SITE INFORMATION AND CORRESPONDENCE_1988-1991

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David Wang, P.E. , Chief Page 5 March 6, 1991 o TCE is the dominant VOC in both the soil and the ground water. However, other VOCs have been identified. o The sources of VOC contamination at DDRW Sharpe are multiple and originated in several forms. Those sources are former disposal pits/trenches and/or spill areas. COMMENTS The Department' s comments are presented in two groups: 1) a general review to highlight main concerns and 2) specific comments on the subject report. GENERAL COMMENTS: Although the RI Report is to be considered a draft final document, the Department 's review finds several areas where data will have to be re-interpreted or additional data collected. Three specific areas of concern are: 1. Water Level Interpretation: Monthly ground water elevations were determined from October 1987 through September 1989 . These data were averaged and the resulting values contoured to produce Figures 9 . 0-2 through 9 . 0-5 . The Department is aware of our past general acceptance of this convention. However, with the development of DDRW Sharpe's computerized water level recording system, we feel this issue needs to be revisited. Recommendation: Recompilation of water level be considered based on computerized data. This data is important in order to substantiate the adequacy of well placement and plume definition, data illustrating the variation and frequencies of ground water flow directions should be provided. Flow directions should be based on recent water level surveys if historical data are not usable. 2 . Plume Definition: Plume definition is a dynamic process and subject to interpretation and best professional judgement. Plumes 4 and 5 have been significantly influenced by off-site agricultural well pumping. It is the Department ' s conclusion, from the data presented, that additional work is necessary to completely define Plumes 4 and 5.