The Savannah River Site’s liquid waste contractor has expanded a stormwater drainage basin that now holds up to 7.3 million gallons of water in response to the February 2013 discovery that contaminated water was seeping into a nuclear waste vault.

Dean Campbell, the spokesperson for Savannah River Remediation, or SRR, explained that the old configuration of the basin held the maximum volume of rain that, statistically, would be predicted to fall about every 25 years.

“The new basin configuration allows for the volume of rain that could be expected to be received during the highest rainfall event occurring during a 100-year period,” he explained.

Vault 4 is located near Sedimentation Basin 4 of the Saltstone Disposal Facility, or SDF. The vault is a large rectangular cement structure where low-level radioactive waste was disposed, but is no longer used for disposal operations.

Stormwater typically drains from the land near the large cement vaults into the drainage basin, where it is sampled and controlled to verify that no contaminants will reach the waterways.

SRR initiated the Vault 4 Stabilization Project in February, which included placement of a thin, clean grout cap on Vault 4 cells in order to reduce radiation exposure to workers and coating of the Vault 4 roof with an elastomeric coating to minimize rainwater intrusion. An elastomeric coating is a natural or synthetic rubber that is able to resume its original shape when a deforming force is removed.

In addition to improvements, SRR also is constructing a new basin in the area that is expected to hold 7.3 million gallons. Work on the basin is expected to be completed next month.

Campbell also said that roof coating will be completed on five of the six Vault 4 cells that have been identified as requiring coating by the end of September.

He added that the project is intended to enhance the stability of Vault 4 until the Saltstone Disposal Facility closure process is initiated.

“After the SDF is closed, the entire facility will be covered with a specially engineered closure cap which is designed to prevent water infiltration,” he said. “The work being performed demonstrates DOE’s continued protection of the environment and human health.”

Derrek Asberry is the SRS beat reporter for the Aiken Standard.