Academic literature on the topic 'Shallow Bedrock Regions'

The potential for ground water contamination by agricultural chemicals exists in many regions of the world. A collaborative effort between Hungarian and United States scientists has developed a general strategy to estimate the regional vulnerability of ground water to agricultural chemicals. The midwest U.S. and most of Hungary are major agricultural regions with similar hydrogeologic settings. Many areas where ground water provides public drinking water supplies in these regions are vulnerable to ground-water contamination. The vulnerability of shallow, unconsolidated aquifers and thinly-covered bedrock aquifers to agricultural chemicals is being investigated in an initial application of the strategy. This strategy integrates elements of overlay methods of vulnerability estimation, process-based modeling methods, and statistical methods. Strategy steps include: identifying characteristics of ground water needed to classify regional ground water resources; mapping the spatial distribution of aquifer classes (unconsolidated and bedrock) using a regional geographic information system; and estimating the occurrence of agricultural contaminants by applying leaching models to representative conditions in each aquifer class. In the U.S. project, pedologic data bases are being used for both mapping aquifer classes and model input. Estimated vulnerability will be evaluated against data from a regional survey of shallow aquifers recently completed in the Midwest. The Hungarian project is developing new maps of basic hydrogeologic characteristics with data that can be used to model vulnerability of the 1-meter root zone, the unsaturated zone, and the saturated zone.

Glaciotectonic deformation has a large impact on the stratigraphical and lithological variability of Quaternary deposits and the shallow subsurface pre-Quaternary sediments. Mapping of the distribution of glaciotectonic deformation involving pre-Quaternary and interglacial deposits has been carried out, and the density of glaciotectonic deformation analysed, on the basis of data from the well database ZEUS, at the Geological Survey of Denmark. Glaciotectonic deformation is widespread in Denmark. It is recognised in glacial terrains within morphological well-defined glaciotectonic complexes, and in areas with no obvious glaciotectonic related morphology as well as in areas covered with postglacial deposits. The dislocated bedrock is usually not transported for long distances, although rafts of pre-Quaternary bedrock may be transported up to 50 km or more. On a large scale, regions have been located showing high intensity of glaciotectonic deformation. Some of these regions are in good agreement with records from exposures and the geomorphology, others cannot be recognised without well log information.

A compilation of published and new limnological data from 1489 shallow lakes and ponds in northern Canada, sampled between 1979 and 2009, revealed significant patterns that correlated with landscape features and climate. Lakes and ponds underlain by Archean or Proterozoic bedrock had lower specific conductivity and pH. Vegetation cover had a lesser influence on these parameters. Forested landscapes tended to have higher phosphorus and nitrogen, as did younger rock types. Dissolved organic carbon was higher, but dissolved inorganic carbon was lower in forested regions. Phytoplankton biomass of the surface waters, as estimated by chlorophyll a concentrations, was positively correlated with July air temperature and nutrients, and was higher in forested relative to polar desert regions. There were no significant differences in the measured limnological variables between shallow (<2 m depth) and deep lakes (>2 m); however, all water chemistry parameters were negatively correlated with depth. Despite large variability within and among regions, spatial trends in water chemistry were associated with geology, vegetation, and climate at a continental scale.

Abstract. Numerical simulation of glacier dynamics in mountainous regions using zero-order, shallow ice models is desirable for computational efficiency so as to allow broad coverage. However, these models present several difficulties when applied to complex terrain. One such problem arises where steep terrain can spuriously lead to large ice fluxes that remove more mass from a grid cell than it originally contains, leading to mass conservation being violated. This paper describes a vertically integrated, shallow ice model using a second-order flux-limiting spatial discretization scheme that enforces mass conservation. An exact solution to ice flow over a bedrock step is derived for a given mass balance forcing as a benchmark to evaluate the model performance in such a difficult setting. This benchmark should serve as a useful test for modellers interested in simulating glaciers over complex terrain.

Abstract. Numerical simulation of glacier dynamics in mountainous regions using low-order, shallow ice models is desirable for computational efficiency and their capability of including ice dynamics in estimates of mountain glacier wastage worldwide. However, these models present several difficulties when applied to complex topography. One such problem arises where dynamical mass flux over steep topography produces spurious mass at a grid cell flux boundary if upstream cells receive positive mass balance. This paper describes a vertically integrated, shallow ice model using a second order flux limiting spatial discretization scheme that enforces mass conservation. An exact solution to ice flow over a bedrock step is derived for a given mass balance forcing as a benchmark to evaluate the model performance in such a difficult setting. This benchmark should serve as a useful test for modellers interested in simulating glaciers over complex terrain.

