PURPOSE: This rule specifically defines words used in Chapter 4 concerning monitoring wells, otherwise the definitions contained in 10 CSR 23- 1.010 apply.

1. (1) Extraction well means any well more than ten feet (10') in depth utilized in the remediation of a site. These include, but are not limited, to the following: wells serving pump and treat systems, wells to capture a contaminant plume or alter the direction or magnitude of groundwater movement, leachate recovery wells that are not a part of the original landfill construction and other associated wells. Passive and active methane wells in landfills are exempted from these rules, but are regulated under the Solid Waste Law.
2. (2) Monitoring well means a well that is constructed to obtain site-specific water quality, contaminant movement or hydrologic data from proposed or existing waste disposal, waste processing, waste storage, hazardous materials release or other sites which may impact groundwater quality. This includes extraction wells used in the remediation of the site, piezometers for the collection of geologic and hydrologic data, observation wells and field screening technologies such as soil gas monitoring or push-in well screen temporary wells greater than ten feet (10') in depth but excludes wells constructed in the tank pit used as a part of an underground storage tank leak detection system and piezometers used to monitor the geotechnical performance of dams. Monitoring wells less than ten feet (10') in depth are exempt from reporting rules but must be plugged (see 10 CSR 23- 4.080(5)).
3. (3) Nominal diameter means the term used to describe the standard sizes for casing. Depending on the wall thickness, the inside diameter of the casing may be less than or greater than the number indicated. For example, two-inch (2") nominal Schedule 40 polyvinyl chloride (PVC) casing has a standard outside diameter of 2.375 inches, and an inside diameter of 2.067 inches; two-inch (2") nominal Schedule 80 PVC casing has the same outside diameter, but has an inside diameter of only 1.939 inches.
4. (4) Open-hole completion means a monitoring well cased through all overburden material and upper water producing zones, completed in bedrock, with no well screen or filter pack.
5. (5) Piezometer means a groundwater monitoring well, screened or opened to a saturated interval, installed for the specific purpose of determining either the elevation of the potentiometric surface or the physical, chemical, biological or radiological properties, or both, of groundwater at some point within the saturated zone.
6. (6) Potentiometric surface or piezometric surface means an imaginary surface representing the total head of groundwater and is the level to which water will rise in a well.
7. (7) Protective casing means the casing set from a point below the frost line and extends at least one and one-half feet (1 1/2") above the finished grade. The bottom of the casing must be at least three feet (3') below ground surface. This casing is set to protect the monitoring well from damage.
8. (8) Riser pipe means the casing extending from the well screen to or above the ground level.
9. (9) Water table observation well means any monitoring well, in which the screen or open borehole intersects a water table, which is installed for the specific purpose of determining either the elevation of the water table or the physical, chemical, biological or radiological properties, or both, of groundwater at the water table.
10. (10) Temporary monitoring well means a well or hole used for field screening purposes such as soil gas monitoring, push-in type holes, auger holes, etc. that are greater than ten feet (10') in depth and are plugged within thirty
11. (30) days of completion. These wells may or may not have temporary pipes installed for various purposes.
12. (11) Concrete means a slurry mixture with a ratio of ninety-four pounds (94 lbs.) of cement, equal volumes of dry sand and gravel and five to six (5—6) gallons of water from a known safe and uncontaminated source. The ratio of sand and gravel to cement may not exceed three parts to one (3:1).

AUTHORITY: sections 256.603, 256.606 and 256.626, RSMo (1994).* 10 CSR 23-4 Emergency rule filed Nov. 16, 1993, effective Dec. 11, 1993, expired April 9, 1994. Original rule filed Aug. 17, 1993, effective March 10, 1994. Amended: Filed July 13, 1994, effective Jan. 29, 1995. Amended: Filed Nov. 1, 1995, effective June 30, 1996. *Original authority: 256.603, RSMo (1985), amended 1991; 256.606, RSMo (1991); and 256.626, RSMo (1985), amended 1991.