BACKGROUND
Prior to 1995, the lead regulatory agency for the former Omega facility was the State of California Department of Toxic Substances Control (DTSC). During the 1980's, several assessments of subsurface conditions were performed, including sampling of soil gas and groundwater. In 1987, a 500-gallon underground storage tank was removed. From 1991 through 1994, DTSC, with EPA's Superfund Division support, actively pursued the owner/operator of the Omega facility to remove the wastes and cleanup the Omega Site. Because the owner/operator failed to address releases and threats of releases of hazardous substances at the Omega Site, DTSC requested that EPA’s Emergency Response Section assess the need for a removal action at the Omega Site. Through this site assessment, EPA determined that a removal action was necessary and issued an Action Memorandum on May 3, 1995. On May 9, 1995, EPA issued a Unilateral Administrative Order (UAO) to approximately 170 major generator potentially responsible parties (PRPs), all of whom sent 10 tons or greater of hazardous materials to the former Omega property, to perform removal activities at the Site. These major contributing parties thereafter formed a workgroup called the Omega Chemical Site PRP Organized Group, or “OPOG”. During 1995, EPA oversaw removal activities performed by the PRPs under the 1995 UAO that included the removal and off-site treatment of approximately 3,000 drums of hazardous waste, 60 cubic yards of hardened resin material, hundreds of empty contaminated drums, numerous cylinders and various other smaller containers. The UAO also required emptying two rainwater sumps and four evaporators, cleaning two cooling towers, removal of 67 refrigerant gas cylinders, decontamination of remaining equipment and structures, and disposal of 40,000 gallons of rinsate and decontamination water.
In 1996, OPOG, with EPA oversight, undertook the collection and analyses of some preliminary subsurface soil and groundwater samples at the former Omega property and surrounding locations. Investigation work in 1996 consisted of conducting a shallow soil gas survey at the former Omega property that included 31 samples collected at three different depths. This soil gas survey allowed for further analysis of the Omega Site's geology and hydrogeology, and the identification of any materials considered "grossly contaminated." The only grossly contaminated material identified was near-surface soil contained within the loading dock sump; that material was excavated and removed from the former Omega property. A preliminary groundwater investigation conducted in 1996 concluded that elevated levels of volatile organic compounds were present in groundwater downgradient of the former Omega property.
Groundwater within the OU-2 area is used as a source of drinking water by several municipal and private water purveyors. Most of the drinking water wells located in the OU-2 area draw water primarily from deeper portions of the aquifer from depths at or greater than 200 feet below ground surface (bgs) and are not currently impacted by groundwater contamination. However, a few drinking water wells in the area draw water at about the 200 feet bgs level and have had some contaminants detected. These wells are currently equipped with wellhead treatment units which are comprised of granular activated carbon (GAC) filters. The GAC filter removes the contaminants from the water to ensure that it meets drinking water standards. Drinking water for the Cities of Whittier, Santa Fe and Norwalk is tested regularly prior to distribution to the public, and all tap water meets State and Federal drinking water standards.
On April 1, 1999, EPA issued Special Notice Letters to the PRP group and commenced negotiations for the performance of additional work at the Omega Site. On February 28, 2001, a Partial Consent Decree was entered by the United States District Court memorializing the terms of this agreement. Under this agreement, the Settling Defendants agreed to pay a portion of past costs and perform the following work at the Omega Site:
1) Implementation of a Remedial Investigation / Feasibility Study (“RI/FS”) for contamination in the vadose zone (i.e., the soil) within the “Phase 1A area” of the Omega Site. The “Phase 1A” area includes soil and groundwater contamination on and near the former Omega property. The Phase 1A area is also known as OU-1;
2) Performance of an Engineering Evaluation and Cost Analysis (“EE/CA”) addressing groundwater contamination in the Phase 1A area;
3) Implementation of the response action selected in EPA’s Action Memorandum at the conclusion of the EE/CA;
4) Performance of a risk assessment within the Phase 1A area; and
5) Installation of up to three groundwater monitoring wells at locations downgradient of the Phase 1A area and upgradient of the City of Santa Fe Springs water supply well.
In early 1999, OPOG undertook additional field investigation activities with EPA oversight. Field activities included the installation of three groundwater monitoring wells immediately downgradient of the former Omega property; collection of soil and soil gas samples from each well boring, and the collection of groundwater samples for laboratory analysis. Aquifer tests were also performed on the newly-installed wells. In August 2001 and March 2002, OPOG installed another three monitoring wells, including one well located on the upgradient (northeast) side of the former Omega property. Work under the Partial Consent Decree is conducted under EPA oversight.
