* TransCanada buys BP's 40 pct of Alberta gas storage site
* C$210 mln agreement also brings control of marketing firm
* TransCanada adds 27 bcf of storage capacity
CALGARY, Alberta, Nov 20 (Reuters) - TransCanada Corp said on Tuesday it would pay C$210 million ($210 million) for BP Plc's 40 percent stake in the Crossfield Gas Storage facility, 50 kilometers (31 miles) north of Calgary, Alberta, to consolidate ownership of the operation.
TransCanada, the country's largest pipeline company, said the acquisition would give it full control of the site it has operated since last year and adds 27 billion cubic feet of natural-gas storage.
The Crossfield facility is located on TransCanada's pipeline system, which carries Western Canadian gas to Eastern Canada, as well as to California and the Pacific Northwest, and has a capacity of 68 bcf.
Under the agreement, BP also surrenders its stake in CrossAlta Gas Storage and Service Ltd, which markets natural gas, and its other interests in the Crossfield region. The deal is expected to close by the end of March, 2013.