Vegetation Considerations When Converting a Mill Pond into a Public Park: Hershey’s Mill Dam Redevelopment Project
Justin Laughlin
Gannett Fleming, Inc.
Baltimore, MD
Authors: Justin Laughlin, Ashley McGinnis, & Eric Neast, Gannett Fleming, Inc.
The Hershey’s Mill Dam redevelopment project in East Goshen Township, Chester County, Pennsylvania was completed in 2022. Originally constructed in the late eighteenth century as a source of water to power a gristmill, the dam was an earthen structure approximately 400-feet long and 14-feet high which formed a 2± acre impoundment. To eliminate dam safety risks, the Township decommissioned Hershey’s Mill Dam by breaching the embankment coupled with various improvements to convert the dewatered reservoir into a public park setting.
Major site improvements included reconnecting two unnamed tributaries of Ridley Creek through the dewatered reservoir, an open water pond feature, a boardwalk, walking paths, paved parking area, and landscaping. The improvements were located almost entirely within the footprint of the dewatered reservoir which was comprised of wetlands and saturated soils. The dam embankment was breached in December 2020 with stream channel restoration following in 2021. The stream design included two new channels that were stabilized with riffle grade controls and step pools to drop the elevation between the relic reservoir bed and the new channel elevation at the dam breach. A small offline open water recreational pond with surrounding boardwalk and trails was included for public enhancement.
To create a natural wetland habitat an aggressive planting plan was pursued. Vegetation considerations were a major focus on how the site would service the public, provide recreational/educational opportunities, and improve the ecological function of the site. The landscaping design provided a balance of native plants to enhance the site with canopy trees, understory trees, and meadow establishment, requiring minimal maintenance. The strategic planting included plans to use the vegetation to enhance the wetland, limit invasive species, and prevent pedestrians from accessing private property.
This presentation focuses on the process from start to finish turning a dilapidated mill pond into a functional public park. The discussion will cover vegetation considerations, lessons learned working in wetland conditions, collaborating with contractors, dealing with historic floods during construction, and designing a natural stream channel within the context of a park.
About Justin Laughlin
Justin is a Senior Environmental Scientist with Gannett Fleming in their Baltimore office where he is responsible for conducting stream restoration and water quality improvement projects throughout the Mid-Atlantic region. Duties include contract and project management; stream restoration assessments; ecosystem restoration design and construction oversight; senior level technical and peer reviews; mentoring and training of junior staff; best management practices (BMP) design including regenerative stormwater conveyances; stormwater outfall design; permitting; and post-construction monitoring.
His stream and ecosystem restoration experience has included streams, dam removal, nontidal wetlands, fish passage, T&E species recovery, habitat enhancement, and reforestation throughout the continental U.S. He has over 20 years of experience in the environmental field including over 11 years in the consulting industry. Justin obtained his Bachelors of Science degree in Forestry from Mississippi State University and his Masters of Science degree in Forestry, Wildlife and Fisheries from the University of Tennessee. He is a professional disc golfer that enjoys a day on the river.