GAIL MARTIN, Independent Editor
Computer modeling of Chemtura’s groundwater remediation plan shows that more needs to be done, and quickly, to ensure the company will meet its cleanup deadline of 2028.
The computer model, an exercise completed once every five years by Chemtura, is recommending significant changes to the pump-and-treat program, including adding extraction wells to the treatment system, and making use of the relatively new technology of in-situ remediation.
In-situ remediation would place chemicals in the ground in particularly contaminated “hot spots” near the Chemtura property. The ensuing chemical reactions would transform the contaminants to benign chemicals, as a means of speeding up the cleanup.
Steve Quigley, of Conestogo Rovers & Associates, spent more than an hour outlining the various recommendations that have come from the computer modeling exercise at the Nov. 1 Chemtura Public Advisory Committee meeting.
He emphasized that the computer model is simply that, a model, and any changes to the pump-and-treat remediation program will have to be carefully monitored.
Quigley also noted that the modeling revealed several areas where there is not enough information about the hydrogeology under Elmira to be able to determine the best course of action.
One of the key recommendations of the modeling, therefore, is to do more investigation to fill in these “data gaps” before proceeding, said Quigley.
The plan for in-situ remediation will also have to be more thoroughly investigated, said Quigley.
It’s the first time CRA has proposed this kind of technology for Chemtura’s remediation plan, as a supplement to its pump-and-treat program.
“Not until recently, very recently, has it become feasible for us to consider doing in-situ, in place remediation of NDMA in groundwater,” said Quigley. “Laboratory tests done recently have suggested that this may work. We believe that it will work, and we want to pilot test that technology, to develop a feasible program of remediation of the aquifer.”
This, combined with adding additional extraction wells and increasing the pumping rate of these wells significantly, are among the recommendations that CRA presented at the CPAC meeting.
CRA also recommended to only pump in areas that will provide a significant result, which could result in moving wells in areas that are seeing low concentrations of NDMA and chlorobenzene.
CPAC members expressed concern about some of the findings of the report, most notably the need for a vastly increased extraction rate for the contaminated groundwater. Currently, Chemtura extracts and treats up to 1 million gallons (3,785 cubic metres) of water per day.
The modeling shows the need to increase the overall pumping rate by 300 times, both by adding additional wells and by increasing the pumping rate on existing extraction wells.
Councillor Mark Bauman expressed concern that there would be enough groundwater under Elmira to be pumped at that rate, without lowering the water table.
CPAC member Sebastien Seibel-Achenbach noted that the new pumping rates for current extraction wells is approximately three times what was set in a prior study, completed ten years ago.
“Are we confident that even three times (pumping rate) will be sufficient to do the job?”asked Seibel-Achenbach.
“I think we are confident,” replied Quigley. He said that the previous optimization study was done with containment of the contamination in mind, while this current model is focussing on the remediation.
CPAC chairman Dan Holt then raised the fact that the pumping rates for the extraction wells have not always hit their targets.
“If they were lower historically, how can we be assured that the new pumping rates, as much as three times, will be met?” asked Holt.
Quigley noted that the lower pumping rates from the past had a lot to do with restrictions placed on the system until the ammonia treatment system was in place, as well as the more recent problems Chemtura has had in regulating the biological organisms used in the ATS.
“Is there a 100 per cent guarantee we can achieve these pumping rates? No, but now that we’ve worked through these other problems, we’re in a better position to achieve them,” said Quigley.
Elmira resident Alan Marshall congratulated CRA for “finally” considering in-situ remediation, which he referred to as source removal of contamination, something he has been pushing for over many years.
However, Marshall raised concerns about in-situ remediation, noting that there is potential for the process to create “dangerous byproducts” that would complicate the contamination problem in Elmira. He cited an instance when potassium permanganate was used for in-situ remediation.
“CRA would never consider using potassium permanganate,” said Quigley, who noted that this particular chemical produces toxic byproducts, and also has the additional problem of being purple in colour.
He noted that there are other chemicals that have proved effective in treating NDMA, and reiterated CRA’s plan to do a pilot project first, prior to developing a longer-term remediation program.
CPAC members once again raised the issue of whether Chemtura would face any penalties, should it not meet its cleanup deadline of restoring Elmira’s groundwater to drinking water standards by 2028.
Bill Bardswick, director of West Central Region for the Ministry of the Environment, reiterated that if Chemtura did not meet its deadline, it would not be in compliance with the control order that the MOE has imposed.
He also told CPAC members that they should be encouraged by CRA’s report.
“When I came here tonight, I said this is good news, that they are going to be making some major changes,” said Bardswick. “They are going to be pumping a lot harder, they’re moving things around, it’s not static. This is what we always thought would need to happen, and it is happening. It’s good news.”
Work on the updated remediation plan will get underway quite quickly, with a work plan to resolve “data gaps”and pumping tests on existing wells to be completed by the end of this month. In-situ remediation testing will require MOE approval, but the work plan will be submitted by Dec. 15, 2012.