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Rcid Middlclon & Assueiaics <br /> Scp�emhcr 2, 199? <br /> Pagc : <br /> Pr��P�75�d pund expansiun will consist uf lateral enlargemenr of the pond area widiout a change <br /> in design water surface elevations. Thereti�re, mndifica:�on of the dam will not he necessary. <br /> Prior to modification of the pond, however, the City of Gverett requcsis an evaluatinn of thc <br /> existing stnrmwa�er detentiun F�cility and surrounJing area. <br /> SCOPE <br /> The purpose of our g�itechnical engineering scrvices is to evaluate suhsur(ace soil and <br /> ground water conditions at the site as a ba�is for evaltiating the existing condition o(the earth <br /> dam and for developing gmtechnical recommendations for enlargement of the delention pond. <br /> Our specific scope of our services includes the following tacks: <br /> �. Review availahle information regarding design and construction of the earth dam anJ <br /> delemion pond, including J�.eign drawings, suhsurface explurations and daily construclion <br /> monitoring ficld repans. <br /> 2. Perform a surfAce reconnaissanee of the site, panicularly in the dam ahutment areas, a� <br /> evaluate seepage and erosion conJitions. <br /> 3. Urill threc augcr horings to depths ranging from IS to 31.5 feet in the dam emhankmem, <br /> and excavate five hackhoe t�.et pits to depths ranging from 10 to 14 feet in the vicinity ul <br /> the existing detention pond. <br /> 4. Cvaluate pertinent physical and engineering characteristics of the siie soils hased u❑ <br /> lahoratory� t�,cts performed on samples oMained from the exploratiun�. <br /> 5. Evaluate the s�ahility and permeahility of the existing earth dam. <br /> 6. Gvaluate Ihe soil permeahiliry in the general area uf the existing detentiun pund. <br /> 7. Pruvide g�rqechnical recommenda�ions for Ihe pruposed enlar}emrm nf thr exisiinE <br /> Jetention pond. <br /> SITE DESCRIPTION <br /> SUHFACE CONDITIONS <br /> The slormwater detention facility, which cuntAins surface wa�er runoff from portions of the <br /> Fluke Manufacturing facili�y and the 13oeing facility, is locnt�d in a natural ravine that Vends <br /> generally nnrth-south, as xhown un ihc Site Plan, I'igure 2. The native ravine slupes, which are <br /> inclinul at npproximately 20 to 50 penent, are vegetntui wi�h mature secnnd-gruwth furest <br /> consisting of cedar, tir, yew, and alder trees with dense undergrowth. The earth dam crosxes <br /> the ravine in nn easl-west Jirection. 7he upstream and duwnstream faces of the dnm slupe at an <br /> inclinatiun of 33 percent, or 3H;I V Qioriwmnl:vertical). 7'he crest of the Jam, which measures <br /> appruximatcly 40 feet wide hy ISO feet long, is IucaieJ at nn clevation uf approximately 4G8 feei <br /> (Bocing Jnlum). lhe crest is .i�pruxima�cly ?0 Icet ah�wc Ihc ups�reant Isouth) toe and 30 fect <br /> c , „ r �� F � �� , . � . <br /> i-ilv rvn. ul2q Icn u lU <br />