Almost five months after the first of a group of wells in the Prosser Dam neighborhood turned up dry, residents continue to search for the reason that, to date, six pumps have been found pumping nothing but air, and water levels in the area have been ebbing.
‘We’ve been pressing ourselves to figure out what’s causing this,’ said Prosser Dam resident Gregg Bashford. ‘Is it something we’ve been doing? Is it Mother Nature? Is it the Public Utility District and the developments?’
Bashford lives north of the cluster of residents whose wells have stopped producing and hasn’t seen his water interrupted, but he has watched his static water line – the level of the water in his well when the pump isn’t running – drop ten feet since 2005.
Carol Pauli, who lives a third of a mile to the south of Bashford, hasn’t noticed a drop in her well, but is concerned by what’s been happening to her neighbors.
‘We’re looking at a lot of engineering reports and asking a lot of questions, and sometimes we don’t seem to get very good answers,’ Pauli said. ‘We’re just trying to get as much documentation as we can.’
But anyone looking for specific information on the water table and hydrogeology under the Prosser Dam neighborhood has a hard search ahead of her. As with most people in the Truckee area who own their own wells, the homeowners just south of Prosser Reservoir have never had a reason to systematically gather data on their water supply. Several of the wells affected by the recent decline in the water table have been producing for more than two decades, and none of the residents interviewed for this article could think of a well in the area that had dried up before this summer.
‘We’ve serviced our well frequently and we have had absolutely no change in our water level for 20 years,’ said Anne Collin, who lives next door to Carol Pauli. Collin’s well was drilled in 1978, and she began drinking out of it a decade later when she and her husband moved into their house. This fall her static water line dropped 36 feet, prompting her to spend $9,000 to install a new pump and bore another 100 feet of depth.
Robert Yoder, whose well gushed 100 gallons per minute until it went dry this summer, also remarked on the surprising jolt that brought an era of steady water to its end. Yoder has lived on Prosser Dam Road for 21 years, and estimated that, ‘a handful, can’t imagine there was more than ten,’ new houses have been built in the area in the last decade.
‘A couple of people have put in a koi pond or something like that,’ Yoder said, ‘But to go from a hundred-gallon-per-minute well – which is just a massive well – because someone put in their koi pond…’
With no other blatant changes on the horizon, some homeowners have explained their wandering water table by pointing toward Gray’s Crossing and the golf course attached to it. The development, which is far from complete, straddles both sides of the southern portion of Prosser Dam Road. With its empty lots, ‘coming soon’ signs, and 189 million gallon-per-year throat, it stands out as an obvious culprit to the frustrated Prosser Dam residents who drive through it every day to reach their homes.
‘It just seems like too much of a coincidence that these wells went dry as soon as they started irrigating Gray’s Crossing,’ Pauli said. ‘The construction of Gray’s Crossing has modified stream crossings, wetlands, and meadows, and I think it has changed some of the ways that aquifers are going to be recharging.’
According to the draft Environmental Impact Report for the project, the greens themselves require roughly 81.4 million gallons of irrigation each year. Residents of Prosser Dam Road assert that they have seen their static water lines fluctuate in time with the sprinklers on the links.
Dick Furtado, who lives near the southern end of the neighborhood, stated that after The Golf Club at Gray’s Crossing began watering in May, his static water line dropped ten feet. Pauli, Bashford, and Furtado saw their water levels rise through November and December, and attributed the increases to the fact that the groundskeepers had recently stopped watering. The actual dates of irrigation on the golf course could not be confirmed because the staff of East West Partners – the developer behind Gray’s Crossing – declined to return phone calls.
But for the residents who think Gray’s Crossing has slurped the water from their faucets, the issue eventually has less to do with the development itself than with the agency that sells the water.
Tim Taylor, President of TDPUD’s Board of Directors says no direct link can be drawn between the water supplied to Gray’s Crossing and the declines in the water table in the Prosser region.
Taylor explained that since Gray’s Crossing receives water from TDPUD, its water might originate in any of the utility’s 11 wells, which are scattered from Tahoe Donner to Glenshire.
‘You could also make the debate that we’re helping recharge their aquifer when Gray’s Crossing puts all that water on its lawn,’ Taylor said. ‘Because the water percolates down into the (Prosser Dam Residents’) shallow aquifer.’
Taylor further asserted that TDPUD does not operate any wells close enough to the Prosser Dam neighborhood to affect water levels in that area. According to Taylor, TDPUD’s closest well sits near the Old Greenwood development on the south side of Interstate 80, roughly 4,000 feet from the Prosser Dam Neighborhood. Taylor said the depth of the Old Greenwood well – 1,100 feet – and its distance from the private boreholes preclude it from affecting the water they draw on.
‘The sphere of influence for [the Old Greenwood well] has about a 1,000-foot radius,’ Taylor said. ‘That’s still 3,000 feet away from, and 1,000 feet below [the private wells].’
