established by the New England River 

 Basins Commission (NERBC, 1980). 



Box 1.4 



"Clearly Contaminated? " 



Required detection limits for these 

 bulk sediment chemical analyses are 

 given in the guidance document (Table 

 LA., EPA/NED, 1989). The unstated 

 null hypothesis that would be tested in 

 this particular action box under the 

 current guidelines is: 



H : Bulk sediment contaminant 

 levels are not significantly 

 higher than those 

 contamination levels classified 

 as now" in the 1980 NERBC 

 guidelines. 



Rejection of the null hypothesis would 

 place you in box 1.5; acceptance would 

 lead to box 1.9 and unconfined open- 

 water disposal. 



Underlying Assumptions : The 

 underlying assumption, regardless of 

 which guidelines are being followed, is 

 that the dredging site has been 

 sampled sufficiently to characterize the 

 variability of contaminant levels at the 

 site. 



Sources of Uncertainty: There are 

 several very important sources of 

 uncertainty associated with this 

 decision point 



a) As mentioned above, the potential 

 variability in the contaminant level 

 at a dredging site is great, based on 

 the patchiness of sediment types 

 and pollution history of an area. 

 The EPA/NED guidance document 

 is not specific concerning objective 



standards that determine exactly 

 how many samples need to be 

 taken. A sampling plan is worked 

 out jointly between the NED and 

 the applicant or technical 

 consultants. The NED reviews each 

 plan "for adequacy" based on past 

 knowledge of sampling in the area 

 and information about past spills 

 and point sources of 

 contamination. Even with such a 

 review, contaminants can be 

 distributed patchily within harbors, 

 and it is possible that an approved 

 sampling plan can miss these 

 "hotspots". 



b) A total of 8 metals and 3 classes of 

 organics are usually tested, 

 although, where needed, analytes 

 are chosen from a more extensive 

 list. There is no clear guidance 

 regarding what objective 

 standard(s) can be used to classify a 

 sediment as contaminated when 

 there are varying levels in each of 

 these 11 components. For example, 

 it may happen that one or more of 

 the metals from a permit sample 

 may be in the "highly 

 contaminated" class according to 

 the NERBC classification scheme, 

 while the remaining contaminants 

 fall in the "low" or "moderate" 

 NERBC range. These high, low, and 

 moderate designations are based on 

 practical experience and historical 

 information with sediment 

 concentrations in New England 

 ports and harbors. The decision to 

 go to the next action box (and 

 require bioassay testing) is based 

 on best professional judgement. 

 This decision is somewhat 

 subjective, because there is a lack of 



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



