One of the old lock gates at Lowell National Park that needed to be replaced.
It’s been thirty years since Hardwick Post & Beam built seven replacement lock gates* to control the flow of the Marrimack River into the canal system of the Lowell National Historic Park. The Canal System has 5.6 miles of canals.
Lowell, MA is considered the birthplace of the industrial revolution in the U.S because the first water-powered cotton mills were established there in the early 1800’s. The site became a National Historic Landmark in 1977. But the old wooden lock gates needed to be replaced to make the watertight lock chambers functional and safe.
In 1986, our reputation for craftsmanship and our can-do approach to challenges landed us the job of constructing and installing the wooden gates. We were sub-contractors for J.F. White, the general contractor overseeing the entire renovation project that would connect the National Park to the city.
We built the gates out of Southern Yellow Pine. First we assembled them in our shop with mortise and tenon joinery to make sure the fit was perfect. Then we disassembled them to have the wood pressure-treated, and then trucked all the pieces to Lowell to assemble the gates again at the lock sites. The construction of the gates went smoothly. But the installation of these massive structures in canals that flow through Lowell was trickier!
HP&B founder Ridge Shinn stands in the lock chamber before a new gate, while pumps keep water from filling the chamber.
We installed one gate in a canal in the heart of downtown, which required rerouting traffic and avoiding electrical wires.
Another lock that needed gates was inside a building. Hmmm. We removed the roof to lower the gates in place using a 100-ton hydraulic crane. Only two such machines existed in Massachusetts at the time. But in the middle of the installation, the crane operator received a call from his company that he was urgently needed to replace a Charles River footbridge near Harvard College. He began packing to leave.
Wait, wait – you can’t leave now! The general contractor’s large truck roared in and parked in front of the crane, blocking its exit. Consequently the operator stayed and finished the job.
From that early experience building locks, we went on to decades of building timber frame houses, barns, and public buildings. (More straightforward?)
Canals allow large boats to bypass unnavigable stretches of rivers: rapids, falls, boulders, and shallow stretches. Locks built on these canals enable the boats to travel uphill our downhill. The lock operator accomplishes this by letting water in or out of a masonry lock chamber that encloses the boat. Here are two simple animations that illustrate boats in a watertight lock chamber, one boat being raised to a higher level, and another being lowered.
While the Lowell locks were built for transport in the 1790’s, by the 1820’s the drop in water level was used to power textile mills.
