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NPL Site Narrative for Del Amo

Los Angeles, California

Federal Register Notice:  September 05, 2002 (PDF) (9 pp, 193K, About PDF)

Conditions at Proposal (December 1, 2000): The Del Amo site should be placed on the National Priorities List (NPL) because contaminated ground water beneath the site could effect water that people drink. The Del Amo site is located within the Los Angeles city limits, Los Angeles County, California, in proximity to the Cities of Torrance and Carson. From the early 1940s to the early 1970s, a 280-acre synthetic rubber manufacturing facility operated on the property. The facility consisted of the following three plants: a butidiene plant, a styrene plant, and a copolymer plant. The facility was dismantled in the early to mid 1970s, and the property is currently occupied by a business park. The Montrose Chemical Corporation NPL site is located approximately 600 feet west of the Del Amo site.

The 1998 Final Groundwater Remedial Investigation Report identified the following 12 areas of concern for ground water contamination on the Del Amo site: 1) cyclohexane tanks associated with the former copolymer plant in the northern portion of the site, 2) pits and trenches in the former copolymer plant area, 3) XMW-20 non-aqueous phase liquid (NAPL) in the former styrene plant area in the western portion of the site, 4) volatile organic compound (VOC) tanks associated with the former styrene finishing/benzene purification unit, 5) VOC tanks and/or pipelines associated with the former styrene finishing unit, 6) tank farm in the former styrene plant area, 7) VOC storage tanks associated with the former ethylbenzene production unit number 1, 8) VOC storage tanks associated with the former ethylbenzene production unit number 2, 9) utility tanks in the former styrene plant area, 10) waste pit area and underground petroleum pipelines in the southern portion of the site, 11) underground benzene pipeline in the southeast portion of the site, and 12) laboratory underground pipelines in the former butadiene plant area in the eastern portion of the site. The Del Amo HRS Documentation Record focuses on two of these 12 areas of concern (the XMW-20 NAPL and the waste pit area).

The XMW-20 NAPL is composed primarily of benzene (90 percent) with lesser quantities of toluene, ethylbenzene, and styrene. It is located approximately 50 feet from the historic location of a 500,000-gallon crude benzene storage tank and extends laterally over an area of approximately 17,500 feet. The NAPL is limited to the saturated zone, occurring as isolated blobs in a smear zone that extends vertically from the water table, at approximately 60 feet below ground surface, to 30 feet below the water table.

The waste pit area occupies approximately 3.7 acres in the southern portion of the site and consists of six disposal pits (Pits 2A through 2F) and two evaporation ponds (Ponds 1B and 1C). The pits and ponds received process wastes from the styrene manufacturing plant. The pits and ponds are currently covered with fill material, weeds, and miscellaneous debris, and the 3.7-acre parcel is surrounded by a double row of fences. Hazardous substances in the waste remaining in the pits and ponds include benzene, ethylbenzene, and naphthalene. The pits and ponds are evaluated as two separate sources in the Del Amo HRS Documentation Record.

Ground water proximal to the XMW-20 NAPL is contaminated with benzene at concentrations up to 1,200,000 µg/L. Soils located beneath the waste pit area have come to be located below the top of the water table, due to rising ground water levels. These soils are contaminated with the same hazardous substances that are found in the waste remaining in the pits (e.g., benzene, ethylbenzene, and naphthalene). There are 17 municipal drinking water wells within 4 miles of the Del Amo site.

Status (September 2002): EPA is considering various alternatives for this site.

For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet at ATSDR - ToxFAQs (http://www.atsdr.cdc.gov/toxfaqs/index.asp) or by telephone at 1-888-42-ATSDR or 1-888-422-8737.

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