Saturday, September 22, 2012

Of riffles and muck

September 21, 2012 - With the diversion channel finally in place, RC&D began removing sediment from the impoundment this week.  Sediment was trapped by the dam over hundreds of years.  It is stratified into two layers: a surficial layer of silt (muck) and a layer of sand.  Beneath the sand is the historic floodplain of the Mill River.  Crews are removing the silt layer and placing it in an upland reuse area nearby.

Also this week, crews began building a riffle where the Mill River enters the (former) impoundment.  Above is a picture of the excavator as it builds the riffle.  Below is a short video clip.

Finally, crews graded the channel for the Mill River at the downstream end of the project area.  Eventually, the crews will construct a riffle here and build river banks.  I took this picture standing at the upstream end of where the spillway of the dam used to be.