Clark Water and Carta Advisors Create a Blueprint for Success at Shockoe Diversion Structure Project

Since mid-2023, Clark Water has been leading improvements on the Shockoe Diversion Structure project in Richmond—a key part of the city’s combined sewer overflow system. The project is designed to alleviate sewage and stormwater overflow during rain events in the City of Richmond and includes the installation of mechanical trash rake screens to prevent debris from passing through, two crest gates to minimize upstream flooding, and upgrades to supporting infrastructure to alleviate sewer overflow.

To tackle the project’s complexity, Clark Water partnered with Carta Advisors, a strategic advisor to Clark, to reduce uncertainties and drive progress through on-site visits and design consultations.

Navigating a Challenging Site

As work progressed on new diverter walls to support the trash gate equipment, the team encountered several challenges. The confined site, paired with aging infrastructure from the 1970s and a constant flow of water through the active sewer system, made it unsafe to isolate the work area. These conditions ruled out the originally planned cast-in-place walls.

Alternative precast options were explored, including proposals to cast each wall section as a single 18-foot solid piece. However, due to the tight work environment and the limited capacity of the existing five-ton overhead gantry crane, installing full-height sections was not feasible.

Ideas Become Solutions

To address the site limitations, Clark Water explored self-performing the precast concrete work and partnered with Carta Building Solutions Group, a Clark strategic partner offering engineering and consulting services, to support the structural design and execution of the new diverter wall sections.

Recognizing the complexity of the site conditions—including continuous water flow through the channel and limited crane capacity—Carta developed an innovative solution: dividing each 18-foot wall into five individually cast shell sections that could be stacked in place. Each shell included a stay-form system to create a hollow interior cavity, significantly reducing weight. Once installed, the shell cores were filled with concrete to form a monolithic structure.

Following design approval from engineer of record Greeley and Hansen, the team fabricated, reinforced, and placed all 54 precast sections on site. The effort culminated in a successful topping out, marking a major milestone for the project. 

“Seeing an idea go from paper to reality is a definite high point in my career. Jeff Diguette and the entire Carta team exemplify what it means to be One Team - One Clark”

Jeff Tousley, Senior Superintendent for Clark Water

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Continuing their partnership, Clark Water and Carta recently designed and developed temporary support for the arch sewer emergency gatehouse (ASEG) replacement at Shockoe using a detailed as-built survey of the existing gate housing structure. 

Despite the project’s complexity, the exemplary teamwork between Carta and Clark Water serves as a testament to how Clark’s vast expertise empowers our teams to consistently build what matters for the communities in which we live, learn, and thrive.