- State News
- Gas Industry
Safety Issues Prompt Further Drawdown of Crawford County's Tamarack Lake
By Pennsylvania Fish and Boat Commission
August 3, 2012
The Pennsylvania Fish and Boat Commission (PFBC) has announced that serious dam safety issues at Crawford County’s Tamarack Lake Dam A have prompted the agency to begin a second drawdown of the lake by an additional five feet.
The PFBC and the Department of Environmental Protection (DEP) have been monitoring seepage paths within Dam A near Meadville since the problems were first discovered late last year. That led to the lake being lowered by five feet in November.
“Since then the seepage has worsened into what are termed boils,” Jack Rokavec, PFBC chief of engineering. “In addition, on July 31, while geotechnical engineers were performing borings on the crest of the dam, the drill encountered an approximate 2-foot vertical void within the embankment adjacent to the outlet conduit. These conditions have confirmed previous suspicions that seepage paths and voids have developed along the outlet conduit and are eroding the dam's embankment and foundation materials, which is a very serious situation.”
“Failure of the dam is not imminent, but worsening conditions could change rapidly, particularly during a high pool elevation from a large storm event,” he added. “In an effort to prevent the dam’s failure and protect life and property, we will lower the lake by an additional 5 feet, bringing it down to a total of 10 feet.”
PFBC engineers began lowering the lake Tuesday night. The lake will be lowered by approximately 6-12 inches per day, depending on the withdrawal rate and rain events. The additional drawdown could take a few weeks to accomplish.
As a result of the additional drawdown, the PFBC has closed the lake to all public use, including fishing, boating and walking on the lake beds. Signs will be posted at the property and security fencing will be placed around the dams themselves to prevent people from walking on the dam crests.
During the next week, PFBC biologists will attempt to salvage as many fish as possible and move them to nearby waters, which have not yet been identified.
“We will collect as many fish as we can through netting and electrofishing, but it is impossible to capture all of them,” said Dave Miko, chief of the PFBC Division of Fisheries Management. “Fish die during any drawdown and salvage effort because many hide around structures where we simply can’t reach them, and others become buried in the mud when they are slow to exit the lake with the remaining water.”
“This salvage effort will be particularly challenging given the timing of the emergency drawdown,” he added. “The warm water temperatures will only worsen with the expected weather conditions and the loss of fish is anticipated to be greater than is typical. Anglers and the general public should expect to see this.”
The PFBC first lowered Tamarack Lake by four feet last November after consulting with DEP dam safety officials. Last month the PFBC hired engineering firm Tetra-Tech to perform geotechnical investigations, install monitoring wells, recommend seepage/boil control measures and develop conceptual improvements at both the north and south dams. Their final report is expected to be completed by November.
“We recognize the lake is a popular attraction, and under normal conditions the PFBC strives to place the state’s natural resources first,” said Rokavec. “However, when conditions warrant, engineers and DEP’s dam safety staff will take all appropriate actions to protect the public and property downstream of this high-hazard flood control dam.”
Located in Crawford County, Tamarack Lake is a 556-acre reservoir located three miles southeast of Meadville. The lake is owned by the Commonwealth of Pennsylvania. Its primary function is that of a flood control dam for the Meadville community. It is maintained by the PFBC for public fishing and boating. The reservoir is unique because there are dams at both ends of the reservoir with a shallow area in the middle. Maximum depth in the lake is only about 15 feet.