Hydrogeologic Investigations for the Tonopah Desert Recharge Project

The Tonopah Desert Recharge Project began operating in January 2006, demonstrating that it is capable of storing the maximum permitted annual volume. M&A is now engaged in investigations to develop a wellfield for recovering this stored water. These investigations include exploratory drilling and hydrologic testing to characterize aquifer characteristics and groundwater quality.

Overview

The CAP conveys Colorado River water to users in central and southern Arizona. Because Arizona’s allotment of CAP water has historically exceeded customer demand, M&A was hired to investigate the feasibility of storing surplus water underground, where it would be available for future recovery during times of shortage — particularly during shortages on the Colorado River.

Services

M&A has been involved in many phases of this project. Beginning in 2000, we investigated six groundwater basins in western Arizona to determine the suitability of artificially recharging 200,000 to 300,000 AF/yr. We then conducted feasibility studies for selected sites, identifying the most favorable ones based on a range of criteria. The CAWCD selected the Tonopah Desert site, located about 50 miles west of Phoenix, as the highest priority. M&A supported the design and permitting of the recharge project and prepared a preliminary design for recovery facilities. We are now helping the CAP and Arizona Water Bank plan for the recovery of this water.

Managed Aquifer Recharge

  • Characterized hydrogeologic conditions and conducted drilling, hydrologic testing, and groundwater flow modeling to support facility design and permitting
  • Worked with the client and its engineering consultant to develop a design for the recharge facility
  • Prepared a preliminary wellfield design for recovering stored water
  • In 2009, developed a recovery plan for pumping 100,000 AF/yr for 20 years; updated this plan in 2015 (to pump 10,000 to 30,000 AF/yr through 2045) when the CAP decided to scale back
  • Designed a conceptual wellfield and estimated construction and operating costs for various wellfield scenarios

Groundwater Modeling

  • Modeled the effects of full-scale recharge operations to project the maximum “area of impact” and the transport of selected chemical constituents
  • Revised the model to evaluate the possibility of recharge-induced flushing of nitrates from the vadose zone
  • Used a numerical model to project drawdown and pumping lifts under various scenarios to minimize operating costs for the wellfield

Permitting & Compliance

  • Conducted pre-application meetings with regulatory agencies
  • Prepared required permit applications with supporting hydrogeologic reports, monitoring plans, and contingency plans
  • Designed and installed an automated data-acquisition and telemetry system to monitor groundwater levels in wells and piezometers