Definitions for Underground Utility Terms G-I

Gas Detector: A device used to detect the presence of hazardous gases, such as natural gas or carbon monoxide, in underground utility systems.Gas Detector

Gas Meter: A device used to measure the volume or flow rate of natural gas or other gases in underground utility systems, enabling accurate billing and monitoring of gas consumption.Gas Meter

Geosynthetic Liner: An impermeable or semi-permeable membrane or liner installed in underground containment systems, such as landfills or wastewater lagoons, to prevent seepage or leakage.Geosynthetic Liner

Geosynthetic Materials: Synthetic materials, such as geotextiles, geogrids, or geomembranes, used in underground utility projects for soil stabilization, filtration, separation, or erosion control.Geosynthetic Materials

Geotech Report: A Geotech Report, also known as a Geotechnical Report or Geotechnical Engineering Report, is a document that provides a comprehensive assessment and analysis of the soil, rock, and other geological conditions at a specific site. Learn More…

Geotechnical Investigation: A study or assessment of the soil and rock properties at a site, including their strength, composition, and stability, to inform the design and construction of underground utility infrastructure. Geotechnical Investigation

Geothermal Heat Pump: A system that uses the stable temperature of the ground or groundwater to provide heating, cooling, and hot water for buildings or facilities through underground piping loops. Geothermal Heat Pump

Geothermal System: An underground system that harnesses the natural heat from the Earth for heating or cooling buildings, utilizing pipes or loops buried underground. Geothermal System

GIS (Geographic Information System): A computer-based system used to capture, manage, analyze, and present spatial data related to underground utilities. GIS (Geographic Information System)

GPS Surveying: The use of Global Positioning System (GPS) technology to accurately determine the location and coordinates of underground utilities, aiding in mapping and utility detection. GPS Surveying

Grade Control: Measures taken to ensure the correct slope or gradient of underground utility lines to facilitate proper flow and prevent blockages. Grade Control

Gravel Pack: A layer of graded gravel or sand placed around underground well screens or boreholes to filter out fine particles, preventing clogging and ensuring efficient water or fluid extraction. Gravel Pack

Gravitational Settling Chamber: An underground chamber or structure designed to remove sediment or heavy particles from water or wastewater through gravitational settling, enhancing water quality. Gravitational Settling Chamber

Gravity Sewer System: An underground sewer system that relies on gravity to transport wastewater or sewage from higher to lower elevations, using downward slopes and gravity flow. Gravity Sewer System

Grease Trap: An underground chamber or device installed in wastewater systems, such as kitchen or restaurant drains, to capture and prevent the discharge of fats, oils, and grease into the sewer system. Grease Trap

Green Infrastructure: Design strategies and practices that use natural or engineered systems in underground utility planning to manage stormwater, reduce runoff, and enhance environmental sustainability. Green Infrastructure

Ground Fault Circuit Interrupter (GFCI): A safety device installed in underground electrical circuits to quickly detect and interrupt electrical faults, protecting against electric shocks or accidents. Ground Fault Circuit Interrupter (GFCI)

Ground Penetrating Radar (GPR): A non-destructive geophysical method that uses radar pulses to image and detect objects beneath the ground surface, commonly used in utility locating. Ground Penetrating Radar (GPR)

Grounding Electrode: A conductive element, such as a ground rod or plate, installed in underground electrical systems to provide a safe path for the dissipation of electrical currents. Grounding Electrode

Grounding Rod: A metal rod driven into the ground and connected to an electrical system or equipment to facilitate grounding and safety. Grounding Rod

Grounding System: A network of underground conductors, rods, or plates used to safely dissipate electrical currents into the ground, protecting personnel and equipment from electrical hazards. Grounding System

Groundwater Monitoring Well: A well installed in the ground to measure the water level, quality, and movement in underground aquifers for environmental monitoring purposes. Groundwater Monitoring Well

Groundwater Recharge Well: An underground well or structure designed to introduce water into an aquifer, replenishing groundwater resources and maintaining sustainable water levels. Groundwater Recharge Well

Groundwater Remediation: The process of treating or removing pollutants, contaminants, or toxins from groundwater sources, restoring water quality and ensuring environmental protection.

