A steep drainage ditch is what this is. There is a parking lot on MacArthur Blv., which gives access to the trail down to the C&O Canal towpath. This trail takes you by an old rusty steel bridge. You can put-in below that and run the pipeline beneath the Clara Barton Parkway, which runs parallel to the Potomac River. This run begins immediately after the water comes out of the pipe beneath the parkway, and the run is about 40 yards long. It consists of two 10- to 12-foot falls back-to-back with a lttle class-4 run out into the C&O Canal. It takes either a lot of hard rain or a quick burst of hard rain. Either way, it has to be caught DURING a hard rain. It comes right off neighborhood streets so it comes up and goes down quickly. I believe no one has ever run this stream so it is open to a first descent!
As for the takeout, you can paddle across the canal and take the trail bridge back over the canal and up the trail to the MacArthur Blv. parking lot.
_Lat/longitude coords are a rough estimate, based on online maps._