10/24/1996 BOARD OF HEALTH Minutes

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i Table : Exposure opportunity estimates for the residents of AP 62 Lot 241 between 1993 and 1996. Dates of exposure were estimated using a groundwater flow velocity of 2 feet per day and the locations where TCC and PCE were detected in private ars monitoring wells. We]I Scenario Earliest Possible Latest Possible well Duration of well Estimated TCE Well Contamination Contamination Contamination Concentration TCE worst Case Spring 1996 Spring 1996 months 1000 ppb Reasonable Exposure Spring 1996 Spring 1996 months 547 ppb CE worst Case 1993 ' Spring 1996 3 years 150 ppb ti Reasonable Exposure 1993 ' Spring 1996 3 years 16 ppb 1. The distance between AP 62 Lot 241 and monitoring well AW-40 (the closest well do gradient from AP 62 Lot 241 in which TCE was not detected) is approximately 150 feet. 2. The distance between AP 62 Lot 241 and AP 69 Lot 32 (the southernmost well where PCE was detected) is approximately 2710 feet. From this distance it can be estimated that PCE first reached the well at AP 62 Lot 241 in the summer of 1992. However, because the current residents ofthis house first started living there in 1993, the current residents of AP 62 Lot 241 could not have been exposed to PCE in the groundwater before 1993. The previous residents of this house could have been exposed*to PCE during this earlier period (see Table 3e . 3. The opportunity for exposure to TCE and PCE in this well ended when a carbon filtration unit was installed on this well during the spring of 1996. 4. The maxinium concentration of TCE that was detected in the off-site area affected by the TCE Plume (see Table . 5. The mean concentration of TCE in seven water samples taken from AP 62 Lot 241 and two water samples taken from AW- (the closest upgradient monitoring well). . The maximum concentration of PCE that was detected in the off-site area affected by the PCE plume (see Table . 7. The mean concentration of PCE that was detected in the off-site area affected by the PCE plume (see Table . . 1t is not known n in what month during 1993 the current residents of AP 62 Lot 241 moved to this house. To estimate the duration of well contamination, it has been assumed that the move occurred In the spring.