HUSTON CREEK WASTEWATER TREATMENT PLANT - Executive Summary
This document comprises the Risk Management Plan (RMP) for the Crestline Sanitation District (District) facility located at 246 Huston Road in Crestline, California 92325 (also referred to within the District as the Huston Creek Wastewater Treatment facility). The District also operates one other stationary source subject to the federal RMP regulations. A separate RMP has been submitted for that facility. |
The purpose of this document is to comply with the risk management planning requirements as set forth in Section 25535(d) of Article 2 of Chapter 6.95 of the California Health and Safety Code (also known as the California Accidental Release Prevention Program - CalARP) and Part 68 of Title 40 of the Code of Federal Regulations (40CFR Part 68), also known as the federal Accidental Release Prevention Requirements: Risk Management Programs or the federal RMP.
The scope of the RMP includes all operations conducted at the facility which involve the storage, handling and/or use of chlor
ES 1.0 DESCRIPTION OF STATIONARY SOURCE AND REGULATED SUBSTANCES HANDLED
The Crestline Sanitation District was formed on January 21, 1946 to provide sewer service to the Lake Gregory area of California. The Crestline Sanitation District is the largest enterprise Sanitation District in San Bernardino County and presently serves over 5200 residential and commercial connections. At present, the District has approximately 90 miles of sewer lines. The District's collection system has three pumping stations. These stations pump raw sewage up to higher elevations and allow flow by gravity to the Huston Creek Wastewater Treatment Plant.
The Huston Creek Wastewater Treatment Plant has been in operation since 1950. Since that time, the plant has undergone several modifications and expansions. The most recent such expansion was completed in 1988. The facility is classified as a secondary treatment plant and process units consist of comminution, grit removal, primary clarification,
fixed nozzle standard rate trickling filter, secondary clarification and disinfection. As a part of the wastewater treatment process, chlorine is utilized for water disinfection. Provided below, is a brief description of the storage, handling and use of chlorine at the facility.
STORAGE, HANDLING AND USE OF CHLORINE
Chlorine is utilized to disinfect cleaned/treated water prior to discharging (this is also known as final disinfection of the effluent). Chlorine is a regulated substance subject to the federal RMP requirements. The chlorination process consists of four main components:
A maximum of two one-ton containers of chlorine and five 150 pound cylinders of chlorine (a maximum inventory of 5000 pounds);
Fixed and paced rotometers;
The chlorine injector to control the injection of chlorine and maintain a vacuum on the gaseous chlorine system;
Figure ES-1 presents a simplified flow diagram of the process. One ton containers and 150 cylinders containing liqu
id chlorine are delivered to the facility via truck. Before the containers and/or cylinders are accepted, plant operators inspect the containers/cylinders and valves for any signs of leakage or improper alignment of the valves. Once accepted, the one ton containers are off-loaded utilizing the hoist, placed in special cradles, chained to the floor, dated, and the cylinder identification numbers are recorded on the chlorine inventory forms maintained in the storage room. The 150 pound cylinders are strapped and safety chained to anchored cradles in the walls of the storage room.
Chlorine gas travels (under vacuum) from the container, through the container-mounted regulator, and into an automatic switchover module. From there the chlorine gas travels (under vacuum) to the gas feed unit, where fixed and paced rotometer units measure out the proper amount of chlorine. The fixed rotometer is set manually while the paced rotometer is tied to the plant effluent flow meter and increases
or decreases with water flow.
Chlorine gas then exits the rotometers and enters a hard piped injector. The injector injects chlorine gas into the water stream. As a result of having chlorine injected into it, the water contains elevated levels of diluted chlorine. This chlorine solution is then transferred via piping to the three end use points where it is mixed with the water to be treated.
ES 2.0 ACCIDENTAL RELEASE SCENARIOS
The RMP regulations require that at least two types of release scenarios be evaluated for their potential to impact off-site populations:
the worst case release; and
an alternative release (that is more credible).
A number of hypothetical accidental release scenarios were postulated and evaluated for the RMP. These scenarios were categorized into worst-case release scenarios and alternative release scenarios. Each of these categories of hypothetical accidental release scenarios is discussed below.
Worst-Case Release Scenario
In this scenario
, one of the one-ton containers of chlorine on site experiences a catastrophic failure due to an unknown external event. This scenario could be initiated by an external event (i.e., an airplane, missile or meteorite impacting the chlorine building where the ton containers are located). It is highly improbable that this scenario would be initiated by a seismic event. However, the possibility of this scenario being initiated by a seismic event can not be completely discarded. This scenario is considered to be extremely unlikely. In the highly unlikely case that this scenario occurs, approximately 2,000-pounds of chlorine would be released. The release of chlorine could occur outdoors or indoors. Since the release can occur out-doors (i.e., outside of the chlorine storage building) the enclosure provided by the chlorine building was not taken into account in evaluating the off-site consequences. Rather, it was assumed that the chlorine released during the catastrophic accident was
released outdoors forming a cloud of chlorine vapor. The resulting vapor cloud was assumed to freely migrate off-site. Utilizing the methodology specified by USEPA, the estimated vulnerable zone for this accidental release scenario is approximately 1.3 miles.
