Taunton Water Treatment Facility - Executive Summary
Accidental Release Prevention and Emergency Response Policies |
The Taunton Water Treatment Facility (WTF) follows guidelines established by the Chlorine Institute, Inc. (CI) and applicable design codes and standards, to ensure adequate accidental release prevention for its chlorine disinfection facilities. The Chlorine Storage Room was designed and constructed in accordance with CI recommendations, as well as local and state building code requirements. Chlorine piping and equipment design also complies with CI criteria, and appropriate ASTM specifications. WTF staff follow CI procedures for operation and maintenance of the chlorination facility, and receive training in these procedures. In the event of a release from a ton container, the WTF has a CI "Kit B" which is designed to contain most leaks from such containers. All of these measures have resulted in a successful accidental release prevention program for the WTF's chlorination facility.
The Lakeville Fire Department has i
ncluded the chlorination facility at the Taunton WTF in its community Emergency Response Plan (ERP), which includes an ERP that is specific to the WTF. The ERP includes means of informing the public of accidental releases of chlorine. In case of a chlorine release, the WTF notifies the Lakeville Fire Department and the Emergency Management office located at the Taunton City Hall.
Stationary Source and Regulated Substances Handled
The stationary source is the Taunton Water Treatment Facility (WTF), a municipally owned and operated water treatment plant located in Lakeville, MA. The only substance at the WTF which falls under the 40 CFR 68 regulations is chlorine, which is used for the purpose of pre- and post - chlorination. Raw water is pre-chlorinated to reduce or eliminate algae and bacterial growth, to assist in the removal of taste, odor, and color, and to oxidize iron and manganese to an insoluble form. Post-chlorination is provided for filtered water effluent disinfection
. The WTF keeps two ton containers on-line and stores two ton containers inside the Chlorine Storage Room.
Worst-Case Scenario and Alternative Release Scenario
In accordance with EPA's Risk Management Program Offsite Consequence Analysis, the worst- case scenario for the WTF consists of the release of the entire contents of a full, one-ton container of chlorine over a ten-minute period at an outside location. This release, taking into account weather conditions of a wind speed of 1.5 meters/second, "F" stability class and an ambient temperature of 25 degrees Celsius, results in a distance to toxic endpoint of 1.3 miles for an urban setting. No active or passive mitigation systems were considered for this scenario.
For the alternative release scenario, several options were investigated. One of the more conservative alternatives, which was reported here, was the release of gaseous chlorine from a 0.75-inch diameter hole in a full ton container. The release was assumed to occur a
s the result of the 0.75-inch valve on the container being sheared off. This scenario resulted in a release of chlorine vapor inside the building, and then to the outside air, assuming the door to the building was open. The parameters which we considered to determine the distance to toxic endpoint were the "average" weather conditions for the alternative release scenario provided in the above guidance of 3 meters/second, "D" stability class, and an ambient temperature of 25 degrees Celsius, and the use of the building housing the ton containers as a passive mitigation system.
Applying these parameters resulted in a distance to toxic endpoint of 0.62 miles in an urban setting, about one-half that of the worst-case scenario.
General Accidental Release Prevention Program and Chemical-Specific Prevention Steps
As described previously, the design, operation and maintenance of the chlorine disinfection facility at the WTF has been in accordance with CI guidance documents and applicable
industry standards and codes. The WTF has contracts with equipment suppliers to ensure that highly skilled individuals maintain equipment on a regular basis, and that these same individuals instruct WTF maintenance staff if any equipment modifications or improvements are made. The chlorine supplier also provides refresher training to operators and maintenance staff on a regular schedule. In addition, the WTF benefits from cross-training, as several employees are knowledgeable about the operation and maintenance of the chlorination process. A sound design basis and scheduled maintenance and operator training have been key to the highly successful operation of the chlorine disinfection facility.
Five-Year Accident History
There have been no accidental releases of chlorine in the last five years.
Emergency Response Program
The WTF does not have its own written Emergency Response Plan, but is included in the Town of Lakeville's Emergency Response Plan. In case of a chlorine relea
se, the WTF notifies the Lakeville Fire Department and the City of Taunton Emergency Management office.
Planned Changes to Improve Safety
The whip from the chlorine ton containers was formerly connected to valves attached to a cast iron header which served the ton containers. In 1994, the cast iron header was replaced with a new schedule 80 polyvinyl chloride (PVC) header, and the valves were attached directly to the chlorine ton containers. These measures were taken to improve safety at the WTF. Under this new system, if the connecting whip from the ton container ruptured or was disconnected while the container was in use, the valves on the ton container would automatically shut off the source of chlorine.
Because of the safety concerns associated with the transportation and handling of elemental chlorine, the WTF is planning to replace the current chlorine disinfection process with a sodium hypochlorite disinfection system.