The New York State Department of Environmental Conservation (DEC) has approved the conceptual plan for a groundwater recovery and treatment system proposed by Cornell University for its former low-level radiation disposal site (RDS) in the Town of Lansing, north of Tompkins County Airport.

According to Donna Connery, project manager for Cornell's Environmental Compliance Office, the planned recovery system consists of a row of wells to be drilled along Snyder Road to capture groundwater contaminated with paradioxane, a solvent used in experiments that measure radioactivity going back four decades. The groundwater also contains very small amounts of the radionuclide tritium at levels significantly cleaner than drinking-water standards, she said.

Groundwater will be pumped to an existing treatment plant nearby at Cornell's former chemical disposal site (CDS), where it will be passed through an ultraviolet oxidation system to treat paradioxane. "The treated water will have to meet discharge requirements established by the DEC before it is released to an out-fall pond and then an intermittent stream that eventually reaches Cayuga Lake, about four miles west of the site," Connery explained.

Construction of the groundwater recovery system could begin later this year. Operation of the RDS groundwater recovery and treatment system is expected to continue for 10 years, with ongoing monitoring.

Between 1956 and 1978, the two-acre site was used to bury research materials containing low-level radioactivity, in accordance with state and federal regulations in effect at that time. Studies of the site and monitoring have been under way since 1984. A risk-assessment study of current conditions shows the site does not pose health risks, Connery said.

"Although the site contains irradiated research materials," Connery explained, "the paradioxane is of current concern, because it has migrated several hundred feet from the site." Paradioxane is considered a probable human carcinogen.

Cornell has worked with the DEC and the state's Department of Health to evaluate several alternative solutions for final cleanup of the site. According to Connery, Cornell's recommended

cleanup plan addresses the disposal area itself and a groundwater plume that extends about 400 feet southwest of the site to Snyder Road. In addition to the groundwater recovery and treatment system, Cornell's plan includes construction of an underground barrier wall around the former disposal area.

The proposed final plan calls for an underground clay wall around the waste area and injecting cement grout into fractured rock to encapsulate the most highly contaminated groundwater on site. This is similar to methods used at the CDS, 800 feet to the east, but the RDS barrier wall would extend deeper, about 40 feet into the bedrock. "This should contain the disposal area and prevent future releases from the site," Connery said.

Connery said DEC criteria for cleaning up the site include protection of human health and the environment; compliance with state standards, criteria and guidance; short-term effectiveness during construction; long-term effectiveness; reduction of the toxicity, mobility and volume of the waste; ability to implement the plan; and cost. The proposed plan is estimated to cost about $10 million, plus annual operating and monitoring expenses.

The DEC will seek public comment on the final clean-up plan, and an announcement of the DEC's public meeting will be made when the date is set. Field investigations and risk assessments were outlined at a public meeting in March 1998, as well as in articles by local news media throughout the 1990s and in a series of newsletters issued by Cornell. The most recent newsletter was mailed in February to more than 600 residents, property owners and other interested parties. Additional copies of newsletters are available at Cornell's Environmental Compliance Office.

Copies of detailed documents related to both sites are available for review at the following locations:

• Tompkins County Public Library, 312 North Cayuga Street, Ithaca.
• Lansing Village Hall, 2405 North Triphammer Road, Lansing.
• Cornell's Environmental Compliance Office, 130 East Hill Plaza, Ithaca.