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Big Otter River Fecal Coliform TMDL: A Case Study

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  012067,  2001 ASAE Annual Meeting. (doi: 10.13031/2013.7381) @2001
Authors:   K. M. Brannan, T. A. Dillaha, M. L. Wolfe, S. Shah, S. Mostaghimi, C. D. Heatwole, M. Al-Smadi, J. Miller
Keywords:   TMDL, watershed, water quality, hydrologic modeling

The authors developed fecal coliform TMDL plans for five impaired segments in the Big Otter River (BOR) basin in Virginia. These stream segments are Sheep Creek, Elk Creek, Machine Creek, Little Otter River, and the BOR. The many sources of fecal coliform in BOR basin were identified. Some examples of sources of fecal coliform include failing septic systems, livestock, and wildlife. Next, the significant sources were quantified and used in a watershed model to develop a TMDL plan. The watershed model used was HSPF. The water quality criterion of the TMDL plan was that the 30-day geometric mean of fecal coliform should not exceed 190 cfu /100 ml, which includes a 5% margin of safety. Some common source reductions were required in all five plans. One was the almost complete exclusion of cattle from the streams of BOR basin. Another was the reduction in wildlife sources. For example, complete exclusion of cattle from streams and a 50% reduction in fecal coliform from direct deposition of wildlife in streams in the Lower Big Otter River subwatershed. Most of the reductions are achievable using agricultural and urban BMPs, but others may not be. The development of these and other fecal coliform TMDL plans in Virginia have led to actions to improve the TMDL process, along with a reassessment of water quality standards and the use classification of water bodies.

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