Estimating the total costs for cleaning up a leaking underground storage tank in California and determining the progress of such a cleanup may become easier once UC Davis researchers complete an update of the state of California's manual for dealing with such underground tanks. State regulatory agents use the manual to determine what cleanup measures are necessary to protect public health and the environment and to preserve ground water quality. Such environmental cleanups for the nearly 20,000 leaking fuel tanks in California are estimated to cost $150,000 each. Contracted by the California State Water Resources Control Board, UC Davis researchers, working with Lawrence Livermore National Laboratory, will review how state and local agencies arrive at clean-up requirements and review state-of-the-art approaches for cleaning up fuel tank leaks. The researchers will expand the manual to include a risk-based decision-making approach for investigating and cleaning up leaks. Among situations to be dealt with are cases of soil-only contamination, soil contamination that threatens ground or surface water, and contamination that threatens drinking water, according to Miguel Marino, a professor in UC Davis' land, air and water resources department, who is one of the project researchers.