This article includes a list of general references, but it lacks sufficient corresponding inline citations .(July 2013) |
Utility location is the process of identifying and labeling public utility mains that are underground. These mains may include lines for telecommunication, electricity distribution, natural gas, cable television, fiber optics, traffic lights, street lights, storm drains, water mains, and wastewater pipes. In some locations, major oil and gas pipelines, national defense communication lines, mass transit, rail, and road tunnels also compete for space underground. [1]
Public utility systems are often run underground—some by the very nature of their function, others for convenience or aesthetics. In the United States, it is estimated that subsurface lines amount to over 20,000,000 miles (32,000,000 km) in total. [2] Before digging, local governments often require that the underground systems' locations be denoted and approved, if it is to be in the public right-of-way.
Pipeline markers, signs, or other indicators may or not be visible to warn of the presence of underground utilities. For various reasons, including security, the precise location of the utilities may not be indicated. The only way an excavator can know the precise location, number, and types of utilities is to contact the underground utilities coordinator, and request that the locations be marked. In most jurisdictions, there is no charge for this service, but advance notification is a legal requirement.
In the UK, to follow HSG47 [3] and PAS128 [4] guidelines, it is recommended that a Desktop Utility Search is carried out. A Utility Search, also known as a C2 Utility Search or PAS128 (D) utility search, is the initial step in identifying utility asset owners and locating their buried and overhead assets and apparatus. A Utility Search is essential for development projects as it provides valuable insight into the presence and location of underground and overhead utility assets. As well as providing a understanding of the networks within the vicinity of a site, this information can help to prevent accidents, disruptions, and costly delays during construction. [5]
Because of the many different types of materials that go into manufacturing each of the different types of underground lines, different detection and location methods must be used. The two general methods are called passive locating and active locating.
Passive locating uses signals that occur naturally on some utility lines. This method often fails to locate 60% or so of utility lines,[ citation needed ] and misidentifying utilities is an associated risk. Active locating, on the other hand, is more accurate. It makes use of signals that the locators generate through a transmitter. Then, with the help of a receiver, locators can trace as well as identify what type of utility line lies underground.
The active method is the most suitable for locating conductive metal pipes and cables. This process often involves using a piece of electromagnetic equipment, consisting of a transmitter and a receiver. For other types of pipe such as plastic or concrete, a metallic tracer wire or conductive foil (detectable tape) may be buried alongside or immediately above the pipe, to aid in locating it. In the absence of such a conductive tracer, other types of radiolocation or modern ground-penetrating radar must be used. Location by these technical means is necessary because maps often lack the pinpoint precision needed to ensure proper clearance. In older cities, it is especially a problem since maps may be very inaccurate, or may be missing entirely.
A few utilities are permanently marked with short posts or bollards, mainly for lines carrying petroleum products. This may be done because of venting requirements, and also serves to indicate the location of underground facilities that are especially hazardous if disturbed.
As of 2022 [update] , utility locators depend primarily on three types of utility locating equipment to do their job, including GPR, electromagnetic profiling locators, and radio frequency pipe locators. These tools are produced by a number of manufacturers, and are widely available throughout the world. Some of the large manufacturers include Leica, RIDGID, and Schonstedt. With advances in technology, these tools continue to improve, [6] and locators in the field are able to be more accurate.
Many utilities are now mapped out on GIS mapping services like ESRI, which improves both accuracy and process transparency. Some of the current locate wands are able to relay their information and sync up with GIS systems to expand and correct the information on the map, which helps to update the map very rapidly.
In the US, Canada, Australia, and New Zealand, many large locate companies handle millions of tickets every dig season, [7] and need a way of managing these tickets and sending them through to a unified call center (for example, Underground Service Alert).
The Common Ground Alliance (CGA) publishes the Damage Information Reporting Tool (DIRT report) every year, which gives a fuller picture of the effects of utility locating throughout North America. In recent years, DIRT has demonstrated a trend of greater excavation damage incidents over time. [8] This report does not contain every single incident, as stakeholders voluntarily submit underground damages and near-miss reports, but it is the most complete repository of utility damages anywhere in the world. Utility Locators and other stakeholders depend on data like this to learn about risks and to justify continued investment in the industry.
