## 2 Experimental Setup  
Three 3.7 m long horizontal soil columns (Figure 1) were improved using different ureolytic biocementation treatment approaches to investigate the spatial uniformity and extent of MICP, as well as the success of post-treatment NH4+ byproduct removal as a function of different soil materials and treatment techniques. Although additional experimental details are provided in [19; 24]'s works, a summary of all relevant details is provided here. All columns contained concrete sand, a clean, poorly graded alluvial sand (D\({}_{10}\) = 0.23 mm, D\({}_{30}\) = 0.54 mm, D\({}_{60}\) = 1.54 mm, fine content = 1.1%, e\({}_{\min}\) = 0.35, e\({}_{\max}\) = 0.60) that has been used extensively in past MICP experiments [17; 19; 24]. Each column contained 0.14 m\({}^{3}\) of concrete sand that was prepared to similar initial porosities (between 0.30 and 0.32), relative densities (between 56% and 67%), and had pore volumes (PVs) between 48.5 L and 50.7 L (average value of 49.9 L). Columns received different biological treatment injections intended to either enrich soils for native ureolytic microorganisms (Columns 1, 2) or augment soils with _S. pasteurii_ bacteria (Column 3) uniformly across column lengths. To examine the effect of urea hydrolysis rates on the spatial uniformity and extent of biocementation,different treatment techniques were applied to either achieve a high ureolytic rate with stimulation (Column 1) or augmentation (Column 3) or achieve a low ureolytic rate using stimulation (Column 2). Differences in ureolytic rates were achieved by either controlling the augmented cell densities (Column 3) or varying the applied yeast extract concentrations during enrichment injections (Columns 1, 2), which altered enriched ureolytic cell densities and reaction rates. Supplementary Table S1 presents the treatment schemes, including solution chemical constituents and concentrations, numbers of injections, and injection volumes and durations. All treatment solutions were injected using small electric pumps (Wayne Inc., Harrison, OH, USA, 0.1 HP). In summary, all columns received treatment solutions over three treatment phases, namely (1) stimulation or augmentation, (2) cementation, and (3) NH\({}_{4}\)\({}^{+}\) rinsing. Following enrichment treatments in Columns 1 and 2, however, a flush solution was applied immediately before the first cementation treatment to remove aqueous carbonate species expected after enrichment. Once ureolytic activity was established, nine cementation injections containing identical calcium and urea concentrations (250 mM) were applied to the columns over nine days in the high-rate columns (Column 1, 3) and over eighteen days (one injection every two days) in the low-rate column (Column 2). Shear wave velocity (V\({}_{\text{s}}\)) measurements were obtained using bender element sensors placed at four different locations that were 0.31 m (V\({}_{\text{s1}}\)), 1.33 m (V\({}_{\text{s2}}\)), 2.35 m (V\({}_{\text{s3}}\)), or 3.37 m (V\({}_{\text{s4}}\)) from the injection source (Figure 1). Vs measurements were conducted at all locations before and after all cementation injections and allowed for the non-destructive monitoring of biocementation progression in time and with distance from the injection location. Initial Vs values at the four different measurement locations in all three columns had an average value of 204 m/s (standard deviation of 37.4 m/s) prior to starting all treatments. Following all cementation injections, 10.5 PV (525 L) of a high-pH and high-ionic-strength rinse solution was applied to each column to remove produced NH\({}_{4}\)\({}^{+}\). During rinse injections, aqueous NH\({}_{4}\)\({}^{+}\) concentrations were measured at four sampling port locations in each column (labeled P\({}_{1}\) through P\({}_{4}\) in Figure 1) to evaluate NH\({}_{4}\)\({}^{+}\) byproduct removal with the effects of rinsing on biocementation integrity, also assessed using Vs measurements.