cause sediments typically pose long-term risks, monitoring often must span decades to assess risk reduction.
The ultimate goal of monitoring is protection—that is, ensuring that short-term and long-term risks are minimized, by providing sufficient information to judge that the remedy is effective, or to adapt site management to optimize the remedy’s performance to achieve risk-based objectives. Management adaptation may entail modification of dredging procedures—for example, if short-term exposures exceed expected magnitudes—or modification of the remedy itself by amendment or modification of the record of decision (ROD) if long-term risk reduction proceeds more slowly or more rapidly than expected.
An effective sediment-monitoring plan takes into account the successive stages of sediment cleanup: site characterization; selection, planning, and implementation of the remedial action; effectiveness assessment; and adaptive management.1 Monitoring should build on the studies previously performed for the remedial investigation and feasibility study (RI/FS), which should have
Determined the nature and extent of contamination and any trends in time (for example, due to natural recovery).
Supported or developed a conceptual site model.
Provided information to assess risks to the environment and people.
Evaluated remedial alternatives, including a quantitative comparison of risks associated with implementation of each one.
Once the remedy is selected and implementation begins, monitoring extends the record of site conditions into the future.
Monitoring should be based on and inform the conceptual site model.
In general, adaptive management is the testing of hypotheses and conclusions and re-evaluation of site assumptions and decisions as new information is gathered (see Chapter 6 for further discussion). It is an important component of the updating of the conceptual site model (EPA 2005a).