West Hickman Waste Water Treatment Plant - Executive Summary
Risk Management Plan |
West Hickman Wastewater Treatment Plant
The Risk Management Plan for West Hickman Wastewater Treatment Plant has been prepared in accordance with EPA "Risk Management" and is designed specifically for the above specified location. West Hickman Wastewater Treatment Plant is located in Nicholasville, Kentucky, 3174 Ashgrove Road. The probability of a release at this plant is classified as low to medium. The enclosure of the chlorine and sulfur dioxide rooms should prevent any major release from leaving the area. Should a leak of a chlorine cylinder or sulfur dioxide cylinder occur, the onsite personnel (LFUCG employees) would be immediately vulnerable to exposure. In the event of a release, there may be possible human health impacts to on-site employees and the population in the surrounding area. A worst case release could affect an area over a 4.0 mile radius and impact a sizeable residential and institutional population. The Lexington Fay
ette Urban County Government (LFUCG) Division of Sanitary Sewers has invested considerable time in devising and implementing accidental release prevention programs and emergency response policies to prevent an accidental release from occurring.
The LFUCG and personnel of West Hickman Wastewater Treatment Plant apply a holistic and proactive approach towards risk management. The LFUCG has devised a reliable maintenance program, identifying management, policies, preventive maintenance practices and plans and procedures to identify and minimize risk at the plant. Preventive maintenance consists of daily and weekly checks of plant equipment. All equipment is loaded on a database maintained by the LFUCG. A data sheet is printed out daily indicating the maintenance and check schedule of all equipment and process procedures.
The LFUCG Division of Sanitary Sewers manages risk proactively through reduction, avoidance, and thorough communication with one another and the Local Emergency P
lanning Committees. To date no accidents or leaks have occurred at the West Hickman facility. The possibility of risk situations are reduced by conducting manual inspections and routine maintenance checks on a regular basis. LFUCG management and employees identify, evaluate, and analyze potential risk situations in order to minimize a potential hazardous event at the facility. Communication and practice with the LEPC ensures preparedness in the unlikely event that a leak should occur.
In the unlikely event that a chlorine or sulfur dioxide leak would occur, LFUCG employees, and the Local Emergency Planning Committee are well prepared and trained to remediate and or mitigate the situation. LFUCG employees are trained in handling chorine and sulfur dioxide. They are also trained on initial startup procedures, normal operating procedures, temporary operating procedures, emergency operating procedures, emergency shutdown procedures, normal shutdown procedures, and startup following a
turnaround or after an emergency shutdown procedure.
Response to a large chemical release at the West Hickman Wastewater Plant will include, but not be limited to the following agencies: Lexington Fire Department, DEEM, Jessamine County LEPC, and Jessamine County Fire Department. Other responding agencies are: State Fire Marshall's Office, Kentucky Emergency Response Commission (KERC), Kentucky DES Area Coordinator, Natural Resources and Environmental Protection Agency, Chemtrac, and public works personnel.
The regulated substances at the West Hickman facility are chlorine and anhydrous sulfur dioxide. Worst case and alternative release scenarios were developed for both of these regulated chemicals in order to determine the impact it would have on the immediate community. The risk analysis for both was modeled with EPA's OCA Guidance Reference Tables and Equations. The results for this modeling is described below, however, it should be noted that the likelihood of leaks of this si
ze and nature occurring are absolute worst scenarios and are not likely to occur.
The West Hickman WWTP has invested millions of dollars to ensure the proper precautionary systems and equipment were installed to protect against leaks to the atmosphere. These precautionary measures are best exemplified in the alternative release scenarios for both chlorine and sulfur dioxide and are described later in this report.
The worst case scenario for both chlorine and sulfur dioxide was modeled to determine offsite consequence analysis. The EPA defines a worst case release as the following:
7 The release of the largest quantity of a regulated substance from a vessel or process line failure, and
7 The release that results in the greatest distance to the endpoint for the regulated toxic substance.
Mitigation measures were not factored for the off-site consequence analysis for both scenarios. Thus, the scenarios assume that full enclosure does not exist.
The largest quantity of both chemi
cals was determined by taking into account administrative controls rather than absolute capacity of the pipes. West Hickman uses administrative controls that limit the quantity of chlorine and sulfur dioxide that can be stored in a pipe at any one time.
