Effects of Soil Amendments and Other Practices on the Success of the Virginia Department of Transportation's Non-tidal Wetland Mitigation Efforts

About the report:

Construction of created wetlands to mitigate for highway impacts requires more than $100,000 per ha of impacts. A detailed study of soil, hydrology, and vegetation at 10 recently constructed non-tidal mitigation sites indicates excessive soil compaction and a lack of organic matter continue to limit mitigation success. Detailed hydrologic studies at two mitigation sites (Charles City and Sandy Bottom) point out significant differences in their hydrologic regime vs. adjacent natural wetlands related to soil reconstruction procedures. Results from two compost amendment experiments at Charles City indicate that approximately 100 Mg/ha of organic amendment is optimal for reconstructing hydric soil conditions when natural organic enriched soil materials cannot be returned. Overall mitigation success would improve from (1) utilization of appropriate organic amendments, (2) tillage/ripping protocols at all sites to meet target density specifications, and (3) reconstruction of a soil-geologic profile that is similar in texture and permeability to natural wetland soils. These reconstruction guidelines will help ensure that VDOT complies with existing mitigation regulations in the most cost-effective manner.

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