Well drilled at Trinitas to test aquifer level

A 503-foot well was completed last week at the Ridge at Trinitas, the first of two to be dug in west Calaveras County in an attempt to learn more about the area’s declining aquifer.

Calaveras County Water District is partnering with the U.S. Geological Survey to drill the two wells, which will tap into sub-basins of the enormous aquifer known as the Eastern San Joaquin Groundwater Basin.

The aquifer, which lies partly underneath a 30,000-acre area ranging from Camanche to Valley Springs, is considered by the California Department of Water Resources to be “critically overdrafted.” But little else is known about it.
   

“These wells collectively represent your first effort at monitoring groundwater in the area,” John Izbicki, a USGS hydrologist told the CCWD board of directors at their Dec. 16 meeting.

Both agencies hope the wells shed light on how quickly water is recharged in the aquifer and what effect pumping in San Joaquin County has on the declining levels. But answers to those questions will come only after several years of data are compiled.

To start, the wells will be used to collect data on the water’s chemistry, flow and age. To do so, the 10-inch diameter, more than five-story deep well at the Trinitas golf course contains four two-inch monitoring wells, which are simply PVC pipes that allow for data collection.

“All they need is just enough diameter to get scientific equipment down the tube,” explained Ed Pattison, the district’s water resources manager.

Three of the four pipes will monitor different layers of rock that hold water, while the fourth monitors the area’s water table, according to Pattison.

USGS will use two methods to date the water. One will measure the level of tritium, an element that went underground in the 1950s after atmospheric nuclear testing. The other will be carbon dating, which is accurate up to 20,000 years.

“Chances are your water is younger than that,” Izbicki said.

At least one minor discovery has been made. In digging the well at Trinitas, USGS passed through a lot of clay. This complicated the process, as clay walls require additional precautions to prevent inward collapse. It also means the region’s groundwater moves very slowly.

“You would have preferred not to see clay,” Izbicki said. Pattison countered that clay can protect water quality.

A second well will be drilled in early January, several miles east and uphill from the Trinitas golf course.

“Two monitoring wells is a start,” said Loren Metzger, a Sacramento-based hydrologist with the USGS’s Water Resources Division, “but to really adequately monitor the area, two more would be good.”

In an ideal world, according to Izbicki, they would drill eight wells.

Finding willing landowners has been difficult, said Pattison. Many have been unwilling to sign over to CCWD what amounts to “perennial access” of the well area.

CCWD is paying for its share of the wells’ construction with a $250,000 grant for groundwater projects awarded by the state’s Department of Water Resources.

The project is getting under way as the state is beginning to push for greater local management of groundwater resources, said Phil McCartney, the newly minted president of the CCWD board of directors. 

And since adopting a groundwater management plan in 2001, CCWD has been the lead agency for managing groundwater in the Camanche-Valley Springs.

At a recent meeting, McCartney asked a state official: “Are we mandated by the state?” The official responded: “ ‘Not yet, but you better get started.’ ”