Private lake. Crucial drinking water source. Popular recreation area. Restricted homeowners association lacking a degree of pedestrian mobility.
And in the middle of it a bridge past its service life. For Frederick County, Md., it was an opportunity to do something never before done in the state.
“The beams used for the Boyers Mill Road Bridge replacement are the largest and longest precast concrete beams ever used for a bridge in the state of Maryland,” Frederick County Dept. of Public Works Project Manager Jennifer Bohager told Roads & Bridges. “The county determined there were lower life-cycle costs for using precast concrete beams, versus doing steel again. Added to which, many of our other bridges require painting and similar maintenance; we wanted to eliminate that need. This was crucial because this bridge is over a drinking water resource for the county and adjacent homeowners association. Now—no painting over the water source. Environmental impacts to the lake are significantly reduced.”
Precast in Pennsylvania and freighted in across the state line, the 150-ft beams were a bear just to get into the project site.
“Delivery of those beams caused a great challenge for us,” Bohager said, “given the steep nature of the grade and the general tightness of the work site. The south end of the site had very limited real estate; site constraints kept us from having a staging area like we did on the north end of the project.”
In order to meet this challenge and maintain public safety on Boyers Mill Road, crews employed a set of tandem cranes, one on the ground and another on a barge in the lake. One crane would guide each beam to be positioned against the abutment, until its twin could reach the beam, then take over and hoist it for placement.
“This was all done during daytime hours,” Bohager said. “Heavy-load permits restricted night erection due to beam size, weight, and Boyers Mill Road having so many horizontal and vertical curves. Also there’s no lighting on the lake, so it had to be done during the day, 9 a.m. to 3 p.m. That was it for time.”
In this way, crews were able to erect the 300-ft structure, doubling the span of the previous bridge.
The new bridge is 41 ft wide overall with two driving lanes, two shoulders and a pedestrian walkway—an important addition for the surrounding community.
“There is a trail that circumnavigates the entire lake, but the community, which is about 5,000 strong, lacked access directly across the lake for foot traffic,” David Borusiewicz of Wallace Montgomery, the project’s designer, told Roads & Bridges. “So the addition of the sidewalk was very important to community mobility.”
Location: New Market, Md.
Owner: Frederick County Division of Public Works
Designer: Wallace Montgomery
Contractor: Concrete General Inc.
Length: 300 ft (1,100 linear ft total project)
Completion Date: May 24, 2017