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Tetco Takes Steps to Protect System from Potential Mining Subsidence

Texas Eastern Transmission LP (Tetco) has asked FERC for authorization to undertake certain activities to protect its pipeline system in Pennsylvania from potential ground subsidence during longwall coal mining that is planned by Emerald Coal Resources LP.

Specifically, the Spectra Energy pipeline is seeking permission to excavate, elevate, replace and/or abandon by removal certain sections of five different pipelines and associated facilities located in Greene County, PA, which it believes could be exposed to potential ground subsidence as a result of Emerald's planned longwall mining activities. Longwall mining is a form of underground coal mining where a long wall of coal is mined in a single slice.

Tetco has called on the Federal Energy Regulatory Commission (FERC) to approve its request by Feb. 1 in order for the pipeline to have the time to prepare for elevation and replacement work that is to begin in April, immediately following the end of the 2013-2014 winter heating season.

The pipeline said it anticipates that the elevation activities will be completed within about four months of the commencement of construction. Reinstallation of the pipelines below ground is expected to start in April 2015, and the entire project is targeted for completion by Oct. 31, 2015, provided there are no significant changes to the mining schedule, Tetco said.

Emerald has told Tetco that it will begin the longwall mining activities at the start of 2014. Due to the risk to the integrity of the pipelines and the interruption of service that longwall mining activities could introduce, including possible buckling due to potential ground subsidence where coal has been extracted, Texas Eastern said it has designed its project to protect its facilities that traverse Emerald's mine, and to ensure that certificated levels of service are maintained through the duration of the mining activities.

Tetco proposes to excavate and elevate sections of Lines 2 (24-inch diameter), 10 (30-inch diameter), and 25 (36-inch diameter) to monitor potential strains and stresses on those pipelines due to the mining activities. Concurrent with pipeline elevation, portions of three of those lines (10, 15 and 25) will be replaced with new pipe. It also plans to isolate existing lateral Line 10K (4-inch diameter), which connects Lines 10 and 15 to an existing meter and regulating (M&R) stations, by installing temporary aboveground piping from Lines 10 and 15 to the M&R station.

Additionally, a crossover between Line 2 and Line 25 will be relocated upstream of the mine panel in order to eliminate the existing pipeline crossover within the longwall mining panel and improve the spacing of the pipelines.

Tetco, which has the capacity to deliver 6.7 Bcf/d of natural gas from the Gulf Coast to Northeast markets, requested that the costs associated with the project be rolled into its existing rates.

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