projects are made up of component subprojects which are implemented 



by construction and operation activities . Any activity which leads 



to an environmental disturbance sets off a series of ecological effects. 



If these effects degrade the ecosystem, they cause an adverse impact that 



detracts from human needs. The elements of the cycle are defined in 



Table 1. 



Table 1. Definition of the Cause and Effect Elements of the Impact Cycle 



Element 



Definition 



Program 



Project 



A broad initiative taken to fulfill some human 

 need or needs such as offshore oil recovery, 

 middle-income housing, or outdoor recreation. 



A specific physical element of a program such 

 as a refinery, crew base, housing subdivision, 

 or marina. 



Subproject 



Construction activity 



Operations activity 



Environmental 

 disturbance 



A discrete physical component of a project such 

 as site preparation, a bulkhead or pier. 



An individual work process involved in the 

 construction of a project facility such as land 

 clearing or dredging. 



An individual work process in the continuing 

 operation of a project such as pumping oil or 

 discharging wastes. 



An ecosystem perturbation caused by a disruptive 

 activity such as a toxic discharge or elimination 

 of wetlands. 



Ecological effect 



A reaction of an ecosystem to a disturbance 

 such as oxygen depletion, turbidity, or 

 siltation. 



Environmental impact 



An environmental alteration that affects the 

 fulfillment of human needs. 



For offshore oil and gas recovery programs, the chain begins with a 

 direct or primary development project (e.g., a submerged pipeline or a 

 plat-i^orm fabrication yard). The component subprojects of OCS-related 

 projects (e.g., individual initiatives such as navigation improvement 

 channel or a bulkhead) are implemented with activities that are the same 

 as those encountered in other waterfront or offshore work (e.g., dredging, 

 pile -driving). These activities cause disturbances that have recognized 

 efjfects on fish and wildlife resources and their habitats. An example 



is given on the following page. 



