Water Well Journal
Issue link: https://read.dmtmag.com/i/557876
D oes a grouting challenge ever have you stumped from time to time? If so, you're not alone. Almost every water well contractor has faced a grout- ing nightmare at least once, whether it was an engineer's specifications during the bidding process or an unforeseen condition on a job site. "We had one well in eastern Wash- ington a year or two ago where we had significant downflow in the well," says Steve Schneider, MGWC, vice president of drilling operations at Schneider Water Services in St. Paul, Oregon. "The downflow was not expected in that case, so the best laid plans went through the window." The plan called for cement grout to be placed in the borehole through a shoe to about 200 feet. Instead, it brought it up only 20 feet. "We had to regroup during the con- struction as to how we were going to approach it," Schneider says. To deal with the downflow, they added bentonite chips on the cement up to 200 feet, then topped the chips with more cement. Grouting challenges in the field are rare, but they do happen. George Dugan, southeastern regional manager at CETCO Drilling Products Group in Dayton, Texas, says contractors contact him most often during the planning process to talk through the best product for the job. A one-size-fits-all approach rarely works well because state regulations, engineering requirements, depth of the well, type of formation, and the materi- als and equipment you're using to con- struct the well all play a role in the type of grout you select. So, whether you're selecting a grout during the planning process or trouble- shooting from the job site, here are a few tips to help you avoid a nightmare. Bentonite chips For some, bentonite chips are their sealant of choice because they offer a highly tolerant seal with no mixing or equipment required. "They're our go-to grout whenever the conditions are favorable," Schneider says. "They swell several times their original size if they're unrestricted, they're easy to place, and they're cost effective." They also won't migrate and drying and rehydrating doesn't affect them, making them typically good for perma- frost or earthquake-prone areas. "They're very tolerant to (drying and rehydrating) and they've been doing that for millions of years," says Stewart Krause, senior sales manager for Wyo-Ben Inc. in Billings, Montana. "As long as we don't contaminate them in some significant way, shape, or form, they're going to continue to do that and perform very well." State regulations, however, may limit their applications. Some states prohibit bentonite chips to be poured down the annular space of domestic water wells. "States and entities are going through a learning curve on the chips as to what they're comfortable with," Schneider says. "We have certain regulatory agencies, like Oregon, that restrict the chip bentonite to less than a 200-foot placement and not more than 50 feet of water. So, on deep placements in Oregon I have to use cement." Some states also limit how deep you can pour the chips, but Krause says he has used them on sites with wells in excess of 1600 feet with a static water level at 23 feet with good results. "We tagged it to make sure it was going to the bottom," he says. "We poured some, measured it, poured some more, and measured it. We were able to document we were able to do it." On deep wells, Schneider says he has found the manufacturers' recommended pour rates of two or three minutes per sack to be too slow. "We've found on really deep place- ments, the slow pour rate is a major detriment," he says. "If you want to place chips to an extreme depth— maybe 1000 feet in an annulus—you need to pour faster because it gradually collects residue over time. It's very time dependent. As you keep pouring chips in and doing that over hours, it has more time to collect, swell, and start choking off your annulus." Besides state regulations, the water in the borehole may make bentonite chips a less than ideal choice. For exam- ple, you won't want to put the chips in saltwater applications because salt dam- ages the bentonite. They also may not be appropriate for water with a high amount of total dissolved solids (TDS). "TDS is just an indicator," Schneider says. "If it gets over 800 parts per mil- lion, we want to be consulting with the manufacturer to make sure it will be okay." The most important consideration when looking at bentonite chips is the amount of annular space. Schneider, who does a lot of deep-set municipal wells, prefers to have at least a 4-inch diametrical distance space in order to properly place the chips. In some instances, you can still use bentonite chips when the annular space is 3 inches or less. Avoid grouting headaches by choosing the right sealant for the job. By Jennifer Strawn GROUT continues on page 32 No matter what grout you choose, good drilling practices are critical to grouting success. WWJ September 2015 31 Twitter @WaterWellJournl OVERCOME GROUTING CHALLENGES