Mill Creek Stream Restoration, Cecil County, MD

GTA provided stream restoration design, construction observation and management for a 940-foot section of severely degraded and eroded channel that was historically relocated to construct a potable water reservoir for the Town of Perryville, Maryland. Due to the existing degraded channel being located between the reservoir’s berm to the north and private property to the south, there was no room to relocate the stream to a more natural channel and restoration and stabilization practices were restricted to occur along the existing alignment.

To remedy the precarious situation, GTA strategically designed rock vane structures to replace a previous gabion basket structure. The previous gabion structures were failing and began to scour and erode the impoundment berm adjacent to the stream. Where eroded banks and a previous 2.5 to 3.0-foot drop in elevation existed, GTA installed a series of rock cross vane step pools (double and single drop vanes with 0.5-foot elevation drop) spaced out at one channel width apart to accommodate for slope. The step pool rock vane structures now provide continued grade control while helping to step down the flow. An imbricated rip-rap wall was also installed and keyed into the eroding impoundment berm located on the stream’s left bank to protect the integrity of the berm and prevent further scouring and erosion during storm events. Already storm tested, the stream is functionally restored and its adjacent buffer was planted with herbaceous and woody riparian vegetation.