Washington utilities Avista (NYSE:AVA) and Tacoma Power will not delay their entry into the Western Energy Imbalance Market (WEIM) next month, despite the Bonneville Power Administration’s decision to postpone joining by two months.

All three entities were scheduled to begin trading in the WEIM on March 2, but BPA last week said it would put off joining until May 3 to address technical and training issues among its large base of generation and transmission customers, most of which are publicly owned utilities. (See BPA Postpones Western EIM Entry by 2 Months.)

Given the complex and time-consuming logistics of integrating members into the WEIM, market operator CAISO in 2018 implemented a policy of only one go-live date each year for new members, typically in early April. The ISO had already accommodated BPA by pushing this year’s entry date to March, just ahead of the peak season for snowmelt and hydroelectric generation in the Pacific Northwest.

In letting the go-live date slip to May, CAISO is making another exception for the federal power marketing agency, which operates about three-quarters (15,000 miles) of the Northwest’s transmission system and will greatly expand the reach of the WEIM.

“In this case, the ISO has accommodated our delay to a May timeline, just looking at all the work that’s been completed and how close we are,” BPA EIM Program Manager Roger Bentz said Jan. 27 during an agency workshop.

But BPA’s postponement will have no impact on the timelines for Avista and Tacoma Power, which both confirmed Monday that they plan to join the WEIM on the original schedule.

“We are not delaying our entry,” Avista spokesperson Annie Gannon told RTO Insider. “We are staying with our date of March 2 since we are on schedule with all of our testing.”

Tacoma Power will also stay the course despite its “strong dependency with BPA,” spokesperson Rebekah Anderson said.

“After assessing the impacts that BPA’s postponement could have on our transition plans, our EIM team determined that the risks and impacts of going live without BPA are low enough to keep the March date,” Anderson said in an email.

As a municipal utility, Tacoma Power has status as a BPA “preference customer,” giving it priority access to the agency’s relatively low-cost hydroelectric output and the transmission network used to deliver it. The utility also operates four of its own hydroelectric projects, which are together rated at more than 800 MW of nameplate capacity. Unlike most of BPA’s preference customers, the utility operates its own balancing authority area as well.

Avista’s BAA covers parts of Eastern Washington and the Idaho Panhandle. The Spokane-based utility controls nearly 3,600 miles of transmission and 1,858 MW of generation, including 1,025 MW of hydro.