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El Rio Preserve Bank Protection Project

Project Status:  Construction of Bank Protection started June 2020
Santa Cruz River sediment relocation to preserve expected to occur January 2020 to April 2020



The El Rio Open Space Preserve is owned and managed by the Town of Marana.  The Preserve is 104 acres, comprised of parcels 226-01-0170, 226-03-0130, and 226-03-0120. It was an active gravel pit in the 1960s and 1970s to provide materials for the construction of I-10. It is located adjacent to the Santa Cruz River and an earthen berm protected the gravel mining operation from typical river flows. It is within an area of rich riparian habitat for nesting and migratory birds.  In fact, around 240 bird species have been observed within the Preserve.  Marana has a series of improvement projects planned for the Preserve. For current information on what Marana has planned and their schedule, please see Marana’s Website at: http://www.maranaaz.gov/elrio.

In the past, high flows in the Santa Cruz River would occasionally overtop the earthen berm and flood the pit. In 2014 the earthen berm protecting the Preserve breached, causing more frequent influxes of water, sediment and trash into the pit.  This compromised some of Marana’s earlier efforts to restore the site.

flood trash
To protect the Preserve from frequent flooding, allowing for restoration and further enhancements, the Pima County Regional Flood Control District (District) has been asked by Marana to design and construct bank protection along the northern side of the Preserve at the Santa Cruz River.  This would replace the eroded earthen berm that previously protected the lakes.  The intent of the bank protection is to help minimize the damage from frequent flooding.  This includes reducing the amount of trash and invasive species that flow in during a storm event.  The bank protection will be constructed from soil cement and is being designed to protect the Preserve from receiving flows up to the 25-year event. 

The El Rio Preserve Bank Protection project construction plans are 100% complete and can be found below. In June 2020, The District, and its contractor Borderlands, have started construction within the Preserve.

Located south of the Town of Marana’s El Rio Open Space Preserve, the Pima County Los Morteros Conservation Area and Heritage Trail received enhancements in June 2019 to improve the educational opportunities of the site that embodies the major traditions of the region, including Native American, Spanish, Mexican, and the American Territorial.

Complete Plans


The following design documents are currently available:

*It is important to note that these are not final construction documents and some details may have changed between the 100% and 50% design.

Project Updates and Schedule

June 29, 2020

Last week at the El Rio Preserve Bank Protection project Borderlands continued excavating the bank protection toe trench and stockpiling the material by the soil cement plant.  The soil cement plant was delivered and Borderlands has started to assemble it.  This week it will be more of the same work, excavating the trench to final depth and the stockpiling soil to the quantity that we will need for this project as well as the levee modification work across the river.  The soil cement plant should be assembled and tested by 7/6/20.  We anticipate starting placement of soil cement the week of 7/13/20.  Our tentative completion date for the project is October 2020.  No Saturday work is going to occur yet but Borderlands is working on their schedule that will show proposed Saturday activity once the soil cement plant is in production.  

June 19, 2020

Borderlands has begun excavating the toe trench for the soil cement. On this project our soil cement goes 12 feet below finished grade. Once the proper depth of the toe trench is reach and confirmed by our construction management team, soil cement placement can begin. We believe excavation will take us until 7/5/20. There is now a lot of heavy equipment moving quickly on site, so please remind folks to obey the construction tape and signage. While we’re excavating you’ll also see the stockpile on the Pima County parcel continue to rise. That stockpile will have enough material to make soil cement for both the Preserve bank protection as well as future levee project across the river scheduled to bid in October 2020. Any material in excess of what is needed for the two projects will be placed on stockpile area #4 (far east adjacent to the Loop) as agreed upon with Marana to get the enter area up to an elevation of 2077 feet. A soil cement plant will be setup on the Pima County parcel starting 6/24/20. It will take about 10 days to set up the plant, calibrate it, and produce a test run. Borderlands will be providing an updated comprehensive schedule that will include hours. 


Sediment Removal and Relocation Project

This project is separate from, but contributes to the overall design of El Rio Preserve. It entails removing built up sediment within the Santa Cruz River and placing it within the Preserve to create an island and build up other areas as part of the master plan. This project is pending Town of Marana and Board approval, but construction is expected to occur between mid-January 2020 and April 2020.



New earthen berm, soil cement bank protection will be constructed on the right hand side of the berm in the direction this image is looking.


Looking the opposite direction along the new earthen berm where the future soil cement will be on the left.


Information related to Funding will be placed here as it becomes available.

Public Outreach

El Rio Project Moving Forward with Santa Cruz Bank Protection - Tucson Local Media 1/1/2020
Protecting wildlife part of Santa Cruz River construction projects - Pima County FYI Newsletter 2/14/2020