Major gas pipelines snake underneath the Sacramento region like shadow interstates, requiring consistent inspection and repair to avoid a disaster like last week's San Bruno explosion.
About 100,000 local properties sit within a quarter-mile of these large pipelines, according to a Bee analysis of state and local geographic data.
The biggest cluster of transmission pipeline sits underneath North Sacramento. Multiple lines also run between downtown Sacramento and Davis, according to the California Energy Commission. The commission shared data on "major gas pipelines" ranging in size from 2 inches to 42 inches in diameter; the San Bruno line that exploded was 30 inches in diameter.
Pacific Gas and Electric spokesman Paul Moreno could not give specific details on the age or condition of Sacramento's transmission lines. Statewide, the company conducts hundreds of thousands of inspections each year to ensure pipeline integrity, and the large majority of PG&E's lines were built after 1950, Moreno said.
Investigators are still trying to figure out how the pipeline in San Bruno ruptured, killing at least four people. In December 2008, a separate explosion and fire caused by a natural gas leak in a PG&E pipeline destroyed a house at Paiute Way in Rancho Cordova, killing one person and hospitalizing five others.
PG&E has come under public pressure to release a list of transmission lines it deems high risk, but so far has refused to do so.
By sheer size, the Sacramento region's two largest natural gas pipelines run through rural Yolo County, both underneath the small community of Winters. One of the lines is 36 inches in diameter; the other is 42 inches, city officials said.
"I could only imagine if a 42-inch line blew like that," Winters City Manager John W. Donlevy Jr. said, noting that the lines under his town are bigger than the one running underneath San Bruno. "If one of our lines blew under full pressure, it would probably be seismic."
The 42-inch line in Winters was built during the 1960s and the 36-inch line was built during the 1990s, Donlevy said.
Most Winters residents are aware of the lines, and the city takes pains to ensure no excavation projects accidentally hit them. Still, Donlevy has heard from several residents during the last week concerned about the lines. "We have had a bunch of people who have called saying, 'Oh my God!' " Donlevy said.
Donlevy tells them that the city has a good relationship with PG&E and that city officials are vigilant when planning projects near the lines. "PG&E is regularly in contact with our Fire Department and police about any issues," he said.
The third-largest pipeline in the region is between 19 and 26 inches in diameter and runs through another rural section of Yolo County before going underneath part of east Woodland.
"We are definitely aware of it," said Woodland City Manager Mark Deven. "We factor it into our planning."
Woodland safety officials have prepared detailed emergency plans that lay out their response in the event of a rupture of the pipeline and other, smaller lines running through the city, Deven said.
Woodland refrains from loudly proclaiming exactly where the pipeline runs because of the threat of sabotage, Deven said. The state Energy Commission takes the same tack – the map of major pipelines it shared with The Bee was at a regional scale.
The Bee matched the pipeline locations provided with official parcel data from each of the four counties, roughly determining which parcels were within a quarter-mile of the pipelines. An interactive map showing the neighborhoods around the pipelines throughout the region is at www.sacbee.com.
A large swath of the South Natomas and North Sacramento neighborhoods has the most properties close to a natural gas transmission line, The Bee's analysis found.
About three-quarters of the properties in that area are within a quarter-mile of a line. The transmission lines running under the area range in size from 2 to 18 inches in diameter, smaller than the San Bruno line that ruptured.
