SITE INFORMATION AND CORRESPONDENCE_1

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DEL MONTE/DISCO Page 2 In accordance with current regulation the responsible parties shall perform a comprehensive documented receptor survey surrounding the site for the purpose of determining potential human/ecological health risks and prioritization purposes. This survey shall address exposure pathways including dermal, inhalation and ingestion routes. Appropriate documentation shall support any claim of no significant risk. Regarding water supplies, all known wells and surface water locations shall be reported in tabular and graphical formats. Please include boring logs, screened interval, current status, historical, present and projected pumping rates with seasonal use patterns when available. During the next quarterly monitoring event the responsible parties shall at a minimum obtain ground water sampling data from all wells within a 200 foot radius of MW-DIS-1 to include all piezometers and MW-DIS-4 and 8S for the purposes of determining current dissolved constituent concentrations. Please analyze and report results for ground water samples from these wells for BTEX, MTBE, and TPH as gasoline including standard monitoring well physical data as provided in past reports. All other wells should be monitored for physical parameters to aid in gradient determination and static water elevation. PHS/EHD formally requests your compliance with the directive above and requires the submittal of a work plan to this agency for review no later than April 15, 1997. PHS/EHD is aware that a draft work plan has been prepared and circulated to the responsible parties and their legal counsel for comment prior to the issuance of this correspondence. In the event the above listed directives are not included PHS/EHD will add these scope of work directives to the work plan during the approval process. The following section of this correspondence is dedicated to comments on the content of the quarterly monitoring report dated February, 1997. Figure 3 plot plan view shows a "ZONE OF SIGNIFICANT BTEX CONTAMINATION IN GROUNDWATER'. This depiction is inaccurate and must be modified considering the absence of lateral and vertical definition at this site particularly in the down gradient direction. PHS/EHD does not concur with a majority of the "Summary/Conclusions" presented in the February 1997 report. Any comments regarding the stability of BTEX and TPH as gasoline concentrations in the plume or at the fringe at any site where delineation is incomplete is strictly speculative as is the case at this site. Benzene concentrations have fluctuated from 32,000 ug/1 as of 6/26/91, to 64,000 ug/l as of 7/20/93, to 65 ug/1 as of 10/18/95, to 8,900 ug/l as of 12/20/96 in MW-DIS-1 alone disqualifying the reliability of any plume stability references. The report also states that "Based on the water level gauging and groundwater sampling during August 1996, the following summary points are provided below:" ... "MTBE was not detected in any of the monitoring wells sampled." page 17, bullet number 5, under the "Summary/Conclusions" title. This statement is incorrect and misleading. MTBE has been detected and reported in Table 3 of this report in samples from MW-DIS-2 at 4.3 ug/1 on 8/15/96 and due to a 1:200 dilution in MW-DIS-1 reported as <100 ug/l. The actual concentration of MTBE is, therefore, unknown which prompted the directive regarding future sampling,dilutions, and quantification refinement above. Please correct this error.