Beaver Dam Wash Bridge Project Introduction Nick Hont, P.E. Mohave County Flood Control District Engineer

In January 2005, an extreme flood caused irreparable damages to the Beaver Dam Wash Bridge on Mohave County Highway 91.

Mohave County selected URS Corp. through quality based selection to perform an engineering evaluation of the condition of the existing bridge. The engineering study included hydrology, hydraulics, geotechnical engineering and structural engineering. The geotechnical engineering analysis determined that the existing bridge pile foundations would not provide adequate bearing capacity when excessive scouring occurs during an extreme flood event. The County has applied for Federal Emergency Relief funds to replace the damaged structure with a new bridge built to current standards.

The FHWA has determined that the project costs are eligible for reimbursement with Federal-aid Emergency Relief Program funds, and Mohave County will be reimbursed for approximately 94% of the project costs. The new bridge will be lengthened, will be designed to handle heavier traffic loads (such as the HS 20 trucks), and will include a new, separate pathway for schoolchildren and other pedestrians. The estimated total project cost is about 9 million dollars. It includes fees for the engineering evaluation, design, permitting, necessary right-of-way acquisition and construction.

To finance the project cost until reimbursement is received from FHWA through ADOT, Mohave County obtained a Highway Extension Loan, for which the interest rate will also be reimbursable. The construction is anticipated to bid later this year. Mohave County has and IGA with the ADOT Flagstaff District to bid and manage the construction. The new bridge's length and realignment with the downstream channel, along with deeper piles, will allow it to withstand heavy flows and debris, will prevent excessive erosion and scour of the banks, will provide a more stable and more hydraulically efficient bridge, and will reduce the potential for breach and overtopping of the bridge and roadways.

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