West Ridge Drive repairs and maintenance could cost the city $1 million in 2020.
The road, constructed in 2013 for the West Dickinson Roers Development and later accepted by the city, provides access to Family Fare Supermarket and Menards.
There have been problems with West Ridge from the outset, Public Works Director Gary Zuroff said, including settlement issues and voids under the concrete.
A report completed by Highlands Engineering was presented to city staff and commissioners at a city work session Tuesday.
The report also looked at adjacent Roughrider Boulevard and Legend Drive, and 38th Avenue West, Engineer Andrew Schrank said.
Investigating the extent of voids under the pavement, Highlands did 56 test locations at 200-foot increments.
"We cored through the pavement and measured pavement and base thicknesses," Schrank said. "We did what's called (dynamic cone penetrometer) testing, which gives you a baring value of the subgrade soils to a depth of about six feet."
Only one void was found, at one and three quarter inches, near West Ridge and 38th Avenue intersection.
Schrank also reported a "fair amount" of variability in pavement and base thickness.
"Usually you want your pavement to be within a quarter-inch of the specified, base within a half inch, and some of this was outside of that range," he said.
Highlands estimated an "adequate" design life of about 30 years for the subdivision roads.
"Even in the thinner sections, it looks like the design is sufficient," Schrank said.
Most of the settlement there has already occurred.
"The lack of voids tells us the road is probably settling uniformly," Schrank said. "You're not getting just pockets where there's voids underneath your pavement, but everything's moving together, which is a good sign."
Three options were provided to the city.
Rehabilitation and continued maintenance for all three roads would cost less than $1 million.
"That would be repairing any cracked or settled areas, adjusting all utilities," Schrank said. "There are two major areas, one in front of Menards and one by Family Fare. Those are the largest repairs."
A second option: foam injection for all three roads, costing roughly $3 million.
"This would help reduce your maintenance costs, but it is substantially more expensive and it is very difficult to estimate," Schrank said. "You really don't know what you're getting into until you start the project."
A third option provided as a reference, but not recommended, was a complete reconstruction, with West Ridge Drive alone costing $3.6 million.
"Since we did see a lot of areas where you had no voids and the design life was found to be adequate, we don't think this would be a good investment," Schrank said.
The city will ready a plan in hopes of taking action in Spring 2020.
"If we're leaning toward the maintenance option," City Administrator Joe Gaa said, "let's put together an actual plan of what that means and what that $1 million is going to fix and bring that plan, and here's how we'll fund it. That's what we'll bring to a meeting."
Mayor Scott Decker supported putting together a comprehensive plan first.
"I don't think we're going to be able to fix anything this fall anyway," he said. "At a further meeting, we'll have a discussion on where the money will come from."
He added, "I think the maintenance plan is far better than reconstructing it."