Washington Closure Hanford has renegotiated its subcontract with Stoller Corp. to operate Hanford's Environmental Restoration Disposal Facility.

The revised contract is technically considered an extension, taking Stoller's operation of the landfill for low level radioactive waste to the original contract end date of Feb. 28, 2010.

The remaining work is valued at abut $18.5 million.

Washington Closure Hanford renegotiated the subcontract because of the many unexpected items and contaminants being found during Hanford cleanup and sent to the landfill, including mercury.

The contract had been awarded on a fixed unit price and has been converted to a time and material contract.

The revised contract also gives Washington Closure more oversight as it deals with new processes and processes that need to be changed as anomalies in waste are found, said Washington Closure spokesman Todd Nelson.

"We are very pleased with progress that has been made, improvements made and general operation of the facility," Nelson said.

Changes in operations were made after a worker was found to be falsifying test data in early 2007.

An average of more than 200 truckloads of waste are being disposed of at ERDF each day, said Jim Van Vliet, Stoller vice president for Northwest operations.

"We appreciate the confidence WCH and DOE have shown in Stoller and we look forward to becoming an even larger contributor to DOE's environmental management program," said Nick Lombardo, Stoller chief executive officer.