Castle Rock residents report strong chlorine smell; officials say water safe

Castle Rock residents have reported a strong chlorine smell, discolored water and changes in taste after Castle Rock Water began a routine maintenance change on Feb. 2 that temporarily converted the system from chloramine to free chlorine. Apres Coffee owner and Castle Rock resident Madison Vonderach said, "Something's not right within our water," and added that "close to five different families" have told her they noticed health concerns.

Town utility communications state the change to free chlorine is a planned maintenance action and that the water "remains safe for drinking, bathing, cooking, and all other household uses." The Castle Rock Water notice says the system "is now running on free chlorine disinfectant and will continue to do so until May" and that "chlorine levels are below the State and Federal regulations' maximum of 4.0 parts per million (ppm)."

Several residents described health effects and strong odors. One resident reported that tap water has been making her family nauseous and giving her dog diarrhea. Another said his shower smells "like a swimming pool" and that the water gave him a sore throat. Additional reports noted headaches and a stomach bug in some households. At the downtown Wide Awake Eatery, assistant general manager T.A. Ike said, "Down here, I haven't tasted anything."

Castle Rock Water's public statement explains why the change was made and what residents may notice: "Free chlorine dissipates into the air faster, causing a much stronger smell than chloramine." The utility also warned that "Free chlorine can cause the water to be more drying and, coupled with the dry weather and hot showers, skin irritation could be more prevalent." The town advised residents that if home testing shows chlorine above 4.0 ppm, they should contact Castle Rock Water so the utility can come test the water at the home.

Utility materials and on-record comments describe the disinfectant swap as a measure to address pipe buildup and biofilm. Castle Rock Water materials note the town previously changed disinfectants in 2013, "In 2013, Castle Rock Water switched from using chlorine to chloromine as a disinfectant", and explain that "When biofilm develops on the pipes, chlorine needs to be used." The town says this procedure is common among water utilities nationwide and that Colorado Department of Public Health and Environment reviewed and provided permission for the activity and is receiving the utility's increased sampling data.

A utility spokesperson has been quoted reassuring the public that "The bottom line is, water is safe to drink," and that "There's no danger to public health." Some town materials identify a Castle Rock Water director by name, rendered in different sources as Marlowe and as "Mark Marlo", and those name discrepancies have not been reconciled in the town's unsigned release. Castle Rock Water also told residents the utility expects this type of maintenance may be needed again in the future, "but it could be anywhere from four to 10-plus years before it is necessary." The system is set to switch back to chloramine sometime in May while the town and state continue increased sampling and monitoring.