08-10-2025, 08:42 PM
Overview of Excavated Dam Building
Excavated dams—also known as “sunk” dams—are a common solution for water storage in areas with suitable subsoil conditions. Unlike embankment dams, which rely on built-up earth walls, excavated dams are carved directly into the terrain. This method is especially effective when sealing clay is available within a few feet of the surface, allowing for natural compaction and water retention.
The construction process demands careful planning, efficient material handling, and a deep understanding of site topography. The method outlined here is optimized for rectangular dams built with dozers or track loaders, adaptable to sloping sites and various machine sizes.
Terminology Clarification
- Sealing Clay: Impermeable clay layer used to line the dam floor and walls to prevent seepage.
- Over-Excavation: Digging beyond the final dam footprint to allow for clay placement and compaction.
- Ramp Formation: Sloped earth structures created during excavation to facilitate material movement and shaping.
- Corner Fanning: Technique of distributing excavated material in a radial pattern to form dam corners.
- Batter: Sloped face of the dam wall, typically formed during cleanup and shaping.
Initial Excavation and Over-Excavation Strategy
The process begins by over-excavating the dam footprint. This involves digging beyond the planned perimeter—typically three times the depth to sealing clay—to allow for a 2-foot clay layer over the topsoil. The dam is divided into two halves for excavation, with adjustments made to balance material distribution if one corner is lower than the other.
Key steps include:
Once the first two layers are removed, the corners are shaped using a “V” cut—aligned with the final corner geometry—to prevent future damage to the sealing layer. If using a non-tilt blade dozer or track loader, a fillet may be added to ease cleanup.
At this stage, the dam should exhibit:
After topsoil is removed and corners are formed, the dam undergoes a two-pass cleanup:
Topsoil Management and Re-Grassing
In some cases, topsoil and grass are stripped before excavation and replaced afterward to promote vegetation. The dam is divided into three triangles from the mouth to each back corner, and topsoil is distributed along the back and sides. Once construction is complete, the soil is spread evenly over the banks.
Silt Ponds and Overflow Structures
These are constructed last to avoid interference with main excavation. Material from these features may be used to reinforce dam banks.
Measurement and Capacity Calculation
To estimate dam volume and water capacity:
An operator once built four dams for a yabby farm using a Caterpillar 950 loader. The top gravel was removed for road construction, and the excavation was dictated by truck schedules. Reflecting on the experience, he noted that a structured method like the one above would have reduced machine movements and improved efficiency. It’s a classic example of how planning and technique can transform outcomes.
Regulatory Humor: The Beaver Dam Incident
In a widely circulated letter from Pennsylvania’s Department of Environmental Quality, a landowner was cited for unauthorized dam construction—only to reveal that the culprits were local beavers. His satirical response highlighted the absurdity of regulating wildlife and became a viral example of bureaucratic overreach. It’s a reminder that not all dams are man-made, and nature often has its own agenda.
Recommendations for Efficient Dam Construction
- Uneven corners: Redistribute material from higher banks
- Poor sealing clay: Import clay or use bentonite additives
- Machine limitations: Use fillet cuts or alternate ramp angles
- Water seepage: Apply additional clay layers or install a synthetic liner
Conclusion: Earthmoving with Precision and Purpose
Excavated dam construction is both an art and a science. It requires a blend of topographic insight, mechanical skill, and material management. When executed with care, the result is a durable, well-sealed water reservoir that serves agricultural, recreational, or industrial needs. Whether you're shaping corners with a dozer or calculating capacity with a tape measure, every step matters—and every dam tells a story of earth moved with intention.
Excavated dams—also known as “sunk” dams—are a common solution for water storage in areas with suitable subsoil conditions. Unlike embankment dams, which rely on built-up earth walls, excavated dams are carved directly into the terrain. This method is especially effective when sealing clay is available within a few feet of the surface, allowing for natural compaction and water retention.
The construction process demands careful planning, efficient material handling, and a deep understanding of site topography. The method outlined here is optimized for rectangular dams built with dozers or track loaders, adaptable to sloping sites and various machine sizes.
Terminology Clarification
- Sealing Clay: Impermeable clay layer used to line the dam floor and walls to prevent seepage.
