Cheney well redrilling proceeding smoothly

City of Cheney officials hope that, with some luck, they will soon be doing pump testing on the city's redrilled well 3.

As of Nov. 13, crews with Blue Star Enterprises had reached a depth of 700 feet - 150 feet deeper than the previous well shaft that was decommissioned and cemented prior to the current drilling operation. That well ceased being a water producer around 2012, and the city has estimated it will cost $1.8 million to redrill and replace it.

Blue Star began drilling the new shaft next to the old one on Erie Street in September. Public Works Director Todd Ableman said the drilling operation was going smoothly, with the well already producing some water.

So far, most of the drilling has been through various soils and basalt, but officials had anticipated hitting a layer of sand around 680 feet, the level Eastern Washington University found sand with their nearby well during a redrilling project over a year ago. The university's well went down around 1,100 feet, and Ableman expects well 3 to eventually end up there as well.

"We figure there is a bigger region (of water) that will give us more gallons per minute," he said in a June 18 Cheney Free Press story.

In an Oct. 17 interview at the well site, Ableman said crews were drilling a 24-inch shaft down to about 166 feet, after which they dropped to a 20-inch shaft down to about 750 feet and then 16 inches the rest of the way. At 750 feet, the shaft will be sealed to above layers.

"(We) have not hit the sand region, but would expect this to happen this week as we approach the 750 foot seal depth," Ableman said in a Nov. 13 email.

As crews drill down, a casing is installed inside the shaft as the drill descends. Once the sand layer is reached, crews will begin a process called "mudding" where the layers are sealed off to protect lower levels of water from being infiltrated by water from above.

"It's like a straw going down through several layers of liquid," Ableman said at the site. "You can't allow that upper levels to drain down."

Once the drilling is down to the level where the city anticipates a good supply of water, crews will begin doing pump tests. Ableman said the initial production at that level could be between 1,000 - 1,200 gallons per minute, but what isn't known is for how long that could be maintained.

So far, the well has been averaging about 1,000 gallons per minute as crews descend through the strata.

"It could be only for 72 hours, we don't know," Ableman said. He added that without solid testing, "After a couple of years, we could have a drop in capacity."

A similar situation has developed at Cheney wells 4 and 5. Both have experienced longevity problems, with the loss in capacity forcing the city to "dial down" the pumps, resulting in a lower gallons per minute rate.

Once pump tests are done, the city's engineer will calculate the maximum pumping capacity of the well in order to maintain a good level and prevent a draw down of the nearby water table. Once that's known, the engineer can begin designing the size of the well house and the size of various pumps not only for water but also for chlorination, fluoridation and needed telemetry.

Also, the city's hydrologist will be able to make a determination on what type of well column protection will be used - whether it's open bore or liner construction. There are pros and cons for both, depending on the stability of the rock formation. Both will need to provide protection against accidental cave-ins, something officials think likely happened with the previous well 3 shaft that was drilled in the 1960s and rehabilitated in 2012.

Either way, Ableman hopes the current progress on the redrilling is moving quickly towards doing pump tests soon while the weather is still good.

"We all agree we don't want to be doing pump testing in January," he added.

John McCallum can be reached at [email protected].