Cholla Water Treatment Plant - Executive Summary
Executive Summary |
In June 1996, the U.S. Environmental Protection Agency (EPA) issued Risk Management (RM) program regulations (40 CFR, Part 68). Regulated under the Clean Air Act Amendments (CAAA), Section 112(r), the RM program requires facilities that store large amounts of listed hazardous chemical substances to prepare and implement risk management plans to reduce the probability of accidental releases and minimize the health risks to the public and the environment.
The RM program regulates 77 listed toxic substances and 63 listed flammable substances. Of the 140 toxic and flammable chemicals regulated by the RM program, the Cholla Water Treatment Plant (CWTP) has only one such listed chemical (anhydrous chlorine) that is used to disinfect drinking water provided to the residents of Glendale. The terms anhydrous chlorine and chlorine are used interchangeably and specifically refer to a chemical listed in the RM program regulations. When used as a disinfectant, chlor
ine prevents the spread of waterborne diseases and has been used for years in the water treatment industry. When properly used, chlorine has proven to be both safe and effective.
In addition to the CWTP, the RM program regulations apply to an estimated 7,200 public and private drinking water and wastewater treatment facilities nationwide where chlorine and/or ammonia are used as disinfectants. As with other facilities across the U.S., the City of Glendale views the RM program as a vehicle to communicate emergency response procedures to the public and emergency planning agencies.
The major driving force in the development of the RM program regulations is reducing the risk to public health by minimizing the potential of a chemical release. At CWTP, there is a multi-layer system in place to meet this goal. As part of the RM program, operators are trained in dealing with the day-to-day handling of chlorine. Chlorine detectors are located in areas where chlori
ne is stored and/or used and provide a warning in the event of a release. Trained personnel respond to chlorine alarms to assess whether a chlorine release poses an imminent danger to employees or the public. While safety features such as a low pressure chlorine delivery system make a significant release unlikely, in the event that a release does occur, response plans have been developed. The emergency response plans include assistance from outside agencies, as well as operators trained to take appropriate action such as contacting the Glendale Fire Department (GFD). The GFD's emergency response time is 5 minutes or less.
Within the management and administrative roles of the CWTP, responsibility has been defined to coordinate and implement the RM program. Overall development and management of the RM program is the responsibility of the RM Program Manager. The RM Program Coordinator reports to the RM Program Manager and is responsible for coordinating the impl
ementation of the RM program. The CWTP Safety Administrator is responsible for the overall record keeping of the RM program and reports to the RM Program Coordinator. The Senior Operator is responsible for the day-to-day implementation of the RM program and reports to the RM Program Coordinator. Additional program oversight is provided by the City of Glendale's Environmental Resources Administrator and Employee Safety Manager who act as external auditors of the program's implementation and overall quality.
For the CWTP, the following personnel have been assigned to coordinate and implement the RM program:
* The Superintendent of Plant Operations is the designated RM Program Manager
* The Plant Operations Supervisor is the designated RM Program Coordinator
The Plant Operations Supervisor is also the delegated coordinator for the Occupational Safety and Health Administration (OSHA) Process Safety Management (PSM) program in place at CWTP. The requirements of the PSM progr
am largely parallel RM program requirements. Because of the similarities in the two programs, the RM Program Coordinator will be referred to as the RM/PSM Program Coordinator throughout this document.
Worst Case and Alternate Case Release Scenarios
CWTP modeled three potential release events for chlorine and followed EPA guidance to identify a worst case release scenario (WCS) and alternate case release scenarios (ACS) as defined by the EPA regulations. Toxic endpoints were identified using EPA-approved methods.
A "worst case scenario" is defined by the EPA as the result of a release from the largest container and/or pipe over a span of 10 minutes. The distance to a toxic endpoint is defined by emergency response planning guidelines level 2 (ERPG-2) as a concentration a person can be exposed to for up to 1 hour without experiencing serious health effects. The distance to a toxic endpoint is used to determine the affected geographical area and population for emergency plan
ning purposes. The ERPG-2 value for chlorine is 3 parts per million by volume (ppmv).
EPA states that a WCS is useful for encouraging "community dialogue". However, because the WCS does not necessarily represent events likely to occur, it is more useful for discussion purposes than for emergency planning purposes. An "alternative release scenario" is a release scenario more likely than the WCS and can be used for emergency response planning.
