muddy run pumped storage project (ferc no. 2355) - Exelon ...

SECTION 1.0
MUDDY RUN PUMPED STORAGE PROJECT (FERC NO. 2355)
EXHIBIT A-PROJECT DESCRIPTION
PROJECT STRUCTURES
The Muddy Run Power Project (Muddy Run Project or Project) is a pumped-storage hydroelectric
generating facility located approximately 22 miles upstream of the Chesapeake Bay on the eastern
shoreline of the Susquehanna River, within Drumore and Martic Townships, Lancaster County,
Pennsylvania.
The Project (Figure 1-1) consists of: 1) a main dam embankment, 2) the east dike, 3) recreation pond dam
and spillway 4) canal dam embankment, 5) upper reservoir spillway 6), intake structure 7) a powerhouse
and 8) primary transmission line.
The recreation pond’s sole purpose is for environmental mitigation and recreation, and its water levels are
not affected by fluctuations within the Power Reservoir. The recreation pond impoundment level is
maintained by an uncontrolled open channel spillway.
1.1. Main Dam Embankment
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 Muddy Run Main
Dam Embankment (Main Dam) (National Inventory of Dams (NID) PA00266) is 4,800 feet long, has a
maximum height of 260 feet, and has upstream and downstream slopes of 2.5H:1V and 2.2H:1V,
respectively. The downstream slope includes a 20-foot wide bench/road at midslope across the highest
section of the dam. The top few feet of the embankment (above the maximum normal reservoir level) are
constructed with upstream and downstream slopes of 1.5H: 1V.
The crest of the dam is at elevation 533 feet, is 34 feet wide and is traversed by a 20-foot-wide two-laned
roadway (River Road). The crest provides 13 feet of freeboard when the Muddy Run Reservoir water
level is at elevation 520 feet.
The Main Dam embankment is constructed as a “zoned” embankment with an impervious core. The
structure includes two filter zones on each side of the core and upstream and downstream rockfill shells.
The rockfill consists of excavated schist bedrock. Less weathered rockfill was placed on the downstream
slope and upper parts of the upstream shell. More weathered rockfill was placed in the downstream shell
and lower parts of the upstream shell under a 20-foot-thick “fresh rock” cover. The downstream shell also
includes a zone of 10-foot-thick random material layers alternating with 3-foot-thick layers of weathered
rock.
A-2