The toxic worst case release for chlorine via a pipe leak at West Hickman is 4,000 lbs with a release rate of 400 lbs/min. The duration of the release is 10 minutes with wind speed calculated at 1.5 m/sec. Considering these factors, the maximum effected radius or distance to the endpoint is calculated at 2 miles (based on EPA's OCA Guidance Reference Tables for Chlorine Gas). Within this 2 mile radius, approximately 23,000 people could potentially be effected. Residences, schools, hospitals, and recreation areas are all within this specified area and could possibly be impacted in the event of a release.
The toxic worst case release for anhydrous sulfur dioxide via a pipe leak is 4,000 lbs with a release rate of 400 lbs/min. The
duration of the release is 10 minutes and wind speed is calculated at 1.5 m/sec. Considering these factors, the maximum effected radius or distance to the endpoint is factored at 2.0 miles (based on EPA's OCA Guidance Reference Tables for Sulfur dioxide). Within this 2.0 mile radius, approximately 23,0001 people could potentially be effected. Residences, schools, hospitals, and recreation areas are all within this specified area.
Alternative releases were also modeled for both chlorine and sulfur dioxide. The alternative releases depict a more accurate picture of offsite consequence analyses and are more realistic than the worst case scenarios. Passive mitigation measures were used to determine and factor alternative release scenarios.
The passive mitigation considered for both alternative scenarios was enclosure. Modeling for the alternative releases was based on EPA's OCA Guidance Reference Tables and Equations for gas pipe leaks.
The maximum quantity release for chlorine a
t West Hickman via a pipe leak, using passive mitigation measures is 1,536 lbs with a release rate of 25.6 lbs/min. The duration of the release is 60 minutes with wind speed calculated at 3.0 m/sec. Considering these factors the realistic distance to an endpoint or offsite analysis is actually 0.60 mile with only 25 people affected. The number is significantly reduced from the worst case scenario due to the mitigation measures in place at the facility.
The maximum quantity release for sulfur dioxide at West Hickman using passive mitigation measures is 1,428 lbs with a release rate of 23.8 lbs/min. The duration of the release is 60 minutes with wind speed calculated at 3.0 m/sec. Considering these factors the realistic distance to an endpoint or offsite analysis is actually 0.70 mile with only 25 people affected, the same as chlorine with the mitigation measures in place.
In addition, the chlorine and sulfur dioxide rooms of the plant have been designed such that even in worst
case scenarios, minimal levels of toxic gas will be released into the atmosphere. If a chlorine leak does occur it will be detected by leak detectors in the chlorine room and or in the scale room. These detectors are calibrated to react with a minimum of 1ppm chlorine gas. If a chlorine gas leak is detected, an internal alarm within the chlorine building will be activated. Also, an external alarm and a red flashing light located on the exterior of the building will be activated, In addition to these alarms, an alarm will appear and be heard on the computer in the Administration Building, on the P-3 panel in the digester building, and on the P-6 panel in the new nitrification building. Also, flashing amber lights will be activated throughout the tunnel system of the plant.
Many precautionary measures are taken to prevent leaks from occurring. Preventive maintenance and constant system monitoring are two of the most important elements comprising proactive risk management at Wes
t Hickman. The following is a brief description of the chlorine and sulfur dioxide process at the facility. Chlorine is pulled into the system through the piping systems. Before it goes into the chlorinator room it goes through an automatic switch over system that is designed to monitor the chlorine gas pressure in the feed lines. If the chlorine gas pressure drops below a certain set point that has been pre-determined, the switch over system will switch from one bank to the other. Once the chlorine gas is fed through the storage system in the scale room, it then enters into the chlorinator room.
The chlorine gas is then pulled through the five main chlorinators in the chlorinator room. The five units have the capability of feeding five hundred pounds each of chlorine per day. These five units provide chlorine for the post-chlorination system. The chlorine is fed through injectors which are operated with plant water.. The chlorinators are used for various plant processes thr
oughout the plant, and feed chlorine through four different chlorine injectors, which also uses plant water to operate. Chlorine is provided to various points of the plant through these four injectors.
