US natural gas pipeline companies added about 2,400 miles of pipeline as part of 25 projects in 2011, helping to improve service in congested areas including California, Florida and parts of the Northeast, the Energy Information Administration said on Friday.

The new lines increased capacity by 13.7 billion cubic feet a day, about the same increase as in 2010 but less than that in 2008 and 2009 when a total of more than 60 bcf of capacity was added to keep pace with increasing shale-gas production, as well as new LNG terminals and storage facilities.

“Natural gas pipeline capacity additions in 2011 were well above the 10 bcf/d levels typical from 2001-2006, roughly the same as additions in 2007 and 2010, but significantly below additions in 2008 and 2009,” the EIA’s report said.

More than half of the new lines, or some 1,500 miles, were built by the six largest projects, representing capacity of 8.2 bcf, the agency said.

On Your “MARC”

The new pipelines have been built in part to take the increasing production of major shale gas fields such as the Marcellus. Pennsylvania’s portion of the giant Northeast play produced 606.8 billion cubic feet of gas from July to December of last year, up from 435.3 billion in the first half of the year, and more than twice the level recorded in the second half of 2010, according to the state’s Department of Environmental Protection.

Among planned new pipelines in Pennsylvania is the MARC 1 project, which will take gas from the northern part of state, which has seen some of the most intensive gas drilling since 2008.

Construction of the pipeline was recently approved by the Federal Energy Regulatory Commission, subject to obtaining the necessary approvals from the Pennsylvania DEP, but is being opposed by environmental groups who argue that the line, and local gathering lines that will feed it, will damage natural species and habitats and disrupt local communities.

Much of the new capacity was built to transport gas between states rather than within states. Within the new interstate pipelines, five – Golden Pass, Ruby Pipeline, FGT Phase III, Pascagoula Expansion and Bison Pipeline – added 80% of the new capacity, representing 6.1 bcf a day.

The US natural gas pipeline network includes more than 200 systems; 305,000 miles of interstate and intrastate pipelines, and more than 1,400 compressor stations, according to the EIA.