compensatory mitigation sites and the use of conservation covenants. Several performance standards are listed, including the following:
Three-quarters of all cells at a site should have at least 35 percent survival of planted stock. (“Cells” and “survival” are defined in example 3 of Table 1.)
Areal cover of 80 percent, excluding open water areas, by noninvasive hydrophytes should occur by a specific date. Purple loosestrife (Lythrum slicaria), cattails (Typha latifolia, Typha angustifolia, and Typha glauca), common reed (Phragmites australis), and reed canary grass (Phalaris arundinacea) are listed as invasive species.
No unstablilized slopes should be present.
This document is periodically reviewed and revised based on experience and “lessons learned.”
Norfolk District's 1995 Guidelines. Norfolk District has a document dated 16 November 1995, entitled Branch Guidance for Wetlands Compensation Permit Conditions and Performance Criteria, that covers topics such as required information for site design plans, performance bonds, and requirements for hydrological data assessment before planting. The document stresses the need for flexibility: “This guidance is intended to be flexible; it is the decision of project managers and their supervisors whether any condition is appropriate for a particular wetland construction project.” Point 6 of the document lists performance standards, or “performance criteria. ” These performance standards include:
Hydrology must meet the criteria for a wetland as per the Corps of Engineers Wetlands Delineation Manual, with growing season specified. The number of days with saturation to the soil surface should also be specified in order to allow some control over the wetland type that would develop on a site.
At least 50 percent of all plants must be facultative or wetter.
For woody vegetation, stem counts of 400 per acre must be achieved until canopy cover is 30 percent or greater.
In areas of emergent herbaceous vegetation, areal cover must be at least 50 percent.
Baltimore District's 1994 Guidelines. Baltimore District's 1994 guidelines, entitled Maryland Compensatory Mitigation Guidance, were developed by the Interagency Mitigation Task Force, with representatives from eight state and Federal agencies. Guidelines include information about topics such as replacement ratios, site selection, monitoring reports, sampling methods, and performance standards. Different performance standards are given for tidal emergent wetlands, non-tidal emergent wetlands, non-tidal scrub-shrub wetlands, and non-tidal forested wetlands. For example, tidal emergent wetland performance standards include: