St. Cloud Water Treatment Plant - Executive Summary
Safety is a top priority at the St. Cloud Water Treatment Plant (WTP). In accordance with this, a Hazard Control Committee is in place for the St. Cloud Public Utilities (Water & Wastewater). This committee meets on a monthly basis to review accidents and make recommendations, discuss accident prevention and conduct safety audits at the two plants. |
The operators at the WTP are taught to respect the hazards these chemicals represent and to treat them accordingly.
The WTP produces the drinking water for the City of St. Cloud. Part of the process to produce drinking water is disinfection. St. Cloud disinfects with chloramines (a combination of chlorine and ammonia). The WTP would not have any more than 18,000 lbs. of chlorine at any one time.
WORST CASE SCENARIO - The release of 2,000 lbs. of chlorine gas at a rate of 110 lbs./min. for 10 minutes. The math doesn't work because of the passive mitigation component. The release of the chlorine in an enclosed room would slow down th
e release of the chlorine gas. Also the chlorine scrubber (active mitigation) would vent the chlorine from the room and neutralize it. This would further reduce the chlorine release.
ALTERNATIVE SCENARIO - Transfer hose failure (closest scenario to what could happen at WTP).
The vacuum regulator attaches directly to the chlorine cylinder and the transfer hose follows. If the transfer hose loses its integrity, a valve in the vacuum regulator will close (shutting off the chlorine) due to the loss of vacuum. The only way for chlorine to escape would be if the vacuum regulator was knocked off of the chlorine cylinder. Again both passive and active mitigation were taken into account reducing the release substantially.
The WTP complies with the OSHA PSM rule. This, along with the RMP rule, provides a comprehensive safety program. Two of the steps St. Cloud has taken to enhance the prevention program are as follows:
Put all components of the chlorine system on a more rigorous inspect
ion schedule. Use vacuum regulators that attach directly to the chlorine cylinder. This is important because any loss of vacuum will cause the valve in the regulator to close. Thus, the only way for chlorine to be released is for the vacuum regulator to be knocked off of the cylinder.
There have been no reportable accidents at the St. Cloud Water Treatment Plant in the history of the plant.
In the procedure for changing chlorine cylinders, it states that if the chlorine detectors go into alarm, WTP personnel will evacuate the chlorine cylinder room and call the St. Cloud Fire Department. The Fire Department HazMat Team and St. Cloud Emergency Management will take control of all activities from this point on.
The WTP has trained with the HazMat Team which is one of seven state regional emergency response teams. Further training at the WTP is also planned.