2014 Potomac Hollow

Local roadways and bridges must have local champions dedicated to maintaining and upgrading their condition. Like almost all municipal governments, Allegany County, Maryland, doesn’t have large budgets or heavy cranes at its disposal. Oftentimes, the county has to use its own forces to repair and replace some of the bridges in its inventories to maximize its funding. When Allegany County officials saw the Hillman Composite Beam (HCB®), they decided it could afford them another way to replace their existing bridges — potentially with their own crews. Once they picked a pilot project, they requested funding through the Federal Highway Association (FHWA) Innovative Bridge and Deployment (IBRD) program.

Not only did Allegany County successfully secure the funds for the superstructure, but it also received funding for the use of Geo-synthetically Reinforced Soil (GRS) abutments. As such, Potomac Hollow Road Bridge became a true pilot project for technologies that the county could evaluate for use in the future, without straining its budget.

In 2014, the contractor, Carl Belt Inc., began the project by removing the old bridge. The lightweight HCBs were ideal, as the site is a narrow road that would be difficult for large equipment to access. The six beams, delivered on one flatbed, were set directly on the compacted granular soil backfill of the GRS abutments in less than half a day. The 2-inch space between the adjacent beam flanges were covered with thin FRP strips, thus eliminating deck forming. The beams were filled with self-consolidating concrete from a local ready-mix supplier in a couple of hours.

Today, Allegany County has a new bridge that will last longer with less maintenance. The county also has a prototype for other projects using HCBs.

Project Specs:

  • Single Span
  • Length: 30 ft. (9.1 m)
  • Width: 25 ft. (7.6 m)

HCB Piece Weight:

  • Empty: 1,100 lbs. (500 kg)
  • Filled: 5,200 lbs. (2,360 kg)

Owner: Allegany County Department of Public Works

Contractor: Carl Belt Inc.

Completion date: September 2014

Project Sheet: Click here for downloadable PDF version

“The technical expertise that HCB Inc. provided was fantastic. They answered any questions we had and worked with us to develop some techniques for erecting them. Using HCBs reduced trucking substantially. We were able to move four beams per truckload. If we had used conventional beams, we would have had to use significantly more trucks. Located in a marine environment, Knickerbocker Bridge was a great application for HCBs because it will withstand corrosion better than steel or concrete.”