INNOVATION Mar-Apr 2020

the flow—a small investment that is far more cost-effective than trying to stop uncontrolled flow after the fact. The first attempt to control flow from the ill-fated exploratory borehole (now known as the Coldstream Ranch Well, or CRW), started a week after the artesian aquifer was encountered. The drillers tried to pump grout (a sealant containing cement and clay) through two small two-inch diameter pipes into the centre of the crater. This was ineffective, so the drillers installed a six-inch diameter well casing in the hole and, over the next few months, made several unsuccessful attempts to plug it with grout but water continued to flow from the CRW. It was the start of a 50-year saga. EARLY FAILED ATTEMPTS TO CONTROL FLOW In 1966, a 30-inch diameter steel casing was driven down around the outside of the previously installed casing. Water initially flowed up through the casing, but another crater started to form when the casing reached a depth of 45 metres. Within 30 seconds of moving the drill rig away from the casing, the crater expanded to a width of 10 metres and a depth of 24 metres. It swallowed up well casings and grout pipes that had been stored nearby. About 50 dump trucks filled with gravel and 1,940 sacks of cement grout were required to backfill around the casing. Once the concrete plug stabilized, most of the artesian flow was contained within the 30-inch casing; however, it was impossible to shut in the well because groundwater flowed up around the cement plug. Pipes were installed to direct the CRW flow to natural drainage courses, mainly Coldstream Creek, located about 350 metres from the CRW. Because the 30-inch casing had an open bottom and no well screen to prevent aquifer materials from entering the well, sand and gravel eventually pushed up into the bottom of the casing. Consequently, the CRW gradually clogged and groundwater started seeping around the wellhead. So, in 1979, workers drilled a 16-inch diameter casing inside the 30-inch casing and outfitted it with a well screen. This directed the flow through the two casings and, so long as the well was not shut in, there was no seepage at surface. Thus, the well was left to flow. Some water was used for irrigation, but the majority was discharged to Coldstream Creek. SUCCESSFUL PLUGGING PROGRAM Over time, the screen in the 16-inch casing clogged and the casings deteriorated. By 2009, an outside consultant, Golder Associates Ltd., was retained to evaluate options for closing the CRW for good. One leading option was to drill a large-capacity relief well (RW3) near the CRW, to lower aquifer pressures and halt

An early (1966) attempt to control the artesian flow involved the installation of a 30-inch diameter steel casing.

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