What is Perchlorate?
Perchlorate in Southern Nevada
Perchlorate in Drinking Water
Perchlorate is a chemical compound made up of one chlorine atom bonded to four oxygen atoms. It is commonly used as an ingredient in solid rocket propellant, fireworks, flares, matches, and munitions. Although most perchlorate is man-made, it can also be naturally occurring. Like salt, perchlorate dissolves easily in water. Perchlorate is known to interfere with thyroid function, and is considered an environmental contaminant.
Perchlorate was detected in the Lower Colorado River in 1997. The perchlorate was traced upstream to the Las Vegas Wash, which discharges into Lake Mead. Located upstream from the detection point in the Las Vegas Wash were two perchlorate manufacturers.
It was ultimately determined that perchlorate was entering the Las Vegas Wash through contaminated groundwater and surface water stemming from Kerr-McGee, a manufacturing facility near Henderson, Nevada.
Perchlorate-contaminated groundwater was also found to originate from the former Pacific Engineering and Production Company of Nevada (PEPCON) site, a chemical manufacturing facility owned by American Pacific Corporation (AMPAC).
Perchlorate was manufactured at the Kerr-McGee facility from 1945 to 1998, and at the AMPAC facility from 1958 to 1988.
After the sources of perchlorate had been identified, remediation plans were enacted to begin removing perchlorate from affected groundwater and surface water.
The Nevada Environmental Response Trust (NERT), owner of the property where the Kerr McGee facility was located, currently extracts perchlorate-contaminated groundwater and treats it in aboveground tanks that biologically remove the perchlorate from the groundwater. NERT is currently field-testing a variety of different technologies to determine what will be the most effective solution for the future treatment of perchlorate-contaminated groundwater.
Endeavour, LLC was formed in 2015 to continue operation of the AMPAC Groundwater Treatment System. Similar to NERT’s groundwater extraction and treatment system, Endeavour’s system also uses aboveground tanks to biologically treat extracted perchlorate-contaminated groundwater.
After perchlorate has been removed from the groundwater, NERT and Endeavour each discharge their treated groundwater to the Las Vegas Wash, as authorized by their respective National Pollutant Discharge Elimination System permit.
As of January 1, 2019, remediation activities in Southern Nevada have resulted in the removal of more than 6,320 tons of perchlorate from the environment. Data from the Northshore Road sampling point in the Las Vegas Wash, downstream of Lake Las Vegas, show a reduction from a high of 1200 parts per billion (ppb) in October 1998 to 53 ppb in April 2019. Data from the Willow Beach, Arizona sampling point in the Colorado River, approximately 11 miles downstream of Hoover Dam, show a reduction from a high of 9.7 ppb in June 1999 to 1.0 ppb in April 2019.
On June 26, 2019, the Environmental Protection Agency (EPA) published a proposed rule regarding the regulation of perchlorate in public drinking water systems, and on June 18, 2020, the EPA made a final determination to not issue a national regulation for perchlorate. Although there is no federal standard for perchlorate, the Nevada Division of Environmental Protection has established 18 ppb as a provisional action level for Nevada. The Las Vegas Valley Water District’s 2020 Water Quality Summary indicates that the average concentration of perchlorate in its water is 0.5 ppb, well below Nevada’s provisional action level.