Aguilar, Alex M.

Thompson Engineering

State Study 225

Tech Report

Mississippi

Mississippi. Dept. of Transportation

The objective of this project was to establish baseline turbidity conditions at select construction sites by establishing a water quality monitoring program and documenting MDOT approved BMPs on site. In 2009 the United States Environmental Protection Agency (EPA) proposed a numeric turbidity limit for stormwater runoff at construction sites. The proposed limit of 280 NTUs was stayed due to a miscalculation, and EPA has not released a new numeric limit for turbidity. Current Mississippi Department of Environmental (MDEQ) Water Quality Standards (WQS) require that turbidity 750 feet downstream from the point of discharge not exceed the background turbidity levels upstream of the discharge point buy 50 NTU. MDOT has no method of evaluation in place to measure turbidity at construction sites; and therefore, no background data are available to indicate how current erosion and sedimentation BMPs are performing with respect to potential increases in turbidity. Methods of analysis used in this report included the collection of turbidity data from seven sites where MDOT construction posed a potential threat to waters of the state. Prospective sites had to meet certain criteria in order to be used for the study.

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09-2118-0034

US Transportation Collection