Slope instability and the construction of secondary roads across glaciolacustrine sediments : Morice River Valley, west central British Columbia

Abstract

Glaciation in the coastal mountain ranges of British Columbia has left glaciolacustrine deposits in many valleys. This report investigates a section of road in northwestern British Columbia that is unstable due to the presence of glaciolacustrine soils. Glaciolacustrine soils are deposited during the existence of glacial lakes. The deposits consist of fine grained silt and clay, and they are recognized by their varved structure. Combined with high pore water pressure, and steep slopes, glaciolacustrine soils create slope stability problems. The study section of road is located in the Morice River Valley. In the past, attempts at controlling slope failures have had varied success in this region. In the sites studied in this report, groundwater patterns seem to be the largest contributor to slope instability in glaciolacustrine deposits. The most successful remediation designs have dealt with the local groundwater patterns that create high pore water pressure seen in these deposits. The report presents varied options for controlling slope movement in the area. The designs included range from complete relocation of the route to more stable terrain, to minor yearly maintenance. The report concludes by presenting further investigations that should be completed prior to deciding on any final design for the area.