Tapia Water Reclamation Facility - Executive Summary
Chemicals are widely used in industry, in the home, in the environment. They are transported on roads, water, and railways. The Tapia Water Reclamation Facility (Tapia WRF) uses chemicals as a necessary part of treating wastewater and producing recycled water. Chlorine is used to disinfect recycled water, to provide safe water for irrigation or for discharge to the environment. Storing large qualities of chlorine can be a hazard. As the agency responsible for operating Tapia, Las Virgenes Municipal Water District (LVMWD) takes our safety obligations in storing and using chlorine as seriously as we do providing safe, high quality recycled water. The following document describes what might happen in the unlikely event of an accident involving chemicals at Tapia, steps taken every day to ensure safety, and what to do in event of an emergency. For questions or concerns, please contact Brian Whitaker/Principal Engineer at 818/251-2158.
Accidental Release Prevention and
Emergency Response Policies
LVMWD's Tapia WRF accidental release prevention policy involves a unified approach that integrates proven technology, staff fully trained in safe operation and maintenance practices, and tested management system practices. All applicable procedures of the State of California and U.S. Environmental Protection Agency (EPA) Prevention Program are adhered to, including key elements such as training, systems management, and emergency response procedures.
This document complies with the EPA's Risk Management Program, under Section 112 (r) of the Clean Air Act (CAA) Amendments of 1990, 40 Code of Federal Regulations (CFR) Part 68 and the California Accidental Release Prevention (CalARP) Program under California Code of Regulations (CCR) Title 19, Division 2, Chapter 4.5. These regulations require facilities storing large quantities of certain chemicals like chlorine and sulfur dioxide to prepare a Risk Management Plant. Tapia WRF has a chlorination system
that uses chlorine gas fed from liquid chlorine containers and a dechlorination system that uses sulfur dioxide gas fed from liquid sulfur dioxide containers. This document summarizes LVMWD's existing health and safety programs, internal response policies and procedures, and ongoing actions that are designed to prevent or minimize impacts of any accidental releases of chlorine or sulfur dioxide to the environment. LVMWD has prepared a detailed and comprehensive emergency response plan to handle any potential accidental releases. This plan is designed to safeguard people both on and off site. LVMWD and Tapia have an excellent record in preventing accidents from occurring in over 30 years of operation.
General Facility and Regulated Substances Information
The Tapia WRF, operating since 1965, is located at 731 Malibu Canyon Road in Los Angeles County. The plant, located on a 20-acre property, is about 5 miles south of the 101 (Ventura) Freeway in Malibu Canyon, adjacent to Malibu C
reek. Wastewater from the LVMWD service area and its joint venture partner, Triunfo Sanitation District of Ventura County, is treated at the Tapia WRF. The highly treated, disinfected water produced at Tapia is either discharged into Malibu Creek or pumped to customers as recycled water for irrigation uses. Treatment at Tapia WRF includes preliminary screening, primary settlement and treatment, secondary sedimentation and treatment, tertiary treatment, and chlorination and dechlorination. The Tapia WRF handles wastewater flows up to 16.1 million gallons per day (mgd), with an average flow of between 9 to 10 mgd.
The facility currently stores chlorine and sulfur dioxide; both regulated toxic substances under federal RMP and CalARP regulations. Chlorine is stored in two, 21-ton bulk steel storage tanks containing a maximum in each tank of 18 tons of chlorine. Sulfur dioxide is stored in two, 8-ton bulk storage tanks containing a maximum in each tank of 7 tons of sulfur dioxide. F
acilities storing more than 2,500 pounds of chlorine and 5,000 pounds of sulfur dioxide are required to prepare a RMP in accordance with federal RMP and CalARP regulations.
Both liquid chlorine and sulfur dioxide are brought to the plant and transferred to the bulk storage tanks. Either liquid or gaseous chlorine and sulfur dioxide can be withdrawn from the tanks. Leak detectors monitor continuously for leaks in the bulk storage areas and in the chlorination and sulfonators rooms. The leak detectors are self-contained, electrically operated devices designed to detect 0.5 ppm by volume of chlorine or sulfur dioxide in the air. If a leak occurs, a level of 0.5 ppm will turn on a red warning light on top of the building and will sound an audible alarm. The detector also will send a signal to the central computer system that activates an alarm on the annunciator board in the control building and also lights a panel alarm on the detector unit itself in the equipment room.
