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M <br />M <br />M <br />M <br />� <br />CASCADE GEOTECHNICAL <br />March 27, 1991 <br />The December Partnership <br />Job No. 9102-18G <br />Paqe 5 <br />surface. <br />The eite lies within an area that has been qeologically mapped as <br />"Vashon Till", as shown on the ��Geologic Map of the Everett 7.5- <br />Minute Quadra�qle, Snohomish County, Washinqton", by ,7ames P. <br />Minard, 1985. The native denae to very denae silty sand that we <br />observed in the test pits is consistent with this classification. <br />CONCLV8ION8 AND RECOM!(ENDATIONB <br />Zt is our conclusion that the uncontrolled fill, organic soils and <br />peat noted above the native dense to very dense silty sand are <br />unsuitable for supportinq structural loads ae unsuitable <br />differential settlement would occur. The site appears suitable for <br />the propoRed development if special precautions arP used to <br />minimi2e 2he potential for differential settlement. We recommend <br />that the structural loads including slab-on-grade floora be <br />supported on a deep seated foundation which penetrates below the <br />fill and organic material into the native bearing soil. These <br />foundations should also be designed to resist potential downdrag <br />forces on the piles or other deep foundations. <br />� The on-site soils are extremely moisture sensitive due to the <br />t' amounts of fine-grained material. Due to the proximity of the <br />�A <br />wetland and the on-site moisture sensitive soil�, we recommend that <br />� all earthwork take place durinq the dry summer months to avoid <br />excessive costs and construction problem3 associated with soil <br />�deterioration and the oif-site effects of sedimentation and <br />_ erosion. We recommend that we be engaqed to review the final plans <br />once they become available to provide any alternative or additional <br />� recommendation� as necessary. <br />� <br />A <br />