A collapsed culvert under Boundary Drive has caused rising water levels in neighbouring homes and concern from city staff.
The city became aware of the problem when affected residents expressed concerns about high water tables north of Central Avenue and along 17th Street in an environmentally sensitive wetland area.
Hal Wright, manager of operations for the city’s public works and operations, pointed out they originally thought it was due to the record high levels of precipitation this year.
“Especially in June when we had almost three times greater than the recorded record, as well as in November there was quite a bit of moisture,” he said. “Just to be sure I had the crews go out and check the flows under the roadways and blockages so we’re sure there was free flow.”
During the inspection, city workers found the pipe blocked under Boundary Road, just south of the Triangle Gardens subdivision.
“We were unable to get through with our equipment, and we used a camera on both ends of the pipe and found that it had collapsed,” Wright explained.
“The actual pipe had collapsed with earth on top of it. We’re unaware of when this happened, whether it was the high rains in June, but the fact remains that we have a block in there and we have to clear that.”
Wright pointed out this particular culvert is a corrugated metal round pipe that goes from one side of the road to the other and actually connects to two manholes. Pipes from the upstream side and also pipes on the downstream side connect to the culvert so that it completes the passageway beneath the road.
This allows water to flow from one side to the other without damaging the road. The water comes from Ward’s Lake, through the city and eventually ends up in the Kettle River.
City staff are currently working to replace the culvert immediately to avoid potential flooding and/or damage to and upstream of Boundary Drive.
Though the culvert has collapsed, Wright added there is no concern for a sinkhole or collapsing of the road.
“The pipe is two feet in diameter, and six to nine feet (two to three metres) below grade,” he said. “From the camera, it looks like it has been there for a while (and) it shouldn’t affect the road surface.”
Additionally, the existing culvert system is old and does not incorporate recommended best practices, including a proper inlet/outlet structure. The replacement of the pipe would also include entrance barriers to prevent animals and small children who may be attracted to exploring the culvert.
According to a staff report presented at Monday’s city council meeting, estimated costs of the remedial work, including survey, engineering, procurement and construction is $55,000; however, prices are subject to change.
“We’re in the planning stages and we’re out for tender,” said Wright. “This is also an important time to make sure we don’t add to the problem.”
Two options to replace the pipe include tearing up the road and replacing the entire pipe before burying it again, or tunneling a new pipe to replace the existing one.
They are still discussing costs of the repair, as this amount has not been budgeted for 2012, Wright added.
Coun. Gary Smith noted city staff is working very hard and diligently to make sure the city’s infrastructure levels are maintained.
“We’re doing the proper things and the proper time,” said Smith. “These things happen, and it’s almost impossible to predict. It’s like doing renovations on a house: sometimes when you open things up you think, ‘Oh my God, what did I get myself into?’ Sometimes you have to deal with things as they come up and this is one of those cases.”
The site of the damaged culvert is also located within an environmental sensitive area (ESA).
The staff report noted, “Given the proximity of the culvert to sensitive terrestrial and aquatic habitat within the ESA, best management practices and site specific environmental mitigation measures will be implemented during construction to help minimize the overall environmental impacts of the culvert replacement on adjoining sensitive environmental habitat.”
As such, a qualified environmental professional will be on-site during construction.
Wright noted the Ministry of Environment would dictate the timeline for replacement of this culvert, but the estimated timeline for commencing this project is in February 2013.
Originally posted in the Grand Forks Gazette.