Blomquist (J Avenue) Water Treatment Plant - Executive Summary |
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The Cedar Rapids Blomquist (J Avenue) Water Treatment Plant is located on approximately five acres in the northeastern quadrant of Cedar Rapids. The City of Cedar Rapids obtains all of its water from a series of shallow alluvial (gravel packed) wells along the Cedar River. The plant continuously produces high quality water in sufficient quantities and at pressure levels necessary to meet the residential, commercial, industrial and fire protection needs of the community. The J Avenue Water Treatment Plant is designed and operated to maintain compliance with the Safe Drinking Water Act (SDWA). Federal and state requirements are defined in a Public Water System (PWS) Operating Permit issued by the Iowa Department of Natural Resources (DNR). The J Avenue Water Treatment Plant was built in 1929 and has undergone a number of major and minor improvements that have expanded water production capacity from the original design of 12 million gallons per day (mgd) to the current capacity of 4 5 mgd. Administration, Operations, Maintenance and Warehouse buildings provide the support and control functions for water treatment. Treatment processes include aeration, lime softening, re-carbonation, chlorination, fluoridation, filtration, phosphate addition, and distribution system pumpage & distribution. The J Avenue Water Treatment Plant handles, uses, and stores chlorine, an EPA-regulated substance, in amounts exceeding the regulatory threshold of 2,500 pounds. The process of chlorination for disinfection of water is not included in the North American Industry Classification System (NAICS) codes listed by EPA in 40 CFR 68.10(d) although the Water Utility is subject to Occupational Safety and Health Administration Process Safety Management (PSM) requirements. This qualifies the J Avenue Water Treatment Plant as a Program 3 process. Chlorine is added as a disinfecting agent, as it is in 98 percent of U.S. water supplies, to kill disease-causing organisms and to help ensure t he continued microbiological safety of the water as it reaches the customers tap. Chlorine is historically the preferred disinfecting agent for drinking water, having been introduced to the United States for water treatment in 1908. Trace amounts of ammonia are added to the water which reacts with chlorine to form chloramines as part of the chlorination process called chloramination. All chlorine is stored and processed in the chlorine container room in the lower level of the Control Building. A maximum of 17 one-ton containers (34,000 pounds of chlorine) may be maintained in the inventory. The Chlorine Container Room is separated from the rest of the building by fire-resistant walls and is equipped with an observation window and chlorine leak detectors designed to sound audible and visible alarms if a chlorine leak is detected. The chlorine gas leak detectors are integrated into the plant Supervisory Control and Data Acquisition (SCADA) System which allows operators to monitor any potential gas leaks remotely from the control room. Operators also monitor the process by closed-circuit television cameras. Five one-ton containers are on-line at any one time with an additional five ton-containers on standby. Leaks in the chlorination system can be controlled by closing remote control isolation valves and switching to the standby bank of chlorine tanks. The Chlorine Container Room is normally unmanned but operators visit the area routinely and respond to any trouble alarms which may occur. The offsite consequence analysis includes consideration of two chlorine release scenarios, identified as "worst-case release" and "alternate release scenario." The worst case scenario is defined by the Environmental Protection Agency (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 alternate scenario is defined as "more likely to occur th an the worst-case release scenario." EPA regulations require the use of tables or atmospheric dispersion modeling to determine the distance traveled by the chlorine released before its concentration decreases to the toxic endpoint. The endpoint is the distance a toxic gas/vapor cloud will travel before dissipating to the point that serious injuries from short-term exposures will no longer occur. The toxic endpoint selected by EPA for chlorine is 3 parts per million (ppm), which is the Emergency Response Planning Guideline Level-2 (ERPG-2). The ERPG-2 concentration is defined by the American Industrial Hygiene Association 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 or symptoms which could impair an individuals ability to take protective action. The residential population within a circle with a radius corresponding to the toxic endpoint distance has to be defined, "to estimate the population potentially affected." The worst-case release scenario at the J Avenue Water Treatment Plant involves the failure of a single one-ton container (a total of 2,000 pounds of chlorine). The offsite consequence analysis was performed using the 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, and consideration of the population within a full circle with the radius corresponding to the toxic endpoint distance. EPA sets these conditions to simplify the off-site consequence analysis and ensure a common basis for comparison even though these assumptions may be unrealistic or not even possible. Look-up tables in EPAs publication, "Risk Management Guidance for Wastewater Treatment Plants (40 CFR Part 68)," was used as the process chemistry and process technology is similar for chlorine disinfection of water and was tewater. The distance to the toxic endpoint for chlorine taken from Exhibit 4-3 of the EPA Guidance Document was determined to be 1.3 miles with a potentially affected population of 12,000. The alternative release scenario involves the failure of a 1-inch forged steel pipe connected to five 1-ton containers. The amount of chlorine released is 4,380 pounds, at an average rate over one hour (the duration of the release) of 14.6 pounds/minute. This release is limited by the flow through the 5/16-inch valves on each of the one-ton containers. The distance to the toxic endpoint for chlorine taken from Exhibit 4-12 of the EPA Guidance Document was determined to be 0.2 miles with a potentially affected population of 100. The toxic endpoint was calculated using the formula for a vapor release (QR = 190 x Ah), where: QR = Quantity Released (pounds) 190 = Chemical-specific factor for chlorine at a tank pressure of 113 psia and temperature of 77 0F Ah = Hole area (squ are inches) Accidents reported to EPA involving chlorine systems have been caused by rust holes, failure of a diaphragm, leaks during hookup to a tank, a packing nut leak, faulty cylinders, removal of a valve in error, faulty valves, leaking gaskets, and a blown pressure gauge. Each of these incidents, while potentially serious, can be easily controlled through maintenance or process system safety features that would prevent a catastrophic release. The Water Departments general accidental release prevention program is based on the following key elements: 7 High level of training of the operators 7 Preventive maintenance program 7 Use of state-of-the-art process and safety equipment 7 Use of accurate and effective operating procedures 7 Performance of a hazard review of equipment and procedures 7 Implementation of an auditing and inspection program Chemical-specific prevention steps include the availability of respiratory protection devices [an air purif ying respirator (APR) is worn by mechanics during the connection / disconnection of chlorine ton-containers and a self contained breathing apparatus (SCBA) is available for emergency use], awareness of the hazardous and toxic properties of chlorine, and the presence of chlorine detectors throughout the Chlorine Container Room. Water Treatment Plant Operators are required to maintain an operator license issued by the Iowa Department of Natural Resources. Operators must complete a minimum of 10 - 20 hours of continuing education credits every two years to keep their license current. No accidental releases of chlorine have occurred at the Blomquist (J Avenue) Water Treatment Plant in the past five years. No documentation could be found that there has ever been any significant chlorine leaks since the plant was built in 1929. The Water Department has an emergency response program, which has been coordinated with the City of Cedar Rapids Fire Department (CRFD). The CRFD has a profess ional, well-trained and well-equipped Hazardous Materials (HAZMAT) Response Team and is a member of the Linn County Local Emergency Planning Committee (LEPC). The CRFD HAZMAT Response Team periodically conducts training and drills in responding to a chlorine ton-container leak at the Water Utility. A Chlorine Institute Emergency "B" Kit, which includes the necessary tools and equipment for repairing ton container leaks, is available on-site for use by the HAZMAT Team. The CRFD also has an agreement for mutual aid and assistance with the City of Marion Fire Department. Water Utility operators have been trained to provide a controlled response to chlorine leaks but limited to conducting an initial assessment and providing any necessary technical advice and support to the CRFD HAZMAT Team. |