Ten Mile Water Treatment Plant - Executive Summary

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Description of water system for Helena, Montana 
The City of Helena's Water Division (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 1997 is 1.777 BG* with a peak day of 10.4 MG*. 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 infiltration galleries. 
The department's two treatment plants are maintained, ev 
aluated 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 (Forest Estates, Hale, Eureka, 
Dahlhausen, Reeders Village) linked together with 185 miles of water transmission and 
distribution pipelines. The Chessman (530 MG) and Scott (195 MG) 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 operational 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, and the outlook is not good 
and recycling on surface water treatment plant is likely scenario. 
Accidental Release Prevention 
To prevent chlorine release it is standard operating procedure to have two operators work on tank 
changes or to work on the Chlorine Pressure Reducing Valves (CPRV's). An emergency repair 
kit is stored close to the cylinders. Self Contained Breathing Apparatus (SCBA) are stored in an 
adjacent room. They are wall mounted with quick release brackets. An oxygen cylinder is also 
stored by the SCBA's. Regular maintenance is performed on all chlorination equipment and 
safety equipment. Work orders are generated for chlorination equipment and all safety 
equipment, i.e. SCBA's. All work orders are track 
ed by computer. 
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. Two to 
eight tons of chlorine are stored at this facility in 150# and ton cylinders. No more than two ton 
cylinders are on line at a time. One cylinder is in actual use and the other is in standby. The 
online tanks are on tank mounted isolated regulators called Chlorine Pressure Reducing Valves 
(CPRV's) 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 feed would stop at the CPRV 
attached to each tank. No flammable substances or other restricted items are stored in the 

hlorine tank rooms. The room has a chlorine detector connected to an alarm panel, annunciator 
horn, computer, and autodialer. All unacknowledged alarms initiate the autodialer which calls all 
on duty and off duty personnel till acknowledged. If the alarm conditions exists after an hour it 
again starts calling operators out. All alarms and autodialers are on batteries, uniterruptable 
power supplies, and back up electrical generator. 
Worst-Case Scenario 
The worst case scenario would be the total loss of one ton of chlorine through catastrophic valve 
or tank failure. Response time could be so limited (less than 15 minutes) that under the right 
conditions total loss of one ton of chlorine is possible.  
Alternate Scenario 
Valve failure or leak while tank is being worked on. Disregarding minor releases the less worst 
case scenario would be CPRV failure, CPRV to tank connection, or tank valve leak. Operators 
would close the tank valve either shutting chlorine off or reducing the flow to a 
manageable level 
for repairs. 
Accidental Release Prevention. 
Operators are trained in the proper way to change CPRV's and tanks. Regular maintenance is 
kept on the CPRV's, lines, and feeders. Cylinders with exceptionally difficult or tight valves are 
rejected and returned. Self contained breathing apparatus and tanks are kept in a separate 
adjacent room along with emergency oxygen. Operators are trained in proper leak detection and 
correction. Two operators are required for tank changes or repairs. A third operator is notified of 
any leaks and told to notify emergency responders if communication is lost for more than 20 
minutes . 
Five Year Accident History. 
No accidents or chlorine releases in the last five years. 
Emergency Response Program 
As per written emergency manual. The manual is stored by the MSDS manual. These manuals 
along with the operations manual are stored in the plain view. Another emergency response 
manual is stored near the SCBA's. 
Planned Changes 
Continuing r 
eview and training. Updates to manuals and procedures as required.
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