Employing Best Monitoring Practices for Construction Site Runoff

By on July 21, 2011

New U.S. EPA effluent limitations governing construction sites larger than 20 acres will take effect August 1, 2011. These guidelines require site operators to implement runoff prevention measures along with daily stormwater discharge monitoring. As of now, average daily turbidity values must not exceed 280 NTUs. The new regulations will extend to sites disturbing between 10 and 20 acres starting February 2014.

Real-time, continuous monitoring systems can help site operators meet the EPA’s increasing demands — overcoming the hassle, time, and manpower associated with traditional water sampling.

Environmental Effects

The new regulations are part of efforts to reduce water pollution caused by construction site runoff. When rain events occur, exposed soil can easily be carried to stormwater drains and nearby bodies of water. The foreign sediment that ends up in lakes and streams “can reduce the amount of sunlight reaching aquatic plants, clog fish gills, smother aquatic habitat and spawning areas, and impede navigation,” according to the EPA. Additionally, sediment carried by rainwater introduces pollutants such as heavy metals, turbidity, and nutrients into aquatic environments and potential drinking water resources.

Construction Site Real-time Monitoring

Monitoring runoff at construction sites is often challenging because rain events are unpredictable and do not always occur during traditional work hours. However, real-time monitoring and data logging can simplify the process.

Advanced data collection can be achieved with NexSens data loggers, which can come equipped with numerous real-time telemetry options and interface with a vast array of sensor systems, including many weather and hydrological sensors, as well as multi-parameter sondes. Using sensor data, the data logger can trigger automatic sampling when certain parameters are met. For instance, it can trigger a water sampler when rainfall or water levels reach a certain value.

The OTT Pluvio² is one of the precipitation measurement devices that can be paired with a NexSens data logger. This instrument measures the amount and intensity of precipitation and is able to factor in variables such as temperature and wind. The data received in a rain event through such a device would be transmitted to the data logger. Depending on the parameters set within the data logger (i.e. one minute of continuous rainfall), a water quality monitoring device, such as a YSI 6920 water quality sonde, could be triggered to collect information from the runoff water. The sonde is able to collect parameter data including dissolved oxygen, temperature, conductivity, turbidity, and pH.

NexSens iChart software for Windows is designed to work with NexSens data loggers and takes most of the labor out of data processing. The software generates reports in multiple formats and can publish the information to platforms including a Web data center. This is especially useful for stormwater runoff monitoring, when weather events can occur at any time. iChart can be configured to send alarms via email, text message, or other means to notify users that water data is exceeding predefined parameters.

For more information, contact a Fondriest Environmental application engineer at 888.426.2151 or email customercare@fondriest.com.

Image Credit: http://www.flickr.com/photos/compujeramey/4533672738/

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