Rising Groundwater: Unexpected Consequences Downgradient of a Freeway Expansion

Shortly after construction of a major freeway expansion, groundwater rose to the surface at an adjacent industrial park in coastal Southern California. Construction included a mechanically stabilized earth wall for support of the freeway expansion. Soil cement mixing was used to stabilize soils at the toe of the wall where the wall transected small alluvium-filled canyons. Upgradient of the soil cement zones, stone columns were installed through alluvial soils to bedrock in order to mitigate liquefaction. Stone columns were covered with a gravel drainage blanket. No formal analysis of the hydrogeologic conditions was apparently conducted as part of the engineering design. Application of basic hydrogeologic principles to develop a conceptual model, rough calculations, as well as three-dimensional groundwater flow modeling clearly illustrated why one might expect rising groundwater downgradient of the mechanically stabilized wall.