On February 4, 2018 (Super Bowl Sunday), the City of Juliaetta’s Public Works staff was at home enjoying the game, when calls started to come in from citizens complaining of no water. The public works department began searching for the cause by driving to each of the City’s three water storage tanks, and the surface water treatment plant. When an obvious leak was not found, they began closing valves and isolating portions of the system. The City was able to stop losing water after isolating the lower pressure zone, but the cause was not discovered. The water system had lost pressure and an estimated 300,000 gallons of water during the event. The following day a Circuit Rider with Idaho Rural Water and a representative from Great West Engineering were onsite to assist the City with evaluating what may have gone wrong. It was discovered that a water main break had occurred on a 6-inch ductile iron line within the Potlatch River. The break was caused by flood-stage flows that crested at 8,490 cfs the day of the break. In comparison, average flows of the Potlatch River at Juliaetta are 500 cfs. The broken main line was the sole connection to a vital water supply well (Well No. 5) and five homes on the east side of the Potlatch River.
The new infiltration gallery was constructed 6 feet deeper and closer to the river than the previous gallery. The infiltration gallery is a 200-foot chamber that is wrapped in geotextile fabric and then surrounded by clean drain rock. The infiltration gallery filters out dirt and other debris so that the water entering the treatment plant is clean and able to be treated to drinking water quality standards. During the first year of operation the new infiltration gallery produced higher quality and quantity of water than the old gallery, and for the first time in many years the City has been able to draw water from the infiltration gallery during summer months. The new SCADA system allows the City to monitor the entire surface water treatment plant, three storage tank water levels, a pressure boosting station, and two water wells from a central location. With the addition of the SCADA system the City is now able to treat surface water 24 hours a day if necessary, without the need of having an employee onsite. With the upgrades to the treatment plant the City can operate both treatment basins at the same time to meet peak water demand, previously the City could only use one treatment basin at a time.
The installation of the new water line beneath the Potlatch River had its own challenges. A geotechnical analysis was performed, and it was discovered that there was a layer of solid basalt that would have to be drilled through. On the first attempt to horizontal directional drill the was unable to make it through the basalt, the drilling head was destroyed. Great West worked closely with the drilling contractor to come up with a new alignment for the waterline and on the second attempt the directional drill was successful. The new water line is more than 10 feet below the river bottom and completely encased within the solid basalt layer.
The project was completed $40,000 below budget, which allowed the City to retain approximately $10,000 of their anticipated match. The system has been in operation for six months and has been performing as expected. Although the project has been completed, Great West will continue to work closely with the City to answer questions and provide technical assistance as needed.
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