Introduction

Superstition Mountains Recharge Project (SMRP) provides underground water storage capacity in the East Salt River Valley. The project was completed in 2011 and has a capacity of 25,000 acre feet of water.

In 2002, CAP initiated a siting study for the SMRP. The goal of the study was to locate areas in the east valley sub-basin of the Phoenix AMA suitable for a large-scale surface spreading recharge project. The East Salt River Valley is an area of historic groundwater decline that has resulted in land subsidence and the formation of earth fissures.

The East Salt River Valley continues to grow and the reliance on groundwater is becoming more critical. Developers are relying on the Central Arizona Groundwater Replenishment District (CAGRD) to meet their 100-year assured water supply. It is projected that the CAGRD will have a storage obligation of up to 85,000 AF per year in the east valley. A large-scale recharge project will be required to meet the storage obligation.

Earth fissure
Earth fissure at the corner of Baseline and
Meridian Road in the East Salt River Valley

CAP contracted with GeoTrans to conduct a recharge feasibility study. The study was broken into two phases: Phase A involved collecting all available data, evaluating the data, developing a ranking criteria for all available sites, and choosing individual sites for further on-site investigations. Phase B involved on-site investigations including soil analysis, infiltration testing, and fatal flaw analysis.

The study area for the Phase A work was defined as east of the Roosevelt Water Conservation District Canal, south of the Salt River Project South Canal, north of the Phoenix active management area boundary, and 5 miles east of the CAP canal (approximately 410 square miles). The eastern boundary was set at 5 miles from the CAP canal because further east would be cost prohibitive to build a project.

subregions selected for on-site field investigation
Six subregions selected for further on-site field investigation

The Phase B investigation involved on-site soil and infiltration testing to determine if the sites were suitable for a recharge project.

Project Design

The project is designed as a phased construction. The initial phase includes 40 acres of basin bottom and will be constructed on U.S. Bureau of Reclamation lands with a permitted volume of 25,000 acre-feet per year. The second phase increases the basin acreage to 154 acres and includes Arizona State Trust land with a permitted volume of 56,500 acre-feet per year.