Date of Award

5-2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Biosystems Engineering

Advisor

Privette, Charles V

Committee Member

Hayes , John C

Committee Member

Sawyer , Calvin B

Abstract

The conventional method of controlling sediment-laden runoff on construction sites is the use of sediment basins. These basins slow the velocity of runoff and allow the particles to settle from the water column before discharge to surface waters offsite. This best management practice, however, may create a reservoir for pathogenic bacteria. Sediment is known to provide protection for bacteria; therefore, while these basins decrease sediment loadings to water bodies downstream, they may introduce harmful levels of pathogenic bacteria into these surface waters. In addition to causing human health risks, these high bacteria levels alter natural biological makeup of downstream ecosystems.
Fecal coliform is the current South Carolina Department of Health and Environmental Control (SC DHEC) standard indicator for pathogenic bacteria. This water quality contaminant is the most common impairment of any other pollutant for South Carolina's rivers and streams. In fact, fecal coliform impairments account for approximately one third of total number of surface water impairments in South Carolina. Impairments due to fecal coliforms cause economic losses for South Carolina when beaches, recreational areas, or oyster beds must be closed until these bacteria levels diminish.
This thesis describes the transport, location, and fate of bacteria in construction site sediment basins. Five sediment basins, located in Anderson, South Carolina were sampled during and after rain events to explore trends that exist between various particle sizes and Escherichia coli densities, reveal E. coli densities within sediment layers of various depths over time, and determine the densities of E. coli entering and exiting the basins.
Results provide evidence to suggest that sediment basins are a reservoir for pathogenic bacteria, as net die-off rate of E. coli was slower in the sediment layer than the water column above. Furthermore, inflow E. coli densities recorded were less than outflow E. coli densities. Results showed that most E. coli attached to smaller particles with diameters less than 0.004 mm. These particles do not settle out of the water column quickly and are often passed through the basin during frequent or intense storms. Consequently, high levels of bacteria are passed to downstream waters. Lastly, the high, persistent E. coli densities found in the top sediment layers revealed that resuspension of this top layer during rain events can increase the bacteria levels in the discharge of sediment basins.
This research provides considerable evidence that man-made construction basins can cause detrimental effects to South Carolina surface waters. With this knowledge, better stormwater management practices may be developed with the goal of remediating impaired surface waters of South Carolina.

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