Aerial view of the site.

A team led by URS Corp.'s Washington division, the former Boise-based contractor Washington Group International, is on the verge of winning one of the biggest environmental cleanup contracts of the year.

The team is set to win a contract worth an estimated $2.6-billion annually to decommission the U.K's main nuclear fuel plant at Sellafield, in Cumbria inn northern England. Its team, Nuclear Management Partners Ltd., was chosen July 11 as "preferred bidder" for the contract. Team members also include AMEC plc and French nuclear technology firm AREVA.

The winning team bested bids from key competitors CH2MHill Nuclear Services Ltd., Fluor Ltd. and Bechtel Inc. A team headed by Utah-based EnergySolutions Inc. had submitted a bid but dropped out of the competition within the last two months, sources say.

The Nuclear Decommissioning Authority aims to complete negotiations and sign the contract this October. Nuclear Management Partners will earn fees of around $100 million annually under the 60-month contract, extendable to 17 years.