EPA and DEQ address Tie Plant's issues

There are six issues with recommended courses of action outlined in the most recent five-year review of the remedial actions performed under the Superfund program for the Burlington Northern Somers Tie Plant by the Montana Department of Environmental Quality and the U.S. Environmental Protection Agency.

“The town (of Somers) can expect to see more work being conducted, they can call the agencies with any questions and we’re happy to let them know what’s going on,” DEQ Project Officer Lisa DeWitt said.

The EPA determined the risk assessment performed in 1987 contains uncertainty due to changes in cleanup standards, consideration of all contaminants and the potential for vapor intrusion. Naphthalene was not considered a carcinogen in 1987 but is now considered a Class C Possible Human Carcinogen, thus affecting cleanup goals.

The recommended course of action for this is to re-evaluate the risk assessment and determine if a new risk assessment is warranted. This includes looking at changes in cleanup standards, consideration of all contaminants, and the potential for vapor intrusion. The risk associated with naphthalene needs to be reassessed as well as for 2,4-dimethylphenol (a phenolic compound). The milestone date for this course of action is Sept. 30, 2013.

The second issue states that concentrations of 2,4 dimethylphenol, naphthalene, benzene, toluene, ethylbenzene, xylenes, 1-methylnapthalene, 2-methylnapthalene and napthalenes have been detected at levels that exceed DEQ Montana Numeric Water Quality Standards.

The current recommended course of action for these constituents is to determine cleanup goals for each and fully characterize the nature and extent each exceeds standards. The milestone date for this course of action is also Sept. 30, 2013.

The third issue in the review indicates that contaminants exist beyond previously defined plume boundaries. Concentrations of 2,4-dimethylphenol are increasing in downgradient wells, which means that the plume is not stable without remedy pumping. Benzene was also found at these locations in excess of Record of Decision standards.

“We think the sampling results are showing contamination beyond where we had previously thought,” EPA project manager Diana Hammer said. “So our question is how far does it go and does it pose an additional risk to public health or the environment.”

The recommendation for this is to conduct environmental investigations to determine the nature and extent of the contamination and the potential for contamination migration. This information will help determine the actions needed to resolve the problem. The milestone date is set for Sept. 30, 2014.

The fourth issue is in regards to the potential for vapor intrusion into residential homes. The recommendation is to conduct vapor intrusion screenings to completely evaluate the vapor intrusion pathway by Sept. 30, 2013.

The fifth issue states that the Somers town well is not being sampled for more mobile constituents such as 2,4-dimethylphenol and benzene. Both of these have been detected outside of the controlled groundwater area.

“Burlington Northern is required to sample the town water regularly for contamination, and we don’t see it, that just confirms that the town well is not impacted,” DeWitt said. “I would be surprised if it ever got there, groundwater does not flow in the direction of the site, but goes the other way. This is a very conservative measure to ensure protectiveness.”

It is recommended that monitoring of the Somers town well begin immediately for volatile organic compounds such as benzene and phenols such as 2,4-dimethylphenol because of their fast migration rates.

The final issue is that new sampling information indicates groundwater contamination exists beyond what was previously expected and that enforceable soil and groundwater boundaries institutional controls are not in place.

The recommendation is to get those controls in place and to increase the size of the controlled groundwater area as necessary by Sept. 30, 2015.

To see the entire five-review, go to http://deq.mt.gov/fedsuperfund/BNS.mcpx or request a CD copy by contacting Hammer at hammer.diana@epa.gov or by calling 457-5040. Or by contacting Lisa DeWitt, DEQ Project Officer, at lidewitt@mt.gov or call 841-5037.