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Four new groundwater monitoring wells

South Sonoma Valley wells will provide new information

By Jay Gamel

While the county’s Groundwater Sustainability Agency (GSA) has been monitoring groundwater through residential and commercial wells volunteered for the program since 2017, four new wells specifically designed to capture a broad range of information will soon be expanding the available data.

The Sonoma Valley Fire District approved the installation of the first of four new groundwater monitoring wells on a small piece of their property on Felder Road, just off Arnold Drive. It is expected to be producing results by this year.

California experienced droughts from 2007 through 2009 and from 2012 through 2016, both resulting in measurable impacts to the state’s groundwater system, including noticeable subsidence of ground levels throughout the Central Valley and even here in Northern California.

The groundwater losses resulted from those droughts proved severe enough for the state to mandate future groundwater monitoring and conservation, identifying several critical areas, including Sonoma Valley, Petaluma Valley and the Santa Rosa plain. All three areas now have mandated groundwater agencies charged with collecting data and handling future conservation and regulation, if necessary, of all local groundwater.

Under the 2017 Groundwater Sustainability Act, counties that do not develop their own groundwater conservation rules will have state rules imposed. So far, the state has been generous in endowing agencies set up in all three critical areas of the county, including the current underwriting of $828,000 in costs to drill and implement data gathering from the new wells, according to Sonoma Water spokesperson Ann Dubay.

“We are still negotiating with property owners and must do an environmental assessment,” Dubay said, concerning the other three wells, “so the locations could change.” The wells are tentatively scheduled to be drilled near the intersection of Highways 121 and 116; near the intersection of Burndale and Herschel roads; and at the County Corporation Yard at the intersection of 8th St. East and Hamblin Road.

The cost of drilling, constructing and monitoring the four wells will be funded by a grant from the California Department of Water Resources, through the California Drought, Water, Parks, Climate, Coastal Protection, and Outdoor Access for All Act of 2018 (Proposition 68 on that year’s ballot).

Mitchell Buttress, a hydrogeologist at Sonoma Water, will oversee developing the wells as project manager.

“These wells will not deliver water,” Buttress said. “They are strictly for monitoring groundwater conditions. They are different from supply wells mainly in that they are smaller in diameter.” He said these monitoring wells have a 2.5-inch diameter vs. a 6-inch diameter or more for working water supply wells.

He noted that monitoring wells have many more sensing points than supply wells and can measure chlorides and other elements not usually available with supply well monitors.

“These dedicated monitoring wells will be significantly more capable of producing good data relative to monitoring an existing supply well,” Buttress said, since they are constructed specifically to monitor discreet aquifer zones, whereas supply wells often have longer screened intervals that span several aquifer zones.

“Additionally, we are often not able to install pressure transducers or other monitoring devices in active supply wells due to pumps and associated equipment,” he added.

The wells will be monitored by people, though telemetry can be added, if needed. “However, it is important to have periodic manual water-level measurements to calibrate the transducer data, so we like to visit the sites quarterly, nevertheless,” Buttress concluded. Dubay said that drilling and well construction will take approximately one week at each location, and the footprint of each well will be very small. “The visible evidence of each well at the ground surface will be an approximately 2’x2’ flush mount steel vault,” she said. The data collected from these wells will be made available to the public via an online portal at Sonoma Water, sometimes referred to as the Sonoma County Water Agency.