Both the c
hlorine and sulfur dioxide systems contain rupture disks and expansion chambers to relieve excess pressure. Pressure relief valves on the evaporator discharge lines automatically relieve excess gas pressure that would otherwise develop if an evaporator were isolated by valve closure.
The chlorination and dechlorination facilities are also provided with emergency generators. These generators will start within one second and will supply power to the leak detectors, lighting, and ventilation systems.
The chlorine and sulfur dioxide processes are checked twice during every 8-hour daytime shift as part of the normal rounds at Tapia WRF. Emergency showers and eye wash stations are provided outside the chemical storage rooms. The main control building has four self-contained breathing apparatus with one air supply. Fire extinguishers are available at both the chlorine and sulfur dioxide rooms.
The chlorine and sulfur dioxide bulk storage tanks and the chlorination and sulfonator equipm
ent are enclosed in a building. Continuous ventilation of the buildings provided for employee safety is interrupted should either the chlorine or sulfur dioxide leak detector detect 0.5 ppm of either chlorine or sulfur dioxide in the room minimizing any release.
The single road entry into the Tapia WRF, at Malibu Canyon Road, is controlled by a gate and phone security system. Visitors and contractors must dial the control building and be approved by Tapia WRF staff prior to entry. The plant is staffed during the day, year round, and alarms notify on-call staff during off-hours of any problems or situations that require followup investigation.
Offsite Consequence Analysis Results
As required by 40 CFR and 19 CCR, Division 2, Chapter 4.5, the offsite consequence analysis includes consideration of two release scenarios, identified as "worst case" and "alternative" release scenarios. The worst-case release scenario requires that a release of the entire contents of the single larges
t vessel of either chlorine or sulfur dioxide or pipe be evaluated for offsite impacts. An alternative release scenario is required for both substances.
Chlorine was selected for the worst-case release scenario because its bulk storage tanks are greater in volume than the sulfur dioxide tanks. Only passive or administrative controls can be considered under this scenario, when evaluating potential offsite impacts. Thus, the additional safety measures currently in place at Tapia WRF cannot be considered in estimating the effects, although they would considerably reduce the potential range and impact of a release.
The worst-case release scenario used for Tapia WRF is the rupture of one chlorine bulk storage tank with a maximum capacity of 18 tons, resulting in a release of 36,000 pounds of chlorine over a 10-minute duration. The chlorine bulk storage tanks are in an enclosed building, which provides containment of any chlorine release. Therefore, in accordance with EPA guidance,
the passive mitigation of the building was considered. The release rate reduction from the enclosed building is approximately 55 percent of the release rate from the bulk tank, per guidance from EPA regarding control efficiencies levels for buildings storing chlorine. The release rate therefore, is assumed to be 1,980 pounds per minute (lbs/min) for this scenario. In practice this type of total release of a bulk tank would be unlikely during the lifetime of the plant given the significant strength of the thick-wall steel storage tanks and characteristics of chlorine that make rapid releases through anything but a significantly large opening impossible. In the worst-case release scenario, the released liquid is assumed to quickly volatilize and flow along the ground as a heavy vapor cloud.
The distance to the toxic endpoint was estimated using the EPA model RMP*Comp version 1.06, a method of calculation set by EPA to ensure the broadest possible public notification and that local
emergency response planning takes into account the greatest possible impacted area surrounding the release point. The toxic endpoint selected by EPA and CalARP was 3 ppm. In addition, all required EPA-model input parameters where included in completing this activity, including meteorological conditions that cause the largest affected area-Stability F class, wind speed of 1.5 meters per second (3.4 miles per hour), ambient temperature 25 C (77 F), and an average humidity of 50 percent. Using these parameters, highly unlikely to occur simultaneously in the area where Tapia WRF is located, results in the dispersion modeling analysis for this worst case indicate that this scenario has an offsite impact.
