High Resolution Site Characterization Research Articles

Critical review of the environmental management of a DNAPL contaminated site in Resende, Rio de Janeiro, Brazil

The current nonconformity of most Brazilian states regarding the environmental guidelines established by the Conama 420 resolution makes clear that there are still many challenges to be faced on the management field of contaminated sites. The analysis of a factual remediation operation in an industrial site in the city of Resende, Rio de Janeiro state, show that traditional site investigation techniques are still being applied as main tools of characterization, data collection and decision-making in the management of the area. The site has had its investigation start in the late 90’s through multiple soil sampling and monitoring wells installation, pointing DNAPLs (dense non-aqueous phase liquids) among the chemicals of interest. The industrial site has undergone remediation for over 10 years now and has not been closed yet. More recently, the efficiency reduction of the primary remediation system, a dual-phase extraction system with over 50 installed wells, led to the implementation of in-situ stimulated bioremediation. Performance reports show lower efficiency than expected, hinting that a lackluster CSM (conceptual site model) might be leading to poor decision making. Despite being adequate remediation techniques, previous efforts and literature indicate that the site must undergo new investigation steps employing high-resolution site characterization (HRSC) techniques such as the MIP (membrane interface probe), allowing the refinement of the current CSM and the optimization of current remediation efforts.

γ-Ray Log Tool for Detecting the Presence of Low-Permeability Lenses in High-Resolution Modelling of Contaminated Sites

In contaminated sites, remediation measures mostly depend on previous high-resolution site characterization (HRSC) results. In the case of industrial sites, where there is a high pollution risk for groundwater, many hydrogeological models are often achieved using stratigraphy results of geological drilling after the monitoring network design. This approach is only sometimes possible when contaminant back diffusion from small low-permeability lenses and layers occurs within a high-permeability aquifer. This framework needs a significant resolution that can be obtained by coupling preliminary stratigraphic data with specific in situ activities. Results from these additional investigations may help to locate low-permeability layers and, consequently, to identify the most vulnerable areas towards which groundwater management must be deepened. The use of gamma rays in combination with the analysis of the pluviometric and hydrometric data and together with the time series of the concentrations of a given analyte can provide indispensable support for site characterization, the development of numerical groundwater contamination models and remediation procedures when back diffusion occurs. In this study, within an industrial site in the province of Benevento (Italy), based on stratigraphy, a 3D hydrogeological model has been set up and coupled with results of natural gamma radioactivity logs to detect the release of Chromium VI from low-permeability lenses.

Combined Well Multi-Parameter Logs and Low-Flow Purging Data for Soil Permeability Assessment and Related Effects on Groundwater Sampling

Cost-effective remediation is increasingly dependent on high-resolution site characterization (HRSC), which is supposed to be necessary prior to interventions. This paper aims to evaluate the use of low-flow purging and sampling water level data in estimating the horizontal hydraulic conductivity of soils. In a new quali-quantitative view, this procedure can provide much more information and knowledge about the site, reducing time and costs. In case of high heterogeneity along the well screen, the whole procedure, as well as the estimation method, could be less effective and rigorous, with related issues in the purging time. The result showed significant permeability weighted sampling, which could provide different results as the pump position changes along the well screen. The proposed study confirms this phenomenon with field data, demonstrating that the use of multiparameter well logs might be helpful in detecting the behaviour of low-permeability layers and their effects on purging and sampling. A lower correlation between low-flow permeability estimations and LeFranc test results was associated with high heterogeneity along the screen, with a longer purging time. In wells P43, MW08 and MW36, due to the presence of clay layers, results obtained differ for almost one order of magnitude and the purging time increases (by more than 16 min). However, with some precautions prior to the field work, the low-flow purging and sampling procedure could become more representative in a shorter time and provide important hydrogeological parameters such as hydraulic conductivity with many tests and high-resolution related results.

Application of High-Resolution Site Characterization for Contaminated Land Investigation

Application of High-Resolution Site Characterization for Contaminated Land Investigation

Introduction to Special Issue on Mine Water Inrushes: Risk Assessment, Mitigation, and Prevention

Water inrush is a hazard that affects safety and production in many coal mines in China. Chinese mining engineers and scientists have made significant progresses in predicting, preventing, detecting, and mitigating this unique water hazard. The approximately 20 papers in this special issue present the latest research results and practices in six aspects: water inrush risk assessment, numerical simulation for water inrush prediction, high-resolution site characterization technique, rapid determination of water inrush point and water sources, early warning monitoring techniques, and engineering measures that have been used to prevent and mitigate water inrush events.

