Wednesday, August 29, 2012

Changing Habitat in the (Former) Impoundment

8/28/12 - This week, the contractor is constructing a diversion channel around the Hopewell Mills Dam impoundment.  While the water was drawn down almost three weeks ago, the sediment is still wet and mucky. The diversion will help dry out the sediment so that heavy equipment can excavate the new channel and shape the floodplain.

The wet sediment, meanwhile, hosts migratory shorebirds as they head south.  Birdwatchers have seen Killdeer (Charadrius vociferus) and Least Sandpipers (Calidris minutilla).  Both species feed on insects found in mudflats, so it's not surprising that they are flocking to the impoundment.  The photo abov shows 1) the new channel of the Mill River towards the upstream end of the impoundment; and 2) the mudflat habitat that is popular with the shorebirds.  The mudflat condition is only temporary; at the end of the project, the Mill River will meander through a meadow planted with native trees and shrubs. 

It is exciting to watch the site change.  Compare the photo above, taken 8/28/12, with the one below, taken from the same point three weeks ago.

Friday, August 24, 2012

The first riffle in 200 years

August 23, 2012 - The Mill River flows freely through the former Hopewell Mills Dam spillway site for the first time in 200 years.  Like all free-flowing rivers, the Mill River now has the power to move bed material and build habitat.  We humans frequently engineer and construct habitat features like pools and riffles.  Yet, rivers have been doing that work without our help for eons.  Within a week of fully removing the spillway of the old dam, this riffle developed.  Note the slight turbulence caused by the cobbles and small boulders -- riffles aerate the river water.  Riffles are also "kitchens" where stream insects live and fish feed.  Contractors still have a lot of work to do to excavate contaminated sediment and shape the new stream channel.  But, this naturally-formed riffle reminds us that once the construction crews leave the site, Mother Nature and the river will take it from there.

In this picture, taken the same day, construction crews install dwatering pipes through the earthen berm dam.  While the spillway of the dam is gone, thousands of yards of material still fill the old floodplain.  This artificial fill will be removed so that the Mill River can regain floodplain habitat and function.

Wednesday, August 15, 2012

And The Walls Came Down

Today's work included more removal of the earthen dam, and chipping away at the walls. After much hammering, the walls came down. Water levels are up, due to recent rain (downpours), so a diversion channel will be constructed through the eastern side of the dam to further drain the impoundment. By next week, much of the recognizable dam will be gone!

Tuesday, August 14, 2012

Millions of Herring

Brian Graber (American Rivers) and Rachel Calabro (Save the Bay) discuss the Hopewell Mills Dam removal and the Mill River Restoration.

Friday, August 10, 2012

Chipping Away At the Spillway

Beth Lambert from the MA Division of Ecological Restoration passed along this photo this morning of the construction crew starting to break apart the Hopewell Mill Dam's spillway. While removing the dam includes months of construction work, the spillway removal is the classic dam removal moment!

Thursday, August 9, 2012

A River Returns

Today, the impoundment continues to drain, and the old channel is beginning to appear. Project partners spent the day meeting with media and documenting the progress. Mary Griffin, Commissioner of the Massachusetts Department of Fish and Game was on site to speak with reporters. Yesterday, Save The Bay was on hand to speak with Channel 12 in Providence. An industrial archaeologist was on site today to document parts of the old Hopewell Mill that can be seen in the earthen embankment of the dam. This photo shows what was once one of the interior walls of the mill.

Wednesday, August 8, 2012

The First Scoop

The impoundment has been drained by allowing water to flow through the old dam gates. Water now flows under the dam, and the spillway is dry. Excavation of sediment behind the dam is beginning and the spillway will be lowered slowly as the impounded sediments dry.

Monday, August 6, 2012

Work begins at Hopewell Mills

Work has begun at Hopewell Mills, and lowering of the spillway will start this week. Trees have been cleared from the top of the dam, roots and all. These trees with their root wads will be reserved and used in the former impoundment to give structure to the new stream channel and provide habitat and bank stability. The construction crew will be lowering the impoundment by moving gates that exist in the old dam, releasing water downstream. When water levels drop, the concrete spillway will be lowered using a hydraulic hammer. This part of the work will most likely begin on Thursday.