PPL Challenge #2

Determine the most practical means of dealing with the silt and sediment accumulations within the Holtwood reservoir.

About PPL Corporation:

Based in Allentown, Pa., PPL Corporation (http://www.pplweb.com) is a FORTUNE 500 company that delivers electricity and natural gas to nearly1.4 million customers in Pennsylvania; markets wholesale energy in 42 U.S. states and Canada; generates electricity at power plants in Pennsylvania, Maine, and Montana; and delivers electricity to 2.4 million customers in southwest Britain and nearly 2 million customers in Chile, Bolivia, Brazil and El Salvador.

The Holtwood Hydro Power Plant/Lake Aldred Reservoir:

PPL Holtwood is a 102,000 kilowatt hydroelectric facility located on the lower Susquehanna River in Lancaster County, Pa. The plant has 10 main hydroturbine-generators that produce energy using water from the river. The facility consists of a 2,368 foot dam which forms Lake Aldred and provides the storage reservoir for the hydroelectric plant. The reservoir covers an area of 3.75 square miles and contains over 6 billion gallons of water.

Background Information:

The Susquehanna River is the second largest river on the Atlantic Coast. Only the St. Lawrence on the Canadian-United States border exceeds it. The Susquehanna drains an area of over 27,500 square miles and supplies nearly 60 percent of the fresh water to the Chesapeake Bay. It is a very old river basin that has been shaping the landscape of the current New York, Pennsylvania and Maryland region for over 250 million years. The river has been a source of life for animal and mankind alike. It has also been a source of death and destruction during periods of severe flooding caused by winter ice or summer storm.

Erosion and sediment transport are natural processes that have been going on throughout the course of geologic history within the basin. Mankind has contributed to the erosion process through a variety of activities including mining, forestry, agriculture, industry and development. Sources are varied and involve everyone residing in the Susquehanna River watershed. As the sediments and other materials enter the streams and rivers, they are transported downstream. Construction of the dams on the lower Susquehanna created large reservoirs, which allow the sediment and materials to settle to the river bottom. All but a very small quantity of sediments enters the river above the Holtwood area, because the dam is close to the mouth of the river at the Chesapeake Bay. Most of the sediment is transported during floods (river flows exceed 400,000 cubic feet per seconds). The high flow velocity allows the river to carry large sediment volumes, derived both directly from the watershed itself and from scouring and resuspension of sediments deposited in upstream reservoirs. (Scouring is the process of removing material that had been previously deposited. Resuspension is the part of that process where particles once again move with the flow of the river.)

The question to be addressed by the students is whether PPL should become involved in some form of sediment management program within the Lake Aldred reservoir.

One of the primary environmental concerns is the resuspension and transport of large quantities of material to the Chesapeake Bay. Dredging behind the dams can be a solution, but it carries a high economic cost and a potential environmental risk. If the material is dredged, what can be done with the material considering the potential, contaminants including hazardous products?

The U. S. Environmental Protection Agency (EPA) has been working on the contaminant issue for several years on a national level.  Its focus has been on determining the environmental impact of contaminants found in sediments already deposited in streams.  The EPA’s findings could result in stricter water quality standards, mixing zone restrictions and could play a role in state water-quality development decisions.

On a regional basis it is advantageous to help develop solutions to nonpoint source pollution, namely to stop the sediment from reaching the river. PPL Corporation has been active in developing projects dealing with this issue such as riparian buffer zones, wetlands, coal stripping reclamations and biosolids use, all of which help to reduce sediment.

Suggested Approaches/Considerations:

Suggested Research Areas: For additional details consult: PPL Expectations:

Develop strategies for dealing with the current and future sediment accumulations in the Holtwood reservoir. The strategies should include a description of the possible solution and cost estimates. Make a final recommendation based on technical, environmental and economic feasibility and evaluation.

Oral Presentation:

If you are selected to give an oral presentation for this problem, the presentation will be held on Thursday, April 11, 2002, at PPL headquarters in Allentown, Pa. You will be given directions and an agenda later.

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