Los Angeles City Oil Field, Los Angeles, California, United States

• Recent land use controversies
After an explosion which leveled a Ross Dress for Less in the Fairfax District in 1985, caused by an overnight accumulation of methane which had seeped up from the underlying Salt Lake Oil Field, construction over Los Angeles's old oil fields became much more controversial and difficult. The city defined "methane zones" around all oil fields within its limits, and then enacted ordinances to ensure that new and existing structures within these zones were sufficiently ventilated to prevent the accumulation of explosive levels of methane. Mitigation systems for modern buildings include subsurface barriers, ventilation systems, methane detectors, and alarms. Thousands of buildings in the Los Angeles area have such systems, including the Staples Center and Los Angeles Convention Center.
Construction of the Belmont Learning Center, now known as the Edward R. Roybal Learning Center, "the nation's most expensive high school" began in 1988 adjacent to, and partially above, the former oil field, and within a methane zone. Soil tests in the early 1990s showed methane at high levels, possibly migrating up from old wellbores (not all of which were mapped, let alone abandoned to modern standards). Construction of the complex continued intermittently, with partial demolition and reconstruction after additional contamination and an earthquake fault were found. The Learning Center eventually was completed at a cost of $377 million, not far from the area that was the field's center of operations 100 years before.