16298 November 1, 2016 Page 2 The test borings were drilled on October 18, 2016 using a track-mounted, hollow-stem auger drill. Samples were taken at approximate 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 Plates 6 through 8. Soil Conditions The upper soils revealed in the test pits and borings was very consistent, consisting of loose to medium-dense, unengineered fill soil that was generally comprised of gravelly silty sand. We suspect that this fill soil was imported to the site from a nearby reservoir site. The depth of the fill varied from approximately 10 to 27 feet. Native soils were revealed below the fill soils. The native soil consisted mostly of gravelly silty sand, but some layers of less silty sand were revealed. The native soil directly below the fill was generally in a loose to medium-dense condition. However, the soil became very dense at depth ranging from approximately 13 to 35 feet, with the greater depths located on the western side of the property. The test borings were the deeper explorations, and they extended to a maximum depth of approximately 41 feet. Groundwater Conditions No groundwater seepage was observed in the explorations, 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. It should be noted that groundwater levels vary seasonally with rainfall and other factors, with the highest and/or the most flow of groundwater generally occurring in the winter and early spring months. It is possible that groundwater could be found in more permeable soil perched on the very dense native soils during this time period. 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 only at the locations tested. Where a transition in soil type occurred between samples in the borings, the depth of the transition was interpreted. The relative densities and moisture descriptions indicated on the test pit and boring logs are interpretive descriptions based on the conditions observed during excavation and drilling. The compaction of test pit backfill was not in the scope of our services. Loose soil will therefore be found in the area of the test pits. If this presents a problem, the backfill will need to be removed and replaced with structural fill during construction. GEOTECH CONSULTANTS,INC.