Mason Water Treatment Plant - Executive Summary
'68.155(a) Accidental Release and Emergency Response Policies |
The Mason Water Treatment Plant (WTP) has emergency response procedures in place, as documented in the facility's Emergency Action Plan. City staff responsible for the operation and maintenance have endorsed this Emergency Action Plan. The City of Mason WTP has procedures in place, including onsite activities and coordination with offsite responders, that must be followed in the event of a chlorine leak. All personnel involved in handling chlorine are trained with regard to chlorine safety and accident prevention.
'68.155(b) Stationary Source and Substance Handled
The stationary source subject to 40 CFR Part 68 is the chlorination system at the City of Mason WTP. The Mason WTP is a facility that uses pressure filters to remove iron and manganese from groundwater. Chlorine from one-ton containers is used for prechlorination and disinfection. Currently, Mason WTP has an average daily plant production rate of 3.2 mgd a
nd peak production of 5.5 mgd. Once the current expansion is complete, Mason WTP will have a total filtering capacity of 7.0 mgd and a firm treatment capacity of 6.1 mgd.
Located in the Filter and Administration Building, the Mason WTP chlorination system consists of three rooms: the Chlorine Storage Room, the Chlorine Feed Room, and the Chlorine Scrubber Room. The western portion of the Chlorine Storage Room contains a loading/unloading area and a storage area, while the eastern portion contains the two active one-ton chlorine containers that feed chlorine to the chlorinators. A 2-ton crane with a monorail unloads the one-ton containers from the delivery truck to their appropriate place in the storage area. The WTP keeps two backup containers in the storage area and has space for empty one-ton containers on two remaining sets of roller chocks. The maximum inventory of chlorine in the Chlorine Storage Room and onsite is 4 one-ton containers of chlorine, approximately 8,000 lbs o
At the Mason WTP, a vacuum regulator, connected to the container valve of each active container, feeds pressurized liquid chlorine to the chlorinators as a gas. Vacuum chlorine feed reduces the likelihood of a release into the environment. The two vacuum regulator valves are then connected into the PVC manifold piping. Extending from the Chlorine Storage Room to the Chlorine Feed Room, the manifold piping conveys the gaseous chlorine to the eight chlorinators and eight injectors provided for solution chlorine feed at various process locations.
The Chlorine Storage Room and the Chlorine Feed Room each have a chlorine leak detector to alert employees of any exposure in the unlikely event of a chlorine leak. In the Chlorine Feed Room the chlorine leak detector is located next to the chlorinators. In the Chlorine Storage Room the detector is located next to the active chlorine containers. An audible alarm automatically sounds inside and outside of the building when chl
orine levels reach 1 ppm. The leak detectors also alert the main SCADA system, turn off the ventilation in the chlorine system rooms, and turn on the emergency chlorine scrubber.
'68.155 (c) Offsite Consequence Analysis
As a Program 3 Process with one toxic gas, one worst-case release scenario and one alternative release scenario will be assessed for the chlorine system rooms. The City of Mason WTP 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, October 1998, (WWTP Guidance), as a source to determine offsite consequences. This guidance specifically addresses the chemicals commonly found at WWTPs. Since the chlorination process for WTPs is similar to the chlorination process at WWTPs, this guidance document is applicable to the Mason WTP's chlorination process.
The worst-case release scenario was determined in accordance with the requirements provided in 40 CFR 68.22 and 40 CFR 68.25(b,c). For
the Mason WTP facility the worst-case scenario is a total release from one of the one-ton containers of chlorine (greatest amount held in a single vessel). The facility is also required to complete at least one alternative release scenario. The alternative release scenario was evaluated in accordance with the guidelines provided in 40 CFR 68.22 and 40 CFR 68.28. Although the chlorination system is enclosed and the WTP has a chlorine scrubber, neither of these mitigation systems were considered in the analysis of the alternative release scenario.
'68.155(d) Accidental Release Prevention Program
The Mason WTP facility has a documented Prevention Program for the chlorination facility 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, Inci
dent Investigation, and Compliance Audits.
Mason WTP is equipped with leak detection monitoring to decrease response time in the event of a chlorine leak. One chlorine leak detector is located next to the active containers in the Chlorine Storage Room and the other chlorine leak detector is located next to the Chlorinators in the Chlorine Feed Room. An audible alarm automatically sounds inside and outside of the building when chlorine levels reach 1 ppm. Also, Mason WTP employees who are involved in chlorine operations are trained in specific procedures regarding handling and storage of chlorine at the facility.
'68.155(e) Five-Year Accident History
The Mason WTP facility has had no accidental releases of chlorine 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 City of Mason WTP is a non-responding facility, as defined by OSHA and USEPA (29 CFR 1910.120 and 40 CFR part 311). Therefo
re, the City of Mason WTP 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 Mason WTP Emergency Action Plan outlines actions required to respond to a chlorine emergency and has coordinated this plan with the City of Mason Fire Department and the Turtlecreek Township Fire Department personnel as the designated first responders in the event of a chlorine emergency. Mason WTP employees are not designated responders to a chlorine release. As specified in 40 CFR 68.90, Mason WTP'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
Conducted in May 1999 per OSHA 29 CFR 1910.119(e), the Process Hazard Analysis (PHA) identified recommendations for safety improvements in five areas: Alternative Disinfection Methods, Standard Operating Procedures, Mainten
ance, Training, and the Emergency Action Plan. According to the Process Safety Management Plan, any safety improvements will be investigated concerning their impacts on other systems and/or procedures before implementation. Additional recommendations may be made upon review of any accidents and/or every five years when the PHA is updated.