Evidence suggests the subgrade surface is warping on some sections of Hays streets, and commissioners at Thursday’s meeting said the city needs to find out why before continuing scheduled maintenance.

The commission had been asked to approve a contract for supplemental diamond grinding on sections of Canterbury and 27th streets. A subcontractor with Hays-based APAC began the work in early June, but the city chose to suspend the contract due to that company’s inability to achieve the desired outcome. The subcontractor was Garden City-based Interstate Grinding.

“This company has done work for the city before, and they were the low bid. We had no reason to reject them at the time,” Public Works Administrator Greg Sund said. “At the same time, I don’t think they fully understood, nor did we, what was involved in doing some diamond grinding on these streets.”

Those particular street sections still are affected by “dips” of approximately ? of an inch, which suggests the pavement is warping, Sund said, noting the previous contractor didn’t think it had the capabilities to make the road even.

City staff had suggested entering a contract with Iowa-based West Fork LLC to finish the diamond grinding, which is intended to smooth the road’s surface and improve drivability. That cost was approximately $168,000, in addition to a still undetermined amount the city will pay APAC for the work completed.

City officials have indicated they will not pay the full price of the initial contract — approximately $164,000 — but believe some compensation is warranted for the service provided.

West Fork has larger equipment and would have the capabilities to even out the surface and eliminate the dips, Sund said.

Several commissioners spoke against continuing to invest money in short-term fixes until it is clear why the pavement is warping. Similar issues have occurred on Commerce Parkway and 41st Street, both of which have been diamond-grinded.

“I would be inclined to do nothing, learn more about what’s causing the problem before we spend … over $150,000 to fix something we don’t know what’s causing it,” Commissioner Henry Schwaller IV said. “And what we may do is just put a Band Aid on it, because Commerce Parkway is still pretty wobbly. As you said, there’s only so much you can grind before you start hitting metal, and then it’s all over.”

Schwaller inquired if the pavement structure presents a public safety emergency, and Sund said there is no imminent danger.

“It’s an acceptance of travel more than anything,” Sund said. “People want a smoother surface, and we told them we would get them that.”

Sund said city staff is working to obtain core samples and possible geo-tech services to help identify the cause of the problems.

“The company that is doing our pavement assessment said that there isn’t even a rating for this for pavement failure,” Sund said. “It’s so rare, they don’t even rate it. We don’t know why it’s happening here.”

The commission’s consensus was not to pursue additional diamond grinding at this time. City staff will report back later regarding efforts to diagnose the problem and options for fixing it.

Also at Thursday’s meeting, commissioners met in executive session for a total of 30 minutes to discuss a matter of attorney/client privilege.