Sophisticated Stormwater Quality Modeling is Worth the Effort.
Annual runoffs and pollutant loads for six homogeneous Nationwide Pollutant Discharge Elimination System (NPDES) stormwater sites in Portland, Oregon, were simulated using SIMPTM, the Simplified Particulate Transport Model, calibrated to local runoff quality data. Results clearly showed that current linear or exponential sediment accumulation models fail to represent the seasonal variation of accumulation and runoff quality without resorting to arbitrary seasonal rates that depend upon the results they would compute. And the calibrated model results suggested that simplified annual pollutant load calculations, of concentration times volume, could overestimate expected loads by up to seven times. In addition, results of a street sweeping testing showed that tandem street sweeping (i.e. mechanical followed by vacuum) was much more effective than previously concluded by the Nationwide Urban Runoff Program (NURP).
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