Norwich — When the Yantic River water level is low, the Upper Falls Dam looks like it has had a few teeth knocked out.

And another section is teetering and looks about to join its mates in the deep pool of water beneath the dam.

The city has no plans to either demolish or repair the dam, which serves no function and is not a barrier to fish migration, city Public Works Director Patrick McLaughlin said. City officials for years considered removing the river channel portion of the dam to reduce Yantic River flooding upstream at the Sherman Street bridge and in the Norwichtown area.

McLaughlin said the removal was considered again as part of a plan to replace the Sherman Street bridge — known locally as the Canada Bridge, supposedly for the builder, who was named Canada.

But state Department of Energy and Environmental Protection officials determined the removal of the dam would only reduce flooding by about a foot, not significant enough to justify the costs. Bridge designers instead raised the height of a planned new span above projected flood levels, McLaughlin said.

Because of the location of the Yantic Falls natural gorge a short way downstream, fish historically did not reach the Upper Falls area, so the city is not under any obligation to provide a fish passageway there, McLaughlin said.

The granite dam dates to the 1860s, when it first provided the waterpower to run machinery in the Falls Mill downstream and later generated electricity to power the mill, City Historian Dale Plummer said. Earthworks built up behind the dam form a gentle slope, except for an open narrow channel that flows through a 3-by-3-foot square hole at the base, where a wooden and metal control gate decayed years ago.

The hole, however, is no longer square, as stones that lined the opening were among the first to drop into the river. One long stone remains in place atop the opening, but above that is jagged dark space. Along the top of the dam, the second layer of stones is mostly missing. When the river is high enough, water seeps through the stonework as it cascades down the face of the dam.

The dam stands in the heart of an industrial enclave that existed from the 1600s to the 1960s, when Falls Mill closed, Plummer said. Of course, prior to English settlement, the entire area was a centerpiece for Native Americans, he said. The Mohegan tribe’s royal burial ground is located nearby in what is now the Chelsea Parade area, and the Yantic Falls area is the site of the 1643 Mohegan-Narragansett battle.

In early Colonial times, there was a gristmill at the foot of the natural gorge of Yantic Falls, flaxseed and linseed pressing operations to make oil, and a century later, early manufacturing ventures started with Christopher Leffingwell’s paper mill and chocolate mill with a dam a bit farther upstream in 1766, Plummer said.

The entire area, from north of the current Sherman Street bridge, to the base of the natural gorge became a “commonwealth site,” Plummer said, with space rented to various mill operators into the early 19th century. Eventually, the much larger Falls Mill took over the area and built what is now the Upper Falls Dam in 1860 and the small powerhouse in the early 20th century. The remnants of Leffingwell’s mill could be seen falling into the widened river and mud in an 1860s photo, Plummer said.

“It’s a very, very, very, complex site,” Plummer said, “very important in understanding the industrialization of the area. That dam is part of its evolution.”

Today, visitors can see remnants of the historic significance of the area. It is a popular spot for curiosity seekers after storms, when the river, nicknamed “Frantic Yantic,” shows its power.

The city received a federal grant in the 1990s to develop the Upper Falls Heritage Park. A long driveway led to the dam and powerhouse, which was renovated into a museum. Old mill grinding stones that littered the area were arranged to line the driveway and cul de sac. Lack of funding and the isolation of the area led officials to close the powerhouse and board it up for protection.

“It just has layers and layers and layers of history going back to the 1600s, and Native Americans before,” Plummer said. “It’s had a whole variety of presence from the Native Americans on down. The variety of industrial processes used there is pretty wide and varied and incredible.”

c.bessette@theday.com