Exeter Great Dam Removal, Exeter NH Habitat and Climate Resiliency

Gloucester, MA

• 136 W x 16 H foot dam • Dammed since the 1640’s • 107 SM watershed • 4.5 mile impoundment • Municipally owned since 1981 • LOD July 25, 2000 (16 year effort to remove) Exeter Great Dam

Gloucester, MA

Exeter has been about river herring since its founding. Downtown Exeter: Surrounded by Infrastructure

Gloucester, MA

NOAA Funding

2008: $107,000.

2015: $611,000. Inefficient Fish ladder built in the 1960’s (Target Species Alewife)

Gloucester, MA

Alewife Returns 1981 – 2016 ~2,000/year

High 1981: 15,626

Low: 0..muli-year Bridge View Photo Station, July 2016

Gloucester, MA

3 Construction Bids 1.11 mil 1.43 mil 1.43 mil Access Road Construction, July 2016

Gloucester, MA

Bedrock channel in area of dam Bridge View Photo Station, July 2016

Gloucester, MA

Town voted to remove dam in 2013 Bridge Station July 2016

Gloucester, MA Extreme Low Flow Conditions, July 2016

Gloucester, MA

Colonial era structure found in sediments behind dam Dam Cut and Water Intake Structure, July 2016

Gloucester, MA

Right abutment of dam took many days to break and cut apart.

The rest simply crumbled Water Intake Structure and Historic Structure, July 2016

Gloucester, MA

Always assume an old dam is buried behind an existing dam. Water Control and Concrete Work July 2016

Gloucester, MA

Super Sacks instead of a porta- dam Water Control and Concrete Work July 2016

Gloucester, MA Bypass Channel August 2016

Gloucester, MA

Dam removals almost always require field adjustments Resting Pool, August 2016

Gloucester, MA Upstream Photo Station, May 2012

Gloucester, MA

Standing impoundment next to municipal park with boat ramp Upstream Photo Station Boat Ramp, July 2016 (Near Pump Station)

Gloucester, MA Upstream Photo Little River Photo Station, May 2012

Gloucester, MA

Philips-Exeter walking bridge in distance Upstream Little River Photo Station, July 2016

Gloucester, MA Little River, September 2016

Gloucester, MA Philips Exeter Academy Bridge, July 2016

Gloucester, MA

Three generations of bridge repairs Downstream from Exeter Bridge September 2016

Gloucester, MA Upstream Photo Station, July 2016

Gloucester, MA

Confluence of Little River and Exeter River Greening up, September 2016

Gloucester, MA

Extreme low flow and water withdrawal impact October 13 2016

Gloucester, MA Natural Grade Control July 2016

Gloucester, MA

Insufficient upstream geotech completed and missed this bedrock formation Collateral Damage (Juvenile Sea Lamprey) July 2016

Gloucester, MA

Dam removals always have collateral damage. Main Channel Creation and Rock Weir August 2016

Gloucester, MA

Public concerns that we “drained” the river! Historic Mitigation August 2016

Gloucester, MA

One or two channels? Switch Sides, August 2016

Gloucester, MA About 1 CFS Upstream September 2016

Gloucester, MA Just waiting for rain! September 2016

Gloucester, MA 10 CFS October 20 2016

Gloucester, MA

A little bumpy 20 CFS October 20 2016

Gloucester, MA

Dual Channel Outcome

Success?

Questions?