EPA Expands Contaminated Groundwater Cleanup on Saint Thomas
EPA Expands Contaminated Groundwater Cleanup on Saint Thomas
The funding, passed by Democrats and Republicans two years ago, expands the existing groundwater pump and treatment system to include additional wells and upgrades all existing treatment equipment.
Note: Google Gemini assisted me with locating archived data from the Morbidity and Mortality Weekly Report, published by the Centers for Disease Control on February 11, 1994. Gemini did not write or draft any portion of this report, but it did help me organize my thoughts. All text following the Tutu Wellfield History and EPA Findings section is written verbatim from the Environmental Protection Agency’s summary.
In late February, the U.S. Environmental Protection Agency (EPA) announced that the Tutu Wellfield in Saint Thomas, U.S. Virgin Islands, is among the over 100 sites across the United States getting more than $1 billion for cleanup projects as part of the Bipartisan Infrastructure law.
The Tutu Wellfield is a manmade network of extraction points offering freshwater access. The wellfield includes the surrounding area above ground. These wells are fed by aquifers, a naturally occurring geological feature of Saint Thomas.
What is a Wellfield?
A wellfield is the land above and surrounding a system of wells where humans drilled into an aquifer to extract fresh water. Rainwater eventually seeps through the ground and into the aquifer.
How is Groundwater Stored?
In an essay published on LinkedIn, Brian P. Neff writes, “Groundwater is physically available throughout the entire USVI in three types of aquifers (water-saturated soil and geologic material). A volcanic rock aquifer underlies all of Saint Thomas and Saint John and most of Saint Croix.”
Neff explains that as the islands aged, shallower portions of volcanic rock weathered, developing fractures. The fractures hold groundwater and allow it to flow. The aquifers then connect fractured zones, allowing wells to draw groundwater, sometimes yielding up to several hundred gallons per hour when pumped.
The second type of aquifer consists of large carbonate rock and can be found throughout the Kingshill Aquifer in Saint Croix.
And finally, alluvial aquifers consist of eroded material that is transported by moving from guts and streams. Alluvial aquifers sit on the fractured volcanic rock and make up a portion of the Kingshill aquifers.
The aquifers are a labyrinth of underground chambers that collect water on Saint Croix, Saint John, and Saint Thomas. This underground system is known through surveys and extraction points (wells) but is largely unexplored by humans. Estimates of how much freshwater each island holds underground remain unknown.
What’s New?
In 2018, the EPA determined that this system needed to be expanded and enhanced.
The funding, passed by Democrats and Republicans two years ago, expands the existing groundwater pump and treatment system to include additional wells and upgrades all existing treatment equipment to accommodate additional flow rates and more efficiently address the source of contamination.
The work to expand and enhance the system is estimated to cost about $14 million.
The Bipartisan Infrastructure law offers President Joe Biden and his administration new tools and programs designed to support new cleanup projects at 25 Superfund sites and continue other cleanups at over 85 Superfund sites in the United States.
Tutu Wellfield History and EPA Findings
The Tutu Wellfield site is located in east-central Saint 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 the cleanup of the entire site.
Immediate actions taken in 1987 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. Due to the impact of the Hurricanes in Sept 2017, the plants lost power and became inoperable. EPA assessed the two treatment plants and necessary repairs were completed in June 2021.The plants were being operated again by the Department of Planning an Natural Resources but are again shut down due to resource issues.
Due to the likelihood of a continuing source of VOCs in the groundwater in the vicinity of the Curriculum Center, in 2018 EPA completed a Focused Feasibility Study to determine the nature and extent of the source in this area. EPA reissued a Proposed Plan on July 14, 2021, which explained the cleanup alternatives considered in the focused feasibility study and indicated EPA's preferred cleanup alternative for continuing to cleanup the site. The Proposed Plan to clean up the sources areas was available for public comment from July 14 to August 13, 2021. The Record of Decision to cleanup the groundwater in the vicinity of the Curriculum Center was issued in September 2021. The Government of the Virgin Islands supports EPA's decision.
EPA completed the Remedial Design of the focused feasibility study for the cleanup of the groundwater in the vicinty of the Curriculum Center in December 2023.
A third Five Year Report report was issued in September 2019. EPA is preparing the Fourth Five Year report and is expected to be released in Summer 2024.