Modeling Sediment Disposal in Inshore Waterways of British Columbia, Canada

Abstract

In support of the environmental assessment and regulatory approval process and as an interim guidance for field work, a number of numerical modeling studies of the sediment disposals were recently carried out by ASL Environmental Sciences Inc. at the designated/potential disposal sites in inshore waterways of British Columbia, Canada, using the 3D numerical model COCIRM-SED and the short-term fate model of sediment disposal STFATE. In these applications, STFATE was used to provide initial distributions of suspended sediment and bottom accumulation in details, typically within the first hour of the sediment disposal operation, as a useful interim guidance for field work and input to the 3D model COCIRM-SED, which was then adapted to examine the transport and fate of all disposal materials over much larger spatial scales and longer periods of time. This paper reports the model approaches and the detailed model results in the Brown Passage application. Introduction Dredged marine sediment and excavated terrestrial overburden from coastal engineering projects are commonly disposed at designated sites in ocean and coastal open waters via release from barges or pipelines. However, the sediment disposal in these areas can have adverse environmental impacts, especially on marine life and fish habitats, in the form of bottom accumulation and increasing total suspended sediment (TSS) levels in the water column (Fissel and Jiang, 2011). Thus, the shortterm (with durations of hours to about a day) and long-term (with durations of days to months) transport and fate of the disposal sediment during and after the disposal operations are of particular concern to coastal engineers and environmental scientists in assessing potential environmental effects and obtaining regulatory approval. The progress realized in advanced circulation and sediment transport numerical models provides useful and reliable tools in quantitatively predicting transport and fate of disposal sediment. Recently in ASL Environmental Sciences Inc., numerical modeling studies of the short-term and long-term transport and fate of the disposal sediment were successfully carried out at a number of designated/potential sediment disposal sites in the inshore waterways of British Columbia, Canada (Figure 1). These studies used the ASL’s own 3D COastal CIRculation and SEDiment transport Model (COCIRM-SED) and the Short-term FATE model of sediment disposal (STFATE), developed by the U.S. Army Corps of Engineers. The model results were used to address the potential impacts of the sediment disposal on the natural environment of receiving ambient ASL Environmental Sciences Inc., #1 – 6703 Rajpur Place, Victoria, BC, V8M 1Z5, Canada, jjiang@aslenv.com and dfissel@aslenv.com 40 1A _5 12 20 _A S C E _T es t.j ob _P ro ce ss C ya n_ 08 /2 4/ 20 12 _0 6: 48 :3 4 40 1A _5 12 20 _A S C E _T es t.j ob _P ro ce ss M ag en ta _0 8/ 24 /2 01 2_ 06 :4 8: 34 40 1A _5 12 20 _A S C E _T es t.j ob _P ro ce ss Y el lo w _0 8/ 24 /2 01 2_ 06 :4 8: 34 40 1A _5 12 20 _A S C E _T es t.j ob _P ro ce ss B la ck _0 8/ 24 /2 01 2_ 06 :4 8: 34