Revealing What Lies Beneath: How GPR Supports Safer, Smarter Dam Removals

Legacy dams across the U.S. are aging, under-documented, and often structurally compromised. As more communities and agencies move toward decommissioning these outdated structures, the need for reliable, non-invasive tools has never been greater. At HydroGeo Environmental, we use Ground-Penetrating Radar (GPR) and other geophysical technologies to uncover what lies beneath—bringing critical subsurface data to engineers, planners, and restoration teams.

The Hidden Risks of Legacy Dams

Removing a dam isn’t just demolition—it’s a complex environmental and engineering challenge. Each site brings unique risks, often buried beneath years of sediment and forgotten infrastructure:

1. Aging, Unknown Infrastructure

Most legacy dams are poorly documented. Foundations, concrete cribs, or abandoned pipes may be hidden from view. GPR helps locate these structures before they become costly surprises during removal.

2. Sediment Accumulation and Contamination

Decades of trapped sediment often contain unstable layering or even contaminants. GPR can estimate sediment thickness and highlight zones prone to slumping or requiring special handling.

3. Obstructed Fish Passage and Habitat Fragmentation

Dams disrupt fish migration and aquatic ecosystems. Our GPR surveys help restoration teams plan reconnection routes with a clear picture of subsurface conditions.

4. Altered Hydrology and Flood Risk

Even after removal, legacy materials can restrict flow and increase flood risk. GPR helps identify lingering obstructions that may compromise long-term restoration goals.

5. Liability and Ownership Uncertainty

When historical ownership is unclear or liability is in question, defensible GPR data strengthens grant proposals, regulatory submissions, and due diligence documentation.

6. Community Safety and Expectations

Low-head dams are hazardous, and public support is often tied to safety improvements. Subsurface mapping supports transparent, data-driven engagement with stakeholders.

How GPR Adds Value to Dam Removal Projects

Our Ground-Penetrating Radar services support every phase of dam removal and river restoration:

• Legacy Sediment Mapping
  Estimate sediment volumes and identify high-priority coring targets to reduce planning uncertainty.

• Detection of Buried Structures
  Locate old mill foundations, pipes, training walls, or other infrastructure before excavation begins.

• Stability Planning for Drawdown
  Understand sediment layering, compaction, and perched zones to plan safe, phased drawdowns.

• Baseline Documentation
  Capture pre-removal conditions with visual data that satisfies permitting and regulatory requirements.

• Identifying Restoration Barriers
  Know where compacted layers or buried debris could hinder stream reconnection or floodplain restoration.

• Strengthening Funding Proposals
  Use high-resolution visuals and verified data to support grant applications and public engagement.

Plan with Confidence

Removing a dam is only the beginning. What lies behind it—buried structures, unstable sediment, or flow obstructions—can drive up costs and risk. HydroGeo Environmental provides the insight you need to plan with confidence. Our team combines GPR technology with decades of field experience to deliver actionable data for safer, smarter dam removals.

Ready to see what’s beneath the surface?
Contact us today to learn how GPR can support your next restoration project.