In this work we assessed the shallow geothermal heat-exchange potential of a fluvial plain of the Central Apennines, the lower Metauro Valley, where about 90,000 people live. Publicly available geognostic drilling data from the Italian Seismic Microzonation studies have been exploited together with hydrogeological and thermophysical properties of the main geological formations of the area. These data have been averaged over the firsts 100 m of subsoil to define the thermal conductivity, the specific heat extraction rates of the ground and to establish the geothermal potential of the area (expressed in MWh y−1). The investigation revealed that the heat-exchange potential is mainly controlled by the bedrock lithotypes and the saturated conditions of the sedimentary infill. A general increase in thermal conductivity, specific heat extraction and geothermal potential have been mapped moving from the coast, where higher sedimentary infill thicknesses have been found, towards the inland where the carbonate bedrock approaches the surface. The geothermal potential of the investigated lower Metauro Valley is mostly between ~9.0 and ~10 MWh y−1 and the average depth to be drilled to supply a standard domestic power demand of 4.0 kW is ~96 m (ranging from 82 to 125 m all over the valley). This investigation emphasizes that the Seismic Microzonation studies represent a huge database to be exploited for the best assessment of the shallow geothermal potential throughout the Italian regions, which can be addressed by the implementation of heating and cooling through vertical closed-loop borehole heat exchanger systems coupled with geothermal heat pumps.

Abstract This paper presents the selected results of GPR (ground penetrating radar) and ERT (electrical resistivity tomography) surveys carried out on the sites in Poland where shallow karst forms were found in gypsum deposits. The aim of the surveys was the noninvasive detection of karst forms as well as weathered and fractured bedrock which may threaten the stability of the surface and, consequently, may cause damage to buildings, as well as overground and underground infrastructure. The geophysical surveys were conducted at a depth of only a few meters, i.e., to the depth of buildings foundations. GPR surveys were carried out in short-offset reflection profiling mode with standard orientation of the antennae set; however, on one site, different orientations of antennae were tested. During ERT surveys, different measurement arrays were applied in order to analyze which array was optimal for the detection of karst forms as well as weathered and fractured bedrock. Complex interpretation of geophysical surveys resulted in reduced ambiguity and revealed some regions, dangerous for surface stability. Due to the fact that gypsum deposits were investigated to the depth of maximum 10 m; therefore, hydrological processes were analyzed in the paper instead of hydrogeological processes.

