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Turbidity Monitoring: Addressing Gaps for Erosion and Sediment Control in Canada

  • Mielhausen, J., Villard, P. and Lawson, M. (2020). Turbidity Monitoring: Addressing Gaps for Erosion and Sediment Control in Canada.Canadian Standards Association, Toronto, ON.

Executive Summary

Construction activities can result in soil erosion and the transport of sediment beyond the limits of an active work area. Sediment generated from the exposure of erodible soils on construction sites can be carried by stormwater runoff and is ultimately released to watercourses, wetlands, important natural features, private property, and existing drainage infrastructure. This can then lead to the degradation or destruction of aquatic and terrestrial biota and associated habitats, the loss of structural integrity and functionality of watercourses and other natural features, flooding, and costly infrastructure maintenance.

To help prevent both short-term and long-term adverse impacts to the environment throughout the lifespan of a construction project, it is important that effective, industry-wide practices that foster the proper inspection and monitoring of erosion and sediment control (ESC) measures be developed. These practices, coupled with effective and dynamic ESC plans are critically important components of successful construction projects, and when implemented and properly maintained, can effectively minimize impacts to infrastructure and the environment.

The recently published CAN/CSA-W202, Erosion and Sediment Control Inspection and Monitoring is a first of its kind National Standard of Canada. While it goes a long way towards harmonizing a set of national requirements for inspecting and monitoring ESC measures, there exists an opportunity to provide further guidance on implementation. Specifically, while the standard provides turbidity monitoring performance targets, it does not instruct users as to how to conduct monitoring or how to set up ESC measures to meet the prescribed targets. As such, the objective of this research project was to help ESC stakeholders in Canada better understand what it takes to meet their turbidity monitoring targets in terms of ESC measure implementation and the use of various technologies available to monitor their project sites. Through a series of case studies (both literature-based and survey-based), this research demonstrates the challenges and successes experienced on past construction projects where turbidity monitoring was a requirement. In doing so, the report provides readers with context that will allow them to make informed decisions about their site management, ESC methods, and turbidity monitoring efforts.

Based on the results of the case studies, the most common challenges associated with turbidity and total suspended solids (TSS) monitoring were identified as equipment maintenance, accounting for natural variability in telemetry-based monitoring technologies, and meeting standard targets based on pre-development levels of turbidity and TSS in receiving watercourses. This report provides recommendations to improve ESC effectiveness and turbidity, and TSS monitoring protocols specifically to address such challenges. Turbidity and TSS monitoring successes were associated with using continuous data collection equipment, reprogramming telemetry-based systems to account for natural variability, as well as reducing the duration of turbidity and TSS exceedances.

This report also provides a description of “lessons learned” when applying various turbidity monitoring technologies across different scenarios. Based on issues commonly experienced on-site, recommendations to inform successful site management and turbidity and TSS monitoring, were provided. These recommendations included incorporating project phasing and considering weather constraints, identifying sediment sources and considering these locations in monitoring station setup, and maintaining open and effective communication during ESC projects.

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