Industry leaders in damage prevention like the Common Ground Alliance and IR-Saving Lives are the biggest promoters of utility locating, and encourage other stakeholders to take utility locating seriously. The CGA also has published a paper called "Insights into Improving the Delivery of Accurate, On-Time Locates",[ citation needed ] which has expert information on how to improve the locating industry in the US and Canada (not to be confused with the Canadian Common Ground Alliance (CCGA), a companion organization to CGA in Canada).
Other technologies and equipment are identified in Technology Reports by CGA [9] and in a major study by the Pipeline and Hazardous Materials Safety Administration in 2017 entitled A Study on Improving Damage Prevention Technology. [10]
"Call before you dig", "Know What's Below! Dig With Confidence!", "Dial before you dig", "Digger's Hotline", "One-call", "Miss Utility", "Dig Safe", "Click before you dig", or Underground Service Alert are services that allow construction workers or property owners to contact utility companies, who will then denote where underground utilities are located via color-coded markings typically up to and not past the user's service connection or meter. Utility lines on the other side of the meter or service connection are considered to be part of the customer's property, and will typically not be located by these services.
Failure to call such a number ahead of time may result in a fine or even a criminal charge against a person or company, particularly if such negligence causes a major utility outage or serious accident, or an evacuation due to a gas leak. Hitting a water main may also trigger local flooding or require a boil-water advisory.
The following is a partial list of countries with one-call services for utility location:
Utility color codes are used to identify existing underground utilities in construction areas, to protect them from damage during excavation. Colored lines, flags, or both are used to mark the location and denote the type of underground utility. A special type of spray paint dispenser, which works when the can is upside-down, is used to mark lines, often in a fluorescent color. On flags, a logo often identifies the company or municipal utility which the lines belong to.
Flags may also be an advertisement for a company which has installed an irrigation system for lawns or gardens. In this case, each sprinkler head is usually marked, so that landscaping crews will not cover or bury them with soil or sod, or damage them with tractors or other construction equipment while digging holes for trees, shrubs, or other large plants or fenceposts. This is also important because a vehicle (tractor, truck, or otherwise) can break a sprinkler or the hard-PVC pipe or joint it is mounted on, simply by driving over it, particularly on newly moved soil which is uncompacted and therefore unsupportive of such weight.
The national standard for Australia uses the following color guide: [15]
Orange | electricity |
Yellow | gas |
Blue | water |
White | communications |
Red | fire services |
Cream | sewerage |
Purple | reclaimed water |
Silver/Gray | steam |
Brown | oils, flammable liquids |
Light blue | air |
Pink | Unidentified services |
Black | other liquids |
In Germany, the colors used for temporary marking of underground utilities are not standardized like in other countries. However, permanent marker signs are used for utilities like hydrants, drinking water lines and natural gas lines. A permanent marking of cables and sewage lines is not usual if they run in the public right-of-way. The standard for permanent markers in Germany uses the following colors: [16]
White with red frame | fire services (hydrants, suction points etc.) |
Blue | drinking water |
Yellow | gas |
Green | sewage and drain lines |
Orange or | hot water/steam lines for district heating |
Red | |
White or | high-voltage power lines and telecommunication cables |
Grey | |
Brown | lines for oil and other flammable liquids |
India uses a convention similar to the US, for marking underground utilities such as telephone, gas, water and electricity. The system is based entirely on convention without any written standard. These markings are color-coded, and are painted by contractors onto the pavement. [17]
The main colors based on the convention are used in the same way as in the US: red for electricity, yellow for gas, and blue for water. However, other colors have other meanings. Green is used for telecommunication conduits. White is used as general communication between contractors; white is also used to note the details of road surface markings so that markings can be easily restored after the road construction is completed; a few telecommunication companies also use white color for their utility locations. Orange and other colors are used by local authorities to mark improvements and other details not related to utility locations. [17]