Due to high velocity, high frequency and the lack of warning signs, shallow landslides represent a major hazardous factor in mountain regions. Moreover, increasing urbanisation and climate changes triggering intense rainfall events make shallow landslides a source of widespread risk. The interest of the scientific community in this process has grown in the last three decades with the aim to perform robust shallow landslide hazard assessment at regional scale. Generally, these slope failures involve relatively small volumes of material sliding along with a planar shallow rupture surface. In the literature it is widely accepted that shallow landslides involve only slope deposit (or colluvium) and the sliding surface correspond to the discontinuity between bedrock and the overlying loose material. The fieldwork conducted in this thesis highlighted that often shallow landslides involve also the weathered and fractured portion of bedrock. In this framework, the implementation of shallow landslides susceptibility modelling should take into account the engineering geological properties of slope deposits, as well as of the underlying bedrock. In this thesis a fieldwork-based method is proposed to acquire, process and spatialize engineering geological properties of slope deposits and bedrock. The aims of this thesis were to compile a new multi-temporal shallow landslide inventory, characterize the engineering geological properties of slope deposits and bedrock, implement and compare shallow landslide susceptibility modelling by means a physically-based and a data-driven methods and explore the role of bedrock in shallow slope failures. The study area corresponds to a 242 km2 portion of the Garfagnana basin (Northern Apennines), a mountainous region where the elevation ranges between 150 and 2000 m a.s.l. characterized by an incised and rugged morphology with steep slopes (average 28° degrees) and a mean annual rainfall between 1500 and 2500 mm/year. From a geological point of view, the Garfagnana basin is a narrow intra-mountainous valley, interposed betweeen the Alpi Apuane metamorphic complex to the east and the sedimentary northern Apennine’s ridge to the west. The fieldwork and laboratory tasks carried out to map engineering geology characters of slope deposits consisted on a set of hundreds of field sampling points, with the acquisition of depth to the bedrock, geotechnical horizons, unit weight, as well as soil samples for lab analysis. The distribution of points was chosen by observing that engineering geology properties of slope deposits depend on both bedrock lithology and morphometric conditions. In order to obtain the map distribution of engineering geology parameters, we implemented a spatial analysis by clustering morphometric variables stratified as a function of bedrock lithological units. In order to investigate the engineering geology characteristics of the bedrock, a field survey aimed to classify rock masses was conducted. For each survey site, 200-400 Schmidt hammer rebound measures, bedding and joint data, GSI (Geological Strenght Index) and samples for laboratory analyses (unit weight and slake durability test) were collected. The field data were processed and spatially analyzed by means uni-variate and multi-variate cluster analysis in order to delineate domains with different bedrock geo-mechanical properties. The shallow landslide susceptibility analysis was performed using both data-driven, Information Value, and physically-based, a modified version of SHALSTAB model (PROBSS), methods. The numerical modelling faced three issues: a) the comparison of PROBSS and Information value (IV) in the prediction of shallow landslides involving SD; b) the training and cross-validation of IV models using shallow landslides involving bedrock or not; c) implementation of a physically-based model to predict involving bedrock shallow landslides. First of all, the results highlight that the field-based methods proposed here to evaluate engineering geological properties of slope deposits and bedrock are adequate for the implementation of regionalised physically-based susceptibility models. The comparison between PROBSS and IV highlights that the simplification of shallow landslides adopted by the infinite slope model which do not take into account the occurrence of a sliding surface located below the slope deposits / bedrock discontinuity, may affect the performance of physically-based susceptibility models. The accuracy of IV model is slightly better that PROBSS model. Having implemented two data-driven susceptibility models using two different training datasets highlighted the different characteristics that slope deposits and bedrock involving shallow landslides have, suggesting and demonstrating that the latter occur in conditions that the physically based model cannot predict. By placing the slip surface below the discontinuity between slope deposits and bedrock and providing shear strength parameters compatible with a weathered and fractured rock material, satisfactory accuracy result was obtained with PROBSS model.

