3530 COLBY AVE COCOON HOUSE Geotech Report 2022-10-25

Cocoon House JN 16422 November 3, 2016 Page 2 The test borings were drilled on October 11, 2016 using a small track-mounted, hollow-stem auger drill. Samples were taken at approximate 2.5- to 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 3 through 6. Soil Conditions The test borings generally encountered native, medium-dense to dense silty sand at a depth of 2.5 feet below the existing site grade. However, 7 feet of loose fill soils with wood debris were encountered in Test Boring 3 between the existing church building and the adjacent alley. It is possible that this fill is due to an existing or old utility trench. Dense to very dense sand was encountered below the fill or the native silty sand at depths ranging from 7 to 12 feet. Very dense silty sand was encountered at a depth of 21 feet in Boring 4 below the cleaner sand layer. No obstructions were revealed by our explorations. However, debris, buried utilities, and old foundation and slab elements are commonly encountered on sites that have had previous development. Groundwater Conditions Perched groundwater seepage was observed at a depth of 18 feet in Test Boring 4 north of the proposed new building. However, the test borings 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 levels and greatest amount of groundwater revealed in the winter and early spring months. Some groundwater could be found perched on dense soils at more shallow depths during this 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. If 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 boring logs are interpretive descriptions based on the conditions observed during drilling. CONCLUSIONS AND RECOMMENDATIONS GENERAL THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FINDINGS FOR THE PURPOSES OF A GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSIONS ARE GEOTECH CONSULTANTS,INC.