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GEOWEB Slope Protection System: Surface slide repair of dam

News | June 10, 2024 | By:

Lake Overcup, located north of Morrillton in Conway County, Ark., is a hidden gem for fishing enthusiasts. Notorious for its crappie honeyholes, this lake not only attracts avid anglers, but also big game hunters, bird enthusiasts, and those just seeking a serene and tranquil retreat.

On the 1,025-acre lake rests the Overcup Dam, a mile-long dam constructed by the Arkansas Game and Fish Commission (AGFC) in 1963. Since its inception, the AGFC has performed routine inspections, maintenance, and repairs to the dam and surrounding areas.

Lake Overcup Dam Background

Native soils had been used to cover the clay foundation on the dam’s backside, which led to unplanned foundation movements that compromised the dam’s integrity. Areas around the dam have been known for these surface slides with the first occurrence dating back to 1987. To repair these surface slides, rip rap was used and seemed to be stable for a few years.

During a routine inspection in 2017, a noticeable slide on the backside of the lake’s dam was discovered. The AGFC worked with engineering firms to conduct a variety of tests to confirm the dam was not facing imminent failure, but repairs would need to be completed to prevent further damage.

Since the structural instability became evident by the foundation movements, the AGFC ordered a structural report to investigate the rip rap application used to fix these slides in the past. It was determined that the rip rap method used was not stable or a reliable long-term solution, so a new design for the dam rehabilitation was required.

Evaluating Foundation Stabilization Solutions

In January 2020, the AGFC submitted a project evaluation to Presto Geosystems’ engineering team to evaluate using the GEOWEB® Soil Stabilization System to repair the surface slides on the downstream face of the dam. In addition to the slope repair, a levee overlooking the lake and an access road leading up to the dam also needed to be stabilized. The total project size was estimated to be around 35,000 square feet.

Presto Geosystems project evaluation example.

Benefits of Using Geocells for Erosion Control and Soil Stabilization

The GEOWEB Geocells are a three-dimensional, honeycomb-like structure that provides stability and strength to cohesionless soils. Made from robust high-density polyethylene (HDPE), the GEOWEB panels prevent significant soil movements by confining the infill to each individual cell. Infill options vary from vegetation to aggregate, and hard-armored concrete to on-site/low-quality fill. By separating the infill into smaller segments, the system resists movement and prevents soil erosion.

The GEOWEB System is recognized as the industry’s most complete geocell system, designed with fully engineered components to withstand the most challenging site conditions. The system includes proper integral components with higher performance strength and faster installation than with alternative methods.

Repairing Surface Slides Using GEOWEB Geocells

Based on the calculated outputs from the Lake Overcup Dam project evaluation, the GEOWEB Slope Protection System was the perfect long-term solution to repair the dam’s surface slides.

After a lengthy national recess, construction began in late spring 2022. The contractor, Curtis Construction, was working on a very tight construction schedule, often working 24 hours a day, to make sure this project was completed that summer.

A mid-size GEOWEB Geocell System, four inches deep (GW30V4), was selected and installed over Mirafi’s 180N geotextile on the 3:1 slope. The panels were connected using the integral ATRA® Keys at each interleaf and end-to-end connections. The GEOWEB System was anchored using the 16-inch, HDPE ATRA Speed Stake.

Given the tight construction timeframe, Curtis Construction was able to complete the project that summer, thanks to the ease of installing the GEOWEB panels with their integral components.

Project Results

The GEOWEB cellular confinement technology is a versatile system capable of creating long-term and reliable results for many of the common problematic areas in dams and levees.

GEOWEB Geocells function as the support structure for unpaved roadways, capable of supporting maintenance vehicles. They also function as surface erosion control solutions, preventing the formation of rills or the collapse of unstable soils due to water flow, wave action, and other ecological events.

Finished: GEOWEB vegetated slope repair.

The GEOWEB Geocells met all the project requirements, budgets, and timelines marking this project a success for AGFC. Learn more about Presto GeoSystems here.

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