Montgomery County Resource Recovery Facility - Executive Summary
1.0 EXECUTIVE SUMMARY |
1.1 ACCIDENTAL RELEASE PREVENTION AND EMERGENCY RESPONSE POLICY SUMMARY
The United States Environmental Protection Agency (USEPA) has established a regulatory program to prevent accidental releases of certain regulated substances that may potentially affect public health and the environment. The rule (40 CFR Part 68) requires that some 66,000 facilities across the United States in various industries develop a Risk Management Program (RMP). The RMP incorporates various required elements into a program designed to prevent accidental releases of regulated substances and establish emergency response preparedness in the event of an accidental release of such regulated substances. RMPs must be submitted to the USEPA by the owner or operator of any facility that has a process containing more than a threshold quantity of any of the regulated substances that is covered under the RMP rule. Pursuant to the RMP rule, Ogden Martin Systems of Montgomery, Inc. (OMSM) has subm
itted this RMP for anhydrous ammonia.
Anhydrous ammonia is a commonly used chemical with various applications in industry and agriculture. By volume, ammonia is the fourth largest industrial chemical produced, over 80% of which goes to agricultural fertilizers (1). In addition to ammonia's application as a fertilizer in crop production, some other common uses for ammonia include: air pollution control system reagent, food production and processing, textile and chemical manufacturing, refrigeration (such as refrigerated warehouses) and metal treating.
Anhydrous ammonia is used at the Montgomery County Resource Recovery Facility (the Facility) exclusively as a reagent in the facility's nitrogen oxide (NOx) control system. The NOx control system is an important part of the Facility's air pollution control equipment that reduces nitrogen oxides to within permitted limits. Nitrogen oxides are pollutants that contribute to acid rain and photochemical smog. Nitrogen oxide (NO) is a
colorless gas produced during high temperature combustion. In ambient air, nitrogen oxide is oxidized to nitrogen dioxide (NO2). Nitrogen dioxide reacts with water in ambient air to form nitric acid, which contributes to the formation of acid rain; and, nitrogen oxides also contribute to the formation of photochemical smog by reacting with sunlight to form ozone (O3) in the atmosphere. The Facility's NOx control system reduces nitrogen oxides by the injection of anhydrous ammonia into the furnace section of the boilers. In the boilers, a reaction takes place between the ammonia, nitrogen oxide and oxygen. The resulting products of this reaction are the major components in the air we breathe - nitrogen gas (N2) and oxygen - and water. A significant environmental benefit is achieved through the use of anhydrous ammonia in the operation of the NOx control system.
OMSM operates the Montgomery County Resource Recovery Facility located in Dickerson, Maryland in a manner that is protec
tive of the health and safety of OMSM employees, Contractor employees, the public and the environment. In addition, OMSM is committed to operating the Facility in full compliance with applicable Occupational Safety and Health Administration (OSHA) requirements, federal regulatory requirements and applicable state and/or local requirements.
OMSM previously developed an OSHA Process Safety Management (PSM) Program for anhydrous ammonia. The OSHA PSM rule guides employees in the preventive maintenance, safe management and operation of processes that use regulated substances, and aims to protect employees from accidental releases of these materials onsite. The USEPA's RMP regulation builds and expands upon the OSHA PSM program by requiring facilities to evaluate offsite impacts to public and environmental receptors, in the event of an accidental release. Key elements of the OSHA PSM program have been incorporated into the USEPA RMP regulation.
As part of the USEPA RMP effort, OMSM has up
dated the OSHA PSM program for anhydrous ammonia and the associated Process Hazard Analysis (PHA). Among the other important components of OMSM's RMP are the policies and procedures for operation and maintenance of the facility, and facility-specific Emergency Response Plan (ERP). OMSM has operated the regulated process for a number of years now without a release due to these solid preventive maintenance programs, safe design and operating practices, and established training programs.
OMSM's Facility Manager has the primary responsibility for this RMP and its implementation.
1.2 STATIONARY SOURCE DESCRIPTION
The Montgomery County Resource Recovery Facility is a waste-to-energy (WTE) facility that burns municipal solid waste and recovers steam to produce electricity. Each day, this WTE facility can convert 1,800 tons municipal solid waste from Montgomery County into electricity.
One process at the Facility involves the use of a substance regulated under 40 CFR Part 68, thereby req
uiring the preparation and implementation of an RMP. This covered process is the NOx control system (discussed in Section 1.1 above) which utilizes ammonia injection for NOx control. The specific NOx control system utilized at the Facility is a Selective Non-Catalytic Reduction (SNCR) system. Anhydrous ammonia is the reagent utilized in the Facility's NOx control system in order to significantly reduce nitrogen oxide emissions, as discussed above.
