SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Mr. Nathan Esformes -2- 28 Nbvember 1995 Condor used the results of the DHS report to estimate how much chloroform a single swimming pool would discharge annually to the soil, assuming the average of 51 ppb chloroform concentration and that 150 gallons of pool water are back-flushed to the surrounding soils twice per year during pool maintenance. Under these assumptions, Condor estimated that one swimming pool would discharge 57,916 4g of chloroform annually to the soil. One source of error in this estimate is the assumption that chloroform concentrations in public pools are reflective of chloroform concentrations in private pools. It is likely that less chlorine is needed for maintaining a private pool than a public pool. The limited data from the two private outdoor pools in the Triple E area suggests that pools north of MW-7 may not contribute as much chloroform to the soils and ground water as the estimate of 57,916,cg, which is based on data from public pools. Even assuming the estimate accurately reflects conditions north of MW-7, 57,916 /.zg of chloroform discharged annually from each swimming pool would not increase chloroform concentrations in ground water significantly. Assuming all of the chloroform was able to migrate to the ground water annually, the aquifer is 20 feet thick (the length of the screened interval), and there are 14 swimming pools each contributing 57,916 µg chloroform annually to the ground water over an area of 1,200 feet (the distance north from MW-7 of the 14 pools) by 2,545 feet (the distance between MacArthur Drive and Fair Oaks Road), it would only result in 0.0011 �tg/l chloroform in ground water. This is insignificant compared to the maximum level of 43 ,ug/l chloroform detected in MW-7. Septic tanks The report states septic systems are a potential source of trihalomethane compounds in ground water since all of the residences north of MW-7 are on private septic systems and because chlorinated compounds may be discharged to the soil from septic system leach lines. There is no reason to suspect that chlorinated compounds are discharged to private septic systems in amounts that would result in significant concentrations of chloroform in the ground water. Community Water Supply At the 7 July 1995 ineeting between Triple E representatives and our staff, Triple E representatives stated that none of the domestic wells downgradient of MW-7 is currently being used since all of these residents are now using a chlorinated community water supply. However, as the report states, only residents of Maurland Manor are connected to the community well system, while the other residents north of MW-7 still use private wells. Therefore, the source and concentrations of the chloroform in the ground water north of MW-7 are still a concern. The report also provides information showing that none of the wells which supply water to Maurland Manor have had detectable concentrations of chloroform, even though water from these wells is occasionally chlorinated. Since the water is used only at Maurland Manor, which is approximately 2,800 feet north (downgradient) of MW-7, chloroform concentrations in ground water immediately downgradient of MW-7 would not be impacted by this water. Need for Additional Monitoring Wells North of MW--7 As we have stated in the past, the extent of chloroform contamination north of MW-7 has not been determined. The information presented in the report does not support Triple E's conclusion that