Notice of Intent to Award to Arizona State University

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Enzyme induced carbonate precipitation (EICP) offers the potential for cost effective and sustainable lining and repair of water conveyance channels using natural materials. In EICP, urea, calcium chloride, and the enzyme urease are used to induce calcium carbonate precipitation in the form of calcite as a binding agent between soil particles, significantly increasing the strength and erosion resistance of the soil without the use of Portland cement or synthetic polymers. EICP has the potential to significantly reduce the cost and environmental impact of Reclamation construction and maintenance activities that rely upon Portland cement and other add mixtures. The urease required for EICP may be extracted from vegetation or other plant products (e.g., soy beans or jack beans) or from microbial or fungal sources. EICP has been shown to yield unconfined compressive strengths of up to 20 TSF in sandy soils with as little as 1 percent precipitated calcite (by dry weight of soil). EICP may be accomplished by mixing and compacting the soil or by percolating the EICP solution into the ground. Precipitation of 1 percent calcite by weight will not in itself significantly reduce the permeability of the soil, facilitating percolation of the EICP solution into the ground. However, if low permeability is desired along with high strength and low erodibility, adding small amounts of sodium bentonite has been shown to significantly reduce the permeability of the improved soil. EICP may also be useful for fugitive dust control and improving low volume roads.

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