Quarles Water Treatment Plant - Executive Summary
Executive Summary |
Chemicals are widely used in industry, in the home, in the environment. They are transported on roads, water, and railways. We at the Quarles Water Treatment Plant (WTP) use chemicals, too. For example, we use chlorine to disinfect our water to provide safe water discharges to the environment or for landscaping or irrigation uses. Storing large qualities of chlorine can be a hazard. We take our safety obligations in storing and using chlorine as seriously as we do take providing the environment safe disinfected water. The following document describes what could happen if there were to be an accident, the steps we take everyday to ensure a safely operating plant, and what to do in event of an emergency. Please feel free to contact A. Roy Fowler III at 770-426-8788 if you have any questions.
Accidental Release and Emergency Response Policies
It is the policy of CCMWA to operate the Quarles WTP safely, reducing to the greatest exte
nt possible any hazards associated with the chlorine system and reducing any subsequent risk to the surrounding community, personnel, and environment. Safe operation depends upon proper storage of chlorine, proper handling of the chlorination system, and inherent safety features in the design of the chlorination system.
The Quarles WTP accidental release prevention policy involves a unified approach that integrates proven technology, trains staff on operation and maintenance practices, and uses tested management system practices. All applicable procedures of the Risk Management Program Prevention Program are adhered to, including key elements such as training, systems management, and emergency response procedures.
This policy includes working with the surrounding community and local emergency response agencies, to promote a spirit of cooperation and teamwork, to orchestrate an effective contingency plan in the unlikely event of a process incident occurring at the Quarles WTP. The e
mergency response plan includes procedures for notifying the Cobb County Fire and Emergency Services.
This document complies with the U.S. Environmental Protection Agency's (EPA's) Risk Management Program, under Section 112 (r) of the Clean Air Act (CAA) Amendments of 1990, 40 Code of Federal Regulations (CFR) Part 68. The Quarles WTP has a chlorination system that uses chlorine gas fed from liquid chlorine containers. The Quarles WTP facility has prepared a detailed and comprehensive emergency response plan to handle any potential accidental releases that is designed to safeguard both on- and off-site people. To date, we have had an excellent record in preventing accidents from occurring.
General Facility and Regulated Substance Information
The Quarles WTP facility, operating since 1953, is located in Cobb County, Georgia. The primary activity at the Quarles WTP is municipal water treatment, including chlorination of water for taste and odor control. The Quarles WTP has a prese
nt capacity of 64 million gallons per day (MGD). The sludge lime by-product from the facility is applied to farm land.
The facility currently stores chlorine in sixteen one-ton steel storage cylinders. This chlorine storage exceeds the listed threshold quantity in the RMP Rule. Some of the chlorine is used to generate chlorine dioxide, which is used as it is generated, and is not present in the process in amounts greater than the threshold quantity in the RMP Rule.
A chlorine leak detector monitor continuously checks for leaks in the cylinder storage area and in the chlorinator room. The facility also has additional alarms for process control. These alarms are annunciated at the chlorine central control panel at the Quarles WTP.
Both the cylinder storage area and the chlorinator room are enclosed in a building. The building is equipped with a manually operated ventilation system. Emergency showers and eye wash stations are provided at the building along with smoke alarms.
fsite Consequence Analysis Result
The offsite consequence analysis includes consideration of two release scenarios, identified as "worst case" and "alternative" release scenarios. The worst-case scenario requires that that single largest vessel or pipe be evaluated for off-site impacts from chlorine. An alternative release scenario is also required for chlorine.
Worst-Case Release Scenario
Only passive or administrative controls are allowed under the worst-case scenario to reduce off-site impacts. As required by the RMP Rule, the worst-case scenario used for the Quarles WTP is the rupture of one chlorine cylinder with a maximum capacity of 1 ton, resulting in a release of 2,000 pounds of chlorine over a 10-minute duration. The chlorine cylinder storage area is in an enclosed building, which results in a passive mitigation of any chlorine release. The release rate reduction from the enclosed building is approximately 55 percent of the release rate from the cylinder, per guidance f
rom EPA regarding control efficiencies levels for buildings storing chlorine. The release rate will, accordingly, be 0.83 kg/s.
