Contaminated and Hazardous Waste Site Management

Glossary L

Laboratory Receipt Date: The date on which a sample is received at the Contractor's facility.

Lacustrine: Formed in, produced by or pertaining to a lake.

Lacustrine Deposits: Sediments laid down in a lake. Includes gravelly deposits at the margin and clay in deeper water. Sediments commonly show seasonal banding or varve clays.

Lagoon: A shallow pond where wastewater is stored and/or partially treated through exposure to sunlight, oxygen, and microorganisms.

Landfarming: The practice of spreading organic wastes over an area of land, then relying on natural microbial degradation (and volatilization) to degrade the wastes. Can also treat shallow soils contaminated by some organic chemicals.

Landfill: A disposal facility where waste is placed in or on land. Sanitary landfills are disposal sites for non-hazardous solid wastes. The waste is spread in layers, compacted to the smallest practical volume, and covered with soil at the end of each operating day. Secure chemical landfills are disposal sites for hazardous waste. They are designed to minimize the chance of release of hazardous substances into the environment.

Leach, Leaching: The process by which soluble chemical components are dissolved and carried through soil by water or some other percolating liquid.

Leachate: A solution produced by the percolation of liquid through soil or solid waste, and the dissolution of certain constituents in the water.

Leachate Collection System: A system that gathers liquid that has leaked into a landfill or other waste disposal area and pumps it to the surface for treatment.

Leakage: The flow of water from one hydrogeologic unit to another. It may be natural or man-made.

Lens: A geologic deposit surrounded by converging surfaces so that it is thick in the middle and thins out towards the edges.

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

Liquid Limit (LL): The lower limit for viscous flow of a soil.

Liquidity Index (LI): Quantitative value used to assess whether a soil will behave as a brittle solid, semisolid, plastic, or liquid. LI is equal to the difference between the natural moisture content of the soil and the plastic limit (PL) divided by the plasticity index (PI).

Lithology, Lithologic: A system for the description of rocks, with respect to mineral composition and texture.

Long-term Remedial Phase: Distinct, often incremental, steps that are taken to solve site pollution problems. Depending on the complexity, site cleanup activities can be separated into several of these phases.

Losing Stream: A stream or part of a stream in which water flows from the stream bed down into groundwater. Also called an influent stream.

Lower Explosive Limit (LEL): the concentration of a gas below which the concentration of vapors is insufficient to support an explosion. LELs for most organics are generally 1 to 5 percent by volume.

Lysimeter: A suction device used in the unsaturated zone to collect soil pore water. It is capable of retaining the accumulated water within the sampling container. Laboratory Control Sample (LCS): a control sample of known composition. Aqueous and solid laboratory control samples are analyzed using the same sample preparation, reagents, and analytical methods employed for the samples received.