At 9:30 a.m., a worker of a sugar refinery noticed three puddles on the ground next to the containment system of the acid tanks. Upon closer inspection, he saw that the leak was coming from a nozzle on the storage tank containing 4.4% hydrochloric acid solution used on certain Sundays during the sugar processing campaign to clean the evaporators. The automated effluent management system installed on the secondary containment was discharging the solution onto the ground outside the secondary containment instead of circulating it back to the tank (which it is supposed to do if acid is detected in the secondary containment). The worker notified the refinery’s safety coordinator, who had the area evacuated. The pump in the secondary containment that was feeding effluent onto the ground was shut off. The leak was stopped by pumping the 3 m³ of acid remaining in the tank to a nearby tank. The puddles were absorbed by the area’s porous asphalt. Wearing the appropriate PPE, the safety coordinator hosed off the area to dilute the effluent. The mix of water and effluent drained into the stormwater gully pit. This gully pit drains into a gutter that leads to the ocean 100 m away. Effluent discharges onto a beach of pebbles and seeps into a strip along the shoreline.
As no acid was seen on the ground when the workers started their shift at 7:00 a.m., the leak occurred over a maximum of 2.5 hours. No more than about 100 l leaked out of the secondary containment. The shoreline was visually inspected on 16 May. No dead fish were found.
The leak was probably due to the recent replacement of part of the pipe (the work ended just three days prior to the leak). This work may have weakened the tank’s nozzle and caused it to crack.
In addition, a failure of the pH sensor on the pump in the secondary containment surrounding the tanks of acid caused the automatic valve to open and discharge acid outside the secondary containment (pH<5.5: automatic valve closed and effluent pumped to the acid tank; pH>5.5: valve opened to outside the secondary containment).
Following this incident, the operator removed the pump’s control of the pH meter. Now, the pump is started manually after the pH has been checked by in-house teams. An alarm on the pH meter activates when the pH falls below 5.5 so that teams can intervene if acid is present in the secondary containment. A check of the pH meter is included in the instrumentation monitoring plan used in the refinery’s control room.
Nozzles and welds as well as the integrity of the hydrochloric acid storage tank are checked by a contractor. The operator has updated the procedure for managing chemical ground spills and heightened the awareness of first responders.
