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HEREFORD MANOR LAKES
Information Paper

INTRODUCTION

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.

Lower Hereford Manor Lake DamThe impoundments are very popular with outdoor recreation enthusiasts in southwestern Pennsylvania.

LOWER LAKE

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.

UPPER LAKE

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 PROCEDURE

Upper Hereford Manor LakeDam 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.

The 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.

Dam evaluationBecause 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

Drainage ditchA 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 cfs.

REPAIRS TO THE DAM/SPILLWAY

PFBC engineers developed and reviewed several rehabilitation alternatives. After considering each option the PFBC prefers a “single dam” option. 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.

Additionally, 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

Upper Hereford 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.

The 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 $83 million.


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