A process for hardening and rendering a roadbed water resistant by measuring and ensuring the clay content of the roadbed soil is a minimum of 12%, amending the soil to bring the clay content within this range. Treating the top six inches of the roadbed soil with an enzyme formulation and removing and setting aside the treated roadbed soil. Applying two mixtures of organo-silane solution to soil remaining in the roadbed in two separate steps, allowing the treated soil to cure between applications. Adding the enzyme treated soil back onto the roadbed, compacting and crowning the soil, then spraying the surface of the treated roadbed and its associated shoulders with the organo-silane mixture. Once again, the organo-silane mixture is applied in a two step process with two different dilutions of the organo-silane formulation to form a hardened and water resistant envelope of soil within the roadbed.