Technical Glossary - L

Landfill Gas: Gas generated by the natural degrading and decomposition of municipal solid waste by anaerobic microorganisms in sanitary landfills. The gasses produced, carbon dioxide, and methane can be collected by a series of low-level pressure wells and can be processed into a medium Btu gas that can be burned to generate steam or electricity.

Lagoon: 1. A shallow pond where sunlight, bacterial action, and oxygen work to purify wastewater; also used for storage of wastewater or spent nuclear fuel rods. 2. A shallow body of water, often separated from the sea by coral reefs or sandbars.

Land Application:
Discharge of wastewater onto the ground for treatment or reuse.

Land Application:
The even distribution of the land of effluent from animal husbandry, soil improvers, fertilizers, crop-care products and wastewater treatment sludge, etc.

Land Ban:
Phasing out of the land disposal of most untreated hazardous wastes, as mandated by the 1984 RCRA amendments.

Land Disposal Restrictions: Rules that require hazardous wastes to be treated before disposal on land to destroy or immobilize hazardous constituents that might migrate into soil and ground water.

Land Farming (of Waste):
A disposal process in which hazardous waste deposited on or in the soil is degraded naturally by microbes.

Landfill: An installation designed to treat and store waste under optimal safety conditions. The European Union recognizes three classes of the landfill: stabilized hazardous waste landfills, called class 1; landfills that take in the household and similar waste, called class 2; and inert waste, or class 3, landfill sites. In the United States, there are two classes of the landfill: Class 1 for non-hazardous solid wastes and Class 2 for hazardous wastes.

A modern engineered way to deposit waste into the ground and still protect the environment. As the landfill is built, the base of the cell is lined with a protective layer and materials are installed to monitor and collect leachate and gas emissions. As waste is deposited over the liner, it is compacted with heavy machinery in an effort to get the maximum amount of waste in an area. At the end of the day, the waste is covered with soil or special fabric cover (unless specifically exempted by state regulators.) Once the lined area is completely full, it is covered with an engineer-designed cap. Regulations mandate the periodic testing of ground water, leachate levels, and gas emissions. Landfills are accounted for a separate line of business within the WMI organization. Different types of landfills include MSW, C&D, Asbestos Monofil, Ash Monofil, Special Waste and Hazardous Waste.

Landfills: 1. Sanitary landfills are disposal sites for non-hazardous solid wastes spread in layers, compacted to the smallest practical volume, and covered by material applied at the end of each operating day. 2. Secure chemical landfills are disposal sites for hazardous waste, selected and designed to minimize the chance of release of hazardous substances into the environment.

Landfill, Construction & Demolition (C&D):
A landfill that has been permitted by a state regulatory agency to accept Construction and Demolition waste. This type of landfill must have properties and design features specific to this type of landfilling that have been established by the state regulatory agency.

Landfill Footprint:
Parcels of land that are designated and permitted to perform landfilling activities. This would include the entrance, staging area, buffer area and the area that will accept waste for disposal (the waste footprint area).

Landfill Gas:
Municipal solid waste contains significant portions of organic materials that produce a variety of gaseous products when dumped, compacted, and covered in landfills. Anaerobic bacteria thrives in the oxygen-free environment, resulting in the decomposition of the organic materials and the production of primarily carbon dioxide, and methane. Landfill gas consists of 50-60% methane and 35-40% carbon dioxide.

Landfill Gas Generators: Utilizing landfill gas to fuel a generator.

Landfill Gases: Gases arising from the decomposition of organic wastes; principally methane, carbon dioxide, and hydrogen sulfide. Such gasses may cause explosions at landfills.

Landfill, Hazardous Waste:
Wastes that exhibit certain characteristics may be regulated by RCRA. A waste may be considered hazardous if it is ignitable (i.e., burns readily), corrosive, or reactive (e.g., explosive). Waste may also be considered hazardous if it contains certain amounts of toxic chemicals. In addition to these characteristic wastes, EPA has also developed a list of over 500 specific hazardous wastes. Hazardous waste takes many physical forms and may be solid, semi-solid, or even liquid. A hazardous waste landfill is built to specific regulations to allow for the disposal of waste designated by regulatory agencies as being hazardous. These regulations are far more stringent that for an MSW landfill. WMI has 5 secure hazardous waste landfills permitted under RCRA. These sites all operate under the name "Chemical Waste Management" (CWM).

Landfill, Municipal Solid Waste (MSW):
A landfill that has been permitted by a state regulatory agency to accept municipal solid waste. This type of landfilling must have properties and design features specific to this type of landfill that have been established by the state regulatory agency.

