Upper and Lower Hereford Manor Lakes are located near Zelienople on Doe Run, a tributary of Conoquenessing
Creek, Franklin Township, Beaver County. The dams appear to have been constructed by Mr. J. H. Cunningham
in conjunction with strip mining operations prior to 1958. The Commonwealth of Pennsylvania acquired
the property in 1973.
The impoundments are very popular with outdoor recreation enthusiasts in southwestern
The drainage area above the lower dam is 1.38 square miles and the normal
pool covers 45 acres. The height of the dam is 37 feet with a length of 1000 feet. The dam’s
embankment is a homogeneous earth fill structure without any drainage. A concrete spillway equipped
with a flashboard controls the lake level.
The drainage area above the upper dam is 1.96
square miles and the normal pool covers 23 acres. The height of the dam is 40 feet with a length
of 557 feet. The embankment is a homogeneous earth fill structure without a toe drain. A spillway
cut into bedrock and a six inch diameter cast iron drain control the lake level.
UPPER LAKE DRAWDOWN
Dam inspections and evaluations in recent years have disclosed that the dams were constructed
in ways that would no longer be permitted for impoundments of this type. Furthermore, the emergency
action plan indicates a failure in either dam would inundate approximately 27 residents and 6 homes.
PFBC retained L. Robert Kimball & Associates
of Ebensburg, PA, to conduct geotechnical drilling and laboratory work. The drilling
began in July 1989 and was completed in August 1989. The geotechnical confirmed that the
fill material used in the construction of both dams is unacceptable (according to today’s standards) and was
not properly compacted.
Upon receiving the geotechnical report, the Fish and Boat Commission in cooperation
with the Department of Environmental Protection, Division of Dam Safety, determined the Upper Hereford
Manor Lake must be drawn down in the interest of public safety. The drawdown began in spring 2003.
The goal was to draw down this 23-acre lake by 10 feet to increase storage capacity to protect the
lower dam and to alleviate pressure on the upper embankment.
Because the dam did not have a drawdown
structure (drawdown structures are required by modern dam safety standards) the PFBC had to lower
the lake level by a large siphon. Once the lake was lowered construction crews cut an additional
spillway through the bedrock adjacent to the dam’s
right (looking downstream) abutment. The cut directs the outflow form the upper lake into a drainage
ditch which bypass the lower lake altogether.
HYDRAULIC AND HYDROLOGICAL ANALYSIS
A complete hydrologic
review was performed on both Upper and Lower Hereford Manor lakes. Results showed that Upper Hereford
can pass 17% and Lower Hereford can pass 9% of the current Spillway Design Flood (SDF). The SDF for
Upper Hereford Manor Lake is 11,195 cubic feet per second (cfs); for the lower lake, the SDF is 19,500
REPAIRS TO THE DAM/SPILLWAY
PFBC engineers developed and reviewed several rehabilitation alternatives.
After considering each option the PFBC prefers a “single
The “single dam” option
will replace both dams with one new dam. The new dam would be constructed using roller compacted
concrete and located midway up the existing lower lake. This will allow for the pool behind
the new dam to remain on PFBC property. The new dam would be much larger than either of the existing
dams. The elevation of the top of the new dam would be 1,000, which is 19 feet higher than the top
of dam elevation of the upper lake. The new dam would be 1,850 feet in length. The new lake would
have a maximum area of 107 acres and a normal pool of approximately 92 acres.
a small lower lake could potentially be maintained below the new
dam. This small lake would act as the plunging pool for the new dam but would be large enough to
maintain a fishery. The area of the small lake would be approximately 15 acres in size. If the
necessary funding can be secured it will taken approximately two (2) years
for design/permitting and an additional two (2) years for construction. The PFBC anticipates the
repairs will be functional for 50 years.
PFBC DAM FUNDING NEEDS
Manor Lake is one of five (5) PFBC lakes drawn down in recent years to address dam safety concerns.
The Commission continues to work to secure funding for repairs on each of the dams.
Commission remains optimistic that a funding source outside of the day-to-day operating revenues
in the fish and boat funds will be found and will be available for the substantial infrastructure
improvement needs the Commission has. The total need for dam repairs alone is estimated at more than