C. T. Perry Water Treatment Plant - Executive Summary
Policy Statement |
It is the policy of the C. T. Perry Water Treatment Plant (WTP) and the Montgomery Water Works and Sanitary Sewer Board (MWWSSB) to operate the WTP safely, reducing to the greatest extent possible any hazards associated with the processes and reducing any subsequent risk to the surrounding community, personnel, and the environment. The policy includes working with the surrounding community and local emergency response agencies to promote a spirit of cooperation and teamwork, and to orchestrate an effective contingency plan in the unlikely event of a process incident occurring at the Perry WTP.
Stationary Sources and Regulated Substance Handled
Primary Activities: Drinking water treatment is the main activity.
Use of Regulated Substances: Chlorine is used primarily as a disinfectant. Other possible uses of chlorine are odor control and iron removal.
Quantities of Chlorine Handled or Stored
Amount Handled: Two 1-ton containers, equivalent to 4,600 pounds;
tored: Twelve 1-ton containers, equivalent to 27,600 pounds
Chlorine Worst-case Release Scenarios
Failure of two liquid chlorine cylinders resulting in a release of 4,600 pounds of chlorine in 10 minutes. There are no administrative controls in place. The 12 containers are stored in an enclosed building that provides passive mitigation. The release rate is 1.91 kg/s, which is modeled using DEGADIS 2.1.
Distance to Endpoint: Under the worst-case weather conditions prescribed by the RMP rule, the distance to a toxic endpoint of 3 ppm is 2.37 miles, beyond which there will be enough dispersion to no longer pose a hazard to the public.
Chlorine Alternative Release Scenarios
Release of chlorine from a pipe 3/8-inch in diameter connecting the chlorine container to the evaporator. For a release duration of 15 minutes, the release rate is 0.1 kg/s. Chlorine sensors at the Perry WTP detect concentrations of chlorine greater than 5 ppm and activate the chlorine scrubber. The chlorine
scrubber can remove chlorine with an efficiency rate of 99 percent. The release rate from the scrubber of 0.001 kg/s is modeled using DEGADIS 2.1.
Distance to Endpoint: Under realistic weather conditions of 3.0 m/s wind speed and a wind stability class of "D," chlorine could travel 0.07 miles or 0.11 kilometers before dispersing enough to no longer pose a hazard to the public.
Accidental Release Prevention Program and Chemical-specific Prevention Steps
The Perry WTP is in compliance with the RMP Rule, 40 CFR 68. The facility has conducted a comprehensive review of all systems such as administrative, technical, and O&M procedures, in addition to the other required program elements of the RMP rule. A hazard review was conducted at this facility using a checklist extracted from the Guidelines for Hazard Evaluation Procedures.
Five-year Accident History
During the past 5 years, the Perry WTP had one accidental release of chlorine gas. It occurred on November 22, 1994. The release l
asted for 5 to 10 seconds and fewer than 10 pounds of chlorine gas were released. One person onsite was injured, hospitalized for the night, and missed 6 days of work. No one offsite was injured, and no evacuation was necessary.
Emergency Response Program
The MWWSSB has an Emergency Response Program, which applies to the Perry WTP, that coordinates response efforts with the local fire department's HAZMAT team, the police department, and the hospital. Response activities also have been discussed with the Alabama Emergency Management Office Agency.
Planned Changes to Improve Safety
It was observed that the Perry WTP has the necessary equipment and the operating and training procedures required for the safe operation of the chlorination system. The changes to improve process safety identified during the hazard review, and those identified in the report, Vulnerability Analysis of the Water and Wastewater Systems, is provided below:
Upgrade site security by modifying or constructing a
new gate that can be remotely controlled from the control room, along with a security access code entrance.
In response to the recommended improvements to the safety of the process, the following changes have been implemented:
1. Fenced the entire site of Perry WTP.
2. Provided adequate fire extinguishers at appropriate points throughout the facility.