these can be generalized from one case to another or from one documented 

 case history to another. 



Once the individual disturbance evaluations have been made and the 

 full range of effects is outlined, the job remaining is to consider 

 additive effects . This is easy enough if disturbances in two cases are 

 the same and are therefore directly additive. For example, the effects 

 of turbidity from hydraulic dredging of a channel may be added to those 

 of dragline dredging of a boat basin, because the disturbance (release 

 of suspended solids) is the same in both cases. But it is not so 

 simple if the disturbances are different. For example, the eutrophication 

 effects of channel dredging are difficult to add to those of sewage 

 discharge during facility operation. No firm rules are available to guide 

 this additive process; it must be worked out on the basis of experience. 



There is another category of concerned called cumulative impacts , 

 also known as incremental impacts or loss by attrition. The problem is 

 widely recognized, but there are no accepted rules for solving it. The 

 assessor's reaction most often will be simply to point out specifically 

 those alterations which will add to the known accumulated alterations of 

 the past. Usually the project sponsor has no better ground rules than 

 the assessor for deciding "how much is too much" for an ecosystem, and 

 will supply no information on the subject. No solution is offered here 

 because the acceptable limits of cumulative impacts is more a policy 

 matter than a technical one. It is expected, therefore, that the assessor 

 will pass this problem along for resolution at steps 5 and 6 in most cases, 

 unless policy on such matters has been decided in advance for the area and 

 the type of activity in question. 



The judgment of whether any impact is significant usually requires 

 the assessor to look beyond the limits of the project area. A key 

 question is, how large an area should be considered in relation to the 

 effects of the project. It is usually necessary to set some boundaries 

 for the area under consideration, particularly for large-scale projects 

 with potentially serious adverse impacts . The ecological effects should 

 then be determined in sufficient detail to make a thorough analysis for 

 each of these: (1) the project area; (2) the immediately adjacent 

 ecosystem; and (3) the wider area ecologically affected by the project 

 for each of the following situations: (a) under optimal conditions 

 (without any human interference); (b) as the areas presently exist, 

 having been influenced by society; (c) as they will be affected by other 

 activities occurring or expected to occur (cumulative impact ); (d) as they 

 will be affected by the project itself (e.g., by dredging, filling, or 

 construction); (e) as they will be affected by each of the known 

 alternatives to the project; (f) as t hey w ill be affected by combinations 

 of secondary activities induced by the project or its alternatives. 



While this depth of analysis may usually be required for large OCS- 

 related projects, routine smaller permit cases may require much less 

 complex assessment. However, the same concepts apply. 



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