Water Treatment Plant Drainage Design

Ponding surface runoff and inadequate drainage around the potable water storage tanks at the City of Harrisonburg’s Water Treatment Plant had led to subsidence issues, threatening the stability of critical infrastructure. To address these concerns, Colman Engineering provided civil engineering design services to develop an effective drainage solution that would protect the facility while minimizing land disturbance and regulatory impacts.

The project began with a detailed site survey to map existing tanks, utilities, structures, and topography, providing essential data for design. Colman Engineering then analyzed the existing drainage patterns to determine the optimal approach for redirecting runoff away from the tanks. The resulting design incorporated carefully planned grading and stormwater conveyance structures—including channels, storm inlets, pipes, and curb and gutter systems—to ensure water was efficiently managed without overwhelming downstream systems. Given the site’s constraints, Colman Engineering worked to keep land disturbance below the 10,000-square-foot threshold, avoiding additional permitting requirements while still achieving effective stormwater control.

In addition to mitigating drainage concerns, erosion control measures were incorporated to prevent sediment from leaving the site or impacting nearby properties or waterways. Throughout the process, Colman Engineering remained actively involved in construction administration, responding to contractor inquiries, conducting site visits, and making plan adjustments as needed to ensure the successful implementation of the design.

By addressing subsidence risks with a thoughtful and efficient drainage system, Colman Engineering helped the City of Harrisonburg safeguard its water treatment infrastructure, ensuring long-term reliability and compliance with stormwater management standards.