Modifications to the extracellular polymeric substance, predominantly extracellular polysaccharide, of a biopolymer produced by Rhizobium tropici ATCC 49672 yield a stable dry salt transported more easily than a fluid or gel and more stable than either. The salt may be re-constituted with water on-site. Embodiments may be employed as a soil amendment for soil strengthening, reducing hydraulic conductivity, erosion control and dust control as well as a metal chelator for contaminant remediation. Based on comparison with dextran standards, an embodiment demonstrated a molecular weight over 511,000 D. Embodiments include a day salt that is precipitated from solution and in use is re-hydrated back to original form. When added to a sandy soil at 0.1% by dry weight, an embodiment decreased the hydraulic conductivity by three orders of magnitude. These properties make embodiments of the present invention an attractive, “green” alternative to petroleum-based synthetic polymers for such applications as rapid roadway construction and soil erosion prevention.