Estimating the total costs for cleaning up a leaking underground storage tank in California and determining the progress of such a cleanup may soon become easier. UC Davis researchers are in the midst of updating the state of California's manual for dealing with problem 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 are estimated to cost $150,000 each and, according to the California Environmental Protection Agency, there are 20,000 underground storage tanks that need to be removed. 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 cleanup requirements, review state-of-the-art approaches for cleaning up fuel tank leaks, and use their expertise to expand the manual to include a risk-based decision-making approach for investigating and cleaning up leaks. Among contamination 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 project researcher Miguel Marino, of UC Davis' land, air and water resources department.