Council Bluffs Water Works - Executive Summary |
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Accidental Release Prevention and Emergency Response Policy Chlorine is commonly used in water treatment operations such as CBWW's facility in Council Bluffs. CBWW recognizes that with chlorine use there are necessary safety precautions in order to protect the safety of their employees and of the nearby community. It is CBWW's policy to design and operate a safe facility. This is accomplished through the experience and training of our personnel. Our emergency plan includes procedures for notification of local authorities and potentially affected neighbors. Employees are trained to handle minor leaks. Source and Regulated Substances The plant provides water for the city of Council Bluffs and surrounding areas. The main water supply is the Missouri River. In addition, the plant has two groundwater wells. The intake water is treated in preliminary settling basins to remove sand and heavy silt. Chemicals are added at the rapid mixers and allowed time to react and form floc (ag gregate particles) in the flocculation basins. Additional solids are removed at the sedimentation basins. The pH is adjusted in the recarbonation chambers and then the water is filtered. The treated water is stored prior to distribution. Council Bluffs Water Works (CBWW) uses chlorine, chlorine dioxide, and ammonia for disinfection in the water treatment process. Chlorine is the primary disinfectant. The current chlorine handling and storage facilities were constructed in 1997. The chlorine system operates on valve mounted vacuum regulators. The facility uses one-ton containers of chlorine which are delivered by truck transport. A two-ton capacity hoist is used to transfer the containers between the storage area and the dock. The maximum intended inventory for chlorine is 16,000 pounds. Typical inventory is 10,000 to 12,000 pounds of chlorine. Chlorine is the only regulated chemical that is on site above the process safety management (PSM) and risk management (RM) program thr esholds. Though not above the PSM or RM thresholds, chlorine dioxide and ammonia are also addressed in the PSM and RM programs in regards to general duty requirements. Alternate disinfectants are chlorine dioxide and chloramines. Since chlorine dioxide is an unstable gas, it is generated on site by reacting chlorine and sodium chlorite solution. The chlorine dioxide generator and associated equipment are located in a dedicated room installed during the 1997 construction project. Chloramines are formed from the reaction of chlorine (hypochlorite ion acid) and ammonia. Ammonia is applied through ammonium hydroxide. The ammonium hydroxide is applied as purchased with no mixing or modification. Worst-Case Release Scenario Chlorine is stored as pressurized liquid in one-ton containers. Consistent with regulatory requirements for this process, the worst case release is the greatest amount in a single vessel. The worst case release quantity for CBWW is the amount held in a full one-to n container. The full container (one ton chlorine) is assumed to be released over a time frame of 10 minutes. No administrative controls or mitigation were considered for the worst case release of chlorine. Due to the presence of buildings and trees in the vicinity of the chlorine process, the topography is urban. The resultant radius of influence for the worst case scenario is 1.3 miles. Alternate Release Scenario The alternate release scenario for the chlorine process assumes a fusible plug fails due to corrosion, thus releasing liquid chlorine. The plug diameter is 3/4 inches; however, the diameter of corroded area is assumed to be 3/16 inches. Though it is likely that the container will not be full, the scenario is based on a full container. The alternate release for CBWW is the amount held in a ton cylinder of chlorine. Chlorine containers are stored inside closed building and the release is assumed to be mitigated (a release in enclosed building). The release occurs und er typical conditions (including wind speed). This release rate is 88 lb/min. The release is assumed to occur over a 23-minute period and has an endpoint of 0.1 miles. Administrative Controls and Mitigation Measures The chlorine building is divided into separate areas for storage, chlorination, and chlorine dioxide. The structure is complete with a ventilation system. The storage and chlorination rooms are equipped with chlorine gas detectors. Audible alarms alert operators if there is a chlorine gas leak. A remote signal is sent to the control room SCADA system to help alert the operator of a chlorine leak. Each of these rooms has an external entrance which is locked to prevent unauthorized entry. There are no flammable or combustible materials stored in these areas. CBWW has policies and procedures in place to decrease the likelihood a chlorine release event and to minimize the consequence if there is a release. Operators are trained in the proper usage and handling of chlo rine. General Release Prevention Program and Prevention Steps The chlorine process complies with both the EPA prevention program level 3 requirements and the OSHA PSM requirements. The facility is operated according to manufacturer recommendations and Chlorine Institute recommendations. Five Year Accident History CBWW did not have any releases from covered processes that resulted in deaths, injuries, or significant property damage on site, or known offsite deaths, injuries, evacuations, sheltering in place, property damage, or environmental damage. Emergency Response Program The emergency action plan has been coordinated with Pottawattamie County Emergency Management Agency. Planned Changes The current chlorine process (a vacuum system) was installed in 1997. This system replaced the old pressurized system. CBWW continues to improve their process safety management program. |