City of Moore Haven Water Treatment Plant - Executive Summary
Executive Summary |
The City of Moore Haven is a small, rural community in Glades County. The City of Moore Haven provides water service to approximately 2,000 people in and around the City of Moore Haven. The City of Moore Haven owns and operates a water treatment plant (WTP) located at 4725 U.S. 27, Moore Haven. The WTP site is approximately 26.46 acres and is located approximately 9.3 miles from the center of the City. The WTP uses chlorine gas as a disinfectant and to remove organics.
The WTP has a dedicated Chlorine Building located on-site. Chlorine gas is stored on the site in three one-ton containers. The maximum chlorine inventory at the site is 6,000 lbs. The following characteristics of the City of Moore Haven WWTF subject the facility to Rule 40 CFR Part 68, which requires development and implementation of a Risk Management Program (RMP):
q The facility is a stationary source; and
q The facility handles, uses, and stores a toxic substance regulated by 40 CFR 68.130
(e.g. chlorine gas); and
q The handling, use, and storage of chlorine meet the definition of a "process;" and
q The chlorine is present in quantities above the threshold quantities established by the Rule (e.g. 2,500 lbs for chlorine).
The City of Moore Haven WTP is considered by the regulation to be a Program Level 3. This is the highest level program and requires the most extensive risk management plan. The criteria for Program Level three follow:
q Public receptors are within the distance to the endpoint for a worst-case scenario release; and
q The process is subject to the OSHA PSM standard since the chemical use, chlorine is included in Appendix A of 29 CFR 1910.119 and the quantity stored and handled exceeds the threshold quantity for chlorine of 1,500 lbs.
The Level 3 Risk Management Program is basically comprised of three sections: Hazard Assessment; Prevention Program; and Emergency Response Plan.
The Hazard Assessment for a toxic gas involves modeling the consequences o
f at least two release scenarios, the worst-case and an alternative case. The worst case scenario involves the largest container of the regulated substance being released into the environment over the period of ten minutes. The Environmental Protection Agency's (EPA) air model RMP Comp* Version 1.06 was used to simulate the worst case scenario. The model uses input data to generate the estimated distance from the point of release to the toxic endpoint. The toxic endpoint is defined for chlorine gas as the point where the concentration of chlorine gas in the air is 0.0087 mg/L. For the worst case scenario, the release rate was 110 lbs/minute and the distance to the toxic endpoint was 2.2 miles (distance from the chemical handling facility).
The alternative case release scenario is one that is more likely to occur than the worst-case and has off-site consequences (e.g. the distance to the toxic endpoint is further than the distance to the site boundary). In the alternative releas
e case, the RMP Comp* model allows the user to enter more site specific data, including consideration of active mitigation devices (these were not allowed for the worst case scenario). Two alternative case release scenarios were considered for the Dunes WWTF, both resulted in the distance to the toxic endpoint of 0.3 miles (1,584 feet) or less.
The second section of the Risk Management Program is the Prevention Program. This section is the heart of the RMP and account for a large portion of the document's thickness. The Prevention Program includes detailed information and discussion regarding the management system at the facility; five-year accident history; process safety information review; process hazard analysis; procedures for operation, training, maintenance, management of change, compliance audit, incident investigation, employee participation, and hot work; and contractor selection. The Prevention Program provides documented guidance to facility staff regarding day to day
operation regarding chlorine storage, handling, and use. The Prevention Program is intended to educate staff and thereby reduce the probability of release due to improper operations, inadequate maintenance, ignorance of the hazards, or lack of safety awareness.
The City of Moore Haven has employed chlorine gas as a disinfectant at the current WTP since 1992. There have been no uncontrolled releases in chlorine gas which caused injury or death to on-site or off-site persons. The chlorination system which uses chlorine gas at the facility is vacuum operated. The system employs active mitigation devices which include vacuum induced gas withdrawal, fail-close valves (vacuum regulator), secondary check valves, isolation valves, sensors (high/low vacuum, low water pressure, chlorine gas detector) which are connected to an alarm system, pressure relief valves, ventilation systems, and automatic container switchover system(via vacuum regulator). These active mitigation devices have attr
ibuted to the successful and safe operation of the system since startup. The existing system is capable of continuing to provide safe utilization of chlorine gas as a disinfectant. Improvements to the facility will include continued maintenance of the existing system and investigation into new technologies as they are developed.
The third component of the Risk Management Program is the Emergency Response Plan. The emergency response plan documents the activities to be performed in the event of an uncontrolled release of chlorine gas into the environment. The plan provides detailed how-to information regarding movement, notification, personnel accountability, site control, release remediation, first aid, personal protective equipment, and coordination with professional emergency responders. The facility staff is primarily responsible for protection of on-site persons and notification of outside organizations which will takes steps to provide protection for off-site persons. The G
lades County Emergency Management Office will coordinate off-site activities and release remediation once contacted by the 9-1-1 dispatcher.