Environmental Sciences DivisionPublication No. 4524Thii report has been reproduced directly from the best available copy.
5-8A-3 Temperature recorder data indicate that at no time during this study did temperatures at the reference sites (MAK 13.8, BBK 12.5, and Ohio River intake) exceed the temperature limit proposed for the effluents. Furthermore, there were no bi-hourly temperature observations of instream sites that exceeded the proposed or interim effluent limits at these sites. However, the stream reaches associated with Outfalls KO01 and KO1 1 did have higher temperatures than comparable reference stream reaches. No reference site was established on Little Bayou Creek.The proposed monthly temperature limit was exceeded in Outfalls K010/011 on four occasions during the study period (July 1993, July 1994, and July and August 1995 and KO10 appear to be the greatest thermal contributors to their respective receiving streams. However, discharges from Outfalls KO08 and KO09 also contribute to the total thermal load on Big Bayou Creek. Nonetheless, there were no exceedances of the proposed or interim effluent l i m i t s at any of Big Bayou Creek's instream sampling sites (BBKs 12.5, 10.4, 10.0, and 9.1), although exceedances did occur in Outfall KOOl, which discharges into Big Bayou Creek. Temperatures in the outfalls and the receiving streams were elevated compared with the reference sites.Discharges from Outfalls KOO1, K006,
Benthic Macroinvertebrate Community
MonitoringThe purpose of this subtask was to evaluate benthic macroinvertebrate data collected since 1991 for the PGDP Biological Monitoring Program (BMP) specifically for evidence that may suggest adverse thermal effects. Benthic macroinvertebrate samples have been collected quarterly (March, June, September, and December) since September 1991 from three study sites downstream of effluent discharges from PGDP, including two sites on Big Bayou Creek (BBK 9.1 and BBK 10.0) and one site on Little Bayou Creek (LUK 7.2). Two reference sites were sampled concurrently, including one on Big Bayou Creek upstream of all effluent discharges (BBK 12.5) and one on Massac Creek (MAK 13.8) southeast of the PGDP Reservation. A l l samples collected from each quarter of the first year of the study (September 1991-March 1992 were processed to provide a more detailed baseline. In subsequent years only samples collected in the March, September, and December sampling periods were processed.At each site on each sampling date, three random samples were taken from a riffle with a Surber sampler. Organisms were identified to the lowest practical taxon and enumerated.Most major taxonomic groups of macroinvertebrates typically found in streams were represented at all study sites and reference sites during the 4 years covered by the BMP study. Included at these sites was a mixture of taxa often considered tolerant (e.g., worms and true midges) and intolerant (e.g., mayflies, stoneflies, and caddisflies) of poor water quality. No obvious patterns of presence/absence of tax...