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Magma FRS

Magma Flood Retarding Structure

Rehabilitation Fact Sheet


  1. Magma Flood Control District
  2. Florence-Coolidge Natural Resource Conservation District

Project Location: Pinal County, Arizona

Authorization: Watershed Protection and Flood Prevention Act, Public Law 83-566, as amended, and Public Law 106-472, Small Watershed Rehabilitation Amendments of 2000.

Estimated Construction Cost: $11 million
Projected Construction Start:
January 2011

Project Summary:

The Magma Flood Retarding Structure (FRS) was originally constructed by the Soil Conservation Service (now the Natural Resources Conservation Service–NRCS) in 1964.  It is operated and maintained by the Magma Flood Control District.  The 5.5-mile-long earthen structure provides flood protection to a portion of the Town of Florence, Arizona, including:

  • an estimated 1,100 current residents,

  • 500 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.

The FRS has developed safety deficiencies and inadequacies since the time of its construction related to embankment cracking and emergency spillway capacity.  To address these concerns, the project Sponsors, with assistance from the NRCS, recently completed a Supplemental Watershed Plan and Environmental Assessment (Plan/EA).  The Plan/EA calls for rehabilitation of the Magma FRS to provide for continued flood protection while meeting current dam safety and performance standards.  The total flood damage reduction benefit from the rehabilitation project is estimated at $29 million.  NRCS is currently working with the sponsors to prepare engineering designs and construction plans for this high priority dam rehabilitation project.