City of Ravenna Water Treatment Plant - Executive Summary |
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This current submission of RMP program is a modification of the prior program submission sent to the US Environmental Protection Agency on 05/25/1999. It is being modified to address the requirements of the Ohio EPA as requested in a 11/08/2000 letter to Mark Bregant in which the Ohio EPA, Division of Air Pollution Control requested that the Program Level be changed from Program Level 2 to Program Level 3. It also adresses the Chlorination system upgrade that occured after the last RMP submission. 1 The City of Ravenna Water Treatment Plant (RWTP) Accidental Release Policy involves a unified approach that integrayes technology, procedures and management practices. All applicable procedures of the U.S. Environmental Protection Agency (USEPA) Prevention Program are adhered to. The Ravenna Water Treatment Plant Emergency Reponce Program involves the preperation of responce plans which are tailored to the Ravenna Water Plant Facility and to the emergency responce services available in the community, and is in compliance with the USEPA Emergency Program requirements. 2 The Ravenna Water Treatment Plant was built and put on line in June 1984 to supply water to the City of Ravenna residences, part of Ravenna Township and Rootstown Water Service Company to the south. The water system currently serves the entire City of Ravenna, parts of Ravenna Township and approximately one third of the supply to the Rootstown Water Service Company. An Emergency Water line to the City of Kent to the west is currently being engineered and an agreement to provide water to Portage County is benig worked on. The Water Plant is located at 5383 Lakewood Road next to the Lake Hodgson Recreational Facility and Reservoir. The plant includes a chlorination room, that containes liquid chlorine cylinders, a chlorinator and various safety devices. The amount of chlorine handeled is four one ton containers. The chlorination system was upgraded form a pressure system to a vacuum system in the summer o f 1999 due to safety concerns. The chlorinator and equipment room is normally unmanned and can only be entered from a seperate outside entrance apart from the main building. Water Treatment Operators visit the facility or room daily per shift and respond to any trouble alarms which may occur. 3 The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as "worst case scenario" and alternate 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 inspecified failure. The alternative scenario is defined as "more likely to occur than worst case scenario". Atmospheric dispersion modeling has been performed to determine the distance traveled by the chlorine released before it's concentration decreases to the "toxic end point" selected by EPA of 3 ppm, which is the Emergency Responce Planning Guideline L evel 2 (ERGP-2). This is defined by the American Industrial 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 experiecing or developing irreversable or other serious health effects or symptoms which could impair an individual's ability to take corrective action". The residential population within a circle with a radius corresponding to the toxic end point distance has been defined "to estimate the population potentially affected". The worst case scenario at the Ravenna Water Treatment Plant involves a failure of four ton containers which could be connected concurrently (a total of 8,000 lbs of chlorine). The offsite consequence analysis for this scenario was performed for two sets of conditions. The first set followed conditions predefined 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 end point and c onsideration of the population residing within a full circle with a radius corresponding to the toxic end point distance. EPA set these conditions to facillitate the performance of the offsite censequense analysis, however, the assumptopn used may be unrealisticbecause: a. Only a fraction (about 26% of the total) of the compressed liquified chlorine released to the atmosphere flashes as a vapor. The remaining unflashed liquid forms a liquid-droplet aerosols. This results in the formation of a very dense chlorine cloud consisting of vapor and liquid droplets, with dispersion chasteristics significantly different than a cloud consisting of only chlorine gas b. It is not appropriate to compare a 10-minute release to a one hour average standard. The 3 ppm one-hour ERPG can be modified using available time of exposure/concentration relationships to match the ten minute release time; the value obtained is 7.3 ppm. c. Only the population within an elliptical plume extending downwind of the release point is potentially affected. This plume area or footprint, is approximately 11% (one tenth) of the area of the full circle. EPA-mandated meteorlogical conditions, namely stability F, wind speed of 1.5 m/sec. and an average humidity of 63% were used for both sets. When atmospheric dispersion modeling for the worst case scenario was performed using EPA assumptions, a distance to the toxic end point of 1.9 miles and an estimated residential population affected of 4,000 was obtained. When the same modeling was performed with the second set of conditions, namely using a vapor/aerosol release, a 10-minute average ERPG-2 of 7 ppm and a consideration of plume footprint only, a distance to toxic endpoint of 0.1 miles and an estimate of population of 20 resulted. The alternative release scenario involves the rupture of the fleable connections (pigtails) connected to two ton containers, possibility due to an additional mitigation system installed in the conversion of the pre-existing chlorine to a remote vacuum type, with pressurized chlorine gas piping replaced with vacuum piping. This conversion significantly reduced the amount of chlorine released in case of a pigtail rupture. 4 The General Ravenna Water Treatment Plant accidental release prevention program is based on the following key elements: -Process Safety Information -Process Hazard Analysis -Operating Procedures -Training -Mechanical Integrity -Management of Change -Prestartup Review -Compliance Audits -Incident Investigation -Employee Participation Plan -Hot Work Permit -Contractors Chemical-specific prevention steps include avalibility of self-contained breathing apparatus (SCBA) worn by the operators during connection/disconnection of chlorine supply, awareness of hazardous and toxic properties of chlorine, and the presence of externally mounted detector for the chlorine room. 5 No accidental releases of chlorine have occured at this facility (RWTP) in the past 5 years. 6 The RWTP has an emergenc y responce program, which has been coordinated (reviewed) by the City of Ravenna Fire Department, which is a member of the local Emergency Responce Planning Committee (LEPC). This program includes an emergency responce decision tree and notification program. Emergency responce drills and drill evacuations are conducted every 12 monts; energency operating and responce procedures are also reviewed at this time. 7 Three (3) changes to improve safety (recommended actions) were identified in April 1999. These recommended actions have now been evaluated and implimented as required. |