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a <br /> 1386 EAST IBEAMER STREET <br /> ECa� ESTERN WOOD.WD, CA 95695-9603 <br /> GEO—ENGINEERS <br /> � FAX(916)662-0273 <br /> z. :>�'� <br /> CALIFACON'1'RACTOIi#513857 A CO�tPORATION��y=,a ics, ,-",-" o (916) 668-5300•- <br /> f1 REGISTERED GEOLOGISTS OCT 2 4 1981 <br /> Mrs. Diane Hinson, REHS VlrO`!i�'11`1fAti0tober 7, 1991 <br /> San Joaquin County Environmental Health <br /> PO Box 2009 <br /> Stockton, CA 95201 <br /> RE: Destruction of shallow vapor extraction „fells and completion <br /> of initial vapor extraction for soil reme-diation to the 40 foot <br /> depth. , Regal Station 604, 1448 N. El Dorado Street, Stockton, <br /> California, Figures 1 and 2. <br /> Dear Mrs. Hinson: <br /> Western Geo-Engineers has completed the first phase of remediation <br /> to the above mentioned site, removing aged gasoline range <br /> hydrocarbons from the soil in the vadose zone beneath the tank <br /> field and pump island areas. This finalized the clear.-up of <br /> contaminated soil at this site. The removal of the hydrocarbon <br /> contaminants from the soil was performed in two phases: PHASE I, <br /> Overexcavation and aeration. PHASE II, In-Situ Vapor Extraction. <br /> Phase I. <br /> i <br /> OVEKIEXCAVATION AND AERATION OF CONTAMINATED SOIL. <br /> SITE HISTORY <br /> Five 10,000 gallon carbon steal single walled tanks were removed <br /> from the site on September 26-28, 1989. The tanks were designated <br /> as and contained the following: Ti (ID# 39-1081-1)-nearest <br /> budding, premium unleaded gasoline, T2 (ID# 39-1081-2)-north of <br /> T1, regular gasoline, T3 (ID#F 39-1081-3)-north of T2, regular <br /> gasoline, T4 (ID# 39-1081-4)-north of T3, unleaded gasoline, and <br /> T5 (ID# 39-1081-5)-north of T4, unleaded gasoline. Only tank T4 <br /> showed any idication of failure, the bottom of the fillup end had <br /> corrosion with possible pin hole leaks. s <br /> } <br /> Sampling of the tank excavation occured on Eeptemkier "29; 1989 and <br /> sampling of the product line trenches occuring on October 5, 1989, <br /> see Table 1 and Figure 4A. <br /> Over excavation of the tank excavation occured and was sampled on <br /> June 26, 1990. The excavation was expanded vertically to the 25 s <br /> foot depth. The pump island area was demolished and over <br /> excavated to the 13 foot depth on August 22, 1990, with samples be <br /> obtained on that date, see Table 1 and Figure 45. These two over <br /> excavations removed the contaminated soil from beneath the tank <br /> - <br /> --field and the-_c-enter-pump.island.- Theeastern_-and-western--pump - <br /> island excavations were expanded and deepened on September 6, 1990 <br /> to the 20 foot depth and sampled, see Table I and Figure 4C. <br /> During all over excavations a HNu photoionizing detector was used <br /> " to field screen for the presence of contaminated . soil or more <br /> page 1 <br />