Castle Rock switches to chloramine to treat drinking water


The Castle Rock Plum Creek water treatment plant will be the first to treat the town’s drinking water with chloramine, after years of treating water with chlorine.

The plant is making the switch because Plum Creek will be the first water treatment facility in Castle Rock to treat surface water, part of the town’s effort to transition its water source to renewable water, said Mark Marlowe, utilities director.

“Surface water has higher levels of natural organics than well water,” Marlowe said. “Chlorine can react with the organics; chloramine does not react as much.”

Chloramine is formed when ammonia is added to chlorine to treat drinking water, according to the EPA. When it makes the switch, Castle Rock will join Denver, Aurora, Centennial and Englewood, which are among the municipalities that use chloramine to treat drinking water.

At present, Castle Rock consumers get most their water from non-renewable sources through the town’s underground wells. The town aims to transition to consuming 75 percent of its water from renewable sources by 2065, when Castle Rock is expected to reach its population build-out.

The Plum Creek water treatment facility is the first of the town’s facilities to cull from a surface source and is expected to get the town nearly halfway to its goal, treating 35 percent of the town’s water from renewable sources, according to the Town of Castle Rock.

While chloramines are expected to enhance the water’s taste and smell, chloramine-treated water cannot be used for kidney dialysis treatment, for fish, reptile and amphibian tanks or for industries that rely on highly processed water.

The town notified its water customers about the switch in the May water bill and in the first week of May distributed a letter among businesses that might be impacted by the switch, such as pet stores and medical offices.

“We’re following a treatment that works, is effective and helps us make the transition to renewable water,” Marlowe said. “It’s very safe.”

During the transition, the town will have to flush the water system, which could result in water flushing in the streets and through select fire hydrants. Where possible, the town will flush water into town parks and open space, Marlowe said. Flushing of the water system is expected to take place in mid-May.

For more information about chloramine treatment, visit For more information about the Plum Creek water treatment facility and the town’s long-term water plan, visit


More about chloramines from the EPA

• What are chloramines?

Chloramines are disinfectants used to treat drinking water. Chloramines are most commonly formed when ammonia is added to chlorine to treat drinking water.

• How long has monochloramine been used as a drinking water disinfectant?

Monochloramine has been used as a drinking water disinfectant for more than 90 years.

• How many people/water utilities use monochloramine?

More than one in five Americans use drinking water treated with monochloramine.

Source: Environmental Protection Agency, Basic Information About Chloramines, 2009.



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I weep for the residents of Castle Rock that now have chloramines in their water. I urge all of you to research the use of chloramines. Chloramines cannot be filtered easily (in fact, it is thought that there is NO filter on the market that can filter it at all). As a Denver resident and avid gardener that has been concerned about the use of chloramines for several years, I hope some residents read this comment and get educated on the issue. Read the reports about chloramines leaching lead from pipes in Washington D.C. There is a Facebook group where you can ask questions and a website to start here:

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