Property owners in a west Santa Rosa, Calif., neighborhood whose wells were contaminated by a chemical spill have inundated local government agencies with claims of damages that collectively exceed $500 million. Toxic amounts of cleaning solvent were found earlier this year in the groundwater surrounding about 100 homes. More than 20 private wells were found to be contaminated.

The solvent, suspected to have been spilled by a local dry cleaner 10 years ago, is considered carcinogenic. Discovery of the spill forced state and county health officials to provide filter tanks for those landowners whose wells were directly affected.