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City moves to improve chemical safety

Switch being made from gaseous to liquid chlorine at two water treatment plants


by: POST PHOTO: JIM HART - This collection tank attached to pipes and collection boxes at Brownell Springs provides about 13 million gallons of water each month for Sandy residents. The collection boxes are 90 years old (not pictured at right), while the tank had to be replaced after the storm of 1996 when a large tree fell on it.Incrementally, the city of Sandy is working its way into the 21st century, this time by changing its water treatment plant at the old Brownell Springs and at Alder Creek from gaseous to liquid sources of chlorine.

Treatment plant operator CH2M HILL suggested the switch to liquid sodium hypochlorite (similar to household bleach), to improve operator and environmental safety.

Should there be a chemical spill, it is very difficult to control the gaseous form of the chemical, but the liquid form is dense and easier to contain and transport.

by: POST PHOTO: JIM HART - This more-than-40-year-old building must be replaced when the city of Sandy changes from gaseous to liquid chlorine at the water treatment plant at Brownell Springs. By looking at the tree and power pole in the background, one can see that the building without a foundation is leaning downhill.Across the nation, there are many water treatment plants using the safer form of liquid chlorine.

The liquid form also is used at the Sandy sewage treatment plant, said Public Works Director Mike Walker, because from April to November liquid effluent from that plant is used for irrigation.

At other times of the year, ultraviolet rays are used for disinfection.

In the final product from the city’s two water treatment plants — potable water delivered to the faucets of Sandy residents — there will be no noticeable change.

But making the change is not a simple, or inexpensive, process. In addition to different injection equipment, the building housing the chemical and equipment at Brownell Springs must be replaced.

Walker said the concrete-block building was placed on a concrete slab in the early ’70s. Unfortunately for the city, the slab was poured on top of fill dirt without a foundation.

More than 40 years later, the building and its slab are now leaning downhill.

This project, which will cost more than $200,000, has been on the capital projects list for a couple of years, waiting for the city’s largest water project to be completed.

“We had to put (the liquid chlorine project) on hold while we worked on the Bull Run water project,” Walker said. “The cost (for Bull Run water) came in lower than expected, so we decided to proceed with (changing chlorine gas to liquid).”

Treatment plants have been changing to liquid sodium hypochlorite for the past 15 years or more, Walker said.

“Even 15 years ago, we knew it was not wise to invest in gaseous chlorine for disinfection,” Walker said, “So now it is definitely time to make the switch.”

Walker said he expects state regulators to impose expensive safety measures for those plants still operating with gaseous chlorine, and by taking this measure (switching to liquid) now, the city dodges a bullet and saves money in the process.

The proposed project for treatment improvements at Alder Creek and Brownell Springs received bids from three companies. The Sandy City Council recently awarded the project to Stettler Supply Company for a bid not to exceed $219,975. Other higher bids were received from McClure and Sons and K2G Contractors.

For more information, call Walker at 503-489-2162.