Thousands of people are being relocated from their homes near Los Angeles as workers for the local gas company, Southern California Gas, try to cap a major leak at a nearby storage facility that began in October.
The leak is sickening some residents and causing the large-scale release of methane, a gas that scientists consider a major contributor to global climate change.
Residents have suffered symptoms that include "nausea, abdominal discomfort, dizziness, light-headedness, some shortness of breath ... even some nosebleeds," said medical toxicologist Cyrus Rangan of the Los Angeles County Department of Public Health.
The symptoms are triggered not by odorless methane but by sulfur-based additives, including mercaptan, which are incorporated into natural gas in small amounts to alert people to a leak.
The additives give the gas the smell of rotten eggs, but not everyone is affected in the same way.
You could have three people in one room, Rangan explained, and one person may smell nothing and a second may notice an odor, "and a third person may say, 'Not only do I smell something, but I feel all these symptoms.' "
Paula Cracium, an employee at Shepherd of the Hills Church in Porter Ranch, recalled that when the problem started October 23, "we actually thought we had a gas leak [in the church] and were sort of scrambling around to see what the issues were and [asking] were our people safe."
Today, dozens of filters provided by the gas company clean the air inside the church.
Cost to neighborhood
Cracium, president of the Porter Ranch Neighborhood Council, says the leak has upended this community of 30,000. More than 2,200 people have been temporarily relocated, and more than 3,000 others are in the process of moving.
Southern California Gas Company is paying the costs for those who leave. Company officials say the leak, at the Aliso Canyon Storage Facility, will not be capped until at least late February.
Hundreds of expensive homes are nestled just below the 1,450-hectare facility, which was the site of an oil field that predates the homes on these hillsides. Today, the facility is used to store natural gas for 20 million consumers. Some of its equipment dates to the 1970s, and the company was in the process of upgrading it. The breach occurred in an 18-centimeter pipeline far underground.
The gas company says some of the world's top experts are working to stop the leak, and scientists are closely monitoring emissions.
Cost to environment
Damage to the atmosphere, however, is occurring daily, says attorney Tim O'Connor of the Environmental Defense Fund, an advocacy group.
"We're looking at methane, which is contributing climate-change gas equal to about 4.7 million cars per day," he said.
This comes as California has been aggressively moving to limit the emissions of man-made greenhouse gases. Methane is one of the worst, according to O'Connor.
Methane is an explosive gas, but experts say there is little danger of a blast as the gas is dispersed into the atmosphere. Aside from the physical effects of chemicals like mercaptan, scientists are monitoring levels of benzene, a known cancer-causing agent, which is found in the gas in trace amounts.
Cost to company
Benzene is dangerous only in large quantities for extended periods, said Rangan, but levels need to be watched closely.
"We want to be sure that we are monitoring every single day because we've got a lot of ever-changing environmental conditions up there [in Porter Ranch neighborhoods], so we're not exactly sure what tomorrow's benzene levels are going to be unless we check for it," he said.
Exposure to even trace levels of a known carcinogen angers some residents, who want the facility closed. Others say they want answers before it reopens.
One estimate says the leak could cost the company $900 million, and some analysts say the final cost could be much higher. Residents worry that the value of their homes is being affected and business owners say they are losing income.