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Here's how the Porter Ranch gas leak could lead to power outages

A major consequence of the natural gas leak and near-shutdown of the Aliso Canyon Natural Gas Storage Facility near Porter Ranch is the possibility that gas supplies could run short, triggering state orders to shut down gas-fired power plants.

State utility regulators and large utilities — like Los Angeles Department of Water and Power and Southern California Edison — are collaborating on a plan to  parcel out the remaining gas supply among 18 local power plants if a shortage develops. They're also  considering plans for shutdowns if necessary.

The planning comes as the Aliso Canyon storage facility remains under state orders to halt underground gas injections until officials have inspected and deemed safe all 114 wells at that the facility. Last fall, one of those wells ruptured, setting off a massive four-month gas leak that drove thousands of families from their homes and has left lingering questions about long-term health and environmental consequences. 

Many residents want the facility closed permanently. But experts say such a move would seriously undermine energy reliability throughout Southern California. 

"In a worst case scenario, they may curtail gas supply to electric generators," Los Angeles Department of Water and Power General Manager Marcie Edwards warned the utility's governing board recently.

The Aliso Canyon Natural Gas Storage Facility covers 3,600 acres of Aliso Canyon above Porter Ranch. The field can store up to 86 billion cubic feet of gas in a rock formation 9,000 feet underground. The California Public Utilities Commission has ordered the gas company to reduce the volume of available gas to 15 billion cubic feet, or about one-fifth its capacity. The Aliso Canyon field now holds about three days’ worth of gas on a peak usage day.

The near-shutdown has highlighted the reliance of Southern California Gas Company on one major underground gas storage field to supply gas customers throughout Los Angeles and Orange County.

The top safety officer at the California Public Utilities Commission said in a hearing earlier this year that the gas industry and state regulators had no contingency plan for operating without the Aliso Canyon storage field. The facility has been described by scientists at the Sandia National Laboratory as being critical to ensure the Los Angeles region would have a steady supply of energy following a major earthquake that severed interstate pipelines crossing the San Andreas Fault.

The plight of Fred Fletcher, assistant general manager of Burbank Water and Power, illustrates how important gas storage is to the power plant he operates on Magnolia Avenue.

He's got plenty of natural gas because Burbank is part of a consortium that has its own gas wells outside California. But his gas is shipped through SoCal Gas pipelines and stored at Aliso Canyon.

"We never counted on the fact that perfectly good wells that haven't failed would be taken out of service out of fear," Fletcher said.

With SoCal Gas storing scant amounts now at the facility, Fletcher worries gas supplies could run short during peak demand times like a stretch of hot summer days. He worries he might have difficulty taking delivery of his own gas supply.

Under emergency plans triggered if gas supplies are low, electrical power plants would be among the first to be cut off to spare residential and small business customers. More than a dozen power plants run by Los Angeles DWP, Southern California Edison and several cities and utilities in the greater L.A.-area face that risk.

"It's a very high probability that our electric generation plants operations will be curtailed," said Colin Cushnie, Southern California Edison vice president for energy procurement and management.

Plant shutdowns -- if not carefully planned on a regional basis — could put the electrical grid at risk of a cascading blackout, he said. That's because electrical plants and transmission lines must carry a certain minimum load or risk automatic system shutdowns.

"We would have huge circuit breakers that would start to shut down big sections of the L.A. Basin so that the remaining equipment is not broken," Cushnie said.

What makes Aliso Canyon's storage reservoir so critical is its close proximity to 18 gas-fired power plants in L.A. and Orange County. Gas moves slowly in pipes, only about 20 miles an hour, so supplies need to be close by when power plants need gas. SoCal Gas has other storage fields in Santa Clarita, Playa del Rey and Goleta, but they are too far away from power plants or too small to substitute for Aliso Canyon's large storage reservoir.

Aliso Canyon normally holds 60 percent of the company's gas supply. It is big enough to cover the region's gas needs for the coldest and hottest weather streaks.

When full, Aliso Canyon storage field and the network of SoCalGas pipes also help regulate the pressure of gas throughout the L.A. and Orange County region. If the pressure is too low, a swift intake of gas when a power plant fires up in one part of the system could leave other parts of the network with too little gas.

"We'll draw more gas than there is molecules there, and the pressure will start to drop and if the pressure gets below a critical point, we'll have to shut some plants down," Fletcher said.

The Burbank plant is fairly small, producing about 300 of the region's 10,000 megawatts of power each day. Across the region, experts estimate a low gas supply would require power plants to reduce their collective generation by about 9,800 megawatts, nearly one-tenth of their overall output.

Homeowners and small businesses are unlikely to have their gas supplies cut off because too much labor would be required by the gas company to check and re-light so many individual gas appliances.

It's not just utilities raising the alarm about potential shortages. It's also being sounded by the top officials at the state Public Utilities Commission, the California Independent System Operator and the California Energy Commission. They have warned Gov. Jerry Brown that energy reliability is at risk while Aliso Canyon is operating below capacity.

Energy Commission Chairman Robert Weisenmiller said state-ordered shutdown of power plants are a possibility. 

LADWP, Edison and other electric providers are working with the state agencies to coordinate how they will use gas during a possible shortage in order to avoid shutdowns. A public hearing on that process is expected in early April.

One possibility is that local utilities will have to reduce overall output by 10 percent to get around reduced gas supplies.

For his part, Burbank Water and Power's Fletcher wants the Public Utilities Commission to permit more of Aliso Canyon's wells and storage capacity to come back online more quickly.

"We've only had one well fail. What we didn't anticipate was the fact that the policy makers wanting to shut it all down at once instead of taking it one at a time," Fletcher said.

He's talking about a proposal by Sen. Fran Pavley. She represents Porter Ranch and authored a bill known as SB380 that would keep Aliso Canyon from returning to full operation until the wells are all deemed safe.

"This is not a political decision, this should be based on independent review of people who know what they are doing," Pavley said.

It gives the PUC a July 2017 deadline to complete a study of the feasibility of minimizing or shutting down the Aliso Canyon storage field.

Her bill, which is awaiting action in the Assembly, does have an exception: it would allow Aliso Canyon to resume operations if the state public utilities and energy commissions decide it's necessary to ensure energy reliability in the region.