Southern California air pollution regulators on Thursday granted a variance to the nation’s largest municipal utility in Los Angeles to burn diesel fuel in three local generation plants, if necessary, to conserve on constrained amounts of natural gas due to the continuing shutdown at Southern California Gas Co.’s (SoCalGas) Aliso Canyon storage facility.

The South Coast Air Quality Management District’s (SCAQMD) hearing board granted the Los Angeles Department of Water and Power (LADWP) a “temporary, limited exemption” from air pollution regulations this summer that allows the city-owned utility to burn diesel fuel in three of its four gas-fired generation plants in order to avoid rolling blackouts.

The SCAQMD unit’s action comes as weather forecasters are calling for downtown Los Angeles temperatures to spike Sunday and Monday, hitting potentially triple digits. LADWP on Thursday appealed to its customer base in the nation’s second-largest city to conserve.

LADWP officials sought the exemption as a means to limit the possibility of rolling blackouts for more than 2 million customers due to inadequate gas supplies as a result of the four-month old storage well leak that closed Aliso Canyon (see Daily GPI,Feb. 18).

State officials, SoCalGas and LADWP warned earlier in the spring about rolling blackouts being a possibility as a result of gas supply imbalances (see Daily GPI, April 5).

SCAQMD’s hearing board granted a 90-day exemption, or variance, to allow LADWP to burn diesel fuel rather than natural gas in generation units at three plants: Haynes in Long Beach, Harbor Generating in Wilmington, and Valley Generating Station in Sun City. The variance is in effect through Sept. 13.

The variance is effective only if SoCalGas curtails supplies to LADWP, the air pollution regulators stressed.

“In the event of any potential blackouts this summer, the operation of LADWP’s units on diesel fuel will ensure a continuous supply of electricity to protect the health and safety of Los Angeles residents and businesses,” said Wayne Nastri, SCAQMD acting executive director. “It will also result in less air pollution than would otherwise occur from the use of thousands of significantly dirtier diesel backup generators at many hospitals, police stations and other businesses.”

Unlike utility generation plants, diesel backup generators at businesses and various institutions typically have few, if any, air pollution controls, a SCAQMD spokesperson said.

The five-member (one vacant seat) SCAQMD hearing board voted 3-1 to grant the variances, putting a number of contingencies on the utility’s use of them, including by July 15 submitting a comprehensive plan to mitigate excess emissions from the operation of diesel-fired generation; paying up to $2.9 million in environmental fees for burning diesel; giving public notice by Monday (June 20) and holding public meetings by July 15 for the three communities around the power plants slated for possible diesel use; and limiting diesel-fired operations to no more than 11 to 30 hours/generating unit.

The variance covers up to 12 generation units at the three different power plant sites. The remaining 13 electric generation plants in the region affected by the gas storage field outage are not part of LADWP and can only run on natural gas, the SCAQMD spokesperson said.