Community Partner

City of Gresham

First Advisor

Joseph Maser

Date of Award

Spring 2012

Document Type


Degree Name

Master of Environmental Management (MEM)


Environmental Science and Management




Water quality management -- Oregon -- Gresham, Water -- Pollution -- Oregon -- Gresham -- Measurement, Urban runoff -- Management, Runoff -- Purification




We examined the treatment trains at the Columbia Slough (CSWQF) and Fairview Creek Water Quality Facilities (FCWQF) in Gresham, OR and assessed their effectiveness at removing pollutants including nutrients, TSS, metals, pesticides, PAHs, and VOCs. Time-paced, fixed volume composite samples were collected during storm events at the inlets and outlet of the CSWQF and at the inlets and outlet of each treatment train component of the FCWQF. In addition, long-term data collected at the FCWQF was analyzed. Composite data collected during November 2-3, 2011 and March 5-6, 2012 showed that the treatment trains can measurably reduce the event mean concentration (EMC) of most pollutants present in stormwater. Removal efficiencies ranged from a low of 11 to 34 percent for nutrients to a high of 58 to 70 percent for TSS. Long-term data from the FCWQF confirms the findings of the individual sampling events and demonstrates that the FCWQF treatment train significantly reduces the EMCs of NH3-N, TKN, BOD5, most of the heavy metals tested for, bacteria, TSS, and turbidity. When compared to data available from the International Stormwater BMP Database, effluent concentrations at the FCWQF were comparable to or lower than those in the BMP Database for nutrients including TKN, OP, and TP; metals including DCu, TCu, TNi, DPb, and TPb; and TSS. Effluent concentrations at the FCWQF were higher than those in the BMP Database for DZn, TZn, turbidity, and bacteria. When comparing the two facilities, the FCWQF generally reduced pollutant concentrations to a greater degree than did the CSWQF. Pollutant removal efficiency was potentially limited by rainfall intensity and seasonal factors, with removal efficiencies being higher for the spring event than the fall event. It is recommended that long-term monitoring be continued at both facilities until the pollutant removal efficiency of the entire CSWQF and the FCWQF treatment train components can be statistically quantified. Changes in sample collection methods and flow measurement are recommended that could improve the accuracy of pollutant concentration estimates considerably. Finally, it is recommended that further research be conducted to determine if significant relationships can be established between particle size and the following pollutants: heavy metals, total phosphorus, and PAHs. Defining these relationships may make it possible to estimate pollutant concentrations using the stormwater particle size distribution analysis.


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A project report submitted in partial fulfillment of the requirements for the degree of Master of Environmental Management.

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