WILLEMSTAD – Pollution at the former Isla refinery consists of a complex mixture that includes crude oil, petroleum products, asphalt, sulfuric acid, heavy metals and asbestos, according to a TU Delft study examining how the industrial area could eventually be cleaned.
However, researcher Annika van der Nat warns that detailed information about the extent and concentration of contamination was not available to her, making it impossible to produce a definitive remediation plan.
The finding is one of the most significant limitations identified in the graduation study “Reclaiming the Isla,” which examines a nature-based approach to cleaning and redeveloping the refinery.
The pollution analysis was based on publicly available literature, interviews with Curaçao experts and a visit to the refinery property. That information allowed the researcher to establish a general picture of where different types of contamination are likely to occur, but detailed contamination data were either unavailable or were not provided for the research.
The report identifies transportation infrastructure inside the refinery as one area of particular concern. Oil and petroleum products moved between storage tanks, processing facilities and shipping points through an extensive network of pipelines.
According to the study, this means contamination can particularly be expected around pipeline routes and docking areas. Construction and repairs carried out over decades also created a high probability of asbestos contamination in and on the soil.
Historical environmental studies cited in the thesis paint an equally troubling picture.
A Dutch government environmental investigation in 1983 and an environmental audit associated with the 1985 ownership transfer documented numerous direct discharges into the Schottegat.
The report says these included oil spills and leaking tanks. Cooling-water discharges of approximately 3,500 cubic meters per hour were also associated with pollution and odors.
Sediment in the western Schottegat was found to be severely contaminated with oil and, according to the historical material cited by Van der Nat, would have been classified as chemical waste under Dutch standards.
The study also refers to approximately four hectares of contaminated land near Valentijn Bay where barrels containing sulfur, catalysts and other toxic materials had been dumped.
Instead of relying exclusively on conventional excavation, incineration or containment, Van der Nat investigates whether plants could become part of the solution.
The process, known as phytoremediation, uses vegetation and microorganisms to remove, degrade or stabilize pollutants in soil and water.
The report argues that conventional methods can sometimes move the environmental problem rather than eliminate it. Contaminated soil may be transported elsewhere, while capping leaves pollutants in place and incineration can create emissions.
Nature-based remediation is generally much slower but can be less invasive and, depending on conditions, less expensive. The thesis notes that these methods can require years or even decades to work.
For Isla, the researcher proposes six different plant-based remediation systems, depending on the type and location of contamination.
Plants considered include mangroves, Klein grass, Manzanilla trees and local flowering shrubs. The selection considers whether plants can survive Curaçao’s dry climate and the particular contamination present, while favoring native or non-invasive species.
The report nevertheless makes an important qualification: the proposal cannot substitute for a detailed professional environmental assessment.
Before a final remediation strategy could be developed, considerably more information would be required about contamination concentrations, depth, groundwater movement and conditions across individual parts of the enormous refinery complex.
The research therefore provides a possible framework for cleaning Isla rather than a ready-to-execute remediation plan.