33 



the evaluation of the sediments during 

 the permitting process was correct. 

 Rejection of the null hypothesis would 

 lead to the next level (Box 2.5 in Tier 

 2). 



The frequency of successional 

 monitoring can be decreased to once 

 per year or less in the n+1 and 

 following years. A late summer to 

 autumn survey is adequate to map the 

 distribution of well established adult 

 populations. Deposit-feeding taxa are 

 recognized from REMOTS® images by 

 the presence of feeding voids at depth 

 in the sediment. Once these taxa are 

 recruited in the spring, it takes the 

 whole summer for them to grow and 

 move into the deeper sediment layers. 

 Well-developed feeding voids are 

 produced during the summer and fall 

 when water temperatures are high and 

 benthic metabolic rates are 

 correspondingly high. By mapping 

 these seres in the later summer or 

 autumn, one is more likely to 

 characterize successional stages 

 accurately than if surveys were 

 conducted in the winter or early 

 spring when benthic organisms are 

 relatively inactive. 



Once a disposal mound converges 

 with the ambient seafloor (reference 

 stations) in terms of the frequency of 

 encountered equilibrium successional 

 stages, monitoring may be reduced to 

 once-every-other year or be tied to 

 specific pre-conditions such as 

 reactivation of an area for disposal or 

 passage of a major storm. The 

 frequency of long-term monitoring of 

 disposal mounds that continue to yield 

 expected responses (i.e. monitoring 

 results go no further than Tier 1) is a 



management decision based on the 

 sensitivity of the site to fishing 

 interests, vulnerability of the site to 

 storm surges, or the occurrence of 

 regional hypoxia. 



4.2.2 Tier Two: Physical Effects and 

 Related Management Decisions 



Box 2.5 "Evaluate Physical Effects " 



Tier 2 variables are addressed only 

 if anomalous colonization rates are 

 observed in the Tier 1 monitoring ("no" 

 outputs from Boxes 2.2 or 2.4, Figure 

 2). If anomalous rates of colonization 

 are documented in Tier 1, we attribute 

 this to physical or chemical properties 

 of the deposited dredged material. 



Box 2.6 "Has Change in Physical 



Attributes of Mound 

 Occurred? " 



If one arrives at this box via Box 

 2.2, initial recruitment patterns would 

 be anomalous if the sediment grain- 

 size of the initial dredged material 

 deposit (e.g., a high sand component) 

 is different than the ambient bottom 

 (e.g., a primarily silt-clay bottom). If 

 one arrives via Box 2.4, the physical 

 effects that are known to affect the 

 normal (i.e., expected) patterns and 

 rates of colonization adversely are 

 sediment erosion and scour. This 

 process commonly is associated with 

 the apex of disposal mounds; it is quite 

 possible for the tidal stream to diverge 

 and increase in velocity (and 

 turbulence) as it passes over the 

 mound. Surface sediment scour 

 results in a loss of fines, and a coarse 

 residue of shell and sand may armor 

 the surface. The initial period of scour 



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



