<p><p><h2>Preferred Design Procedure</h2>There is no FHWA or other general design method or procedure for the bio-treatment for subgrade stabilization applications. This technology is in the research phase. Most experiments are confined to laboratory studies, and there is some, but limited, field use.</p><p>Design procedures or processes were found in the following references. These may serve as a starting point for design.</p><p>A summary of microbial induced cementation treatment formulations is presented in DeJong et al. (2006).</p><p>In Kucharski et al. (2006) the rate of conductivity increase was converted to urea hydrolysis rate by determining the conductivity change resulting from the complete hydrolysis of urea. A standard curve was generated and the amount of ammonium present at the end of hydrolysis was determined to ensure that the reaction had gone to completion.</p><p>Perkins et al. (2000) presents some design procedures for biofilm production experiments. Ottawa F-110 sand was used for all experiments.</p><p>Whiffin et al. (2007) presents the laboratory design procedures of microbial carbonate precipitation.</p></p>