56th Street over Middle Branch Black River

Routine Bridge Inspection

Load Rating Analysis

Bridge Design

Road Design

Environmental Review

Scoping

Hydraulic Analysis

Maintaining Traffic

Special Provision

As part of performing routine bridge inspections for the Allegan County Road Commission, LSE has inspected the 56^th St Bridge over the Middle Branch Black River for several years. The existing structure is a single span steel I-beam bridge with a concrete deck on concrete abutments. The concrete deck was experiencing significant cracking. Additionally, the stream bottom was beginning to scour beneath one of the abutments. The combination of these as well as corroding of the steel beams warranted a structural review. A load rating analysis confirmed the structure was only capable of safely carrying reduced loads. The structure was rated in poor condition.

With the deteriorating condition of the bridge, LSE applied for funding for the replacement through the Local Bridge Program on behalf of Allegan County. Upon receiving funding, the road commission selected LSE to design a replacement structure.

The new structure consisted of prestressed concrete I-beams on pile supported curtainwall abutments. Adjustment of the road profile was necessary to meet current highway standards, so reconstruction of the approach roadway was included in the design. Existing conditions indicated a solution to drainage issues was also necessary, thus drainage structures were proposed at the low point.

LSE continues to perform routine inspections of the 56^th St bridge to monitor deterioration as well as to provide scoping of maintenance or preventative measures for the Road Commission.