132 • Wetlands: Their Use and Regulation 



compounding adverse effects. An areawide wetland 

 review may uncover further unforeseen impacts. 



One of the major problems in mitigating proj- 

 ect impacts is the difficulty of mitigating cumulative 

 and secondary impacts. The lack of reliability in 

 impact prediction complicates the mitigation proc- 

 ess. As an example, a short-term, isolated, primary 

 impact of a dredging operation is suspension of sedi- 

 ment in the water column. The narrow approach 

 toward mitigating this effect might include avoiding 

 periods of fast tidal currents and deploying silt cur- 

 tains. However, secondary impacts may include the 

 release of excess nutrients and toxic contaminants. 

 Long-term cumulative impacts from repeated 

 dredging and other excavation at many sites 

 throughout a single estuary might include low-level, 

 but widespread, bioconcentration of metals and 

 synthetic organic compounds, with consequent 

 chronic, sublethal effects within the food chain. 

 Mitigative measures designed merely to minimize 

 the direct, localized effects of separate dredging 

 operations may fail to address systemwide, indirect 

 effects. 



General Requirements 



Mitigating impacts on wetlands may take the 

 form of standard conditions attached to individual 

 dredge or fill permits, conditions incorporated into 

 general nationwide and regional permits, and the 

 best management practices (BMP's) prescribed for 

 activities exempted from any permits. While the 

 nature of general prescription has eased the regu- 

 latory burden of issuing individual permits cover- 

 ing site-specific situations and has set approximate 

 standards for common development practices, it 

 overlooks the likelihood of environmental damage 

 that may occur because specific wetland functions, 

 values, and sensitivities are not considered. As an 

 example, disposal of spoil from maintenance dredg- 

 ing might be required under a regional general per- 

 mit to avoid discharge in or near active currents. 

 This practice could lead to several shallow-water 

 spoil sites in a wetland area with long-term effects, 

 such as chronic resuspension of sediments from 

 wind and waves, periodic disruption to bottom- 

 dwelling populations, and possible bioaccumulation 

 of toxic chemicals (37). Under an individual per- 

 mit, however, site-specific conditions might stipu- 

 late long-term disposal within a diked containment 



site to avoid contamination of a nearby wetland 

 heron rookery or of a municipal ground water 

 supply. 



BMP's are applied to common activities such as 

 minor road construction for maintenance of natural 

 surface and subsurface drainage or pipeline installa- 

 tion for sediment control. A representative BMP 

 for a minor road might be to install culverts through 

 the causeway fill with spacing, elevation, and 

 capacity needed to maintain lateral drainage, in- 

 cluding stormflows and the passage of fish cind other 

 aquatic animals (37). The application of BMP's on 

 an indiscriminate basis can reduce the effectiveness 

 of mitigation measures by overlooking limiting, site- 

 specific conditions. To ensure their effectiveness, 

 adequate site investigations are necessary to show 

 that critical or sensitive wetland values and func- 

 tions are not jeopardized and that local environ- 

 mental conditions will not negate normal BMP ef- 

 fectiveness. For example, where there is unchan- 

 neled sheet flow in a marshland, the required num- 

 ber and spacing of culverts will be quite different 

 than where surface flow is already channeled; other- 

 wise, the usual BMP approach could cause adverse 

 hydrologic impacts by promoting channeling. In 

 conclusion, BMP's generally are appropriate where 

 impacts from a specified activity are localized, con- 

 sistent, and predictable; the mitigative measures 

 are highly standardized and proven effective; and 

 the landowners or developers responsible possess 

 the necessary technological and management capa- 

 bilities to use these practices effectively. 



Controversy over mitigation arises over applica- 

 tion of blanket stipulations of mitigation require- 

 ments as opposed to case-by-case tailoring of per- 

 mit conditions. Blanket stipulations gready increase 

 the uncertainty over the effectiveness of mitigation 

 requirements, and developers complain that they 

 are required to meet blanket stipulations that are 

 not applicable to their specific permit situation. 

 Because it lacks resources to undertake the exten- 

 sive site investigations or studies to determine the 

 effectiveness of different mitigation measures, the 

 Corps has been forced to use stipulations recom- 

 mended by its staff and staff from other resource 

 agencies. GAO, in a report to the Congress on im- 

 proving wetlands permit processing in Alaska, 

 concluded: 



