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El Rio Preserve Bank Protection Project

Project Status:  Complete




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.

Project Completion

As of December, 2020, the project has been listed as substantially completed. Landscaping, minor improvements, and general maintenance of the project site will continue. A Completed Project Report provides total project details.

Virtual Tour Video

El Rio Preserve Bank Protection Virtual Tour - American Society of Civil Engineers, Southern Arizona Branch

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

January 20, 2021

Soil cement production is complete and over the next the plant will be demobilized.  The finishing work on the soil cement is taking Ashton longer than they initially budgeted and that is pushing handrail work out into February.  Late last week, the District confirmed the necessary elevations of the soil cement, and Marana’s Psomas design team will soon begin to survey the underpass for a future Loop project.  

December 16, 2020

Ashton has been laying down soil cement at the Lower Santa Cruz River levee.  Ashton anticipates being done with soil cement placement this Friday (12/18/2020).  The Construction Management team surveyor and the contractor’s surveyor will both do a final grade check on Monday (12/21/2020) to confirm the necessary elevations have been reached before the soil cement plant begins to be demobilized.  After the elevations are confirmed next week, Ashton will begin working on finishing soil cement trimming, grading the backfill against the new soil cement, and then the installation of handrail.  The final step, as with the El Rio Preserve Bank Protection project, will be hydroseed application.  It is still anticipated that the project will be completed by mid-January 2021. 

October 30, 2020
Substantial completion has been granted on the El Rio Preserve Bank Protection project. Borderland’s subcontractor is still finishing up handrail painting and post and cable work. The subcontractor will be bringing a larger crew on site this Saturday to finish up the work, after which the remaining seeding will occur. We anticipate being fully done by next Friday.  

At the Lower Santa Cruz Levee we were scheduled to start soil cement on 11/02/2020, however this morning we heard from CalPortland that they are unable to get a delivery to Ashton on Monday due to the rationing that is still occurring. We may be looking at another week before we can get a steady supply to cement for the soil cement plant.

October 23, 2020
El Rio Preserve Bank Protection project handrail and post and cable installation continues. Final grading touch up work and ripping in advance of seeding has started onsite. Today Borderlands also had a person bagging bufflegrass within the District’s property line at the El Rio Preserve. They anticipate the seeder will be onsite next Wednesday which would put next Friday as a final walk through.  

The Lower Santa Cruz Levee project is awaiting a soil cement mix design from Ashton to review. Originally soil cement production was anticipated to start on 10/26/2020, however there is a cement shortage being experienced throughout the State which has the project delayed to 11/02/2020. We have 22 tons of cement in our silo onsite, but that is not enough to start production with.

October 16, 2020
The bank protection project handrail installation is still underway and post and cable fence installation has started. Please note that the post and cable is actually being located inside new right of way on the top of the berm for ease of maintenance vs. on the actual property line which would be in an area that may be inundated when the ponds have water.

At the levee project, the existing soil cement has been milled for a key-in to the new soil cement section. The soil cement plant is anticipated to begin production on 10/26/20. The team has had two conversations with Marana and their designer Psomas regarding an anticipated Loop project and their request to the District to modify the northern end of the project to assist Marana with their property negotiations with CalPortland.  Keeping in mind what is best for the levee, we cannot accommodate Marana’s request.

A new District project named the Santa Cruz River Management Plan, has begun a 15% concept for a wildlife crossing along this section of levee.  

October 9, 2020
The installation of handrail approaches completion. Next week the handrail will be finished and post and cable fence installation will begin. After that its grading touch up work and hydroseeding. The remaining dirt piled in the staging area will be use to address some grading touch up work prior to hydroseeding. One of the areas we’d like to touch up is the existing slope of the Preserve that ties into the new earthen bank protection which is eroded and riling. As Borderlands will be onsite grading they’ve offered to do that one additional location at no extra cost to our project or to Marana. Borderlands will be moving the rock screening pile offsite prior to hydroseeding.

The levee project is continuing the build the stockpile for soil cement construction and we will be starting soil cement production the week of 10/26/20.  

September 30, 2020

Borderlands continues to make progress on the handrail, post and cable, and punch list items.  The ASCE virtual tech tour for the El Rio Preserve Bank Protection project has officially been released. You can view it here:  https://youtu.be/__iPo8d2KCQ

At the Lower Santa Cruz Levee modification project, Ashton has begun setting up the soil cement plant.  They have also started to haul material from the river to the stockpile. Ashton has hauled all of the material that was remaining at the El Rio Preserve staging area.  Next week Ashton will have the plant set up and begin calibrating it. 

September 25, 2020
Borderland has made progress on the handrail and grading touch up work. Next week should see the start of the post and cable fence as handrail is completed.  

