The Louisville District Army Corps of Engineers (USACE) recently released a guidance document regarding modifications and standardization of wetland and stream mitigation in areas regulated by the Louisville District which they are considering for future mitigation projects. The document primarily discusses mitigation ratios and performance criteria in order to request release from further monitoring.
The document has been described as a “living document” allowing for modifications based on feedback from the public and as information is obtained from annual monitoring reports. Early discussions with some staff at the Indiana Department of Environmental Management (IDEM) indicated that the document is being reviewed internally; therefore, Williams Creek has not confirmed if the IDEM will adopt the same guidance. Williams Creek is continuing to coordinate with the USACE and IDEM regarding specific items of our concern regarding performance criteria.
A summary of the guidance document is below and a link to the document can be found here Louisville District Mitigation Policy_2017. Wondering how this updated policy might affect your property? Contact us with your questions.
Mitigation Ratio Comparison:
Establishment of wetland mitigation:
- Forested Wetland = 3:1 from previous 4:1
- Emergent/Scrub-shrub wetland to Emergent/Scrub-shrub mitigation = 2:1 from previous 2:1 (emergent) and 3:1 (scrub-shrub)
- Emergent/Scrub-shrub wetland to Forested wetland mitigation = 1:1
Preservation of existing wetland is 10:1
Summary of Mitigation Concepts Clarification
- Mitigation sites should look natural and should be designed to not require structural controls (i.e. no outfall controls, no deep excavations, berms, cells, etc.)
- USACE will continue to not allow mitigation in areas being used for stormwater management.
- If the 404 permit requires mitigation for conversion of forested to emergent wetlands for utility lines, mitigation would be required at a 1:1 ratio.
- Section 10 and Section 404 impacts will continue to require mitigation for impacts over the prescribed thresholds.
- Impacts associated with impoundments streams for the purpose of constructing a pond will consider both the dam and inundated waters as an impact.
Forested/Scrub-shrub Wetland Mitigation and Riparian Corridor Mitigation Performance Criteria
Clarified density of woody stems depending on installation of bare root saplings to 3-gallon trees.
|Bare Root||3-Gallon Container|
|Minimum 300 trees per acre||Minimum 200 trees per acre|
|No species can exceed 20 percent of total population of planted species (minimum 5 species)||No species can exceed 20 percent of total population of planted species (minimum 5 species)|
|Minimum 5 Year Monitoring||Minimum 5 Year Monitoring|
|50 percent survival plant list||75 percent survival plant list|
|No species may make up more than 15 percent of surviving stock||No species may make up more than 15 percent of surviving stock|
|50 percent of the surviving 150 trees must be 15 ft in height AND 3 inches dbh before release||50 percent of the surviving 150 trees must be 15 ft in height AND 3 inches dbh before release|
|50 percent of the surviving 150 shrubs must be 3 ft in height before release||50 percent of the surviving 150 shrubs must be 3 ft in height before release|
|Less than 5 percent of invasive/exotic species may be present and 0 percent of species from USACE specified list||Less than 5 percent of invasive/exotic species may be present and 0 percent of species from USACE specified list|
Emergent Wetland Performance Criteria
- Planting plan should include a minimum of 10 species
- Minimum 5 year monitoring
- 75 percent of initial planted species shall be alive (Williams Creek assuming live plant material)
- No one species may make up more than 20 percent of the total vegetative cover for the site
- Less than 5 percent of invasive/exotic species may be present and 0 percent of species from USACE specified list
- Combined surface area of open water and/or bare ground shall not exceed 10 percent