SITE INFORMATION AND CORRESPONDENCE_1988-1991

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Antonia Vorster -8- 25 August 1989 location and consistency of results. Such changes require a data review which should be accomplished for the most part by simply qualifying and compiling the analytical database as discussed above. This is an approach, which can save substantial money over time, that has been suggested to USATHMA and Hunter/ESE in the past. b. Determination of the "10 worst leaks" (page 3-44 of Work Plan) as part of the sanitary/storm sewer study should be reviewed by the Agencies. The criteria, locations, and number of sites to investigate should be acceptable to all parties before any sampling commences. C. The proposed methodology for statistically comparing on-site and off- site Arsenic levels (page 3-52 of the Work Plan) is questionable. Determining the "on-site population" of Arsenic values is crucial . On- site Arsenic sampling has been coincident with TCE sampling (an issue previously pointed out) and has included both apparent "hotspots" and non-contaminated (background) areas. To consider this as a single "population" for comparison with off-site values would be in error. Similarly, care must be taken when collecting off-site samples to establish "background" levels; inclusion of off-site Arsenic sources which skew the population does not provide a legitimate comparison with on-site values. d. We questioned USATHMA's methodology for Selenium analysis in our 27 January 1988 comments (page 4, comment 12) but have never received a response. The present Work plan proposes a USATHMA method SD21 which is not referenced or described. It is still not clear if Selenium analysis is appropriate. e. Collecting split spoon samples at 5-foot intervals for the first 100 feet, and 10-foot intervals for the remainder , with mud-rotary drilling is neither adequate nor standard practice in the industry. Proper geophysical logs (spontaneous potential , resistivity, and lateral resistivity) or continuous cores (split spoon, pitcher barrel , or wire line) should be used. Geophysical logs are easily both the least expensive and time consuming, and in many ways probably the most useful . Geophysical logs must be produced with proper equipment and methodology, something we have witnessed Hunter/ESE not doing in the past. Regardless of the logging method used, Iithologic screenings, along with proper solids control in the mud, should also be collected and logged for control . f. The method of well development should be specified. The proposed method should accomplish surging of the well for adequate development. g. Adequate purging should be based on equilibration of ground water parameters (temperature, conductivity, pH) , not simply casing volumes removed.