Grinnell’s new million-gallon water tower is expected to enter service within the next several weeks, significantly increasing the city’s water storage capacity as part of a broader series of improvements to its water system.
“It’s all built,” Water Director Keagan Richmond said. “There’s electrical installation happening right now. We’re hoping to disinfect the water tower next week, and after that and a couple of favorable tests, we should be able to use it.”
The new tower will hold one million gallons, more than three times the 300,000-gallon capacity of Grinnell’s existing tower.
The older tower will remain in service for the foreseeable future, Richmond said.
According to Richmond, the added storage will help the city maintain water supplies during emergencies while also preparing for future growth.
“The new tower’s larger water saving capacity will give the city a stronger water reserve to meet fire protection needs and support future growth,” Richmond said. “It also gives us flexibility and reaction time in case of main breaks, power outage or treatment plant issues.”
Both towers will feed the same distribution system, serving approximately 9,500 to 9,600 Grinnell residents.
Richmond said the tower essentially functions as a storage tank — water pumped into the city’s distribution system fills the tower, and the stored water can then flow back into the system as the demand changes.
The approximately $3.7 million tower is one piece of what Richmond described as Grinnell’s Water Improvement Projects, a collection of infrastructure upgrades that began around the start of 2023 after several years of planning.
Richmond said the city accelerated those plans as the existing water treatment plant aged and its softening equipment was taken out of service in 2022.
“The treatment plant was on its last legs,” Richmond said.
Without the softening system, he said, the water remained consumable but had significant amounts of dissolved magnesium and calcium, or hardness, which made it less desirable for some residents.
The largest part of the improvement effort is a new nanofiltration water treatment plant, which Richmond said is expected to enter service in January. The treatment plant and related well improvements were bid at approximately $28 million, which is a close estimate of the final cost.
Other projects include a $1.6 million well transmission line, completed last construction season, and a new $3.3 million well named, “Jordan Well No. 10” (Well 10).
Unlike the water tower, which primarily provides storage, the new treatment plant will directly affect the quality of Grinnell’s drinking water.
Richmond said nanofiltration is a high-pressure filtration process similar to reverse osmosis.
Water is forced through membranes that remove contaminants before the treated water enters the distribution system.
The system is also expected to reduce radium levels in the water. Richmond said current water averages roughly seven picocuries of radium per liter.
While nanofiltration can reduce the amount to nearly zero, some untreated water must be blended back into the finished water to maintain enough mineral hardness to prevent damage to plumbing.
Richmond expects the resulting water to contain between one and two picocuries of radium per liter, below the federal regulatory limit of five.
The city is also continuing to replace aging water mains.
Richmond estimated that roughly five miles of new mains have been installed in the last five years, with additional work expected next construction season around the treatment plant and potentially on Eighth Ave., Country Club Drive and Broad Street. Altogether, bids for the tower, treatment plant, well improvements, Well 10 and transmission line total approximately $36.6 million.
Richmond said costs have shifted somewhat because of modifications to the original construction contract, and that the city has incrementally increased water rates to pay for the improvements.