Selection and emplacement of the appropriate filter pack;

Selection and emplacement of the annular sealants;

Providing proper security of the well;

Surveying the locations and elevations of the tops of the casings; and

Adequately developing the well.

All documents pertaining to the design, construction, and development of RCRA

monitoring wells should be kept by the owner/operator in the facility operating record and

submitted as part of the operating permit.

6.9

Specialized Well Designs

There are two cases where special monitoring well designs should be used:

Where the owner/operator has chosen to use dedicated pumps to withdraw

ground water samples; or,

Where separate low density and/or high density immiscible liquid phases may

be present.

Dedicated pumps should be fluorocarbon resin or stainless steel positive gas

displacement bladder pumps, or equivalent devices approved by the Regional Administrator.

The design of the dedicated sampling system should allow access to the well for the purpose

of conducting aquifer tests, maintaining the well (e.g., redevelopment procedures), and making

water level measurements. Dedicated sampling systems should be periodically inspected to

ensure that the equipment is functioning reliably. Samples should be withdrawn from the

system to evaluate the operation of the equipment, and the equipment should be checked for

damage.

Where light and dense phase immiscible layers are present, or are determined to

potentially occur after considering the waste types managed at the facility, specialized well

systems should be designed to allow collection of discrete samples of both the light and dense

phases. In certain cases, well screens that extend from above the water table to the lower

confining layer may be appropriate, but more frequently the presence of immiscible phases

will require that well clusters (or nests) or multilevel sampling devices be installed. Where

well clusters are employed, one well in the cluster may be screened at horizons where floaters

are expected, and another may be screened at horizons where dense phases are expected.

Other wells may be screened within other portions of the aquifer.

November 1992

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