Lake Wildwood WWTP - Executive Summary |
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Nevada County Dept. of Transportation and Sanitation has instituted a Risk Management Program for their wastewater treatment facility, Lake Wildwood 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 Manage ment Plan (RMP) is being filed as required 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 Nevada County Dept. of Transportation and Sanitation provides wastewater collection and treatment for several unincorporated communities in Nevada County. Its wastewater treatment facility, Lake Wildwood Wastewater Treatment Plant, is located at 12622 Pleasant Valley Road, Penn Valley, CA in Nevada 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 in a semi-rural area near the dam forming Lake Wildwood. There are 4 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 scal es and trunnion sets 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 reduced to vacuum at a vacuum regulator valve mounted directly onto the ton container's gas valve. From there, the gas under vacuum is metered through rate valves and rotameters in chlorinators or 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 Nevada County Dept. of Transportation and Sanitation that the receipt, storage and handling of chlorine and sulfur dioxide at its facility be done in a manner which meets regulatory requirements and minimizes the probability and severity of accidental releases of chlorine o r 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, Nevada County Dept. of Transportation and Sanitation 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 process; 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 scena rio 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 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 is the release of chlorine or sulfu r dioxide 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 30 minutes. ADMINISTRATIVE CONTROLS Administrative controls in effect at Nevada County Dept. of Transportation and Sanitation which were considered to mitigate the severity of the Worst Case and Alternative Case release scenarios include Nevada County Dept. of Transportation and Sanitation'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. MITIGATION MEASURES 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 Nevada County Dept. of Transportation and Sanitation are categorized as administrative (management) programs; procedures, training, and engineering controls; and emergency response programs. Nevada County Dept. of Transportation and Sanitation 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 Nevada County Dept. of Transportation and Sanitation's operations. The program and document mangement procedures included in the PSM Program will be used as the management system for the Risk Management Program. CHEMICAL-SPECIFIC RELEASE PREVEN TION STEPS Release prevention steps specific to chlorine and sulfur dioxide have been identified and implemented. These include, among other things, removing unused header support structures to improve access to the ton containers, and creation of numerous facility-specific operation procedures 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 Nevada County Dept. of Transportation and Sanitation's Emergency Response Program applicable to chlorine and sulfur dioxide has been coordinated with Nevada County Department of Environmental Health, the local agency responsible for hazardous materials inventory reporting and release response coordination. It consists of notification of the public agency assigned responsibility for First Response to hazardous materials release emer gencies and evacuation of persons on site to designated areas upwind of the released gas. First Responders have participated with Nevada County Dept. of Transportation and Sanitation personnel in response drills. PLANNED CHANGES TO IMPROVE SAFETY All of the improvements and mitigation measures identified in the process hazard analysis which Nevada County Dept. of Transportation and Sanitation 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. A study will be conducted in the near future to evaluate the desirability of eliminating chlorine as a process chemical at this plant. |