Todd Engineers: Hayfield

Hayfield Groundwater Storage Program
Metropolitan Water District
Riverside County, California

Metropolitan Water District is developing a significant water storage project in the Hayfield Groundwater Basin in northern Riverside County. The project consists of recharge basins to store excess water from the nearby Colorado River Aqueduct during wet years and extraction wells to recover groundwater during dry years. Todd Engineers and Kennedy/Jenks Consultants (Kennedy/Jenks/Todd) have had the opportunity to assist Metropolitan with numerous components of the storage project from preliminary facilities designs and planning workshops to field investigations and database management.

Key Issues
Large-scale storage and recovery project Conjunctive use of water resources Complex heterogeneous basin hydrogeology Arid environment

Services Provided
Pilot production well installation and testing GIS-based mapping Exploration program design and implementation

In 2002, Kennedy/Jenks/Todd drilled and installed the first two pilot production wells in the basin using an innovative approach that combined rotary and cable tool drilling to depths of up to 1,436 feet. An evaluation of the hydrogeologic data indicated that more favorable aquifers were more likely located in the upper portions of the alluvial fans, away from the fine-grained sediments associated with the central portion of the basin.

Kennedy/Jenks/Todd developed and implemented an exploratory borehole/test well program that provided aquifer parameters and hydrogeologic data from all portions of the project area, including areas where no previous data existed. The main objective of the project was to better define the hydrogeologic framework of the storage project site and locate areas of more favorable aquifers and well yields.

During 2003, we sited, drilled, installed and tested nine test wells and two monitoring wells that identified several areas of higher well yields. For example, well yields in the more permeable areas are expected to exceed 2,700 gallons per minute (gpm), more than twice the yield anticipated in the central portion of the basin. This information will allow for an optimization of facilities at the site and will ultimately improve project economics.

This cross section depicts the alluvial fan facies encountered in Cholla Wash and demonstrates higher permeable zones west of the H-14P and H-15P test well locations. The exploration project will target more permeable facies on other alluvial fans in the basin.

Our current work is focused on water quality. Kennedy/Jenks/Todd is investigating areas of elevated nitrate with a sampling and analyses program that involves perforating existing wells, well development, and groundwater sampling. Analyses will include nitrogen and oxygen isotopes to evaluate potential nitrate sources and age dating by tritium, helium-3, and chloroflurocarbons to better understand local recharge and travel times throughout the basin.