Research Reports

Improved Automatic Sampling for Suspended Solids

Principal Investigator:

Greg DeGroot, John S Gulliver

November 2010

Report no. MnDOT 2010-38

Projects: Estimating the Size Distribution of Suspended Sediments in Minnesota Stormwater

Topics: Storm water

Portable automatic field samplers have been found to overestimate concentrations of suspended sediment larger than 88 micrometers (coarse silts and sands) when sampling using existing methods. Samplers configured with intake manifolds were also found to substantially oversample coarse silts and sands. This research improves the performance of automatic water samplers for sampling coarse silts and sands. A sampling intake was developed that extracts samples from multiple locations in the cross-section. The new sampling intake increases the range of sediment size where sampling accuracy is within +/- 10% to sand particles less than an equivalent diameter of 250 micrometers. The sampling intake also performs with a predicted bias at larger sediment sizes. The new intake thus demonstrates improved sampling accuracy and precision.

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