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November 15, 2005 The Water Report <br />Sediments <br />Design Factors <br />Level 2 <br />Triggers <br />Programmatic <br />Goals <br />"CSM" <br />Appropriate <br />Approach <br />purposes of the initial site /sediment characterization, the project proponent will be required to prepare <br />and submit a sampling and analysis plan for additional data collection. This additional data collection <br />may provide sufficient analytical data to make a management decision. For example, for a site <br />investigation project, if the analytical data were all below appropriate sediment screening levels and there <br />was no "reason to believe" that bioaccumulation issues are present at the site, the investigation may be <br />concluded at this point with the decision of no unacceptable risk from sediment at this site. <br />The transition from Level 1 to Level 2 occurs when the screening of collected data indicates the <br />need for additional tasks that are required to reach a management decision, whether it is assessment of <br />direct toxicity, indirect bioaccumulation effects, or other tasks as shown on Figure 2. The transition from <br />Level 1 to Level 2 can be triggered by exceedences of appropriate sediment screening levels or other <br />analytical results that indicate a need for more detailed assessment of the sediment or water column. <br />Considering Program Objectives <br />Within a risk -based framework, conceptual site models and project sampling and analysis plans are <br />developed and used to address specific programmatic goals. Knowledge of these programmatic <br />objectives must be factored into the assessment process to ensure that a complete set of information is <br />collected and analyzed to aid decision - making. The degree of success achieved in using a specific <br />sediment assessment framework within the context of a regulatory program will be determined in large <br />part by the extent to which program- specific objectives are acknowledged and accounted for when <br />designing and applying the assessment framework. <br />Conceptual Site Model <br />Following the initial data collection and analysis, a conceptual site model (CSM) for the site is <br />developed. A CSM identifies and describes contaminant sources, the processes linking those sources to <br />the sediment in question, the physical, chemical, and biological processes occurring within the sediment <br />that affect exposure, defines the receptors of concern, and how receptors of concern are exposed to the <br />contaminants associated with the sediment. A CSM allows for a graphical representation of the <br />relationships between receptors and resources in the environment and the stressors to which they may be <br />exposed. The CSM also can provide an avenue for beginning to address uncertainties in the relationships <br />and exposure pathways and presence /absence of important receptors at a particular project site or disposal <br />location. <br />A CSM is invaluable in establishing the appropriate technical and managerial approach for <br />addressing the specific issues associated with a project, whether it is a site assessment or a dredging <br />project. A generic CSM for a contaminated site assessment is presented in Figure 4 and a generic CSM <br />for a dredging project is presented in Figure 5 (next page). <br />Figure 4. Site Investigation Generic Conception Site Model <br />Potential Receptors <br />Media of Exposure <br />Secondary <br />Tertiary <br />Concern Pathway <br />Media <br />Pathway <br />Media <br />;_ <br />m <br />d <br />m <br />N <br />iLL <br />2 <br />'O <br />ro <br />� <br />S <br />P. Contact <br />vi <br />—0 Bioaccumulation <br />—► Tissue ► X❑ <br />X_x <br />XJ <br />Sediment <br />I <br />Resuspension, <br />Solubilization <br />Water <br />Column <br />Direct Contact <br />- — - -►OX <br />Copyright© 2005 Envirotech Publications; Reproduction without permission strictly prohibited. 13 <br />