Hydrovac Glossary
90 terms and definitions for the hydro excavation industry. From equipment specs to safety regulations.
8
A
Air Excavation
Air excavation is a non-destructive digging method that uses compressed air to break up and loosen soil, which is then removed by a powerful vacuum system. It is the driest alternative to hydrovac excavation.
Air Mover
An air mover is a vacuum excavation truck that uses compressed air rather than pressurized water to loosen soil, combined with a vacuum system to remove the dry spoils. It is the primary equipment for air excavation.
APWA Color Code
The APWA (American Public Works Association) color code is the standardized system of colors used nationwide to mark the location of underground utilities, with each color representing a specific type of utility infrastructure.
As-Built
As-built drawings are revised construction documents that record the actual installed positions, dimensions, and conditions of infrastructure as it was built, rather than as it was originally designed.
Atmospheric Testing
Atmospheric testing is the process of using gas detection instruments to measure oxygen levels, flammable gas concentrations, and toxic gas levels in an excavation or confined space before and during worker entry.
B
Backfill
Backfill is the material used to refill an excavation after work is completed, or the act of placing that material. Proper backfill selection and compaction are critical to preventing settlement, utility damage, and pavement failure.
Bell Holing
Bell holing is a hydrovac excavation technique that creates a bell-shaped or cylindrical hole around a specific point on a buried utility, typically at a pipeline joint, fitting, valve, or connection point that requires inspection, maintenance, or repair.
Boiler
The boiler on a hydrovac truck is an onboard water heating system that raises the temperature of the pressurized water supply, enabling excavation in frozen ground and improving digging efficiency in cold weather conditions.
Boom
The boom is a hydraulically operated, articulating arm mounted on a hydrovac truck that supports and positions the vacuum dig tube over the excavation point, allowing the operator to reach work areas from the truck's parked position.
C
Call Before You Dig
Call Before You Dig is the national public awareness campaign that promotes the use of the 811 system and reminds excavators and homeowners to have underground utilities marked before any digging project begins.
Cave-In Protection
Cave-in protection refers to the systems and methods used to prevent the walls of an excavation from collapsing onto workers, including sloping, shoring, and shielding. OSHA requires cave-in protection for excavations deeper than 5 feet.
Centrifugal Blower
A centrifugal blower is a type of vacuum producer that uses a high-speed impeller to accelerate air outward, creating suction through centrifugal force. It produces high airflow volumes ideal for moving large quantities of loose material.
Certificate of Insurance
A certificate of insurance (COI) is a document issued by an insurance company that verifies a hydrovac contractor holds active insurance policies meeting specified coverage types and minimum limits.
CFM (Cubic Feet Per Minute)
CFM stands for cubic feet per minute and measures the volume of air moved by a hydrovac truck's vacuum system. Higher CFM ratings indicate greater airflow capacity and faster material removal from the excavation.
Change Order
A change order is a formal document that modifies the original scope of work, schedule, or contract price for a hydrovac project after the contract has been executed.
Chassis
The chassis is the truck frame, cab, engine, and drivetrain that serves as the base vehicle upon which the hydrovac equipment body is mounted. Chassis selection determines the truck's road performance, weight capacity, and maneuverability.
Competent Person
A competent person in excavation work is an individual designated by the employer who is capable of identifying existing and predictable hazards and has the authority to take prompt corrective measures to eliminate them, as defined by OSHA.
Confined Space
A confined space is an enclosed or partially enclosed area large enough for a worker to enter but not designed for continuous occupancy, with limited entry or exit points. Deep hydrovac excavations and utility vaults may qualify as confined spaces.
Critical Infrastructure
Critical infrastructure refers to essential systems and assets whose disruption or destruction would have a debilitating impact on public safety, economic stability, or national security, including energy, water, and communications networks.
Cross-Bore
A cross-bore is the unauthorized or inadvertent intersection of one underground utility through another, most commonly a gas line installed through a sewer lateral using trenchless methods without proper utility locating.
