Mt. Shasta Wastewater Treatment Plant - Executive Summary
The City of Mt. Shasta has instituted a Risk Management Program for their Wastewater Treatment Plant, as required by Federal Accidental Release Prevention (ARP) Program regulations at 40 CFR Part 68. The Risk Management Program identifies the equipment, procedures, maintenance, inspection, and training associated with Regulated Substances (RS's) handled at this facility in excess of Federal threshold quantities; describes the structured assessment of hazards which was conducted to assess possible effects on employees and offsite public and environmental receptors; provides the results of an offsite consequences analysis; defines a prevention program, emergency response program, and mitigation measures to reduce the probability and magnitude of accidental releases of RS's; and establishes a schedule and responsibilities for implementation of mitigation measures and auditing of program elements. This Risk Management Plan (RMP) is being filed as required by ARP regulations in order to r |
eport the elements of the current Risk Management Program and to describe further measures planned to mitigate or prevent accidental releases of RS's.
STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED
The City of Mt. Shasta operates and maintains a wastewater treatment plant, located above the east bank of the Sacramento River in the City of Mt. Shasta, CA in Siskiyou County, and uses chlorine, an RS, for disinfection in quantities greater than the Federal threshold quantity for this RS. There is one full-time employee and a half time employee at this site. The plant is normally manned on the day shift Monday through Friday, and a telephone dialer system alerts operators to alarm conditions when the plant is not manned.
Chlorine is received in ton containers by truck, handled with an electric hoist, and stored on trunnions inside the building. The chlorine is used for disinfection of wastewater effluent prior to discharge. Pressurized chlorine gas within a ton container is r
educed to vacuum by tank-mounted vacuum regulator valves, metered through rotameters and rate valves automatically in proportion to flow and setpoint chlorine residual, and drawn into water solution by the passage of pressurized water through an injector.
ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES
It is the policy of the City of Mt. Shasta that the receipt, storage and handling of chlorine at its facilities be done in a manner which meets regulatory requirements and minimizes the probability and severity of accidental releases of chlorine to the atmosphere, in order to protect the health and safety of its workers, the public, and the environment. In order to accomplish this goal, the City of Mt. Shasta has gathered safety information on chlorine and on the process, equipment and procedures involving chlorine; performed a structured assessment of hazards of the process and external events which might affect the process; performed an offsite consequences analysis o
f defined release scenarios; established a written program for prevention and mitigation of accidental releases; and established a written emergency response program coordinated with emergency response agencies.
WORST CASE RELEASE SCENARIO
A single "worst case" release scenario is required to be considered for each stationary source, resulting in the maximum distance to an endpoint for all toxic RS's contained on site above the threshold quantity.
The worst case release scenario for toxic chemicals is defined in the ARP regulations as the release of the contents of the largest single container of RS (in this case chlorine) over a period of 10 minutes. The scenario considered the release of the contents of the largest container of chlorine on site, in this case 2000 lb. This release scenario is not physically possible, due to the characteristics of chlorine. The air dispersion modeling resulted in a toxic endpoint located beyond the plant's property line.
ALTERNATIVE CASE RELEASE S
An "alternative case" release scenario is required to be considered for each toxic RS handled in quantities greater than the threshold quantity at the site.
The "alternative case" scenario is described in the ARP regulations as a likely release resulting in offsite effects, considering administrative controls and mitigation measures in place, and is to be determined by the facility operators as part of the Process Hazard Analysis required to be performed during RMP development. The "alternative case" considered for this facility is the release of chlorine from the gas valve of a ton container due to an operator error during hookup, with the release secured by emergency responders by closing the gas valve after 10 minutes. The air dispersion modeling resulted in a toxic endpoint located beyond the plant's property line.
Administrative controls in effect at the City of Mt. Shasta which were considered to mitigate the severity of the Worst Case and Al
ternative Case release scenarios include the City's written policies and procedures for training of operators and maintenance personnel, written procedures for control of the inventory of chlorine at the facility, and policies regarding quality level of replacement materials and components for the chlorine system.
No mitigation measures were considered to limit the severity of the Worst Case scenario. No passive mitigation measures were considered to limit the severity of the Alternative Case scenario. Active mitigation was considered for the Alternative Case, in the form of the timely response of properly trained and equipped personnel following established emergency response procedures.
GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAMS
General accidental release prevention programs instituted by the City of Mt. Shasta are categorized as administrative (management) programs; procedures, training, and engineering controls; and emergency response programs.
ty of Mt. Shasta has instituted a Process Safety Management (PSM) Program meeting OSHA requirements at 29 CFR 1910.119 covering the disinfection process at the Wastewater Treatment Plant. This constitutes the general accidental release prevention program for the City's operations at this facility. The program and document management procedures included in the PSM Program will be used as the management system for the Risk Management Program.
CHEMICAL-SPECIFIC RELEASE PREVENTION STEPS
Release prevention steps specific to chlorine have been identified and implemented. These include improvements in operating procedures and training, and installation of a vacuum gauge on the gas header piping.
FIVE YEAR ACCIDENT HISTORY
There have been no accidents involving chlorine at this facility within the past five years resulting in injuries or offsite consequences.
EMERGENCY RESPONSE PROGRAM
The City of Mt. Shasta's Emergency Response Program applicable to chlorine has been coordinated with
Siskiyou County Public Health Department, the agency responsible for hazardous materials inventory reporting and release response coordination. The City of Mt. Shasta maintains First Responder capability with respect to chlorine releases at its Wastewater Treatment Plant. The emergency response program is being coordinated with the seven-county Shasta-Cascade HazMat Response Team (SCHMRT) now being organized.
PLANNED CHANGES TO IMPROVE SAFETY
All of the improvements and mitigation measures identified in the process hazard analysis which the City of Mt. Shasta committed to accomplish have been completed or are in progress. Any other measures identified by employees during workplace hazard surveys, or as a result of audit activities, will be thoroughly reviewed and considered for implementation. It is planned to seal off the doorway connecting the chlorine storage room and the rest of the Operations Building, and improve access around the chlorine ton containers. All ton containe
rs owned by the City are being sold to a chlorine supplier.