Flint Lake Treatment Plant 2 - Executive Summary
a. The Valparaiso Water Department (VWD) accidental release prevention policy involves an approach that intergrates technologies, procedures and management practies. All applicable procedures of the US Environmental Protection Agency Prevention Program are adhered to. The VWD Release Plan uses the emergency response services available in the community, (Local Fire Dept. & HAZMAT). |
b. The Flint Lake Treatment Plant 2 was built in 1993 to disinfect and treat ground water from eight deep wells and is located at 2101 Wesley Road. This treated water serves the City of Valparaiso and the Lakes Area Conservancy District area. The treatment plant includes a chlorination room, which contains chlorine containers, V-notch chlorinators, a motor control room, which contains flow recorders, various electrical panels, a filter room, which contains horzontal pressure filters, and filter control panel, a pump room, which contains high lift pumps, and safety equipment, and chemical storage rooms, wh
ich contain potassium permanganate, orth-poly phosphate, and fluoride. The amount of chlorine handled is four one ton containers. The facility is unmanned with water treatment personal visting the facility daily and responding to any trouble alarms which may occur.
c. The Off-Site Consequence Analysis includes consideration of two chlorine release scenarios, identified as "Worst Case Release" and "alternative scenario". The first scenario is defined by EPA, which states that "the owner or operator shall assume that the maximum quantity in the largest vessel is released as a gas over 10 minutes", due to an unspecified failure. The alternative scenario is defined as "more likely to occur than the worst case release scenario".
Atmospheric dispersion modeling had to be performed to determine the distance traveled by the chlorine release before its concentration decreases to the "toxic endpoint" selected by EPA of 3 PPM, which is the Emergency Response Planning Guideline Level 2 (ERPG-2)
. This is defined by the American Hygiene Association (AIHA) as the "maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour wiyhout experiencing or developing irrevesible or other serious health effects for symptoms which could impair an individual's ability to take protective action". The residential population within a circle with a radius corresponding to the toxic endpoint distance had to be defined to estimate the population potentially affected.
The worst case release scenario at Flint Lake Treatment Plant 2 involves a failure of a one ton container which is connected by a vacuum piping system to chlorinators (a total of 2,000 lbs of chlorine). The Off-Site Analysis for this scenario followed conditions pre-defined by EPA, namely the release of the entire amount as a gas in 10 minutes, use of the one hour average ERPG-2 as the toxic endpoint, consideration of the opoulation residing within a full circle with a r
adius corresponding to the toxic endpoint distance. EPA set these conditions to facilitate the performance of the Off-site Analysis; however, the assumptions used may be unrealistic because:
(1) Only a fraction (about 26% of the total) of the compressed liquefied chlorine released to the atmosphere flashes as a vapor. The remaining unflashed liquid forms liquid-droplet aerosols, resulting in the formation of a very dense chlorine cloud consisting of vapor and liquid droplets, with dispersion characteristics significantly different than for a cloud consisting only of chlorine gas.
(2) Only the population within an elliptical plume extending downwind of the release point is potentially affected. This plume area, or footprint, is approximately 6% (one twenth) of the area of the full circle.
EPA-mandated meteorolgical conditions, namely Stability F, wind speed of 1.5 m/sec, highest daily maximum tempature (116 degrees F), and average humidity (65%) was used.
When atmospheric disper
sion modeling for the Worst Case Scenario was performed using EPA's RPM*COMP Program, a distance to toxic endpoint of 0.9 miles and an estimate of residential population potentially sffected of 1,141 was obtained.
The Alternative Scenario invloves a release from a horizontal cylinder tank occuring through a valve in the top of the tank. The amount of chlorine released is 317 lbs, at an average rate over one hour (the duration of the release) of 10.5 lbs/min. When atmospheric dispersion modeling was performed using EPA's RMP*COMP Program, a distance to toxic endpoint of 0.1 miles and an estimated of residential population potentially affected of 41 was obtained.
Actuation of the chlorine detector is an active mitigation measure considered. An additional mitigation system installed was the conversion of the existing chlorinators to a remote vacuum type, with all pressurized chlorine gas piping replaced with vacuum piping. This change reduced the potential for a chlorine gas leak from
a pigtail rupture by making the system operate under a vacuum.
d. The general accidental release program is based on the following key elements:
(1) Training of treatment plant personnel.
(2) Preventive maintenance program.
(3) Use of state-of-the-art process and safety equipment.
Chemical-specific prevention steps include availabilty of self-contained breathing apparatus (SCBA), chlorine container emergency repair kits, awareness of the harzerdous and toxic properties of chlorine, presence of chlorine monitors, and outside warning lights.
e. No accidential release of chlorine have occured at this facility in the past five years.
f. The facility has a Chlorine Release Plan, which has been reviewed by the Valparaiso Fire Department.