Anhydrous Ammonia System
A maximum quantity of approximately 10,000 gallons of anhydrous ammonia is stored under approximately 50 psig pressure at the Facility. Administrative controls (at 62.5 % of tank capacity) are used to ensure that this maximum is not exceeded.
Both passive and active mitigation measures are used by the Facility to limit the likelihood and/or severity of an accidental release of anhydrous ammonia. Passive mitigation systems do not require human, mechanical or energy input, such as the concrete dike that surrounds
the storage tank area. Conversely, active mitigation systems do require human, mechanical or energy input for initiation. Leak detectors and alarms, excess flow valves, pressure relief valves, emergency shut-off devices and a water spray system are examples of the active mitigation systems in place at the Facility.
1.3 WORST CASE AND ALTERNATIVE CASE ACCIDENTAL RELEASE SCENARIOS
Worst Case Accidental Release Scenario
For each covered process at a facility, 40 CFR 68 requires that a "worst case" accidental release scenario be developed based on several worst case assumptions, as discussed herein. The most unlikely, worst case accidental release scenario for the SNCR system as defined by the regulation could only occur as a result of catastrophic failure of the anhydrous ammonia storage tank. Such an occurrence would only be precipitated by a most unusual event or an unlikely set of conditions.
The regulation specifies that the worst case accidental release quantity for the Facilit
y must be the maximum amount of anhydrous ammonia held in the largest, single vessel taking into account administrative controls that limit this maximum storage quantity. A release rate of 10-minutes is specified in the regulation for the worst case analysis of substances that are normally gases at ambient temperature and handled as a gas or as a liquid under pressure, such as anhydrous ammonia. This release rate is based on the USEPA's Technical Guidance for Hazards Analysis, which is consistent with other mechanisms used for community emergency planning activities under the Emergency Planning and Community Right-to-Know Act (EPCRA). Furthermore, the regulation stipulates that active mitigation systems (such as excess flow valves, and the Facility's deluge system) cannot be considered in defining the worst case scenario, and assumes that all released ammonia would behave as a gas in defining the worst case scenario. Based on these parameters set by the regulation, none of the Facility
's active or passive mitigation systems were considered in the worst case accidental release scenario.
Additional conservative assumptions have been specified by the USEPA in the analysis of the worst case accidental release scenario. These assumptions are a low wind speed, a highly stable atmosphere and use of the maximum ambient temperature over a three-year period. These worst case assumptions are used to predict a highly conservative distance to a "toxic" endpoint as specified by the regulations. For anhydrous ammonia, the "toxic" endpoint is specified as an airborne concentration of 0.14 milligrams per liter (mg/L) or 200 parts per million (ppm). This endpoint is based upon the Emergency Response Planning Guideline (ERPG-2) as developed by the American Industrial Hygiene Association (AIHA). This value represents the maximum airborne concentration below which nearly all individuals could be exposed for one-half to one hour without experiencing or developing irreversible or other s
erious human health effects or symptoms that could impair their ability to take protective action.
For OMSM, the worst case accidental release scenario for anhydrous ammonia, as defined by the USEPA, would involve a release of 10,000 gallons of anhydrous ammonia (as a gas), over a period of ten minutes. The distance to the "toxic" endpoint for anhydrous ammonia was determined using the Areal Locations of Hazardous Atmospheres (ALOHA) air dispersion model. ALOHA was selected because it is the publicly available air dispersion computer model used by over 3,000 Local Emergency Planning Committees (LEPCs) and fire departments for emergency response and planning purposes.
Based upon the "worst case" assumptions discussed above, the worst case accidental release scenario is projected to reach an off-site endpoint. Public and environmental receptors are located within this projected area. Public receptors are defined by the regulation to include off-site residences; institutions; industr
ial, commercial and office buildings, and parks or recreational areas inhabited or occupied by the public. Environmental receptors as defined by the regulations include National or State parks, forests or monuments, officially designated wildlife sanctuaries, preserves, refuges, or areas and Federal wilderness areas.
The worst case accidental release scenario requires that the assumption be made that an ammonia release would disperse in a circle in all directions from the Facility to the endpoint (as defined above). Whereas, a gaseous release of ammonia would most likely take the form of an elongated plume dispersing only in the downwind direction from the Facility and impacting, more realistically, a much smaller area.
"Secondary" Worst Case Accidental Release Evaluation
The USEPA regulations require that the worst case accidental release of anhydrous ammonia be modeled as a gaseous release over a period of ten minutes. However, this requirement does not allow for the consideration
of actual thermodynamic properties, which would predict a two-phase release of gas and liquid. Instantaneously, approximately 25% of the anhydrous ammonia would flash off as a dense gas. The remainder of the anhydrous ammonia would either be incorporated into the escaping gas cloud as an aerosol or remain as a cold liquid that would pool inside the containment dike. The liquid in the dike would then evaporate as it absorbs heat from the surroundings, typically over a number of hours, thus slowing the release rate.
