Lancaster County and Pennsylvania have emerged as national leaders in a rather obscure but environmentally significant movement to rip out dams.

For the 12th year in a row, Pennsylvania in 2014 tore down more dams than any other state: 17.

Since the mid-1990s, when the initiative began to return streams and rivers to as free-flowing as possible, Lancaster County has seen 21 mostly old mill dams breached, tops in the state.

The latest to be dismantled was the removal in July of the SICO Dam on the Little Chiques Creek in Mount Joy Borough. The stone masonry span, 80 feet long by 4 feet high, was originally built by a private landowner for recreation.

Pennsylvania has approved more than 350 dam-removal projects in the last 20 years. Removal is mostly paid for through state and federal grants. 

The trend delights American Rivers, a Washington, D.C.-based national non-profit conservation organization dedicated to protecting and restoring America's rivers.

“The river restoration movement in our country is stronger than ever,” said Bob Irvin, the group’s president, in announcing 72 dams in 19 states had been removed in 2014.

“Communities nationwide are removing dams because they recognize that a healthy, free-flowing river is a tremendous asset.”

Pennsylvania’s initiative took off around 1995 when the state’s regulations on dams were amended to encourage the removal of dams no longer serving a purpose.

Pennsylvania, because it is one of the oldest states in the nation, has many small dams that once drove mills.

“Removing these types of dams eliminate public safety concerns and bring about environmental benefits by returning streams to their natural, free-flowing habitat,” says Amanda Witman, a DEP spokeswoman in Harrisburg.

Indeed, low-head dams have long been a safety hazard for paddlers as the drop often can’t be seen until it is too late.

But environmental benefits have been the chief driver behind the dam purging.

The Pennsylvania Fish and Boat Commission, which has partnered with DEP and American Rivers for many dam removals, says taking down the blockages has opened up hundreds of miles of streams to resident and migratory fish.

When a free-flowing stream is blocked, it traps sediment, accumulates pollutants, depletes oxygen and water quality, and warms water temperatures that are unhealthy for many organisms. Sometimes, the dams cause more flooding.

Since some 74 percent of all dams in Pennsylvania are privately owned, landowners must give permission for dams to be removed.  

Not all dam removals are welcome. Sometimes, the dams and impoundments they form become fixtures or landmarks.

For example, the Rock Hill Dam on the Conestoga River near Millersville was removed by the Fish and Boat Commission in 1996 to give migrating American shad in the Susquehanna River access to historic spawning grounds in 18 miles of the Conestoga.

But the project was not without controversy. An unsuccessful save-the-dam movement grew up. The stone and cement dam, built around 1900 to produce electricity, had become popular as a fishing spot and for wading.

During a public comment period, 109 residents urged the state to let the structure remain. Some said the dam with its tumbling, sparkling water was an historic and aesthetic landmark.