Technology Evaluation Report for the NoVOCs(Trademark) Technology Evaluation Superfund Innovative Technology Evaluation Program. Volume II: appendix B: Hydrogeologic Investigation of the Aquifer Treated by the NoVOCs(Trademark) System

摘要

In support of the U.S. Environmental Protection Agency (EPA) superfund Innovative Technology Evaluation (SITE) Program, Tetra Tech EM Inc. (Tetra Tech) is evaluating the MACTEC Inc. (MACTEC) NoVOCsTM in-well volatile organic compound (VOC) stripping system at Installation Restoration (IR) Site 9 at Naval Air Station (NAS) North Island in San Diego, California. The NoVOCs(Trademark) system is a patented recirculating well that is designed for the in situ remediation of groundwater contaminated by VOCs. In April 1998, the Navy initiated operation of the NoVOCs(Trademark) system. By June 1998, the pumping rate had been reduced from the design rate of 25 gallons per minute (gpm) to approximately 5 gpm because not all water pumped at higher rates could be injected into the aquifer. The NoVOCsTM system was shut down on June 19, 1998, to evaluate the cause of the problem. Suspected causes for the poor injection performance included (1) biofouling or scaling of the screen intervals and formation near the NoVOCs(Trademark) system, (2) design problems with the NoVOCs(Trademark) well, in particular the sizing of the recharge screen, and (3) possible differences in hydraulic characteristics between the upper and lower portions of the aquifer. EPA directed Tetra Tech to conduct the hydrogeological study at the demonstration site to provide information on the recharge capacity of the NoVOCs(Trademark) system and the hydraulic characteristics of the aquifer in the vicinity of the NoVOCs(Trademark) system. The groundwater study included: (1) a tidal influence study to evaluate natural variations in water level at the site due to tides in San Diego Bay, and (2) a series of groundwater pumping tests in the shallow and deep portions of the aquifer, including step drawdown tests, a 32-hour constant pumping rate test, an injection test, and a dipole flow test to evaluate the aquifer characteristics in the vicinity of the NoVOCs(Trademark) system.