3505 SHORE AVE 2016-01-01 MF Import

Geotechnical Engiueering Lettcr 3505 Shore Avenue Dack Addition Evcrett,Weshington May 26,2010 NGA Filc No.827110 Page 8 water flow is encountered during cons►ruction,this flow should be diverted around areas to be developed and away from the stcep alope,and the exposed subgrades should be maintained in a scmi�dry condidon. If wet conditions are encountercd, altemative site stripping and grading techniques cnight be necessary such as covering exposed subgrade with a layer of ctushed rock for protection. If wet conditions are encountered or construction is attemptcd in wet weather, the sub�sde should not be compacted as this could cause furihcr subgrade disturbence. In wet conditions it may be nxessery ro cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protxt the moisture sensitive soils from disturbance by machine or foot traY�ic during conshuction. The preparcd subgrade should be protecced from constcuction hafTic and surface water should be diverted rround prepared subgrade. Stmcture Setbacks Unceriainties releted to building along the top of stcep slopes are typically addmssod by the use ot building setbacks. The purpose of the setback is to establish a"buffer wne" between the structure and the top of the slope so that ample room is allowed for nocmal slopc rocession during a reasonable life span of the snucture. In a general sense,the greater We setback,the lower the risk of slope failures to impact the structure. From a geological standpoint, the setback dimension is based on the slope's physical c6azacteristics, such as slope height, surfece angle, material composidon, end hydrology. OtLer facW:s such as historical slope activity,iate of rcgression, and ffie type and desiied life span of the development are important considerations as well. In our opinion,the proposed setback of over 50 fat&om fl�e top of the steep slope to the deck foundations should be adequate and provide a reasonable usable life span for tLe shucture. This setback frnm the steep siope should reduce potential impact oF the planned development on the steep slope,and to also reduce lhe risk of undermining the residence should any slope failurcs take place. We should be retained to evaluate the foundation selback distances and subgrade soil prior to placing foundalion fonns. Any proposed development within the sdback area, otl�er lhan light decks ar patios, should be the subject of a specific geotechnioel evaluation. Under no circumstances should water be allowed to concenvate on the slopes,during or ufler conswcflon. NELSON GEOTECHNICAL ASSOCIATES, INC. � ! �,� � r es