Ocean State Power - Executive Summary

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EXECUTIVE SUMMARY 
This executive summary includes a brief description of Ocean State Power's (OSP) facility risk management program.  This information is being submitted in accordance with USEPA's Risk Management Plan (RMP) Rule under Section 112(r) of the Clean Air Act.  The following elements are described per the RMP*Submit Users Manual (Version 1.07) January 4, 1999. 
 
1.    Accidental Release Prevention and Emergency Response Policies 
 
OSP has developed and maintains an active emergency prevention and response program in accordance with applicable regulations.  This program consists of two primary elements: Emergency Prevention and Response Plan and an Emergency Response Procedures Handbook.  OSP is prepared to respond to emergencies quickly and effectively.  The primary goal is to protect the health and safety of plant personnel and the public, and to minimize damage to the environment and plant equipment in the unlikely event of an accident.  An Emergency Coordinator/Qualified 
Individual (EC/QI) is responsible for implementing and overseeing emergency response activities onsite.  If the primary EC is not available, there is an assistant, plus alternate individuals who have received adequate training and have been delegated authority.   The facility's Procedures Handbook provides actions for proper notifications within OSP's emergency response organization to activate necessary resources.  OSP has an ongoing employee health and safety training program conducted by qualified instructors.  Facility personnel are trained in functional areas that correspond to their emergency response duties and responsibilities.  Drills are conducted for site emergency managers on a periodic basis to exercise procedures and maintain readiness.  Integrated drills are conducted in conjunction with the Harrisville Fire Department to coordinate offsite emergency response procedures. 
 
2.    Description of Facility and Regulated Substances Handled 
 
OSP is a 500 megawatt (MW) combine 
d cycle gas turbine electric generating facility that operates on a continuous basis.  The area surrounding the plant is gated and public access is restricted.  Natural gas, the primary fuel, is delivered by either Tenneco or Algonquin pipelines to metering stations located at the northeast property boundary.  No. 2 oil, used for emergency backup fuel, is stored in two, 1,000,000-gallon aboveground tanks, located in a fully contained area.  The power plant consists of two identical phases.  Each phase includes two GE Frame 7 combustion turbine generators, two heat recovery steam generators/boilers with supplemental firing using ductburners, and one steam turbine generator.  Auxiliary equipment includes an electrical switchyard, wet mechanical cooling towers, and a zero discharge water treatment system.  Other facility components include selective catalytic reduction (SCR) systems; two 150-foot concrete stacks equipped with continuous emissions monitoring systems; two emergency diesel g 
enerators; and oil and chemical storage.  The plant is operated from the control room.  Operators have access to plant operating data from the computerized distributed control system (DCS) and a central data acquisition and handling system (DAHS). 
 
Aqueous ammonia (29 weight percent concentration in water) is the only regulated substance used in a process that is above the threshold quantity identified in 40 CFR Part 68.130.  Ammonia is used as a reducing agent for the SCR NOx emissions control system for the combustion turbines.  Aqueous ammonia is evaporated in hot air and injected into the flue gases upstream of a catalyst located in the heat recovery boilers to convert NOx emissions into nitrogen and water.  The amount of ammonia injected and the NOx/NH3 emissions in the exhaust stack gases are continuously measured and recorded.  The SCR system is comprised of subsystems - aqueous ammonia unloading area, a storage tank to provide four weeks capacity, two ammonia transfer pumps ( 
one back-up) to transfer solution to the four ammonia flow control/evaporator units, and four ammonia injection systems (one per HRSG).  The unloading area includes an unloading pump rated for eighty gpm with vapor recovery, and concrete berm to collect an accidental spill from truck delivery.  There are several interlock functions within the ammonia supply line that could activate an emergency shutoff valve.  Isolation valves and a bypass valve are provided as a contingency, should the ammonia flow control valve have to be taken out of service.  Ammonia leak detection devices are also provided.  
 
3.    Worst Case Release Scenario:    Failure of Aqueous Ammonia Storage Tank  
 
OSP stores 29 weight percent aqueous ammonia in one of two 60,000 gallon tanks.  An "administrative control" enforced by OSP includes the use of only one storage tank.  The worst case release from either storage or from process lines is predicted to be less than the distance to any public or environmental receptor.  
Therefore, an analysis of alternative release scenarios is not required.  OSP believes the design of the ammonia tank containment should be considered a "passive mitigation" under the RMP, and has requested a written determination from RIDEM/EPA regarding the tank containment.  A response has not yet been received.  Therefore, this RMP has been developed assuming the ammonia tank containment is passive mitigation.  The following is a description of the tank's design and assumptions used to predict a worst case release scenario. 
 
