Jackson Pike Wastewater Treatment Plant - Executive Summary
The Jackson Pike Wastewater Treatment Plant (WWTP) Chlorination Facility utilizes more than a threshold quantity of chlorine (2,500 pounds) and the Digester System contains more than the threshold quantity of methane (10,000 pounds) in the process. Therefore, this facility is required to submit a Risk Management Plan (RMP) as defined in 40 CFR 68.150 by June 21, 1999 (three years after publication of the final rule). Since public employees are covered under the state of Ohio's Public Employee Risk Reduction Program (PERRP), Jackson Pike WWTP is subject to OSHA's PSM standard (29 CFR 1910) and is therefore subject to Program 3 requirements. |
USEPA's RMP rule requires that covered facilities prepare an executive summary. The following pages represent the executive summary, summarizing the items required as described in 40 CFR 68.155 (a) through (g).
68.155(a) Accidental Release and Emergency Response Policies
Jackson Pike WWTP has emergency procedures in place, as documented in the
facility's Emergency Action Plan. This plan has procedures for both onsite activities and coordination with offsite responders that must be followed in the event of a chlorine or chlorine leak. All personnel involved in handling chlorine or chlorine are trained on chlorine/chlorine safety and accident prevention.
68.155(b) Stationary Source and Substance Handled
The stationary source subject to 40 CFR Part 68 is the Jackson Pike Chlorination Facility and the Digester Gas System. Jackson Pike WWTP is a 68 million gallon per day (MGD) design capacity advanced secondary wastewater treatment plant. Disinfection of the treated wastewater stream involves the use of chlorine. Jackson Pike's Chlorination facility is divided into two separate areas: an outside covered storage area and an indoor Chlorination Room. The storage area can hold three banks of ten one-ton containers of chlorine, however the maximum intended inventory is eighteen one-ton containers of chlorine. The ton container
s store chlorine as a pressurized liquid. The Chlorination room has two scales that can each hold one chlorine container. There is only a single one-ton container of chlorine on-line at any time, and no backup containers are kept inside the Chlorination room. The chlorine is fed as a liquid into an evaporator (one evaporator for each scale), where the chlorine is converted to a gas, fed through a chlorinator, and then pulled under a vacuum and injected into various process waters. The chlorination process is only used for 6 months from May 1 to November 1 each year. Chlorine containers are delivered just before the start of the season, usually mid to late April, and any containers remaining at the end of the chlorination season are shipped back to the supplier as soon as possible. Therefore, the chlorine is on site for no more than seven months per year.
Jackson Pike WWTP is equipped with safety devices to prevent a release and decrease response time in the event of a chlorine l
eak. Several chlorine leak detectors are located throughout the Chlorination Room and Storage area. Audible alarms automatically sound inside and outside the building when chlorine levels reach three part per million (3 ppm). A chlorine scrubber is connected to the Chlorination Room exhaust and has the capacity to contain an overfilled one-ton container of chlorine. The scrubber is automatically turned on when the chlorine leak detectors alarm at 3 ppm. In addition, the chlorinators are vacuum fed. The vacuum condition causes air to be drawn into the unit when a leak occurs, rather than chlorine gas escaping from the system.
Anaerobic digestion is a biological treatment process to stabilize solids removed from the flow stream during the treatment of wastewater. During biological degradation of solids, gas is produced that contains approximately 65% methane. The process is contained in six cylindrical concrete tanks each covered with a duel memebrane hemisphere-shaped cover. T
he covers enable the collection and containment of the gas and provides a mechanism to maintain a constant pressure on the gas system. There are two sludge holding tanks connected to the digester gas lines. Additional methane may accumulate in these holding tanks due to bio-activity of the stored sludge. The digester gas is produced in the anaerobic digesters, and then is piped to any or all of the following endpoints: waste gas flares; burners in the process boilers or burners in the sewage sludge incinerators.
Natural gas may also be combusted in the process boilers and in the sewage sludge incinerators. Natural gas is typically 85% methane. The piping for the natural gas line does connect to the digester gas piping at the two incinerators and the four process boilers that burn both digester gas and natural gas.
Several methane detectors are located throughout the Digester System in tunnels and next to process equipment. These methane detectors signal a caution alarm with me
thane concentrations are 20% of the lower explosive limit (LEL), a warning alarm at 30% of LEL, and full alarm at 40% of the LEL.
68.155(c) Offsite Consequence Analysis
One worst-case release scenario and one alternative release scenario for chlorine has been assessed for the Chlorination Facility. One worst-case release scenario and one alternative release scenario for methane has also been assessed for the Digester Gas System. The Jackson Pike WWTP has chosen to use the US EPA Risk Management Program Guidance for Wastewater Treatment Plants (40 CFR Part 68), US EPA 550-B-98-010, revised March 1999, (WWTP Guidance), as a source to determine off-site consequences. This guidance specifically addresses the chemicals commonly found at WWTPs, such as chlorine and methane in digester gas.
