Flat Rock Dam Fish Passageway,
Montgomery County, Pennsylvania

Home 5 Selected Projects 5 Dams 5 Flat Rock Dam

Overview: Built in the early 1800s as part of the Schuylkill Navigation System, the Flat Rock Dam is a gravity dam located along a section of the Schuylkill River in the Lower Merion Township of Montgomery County, Pennsylvania. To assist in fish migration, Pennsylvania’s Department of General Services (DGS) planned to install a fish ladder on the dam. GeoStructures provided a geotechnical investigation to characterize the subsurface of the site.

The completed 200-ft, S-shaped structure along the west bank of the Schuylkill River involves 21 upward sloping chambers that allow fish to climb 15 ft and reach the 10-ft deep impounded waters on the upstream side of the dam.

The geotechnical exploration provided by GeoStructures involved 4 core borings on the rip rap of the west bank using a special skid rig. The rig was precariously cantilevered over the rapids on the downstream side at two locations. Expertise provided by our engineers on this project included:

  • Specialized drilling in a precarious setting over the river
  • Detailed rock characterization for compressive strength, hardness, weathering, fracturing, and discontinuities
  • Quantifying rock cut for attraction chamber and valve pit
  • Sliding/uplift stability for tanks of the passageway
  • Bearing capacity of alluvial soils below the higher chambers
  • Assessment of rock in terms of scour and countermeasures
  • Retaining wall design
  • Cut slope design/stability for soil cuts
  • Dewatering criteria

Connect with us.

Providing state-of-the-art geotechnical engineering services with an unwavering commitment to excellence and innovation.

Percolation and Permeability In-Situ Testing 

Drilling Services and Subsurface Investigations

Foundation Investigation and Design

Highway and Bridge Geotechniques

Support of Excavation and Underpinning

Soil-Structure Interaction Analysis and Modeling

Soil Dynamics & Site-Specific Response Spectra

Vibration Monitoring and Analyses

Forensic Evaluations

Slope and Retaining Wall Evaluation and Design

Lime and Cement Stabilization

Mine Subsidence Analysis and Remediation

Sinkhole Evaluation and Remediation

Soil Improvement Techniques

Dam Analysis and Rehabilitation

Environmental Services

Landfills, Ponds, and Lagoons

Pavement Design and Rehabilitation

Construction Inspection and Materials Testing

Geotechnical Laboratory Testing

Concrete and Cement Testing

Petrographic Analysis

Instrumentation and Special Testing

Asphalt Testing

View All Services >

3-D Dynamic Finite Element Analysis



Institutional & Educational


Industrial, Pharmaceutical, & Gene Therapy

Landfill Expansion Design


Research & Forensics


Water & Wastewater

View All Selected Projects >

Who We Are 

Who We Are

Meet Our Team

Contact Us 

Pay Invoice

Contact Us