Washington on Wednesday held a special cap-and-trade auction of more than a million carbon allowances to keep emitters’ costs in check after May’s quarterly auction cleared at an unexpectedly high price.

The state’s Department of Ecology was forced to hold the cap-and-trade program’s first Allowance Price Containment Reserve (APCR) auction, a mechanism designed to keep carbon prices in check, after prices broke through a soft cap that triggers a requirement to tap the reserve. The May 31 auction settled at $56.10 per allowance, far exceeding the February clearing price of $48.50 and smashing through the $51.90 soft cap. (See Wash. Cap-and-Trade Auction Prices Break Soft Cap.)

Wednesday’s auction took place as Washington grapples with the highest gasoline prices in the U.S., something cap-and-trade critics blame on the program. Meanwhile, the state’s Democratic officials — including Gov. Jay Inslee — point their fingers at alleged price-gouging by oil refiners. (See Inslee Challenges Cap-and-trade Role in High Wash. Gas Prices.)

The APCR auction will release 1,054,809 allowances, half of which were offered at a Tier 1 price of $51.90 and the other half at a Tier 2 price of $66.68, which reflects a benchmark set by the open market. Wednesday’s auction was open only to entities that need to cover direct emissions and closed to financial traders of allowances.

May’s auction offered 8.585 million vintage 2023 and 2.45 million vintage 2026 allowances, earning $557 million in revenue for the state. The next quarterly auction, scheduled for Aug. 30, will offer another 8.585 million vintage 2023 allowances to all participants, including traders.

The Ecology Department will announce the results of the APCR auction Aug. 16.