Cyclone Separator
A cyclone separator is a device inside the hydrovac truck's debris tank that uses centrifugal force to separate soil and debris from the airstream, protecting the vacuum blower from damage caused by ingesting solid material.
D
Daylighting
Daylighting is the practice of exposing underground utilities or structures to visible light by carefully excavating the soil above them. The term refers to literally bringing buried infrastructure "into the daylight" for visual inspection and verification.
Debris Tank
The debris tank is the large holding vessel on a hydrovac truck that collects and stores the excavated soil-water slurry during hydro excavation operations. Tank capacity directly impacts how long the truck can work before requiring a dump.
Deep Dig
Deep dig refers to hydrovac excavation at depths exceeding typical utility burial depths, generally beyond 8 to 10 feet. Deep digs require additional vacuum power, longer dig tubes, and careful attention to OSHA excavation safety standards.
Dig Law
Dig laws are state-level statutes that govern excavation activities near underground utilities, establishing requirements for notification, utility marking, excavation practices, tolerance zones, and penalties for non-compliance.
Dig Tube
The dig tube is the large-diameter pipe at the end of the hydrovac truck's boom through which the vacuum pulls excavated soil, water, and debris from the dig site into the debris tank.
Directional Boring
Directional boring is a trenchless construction method for installing underground pipes, conduits, and cables along a prescribed bore path using a surface-launched drilling rig, without the need for continuous open-cut trenching.
E
Excavation Contractor
An excavation contractor is a company that performs excavation services, including earthmoving, trenching, grading, and utility installation, with hydrovac excavation contractors specializing in non-destructive methods.
Excavation Permit
An excavation permit is an official authorization from a local government or property owner that grants permission to excavate in a specific location, often required before any digging can begin in public rights-of-way.
F
G
GIS
GIS (Geographic Information System) is a technology platform for capturing, storing, analyzing, and displaying geographically referenced data, widely used in the utility industry to manage underground infrastructure records.
GPM (Gallons Per Minute)
GPM stands for gallons per minute and measures the flow rate of water delivered by a hydrovac truck's pump system. GPM determines how quickly water is applied to the soil and affects both excavation speed and water tank endurance.
H
Hand Excavation
Hand excavation is the manual removal of soil using non-powered hand tools such as shovels, spades, and trowels. It is the oldest form of non-destructive excavation and is still required in certain sensitive situations.
Hard Locate
A hard locate is the physical exposure of an underground utility through excavation, typically using hydrovac potholing, to visually verify its exact position, depth, size, material, and condition.
Horizontal Directional Drilling
Horizontal directional drilling (HDD) is a trenchless technology used to install pipelines, cables, and conduits underground along a controlled bore path without excavating a continuous trench from the surface.
Hose Reel
A hose reel is a mechanical spool mounted on a hydrovac truck that stores, deploys, and retracts the vacuum hose or water hose, enabling the operator to extend the working reach of the truck for remote digging applications.
Hourly Rate
The hourly rate is the primary billing method for hydrovac services, covering the cost of the hydrovac unit, operator, and standard supporting equipment for each hour of active work on the job site.
Hydro Excavation
Hydro excavation is a non-destructive digging method that combines pressurized water to break up soil with an industrial vacuum to remove the resulting slurry, providing the safest and most precise method of excavating near underground utilities.
Hydrovac
Hydrovac is the commonly used short form of hydrovac excavation, a non-destructive digging method that uses pressurized water to break up soil and a powerful vacuum to extract the resulting slurry into a debris tank.
Hydrovac Truck
A hydrovac truck is a specialized vehicle equipped with a pressurized water system and an industrial vacuum system, purpose-built for non-destructive hydro excavation of soil near underground utilities.
I
K
L
M
Mass Excavation
Mass excavation is the large-scale removal of earth, rock, or other materials from a site, typically for foundation construction, grading, or site preparation. It is performed with heavy mechanical equipment such as excavators, bulldozers, and loaders.
Mobilization Fee
A mobilization fee is the charge for transporting hydrovac equipment, personnel, and supporting materials from the contractor's base of operations to the designated job site.
