Dual bridge project in Princeton recognized for excellence by Alliance for Action

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Mercer County has received the 2022 Distinguished Engineering Award by the New Jersey Alliance for Action for the county’s engineering of two structures, Mercer County Bridge No. 330.1 and Bridge No. 331.1, carrying Alexander Street over Stony Brook and Alexander Street over Alexander Creek in the Municipality of Princeton.

Mercer County and the New Jersey Department of Transportation (DOT) undertook simultaneous bridge replacement projects to minimize the closure of Alexander Street, which carries a considerable amount of traffic volume and serves as a main access road between downtown Princeton, Princeton University and West Windsor Township, according to information provided by Mercer County Executive Brian M. Hughes.

DOT completed replacement of the bridge over the Delaware and Raritan Canal immediately east of Bridge 330.1.

The design of this project was driven by requirements determined through intensive coordination with the various stakeholders: Municipality of Princeton, Princeton Historical Society and State Historic Preservation Office, Delaware & Raritan Canal Commission, Princeton University, DOT, utility owners, West Windsor Township and Green Acres, according to the statement.

“Mercer County is grateful for the recognition by the Alliance for Action,” Hughes said in the statement. “We have in our DOT a team of exceptional engineers, and I thank the team for their contributions to this enormously challenging and complicated project and congratulate them on receiving this prestigious award.”

Bridge 330.1 was previously a single span, simply supported pony truss structure supported on concrete abutments. The previous truss bridge, which was intended to be a temporary structure, was in need of replacement due to the poor condition of the deck, superstructure and substructure, according to the statement. The bridge width was also substandard and limited the passage of larger transit vehicles. It was deemed Structurally Deficient with Sufficiency Rating of 7.4 out of 100.

The adjacent structure to the west, 331.1, was a three-sided box beam culvert and was also in need of replacement. While its structural and geometric conditions were not as critical as Bridge 330.1, it was logical to replace the structure at the same time while Alexander Street was closed, according to the statement.

The replacement structure for the former truss bridge is a single span, with simply supported steel beams on concrete abutments and concrete footings. Bridge components also include concrete wing walls, a concrete bridge deck and concrete bridge approach slabs, according to the statement. The deck and approaches were overlaid with 1-inch-thick Polyester Polymer Concrete (PPC) to protect the concrete deck. White bridge railings and brown powder-coated guiderail are consistent with similar elements installed on the adjacent Delaware and Raritan Canal Bridge.

Roadway work included hot-mix asphalt paving, new striping, new guiderail and approach guiderail systems, and landscaping.

The proposed cross section at Bridge 330.1 consists of two 12-foot travel lanes, two 5-foot shoulders and one 8-foot sidewalk. Bridge 331.1 was replaced with a similar three-sided culvert and received similar railing and guiderail treatments as the adjacent structure. It consists of two 12-foot travel lanes, two 5-foot shoulders, one 5-foot sidewalk and one 8-foot sidewalk. The culvert and approaches were overlaid with 1-inch-thick PPC to protect the concrete deck.

Van Cleef Engineering Associates of Freehold was contracted by the County of Mercer to provide design services for the reconstruction of the structures, and Marbro Construction LLC of West End was awarded the contract.

The New Jersey Alliance for Action is a non-partisan and non-profit association representing thousands of business, labor, government, utility, education, professional and other New Jersey leaders. It will present the award at its ninth annual Distinguished Engineering Awards Breakfast May 12 at the Forsgate Country Club in Monroe.