Modeling and monitoring construction site sediment control measures to improve design, performance, and longevity

Construction activities involve mass grading, removal of existing vegetation, and excavation, exposing bare soil to rainfall. During storm events, soil particles are detached and carried in surface runoff, causing a multitude of adverse impacts to aquatic ecosystems and civil infrastructure. Construction site sediment yields are typically tens to hundreds of times greater compared to agricultural lands. Therefore, controls must be implemented to limit the quantity of sediment and other pollutants that enters waterways. Stemming from the Clean Water Act, federal, state, and local governments require sediment generated by construction projects be treated on-site by erosion and sediment control measures (ESCMs). Despite these efforts, few have analyzed the effect of rainfall characteristics on sediment in roadway construction runoff; these data are critical to properly designing ESCMs such as inlet protection devices.  To address this, in chapter 1 I collected grab samples from sediment laden runoff during storm events at various road construction sites in central Ohio. Samples were analyzed for total suspended solids (TSS), turbidity, and particle size distributions (PSD) and correlated to rainfall characteristics. Significant positive correlations were observed between TSS and turbidity. Further 10-, 30-, and 60-minute rainfall depths preceding sample collection were significantly correlated with TSS and turbidity. This suggests that higher preceding rainfall depths detach more sediments, leading to higher TSS concentrations and turbidity. Results from this chapter assist regulatory agencies in the design and implementation of ESCMs and inform the basis for target sediment concentrations and soil types for full scale testing and modeling of ESCMs in subsequent chapters. Two common ESCMs utilized on construction projects are inlet protection devices (IPDs) and sediment basins. IPDs are a temporary ESCMs that surrounds a storm sewer inlet to limit the amount of sediment discharged into receiving waterways. IPDs typically function by ponding water to allow for sedimentation, filtering out sediment from runoff, or both. However, only a handful of studies have investigated the performance of a wide range of IPDs using full-scale testing. Consequently, in Chapter 2, I assessed 27 IPDs using simulated Ohio construction site runoff conditions, revealing reduced performance when unintentional bypass of IPDs occurred and emphasizing the importance of minimizing untreated flows for IPD effectiveness. Additionally, water quality was not significantly different among different IPD types. Insufficiently maintained IPDs also pose substantial environmental and safety risks; limited research exists on IPD performance without maintenance. Chapter 3 addressed this question by assessing 15 IPDs across five consecutive runoff events without maintenance. Results from this chapter indicated that maintenance frequencies are variable between IPD types, with some devices requiring maintenance after 12. 2 mm of simulated rainfall while others still did not need maintenance after 30. 5 mm of simulated rainfall. Sediment basins are another common ESCM that function by pooling sediment laden runoff, allowing sediment to settle while releasing water at a controlled rate. Construction projects are often space constrained, thus finding the space to implement properly sized sediment basins can be challenging. Furthermore, the longer sediment laden runoff is stored in sediment basins, the likelihood of overflow increases during follow-on storm events, washing untreated runoff into waterways. Currently, little if any research exists on the performance of sediment basins that dewater in less than 48 hours. If substantial treatment of sediment occurs with shorter dewatering times, it would allow for treatment of consecutive storm events. In the last chapter of my dissertation, I studied the performance of three sediment basins utilizing shorter dewatering times of 10-, 20-, and 30-hours. Additionally, I developed a sediment basin performance model using fiel collected data, pond routing models, and particle settling theory. Findings from this chapter suggest that substantial removal of sediment (e. g. , 80%) occurs with just 10-hours of hydraulic retention time. Goodness-of-fit between observed and modeled values also suggest that developed models are adequate at predicting sediment removal in sediment basins, with less than 5% difference between measured and modeled TSS removal.