Plymouth Creek Restoration Project

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Plymouth Creek Restoration Project
Plymouth Meeting, PA

One of the Commonwealth’s most impervious corridors surrounds Plymouth Creek in Montgomery County’s Plymouth Meeting. Adjacent to the Metroplex, the region’s largest open air shopping center, an eight acre drainage basin receives runoff from six square miles of parking lot and road before it passes into Plymouth Creek (which feeds into the Schuylkill River a few miles downstream). Although technically in compliance with regulatory requirements, the basin had the tendency to flood during peak storm events.

PA DEP employee Dominic Rocco often drove along Route 476 and saw the site under many different conditions. He realized that not only was it ripe for a retrofit, but thought it could become a highly visible demonstration of what stormwater best management practices could accomplish in terms of flood control, water quality improvement, and aesthetic enhancement. A conversation with the Montgomery County Conservation District led to a collaborative effort that included the local CCD, Rocco’s agency, the owner of the Metroplex Shopping Center, and the Pennsylvania Horticultural Society’s TreeVitalize program.

“Everyone is a stakeholder in this. It affects residents in these townships, people who use the bike path along the creek, everyone who drives the Blue Route – it’s a real community project.”
-Dominic Rocco, Department of Environmental Protection

Montgomery County Conservation District undertook a careful site investigation and drafted a site plan with the assistance of a landscape architect firm. Phase I of the project, which was completed in fall 2007, sought to stabilize and revegetate the basin by planting some 400 trees and shrubs and installing more than 1,700 plugs of herbaceous plants. Phase I tasks were accomplished with the help of dozens of volunteers—from state employees and conservation minded citizens to staff of the property owner and students from local area schools. Phase II, scheduled for Spring 2009, will involve adding two additional sediment forebays, converting a meadow, and installing live stakes for channel protection.

In addition to reducing flooding, stabilizing stream banks, and filtering pollutants before they enter Plymouth Creek, the Metroplex restoration project showcases best management practices in action.

“I hope that other developers see the improvement of this approach over traditional stormwater management methods, as well as the aesthetic benefits and lower maintenance costs. It’s important for people to see that these BMP’s can actually be implemented and are not just something you see in a manual.”
-Susan Harris, Montgomery County Conservation District

PROFILE

Situation: An eight-acre stormwater basin along Plymouth Creek drains 6 square miles of highly impervious surface and is susceptible to major flooding during peak storm events. This project is a collaborative effort to restore the basin to a more naturalized state.

BMPs:

Revegetate Using Native Species: Naturalized Basin (BMP Manual reference: BMP 5.6.3)
Vegetated Swale (BMP Manual reference: BMP 6.4.8)
Sediment Forebay

Benefits:

Soil stabilization
Flood prevention
Pollutant reduction
Improved Habitat

Site:

Metroplex Shopping Center
Plymouth Meeting, Montgomery County PA

Players

Goldenberg Group (Property Owner)
PA DEP – SE Region
Montgomery County Conservation District
McCloskey & Faber, P.C. (Landscape Architects)

Cost

$59,020

Funding

Tree Vitalize watershed grant
The Goldenberg Group
In-kind services from volunteers and partner organizations

BENEFITS

The retrofitted basin not only looks more visually appealing, it provides a variety of environmental and economic benefits to the developer and the community.

Financial

Increased property value
Little to no change in maintenance costs
Saved resources
recycles more than $37,000 worth of water
provides $31,000 worth of erosion control
supplies $62,000 worth of air pollution control and
produces $37,000 worth of oxygen

Quality of Life

More aesthetically pleasing
Increased oxygen; one tree produces nearly 260 pounds of oxygen per year
Cleaner water

Environmental

Reduction in flooding
Stabilization of soil against erosion and sedimentation
Increased filtration of stormwater pollutants
Decreased air and stream temperature elevated by urban development
Improved habitat for aquatic wildlife

PLANNING

The Metroplex is a former Brownfield site that was remediated and redeveloped in 2000. It is now the largest open air shopping center in Montgomery County, PA at 778,190 square feet.

After an intensive site investigation involving the examination of inflows, depth of soil, ponding and washouts of water, Montgomery County Conservation District developed the initial conceptual plan for the basin.

The plan addressed the collaborative group’s priorities for the area:

Reduce flooding;
Filter stormwater traveling through the area; and
Stabilize the stream bank’s sandy soils.

McCloskey and Faber, a local landscape architecture firm, collaborated on the development of a detailed project plan. The final plan integrated a large shrub layer along the banks of the creek with clusters of tree plantings set back from the banks to allow access for efficient mowing and maintenance. Besides the plantings and stabilization, a gabian wall and river stone spillway will be constructed to control peak rate and volume.

