The Los Angeles Department of Water and Power (DWP) wants an exemption to proposed clean-air rules so that it doesn't have to replace toxic soot-producing diesel equipment with cleaner-burning models, according to the Los Angeles Daily News newspaper. Environmentalists said the DWP's efforts are at odds with the utility's "green" programs, which include subsidizing the private sector for using less-polluting engines. The clean-air rules are designed to reduce diesel soot, which is responsible for 70 percent of the cancer risk from air pollution in Southern California. However, managers with the DWP said diesel is more reliable and available than compressed natural gas to fuel the dump trucks, hydraulic lifts, bucket trucks, and other heavy-duty vehicles that respond to power outages and other emergencies in far-flung areas. "Our territory is quite large and we have transmission systems that go into Arizona, Nevada, up to the Oregon border," said Randy Howard with the DWP. "Many of those areas would not have the support to fuel those vehicles." Officials with the South Coast Air Quality Management District (AQMD) counter that CNG-fueled vehicles make up less than 1 percent of DWP's 1,000-vehicle heavy-duty fleet, leaving plenty of diesel vehicles to respond to emergencies in remote areas. And the utility can already apply for an individual exemption for diesel vehicles that are based five miles from a natural gas fueling station. "At this point we aren't inclined to give them a blanket exemption," said AQMD spokesman Sam Atwood. "We'd like the DWP to make more of a good-faith effort. They need to focus on purchasing alternative-fuel vehicles and not looking for blanket exemptions." "My hope is that the DWP is not only committed to clean air from an energy-generation perspective but also committed to cleaner solutions in vehicles that deliver service to their consumers," said Todd Campbell, policy director at the Coalition for Clean Air. The DWP has purchased several CNG trucks, but managers said they can use them only in areas near CNG fueling stations. Los Angeles leaders said the DWP may have a valid need for an exemption, but the utility must first prove it's not simply trying to delaying the clean-up of its fleet. "We have thousands of transmissions lines in remote areas. Diesel might be justified over alternative fuels. But I want to see a justification," said Councilman Tony Cardenas, who chairs the Council's Energy, Commerce and Natural Resources Committee. "They need to show us it will hinder their ability to maintain facilities in an emergency."