MCAS EL TORO'S 'GROUND ZERO'

The most contaminated portion of the base was in the Southwest quadrant, an area occupied by the Marine Wing Support Group 37. The 200 acres of MWSG-37 contained 11 of the 25 contaminated sites identified by the Navy and EPA.

EPA traced the “hot spot” to the MWSG-37 maintenance hangars: “…the primary VOC source is present beneath Buildings 296 and 297, extending to the south with decreasing concentrations to the southern Station boundary. Several smaller source areas exist in the soil beneath Site 24, including a PCE soil gas plume located west of Building 297. The VOC [Volatile Organic Compounds] concentrations in soil gas generally increase with depth, and the highest concentrations occur near the water table. VOCs in the area of Buildings 296 and 297 extend to groundwater directly beneath those buildings.”

SITE 7: Drop Tank Drainage Area No. 2:

Site 7 is referenced as Drop Tank Drainage Area Number 2 and is located in the southwestern quadrant north and west of Hangars 295 and 296. Site 7 was previously used for aircraft drop tank storage and drainage. Aircraft drop tanks were drained and washed on a concrete apron from approximately 1969 to 1983. Contamination is from JP-5 and waste lubricating oil disposed of on area soil as a dust suppressant. Shallow groundwater underlying the site is contaminated by volatile organic compounds, including trichlorothene, carbon tetrachloride, and tetrachloroethene.

SITE 8: DPDO Storage Area:

The DRMO was the storage area for containerized liquids, scrap, and salvage materials from El Toro and MCAS Tustin. Scrap materials included mechanical and electrical components and various types of liquids. Non-radiological contamination included VOCs, SVOCs, pesticides, PCBs, TPH, TRPH, herbicides, and metals. Radiological surveys and soil sampling indicated Radium 226 (Ra 226) concentrations greater than background levels. An analysis of data obtained from radiological surveys and soil sampling showed Ra 226 concentrations greater than background levels for Units 1 and 4 at Site 8. Concentrations were found to be consistent with background levels for Units 2, 3 and 5.

SITE 9: Crash Crew Pit No.1:

Between 1965 and 1971, site was used as a training area for crash crew. During training exercises, two pits were filled with water and covered with various mixtures of residual fuels and other combustible fluids (e.g., JP-5 fuel, aviation gasoline, crankcase oil, and other wastes). The mixtures were then ignited and extinguished by the firefighters. An estimated 123,700 gallons of waste liquids were used in the west pit training exercises. The east pit operations are believed to have been similar. Chemicals detected at site include VOCs, SVOCs, TPH, dioxins, and metals above MCAS El Toro background levels.

SITE 10: Petroleum Disposal Area:

From 1952 through 1970, an estimated 52,000 gallons of liquid wastes, including crankcase oil, antifreeze, hydraulic and transmission fluids, motor oil, and solvents, were sprayed over the site for dust control. Chemicals detected include VOCs, SVOCs, and metals above MCAS El Toro background levels.

SITE 11: Transformer Storage Area:

From 1968 to 1983, site was used for storage of electrical transformers on a concrete pad (Unit 1) and a storage yard (Unit 3) at the site. Reportedly, five transformers containing PCBs (polychlorinated biphenyls) leaked onto the concrete pad and then onto the unpaved surface of the storage yard or into an asphalt-lined drainage ditch (Unit 2) adjacent to the concrete pad. PCBs were commonly used as a coolant in transformer oil; however, use of PCBs in this manner was discontinued in the late 1970s. In 1983, all transformers were removed and properly disposed of off-site.

SITE 12: Sludge Drying Beds:

Located west of Bldg. 493, this site includes secondary treatment plant dewatered sludge in drying beds. Contamination included VOCs, SVOCs, pesticides, PCBs, TPH, TRPH, herbicides, and metals. Eighty cubic yards of sludge was plowed under at this location. An analysis of data obtained from radiological surveys and soil sampling showed Ra 226 concentrations were found consistent with background levels for this site. The WWTP at Site 12 ceased operation in the early 1970s. The IWWTP was dismantled by 1961. DON investigation suggested that the above ground concrete treatment tanks were demolished in place and then covered with approximately 5 to 7 feet of fill material. The sludge at this facility was dewatered in the two drying bed areas (east and west). When the plant closed, the sludge remaining in the drying beds was abandoned in place. The earthen berms surrounding the sludge beds were combined with imported fill material and graded in place. The drainage ditch (Unit 3) is an unimproved earthen channel that skirted both sludge drying bet areas into a catch basis, which connects to the lower reach south of Plant Road via concrete culverts.

SITE 14: Battery Acid Disposal Area:

Heavy metal, organic compound, and petroleum hydrocarbon contamination from battery acids oil wastes and paint wastes disposed on soil. Shallow groundwater underlying this site is contaminated by volatile organic compounds, including trichlorothene, carbon tetrachloride, tetrachloroethene, trichlorothene and carbon tetrachloride.


SITE 21: Material Management Group & Supply Center Storage:

The site was part of the supply distribution center for MCAS El Toro and other Marine facilities and was used for the storage of drummed materials since approximately 1946. Soil contamination came from leaking drums. All drummed materials stored at the site were removed in 1995. Chemicals detected at the site included VOCs, SVOCs, TPH, pesticides, herbicides, PCBs, and metals above background levels.

SITE 22: Tactical Air Fuel Dispensing System (TAFDS) Operations Area:

Soil and groundwater contamination from leaking tanks, fittings and hoses. The site was former aircraft fuel storage and dispensing facility. Fuel storage was first observed in aerial photographs dating from approximately 1952 and historically occurred in two areas: an eastern fuel-dispensing area and a western fuel-dispensing area. Heavy staining was observed at both locations and the western fueling area has a documented history of spills. Chemicals detected at the site included VOCs, SVOCs, TPH, pesticides, and metals above background levels.

SITE 23: Wastewater Treatment Plant Sewer Lines:

The Navy conducted a Resource Conservation and Recovery Act (RCRA) facilities assessment (RFA) at MCAS El Toro. The purpose of the RFA was to evaluate whether an additional 140 sites at El Toro would require further investigation. The final RFA Report was submitted in July 1993 (Jacobs Engineering 1993b). Based on an evaluation of the sampling visit results, 25 solid waste management units/areas of concern were recommended for further action. Site 23 (Wastewater Treatment Plant Sewer Lines) was evaluated in the RFA and recommended for no further action.

SITE 24: VOC Source Area:

VOCs are present in soil and groundwater. VOCs present at the site include TCE, PCE, 1,1-dichloroethene (DCE), and carbon tetrachloride. The primary VOC source is present beneath Hangars 296 and 297, extending to the south with decreasing concentrations to the southern base boundary. Several smaller source areas exist in the soil beneath Site 24, including a PCE soil gas plume located west of Building 297. The VOC concentrations in soil gas generally increase with depth, and the highest concentrations occur near the water table. VOCs in the area of Hangars 296 and 297 extend to groundwater directly beneath those buildings.