Main Street Water Reclamation Facility - Executive Summary
EXECUTIVE SUMMARY |
Gainesville Regional Utilities (GRU) owns and operates the Main Street Water Reclamation Facility (WRF), located at 200 Southeast 16th Avenue in Gainesville, Florida.
The Main Street WRF has served the citizens of Gainesville since 1930. The process began as a simple Imhoff treatment process, and continued to improve and expand to meet Gainesville's growing population. Today, the plant serves residents in the southeast and southwest areas of the City. Pumping upgrades in 1992 allows wastewater to transfer between the Main Street and Kanapaha WRFs. These upgrades have increased Main Street's plant removal capabilities to above 99 percent.
Like the majority of municipal wastewater treatment plants in the United States, gaseous chlorine is used at the Main Street plant as a disinfectant to destroy pathogenic organisms in the treated wastewater prior to discharge or reuse. The popularity of chlorine as a wastewater disinfectant is due to its effectiveness and re
latively low cost compared to other disinfection technologies. Sulfur dioxide is used to dechlorinate the treated effluent after disinfection has occurred and prior to its discharge to surface water.
The same properties that make chlorine and sulfur dioxide valuable as treatment chemicals also make it necessary to observe certain safety precautions as safeguards to our workers, our community, and the environment. Chlorine and sulfur dioxide are both notably irritating to the eyes, nose, throat and lungs. More serious human health effects could result from much higher chemical exposure, such as intense coughing, chest pains, and in extreme cases, death.
GRU's commitment at the Main Street plant is to store, handle and use these chemicals in a manner that achieves the needed benefits of their use while minimizing both onsite and offsite risks. This is accomplished by designing a safe process, maintaining the process in optimum working condition, operating safely through documented
procedures and extensive training, and providing an emergency response capability to minimize the consequences of a gaseous chemical release, should a process accident ever occur. Our commitment to employee and community protection is demonstrated in the fact that over Main Street's 69-year history, there have been no chlorine or sulfur dioxide accidents that resulted in death, serious employee injury or offsite consequences.
Accidental Release Prevention and Emergency Response Policies
It is GRU's policy to adhere to all applicable Federal, State of Florida and local rules and regulations. This specifically includes compliance with the Occupational Safety and Health Administration (OSHA) and Environmental Protection Agency (EPA) rules for chlorine and sulfur dioxide accidental release prevention and emergency response.
The primary measures for accidental chlorine and sulfur dioxide release prevention are contained in the document Process Safety Management/Risk Management Program
for Main Street Water Reclamation Facility. This process safety management (PSM) document was prepared in conformance with the OSHA and EPA risk management rules, as well as industry-specific guidelines and best management practices relevant to release prevention. Main Street's Plant Manager has the responsibility for ensuring that this program is implemented in the workplace as written.
GRU's emergency response program is based upon the Chlorine Institute's Pamphlet 64, Emergency Response Plans for Chlorine Facilities. The Main Street emergency response plan relies on a team of onsite trained personnel and, as necessary, offsite mutual-aid groups such as fire and rescue services. The emergency response plans at Main Street are based on the Incident Command system, where onsite responders work in coordination with local hazardous materials response teams to implement the Main Street and regional response plans. Main street's personnel receive annual emergency response training,
which includes the donning of protective equipment and hands-on application of the gaseous cylinder repair kits kept at the plant.
Stationary Source and Regulated Substances Handled
Chlorine and sulfur dioxide are both received by the facility by truck and are stored in one-ton chlorine cylinders fabricated to Department of Transportation (DOT) specifications. Upon arrival at the site, all cylinders are thoroughly inspected and if there is any doubt about the integrity of the cylinder, it is promptly refused. Once accepted, the cylinders are stored inside an enclosed building equipped with chlorine and sulfur dioxide gas detectors that immediately notifies the operators of a release should a leak occur. Four cylinders are connected to the chlorine process: two are in-use, and two are as standby. The standby cylinders will automatically switchover when the in-use cylinders become empty, ensuring continuous disinfection. This same arrangement also applies to sulfur dioxide, with
two cylinders on-line and two on standby. The maximum intended chlorine inventory at Main Street is 10 cylinders, or 20,000 pounds of chlorine, and the maximum intended inventory for sulfur dioxide is 9 cylinders, or 18,000 pounds.
The Worst-Case and Alternative Chemical Release Scenarios
As part of Main Street's emergency prevention and response efforts, a hazard assessment was conducted in compliance with EPA requirements contained in 40 CFR 68, Subpart B. The hazard assessment included the development of worst-case and alternative release scenarios.
