Sept 23 (Reuters) - The California Public Utilities Commission (CPUC) has told Southern California Gas Co (SoCalGas) to take immediate steps to increase the amount of gas it has in storage to maintain reliable service this winter.
"To maintain reliable delivery to ... customers during the winter, SoCalGas should take immediate action to increase injections at all available storage facilities," CPUC Executive Director Alice Stebbins said in a letter to SoCalGas made available on Friday.
Officials at SoCalGas, a unit of California energy company Sempra Energy, were not immediately available for comment.
Gas supplies have been tight in Southern California for years due to pipeline limitations and reduced availability of SoCalGas' biggest storage field at Aliso Canyon in Los Angeles, following a leak at the underground cavern between October 2015 and February 2016.
The CPUC "continues to be concerned about the current status of (SoCalGas') storage inventory, system operations, and ability to provide natural gas this winter," Stebbins said.
SoCalGas had about 72.1 billion cubic feet (bcf) of gas in storage on Monday, compared with 80.5 bcf at this time last year and a five-year (2014-2018) average for Sept. 23 of 84.9 bcf.
One billion cubic feet of gas is enough to supply about 5 million U.S. homes for a day.
In July 2018, the CPUC increased the amount of gas SoCalGas could store in Aliso to 34 bcf from 24.6 bcf. That is well below Aliso's peak capacity of 86.2 bcf.
Before the Aliso leak, SoCalGas' four storage facilities - Aliso, Honor Rancho, Playa Del Rey and La Goleta - could hold about 135.3 bcf. But with limitations on Aliso, the four fields can hold around 83 bcf.
Moreover, the low amount of gas in storage is being exacerbated by ongoing pipeline maintenance.
"With pipeline capacity reduced by maintenance on Lines 235-2 and 4000, SoCalGas is unlikely to be able to close the inventory gap and may fall farther behind," Stebbins said.
SoCalGas said on Sept. 11 the preliminary return to service date for Line 235-2 is Oct. 14. Line 235-2 shut after it ruptured on Oct. 1, 2017.
After that rupture, SoCalGas took the adjacent Line 4000 out of service for inspection and maintenance. The utility returned Line 4000 but kept it and another pipe, Line 3000, at reduced pressure until Line 235-2 returns.
SoCalGas said it planned to shut Line 4000 again for work from Sept. 19-Nov. 14.
Reporting by Scott DiSavino Editing by Tom Brown