= No dig 2006 =

= Glossary =



Caisson Shaft
Shaft constructed by preforming the structure at the surface and then sinking it into the ground by excavating.

A rock or substance formed of calcium carbonate or magnesium carbonate by biological deposition or inorganic precipitation, or containing those minerals in sufficient quantities to effervesce when treated with cold hydrochloric acid.

A large, more or less circular, basin-shaped volcanic depression whose diameter is many times greater than the volcanic vent.

The optimisation of parameters such that the computer or physical model best fits the observed field measurements

Principal module which is part of a shield machine as in microtunnelling or of a TBM. Two or more may be used, depending on the installation dimensions required and the presence of an articulated joint to facilitate steering.

Canopy angle
Generally, a measure of the openness of a stream to sunlight. Specifically, the angle formed by an imaginary line from the highest structure (for example, tree, shrub, or bluff) on one bank to eye level at midchannel to the highest structure on the other

Capillary fringe
The zone above the water table in which water is held by surface tension. Water in the capillary fringe is under a pressure less than atmospheric.

Carbonate rocks
Rocks (such as limestone or dolostone) that are composed primarily of minerals (such as calcite and dolomite) containing the carbonate ion (CO32-). Casing Pipe Method
Method in which a casing, generally steel, is pipe jacked into place, within which a product pipe is later inserted.

Casting basin
A place where elements for immersed tunnels can be fabricated in the dry, and which can be flooded to allow the elements to be floated out and taken away. Generally used for concrete tunnels.

Catastrophic Rainfall Event
Rainfall event of return frequency far in excess of any sewerage design performance criteria typically, say, a 1 in 200 year storm Catchment Area
Area draining to a drain, sewer or watercourse

Sub-division of the system(s) under study by considering pipe characteristics, environmental factors and strategic factors.

Cathodic Protection
Electrical means of protecting ferrous (usually steel) mains from corrosion. Caulking
General term which, in trenchless technology, refers to methods by which joints may be closed within a pipeline or between lining segments.

Closed circuit television used to carry out internal inspection and survey of pipelines.

CCTV Surveying
A method of assessing the condition or status of a water main or public sewer, using cameras.

A below-grade portion of a building. See also basement. Center pivot irrigation
An automated sprinkler system involving a rotating pipe or boom that supplies water to a circular area of an agricultural field through sprinkler heads or nozzles.

Certification Body
Impartial body, governmental or non-governmental, possessing he necessary competence and responsibility to carry out certification of conformity according to given rules of procedure and management

Cess Pit

An underground covered watertight tank used for receiving and storing sewage from premises.

Cess Pool

See Cess Pit.


Part of a manhole or inspection chamber manufactured as a single entity and intended to be joined with other chamber units

Chamber Unit

Component part of a manhole or inspection chamber manufactured as a single entity and intended to be joined with other chamber units

Chamber Unit

Component part of a manhole or inspection chamber manufactured as a single entity and intended to be joined with other chamber units

Channel scour

Erosion by flowing water and sediment on a stream channel; results in removal of mud, silt, and sand on the outside curve of a stream bend and the bed material of a stream channel.


The straightening and deepening of a stream channel to permit the water to move faster or to drain a wet area for farming.

Chemical Stabilisation

Renovation method in which a length of pipeline between two access points is sealed by the introduction of one or more compounds in solution into the pipe and surrounding ground and, where appropriate, producing a chemical reaction. Such systems may perform a variety of functions such as the sealing of cracks and cavities, the provision of a new wall surface with improved hydraulic characteristics or ground stabilisation.

Chlordane Octachloro-4,7-methanotetrahydroindane.

An organochlorine insecticide no longer registered for use in the U.S. Technical chlordane is a mixture in which the primary components are cis- and trans-chlordane, cis- and trans-nonachlor, and heptachlor.

Chlorinated solvent

A volatile organic compound containing chlorine. Some common solvents are trichloroethylene, tetrachloroethylene, and carbon tetrachloride.


A class of volatile compounds consisting of carbon, chlorine, and fluorine. Commonly called freons, which have been in refrigeration mechanisms, as blowing agents in the fabrication of flexible and rigid foams, and, until banned from use several years ago


See Polycyclic aromatic hydrocarbon (PAH).


