The Rhone-Poulenc, Inc./Zoecon Corp. Site covers about 5 acres in East Palo Alto, Santa Clara County, California. It is surrounded by residential and industrial areas.

Rhone-Poulenc, Inc., formerly manufactured pesticides containing arsenic at the plant. Zoecon Corp., which purchased the site in 1972, produces agricultural chemicals, but no contamination has thus far been traced to its operations. Monitoring wells on the site are contaminated with arsenic and metals such as lead, cadmium, mercury, and selenium, according to analyses conducted by a consultant to Rhone-Poulenc. Contamination is believed to have resulted from leaking underground storage tanks. About 58,000 people depend on wells within 3 miles of the site as a source of drinking water.

Rhone-Poulenc is working with the California Regional Water Quality Control Board (CRWQCB) to determine the extent of ground water contamination. CRWQCB issued a Cleanup and Abatement Order to the company in December 1983. This is one of 19 sites in the South Bay Area of San Francisco. Facilities at these sites have used a variety of toxic chemicals, primarily chlorinated organic solvents, which contaminate a common ground water basin. Although these sites are listed separately, EPA intends to apply an area-wide approach to the problem as well as take specific action as necessary.