Construction Glossary

A.M. Peak Hour: A.M. peak hour is identified by a one hour period in the morning when traffic flow increases. The a.m. peak hour typically occurs between 6:30 a.m. and 9:00 a.m. Traffic volumes occurring during the a.m. peak hour are used to calculate the overall operation of a roadway or intersection.

Abutters: The owner of property that abuts (touches) another property.

Aggregate: Broadly, aggregate is a class of minerals and materials used in construction. The exact aggregate used varies greatly between types of construction jobs, but it often consists of sand, gravel, stone, recycled concrete and sometimes lighter materials like clay and pumice. Aggregate is a major component of asphalt concrete (used to pave roads, driveways and parking lots) and concrete (used to pave sidewalks and make curbs, barriers and other structures).

Back Filling: Earth, soil, or other material used to replace previously excavated material, as around a newly constructed foundation wall.

Backflow Preventer: A device used to protect potable water supplies from contamination or pollution due to backflow. In water supply systems, water is normally maintained at a significant pressure to enable water to flow from the tap, shower, or other fixture. Also used in wastewater to protect below grade plumbing fixtures from pipe surcharge.

Berm: An earthen or asphalt mound used to direct the flow of runoff around or through a structure.

Bioretention: A water quality practice that utilizes landscaping and soils to treat urban stormwater runoff by collecting it in shallow depressions. It then filters the runoff through a fabricated planting soil media.

Bollard: A vertical post meant to control pedestrian and vehicle traffic. Often placed next to each other near alleyways or entrances to indicate a no-car zone or an authorized vehicles only zone.

Catch Basin: Box-like underground concrete structure that is part of the storm drain system. It has openings along the curbs and gutters designed to collect Stormwater runoff from streets and pavements. A catch basin is a curbside receptacle whose function is to convey water from streets and other impervious surfaces into the storm drainage system. The design of this drainage structure includes a sump and hood that captures and temporarily stores some pollutants such as oils and sediment. Maintenance to clean out the sump removes the stored pollutants and prevents them from washing further into the storm drain system and into receiving waters such as the Charles River and Alewife Brook.

Catenary Wires: A system of overhead wires used to supply electricity to a locomotive, streetcar, or light rail vehicle – Used in this area to power MBTA vehicles.

Cold Patch: Asphalt mixture used to repair cracks and potholes on less-trafficked roads, so-called “cold” because it bonds following evaporation or compaction without needing to be heated up first.

Combined Sewer: Sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. Most of the time, combined sewer systems transport all of their wastewater to a sewage treatment plant, where it is treated and then discharged to a water body.

Combined Sewer Overflow: A regulator structure placed in a combined sewer system that allows the discharge of excess wastewater to a receiving water body. These structures are permitted by EPA to protect property from flooding.

Contraction: As the seasons change from summer to winter and the temperature grows colder, the base, subgrade or overlay can contract, causing major cracking.

Conduit: Any channel or pipe for directing the flow of water. Conduits are also used to house electric and communication cables.

Conveyance System: Any channel or pipe for collecting and directing stormwater or wastewater.

Culvert: A channel or a large diameter pipe that crosses under a road, sidewalk, etc.

Detectable Warning Panel: Textures surfaces installed near stairs, railroad platforms and curbs used to warn blind and visually impaired persons about a potentially hazardous walking area. Also known as truncated domes.

Detention Pond: A stormwater system that delays the downstream progress of stormwater runoff in a controlled manner. This is typically accomplished using temporary storage areas and a metered outlet device. (As opposed to a less common Retention pond).

Easement: An easement is a legal right to use someone’s land for a particular purpose. For example, the City may have an easement to use a portion of a property to create an ADA-compliant accessible public sidewalk.

Eminent Domain: The right to take private property for public use.

Expansion: As the seasons change from winter to summer and the temperature grows warmer, the base, subgrade or overlay can expand, causing major cracking.

Frost Heave: Used to describe the swelling of soil due to ice building from underneath the ground up to the surface. Frost heaving can cause cracks and potholes during the winter and spring.

Facade: Any side of a building facing a public way or space and finished accordingly.

Frontage: A strip or extent of land abutting on a street or water.

Full Depth Reconstruction: The reconstruction of an existing roadway involving the gravel sub-base and pavement layers.

Grading: Grading in civil engineering and landscape architectural construction is the work of ensuring a level base, or one with a specified slope, for a construction work such as a foundation, the base course for a road or a railway, or landscape and garden improvements, or surface drainage.

Grinding: Surface grinding is used to produce a smooth finish on flat surfaces. Also used to scarify existing pavement in preparation for new pavement.

Grind and Overlay: Roadway surface grinding of 2-4” that is then replaced with new pavement layer.

