Broad Creek II WTP - Executive Summary
Risk Management Plan Executive Summary |
Broad Creek II Water Treatment Plant
The Anne Arundel County Broad Creek II Water Treatment Plant (BC2WTP) located in Annapolis, Maryland is designed to treat up to 4 million gallons of drinking water per day. The BC2WTP provides drinking water for over 20,000 people in Anne Arundel County. The facility is designed to primarily remove solids and metals from ground water before providing the water for drinking water purposes in the distribution system in South Central Anne Arundel County. As part of this treatment system, chlorine is used to effect disinfection. Chlorine is stored at the facility in one-ton cylinders. Chlorination is a common process used by many water treatment plants in the United States.
Anne Arundel County Department of Public Works personnel have designed and implemented a Process Safety Management (PSM) program to ensure safe operation of the chlorination process. As part of the PSM program, a process hazards analysi
s has been conducted to evaluate the safety of the process. The minimum amount of chlorine needed to meet this facility's Safe Drinking Water Act requirements is stored in an enclosed brick building. Standard operating procedures have been written for the safe handling and use of chlorine cylinders. Annual training is provided to facility personnel in the safe handling and use of chlorine, and a strict preventive maintenance program has been implemented for the process. A monitor has been installed in the building to detect any leaks. If a leak is detected, the building ventilation system shuts off automatically, preventing any chemical from escaping from the storage building. In the event of a leak, Anne Arundel County Hazardous Materials (HAZMAT) unit is contacted and, if necessary, they will slowly and safely mitigate the situation under controlled conditions. No releases of chlorine have occurred at the facility that have resulted in any off-site impacts.
t of this Risk Management Plan, BC2WTP evaluated scenarios that potentially could result in a release of chlorine from the facility. One scenario evaluated an uncontrolled release of the entire contents of a one-ton cylinder of chlorine. This release scenario, which was approximated by using the Anne Arundel County HAZMAT unit's computerized air dispersion models, indicated that such an unmitigated "worst-case" release would have off-site impacts.
Measures including leak detection alarms and automatic ventilation shut off, are installed at the storage room to mitigate a potential leak, so it is unlikely that the entire contents of a one-ton cylinder would be released without being safely contained in the storage building. Alternative release scenarios were also conducted to evaluate "more likely" releases from the chlorination process. Based on the process hazard analysis conducted at the BC2WTP, a likely scenario is a leak of chlorine at the connection on a one-ton cylinder. Mo
deling conducted by the Anne Arundel County HAZMAT unit indicated that such a leak would have some off-site impact.
Building mitigation was not considered in the modeling evaluations of either scenario. Therefore, the results overestimate the actual area that would be affected by a potential leak. Coordination between the Anne Arundel County Fire Department HAZMAT unit and facility personnel ensures safe facility operation as well as emergency response to any chemical situation. This relationship between the HAZMAT unit and BC2WTP personnel has fostered open communication and coordination of emergency response procedures and the safe handling and storage practices for chlorine. In addition, HAZMAT unit personnel were directly involved in the development of this Risk Management Plan for the BC2WTP, both in conducting release scenario modeling and by providing input to the emergency response program at the facility. Through this cooperative effort and the ongoing process safety m
anagement procedures at the facility, Anne Arundel County will continue to operate the BC2WTP in an environmentally safe manner.