OPERABLE UNIT 1: SOIL AND GROUNDWATER AT OR NEAR THE FORMER OMEGA PROPERTY
OPOG completed a work plan to implement the OU-1 vadose zone RI/FS, which was approved by EPA in September 2003. Additional work plan addenda were also submitted to EPA to support supplemental data collection. Data collection for the OU-1 RI was completed in 2006 and the RI report was completed in November 2007. The OU-1 FS report was completed in May 2008.
The EE/CA, completed by OPOG in 2005, evaluated potential response actions which could contain contamination within the OU-1. Cleanup alternatives evaluated in the EE/CA are summarized in EPA's Proposed Plan dated August 2005. EPA issued an Action Memorandum in September 2005, which authorized construction and operation of a groundwater pump and treatment system based on the results of the EE/CA. Construction of the pump and treatment system was completed in 2009, after which the system began operating.
In September 2008, EPA issued a Record of Decision (ROD) selecting a soil cleanup remedy for OU-1. The remedial action selected in the ROD consists of a soil vapor extraction (SVE) system to remove and treat the chemical vapors in the soil within OU-1. A series of SVE wells will be used to pull the contaminant vapors out of the soil and into a granular activated carbon (GAC) filter. Once the contaminants are removed by the GAC filter, the clean air created through this process will be released into the atmosphere.
OPOG has agreed to implement the OU-1 soils remedy under EPA oversight, and will begin design work in late 2010.
OPERABLE UNIT 3: INDOOR AIR AT OR NEAR THE FORMER OMEGA PROPERTY
In 2004, OPOG collected indoor air samples from buildings on and near the former Omega property to evaluate whether vapor intrusion from contaminated soil and groundwater was occurring in these buildings. When it became apparent that further reduction in contaminant levels was necessary, EPA and OPOG began evaluating more permanent mitigation measures. On April 6, 2006, EPA issued an Action Memorandum to address indoor air contamination at Skateland by implementing a sub-slab depressurization (SSD) system. OPOG organized and funded the purchase of the Skateland property in September 2006 and implemented an EPA-approved response action that permanently discontinued its use as a commercial building.
After further studies found that vapor intrusion was occurring in other buildings within or near OU-1, EPA entered into an agreement with OPOG in 2009 to address the indoor air contamination. Under the agreement, OPOG has installed an interim SVE system, an SSD system, and is taking other measures to address vapor intrusion at buildings in the OU-1 area. These actions will be consistent with (and in some respects are an early start on) the long-term cleanup of the OU-1 soils. The agreement also requires OPOG to continue indoor air monitoring in several buildings near the former Omega facility, and perform other actions. EPA oversees OPOG’s OU-3 work.
OPERABLE UNIT-2: GROUNDWATER
In August 2010, EPA completed an OU-2 RI/FS, which evaluates the nature and extent of OU-2 groundwater contamination, assesses the potential risks posed by this contamination to human health and the environment, and develops and evaluates alternative remedial actions to address the contaminated groundwater.
In August 2010, EPA issued a Proposed Plan for OU2 that identifies its preferred interim groundwater containment remedy. An interim remedy can be put in place in a more timely manner than a full final cleanup remedy. EPA held a public meeting on August 31st in Whittier, and the public comment period for the Proposed Plan initially was from August 23 to September 21, 2010. EPA received two requests to extend the comment period an additional 30 days each and the final comment period end date was November 22, 2010. In addition to the August 31st public meeting, EPA made abbreviated presentations on the Proposed Plan at various water agencies and associations, and at city council meetings in Norwalk and Santa Fe Springs. On December 14, 2010 at the request of the Cities of Norwalk and Santa Fe Springs, EPA presented information on the proposed plan at a city-hosted community meeting in Santa Fe Springs.
After considering public comments, EPA selected an interim remedy to capture, contain, and treat contaminated groundwater. The selected interim remedial action is presented in the Record of Decision (ROD) dated September 20, 2011 found in the Documents and Report Section below. The overall objective of the interim remedy is to protect human health and the environment by preventing further spreading of the contaminated groundwater. Once the contaminated groundwater has been extracted and treated, it is expected to be used for drinking water and will meet state and federal drinking water standards.
A ROD fact sheet summarizing the decision and a notice in the local newspaper will be published advising the public about the ROD availability on-line and in the Site's information repository - the Whittier Public Library.