Water supply managers in California are facing an increasingly complex array of threats to water quality as more contaminants are discovered and regulated, and as laboratory analytical techniques improve. Perchlorate, a component of solid rocket motors, has been detected in 246 of 3900 drinking water sources tested in California (as identified by the California Department of Health Services [DHS]). This chemical is considered a contaminant because it mimics iodide when ingested and can disrupt thyroid function. Earlier this year, DHS lowered the advisory drinking water action level for perchlorate from 18 parts per billion to 4 parts per billion.

To provide a neutral forum in which diverse, late-breaking technical, legal and policy developments surrounding rocket fuel contaminants could be presented about perchlorate and NDMA, the Groundwater Resources Association of California (GRA) convened the fourth Symposium in its Series on Groundwater Contaminants, "Perchlorate and NDMA in Groundwater: Occurrence, Analysis and Treatment", on April 17, 2002 in Baldwin Park, CA (San Gabriel Valley). The location of the Symposium was selected because the San Gabriel Valley overlies one of California's largest groundwater perchlorate plumes. 235 groundwater and water resources professionals attended the Symposium.

The nation's largest perchlorate contamination site is near Las Vegas, which affects Californians because much of southern California draws its water from the lower Colorado River. Kevin Mayer, Perchlorate Coordinator for U.S. Environmental Protection Agency (USEPA) Region 9, stated that a perchlorate manufacturing facility near Las Vegas has released a massive amount of perchlorate into Lake Mead. At one point, more than 870 pounds of perchlorate per day was being released to Lake Mead. He also noted that Hoover Dam still releases more than 1,000 pounds of perchlorate per day into the lower Colorado River Basin where concentrations are in the range of 5 to 9 parts per billion.

Carol Williams, Watermaster Executive Officer for the Main San Gabriel Basin, recounted how after many years of cleaning up solvents in San Gabriel Valley Basin aquifers, perchlorate was discovered. All of the La Puente Valley Water District's supply wells were shut down as a precautionary measure due to the detection of perchlorate. Existing groundwater treatment systems, designed to remove solvents, were found to be ineffective at removing perchlorate. Williams described a unique collaborative effort between water suppliers, the "potentially responsible parties", and state and federal regulatory agencies administering the cleanup. Agreements were reached to use wellhead treatment as part of the approved cleanup program rather than costly and redundant efforts that would result from suppliers and responsible parties acting independently. The agreement was a major breakthrough in bringing together parties with diverse and opposing interests, many of which have been in litigation for years.

A variety of technologies for removal of perchlorate from drinking water were also presented. While perchlorate poses a vexing treatment challenge to California's drinking water providers, discussions of new and promising technologies indicated a reason for continuing optimism.

NDMA (nitrosodimethylamine), also associated with rocket fuel, poses a similarly difficult challenge with even lower advisory action levels - ten parts per trillion. This incredibly low number can be thought of as one dime in a hundred billion dollars. Contamination of surface and groundwater supplies from NDMA at missile and other rocket fuel sites was characterized as a significant concern, but the formation of NDMA during chlorination of drinking water or the treatment of sewage for wastewater recycling raises even greater concerns. Additional sources of NDMA include consumption of cured meats, tobacco, and beer, which may contain up to 100, 200, and 5 parts per billion, respectively. NDMA is considered by health experts to be a potent carcinogen.

Bill Mitch, a Ph.D. candidate at the University of California, Berkeley Department of Civil and Environmental Engineering, presented information about his studies with Dr. David Sedlak on the formation of NDMA during chlorination for drinking water treatment. The widely used disinfectant monochloramine was described as a precursor to NDMA formation during chlorination. Monochloramine is used to decrease the formation of trihalomethane compounds such as chloroform during drinking water chlorination. NDMA's carcinogenic properties are 1,000 times more potent than trihalomethanes, and NDMA may occur at ten times California's advisory action level in some drinking water.

GRA is a statewide, not-for-profit organization of more than 750 water resources and groundwater professionals dedicated to resource management that protects and improves groundwater. GRA's Series on Groundwater Contaminants was developed to address the growing debate about the health of California's groundwater.

• Perchlorate & NDMA Symposium - Prior To Event Announcement
  
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