Optimization evaluations at Superfund sites have become increasingly common over the past decade. These reviews routinely consider green remediation and environmental footprint reduction, since optimization is designed to promote the sustainability of the selected remedy. An optimization review conducted in 2012 at the Ogallala Ground Water Contamination Superfund site in Nebraska found that the selected remedy has been quite successful. However, the reviewers made several recommendations to improve effectiveness, reduce costs, improve technical performance, close out the site, and reduce the environmental footprint. EPA presents the findings of the optimization review in a January 2013 document entitled "Optimization Review: Ogallala Ground Water Contamination Superfund Site Operable Unit 2 (Tip Top Cleaners)."
The Ogallala Ground Water Contamination Superfund site was identified in 1989 through municipal well sampling. Tetrachloroethene (PCE), a solvent commonly used in dry cleaner operations, was the primary groundwater contaminant of concern identified for remediation purposes. Two main groundwater plumes were identified during investigations by the Nebraska Department of Environmental Quality (NDEQ) and EPA. A southern plume and its sources are called Operable Unit (OU) 1. The northern plume, which originates at the former Tip Top Cleaners, identified by NDEQ in the early 1990s, is addressed as OU2.
A comprehensive remedial investigation (RI) was conducted in 1995 and 1996, including the OU2 area. A comprehensive feasibility study was published in 1997. Additional investigations, including direct-push groundwater sampling, were conducted by NDEQ in 2000 to define the plume.
Tip Top Cleaners was a dry cleaning business, in operation until the 1990s, located in a neighborhood of mixed residential and commercial land use. The building was used primarily for storage, or was unused for a period of time, until April 2011, when the structure was demolished to excavate the remaining contaminated soil at the site. The site is now a concrete-paved parking area, with no change in land use anticipated.
The groundwater contaminant plume extends from the former dry cleaner east-southeast through the central portion of Ogallala in an area of residential and commercial land use. The plume may extend south of U.S. Highway 30 into an area of sand and gravel mining. One residential well located approximately 1,600 feet downgradient of the site was identified, but it became inoperable and was abandoned.
An optimization evaluation typically considers: 1) goals of the remedy, 2) available site data, 3) the conceptual site model (CSM), 4) remedy performance, 5) protectiveness, 6) cost effectiveness, and 7) closure strategy. An optimization evaluation includes reviewing site documents, interviewing site stakeholders, potentially visiting the site, and compiling a report. The report includes recommendations for protectiveness, cost effectiveness, technical improvement, site closure, and environmental footprint reduction.
During 2000 and 2001, independent Remediation System Evaluations (RSEs) were conducted at 20 operating sites, with pump-and-treat groundwater systems funded and managed under the Superfund program. Based on the opportunities for system optimization that arose from those RSEs, EPA's Office of Superfund Remediation and Technology Innovation has incorporated RSEs into a larger post-construction strategy for Superfund-led remedies. EPA has...