Abstract: The present disclosure discloses an earthen dam structure including a core wall that includes a homogeneous mixture of clay, sand, powdered tire rubber and Portland cement. Additionally, the core wall contains the powdered tire rubber in an amount sufficient to increase a modulus of elasticity of the core wall to over 10 MPa while keeping a hydraulic conductivity of the core wall under 100 feet/year. The earthen dam structure further includes an upstream embankment portion and a downstream embankment portion, each positioned adjacent to the core wall, and a spillway configured to prevent water from overtopping a crest of the core wall.