The Magma Flood Retarding Structure (FRS) is located near the Town of Florence in Pinal County, Arizona. The dam was originally designed to protect downstream agricultural areas from the 100-year flood. Construction of the Magma FRS was completed by the Soil Conservation Service in 1964. It is currently operated and maintained by the Magma Flood Control District (FCD).
Today, the 5.5-mile-long earthen structure provides flood protection to portions of the Town of Florence and unincorporated Pinal County (including parts of San Tan Valley) comprising an estimated 6,300 residents, 2,750 residential and commercial properties, agricultural land, and related infrastructure. Additional residents and structures will be protected in the future as development continues to occur in the downstream benefitted area.
Since the time of its original construction, the FRS has developed safety deficiencies related to embankment cracking and emergency spillway capacity. As a result, the Magma FRS is currently classified by the Arizona Department of Water Resources (ADWR) to be “unsafe non-emergency.” The ADWR classification means that the structure has confirmed safety deficiencies and requires either repair or removal.
To address these concerns, the Magma FCD requested assistance from the Natural Resources Conservation Service (NRCS) under the Watershed Rehabilitation Program. Following 1) a series of technical investigations, 2) evaluation of a number of rehabilitation or replacement alternatives, and 3) completion of the Supplemental Watershed Plan and Environmental Assessment (Plan/EA), the Final Design of the rehabilitation was recently completed in February, 2011.
The Final Design of the rehabilitation of the Magma FRS provides for continued flood protection while meeting current dam safety and performance standards. The total project cost for the rehabilitation is estimated at $14 million (including both design and construction). The estimated annual flood damage reduction benefit of the project is $1.3 million. These benefits will continue to accrue for the 100- year design life of the completed project.
Under the NRCS Watershed Rehabilitation Program, the local sponsor (Magma FCD) is responsible for providing 35 percent of the total project costs. The Magma FCD is currently working with NRCS to finalize documentation and award a construction contract prior to the end of the 1st Qtr. of 2011. Construction is anticipated to begin in the 2nd Qtr. of 2011 and to be complete 15 months thereafter.
If you would like further information and details about status of the MFRS Rehabilitation Project, please contact the General Manager (see the “contact us” webpage for details).