CContaminated and Hazardous Waste Site Management

Glossary W

Waste Treatment Plant: A facility that uses a series of tanks, screens, filters and other treatment processes to remove pollutants from water.

Water Balance (Hydrologic Budget): A record of the outflow from, inflow to, and storage in a hydrologic unit like an aquifer, drainage basin etc.

Water Purveyor: A public utility, municipal water company, county water district or municipality that delivers drinking water to customers.

Watershed: The land area that drains into a stream or other water body.

Water Table: Upper surface of a zone of saturation, where that surface is not formed by a confining unit; water pressure in the porous medium is equal to atmospheric pressure (the phreatic surface). The surface between the vadose zone and the groundwater; that surface of a body of unconfined groundwater at which the pressure is equal to that of the atmosphere.

Weathering: The process during which a complex compound is reduced to its simpler component parts, transported via physical processes, or biodegraded over time.

Well Development: This operation helps make water enter the well more easily and can make the difference between a satisfactory and an unsatisfactory well. Different techniques for well development can be used, the aim is to remove the smaller sized particles from the aquifer surrounding the well screen and to provide a coarser filter zone around the screen. The smaller sized particles are drawn into the well screen and can then be removed by bailing or pumping.

Wellhead: The area immediately surrounding the top of a well, or the top of the well casing.

Well Interference: When the area of influence, or the cone of depression around a water well comes into contact with or overlaps that of a neighbouring well pumping from the same aquifer and thereby causes additional drawdown or drawdown interference in the wells.

Well Log: A record describing geologic formations and well testing or development techniques used during well construction. Often refers to a geophysical well log in which the physical properties of the formations are measured by geophysical tools, E-logs, neutron logs, etc..

Well Point: Also referred to as sand points, gravel points, are used in shallow permeable unconfined (usually) aquifers generally less than 30 feet deep. Well points consist of a short length of screened pipe with a sharp point on the bottom end. As the pipe is driven into the ground, additional lengths of pipe are added to the top end. Sand points are also available with a check valve at the lower end to enable the pipe to be washed down in sand and fine gravel aquifers. Water can be pumped down the pipe and it passes out the check valve at the bottom and washes

the sand up the hole to the ground surface.

Well Screen: A cylindrical filter used to prevent sedimentfrom entering a water well. There are several types of well screens, which can be ordered in various slot widths, selected on the basis of the grain size of the aquifer material where the well screen is to be located. In very fine grained aquifers, a zone of fine gravel or coarse sand may be required to act as a filter between the screen and the aquifer.

Well Seals: Cover for the top of the well.

Well Yield: The volume of water discharged from a well in litres per minute (L/min), litres per second (L/s),or cubic metres per day (m3/day).

Wettability: The relative degree to which a fluid will spread on (or coat) a solid surface in the presence of other immiscible fluids.

Wet Weight: The weight of a sample aliquot including moisture (undried).

Wide Bore Capillary Column: A gas chromatographic column with an internal diameter (ID) that is greater than 0.32 mm. Columns with lesser diameters are classified as narrow bore capillaries.

Willow Ring: A circle of (phreatophyte) shrubs/trees (usually willows) that form around periodically ponded low areas. These plants indicate very wet soil conditions.

Windrow: A low, elongated row of material left uncovered to dry. Windrows are typically arranged in parallel.

Winkler Titration: A chemical method used to estimate the amount of dissolved oxygen in water.