Calhoun Wastewater Treatment Plant - Executive Summary
The purpose of this document is to develop a Risk Management Program (RMP) for the City of Calhoun wastewater treatment plant that complies with the requirements of Clean Air Act risk management regulations contained in 40 CFR Part 68. The program includes a hazard assessment that evaluates both a worst-case scenario and an alternative scenario, a prevention program, and an emergency response program. This document serves a vital community right to know function by informing the public of potential risks associated with the releases of chlorine and sulfur dioxide and describes the Citys efforts to minimize such risks.
Section 112(r) of the 1990 amendments to the Clean Air Act required certain facilities to take steps to prevent accidental releases of hazardous substances and to reduce their potential impact on the public and the environment. The U. S. Environmental Protection Agency (EPA) issued "Chemical Accident Prevention Provision," rules
(contained in 40 CFR Part 68) to implement the 112(r) requirements. Under this rule, all covered facilities must implement a risk management program and file a risk management plan with the EPA by June 21, 1999. A covered facility would be one that uses, stores, manufactures, handles, or moves any of the 140 chemicals listed in 40 CFR Part 68 at quantities exceeding the threshold levels as provided in the regulations.
The City of Calhoun wastewater treatment plant (WWTP) is a covered facility because of the usage and storage of chlorine and sulfur dioxide. Chlorine and sulfur dioxide are both regulated substances, and the respective threshold quantities are 2,500 pounds and 5,000 pounds under the regulations. The chlorination facilities at the Calhoun WWTP consist of eight 1-ton cylinders of chlorine (potential for a total of 16,000 pounds of chlorine) and four 1-ton cylinders of sulfur dioxide (potential for a total of 8,000 pounds of sulfur dioxide). Sin
ce the storage quantities of chlorine and sulfur dioxide both the exceed threshold, Calhoun WWTP is a covered facility under the Risk Management Plan rules.
The City of Calhoun owns and operates a 16 million gallon per day (MGD) WWTP in Calhoun, Georgia. The WWTP provides sewage treatment to the local residential population and the numerous industries that are located in the city. The WWTP is a biological activated sludge treatment system with carousel aeration basins. Sludge stabilization is provided by aerobic digesters, and the City disposes of the sludge by contract land application. Effluent disposal is into the Oostanaula River. Prior to discharge, the treated effluent is disinfected using chlorine and dechlorinated using sulfur dioxide to prevent the formation of chlorinated byproducts. The RMP focuses on the chlorination and dechlorination facilities at Calhoun WWTP.
Based on the quantities of chlorine stored at the Line Creek WWTP, it is very likely that
there will be off-site consequences for public receptors in the event of a worst-case release, and therefore Line Creek WWTP will not qualify as a Program 1 facility. Since Georgia is a federal OSHA state (i.e., Georgia has not been delegated OSHA responsibilities), state and local governments within Georgia are not subject to OSHA PSM standards, and therefore Line Creek WWTP will not be a Program 3 facility. Thus, Line Creek WWTP will be classified as a Program 2 facility.
OFF-SITE CONSEQUENCE ANALYSIS
The off-site consequence analysis consists of two components: a worst-case release scenario and an alternative release scenario.
Worst-Case Release Scenario
Worst-case scenario has been defined as the release of the largest quantity of a regulated substance from a single vessel or process line failure that results in the greatest distance to an end point (DTE). The DTE is the distance a toxic vapor cloud will travel before dissipating to the point that serious injuries from
short-term exposures will no longer occur. In the case of Line Creek WWTP, the worst-case scenario would involve the sudden release of the contents of a 1-ton cylinder of chlorine.
RMP Program Guidance for Wastewater Treatment Plants (RMP guidance) was used to estimate the DTE associated with a worst-case release. The calculations did not consider any passive mitigation systems. The guidance assumes that the contents of a 1-ton cylinder (2,000 pounds) are completely released over a 10-minute period with a corresponding release rate of 200 lb/min. The model assumes a wind speed of 1.5 meters/second and an atmospheric stability class F.
