Missouri River Treatment Plant - Executive Summary |
Description of water system for Helena, Montana The City of Helena's Water Department (HWD) goal is to ensure customer satisfaction by consistently delivering high quality water today and in the future. The HWD serves more than 25 thousand customers with 9364 service taps including 155 fire lines with an average of 5.2 million gallons of water per day on an annual basis. The total annual gallonage from all sources for 1998 is 1.866BG* with a peak day of 12.2MG*. To supply this amount of water, we operate two surface water treatment plants--the Missouri River Water Treatment Plant (MRTP) located at 2560 Canyon Ferry Road, and the Tenmile Water Treatment Plant west of Helena at 1115 Rimini Road. The Tenmile Water Plant is in operation year round while the MRTP is used only during the summer months for peak demands. Additional water is obtained from the Hale system which consists of the Oro Fino and Eureka well collectors. The department's two treatment plants are maintained, evaluated and upgraded to stay abreast of advancements in technology, health science and governmental regulations. The Helena water distribution system consists of five finished water storage reservoirs (Malben, Winne, Hale and Upper Hale, Woolston) and pumping stations (Forrest Estates, Hale, Eureka, Dahlhausen, Reeders Village) linked together with 185 miles of water transmission and distribution pipelines. The Chessman (530MG) and Scott (195MG) reservoirs in the Tenmile watershed also provide additional water for the Tenmile Water Plant during low flows. These reservoirs are filled with spring run off water. Carollo Engineers of Boise, Idaho completed a Water Master Plan Update for the City of Helena in April 1997. The Public Works Department has copies of the Water Master Plan if customers would like to review it. Phase one of this update determined that the existing Missouri River Treatment Plant should be rehabilitated or replaced due to age of equipment, public health risks, and oper ational safety issues. Plant replacement or rehabilitation costs were significant. The least costly scenario was to replace the capacity of the existing plant with high quality groundwater supplies if available. Test drilling of these wells has started in 1998. The Facility and Regulated Substances This is a local government owned and operated facility for the production of potable water for the City of Helena. The only reportable regulated substance for the RMP plan is chlorine. One to two tons of chlorine are stored at this facility in ton cylinders. No more than two ton cylinders are on line at a time. The online tanks are on isolated regulators that reduce the chlorine pressure to a vacuum state. Chlorine feed equipment supplies a vacuum to the tanks allowing the release of chlorine to the feeders. All feed lines supply chlorine below atmospheric pressure. Should a leak develop the feeders would be unable to supply enough vacuum to continue the release of chlorine and the f eed would stop at the Chlorine Pressure Reducing Valve(CPRV) attached to the tank. Each tank has its own CPRV. No flammable substances are stored in the chlorine room. Two operators are required for changing chlorine tanks as part of our standard operating procedures. Self Contained Breathing Apparatus(SCBA) are stored in an adjacent room on wall mounted quick release brackets. An emergency repair kit is available. A chlorine detector is installed in the room connected to an alarm panel and autodialer. If an alarm condition exists it will call personnel till acknowledged. All alarms and autodialers are on uninterruptable power supplies, batteries. Worst-Case Scenario The worst case scenario would be the total loss of one ton of chlorine through catastrophic valve or tank failure. There are no mitigation controls. Response time could be so limited(less than an hour)that under the right conditions total loss of one ton of chlorine is possible. Alternate Scenario Valve failur e or leak while tank is being changed. The least worst case scenario would by CPRV failure, CPRV to tank connection, or tank valve leak. Operators would close the tank valve thus shutting off the chlorine so repairs can be made. Accidental Release Prevention Operators are trained in the proper way to change tank CPRV's. Regular maintenance is kept on the CPRV's, lines, and feeders. Cylinders with exceptionally difficult or tight valves are returned. SCBA's are kept in a separate room. Operators are trained in proper leak detection and correction needed. Two operators are required for tank changes or repairs. A third operator is notified of any leaks and told to notify emergency responders if no communications for more than 20 minutes. Five Year Accident History No accidents in the last five years. Emergency Response Program As written in the plant emergency response manual. This manual is stored on the office desk. These manuals are stored in plain view by office door. Planned Changes New improvements include a groundwater supply in combination with a new Missouri River Treatment Plant. This includes a new clearwell, chlorine equipment, and high service pump station. Storage includes a new east side reservoir. This new construction will begin in one to two years from now depending on budget restraints and final approval from City and Community advisory groups. |