HOPKINTON — When a series of hurricanes ravaged the Northeast in the late 1930s sending floodwaters gushing downstream across New Hampshire and into Massachusetts, the Army Corps of Engineers set to work building the largest flood-control project east of the Mississippi.

On Saturday, the Corps celebrated the 50th anniversary of the Hopkinton-Everett dams with a ceremony at their office.

Park ranger Jen Samela said the two dams that comprise the project were built in response to the hurricanes that hit New England in 1936 and 1938. During the storms in 1936, smaller rivers like the Contoocook in Hopkinton sent flood waters rushing into the Merrimack. That water headed downstream in a devastating surge that wreaked havoc all the way to the Atlantic. The Army Corps of Engineers knew at that point that some dams were needed to keep the smaller rivers from dumping so much water into the Merrimack at once, but if they weren't motivated enough, the Great Hurricane of 1938, which left a swath of destruction from Florida to Maine, sealed the deal.

Building begins

But it wasn't until 1959 that actual construction got going and the dams were completed in 1962 — the Hopkinton on the Contoocook River, and the Everett located two miles away in Weare on the Piscataquog River. Hopkinton Dam stands 76 feet high and 790 feet long, while the Everett Lake is 115 feet high and 2,000 feet long. Behind the dams are three “storage areas” where the water accumulates including Everett Lake, Elm Brook Pond and Hopkinton Lake.

The two dams look like separate structures in normal conditions, but when the rains come, they work together in unison to hold back up to 51 billion gallons of water in the land between them.

“The flood waters can cover up to 8,000 acres when the dams are completely full,” said Samela. “But that only happens in a 500-year flood and we haven't had one of those yet.”

Thus far, the dams have rarely come close to capacity. The highest water levels in recent memory were during the Mother's Day Flood of 2006.

“That was first time I got to see the project do what it was meant to do,” said Park Ranger Karen Hoey. “It was unbelievable to me.”

But despite the damage to some parts of the state, that flood wasn't record-setter. It was the flood in the spring of 1987 when rain and snow-melt brought the Hopkinton-Everett Dams their highest waters ever and the lakes were at 95 percent capacity.

“When you work here, you do look at rain a little bit differently than most people,” said Hoey. “Especially in the spring.”

Fair-weather fun

When the dams aren't holding back torrents of flood waters, the space between them creates ideal recreation space, according to Hoey.

Elm Brook Park offers a perfect white sandy beach, pavilions where groups can hold events, bath houses, even a park for flying remote control airplanes. Kayakers enjoy the peace and quiet of the rocky pond, and walkers can be seen getting their exercise each morning, Hoey said.

“It's the best-kept secret in Hopkinton,” said Hoey, who started working at the dam as a seasonal employee when she was studying psychology at Colby-Sawyer College and became a full-time ranger after she graduated.

In addition to Elm Brook Park, the dams have made room for an OHRV park with 18 miles of trails for off-road vehicles and snow mobiles, and Clough State Park which has boat ramps and good fishing as well as trails for hiking and mountain biking.

All in a day's work

For the rangers and the volunteers who man the Hopkinton-Everett Dams, every day is just a little bit different than the one before. The rangers offer guided tours to folks who stop by, visit schools to talk about the project to students, ensure the parks are in good shape and keep an eye on the dams to ensure that they're always ready for rain, said Hoey.

During the summer, the gate to Elm Brook Park is manned by volunteers who trade hours collecting the $1-per-person entrance fee in exchange for exclusive camp sites at the park that they call home for the season.

The biggest challenge the rangers face, said Hoey, is making people understand that the primary purpose of the project is flood control, not recreation.

“We had to shut down early one day because of the conditions, and people were not happy,” she said. “But I love this job. I learn something new every day.”

For more information visit http://www.nae.usace.army.mil/recreati/hel/helfc.htm

nfoster@newstote.com