Relationship between suspended sediment concentration and turbidity at construction sites

Stormwater runoff from construction sites can transport eroded sediment to nearby water bodies, degrading water quality and impairing biotic communities. Turbidity is a relatively easy characteristic to measure and can be used to estimate sediment loads from construction sites if reliable relationships between turbidity and total suspended solids (TSS) are established. These relationships are investigated in this study for construction sites in Minnesota. Laboratory protocols have been developed herein for studying the factors that impact turbidity from construction site soils. Experimental procedures include the use of a rainfall simulator to generate runoff and turbidity values from soils carefully packed in appropriate test boxes. Turbidity characteristics of 14 different soils from construction sites were investigated using the laboratory protocols. Trends in turbidity with sediment concentrations were well represented by power functions. The exponent of these power functions was relatively constant between soils. The log-intercept, or scaling parameter, varied substantially among the different soils. Multiple soil properties were evaluated for each soil. An extensive regression analysis resulted in a model using percentage silt, interrill erodibility, and maximum abstraction that best represented the intercept term. A power value of 7/5 was chosen to represent all soils.