A leachate storage tank at the Glassmullagh landfill site has been damaged, causing the potentially toxic liquid to leak from the inner tank into the surrounding outer tank.

The incident happened in March 2016 and the Northern Ireland Environment Agency (NIEA) was notified on April 21. NIEA has permitted Fermanagh and Omagh District Council (FODC) to store the leachate in a concrete storage tank at the site until the steel tank is repaired. The process is expected to take six months.

NIEA told The Impartial Reporter that no leachate has escaped into the environment. The concrete tank will be inspected and emptied every day until the tank is repaired and NIEA staff will “routinely” monitor the waterways close to the site to ensure the dangerous chemicals are not impacting the water.

Leachate is the liquid formed when water flows through landfill waste and reacts with the different materials, metals and liquids. A 2010 study by the UK Environment Agency found that the substances uncovered in more than five per cent of leachate samples included: arsenic, cyanide, dichloromethane, methy chlorophenoxy acetic acid, nitrogen, phenols and toluene.

“There was no release to the environment as the leachate was caught in the surrounding bund, as its designed to do,” an NIEA spokesman stated. “After the incident the leachate tank and bund were pumped out so there is no leachate remaining in these tanks. Since that time the leachate storage tank has been empty so there is no risk of any leak to the environment.”

Glassmullagh landfill is situated about five miles outside Enniskillen. It was operational for 39 years, between 1967 and 2006. Because it is an old landfill, it does not have the engineered lining which is common with modern landfills. As a result, leachate must be continually pumped into a storage tank and transported for treatment at Fermanagh’s leachate treatment plant at Drumee.

A report to the FODC Environmental Services Committee last Wednesday stated: “This failure should not have happened, however it is vital that remedial works are undertaken to rectify the situation at the earliest opportunity.”

The report continued: “The existing leachate storage tank is constructed using panels of glass fused (TRIFUSION) steel. It has a capacity to store 200m³ of raw leachate. The tank is surrounded by a larger tank constructed with the same materials. The outer tank acts as a bund. This reduces the environmental risk if the inner leachate tank fails/ leaks.

“The leachate storage tank has failed as a result of emptying the inner leachate tank. Once emptied, the volume of rainwater in the outer bund tank created inward hydraulic pressure, which in turn has caused the steel panels in the bottom two rings of the inner tank to crease and fracture. Once the panels crease, the panels have exceeded their elastic limit and therefore will not return to the pre-pressure shape. The inner tank is no longer water tight and leachate will leak into the outer bund.”

The cost of repairing the storage tank will be between £30-£35,000. Extra works, costing £4,000, have been suggested to avoid this situation occurring in the future. Council officials have recommended that FODC proceeds with a single tender action using the original installers to repair the existing tank. The Council is hopeful that its insurers will cover the repair costs.

A spokesman from NIEA told The Impartial Reporter: “Glassmullagh closed landfill has a waste management licence and associated water discharge consent issued by the NIEA. To meet the conditions set by NIEA, Fermanagh and Omagh District Council has implemented a range of measures to minimise the impact on the environment which include site capping, retro-fitted gas extraction wells and a gas engine, leachate collection systems and pumps, cut off drains, surface water management, reed beds and a comprehensive surface and groundwater monitoring programme.”

Since April 21 the leachate storage tank has been empty “so there is no risk of any leak to the environment,” he said. “In the interim, the landfill operator is utilising a concrete storage tank at the site to store leachate. This is inspected and emptied on a daily basis. The surface water and groundwater around the Glassmullagh site are also monitored on a regular basis and the operator has been instructed to inform NIEA immediately of any impact on water quality.
“The landfill operator is currently assessing the options to repair or replace the damaged leachate storage tank. It may take six months to implement the selected option.”

He said NIEA is “content” that FODC is meeting the Landfill Regulations. He concluded: “As an additional precaution NIEA staff routinely monitor the waterways adjacent to the site to ensure there are no impacts.”