British Columbia Mine Reclamation Symposium

Sediment control during instream construction using a regression analysis : Robert Service Way Reconstruction Project, City of Whitehorse, Yukon Snider, R. C.

Abstract

During the Summer of 1997 the City of Whitehorse undertook reconstruction of the Robert Service Way, one of the two key access routes to the downtown core of Whitehorse, Yukon. Based on previous fisheries investigations, it was determined that the road embankment fill required for reconstruction would cover critical rearing, overwintering and spawning habitat for chinook salmon. A fisheries compensation agreement was reached whereby the City would construct three compensation channels within the Yukon River to provide spawning and rearing habitats for the salmon. During instream fill placement and construction of the compensation channels, there was a requirement to monitor suspended solids levels on a daily basis, and more frequently during specific construction activities. An agreement was reached between the City of Whitehorse and the Department of Fisheries and Oceans (DFO) to monitor total suspended solids (TSS) daily using a portable turbidity meter based on a regression analysis of TSS and turbidity. The relationship was established through the collection of samples prior to and during construction with a total of 38 samples being collected. Two separate regression analyses were used to correlate TSS and turbidity measurements for varying sediment concentrations. A TSS to turbidity ratio of 1.5:1 was calculated for turbidity measurements from 0 to 80 NTU, while a ratio of 0.8:1 was determined for turbidity measurements over 80 NTU. Suspended solids monitoring indicated that the total suspended solids limit of 25 mg/L (above background) was met on all occasions except for selected periods during compensation channel plug removals. The use of a portable turbidity meter and regression of TSS and turbidity provided a valuable tool in monitoring and controlling upstream construction activities.

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