The base purchase price is $270m in cash (before post-closing adjustments), plus a three-year earnout provision for up to an additional $50m payable in 2014.

The acquisition is expected to be closed in April 2011, subject to certain conditions, including the expiration of the required waiting period under the Hart-Scott-Rodino Act.

Texas-based Kirby operates inland tank barges and towing vessels, transporting petrochemicals, black oil products, refined petroleum products and agricultural chemicals throughout the US inland waterway system.