ECT assisted Tampa Electric Company in preparing a supplemental 316(a) demonstration for reissuance of its thermal variance for Big Bend Station in Hillsborough County, Florida, in response to an Amended Consent Order for compliance under 40 CFR 125.73(c). ECT’s scope included field studies and use of infrared satellite imagery to further characterize the spatial extent of the thermal plume, and to confirm available knowledge of the extent of impingement of the thermal plume on the bottom in the receiving waters. Quarterly sampling of the benthic macroinvertebrate community was conducted to further define the horizontal extent of potential effects of the plume on the bottom community.
These results were combined with data from previous 316(a) studies at Big Bend as well as data from extensive monitoring programs by others over the past two decades on the fish and benthic macroinvertebrate communities to support preparation of a biological report for reissuance of the thermal variance. The biological report also used the available literature from Tampa Bay as well as results of rigorous statistical analyses of the combined datasets to demonstrate the protectiveness of the existing thermal variance at Big Bend Station. The demonstration showed (1) neither the nature of the thermal discharge nor the balanced indigenous population (BIP) in the receiving water body had changed since the variance was originally issued, and (2) the key elements for a BIP defined by relevant regulatory criteria were present, and therefore the existing variance was protective.