Pemaco

Investigation and Cleanup Activities

In 1998, the EPA selected the most effective and efficient method to clean up soils left behind after excavating the underground storage tanks. Commonly used throughout the country, soil vapor extraction removes vapors from the soil, then treats them with a thermal oxidation system. The treatment system burned the vapors as they passed through a heated system. The system included automatic safeguards to shut down in the event of malfunction, and it was tested to guarantee that emissions were within limits required by County, State and Federal Agencies.

The filter and thermal heating system worked as follows: 1) the soil gas passed through a filter system where a majority of contaminants were captured on filter material; 2) the unfiltered contaminants in the soil gas were then treated in a heated chamber that broke down the contaminants under temperatures exceeding 1,400 degrees F.

During incineration, most of the contaminants were reduced to non-toxic compounds, such as carbon dioxide and water. In 1998, the EPA collected weekly data on VOCs going into and coming out of the incinerator. The air at the fence line was sampled weekly to verify that no VOCs were leaving the site. EPA turned off the system later in 1998, because the sampling program did not measure potential dioxin emissions. However, based on tests of similar systems used on other projects, it is believed that emissions of VOCs, dioxins and other chemicals were low and did not pose an elevated threat to public health.

Initial Actions

In September and October 1997, EPA conducted the first phase of the site cleanup by removing 29 underground storage tanks and several above-ground storage tanks. As part of the first phase, the facility was demolished, including removal of all piping, asphalt and concrete as well as the demolition of a large burned-out warehouse. Finally, the site was graded and grass was planted to prevent soil erosion.

Initial Actions

In November and December 1997, the EPA tested the site to determine the extent of contamination. It was found that soil beneath the site was contaminated with several different volatile organic compounds (VOCs). These included several compounds that are commonly found in gasoline, such as toluene and xylene. Groundwater beneath the site was also contaminated with similar chemicals. Various methods to cleanup the site were evaluated.

Initial Actions

In April 1998, the EPA started construction of a system to treat the VOCs in the ground beneath the site. The system was designed to remove and destroy underground soil vapors which would otherwise contribute to contamination of the groundwater, possibly impacting a drinking water aquifer. The VOCs beneath the site were extracted by on-site vapor extraction wells and then treated using granular activated carbon (GAC) and thermal oxidation. The GAC removed certain contaminants before the VOCs entered the thermal oxidation unit. The thermal oxidation unit destroyed the contaminants in a high temperature chamber designed for this purpose. EPA conducted additional testing of groundwater and soil to determine if further cleanup was necessary.

Remedy Selected

EPA signed the Record of Decision for the Pemaco Superfund site on January 13, 2005. The final remedy selected for the site is as follows:

• Soil cover and revegetation to address surface and near-surface soils.
• Treatment of upper vadose soils and perched groundwater, using a high-vacuum dual-phase extraction system [HVDPE]. This process uses ultraviolet oxidation [UV Ox] and granular activated carbon [GAC] for water treatment, and flameless thermal oxidation [FTO] and GAC for treatment of vapors.
• Treatment of the lower vadose soils and exposition groundwater, using electrical resistance heating [ERH] with vapor extraction [VE], vacuum-enhanced groundwater extraction, groundwater pump and treat [Groundwater P&T] and monitored natural attenuation (MNA). This process will use UV Ox and GAC for water treatment, and FTO and GAC for treatment of vapors.

· Indoor air sampling and additional vapor monitoring on Walker Avenue and 59th Street during FTO operations.
· Re-design of the FTO unit so that the heat exchanger vapor-phase GAC adsorption unit are installed to the post-exhaust side of the FTO unit to reduce the possibility of dioxin release to the environment, and
· Thorough emission monitoring of the FTO unit, including analysis of vapor samples for dioxins and other chemicals.

Remedy Design

EPA finalized the entire treatment system during the Summer of 2006. However, construction on the underground conveyance piping and groundwater extraction wells began the Summer of 2005 when the City of Maywood started construction on the Maywood Riverfront park. EPA completed the design of the ERH system and the rest of the treatment plant the Summer of 2006.

Cleanup Ongoing

EPA coordinated construction of the remedy for the Pemaco Superfund site with the construction of the Maywood Riverfront Park. As a result of this coordination effort, on-site construction of the remedy began on August 5, 2005. On-site construction included the installation of the groundwater extraction wells, vapor extraction wells, and underground piping that would transport both groundwater and vapor to the treatment plant. During August 2006, EPA continued its construction activities by building the foundation for the treatment plant and raising the walls for the treatment building. Construction of the treatment plant was completed by early December 2006 and EPA continued installation of the vapor recovery wells and electrodes located in the ERH source area. The soil vapor monitoring probes were installed along Walker Avenue during January 2007. EPA conducted indoor air sampling in the homes on 59th, and 60th Street during February 2007. The results showed that the subsurface contamination from the Pemaco site was not impacting the indoor air quality of the homes.
The contractors continued delivering and hooking up the equipment inside the treatment plant during early 2007. EPA turned on the groundwater treatment system during April 2007. The vapor treatment system was turned on during May 2007, and the ERH system was turned on during late August 2007. EPA continues to monitor both the groundwater treatment system and vapor monitoring system on a daily and weekly basis. EPA has collected samples for volatile organic compounds in both the vapor and groundwater waste streams. Sampling includes both instrumental monitoring as well as analysis of samples collected from various components of the treatment plant. EPA has also performed dioxin and furan testing on the vapor before it leaves the treatment plant. The sampling results show that the cleanup is proceeding in a safe manner and cleanup activities are not impacting residents living in the neighborhood close to the site or the park.

Cleanup of the groundwater and vapors will continue until cleanup levels are reached. This cleanup will likely include bioremediation. A pilot test has been conducted to determine the effect of injecting sodium lactate into the groundwater plume. EPA continues to monitor the results of the in-situ bioremediation at the site.

EPA has been conducting community meetings every 4 to 6 weeks. During late 2007 meetings were held during August and October. EPA also held meetings on January 31,2008, March 27, 2008, September 4, 2008, and February 26, 2009. EPA will continue to discuss the status of the cleanup and various sampling results at community meetings, and will send out email updates, as needed. A meeting will be scheduled during early 2010.

EPA signed the Preliminary Closeout Report for the Pemaco Site in September 2007. This report documents the completion of the construction activities associated with implementing the remedy at the site.