The cylinder rupture resulting in a chlorine release could be caused by catastrophic events, such as an earthquake. The released liquid is assumed to quickly volatilize and to disperse as a vapor cloud. The distance to the toxic endpoint was estimated using the EPA-approved model DEGADIS 2.1. The toxic endpoint was conservatively set by EPA to ensure public notification and that local emergency respond planning takes into account the greatest possible impacted area surrounding the release point. In practice this type of total release of a cylinder would be unlikely and never occur during the lifetime of the plant. The toxic endpoint selected by EPA was 3 ppm. In addition all required EPA-model input parameters were included in completing this activity, including conservative meteorological conditions-Stability F class, wind speed of 1.5 meters per sec
ond, highest daily maximum temperature, and average humidity. The results of the dispersion modeling analysis for this worst case release scenario indicate that this scenario has an offsite impact.
Alternative Release Scenario
The alternative release scenario is more of a possible release scenario that could occur compared to the worst-case release scenario. Based on the process hazard analysis performed for the chlorine system, an alternative release scenario was selected. Unlike the worst case release scenario, active controls can be applied to minimize the leak or impacts. Active controls consist of mechanical, electrical, or human input. The scenario used for chlorine was a leak from a connecting pipe leading from the tank to the feed manifold.
As with the worst-case scenario, the building mitigation was considered. Under this scenario, the amount of chlorine released was calculated to be 0.018 kg/s. The same modeling approach was used as for the worst case release scenario
, except meteorological conditions were adjusted to more common conditions of Stability D Class, wind speed of 3.0 meters per second, average air temperature of 78 degrees F, and average humidity of 50%. The results of the dispersion modeling analysis for the alternative release scenario indicates that this scenario has an offsite impact.
Finally, no chlorine releases that could have cause safety or health hazard (no deaths, injuries, property or environmental damage, evacuations, or sheltering in place) occurred at the Quarles WTP during the last five years. Some minor, incidental releases may have occurred over this period, but they were quickly handled by staff, were neutralized, or posed no safety or health hazards.
Summary of the Accidental Release Prevention Program and Chemical-Specific Prevention Steps
The CCMWA's Quarles WTP is in compliance with the RMP Rule, 40 CFR 68. The facility has conducted a comprehensive review of the chlorine system, as well as of administrative
, technical, operating and maintenance procedures, in addition to the other required program elements of the RMP rule. A hazard review was conducted at this facility using a "What-If" analysis.
Chemical-specific prevention steps include availability of self-contained escape breathing apparatus, awareness of the hazardous and toxic properties of chlorine, and the presence of chlorine detectors and alarms.
The Quarles WTP accidental release prevention program is based on the following key elements:
7 Detailed management system and clear levels of responsibilities and team member roles
7 Comprehensive safety process information that is readily available to staff, emergency responders, and contractors
7 Comprehensive preventive maintenance program
7 Completed a process hazard analysis of equipment and procedures with operation and maintenance staff participation and review
7 Use of process and safety equipment
7 Use of accurate and effective operating procedures, written with operations
and maintenance staff participation
7 High level of training of operators and maintenance staff
7 Implementation of an incident investigation, inspection, and auditing program using qualified staff.
Five-year Accident History
The CCMWA's Quarles WTP has never had a release of chlorine resulting in offsite injury or dispersion, or an onsite injury.
Emergency Response Program
The CCMWA's Quarles WTP has an Emergency Response Program, which coordinates response efforts with the Cobb County Fire and Emergency Services' Hazardous Materials (HAZMAT) team, the police department, and the hospital. Response activities also have been discussed with the Cobb County Resources Council.
Planned Changes to Improve Safety
It was observed during the hazard review that the CCMWA's Quarles WTP has the necessary equipment and the operating and training procedures required for the safe operation of the chlorination system. The following recommendations for improving the safety of the chlorination
process were made:
1. Provide a copy of the updated emergency response procedures for chlorine to the Cobb County Fire and Emergency Services.