SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Mr. Robert Garcia • - 3 - • 25 May 2000 12. In Table 4-2 (Summary of Analytical Results), "ND" is used to show that contaminants were not detected. In future reports, nondetections should be listed as "nondetect above the reporting limit" (e.g.,ND<0.050 mg/1). This information needs to be included for data points collected from December 1999 to the present. 13. The units used in the tables and plots are not consistent. Table 4-2 shows mg/1 for TEH concentrations, whereas the TEH Concentration Verses Time plots use 4g/1 for TEH. Leprino needs to confirm the listed units on the data plots and, for consistency, use the sante units for tables, plots, and maps. 14. Table 4-2 shows that analyses for BTEX and n-butyl-benzene were not performed during the December 1999 monitoring in several wells. However, the analytical data report shows that EPA Method 8021 B was performed and this method includes the chemicals listed above. The data table needs to be revised to reflect the actual analytical results. 15. The report presents several recommendations, including revision of the monitoring and reporting program (MRP) and abandonment of two wells (MW-15 and MW-17). We concur that revision to the MRP is necessary and a draft revised MRP is enclosed for your review and comment. I have the following continents on the recommendations which I discussed with Mr. Brendan Shine of HSI during our 5 May 2000 telephone conversation: • The report states, "Wells MW-2, MW-7, MW-8, MW-9, and MW-10 should only be used as water level measurement points..."We concur that data from these wells show consistent nondetections of TEH, BTEX, free-phase product, and n-butyl-benzene since November 1994, with the exception of two anomalous data points (i.e. explained as either false positives or laboratory error). Also, the wells are either upgradient or crossgradient of the contaminant plumes. Therefore,the draft revised MRP includes this change. • The report recommends elimination of n-butyl benzene from the MRP. We concur with this recommendation due to a lack of detections over several quarters in all site wells (except a reported false positive in March 1997). • The report recommends elimination of BTEX from the MRP except for MW-16 and MW-18. Based on the data presented in this report,we have eliminated BTEX from the draft revised MRP except for MW-16, MW-17, and MW-18,which all contained BTEX constituents within the last four monitoring events. Once four consecutive monitoring events show nondetections for each constituent, BTEX may be reconsidered for elimination from the MRP. • The report recommends, "deep monitoring well MW-13 should be abandoned..." HSI states that the well may serve as a conduit for vertical migration of contaminants to the lower water-bearing zones due to improper well construction. HSI also states that it is unclear which zone the well is intended to monitor. Currently, MW-13 serves as a sentry for potential vertical migration of contaminants to lower water-bearing zones within an area of shallow zone free-phase product. Following my discussion with Mr. Shine, I also am concerned with the potential that the well may become a conduit for vertical