Recent legislation in several states has called for the removal of methyl tert-butyl ether ͑MTBE͒ from gasoline. In order to comply with Federal Clean Air Act requirements for carbon monoxide and ozone attainment, ethanol is being considered as a replacement for MTBE. The objective of this study is to evaluate the potential impact of ethanol on benzene plume lengths in subsurface environments following accidental spills of ethanol-blended gasoline. Two types of studies were conducted here. First, laboratory studies were performed using a pure culture indigenous to a gasoline-contaminated aquifer to evaluate the effect of ethanol on the rate of benzene biodegradation under aerobic conditions. Results from microbial studies showed that the biodegradation of 25 mg/L benzene was severely inhibited in the presence of 25 mg/L ethanol. While the enzymes responsible for benzene biodegradation by the culture were inducible, ethanol degradation appeared to be constitutive. Second, a two-dimensional model was developed to quantify the impact of ethanol on benzene plume lengths using weighted-average aerobic and anaerobic biodegradation rates for benzene in the presence and absence of ethanol. Model simulations indicated that benzene plume lengths are likely to increase by 16-34% in the presence of ethanol.
field investigations and numerical modeling were conducted to evaluate transport and fate of chlorinated solvent contamination in a fractured sedimentary bedrock aquifer (sandstone/siltstone/mudstone) at a Superfund site in central New Jersey. Field investigations provided information on the fractured rock system hydrogeology, including hydraulic gradients, bulk hydraulic conductivity, fracture network, and rock matrix, and on depth discrete contaminant distribution in fractures (via groundwater sampling) and matrix (via detailed subsampling of continuous cores). The numerical modeling endeavor involved application of both an equivalent porous media (EPM) model for flow and a discrete fracture network (DFN) model for transport. This combination of complementary models, informed by appropriate field data, allowed a quantitative representation of the conceptual site model (CSM) to assess relative importance of various processes, and to examine efficacy of remedial alternatives. Modeling progressed in two stages: first a large-scale (20 km x 25 km domain) 3-D EPM flow model (MODFLOW) was used to evaluate the bulk groundwater flow system and contaminant transport pathways under historic and current aquifer stress conditions and current stresses. Then, results of the flow model informed a 2-D DFN transport model (FRACTRAN) to evaluate transport along a 1,000-m flowpath from the source represented as a 2-D vertical cross-section. The combined model results were used to interpret and estimate the current and potential future extent of rock matrix and aqueous-phase contaminant conditions and evaluate remedial strategies. Results of this study show strong effects of matrix diffusion and other processes on attenuating the plume such that future impacts on downgradient well fields under the hydraulic stresses modeled should be negligible. Results also showed futility of source remediation efforts in the fractured rock, and supported a technical impracticability (TI) waiver for the site. O Exhibit 3. Example of fractures observed in cores and acoustic televiewer (ATV) and inferred from the FLUTe liner transmissivity tests along with comparison of estimated fracture frequency (over 3-m intervals) and estimated apertures from transmissivity profiling at MW-16. Charles E. Williams, PE, CGWP, is a geological engineer/hydrogeologist with the Kansas City District of the US Army Corps of Engineers. He has nearly 30 years of environmental investigation/remediation experience in the private sector and state/federal government. He recently spent six months in Afghanistan assisting military drilling teams in exploring for and developing groundwater resources at bases.
The Gowanus Canal Superfund Site in Brooklyn, New York, is an approximately 1.5‐mile (1.61‐km) long estuary that was historically converted into a canal for industrial and commercial purposes. Three manufactured gas plants (MGPs) were formerly located on the Gowanus Canal and discharged waste into it. Surface sediments remain highly contaminated with polycyclic aromatic hydrocarbons (PAHs) long after the MGPs were razed. A hydrogeologic assessment indicates that groundwater passes through the deeper coal tar–contaminated sediment prior to discharging to the canal. This study was undertaken to investigate if groundwater passing through coal tar–contaminated sediment could be responsible for the ongoing contamination of both surface sediments and surface water in the canal. PAH compound distributions in surface water samples collected from the tidal canal at low tide were compared with PAH compounds found in adjacent groundwater‐monitoring wells, point sources (combined sewer overflows [CSOs]), and surface sediments. The results indicate a strong correlation between PAH contaminant distributions in groundwater, sediment, and surface water, indicating that contaminated groundwater passing through the deeper coal tar–contaminated sediments is the primary mechanism contributing to the contamination of both surface sediment and surface water in the canal. Therefore, any sediment remediation efforts in the Gowanus Canal that fail to evaluate and control the upward transport processes have a high chance of failure due to recontamination from below. ©2016 Wiley Periodicals, Inc.
Each year the National Low-Level Waste Management Program publishes a state-by-state assessment report. This report provides both national and statespecific disposal data on low-level radioactive waste commercially disposed in the United States. Data in this report are categerized according to disposal site, generator category, waste class, volumes, and radionuclide activity. Included in this reportare tables showing the distribution of waste by state for 1992 and a comparison of waste volumes and radioactivity by state for 1988 through 1992; also included is a list of all commercial nuclear power reactors in the United States as of December 31, 1992. This report distinguishes between low-level radioactive waste shipped directly for disposal by generators and waste that was handled by an intermediary, a reporting change introduced in the 1988 state-by-state report. NOTICE The information presented in this report is meant to be inforrnative to the reader and provide accurate disposal figures for the commercial low-level radioactive waste being shipped for disposal within the United States. Comments and suggestions as to how this document may better address your needs for information on this subject are welcomed. Comments may be sent to the address listed below:
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