The Cabin John watershed has a drainage of approximately 26 square
miles. Its headwaters begin in the heart of Rockville, near the
intersection of Route 355 and Route 28, and the stream flows south
for 11 miles into the Potomac River. The watershed has been heavily
impacted by development that took place around the I-270/I-495 transportation
corridors before environmental regulations for stream buffers and
stormwater management were put in effect. As a result, there are
few onsite stormwater runoff controls in Cabin John.
The mainstem and a portion of the western tributaries do receive
some protection in the form of buffers established as part of the
County's stream valley park system. However, this is not enough
to protect the habitat quality and stream conditions within the
park from the detrimental impacts that have resulted from unmitigated
flows from highly impervious areas located upstream. Several regional
stormwater ponds were put in place to control drainage from Montgomery
Mall, the office parks at Democracy, and I-270. This treats only
a fraction of the total impervious area in this watershed. Impacts
within this watershed include accelerated stream channel downcutting
and widening, as evidenced by toppled trees and exposure of sewer
lines originally buried 10-20 feet below the bottom of stream channels.
In the 1998 Countywide Stream Protection Strategy, there were only
three tributaries identified in the Cabin John watershed that maintained
a good resource condition capable of supporting a diverse fish community.
Cabin John Summary Document and Maps
4 pp, 8.6Mb)
Montogmery County’s Cabin John Creek Watershed Implementation Plan (PDF, 43pp, 2.57Mb)
Similar to the other two more urban watersheds in the County, the Montgomery County Draft Cabin John Creek Watershed Implementation Plan (WIP) first recommends prioritizing full implementation of high and low priority projects during the County’s MS4 permit cycle through 2015. Fewer opportunities exist overall compared to the Anacostia and Rock Creek watersheds. Next, the plan targets implementation of other potential projects. The Plan emphasizes ESD on both public and private property. Finally, the Plan targets outreach for pollutant load reduction but not impervious cover credit. The Plan found limited or no opportunities for riparian reforestation or stream restoration. In future permit cycles, the Plan targets remaining potential projects, along with ESD and some riparian reforestation for impervious cover and pollutant load reduction. According to the model employed in the Countywide Coordinated Implementation Strategy, implementation of the Cabin John WIP will achieve bacteria Waste Load Allocations (WLAs) in the MS4 permit area by 2025.
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