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Case Study

A pre-remedial wetland depression did not have to be retained as a vernal pool in habitat mitigation plans

By Patrick O. Gwinn, Principal, Technical Director, Toxicology, Health, and Ecological Sciences
Stan Pauwels, Ph.D., Senior Consultant


A pre-design investigation at a forested palustrine wetland requiring future sediment remediation identified a temporarily inundated depression with potential vernal pool characteristics. Two visits in early spring failed to confirm its status as a functioning vernal pool. However, state and federal regulators insisted on its inclusion in habitat mitigation and long-term monitoring plans, citing concerns about potential habitat loss. This demand posed challenges due to the need for meeting strict post-mitigation vernal pool requirements, which would be unattainable. 


We conducted two visits to the depression in early spring to identify vernal pool characteristics, focusing on finding obligate indicator species. While one obligate male frog was heard calling during the first visit, no signs of any amphibian breeding (e.g., mating calls, egg masses, tadpoles) or of any obligate invertebrate vernal pool species (i.e., fairy shrimp) were observed during the subsequent visit. Two secondary vernal pool species (i.e., fingernail clams and spire snails) were present but not indicative of an actual vernal pool without the presence of obligate indicator species. Additional review identified three previous surveys performed at this location over the previous decade and a half, all of which showed that the depression did not serve as a functional vernal pool.  


Integral showed conclusively that the depression identified in the pre-remediated forested palustrine wetland was not a vernal pool and should therefore not be retained as one in the habitat mitigation plans. The regulators agreed with this opinion, which avoided costly and unnecessary future mitigation and monitoring efforts at this location.    

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