Subsurface Mapping & Investigations of Levees
Detecting Internal Anomalies That May Signal Weakness
Tremaine has over 30 years of experience in subsurface mapping & investigation, archeology, and cultural resource management, with deep expertise supporting agencies and engineering firms in evaluating levee conditions and identifying areas of elevated risk.
Our surveys and reports provide clear, data-driven insights such as:
Capablities
Tremaine’s non-invasive subsurface investigation methods, combined with our Subsurface Assessment of Flood Risk (SAFR™) approach, address long-standing challenges in levee performance assessment by strengthening characterization of embankments and foundations, detecting internal anomalies that may signal weakness or seepage pathways, and improving the identification of levee penetrations such as relic pipes, aging box flumes, and historic repair zones. SAFR™ integrates continuous high-density with historical and geomorphic context to provide a clearer, more reliable understanding of the subsurface conditions critical to levee
Inverse model of EM data showing a prominent sand ridge extending near the top of the levee
Selected Recent Subsurface Mapping Projects for Levee Evaluation
Bear River Levee (CA) – EMI Seepage Screening:
EMI Seepage Screening: Tremaine conducted a pilot Electromagnetic Induction (EMI) survey across five levee reaches with known breach and scour history to map subsurface conductivity contrasts and support seepage-risk evaluations.
The EMI data revealed several discrete stratigraphic features, including a narrow cross-levee anomaly expressed as a dark-blue, low-conductivity zone, indicating coarse alluvial channel deposits. Such materials may represent preferential seepage pathways or zones susceptible to underseepage, piping, or differential settlement.
These findings refined the subsurface conceptual site model (CSM), improved boring-location targeting, and strengthened engineering and regulatory documentation for agencies such as USACE, DWR, and CVFPB.
Mokelumne Aqueduct (EBMUD) – Through-Levee Void Detection:
Mokelumne Aqueduct (EBMUD) – Through-Levee Void Detection: Tremaine conducted a focused subsurface investigation at six Mokelumne Aqueduct levee crossings to identify air- and water-filled voids to depths of approximately 25 feet. A combined Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) approach was used to map resistivity and chargeability anomalies and delineate aqueduct geometry.
Joint-inversion modeling enhanced accuracy and reduced interpretive uncertainty, providing EBMUD engineers with a defensible subsurface model for risk assessment, O&M planning, and regulatory compliance for this critical lifeline infrastructure.
Prairie du Pont Levee, East St. Louis – EMI Stratigraphic Mapping:
Tremaine supported a regional levee improvement effort by mapping upper-stratum variability across the Prairie du Pont District, an area with long-standing underseepage issues. EMI data clearly defined ridge-and-swale geomorphic patterns, expressed as alternating high- and low-conductivity zones corresponding to clay/silt and sand deposits.
These stratigraphic contrasts enabled more accurate boring placement, improved seepage-pathway modeling, and more reliable estimation of seepage-berm fill volumes. The results informed design development and regulatory coordination with USACE and state flood-protection agencies.