Browsing by Subject "Bogs"

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    Validation of Wetland Mitigation in Abandoned Borrow Areas – Phase II
    (Minnesota Department of Transportation, 2016-03) Johnson, Kurt W.
    Road construction in northeast Minnesota often causes wetland impacts that require compensatory mitigation. Borrow areas excavated for road construction material can be developed into wetland mitigation sites if hydric vegetation, hydric soils and adequate hydrology are provided. Fourteen wetland mitigation sites were constructed north of Virginia, Minnesota along the U.S. Trunk Highway 53 reconstruction project corridor. The sites were established with the goal of mitigating for project impacts to seasonally flooded basin, fresh meadow, shallow marsh, shrub swamp, wooded swamp, and bog wetlands. Monitoring results indicate that the 14 mitigation sites range in their potential to receive wetland mitigation credit. All but one of the sites consistently meet wetland hydrology criteria. The sites contain a variety of plant communities dominated by wet meadow, sedge meadow, and shallow marsh. Floristic Quality Assessment (FQA) condition categories for the sites range from "Poor" to "Exceptional." Invasive plant species, particularly reed canary grass and narrow leaf cattail, are present on a number of sites and should be controlled. Tamarack and black spruce plantings have been successful on some of the drier areas and should be expanded to increase the quality and potential mitigation credit for other sites. These sites have shown the potential for creating mitigation wetlands in abandoned borrow pits in conjunction with highway construction. Adaptive management, particularly water level regulation, early invasive species control, tree planting, and continued long-term annual monitoring can make mitigation sites like these successful options for wetland mitigation credit. Continued site monitoring to determine potential for mitigation credit is recommended.
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    Wetland Mitigation in Abandoned Gravel Pits
    (Minnesota Department of Transportation, 2010-03) Johnson, Kurt W.
    It is becoming increasingly difficult to provide on-site mitigation for wetland impacts due to road construction in northeastern Minnesota counties that retain greater than 80 percent of their pre-settlement wetlands. Abandoned gravel pits are one of the few remaining areas that can serve as wetland mitigation sites. The overall goal of the project is to develop cost-effective methods for creating functional mitigation wetlands on abandoned gravel pit sites to compensate for wetland impacts due to road construction. Two approximately 1-hectare wetland creation demonstration sites were established in adjacent abandoned gravel pits within the U.S. Trunk Highway 53 reconstruction corridor to evaluate techniques for wetland establishment. Wet meadow and shrub swamp wetlands were attempted on one site, and wooded swamp and bog wetlands on the other. Wetland seed mixes provided both positive and negative effects on the developing plant communities on both sites initially but their effect was limited to the first year. Alder thicket and bog donor soil applications had positive effects but not until the third year of the study. Hardwood willow cuttings were effective for establishing a shrub component. Conifer seedlings did not survive unless planted on soil mounds. Fertilizer proved ineffective for promoting wetland plant growth during the study period. The use of straw mulch is questionable on saturated wetland sites such as those in this study.