Field evaluation of 1.75 groundwater profiler and field screening device for on-site contamination profiling of chromium(VI) in groundwater

Groundwater contamination by toxic heavy metals pose serious health hazards to humans and the environment. The remediation of contaminated groundwater requires effective characterization of the concentrations and spatial distribution of heavy metals. Groundwater samples from long screening monitoring wells do not provide an accurate representation of the distribution of heavy metals with depth, as the data obtained from the well are an average along the screen length. This study reports the development and application of two new technologies, a direct push 1.75 groundwater profiler (GWP) that obtains groundwater samples from multiple depths in a single push, and a portable field screening device that uses novel disposable sensors to facilitate rapid, cost-effective, on-site detection of heavy metals in groundwater, surface water, and sediment pore water. Extensive fieldwork was performed at a chromium(VI)-contaminated site to evaluate and validate these two technologies for on-site contamination profiling of Cr(VI) in groundwater. A preliminary investigation was performed with an OIHPT logging tool to determine formation lithology and relative permeability for identifying potential groundwater sampling intervals and contaminant migration pathways in the subsurface. Groundwater samples from selected depth intervals were collected and analyzed by an outside laboratory analysis for total chromium and hexavalent chromium as per EPA standards 6020 (SW) and 7196, respectively. The excellent comparison of the field results with the laboratory test results confirm the potential of these technologies in obtaining high resolution site characterization data to improve the management of heavy metal-contaminated hazardous sites.

Evaluation and application of the optical image profiler (OIP) a direct push probe for photo-logging UV-induced fluorescence of petroleum hydrocarbons

The presence of free phase petroleum fuels in the subsurface (often called light nonaqueous phase liquids/LNAPL) is a hazard in almost every town and city in the modern world. Leaking underground storage tanks and the resulting contamination and hazards have proven to be a challenge to investigate and remediate. One issue is adequately characterizing the presence and spatial extent of LNAPLs in the subsurface. Experience has shown that conventional soil coring methods and groundwater monitoring methods are fraught with limitations that can lead to significant errors in the estimation of the amount and spatial distribution of LNAPLs in the subsurface. This leads to the development of inaccurate conceptual site models and costly errors in remedial actions. A new direct push logging tool, the optical image profiler (OIP), has been developed to obtain high resolution site characterization data to more accurately define the presence and extent of LNAPLs in unconsolidated materials. The OIP system uses a downhole ultraviolet light-emitting diode to induce fluorescence of fuel LNAPL. A small complimentary metal–oxide–semiconductor camera mounted inside the probe behind a sapphire window captures photographic images of visible range fluorescence as the probe is advanced by direct push methods. In situ images of subsurface fuel fluorescence have not previously been available to the investigator and may further the understanding of LNAPL behavior. The OIP software also provides a log of percent area fluorescence (%AF) based on analysis of the images. An electrical conductivity (EC) dipole on the probe provides a log of bulk formation EC that is often a good indicator of formation lithology. The information presented here explains the basic design and operation of the OIP system in the field. Bench tests confirm the capability of the OIP system to detect a range of petroleum fuels. Field studies with the tandem EC and %AF logs are used to identify LNAPL and its migration pathways in the subsurface. These capabilities can improve the management and remediation of LNAPL-impacted sites and reduce long-term costs associated with cleanup and closure.

The integrated contaminant elution and tracer test toolkit, ICET3, for improved characterization of mass transfer, attenuation, and mass removal

It is evident based on historical data that groundwater contaminant plumes persist at many sites, requiring costly long-term management. High-resolution site-characterization methods are needed to support accurate risk assessments and to select, design, and operate effective remediation operations. Most subsurface characterization methods are generally limited in their ability to provide unambiguous, real-time delineation of specific processes affecting mass-transfer, transformation, and mass removal, and accurate estimation of associated rates. An integrated contaminant elution and tracer test toolkit, comprising a set of local-scale groundwater extraction-and injection tests, was developed to ameliorate the primary limitations associated with standard characterization methods. The test employs extended groundwater extraction to stress the system and induce hydraulic and concentration gradients. Clean water can be injected, which removes the resident aqueous contaminant mass present in the higher-permeability zones and isolates the test zone from the surrounding plume. This ensures that the concentrations and fluxes measured within the isolated area are directly and predominantly influenced by the local mass-transfer and transformation processes controlling mass removal. A suite of standard and novel tracers can be used to delineate specific mass-transfer and attenuation processes that are active at a given site, and to quantify the associated mass-transfer and transformation rates. The conceptual basis for the test is first presented, followed by an illustrative application based on simulations produced with a 3-D mathematical model and a brief case study application.

