NORTHWEST BRANCH ANACOSTIA RIVER
Streambank Stabilization/Pipeline Erosion Control
A 22-inch diameter natural gas pipeline that crosses the northwest branch of the Anacostia River in Maryland had become exposed due to streambank erosion and lateral migration of the channel. Previously placed rock failed to remediate the pipeline erosion issue. If left uncovered and unprotected, the pipeline exposure risked further damage due to continued erosion.
After the Submar construction crew sandblasted and recoated the pipeline to restore its integrity, they installed a system of Submar Mats, articulated concrete revetment mattresses, over a woven geotextile material. The mats allow natural vegetation and retain the grade to ensure streambank stabilization and prevent future stream bed degradation. Material from the stream bed then was placed on top of the mat system in the form of constructed riffles to dissipate stream velocity. The crew then placed stones on the toe of the banks above the thalweg and installed a rock sill downstream of the mat system to aid in preventing further stream bed degradation. Upon completion of the final grading, the crew installed pipeline erosion control blankets on the banks and placed seed and straw (Best Management Practices).