N
Non-Destructive Digging
Non-destructive digging (NDD) is a synonym for non-destructive excavation, encompassing any excavation method that does not use mechanical force and therefore cannot damage underground utilities, with hydrovac being the most common method.
Non-Destructive Excavation
Non-destructive excavation (NDE) refers to any digging method that removes soil without using mechanical force that could damage underground utilities, including hydrovac excavation, air excavation, and manual hand digging.
Nozzle
A nozzle is the tip attached to the end of the water wand that shapes and directs the pressurized water stream during hydrovac excavation. Different nozzle types produce different spray patterns for various soil conditions and applications.
O
One-Call
One-call is the common shorthand for the one-call notification system, also known as the 811 system, which excavators use to request utility locates before digging.
One-Call Center
A one-call center is a centralized notification system that receives excavation notices from contractors and homeowners, then distributes those notices to all utility operators with infrastructure in the planned dig area.
OSHA
OSHA is the Occupational Safety and Health Administration, the federal agency that sets and enforces workplace safety standards in the United States, including excavation safety regulations that directly govern hydrovac operations.
P
Per-Foot Pricing
Per-foot pricing is a billing method where hydrovac services are charged based on the linear feet of trench excavated, commonly used for slot trenching, pipeline exposure, and fiber optic installation projects.
Positive Displacement Blower
A positive displacement (PD) blower is a type of vacuum producer that traps and moves a fixed volume of air with each rotation, providing consistent suction performance regardless of changes in restriction or depth.
Pothole Test Hole
A pothole test hole is a small-diameter excavation created to expose and verify the location, depth, and condition of a buried utility, synonymous with potholing in hydrovac industry terminology.
Potholing
Potholing is the process of digging a small, precise test hole to expose and verify the exact location, depth, and condition of underground utilities. It is the most common application of hydrovac excavation and is considered the industry gold standard for utility verification.
Precision Excavation
Precision excavation is a controlled digging technique that removes soil with exactness and accuracy, targeting specific locations and depths while minimizing disturbance to surrounding soil and infrastructure.
Prevailing Wage
Prevailing wage is the government-mandated minimum hourly wage rate that must be paid to workers on publicly funded construction projects, as determined by the Department of Labor or equivalent state agency.
PSI (Pounds Per Square Inch)
PSI stands for pounds per square inch and measures the pressure of the water delivered by a hydrovac truck's pump system. Operators adjust PSI based on soil conditions and proximity to underground utilities.
PTO (Power Take-Off)
PTO stands for power take-off, a mechanical device that transfers engine power from the truck chassis to the hydrovac equipment, including the vacuum blower, water pump, and hydraulic systems.
Q
R
Remote Dig
Remote dig is a hydrovac excavation technique where the truck is positioned at a distance from the excavation point, using extended hose lengths to reach the dig site. It is used when the truck cannot access the immediate work area.
Right-of-Way
A right-of-way (ROW) is a legal right to pass through or use a specific strip of land, commonly granted for the installation, maintenance, and access of roads, utilities, pipelines, and other infrastructure.
Rotary Nozzle
A rotary nozzle spins a concentrated water jet in a circular pattern, combining the cutting power of a straight jet with broader area coverage for efficient soil removal in hydrovac excavation.
S
Scope of Work
A scope of work (SOW) is a detailed description of the specific tasks, deliverables, timelines, and standards that define what work will be performed under a contract for hydrovac excavation services.
Shaker Deck
A shaker deck is a vibrating screen system installed on some hydrovac trucks that separates water from the excavated soil, allowing the water to be recycled back into the water tank and extending the truck's operational time between refills.
Shoring
Shoring is a system of structural supports installed in an excavation to prevent the walls from collapsing inward. OSHA requires cave-in protection, which may include shoring, for excavations deeper than 5 feet.
Slot Trenching
Slot trenching is a hydrovac excavation technique that creates narrow, precisely defined trenches for installing pipes, cables, conduits, or drainage systems without disturbing surrounding soil or utilities.