Landfill Sites: A landfill is a carefully designed structure built into or on top of the ground in which rubbish is isolated from the surrounding environment (groundwater, air, soil). Landfills are not designed to break down waste, merely to bury it. The modern landfill offers much more protection for the environment and for local people than traditional dumps did. Problems with odors, litter, vermin, etc., are greatly reduced by the careful management of the site.

Landfilling: The final disposal of solid waste by placing it in a controlled fashion in a place intended to be permanent. The Source Book uses this term for both controlled dumps and sanitary landfills.

Landscape: The traits, patterns, and structure of a specific geographic area, including its biological composition, its physical environment, and its anthropogenic or social patterns. An area where interacting ecosystems are grouped and repeated in similar form.

Landscape Characterization: Documentation of the traits and patterns of the essential elements of the landscape.

Landscape Ecology:
The study of the distribution patterns of communities and ecosystems, the ecological processes that affect those patterns, and changes in pattern and process over time.

Landscape Indicator:
A measurement of the landscape, calculated from mapped or remotely sensed data, used to describe spatial patterns of land use and land cover across a geographic area. Landscape indicators may be useful as measures of certain kinds of environmental degradation such as forest fragmentation.

Langelier Index (LI): An index reflecting the equilibrium pH of water with respect to calcium and alkalinity; used in stabilizing water to control both corrosion and scale deposition.

Laser: A very intense, uniform beam of electromagnetic radiation. It is an Acronym for Light Amplification by Simulated Emission of Radiation.

Laser Induced Fluorescence: A method for measuring the relative amount of soil and/or groundwater with an in-situ sensor.

Latency: Time from the first exposure of a chemical until the appearance of a toxic effect.

Latent Heat: A change in the heat content that occurs without a corresponding change in temperature, usually accompanied by a change of state (as from liquid to vapor during evaporation).

Latent Load: The cooling load caused by moisture in the air.

Lateral Sewers:
Pipes that run under city streets and receive the sewage from homes and businesses, as opposed to domestic feeders and main trunk lines.

The angular distance north or south of the equator, measured in degrees of arc.

Laundering Weir:
Sedimentation basin overflow weir.

Layoff (Electric Utility):
 The excess capacity of a generating unit, available for a limited time under the terms of a power sales agreement.

Lay Up: Lay up is another term for cold storage and describes the status of equipment (such as a power plant) that has been placed in storage ("mothballed") for later use.

LC 50/Lethal Concentration:
Median level concentration, a standard measure of toxicity. It tells how much of a substance is needed to kill half of a group of experimental organisms in a given time.

LD 50/ Lethal Dose: The dose of a toxicant or microbe that will kill 50 percent of the test organisms within a designated period. The lower the LD 50, the more toxic the compound.

Ldlo: Lethal dose low; the lowest dose in an animal study at which lethality occurs.

Water that collects contaminants as it trickles through wastes, pesticides or fertilizers. Leaching may occur in farming areas, feedlots, and landfills, and may result in hazardous substances entering surface water, ground water, or soil.

Leachate: Liquid (which may be partly produced by the decomposition of organic matter) that has seeped through a landfill or a compost pile and has accumulated bacteria and other possibly harmful dissolved or suspended materials. If uncontrolled, leachate can contaminate both groundwater and surface water.

Leachate Collection System:
A system that gathers leachate and pumps it to the surface for treatment.

Leachate Pond: A pond or tank constructed at a landfill to receive the leachate from the area. Usually, the pond is designed to provide some treatment of the leachate, by allowing settlement of solids or by aeration to promote biological processes.

Leaching: The process by which soluble constituents are dissolved and filtered through the soil by a percolating fluid.

Lead (Pb): A heavy metal that is hazardous to health if breathed or swallowed. Its use in gasoline, paints, and plumbing compounds has been sharply restricted or eliminated by federal laws and regulations.

Lead Service Line:
A service line made of lead which connects the water to the building inlet and any lead fitting connected to it.

Leaded Gasoline: Gasoline containing tetraethyl lead, an important constituent in antiknock gasoline. Leaded gasoline is no longer sold in the United States.

Lean Burn: Lean-burn is the ability to ignite air and fuel mixtures that contain higher amounts of air than normally used.

Legionella: A genus of bacteria, some species of which have caused a type of pneumonia called Legionnaires Disease.

Lethal Concentration 50: Also referred to as LC50, a concentration of a pollutant or effluent at which 50 percent of the test organisms die; a common measure of acute toxicity.

Lethal Dose 50:
Also referred to as LD50, the dose of a toxicant that will kill 50 percent of test organisms within a designated period of time; the lower the LD 50, the more toxic the compound.

Life Cycle Assessment (LCA): A compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product or system throughout its life cycle.

Life Cycle Cost:
Amount of money necessary to own, operate and maintain a building over its useful life.