There are no legal color code requirements for buried utilities and surface markings, however a general convention is used and encouraged by the government health and safety department - Worksafe. [18]
Underground Duct | Surface Marking Color | Surface Marking Letter | Utility |
Orange | E | Electricity | |
Yellow | G | Gas | |
Blue | Blue | W | Water |
White | Blue | ||
Green | Purple | T | Telecommunications, commonly used by Chorus for copper and fiber optic cables. |
Light Grey | Red | SS | Waste Water / Sewer |
Dark Grey | Pink | SW | Storm Water / Drainage |
Red | Regional Utility Specific, commonly used by UFF for fiber optic cables. | ||
Purple | Regional Utility Specific, known to be used by Telstra Saturn Cable Television | ||
Light blue | Regional Utility Specific, known to be used by Telstra Clear | ||
Pink | Regional Utility Specific | ||
Black | Most commonly used for non-potable water on farms however can be an outer duct for roadside utilities. Worksafe encourages the use of a 5mm wide or larger colored stripe to indicate the content of the black duct using one of the color codes above. A plain black microduct or 2-pair telephone cable is often used by Chorus for premises drop cables. |
The national standard for the United Kingdom uses the following color guide: [19]
Red | electric power lines, conduit, and cables |
Orange | telecommunication, alarm or signal lines |
Yellow | gas, oil, steam, petroleum, or other flammable material |
Green | sewage and drain lines |
Blue | drinking water |
Purple | reclaimed water, irrigation, and slurry lines |
Pink | temporary survey markings, unknown/unidentified facilities |
White | proposed excavation limits or route |
Canada and the United States use the American Public Works Association (APWA) Uniform Color Codes for temporary marking of underground utilities: [20] [21] [22] [23] [24] [25]
Red | Electric power lines, Cables, Conduit, Lighting Cables |
Orange | telecommunication, alarm or signal lines, cables, conduit, Phone, Cable TV, or Fiber Optic |
Yellow | Natural Gas, Oil, Steam, Petroleum |
Green | Sewer or Drainage |
Blue | Drinking Water |
Purple | Reclaimed water |
Pink | temporary survey markings, unknown/unidentified facilities |
White | proposed excavation limits or route |
Some municipalities use pink paint to make lines and codes on the pavements related to required street improvements such as ramp replacement, asphalt grinding, and form injection. These markings are not directly related to utility location. [26]
A color code is a system for encoding and representing non-color information with colors to facilitate communication. This information tends to be categorical though may also be sequential.
Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the IBM PC compatible industry within three years. The term can now refer to the computer display standard, the 15-pin D-subminiature VGA connector, or the 640 × 480 resolution characteristic of the VGA hardware.
A trench is a type of excavation or depression in the ground that is generally deeper than it is wide, and narrow compared with its length.
The Color Graphics Adapter (CGA), originally also called the Color/Graphics Adapter or IBM Color/Graphics Monitor Adapter, introduced in 1981, was IBM's first color graphics card for the IBM PC and established a de facto computer display standard.
Electrical wiring in North America follows the regulations and standards applicable at the installation location. It is also designed to provide proper function, and is also influenced by history and traditions of the location installation.
8-1-1 is an N-1-1 telephone number in Canada and the United States. In Canada, the number is used for non-urgent health services. In the United States, 8-1-1 provides a uniform national phone number to access local utility location services.
A gas cylinder is a pressure vessel for storage and containment of gases at above atmospheric pressure. Gas storage cylinders may also be called bottles. Inside the cylinder the stored contents may be in a state of compressed gas, vapor over liquid, supercritical fluid, or dissolved in a substrate material, depending on the physical characteristics of the contents. A typical gas cylinder design is elongated, standing upright on a flattened or dished bottom end or foot ring, with the cylinder valve screwed into the internal neck thread at the top for connecting to the filling or receiving apparatus.
