Transport Dear Mr. Giannopoulos, I recently attended the public workshop in Sacramento regarding the fate and transport of ethanol in the environment. We believe that these comments will help to clarify and expand the LLNL conclusions presented at the Sacramento public workshop regarding impacts on the BETX plumes due to the use of ethanol-blended gasoline. These results presented by LLNL are consistent with two other recently completed modeling efforts to assess this issue. The Malcolm Pirnie report concluded that a primary disadvantage of adding ethanol to gasoline is the potential impact of ethanol biodegradation on the natural biodegradation of other gasoline constituents present in the groundwater.
Ethanol is known to readily biodegrade under a variety of aerobic and anaerobic conditions.
However, as ethanol is aerobically biodegraded, oxygen and other electron acceptors, as well as nutrients will become depleted in the groundwater. As a result, BTEX plumes may be lengthened due to the delay in biodegradation in the presence of ethanol. The potential impact of increasing BTEX plume lengths is either a greater probability that drinking water well fields could be impacted by BETX or higher BTEX concentrations at wells that are already contaminated. Additional migration of the BETX plumes could also cause greater property damage due to plumes extending beyond the boundaries of the source property. These impacts would result in higher cleanup costs for BTEX plumes, if cleanup is warranted.