Douglasville (Sweetwater) - Executive Summary
Sweetwater Creek Wastewater Treatment Plant (SWCTP), located at 1413 Roberts Road, Douglasville, GA, has one independent chlorine injection system. The chlorine storage and chlorination process is located within two adjacent rooms comprising the chlorine process building. The 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. 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 has a chlorine detector to monitor leakage in the chlorine storage and chlorinator rooms. Chlorine sensors are located at twelve inches above floor level in both rooms. The detector will automatically
alarm at the facility and at the main control room panel.
The SWCTP normally stores a maximum of 2 one-ton cylinders at the site at any one time. All cylinders are stored indoors in a building with doors, which seal. During chlorine deliveries, the delivery truck backs up to the unloading area. The building doors are opened and the chlorine cylinders are brought inside via a crane.
Normally, the chlorine storage and chlorinator rooms are secured with doors that remain closed and locked except when chlorine is being unloaded. All chlorine cylinders are stored within the chlorine storage room. If a chlorine leak is detected, the chlorine alarm will sound and the Operator will notify the Plant Supervisor and appoint a Standby Operator. The Operator and Standby will don the Self-Contained Breathing Apparatus (SCBA) and the operator will then investigate the cause for the alarm. 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. The exhaust fans will be activated from the exterior of the building. The air inside the building is evacuated and fresh air is drawn into the building through upper and lower vents respectively.
The Worst Case chlorine 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 (3) miles in r
adius (EPA CEPP Risk Management Program Guidance For Wastewater Treatment Plants EPA 550-B-98-010 October 1998). There are about 7,000 people living in the Worst Case release area who could be affected by this type of release. Located within this area is one (1) school. That school is Factory Shoals Elementary School.
The Most Likely case release assumes a release of chlorine occurs due to a pipe break in the chlorine storage or chlorinator rooms. 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 cylinder.
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 60 minutes (300 l
bs). 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 SWCTP has only one (1) one-on cylinder hooked up to the header and a maximum discharge rate from that system would 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 Plants EPA 550-B-98-010 October 1998). It is estimated that there are no people are living in the Most Likely Case release area that could be affected by this release. (There is one lot in an adjacent plan subdivision,
which is within one tenth of a mile.) There are no schools located within this area. There are no hospitals, parks or other sensitive receptor located within this area. Fairway 4 of the adjacent golf course could be marginally affected by this release. In fact most of this release would be contained on the Douglasville-Douglas County Water and Sewer Authority 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).