Equipment used in soil vapor extraction was used to reduce the level of carbon tetrachloride on the Hanford Site.

RICHLAND, Wash. – Regulators have approved the completion of a cleanup project on the Hanford Site that began nearly 25 years ago that successfully removed nearly 90 tons of deep-soil contamination and reduced groundwater risk using a remediation technology known as soil vapor extraction.

   EM’s Richland Operations Office (RL) and contractor CH2M HILL Plateau Remediation Company (CH2M) employed the technology to clear contamination by the chemical carbon tetrachloride, which was used in Cold War plutonium processing operations. It spread to an area approximately three-fourths of a square mile and approximately 200 feet in the ground in the 200 West Area.

   “This is a major accomplishment and success in our primary goal of protecting the groundwater, which also protects the Columbia River,” said Michael Cline, director of the RL soil and groundwater division.   

   Nearly 90 tons of contamination has been removed since workers began operating the soil vapor extraction system to clean up carbon tetrachloride in 1992. 

   The system was shut down in 2012 after carbon tetrachloride levels were below final cleanup levels. A study performed from 2012 through 2015 showed the chemical was sufficiently removed, leaving no continuing source.

   The U.S. Environmental Protection Agency approved a soil vapor extraction action report in August, completing all actions associated with removal of carbon tetrachloride in that area.

   “Our team of experts worked to track the contamination and maintain the systems to assure removal of the largest amount of contamination possible,” said Karen Wiemelt, vice president of CH2M’s Soil and Groundwater Remediation Project. “Due to the expertise of our team and other support groups we achieved the legal cleanup level for carbon tetrachloride and were able to permanently end soil vapor extraction operations.” 

   Removal of contamination from the vadose zone was crucial because it reduced the amount of contamination reaching the groundwater.