Turkey Branch Stream Restoration Project
The $3,500,000 Turkey Branch Restoration project is the Department of Environmental Protection’s (DEP's) largest restoration effort to date. On March 15, 2007 DEP staff toured the restoration site with members of the Stormwater Partners Network. According to Don Dorsey, DEP Watershed Planner, the restoration will consist of two new wetlands ponds at Matthew Henson State Park and a retrofit of the dry ponds at Peppertree Stormwater Management Ponds to create wetland ponds. The wetlands stormwater ponds will differ from the traditional wet ponds in that they will be much shallower (about 6") and will be vegetated. Matthew Henson stormwater ponds will have two cells (retention areas) which will include a deep fore bay which will be used to capture sediment and trash. There is also a dry pond by Home Depot which manages stormwater in the watershed, but is not part of this restoration effort. The ponds are designed to manage large storms (the 1 year storm.) When we asked about DEP's efforts to improve hydrologic functions in the in watershed, they noted that they were doing the following:
  • Installing a Rainscapes project at Kensington Fire Department on Bel Pre Road.
  • Installing a Rainscapes project at Aspen Hill Library.
  • Implementing a riparian reforestation effort in portions of the stream.
  • Pam Rowe (Rainscapes Coordinator for the Department of Environment) will be working with schools to implement Rainscapes projects (4 MCPS watershed schools).
  • Pam Rowe will also start working with homeowners in Wheaton Woods to install Rainscapes projects on their properties.
  • The Turkey Branch sub-watershed is one of three sub-watersheds that DEP will in 2007 focus on installing Rainscapes Practices on commercial properties.

Dan Harper, DEP Manager, noted that the base (dry weather) flow in Turkey Branch was not too bad; better than the baseflow in Sligo Creek. Dan also noted that they will be taking over the stormwater maintenance on the stormwater structures in the County schools in the Turkey Branch sub-watershed. They will also be installing a flow gauge in conjunction with U.S. Geological Survey (USGS.) The flow meter will be used to provide feedback on the effectiveness of the stormwater controls. See waterdata.usgs.gov/nwis/uv?01647850.

When we asked about DEP's efforts in saving native vegetation or habitats, restoring natives, and preventing the spread of invasives at the restoration site, the DEP reps noted that the forested areas cleared was heavily impacted by both invasive vines and impervious surfaces from the old Arbor Nursery that was abandoned over 20 years ago. Aerial photos from the past 40 years were provided by Don Dorsey. Dan Harper noted that if the forests were in good condition, they would have selected another site for the ponds. One site was already cleared. Since the sites were so heavily impacted, there was little native habitat or vegetation to save. Part of the restoration effort was going to include trying to "save" trees down stream of the ponds that are enveloped with invasive vines. DEP sees this project not only removing invasives and impervious surfaces (concrete paving), but creating wetland habitats using native plants. DEP will provide deer protection for new vegetation. Geese will be addressed by allowing grass to grow tall. DEP will take responsibility initially in keeping invasives under control. Eventually, this effort will be turned over to the Parks (M-NCPPC.) Tree plants will be planned to allow access of heavier mowing equipment that can be used to manage invasives until the trees have time to grow.

When the Arbor Nursery closed, extensive concrete surfaces remained. Enough concrete surface area remained that the restoration contractor had plenty of parking for their many construction vehicles. As part of the restoration, nearly all the concrete slabs will be removed. The concrete slabs were impacting the habitat potential of the site. Ariel photos, some dating back to 1951, showed how the area has dramatically changed over time. Like the Matthew Henson Park, DEP is also removing concrete from the Peppertree site and create a wetland.

  Near Georgia Ave. we were shown Coir fiber (made from coconuts) logs, which were installed to stabilize the stream banks. These logs will trap sediment when flood waters recede. Over time the "logs" will bio-degrade. DEP is hoping that sampling will take root by then and the stream banks will be strengthen by their root system.

Coir fiber logs lining tributary stream - March 15, 2007

DEP showed us a 24" WSSC sanitary line that they were trying to backfill. Using step structures (shown on the photo to the left), the 24" sanitary line is now nearly buried. A little more work remains and it will be totally submerged. Originally, erosion left the sanitary main almost completely exposed (see photo below of main exposed.) As part of the watershed restoration, WSSC was coming in the re-line the sanitary lines the cross Turkey Branch.

WSSC Sanitary Main - March 15, 2007

Exposed sewer line before restoration

The stream restoration will use a "modified" Rosgen methodology (an aggressive, formula-based approach to stream restoration.) The structures are being installed at key locations to redirect flow. No attempt will be made to reconstruct the original stream route since DEP wants to minimize disruptions. Floodplain structures are being built along the stream to absorb much of the increased flow. The floodplain shelf structure is about 5' wide and can be seen on the bottom of the photo below. Over time sediment will be deposited in the floodplain. In other sections, dead trees will be used to line the branch and capture sediment (similar to the Coir fiber logs). Over time DEP hopes that these to will result in samplings taking root and stabilizing the stream banks.

The "modified" Rosgen stream restoration along the branch.
The rip rap in the center is protecting a large sanitary main that is partially exposed.
In the background, trees are shown to be smothered by invasives.
According to DEP, they are planning on "rescuing" these trees.

DEP was agreed that the Turkey Branch would require a long-term effort (maybe ten years.) They also agreed that a good indicator for success would be raising the biological health level one level - from poor to fair. Dan Harper noted that due to development in the Turkey Branch watershed, bring the branch to good biological health may not be feasible.

This information is based on conversations with Department of Environment staff (Don Dorsey, Dan Harper, Mark Wilcox and Pam Rowe) who toured the restoration site with Stormwater Partner Network members (Steve Drydan, Jim Fary and Ed Murtagh) on March 15, 2007 and an April 3, 2007 presentation by Pam Rowe (Rainscapes Coordinator from DEP) to an inter-watershed meeting at the White Oak Library. The restoration project, which started in January 2007, is expected to be completed in the Winter of 2007.

Detailed information on the Turkey Branch Restoration effort (PDF file)

Ed Murtagh