Among all-natural hazards, earthquakes are the most damaging in terms of loss of lives and damage to infrastructure. Amplification and liquefaction are the major effects of earthquake that cause massive damages to infrastructures and loss of lives. Subsurface soil layers play a very important role in ground shaking modification. These ground shaking modifications when a seismic wave passes through soil are estimated by understanding of site effects. Site effects are the combination of soil and topographical effects, which can modify (amplify and deamplify) the characteristics (amplitude, frequency content and duration) of the incoming wave field. There are two stages of site effect evaluation. First is site characterization which is done by classifying the site based on soil properties. Next step is to estimate amplification of possible motions through these site classes. This is done by amplification factors or site coefficients in various provisions. Widely it has been agreed that site effects/amplification are different for deep and shallow soil deposits. Classifying the sites based on 30 m average shear wave velocity (Vs30) is useful for zonation studies because site amplification factor was defined as a function of Vs30 such that the effect of site conditions on the ground shaking can be taken into account. However, the definitions of site classes in different codes are not consistent. Seismic site classification and amplification for seismic micro zonation are obtained on basis of Vs30 irrespective of bedrock depth in Asia. As shear stiffness and the time period of soil column affect soil response most, parameters representing them are used for classification worldwide. Various codes use shear velocity (Vs) 30 and SPT-N as defining parameter for the purpose. Despite their wide use, the seismic site classification schemes considering top 30-m soil layers are being applied to dissimilar bedrock profile and are under significant research scrutiny. In this study, an attempt has been made to estimate amplification of shallow bedrock sites in Bangalore, Chennai, Coimbatore, and Vizag city in the Intraplate region using most appropriate input parameters. Initially dynamic properties of shallow bedrock sites are estimated by carrying out experimental studies of Multichannel Analysis of Surface Wave and Standard Penetration Test (SPT). Then new shear modulus (Gmax) versus SPT N correlation has been developed to overcome limitations in the existing similar correlations. Further for response calculation purpose, input layer, dynamic model curves and suitable Gmax correlations for different soil types have been identified by parametric study. Finally, a nonlinear site response has been carried out and amplification factors for shallow bedrock sites are estimated and presented in this thesis. In the first part of this work, preliminary site response analysis of hypothetical shallow bedrock sites has been carried out and mismatching of site classification and amplification factor is highlighted. Further, limitation of routinely used shear modulus correlation for stiffness estimation, dynamic models (shear modulus and damping curves), the input level of site response has been highlighted. Characterization of the subsurface and estimation of dynamic properties requires understanding of site effects and amplification. Even though several destructive earthquakes have caused extensive damages in shallow bedrock sites in Peninsular India, which is part of intraplate region, very limited systematic attempt has been made to estimate the dynamic properties of several sites in these regions. Soil dynamic properties in the form of shear wave velocity or shear modulus are required to estimate site effects and amplification. Experimental studies are carried out in shallow bedrock regions of South Peninsular India to obtain shear velocity and SPT N profiles. For these profiles, average 30 m values as per NEHRP and average till soil column, are estimated. It is observed that these values are different than average values up to rock because of inclusion of rock shear wave velocity values of the soil average values in shallow bedrock sites. Hence, 30 m average concept results in stiffer site class than soil average values. Misinterpretation of site class and following NEHRP provisions in shallow bedrock sites can lead to incorrect site coefficients and hence incorrect design force parameters. Literature review shows that several site response studies are being carried out by estimating shear modulus of soil layers considering SPT N values. Even though SPT N data are widely used for site response and seismic micro zonation, very few studies are available for in situ correlation between shear modulus versus standard penetration test (SPT) N values using field experiments. It is found in this study that many of the currently used Gmax correlations are not suitable for a particular soil type. Hence, in this study available correlations between SPT N and shear modulus are compiled and reviewed. New correlations are proposed by combining author’s data with available old data from each researcher separately in two ways (a) using all the data and (b) eliminating assumed and extrapolated data i.e. measured data. This study shows that correlations using measured data are better than correlations using all the data (including extrapolated). Further, another set of correlations is developed by combining three and more data sets by considering all the data and measured data separately. Three and more data combinations give the best correlation when compared to the original independent correlations and two data combined correlations. A new correlation has been developed considering measured, old and new, data from Japan and India, where N values are measured with hammer energy of 78%. Modification factors for old and new correlations are suggested for the other regions, where SPT N values are measured with different hammer energy. Representative evaluation of soil response requires the input parameters to be close to the physical behavior of soil column in the site. Several site response studies are carried out in South India considering limited representative parameters such as intraplate recorded earthquake data, soil specific shear modulus correlation, best soil dynamic model and input layer. Several site response analyses are being carried out using existing few shear modulus reduction and damping curves without knowing their suitability. Similarly, input ground motion for site response is being given at the depth of rock layer or borehole termination depth or 30 m. As per our knowledge, there is no clear cut guideline regarding the use of suitable Gmax correlation for the specific soil column, best shear modulus reduction and damping curves for typical soil and appropriate input layer in the site response study of shallow bedrock sites. As part of this study, an attempt has been made to identify suitable Gmax correlation for different types of soil column such as sand, clay and gravel alone or the mixture of all (sand, clay, gravel, sandy soil). Sites with earthquake data recorded at the surface, soil profiles along with SPT N values and shear wave velocity are selected from K-NET (Japanese website) data set for this study. Collected earthquake data consist of moment magnitude (Mw) of 5.0 to 9.0, which are recorded at different epicentral distances. Site response analysis has been carried out by considering earthquake data recorded at a rock site as an input ground motion to the soil profiles published in K-NET data site. Surface ground motion and response spectrum are obtained from different Gmax correlations. The results obtained are compared with surface recorded earthquake same event. The study shows that peak ground acceleration (PGA), response spectrums (RS) and amplification factor (AF) obtained from very few Gmax correlations are comparable with the recorded PGA, response spectrum and amplification factor. Over the years, several researchers have presented a variation of shear modulus and damping ratio with shear strain for different materials. Of several modulus and damping curves available for different soil type from existing literature, set of curves are selected such that only few input parameters are required to use this curve in site response analysis. Selected curves are then used for representing corresponding soil type in the evaluation of soil response. Soil profiles of sites having a surface and bedrock motion recordings are selected from the Kiban-Kyoshin Network data (KiK-net, http://www.kyoshin.bosai.go.jp/). Site response study has been carried by giving rock recorded data as input and surface response is evaluated for each site by changing modulus and damping curves. The evaluated surface response is compared with recorded data for different soil types. Comparison concentrated to identify the best match regards the shape of spectral curve and PGA value. Based on analysis, appropriate dynamic model curves for each soil type has been identified. Further an attempt is made to identify the input layer shear wave velocity beyond which change in response is insignificant. For the purpose, soil density and modulus and damping curves were kept constant by a parametric study by giving input at recorded level. Using same Kik-net data, site response analysis is carried out by considering constant properties and changing input level. Estimated response by giving input at different depth is compared with original response, the layer in which response changes are considerable is considered as cutoff layer. Shear wave velocity of cut off layer is almost similar in most of profiles considered in the study. This study shows that the input given below the soil layer of having shear wave velocity 500 (±100) m/s and above is predicting response close to recorded data irrespective of the soil type. Parametric study results obtained in this chapter are used as an input / guideline for site response studies of shallow bedrock sites. Shear stiffness of the column above the input level has been estimated using shear wave velocity profiles discussed previously. It is found that few locations do not have Vs profiles, hence few SPT N profiles are selected and added. In total 64 shallow bedrock sites are considered for analysis. In previous studies on subject, for most of the site response analyses was carried out in the intraplate shallow bedrock sites, considering synthetic data or active region ground motion data were considered. In this study, for first time available intraplate data are compiled and acceleration time histories are selected based on regional seismicity. A total of 13 intraplate motions recorded in stable continental regions is selected and baseline corrected. These motions have PGA varying between 0.05-0.17g and is in accordance with the hazard maps suggested for these regions by various researchers. Site response calculations are done using a one-dimensional non-linear approach in DEEPSOIL v5.1 software. Water table information and Index properties in the study are obtained from soil reports for the corresponding bore logs. In total, 832 analysis has been carried out and surface spectral values are compiled. Amplification factors are calculated using Ratio of Response Spectra (RRS) method from the spectral results for different time period ranges. Initially amplification factors are evaluated considering the period ranges 0.1-0.5 and 0.4-2.0 s which are similar to the International Building Code (IBC) and compared. The study shows that IBC period range does capture variation of the spectrum of intraplate shallow bedrock sites. Hence the new period range has been derived by considering spectral signatures of input and surface response spectrum. Amplification factors are calculated for new period range 0.01-0.06 s and 0.05-1.0 s. Significant amplification is observed in 0.05-1.0 s period range and amplification factor corresponding to this range is proposed as a final result. Soil profiles used in the study are grouped as five groups based on the stiffness of the soil column above input based on similarity in spectral signatures. The five groups are G1 with shear modulus <50 MPa, G2: 50-100 MPa, G3: 100-150 MPa, G4: 150-250 MPa and G5: >250 MPa. Average amplification for each group has been estimated and compared with previous studies. This study shows that amplification of short period range is comparable with PGA ratio amplification factor estimated in the region. Spectral amplification for the period range 0.05-1.0 s is less than short period amplification and IBC values. These values are calculated for each stiffness group and are decreasing with an increase in stiffness, with 3.24 for the group with modulus less than 50 MPa to 1.84 for the group with modulus greater than 250 MPa.

