Rochester Hills City Council on Sept. 8 approved an increase to the contract for the Brewster Road rehabilitation project after fieldwork showed the pavement was thicker than design plans indicated.

City engineering staff told council the project was designed using available as-built plans and pavement core data that indicated roughly a 5-inch hot mix asphalt (HMA) section. Milling operations revealed an average closer to 6.5 inches across the two-mile corridor, increasing material needs. The council authorized an additional $150,000 to the construction contract plus a $100,000 project contingency, bringing the new not-to-exceed project amount to $2,734,503.29.

The increase was necessary, city engineer Tracy Ballen and consultant Mark Lock of OHM Advisors said, because contractor milling set a depth to remove all asphalt and uncovered a deeper-than-expected section in multiple locations. Lock said unexpected underground variations are a common risk on long road projects. “By increasing the thickness of it to 6 and a half inches, it opens your up to much more opportunities to do something different, more cost efficient, and not have to take the entire 5 off every time you wanna do this,” Lock told council.

Council members pressed staff on how the discrepancy happened and on steps to reduce similar surprises in future projects. Lock said the design team had taken more borings than typical and used an average depth for design; he explained borings can vary widely (one showed up to 10 inches at a single spot) and the milling process produced an even surface that exposed the greater average depth. Staff said the thicker new pavement section should improve long-term performance and allow less costly maintenance options in future years.

Mayor Barnett and councilmembers said they had reviewed the issue with staff and the consultant and accepted the recommended course. Councilmember Mangioli, who moved the contract increase, and Councilmember Neubauer, who seconded, both cited the long-term benefit of a stronger pavement section even as they noted the unanticipated cost. Councilmember Walker and others asked for follow-up on procurement and contingency practices to limit similar variances going forward.

The motion passed unanimously.

The project will continue with paving and striping schedules as crews complete the southern mile. City staff said final costs will be known only after completion and that savings could appear in other line items.