To the average person, the concept of a dam can seem deceptively simple—it collects water and then releases it back into the stream below. Some look utilitarian and larger than life, like the Hoover Dam, while others look like part of the natural landscape, like the circa 1934 dam and reservoir in Pymatuning, Pennsylvania. But behind their superficial appearances lie complicated and technical engineering systems that ensure dams are working as they should. The four-year renovation of the Pymatuning dam and gatehouse, which finished in 2017, brought those engineering intricacies to light.

The gatehouse is a fixture on the lake in Pymatuning State Park, located on the border of northwest Pennsylvania and Ohio. The 17,000-acre body of water is the largest man-made lake in the state. It is a favorite spot for outdoor enthusiasts and others who enjoy fishing, boating, swimming, camping, and spotting wildlife among the lake’s picturesque vistas.

Along the south end of the lake is the dam and gatehouse, which control flooding in the Shenango River basin. Pennsylvania first approached the idea of constructing a dam in 1911. Two years later, a flood resulted in several deaths and approximately $3 million in damages. Funding issues pushed the dam’s construction until the early 1930s, but it finally opened in 1934. The stone-and-concrete gatehouse is almost medieval in appearance, with a main tower and a smaller entrance capped with pyramidal-shaped roofs separated by a footbridge.

After 80 years of continuous operation, the gatehouse’s infrastructure was aging. Pennsylvania’s Department of Conservation and Natural Resources (DCNR) discovered structural issues in 2012 that threatened the ability of the dam to work properly, such as deteriorated masonry, mortar, and concrete. The gatehouse also had corroded equipment, outdated electrical feeds, and weathered roofing and windows.

“During large storm events, water builds up behind the dam,” explains Kortney Brown, an engineer with Schnabel Engineering, the firm hired by DCNR in 2013 to design the repairs. The firm works primarily with geotechnical and dam projects, and many of the dams are historic. “Water can be slowly released over time through the spillway and the gates. Without the dam, the water would rush down the valley uncontrolled. It’s sort of like a speedbump.”

On the most basic level, a malfunctioning dam could result in the accumulation of excess water in the reservoir. At its worst, it would create a disaster like the Johnstown Flood in 1889, in which a dam failure caused by heavy rains resulted in the deaths of about 2,000 people in Johnstown, Pennsylvania. While the issues DCNR found with the dam at Pymatuning were not that severe, they needed to be corrected nonetheless. The project was funded through an $8.8 million H20 PA grant from the state’s Commonwealth Financing Authority.

After conducting a second investigation of the dam’s structural issues, Brown and his colleague John Harrison, the project's engineer of record, identified the most pressing problems and designed a way to improve the hydraulics and structural integrity of the gatehouse while preserving its historic character.

Before the gatehouse could be repaired, the water surrounding it had to be temporarily pushed back to allow crews access. This could have been done in a few ways, one which included closing the lake down for at least several years as they lowered the water levels. However, this would have crippled tourism numbers to the park, which brings in millions of dollars to the area’s economy each year, so that option was not considered. Clearwater Construction, the project’s contractor, offered a solution via a 37-foot-high cofferdam, a temporary dam installed upstream of the work area to clear water from around the structure. Once the area had drained, the gatehouse could be repaired and rehabilitated.

The next step in the project was to improve the way in which water flowed in and out of the gatehouse. The infrastructure was aging, but the engineers with Schnabel designed a clever workaround to protect the historic building while improving its functionality.

“We were essentially building a new gatehouse within the historic one,” says Brown. The modernized gatehouse is a reinforced-concrete structure that fits inside the building. It reduced the interior square footage, but it improves the gatehouse's operations while also protecting the historic material. The improved water flow through the gatehouse via the new structure would not be effective, though, if the dam’s existing trash racks and gates weren’t replaced.

The trash racks keep debris like logs and dead fish from building up in front of the dam’s gates. They had failed in some parts and debris had started to accumulate. The main purpose of the gates, which measure 6 feet tall and 4 1/2 feet wide, is to provide a safe flow of water through the gatehouse. They’re a crucial component of the dam, but half were not closing properly.

“Inoperable gates,” says Brown, “could have significant impacts downstream.” This may include negatively affecting the amount of water to maintain fish populations and possibly drinking water as well.

“Fifty years down the line, we don’t want to see inoperable gates,” says Brown. “We want it to operate without fear of failure.” Both the trash racks and gates were replaced with more durable, lasting materials that matched or were hidden within the historic appearance of the gatehouse.

Once the mechanics of the gatehouse were in working order, the team turned to repairs of the structure itself. The modern asphalt roof was not only historically inappropriate; it was also leaking onto the timber inside the building. The roof was replaced with clay tiles. Divers discovered the gatehouse’s original clay tiles at the bottom of the reservoir, which allowed Ludowici Clay Tile, the company that produced the originals, to accurately replicate them. Several of the windows had been broken from vandalism and could not be repaired, so they were replaced with windows sensitive to the gatehouse's historic architecture. The interior, which will be seen mainly by workers overseeing the dam, is now illuminated with new Edison-style bulbs that reflect what would have lit the space originally.

On the surface, the gatehouse’s appearance is certainly an improvement from its earlier appearance. This is what most people will notice when they visit Pymatuning State Park today. However, the real bulk of the work occurred in the interior and beneath the water levels. The public will never see these changes, but without the engineering work that took place, the physical appearance of the gatehouse would be but a minor concern.

“It’s tough to explain these repairs to the public,” says Brown. “The intricacy of the work you can’t see is indescribable.”

The ribbon-cutting event in July of 2017 drew a large crowd excited to see the restored landmark. Locals can rest easy now, knowing that the gatehouse, dam, and reservoir will properly control the lake’s water levels for many decades to come.