Slurry
Slurry is the liquid mixture of water and soil created during hydrovac excavation. It is the primary byproduct of the hydro excavation process and is collected in the debris tank for transport and disposal.
Soft Dig
Soft dig is a non-mechanical excavation method that uses water, air, or vacuum pressure instead of metal buckets and blades to remove soil, eliminating the risk of mechanical damage to buried utilities and structures.
Soft Locate
A soft locate uses non-invasive geophysical methods such as electromagnetic locators and ground-penetrating radar to detect and map underground utilities from the surface without any excavation.
Spoils
Spoils are the excavated soil, rock, and other materials removed from the ground during an excavation. In hydrovac excavation, spoils are collected as a water-soil slurry in the truck's debris tank and must be properly transported and disposed of.
Standby Time
Standby time is billable time during which hydrovac equipment and crew are present on a job site but unable to perform excavation work due to circumstances outside the contractor's control.
Subcontractor Agreement
A subcontractor agreement is a legally binding contract between a general contractor and a hydrovac subcontractor that defines the terms, conditions, and requirements for the hydrovac work to be performed on a project.
Subsurface Utility Engineering
Subsurface Utility Engineering (SUE) is an engineering branch that manages risks associated with underground utilities through systematic identification, characterization, and mapping of subsurface infrastructure during planning, design, and construction.
SUE Quality Level
SUE Quality Levels are the four-tier classification system defined by ASCE Standard 38 that rates the reliability of subsurface utility data from Quality Level D (least reliable) to Quality Level A (most reliable, physically verified).
T
Tolerance Zone
The tolerance zone is the area on either side of a marked utility within which excavation must be performed using non-destructive methods such as hydrovac. It typically extends 18 to 24 inches from the outer edge of the utility on each side.
Trench Box
A trench box, also called a trench shield, is a prefabricated steel or aluminum structure placed in an excavation to protect workers from cave-ins by providing a rigid barrier between the workers and the excavation walls.
Triplex Pump
A triplex pump is a three-cylinder positive displacement water pump used on hydrovac trucks to generate the high-pressure water flow needed to break apart soil during hydro excavation.
U
Underground Utility
An underground utility is any infrastructure system installed below the ground surface to deliver services such as water, sewer, gas, electricity, telecommunications, or stormwater management.
Utility Corridor
A utility corridor is a designated pathway or strip of land containing multiple underground utilities running in parallel, typically located within road rights-of-way or dedicated easements.
Utility Damage Prevention
Utility damage prevention encompasses the programs, laws, best practices, and technologies designed to prevent accidental damage to underground utilities during excavation and construction activities.
Utility Locate
A utility locate is the process of identifying and marking the approximate horizontal position of underground utilities on the ground surface using paint and flags, performed by utility owners or their contractors in response to an 811 request.
Utility Mapping
Utility mapping is the process of documenting the horizontal positions, depths, material types, and conditions of underground utilities to create accurate records for engineering, construction, and asset management purposes.
Utility Mark
Utility marks are the painted lines, flags, and stakes placed on the ground surface by utility locators to indicate the approximate horizontal position of underground utility lines, using standardized APWA color codes.
Utility Strike
A utility strike is an unintended contact with or damage to a buried utility line during excavation. Utility strikes can cause service outages, property damage, environmental contamination, injuries, and fatalities.
V
Vacuum Excavation
Vacuum excavation is a broad term for any excavation method that uses industrial vacuum suction to remove soil from the ground. It encompasses both hydrovac (water-assisted) and air excavation (air-assisted) techniques.
Vacuum Truck
A vacuum truck is a heavy-duty vehicle equipped with an industrial vacuum system and a large storage tank, used to suction and transport liquids, sludge, slurry, or dry materials from job sites.
W
Wand
The wand is the handheld pipe or tube that the hydrovac operator uses to direct the pressurized water stream at the soil during excavation. The nozzle attaches to the end of the wand.
Water Tank
The water tank on a hydrovac truck stores the clean water supply used for pressurized excavation. Capacity typically ranges from 400 to 1,200 gallons and directly affects how long the truck can operate between refills.
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