This report and a companion report, NCHRP Report 218A, "Ecological Effects of Highway Fills on Wetlands - Research Report," will be of special interest and value to people responsible for the environmental assessment of proposed transportation facilities in the area of wetlands. The user's manual, NCHRP Report 218B, presents guidelines for determining the physical and biological effects of locating transportation facilities in wetlands. Although environmental impact assessment is in a general state of evaluation, the guidelines represent the current state of the art and are suitable for immediate implementation. A thorough review of literature pertaining to wetland ecology and the evaluation of several specific cases of highway placement in wetlands provide the basis for the research report, NCHRP Report 218A. The manual presents in detail the physical impacts and potential biological effects from construction activity in wetlands. A feature of the manual is the inclusion of a series of charts to assist in identifying potential biological effects associated with construction activity. A separate chart is included for each construction activity--such as consolidation, displacement, excavation and fill, and culvert placement. Each chart identifies the physical impacts associated with the particular construction activity and the resulting potential biological effects. For example, the placement of a culvert in a wetland can alter subsurface water flow, which could change the mean water level and cause mortality of certain aquatic species in the wetland. The guidelines contained in the manual for determining potential biological effects of construction activity in wetlands are suitable for immediate implementation. An example problem is included. (Author/publisher)
Samenvatting