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Commission approves engineering contract with GBH for Nighthawk road improvements
Summary
The commission authorized entering a contract for engineering services with GBH for the 90th-to‑US‑56 Nighthawk project, instructing staff to bid both crushed‑base/geogrid options with either an asphalt cap or concrete strip; commissioners discussed moisture problems with cement‑treated bases.
County staff and the engineering presenter described the scope and procurement approach for the Nighthawk (90th to U.S. 56) improvement project and the commission moved to enter an engineering services contract with GBH.
The scope presented includes survey and design work, construction oversight and preparation of reimbursement paperwork required by Kansas Department of Transportation cost‑share rules. Staff recommended bidding parallel options: (1) a crushed‑rock base with geogrid and a 3–4‑inch asphalt cap, and (2) a concrete option (strip or panel) in case concrete pricing is more favorable.
The engineering presenter explained why cement‑treated bases have performed poorly at the site: persistent moisture prevents chemical curing of cement‑treated bases, which leads to ongoing failures in low, flat areas. Geogrid with a crushed base and an under‑drain was offered as a long‑term solution in moisture‑prone sections.
Commissioner motioned to enter the contract for engineering services with GBH; the motion carried with recorded support. Staff said survey work will start shortly and some field flags and aerial/drone surveying are planned.
Next steps: staff will finalize the engineering contract with GBH, advertise bid options for both pavement types and return with bid results and recommendations for construction method and scheduling.
