How Did Water Get to the Ironworks? 

Damming a river to run a water-powered factory or mill is a complex undertaking. On the one hand, you must make sure that you have reliable access to the water with enough force and head (height between intake and discharge that creates pressure) to turn the wheels. On the other hand, you must be able to keep the water out or get rid of it quickly when the river is in flood. Disastrous flooding destroyed many mills, water channels and flumes, machinery, and buildings alike. 

The local millwright-engineers in Leverett created a solution here that one scholar has called, “Lowell in miniature.” That is, the mill does not sit in the river, like the older North Leverett Sawmill upstream. Instead, water is diverted away from the Sawmill River through a channeling system that powers several shops (here as many as three, although they were undoubtedly all run by one wheel or set of wheels and a system of belts and pulleys). The river below the North Leverett Sawmill dam was raised a few feet by a low dam across the entire river that was anchored at the ends by bank abutments, which we can still see today. We know from research that the dam was about five feet high. The diversion dam would not have created a “millpond” like the one at the North Leverett Sawmill. On old maps, it is drawn as a widening of the river.

Raising the level widened the river and made it possible to divert some of the water into the mouth of a power canal consisting of a long narrow watered trench. The trench is contained along the low/river side by a linear earth fill berm supported by stone retaining walls that stands today and extends downstream to the Graves Ironworks. 

There had to be some way of keeping river water out of the canal for flood protection and to drain it for maintenance. If the canal mouth was left open and unprotected, then the dam across the river would have had to be of the right height to act as a spillway and contain adequate (major) gate flow capacity to pass all river high water and send floodwaters past the canal mouth (entrance). The dam, though low already, possibly incorporated a wasteway gate to lower the level of the water and prevent it from flowing into the power canal. 

In addition, water flow into the mouth of the canal was likely controlled by wooden gates in a headgate wall across its mouth (partially standing) to control water flow into the canal and shut flow off during floods or for maintenance. Having no control structure at the head of the canal is counterintuitive and would have been a major liability for the Graves’ operations. 

Right now, the water does not reach the headgate except during major floods. After the Graves Ironworks closed and the dam was removed or washed away (we do not know what ended the use of this site), the normal level of the river is low enough to protect the site. Perhaps some of the headgate wall was dismantled and the upstream mouth of the power canal intentionally permanently and crudely dammed to keep water out of the Ironworks site. It is also possible that the canal mouth was subsequently impacted by floodwaters, leaving the canal mouth high and dry as we see it today. 

The long narrow power canal itself served as an elongated millpond as much as a headrace. The force of the long body of deepening flowing water generated the head for the downstream mill wheels. There is some, but not conclusive, evidence on the site for a conjectured secondary gate just above the mill, creating a defined pool called a forebay and controlling the water flow into the mill more precisely. The downstream end of a power canal typically also included a wasteway in the berm to drain the canal for maintenance, flood control, etc. (the upper canal headgate was closed and the wasteway opened to drain the canal), which is likely why there is a break in the berm system down by the mill. 

The Graves Ironworks forebay/upstream mill wall/gate and downstream canal wasteway may have been washed out in floods or intentionally dismantled over time. There is, however, no evidence in the landscape today of water flowing away through the berm to skirt the natural berm to the river side of the mill for any length of time or with great force. 

The end of a power canal also typically included a vertical or inclined trash rack over the mill headrace opening(s) in the upstream mill wall leading to the individual wheel(s) or turbine(s). It screened out floating debris that could damage waterwheels and turbines. 

For information about the rest of this system, see Informational Sign #8 Graves Ironworks.

Researched and written by Pleun Bouricius, Swift River Press Public History and Communications.

How to Find the Remnants of a Dam

Three things to remember when you’re looking for a dam or berm are the same as when you’re looking for a cellar hole:

• Check old maps for known reference points that you can translate to today, but do not assume that roads stay in the same place over time.

• There’s no such thing as a straight or plumb line in nature. If there are abutments on both sides of the river, bingo, you have the remnants of a bridge or dam. If a bunch of stones sit horizontally on top of each other, they were likely stacked by a human being. If they sit at some angle, they might be reflective of geological forces over time. In that case, check what the other rocks are doing in the vicinity. 

• If you see a straight horizontal line in the woods, you may have a cellar hole, old wall, embankment or berm, or dam.

Also remember to stay off any dam or mill foundation. These structures may give way at any moment, and you could break a leg or worse. Consider that they are evidence and remnants of great skills, possessed by townspeople in the past that few have today. Damage is likely irreversible, and towns and historical organizations, not to mention landowners, likely cannot afford to have them rebuilt. Causing these creations to fall is akin to taking a knife to a painting in a museum. And it’s illegal: Mass. Gen. Laws, Part IV, Title 1, Chapter 266, §105 and 107.

Researched and written by Pleun Bouricius, Swift River Press Public History and Communications.