With any road construction technique in wetlands, culverts, ditches, or both may be necessary. Avoid having ditches create additional outlets that will result in drainage of the wetland. Additional methods used for drainage ditches are listed under guidelines that follow for crossing specific wetland types. Road building across these wetland types employs conventional road construction techniques for road fill and drainage structures. These weak mineral soils can be excavated and backfilled with clean granular soils, or they can be covered with clean granular fill and allowed to compress and displace.
Additional fill is added to keep the roadbed at the desired grade.
Culverts and ditches are installed to minimize disruption of normal water flow across the landscape and transport water through and away from the roadbed. Install culverts of sufficient size to handle hydrologic flows for the site and for long-term maintenance needs. If ditches are needed, construct them immediately adjacent to the toe of the fill slope. Filled areas in flow planes should be designed to allow high flows to pass unimpeded. Proper roadbed construction in peat wetlands allows free water flow.