39 



5.0 TIERED MONITORING SCHEME 

 FOR CONFINED AQUATIC 

 DISPOSAL 



5.1 Background 



If the decision is made at NED to 

 allow open-water disposal of dredged 

 material only if capping occurs, then a 

 tiered monitoring strategy (Figure 3) 

 more involved than the one presented 

 in the above section is followed. If one 

 refers back to the management 

 overview (Figure 1), this decision point 

 would be reached if one arrived at Box 

 1.12 via Box 1.10. A quick glance at 

 Figure 3 reveals this decision has 

 important ramifications as far as the 

 commitment to long-term monitoring. 

 Capping is not just an "out-of-sight, 

 out-of-mind" alternative; it is an option 

 which requires long-term model 

 verification and trend monitoring to 

 insure that isolation of disposed 

 contaminants is achieved as originally 

 planned. 



The hierarchical flowchart 

 presented for consideration was 

 derived from the assumption that the 

 mound being monitored is one 

 specifically designated as a capping 

 project, i.e., a major disposal operation 

 that would result from sequential 

 barge-loads of "contaminated" 

 sediment followed by sufficient 

 material to cover and isolate the 

 sediment from the ambient 

 environment. Many of the 

 assumptions behind this hierarchical 

 structure (discussed below) would not 

 be valid for a mound built during 

 routine disposal operations where "de- 

 facto" capping occurs. De-facto 

 capping is the term used by NED to 



describe the staged disposal of small 

 amounts (e.g., 5,000-10,000 m 1 ) of 

 questionable material at that season's 

 routine disposal point within a 

 particular site, along with and 

 followed by sequential disposal of 

 substantial amounts of what was 

 classified during the permit evaluation 

 process as "clean" material. Typically, 

 what would happen is that disposal of 

 contaminated material would occur 

 early in the disposal season, so there 

 might be a total of 20,000 m s (disposed 

 in discrete increments of 2,000 - 5,000 

 m 5 at a time) of questionable material 

 dispersed in various pockets in a 

 mound with a total volume in excess 

 of 200,000 m s . If disposal of 

 contaminated material is scheduled 

 toward the end of a disposal season, at 

 least 3 times the volume of clean 

 material compared to the 

 contaminated sediment volume would 

 be scheduled as an absolute minimum 

 to serve as the cap. 2 



Capping operations under the 

 DAMOS program have been carried 

 out at the New London, Portland, 

 Brenton Reef, and Central Long Island 

 Sound Disposal Sites (SAIC, unpub.). 

 The tiered monitoring plan proposed 

 would be applicable to mounds such 

 as those at Cap Sites 1 and 2, STNH-N, 

 STNH-S, and MQR, where substantial 



2 One could argue effectively that the 

 standard practice of "de-facto" capping at 

 routine mounds would result in another 

 unknown confounding variable if the 

 monitoring strategy presented in Figure 2 

 shows adverse biological impacts (Box 2.8 

 in Tier 3); these negative effects could be 

 due to insufficient capping and not because 

 the initial assessment procedure is faulty. 



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



