2.3.5 Reference Material for Plant and Animal Uptake Evaluations (Cont.)

dredged material that they have no discernable effect on the response being

measured in the test plant or animal. As long as other requirements are met, it is

acceptable to choose reference soil/sediment and/or test species to achieve this

objective. In general, reference soil or sediment will be obtained in the vicinity of

the CDF.

In some cases, it may be appropriate for one reference site to serve more than

one CDF, or to use more than one reference material for a single CDF. This could

occur, for example, when the dredged material or the CDF has a wide range of

grain sizes or organic carbon, when management needs suggest that disposal of

different dredged materials at different locations within the CDF is desirable, or

when disposal of the dredged material at more than one CDF is being considered.

Reference material approach. Reference soil or sediment is generally

collected outside the influence of previous operations at a CDF, but near enough

to the CDF that the reference material is subject to all the same influences (except

previous dredged material) as the CDF. If there is a potential for sediment

migration or there is a reason to believe that previously placed dredged material

has migrated, reference material should be collected from an area outside the CDF

that is not expected to be influenced by material from the CDF. Both the reference

point and reference area sampling approaches described below allow statistically

valid comparisons and are appropriate under specific circumstances as described

below.

Reference point. This approach is used when the area outside the CDF is

sufficiently homogeneous that a single reference location is representative of the

CDF. A single reference location is sampled and the soil or sediment is tested

concurrently with the dredged material. The test results from the reference

material are compared to those obtained from plant or animal bioaccumulation

tests of the dredged material.

Reference area. This approach is used when the area outside the CDF is

heterogeneous and more than one reference location should be sampled to

adequately characterize it. Several reference locations are sampled, and a

composite of all the samples is tested concurrently with the dredged material. The

test results from the reference material composite are compared to those obtained

from plant or animal bioaccumulation tests of the dredged material.

Reference sampling plan. The importance of thoughtful selection of the

reference sampling approach cannot be overemphasized. To ensure that an

appropriate approach is used, information gathered during the site specification

process or other studies should be consulted for both the CDF and the reference

sites. In some instances there are differences in the statistical methods used in

comparing results from the various reference sampling methods to those obtained

from the dredged material being evaluated. There may also be differences in costs

among the approaches; statistical considerations are important in determining

which approach best fits specific concerns and conditions, including feasibility,

technical validity, and cost.

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Chapter 2 Structure and Approach of the UTM