LINCOLN, Neb. — The developer of the Keystone XL oil pipeline plans to start construction next year, after a U.S. State Department review ordered by a federal judge concluded that major environmental damage from a leak is unlikely and could quickly be mitigated, a company spokesman said Monday. The report issued Friday drew criticism from environmental groups, who say they’ll continue to fight the project they view as an environmental threat. The pipeline would carry up to 830,000 barrels of crude oil per day from Canada through Montana and South Dakota to Steele City, Nebraska, where it would connect with the original Keystone pipeline that runs down to Texas Gulf Coast refineries. The State Department has noted that TransCanada has a lower overall spill rate than average in the pipeline industry.