Friends of the Wissahickon’s Guide to Spring Construction at Andorra Natural Area Work zone closed to visitors beginning in mid-March


The first phase of Friends of the Wissahickon’s (FOW) Green Stormwater Infrastructure (GSI) project in Andorra is set to begin construction in mid-March  and will continue until mid-June. During this time, work zones will be closed to the public.

Funded by the Pennsylvania Department of Environmental Protection, the unique GSI project takes a watershed-approach to mitigating damage from uncontrolled surface stormwater flows originating from Northwestern Avenue and the adjacent minimally vegetated parkland. A series of GSI features designed to intercept, treat, convey and infiltrate stormwater will greatly decrease sedimentation carried from this micro-watershed into the Wissahickon Creek, while greatly increasing the quality of the day-use area of the Wissahickon Environmental Center (WEC) and adjacent trails.

FOW consulted with the Philadelphia Parks & Recreation staff at the WEC, District 4, and Natural Lands Restoration staff to help ensure public safety and minimize impacts on park users during construction. With this in mind, FOW asks visitors to the Andorra Natural Area during the construction period to please stay out of the work zone and heed safety signage at all times — even if the crew is not working.

Areas of Impact during Construction

Northwestern Avenue at the Upper Parking Lot

Work will be underway for a few days during the construction period on Northwestern Ave just above the parking lot entrance and will be closed to all vehicle traffic.

Upper Parking Lot

During construction, the Upper Parking lot above the WEC on Northwestern Avenue will be closed to vehicles since it will be the main staging area for the project and will be used for material stockpiles and equipment.

Bike Bypass

This trail will be closed during construction.

Areas NOT Impacted During Construction

The following park amenities at or near the work zone will not be impacted during construction. Nevertheless, please remain aware that construction is underway nearby and any related safety signage should still be followed.

Red Forest Loop and Connector Trail 

This old rocky road bed that runs behind the WEC and along the edge of the day-use area will not be impacted during construction, except for a few specific days based on the construction schedule. From the WEC, this trail will provide the most direct route to Andorra Meadow.

Wissahickon Environment Center and Lower Parking Lot

WEC, the “Tree House,” and public restrooms will be open during normal hours throughout the construction period. The access road from Forbidden Drive and associated parking lot will also be open during this time.

When the GSI project is completed, park visitors can expect to see an enlarged and re-vegetated basin at the upper parking lot with a series of vegetated rock cascades leading from the basin down the hill through the forested canopy. At the WEC day-use area, visitors will enjoy a vegetated rain garden and swale leading to the existing wetland located downhill and along the drive from the WEC. This lower reach of the watershed is Phase II of the project and will be addressed at a later date.

Throughout 2017 and into the winter of 2018, the environmental engineering firm A. D. Marble, based in King of Prussia, has guided the project from concept to final design. Their construction partners, Lancaster-based Flyway Excavating, is the on-site contractor, turning the two-dimensional drawings into 3-D reality.

For the latest GSI updates, visit FOW’s website of follow FOW’s Facebook, Twitter and Instagram feeds.

About Friends of the Wissahickon

Founded in 1924, Friends of the Wissahickon (FOW) is the oldest and largest nonprofit volunteer organization working in partnership with Philadelphia Parks and Recreation to preserve and restore historical park structures and trails, eliminate invasive plant species, and monitor watershed management issues throughout the 1,800-acre Wissahickon Valley Park. With more than one million visits annually, this northern stretch of Fairmount Park was declared what is now known as a National Natural Landmark in 1964. The Park’s Forbidden Drive was named 2018 Trail of the year by the Pennsylvania Department of Conservation and Natural Resources. Follow FOW on Facebook and Twitter. For more information or to become a member, visit

Attachments area