Electrokinetic remediation of metals-contaminated sediments: a technology demonstration involving former waste lagoons

Electrokinetics (EK) is an emerging remediation technology for the in situ removal of heavy metals, volatile organic compounds, and radionuclides from soils and sediments. Naval Air Weapons Station Point Mugu, California will host an EK technology demonstration. The demonstration will consist of installing and operating an EK system, which is engineered to remove cadmium and chromium from former electroplating waste lagoons. The selected site is adjacent to and encroaches on an environmentally sensitive salt marsh area for federally protected wildlife. The electrokinetic process will be used to mobilize and extract heavy metals from the metalscontaminated soil by applying a low amperage direct current across an array of electrodes placed in the contaminated soil. The demonstration will focus on the effectiveness of the EK process for removing heavy metals from the tidal marsh area. The EK demonstration will be used to collect cost-effective data necessary to address both the technical and economic feasibility of using this technology in areas where soils are porous, water is brackish, and the system is susceptible to tidal influences. Introduction The US Army Environmental Center (USAEC) is preparing to conduct a technology demonstration of EK as a method of removing heavy metals from soils. The demonstration is sponsored by the environmental security technology certification program (ESTCP) and the Southwest Division, Naval Facilities Engineering Command (NAVFAC SOUTHWEST DIV). It will be conducted at the Naval Air Weapons Station (NAWS), Point Mugu, California, Site 5 – Old Area 6 Shops. The technology is being investigated for this ecologically sensitive area because of its potential to be a less invasive technology. A key element of the demonstration is to determine the costs associated with the use of the technology. Background Located in Ventura County, California, NAWS Point Mugu Reservation comprises approximately 4,500 acres in the western portion of the Ventura Basin (Figures 1 and 2). The installation is approximately 50 miles northwest of Los Angeles and borders the western slopes of the Santa Monica Mountains. Past military and industrial operations at NAWS Point Mugu included electroplating and metal finishing processes, explosive and propellant manufacturing and use, and the use of lead-based paints. These operations resulted in large tracts of land being contaminated with metals. Site 5 – Old Area 6 Shops Site 5 is a large area where electroplating and metal finishing operations were conducted. The Old Area 6 Shops within Site 5 are located along Beach Road, just west of the south end of Laguna Road (Figure 3). The area of study is approximately 1/2 acre and includes two former waste lagoons located in the center of Site 5. The lagoons are unlined and were used between 1947 and 1978 to receive waste water discharge from electroplating and metal finishing activities. The largest waste generator in the area was the plating shop, which reportedly disposed of an estimated 95 million gallons of plating rinsate between 1948 and 1965. Additionally, up to 60,000 gallons of waste photovoltaic fixer solution and small quantities of organic solvents and rocket fuel were reportedly disposed of in the lagoons from the late 1940s until the early 1950s. In 1988, surface soil and soil boring samples were collected from the Old Area 6 site and analyzed for a number of constituents. Soil samples collected from ten surface and two boring points contained concentrations of volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs). Only soil borings SB5-1 and SB5-2 and surface soil sample SS5-4 (Figure 3) are located about the waste lagoons (PRC, 1993). All soil samples were analyzed for polychlorinated biphenyls (PCB) and pesticides. PCBs were only detected in a duplicate sample from one of the borings. Dichlorodiphenyltrichloroethane (DDT) and its metabolites were detected in only three surface samples. Metal analytes were detected in all locations. In 1994, the Navy authorized the emergency removal of 117 cubic yards of soil from the former waste lagoons. Summary of existing site condition Following the 1994 emergency removal, surface sampling within the lagoons indicated that the levels of chromium and cadmium still exceeded allowable limits for California (22 CCR 66261.24). Because of the