Particle-size Distribution from Urban Land Use and Source Areas
Project Number: BQY29
Project Chiefs: William R. Selbig; Steven R. Corsi
Project Topics: xxxc
Cooperators: Wisconsin Department of Natural Resources
Period of Project: July 2005–September 2007
The primary objective of this study is to characterize particle-size distributions in urban storm-water runoff from specific source areas and land-use categories.
Problem
Sediments in storm-water runoff from urban areas and contaminants associated with these sediments are a substantial source of contamination to receiving waters and associated toxic effects to aquatic organisms.
Treatment options for urban storm water should include specific plans to target sediment as the primary source of contamination to receiving streams. Watershed managers in urban areas need information to help choose the most effective means to reduce sediment-associated contaminants in urban runoff.
Numerous structural best-management practices (BMPs) provide some level of sediment control and are readily available. However, since many of these devices rely on settling of solids, their effectiveness is largely dependent on the range of particle sizes in storm-water runoff. In order to select the most appropriate BMP for sediment control, characterization of particles found in storm-water runoff becomes increasingly important.
Objectives
The primary objective of this study is to address the first step in providing watershed managers with the information needed to make decisions on treatment options: to characterize particle-size distributions in urban storm-water runoff from specific source areas and land-use categories. This information will be used to assist watershed managers and engineers in designing the most appropriate control device for reduction of sediment in urban storm- water runoff. Additionally, data collected from this study will be used to improve calibration of the Source Loading and Management Model (SLAMM) data tables with particle-size distribution curves for specific source areas and land uses.
Approach
This study will characterize particle-size distributions for several urban land uses and source areas. Data will be compiled from existing USGS monitoring stations where particle size distribution is currently included on the list of water quality analytes. In addition, auto-samplers will be installed at five new sites representing two urban source areas (roof tops and parking lots) and two urban land uses (shopping center and strip mall). These study sites were chosen based on the lack of data available to characterize particle-size distribution for these specific types of source areas and land uses within urban watersheds.
Progress
Several runoff samples have been collected and processed for particle-size distribution. Each of the samplers is configured to sample based on increments of time. However, one of the roof-top samplers was reconfigured to sample based on increments in flow. This will provide better sample coverage of a storm hydrograph.
Plans
Three sites will be equipped with area-velocity sensors to measure discharge. This will allow for reconfiguration of the autosamplers to sample based on increments of flow instead of time. This will allow for better sample coverage of a storm hydrograph as well as provide volume estimates for calculation of pollutant loads. Other pollutants will be analyzed in addition to particle-size distribution to increase data sets.
Publications and Reports
Scientific Investigations Report is planned for September 2007.
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