7.3.3

Packer Assemblages

A packer assembly provides a means by which to isolate and sample a discrete

interval in the subsurface. Hydraulic  or pneumatic activated packers are wedged against the

casing wall or screen allowing sample collection from an isolated portion of the well. The

packers deflate for vertical movement within the well and inflate when the desired depth is

attained. Packers are usually constructed from some type of rubber or rubber compound and

can be used with submersible, gas lift, and suction pumps.

If pumps are operated at a low rate, a packer assembly allows sampling of low 

yielding wells, and wells that would otherwise produce turbid samples. A number of different

samplers can be placed within the packers depending upon the analytical specifications for

sample testing. One disadvantage is that vertical movement of water outside the well is

possible with packer assemblages, depending upon the pumping rate and formation properties.

Another possible disadvantage is that the packer material may be chemically reactive, causing

gain or loss of organic contaminants through sorption or desorption.

7.3.4

Decontaminating Sampling Equipment

When dedicated equipment is not used for sampling (or well purging) or when

dedicated equipment is stored outside of the well, the owner/operator's QAPjP should include

procedures for disassembly and cleaning of equipment before each use at each well.

The recommended cleaning procedure for sampling equipment used when organic

constituents are of interest is as follows (Barcelona et al., 1990; Keeley and Boateng, 1987;

USEPA, 1986a):

1.

Wash the equipment with a nonphosphate detergent.

2.

Rinse the equipment with tap water.

3.

Rinse the equipment with pesticide grade hexane or methanol (methyl alcohol).

4.

Rinse the equipment with reagent grade acetone.

5.

Rinse the equipment with organic free reagent water.

If acetone, hexane, or methanol are analytes of interest, a different solvent (which is not a

target analyte) should be chosen (e.g., isopropanol).

The recommended cleaning procedure for sampling equipment used when inorganic

constituents are of interest is as follows (Barcelona et al., 1990; Keeley and Boateng, 1987;

USEPA, 1986a):

November 1992

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