A Field and Laboratory Investigation of Ponded Solvay Process Residue Behavior

A field and laboratory investigation was performed on the site of a former settling basin for approximately 2.7 million cubic yards of Solvay process residue (mostly soda ash) to assess the feasibility of commercially developing the land for residential housing, light commercial structures, recreational facilities, parking lots, and associated utilities. The investigation included a test embankment surcharge program to assess the deformation behavior of the subsurface materials under additional loading. Of particular interest were the magnitude and rate of settlement associated with the surcharge loads. This field effort was undertaken to determine the feasibility of pre-loading as a ground improvement method, to obtain data for the design of future pre-loading schemes and to develop appropriate foundation recommendations for the desired improvements. A subsurface investigation program was performed both before and after the surcharge program. This field exploration included soil test borings with Standard Penetration Tests performed at regular vertical intervals. Undisturbed (Shelby tube) samples of the Solvay process residue were retrieved for laboratory testing. Field behavior was characterized through monitoring of settlement plates and piezometers. Additionally, strength and settlement properties of the Solvay were measured through laboratory testing before and after pre-loading. The results of this case study provide data which may be used to characterize the behavior of the fine-grained, Solvay process residue under loading and to enable the redevelopment of similar sites.