Hydrogeologic Investigations for the Tonopah Desert Recharge Project

The Tonopah Desert Recharge Project (TDRP) began operating in 2006, with storage volumes up to 150,000 AF/yr in 2009 and 2010, demonstrating that it is capable of storing the maximum permitted annual volume. A total of 806,000 AF of CAP water was stored from 2006 through 2014, when recharge operations were suspended due to limited availability of CAP water. M&A provided services for the siting, design, and permitting of the recharge facility, and since 2015 has been engaged in investigations to develop a wellfield for recovering the stored water.

Overview

The CAP conveys Colorado River water to users in central and southern Arizona. Because Arizona’s allotment of CAP water had historically exceeded customer demand, M&A was hired to investigate the feasibility of storing surplus water underground, where it would be available for recovery during future shortages in the supply of water from 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 CAP 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 more recently has been assisting CAP to plan for recovery of stored water.

Managed Aquifer Recharge

  • Characterized hydrogeologic conditions and conducted infiltration testing, drilling, hydrologic testing, and groundwater flow modeling to support recharge facility design and permitting
  • Worked with the client and its engineering consultant to develop a design for the recharge facility
  • Designed and installed monitor wells and vadose zone piezometers
  • Designed and installed an automated data-acquisition and telemetry system to monitor groundwater levels in wells and piezometers

Groundwater Modeling

  • Modeled the effects of full-scale recharge operations to project groundwater level rise and the maximum “area of impact” in support of recharge permit application
  • Modified the model to simulate transport of recharge-induced flushing of nitrates from the vadose zone
  • Calibrated the groundwater model based on water level response to recharge operations, and prepared preliminary projections of drawdown and pumping lifts for conceptual design of onsite recovery wellfield

Permitting & Compliance

  • Conducted pre-application meetings with regulatory agencies
  • Prepared required permit applications with supporting hydrogeologic reports containing demonstrations of recharge feasibility and avoidance of adverse impacts, monitoring plans, and contingency plans

Recovery Planning

  • Designed a conceptual recovery wellfield at the TDRP site, estimated construction and operating costs, and prepared recommendations for characterization of deep part of aquifer
  • Conducted exploration drilling and geophysical logging program to characterize the aquifer to a depth of 1,400 feet at the TDRP site
  • Installed hydrologic test well and conducted aquifer testing program to characterize vertical variations in aquifer hydraulic conductivity and chemical quality of groundwater to a depth of 1,000 feet
  • Based on results of characterization of deep part of the aquifer, assess technical and economic feasibility of recovering water with onsite recovery wellfield, and prepare recommendations for extending recovery wellfield offsite
  • Conduct GIS overlay analysis to identify and rank options for recovery wells outside of the TDRP site
  • Conduct initial surface geophysical surveys to supplement existing data for characterizing hydrogeologic conditions in deep part of aquifer outside the TDRP site