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History Matters

Rocky Gorge Dam, a 'thing of beauty and pleasure'

By Kevin Leonard

6:00 AM EDT, July 5, 2013

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From an enormous command center in West Laurel, Karen Wright and her staff with the Systems Control Group of the Washington Suburban Sanitary Commission constantly check the 10 color-coded computer monitors that ring the curved room. Many of the large screens have multiple displays, allowing them to monitor the entire WSSC system of waterways, sewers, dams, reservoirs and pipes. Weather is also monitored, with feeds from the federal government and the Weather Channel.

A major part of this system is Rocky Gorge Dam, which was renamed in 1967 after T. Howard Duckett, one of the founders of the WSSC. Construction of the dam was necessary in the 1950s to keep pace with the region's expanding population.

Visible from Interstate 95 between Brooklyn Bridge Road and Route 216, the dam affects every resident in the Laurel area, although no one thinks about it until a flood occurs.

The Dust Bowl effect

When the severe drought in the early 1930s produced the Dust Bowl in the Midwest, some of the massive dust storms that blackened the sky reached all the way to the East Coast, including Laurel, and as far north as New York. The drought was not confined to the Midwest: the Washington region suffered through one of its own worst droughts from 1930 to 1936. The water supply for the area was drying up.

It was up to the WSSC, which has been around since 1918, to figure out how to solve the problem of the area's dwindling water supply. The Patuxent River was chosen to be the source, and in 1941 the WSSC announced plans to construct Brighton Dam and the filtration plant in West Laurel. Why was the filtration plant constructed so far away from the dam? Because the site on Sweitzer Lane, which once was the location of the Willis School, is the highest point in Prince George's County.

With so many men off fighting World War II, German prisoners of war, who were housed at a camp near Frederick, were used for manual labor. Although the POWs staged a one-day work strike for Christmas, the WSSC told The Washington Post that the Germans had been providing "excellent service."

Finished in 1944, Brighton Dam and the Patuxent River Filtration Plant in Laurel soon could not keep up with the expanding demand. Another dam downstream was proposed to increase the water supply.

The site for the second dam, just off Brooklyn Bridge Road, was chosen because a station was already in use there. Twelve miles downstream from Brighton Dam, it was pumping water to the filtration plant in West Laurel.

The firm that built Brighton Dam, the Ambursen Engineering Co. from New York, was also chosen to build Rocky Gorge. Started in 1903 by Nils Ambursen, the company specialized in "buttress" dams, which are designed to transmit the weight of the water, as well as the weight of the structure, to the foundation. The company has now been in business for 100 years, with dams built all over the globe.

The June 15, 1953, edition of Constructioneer magazine contained a detailed description of the Rocky Gorge project, still about a year from completion. According to the magazine, the buttresses that are integral to the design are triangular in shape, with one side holding the water back and the other forming the spillway when the gates are opened. The buttresses are 4 feet thick at the foundation, tapering to 18 inches at the top.

The WSSC acquired more than 3,000 acres that would which become the reservoir from a handful of families, most notably the Supplee family, and cleared the trees. Construction on the dam began on March 5, 1952.

Six billion gallons of water

An on-site concrete plant was built to handle the load. Building the dam would require more than 7,600 tons of concrete and 1,000 tons of steel. The cement and steel, and other materials, were shipped by railroad to the Laurel railroad station, where it was loaded onto trucks and brought to the site.

Constructioneer described how the company also built a series of cableways that ran above the dam's site. The cableways were used to place the forms, concrete and other materials in the same way a crane does in high-rise building construction. The operators of the cableways worked in a shed some distance back, without a view of the work site. They were directed by a series of bell signals from centrally located control towers. The system worked so well that the operators could pick up a bucket of concrete from the plant, carry it across the gorge and deliver it to a form with complete accuracy.

According to the old Washington Star, a crew of 185 carpenters, mechanics, riggers, cableways operators, laborers and supervisors worked on the dam; one worker was killed in a construction accident.

Construction, completed in March 1954, cost $3.2 million. Rocky Gorge Dam measures 840 feet across, and is 131 feet high. It has seven floodgates.

When at capacity, the 9-mile-long reservoir stores 6 billion gallons of water in a watershed covering 34,500 acres and reaching depths of 125 feet. Approximately 107,000 evergreen trees were planted around the dam and reservoir.

In its reporting of the completed structure, the News Leader predicted it "is destined to be not only an instrument of service but a thing of beauty and pleasure in years to come."

Monitoring the system

Before computers came along, monitoring the dam was very much a manual task. The WSSC paid stipends to residents scattered along the watershed to monitor rain gauges and report the findings. Commission employees also monitored manual stream gauges.

Both Brighton and Rocky Gorge dams are water storage dams, as opposed to flood control dams. Their sole purpose is to provide the region with drinking water. They are designed to safely hold water up to the top though, on occasion, water has spilled over.

The first flood experienced in Laurel after the dam was completed came on July 26, 1956. According to the News Leader, one resident died and several highways were blocked.

The worst storm in Laurel's history was Tropical Storm Agnes in 1972. Prior to Agnes, the standard capacity height of the reservoir was 2 feet below the top of the dam. After Agnes, the standard was lowered to 3 feet.

Wright and her staff have an extremely difficult job deciding when to open the floodgates. There's a balance between maintaining the water supply at adequate levels and preparing for large storms. Modern technology has certainly helped, but they still have to rely on the unpredictability of the weather to make the call.

They employ computer simulators that show the result of opening any or all of the floodgates, with the current environmental factors of the reservoir and downstream part of the equation.

History Matters is a monthly column rediscovering Laurel's past. Information for this story was found at the Laurel Historical Society's John Brennan Research Library and in the Baltimore Sun photo archives. Do you have old pictures or stories to share about a historic event in Laurel? E-mail Kevin Leonard at info@theleonardgroupinc.com.