Penn State Intercom......April 5, 2001

Lake Perez dam reconstruction to use
an innovative reinforcement system

By Tysen Kendig
Public Information

It's been more than a year since Lake Perez, the 72-acre recreational centerpiece of Stone Valley Recreation Area, was transformed from a watery, warm-weather playground into a parched moonscape.

While outdoor enthusiasts will have to endure one more summer season without water lappingalong the lake shore for their boating and fishing pursuits, engineering buffs will revel in the innovative, environmentally friendly technology being employed to revitalize the aging weir over the next six months.

Leonard S. Fiore Inc. of Altoona was recently awarded the contract to install a dam reinforcement system and renovate the existing spillway.

The reinforcement system is particularly intriguing, as it will be one of only a couple dozen dams in the country to consist of articulating concrete blocks (ACBs).

ACB systems are matrixes of open-celled concrete blocks that are cabled and abutted together to form a contiguous carpet. These 8-by-40 foot carpet sheets are placed over the surface of an existing dam embankment, covered with topsoil taken from the lake floor, and seeded. This system provides an embankment armored against erosion while creating a natural, aesthetic appearance that also protects the concrete blocks from the elements.

The $2.8 million reconstruction project, when completed in September, will result in the largest dam structure in the United States to use an ACB system.

"This is the first project of its type in Pennsylvania," said Paul Schweiger, senior project engineer for Gannett Fleming Inc., which was hired by the University to study and design an alternative, economical solution for the dam's rehabilitation. "This could be a model solution for other dams statewide. It is certainly a high-profile, important project -- both for Penn State and on a national level."

ACB technology has been used to rehabilitate more than 25 dams nationwide over the past 10 years, and has been proven to resist erosion better than other types of dam-armoring systems. Although the existing 520-foot long earthen dam had maintained its integrity over four decades, the ACB system is a preventative defense against dam overflow following storms or exceptionally wet periods.

"The dam needed to be armored as protection against a once-in-a-hundred-years flood event," said Dale Roth, director of recreation and club sports. "In the event that water should rise in the lake and overtop the dam, this system will prevent the embankment from washing away and help protect downstream properties from damage and loss of life."

In addition to the dam overhaul, workers will revamp the adjacent spillway to further protect against overtopping of the dam. The concrete aqueduct, which carries water from the lake into the natural creek bed below, will be excavated and expanded to meet state standards for spillway capacities and upgraded with a new concrete base and drains, which were not previously in place and should help pr event future undermining of the structure.

The overall project began at a much smaller scale in 1999, when inspections revealed leaks that eroded away some of the material beneath the spillway slabs. Although the University looked into repair alternatives to avoid draining the lake, the state Department of Environmental Protection requested expansion of the spillway capacity to meet state standards.

To accommodate the extensive project, the 29-foot deep lake was drawn down in January 2000, forcing a massive relocation of more than a ton of trout, bass and thousands of other lake inhabitants to the east branch of the Little Juniata River. University officials hope to begin refilling the lake immediately upon completion of the project, and expect to have the reservoir completely full by December.

Although the lake bed will remain desolate until then, Roth said that other activities around the lake such as hiking, cabin rentals, the Shaver's Creek Environmental Center and the more than 1,000 acres of fields and woodlands that make up Stone Valley will remain unaffected.

Tysen Kendig can be reached at tysen@psu.edu.

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