The WCS for the CWTP is a release of 2,000 pounds of chlorine in 10 minutes. The distance to the toxic endpoint for the WCS is 1.33 miles, affecting approximately 5.6 square miles and an estimated population of 33,400.
Two alternate case release scenarios (ACSs) for chlorine were evaluated for emergency response planning purposes. The first ACS is based on the results of CWTP's 5-year accident history. Within the last 5 years a single gas release of approximately 100 pounds from a 1-ton container occurred. This incident was used as
a basis for developing an ACS. This ACS could potentially have resulted in an endpoint distance of 0.49 miles. For planning purposes, the modeled results of the ACS did not consider the atmospheric conditions and mitigation efforts associated with the "real" event. Unlike the "real" event, the modeled scenario affected less than 1 square mile and a population of approximately 7,900. The second ACS is based on an operator opening the chlorine container valve before connecting the flexible piping (pigtail) resulting in a release of gaseous chlorine. This ACS resulted in an endpoint distance of 0.53 miles. A population of approximately 8,000 could potentially be affected if this scenario were to occur.
5-Year Accident History
In the past 5 years, the CWTP experienced a single incident meeting the RM reporting requirements. The incident occurred on January 16, 1996 at 12:40 P.M. and lasted for 1 hour and fifty minutes. There was a leak in the chlorine manifold system supplyin
g the chlorine gas to the water treatment process. The leak was a result of a mechanical failure caused by a poorly positioned heating element on a chlorine gas line. Approximately 100 lbs of chlorine was released into the chlorine storage building. The quick response of CWTP personnel and the Glendale Fire Department prevented any injuries on-site and off-site. There was minimal property damage to the facility. During the emergency response, the Glendale Fire Department acted to protect the local community by issuing shelter in place instructions to a school nearby and by evacuating residences directly adjacent to the facility. Environmental professionals from the Arizona Department of Environmental Quality (ADEQ) measured for the presence of chlorine off-site during the incident and did not detect levels that could potentially be harmful to individuals and/or the environment. As a result of this incident CWTP has installed a low-pressure gas delivery system to prevent this typ
e of incident from occurring in the future.
Chemical Release Prevention Program
The CWTP has a chemical release prevention program in place for the chlorine process. This program is required by both the RM program and OSHA PSM regulations. The prevention program for the chlorine process has been in place since 1995. Key provisions of the CWTP prevention program are as follows:
* Written procedures have been prepared for the covered process, including directions for safe start-up and shutdown, operations and emergency shutdown.
* CWTP employees who operate the chlorine system must receive training initially and periodically on safe start-up/shutdown, operations, and emergency shutdown.
* Incidences, including minor releases are investigated to improve the safety of the process.
* Once completed, incident investigations are shared with employees.
* Employees participate in a process hazard analysis (PHA) which identifies potential hazards and ways to improve t
he safety of the process every five years, or when significant changes are made to the process.
* The CWTP has a management of change (MOC) program in place that mandates changes to the chlorine system are reviewed prior to the change to ensure that the change will not compromise safety.
* An equipment design and maintenance program is in place that assures mechanical integrity. Equipment design and maintenance practices are consistent with guidance provided by the Chlorine Safety Institute.
* A preliminary start-up review is also completed prior to returning the covered equipment to service after a major change or prior to a new covered process coming on-line.
* A hot work permit program is in place.
* Contractors who work on or near the RM program process are advised of the hazards of chlorine, provided evacuation instructions in case an incident occurs, and must certify that they are qualified to work near hazardous materials.
Emergency Response Program
TP has an emergency response program in place for the chlorine process. This program consists of personnel trained to recognize releases, assess the situation, and engage the proper emergency response personnel. When external emergency response is required, plant personnel will notify the GFD then establish an incident command system that is transferred to the GFD upon their arrival. Once GFD establishes command, they are supported by CWTP personnel familiar with the affected process. The GFD has access to additional emergency response resources, including the City of Glendale Police Department, Red Cross, Arizona Department of Environmental Quality, and other agencies, as needed.
The CWTP plans to install emergency air scrubbers adjacent to the chlorine cylinder room to limit the potential risk of a chlorine release to the surrounding environment. Emergency air scrubbers act to contain chlorine release by absorption of the chlorine before it can escape to
the outside environment. CWTP plans to install an emergency scrubber within the next year.