A raised pavement marker is a safety device used on roads. These devices are usually made with plastic, ceramic, thermoplastic paint, glass or occasionally metal, and come in a variety of shapes and colors. Raised reflective markers, such as plastic, ceramic, or metal ones, include a lens or sheeting that enhances their visibility by retroreflecting automotive headlights, while glass road studs gather automotive headlights with a dome shape and reflect the lights with a reflective layer within. Some other names for specific types of raised pavement markers include convex vibration lines, Botts' dots, delineators, cat's eyes, road studs, or road turtles. Sometimes they are simply referred to as "reflectors".
A utility pole, commonly referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, telegraph pole, or telegraph post, is a column or post, usually made out of wood or aluminum alloy, used to support overhead power lines and various other public utilities, such as electrical cable, fiber optic cable, and related equipment such as transformers and street lights while depending on its application. A Stobie pole is a multi-purpose pole made of two steel joists held apart by a slab of concrete in the middle, generally found in South Australia.
Road surface marking is any kind of device or material that is used on a road surface in order to convey official information; they are commonly placed with road marking machines. They can also be applied in other facilities used by vehicles to mark parking spaces or designate areas for other uses. In some countries and areas, road markings are conceived as horizontal traffic signs, as opposed to vertical traffic signs placed on posts.
Spray paint is paint that comes in a sealed, pressurized container and is released in an aerosol spray when a valve button is depressed. The propellant is what the container of pressurized gas is called. When the pressure holding the gas is released through the valve, the aerosol paint releases as a fine spray. Aerosol painting is one form of spray painting; it leaves a smooth, even coat, unlike many traditional rolled and brushed paints. Aerosol primer can be applied directly to bare metal and many plastics.
A utility tunnel, utility corridor, or utilidor is a passage built underground or above ground to carry utility lines such as electricity, steam, water supply pipes, and sewer pipes. Communications utilities like fiber optics, cable television, and telephone cables are also sometimes carried. One may also be referred to as a services tunnel, services trench, services vault, or cable vault. Smaller cable containment is often referred to as a cable duct or underground conduit. Direct-buried cable is a major alternative to ducts or tunnels.
A trencher is a piece of construction equipment used to dig trenches, especially for laying pipes or electrical cables, for installing drainage, or in preparation for trench warfare. Trenchers may range in size from walk-behind models, to attachments for a skid loader or tractor, to very heavy tracked heavy equipment.
In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire or a blown fuse or circuit breaker. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
Directional boring, also referred to as horizontal directional drilling (HDD), is a minimal impact trenchless method of installing underground utilities such as pipe, conduit, or cables in a relatively shallow arc or radius along a prescribed underground path using a surface-launched drilling rig. Directional boring offers significant environmental advantages over traditional cut and cover pipeline/utility installations. The technique is routinely used when conventional trenching or excavating is not practical or when minimal surface disturbance is required.
An underground power line provides electrical power with underground cables. Compared to overhead power lines, underground lines have lower risk of starting a wildfire and reduce the risk of the electrical supply being interrupted by outages during high winds, thunderstorms or heavy snow or ice storms. An added benefit of undergrounding is the aesthetic quality of the landscape without the powerlines. Undergrounding can increase the capital cost of electric power transmission and distribution but may decrease operating costs over the lifetime of the cables.
Underground pneumatic boring is a trenchless method of installing underground utilities.
A vacuum truck, vacuum tanker, vactor truck, vactor, vac-con truck, vac-con is a tank truck that has a pump and a tank. The pump is designed to pneumatically suck liquids, sludges, slurries, or the like from a location into the tank of the truck. The objective is to enable transport of the liquid material via road to another location. Vacuum trucks transport the collected material to a treatment or disposal site, for example a sewage treatment plant.
A cable locator or cable avoidance tool (CAT) is an instrument used for detecting the presence and approximate location of buried services in advance of undertaking excavation works. It aims to avoid accidents while excavating. A number of types of detecting technology can be employed by such instruments, including use of magnetic fields, radio frequencies, signal generation, metal detectors, ground-penetrating radar and RFID.
Utility repair tag is a plastic color-coded pavement marker embedded in the top surface of an asphalt utility cut restoration to identify the responsible party of that pavement repair or patch. The tag is not to be used for identification of an underground utility location.