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rer . riar ,r, uryufwrt rroject 939-u1.uZ <br /> Feburary 16, 1988 <br /> Page 2 46 <br /> measured on May 13, 1987 in the four monitoring wells (MW-1, MW-2, <br /> MW-3 and MW-4) at the site indicated a ground-water flow direction <br /> from east to west. The hydraulic gradient calculated between <br /> Wells MW-2 and MW-4 for that time is 0.00363. <br /> The porosity, n, of the aquifer materials, was assumed to be 0.2 based <br /> on values presented by EPA in their manual entitled "Criteria for <br /> Identifying Areas of Vulnerable Hydrogeology under RCRA, Statutory <br /> Interpretive Guidance Manual , Interim Final , July 1986." <br /> On the basis of the values presented above, the velocity of ground <br /> water under -the site in May 1987 was approximately 169 ft/yr. <br /> The Subchapter 15 requirement to "determine the velocity and direction <br /> of ground-water flow under the waste management unit" (Article 5, <br /> Section 2556(a)(4)] can be satisfied by using the values for k and n <br /> presented above, calculating the hydraulic gradient from ground-water <br /> elevations measured in the site monitoring wells, and calculating the <br /> ground-water velocity using the formula also presented above. <br /> Should you have any questions, please call . <br /> Very truly yours, <br /> EMCON Associates <br /> Leona r Alvare <br /> Vice Pre ident <br /> LA:lad <br />