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i <br /> 1 <br /> of native lodgement till sediments. The existing ground surface elevation within the vault <br /> footprint is approximately 518 feet. It is our understanding that the vault bottom elevation will <br /> be at 514.8 feet, such that the vault will be cut into the existing soils at least 3 feet. <br /> Based our previous subsurface exploration and the provided site plan, we anticipate that the <br /> vault footings will bear on very dense lodgement till. Lodgement till consists of an unsorted <br /> ' mixture of sand, silt, clay, gravel, and occasional cobbles. It was deposited at the base of an <br /> active continental glacier and was subsequently compacted to a very dense condition by the <br /> weight of the overlying glacial ice. As such, lodgement till typically possesses high-strength <br /> and low-compressibility attributes and generally forms stable slopes at the inclinations present <br /> in and around the subject site. Given the proposed vault grades and the observed subsurface <br /> conditions underlying the site, it is our opinion that the construction of the detention vault at <br /> ' the proposed location will not significantly increase the risk of slope movement on the subject <br /> and adjacent properties. <br /> ' If you have any questions regarding this letter, please do not hesitate to call. <br /> Sincerely, <br /> ' ASSOCIATED EARTH SCIENCES, INC. <br /> Kirkland, Washington <br /> 1 <br /> ,/0 <br /> ts <br /> �1 ny c SJ c) ., <br /> O'�S C T E?` <br /> Kurt D. Merriman, P.E. <br /> ' Senior Principal Engineer <br /> 1 <br /> 1 <br /> 1 <br /> KDM/pc <br /> KE 140233A 1 <br /> Projects\20140233\KE\WP <br /> 2 <br /> { <br />