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0 <br /> LFR Inc. <br /> substrate in a single injection event. The rationale for using wells rather than injecting <br /> through the tip of a hollow rod advanced by a direct-push drill rig is that the wells <br /> provide a delivery point that can be used again in the event that additional substrate <br /> injection is required, and direct-push rigs typically are not cost effective at depths <br /> greater than 40 feet bgs. While HRC products (especially HRC Plus) have proven to <br /> persist for a long time in aquifers, they are highly viscous even when heated and would <br /> not achieve the design radius of influence (ROI) of 15 feet or more. ROI-limiting high <br /> viscosity was also a concern with undiluted, non-emulsified vegetable oils (soybean, <br /> corn, CAP18T", etc.). While performing emulsification in the field was considered, <br /> non-emulsified vegetable oil was ultimately rejected due to concerns about the difficulty <br /> of emulsifying oil in the field, inability to control droplet size, and uncertainty about the <br /> ROI of the resultant oil. <br /> Substrates that are consumed rapidly in the subsurface, thereby requiring multiple <br /> injection events, were eliminated as a potential substrate. Most of the substrates <br /> eliminated due to short life spans in the subsurface are readily soluble and are quickly <br /> taken up by microorganisms in groundwater. Substrates such as sodium or potassium <br /> lactate, lactic acid, ethanol, molasses, and high fructose corn syrup are usually injected <br /> at least quarterly (or more frequently) and were eliminated from consideration for this <br /> reason. Cheese whey may last as long as one year in the aquifer, but still does not meet <br /> the single injection criterion, and it was eliminated as a potential substrate as well. <br /> EHC was eliminated as a potential substrate because its use met with disappointing <br /> results when it was employed by LFR at another site and because of concerns about the <br /> ability to achieve the design ROI. LFR eliminated HRC early due to cost and high <br /> viscosity, which may limit HRC's ROI. <br /> Emulsified edible oils emerged as the leading substrate category due to their low <br /> viscosity, which allows for large injection ROIs, their long life spans in the subsurface, <br /> and a good track record of remediating the type of Hazardous Substances found at the <br /> Site. <br /> Emulsified vegetable oils meet the Central Valley RWQCB requirement that injection <br /> of any substance not impart any "color" into the subsurface (such as molasses, cheese <br /> whey, or any other "non-clear" liquids) within the Central Valley. <br /> 3.4.2 Substrate Cost Considerations <br /> While substrate costs per pound can vary by a factor of 30 or more (with molasses <br /> available for $0.30 per pound and HRCA for $9.00 per pound), when substrates are <br /> evaluated in terms of overall costs for substrate, method and frequency of delivery, and <br /> likelihood of effectiveness, the price gap narrows considerably. Following is a <br /> discussion of substrate costs, delivery/injection costs, and contingency costs. <br /> The role of a carbon-based substrate in ERD is to provide hydrogen to enable the <br /> process of dechlorination. While many researchers refer to the substrate as a carbon <br /> wp-Phv_IRA-SapO7-ei.i-ab75o.dm:irr Page 15 <br />