Planning Details:

TREE GROUP 1:

FRAXINUS PENNSYLVANICA - 8
ACER RUBRUM - 7
PLATANUS X ACERIFOLIA - 7
AMELANCHIER CANADENSIS - 5

TREE GROUP 2:

BETULA NIGRA - 5
ACER RUBRUM - 6

TREE GROUP 3:

SALIX BABYLONICA - 5
LIQUIDAMBAR STYRACIFLUA - 6

TREE GROUP 4:

AMELANCHIER CANADENSIS - 5
PLATANUS X ACERIFOLIA - 4

TREE GROUP 5:

FRAXINUS PENNSYLVANICA - 5
AMELANCHIER CANADENSIS - 3
QUERCUS PHELLOS - 7

TREE GROUP 6:

BETULA NIGRA - 7

TREE GROUP 7:

ACER RUBRUM - 5
LIQUIDAMBAR STYRACIFLUA - 6

TREE GROUP 8:

FRAXINUS PENNSYLVANICA - 5
LIQUIDAMBAR STYRACIFLUA - 6

TREE GROUP 9:

BETULA NIGRA - 5
PLATANUS X ACERIFOLIA - 4

TREE GROUP 10:

QUERCUS PALUSTRIS - 7

TREE GROUP 11:

SALIX BABYLONICA - 5
BETULA NIGRA - 5
PLATANUS X ACERIFOLIA - 5

TREE GROUP 12:

SALIX BABYLONICA - 8
QUERCUS PHELLOS - 7

TREE GROUP 13:

PLATANUS X ACERIFOLIA - 7
QUERCUS PALUSTRIS - 7

TREE GROUP 14:

QUERCUS PALUSTRIS - 4
BETULA NIGRA - 5

TREE GROUP 15:

QUERCUS PHELLOS – 4
AMELANCHIER CANADENSIS - 5

HERBACEOUS PLUGS:

Cardinal Flower- 150
Blueflag Iris- 150
Switchgrass- 150
Bluejoint Grass- 150
New England Aster- 150

BMP’s

Revegetate Using Native Species: Naturalized Basin
(BMP Manual reference: BMP 5.6.3
Vegetated Swale
(BMP Manual reference: BMP 6.4.8)
Sediment Forebay

The sediment forebay and vegetated swale was lined with an ECS-2 erosion control blanket. Volunteers planted a total of 200 trees and 200 shrubs (refer to Planning for planting details).

In addition, 1,750 herbaceous plugs of a combination of species (Cardinal Flower, Blueflag Iris, Switchgrass, Bluejoint Grass, and New England Aster) were installed.

During Phase II, which is scheduled for completion in 2009, work will take place to continue the naturalization process, including a meadow conversion, additional sediment forebays, and the addition of Live Stakes for channel protection.

REGULATORY

While the Metroplex Shopping Center was in compliance with federal, state, and local regulations, the site owners were interested in the environmental, aesthetic, and long term financial benefits provided by the basin retrofit. In addition, they supported the goal of providing a highly visible demonstration of innovative best management practices in action that could serve as an educational tool for other developers, municipal officials, engineers, and members of the local community. The project was a voluntary, collaborative effort between the DEP, Montgomery County Conservation District, and the property owners (the Goldenberg Group).

RESOURCES

Montgomery County Conservation District - http://www.montgomeryconservation.org
The mission of the Montgomery CCD is to protect and improve the quality of life of the residents of Montgomery County and surrounding communities by providing timely and efficient service, education, and technical guidance for the wise use of soil, water, and related resources. Under a delegation agreement with the PA DEP, the Montgomery CCD is responsible for reviewing Erosion and Sediment Control Plans and inspecting sites for Chapter 102 compliance. Regulatory and permitting requirements can be found under Erosion and Sediment Control.

Montgomery County Planning Commission - http://planning.montcopa.org
The focus of the MontCo Planning Commission is to romote orderly development while preserving valuable county amenities. The Commission’s professional planners develop county plans, model ordinances, and other informational publications and provide technical assistance to the County’s 62 municipalities, and cover a wide range of planning areas, including storm water management, water and sewer, land use, transportation, parks and open space, zoning, and more. Of particular interest is the Water Resources Plan.

McCloskey & Faber - http://www.mcfpc.com
McCloskey & Faber is dedicated to the harmonious integration of project development with the natural resources and character of each site. Our services include Land Use Planning and Management, Environmental Assessment, Site Design and Detailing, Campus Planning, Landscape Design, Recreational Planning, and Expert Testimony.

TreeVitalize - http://www.treevitalize.net/
The Treevitalize program is a collaborative effort that seeks to address the loss of tree cover in Pennsylvania. Research has shown that loss of trees negatively impacts municipalities, neighborhoods and homeowners through increased stormwater runoff, lower air quality and increased energy costs. On the flip side, maintaining and increasing tree cover can positively impact the social and economic environment.

Goldenberg Group - http://www.goldenberggroup.com
The Goldenberg Group specializes in the overall development of large-scale complex real estate, and currently owns and manages nearly 5 million square feet of retail space, including the Metroplex Shopping Center shown in this case study.