Hydrovac Slot Trenching for Utility Installation
8-step process guide with equipment, safety, and cost information.
Slot trenching is the process of excavating narrow, precise trenches for the installation of underground utilities, drainage systems, or other linear infrastructure. Hydrovac slot trenching creates clean, straight-walled trenches as narrow as 6 inches wide, minimizing surface disruption and reducing the volume of material that must be removed and replaced.
This technique is especially valuable for installing new utilities in areas with existing underground infrastructure. The hydrovac process safely excavates alongside and across existing pipes and cables without the risk of damage from mechanical trenching equipment. The narrow trench profile also reduces pavement and landscape restoration costs.
Common slot trenching applications include fiber optic conduit installation, electrical cable runs, irrigation system installation, and drainage piping. The precision of hydrovac trenching makes it the preferred method for projects where the trench alignment must be exact and existing utilities must be protected.
Step-by-Step Process
Route Planning
Survey the planned trench route, identify all crossing utilities through 811 locates and potholing, and establish the trench alignment with stakes or paint marks.
Utility Verification
Pothole at all utility crossings and at regular intervals along the route to verify the exact location and depth of existing underground infrastructure.
Surface Preparation
Mark and cut the trench edges through pavement or hardscape surfaces. Set up traffic control and erosion control measures as required.
Hydrovac Trenching
Excavate the trench to design depth and width using the hydrovac water jet and vacuum. Work in sections, maintaining consistent trench dimensions and grade.
Crossing Protection
At utility crossings, hand-excavate or reduce water pressure to safely expose and pass beneath or above existing utilities without contact or damage.
Bedding and Installation
Place bedding material in the trench bottom, install the new utility (conduit, cable, or pipe), and cover with specified backfill material.
Compaction and Testing
Compact backfill in lifts per specification. Perform any required testing (pressure test, continuity test, etc.) on the newly installed utility.
Surface Restoration
Restore pavement, landscape, or other surface materials to match existing conditions. Clean the work area and remove traffic control.
Equipment Recommendations
- Hydrovac truck with high-flow vacuum for efficient material removal
- Straight jet nozzle for cutting narrow trench profiles
- Extended hose lengths for linear trenching operations
- Grade laser or string line for maintaining trench depth consistency
- Compaction equipment for backfill operations
Safety Considerations
- ⚠Maintain accurate locate marks along the entire trench route
- ⚠Watch for unmarked utilities, especially service laterals
- ⚠Follow OSHA trench safety standards for any trench over 5 feet deep
- ⚠Implement traffic control for work in or near roadways
- ⚠Protect open trench with barriers and warning devices when unattended
- ⚠Monitor for utility crossings that may not appear on records
Cost Factors
- ●Linear footage of trench required
- ●Trench depth and width specifications
- ●Number and complexity of utility crossings
- ●Soil conditions along the route
- ●Surface type (asphalt, concrete, grass, gravel)
- ●Backfill material requirements
- ●Surface restoration specifications and standards
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