Concerns about possible safety issues have arisen after large cracks were found in the slag pile off of Granby Road in Grand Forks.
With this year’s late spring precipitation, an overflow of water from Overton Creek continued to flow into late summer.
A city report noted, “tension cracks have recently opened within the southern portion of the large slag pile located west of Granby Road and immediately adjacent to the Granby River. The cracks were a few inches wide within the past years and have recently increased significantly.”
Sasha Bird, manager of technical services for the city’s public works and operations, pointed out it’s uncertain how much of the cracks are recent.
“According to predecessors, the cracks have been there for a very long time, which is why we want to do the monitoring – to see if they’re moving,” she explained. “At this point we don’t know and our predecessors don’t remember how wide they were. It’s really hard to say how much movement there has been, which is probably a reason why there was a section of fence put up, because they were concerned that people might be walking in there.”
The plan is to set up some monitoring and check it on a monthly basis, Bird added.
A geotechnical engineer recently reviewed the slag pile property to determine the current level of risk and provide short-term recommendations for potential stabilization or correct the problem. The engineer also provided general comments on potential long-term plans.
Bird noted the assessment revealed a low to moderate risk and the pile appears stable reducing any risk for large-scale issues.
A likely cause for the expansion of tension cracks could be the source of water from Overton Creek.
President of Pacific Abrasives Tim Spurgeon pointed out the cracks have been there since the company began operating the pile in the early 1970s.
“The south end has always had some cracks there and I’m not sure if they’ve gotten bigger or smaller, but that’s what the monitoring is for; to see if they have,” he explained. “The pile has been there since the early 1900s, so over a hundred years, and we don’t see it as posing a threat but I certainly think we should go ahead an monitor it to make sure.”
Spurgeon noted there might be some issues with the underflow of the discharge from a creek, which is something that should look into.
“The foremost thing is the safety of the community and we want to make sure that if (the cracks) are an issue, we can make some plans to go ahead and make sure it’ safe,” he added. “We’re the operators there and it’s our responsibility under our agreement with the city to make sure the operations and anything that is operated there is done in a safe manner.”
Bird pointed out the monitoring program was not originally approved in the budget.
“It has to be taken back to council so we have to tell them how much we’re going to be spending, so the financial plan has to be amended. That has to happen first before we go back to the geotechnical and environmental consultant and get them going on providing us with the monitoring program,” she explained. “We would have to hire a BCLS (British Columbia Land Surveyors) to do a survey for the cross-sections and then with the re-routing of Overton Creek, that has to include a Section 9 (Water Act) application to the Ministry of Environment.”
The cross sections, another option labeled as a short-term solution, would be added to the slag piles at 50-metre increments. This slicing would go through the slag from Granby Road down to Riverside Drive.
“Take a piece of pie and cut it in half and you look at it from the face view, that’s the cross section of the pie,” explained Bird, adding a detailed monitoring program for the top of the slag pile would also be included.
The city currently does not have the GPS unit or equipment to complete the task themselves, hence the hiring of a BCLS, Bird added.
As a first step and main priority, city staff and operators at Pacific Abrasives are currently looking to re-route Overton Creek.
“The process to get us to the actual monitoring stage –we want to divert the creek before the freshet (spring thaw) comes around so we avoid having the water going into the crevice anymore,” said Bird. “The rest of it we have time, the biggest priority is to re-route the creek.”
The budget for the project is still unknown at this time, though city staff recommends council approve funding for remediation from the slag fund reserve. Immediate work would alleviate any risk of the slag pile losing stability and danger to community and will begin in the new year, Bird concluded.