The worst-case release scenarios were determined in accordance with the requirements provided in 40 CFR 68.22 and 40 CFR 68.25(b,c). The worst case release scenario for chlorine is the loss of 2,
000 lbs (largest vessel) in 10 minutes. This results in a release rate of 200 lb/min and does have offsite impacts. The alternative release scenarios were evaluated in accordance with the guidelines provided in 40 CFR 68.22 and 40 CFR 68.28. For the alternative release scenarios, the most likely release scenario is identified based on the results of the Process Hazard Analysis (PHA). However, if this scenario does not reach an endpoint offsite, 40 CFR 68.28 requires a different scenario be chosen that will potentially reach an endpoint offsite. At Jackson Pike WWTP, the most likely release scenario of chlorine identified in the PHA will not reach an endpoint offsite due to the active mitigation of the chlorine scrubber. The chlorine scrubber is connected to the Chlorination Room exhaust and has the capacity to contain an overfilled one-ton container of chlorine. The scrubber is automatically turned on when the chlorine leak detectors alarm at 3 ppm. Due to the definition of al
ternative release in 40 CFR 68.28, Jackson Pike WWTP is required to identify a less likely scenario that results in an endpoint offsite as their alternative release scenario for the RMP. Therefore, the alternative release scenario for chlorine accounts for the passive mitigation of the chlorination building but does not consider the active mitigation of the scrubber. The alternative release scenario for chlorine, that results in offsite impacts, is a flashing liquid release through a 3/16 inch opening from a valve, hose, pipe, or fitting.
The worst case release scenario for methane is a release of 5,082 lbs (largest vessel). The resulting vapor cloud explosion results in offsite impacts. The alternative release scenario for methane, that results in offsite impacts, is a vapor cloud fire from the release of 5,082 lbs through a small hole in the system.
68.155(d) Accidental Release Prevention Program
The Jackson Pike WWTP facility has a documented Prevention Program for the
Chlorination Facility and the Digester Gas System that documents release prevention measures. These prevention measures include elements such as Employee Participation, Process Safety Information, Process Hazard Analysis, Operating Procedures, Training, Contractors, Pre-startup Review, Mechanical Integrity, Hot Work Permits, Management of Change, Incident Investigation, and Compliance Audits.
Jackson Pike WWTP is equipped with safety devices to prevent a release and decrease response time in the event of a chlorine leak. Several chlorine leak detectors are located throughout the Chlorination Room and Storage area. Audible alarms automatically sound inside and outside the building when chlorine levels reach three part per million (3 ppm). A chlorine scrubber is connected to the Chlorination Room exhaust and has the capacity to contain an overfilled one-ton container of chlorine. The scrubber is automatically turned on when the chlorine leak detectors alarm at 3 ppm. In additio
n, the chlorinators are vacuum fed. The vacuum condition causes air to be drawn into the unit when a leak occurs, rather than chlorine gas escaping from the system. Several methane detectors are located throughout the Digester System in tunnels and next to process equipment. These methane detectors signal a caution alarm with methane concentrations are 20% of the lower explosive limit (LEL), a warning alarm at 30% of LEL, and full alarm at 40% of the LEL.
68.155(e) Five-Year Accident History
The Jackson Pike WWTP facility has had no accidental releases of chlorine or methane in the last five years that have resulted in on-site injuries or off-site injuries or other impacts.
68.155(f) Emergency Response Program
The Jackson Pike WWTP is a non-responding facility, as defined by OSHA and USEPA (29 CFR 1910.120 and 40 CFR part 311). Therefore the Jackson Pike WWTP has developed an Emergency Action Plan to ensure employee safety instead of an Emergency Response Program, as allowed by
40 CFR 68.90(b). The Jackson Pike WWTP facility Emergency Action Plan outlines actions required to respond to a chlorine or methane emergency and has coordinated this plan with the City Fire Department and the Franklin County Local Emergency Planning Committee (LEPC). City Fire Department personnel are the designated first responders in the event of a chlorine or methane emergency. Jackson Pike WWTP employees are not designated responders to a chlorine or methane release. As specified in 40 CFR 68.90, Jackson Pike WWTP's Emergency Action Plan meets the exception listed in 40 CFR 68.90(b) and therefore, the facility is not required to have the Emergency Response Program of 40 CFR 68.95.
68.155(g) Safety Improvements
Recommendations for safety improvements were identified in the Process Hazard Analysis (PHA) which was completed per OSHA 29 CFR 1910.119(e) in November of 1998. Recommended improvements were identified in three main categories: Standard Operating Procedures, Maintena
nce, and Training. According to the Process Safety Management Plan, any safety improvements will be investigated concerning their impacts on other systems and/or procedures prior to implementation. Additional recommendations may be made upon review of any accidents, system modifications, and/or when the PHA is updated every five years. A program audit, conducted every 3 years can also produce recommendations for safety improvements or program revisions.