Hope for Pennsylvania's Stone Arch Bridges

April 8, 2004
Story by Kate Campbell
Reprinted from Preservation Online, the web-based magazine of The National Trust for Historic Preservation

Project Keystone hopes to save Pennsylvania's stone arch bridges.

The roads snaking through Philadelphia and its four surrounding counties boast the most stone arch bridges in the nation. In 1999, concerns about the safety of the aging stone and mortar bridges prompted the Pennsylvania Department of Transportation (PennDOT) to allocate $500,000 for "Project Keystone," to appraise the bridges and rank those most in need of repair.

PennDOT officials have finished inspecting almost half of the 126 stone bridges scattered throughout Bucks, Montgomery, Delaware, Chester and Philadelphia counties, says Chuck Davies, a PennDOT bridge engineer.

" Those [bridges] that cannot be repaired will be rebuilt in an architecturally sensitive way, " he says. After each bridge is evaluated based on historical significance, structural integrity and traffic volume, the township or county owning each bridge becomes responsible for the cost of its restoration, Davies says.

The oldest bridge in the project has carried traffic continuously since its construction in 1697 and crosses the Pennypack Creek in Philadelphia. The youngest bridges were built in the 1940s. Almost all are still in use.

" This type of construction can have quite a bit of longevity if maintained because all of its elements are in compression-all the stones are pressed together, " Davies says. " But when [the bridges] begin to deteriorate, they do it in an unpredictable way. They can literally be here one day and gone the next. "

On March 13, in honor of the bridges, the Chester County Historic Preservation Network dedicated its sixth annual workshop to bridge restoration. Speakers included state preservation officials, engineers and a PennDOT archaeologist.

" We brought in the main players to discuss what their agencies do, how an advisory council works, who to contact and how to get what you want out of PennDOT, " says Robert Wise, a network board member and director of the workshop.

To find out more about Project Keystone, go to www.pastonearch.org