Stillwater Wastewater Treatment Plant - Executive Summary
The City of Redding has instituted a Risk Management Program for their wastewater treatment facility, Stillwater 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 re |
quired by ARP regulations in order to report 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 Redding operates two wastewater treatment plants. Its Stillwater Wastewater Treatment Plant serves that portion of the City of Redding located east of the Sacramento River. It is located at 6475 Airport Road, Anderson, CA in Shasta County, and uses chlorine and sulfur dioxide for disinfection and dechlorination in quantities greater than the Federal threshold quantity for these RS's. The facility is located on the west bank of the Sacramento River just north of the City of Anderson. There are 6 full-time employees at this site. Chlorine and sulfur dioxide are received in ton containers by truck, handled with an electric hoist, and stored on ton container scales and storage trunnions inside the building. The chlorine is used for
odor control of the influent wastewater, to disinfect the wastewater effluent, and for other process uses. The sulfur dioxide is used to dechlorinate the disinfected effluent for aquatic toxicity control. Pressurized gas within a ton container is withdrawn under pressure and piped to a vacuum regulator valve located in the storage room where the gas pressure is reduced to vacuum. From there, the gas under vacuum is metered through rate valves and rotameters in chlorinators and sulfonators located in a separate room, 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 Redding that the receipt, storage and handling of chlorine at its facility be done in a manner which meets regulatory requirements and minimizes the probability and severity of accidental releases of chlorine or sulfur dioxide 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 Redding has gathered safety information on chlorine and sulfur dioxide and on the process, equipment and procedures involving chlorine and sulfur dioxide; performed a structured assessment of hazards of the process and external events which might affect the processes; performed an offsite consequences analysis of 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 c
ontainer 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 2,000 lb. This release scenario is not physically possible, due to the characteristics of chlorine.
ALTERNATIVE CASE RELEASE SCENARIO
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 cases" considered for this facility are the release of liquid chlorine or sulfur dioxide from a pinhole in one of the fusible plugs on a received ton container, due to a supplier erro
r or damage in transit, with the release secured by application of a Type "B" Ton Container Repair Kit fixture after 60 minutes.
Administrative controls in effect at the City of Redding which were considered to mitigate the severity of the Worst Case and Alternative Case release scenarios include the City of Redding's written policies and procedures for training of operators and maintenance personnel, written procedures for control of the inventory of chlorine and sulfur dioxide at the facility, and policies regarding quality level of replacement materials and components for the chlorine and sulfur dioxide systems.
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 personne
l following established emergency response procedures.
GENERAL ACCIDENTAL RELEASE PREVENTION PROGRAMS
General accidental release prevention programs instituted by the City of Redding are categorized as administrative (management) programs; procedures, training, and engineering controls; and emergency response programs.
The City of Redding has instituted a Process Safety Management (PSM) Program meeting OSHA requirements at 29 CFR 1910.119 covering its disinfection and dechlorination process. This constitutes the general accidental release prevention program for City of Redding's operations. 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 and sulfur dioxide have been identified and implemented. These include, among other things, creation of facility-specific operation procedures for chemical deli
very with check boxes for completion of critical steps.
FIVE YEAR ACCIDENT HISTORY
There have been no accidents involving chlorine or sulfur dioxide at this facility within the past five years resulting in injuries or offsite consequences.
EMERGENCY RESPONSE PROGRAM
The City of Redding's Emergency Response Program applicable to chlorine has been coordinated with Redding Fire Department, the local agency responsible for hazardous materials release response coordination. The City of Redding maintains First Responder capability with respect to chlorine and sulfur dioxide releases at its facilities.
PLANNED CHANGES TO IMPROVE SAFETY
All of the improvements and mitigation measures identified in the process hazard analysis which the City of Redding committed to accomplish have been completed or are in progress. It is planned to eliminate the chlorine and sulfur dioxide pressure piping and mount vacuum regulators directly on the ton container gas valves. All of the other measures ide
ntified by employees during workplace hazard surveys, or as a result of audit activities, will be thoroughly reviewed and considered for implementation.