BCWID #1 Water Treatment Plant - Executive Summary
Facility Description |
The Brown County Water Improvement District #1 Water Treatment Plant provides wholesale treated water to the City of Brownwood, the City of Banks, and Brooksmith SUD. Raw water is processed and disinfected with ammonia and chlorine in the treatment process. The Plant maintains a maximum inventory of 24,000 pounds of chlorine in one-ton containers and a maximum inventory of 9,100 pounds of anhydrous ammonia in a bulk storage vessel. Chlorine is stored at levels above the threshold quantity and is therefore subject to the requirements of the Risk Management Program. While anhydrous ammonia is stored below the threshold quantity, the District has also developed a Risk Management Program for ammonia in the interest of continuously improving safe operations at the Plant.
The Water Treatment Plant has been in service since the 1930's. Chlorine, a chemical required by regulation to be used in the disinfection process, has been in use at the Plant since operation beg
an. Anhydrous ammonia was added to the disinfection process system in the 1980's. No accidental releases of chlorine or ammonia meeting the requirements of the five year accident history have occurred at the Plant.
Offsite Consequence Analysis
The off-site consequences of a potential accidental release of both chlorine and anhydrous ammonia at the Water Treatment Plant were assessed, in accordance with requirements established in 40 Code of Federal Regulations, Part 68. SLAB Atmospheric Dispersion Model, an EPA-recognized computer modeling program, was used for each release scenario.
The worst case scenario is a model of a release under specific conditions established by EPA, including release volume, duration, and weather conditions. Active safety systems in place at the Plant that are designed to minimize the effects of a chlorine release cannot be considered in the worst case scenario.
The worst case release scenario is required to assume the release in a ten minute peri
od of the entire contents of the largest vessel of the regulated chemical onsite, which for the Plant is a one-ton chlorine container. Meteorological conditions required by EPA rules are assumed for the release. The toxic endpoint for the worst case release scenario is estimated to reach a point beyond the facility boundary. Public receptors are located within the release area. No sensitive environmental receptors designated by EPA are affected by this release scenario.
The alternative release scenarios represent the results more likely to occur in the event of a chlorine or anhydrous ammonia release at the Plant. Active safety systems at the Plant are considered for each alternative release scenario. Average weather conditions at the facility are utilized for this release scenario, as recommended by EPA regulations.
For the chlorine alternative release scenario, failure of a pipe in the chlorine feed system is assumed. While the toxic endpoint for the chlorine alternative
release scenario is estimated to reach a point offsite of the facility, no people reside within the release area. One public receptor and no environmental receptors are affected by this release scenario.
For the anhydrous ammonia alternative release scenario, failure of a pipe in the ammonia feed system is assumed. Average weather conditions at the facility are used for this release scenario, as recommended by EPA regulations. The toxic endpoint for the anhydrous ammonia alternative release scenario is estimated to reach a point beyond the facility boundary. No people reside within the release area. One public receptor and no environmental receptors are affected by this release scenario.
The Water Treatment Plant is subject to Prevention Program 2 of the Risk Management Program. In accordance with the requirements of Program 2, the Plant maintains specifications for the equipment associated with the chlorine and anhydrous ammonia feed systems and has documen
ted the codes and standards adhered to in designing, constructing, and operating each system. The safe operating ranges for each system are documented, and each system is operated within these safe ranges.
A hazard review has been conducted for each feed system and identified action items are expected to be completed by December 31, 2002. When a major process change is made to either system, there are procedures to conduct a hazard review. Written procedures for the operation and maintenance of both the chlorine and ammonia systems are also in place at the Plant. Procedures are reviewed and updated on a regular basis by facility personnel.
Plant operators receive training in the operation of each chemical system through classes and on-the-job instruction. Competency is determined through supervisor observation, operator demonstration of activities written exams, and oral tests. Operators receive update training on a regular basis or whenever a procedure has been modified. Only
qualified operators operate the chlorine and anhydrous ammonia systems.
A team of facility personnel conducts a prevention program compliance audit once every three years and whenever a major process modification is made. A compliance audit checklist has been developed based on American Water Works Association recommendations. A system to correct any deficiency discovered during the compliance audit is in place.
In the event of an accidental release, or a situation that could lead to an accidental release, the Plant has procedures to investigate such incidents, develop findings and recommendations for corrective action, and implement the recommendations.
Facility personnel are trained and equipped to perform necessary emergency response activities in the event of a significant chlorine or ammonia leak at the Plant. In the unlikely event a chlorine or ammonia release requiring the assistance of emergency response personnel occurs, plant personnel are responsible for responding t
o the accident, coordinating the emergency response effort, and notifying potentially affected areas in the surrounding community.