Wetland assessments are performed when known impacts have occurred to a wetland and when potential wetland exposure routes have been identified based upon preliminary site investigations results. The principal objectives of a wetland assessment are to investigate the nature and extent of site related impacts to the wetlands and to determine an appropriate remedial strategy to mitigate impacts. Major investigative elements of an assessment include:
- Initial reconnaissance investigation
- Review of historic Site data
- Sediment sampling and analysis
- Surface water and groundwater sampling and analysis
- Surface water stage flow data and tidal effects
- Background samples (sediment, surface water and groundwater)
Supplemental analyses: sediment toxicity and the need for remediation include total organic carbon content, equilibrium partitioning, and acid volatile sulfide/simultaneously extracted metals (AVS/SEM).
Key Concepts:
- Anaerobic conditions within wetlands generally dominate, reducing the bioavailability of most metals.
- High organic content and continual organic loading in a wetland system reduces the toxicity of many organic compounds.
Remediation of a wetland environment is required when assessment results indicate contaminant levels are significantly above regulatory criteria, which suggest potential ecological exposure. Various remediation alternatives are available for a wetland environment, including:
- No action required (if levels do not indicate toxicity/bioavailability)
- Chemical Amendments (i.e., compost, organic carbon)
- Hydrologic Enhancement (i.e., promote flooded, anaerobic conditions)
- Excavation
- Capping
All wetland remediation projects will eventually require compensatory mitigation for the unavoidable temporary or permanent impacts resulting from contamination and/or construction in the wetland environment.