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Drilled wells penetrate about 100-400 feet into the bedrock. Where you find bedrock at the surface, it is commonly called ledge. To serve as a water supply, a drilled well must intersect bedrock fractures containing ground water.

• The casing is usually metal or plastic pipe, six inches in diameter that extends into the bedrock to prevent shallow ground water from entering the well. By law, the casing has to extend at least 18 feet into the ground, with at least five feet extending into the bedrock. The casing should also extend a foot or two above the ground’s surface. A sealant, such as cement grout or bentonite clay, should be poured along the outside of the casing to the top of the well. The well is capped to prevent surface water from entering the well.
• Submersible pumps, located near the bottom of the well, are most commonly used in drilled wells. Wells with a shallow water table may feature a jet pump located inside the home. Pumps require special wiring and electrical service. Well pumps should be installed and serviced by a qualified professional registered with your state.
• Most modern drilled wells incorporate a pitless adapter designed to provide a sanitary seal at the point where the discharge water line leaves the well to enter your home. The device attaches directly to the casing below the frost line and provides a watertight subsurface connection, protecting the well from frost and contamination.
• Older drilled wells may lack some of these sanitary features. The well pipe used was oftene ight-, 10- or 12- inches in diameter, and covered with a concrete well cap either at or below the ground’s surface. This outmoded type of construction does not provide the same degree of protection from surface contamination. Also, older wells may not have a pitless adapter to provide a seal at the point of discharge from the well.

National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

Contaminant	Secondary Standard
Aluminum Color 15 (color units) Copper 1.0 mg/L Corrosivity Fluoride Foaming Agents Iron Manganese Odor pH Silver Sulfate Total Dissolved Solids Zinc	0.05 to 0.2 mg/L 250 mg/L 15 (color units) 1.0 mg/L noncorrosive 2.0 mg/L 0.5 mg/L 0.3 mg/L 0.05 mg/L 3 threshold odor number 6.5-8.5 0.10 mg/L 250 mg/L 500 mg/L 5 mg/L

  143.1  Purpose.
  143.2  Definitions.
  143.3  Secondary maximum contaminant levels.
  143.4  Monitoring.

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