The Brickyard area of Lilydale Regional Park is a place of historic and recreational significance to the city of Saint Paul. Slope instability and decreased water quality in downstream Pickerel Lake (which drains to the Mississippi River) prompted the city to hire Barr to study slope-stability and erosion issues and develop concept-level recommendations for slope stabilization, stormwater management, and erosion control.
After a large slope failure toward the north end of the study area (the North Knob), we collected soil borings and conducted geotechnical modeling to evaluate the influence of topography, soil strength, and seepage and saturation on slope stability. We also developed a hydrologic and hydraulic model to assess drainage patterns in the area and their effect on erosion.
Barr reviewed a history of previous landslides and assessed existing conditions for the risk of large-volume landslides, soils falling from significant heights, and people being caught in a slide from above the failure surface. No area of the park was considered to be without risk, since the uncertainties of weather, soil type and strength, and human activity always pose some risk of unexpected soil movement. Identification of high-risk zones, however, has helped the city manage public access to certain areas of the park. The city is in the process of implementing a series of recommendations from Barr, including stabilization of the North Knob and a small stream channel that crosses the area.