Davis Water Pollution Control Plant - Executive Summary |
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The City of Davis has instituted a Risk Management Program for their wastewater treatment facility, Davis Water Pollution Control 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 requir ed 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 Davis's Water Pollution Control Plant is located at 45400 Co. Rd. 28H, Davis, CA in Yolo 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 rural area between the Yolo County Sanitary Landfill and the Yolo Bypass. There are 14 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 in a fenced enclosure. 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 dechlo rinate the disinfected effluent for aquatic toxicity control. Liquid chlorine or sulfur dioxide is withdrawn from ton containers and evaporated to gas in an electrically-heated evaporator with a water bath surrounding a pressure vessel. Pressurized gas from the evaporator is reduced in pressure at a pressure reducing valve and further reduced to vacuum at a vacuum valve. From there, the gas under vacuum is metered through rate valves and rotameters in chlorinators and sulfonators, and drawn into water solution by the vacuum induced at a submerged high-speed impeller in an inductor unit. ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICIES It is the policy of the City of Davis 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 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 Davis 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 scenario for toxic chemicals is defined in the ARP regulations as the release of the contents of the largest single cont ainer 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 error o r damage in transit, with the release secured by application of a Type "B" Ton Container Repair Kit fixture after 60 minutes. ADMINISTRATIVE CONTROLS Administrative controls in effect at the City of Davis which were considered to mitigate the severity of the Worst Case and Alternative Case release scenarios include the City of Davis'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 system. 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 equiped personnel. GENER AL ACCIDENTAL RELEASE PREVENTION PROGRAMS General accidental release prevention programs instituted by the City of Davis are categorized as administrative (management) programs; procedures, training, and engineering controls; and emergency response programs. The City of Davis 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 the City of Davis'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 PREVENTION STEPS Release prevention steps specific to chlorine and sulfur dioxide have been identified and implemented. These include, among other things, confirming that the alarm autodialer system will not be affected by Y2K-induced hazards, and creation of a facility-specific written procedure for chlorine and sulfur dioxide delivery 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 Davis's Emergency Response Program applicable to chlorine and sulfur dioxide has been coordinated with Yolo County Office of Emergency Services, the local agency responsible for hazardous materials inventory reporting and release response coordination. The Water Pollution Control Plant maintains First Responder capability with respect to chlorine and sulfur dioxide releases at its facility. PLANNED CHANGES TO IMPROVE SAFETY All of the improvements and mitigation measures identified in the process hazard analysis which the City of Davis committed to accomplish have been completed or are in progress. Any other measures identified by employees during workplace h azard surveys, or as a result of audit activities, will be thoroughly reviewed and considered for implementation. In the 1999/2000 City of Davis budget, funds are allocated for a study of the WPCP disinfection system. |