Gunner's Branch Stream Restoration


Gunner’s Branch Bridge Replacement and Stream Restoration

Germantown, Maryland

CPJ Environmental Services Department (CPJ) was awarded a contract with the Maryland-National Capital Park and Planning Commission (M-NCPPC) to provide consulting services for the stabilization of several severely degraded stream segments along Gunner’s Branch, Little Falls, and Paint Branch Streams in Montgomery County, Maryland. The purpose of the Task Order is to design restoration practices that will stabilize eroded areas and provide improvements to protect, repair, or replace existing infrastructure threatened by stream erosion. Per direction of Mr. Andrew Frank, Project Manager at M-NCPPC, CPJ conducted a series of field walks with M-NCPPC staff and other interested parties to review existing stream restoration concepts, discuss design approaches, identify site constraints and access points, investigate existing erosion problems and threatened infrastructure, and examine in-stream and riparian habitat improvement needs. 

Design issues at the Gunner’s Branch project area included replacement of an existing pedestrian bridge as well as stream restoration design to reduce future impacts from stream erosion and improve accessibility. A 50’x8’ Pony Truss design with a Douglas Fir decking and weathering steel finish of similar design to the existing deteriorating bridge was proposed. A new bridge alignment was proposed to solve several of the design problems associated with the existing location. By locating along a stabile stream reach we reduced the chance that the abutments will be compromised in the future. CPJ also recommended a slightly extended bridge span due to the likelihood that the cross sectional area within the Gunner’s Branch will develop further and cause additional widening of the stream. The existing scour areas adjacent to the trail was stabilized through a combination of a stone toe and fill section, while the opposite stream bank will be excavated to maintain a stable cross section. The top of the banks were given added protection with the establishment of a single height log barrier to discourage access into the stream at these areas.

© 2010 Charles P. Johnson & Associates, Inc.