EPA defines a worst-case release as a scenario involving the greatest amount held in a single vessel or pipe. In Main Street's case, this involves the release of the entire contents of a one-ton chlorine cylinder or sulfur dioxide cylinder. The release is assumed to occur over a 10-minute period. Applying the worst-case parameters to the Main Street situation results in a distance to chlorine endpoint (defined as 0.0087 milligr
ams per liter) of 1.3 mile, and a distance to sulfur dioxide endpoint (0.0078 milligrams per liter) of 1.3 mile. In other words, any human or environmental receptors within 1.3 mile of the chemical storage building are within the worst-case distance.
EPA defines an alternative release as a scenario more likely than the worst-case, but that nevertheless results in an impact offsite (unless no such release is possible). Passive and active mitigation measures (gas release detection, operator response, etc.) are considered in this scenario. Without an accident history on which to base a more likely scenario, a scenario was selected based on information provided in the Chlorine Institute Pamphlet 74, Estimating the Area Affected by a Chlorine Release. In both the chlorine and sulfur dioxide cases, the scenario involved the release of gas through a faulty fuse plug on the gas cylinder. Response time is conservatively assumed to occur in 30 minutes. This scenario results in a distance
to endpoint of less than 0.1 mile. There are no public or environmental receptors affected by this release.
The distance to endpoint calculations were performed using EPA's RMP*Comp model. The RMP*Comp model was developed specifically for compliance with the accidental release prevention requirement for predicting the travel distance of an accidental release.
General Accidental Release Prevention Program and Specific Prevention Steps
GRU's PSM document contains 13 essential release prevention elements. Some of the key accidental release prevention elements of the PSM program are as follows:
* Process hazard analysis: This analysis was performed for each step in the chemical processes to identify potential process failure scenarios and the appropriate prevention or response measures. The process hazard analysis will be updated every 5 years.
* Operating procedures review: The review was conducted to ensure that operators are given clear, written instructions for safel
y operating the chemical processes.
* Training programs: Training is given to each employee assigned to the process with continuing operator training thereafter, with an emphasis on safe chemical handling and emergency response. GRU has been on the forefront among utilities in chlorine safety training. GRU's Utility Training Officer, for example, helped in the preparation of the training manual entitled Chlorine Handling, Containment and Emergency Response.
* Contractors: GRU ensures through its contract provisions that contractors supplying or working with chlorine and sulfur dioxide are held to a standard of safety performance that complies with GRU's safety goals and objectives, and also meets relevant agency requirements. For example, GRU personnel make unannounced visits to the supplier's site to ensure that rules and guidelines concerning chlorine and sulfur dioxide cylinder integrity are being followed.
* Mechanical integrity: The integrity and reliability of the process
is maintained by implementing preventive maintenance and routine inspection and testing procedures.
* Management of Change: The management of change procedures provide a systematic approach to evaluate and control the safety and health aspects of any significant change to the process chemicals, technology, equipment and operating procedures.
* Incident Investigation: GRU investigates within 48 hours any accidents or "near misses" that could have resulted in a chlorine release, in order to develop measures to prevent a recurrence.
The above elements are only part of GRU's aggressive safety program. In addition to the 13 PSM elements, GRU has established related OSHA safety programs such as hot work and confined space. These OSHA safety programs apply to both GRU and contractor employees.
Five-year Accident History
There have been no accidents involving chlorine at the Main Street plant in the past five years.
Emergency Response Program
Main Street plant operators are provid
ed with annual safety training that includes hands-on practice of assessing and repairing a leaking cylinder using a leak simulator. Plant personnel also review the emergency response flow diagram and emergency plan on an annual basis. The emergency response plan covers all aspects of emergency response including escape procedures and routes, procedures for post-evacuation employee accounting, notification procedures, rescue and medical duties, and response procedures for spills or leaks. If a major chemical leak were to occur, the emergency plan requires immediate notification of the regional hazardous materials response teams for assistance, including orderly evacuation or sheltering-in-place of the surrounding community.
Planned Changes to Improve Safety
GRU is committed to exploring ways to further reduce or eliminate the possibility of a release from its disinfection process. Toward this end, an alternative disinfection study is being conducted to evaluate the effectiveness
and feasibility of using an alternative chemical disinfectant to replace chlorine. Substitution of chlorine using another disinfectant may also eliminate the need for sulfur dioxide. GRU is committed to continuously improving the safety of its operations for the benefit of its personnel, the citizens of Gainesville and the environment.