Granite underlies substantial areas of Southeast Asia. It forms the core of many of the major uplands. Yet exposures are scarce. High rainfall, consistently high temperatures, and the naturally abundant vegetation have together caused the granite to be deeply weathered. Most of the land surface is underlain by a more or less thick mantle of weathered rock or regolith. Only where the regolith has been removed by natural agencies, for example on some hill crests and steep midslopes, in river channels, and in coastal areas, is the bedrock naturally exposed, though road cuttings, quarries, and other artificial excavations provide excellent sections. Anthropogenically induced and accelerated soil erosion have also revealed bedrock morphology in places. The granitic terrains consist essentially of high ridges rising abruptly from the valley floors or adjacent plains. In detail, slopes, river channels, and rocky coasts strewn with granite blocks and boulders are characteristic of the region, and the nature of granite weathering has also influenced the character of the sediment load transported to rivers and coasts. Though the granites of Southeast Asia are well documented geologically and as sources of tin and other minerals, there are few modern accounts of their geomorphological aspects. Early travellers like Logan (1848) made astute observations relevant to the development of granitic forms, and the officers of the geological surveys of Malaya and, later, of Malaysia have, taking their lead from the first director onwards, noted salient features of the granitic terrains they mapped. These observations and interpretations, taken together with the few specifically geomorphological studies of particular features, and analyses of granitic landforms in other countries, permit the granitic terrains of Southeast Asia to be placed in context. Granitic rocks are widely distributed in Southeast Asia, particularly in the mainland states (Hutchison 1989). Those of the Malay Peninsula were emplaced at various depths: shallow epizonal, deep catazonal, but mostly mesozonal emplacement at 5–11 km depth. In plan, granites are widely distributed (Gobbett and Tjia 1973; Chinese Geosciences Research Institute 1975; UNESCO 1980). In the Malay Peninsula, granites occupy the cores of major regional anticlines, and many plutons are exposed in the breached crests of such structures.