Holding Pond: A pond or reservoir, usually made of earth, built to store polluted runoff for a limited time. (Detention Basin)

Illegal Discharge: Any non-stormwater flow either intentionally or inadvertently discharged to the City's storm drainage system. This does not include discharges authorized by an NPDES permit or discharges resulting from firefighting activities.

Illicit Connection: Any connection to a storm drain system for which there is no permit or that is used for an illegal discharge. This includes, but is not limited to: (1) any connections that convey sewage, process wastewater and wash water to the storm drain system, (2) all connections from indoor drains or sinks, and (3) all unapproved, undocumented drains from loading docks and hazardous materials handling areas directly connected to the storm drain system.

Infrared Repair: In the paving world, an infrared repair is the process of heating up existing asphalt to a workable temperature (300° F), then removing the deteriorated pavement 3” to 4” deep. New replacement asphalt is raked in and compacted with a vibratory roller. Infrared repairs are the most cost-effective type of asphalt repair: The finished product has the same or better life expectancy as the surrounding asphalt, and it costs far less than getting the pavement removed wholesale.

Line Striping: The marking of parking lots, roadways, etc. used to help guide traffic and enhance safety.

Loam: Soil composed of roughly 40% sand, 40% silt and 20% clay, though varieties of loam with a slightly different makeup and consistency exist too, used as a host soil for plant materials.

Membranes: Membranes are waterproof, weather-resistant, slip-resistant polyurethane coatings designed to give protection, whether indoors or out.

Milling: Pavement milling is the process of removing at least part of the surface of a paved area such as a road, bridge, or parking lot. Also knows as scarifying.

Pathway: A transition strip occupied by a temporary facility to be used for pedestrian traffic until such time as permanent sidewalks are constructed.

Porous Pavement: A range of sustainable materials and techniques for permeable pavements with a base and subbase that allow the movement of stormwater through the surface. In addition to reducing runoff, this effectively traps suspended solids and filters pollutants from the water.

Pulverizing: The process of grinding existing asphalt and recycling it with new asphalt mix, emulsion and underlying material to produce a quality base layer. Pulverizing requires the use of a large construction vehicle called a road reclaimer, which moves along the road slowly, pulverizing and recycling at the same time.

Raised Castings: A manhole cover that extrudes 2 inches from the ground.

Raveling: Loss of pavement or concrete material caused by deterioration, ultraviolet exposure, traffic frequency, weather conditions, material mix design or compact during construction or installation.

Reclamation: A process that includes full-depth pulverization of asphalt and laying a fresh layer of asphalt over the recycled pavement base.

Right of Entry (ROE): The right of a person to go onto another's real property without committing trespass.

Riprap: Rocks or broken pieces of concrete often placed in areas where the flow of stormwater is expected to cause erosion. The riprap serves as "armor" for areas of channels and detention basins to minimize the occurrence of erosion.

Rutting: Vertical groove created in the wheel paths of traffic, caused by unstable or insufficient compaction.

Spalling: An advanced problem formed in constructed joints or concrete cracks in which fragments chip off or break away from the edges of the concrete.

Subgrade: Subgrade (aka: formation level) is the native material underneath a constructed road, pavement or railway track.

Sump: A pit or tank that catches liquid runoff for drainage or disposal.

Squeegee: Method used to apply sealcoat. Sealcoat is applied to the surface and spread using the squeegee. This can help force sealcoat into cracks and voids that spraying can’t reach. This approach is often used prior to the spray approach.

Temporary Striping: Markings on the ground, such as pavement markings or road surface markers, that will eventually be removed.

Transition Strip: A portion of the public street abutting a tract of land lying between the traveled portion of the street and the property lines.

Treatment Control: Treatment methods to remove pollutants from stormwater.

Trenches: Trenches are used to place easily damaged and obstructive infrastructure or utilities (such as gas mains, water mains or telephone lines) underground.

Truncated Domes: Textures surfaces installed near stairs, railroad platforms and curbs used to warn blind and visually impaired persons about a potentially hazardous walking area.

Underground Storage Tanks (UST’s): Storage tanks that have at least 10% of their storage capacity underground.

Valve Box: An access structure that allows a water or gas valve to be operated from the ground surface.

Vibratory Roller: Tool used to compact a new asphalt.

Water Gate: A type of valve used to isolate flows in a water system.

Water Main: A principal pipe in a system of pipes for conveying water.

Watershed: A geographical region of land or "drainage area" that drains to a common channel or outlet. Drainage of the land can occur directly into a waterbody, or through a series of systems that may include storm drains, roadside swales, and/or tributary channels. A watershed is made up of the land area that drains to a specific body of water. Cambridge lies within two watersheds, the Charles River and Mystic River watersheds. Everyone lives in a watershed. Check out the Cambridge watershed map.

Yard: For most uses in the paving world, “yard” refers to a cubic yard (3 ft. x 3 ft. x 3 ft.) rather than the standard 3ft. length measurement.

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Dept of Public Works

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Cambridge MA 02139


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