Brilliant Dam and Brilliant Expansion TGP Monitoring 2009

Author: Golder Associates Ltd

TGP levels in the lower Kootenay River downstream of BRX were monitored over a range of operating and flow conditions to determine the magnitude of any changes in downstream TGP due to operation of BRX. These data were collected to reassess and potentially modify the TGP Model that predicts gas formation from each of the spillways on BRD. The 2009 TGP monitoring program was designed to collect the data required to meet the following objectives: 1) verify that the operation of BRX does not increase TGP levels; 2) extend the baseline TGP spot measurement data so that TGP formation downstream from BRD can be accurately modeled; 3) provide sufficient information to define changes in downstream TGP levels due to operation of the BRX power plant and changes in gas formation from the existing spillways as a result of changes in tailwater elevation; 4) verify the environmental assessment predictions by comparing the observed changes in TGP attributable to the power plant to those predicted as described in the PAC application documentation; and, 5) make adjustments in the TGP Model based on monitoring results to reflect potential reductions of TGP production as a result of tailwater elevation changes, and make recommendations on the preferred spill gate operations sequence to minimize TGP production.

Both the empirical and Model data indicate that the operation of BRX has resulted in a substantial reduction in TGP as measured in the tailwater of BRD below the mixing zone near the Brilliant Highway Bridge. This reduction was attributed to the diversion of discharge through BRX that otherwise would have been spilled. The BRD Spillway TGP Model was updated with the 2009 data, with the Model results indicating an overall reduction in TGP produced by all Spillways under most operational settings. This reduction in TGP by individual Spillways was attributed to a reduction in tailrace elevation in the Spillway plunge pool. However, the revised Model also indicated potential interaction between the BRX generation plume and spill from Spillways 6, 7, and 8 when operated at the maximum gate setting.

Both the empirical and Model data indicate that the operation of BRX has resulted in a substantial reduction in TGP as measured in the tailwater of BRD below the mixing zone near the Brilliant Highway Bridge. This reduction was attributed to the diversion of discharge through BRX that otherwise would have been spilled. The BRD Spillway TGP Model was updated with the 2009 data, with the Model results indicating an overall reduction in TGP produced by all Spillways under most operational settings. This reduction in TGP by individual Spillways was attributed to a reduction in tailrace elevation in the Spillway plunge pool. However, the revised Model also indicated potential interaction between the BRX generation plume and spill from Spillways 6, 7, and 8 when operated at the maximum gate setting.