Final Report Historical Structures Assessment Report for the Muddy ...

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Historic Structures Assessment Report for the Muddy Run Pumped Storage Facility Project Relicensing Application Lancaster and York Counties, Pennsylvania NEWLY RECORDED RESOURCE Muddy Run Pumped Storage Facility On September 21, 1964, FERC granted PECO a license to construct the Muddy Run Project, a pumped storage hydroelectric facility located in Lancaster County, Pennsylvania. Commercial operation at Muddy Run began on April 10, 1967 when Units 1 and 2 were first commissioned. Units 3 and 4 were brought on-line on June 1, 1967. Units 5 and 6 began commercial operation on October 11, 1967. Units 7 and 8 were placed into commercial operation on February 10, 1968. The Muddy Run powerhouse construction was completed in 1968. At its completion, the Muddy Run Project was the largest pumped-storage facility in the world. The Muddy Run Project electrical machinery was designed by the noted engineer Eugene C. Whitney of Westinghouse Electric Company. (Exelon 2009). The general plant configuration remains the same as the original construction. The components of the turbines and generators, however, have been replaced or overhauled at various times since 1983. The trash racks in the cylinder gates were replaced in 2002. The Muddy Run Facility encompasses the following major components and the full descriptions can be found in the Muddy Run Pre-Application Document for The Muddy Run Pumped Storage Project (Exelon 2009): Muddy Run Reservoir (Figure 4-6) The upper reservoir is a 1,000-acre body of water impounding approximately 60,000 acres of water at an average depth of 60 feet. The upper 50 feet are available for power generation. The maximum elevation of the reservoir is 520 feet, which is 410 feet above the normal elevation of Conowingo Pond. Main Dam (Figure 4-7) Muddy Run reservoir was created by building a rock filled dam with a central impervious core across the Muddy Run ravine, approximately 2,500 feet from the Muddy Run Powerhouse. The dam is 4,800 feet long and has a maximum height of 260 feet. The crest of the dam has an elevation of 533 feet, is 30 feet wide, and is traversed by a 20-foot-wide roadway. East Dike The east dike is approximately 800 feet long, has a maximum height of about 12 feet, and has a crest width of 20 feet. It is a zoned earth and rock fill embankment with an impervious core. Recreation Pond Dike The recreation pond dike, located in the drainage for the upper reservoir, about two miles upstream of the main dam, is a zoned earth and rock fill embankment that forms an 100-acre constant level recreation reservoir. The dam is approximately 750 feet long, has a maximum height of about 90 feet, and a crest width of 34 feet. Canal Embankment The canal embankment forms the upper part of the intake channel leading from the upper reservoir to the intake structure. The lower part of the channel is excavated in rock. The embankment has a maximum height of about 35 feet and a crest width of 30 feet. The upstream face of the embankment and the rock cut channel are lined with a 9-inch-thick reinforced concrete slab, extending about 1,000 feet upstream on 22
Historic Structures Assessment Report for the Muddy Run Pumped Storage Facility Project Relicensing Application Lancaster and York Counties, Pennsylvania both sides of the canal from the cylinder gates. The upstream portion of the canal is an unlined soil and rock cut. River Road Bridge crosses this section of the canal. Main Spillway The spillway for the power reservoir is located on the west side of the intake canal. It is a non-gated, concrete, ogee-type structure that is 200 feet long, 20 feet high, has a crest elevation of 521 feet, and discharges into a vegetated natural ravine. Vehicular Tunnel Constructed in 1968 as part of the recreational use plan, a concrete vehicular tunnel is located underneath the former Columbia & Port Deposit Railroad line and provides vehicular access to the powerhouse. The single-lane tunnel is barrel-shaped with octagon-shaped portal ends and has a clearance of 12-feet. The Recreation Pond Spillway This consists of a nearly level rock-cut channel approximately 140 feet wide. The spillway is traversed by a steel and concrete bridge used for pedestrian traffic and recreation area maintenance vehicles. Intake Structure (Figure 4-8) The intakes, which admit water for power generation, consist of four cylinder gates with trash racks. Each intake supplies two units. Each intake includes a cylindrical tower that leads to a 430-foot-deep vertical shaft. The vertical shafts and horizontal power tunnels are concrete lined with a diameter of 24.5 feet. The concrete-lined power tunnels bifurcate approximately 500 feet upstream of the powerhouse. Beginning approximately 400 feet upstream of the powerhouse, the tunnels transition to 14-foot-diameter steel penstocks that continue downstream to connect to one of eight pump turbine units in the powerhouse. Powerhouse (Figure 4-9) The powerhouse has plan dimensions of approximately 600 feet long by 133 feet wide and is constructed entirely of concrete. A gantry crane travels the length of the powerhouse and service bay. The powerhouse turbines each have a hydraulic capacity of 4000 cfs, for a total discharge capacity from the powerhouse of 32,000 cfs. The pumping capacity of the pump turbines is 3,500 cfs, each from a total powerhouse pumping capability of 28,000 cfs. The draft tubes discharge directly to the Susquehanna River, adjacent to the powerhouse. The units are equipped with trash racks between the draft tube outlet and the river. The electrical generating equipment consists of eight motor-generated units (Exelon 2009). Recommendation: The National Register Bulletin 22-Guidelines for Evaluating and Nominating Properties that Have Achieved Significance Within the Past Fifty Years provides guidance for evaluating properties that may be eligible under Criterion Consideration G (properties less than 50 years old):“ the National Register Criteria for Evaluation excludes properties that achieved significance within the past fifty years unless they are of exceptional importance. Fifty years is a general estimate of the time needed to develop historical perspective and to evaluate significance. This consideration guards against the listing of properties of passing contemporary interest and ensures that the National Register is a list of truly historic places. The phrase ‘exceptional importance’ may be applied to the extraordinary importance of an event or to an entire category of resources of any age that are unusual. The phrase "exceptional importance" does not require that the property be of national significance. It is a measure of a property's importance within the appropriate historic context, whether the scale of that context is local, state, or National (National Park Service 1979, rev. 1990, 1996, 1998).” 23
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