Life Cycle Inventory (LCI):
The part of the LCA process that quantities the energy, input of raw material and releases into the environment that are associated with each stage of production.

Life Cycle of a Product: All stages of a product's development, from an extraction of fuel for power to production, marketing, use, and disposal.

Life Extension:
A term used to describe capital expenses which reduce operating and maintenance costs associated with continued operation of electric utility boilers. Such boilers usually have a 40-year operating life under normal circumstances.

Lifetime Average Daily Dose:
Figure for estimating excess lifetime cancer risk.

Lifetime Exposure: Total amount of exposure to a substance that a human would receive in a lifetime (usually assumed to be 70 years).

Lift: In a sanitary landfill, a compacted layer of solid waste and the top layer of cover material.

Light Emitting Diode: A long-lasting illumination technology used for exit signs which require very little power

Light Non-Aqueous Phase Liquid (LNAPL):
A non-aqueous phase liquid with a specific gravity less than 1.0. Because the specific gravity of water is 1.0, most LNAPLs float on top of the water table. Most common petroleum hydrocarbon fuels and lubricating oils are LNAPLs.

Light Water Reactor (LWR):
A nuclear power unit that uses ordinary water to cool its core. The LWR may be a boiling water reactor or a pressurized water reactor.

Lignite: Brownish black coal having qualities in between those of bituminous coal and peat. The texture of the original wood often is visible in lignite.

Limestone Scrubbing:
Use of a limestone and water solution to remove gaseous stack-pipe sulfur before it reaches the atmosphere.

Limit of Detection (LOD): The minimum concentration of a substance being analyzed test that has a 99 percent probability of being identified.

Limited Degradation: An environmental policy permitting some degradation of natural systems but terminating at a level well beneath an established health standard.

Limiting Factor: A condition whose absence or excessive concentration, is incompatible with the needs or tolerance of a species or population and which may have a negative influence on their ability to thrive.

Limnology: The study of the physical, chemical, hydrological, and biological aspects of fresh water bodies.

Lindane: A pesticide that causes adverse health effects in domestic water supplies and is toxic to freshwater fish and aquatic life.

Liner: 1. A relatively impermeable barrier designed to keep leachate inside a landfill. Liner materials include plastic and dense clay. 2. An insert or sleeve for sewer pipes to prevent leakage or infiltration.

Lipid Solubility: The maximum concentration of a chemical that will dissolve in fatty substances. Lipid soluble substances are insoluble in water. They will very selectively disperse through the environment via uptake in living tissue.

Lipofit: Fatty concentrate produced by the treatment of fatty waste using the Lipoval process. The properties of Lipofit are close to those of heavy fuel, except that is has a much lower sulfur content. Under regulations, it is considered a fuel in its own right and can be used in facilities classified 2910B (combustion plants).

Lipoval: This separating process is designed for the treatment of liquid fatty waste mainly from restaurant gully traps (80%), but also from the food industry and wastewater treatment plant oil extractors. The Lipoval process dynamically separates fatty waste into three phases: a fatty concentrate that can be used as a replacement fuel (Lipofit), solid sediment, and a treated aqueous phase discharged into the sewer.

Liquefaction: Changing a solid into a liquid. The process of making synthetic liquid fuel from coal. The term also is used to mean a method for making large amounts of gasoline and heating oil from petroleum.

Liquefied Gases: Gases that have been or can be changed into liquid form. These include butane, butylene, ethane, ethylene, propane and propylene.

Liquefied Natural Gas (LNG):
Natural gas that has been condensed to a liquid, typically by cryogenically cooling the gas to minus 260 degrees Fahrenheit (below zero).

Liquefied Petroleum Gas (LPG): A mixture of gaseous hydrocarbons, mainly propane and butane that change into liquid form under moderate pressure. LPG or propane is commonly used as a fuel for rural homes for space and water heating, as a fuel for barbecues and recreational vehicles, and as a transportation fuel. It is normally created as a by-product of petroleum refining and from natural gas production.

Liquid Brine:
A type of geothermal energy resource that depends on naturally occurring hot water solution found within the earth.

Liquid Injection Incinerator:
Commonly used system that relies on high pressure to prepare liquid wastes for incineration by breaking them up into tiny droplets to allow easier combustion.

List: Shorthand term for EPA list of violating facilities or firms debarred from obtaining government contracts because they violated certain sections of the Clean Air or Clean Water Acts. The list is maintained by The Office of Enforcement and Compliance Monitoring.

Listed Waste: Wastes listed as hazardous under RCRA but which have not been subjected to the Toxic Characteristics Listing Process because the dangers they present are considered self-evident.

Mineralogy, grain size, texture, and other physical properties of granular soil, sediment, or rock.

