Airport Treatment Plant - Executive Summary |
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a. The Valparaiso Water Department (VWD) accidental release prevention policy involves an approach that intergrates technologies, procedures and management practices. All applicable procedures of the U.S. Environmental Protection Agency Prevention Program are adhered to. The VWD Release Plan used the emergency response services available in the community, (local Fire Dept. & County HAZMAT). b. The Airport Treatment Plant was built in 1966 to disinfect and treat ground water from seven deep wells and is located at 3800 Redbow Drive. This treat water serves the City of Valparaiso and the surrounding areas. The treatment plant includes a chlorination room, which contains chlorine containers, V-notch chlorinators, a filter room, which contains four horizontal pressure filters, and chemical storage of Potassium Permanganate and Ortho-poly Phosphate, a motor control room, which contains high lift pumps, various electrical panels, and safety equipment, and a chemical storage room that conta ins fluoride. The amount of chlorine handled is three 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 the 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 unspecified failure. The alternative scenario is defined as "more likely to occur than the worst-case 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 the EPA of 3 PPM, which is the Emergency Responce 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 without experiencing or developing irreversible 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 radius corresponding to the toxic endpoint distance had to be defined to estimate the population potentially affected. The worst-case release scenario at the Airport Treatment Plant involves a failure of a one ton-container which is connected by a vacuum piping system to the chlorinators (a total of 2,000 lbs of chlorine). The Off-site Consequence Analysis 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 distance. Epa set these conditions to facilitate the performance of the Off-site Consequence 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-droplets aerosols, resulting in the formation of a very dense chlorine cloud consisting of vapor and liquid droplets, with dispersion caracteristics significantly different than for a cloud consisting only of chlorine gas. (2) Only the population within an ellipitcal plume extending downwind of the release is potentially affected. this plume area, or footprint, is approximately 6% (one-twenth), of the area of the full circle. EPA-mandated meterological conditions, namely stability F, wind speed 1.5m/sec, highest daily maximum temperture (116 degrees F), and average humidity (65%) was used. When atmospheric dispersion modeling for Worst- case was performed using EPA's RMP*Comp program, a distance to toxic endpoint of 2.20 miles and an estimate of residential population potentially affected of 15,337 wa s obtained. The Alternative Scenario involves the release from a horizontal cylindrical tank occurring through a valve in the top of the tank. The amount of chloine 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 estimate of residential population potential affected of 7 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, all pressurized chlorine gas piping was replaced with vacuum piping. The change reduced the potential for a chlorine leak from a pigtail rupture by making the system operate under a vacuum. d. The general accidental prevention program is based on the following key elements: (1) Training of treatment plant personnel. (2) Preventiv e maintenance program. (3) Use of state-of the-art process and safety equipment. Chemical-specific prevention steps include availability 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 accidental release of chlorine have occured at this facility in the past five years. f. The facility has a Chlorine Release Plan, which has been review by the Valparaiso Fire Department. |