Additional concerns are: 



(a) turbidity and sedimentation from dike construction and from the the 

 containment area discharge; 



(b) the exit of contaminants from the disposal area through the efflu- 

 ent; and 



(c) possible uptake of contaminants by waterfowl or other animals using 

 the disposal area. 



The DMRP has produced a large amount of information on the first two 

 items but information on contaminant uptake and long-term impacts is limited. 



The subject of confinement area effluent quality is quite complex. How- 

 ever, at the risk of oversimplification, it can be stated that the quality of 

 the discharge is greatly influenced by confinement area design and retention 

 time. According to the majority of the literature, most of the potential 

 pollutants, e.g., heavy metals, oil and grease, and PCBs are sorbed to fine- 

 grained clays and silts and are not in a soluble form. Thus, the movement 

 of these potential pollutants is related to the fate of settable solids. 

 Retention of solids through proper design of containment areas and proven 

 engineering practices will result in lower levels of pollutants being dis- 

 charged. Actively growing vegetation in confinement areas also increases 

 the removal of solids from elutriate (Chen et al . 1978). Windom (1977) 

 found overland flow in salt marshes removed nutrients and metals from dis- 

 posal area effluent. 



Chen et al . (1978) concluded from laboratory and field studies that ef- 

 fluent from containment areas generally did not meet water quality criteria 

 for beneficial use of receiving waters (ammonia, total phosphorus, chlorinated 

 hydrocarbons, and most trace metals exceeded levels recommended for aquatic 

 life, drinking water, and irrigation water). There were indications in the 

 studies that efficient retention of solids in disposal areas would result in 

 meeting most standards. With low-density solids, organic detritus, fine iron 

 oxides, and clay-sized minerals, long-term retention time or flocculants may 

 be required to meet water quality standards. 



The significance of the impact of disposal area effluent on receiving 

 waters is largely unknown. Dilution occurring in the receiving waters will, 

 in many instances, reduce many of the constituents to harmless levels. How- 

 ever, the fate and biological impact of persistent substances, such as 

 organohalogens and trace metals, have not been well defined and these sub- 

 stances may constitute a chronic threat to the biota. Hoss et al . (1974) 

 conducted a laboratory study of the effluent from polluted dredged material 

 collected from the Charleston Harbor. They concluded that the effluent may 

 be harmful to larval fishes. Heavy metals and ammonia were implicated as 

 the possible agents causing larval mortality. 



Chen et al . (1978) also noted that heavy metals are generally associated 

 with solids and are removed from the effluent provided that retention time in 

 the containment area is adequate. Those trace metals associated with larger 

 particles exhibit the best retention. An analysis of data from Table 3 dra- 

 matically demonstrates the efficiency of removal of metals when they are 



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