Hydrovac Glossary
Plain-English definitions of 35+ hydrovac terms: equipment, regulations, methods, and the lingo you're likely to hear on a project.
811 (One-Call System)
811 is the national call-before-you-dig number for requesting underground utility marks before excavation in the United States, and state law requires the call. Each state has its own 811 program; calling notifies all member utilities to mark their buried lines on the dig site.
APWA Color Code
The American Public Works Association's uniform color code for marking underground utilities. Red=electric, yellow=gas/oil, orange=communications, blue=potable water, green=sewer, purple=reclaimed water, pink=temporary survey, white=proposed excavation.
Bell Hole
An excavation around a buried pipeline, sized to provide working room for inspection, repair, or tie-in welds. Bell holes are commonly excavated with hydrovac to avoid damaging pipe coatings.
Catch Basin
A storm-water inlet at a curb or low point with a sumped chamber that collects sediment before water enters the storm sewer. Routine catch basin cleaning by vacuum truck is one of the most cost-effective preventative maintenance tasks in a storm-water program.
Cathodic Protection
An electrochemical method of preventing corrosion on metal pipelines and structures. Damaged pipe coatings can compromise cathodic protection — one reason pipeline operators prefer hydrovac for any work near coated pipe.
Climate Zone
A regional classification based on temperature and moisture patterns (humid subtropical, continental, arid, etc.). Affects hydrovac operations through frost depth, soil moisture, and seasonal scheduling considerations.
Combo Truck
A vacuum truck combining hydrovac excavation with sewer-cleaning capability. Most commercial hydrovac contractors run combo trucks because they handle the widest range of jobs.
Daylighting
The practice of safely exposing buried utilities at the surface to verify their location and depth. Synonymous with potholing; both refer to controlled, non-destructive excavation that reveals what's underground.
Debris Tank
The on-board tank where a hydrovac truck stores excavated material (water-soil slurry). Standard combo-truck capacity is 10-12 cubic yards; dedicated hydroexcavators run 12-16 yards.
FBE Coating (Fusion Bonded Epoxy)
A protective coating applied to steel pipelines by heating epoxy powder onto the pipe surface. FBE provides corrosion resistance and electrical insulation; damage from mechanical excavation is the most common preventable threat to this coating.
Fiber Buildout
The deployment of fiber-optic cable infrastructure across a service area. Typically uses a combination of slot trenching (with hydrovac), microtrenching, and aerial installation. One of the largest growth segments for commercial hydrovac demand.
Frost Depth
The maximum depth at which ground freezes in winter. Frost depth varies from 0 inches (warm climates) to 60+ inches (northern Minnesota, Canadian Prairies). Hydrovac trucks with heated water systems can excavate through frozen ground when conventional digging cannot.
GPM (Gallons Per Minute)
A measure of water flow rate. Hydrovac trucks pump 25-80 GPM at the dig site. Higher GPM moves more spoil faster but consumes water more quickly, requiring more frequent refills.
Heated Water System
A boiler or heat-exchanger system on a hydrovac truck that warms the cutting water. Heated systems allow excavation through frozen ground in winter and reduce energy losses to cold spoil during operation.
Hydroexcavator
A truck dedicated to hydrovac excavation (no sewer cleaning capability). Hydroexcavators typically have larger debris tanks and higher water pressure than combo trucks; common in oil & gas pipeline work.
Microtrenching
A trench-cutting method using a saw to cut a 1-2 inch wide slot in pavement for fiber installation. Faster than hydrovac slot trenching but limited to hard surfaces; the two methods are complementary on most fiber buildouts.
Mobilization
The cost of moving a hydrovac truck to and from a job site. Most providers charge for round-trip mileage beyond a 25-50 mile radius from their yard. Mobilization can rival or exceed hourly excavation cost on remote jobs.
MS4 (Municipal Separate Storm Sewer System)
EPA-regulated stormwater systems that municipalities operate. MS4 permits require ongoing maintenance, including catch basin and storm drain cleaning, with documented removal volumes for annual reporting.
One-Call
The general term for the system that notifies utility owners about planned excavation. In the US it's 811; in Canada it's a province-by-province network including Alberta One-Call, BC One Call, Info-Excavation (Quebec), and Ontario One Call.
PFAS (Per- and Polyfluoroalkyl Substances)
A class of persistent industrial chemicals increasingly regulated as environmental contaminants. PFAS-affected spoils require specialized disposal, adding cost and logistical complexity to any hydrovac project on contaminated sites.
Pipeline Exposure
The process of safely uncovering a buried pipeline for inspection, repair, or modification. Hydrovac is the standard method because it preserves protective coatings and avoids strike damage.
Potholing
Creating a small, precise excavation to expose and verify the location of a buried utility. Synonymous with daylighting. Hydrovac potholing is widely regarded as the most reliable way to verify utilities before mechanical excavation.
PSI (Pounds Per Square Inch)
A unit of pressure. Standard hydrovac water pressure is 2,000-3,000 PSI. Higher pressures (up to 5,000 PSI) are used for hard soil, but operators reduce pressure when working near pipe coatings or thin-walled utilities.
Recycling Unit
A hydrovac truck that filters, cleans, and reuses water on-board, dramatically reducing water consumption and disposal volume. Higher upfront cost but lower per-job operating cost on long or remote projects.
Rotary Nozzle
A spinning nozzle tip that distributes water pressure across multiple cutting points. Rotary nozzles are the workhorse for general hydrovac excavation in mixed soil conditions.
Slot Trenching
A narrow (6-12 inch wide) trench cut by hydrovac for utility installation. Slot trenches dramatically reduce surface restoration costs vs traditional open-cut trenching, especially in landscaped or paved areas.
Spoils
The mixture of water and excavated material in a hydrovac debris tank. Spoils handling and disposal — especially for hazardous or PFAS-affected material — is a meaningful cost component of any hydrovac project.
Storm Drain Cleaning
Vacuum-truck removal of silt, debris, and sediment from storm sewer lines and culverts. Routine maintenance restores design flow capacity and supports MS4 compliance.
SUE (Subsurface Utility Engineering)
An engineering practice for identifying and managing the location of buried utilities. Has four quality levels (A through D); Quality Level A — verified by physical exposure, typically via hydrovac potholing — is the highest standard.
SWPPP (Stormwater Pollution Prevention Plan)
A site-specific plan documenting how a construction or industrial site will prevent stormwater pollution. Catch basin and storm drain cleaning by hydrovac is a common SWPPP best management practice.
Tolerance Zone
The buffer on either side of a marked utility within which mechanical excavation is prohibited. Most state programs define this as 18-24 inches of horizontal distance either side of the marks; depth is not marked. Soft-dig methods (hydrovac, hand-digging) are required within the tolerance zone.
Utility Locating
The process of detecting and marking buried utilities using electromagnetic locators, ground-penetrating radar, and One-Call records. Often paired with hydrovac potholing for physical verification at depth.
Utility Strike
Damage to a buried utility caused by excavation. Strikes range from coating nicks ($1,000+) to gas main ruptures ($1M+ plus injuries). Hydrovac's non-contact method dramatically reduces strike risk.
Vacuum Truck
A truck that uses an industrial vacuum to extract material — liquid, solid, or slurry. Hydrovac trucks are a specialized class of vacuum truck that pairs high-pressure water with the vacuum system for excavation.
Water Pump
The high-pressure pump on a hydrovac truck. Standard configuration is a triplex pump producing 2,000-3,000 PSI at 25-80 GPM. Heavy-duty oil & gas applications use plunger pumps to 5,000 PSI.