UP THE CREEK
May 1, 2004
If you were wondering why the summer weather that was here in March suddenly turned to rain, snow, and mud, the answer is simple: we began construction of our new water treatment plant. Construction sites have to be muddy - it is written somewhere.
Ground was first broken on March 22. Mother Nature then imposed her own schedule, so the first concrete pour was delayed until April 13. Since then, progress has been “intermittently steady.” The building foundation and stem walls are done. By May 15, we expect to be ready for masons to begin laying block, and the building shell should be done by mid June. After that, filtration equipment will be installed, and (maybe) ready for operation in August.
The new plant is located about five miles northeast of Cedaredge at a elevation of 7,580 feet. The intake on Surface Creek is 3,000 feet northeast of the plant, and 110 feet higher. Water from the creek intake passes through screens to reject trash and critters, pauses in a sedimentation basin to allow time for some of the dirt to settle out, then travels through a 15-inch diameter pipeline to the plant, arriving at a pressure of 45 psi. This pressure, which is obtained naturally by the elevation change, is used to force the water through the filters. Usually, this type of plant requires pumps running 24 hours a day. By avoiding pumping, we avoid some big expenses.
Chlorine dioxide is added to the water before filtration. This helps eliminate taste and odor, and also oxidizes organic material that could otherwise combine with chlorine to form potentially harmful compounds. The water then passes through two stages of filtration. The first stage is called the “roughing” filter, and is actually a bank of agricultural irrigation filters that are often used in drip irrigation systems to filter out potentially clogging particles.
In the second stage of filtration, using equipment made by Pall Corporation, water is forced through a porous plastic membrane. The membrane pores are very small, and do not allow turbidity, bacteria or intestinal parasites (like Giardia) to pass. The resulting product is clean water, but not quite safe to drink because viruses may still be present - they are small enough to pass through the membrane pores. Therefore, chlorine is added to ensure disinfection.
After chlorination, the water spends about an hour in the “clearwell.” The clearwell is a buried concrete tank holding 97,000 gallons. Its primary purpose is to allow time for the chlorine to do its job. After that, the water is considered potable - a term that means exactly opposite of what it sounds like. A new 12-inch diameter pipeline carries the finished water about half a mile to join the existing distribution system.
The design goals of this plant are to produce water that will meet increasingly stringent regulations on water quality for many years, and to do it economically. The filtration process is automated with very little operator intervention needed. The performance of the plant can be monitored remotely from our office or even from a home computer.
It is gratifying to see this project finally coming to a conclusion after a couple of years of intense paper shuffling. Even mud is more fun than that. We plan to put pictures of the ongoing construction on the Association web site so you can follow along if you wish. Go to www.uscdwua.com and follow the links to get to pictures and other progress reports.