Litter: 1. The highly visible portion of solid waste carelessly discarded outside the regular garbage and trash collection and disposal system. 2. Leaves and twigs fallen from forest trees.

Littoral Zone: 1. That portion of a body of fresh water extending from the shoreline lake ward to the limit of occupancy of rooted plants. 2. A strip of land along the shoreline between the high and low water levels.

Load: The amount of electric power supplied to meet one or more end user's needs. It is an end-use device or an end-use customer that consumes power. The load should not be confused with demand, which is the measure of power that a load receives or requires.

Load Centers:
A geographical area where large amounts of power are drawn by end-users.

Load Diversity: The condition that exists when the peak demands of a variety of electric customers occur at different times. This is the objective of "load molding" strategies, ultimately curbing the total capacity requirements of a utility.

Load Factor: A percent telling the difference between the amount of electricity a consumer used during a given time span and the amount that would have been used if the usage had stayed at the consumer's highest demand level during the whole time. The term also is used to mean the percentage of capacity of an energy facility - such as power plant or gas pipeline - that is utilized in a given period of time.

Load Management:
Steps taken to reduce power demand at peak load times or to shift some of it to off-peak times. This may be with reference to peak hours, peak days or peak seasons. The main thing affecting electric peaks is air-conditioning usage, which is, therefore, a prime target for load management efforts. Load management may be pursued by persuading consumers to modify behavior or by using equipment that regulates some electric consumption.

Loading Factor: Ratio of actual electricity consumed and total potential consumption. Used when analyzing electricity consumption in a large population. A loading factor of 0.5 means that 50% of homes are consuming all of the electricity they are able or that, on average, all of the homes are only consuming 50% of the power they have the potential to consume.

Lockbar: An optional feature of front-load containers. The lock bar allows a customer to lock the container. When the container is emptied, and the container is raised up and over the truck, gravity causes the bar to drop allowing the container to be emptied.

Loop Flow:
The difference between scheduled and actual power flows on electric transmission lines.

Losses (Electric Utility):
Electric energy or capacity that is wasted in the normal operation of a power system. Some kilowatt-hours are lost in the form of waste heat in electrical apparatus such as substation conductors. LINE LOSSES are kilowatts or kilowatt-hours lost in transmission and distribution lines under certain conditions.

Low Density Polyethylene (LOPE): Plastic material used for both rigid containers and plastic film applications.

Low-E: A special coating that reduces the emissivity of a window assembly, thereby reducing the heat transfer through the assembly.

Low Emission Vehicle (LEV): A vehicle certified by the California Air Resources Board to have emissions from zero to 50,000 miles no higher than 0.075 grams/mile (g/mi) of non-methane organic gasses, 3.4 g/mi of carbon monoxide, and 0.2 g/mi of nitrogen oxides. Emissions from 50,000 to 100,000 miles may be slightly higher.

Low Level Radioactive Waste (LLRW): Wastes less hazardous than most of those associated with a nuclear reactor; generated by hospitals, research laboratories, and certain industries. The Department of Energy, Nuclear Regulatory Commission, and EPA share responsibilities for managing them.

Low NOx Burners: One of several combustion technologies used to reduce emissions of Nitrogen Oxides (NOx).

Low Sulfur – Coal: Coal having one percent or less of sulfur by weight.

Low Sulfur – Oil:
Oil having one percent or less of sulfur by weight.

Lower Detection Limit: The smallest signal above background noise an instrument can reliably detect.

Lower Explosive Limit (LEL): The concentration of a compound in air below which the mixture will not catch on fire.

Lowest Acceptable Daily Dose:
The largest quantity of a chemical that will not cause a toxic effect, as determined by animal studies.

Lowest Achievable Emission Rate:
Under the Clean Air Act, the rate of emissions that reflects (1) the most stringent emission limitation in the implementation plan of any state for such source unless the owner or operator demonstrates such limitations are not achievable; or (2) the most stringent emissions limitation achieved in practice, whichever is more stringent. A proposed new or modified source may not emit pollutants in excess of existing new source standards.

Lowest Observed Adverse Effect Level (LOAEL): The lowest level of a stressor that causes statistically and biologically significant differences in test samples as compared to other samples subjected to no stressor.

Lumen: A measure of the amount of light available from a light source equivalent to the light emitted by one candle.

A measure of the efficacy of a light fixture; the number of lumens output per watt of power consumed.

Lumen Maintenance Control:
An electrical control device designed to vary the electrical consumption of a lighting system in order to maintain a specified illumination level.

Luminaire: A complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light, to position and protect the lamps and to connect the lamps to the power supply.

LUX: A unit of illumination equal to the direct illumination on a surface that is everywhere one meter from a uniform point source of one candle; a unit of illumination that is equal to one lumen per square meter.