Concrete buttress will keep road from sliding into Turtle River
A section of road along an eroding bank of the Turtle River near Manvel, N.D., will be buttressed by more than 5,300 tons of concrete to keep the street out of the water.
Grand Forks County Engineer Nick West said the south shoulder of County Road 33, also known as 28th Avenue Northeast, has been "dropping and sliding" off the edge of the road and into the adjacent river since the beginning of June.
Over the course of the summer, he estimated the county has spent as much as $25,000 to fill in the lost portions on a regular basis. The long-term fix for the roadway, a concrete rubble buttress, could tack on an additional $100,000 to be paid out from the county's emergency fund.
"The buttress will, No. 1, stop erosion," West said. "No. 2, it'll act as an anchor for the soil so it doesn't slide into the river."
The buttress will consist of chunks of concrete about 1 foot long and 2 feet wide. The stretch of rubble will be piled about 20 feet wide, 10 to 15 feet tall and 350 feet long.
West hopes the buttress will be a permanent solution and is aiming to begin bidding out the project to contractors next week. From there, a contractor hopefully would be selected by the first week of October, and the project would be wrapped up by the end of that month before the winter freeze.
Manvel City Auditor Joan Sherlock said soil under the south lane of the paved road has washed out twice within about the past month, once the week before Labor Day and once during the holiday weekend.
On both occasions, Sherlock said, the shifting road broke the city's sanitary main, which carries residential sewage under the Turtle River. The broken pipe pumped raw sewage into river, which required the city to contact the State Health Department to monitor the situation.
The sewage pipe since has been fixed, but Sherlock said the city will need to install a new, more flexible pipe system in the future that is able to handle potential shifts in the roadway above.
She said the affected road is largely used by residents from communities west of Manvel to get to Grand Forks.
"Especially now, when it's beet season with all the farmers, they need to slow down or find an alternative route," Sherlock said. "I'm just hoping they get it done before freeze-up so we don't have to worry about the situation."
Up to now, she said the city of Manvel has invested about $15,000 in maintaining the eroding shoulder. West said the city will not be responsible for covering any costs for the buttress.
Before plans for the buttress came into the picture, West reported to the Grand Forks County Commission at its Sept. 6 meeting that the most cost-effective option could be a diversion of the Turtle River to the north side of the road. That idea was scrapped at the commission's Sept. 20 meeting.
Shifting the course of a river can sound "extravagant," West said, but from a technical standpoint, the river near Manvel is essentially a large ditch. He estimated it was as much as 6 feet deep and 30 feet wide.
At first glance, the diversion seemed to be the best option in terms of a permanent, cost-saving fix. But once the engineering team got into the details of the costs of securing the necessary permits and land area, the re-route was no longer feasible.
"Financially, it didn't pencil out," said County Commissioner Tom Falck. "When (West) first told me that, I thought it was just mad, how could you do that? The river's not that deep though—we've got some county drains that are deeper and wider than it is out there—but by the time you acquire adjacent lands, it just didn't work out financially."