Nebraska Highway 79, Agnew North and South

PROJECT

Nebraska Highway 79, Agnew North and South

CLIENT

Nebraska Department of Transportation

LOCATION

Saunders County, Nebraska

Project Details

Currently under construction, this project includes 8.46 miles of N-79 in Saunders County north and south of the town of Agnew. It was resurfaced with the addition of eight-foot shoulders to upgrade the roadway to the minimum design standards. Improvements to the existing pavement included 0.5-inch milling with five-inch Type SPR overlay. Portions of the project were reconstructed to new standards in bridge replacement areas. Thirty roadway culverts were extended or replaced. Two bridge-sized reinforced concrete box culverts and the functionally obsolete bridges over Wagon Tongue Creek and North Oak Creek were replaced. The guardrail was removed and replaced, and surfaced under new guardrail.

Nearly five miles of the Oak Creek floodplain abutted the embankment widening along N-79. This fill required Schemmer to certify that impacts met the FEMA rise requirements. Project schedule was paramount and timing proved a HEC-RAS model undesirable. For a timely rise certification, floodplain analysis of North Oak Creek incorporated LiDAR and survey data to develop accurate normal-depth calculations while staying consistent with the FEMA Flood Insurance Study. Schemmer also worked closely with NDOT Bridge Division to develop detailed construction plans for complex, double broken-back box culverts on new alignment. This design effort included energy dissipation (HEC-14) and 3D earthwork excavation models, and successful USACE coordination.