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♦ M LFR Inc. 3.4.3 Substrate Delivery Considerations Some substrates are limited in the manner that they can be delivered to the aquifer. HRC and HRC-X are highly viscous and are usually delivered using a high-pressure low-flow pump through the tip of an auger on a direct-push drilling rig. These drilling rigs have limitations of the depths they can achieve and typically are not cost effective at depths greater than 40 feet bgs. Since the ROI that can be achieved with HRC is relatively small due to this product's high viscosity, injection points are usually tightly spaced to ensure contact with water in all of the treatment area. This tight spacing leads to many field days for the drilling crews and oversight personnel, leading to high expenses for the field execution of the substrate injection event. Injection using a direct- push rig requires no wells but also leaves no remaining delivery point to the aquifer, and, in the event that more substrate is required, the cost of re-injection will be as high as the original injection event. Sugars, sodium lactate, and molasses can be diluted with water and, depending on the soil formation, can be gravity fed through wells or trenches, pumped under pressure through wells, or delivered through an injection tip on a direct-push rig. Injection of these readily dissolved substrates can be achieved at a reasonable cost. However, since these substrates do not last long in the aquifer, re-injection events are inevitable and the costs associated with re-injections make soluble substrates a less economically desirable option. Non-emulsified oils can be delivered through well screens or via direct-push rods without dilution. Their expected ROIs would be greater than that of HRC but not as large as ROIs for diluted soluble substrates or emulsified oils. Since the non-emulsified oils do not mix with water, achieving uniform distribution is difficult. Non-emulsified oils will also migrate upward through the water column in permeable soils, reducing their ability to treat deeper saturated zones. Field emulsification would address these problems but would also add considerably to field costs and project uncertainty. Emulsified edible oils mix well with water, have relatively low viscosity, and are compatible with a variety of delivery approaches. Injection through well screens is easy to achieve, and large ROIs are expected. Since the substrate has a long lifespan in the aquifer, the need for re-injection is not anticipated, reducing costs associated with additional field injection events. 3.4.4 Recommended Substrate While many substrates could be used with success for the Lincoln Center Phase V IRA, the substrate type selected to best meet project objectives is an emulsified edible oil product. The combination of longevity in the aquifer (expected to be approximately five years), moderate cost per unit of hydrogen, low viscosity, expected large ROI, and easy field mixing and injection make it the most suitable for this project. wp-PhV_IPASep07-Final-06750.dw:IG Page 17