Battelle staff members were recently approached by a client from a Brazilian energy company, who stated, "We know of Battelle's reputation in contaminated sediment remediation and we need your technical support." The energy company had operated a prototype oil shale processing plant since 1972. During the first six years of its operation, the spent shale was discharged to a manmade reservoir that had been built for the discharge. An environmental survey of the reservoir revealed an accumulation of arsenic. Although a risk assessment had indicated a very low level of health risk to the public, the company was sensitive to public concerns about possible exposure and agreed to address the sediment problem. Subsequently, the company entered into an agreement with the state environmental regulatory agency to implement a remedy. After a review of the alternatives, company decision makers concluded that removing the impacted sediments would create a more serious environmental and public health risk than leaving them in place; a sediment cap was determined as the only feasible alternative.

Sediment capping is a containment technology accepted by the U.S. Environmental Protection Agency (U.S. EPA), in which the sediment is isolated from the aquatic environment by depositing a layer of material on the sediment surface. The specific material is selected according to characteristics of the site and remediation goals, but could include sand, clay, or a more reactive material. Multilayer caps composed of different materials are also used.

Adding to the unique challenges of sediment-capping projects, this is the first use of sediment-capping technology in Brazil. Battelle remediation specialists have taken on the assignment to guide the company and its subcontractors through the process of characterizing the site, verifying the effectiveness of a sediment cap in this application, designing the cap, observing installation, and overseeing the performance monitoring. A key element of the design will be the cap materials, thickness, and placement method.

A subordinate, but equally important role is to convince the regulators and, by extension, the public, that a sediment cap is the right technology for the job. This is being done through a series of briefings and information-sharing sessions with the regulators, coupled with U.S. EPA and sediment- capping site visits in the United States to acquire first-hand assurance that sediment-capping is indeed an accepted remediation option. The project is currently in the design phase.

For more information, please contact Mr. Don Salmond at (781) 869-1408, salmondd@battelle.org.