Whew. It works.
The first phase of an $800,000 effort to modify three wells so Payson can store Blue Ridge Reservoir water underground has paid off, putting the worst fears of the town’s water engineers to rest.
Work crews have discovered they can efficiently inject water back into the town’s once-plunging underground water table after enlarging the bore hole and putting new casings on a 700-foot-deep well alongside Payson Parkway, said Town Hydrologist Mike Plough.
“No one really had any sure idea whether this was going to work,” said Plough of the plan to stash excess Blue Ridge water underground to raise the depleted water table under Payson by maybe 150 feet.
“We were a little nervous about it. But right off the bat we had a couple of really good, successful tests.”
That included the injection of water into the Payson Parkway Well, one of three wells the town will eventually retrofit to inject Blue Ridge water back into the ground for later use.
In addition, the town this week is wrapping up a test of its proposed water filtration system for the Blue Ridge water. Several months ago Payson connected a small filtration system up to the Washington Park end point of the pipe from the Blue Ridge Reservoir.
The portable filtration system runs pressurized Blue Ridge water through a straw-like bundle of tubes full of holes so small they can catch any silt, algae or bacteria in the water. The test demonstrated that the filtration system works efficiently on the sparkling clear, low-mineral content Blue Ridge water.
“We had a very good pilot program on the filtration system, which we’re wrapping up this week,” said Plough.
The test gave the town the confidence to move forward on its plans to build a $7.5 million water filtration plant to treat the Blue Ridge water at the end of the not-yet-built, 15-mile-long pipeline buried alongside Houston Mesa Road.
The retrofitting of the Payson Parkway Well validated the town’s long-range plan for making full use of the 3,000 acre-feet annually it will receive from the Blue Ridge pipeline. That water will start flowing in late 2014 or early 2015.
Like every other community in Rim Country, Payson has long depended almost entirely on groundwater pumped out of wells bored in the crushed layers of granite that underlies the region. Rising demand for water caused well levels to drop by 100 to 200 feet, prompting the imposition of tough growth restrictions.
The combination of one of the state’s tightest water conservation ordinances and the collapse of new development stabilized most well levels at roughly 130 to 190 feet below the surface.
The town now uses roughly 1,800 acre-feet annually, about as much water as flows into the underground water table in an average year — not counting the output of the Tower Well in Star Valley, which the town relies on mostly for backup in droughts or emergencies.
Should the town grow to its projected build-out population of about 38,000, it will likely need the additional 3,000 acre-feet from Blue Ridge.
However, it will likely take years to reach that level of use after the Blue Ridge water starts to arrive.
So in the meantime, the town hopes to stash the excess Blue Ridge water underground.
Plough said projections suggest the underground water table will eventually return to its “natural” level — with the top of the water table about 50 feet below the ground surface in most areas. By that time, the town will probably be using the roughly 5,000 acre-feet annually provided by the combination of rainfall and Blue Ridge. That will provide the town with ample stored underground water to weather even long-term droughts. It will also cut the now substantial electrical bill incurred by pumping water from wells that hit the top of the water table at depths of 150 feet or more.
The efforts to push water back down into the existing wells revealed some surprises, with some wells absorbing water quickly and some wells resisting the new water.
Plough said most of the water table consists of layers of crushed granite saturated with water, like a bucket full of gravel.
However, great networks of fissures and cracks run through that overall zone of crushed granite. Those great cracks deep beneath the surface carry water from great distances, much of it likely thousands of years old. Some of the deep wells have tapped into such a slow-motion, underground river, often under great pressure as a result of the weight of the overlying rock.
That pressure causes the water to rise in the well hole when it intersects the fracture zone. In addition, the water that emerges has a different chemistry and mix of ions than the surrounding ground water that has trickled down from the surface.
He said the bottom of the Payson Parkway Well probably taps into such a fissure zone, although the town hasn’t tested the water’s composition to make certain.
Fortunately, the high-pressure water rising from the 700-foot-deep bottom of the well will keep Blue Ridge water injected into the well from entering into the fissure zone, in which case it would eventually drain away instead of remaining safely stored for future use, said Plough.