CRS-55 



TABLE 1. Common Activities Which Impact Wetlands — Continued 



o Habitat destruction by dumping and surfacing 



- Landfill from construction projects 



- Hard-topping for roads, factories, etc. 

 Grading and concreting for drainage ditches 



- Rip-rapping of banks 



- Dumping of mine overburden, spoil, tailings 



- Dumping of dredged material 



- Levee construction 



- Construction of primitive access, logging, and mining roads 

 (especially in steep or rough terrain) 



o Habitat destruction by digging 



- Ditching (main, as well as lateral ditches) 



- Mining (especially placer mining and sand and gravel excavation) 



o Habitat modification by water level manipulation 

 Permanent flooding 



- Alternate flooding 

 Protection from flooding 



- Drainage 



- Lowering of soil water table 



o Habitat modification by indirect methods 



- Erosion and loss of nutrients 



- Chemical modification by leaching of acids, metals, and sulfides 

 from soil; leaching of chemicals from pavement; addition of salts 

 (sodium and calcium chloride); motor vehicle wastes (petroleum pro- 

 ducts, heavy metals); other chemical wastes from factories; etc. 



- Introduction of exotic vegetation 



Source: U.S. Congress. Office of Technology Assessment. Wetlands Technology 

 Assessment Project Proposal . 1981. p. 7. 



Filling 



Filling of wetlands has been undertaken for a variety of purposes, ranging 

 from construction of parking lots or industrial plants to building of cause- 

 ways for transportation corridors. Filling of wetlands has also resulted from 

 disposal of dredged material. Wetlands adjacent to river channels have often 

 been the most cost-effective sites for disposing of dredge spoil. Fills are 