This week at the Lower Santa Cruz Levee Modification project, Ashton has cleared the staging area, made the Cortaro Marana Irrigation District water connection, and have begun hauling the remaining material from the El Rio Preserve Bank Protection project over to their staging area. Survey is occurring on Monday to mark out with pendant fence our easements for CalPortland.

September 18, 2020
This morning the Construction Management team started a punch list at the El Rio Preserve bank protection project. The soil cement plant has been taken down and removed from the project site. In that same staging area there is still a large stockpile of screened cobbles that Borderlands will be taking offsite and a soil stockpile that Ashton will be taking offsite to the levee project across the river. Handrail installation is progressing. Post and cable fence has not started yet. Safety signage is being fabricated for the levee to alert anyone who ducks under the fence that it is not an area of refuge in a storm event due to it being low flow bank protection. There is still some touch up grading work that needs to occur prior to hydroseeding. The final step will be breaching the berms and silt fence that is protecting a section of the effluent channel which is close to the where the low flow pipe outlets. In early October there will be meeting for Marana to join in the field to hand off the gate valve wheel for the low flow pipe which, per the IGA, will be Marana’s infrastructure to operate and maintain.

The Lower Santa Cruz Levee project is still mobilizing. As mentioned last week, we’re looking at October for soil cement production. Earlier this week we were made aware by CalPortland of Marana’s 90% Loop project plans which overlaps with our levee augmentation project.

September 2, 2020
The low flow pipe through the bank protection is now backfilled with soil cement and the forms were coming off on the headwall this morning while we were in the field. The gate and trash racks were onsite for installation. The low flow notch has been widened and is awaiting some final trimming. Riprap should be coming in later this week. On September 12, 2020, Borderlands will begin to dissemble the soil cement plant and take it offsite. Handrail is still ongoing and will be one of the last items to be completed on the project along with the post and cable fence and access gate. Some additional grading/ripping will occur prior to hydroseed (week of September 14, 2020).  Project completion is tentatively expected to be done by mid-October, however with the soil cement work now complete most residents should notice a decrease in construction equipment activity.

The levee project is under contract and the first meeting will take place next week. Ashton is starting to bring material onsite for the soil embankment work. The first draft on a schedule from Ashton shows the levee project producing soil cement in October and the project being completed in early January.

August 27, 2020
This week Borderlands has continued to make progress on the low flow pipe area and handrail. The soil cement plan will run one final time this Saturday (August 26) in order to produce material to refill where the pipe was cut into the soil cement as well as even out the edge of the notch.  We’ll be meeting on Wednesday (September 2, 2020) and we will provide a second update then on the El Rio Bank Protection project.

Regarding the levee - There is an active contract with Ashton for the JOC and they’re projecting a September 14, 2020 start date. We’re coordinating some project details and once we have more information, we will share that.

August 21, 2020
Borderlands set the low flow pipe in the notch and began forming the headwall base. The subcontractor has made progress on the putting up handrail. Borderlands will run the soil cement plant one final time on August 21, 2020 to backfill the pipe and neaten the cut on the notch. That will be the last of the soil cement work and then Borderlands will begin demobilizing the plant the first week of September. We still have some final grading to do in front of the soil cement (removing the berm that protects us from the active channel), at the pipe inlet, and near the notch, as well as placing riprap and applying hydroseed. We will also be signing the access gates and bank protection handrail with signs that communicate the area is maintenance only access and that it is not a refuge location during storm events. We want to make it very clear to anyone who chooses to trespass and walk that alignment that it is not a safe place to watch a storm from because it will overtop in larger events. The Friends of El Rio would like to limit people being able to walk to the islands and the western island can be reached from the bank protection berm until more water is in the ponds.

The levee modification project across the river has been awarded to Ashton. We are currently working on bringing them under contract. Ashton will be utilizing the remaining stockpile onsite for that project. Ashton will set up its soil cement project across the river from the El Rio Preserve and it should be less of a disturbance to the neighbors adjacent to the Loop. September 14, 2020 is the tentative start date.  

August 14, 2020
Borderlands has been working on cutting the low flow drain pipe and the notch into the bank protection. Their subcontractors have been working on installing handrail. Next week the pipe installation will be finished, along with the headwall and gate valve. Riprap will be added to both drains. The soil cement plant, which is quiet right now, will be fired up again to produce material for backfilling the low flow drain pipe and neatening the cut for the notch. Handrail and post and cable fence will be the last items completed on the project in early September. Borderlands, as they begin demobilizing in early September, will hydroseed all of the disturbed areas. We will be leaving 1,000 yards of material stockpiled on site for embankment backfill on the levee project across the river which will start this fall. The material will be seeded to temporarily stabilize it. Once the contractor is selected for the levee project, which should occur August 18, 2020, we will be able to provide the schedule and staging information for that project.

