HEALTH CONSULTATION
Perchlorate Contamination in the Arden Cordova Water Service Area
AEROJET-GENERAL CORPORATION
RANCHO CORDOVA, SACRAMENTO COUNTY, CALIFORNIA
BACKGROUND AND STATEMENT OF ISSUE
The Environmental Health Investigations Branch (EHIB) within the California Department of Health Services (CDHS), under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), is conducting health assessment activities on the Aerojet-General Corporation (Aerojet) Superfund site in Sacramento County, California (See Figure 1). A Preliminary Health Assessment written in December 1988 recommended that when additional environmental information and data became available ATSDR would make another assessment (1). A Site Review and Update written in March 1993 also recommended a health assessment be conducted when more data became available (2).
This health consultation is one in a series that will be performed as part of the ATSDR health assessment process at this site. During this process, data and information on the release of hazardous substances and their impact on public health will be evaluated. Four health consultations have recently been written as part of this series (3-6). CDHS staff are in the process or writing a series of health consultations addressing the perchlorate contamination. In this health consultation, we will focus on describing the perchlorate contamination that has reached the Arden Cordova Water Service (Figure 2) and evaluating the health impact from the exposure that has occurred. We are also in the process of writing several other health consultations that focus on perchlorate exposure to consumers of water from other water purveyors in the area and from private wells in the area. In addition, we are also writing a health consultation that describes the perchlorate groundwater contamination west of the Aerojet Superfund site.
Aerojet began operation in 1951. Since that time, Aerojet has manufactured liquid and solid propellants for military and commercial rocket systems and has fabricated, assembled, tested and rehabilitated rocket engines (1). In addition, between 1974 and 1979, Cordova Chemical Company, a wholly-owned subsidiary of Aerojet, manufactured paint components, herbicides, and pharmaceutical products. Over the years, Aerojet and Cordova Chemical disposed of hazardous waste by burial, open burning, discharge into unlined ponds, and injection into deep underground wells (1). Some of these discharges, including perchlorate, have contaminated the environment have moved off-site of the Aerojet facility boundary (Figure 1). Perchlorate in the groundwater arises from ammonium perchlorate being a main component of solid rocket fuel. In addition to the natural migration of perchlorate-contaminated groundwater from the site, Aerojet is reinjecting treated water, contaminated with perchlorate, at the site's western boundary. The Regional Water Quality Control Board (RWQCB), the California Department of Toxic Substances Control (DTSC) and the U.S. Environmental Protection Agency (USEPA), are the lead regulatory agencies overseeing groundwater investigation and cleanup at Aerojet, and are also investigating other sources of the perchlorate, such as the McDonnell Douglas (now Boeing) and Purity Oil Sales sites.
The Arden Cordova Water Service is one of thirty-eight water systems that compose the Southern California Water Company. Southern California Water Company is a public utility company engaged principally in the production, transmission, distribution, and sale of water to over 240,000 customers, or one out of 30 persons in the State of California. The company stock is traded on the New York Stock Exchange.
The Arden Cordova Water Service is composed of two distinct systems, the Arden System and the Cordova System (Figure 1). These systems are not interconnected, ie. the wells located in the Cordova System serve only the Cordova System customers. The Cordova System has been impacted by the perchlorate contamination whereas the Arden System is located several miles west of the contamination, and thus it is unlikely that it will ever be affected. In the rest of the document, we will only be discussing the Cordova System.
The Cordova System supplies water to 11,650 connections, approximately 36,500 customers, mostly family residences and commercial businesses (7). During the rainy, cool months, groundwater supplies all the water for the Cordova System (8). In the hot, dry months (May to November), the Cordova System water comes from a combination of 33% surface water and 67% groundwater (8). The surface water undergoes conventional treatment for pathogen and turbidity removal after it is drawn from the Folsom South Canal, which diverts water from the American River at Nimbus Dam, below Folsom Reservoir. Prior to the discovery of the perchlorate, the groundwater was drawn from 19 wells (Numbered 1-21, no #2 or #9, see Table 1). All of these wells are located within the Cordova System (Figure 2). Generally speaking, these wells are screened from approximately 200 to 500 feet below ground surface (9). Prior to the perchlorate contamination discovery, the Cordova System did not receive water from any other sources or interties with other water systems, except at one site. The intertie with the City of Folsom was designed be used during peak demand up to 2,400 gallons per minute but not to exceed 300,000 gallons per day.
All water sources serve a single pressure zone with an elevation range of approximately 70 feet (7). The distribution system consists of over 370,000 feet (or 70 miles) of pipe ranging in size from 4 to 24 inches in diameter. There are two clear well/reservoirs in the system which have a total storage capacity of two million gallons. There are a total of 18 low and high lift pumping facilities at the water treatment plants.
All the wells (and the new intertie) are interconnected in a complex system in which distribution of the water is based on demand within the system. In fact, some wells are not typically used, unless supply demands that they start pumping water (Table 1). The water that most Cordova System residents receive is probably a mixture of water from more than one well (or intertie). However, if a house or building is located right next to a well that is pumping, then that house or building probably receives 100% of its water from that well.
One well, Well #21 has a sand/anthracite filter for removing manganese, and controlling hydrogen sulfide odor (7). There are plans to have filters installed at the sites of Well #11 and #12 for manganese treatment and removal by the end of the 1997.
The highest level of nitrate found in the Cordova System wells is 19 ppm nitrate as nitrogen, with the average being 7.4 ppm (10). The drinking water standard for nitrate is 20 ppm. The drinking water standard for nitrate is 45 ppm.
In the 1980s, trichloroethylene (TCE) was found to have contaminated Arden Cordova wells 13, 15, and 16 (10). Freon 113, cis and trans-1,2-dichloroethylene, 1,1-dichloroethylene, and 1,1-dichloroethane have also been detected in well #16. The wells have continued to be used because Aerojet provided groundwater treatment units to cleanup the water pumped from these wells (8). Aerojet installed carbon treatment on well #16 in February 1985 and installed treatment systems on well 13 and 15 in 1986. Since 1990, TCE has also been detected in Well #9; the highest concentration detected was 5.0 ppb in June 1994 (10). Arden Cordova took well #9 off-line in September 1995 (8) and the well casing was filled with concrete (destroyed) in November 1997. TCE has also been detected in Wells #11 (up to 2 ppb) and 14 (up to 2 ppb).
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