The chlorine scale room and the chlorine chlorinator room utilizes a ventilation and a leak detection system for protection of the building and the plant. The chlorine detection systems are Wallace and Tierman leak detection systems. There is one of these in the scale room and it is positioned to monitor the entire room. There is also a chlorine leak detector in the chlorinator room. It is located at the south east corner of the room.
In the event of a chlorine leak in the chlorinator room, or the scale room, the following systems will be activated. If a leak detector detects chlorine gas, the alarm systems will be activated. The alarm system consists of an audible alarm in the building. There is also a visual alarm and an audible alarm outside of the building and a visual a
larm in all basements on the plant site. The leak detector generates an alarm system in the computer controls room as well, so if the operator is in the computer room he will see and hear the alarm on the computer.
The ventilation systems which are associated with the chlorine scale room and chlorinator room are checked nine times per day for operational condition. The louvers and vents are manually turned on for verification of operation and then inspected. The leak detection systems, which have two monitors, one in the scale room and one in the chlorinator room, are also checked, calibrated and upon verification of both units, ventilation and leak detector, the system is then activated to verify operation, The chlorine leak detectors are actually activated, and if the system is working properly, there will be an alarm inside and outside the building. There will also be an alarm at the computer.
In the event that there is a malfunctioning leak detector, a number of things could
occur. If a leak detector has a weak cell or a bad battery the alarm system will be activated. Upon investigation of the alarm, the operator can determine whether it is a true leak or a malfunction of the system using a portable gas monitor. If it is determined that the leak detector has malfunctioned, the individual leak detector can be manually disconnected. This does not disarm the other unit that is in place. The likelihood of having both malfunction is unlikely.
Operations and procedures are very similar for sulfur dioxide. The sulfur dioxide tank room and feed room also have ventilation systems. Sulfur dioxide leak detection is utilized, and there are two leak detector systems located in the sulfur dioxide storage room and one in the feed room.
In the event of a sulfur dioxide leak in the feed or tank room, the following systems will be activated. If a leak detector detects sulfur dioxide gas, the ventilation systems and the alarm systems will be activated. The alarm sy
stem consists of both an audible and visual alarm inside and outside the building, and on the main computer. The ventilation systems will shut down when the leak detectors are activated.
West Hickman Waste Water Treatment Plant has a comprehensive and thorough emergency response plan. In the event of a chlorine or sulfur dioxide leak or spill, all personnel are trained to immediately proceed with the following:
1. Notify Plant Operations Supervisor Senior and then Plant Solids Process Supervisor
2. Two members of the Emergency Response Team will investigate the leak. A minor leak is a release of less than 10 lbs while a major leak is a release of more than 10 lbs.
3. Minor leak-Mechanic HI and ERT member to repair.
4. Major leak-initiate chlorine evacuation plan.
The Local Emergency Planning Committees in charge of responding to West Hickman WWTP are familiar with the facility. To prepare for a chlorine or sulfur dioxide leak, the LEPC are trained annually and go through mock dri
lls at the West Hickman facility.
Proper equipment and process controls of the plant facilitate a safe environment at West Hickman Waste Water Treatment Plant. To ensure smooth and continuous accident free operation, the LFUCG and its' employees are involved with every day processes, training and maintenance. The LFUCG recognizes the importance of their operations to the environment and to the surrounding community. To ensure quality management and control, proactive risk management is in effect every hour of the day.
Proper and thorough training of the employees is emphasized greatly. It is important to have well trained and skilled people handling the day to day operations and maintenance checks at the facility on a daily basis. Initially, each employee involved in an operating process shall be trained in an overview of the process and in the operating procedures. For new employees, this shall be done during the new employee orientation process. Refresher training is given e
very year to each employee involved in operating processes to ensure that employees understand and adhere to the current operating procedures. Monthly safety meetings are held on specific topics to all employees at the facility and five minute tailgate meetings are held on a weekly basis on safety related issues. The LFUCG instills the importance of safety and proper procedures to all of its employees.
Safety inspections of the plant are also conducted on a routine basis and are determined and monitored electronically in an LFUCG data base. Once a month, a full safety inspection of the entire plant is conducted. All records are sent to administration and inspection are kept on a monthly file in the administration building.
To date, West Hickman has not had to deal with any offsite consequences related to the facility. Through preventive maintenance and proactive management the LFUCG will continue to offer this quality operation.