A marshy area where the ground is wet due to the presence of seepage or springs.


Said of water with a pH between 5.5 and 7.4; pH modifier used in the U.S. Fish and Wildlife Service wetland classification system.


A deep, steep-walled, half-bowllike recess or hollow situated high on the side of a mountain and commonly at the head of a glacial valley; and produced by the erosive activity of mountain glaciers.

Civil defence / protection

Protection of the civilian population against the effects of bombs, fallout, and chemical releases.

Class I Liner

Clasification developed by AWWA for a non-structural renovation system.

Class II Liner

Clasification developed by AWWA for a semi-structural lining which has no inherent resistence to external buckling loads.

Class III Liner

Clasification developed by AWWA for a semi-structural liner with sufficient buckling resistence to be free standing.

Class IV Liner

Clasification developed by AWWA for a fully structural liner.


Rock, such as sandstone, or sediment composed principally of broken fragments that are derived from preexisting rocks which have been transported from their place of origin.


General term for vitrified clay pipes.

Cleaning Ball

Spherical device, having an indented surface, designed to be carried through a drain or sewer by the flow to facilitate removal of sediments


The sum total of the meteorological elements that characterize the average and extreme conditions of the atmosphere over a long period of time at any one place or region of the Earth's surface.

Closed Shields

Shields which incorporate a closed pressure chamber and do not allow direct access to the face.


Situation of the installed pipe, such that an interference fit maybe created between the outside of the pipe and the inside of the existing pipe. See Lining With Close-Fit Pipes.

Coastal Wastewater Outfall

The coastal site of discharge of liquid from a pipe. Applied particularly to the point at which a sewer discharges to a treatment works (possibly via a conduit) or receiving water course.

Combined Sewer

A system of sewerage whereby waste water and surface water are carried in the same drains and sewers.

Combined Sewer Overflow

A device on a combined or partially separate sewerage system designed to relieve the system of flows that are in excess of a selected rate. The excess flows are then discharged, possibly after solid material has been removed by a CSO, into a watercourse.

Commercial Withdrawals

Water for use by motels, hotels, restaurants, office buildings, commercial facilities, and civilian and military institutions. The water may be obtained from a public supplier or it may be self-supplied.
Community In ecology, the species that interact in a common area.

Compensation Grouting

A system by which grout is injected into the ground above a tunnel and below man-made surface features. The intention is to ameliorate the effects of surface settlement caused by the tunneling works.


The act or position of having met all legal and regulatory standards.

Compressed Air Method

General term which, in trenchless technology, refers to the use of compressed air within a tunnel or shaft in order to balance ground water pressure and to prevent ingress into an excavation open to the atmosphere.


The ratio of the quantity of any substance present in a sample of a given volume or a given weight compared to the volume or weight of the sample.


In general, the granting of a favor or a point during negotiations. In business terms, can represent a contract allowing the building and/or operation of a facility by another company.


Man-made or adapted water or waste water course or pipe.
Cone of depression The depression of heads around a pumping well caused by withdrawal of water.

Cone Penetration Test

CPT is an in-situ method of testing soil using a Static or Dutch Cone.

Confined Aquifer (artesian aquifer)

An aquifer that is completely filled with water under pressure and that is overlain by material that restricts the movement of water.


Being limited in movement, view, travel, etc. May induce variable psychological responses in persons using underground spaces.

Confining layer

A body of impermeable or distinctly less permeable (see permeability) material stratigraphically adjacent to one or more aquifers that restricts the movement of water into and out of the aquifers.


The flowing together of two or more streams; the place where a tributary joins the main stream.


A coarse-grained sedimentary rock composed of fragments larger than 2 millimetres in diameter.

Consequence Of Failure

Damage that can result from the discharge of large volumes of water associated with a sudden or brittle failure.


The saving of energy by one project alternative in comparison with another.
Constituent A chemical or biological substance in water, sediment, or biota that can be measured by an analytical method.

Construction cost

The cost to create a facility. Depending on the specific context, this term may include land purchase, design fees and all costs necessary to put a facility into operation; or it may be limited only to the costs of physical construction work.

Consumptive Use
The quantity of water that is not available for immediate reuse because it has been evaporated, transpired, or incorporated into products, plant tissue, or animal tissue. Also referred to as "water consumption".

