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The Tutu Wellfield site is located in east-central St. Thomas in the U.S. Virgin Islands. The site consists of a plume of contaminated groundwater covering an area about 108 acres in size. Contamination was first detected when a strong petroleum odor from the Tillet Well, a public water supply well for the area, was reported. An investigation indicated that volatile organic compounds (VOCs) were contaminating several public, institutional, commercial and private wells. Water from some of these wells was transported to other parts of the island. Many contaminated wells, including the Tillet Well, were shut down. After immediate actions to protect human health and the environment, EPA put the site’s long-term cleanup plan in place. Treatment and monitoring of contaminated soil and groundwater are ongoing.
In July 1987, the owner of Tillet Gardens contacted the Virgin Islands Department of Planning and Natural Resources (DPNR) regarding an odor emanating from his well water. Based on groundwater sampling results, DPNR closed 13 commercial and five private wells in the area between July and September 1987. EPA sampled 24 supply wells in 1987 which confirmed previous groundwater sampling results and also detected arsenic, selenium and zinc in some of the supply wells.
In 1990 EPA issued a Unilateral Administrative Order to ESSO Standard Oil S.A. Limited (ESSO), Texaco Caribbean, Inc., (Texaco) and L'Henri, Inc. (O'Henry), which required them to provide water to affected homes until these homes are connected to the public water main and take over EPA' s groundwater monitoring of the drinking water wells in the Tutu aquifer. In 1992 ESSO Standard Oil and Texaco Caribbean, Inc. entered into an Administrative Order on Consent with EPA to conduct a remedial investigation/feasibility study at the Tutu Wells site to fully evaluate the extent and nature of contamination. Field work for the investigation began in April 1992 and was concluded in July 1994.
In April 1995, EPA investigated and identified a suspected underground source of TCE contamination at the Curriculum Center.
EPA placed the site on the Superfund program’s National Priorities List in September 1995
What Has Been Done to Clean Up the Site?
Immediate Actions: In response to the detection of contaminants in groundwater, the Virgin Islands Department of Planning and Natural Resources closed down the Tillet Well and other commercial and private wells in 1987. EPA followed this action with the decontamination of five residential cisterns. An alternate water supply was provided to these residences while monitoring of the remaining wells continued. In March 1990, EPA issued an Administrative Order to three potentially responsible parties – Esso, Texaco and O'Henry Dry Cleaner – to take over the monitoring program and to provide trucked water to additional residences affected by contamination in groundwater. Since October 2005, EPA had taken over the responsibility for providing trucked water to the affected residences. These residences are currently connected to the public water supply system and there is no need for trucking of potable water.
Long-term Cleanup: Following a remedial investigation and feasibility study to determine the nature and extent of site contamination, and to evaluate remedial alternatives, EPA selected a cleanup plan in 1996. The cleanup plan called for extraction and treatment of contaminated groundwater and soil vapor extraction of contaminated soils.
Construction of the groundwater treatment and soil vapor extraction system began in September 2003 and was completed in March 2004. A vapor intrusion assessment was conducted at the Curriculum Center in December 2007.
What Is the Current Site Status?
The site is being addressed in two stages: immediate actions and a long-term cleanup phase focused on cleanup of the entire site.
Immediate actions taken in1987 included:
- closing down of contaminated wells
- providing drinking water to affected residences
These actions immediately reduced the risks posed to the health and safety of the nearby population while longer term investigations and cleanups were, and are, being conducted.
The cleanup plan for the site, selected in 1996, called for extraction and treatment of contaminated groundwater and soil vapor extraction of contaminated soils.
The soil vapor extraction system constructed at the Curriculum Center operated for approximately two years from 2004 to 2006. The soil vapor extraction system was shut down in April 2006 because of a significant decrease in concentrations of contaminants going into the soil vapor extraction system.
By March 2004, two groundwater extraction and treatment systems were constructed to contain and remove chlorinated volatile organic compounds (CVOC). One system is located at the Curriculum Center and consists of three extraction wells, and the second is located down gradient near the center of the contamination plume and consists of two extraction wells. The operation and maintenance of the system has been carried out by EPA from April 2004 to March 2013 and the USVI Government since April 2013. Groundwater is monitored routinely at the site to assess cleanup progress.
Due to the likelihood of a continuing source of VOCs in the groundwater in the vicinity of the Curriculum Center, EPA completed a Focused Feasibility Study to determine the nature and extent of the source in this area. The Proposed Remedial Action Plan to clean up the sources areas is out for public comment. EPA is to hold a public meeting on August 23, 2018 to explain the cleanup alternatives considered and the EPA's Preferred cleanup alternative.