The Saw Mill Run Watershed FloodPlain Management Strategy: Completed in 2016

The US Army Corps of Engineers has been investigating flood risk management solutions for the Saw Mill Run Watershed for nearly 70 years. The focus of this document was to outline non-structural strategies to decrease total volume and velocities of stormwater runoff into Saw Mill Run, decreasing peak flows. Non-structural and Green Infrastructure techniques offer the greatest opportunity to reduce the frequency and severity of flooding within the watershed.

This recommendation section has been divided into four alternatives. These alternatives are not mutually exclusive, but ordered from highest to lowest anticipated impact. Cost, complexity, and potential benefits were all considered.

Alternative 1: Partnership with Government and Transportation Interest

• Because these parcels support critical transportation infrastructure this alternative would not require land acquisition, and instead rely on a partnership between the land owner and the implementing partner. 

• The public owners have a direct stake in reducing the frequency and severity of flooding. The implementing partner would use public land to install and maintain the stormwater management features.

Alternative 2: Large Private Landowners and Unused Impervious Surfaces

The second alternative involves a mix of public/private partnership and property acquisition. 

• Throughout the PA-51 and PA-88 corridors there are large areas of abandoned or underutilized commercial properties with large paved areas. 

• Targeting those parcels with high impervious coverage and little to no active use would offer lower cost acquisition options that could significantly improve retention. 

• The location of parcels adjacent to the stream would also significantly reduce stormwater velocities prior to reaching Saw Mill Run.

Alternative 3: Headwater Flow Reductions

• Neighborhoods upstream of the main stem of Saw Mill Run have developed stormwater management systems that quickly remove runoff into the downstream portions of the basin during heavy precipitation events. 

• These flows from upstream communities, combined with runoff flowing directly into the main stem, combine to produce significant impacts at certain points in the watershed, including the PA-51 and PA-88 Junction.

• The most effective stormwater management programs require a watershed approach, in this case possible modifications to stormwater management practices in the upstream reaches of the watershed.

Alternative 4: Buyout and Relocation of Commercial and Residential Properties

• This alternative is the least desirable of those considered due to the cost, average parcel size, and complexity of acquisition.

The Saw Mill Run Green Boulevard Property Acquisition Study: 

• Completed in 2016

• A decision making matrix to identify priority parcels for inclusion in the Route 51 Green Boulevard. This study completed some of the foundational elements which will enable the transformation of the Route 51 corridor into an amenity which provides a variety of triple bottom line benefits

• The long-term vision for the Green Boulevard is to enhance the economic, environmental, and social health of the corridor. 

• The Route 51 corridor and the Saw Mill Run watershed currently face several challenges such as blighted properties, localized flooding, and impaired water quality.

The goals of this project included:

•  Benchmark national best practices to inform goals and objectives,

•  Develop a decision-making matrix to identify parcels of land for inclusion in the GreenBoulevard planning effort.

• Apply the matrix along the Route 51 and Library Road corridors, and Identify both near-term and long-term priority acquisition parcels.