3.

Properly designed and operated air lift system (requires prior approval of the

Regional Administrator).

Well development methods and equipment that alter the chemical composition of the

ground water should not be used. Development methods that involve adding water (including

water pumped from the well) or other fluids to the well or borehole, or that use air to

accomplish well development, are rarely permissible. Consequently, methods that are

unsuitable in most cases for monitoring well development include backwashing, jetting, airlift

pumping, and air surging. Approval should be obtained from the Regional Administrator

prior to introducing air, water, or other fluids into the well for the purpose of well

development. Any water introduced into the well during well development should be

chemically analyzed to determine its potential impact on water quality. The well

development methods that will generally be approved by EPA are bailing, surging with a

surge block, pumping, overpumping, or combinations of these methods. Airlift pumping may

be approved if the owner/operator can demonstrate to the satisfaction of the Regional

Administrator that appropriate measures will be taken to prevent air contact with the

formation, and to prevent the entry of compressor oils into the well. Monitoring wells should

not be developed before well sealant materials have set or cured.

Ground water should be collected and measured for turbidity periodically during well

development, and at the completion of well development. The final turbidity measurement

should be recorded on the well construction log. If a well yields turbid samples (turbidity

greater than or equal to 5 NTUs) after development, the procedures shown in Figure 14

should be followed. A well that cannot be developed to the point of producing low turbidity

water (e.g., <5 NTUs) may be considered by the Agency to have been improperly completed

(e.g., mismatched formation materials/filter pack/screen slot size) depending on the geologic

materials in which the well is screened. If a well is not producing low turbidity ground water

samples, the owner/operator should demonstrate to the satisfaction of the appropriate

regulatory agency that proper well completion and development measures have been

employed, and that the turbidity is an artifact of the geologic materials in which the well is

screened, and not the result of improper well construction or development. Failure to make

such a demonstration could result in a determination by the Agency that the well must be re 

drilled.

The Agency emphasizes that proper well construction and development procedures, as

well as proper sampling procedures (e.g., selection of appropriate well purging and sampling

rates), are necessary to yield ground water samples that are representative of ambient water

quality. The Agency recognizes that ground water in some wells (both high and low yield) in

fractured rock or karst aquifers may become muddy after periods of rainfall, even though

during fair weather the water is free of turbidity. Careful attention to proper well installation

and development should be exercised with wells completed in very silty geologic units.

Information obtained from any aquifer tests conducted on the well should be used to establish

November 1992

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