A potential wetland mitigation site in the Atlantic Coastal Plain in central New Jersey is characterized in order to determine the prevailing functions of the onsite wetland. At the site, construction of a highway is planned that would result in the loss of part of the wetland. Grain-size analysis and slug tests were performed in order to determine hydraulic conductivity values for the underlying geologic materials. The tests yielded a range of values, which indicated that a fairly homogeneous aquifer underlies the site. Water level data from monitoring wells indicated that water is recharged at the upland portion of the site, which is discharged into the onsite wetlands. Investigation showed that the existing wetland is a water-table type, located topographically in the midline regions of the study area, and is underlain by Geologic-Type-II materials. It is therefore, in direct hydraulic connection with, and functions to discharge groundwater from the aquifer. Groundwater flow at the site was simulated to gain a better understanding of the interaction between the wetland and the aquifer, and to evaluate the possible effects of a created wetland designed for onsite mitigation. Comparisons between observed and simulated groundwater flow indicated that the models support the field-based conclusion that the function of the existing wetlands is to discharge water from the underlying aquifer. Simulated flow patterns pre and post construction of the mitigation wetland indicate that groundwater recharge will be enhanced at the expense of a loss in natural discharge from the existing wetland. This would result in a net 3% reduction in the total acreage of wetland at the site. These findings suggest that the mitigation plan at the site is not hydrologically compatible with the "no net loss of wetlands" goal of wetland mitigation.
|Number of pages
|Northeastern Geology and Environmental Sciences
|Published - 1 Jun 2005