GEOWEB® Retaining Wall System

Project Name: Kaiser Permanente Retaining Wall

Project Location: Gaithersburg, MD

Project Background

The Kaiser Permanente Medical Center in Gaithersburg, Maryland, aimed to install a solar array on its property to reduce energy costs and greenhouse gas emissions. The proposed installation site, however, presented challenges due to its steep slopes, which were unsuitable for supporting the solar array. To move forward with the project, a cost-effective solution was needed to stabilize the site without disrupting the medical facility’s daily operations.

Challenges of Installing a Solar Array on Challenging Terrain

The primary challenge was stabilizing the steep terrain to support the solar array while avoiding the high costs and operational disruptions associated with removing the existing stockpile of soil. The soil removal was not only cost-prohibitive but also would have created significant construction traffic, interfering with the day-to-day functions of the medical center. A sustainable, long-term solution was required to manage the site effectively and support the solar array installation.

Innovative Solution: GEOWEB® Soil Stabilization System

Project Engineer Ted Hastings from Becker Morgan Group collaborated with project owners and key partners, Colonial Construction Materials and Presto Geosystems, to develop a cost-effective and sustainable solution for the site’s unique challenges. Presto Geosystems provided a complimentary project evaluation and recommended the construction of a vegetated, gravity retaining wall using the GEOWEB Soil Stabilization System. This innovative approach was ideal for the project as it enabled the use of on-site fill materials, significantly reducing costs by eliminating the need for soil removal and the importation of off-site materials.

The GEOWEB System, using 6-inch geocell wall panels, was employed to construct a vegetated retaining wall that effectively stabilized the slopes and supported the solar panels. The system’s design facilitated the use of existing soil on-site to infill the wall, reducing costs and minimizing environmental impact.

ATRA® Keys were used to securely connect the GEOWEB sections at each end-to-end connection, ensuring a strong and permanent assembly. This innovative approach simplified installation and reduced construction time.

The retaining wall was then infilled with nutrient-rich topsoil in the front cells to promote vegetation growth, while the remaining soil provided the necessary support for the solar array. Proper drainage was ensured by installing a perforated pipe behind the wall, preventing pore water pressure buildup and enhancing long-term stability.

After constructing the wall, Power Factor hydroseeded the area with Biotic Earth Biotic Soil Amendment, followed by an application of hydraulic mulch and grass seed. This process enriched the less-than-ideal soil with essential nutrients like peat moss, Mycorrhizae, and beneficial bacteria to accelerate the nutrient cycle and promote robust vegetation growth.

Benefits of the GEOWEB® Retaining Wall for Solar Panel Installations

The GEOWEB Retaining Wall System provided a practical and environmentally friendly solution for the solar array installation. Utilizing on-site soil minimized the need for transportation, reducing both costs and environmental impact. The vegetated retaining wall not only stabilized the slopes but also seamlessly blended into the surrounding environment, enhancing the aesthetic appeal of the site. This approach also ensured long-term stability for the solar array and supported the facility’s sustainability objectives

Project Outcome

The project was successfully completed, resulting in a soft-armored retaining wall that both supports the solar array and integrates naturally with the existing landscape. The collaboration between Kaiser Permanente, Colonial Construction Materials, and Presto Geosystems achieved a stable, cost-effective solution that met all project requirements without disrupting the medical center’s operations, setting a standard for future sustainable construction projects.