For many years, harmful chemicals were dumped on the ground around industrial plants in Phoenix. The groundwater polluted by those health-threatening solvents remains at the center of governmental, financial and legal disputes that have been delaying cleanup of the contaminated water that stretches for 15 miles. Fulton Schools Professor Rolf Halden, director of ASU’s Center for Environmental Health Engineering, says the risk of public exposure to the chemicals can be alleviated only by an aggressive cleanup effort.