U.S. Senators Amy Klobuchar (D-MN) and Tammy Duckworth (D-IL) on Tuesday, along with 10 other senators, sent a letter to EPA Administrator Andrew Wheeler to cease issuing Renewable Identification Number (RIN) waivers also known as “hardship” waivers.

These waivers are intended to help small refineries by exempting obligated parties from the Renewable Fuel Standard (RFS) but the Senators allege that the Environmental Protection Agency (EPA) has issued dozens of waivers, including to some large and profitable oil companies, undermining the original intent of the RFS.

“We are extremely concerned about the Environmental Protection Agency’s (EPA) recent actions to continue to improperly grant small refinery hardship waivers under the Renewable Fuel Standard (RFS). EPA’s continued manipulation and misuse of the small refiner waiver authority is undermining the integrity of the RFS and disadvantaging farmers,” the senators wrote. “Rather than follow congressional intent in the Renewable Fuel Standard (RFS) and follow through on the promises made to rural America, the EPA and the Administration are providing waivers, in secret, to help some of the largest oil companies and refiners evade their compliance obligations under the Clean Air Act.”

The Senators say the small refiner waiver provision was not intended to undermine the RFS.

“We request that you cease issuing any further small refinery exemptions, immediately reallocate the remaining gallons, and make public the information regarding any recipients of these exemptions,” they wrote.

The National Corn Growers Association and several ethanol groups have consistently alleged that EPA is undermining the RFS with these waivers.

Senators Tammy Baldwin (D-WI), Michael Bennet (D-CO), Sherrod Brown (D-OH), Dick Durbin (D-IL), Kirsten Gillibrand (D-NY), Mazie Hirono (D-HI), Jeff Merkley (D-OR), Tina Smith (D-MN), Debbie Stabenow (D-MI), and Ron Wyden (D-OR) signed the letter with Klobuchar and Duckworth.