Water Well Journal
Issue link: http://read.dmtmag.com/i/617280
A customer calls to complain his well isn't performing like it used to. Now what? It's a common problem caused by any number of issues. It may be mechanical such as a worn, corroded, or plugged pump. Bacteria or minerals may have accumulated in the well. Or, aquifer depletion could be to blame. Well rehabilitation—or cleaning the well of mineral de- posits, biofouling, or fouling caused by mud, sand, or silt— will often improve a well's yield. But only if that's what is actually causing the problem. And, you must choose the right chemical and mechanical process. "I tell my customers we can't make water that's not there," says Don Watson, owner of Watson Well Service in Eureka, California. "We remove a lot of the material that could be affecting the performance of the well, but sometimes we just wind up with a clean well. There isn't a yield improvement, but that's because they're not getting the water on the out- side." Here is how you can determine when a well rehabilitation is needed and how you can select the right chemicals to get the job done. Step one: Diagnose the problem Knowing the cause of a drop in yield often takes a bit of detective work on the contractor's part. It's important to gather as much information as you can about the well and the water quality before you begin the rehabilitation process. Watson often refers back to any history he has on a well to help. If the database shows the water level is within a couple of feet of a similar low yield period, it may just be a character- istic of that well. "In our region, once you move into the later summer months the formation may not be producing the same level of water it was earlier in the season," Watson observes. "There's really not a lot we're going to be able to do if it's not there in the formation to improve upon." Along with the well's production history, it's good to look at the well's drawdown history or its specific capacity. Other important factors to look for in a well's history include whether it underwent rehabilitation before—and if so, what chemicals or processes were used. Watson compares this information to the current stats he gathers from the well, such as static water level. Because the drought has affected wells in his service area, he often pulls the pump and lets it sit for 24 to 36 hours to see if there are gains in the water level. "In a lot of instances we find that we have gains," Watson says. "That tells me it's not a function of the drought or the formation. The water is on the outside and can't get in." The well log can also tell you the formation and how the well was constructed, which may tell you how successful rehabilitation will be. "Open hole wells or those without screens have a higher probability of experiencing rehabilitation success," says Kevin McGinnis, president of Cotey Chemical Corp. in Lubbock, Texas. "That's because there are fewer barriers to overcome." If a well log isn't available, a visual inspection with a downhole camera can help. "If it's an open borehole in the bedrock, a visual inspection is most helpful so we can see what the condition of that bore- hole is," says Eric Neubecker, MGWC, CVCLD, staff geolo- gist with Raymer Co. in Marne, Michigan. "That leads us in the right direction as to how to effectively rehab that well." It also provides a good look at the construction materials and well design, which can help you determine if rehabilita- tion is appropriate and can help you select a mechanical process for cleaning the well. For example, a video inspection may show Watson if there is breaching on old steel-cased wells. Further damage to the opening when you're trying to mechanically clean or brush a well could be a concern. Take the confusion out of well rehabilitation with tips to diagnose and treat the problem. By Jennifer Strawn WELL REHAB continues on page 20 "Our experience tells us most wells need both properly designed chemicals and mechanical tools used together to achieve the desired results." CLEANING IT UP IS HARD TO DO Twitter @WaterWellJournl WWJ January 2016 19