HR: 0830h
AN: H21D-02    [Abstracts]
TI: Finding Order in Stormwater Chaos
AU: * de Ridder, S A
EM: scottdr@stormwaterinc.com
AF: Stormwater Management Inc., 12021-B NE Airport Way, Portland, OR 97220 United States
AU: Lehman, J M
EM: jeremial@stormwaterinc.com
AF: Stormwater Management Inc., 12021-B NE Airport Way, Portland, OR 97220 United States
AB: A true understanding of baseline stormwater quality is important when defining the scope of a stormwater quality problem and the application of a solution. This is critical when determining regional stormwater quality goals and when assessing the efficacy of stormwater treatment processes relative to these goals. To better understand baseline stormwater quality in the Pacific Northwest for the purpose of designing stormwater treatment processes, raw stormwater quality data from a comprehensive, yearlong study of 5 parking lots and roadways in the Pacific Northwest was thoroughly analyzed for relationships and patterns. Over 60 individual storm events were sampled in an identical fashion using automated, composite methods under a monitoring plan approved by the local regulatory agency (Washington State Department of Ecology). Event mean concentration values were assessed for 15 different physical and chemical water quality parameters. The concentration data was then analyzed using statistical methods to elucidate relationships between water quality parameters and chemical, seasonal, and storm event variables. Several statistically significant relationships were found that both support and challenge common hypotheses regarding stormwater quality dynamics. For example, the observation that parameter concentration decreases with increasing storm depth is contradictory to the theory that larger storms are more important than smaller storms with respect to water quality. This theory is reflected in the specification of a minimum event depth by many stormwater monitoring protocols for the purpose of defining an event of concern. From a toxicity standpoint, the observation contradicts this theory by suggesting that larger storms are less harmful to aquatic ecosystems--and thus less important--due to a dilution effect. Also observed is a significant (P<0.001), predictable relationship between suspended solids and total Zn concentrations. This supports the hypothesis that the removal of suspended solids will result in the removal of metals, an observation this is supported both by logic and the research of others. However, the observation of a predictable relationship of substantial strength is curious and potentially valuable for modeling purposes. Ultimately, this information will: 1) help to accurately define the baseline stormwater quality of the Pacific Northwest; 2) improve the design and implementation of stormwater treatment processes in the region; and 3) advance the fundamental understanding of stormwater.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 1803 Anthropogenic effects
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2005 Joint Assembly