DUXBURY WATER DISTRIBUTION
DUXBURY, PLYMOUTH COUNTY, MASSACHUSETTS
The Duxbury Board of Health requested that the Massachusetts Department of Public Health (MDPH) evaluate the potential for adverse health effects from opportunities for exposure to tetrachloroethylene (PCE) in drinking water for residents of Duxbury who are supplied water from vinyl-lined asbestos-cement (VLAC) pipes. To this end, MDPH gathered all available PCE testing results for the Duxbury water distribution system, reviewed toxicological studies for PCE, and researched the properties of VLAC pipe. MDPH completed this health consultation as part of its cooperative agreement with the U.S. Agency for Toxic Substances and Disease Registry (ATSDR).
In the late 1960s, VLAC pipe was developed because conventional asbestos-cement pipe was found to produce high alkalinity and poor-tasting water. VLAC pipe was manufactured by thinning a resin with PCE and then spraying the mixture onto the inside surface of asbestos-cement pipe. In the late 1970s, it was discovered that VLAC pipe was capable of leaching PCE into the water carried by the pipes. This problem was found to be most pronounced in pipes that are flushed infrequently (e.g., dead end or low-flow pipes). Following this discovery, the manufacture of VLAC pipe ceased in 1980. However, by 1980, approximately 660 miles of VLAC pipe had been installed in Massachusetts (Larsen et al., 1983).
In 1980, the Massachusetts Department of Environmental Quality Engineering (now the Department of Environmental Protection or MDEP) made recommendations to public water suppliers in Massachusetts about how to control PCE concentrations in VLAC pipes (DEQE, 1980). The most effective, but most expensive, solution to the problem was to replace the VLAC pipes entirely. If replacement was not possible, a number of other measures could be implemented including installing bleeders on dead end pipes to increase water flow and looping dead end water mains. In addition to these measures, MDEP recommended, and then required, that all dead end and low-flow areas served by VLAC pipe be tested for PCE according to an established schedule to monitor the effectiveness of the remedial measures at keeping the PCE concentrations below drinking water guidelines or standards (DEQE, 1980; DEQE, 1989).
Between 1969 and 1980, 17 miles of VLAC pipe were installed in Duxbury (approximately 15% of the Duxburys water distribution system). It has been estimated that the VLAC pipes supply drinking water to approximately 785 Duxbury households (approximately 2,330 people1) on 72 streets (CDM, 1997). Sections of VLAC pipe are found throughout Duxbury. Most of the sections of VLAC pipe in the Duxbury water distribution system are dead ends.
Between 1980 and 1996, the Town of Duxbury undertook some steps to mitigate opportunities for exposure to PCE leaching from VLAC pipes. Water from some dead end and low-flow sections of VLAC pipe were tested for PCE starting in 1980. However, the early PCE monitoring program in Duxbury did not include all areas with VLAC pipe and did not follow a regular schedule. Between 1980 and 1996, 26 of the 72 streets with VLAC pipe in Duxbury were tested for PCE. Between October 1990 and April 1995, no testing for PCE was performed. With respect to remedial actions, bleeders were installed in three subdivisions: The Marshes (installed by 1982 according to the Duxbury Water Department), Plantation Drive, and Tinkertown Ponds (the dates when these bleeders were installed are not known) (CDM, 1997).
In 1997, all the streets in Duxbury with VLAC pipe were tested for PCE in response to citizens concerns about opportunities for exposure to PCE. Following this testing, bleeders were installed on all the streets where the PCE concentration in 1997 was found to be above the current drinking water standard (a total of 10 new bleeders). The Ad-Hoc Committee on Water Quality for the Town of Duxbury adopted a PCE testing program that, in addition to meeting the testing schedule established by MDEP, includes annual testing of all streets with VLAC pipe for the next three years and monthly testing for streets where PCE is found at or equal to 4 ppb. The Ad-Hoc Committee also made a recommendation to the Town of Duxbury that all the VLAC pipe in the Duxbury water distribution system be replaced over the next five years (CDM, 1997). MDPH supports the Town of Duxburys efforts to reduce opportunities for exposure to PCE in drinking water from VLAC pipes.