Using this approach, it is predicted that a worst-case release of chlorine will result in a DTE of 3.0 miles, in a rural setting such as Line Creek WWTP, with an end point concentration of 0.0087 mg/L. The worst-case release DTE is estimated to impact 24,767 persons.
Alternative Release Scenario
The alternative release scenario for a covered pr
ocess is one that is more likely to occur than a worst-case scenario. The RMP guidance suggests that the alternative release scenario should reach an endpoint off site, unless no such scenario exists. Based on an evaluation of the processes and procedures at the Line Creek WWTP, it appears that a vapor release scenario is most likely.
RMP guidance was used to estimate the DTE for a vapor release from a hole of = inch in diameter. Calculations in the guidance assume a wind speed of 3.0 meters/sec and an atmospheric stability class D. No active or passive mitigation systems were considered.
For a vapor release hole diameter of = inch, the release rate of chlorine is estimated to be 37 lbs/min with a DTE of 0.3 miles. The alternative-case release DTE is estimated to impact 266 persons.
Off-site Public Receptors
Public receptors include off-site residences; institutions (e.g., schools and hospitals); industrial, commercial, and office buildings; and parks or recreational areas
inhabited or occupied by the public at any time without restriction by the stationary source where members of the public could be exposed to toxic concentrations as a result of an accidental release. A worst case release of chlorine will impact roughly the lower half of Peachtree City and a nothern third portion of City of Senoia. An alternative release of chlorine at Line Creek WWTP will not impact any public receptors.
Off-site Environmental Receptors
Environmental receptors include national or state parks, forests, or monuments; officially designated wildlife sanctuaries, preserves, refuges, or areas; and federal wilderness areas, as identified on USGS maps. Environmental receptors are not impacted as a result of either a worst case release or an alternative release.
Leak Detection Procedure
Chlorine leak detectors are provided in the chlorine cylinder storage area. These detectors have been set to detect leaks at a level of 5 ppm. Chlorine leaks can also be readily detected
by smell even at low concentrations.
Chlorine gas connections under pressure should be periodically inspected for the following:
Discoloration of Joint: If a leak is in progress, cadmium plating provided over bronze and brass fittings will disappear and the base metal will take on a reddish color. Green copper chloride may also form around the leak area.
Moisture Formation: Small droplets of water may appear on the underside of a leaking chlorine joint. It is recommended that chlorine lines be painted in bright yellow so that brown rust holes will be readily visible.
Ammonia can be used to detect chlorine leaks. If ammonia vapor is directed at a leak, a white cloud will form indicating the source of the leak. A plastic squeeze bottle containing liquid commercial ammonia should be kept on site. Leaks may also be detected by applying soap solution to suspected joints and observing for bubbles of escaping gas. A trade product called "Leak-Tec" is also available for the det
ection of chlorine leaks and is preferred by some operations personnel.
Emergency Response Program
The Authority has developed an emergency response program for the purpose of protecting public health and the environment.
The emergency response plan will be coordinated annually with the Peachtree City and Fayette County police and fire departments and the Fayette County Civil Defense the Local Emergency Planning Committee (LEPC). Annual coordination should include facility tours, chlorine safety training, and chlorine response drills. The local coordinating agencies have been provided with a copy of the report, and agreements have been reached with local emergency response agencies.
Response procedures are dictated by the magnitude of the release. For planning purposes three magnitudes of release are considered:
Small leak such as from a rust hole, faulty valve, leaking gasket, packing nut leak, etc
Leak containable within the building area.
Facility-wide evacuation not needed.
Leak can be controlled and managed by plant personnel without outside help.
A medium leak such as from a broken valve housing or blown pressure gauge, etc.
Leak containable within facility boundaries.
Requires evacuation of entire facility.
Leak controllable by plant personnel, but may require outside assistance, traffic control, and limited evacuation.
A large leak such as from a ruptured cylinder.
Release extends beyond facility boundaries.
Requires facility and community evacuation and in-place sheltering.
