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Carroll County to study Piney Run Dam, citing state concerns about emergency risks

Carroll County is embarking on what’s expected to be a two-year-long study to assess any possible deficiencies in Piney Run Dam, provoked by concerns cited by the Maryland Department of the Environment.

The water of Piney Run Reservoir, in which local residents enjoy fishing and boating, is held back by a 74-foot-tall earthen dam that was built in 1974, according to Chris Heyn, county watershed restoration engineer.


The Department of the Environment, or MDE, boosted by grant funding in 2016, inspected a number of dams across the state, including Carroll County’s dam at Piney Run, Heyn said in an interview.

“With changes to the climate and some failures of dams nationwide, MDE is evaluating dams around the state and recently expressed concern that the Piney Run Dam may not meet current criteria,” Heyn wrote in the environmental restoration quarterly newsletter for this fall.


Md. 32 and the Warfield Complex are downstream from the dam. The study will consider how possible changes to the dam would affect the surrounding area, according to Heyn.

“I wouldn’t anticipate any, but that’s why we have to do the study," Heyn said.

Piney Run Dam is the only dam the county owns that is classified as “high hazard” by MDE, according to Heyn.

“Failure of a high hazard dam would likely result in the loss of human life, extensive property damage to homes and other structures, or cause flooding of major highways such as state roads or interstates,” according to an online MDE dam hazard classification fact sheet.

Piney Run Dam is one of 93 high hazard dams in the state, according to Jay Apperson, deputy director of communications for MDE.

MDE officials expressed concern regarding Piney Run Dam’s emergency spillway capacity and tasked Carroll with analyzing the dam’s potential deficiencies, according to Heyn.

There are 10 high hazard dams in Maryland that are similar in age and design to Piney Run Dam, according to Apperson, and the Dam Safety Division has concerns for each. There are about 18 other high hazard dams with deficiencies identified by the division or reported to it by the owner, Apperson wrote in an email.


“In general, it would require an extreme event to cause distress or even failure of these dams but they are required to be designed, operated and maintained to a level commensurate with the risk that a failure would pose,” Apperson wrote. “The state works to manage that risk further by requiring that all high and significant hazard dams in the state have an Emergency Action Plan developed and maintained by the dam owner.”

Upon learning of MDE’s concerns for Piney Run Dam, Carroll County began developing a request for proposals to have its contractors look into the supposed issue and, in the process, learned grant funding was available for the study, Heyn said. The county then shifted its focus to obtaining said grant funding.

Carroll County received a $500,000 grant from the Natural Resources Conservation Service in July, which will cover the cost of the study, according to Heyn. National engineering firm AECOM, which has an office in Germantown, is conducting the study, Heyn said. AECOM staff had its kickoff meeting Friday with county staff, according to Heyn.

The study is broken down into three phases. In the first phase, AECOM will conduct field investigations that involve examining existing conditions such as sediment, soil, rock and erosion, Heyn said. Next, AECOM will evaluate options to address any deficiencies it might find, and the final phase will be the writing of the final report, according to Heyn.

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MDE will be kept up to date, and a draft report will be shared with the department so it can offer feedback along the way to the study’s completion, Heyn said.


The emergency spillway is designed to hold 27 inches of rain over a period of six hours, and the closest Carroll County has come to experiencing that level of precipitation was shortly after the dam was built, according to Heyn. In 1975, Hurricane Eloise dumped a little more than 14 inches of rain over a few days, he said.

“Twenty-seven inches in six hours is the largest anticipated storm that could ever happen in our area," Heyn said.

He wrote in the news letter it is “unlikely” Carroll would experience a storm of this size, but the county sided with MDE’s stance of prioritizing public safety and moved forward with starting a study.

Heyn said MDE inspects the dam annually.

There are “hundreds” of low-hazard dams throughout the county, as well as one significant hazard dam by the Carroll County Farm Museum and Agriculture Center, Heyn said.

There will be a public meeting after the first phase of the watershed study is complete, which is expected to be in January or February, according to Heyn. Residents will be invited to offer comments on the study, he said. The date and time of the meeting will be publicized closer to then, Heyn said.