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i <br /> September 9, 1987 <br /> :# Mr. H. C. Winsor <br /> Manager, Retail Marketing <br /> -^� Environmental Engineering <br /> I ARCO Petroleum Products Company <br /> 515 South Flower Street <br /> _f Los Angeles, California 90071 017-3214-07/1 <br /> I Subject: Addendum to the May 21, 1987, Problem Assessment Report <br /> i ARCO Service Station 434, Lodi, California <br /> FS <br /> '! Dear Mr. Winsor: <br /> j In June 1987, ARCO Petroleum Products Company (ARCO) , the California <br /> Regional *dater 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 /> s the vicinity of ARCO Service Station 434 in Lodi. The objectives <br /> ( were: (1) to see whether a hydrocarbon plume beneath Station 434 <br /> 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 /> Caldwell's (BC) June 29, .1987, vork plan (enclosed as Exhibit A) <br /> describing the additional work. This additional work entailed <br /> in one monitoring well at Well 12, two monitoring wells on <br /> ' American savings and Loan (American Savings) property, and two soil <br /> �I boreholes at the ARCO station. <br /> e July 1987 Investi_gat•ion <br /> 1:� T <br /> 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 /> ` a addendum to the Problem Assessment Report presents the results of <br /> 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 groundwater elevation <br /> contours for the area. Borehole logs are shown in Exhibit B and <br /> i.e monitoring well construction details are shown in Exhibit C. With <br /> the exception of . well development, field methods used by BC in the <br /> --July-1987-work-are-the-same-methods--usedin--the-Apr-il__198.7--investi- <br /> gation. These methods are discussed in Chapter 2 of. the Problem <br /> . t Assessment Report. The three wells installed in July 1987 were <br /> .i <br /> r <br />