Based on this two-phase behavior, a "secondary" worst case accidental release was modeled using the dense gas release and liquid spill volatilization capability of the ALOHA air dispersion model. Consideration was also given to the effect of the containment dike (i.e. passive mitigation). The assumptions for wind speed and atmospheric stability (as specified in the regulation for the worst-case analysis) were used. Based on these modeling conditions, the "secondary" worst c
ase is projected to reach an offsite endpoint and a minimum number of public and environmental receptors. In comparison to the result of the worst case scenario as defined by the regulations, the "secondary" worst case accidental release scenario predicts a reduction to the endpoint distance by almost 40 %, applying the predicted two-phase thermodynamic behavior of anhydrous ammonia.
Alternative Accidental Release Scenario
A more realistic, alternative accidental release scenario was evaluated for anhydrous ammonia, in accordance with USEPA regulations. The alternative release scenario was chosen based upon the results of a Process Hazard Analysis and is summarized below.
Pipe Leak - The analysis considers a break in a 1-inch diameter liquid line between the storage tank and the vaporizers that could result in a release of liquid anhydrous ammonia at a rate of approximately 30 gallons per minute for 120 minutes, before the leak can be detected and stopped or repaired.
s for ambient conditions, including a wind speed, atmospheric stability, and ambient temperature were used for the alternative accidental release scenario analysis. To be conservative, passive and active mitigation systems were not considered in the alternative accidental release scenario analysis.
Using the assumptions discussed above and the ALOHA air dispersion model, the alternative accidental release scenario is projected to reach an offsite endpoint, but none of the residential community and only a minimum number of public and environmental receptors were identified within the endpoint radius.
In the event of an actual release, all of the active and passive mitigation systems/features that are available on the anhydrous ammonia system at the Facility would be used to contain the spread of any accidental release and mitigate potential impacts of the release. The mitigation systems/features include a concrete containment dike around the anhydrous ammonia storage tank and associat
ed equipment, leak detectors and alarms, excess flow valves, pressure relief valves, emergency shutoff devices and a water spray system.
1.4 ACCIDENTAL RELEASE PREVENTION PROGRAM
The Facility has an accidental release prevention program that is based upon a foundation of employee awareness and proactive system maintenance. This program is documented in the RMP, and meets the requirements of the RMP regulation.
The Facility provides process safety information to employees through written materials, such as Material Safety Data Sheets, various operating and maintenance manuals, system descriptions and safety procedures. Employees attend periodic training and contractors are briefed on process hazards prior to working onsite. Preventive maintenance and regular inspections are conducted for maintaining mechanical integrity. Inspections and testing are scheduled through the preventive maintenance program. Hazard analysis documents are reviewed periodically and updated as required. Com
pliance audits are used to evaluate the need for revising or updating the procedures related to the processes.
1.5 FIVE-YEAR ACCIDENT HISTORY
There have been no accidental releases of anhydrous ammonia of any kind since the Facility began operation in May of 1995. Since there has not been an accidental release, there has not been a need for sheltering in place or evacuation; nor has damage to property or environmental receptors ever occurred as a result of an accidental release. In fact, OMSM has operated the Facility in the safest possible manner since it has commenced operations.
1.6 EMERGENCY RESPONSE PROGRAM
The Facility has an Emergency Response Plan (ERP) that defines the sequence of actions to be taken by OMSM employees in the event of an accidental release of anhydrous ammonia. This ERP has been communicated to the local Fire Department and the Local Emergency Planning Committee (LEPC). Individuals who are likely to witness or discover a release have been trained to initiat
e an emergency response sequence by notifying the proper authorities. It is currently OMSM's policy that individuals that have received the requisite training will attempt to secure a release of anhydrous ammonia if the action can be taken without significant risk of injury or death. The Montgomery County Fire and Rescue Services including the Upper Montgomery County Volunteer Fire Department in Beallsville is presently responsible for determining when sheltering-in-place or evacuation of off-site areas is necessary, and for also public notification.
1.7 PLANNED CHANGES TO IMPROVE SAFETY
This RMP incorporates a number of enhancements to the existing Facility procedures, which are designed to improve employee safety awareness and enhance safe operations. These enhancements were developed as a result of the Process Hazard Analysis for anhydrous ammonia. Also, key items have been added to the preventive maintenance program for the anhydrous ammonia. These enhancements ultimately reduc
e the likelihood of an accidental release. Further, emergency response procedures have been reviewed and coordinated with local response entities to increase the speed and effectiveness of a response should a release occur.
1 J. Harte, C. Holdren, R. Schneider and C. Shirley. Toxics A to Z - A Guide to Everyday Pollution Hazards, 1991, University of California Press, 479 pps.