The 21-foot diameter ammonia tank is of vertical, cylindrical, self-supporting, fixed-dome, welded construction designed in accordance with API 620 standard.  A level transmitter is mounted on the tank shell for transmitting tank level readings to the control room.  A 26-foot diameter self-supporting outer tank is used to contain >100% of the liquid volume if the inner tank should fail.  A leak detection system alarms the control room if ammonia accumulates  
between the 2.5-foot space between the inner and outer tanks.  The inner tank is capable of containing 10 psig pressure, and equipped with a safety relief valve and vacuum breaker (used for vapor recovery during deliveries).  The outer tank has a breather vent set at 0 psig.  The outer tank is designed to capture ammonia liquid upon loss of containment to minimize exposure of the public or environment.  It will function without human, mechanical or other energy input.  Both tanks are supported by a concrete ringwall foundation.   
 
A hazard assessment was conducted to establish the "worst case" release scenario, employing EPA's Offsite Consequence Analysis (OCA) Guidance, dated May 24, 1996.  Data for aqueous ammonia solution toxic endpoint (0.14 mg/L), liquid factor (LFA), and distance to toxic endpoint were obtained from the OCA Guidance Document. 
 
   Employing Maximum Containment Area & Enclosure: 
* QR = U0.78 x LFA x A = [Equation D-5] 
where    QR = release rate (lbs/min) 
       U = wi 
nd speed < 0.1 meters/sec (inside building) vs. enclosed tank [Section D.2.4] 
       A = Maximum surface area of the pool = outer tank area = ( [(26/2)2  - (21/2)2]  = 185 ft2 
           QR < (0.1)0.78 x 0.026 x 185  [inside building vs. enclosed tank] 
* Distance to toxic endpoint = 0.06 miles  [Reference Table 2] 
 
In order to more accurately estimate ammonia release rates from the tank, EPA's TANKS Computer Model software, version 3.1, was used.  The release rate, expressed as standing losses, is predicted to be well below 0.01 lb/min at 77oF ambient temperature. 
 
Employing passive controls prevents a worst case release of liquid ammonia that could impact public and/or environmental receptors.  Using the OCA Guidance and/or TANKS, an enclosed containment area results in a reduction of estimated release rate by over 99%.  NOTE:  The Section 2 of the RMP*Submit software will not allow data entry of less than 0.2 pound/min release rate. 
 
4.    General Accidental Release Prevention Program 
 
OS 
P complies with EPA's Accidental Release Prevention Rule and with all applicable state and federal codes and regulations having emergency response requirements, including those listed below: 
* 29 CFR Part 1910.120 - OSHA 
* 29 CFR Part 1910.38(a) - OSHA 
* 40 CFR Part 112 - SPCC 
* 40 CFR Part 355 - EPCRA  
* 40 CFR Part 265, Subparts C, D - LQG 
* 49 CFR Part 194 - DOT 
* Rhode Island Rules and Regulations for Hazardous Waste Management 
* Rhode Island Rules and Regulations for the Investigation and Remediation of Hazardous Materials Releases 
* Rhode Island Oil Pollution Control Regulations  
 
OSP operates 24 hours per day, seven days a week.  During the day shift, staff consists of approximately forty personnel including the General Manager, Plant Manager, and operating and maintenance crews.  The off shifts have at least eleven personnel onsite, including the Shift Supervisor.  The plant emergency response organization is based upon a two-stage activation, initial emergency respo 
nse and expanded emergency response, with the EC/QI in charge of the facility's response to any emergency situation.  The EHS Engineer is responsible for ongoing assessments in accordance with the Emergency Prevention and Response Procedures. 
 
5.    Five-Year Accident History 
 
OSP has been in operation since 1990, and has not had an accidental release of ammonia that resulted in death, injury, or significant property damage on site, or known offsite deaths, injuries, evacuations, sheltering, property damage, or environmental damage.   
 
6.    Emergency Response Program 
 
OSP is required to prepare and submit a RMP that meets Program 1 requirements.  Program 1 requires a facility to coordinate with local emergency responders.  OSP has completed this requirement under OSHA's Process Safety Management (PSM) standard.  The program is reviewed annually and revised as necessary in accordance with the regulations.  
 
7.    Planned Changes to Improve Safety 
 
OSP has an Emergency Prevention and 
Response Plan in place that includes periodic training of personnel.  The EHS Engineer is responsible for ongoing assessments in accordance with the facility's Plan and Procedures.  If an emergency does occur, an Incident Reporting Form would be completed that includes the type of emergency and release, emergency response actions and deviations from the Plan, evaluation of hazards to public health, safety or environment, and proposed measures to prevent similar actions.   
Executive Summary-Ocean State Power Risk Management Plan 
June 16, 1999        Page 2 
 
 
 
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