The role of geological structure and weathering in contaminant fate and transport in fractured bedrock at two sites in the UK

Case studies are presented of two superficially similar fractured bedrock sites in the UK affected by chlorinated solvents. Site investigation used high-resolution site characterization techniques that have allowed a detailed understanding of the distribution of contaminant mass in the source areas, and the development of advanced conceptual site models at both sites. Differences in the amount of weathering, the geological structural style and the amount of organic carbon present meant that the contaminant fate and transport at each site is completely different. At one site deep, pervasive weathering had increased matrix porosity and permeability, whereas clay-infilled fractures in the underlying fresh shale prevented the contaminants from entering fractures at depth and produced a shallow and relatively short plume. At the second site there were very thin soils over a low-grade slate with almost no weathering, and solvent had penetrated to greater depths and diffused into the matrix. A lack of pore space, carbon and biodegradation has produced a deep, long, fast-moving and highly concentrated plume that is affecting a nearby surface water receptor. The decision to obtain high-resolution structural logging and chemical sampling data was the most important choice in the development of the conceptual site model.

Multi-component digital-based seismic landstreamer and boat-towed radio-magnetotelluric acquisition systems for improved subsurface characterization in the urban environment

It is estimated that urban life will be the norm for around 60% of the world’s population by 2040, leading to a more centralized distribution of people and making the city as the main place of residence (Whiteley, 2009). This population centralization inherently implies rapidly expanding cities and imposes the need for more infrastructure within, around and between the present city boundaries. However, infrastructure projects nowadays have to follow strict civil engineering standards that require detailed knowledge of subsurface conditions during different stages of the construction processes. Since direct methods conventionally used for site characterization (e.g., drilling and/or core testing) are still relatively expensive the focus in the last two decades has been on non-invasive, geophysical methods. However, geophysical site characterization in urban areas is not an easy task owing to numerous challenges and various types of noise sources. Challenges such as electric/electromagnetic (EM) noise, pipelines and other subsurface objects (sometimes even unknown or undocumented), the inability to properly couple sensors because of pavement, traffic noises and limited space are common in urban environment. Since geophysical surveys need to be done with the least amount of disturbances to the environment, residents and traffic, new geophysical techniques for fast, non-invasive and high-resolution site characterization are needed. To overcome some of these challenges, a nationwide joint industry-academia project was launched in 2012 TUST GeoInfra, www.trust-geoinfra.se). As a component in the project, Uppsala University developed two new data acquisition systems. These are a fully digital MEMS-based (Micro-machined Electro-Mechanical Sensor) three component (3C) seismic landstreamer and a boat-towed radio-magnetotelluric (RMT) acquisition system. Both systems were specifically designed to address urban environments with the RMT system particularly aiming at efficient and cost-effective geophysical surveying on shallow-water bodies, which constitute 7% of Scandinavia. In this article, we will describe the two systems and present two case studies illustrating their potential. A number of published accounts are now available from the two systems showing what type of problems they can address (e.g., Bastani et al., 2015; Brodic et al., 2015; Malehmir et al., 2015a, 2015b, 2016a, 2016b, 2017; Dehghannejad et al., 2017; Maries et al., 2017; Mehta et al., 2017; Brodic et al., 2017).

High Resolution Site Characterization as key element for proper design and cost estimation of groundwater remediation

Substantial amounts of money are spent each year on cleaning up ground water contaminations that were caused by historical industrial site activities. Too often, however, remedial objectives are not achieved within the anticipated time frame. Moreover, remedial budgets which were estimated prior to the start of remediation turn out to be largely insufficient to meet the remedial objectives. This situation, very common, creates significant troubles for all the stakeholders involved in the remediation project. The reason for not meeting remedial regulatory closure criteria or exceeding remedial budgets is often due to an incomplete conceptual site model. Having conducted high resolution site characterization programs at numerous sites where remediation was previously conducted, ERM has found several recurring themes: • Missed source areas and plumes; • Inadequate understanding of source area and plume architectures (i.e., three-dimensional contaminant distribution); • Inadequate understanding of the effects of site (hydro)geologic conditions on the ability to access contamination (i.e., via remedial additive injections of groundwater/soil gas extraction). This paper explains why remediations often fail and what the alternatives to prevent these failures (and exceeding remedial budgets) are. More specifically, it focuses on alternative investigation methods and approaches that help to get to a more complete (high resolution) conceptual site model. This more complete conceptual site model in return helps a more focused remedial design with a higher remedial efficiency. As a minimum, it will take away a lot of (financial) uncertainty during the decision making when selecting a remedial alternative. Contaminants that have a greater density then water are known to have a greater complexity in terms of both investigation as well as remediation. Therefore, they will be the main focus of this paper.

