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Antonia Vorster -2- 4 August 1988 Since the primary contaminant of concern at the site is total dissolved solids ( salt) which is easily and accurately measured in the field by electrical conductivity, Southwest Hide should seriously consider an open ended drilling program where additional well numbers and locations are determined based on real time field results as drilling progresses. This approach could lead to an single phase of drilling which can save both money and time. Additionally, geophysical techniques prior to additional drilling may be very effective in delineating the plume extent and potentially reducing the number of monitoring wells needed. 2. Two objectives exist regarding source definition in the pond area: delinea- tion of the identified soil contamination west and south of the ponds, and determination if the ponds are leaking. The proposed soil borings will riot adequately meet either objective. The proposed borings west of Pond #1 will not be sufficient to delineate the complete extent of contamination. Addi- tional borings, or an open ended program as described above for monitoring well installation, are needed . To determine if the ponds are leaking, suction lysimeters and/or geophysical techniques should be considered in addition to, or possibly in lieu of, soil borings around all sides of the ponds. If it cannot be definitively shown that the ponds are not leaking, retrofitting per Suchapter 15 will be required. 3. The proposal to drill and log a 100 foot borehole for additional strati- graphic information is reasonable. However, completing the borehole as a well by grouting the lower portion may increase the local TDS and confuse the sampling results. A bentonite plug may be placed to isolate the grouted portion of the borehole from the screened portion, otherwise samples from this well must be analyzed for specific minerals to determine if elevated TDS levels result from contamination or grout. 4. Descriptions and sample results from the two old production wells discovered northeast of the hide processing facility need to be included in the report. These wells should remain open only if they are useful sampling points or Possible e:tract'on wet-IS. T they remain open, measures Must bye" t'k-n to prevent infiltration and/or cross contamination through the wells. Otherwise the wells should be properly abandoned as soon as possible. 5. In addition to the above, I also have the following relatively minor comments: a. The description of well construction should mention that logging was accomplished using continuous cores; b. Sampling and purging procedures need to be included in the work descrip- tion section; c. Actual QA/QC results (standards, duplicate,, spikes, blanks, etc. ) need to be included with the analytical results, not just a description of the procedures;