The Friends of the Wissahickon will soon begin construction on several areas of Forbidden Drive that require erosion control work.

by Lizzie Stricklin

For Wissahickon Valley Park, the most popular and trafficked trail is easily Forbidden Drive. Winding its way from Northwestern Avenue to Lincoln Drive, Forbidden Drive serves as a wide, shaded trail that is easily accessible for the whole family to enjoy.

While this path feels timeless at the heart of the wooded Wissahickon, a great deal of work goes into maintaining this popular destination. In the midst of continuing wear and tear, Forbidden Drive will soon be receiving some much-needed repair.

The Friends of the Wissahickon will soon begin construction on several areas of Forbidden Drive that require erosion control work. This work will be done at three locations, near Valley Green Road, at Mount Airy Avenue and at Kitchen’s Lane, where collapses caused by erosion and flooding have limited the width of Forbidden Drive. Riverlogic Solutions/AKRF has been selected to do this construction work.

“The trails have been in a state of disrepair for several years,” said Maura McCarthy, FOW executive director.”

Recently, however, the condition of these three locations has become increasingly severe and; according to McCarthy, “the next storm event could make impassible.”

“The repairs needed along Forbidden Drive are incredibly urgent in the sense that the next storm could catastrophically exacerbate the current collapses,” she explained. “The report that was generated by an engineer’s assessment after the collapses and prior to FOW’s grant applications emphasized that at any time, with a significant rainfall event, these particular sites could further erode, and it’s not unlikely that one could completely bisect Forbidden Drive and eliminate access.”

The FOW also finds these repairs necessary as the collapses on the watershed provide obstacles for emergency access vehicles, for which Forbidden Drive is the only accessible route through the park, and expose infrastructure, such as sewer lines, beneath the trail.

“ has reduced the width of Forbidden Drive in half in these areas, which can create congestion on the trail if they continue to happen,” McCarthy said. “Also major tree loss and a huge amount of sediment have been discharged into the creek. The situation is unsafe, unattractive, and can increase user conflict.”

Although construction has not yet begun, the FOW has been pursuing this project for about three years.

“The collapses were first identified in 2011,” McCarthy said. “FOW and consultants completed their assessment about 18 months after the original collapses.”

Much of the time since then has been spent fundraising to reach the construction’s $1 million budget through state and private foundation grants as well as individual donor support. The FOW received the first grants for the project in December 2013, and finally have the funding in place this year.

“Also, a major project like this in a waterway requires significant state and federal permitting,” McCarthy added. “It takes time to generate plans and secure the permitting before we can move into construction.”

Over the next six to eight months, Friends of the Wissahickon, with Riverlogic Solutions/AKRF, will be looking at the engineering of the sites and analyzing the hydrology. Although the basic approach has been finalized, the project is now getting into the early planning and development phases.

McCarthy predicted that the design work will be completed by next year and that construction will begin in late 2017. Each of the three sites will require about 12 weeks of repair work, weather permitting.

The goal of this construction is to stabilize the banks both upstream and downstream. The entire more than seven miles of the watershed spanning these three sites has very old, built-up embankment. According to McCarthy, there will be a “top-to-bottom assessment” of the trail and its embankment to come up with a strategy to prevent further collapse. As she noted, “These won’t be the last to collapse.”

“This project is really more about building resiliency at these sites and restoring the existing draining infrastructure, which was installed in the early 20th century,” McCarthy explained. “Because we are at the bottom of the watershed, on bedrock, there is really no opportunity for water infiltration there, so our focus in on moving the water through the sites sustainably. At these three locations, engineers and landscape restoration specialists will be reconstructing the collapsed section of the embankment using natural materials with plant anchoring. FOW strongly believes that our project work should only incorporate materials that would naturally be found in a park or natural lands setting, so we avoid form stone, cement and geotextiles whenever possible.”

As the construction gets underway, any work that will disrupt recreational activity on Forbidden Drive will be announced via a press release from the FOW.

Repair projects such as this are crucial to the upkeep of the Wissahickon and Forbidden Drive, now more than 150 years old. The work of the FOW is driven by the help and support of volunteers and patrons and is well rewarded in the results of these projects. McCarthy does not forget this and encourages more nature enthusiasts to offer a helping hand in keeping the park maintained.

“We need to protect both the park resource and the water resource, and to do that we need people,” she said. “We’re hoping everyone who loves the Wissahickon will be able to contribute in some way … to make sure the Wissahickon is maintained.”