Chemical discharges from Exxon’s Gas-to-Energy pipeline will impact marine water quality

Chemical discharges from Exxon’s Gas-to-Energy pipeline will impact marine water quality – impact assessment

May 01, 2022 News

Kaieteur News – The highly touted Gas-to-Energy project has the potential to not only harm the onshore environment, but also the marine habitat where over 100 species currently dwell.
This is according to the Environmental Impact Assessment (EIA), completed by oil giant ExxonMobil’s Consultant, the Environmental Resources Management (ERM).

Map depicting the Offshore Component of the Gas-to-Energy Project

The document was released to the public on April 20, last, opening a 60 days period for the public to make submissions to the Environmental Protection Agency (EPA) on the proposed project.
According to the EIA, the planned project activities could affect water quality and potentially impact the health of marine biota. Marine biota refers to the organisms living on the seafloor such as shrimp or prawns as well as other species that dwell in the entire water column.
The activities for the installation of the offshore pipeline will potentially impact marine water quality by temporarily increasing the total suspended solids (TSS) concentrations in the water column, according the impact study.
One of the activities that can impact the water quality is the hydrotesting of the onshore and offshore pipeline, a process which will discharge water treatment chemicals into the ocean.
Hydrotesting is performed to test the integrity of the pipelines prior to introducing gas. The project has planned discharges to water associated with the hydro-testing process. Four alternatives were listed in the document for the discharge of hydrotest water but under all four alternatives, there would be a discharge of chemicals into marine waters.
The hydrotest water will contain water treatment chemicals to protect the pipeline during hydrotesting. The chemicals that will be used were not stated, since the final selection has not yet been determined, according to ERM. It was keen to note that, “These chemicals may have different toxicities than the chemicals selected for use in the hydrotesting.”
Some of these discharges also have the potential to clog fish gills, thereby threatening the existence of these aquatic creatures within the project site.
The EIA states, “Planned offshore pipeline installation activities will potentially impact marine water quality as a result of burial of selected segments of the offshore pipeline. Sediments will be disturbed, resulting in a temporary increase in TSS concentrations in the water column. These temporary increases in TSS may have direct impacts on marine biota through clogging of fish gills or, in the photic zone, through light inhibition for photosynthetic organisms.”
It goes on to assure that the concentration of the discharges will decrease over time as the sediments dissipates and settles, however, while large particles will settle faster, the finer particles may travel further.
The Consultant predicts that the intensity of impacts from increased TSS concentrations in the water column from pipeline trenching are considered low during the construction stage. Pipeline trenching is the process in which a narrow trench is dug to allow for the laying of the pipeline. This process is expected to be conducted over several months.
The project
The Gas-to-Energy project is expected to be constructed at Wales, West Bank Demerara. It will involve capturing associated gas produced from crude oil production operations on the Liza Phase 1 (Destiny) and Liza Phase 2 (Unity) Floating, Production, Storage, and Offloading (FPSO) vessels, transporting approximately 50 million standard cubic feet per day, via a subsea pipeline and then to an onshore pipeline to a natural gas liquids (NGL) processing plant (NGL Plant), treating the gas to remove NGLs (i.e., propane, butane, and pentanes+) for sale to third parties, and ultimately delivering dry gas meeting government specifications for use at the power plant.
Construction will begin after the company receives all necessary authorisations, with a target date of August 2022 for start of the NGL Plant site preparation, and will take approximately three years. The combined offshore and onshore pipeline system is targeted to be ready to deliver rich gas by end of 2024, and the NGL Plant is targeted to be operational by mid-2025. The project has a planned life cycle of at least 25 years.
The aspect of the project for which the oil company is responsible, that is to say, the installation of the offshore and onshore pipelines, is set to cost a whopping US$1.3B.
The Government of Guyana will be handling the construction of the power plant.

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