Grout: A cementitious material or substance used to fill voids, stabilize soil, or seal joints in underground utility systems. Grout

Handhole: A handhole, also known as a pull box or junction box, is an access point used to facilitate the installation, maintenance, or repair of underground utility cables or conduits. Handholes are typically small, enclosed chambers with removable covers that allow for easy entry and exit. They provide a protected space for splicing cables, making connections, or accessing utility equipment. Handhole

HDD (Horizontal Directional Drilling) Reaming: HDD reaming is a process used in horizontal directional drilling to enlarge the pilot hole to the desired diameter. It involves using progressively larger cutting tools, called reamers, to remove soil or rock and create a larger borehole. HDD reaming allows for the installation of larger-diameter underground utility lines while minimizing surface disruption and maximizing efficiency. HDD (Horizontal Directional Drilling) Reaming

HDD (Horizontal Directional Drilling) Steering: HDD steering refers to the process of guiding the drill head or tool underground during horizontal directional drilling. It involves the use of specialized equipment, sensors, and monitoring systems to control the direction and inclination of the drill path. Proper steering techniques ensure accurate placement of underground utility lines, avoiding obstacles and maintaining the desired alignment. HDD (Horizontal Directional Drilling) Steering

HDPE (High-Density Polyethylene): A type of plastic commonly used for underground water and sewer pipes due to its durability and resistance to corrosion. High Density Polyethylene (HDPE)

HDPE Conduit: High-density polyethylene conduit, a durable and flexible underground conduit used for the protection and routing of electrical or communication cables. HDPE Conduit

Headwall: A structure or wall at the end of a culvert, pipe, or drainage channel used to protect against erosion and facilitate proper water flow. Headwall

Heat Exchanger: An underground device or system that transfers heat between fluids or substances, allowing for energy transfer or temperature regulation in utility operations. Heat Exchanger

Heat Tracing: The application of electric or steam heating elements to underground pipes or equipment to maintain the desired temperature, preventing freezing or heat loss. Heat Tracing

Horizontal Separation: The required minimum distance maintained between different types of underground utilities, such as water, gas, or electrical lines, to prevent interference or potential hazards. Horizontal Separation

Hot Tap: A method of making a connection to an existing underground pipeline or conduit while it is still in service, allowing for the installation of additional utilities without interrupting flow. Hot Tapping

Hydraulic Modeling: The use of computer simulations and mathematical models to analyze and predict the behavior of water flow in underground utility systems, aiding in design and optimization. Hydraulic Modeling

Hydrodemolition: A method of removing deteriorated or damaged concrete from underground utility structures, such as tunnels or culverts, by using high-pressure water jets, ensuring efficient and controlled demolition. Hydrodemolition

Hydrodynamic Separators: Underground devices designed to remove pollutants, sediment, and debris from stormwater runoff before it enters the drainage system or water bodies. Hydrodynamic Separators

Hydroexcavation: A method of excavation that uses high-pressure water and a vacuum system to safely expose underground utilities or remove soil without causing damage.

Hydrogen Sulfide: A colorless, toxic gas produced by the decay of organic matter, commonly found in sewer systems and a potential risk to worker safety.

Hydrogeology: The study of groundwater systems, including their occurrence, movement, quality, and interactions with geological formations, relevant in underground utility planning and management. Hydrogeology

Hydrostatic Pressure: The pressure exerted by a fluid at rest, such as water pressure within a pipeline or conduit. Hydrostatic Pressure

Hydrovac Excavation: A method of excavation that uses a combination of pressurized water and a vacuum system to safely expose underground utilities. Hydrovac Excavation

Impeller: A rotating component of a pump or turbine in an underground utility system that transfers energy to fluids, generating flow or pressure. Impeller

Impressed Current Cathodic Protection: A corrosion protection technique that uses an external power source to generate a protective electrical current on underground metal structures, preventing corrosion. Impressed Current Cathodic Protection

Inertial Navigation System: A navigational technology that uses accelerometers and gyroscopes to track and record the movement and position of underground utility inspection equipment or vehicles. Inertial navigation System

Infiltration Testing: The process of evaluating the ability of the soil surrounding underground utility structures to absorb or allow water to enter, helping to assess drainage and prevent water damage. Infiltration testing

Infiltration: The unintended entry of groundwater or surface water into sewer lines, often causing overload or system malfunction. Infiltration

Inflow and Infiltration (I&I): The unintended entry of surface water or groundwater into underground sewer systems, often resulting in excessive flows and overloading the system. Inflow and Infiltration (I&I)

Infrared Inspection: The use of infrared thermography to detect temperature variations or anomalies in underground utility systems. Infrared Inspection

In-Line Inspection (ILI): The use of smart pigs or robotic devices to inspect the internal condition of underground pipelines, identifying defects, corrosion, or anomalies. In-Line Inspection (ILI)

Inspection Pit: An underground access chamber or pit used for inspecting, cleaning, or maintaining underground utility pipes or equipment, providing a safe and convenient working area. Inspection Pit

Interceptor Drain: An underground drain or pipe designed to intercept and collect surface water runoff, preventing it from entering sensitive areas or causing erosion. Interceptor Drain

Intrusion Alarm System: An underground security system that detects and alerts for unauthorized access or entry into restricted utility tunnels, vaults, or facilities. Intrusion Alarm System

Inverted Siphon: An underground structure or pipe used to transport water or other fluids across a valley or depression by gravity flow. Inverted Siphon