RICHMOND — Richmond High School’s annual “Bobcat Pride Day” — its own version of the United Way’s Day of Caring — turned an exercise in civics into a history lesson Thursday for a group of students.

The entire student body fanned out throughout town, tidying up at Marcia Buker Elementary School and the town’s waterfront park, for example. Eight students headed to the historic site within viewing distance of the Richmond Dresden bridge spanning the Kennebec River on Route 197.

The Maine Department of Transportation plans to replace the bridge within the next few years, prompting an archaeological dig on the Richmond side of the river to recover artifacts that might be disrupted by ground work related the construction of a new span.

John Mosher of the Maine Historic Preservation Commission was the archaeologist in charge of the site Thursday. He paused from his work skimming soil from the damp, gummy ground to talk about the project. The bridge replacement, he said, will require use of the Adams property where students helped sift — and will also take two properties on the Dresden side of the river.

Because the project is funded primarily through federal sources, “it is subject to a couple of environmental laws,” which include the Historic Preservation Act and another dealing with highways. “Those require that a certain portion of federal funds be devoted toward determining whether or not there are significant archaeological resources,” in addition to the expected environmental impact analyses, Mosher explained.

“We’re here primarily because historic accounts indicated that Fort Richmond would be here, and it’s also a pretty good location for finding

Native American sites — prehistoric Indian camps,” Mosher said. “We know from previous work there’s literally thousands of sites on Maine riverbanks.”

As archaeologists, field assistants and volunteers worked to carefully skim top layers of muddy soil in what they believe is a cellar hole, and deposit it in buckets for sifting, the students stood around large sifting screens suspended by chains from a large tripod structure. With trowels in hand, they sifted through the dirt, breaking apart clumps and regularly shaking the screen back and forth. They found pieces of bone, rodent teeth, nails and a button.

Students said they found the experience new and interesting. Katie Webster, who plans to attend the University of Maine at Orono this fall to double major in history and anthropology, said she wants to be a curator of a natural history museum. It is an interest that primarily stemmed from visiting museums, and one that was further stoked Thursday.

“I love being hands-on like this,” Webster said. “It definitely makes me more interested and realize that I did choose the right thing” to pursue for a career in historical research.

Armed with a considerable knowledge of U.S. history from courses she’s taken in high school, Webster acknowledged, “I’ve never done a lot of local, local history.”

She plans to come back to the dig as a volunteer — maybe as soon as next week, she told a field assistant as students departed.

Freshmen Travis Robbins and Alex Payson also helped sift for artifacts Thursday. Neither knew what they would be doing before arriving at around 8 a.m., and Robbins said the first image he had of an archaeological dig was of digging up bones, artifacts and old stuff. He did find pottery pieces while sifting through the dirt.

Payson found what he thinks were six rat teeth. Robbins said the dig site is in the area of the fort palisade, which stretched about 150- feet-by-200 feet. Payson added students were looking for nails, glass, pottery, bones, “anything that could have been used as tools.”

Before Thursday, “I just knew Fort Richmond was somewhere in Richmond,” Robbins said.

What do they expect to unearth?

When the bridge project first passed through the MHPC for review, Mosher said the commission requested a Phase 1 study for which archaeologists dug several test pits in areas on both sides of the river.

“That initial round of work confirmed that the fort was located here,” he said. “We found evidence both within the park itself and the Adams’ front yard.”

As evidence, Mosher listed artifacts, 18th-century ceramics “and some features like: we thought we’d hit part of the palisade line,” which is basically a stockade that surrounded the fort for defensive purposes.

“We also found what appeared to be cellar hole deposits, and the natural soil is only going to be about 15 inches thick at the most before you hit clay, so you know you’re in a cellar hole when it goes down much deeper than that,” Mosher said.

Because the Maine Department of Transportation moved the alignment of the new bridge so it will travel right through the spot where archaeologists believe the fort existed, “basically they would have buried much of the site and … destroy a significant portion of the fort,” Mosher said. “So we requested what’s called mitigation archaeology. … We are removing a sample of the area that will get destroyed or buried by the bridge, and that data will be sufficient … for reconstructing to the best of our ability frontier life in Richmond (in the) 18th century.”

“The initial fortification built in 1721 required some remodeling only a couple years later and in 1740, it was essentially rebuilt, enlarged and re-fortified,” Mosher said of Fort Richmond. “That fort was decommissioned in 1755 because additional forts were under construction upriver” including Fort Halifax and Fort Western which replaced Fort Richmond.

Fort Richmond was likely made entirely of timber, Mosher said.

Mosher knows of no period images of the structure, but there are descriptions of the fort in letters and a detailed account of the work done in 1740 to rebuild and restock the fort. Historians know there was a chapel, a palisade, a barracks, and a truck house or trading post.

“Part of the reason this fort is here is because of an attempt to colonize Merrymeeting Bay in 1719,” Mosher said. Fort Richmond was built partially in defense of what was known as the Cork settlement, evidence of which people have sought for years. The settlement may have been located in Dresden, Mosher said, somewhere between Abagadasset Point and the southern end of Swan Island.

Maine Historic Preservation Commission archaeologists expect to be on site digging through the summer and welcome volunteers to help. Follow the project on Facebook at “Fort Richmond Archaeological Site.”

dmoore@timesrecord.com