Study of Potential for Groundwater Contamination from Past Dry Cleaner Operations in Santa Clara County

The threat of groundwater contamination posed by dry cleaning operations is primarily a legacy issue. Dry cleaners today have greatly improved usage and handling of solvents. Perchloroethylene (PCE) remains the most prevalent solvent used for dry cleaning. Dry cleaning machinery has evolved substantially and is designed to be leak-proof, air-tight, and to minimize waste generation. Dry cleaning facilities are subject to multiple permits, and are regularly inspected. A few dry cleaners have switched to “environmentally safe” solvents in their operations. Failures and operator error can nonetheless occur, representing a minor continuing threat to groundwater. The greater threat to groundwater quality is from past dry cleaning operations from as long as 50 years ago, a threat which remains significant today.

This study catalogued the locations and years of operations for current and former dry cleaning operations in Santa Clara County. Past dry cleaner operational practices, solvent usage, groundwater subbasin vulnerability, and municipal supply well vulnerability are explored to develop a system to rank the relative risk of groundwater contamination from dry cleaner solvent releases. The systematic ranking of the threat posed by dry cleaners provides a means of prioritizing dry cleaning sites for further investigation. The ranking system will be useful to regulatory agencies for determining which cases warrant more aggressive investigation and remediation.