The industrial history of the Charlie Burch site (hereafter referred to as the “Site”) dates back to the 1950s. In the 1960s, an independent hauler used the Site to bury wastes collected from several manufacturers. In 1967, a Montgomery County judge ordered the landfill closed.
In the early 1980s, the State of Texas (or the “State”) approached several parties, including Rohm and Haas Texas, Inc., (Rohm and Haas) to investigate the Site and develop a plan to properly close the Site. In 1983, after several years of work and under a compliance agreement, the Texas Department of Water Resources issued a letter stating that the Charlie Burch disposal area was closed in conformance with the approved closure plan.
In the early 1990s, the Texas Water Commission asked Rohm and Haas to conduct additional soil and groundwater investigation work. In 1997, after several years of study, the State accepted the Site into the Texas Voluntary Cleanup Program. Under this program, Rohm and Haas is working closely with the State to move towards achieving a final groundwater cleanup objective.
What’s the Problem?
Investigations have revealed that groundwater moving southeast from the Site contains a compound called 1,2-dichloroethane (1,2-DCA). The 1,2-DCA is found in a narrow band between approximately 25 feet and 65 feet beneath the ground surface. Extensive testing shows that there is no detectable soil contamination located either at the ground surface or within approximately 25 feet of the ground surface.
Testing has shown that the 1,2-DCA has not impacted the local drinking water source, which comes from a zone several hundred feet deeper than the current location of the 1,2-DCA plume. Water supplies are routinely tested by municipal authorities to ensure the safety of your drinking water. Additionally, detectable concentrations of 1,2-DCA are identified at depths deeper than 25 feet beneath the ground surface, and the 1,2-DCA plume is isolated from the ground surface by clean soil. Moreover, studies have shown that it is unlikely that detectable amounts of 1,2-DCA in groundwater would move through the soil and reach the ground surface.
What’s been done?
Progress continues. Approximately 91,000 cubic yards of material have been excavated from the Site and hauled away to licensed secure disposal facilities outside of the project area. The former Charlie Burch disposal area has been backfilled with clean fill, graded, and capped with low permeability soils.
Despite having no known history of using 1,2-DCA, Rohm and Haas is committed to removing 1,2-DCA from the Charlie Burch site, and has constructed two groundwater recovery (pump and treat) systems to remove 1,2-DCA from the groundwater. One system is located at the former disposal area, and the other system is located towards the downgradient edge of the groundwater plume at the 13-Acre Tract. The former disposal area system was redesigned and replaced with a new system to improve performance and to enhance capture of the on-site 1,2-DCA plume. This upgraded system became operational in February 2012. Since start up, the systems have removed and cleaned over 230 million gallons of water through December 2012.
Removal of material from the former Charlie Burch disposal area combined with the active groundwater treatment systems has reduced the levels of 1,2-DCA in groundwater. Investigations to identify the precise limits of the impacted groundwater were completed in 2007. Rohm and Haas submitted a Final Response Action Plan to the Texas Commission on Environmental Quality, or TCEQ, which was approved by TCEQ in April 2011. The Final Response Action Plan presents the proposed response actions for dealing with 1,2-DCA in the groundwater. The main features of the Final Response Action Plan include:
- Removal of significant amounts of 1,2-DCA at the Site through continued operation and optimization of the pump and treat systems at the Site;
- Maintenance of groundwater treatment at the Site in order to limit the migration of the 1,2-DCA plume;
- Ongoing evaluation of other treatment options at the Site;
- Treatment of groundwater between the Site and the Subdivision, and between the Subdivision and the 13-Acre Tract, using injections of food-grade materials to enhance natural processes of 1,2-DCA removal; and
- Continued use of food-grade material treatment systems as needed to achieve remediation goals for the Site.
To address portions of the groundwater plume between the Site and the Subdivision, and between the Subdivision and the 13-Acre Tract, a process called enhanced anaerobic bioremediation (EAB) has been tested and approved for use at the Charlie Burch site by the Texas Commission on Environmental Quality (TCEQ). The EAB application involves the injection of harmless organic materials, including vegetable and soybean oils, into the underlying groundwater to provide a long-term source of food that enables the microbial populations to more effectively decompose DCA. As groundwater flows through the treatment zones, microorganisms break them down converting them to harmless end products.
The EAB application is being implemented in a phased approach to facilitate optimization and incorporation of process improvements into subsequent phases. This phased approach allows for flexibility in treating areas predicted to take longest to clean up. The EAB application is designed to inject sufficient organic materials and amendments to persist in the groundwater for up to 4 years, requiring replenishment of those materials (re-injection) on an on-going basis until the groundwater is determined to be clean by the TCEQ. Injection activities associated with the implementation of Phases 1 and 2 of the EAB application were conducted between March and June 2012. Performance monitoring is conducted periodically to measure application effectiveness.
Obtaining necessary access agreements, development of TCEQ-approved work plans, and implementation of Phases 3, 4, and 5 will continue over the next few years. Several treatments may be necessary to replenish the treatment materials before the EAB process is complete.