Contact Recreation
Recreational activities, such as swimming and kayaking, in which contact with water is prolonged or intimate, and in which there is a likelihood of ingesting water.

Substances present in the ground which are not part of the natural soil; usually associated with ground usage.

Degradation of water quality compared to original or natural conditions due to human activity.

Continuous Sliplining
See Lining With Continuous Pipe Continuous Survey
Any survey carried out along some or all of the length of a pipeline, including soil resistivity and soil potential survey.

Contributing Area
The area in a drainage basin that contributes water to streamflow or recharge to an aquifer.

Control Section
Section of a drain or sewer system where hydraulic conditions are known and where any change in those conditions influences the upstream and/or downstream water levels

Conventional Shields
Shields which allow some form of direct access to the soil face. Also known as open shields.

Conventional Trenching
Method in which access is gained by excavation from ground level to the required level underground for the installation, maintenance or inspection of a pipe, conduit or cable. The excavation is then backfilled and the surface reinstated.

Conventional Tunnelling
Method of tunnel construction ranging from manual excavation to the use of self-propelled tunnel boring machines. Where a lining is required, bolted segmental rings are frequently used.

Changes in the distance between fixed points on a (cross-section of a ) tunnel lining as a result of loading on the lining.

Coral Reef
A ridge of limestone, composed chiefly of coral, coral sands, and solid limestone resulting from organic secretion of calcium carbonate; occur along continents and islands where the temperature is generally above 18 C.

Core Sample
A sample of rock, soil, or other material obtained by driving a hollow tube into the undisturbed medium and withdrawing it with its contained sample.

The extent to which pipeline deterioration appears to be a function of a particular set of physical or environmental factors.

Corrosion 'Hotspots'
Localised areas of intense corrosion (often very relevant on ferrous mains) sometimes linked to coating damage.

Cost effective
Having a benefit-cost ratio greater than "1" when all costs and benefits can be monetarised. Otherwise, cost judged to be worthwhile against benefits. When several options are being compared, the option with the highest benefit-cost ratio.

Cost of a project
Totality of expenditures implied by the implementation of that project. If expenditures are spread over time, they must normally be discounted, which is indicated by using the term "discounted cost".

Cost-Benefit Analysis (study)
Cost-benefit analysis consists of identifying and quantifying the costs and benefits and, where possible, ascribing values to them. It is used particularly for non-marketable goods.

Amount of rock and/or soil over the arch of a tunn

Crack lines visible along the length and/or circumference.

Factors by reference to which a decision is taken. Multi-criteria analysis may also be carried out, possibly incorporating cost-benefit analysis as one of the criteria.

A standard rule or test on which a judgment or decision can be based.

Critical Sewers
Sewers with the most significant consequences in the event of structural failure.

A section of utility line where a pipe or cable has to pass under an existing road, railway, river or other area where the surface should not be disturbed.

The upper section in the stepped excavation of a tunnel excavated in two or more horizontally stepped stages. It is the first section to be excavated.

Crystalline Rocks
Rocks (igneous or metamorphic) consisting wholly of crystals or fragments of crystals. CSD
See Crude Sewage Discharge.

Cubic Foot Per Second (ft3/s or CFS)
Rate of water discharge representing a volume of 1 cubic foot passing a given point during 1 second, equivalent to approximately 7.48 gallons per second or 448.8 gallons per minute or 0.02832 cubic meter per second. In a stream channel, a discharge of 1 c

Cut and Cover (construction, method)
Underground construction involving open-cut excavation followed by eventual covering with a slab or arch structure to support a replaced ground surface. A temporary covering at ground level may be provided for the passage of traffic or environmental reasons.

The front end of a mechanical excavator, usually a wheel, which actually cuts through rock or soft ground.

Cutting/Cutter Head
Tool or system of tools on a common support which excavates at the face of a bore. Usually applies to mechanical methods of excavation. CWO
See Coastal Water Outfall.

An area of low pressure around which winds rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. See also Tropical cyclone

Cypress Dome
Small, isolated, circular, depressional, forested wetlands, in which cypress predominates, that have convex silhouettes when viewed from a distance.


JOHANNESBURG +27 (0) 11 643 3038

CAPE TOWN +27 (0) 21 852 3081


2006 nodig.co.za, All Rights Reserved.