PB-85 STREAM RESTORATION

PRINCE GEORGE'S COUNTY, MD

To mitigate for impacts from the construction of the InterCounty Connector, McCormick Taylor identified stream restoration opportunities along portions of Paint Branch and Little Paint Branch.

DESIGN, ENVIRONMENTAL, PLANNING & COMMUNICATIONS, CONSTRUCTION , GOVERNMENT, WATER

THE CHALLENGE

The PB-85 site provided opportunities to improve floodplain reconnection, reduce channel boundary erosion, improve instream habitat for resident and anadromous fish and other aquatic species, provide flood attenuation, and enhance and reforest over ten acres of riparian area along portions of Paint Branch and Little Paint Branch tributaries. The improvements could potentially recover ecological and geomorphic conditions, not only at the site, but also for miles of channel downstream by reducing suspended sediment loads and reducing peak discharges that can erode downstream channel boundaries.

 

The project incorporated stream, floodplain, and wetland restoration efforts along Paint Branch extending from MD 193 (University Boulevard) upstream approximately 4,180 feet.

pb 85

HOW WE HELPED

To achieve these goals, the proposed design strategy focused on two basic concepts:

 

1. Strategically provide instream improvements through isolated structure placement and channel enhancements to reduce erosion and improve aquatic habitat.

 

2. Breach existing agricultural berms along Paint Branch and Little Paint Branch on the BARC property, allowing floodwaters currently contained and directed quickly downstream to disperse, depositing suspended sediment throughout the adjacent floodplain.

pb 85 wetlandcell flooding apr2014
pb 85 paintbranch breach concreteblocks oct2013

Specific design items used to complete the effort include:  

  • Designing proposed berms to protect existing property owners from additional flooding
  • Designing the berm breach and protection treatment to maximize stability, and transport of suspended sediment, nutrients, and water into the floodplain
  • Iterative use of a suspended sediment model to predict sediment advection and dispersion patterns within the floodplain cells to promote sustainability and maximize function of the floodplain.

Based on the proposed design, it is predicted that approximately 425 tons of suspended sediment will be removed from the sites annually, creating a large TMDL credit.

The design strategy was implemented after a detailed site assessment including:

  • Natural resource inventory
  • Wetland/waterways delineation
  • Forest assessment and delineation
  • Surface and subsurface hydrologic studies (groundwater wells and water budgeting)
  • Detailed hydraulics analysis (1- and 2-D modeling)
  • Geotechnical evaluation of existing soils and berms
  • Wetland riparian and instream habitat evaluation
  • Detailed geomorphic evaluations
pb 85 construction photo 8x10
pb 85 wetlandcell2 oct2014

RESULTS

Project construction was completed in Spring 2014. In May and June of 2014, two large storm events accessed the breaches, depositing suspended sediment in the newly created floodplain cells. The project will be monitored for five years and based on initial observations from the first growing season, the project is meeting its intent of reducing the risk of storm flows, flood damage, water quality degradation, and sedimentation to Paint Branch and the Chesapeake Bay.

AWARDS 

2015 MdQI Green/Sustainability/Environmental Award of Excellence

2015 ACEC/MD Engineering Excellence Award