Lake Gaillard Water Treatment Plant - Executive Summary |
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LAKE GAILLARD FACILITY The Lake Gaillard Water Treatment Plant (Lake Gaillard) has one chlorine injection system. The system has six one ton containers of chlorine on line and six containers on standby at any one time. The system is operated under vacuum using gaseous chlorine. There is an automatic switch from online to standby when online containers are empty. The facility has five chlorine detectors to monitor leakage in the chlorine storage and chlorinator rooms. One detector in the chlorine storage room gives a digital readout of the atmospheric chlorine concentration. The sensor is located in the storage room but the readout is located outside this area. Chlorine sensors are located at six inches above floor level in both rooms. The detector will alarm at the main control room panel and automatically start the wet scrubber in the affected area. A chlorine release inside the building will be drawn into the scrubber and neutralized using sodium hydroxide adsorbent. The s crubber has the capacity to adsorb two full one ton containers of chlorine gas (4000 pounds of chlorine). The Lake Gaillard Facility normally stores a maximum of 24 one-ton containers at the site at any one time. All containers are stored indoors in a building with doors, which seal. During chlorine deliveries, the delivery truck backs up to the unloading area. The building doors are opened and the chlorine containers are brought inside. Normally the chlorine storage and chlorinator rooms are sealed with doors that remain closed unless chlorine is being unloaded. All chlorine containers are stored within the chlorine storage room. If a chlorine leak is detected, the chlorine alarm will sound and the wet scrubber starts-up automatically. Air inside the building is evacuated and fresh air is drawn into the building. The scrubber will provide a negative pressure within the building and not allow the chlorine gas to leak outside. The facility also has an emergency response team w ith the proper training and equipment to deal with chlorine releases. The Worst Case chlorine release for this facility assumes that a one ton chlorine container ruptures during unloading outdoors in a rural area. The container discharges a dense gas release under worst case meteorological conditions of F Stability, winds of 1.5 meters per second and ambient temperature of 25 C. All two thousand pounds contained in the one ton container are assumed released over ten (10) minutes. It is only presented for comparative purposes and for non-OSHA facilities to determine under which RMP Program Level the facility fits. The Worst Case Impact Area is three (3) miles in radius (EPA CEPP Risk Management Program Guidance For Wastewater Treatment Plants EPA 550-B-98-010 October 1998). There are about 19,000 people living in the Worst Case release area who could be affected by this release. Located within this area are seven schools. They are the Brushy Plain School, Cedar Lake School, Deer Run School, Ferrara School, Harrison School, Hays School, and North Branford High School. The worst case impact radius includes Bare Plain, Mill Plain and Saint Agnes cemeteries, Saint Augustine's Church, four dams, a portion of Interstate Highway 95, and a portion of the New Haven Trap Rock Railroad. Also in this area are several recreational areas and parks, including Lake Gaillard, Lake Saltonstall, and several small ponds and brooks. The Most Likely release case is that no chlorine will be released outside of the chlorinator building. As indicated above there are two redundant levels of safety controls at the facility should a release occur. First the wet scrubbing system would prevent any released chlorine gas from exiting the building. Second, an alarm would be sounded and the facility's emergency response team would be at the location within a few minutes to shut the system down if all of the automatic controls failed. In order to evaluate a Most Likely release scenario that results in a release that is not contained, it is necessary to assume that all automatic controls fail and the on-site response team must shut off the leaking chlorine container. Under those unlikely assumptions, the following release scenario was addressed. A steady-state leak of up to 5 pounds per minute of chlorine either as a gaseous or a two-phase release. It should be noted that a completely filled one-ton container has a maximum gaseous discharge rate of about 500 pounds per day (0.35 pounds per minute). Significant gaseous discharges above this rate will result in the container freezing up and the discharge stopped. It is also assumed that the container discharges a dense gas release under meteorological conditions of D Stability and 3.0 meters per second at an ambient temperature of 25 C. The Most Likely Case Impact Area is a tenth (0.1) of a mile in radius (EPA CEPP Risk Management Program Guidance For Wastewater Treatment Plants EPA 550-B-98-010 October 1998). Th ere are about 27 people living in the Most Likely Case release area who could be affected by this release. There are no schools, hospitals, parks or other sensitive receptors located within this area. The facility has not had an accidental release of chlorine from this covered process in the five years prior to the submissions of this Risk Management Plan (RMP). |