The alternative release scenario is more likely to occur than the worst-case release scenario, but still is highly unlikely. In accordance with regulations guiding this report, alternative release scenarios were evaluated for both chlorine and sulfur dioxide. Unlike the worst-case re
lease scenario, active controls can be considered in analyzing the alternative release scenario. Active controls consist of mechanical, electrical, or human input.
The alternative release scenario used for both chlorine and sulfur dioxide was a rupture of a pipe leading from the bulk tank to the evaporator. The tanks, evaporators, and associated piping are all in a building; and the building mitigation was considered. Also considered were reductions in the leak due to excess flow valves on the bulk tanks that operate to reduce the liquid chlorine or sulfur dioxide leaks. Under this scenario, the amount of chlorine and sulfur dioxide possibly released was calculated to be 22.6 lbs/min and 22 lbs/min, respectively. The same modeling approach was used as for the worst-case release scenario, except meteorological conditions were adjusted to more common conditions of Stability D Class, wind speed of 3.0 meters per second, average air temperature of 77 degrees F, and average humidity
of 50 percent. The results of the dispersion modeling analysis for the alternative release scenarios for both chlorine and sulfur dioxide indicate that these scenarios have an offsite, but very limited, impact.
Summary of the Accidental Release Prevention Program and Chemical-specific Prevention Steps
Tapia WRF is in full compliance with Federal and State Process Safety Management (PSM) requirements. Chemical-specific prevention steps include availability of self-contained escape breathing apparatus, worn by the operators during connection and disconnection of the chlorine and sulfur dioxide supplies, awareness of the hazardous and toxic properties of chlorine and sulfur dioxide, and the presence of chlorine and sulfur dioxide detectors and alarms.
Tapia WRF's accidental release prevention program is based on the following key elements:
7 Detailed management system and clear levels of responsibilities and team member roles
7 Comprehensive safety process information that is readil
y available to staff, emergency responders, and contractors
7 Comprehensive preventive maintenance program
7 Completed process-hazard analysis of equipment and procedures, with operation and maintenance staff participation and review
7 Use of state-of-the-art process and safety equipment
7 Use of accurate and effective operating procedures, written with operations and maintenance staff participation
7 High level of training of operators and maintenance staff
7 Implementation of an incident investigation, inspection, and auditing program using qualified staff
Five-Year Accident History Summary
The CalARP regulations require that facilities compile a history of accidents involving a release of chlorine or sulfur dioxide that could have cause safety or health hazards (deaths, injuries, property or environmental damage, evacuations, or sheltering in place). The facility must report any accident within the last 5 years. At Tapia WRF, there have been no accidents during at least the cour
se of this required reporting period.
Emergency Response Program Summary
Tapia WRF has established a written emergency response program to be followed by employees to help them safely respond to any accidental release of hazardous substances. This program has been coordinated with the County of Los Angeles Fire Department, which is a member of the Local Emergency Response Planning Committee (LEPC). This program includes an emergency response notification plan. Emergency response drills and drill evaluations are conducted every 12 months; emergency operation and response procedures are also reviewed at that time. In the event of an emergency, communitywide notification systems are in place and the County of Los Angeles Fire Department coordinates the response actions.
Planned Changes to Improve Safety
As new technology and new regulations develop, facilities using chemicals as part of their processes have opportunity to further improve safety. Changes to improve safety (recomme
nded actions) were identified for the two covered processes in 1990 under the State of California Risk Management and Prevention Program (RMPP). In addition, the 1992 process hazard analyses (PHAs) for the two covered processes were reviewed and revalidated in 1998. The PHAs were further reviewed in January 1999 under the RMP and CalARP program requirements. As a result, additional modifications are underway to improve the safety of the chlorination and dechlorination systems, expected to be fully implemented by December 1999. The implementation of these recommendations will further improve the safety of the covered processes.
Most importantly, LVMWD is currently planning to replace the chlorine and sulfur dioxide with safer chemicals for disinfection. The new system will use sodium hypochlorite and will be completed by December 31, 2000.