Staffers at the Environmental Protection Agency strongly criticized the logic behind a recent move to loosen future gas mileage rules for cars, at one point requesting that the EPA's name and logo be removed from a key regulatory report.

Documents released Tuesday provide a window into a tense technical battle between experts at two separate government agencies - the EPA and the National Highway Traffic Safety Administration (NHTSA), an agency of the Transportation Department - and show that just months or even weeks before the rollout of a massive new policy proposal, the two agencies behind it had major disagreements.

The contested policy represents one of the Trump administration's single largest reversals of an Obama-era move to fight climate change by cutting polluting emissions from vehicle tailpipes.

New evidence of an internal dispute will probably strengthen the hand of California and other states suing over the proposed changes. If finalized, the freeze would translate to an average fleetwide fuel economy of about 37 miles per gallon, rather than rising to more than 51 mpg by 2025.

"EPA's technical issues have not been addressed, and the analysis performed … does not represent what EPA considers to be the best, or the most up-to-date, information available to EPA," agency expert William Charmley wrote in a critique less than two months before the proposal was released.

Several weeks later, Charmley, the agency's central point person on the technical aspects of the car standards, sent the White House's Office of Management and Budget comments on a vast regulatory document weighing the costs and benefits of the changes. Charmley wanted EPA's name taken off the document, called a Preliminary Regulatory Impact Analysis or RIA.

"This Preliminary RIA is a work product of DOT and NHTSA, and was not authored by EPA," wrote Charmley, adding: "EPA's name and logo should be removed from the DOT-NHTSA Preliminary Regulatory Impact Analysis document."

The Post reported earlier this month that EPA career staff warned the agency's leaders just days before the proposal's release that the plan for cars and light trucks did not reflect their technical input.

The document as ultimately released has both agencies' names on it.

EPA experts also called "indefensible" some aspects of a program the transportation agency used and said they had corrected "erroneous and otherwise problematic elements of the model's logic and algorithms."

Transportation Department officials countered that EPA was using a "developmental version" of the model and that the agency's changes relied on "strong assumptions" about the future size of the auto fleet and how much people will drive their cars in the future.

The key disagreement centered on the transportation agency's claim that the Obama-era car rules would lead to more deaths. The agency contended upping car mileage per gallon would cost automakers money and make new cars several thousand dollars pricier - leading people to stay in older cars that perform less well in accidents, resulting in more auto fatalities.

Ultimately, the transportation agency prevailed. The joint proposal EPA and NHTSA issued to freeze car fuel standards at 2020 levels through 2026 endorsed the idea that the Obama standards would lead to more deaths.

"It is now recognized that as the stringency of standards increases, so does the likelihood that higher stringency will increase on-road fatalities," said a joint noticeof the proposed regulatory change released two weeks ago.

"As it turns out, there is no such thing as a free lunch."

But EPA's internal analysis suggested the opposite - that freezing the Obama-era rules would lead to slightly more fatalities (seven for every trillion miles driven), cost jobs, and in economic terms, have a net negative impact of $83 billion.

"The EPA material seriously casts the whole proposal in a very negative light with respect to its technical adequacy," said Chet France, former director of assessment and standards at the agency, who now works with the Environmental Defense Fund as a consultant.

In their joint statement, the agencies claimed that the rollback "is anticipated to prevent thousands of on-road fatalities and injuries as compared to" the Obama-era standards.

Little changed between the time of the EPA staff critiques and the final release of the proposed rollback, according to former EPA employee Jeff Alson, a 40-year agency veteran and senior engineer at the agency's Office of Transportation and Air Quality, who retired in April.

"We know at most they made minor changes, because they're still quoting the thousand fatalities per year," said Alson, who worked closely on the standards.

"They may have made some less important changes."

The decision to include the revealing documents directly challenging the rollback's logic was approved by senior EPA political appointees, according to two federal officials with direct knowledge of the matter who spoke on the condition of anonymity to discuss internal deliberations. Including the records in the regulatory docket could influence the shape of the final rule, one of the officials said, since it won't be finalized for months.

The fact that Trump appointees agreed to make such documents public suggests that agency leaders, from acting EPA Administrator Andrew Wheeler on down, harbored serious concerns that Transportation officials used faulty assumptions to justify freezing fuel standards.

An EPA spokesman said the documents show only a limited picture of what was going on.

The emails represent "but a fraction of the robust dialogue that occurred during interagency deliberations for the proposed rule. EPA is currently soliciting comments on eight different alternative standards and we look forward to reviewing any new data and information," said EPA spokesman John Konkus in a statement.

In a statement, NHTSA said, "As is typical for any joint rulemaking, the agencies provided feedback to each other as they developed their policy and analysis for the proposal."

The two agencies have reached different findings about aspects of fuel efficiency targets in the past, but the chasm has never been this wide.

Margo Oge, a former director of EPA's Office of Transportation and Air Quality, said in an email that the transportation agency suggested in 2009 that stricter limits on vehicle greenhouse gas emissions would cost consumers roughly $5,000 per car. After EPA "corrected their inputs," Oge said, NHTSA staff agreed the Obama standards would have increased auto price tags by about $900.

The EPA staff's critiques could empower critics of the proposed rollback, particularly in California.

The Trump administration's proposal would block California's ability to set its own, more-stringent standards. And the state has given every indication it is preparing for a courtroom fight.

Xavier Becerra, California's attorney general, said the freeze is "a brazen attack, no matter how it is cloaked."

And California Air Resources Board Chair Mary D. Nichols said her team "will examine all 978 pages of fine print to figure out how the Administration can possibly justify its absurd conclusion that weakening standards to allow dirtier, less efficient vehicles will actually save lives and money."

Next month, the California air agency will vote on scrapping a provision that would keep California's tailpipe rules in line with the federal government's.

Though the Clean Air Act grants California special authority to restrict auto emissions to clean up its historically smoggy cities, for the past decade policymakers there and back east in Washington had agreed to keep a uniform set of standards so carmakers did not need to meet different rules in different US states.

"The EPA documents challenging the Administration's alleged safety rationale for rolling back fuel economy and tailpipe emissions standards are devastating from a legal perspective," said David Hayes, who served as the Interior Department's deputy secretary under presidents Bill Clinton and Barack Obama.

"If in fact there was internal warfare, that just provides further grist for litigators."

Juliet Eilperin contributed to this report.

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