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possible to describe scenarios on either 

 end of the spectrum (infinitesimally 

 small changes or large scale 

 annihilation) upon which a majority of 

 resource managers could reach 

 consensus whether or not they would 

 be considered adverse; however, it 

 would be the vast middle ground that 

 would lead to heated and unresolvable 

 debate. 



Nonetheless, given our knowledge 

 of the constituents of dredged 

 material, its physical and chemical 

 behavior, and known responses of 

 biological communities to disturbance 

 factors, it was possible to outline (with 

 a reasonable degree of certainty) the 

 steps that would need to occur before 

 an event of sufficient magnitude to be 

 considered adverse would occur. 

 Therefore, even if we have not defined 

 the precise line at which a non-adverse 

 condition becomes an adverse 

 condition, the inherent assumption 

 was that we could monitor for changes 

 in the necessary precursors that 

 eventually would lead to an adverse 

 impact. An essential element of this 

 approach was to monitor within a 

 reasonably scaled domain in which we 

 realistically could expect to detect 

 change based on the magnitude of 

 anthropogenic activity. 



Each tier of the monitoring plan 

 was structured to be focused on 

 detecting change relative to a specific, 

 conservative, early warning threshold. 

 Typically, lower tiers focussed on 

 processes that need to first occur in 

 order for the undesired biological 

 impact to occur, while the highest tiers 

 focussed on changes in the resource 

 itself. The intent for this tiered 



strategy was to prevent adverse 

 impacts from occurring, because early 

 warnings of the potential for such an 

 occurrence would be provided rather 

 than the traditional approach of 

 merely searching for the endpoint of 

 impact. 



It is important to note that an early 

 warning threshold is not intended to 

 represent a point for panic but instead 

 an indication that there is potential for 

 increased risk, because the system did 

 not behave as predicted. This also 

 serves as an indication that the model 

 on which the prediction was based is 

 faulty in some way and therefore 

 needs to be re-evaluated. In the 

 meantime, disposal activities can be 

 modified (if necessary) before the 

 situation progresses further and while 

 investigations are completed at the 

 next tier of monitoring. Conclusions 

 reached at this higher monitoring tier 

 could eventually permit a return to the 

 lower tier or result in a long term 

 change in monitoring and/or site 

 management approach. 



The specific threshold developed 

 for a tier may be somewhat arbitrary 

 by nature (both in magnitude and 

 areal extent), especially if there is little 

 scientific evidence around which to 

 build the tier. This is not inherently 

 faulty, because the primary objective 

 of the threshold is to provide a 

 conservative decision point around 

 which a manageable (i.e., well-defined 

 study domain) and interpretable 

 monitoring plan can be structured. 

 This point can not be overly stressed , 

 for without an established (perhaps 

 even arbitrary) benchmark against 

 which to measure change and at which 



An Integrated, Tiered Approach to Monitoring and Management of Dredged Material Disposal Sites 



