Forbidden Drive Trail Stabilization Project

Current Projects // August 31, 2015

Project Status: Funded; Planning

Funded by: PA Department of Conservation and Natural Resources, PA Commonwealth Financing Authority – Department of Community and Economic Development, Private Donors

Forbidden Drive was originally supported by mortared stone walls for much of its length, evidence of which are visible from the Orange Trail during winter months. Additionally, a rudimentary drainage system comprised of an inboard ditch and cross drains diverted water away from the drive preventing it from becoming over-saturated and placing an undue burden the stone walls.  Overtime, these systems deteriorated from a lack of maintenance and the increasing frequency of large, damaging flood events which has caused Forbidden Drive to become unstable at numerous locations.

Three sections of Forbidden Drive have severely eroded or partially collapsed along the trails waterside edge, restricting the width of the trail and undermining its stability causing potentially dangerous conditions for park users.  You may have seen our banners hanging on the sections of chain link fence on Forbidden Drive.  Beginning in 2016, FOW will hire a contractor to restore these collapsed sections of trail and help us plan a more resilient drainage system for Forbidden Drive.

The Wissahickon Creek Watershed is severely impacted by urbanization and Wissahickon Creek is listed on Pennsylvania’s 303(d) list of impaired waters due to siltation, low dissolved oxygen concentrations, and numerous other factors (US EPA Region III, 2003). Each of the collapse sites are actively eroding and contribute sediment loads to Wissahickon Creek during rain events.  Restoration of these sites will contribute to meeting the established Total Maximum Daily Load (TMDL) for siltation of Wissahickon Creek as established by the US Environmental Protection Agency (EPA) and the Pennsylvania Department of Environmental Protection (DEP) in accordance with Section 303(d)(1)(c) and (2) of the Clean Water Act.

Project goals:

  • Stabilize the trail (and any infrastructure embedded within it).
  • Reforest the embankment slope and restore riparian habitat.
  • Construct drainage improvements necessary to prevent further degradation of the roadway.
  • Create safe, stable conditions for trail users.
  • Assess drainage issues on the entirety of Forbidden Drive; develop plan for future maintenance.