A sanitary landfill project needs an import soil for use as an impervious cap over the refuse. The following soils are available for this purpose:
Soil 1: GC
Soil 2: SC
Soil 3: ML
Soil 4: CL
The design engineer desires a soil with a high clay content because it will help keep water out of the landfill. Which of the available soils appears to be most promising? Why?