Figure ES-2 presents a graphical representation of the vulnerable zones for the worst-case release scenario for accidental releases involving chlorine. Table ES-1 provides a listing of sensitive receptors within the vulnerable zone. As shown, the only sensitive receptors located within the vulnerable zone are recreation areas.
Alternative Release Scenarios
Alternative release scenarios which are considered to be more likely to occur are those which result in the release of anywhere from less than one-pound to up to 10-pounds of chlorine. These scenarios include situations such as the delivery of a leaking one-ton container of chlorine to the facility, a pinhole leak in the chlorine transfer piping and a partial or complet
e failure of the chlorine transfer lines (either 100-percent vapor or chlorine dilution water) at various points in the system (either in-doors or out-doors). In order to be conservative in the estimation of the vulnerable zone, it was assumed that 10-pounds of chlorine was released during an accident involving the complete failure of a vapor transfer line from a one ton container. In such a situation, the loss of vacuum from the system would result in the automatic isolation of the one ton container at the container valve. However, in order to be conservative, it was assumed that the material was released directly outdoors (although the full length of the vapor transfer lines is located indoors. Thus, the system enclosure provided by the chlorine building was not taken into account in evaluating the off-site consequences. Utilizing this assumption is much more conservative in nature and resulted in the estimation of the largest vulnerable zone for these types of accident scenario
s. The resulting cloud of chlorine vapor was assumed to freely migrate off-site. Utilizing the methodology specified by USEPA, the estimated vulnerable zone for these types of scenarios is approximately 0.1 miles.
Figure ES-2 presents a graphical representation of the vulnerable zones for the alternative-case release scenario for accidental releases involving chlorine. Table ES-1 provides a listing of sensitive receptors located within the vulnerable zone. As shown, the only sensitive receptors located within the vulnerable zone are recreation areas.
ES 3.0 FIVE YEAR ACCIDENT HISTORY
During the five years preceding the submittal of this RMP, the facility has NOT had any releases of chlorine which have resulted in:
Onsite deaths, injuries, or significant property damage; or
Known offsite deaths, injuries, property damage, environmental damage, evacuations, or sheltering in place.
ES 4.0 ACCIDENTAL RELEASE PREVENTION PROGRAM AND CHEMICAL SPECIFIC PREVENTION STEPS
Release Prevention Program at the District consists of a series of programs, procedures and policies designed to minimize the risk of accidental releases involving chlorine. These programs include design and operating controls such as compliance with specified codes, the health and safety program, numerous standard operating procedures, the equipment inspection and maintenance program (including a mechanical integrity and preventive maintenance program), site security, the management of change program, pre-start-up review, fire protection and hot work permit program, management of- and safety of- contractors accident/incident investigation procedures, emergency response plan, RMP compliance auditing program, record keeping and a variety of training programs. Details of each of these components of the District's Accidental Release Prevention Program are provided in the document entitled Risk Management Plan (RMP), Volume I - Prevention Program.
There are several detection and monito
ring devices and alarms placed at strategic locations throughout the facility. Table ES-2 provides a summary listing of these devices as well as their sensitivities. In addition, there are portable fire extinguishers located throughout the facility.
ES 5.0 EMERGENCY RESPONSE
The District recognizes that emergency planning and emergency response are an integral component of risk management. As such, the District currently has an emergency response plan and an emergency evacuation plan in place as part of its hazardous materials business plan (HMBP). However, as a measure to improve safety, the District is currently developing a specific emergency response program for emergencies involving chlorine.
ES 6.0 PLANNED CHANGES TO IMPROVE SAFETY
A detailed hazard and operability study (i.e., hazards analysis) was performed on ALL operations involving chlorine in order to evaluate the potential for accidental releases. As a result of this hazards analysis a number of recommendations we
re made to improve the safety of the operations conducted. A summary of the recommended actions is provided in Table ES-3. Table ES-3 also presents the implementation status of the recommended actions. As shown, the District has already implemented a number of the recommendations. Table ES-3 also presents the expected date of implementation for those recommendations not yet implemented.
ES 7.0 FOR MORE INFORMATION
The District recognizes that some persons may be interested in obtaining more detailed information regarding risk management prevention program components not discussed herein. Interested parties that have additional questions regarding the District's Risk Management Plan, are directed to contact:
Mr. Joel Stribling
Sanitation Services Representative
Crestline Saintation District
24516 Lake Drive
P.O. Box 3395
Crestline, California 92325-3395