AZTEC — On Tuesday, Aztec City Commission approved spending $102,764 to install a new water line extension to Tiger Park Lake, or Reservoir No. 3.
The 860 feet of additional pipe will allow the water treatment plant to receive water directly from the 56-million gallon lake while improvements and maintenance to Reservoir No. 1 take place.
Built in the 1950s, Reservoir No. 1, which can hold 10 million gallons, has only been dredged once in the 17 years Andrew Galloway, chief operator at the city's water and wastewater plants, has worked there.
The city maintains three reservoirs, dotted along Navajo Dam Road just south of U.S. Highway 550. The three can store a combined 74 million gallons of raw water. The city also maintains seven storage tanks with a combined total of 6 million gallons of drinkable water scattered around the city.
Water from the Animas River is fed into Reservoir No. 1, pumped up to Reservoir No. 3 and then piped downhill to Reservoir No. 2 before it arrives for treatment at the plant. The three-reservoir system increases detention time to remove sediment from the river water, reducing the amount of chemicals necessary to make the water safe to drink.
Reservoir No. 1 is the oldest, and Galloway wants to replace its adit tower, which serves a vaulted valve system used to drain and fill the reservoir.
"The tower is old, 30 or 40 years or so, and has spalling (deterioration of steel reinforcement bars, or rebar, and concrete by moisture)," Galloway said. "The concrete's crumbling and the rebar's starting to show. It's rusting and needs to go. It's time."
Galloway thinks ice collecting on the tower in the winter has made it vulnerable to collapse, pulling the tower's concrete exterior apart when water levels in the reservoir change.
To do the work, Reservoir No. 1 will have to be drained dry so construction of a new tower can occur. But because the plant must maintain full operations, the new water line will have to be installed at Reservoir No. 3 first, so water can flow directly to the water plant.
Construction of the new line will be done by Maranatha Enterprises, an Albuquerque firm.
The new pipe should be in place by the end of April, Galloway said. Then Reservoir No. 1 can be drained.
"Most of the water in it, roughly 75 percent, will be piped to No. 3, Tiger Lake, and roughly 20 percent will go into the plant. Only 5 percent max will be wasted in the process," Galloway said. "When it's drained, we'll be looking at 6 to 8 feet of mud at the bottom. We'll have to see how soupy it is at the bottom."
Drying the mud for removal will take six to seven months, Galloway said,
"No sense in spending money to dry it out," he said. "We'll let Mother Nature take its course, let the summer sun beat on it."
The city's water treatment plant on Navajo Dam Road produces 500 gallons of drinking water from one source, the Animas River. By treating the river's sediment-laden water, or raw water, the plant can produce more than 2 million gallons of drinkable water in a day.
"The whole project (of rehabilitating Reservoir No. 1) will take around a year," Galloway said. "It's needed."