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1 <br /> • WEISS ASSOCIATES M(i <br /> Gordon Boggs / 10 June 1988 / Page 5 <br /> downgradieDt of the western end of the excavation, where the highest concentrations of <br /> hydrocarbons in soil have been detected, Since, as shown on the boring togs included for <br /> your . convenience as Attachment A, the existing welts are not screened ,into the <br /> unsaturated zone, an additiunal ground water monitoring well will be installed <br /> downgradient of the northern end of the excavation. This well, identified as proposed <br /> monitoring well MW-4 on Figure t of our correspondence dated 30 March 1988 and also <br /> included here for your convenience, will be screened in the upper few feet of saturated <br /> soil and into the unsaturated zone. <br /> 5) ALTERNATIVE REMEDIATION OPTIONS <br /> Since high hydrocarbon concentrations in soil arc apparently only in unsaturated <br /> soil Immediately adjacent to the., ,excavation, the following remediation options are <br /> feasible for the site: <br /> 1) Soil excavation and subsequent treatment of the excavated material. A variety <br /> Of Uii&LAdiit 01JtIOL14 vj*L1 Lc apjilicd to rcducc hydrocarbon conccnrratlons In the <br /> removed soil. This is our preferred remedial option. Details of this <br /> recommended option are presented in Attachment B. <br /> 2) In-$itv biodegradation of hydrocarbons by Stimulation of naturally occurring <br /> microorganisms. <br /> 3) In-situ volatilization by vacuum and forced air venting. <br /> I <br /> 4) Passive remediation involving no action. <br /> A brief description and feasibility assessment of each of these options is presented below. <br /> ` i <br /> 1) Excavation and Treatment <br /> i <br /> This remedial option involves the excavation of hydrocarbon-impacted unsaturated <br /> roil 2nd gubtequent above-ground treatment of tho soil to reduce hydraearban <br /> concentrations to acce-piahle. Fe'-9z hlP treatment options for the soil once it is <br /> removed include: <br /> I <br />