Since construction 30 years prior, yield in two of this rural town’s (in southern Washington state) drinking water wells has been in a steady, long-term decline.
At these problem wells, results of regular water-quality testing were showing increasing amounts of iron and silica, and concentrations of sodium were exceeding advisory levels. More recently, wellfield operators were reporting the sound of water cascading down the casing beneath the pumphouse, and could hear the hiss of air entrained in the discharge line. Utility managers with the town were growing concerned about the longevity of the wells and whether they could continue to meet demand.
The local PUD, who operates the wells for the town, wanted to get things back on track. But where to start? Which of the problems should they address first? And how would they know they were investing in the right fixes, and making the best decisions for their customer owners? The PUD brought in Aspect to problem solve and rehabilitate the wells to recover the lost supply.
Water pumped from one of the town’s water supply wells with high iron oxides and turbidity.
Well Rehabilitation Detective Work
For the PUD, our initial approach examined the usual suspects of declining wellfield performance: well construction records, changes in water quality, regional trends in aquifer levels, and the condition of the pump and motor. As part of our review, we also used a slimline downhole camera to observe the condition of the well screen and casing. Our “nano” camera is designed to be deployed without having to first pull the pump—a significant time and money saver for everyone involved—and provides real-time information to diagnose what’s happening underground.
Our investigation revealed that the water supply wells were suffering from both chemical and physical complications: poor well construction and high iron-sulfide content in the source aquifer was fueling a booming population of slime-forming bacteria. Although each of these problems could be addressed with short-term fixes, they represented long-term maintenance costs and perpetual service interruptions for the PUD. While nearly any drilling outfit is capable of clearing obstructions and replacing damaged casing, our hydrogeologists provided big-picture perspective of the subsurface. Instead of attacking the symptoms of well decline with temporary solutions, we looked to understand the root cause of water problems and make recommendations that will improve pumping capacity for the long-term.
Reducing Long-Term Cost and Gaining Higher-Quality Groundwater
As an alternative, Aspect recommended a phased approach to rehabilitate the water source. First, to address water needs today, we prescribed a series of well rehabilitation treatments to restore the well performance. Second, to address water needs in the years to come, we outlined steps for developing a new source in a higher-quality body of groundwater. In addition to reducing long-term cost, this approach is consistent with the PUD’s mission to serve their customer owners.
Water filtration system necessary to treat water prior to distribution.
Contact Aspect to Learn More About Well Rehabilitation Services
Successful well rehabilitation results from a methodical process.
If you have questions or want to learn more about our well-rehabilitation services, please contact Jon Turk or Andrew Austreng in our Water Resources Practice.