August 7, 2020
This week Borderlands reached final soil cement elevation at the El Rio Preserve Bank Protection project. They have a little bit of touch up work next week before they start installing the low flow drain and creating the notch. The TEP line has been encased in soil cement per our agreement with TEP. We expect handrail and post and cable fence to start next week and run into early September. 

In conjunction with the American Society of Civil Engineers Southern Arizona Branch, the District has been working on a virtual tech tour of the El Rio Preserve Bank Protection project from when we were a little over half way through soil cement placement.  A video will be shared once ASCE SAB has completed it and the District has approved it for release.

The levee work across the river is now open for JOC bid. Once that bid closes on August 18, 2020, there will be  more information about the timeline for that work and if it will use the same staging area, as that will depend on the contractor awarded the project.

July 31, 2020
This week at the El Rio Preserve Bank Protection project Borderlands reached final elevation of the soil cement for the area north of the TEP line and have begun trimming the soil cement. The areas remaining for soil cement work include one segments of the key-in structure that is currently being excavated and the area surrounding the TEP line which needs to be phased in order to work around the powered TEP line. This morning the TEP line was strapped to its support I-beam as Borderlands begins to excavate around it. ADEQ visited the site to perform a dust inspection and found the contractor in compliance.

Next week we are scheduled to have all soil cement complete and fully trimmed. Borderlands will then move into installing the 24” RCP, headwall and gate valve for the low flow drain and cutting the notch. The following week handrail and post and cable fence will start being installed.

July 23, 2020
Currently we’ve received about an inch of rain at the El Rio Preserve. We’ll be shutting down the soil cement operation for a few days to allow the site to dry out. We did receive approval from TEP on our encasement design for their line and were starting to move forward with that before the storms hit.

July 17, 2020
This was the first week of soil cement production and placement at the El Rio Preserve Bank Protection project. We made excellent progress and were able to get 9 feet high out of the toe trench.  The goal is to continue to push hard to get above flow line elevation next week. As the soil cement comes up, Borderlands backfills with native material against it, so over time the entire toe trench will look shallower and the soil stockpile and adjacent berms will come down as that material is being used.  The TEP line crossing the Santa Cruz River has been exposed, and TEP determined that it is fully encased in concrete.  We’ll be working with TEP to encase this line in soil cement as our bank protection is built under and around the existing line.

The ash and woody debris that came down the Canada del Oro Wash from the Bighorn Fire yesterday has reached the effluent channel just outside of our project limits.  Residents should be aware that the shiny black coating visible on some of the rocks and banks is ash, not oil or another biohazard, and that it has increased the turbidity of the water temporarily.

July 10, 2020
Borderlands continued excavation to reach the bottom of the soil cement toe trench and the surveyor confirmed that elevation today. The soil cement plant is set up and they’re starting to run calibrations to soil cement mix design. The stockpile is at its full height. Starting Monday they will begin soil cement operation. Find out more about the soil cement process.

Next week will begin an 8 hour day on Saturday (starting at 7 AM) to push to get the soil cement up above the flow line of the adjacent Santa Cruz River.  There is a berm buffering the site from the river but risks include a breach with the right event.  TEP is looking into a transmission line that they have crossing the Santa Cruz River which was not marked during the design blue stake. It will not impact the overall project time frame but just adds some additional complication for phasing as soil cement is placed. 

The most active time period on the site will be when the soil cement is being laid. Heavy equipment will be moving quickly throughout the site and there have been a few concerning incidents with members of the public ignoring the construction signage and entering the site, from an ultimate Frisbee player going into the toe trench to receive a Frisbee to kids coming over to play in the stockpile. Please remind all of the people you speak with that for their own safety they need to obey the construction signage and stay out of the site, even when the contractor isn’t onsite.

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.

Funding & Management

Location: Town of Marana
District: 3
Funding Source: Flood Control Tax Levy
Managing Department: Flood Control
Design Consultant: Psomas
General Contractor: Borderland
Project Number: CFC.5LKMNA
Project Delivery Method: Design-Bid-Build
Project Budget: $1,210,000
Total Actual Cost:  $2,272,544
Design Cost: $255,323
Construction Cost:  $1,774,219

Public Outreach

El Rio Project Moving Forward with Santa Cruz Bank Protection - Tucson Local Media 01/01/2020
Protecting wildlife part of Santa Cruz River construction projects - Pima County FYI Newsletter 02/14/2020
El Rio Preserve offers rare sanctuary for birds, native species - Pima County FYI Newsletter 10/23/2020


El Rio Preserve Bank Protection Virtual Tour - American Society of Civil Engineers, Southern Arizona Branch