NVOC Regional Sewer Board - Executive Summary |
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NVOC Wastewater Treatment Plant, located at 507 Crestview Avenue, Niceville, FL, has one independent chlorine injection system. The chlorine storage and feed tanks are located outdoors. The chlorination process is located inside a building. The chlorine system has one (1) one-ton container of chlorine on line and one (1) one-ton container of chlorine on standby at any one time. Also, there is a maximum of 2 one-ton chlorine containers in storage. The system is operated under vacuum using gaseous chlorine. There is a Vacuum Regulator-Check Unit (Wallace & Tiernan 500 lb/24 hour capacity) which automatically shuts off the cylinder in the event of a break in the vacuum line. The chlorine supply system can automatically switch between the on-line and standby chlorine containers when the on-line container is depleted. The Facility normally stores a maximum of 4 one-ton chlorine cylinders at the site at any one time. All cylinders not in use are stored outdoors on a loading dock. D uring chlorine deliveries, the delivery truck backs up to the unloading area and the cylinders are taken off the truck via the facility's crane and placed onto the dock. The facility has chlorine detectors to monitor leakage in the chlorinator room and on the shipping dock. The sensors are located at about twelve inches above floor level. The detectors will automatically alarm at the Facility and at the main control room panel. Normally, the chlorinator room is secured with doors that remain closed except when the system is being inspected. Inspection takes place daily. If a chlorine leak is detected, the respective alarm will sound and the Operator will notify the Manager of the Regional Wastewater Treatment Plant. The Operator and Standby will don the Self-Contained Breathing Apparatus (SCBA) and the operator will then investigate the cause for the alarm. The exhaust fans will be activated from the exterior of the building. The air inside the building is evacuated and fre sh air is drawn into the building through upper and lower vents respectively. The Standby will remain outdoors in contact with the Operator ready to call for outside assistance if needed. The Operator and the Standby are trained in chlorine safety and emergency procedures. The Operator will shut the chlorine cylinder. If the leakage is not stopped the Fire Department will be contacted and the exhaust fan will be turned off. The Worst Case release for this facility assumes that a one-ton chlorine cylinder ruptures during unloading outdoors in a rural area. The cylinder discharges a dense gas release under worst case meteorological conditions of F Stability and 1.5 meters per second and ambient temperature of 250C. All two thousand pounds contained in the cylinder are assumed released over ten (10) minutes. It is only presented for comparative purposes and for non-OSHA facilities to determine under which RMP Program Level the facility fits. The Worst Case Impact Area is three miles in radius (EPA CEPP Risk Management Program Guidance For Wastewater Treatment Plants EPA 550-B-98-010 October 1998). There are about 1,800 people living in the Worst Case release area who could be affected by this type of release. Located within this area are seven schools (Okaloosa Watson College, Edge School, Addie R. Lewis Junior High School, C.W. Ruckel Junior High School, Niceville Senior High School, Valparaiso Elementary School, and Plew School). There is also one hospital, numerous doctors' offices, and one church. The Most Likely case release assumes a release of chlorine occurs due to a pipe break in the chlorine storage or chlorinator area. In order to have a leak that emits chlorine outside of the facility, it is necessary to assume the chlorine alarm is activated and the automatic cylinder vacuum loss shut off fails. The alarm would sound and the facility's emergency response team would be at the location within a few minutes to shut the system down at the cy linder. Under those unlikely assumptions, the most likely release case is assumed to be a steady-state leak of up to 5 pounds per minute of chlorine (either as a gaseous or a two-phase release) for 30 minutes (150 lbs). It should be noted that a completely filled one-ton cylinder has maximum gaseous discharge rate of about 500 pounds per day (0.35 pounds per minute). Significant gaseous discharges above this rate will result in the cylinder freezing up and the discharge stopped. The Facility has only one (1) one-on cylinder hooked up to the header and a maximum discharge rate from that system could be 0.35 pounds of chlorine per minute. It is also assumed that the cylinder discharges a dense gas release under meteorological conditions of D Stability and 3.0 meters per second at an ambient temperature of 250 C. The Most Likely Case Impact Area based upon the above conditions is a tenth (0.1) of a mile in radius (EPA CEPP Risk Management Program Guidance For Wastewater Treatment Pl ants EPA 550-B-98-010 October 1998). It is estimated that there are 50 people living in the Most Likely Case release area who could be affected by this release. There is one school located within this area. There are no hospitals or parks located within this area. In fact most of this release would be contained on the facility's property. The Facility has not had an accidental release of chlorine from this covered process in the five years prior to the submission of this Risk Management Plan (RMP). |