Oro Valley staff report rising static water levels at more than half of production wells; operations guided by monitoring and periodic rehabilitation

Oro Valley Water Utility Director Peter Abraham told the commission on Feb. 10 that staff saw static‑water‑level recovery in nine production wells in the most recent year, up from eight the prior year, and that ongoing monitoring and targeted rehabilitation guide well‑field operations.

Abraham said staff collect monthly data from 16 production wells in the main well field, two production wells in the Countryside service area and monitoring data from six nearby non‑Oro Valley wells and additional monitoring wells across the service area. He described the town’s principal groundwater production area as the Big Wash / CDO Wash corridor, where hundreds of feet of alluvial sand and gravel provide transmissivity and higher quality water.

“Once we commissioned the NWRDS and we start bringing in additional sources of supply, I’m really excited to see a couple years of that to see how many more of our wells show recovery,” Director Peter Abraham said, referring to planned new supplies and regional wheeling agreements. Abraham said he expects to see additional recovery over time as imported water reduces demand on local aquifers.

Key technical findings and operational points discussed in the meeting: - Degree of recovery: nine production wells showed static‑level recovery this year versus eight the prior year; earlier years showed fewer recovery wells (three in 2020, five in 2021, four in 2022, eight in 2023). Abraham said the five‑year average of drawdown is approaching zero in several zones, a trend he attributed to reduced pumping and increased use of imported supplies. - Well counts and users: staff track 16 production wells in the main field, two in Countryside, about six nearby non‑utility wells and roughly 250 private exempt wells within and near Oro Valley. Abraham said the Oro Valley Country Club is a major local groundwater user and estimated its pumping at about 400 acre‑feet per year; private exempt wells in the northwest portion of the area together likely represent a significant aggregate use. - Example of well response: well C5 pumped approximately 606 acre‑feet in one year when other nearby wells were offline for rehabilitation; in the next year C5 pumped about 280 acre‑feet and the static level recovered about 3.75 feet after a prior decline of roughly 7.5 feet. Abraham used this pattern to illustrate how concentrated pumpage and well rehabilitation affect localized drawdown and recovery. - Rehabilitation and condition monitoring: staff monitor specific capacity (gallons per minute per foot of drawdown), pumping water level, discharge pressure and flow to detect whether capacity loss is due to screen plugging or mechanical wear. Abraham described standard rehabilitation techniques—brushing and bailing, video inspection, re‑equipping pumps and replacing worn components—and said staff aim to rehabilitate roughly two to three wells per year so that each well is inspected about every 10 years. - Regulatory context: some Oro Valley wells are registered as “recovery wells,” which allows replacement of pumped groundwater with a portion of the town’s Central Arizona Project (CAP) allocation. Abraham noted a regulatory threshold mentioned in the meeting: a five‑year average drawdown below four feet is used to maintain recovery‑well status (as stated by staff during the discussion). - New supplies and infrastructure: staff tripled wheeling capacity at Countryside, which has already reduced Countryside pumping, and Abraham said the entitlement to the Northwest recharge/delivery resource discussed in the meeting (referred to as NWRDS) is 4,000 acre‑feet; the broader CAP allocation figure mentioned in the discussion was 10,305 acre‑feet. Staff do not expect the NWRDS source to materially change well‑field metrics for another year while it is commissioned.

Abraham emphasized that staff collect long time‑series data to draw correlations between annual pumping, static water‑level changes and well performance. He said some anomalies remain and that understanding them requires continued monitoring and operational adjustments to balance duty cycles across the well field.

The commission asked technical questions about measurement frequency and SCADA access. Abraham said most modern well instrumentation provides continuous readings (water level, discharge pressure and flow) and that he reviews the longer time series annually for the purpose of the ADWR report; he indicated a desire to move toward quarterly operational reviews.

Next steps: staff will include these groundwater metrics in the Oro Valley annual report and continue to monitor wells, pursue scheduled rehabilitations and bring additional imported supplies online when available.