by Marlies Henderson | May 16, 2016 | The Lowell Sun

BILLERICA—The Billerica dam over the Concord River and its waterfall are an iconic landmark. If you haven’t enjoyed the scene from the little gazebo yet, go see it soon: A dam may have been there for the past 300 years, but changes are being discussed.

This most recent turn of events in the dam’s story starts in the 1960s and ’70s. The Nyanza Chemical Waste Dump caused deadly contamination in its environs by releasing polluted industrial wastewater into the Sudbury River, a tributary to the Concord River. Nyanza was ordered to pay Superfund settlement money to fund “river restoration,” and it was eventually determined that the Concord River dam in Billerica deserves the focus of restoration attention—because it is an obstacle for fish passage that blocks access to fish habitats in the Concord, Sudbury and Assabet rivers.

The restoration work demanded a project feasibility study, the draft of which recently was presented at the Middlesex Canal Visitor Center near the falls.

As a North Billerica resident without the slightest passion for fishing, I had strong feelings about maintaining the status quo and securing environmental and historical preservation. However, the presentation about the so-called Concord River Diadromous Fish Restoration Project gave lots of food for thought.

The project is in the hands of state and federal fisheries and environmental agencies, aided by an engineering/environmental consulting firm and a historical/archeological group. The purpose of the study is “to evaluate the feasibility of restoring populations of diadromous fish to the Concord, Sudbury and Assabet rivers.”

Diadromous fish depend on passage between ocean and freshwater habitats to complete their life cycle. From a fish and fishing perspective, the Billerica Dam is an obstacle.

The Concord River evolved over 10,000 post-glacial years without a dam. Today’s mill pond was a series of rapids; ideal fishing grounds with Native American encampments. In the 1600s, colonists used the fisheries, and in 1711 the first dam was constructed only to be highly contested by upstream farmers who lost meadow land to the rising water level. In 1800, the dam was raised further to form a summit pond providing water for the Middlesex Canal: It supplied the water to power 20 locks north to the Merrimack River and south to the Charles River—an engineering feat of its day.

After the canal could no longer compete against the iron horse it helped to build, along with its railroad tracks, the Middlesex Canal Company disincorporated and sold the dam and surrounding land to the Talbot brothers in the 1850s. The dam was soon ordered removed, and the dam owner was compensated with a more reliable steam-powered generator for the mill; and yet the useless dam remained, even if its condition deteriorated, and Henry Thoreau himself called for those natural rapids to be restored.

The draft study offers three options: No action; construct a fish ladder; or breach the dam. Although doing nothing sounds attractive, it was soon pointed out that the privately owned dam has not seen maintenance since the 1850s, and may give way at a most inconvenient time—during a flood, causing a disaster downstream. Repairs are needed.

The fish-ladder option would not guarantee a high efficiency of fish passage, yet is the most expensive option to construct—and costly to daily maintain—but it would preserve the early industrial development in Billerica, which colonists initiated, driving out the native population.

Interestingly, the current dam structure does not contribute to flood control. Dam removal decreases upstream water levels up to about one foot, because of the so-called Fordway Bar, a high rock ledge near the Fordway (Pollard Street) Bridge. Thus a breached dam would not affect the town drinking-water intake, or significantly lower water levels in the Elsie Avenue flood plain.

A controlled dam breach would transform the choking water-chestnut-invaded mill pond into a series of fresh-water rapids one could actually paddle, instead of having to portage around the dam!

Another advantage of removal is that the pond will be reduced to a narrow, riverine channel. Archeologists will be able to search the mucky bottom of the former mill pond for fragments of the 1944 exploded Talbot flywheel, remains of the historic floating towpath, an early lower wooden dam, and artifacts of pre-contact Native American “village” sites.

Tribal Historic Preservation offices will be involved with this archeological fieldwork, which reminds us of the sustainable land use of the Native Americans that lasted many millennia before colonists replaced it with unsustainable early industrialization, which generated profit for one century.

There is more to restore than the population of diadromous fish. With Thoreau I hope for the restoration to pre-industrial times; Mother Nature redeemed. The mill-pond drawdown is a bonus, as is the possibility to navigate the Concord all the way to Lowell.

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