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American Pacific Corporation (AMPAC) operated a perchlorate chemical production facility through a former subsidiary at a Henderson, Nevada site from 1958 until 1988. In 1997, subsequent to the discovery of an analytical method that lowered perchlorate (ClO4¯) detection limits significantly, AMPAC investigated the presence of the perchlorate ion in groundwater in the vicinity of this former facility and found it was present in certain areas. AMPAC thereafter initiated an intensive seven-year groundwater characterization program that included the installation of more than 100 groundwater-monitoring wells over a nine-square-mile area.

In selecting the appropriate remediation method for perchlorate, for land restriction and efficiency reasons, AMPAC focused on an in situ (“in place”) biological (ISB) technology and conducted a pilot test in 2002-2003 near the former plant site. This test was successful and demonstrated that through the addition of precise amounts of a non-hazardous electron donor chemical, the naturally occurring bacteria in the groundwater will biodegrade perchlorate. Specifically, the pilot test successfully reduced groundwater perchlorate concentrations from approximately 600,000 ppb to less than 2 ppb. The byproducts of the process include oxygen, water, biomass (from the bacteria) and the chloride ion.

In early 2005, AMPAC submitted a work plan to the Nevada Division of Environmental Protection (NDEP) to construct a full-scale ISB plant to capture perchlorate in the groundwater to the northeast of the former plant site. The work plan was approved in late April 2005. Thereafter, public land occupation and use permits were obtained from Clark County, Nevada, and the City of Henderson. Construction of this facility, which is one of the largest ISB facilities for remediation of perchlorate in the world, began in July 2005 and was completed in December 2006.

Key data for this remediation operation includes:

• AMPAC spent approximately $9,300,000 to construct the facilities, including a 9,000-square-foot building.
• Groundwater conditioning prior to treatment occurs within the 9,000-square-foot building on 1.7 acres of land permitted under a lease-equivalent arrangement with the City of Henderson.
• The system comprises more than 20,000 feet of underground pipelines and conduits from extraction wells, the ISB plant and re-injection well areas.
• Full system startup occurred in December 2006.
• A total of nine extraction wells and six re-injection wells are now operational when needed.
• During the first year of operation, this facility treated an average of approximately one acre foot of groundwater per day.