SITE INFORMATION AND CORRESPONDENCE

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DDT Meeting -2- 13 July 1987 Three basic tasks for further definition of the extent of contamination were proposed by WCC: 1. More soil borings southwest of the sewage ponds (Area 1) to search for contamination hotspots. If samples from these borings do not contain contaminant levels significantly higher than those previously found, WCC does not intend to propose mitigation measures for soil contamination. 2 . Two well clusters should be placed off-site, one down- gradient from area 2 and one down-gradient from area 3 . The proposed placement of these clusters is thought to be beyond the edge of the contaminant plume. WCC feels the contaminant plume in area 2 should be fairly well defined by the proposed well cluster. Placement of the well cluster to define the plume in area 3 is thought to go beyond the optimum placement, but is proposed due to the problem of placing wells in a mature walnut orchard. 3 . WCC proposes to develop a ground water model based on data available from area 2 . They intend to apply this model to area 3 in order to define the extent of contamination, rather than placing wells to determine this. We were told that only ten more well completions with a total of 1200 feet could be constructed in this next phase of work. Reents pointed out that the RI/FS was written so that the scope was total definition of the ground water contamination. REGIONAL BOARD CONCERNS Regional Board representatives voiced concern with the proposal that Area 3 contamination be defined using a model rather than with data gathered from monitoring wells. Placement of monitoring wells to define the contaminant plume was discussed. All parties agreed that the best place to locate monitoring wells, based strictly on technical criteria, is in a mature walnut orchard owned by Mr. Raspo. Strong objections to placing the wells in the orchard were voiced on behalf of Mr. Raspo by DDT and USAEDH representatives. They claimed that well construction would result in damage to the orchard. Ms. Vorster asked if the objection to placing wells in the orchard was strictly a cost concern. We were told that Mr. Raspo is very proud of the orchard, and that DDT considers this a public relations matter. They believe he is afraid of losing this orchard to the Department of Defense which originally condemned some of his property in the early 1940's to build DDT. Regional Board staff is also not convinced the soil contamination does not require mitigation. Even though soil boring samples showed low levels of contaminants when analyzed, soil gas sampling results indicated well defined sources with significant levels. This along with the fact that ground water beneath the source areas presently exists indicates that source control may be warranted.