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� <br />Septetnbcr 23, 2007 <br />Mr. Jeff \Vhitney/l3rookstone Developmem <br />LRA Job No. 7A08d <br />Pagc d <br />thc advancc ouhvash soil unit rclativcll' easily. The intiltrating stonnwatcr would perc;i on thc <br />underlying impen�ious Whiclbey fomiation. The perched groundwater would (low laterally along <br />thc sur�ace of Qic \�Jhidbcy formation and cmcrgc out thc slopc whcrc thc �1'hidhcy fomiation is <br />cxposcd cn the slopc. <br />s��ni;u.t rv oF s�,orr <br />l�he steep slope behveen Mukilteo Lane cmd lhc railroad tracks appears to be composcd of <br />advance ouhvash dcposits ovcrlying Whidbcy formation. Thcsc hvo soil miits arc nomially <br />stable if thc groundwater scepage emcrging oul of thc slone from the contacl of these hvo soil <br />units can be conu'olled. Thc ��egetation cover on die slope will suck up a good portion oC the <br />grounclwater undcr the slopc and the roots of ihe vegelation would tcnd lo anchur the soil <br />particles in place. �I�hcreforc, thc prescnce of thc trccs, shn�bs and bnish on lhe slopc would hclp <br />stabilize thc slone. On thc othcr hmid, lar6c mature lrees with a bcnt ncar the basc of their tnmks <br />or with a do�+�nhill Ican would put a loading on the slope. Where the surticial soils are saturaled <br />and wcakcncd by slormwatcr, thcsc trces ntay topplc and causc slidcs tu occur on thc slopc. <br />RF.COMMENDATIONti <br />Cutting or trimming largc maturc Irecs on slonc �vill reduce loading on thc slope ancl, thcrefore, <br />cnhancc stahilily of thc slopc. Vcgclation covcr on thc slopc, howcvcr, should bc maintaincd <br />and/or restored to provide erosion protection and slope slabiliiation to ihe tilope. 'l�hcrefore, hvo <br />options t�re recommended hercin for cutting trees on ihe slopi; in order not to compromising ihc <br />slahil ity ��f Ihc slopc. <br />fhc �irst uption is tii allo�v cut-down of largc iuoturc trccs on thc slopc. 'I'hcre should bc a <br />rcplantinb plan to rcplacc Ih� cul-down trccs �vith dcep-rooting, short lo medium tall uccs. "Chc <br />Iree cutting �nd replanting should proceed and bc completed in U:e Spring and Sununcr months <br />LIU & ASSOCIATCS, INC. <br />