Nearly one-third of all locally owned bridges in Pennsylvania, low-volume spans that cross creeks or other small waterways, are considered structurally deficient, according to Department of Transportation bridge-safety ratings released yesterday.
Of the 811 in the Philadelphia area, 252 scored the low rating. Nearly all are in use.
The list covers about 6,400 bridges that measure 20 feet or longer and are owned by counties, municipalities or other local entities. Nearly 2,000 of the bridges are classified as structurally deficient, 1,984 have posted weight restrictions, and 200 are closed because they are unsafe for any traffic, PennDot spokesman Rick Kirkpatrick said.
Ever since the deadly Aug. 3 collapse of a highway span in Minnesota, bridge safety has has become a national concern. In August, PennDot released the safety ratings of 25,000 state-owned bridges that measure eight feet or longer. Almost a quarter of those bridges are considered structurally deficient.
The newest ratings, posted on the agency's Web site, should not set off any alarms, Kirkpatrick said.
"People shouldn't think they shouldn't ride on a bridge that is structurally deficient," he said. "It just means there is a higher level of deterioration. But if it's open and there are no weight restrictions, it's safe to travel on."
The oldest subpar bridge in the area carries Fisher's Lane over Tacony Creek and was built in 1801. It has a sufficiency rating of 39 on a scale of 100. It also scored 3, or "serious," on its substructure - 4 or below is considered structurally deficient.
The Minnesota bridge had a sufficiency rating of 50. Locally, 155 bridges come in under 50.
Montgomery County had the most structurally deficient bridges with 62, while Chester County had the fewest, 26.
Among the largest of the spans is the Green Lane Bridge in Philadelphia, at 601 feet. Built in 1928, it carries Green Lane over the Schuylkill and Conrail. It has a sufficiency rating of 48.
The lowest-rated bridge is in Lower Salford in Montgomery County and was built in 1896, an iron-truss structure 117 feet in length that crosses the Perkiomen Creek at Freeman School Road. It has a sufficiency rating of 1 out of a possible 100, and is closed to traffic.
The deck and substructure are rated 6, or "satisfactory," while the superstructure scored just 2, or "critical."
In Philadelphia, another critical bridge is identified as N. St. Martins Lane and takes Willow Grove Avenue over SEPTA tracks. Built in 1883, it has a sufficiency rating of 2.
The rating takes into account a bridge's structural condition, importance, and ability to meet current traffic demands. A bridge is classified as structurally deficient if it receives a 4 or less on a scale of 9 on at least one of the primary structures. A bridge that receives a 1 on any of its primary structures is required to be closed until it can be repaired.
Kirkpatrick said if a bridge is rated as structurally deficient, "it means we're watching it closely and it may get to point where it will have to be closed and restricted."
For a list of local bridges studied by PennDot and their condition, go to go.philly.com/pabridges