The Gronlid crossing, Saskatchewan Provincial Highway No. 6 at the Saskatchewan River

Abstract

A traffic connection between Regina and the northeastern part of Saskatchewan required a crossing of the Saskatchewan River north of Gronlid. Slope instability developed in lacustrine and deltaic sands on the approaches to a ferry site installed in the early 1960s. Alternative ferry sites were considered but a river hydraulics study showed that other sites would not offer any improvement. The creation of a reservoir by projected dam at Nipawin and potential mining development in the area added incentive for the construction of a bridge to replace the original ferry installation.Valuable information was obtained from the ferry site for locating the new bridge and designing the approach roadways. It was possible to locate the bridge and approaches to minimize seepage, foundation, and slope instability problems in a deposit of over 100 m of saturated interbedded deltaic sand, lacustrine silt, and clay. A major artesian groundwater system was found in the bedrock sand of the Swan River Group, whereas groundwater conditions in the surficial stratified drift were mainly hydrostatic.The regional geology was used as a basis for detailed stratigraphic analysis at the site. The stratigraphy consisted of Lower Cretaceous sand and clay shale units underlying a dense unoxidized till. The site geology was divided into three parts: (1) the south valley approach, (2) the river channel crossing, and (3) the north valley approach. The bridge was completed in the summer of 1980.