Innovative strategies for high resolution site characterization: application to a flood plain

Solving complex hydrogeological problems often requires a thorough understanding of (hydro-) geological subsurface conditions. This is especially true for sedimentary deposits with complex architecture, where lithology and/or hydraulic properties can significantly vary over short horizontal and vertical distances. At these sites, a traditional, solely sample-based investigation approach is often not applicable due to limited data accuracy, resolution, and efficiency. Instead, an adapted investigation approach is required that combines exploration technologies of different resolution and investigation scales. This paper aims to demonstrate the feasibility of such a multi-scale approach for the characterization of a test site near the city of Löbnitz, Germany, that is comprised of heterogeneous alluvial deposits. Our focus is on site characterization in terms of lithology and hydraulic properties, as well as on the delineation and characterization of an aggradated oxbow as a typical example of a small scale geological structure.

Methods for Generating Multi-scale Watershed Delineations for Indicator Development in Great Lake Coastal Ecosystems

Watersheds represent spatially explicit areas within which terrestrial stressors can be quantified and linked to measures of aquatic ecosystem condition. We delineated thousands of Great Lakes watersheds using previously proven and new watershed delineation techniques. These were used to provide summaries for a variety of anthropogenic stressors within the Great Lakes. All delineation techniques proved useful, but each had applications for which they were most appropriate. A set of watershed delineations and stressor summaries was developed for sampling site identification, providing relatively coarse strata for selecting sites along the U.S. Great Lakes coastline. Subsequent watershed delineations were used for high-resolution site characterization of specific sites and characterizing the full coastal stressor gradient. For these delineations we used three general approaches: 1) segmentation of the shoreline at points midway between adjacent streams and delineation of a watershed for each segment; 2) specific watershed delineations for sampled sites; and 3) a Great Lakes basin-wide, high-resolution approach wherein sub-basins can be agglomerated into larger basins for specific portions of the coast. The third approach is unique in that it provides a nested framework based on hierarchies of catchments with associated stressor data. This hierarchical framework was used to derive additional watershed delineations, and their associated stressor summaries, at four different scales. Providing anthropogenic stressor metrics in such a format that can quickly be summarized for the entire basin at multiple scales, or specifically for particular areas, establishes a strong foundation for quantifying and understanding stressor-response relationships in these coastal environments.

Investigation of Hazardous Waste Sites and their Environment Using the BGR Helicopter-Borne Geophysical System

The Federal Institute for Geosciences and Natural Resources of Germany (BGR) completed a research and development project aiming at optimizing its helicopter-borne geophysical system for high resolution site characterization. The overall objective was to adapt the existing helicopter-borne geophysical system used for groundwater and mineral exploration to survey conditions where the anomalies to be recorded are much smaller. The BGR helicopter-borne system permits simultaneous electromagnetic (AEM), magnetic (AMAG), and gamma-ray surveying. At the suggestion of the BGR, the AEM system manufactured by Geoterrex-Dighem, Toronto, Canada, was improved compared with the Dighem III system formerly used. The new system operates at five frequencies and the transmitter and receiver dipole moments are increased up to 25%. In addition, the system is now calibrated during flight. The sensitivity to waste objects was augmented by reducing the sensor heights from more than [Formula: see text] (AEM) and [Formula: see text] (AMAG), respectively, to less than [Formula: see text] about ground level by means of installing a magnetic sensor and a laser altimeter in the AEM bird. Enhanced spatial resolution was achieved by decreasing the sampling distance along line from about [Formula: see text] and by reducing the line separation from about a hundred meters to less than [Formula: see text] due to better navigational and positioning instruments. The modified system was tested over two former military training areas south of Berlin, Germany. Special surveys to locate steel drums, scrap metal, steel pipes, petrol tanks, ordnance, buried at depths from [Formula: see text] were carried out with nominal bird heights of [Formula: see text] and flight-line spacings of [Formula: see text]. Due to the extremely weak AEM and magnetic anomalies produced by these materials, suitable detection algorithms were developed to recognize and to identify these weak anomalies. They were tested using an airborne data set collected over an area where thousands of anomalies had been found. Many of them were subsequently verified on the ground. More than 90% of the anomalies selected for verification could be confirmed either by visual inspection of the ground surface or ground geophysical surveying or excavation. The modified AEM system not only allows better detection of waste but also better investigation of the environment. The AEM data could be reliably inverted to resistivity vs. depth sections using multi-layer inversion procedures. These resistivity data provide information about the hydrogeology and lithology, e.g., the depth of the groundwater table or the distribution of clay and silt. Thus, AEM can be successfully used for the hydrogeological and geological mapping of the near surface.