Cost inflation stands in the way of a flood prevention improvement for southwest Minot that includes the Dakota Square area.
Construction costs for the Puppy Dog Coulee project now are estimated at $21 million, up $5 million from the 2021 estimate, City Engineer Lance Meyer told the Minot City Council in an update Monday.
“Currently, our engineers are starting to go out and acquire easements from neighboring property owners, or appraisals and those sorts of things, and start making offers and putting finishing touches on plans,” Meyer said. “Our goal is to have this ready by the end of ’23.”
However, the project needs additional funds.
The city has set aside $7.5 million from money received through the federal American Rescue Plan Act (ARPA). Meyer said the city also can use money from its storm sewer development fund but would need to borrow, use cash reserves or find another funding source to pay the inflationary costs.
Puppy Dog Coulee can generate more than 1,300 cubic feet per second of stormwater drainage, Meyer said in describing the need for the project.
“Sixteenth Street will go under water in about a 10-year storm by several feet, meaning that the road is effectively cut off. You can’t transverse through that for several hours, depending on how intense the storm is,” he said. The street is a main arterial that recently increased in importance as an emergency service route for Trinity Hospital.
Neighborhood flooding of the Green Acres Subdivision, on the west side of 16th Street, and business properties around Dakota Square Mall can occur during storm events of 25 years and greater.
“The frequency isn’t that high, but when they do happen, it’s a pretty severe impact,” Meyer said. Addressing that flood risk would benefit property owners by removing buildings from the 100-year floodplain.
The City of Minot started working on Storm Sewer District 121, from about 16th Street Southwest to 10th Street Southwest, in 2015 when Public Works Department staff alerted the Engineering Department to the deteriorating condition of the Puppy Dog Coulee culverts that lie under the mall area.
Meyer showed the latest images taken by a crew who went inside the culverts last week. Images revealed a significantly worsening problem, with pipes that are rotting away, buckling and breaking up.
“I think that’s the last time we’re going to go down into those. I don’t think it’s a good idea for us to be venturing through those,” Meyer said. “When we see structure loss like this, that makes us very concerned because as time goes on, these pipes will start to essentially crumble into themselves.”
Installed as 84-inch pipes, some have been measured at 76 inches, indicating they are compressing and falling apart, he said.
“They’re also undermined, so as water flows through these pipes, they start to erode the soil around them,” Meyer said, showing an image with more than two feet of erosion behind it. There also are instances in which stormwater is flowing outside the pipes.
“We have a public safety risk. These pipes have partially collapsed before,” Meyer added. “It’s going to happen again. It is only a matter of time.”
Much of the pipe dates to the construction of Dakota Square Mall in 1980.
Storm Sewer District 121 originally was to be a storm sewer assessment district, in which the city uses storm sewer development funds to pay half the cost and special assesses the remainder to benefittng property owners. That was not feasible because only about 12% of the Puppy Dog Coulee land area is within city limits and eligible to be assessed. The drainage area includes about 9,500 acres.
With that limitation and the economic slowdown in about 2016, the city sought federal grant funding. Two requests to the Federal Emergency Management Agency were denied, and the State Water Commission could only shift money from the Souris River flood protection project, Meyer said.
“Costs are starting to increase substantially,” Meyer said. “We’re left running into a kind of perfect storm. We have significant material shortages that we’re seeing out in the industry, labor shortages. There’s just not enough contractors anymore, and the influx of federal funds from the stimulus and other programs have created a tremendous need for contractors and materials. As an example, box culverts have more than doubled in price in the last two years.”
The alternative selected for fixing the storm sewer is replacing 1,600 feet of pipes with box culverts. Meyer said the proposed Puppy Dog sewer project construction is expected to be highly disruptive to the public once in progress, due to its impact on 16th Street and the mall.
The city council suggested visiting with Ward County about cost participation in the project. The Water County Water Resource Board already has plans for an improvement west of Minot to mitigate the speed of water flow through Puppy Dog Coulee. The improvements proposed in Minot would hasten water flow through the city, which could have an adverse impact on downstream landowners unless mitigated.
Tom Klein, chairman of the water board, said the board has set aside the proposed $2 million mitigation project for now because the cost is outweighing the benefit value.