Before problems began to crop up in the Prosser Dam water table, most wells near Prosser Dam Road extended between 100 and 150 feet below the surface. Residents whose wells have gone dry have deepened their wells to as much as 275 feet to find water.
Furthermore, according to John Ulrich, Interim General Manager of TDPUD, the Old Greenwood well became operational in 2002, and has been drawing water from a deep aquifer at a constant rate, a rate that doesn’t change with irrigation schedules.
Over the last few months, TDPUD staff has said there’s another reason why their well can’t affect the private wells in the Prosser Dam area. They have asserted that an impermeable geologic layer divides ground water in the region into two distinct reservoirs.
As Ulrich explained it, TDPUD drilled a test hole near Prosser Dam Road four years ago. The drill was placed 2,000 feet toward Old Greenwood, and soil samples were taken after every ten feet of depth. The samples indicated that the shallow aquifer accessed by the Prosser Wells occupies the first 300 feet below the surface. The ‘aquatard,’ or impermeable layer of material, lies around the 300-foot mark as well, and the groundwater tapped by the Old Greenwood well extends from 300 to 1,200 feet deep.
To avoid drawing on the shallower deposit, ‘TDPUD seals its wells to the aquatard,’ said Ulrich. That means that the Old Greenwood well is designed only to collect water from depths below 300 feet (see sidebar below, Sealing Wells).
Though some of the new and deepened wells in the Prosser Dam area approach the 300- foot mark, the residents interviewed for this article stated their bore logs have shown no sign of the aquatard.
‘They said that the impermeable clay happens somewhere in the first 300 feet and we didn’t hit clay in our (260-foot) well,’ Collin said. ‘It might be in the last 40 feet.’ Then she started to laugh, incredulous and frustrated.
Absent Data
‘If you had ten hydrogeologists, you’d have five come out on one side and five on the other depending on who’s paying ‘em,’ said Bruce MacKay.
MacKay lives in Reno and owns a pump and well service that shares his name. He has worked as a driller for 30 years, worked in the Truckee area for all but five of those, and was one of the first people called when the wells dried up last summer. He may not have a master’s degree, but those who do don’t dispute the fact that getting to know the water beneath our feet can be a tricky business.
‘At any given location within (a greater groundwater basin) there are very site-specific aquifer conditions, and you have to consider that where you’re trying to develop,’ said Dwight Smith. ‘Are there barriers to flow? Are there compartments that you’re working with within the aquifer?’
Dwight Smith has lived in Truckee for the last 15 years, and owns the consultancy, Interflow Hydrology. Over the last five years the name of his company and his stamp, ‘Certified Geologist – State of California,’ have appeared on two studies commissioned by the Placer County Planning Department. Both studies were conducted to quantify the amount of water available for human use in the Martis Valley Groundwater Basin, and have been referenced by Truckee Donner Public Utility District staff.
According to Smith the impermeable layer underneath the Prosser area is not so continuous as a similar layer that extends under Martis Valley near the airport.
‘There’re really no absolutely impermeable layers in our science,’ Smith said. ‘It’s not an aquaclude. It doesn’t perfectly isolate anything from pumping effects. There’re just really no conditions like that out there, especially in our valley.’
As Smith sees it, much of the confusion surrounding the water table near Prosser Dam road stems from a problem endemic to the larger Martis Valley Groundwater Basin. Except for monitoring performed by TDPUD – which focuses almost solely on TDPUD’s own system – there just isn’t enough data on water resources and use in the area.
‘I would like to see a more aggressive water resource monitoring program in place. Our PUD here, they monitor their pumping wells, but that’s not the whole picture,’ Smith said, ‘I would like to see our community move in this direction ultimately, so that we’re collecting regional data on water levels from different aquifers. Having really strong data to work with always makes a world of difference, and that requires pretty rigorous, diligent monitoring to be in place.’
To date, TDPUD has been performing spot checks on static water lines in the Prosser area. The groundwater in the region is of particular concern to the utility. According to its 2004 Water Master Plan Update, TDPUD is planning to drill five more wells in the Prosser area before Truckee town buildout in 2025.
Sealing Wells
Most wells consist of a hole in the ground of a certain diameter, a metal casing inside the hole, and a pump way down inside the casing. Metal casings come in two types: ‘blank’ and ‘screen.’ Screen casings allow water to percolate into the well and down to the pump; blank casings do not. To prevent the highest 300 feet of groundwater from flowing to the pump, the casing in the Old Greenwood well is blank for the top 300 hundred feet and then changes to screen. But there’s more to it than that. Water can potentially flow down the space between the walls of the hole in the ground and the outside of the casing. To prevent that from happening, TDPUD placed a plug – probably of concrete – outside of the casing at the 300-foot mark.
Groundwater 101
Keep an eye out, the Truckee Watershed Council is planning to host Groundwater 101, an informational night that will cover the basic geologic and geomorphic information of the Martis Valley groundwater basin, and groundwater in general. Experts in the field will present. The event will take place within the next weeks, though as yet the date isn’t set. Keep checking: truckeeriverwc.org.
