San Angelo Reclaimed Water Chlorination Facility - Executive Summary
Facility Description |
The City of San Angelo Reclaimed Water Chlorination Facility provides disinfection for treated effluent from the City's wastewater treatment plant. Water is treated with chlorine when necessary and then distributed to agricultural users via an irrigation system. The facility is located along the distribution pipeline to the irrigation canal system. The facility maintains a maximum inventory of 12,000 pounds of chlorine in one-ton containers. This quantity is above the threshold quantity established by the Environmental Protection Agency and the facility is therefore subject to the requirements of the Risk Management Program. No accidental releases of chlorine meeting the requirements of the five year accident history defined by the Environmental Protection Agency have occurred at the facility.
Offsite Consequence Analysis
The off-site consequences of a potential accidental release of chlorine at the Plant were assessed in accordance with requirements estab
lished in 40 Code of Federal Regulations, Part 68. The Environmental Protection Agency's Risk Management Program Guidance for Wastewater Treatment Plants, which provides guidance for chlorine systems such as those at the Chlorination Facility, was used to model a worst case release scenario and an alternative release scenario for chlorine.
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 period of the entire contents of the largest vessel of the regulated chemical onsite, which for the facility 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 offsite of the facility. Public receptors are located within the release area, but no sensitive environmental receptors designated by EPA are affected by the release scenario.
The alternative release scenario represents the results more likely to occur in the event of a chlorine release at the facility. Active safety systems at the facility are considered for the alternative release scenario. Average weather conditions at the facility are used 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. The toxic endpoint for the chlorine alternative release scenario is estimated to reach a point offsite of the facility, and one public receptor, Ranchers Lamb of Texas, is located within the release area. No sensitive environmental receptors designated by EPA are affected by the release scenario.
The Plant i
s 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 feed system and has documented the codes and standards adhered to in designing, constructing, and operating the chlorine system. The safe operating ranges for the chlorine system are documented, and the system is operated within these safe ranges.
A hazard review has been conducted for the chlorine feed system and identified action items are expected to be completed by December 31, 2001. When a major process change is made to the system, there are procedures to conduct a hazard review. Otherwise, a hazard review is conducted every five years.
Written procedures for the operation and maintenance of the chlorine system are also in place at the Plant. Procedures are reviewed periodically and updated whenever a major process change occurs.
Operators receive training in the operation of t
he chlorine system through classes and on-the-job instruction. Competency is determined through supervisor observation and operator demonstration of activities. Operators receive update training at least every three years, or more often as necessary. Only qualified operators operate the chlorine system.
A team of facility personnel conducts a compliance audit of the prevention program 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, procedures are in place to investigate such incidents, develop findings and recommendations for corrective action, and implement the recommendations.
Facility personnel are trained to notify emergency personnel in the event of a significant
chlorine leak. In the unlikely event a chlorine release requiring the assistance of offsite emergency response personnel does occur, the City of San Angelo Fire Department is responsible for responding to the accident, coordinating the emergency response effort, and notifying potentially affected areas in the surrounding community. Communication with the San Angelo Fire Department to maintain up-to-date emergency response planning information.