Hill Air Force Base is No. 1 on a Defense Department list of “priority installations” that will be affected by climate change.

In a letter to Congress, Under Secretary of Defense for Acquisition and Sustainment Ellen Lord wrote that the list “includes scoring and weighting of the five climate-related hazards (recurrent flooding, wildfire, drought, desertification and permafrost thaw) based on the immediacy of the threat.”

Permafrost thaw is not a danger to Hill, which is located about 30 miles north of Salt Lake City, but the base was rated high in all of the other categories — both now and over the next 20 years, according to projections.

“We are aware of the report,” said Hill spokesman Donovan Potter, “but at this point we have nothing to add to it."

Lord’s letter and the accompanying documents came in response to a request from House Armed Services Committee Chairman Adam Smith, D-Wash., Rep. Jim Langevin,. D-R.I., and Rep. John Garamendi. D-Calif. The three lawmakers wanted more information after the January release of a report about the effects of climate change on the Department of Defense, which reported that 74 of 79 “mission-critical” military installations are or will be affected.

Rep. Rob Bishop, R-Utah, is a member of the House Armed Services Committee and represents Hill. He did not immediately respond to a request for comment.

The report does not include any Marine bases; any overseas bases of any branch of the military; and did not consider coastal recreation facilities that could be flooded “but are not mission-critical.” It also offered no information about how climate-related dangers could be mitigated or what the cost of that mitigation might be.

Neither the January report nor the addendum, dated March 22, specified the methodology used to generate the numbers or what they actually mean, but listed Hill Air Force Base with a current weighted sum of 11.25 and a potential of 9 for a total of 20.25. Nine other Air Force facilities tied for second with a total of 18.

The most endangered Navy base is the Naval Air Station at Key West, Fla. (6.25; 8; 14.25); the most endangered Army base is Fort Hood in Texas (10; 8; 18).

According to its information page, Hill AFB is the Utah’s largest employer, with more than 21,000 personnel, and has an annual economic impact of more than $3 billion for the state. It is home to the 75th Air Base Wing, which oversees 1 million acres and more than 1,700 facilities, including the Ogden Air Logistics Complex, Air Force Life Cycle Management Center, Air Force Nuclear Weapons Center, Air Force active duty 388th and Reserve 419th Fighter Wings.

The Salt Lake Tribune will update this article.