Will require the assistance of fire, police, ambulance, hospital, and other local emergency services.
Response Actions for Small Release Scenario
As soon as a chlorine gas leak is detected, the employee who notices the leak must notify the plant operator and emergency coordinator of the leak. If the employee is trained in controlling chlorine or sulfur dioxide le
aks, and the leak is minor and appears controllable, he or she should act immediately to rectify the situation. In no event must the employee act in a manner that will endanger his or her safety. If the leak appears serious enough that one person cannot control the situation, the employee must not act alone. The employee must summon help and in the meantime gather the tools/equipment needed to control the leak. After the plant operator or emergency coordinator arrives on the scene, the employees must jointly attempt to control the leak. Control of leak is the first priority for the employees. Regulatory agencies may have to be notified later.
Response Actions for Medium Release Scenario
A determination that a release is medium rather than small is a judgment call made by the employee detecting the leak based on a visual evaluation of the situation. The employee who noticed the leak should immediately notify the plant operator and emergency coordinator of the leak and alert th
em that the release appears to be medium. If the employee is trained in the control of gas leaks he or she must wear a SCBA and wait upwind of the source for the plant operator and emergency coordinator to arrive at the scene. The plant operator must evacuate the facility of all employees except those who will participate in leak control efforts. The plant operator must also immediately alert the local emergency response agencies that their assistance may be needed in the areas of community evacuation and medical help, if the leak gets worse. After arriving at the scene, the plant operator and the emergency coordinator must wear SCBA units and begin leak control efforts. Control of the leak should be the first priority for the employees. Authorities at PCWASA including the General Manager will be notified of the release. Regulatory agencies will be notified following discussion with the Authority personnel.
Response Actions for Large Release Scenario
Response actions for a larg
e release are similar to a medium-scale release. However, in this scenario, the accident is so major (such as a ruptured cylinder) that the bulk of the response efforts are tailored toward post-release mitigation, community evacuation and medical assistance. Community evacuation if required should be conducted with the assistance of the local police and fire departments. Any residents living in the zone of influence should be temporarily evacuated to an area of safety until such a time that the release gets controlled and the leaking gases are dispersed. Traffic control on roads downwind of the release will be necessary to prevent persons from entering the gas release zone.
Immediate medical assistance should be provided to facility employees and community members requiring assistance. Providing medical assistance will require the support of ambulance service, paramedics, doctors, and local hospitals.
Release notification is of two types: verbal and written. When making a ver
bal notification immediately after the release incident, the following information should be provided to the EPCRA hotline at 1-800-535-0202:
Name of caller
Name of facility
Chemical released (Chlorine)
Date, time and duration of release
Release quantity estimate
Remedial measures undertaken
The verbal notification must be followed by a written notice within 24 hours after the emergency situation is controlled. A release notification form prepared for Authoritys facilities is presented in the Appendix. The release notification form provides the following information pertaining to the release:
Estimate and quantity of release
Date, time and duration of release
Media into which the release occurred
Medical information regarding chlorine
Communication with the Public
Internal and external communications are critical during an emergency. In order for the plant operator and emergency coordinator to be in
constant touch with the repair crew, management, employees, the public, and the media, communication devices such as siren systems, megaphones, hand-held two way radios, cellular phones, and pagers will be provided to the response personnel.
Communication with the general public will generally occur through the media (television, radio and print). To prevent dissemination of misinformation, WWTP personnel should convey accurate and timely information to the media. It is essential that the facility maintain open lines of communication with the public and media, otherwise second-hand information will be presented that can be erroneous or exaggerated and thereby potentially damaging to the facilitys reputation.
The following are standard procedures for interfacing with the media and the public:
Develop model press release statements.
Prepare background information on chlorine and sulfur dioxide for presentation to media.
Provide facts on cause, response actions undertaken, quantity
released, injuries, and community impact.
Train a senior level person such as the General Manager to answer questions.
Be prepared to handle requests for photographs.
Provide opportunity for follow-up visits including a contact telephone number.