Russell Water Treatment Plant - Executive Summary
Executive Summary |
The City of Russell Water Treatment Plant (RWTP) accidental release prevention policy involves a unified approach that integrates technologies, procedures, and management practices. All applicable procedures of the U.S. Environmental Protection Agency (EPA) prevention program are adhered to. The RWTP emergency response policy involves the preparation of response plans which are tailored to the emergency response services available in the community, and is in compliance with the EPA Emergency Response Program requirements.
The RWTP Chlorination Facility has been installed to disinfect the water being treated in the RWTP. This water services the City of Russell. The chlorination station is located at 210 South Front Street, next to the water treatment plant. The station includes a chlorination room, which contains liquid chlorine containers, two chlorinators, and safety equi
pment.The amount of chlorine handled is two one-ton containers. The facility is normally manned. Water treatment operators visit the facility daily and respond to any trouble which may occur.
The offsite consequence analysis includes concideration of two chlorine release scenarios, identified as '"worst case release" and "alternative scenario." The first scenario is defined by EPA, which states that "the operator shall assume that the...maximum quanity in the largest vessel...is released as a gas over 10 minutes,"due to an unspecified failure.The alternative scenario is defined as "more likely to occur than the worst-case release scenario".
Atmospheric dispersion modeling has to be performed to determine the distance traveled by the chlorine released before its concentration decreases to the "toxic endpoint" selected at EPA of 3 ppm, which is the Emergency Response Planning Guideline Level 2 (ERPG-2). This is degined by the American Industrial Hygiene Associat
ion (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action".The residential population within a circle with a radius corresponding to the toxic endpoint distance has to be defined, "to estimate the population potentially affected".
The worst-case release scenario at the Russell Water Treatment Plant involves a failure of the two ton-containers which could be connected concurrently (a total of 4,000 lbs. of chlorine). The offsite consequence analysis for this scenario was performed for two sets of conditions. The set followed conditions pre-defined byEPA, namely release of the entire amount as a gas in 10 minultes, use of the one-hour average ERPG-2 as the toxic endpoint, and consideration of the population residing within a full circl
e with radius corresponding to the toxic endpoint distance .EPA set these conditions to facilitate the performance fo the offsite consequence analysis.
EPA -mandated meteorological conditions, namely Stability F, wind speed of 1.5 m/sec., highest daily maximum temperature (101F ), and average humidity (65%) were used for both sets.
When atmospheric dispersion modeling for the worst case scenario was performed using the EPA assumptions , a distance to toxic endpoint of 2.9 miles and an estimate of residential population potentially affected of 5'000 was obtained. When the same modeling was performed with the second set of conditions, namely using a vapor/aerosol release, a 10-minute average ERPG-2 of 7ppm, and consideration of the plume footprint only, a distance to toxic endpoint of 1.4 mikes and an estimate of population potentially affected of 1,500 resulted.
The alternative release scenario involves the rupture of the flexible connections connecte
d to two ton-containers, posibly due to a tornado.The amount of chlorine released is 317 lb, at an average rate over one hour ( the duration of the release) of 10.5lb/min. Toxic endpoint distances to ERPG-2 levels were obtained.The latter is defined by AIHA as "the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing life-threatening health effects". Thhe typical meteorological conditions used were Stability E, wind speed 2.0 m/s, average air temperature of 62 F, and 63% average humidity. The estimated distances traveled to the toxic endpoints are 4300 ft. for the ERPG-2
Actuation of the chorine detector is an active mitigation measure considered. An additional mitigation system installed is the conversion of the existing chlorinators to a remote vacuum type, with all pressurized chlorine gas piping replaced with vacuum piping. This will reduce significantly the amount of
chlorine released in case of pigtail rupture.
The general RWTP accidental release prevention program is based on the following key elements:
1. High level of training of the operators
2. Preventive maintenance program
3. Use of state-of-the-art process and safety equipment
4. Use of accurate and effective operating procedures.
5. Implementation of an auditing and inspection program.
No accidental releases of chlorine have occurred at this facility in the past five years.