Frontera Creek sits in Rio Abajo, Humacao, Puerto Rico. From 1971 to 1981, industrial properties near Junquito discharged waste directly into the creek. That pollution contaminated soil, sediment, surface water, and air with mercury, the pesticide lindane, and 22 other substances. Those other contaminants include metals such as arsenic, cadmium, and lead, along with volatile organic compounds like toluene, xylene, ethylbenzene, and dichloromethane. EPA added the site to the Superfund National Priorities List (NPL) in September 1983, after an initial assessment completed in 1981.
The contamination caused serious harm early on. In 1977, thirty cows that grazed near the creek died. A housing development called Ciudad Cristiana was built along the creek in 1979, and within a year residents reported health problems. Blood and urine tests found above-normal mercury levels in 500 residents. EPA approved a site investigation plan in 1986 and finished the study by 1991.
In September 1991, EPA signed a Record of Decision (ROD) for Operable Unit 1, focused on source control. The selected cleanup methods included excavation, dewatering, treatment, and off-site disposal. Workers excavated about 800 cubic yards of mercury-contaminated sediment from a ditch leading to the creek and removed contaminated soils from one industrial property. Remedial construction was completed by September 1997, and EPA deleted the site from the NPL on December 29, 1998. The site achieved sitewide ready for anticipated reuse status in June 2006.
Today, all cleanup goals have been met. Human exposures are under control, contaminated groundwater migration has been stabilized, and there are no unacceptable risks under current or reasonably anticipated future land uses. EPA continues monitoring to confirm that affected groundwater stays within the original contamination area. The site now hosts 11 businesses employing 560 people and generating roughly $173.6 million in annual sales revenue, as of December 2024.
Community members who want more information can contact the site team directly. Documents related to the cleanup, including the 1991 ROD and 153 administrative records, are available by appointment at the EPA Records Center in New York, the EPA Caribbean Environmental Protection Division office in Guaynabo, Puerto Rico, or the Puerto Rico Environmental Quality Board office in San Juan.
