Originally published in The Weekly Packet, August 9, 2018
New contractor reviews Callahan mine plan
Work expected to take five to seven years
by Rich Hewitt
A new construction team is gearing up to start work on the next $15 million phase of the Callahan Mine clean-up plan, but work at the SuperFund mine site is not likely to begin until late this fall at the earliest.
The U.S. Army Corps of Engineers, working for the Environmental Protection Agency, earlier this year hired Environmental Quality Management, Inc., a Cincinnati-based contractor with lengthy experience in mine closures. EQM will work with its partner Tetra Tech, an engineering and consulting firm based in Pasadena, Calif, on the Callahan Mine project.
Representatives from EPA, Army Corps, EQM and Tetra Tech inspected the site late last month prior to the annual community update meeting. According to Ed Hathaway, the EPA project manager for the project, much of the effort for the rest of this year will be reviewing the work that has been done and evaluating the design for the next phase of the project.
Hathaway reminded the small crowd of residents that the design for the next phase, which includes stabilizing and capping the tailings impoundment, was developed three years ago.
“The new team has looked at the site and they’ll be reviewing the design to make sure what we’re doing makes sense,” Hathaway said.
Tom Wey of EQM, which is the primary contractor for the project, agreed that analyzing the current design will be the first major task for the new team.
“We’ll look at the current design to see if there are any data gaps we need to fill,” he said. “We’ll be looking for fatal flaws and ways to optimize or streamline the project.”
Two key elements they’ll be reviewing have to do with the waste rock left on site and the drain that was installed to remove water from the tailings pile in an effort to make it more stable, according to Hathaway. Clean rock is needed to build equipment pads on the tailings pile and to build a buttress along the base of the pile as part of the stabilizing process. The EPA plans to use rock on site in order to avoid the heavy truck traffic needed to bring in rock from the outside. The current plan also calls for a rock cover over the impermeable cap slated to be installed over the tailings pile. Hathaway said they are now trying to determine if there is enough loose rock left on the site that could be used for those projects or whether they will need to blast and quarry the rock. They could develop the quarry and begin stockpiling rock as early as late fall or winter.
Hathaway said they also will look at ways to remove more water from the tailings impoundment, including the possibility of installing more drains. The design, he said, called for the installation of 10 drain pipes in the tailings pile, but they only installed one. That one is working well and to date has removed more than three million gallons of water from the pile.
“It’s working. It’s pulling water out of the pile,” Hathaway said. “The problem is that it has not lowered the water table [inside the pile]. It’s possible that there’s a flow of water coming in from another source.”
Removing water from the tailings pile is the key to stabilizing it, and they need to get the water out before they can begin work on reshaping the pile and covering it.
“Ideally, there would be no water in there,” he said. “A dry pile is so much more stable that a pile with any water in it.”
The engineering team will look at the possibility of installing more drains and also will investigate other alternatives that might work, he said.
In a related matter, Hathaway said that the water drained from the tailing impoundment is fairly clean, although it is still being treated using the innovative filter system that utilizes a combination of manure, wood chips and clam and lobster shells. They will continue to filter and test the waste water as long as it is still draining from the pile.
In response to questions from residents about the cover that will be installed to seal the tailings pile, Hathaway said they plan to use a plastic membrane that can be installed in strips and welded together to form the needed impermeable cover. He passed around a small sample of the heavy 60mm plastic that has been in use for the past 20 years or so. The material is designed to last centuries, he said, and other engineers on the team agreed that, so far, it has worked without problems.
Part of the debate about whether to use rock over the plastic cap has to do with longevity. If it is covered, Hathaway said, it is less susceptible to damage from the elements, particularly ultraviolet rays from the sun. On the other hand, if it is uncovered, it is easier to inspect, repair or replace.
Residents also questioned how long it will be before the project is completely done. As he has said before, Hathaway explained that it depends on the funding.
“We’d like to get it done within five to seven years, but it’s doubtful,” he said. “We’d have to have a steady funding stream. We do have the funds to do the shaping and some of the stabilization.”
That phase of the project is expected to take about three years and cost an estimated $15 million. Hathaway stressed, however, that the $15 million is an old estimate. The Army Corps contract with EQM is for not more than $45 million over the next five years. That contract includes all of the rest of the cleanup project, including excavating contaminated sediment from Goose Pond and depositing it in a confined aquatic disposal cell at the deepest part of the old open pit mine.