Proceedings - Teaching and Learning Centre - Simon Fraser ...

Fraser River Action Plan 3rd Research Workshop
Summary
The Wastewater Plume Delineation Study for
the Glenbrook CSO, New Westminster
D. Hodgins
Seaconsult Marine Research Ltd.
A wastewater plume delineation study for the Glenbrook combined sewer overflow (CSO) was conducted in
February 1995 to assist in setting priorities for contaminant monitoring in the Fraser River estuary. The work
was undertaken as part of the component of the Fraser River Action Plan concerned with identifying
contaminants entering the Fraser River. The Glenbrook CSO discharges into Sapperton Channel at New
Westminster, B.C. The wastewater plume was measured in the receiving water using a rhodamine dye tracer and
a towed in situ fluorometer. Two injections of dye were made over two days for different stages of the tide. The
dye plume was also observed on February 17 using the CASI multispectral imager flown on a small airplane.
Three separate images were obtained.
The surveying methods were successful in accurately delineating the plume, particularly the areas of shore
contact and the cross-channel width and depth of the plume. Estimates of secondary dilution were obtained. In
general, it was found that the plume was confined to the north shore of the river, forming a narrow streak less
than 100 - 150 m in width downstream of the outfall. The highest concentrations were observed next to the shore
and the plume remained in continuous contact with the shore from the outfall to the North Arm of the estuary.
The plume was carried upstream on the flood tide for a distance of 2,600 m, near the end of Sapperton Channel.
The plume width was approximately 150 m wide in Sapperton Channel. Mixing was found to be most effective
within 300 m of the outfall, producing a minimum dilution of about 60:1. Dilutions of 100:1 were observed at a
distance of 850 m on ebb flows, and reached approximately 400:1 at the junction to the North Arm. Vertical
mixing was found to be rapid, producing nearly-uniform concentrations over the water column within 200 m of
the outfall.
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