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,,per. _ <br /> �' '� it <br /> r <br /> ' - - <br /> 40th Anniversary 47 <br /> 19 -198 <br /> BROWN AND CALDWcLL __--_-- y <br /> CONSULTING ENGINEERS Scruire facel rare 1117eien(y <br /> September 9, 1987 <br /> Mr. H. C. Winsor i J <br /> Manager, Retail Marketing <br /> Environmental Engineering <br /> ARCO Petroleum ProductE Company rf9ViF;i:?:� ;Irtl. I14,TLTff <br /> 515 South Flower Street <br /> Los Angeles, California 90071 <br /> Subject: Addendum to the May 21, 1987, Problem ASEessmont Report <br /> ARCO Service Station 434, Lodi, California <br /> Dear Mr. Winsor: <br /> In June 1987, ARCO Petroleum Products Company (ARCO) , the California <br /> Regional Water Quality Control Board, Central Valley District <br /> (Regional Board) , San Joaquin Local Health District (County) , and <br /> } the City of Lodi (City) agreed to additional investigative work in <br /> the vicinity of ARCO Sei.vice Station 434 in Lodi. The. objecLives <br /> f were: (1) to see whether a hydrocarbon plume beneath Station 434 <br /> 5. had migrated off site, both downgradient and/or in the direction of <br /> Municipal Well 12 (Well 12) , (2) to investigate the soil quality <br /> near the site of the original leak, and (3) to gather additional <br /> information pertinent to the design of a remedial system. The City <br /> has continued to hold Well 12 out of service since the leak was <br /> reported in December 1986. <br /> On July 8, 1987, the County reviewed and approved Brown and <br /> € ! C.aldwell's (BC) June 29, 1987, work plan (enclosed as Exhibit A) <br /> describing the additional work. This additional work entailed <br /> installing one monitoring well at Well 12, two monitoring wells on <br /> American Savings and Loan (American Savings) property, and two soil <br /> ti <br /> boreholes at the ARCO station. <br /> Jud 1987 Investigation <br /> i The additional investigative work was conducted by BC in July <br /> 1987. The work was conducted as described in BC's work plan. This <br /> addendum to the Problem Assessment Report presents the results of <br /> I ; that work. <br /> Locations of all wells and borings installed to date are shown on <br /> Figure 1. Also shown on Figure 1 are absolute <br /> g groundwater elevation <br /> -' -- �;- contours foC__._the area —Borehole logs--are shown -in -Exh-iliit B—and <br /> monitoring well construction details are shown in Exhibit C. With <br /> f the exception of well development, field methods used by BC in the <br /> July 1987 work are the same methods used in the April 1987 investi- <br /> gation. These methods are discussed in Chapter 2 of the Problem <br /> {; Assessment Report. The three wells installed in July 1987 were <br /> ( <br /> i '„„ 7235STREET SACRAMENTO,CA 95814•(9161444-0123 <br />