- Over-Excavation: Digging beyond the final dam footprint to allow for clay placement and compaction.
- Ramp Formation: Sloped earth structures created during excavation to facilitate material movement and shaping.
- Corner Fanning: Technique of distributing excavated material in a radial pattern to form dam corners.
- Batter: Sloped face of the dam wall, typically formed during cleanup and shaping.
Initial Excavation and Over-Excavation Strategy
The process begins by over-excavating the dam footprint. This involves digging beyond the planned perimeter—typically three times the depth to sealing clay—to allow for a 2-foot clay layer over the topsoil. The dam is divided into two halves for excavation, with adjustments made to balance material distribution if one corner is lower than the other.
Key steps include:
- Excavating the first “floor” and pushing material into the corners.
- Creating a central cut along the back of the dam to access sealing clay.
- Forming ramps from excavated material along the sides and back.
- Bisecting remaining material and pushing it into fan-shaped ramps.
- Cleaning up scraps to form batters along the back and sides.
Once the first two layers are removed, the corners are shaped using a “V” cut—aligned with the final corner geometry—to prevent future damage to the sealing layer. If using a non-tilt blade dozer or track loader, a fillet may be added to ease cleanup.
At this stage, the dam should exhibit:
- Defined corner geometry with compacted material
- Batters formed along the back and sides
- Over-excavation lines marking the toe of each slope
After topsoil is removed and corners are formed, the dam undergoes a two-pass cleanup:
- First pass: Heavy cutting and shaping of banks
- Second pass: Light trimming and polishing for aesthetics and sealing
Topsoil Management and Re-Grassing
In some cases, topsoil and grass are stripped before excavation and replaced afterward to promote vegetation. The dam is divided into three triangles from the mouth to each back corner, and topsoil is distributed along the back and sides. Once construction is complete, the soil is spread evenly over the banks.
Silt Ponds and Overflow Structures
These are constructed last to avoid interference with main excavation. Material from these features may be used to reinforce dam banks.
Measurement and Capacity Calculation
To estimate dam volume and water capacity:
- Measure top and bottom length and breadth
- Measure depth from water level to bottom
- Multiply top length × top breadth
- Multiply bottom length × bottom breadth
- Multiply (top length + bottom length) × (top breadth + bottom breadth)
- Add results from steps 1–3
- Multiply total by depth
- Divide by 6 for volume
- Convert to cubic yards (divide by 27 if measured in feet)
- Convert to gallons:
- Imperial: Multiply by 6.25
- U.S.: Divide imperial gallons by 0.833
An operator once built four dams for a yabby farm using a Caterpillar 950 loader. The top gravel was removed for road construction, and the excavation was dictated by truck schedules. Reflecting on the experience, he noted that a structured method like the one above would have reduced machine movements and improved efficiency. It’s a classic example of how planning and technique can transform outcomes.
Regulatory Humor: The Beaver Dam Incident
In a widely circulated letter from Pennsylvania’s Department of Environmental Quality, a landowner was cited for unauthorized dam construction—only to reveal that the culprits were local beavers. His satirical response highlighted the absurdity of regulating wildlife and became a viral example of bureaucratic overreach. It’s a reminder that not all dams are man-made, and nature often has its own agenda.
Recommendations for Efficient Dam Construction
- Use GPS or laser leveling to set accurate excavation boundaries
- Test soil for clay content before excavation begins
- Maintain blade sharpness for clean cuts and efficient shaping
- Compact clay layers with track rolling to enhance sealing
- Monitor corner elevation during excavation to ensure symmetry
- Keep a log of excavation depth, material movement, and compaction passes
- Uneven corners: Redistribute material from higher banks
- Poor sealing clay: Import clay or use bentonite additives
- Machine limitations: Use fillet cuts or alternate ramp angles
- Water seepage: Apply additional clay layers or install a synthetic liner
Conclusion: Earthmoving with Precision and Purpose
Excavated dam construction is both an art and a science. It requires a blend of topographic insight, mechanical skill, and material management. When executed with care, the result is a durable, well-sealed water reservoir that serves agricultural, recreational, or industrial needs. Whether you're shaping corners with a dozer or calculating capacity with a tape measure, every step matters—and every dam tells a story of earth moved with intention.
