CH2M has walked away from a contract to act as delivery partner for the multi-billion-dollar next phase of the U.K.'s high-speed rail system. San Francisco based Bechtel Inc., runner up in the bidding, will now negotiate for the contract with project owner HS2 Ltd.

Named preferred bidder for a contract to help steer development of HS2 phase 2b from Birmingham, England to Leeds and Manchester in February, CH2M formally quit on March 29. "Protracted delays and ongoing speculation risk further delays to this critical national infrastructure," the company said in a statement.

The speculation reportedly centers on the potential conflict of interest created by the January appointment of former CH2M executive Mark Thurston as the new CEO of HS2 Ltd. He was then CH2M's managing director for Europe, including the U.K.

Unsuccessful contender UK-based contractor Mace raised the conflict issue and is threatening legal action, says British construction publication Building.

"We will now begin talks with the second placed bidder...Bechtel," says an HS2 spokesman. "This is our standard practice."

This is the second time in a week that Bechtel has recovered from bid losses in the U.K. A few days earlier, the firm won substantial compensation from the U.K. Nuclear Decommissioning Authority following a flawed bidding process for a 14-year nuclear deal.