The N end of the city’s plateau zone E of G St, bounded by the N wadi, the river cliff, and the head of the inner wadi, comprising the remotest corner within the walls, also became part of the Roman military quarter. Here, as across the whole N part of the city, the stratigraphy is shallow, rarely deeper than a metre, with bedrock showing in places. Surface indications and magnetometry suggest that much of the region had been built up in pre-Roman times, although there may have been areas of open ground. The street grid had been substantially laid out here, especially H St which ran to the N city wall, but E of this line it seems partly to break down. In particular, in the nominal areas of projected block positions X1–X8, 10th St actually curved off-grid to the S, probably preserving the line of an early approach road to the N end of the Citadel before the stronghold was separated from the plateau by a great quarry and rebuilt. This far N region was presumably mostly residential before AD 165, except for two known sanctuaries beside H St: the so-called Dolicheneum in X7, and a temple of unknown dedication in X9. Under Roman rule it became dominated by insertion of the massive residence known as the ‘Palace of the dux ripae’, here referred to as the Roman Palace. Closures of both G and I Sts on the N side of 10th St, by the building of Roman structures across them, indicates that the zone N of this line became a military enclosure. This was accessible from the civil town only via an entrance on H St, and from the W part of the base area on the plateau, already enclosed by a boundary along the W side of G St, via a smaller entrance on the diverted line of ‘12th St’ at the N-most point of block E3. Within the re-entrant to the continuous base perimeter created by the G St and 10th St lines, more blocks appear to have been taken over by the military.

The Low Level Waste Repository (LLWR) is the UK’s principal facility for the disposal of solid low-level radioactive waste and is operated by LLW Repository Limited. Presently, LLWR Ltd is establishing the long-term environmental safety of disposals of solid radioactive waste at the LLWR, through the submission of the 2011 Environmental Safety Case for the LLWR. This Environmental Safety Case addresses the Environment Agency Guidance on Requirements for Authorisation. Aspects of the submission consider improved vault design, closure design, and quantitative assessments. Each of these issues requires an understanding of the movement of water through the facility and the surrounding geology during operations and following facility closure. Groundwater flow modelling has been used extensively in support of the interpretation of field investigations, the development of the engineering design, and an assessment of the groundwater pathway as one of the major pathways by which contaminants may reach the environment. This paper describes these important aspects of the Environmental Safety Case. The geological environment in the region of the LLWR consists of Quaternary age deposits overlying older bedrock. The facility involves shallow excavations into the Quaternary deposits, originally for trenches, with disposals to a vault system beginning in 1988. In the post-closure phase these disposals are covered by a cap and surrounded by a cut-off wall to minimise the water flow around or through the waste. An innovative modelling methodology has been developed to represent the range of scales that have to be considered from the regional groundwater flow patterns over several kilometres, the scale of tens of metres around the immediate site area, and down to about 1 metre for details of flows within the repository itself in three dimensions. Detailed finite-element models of the flow through geological media and the engineered features are used to interpret site data and assess a credible set of post-closure situations and model cases. In the radiological assessment, a more simplified compartment model is used to assess uncertainties in hydrogeological properties and the long-term evolution of the engineered barriers. Together the approach provides flexible tools for understanding and assessing a comprehensive range of aspects including details of flows within the repository, dilution and migration in the external geology, the long-term evolution of the hydrogeological system, the implications of spatial variability and alternative geological models, and effects of uncertainties.

Abstract A slope failure compromised the integrity of a critical stormwater storage facility at a petroleum storage terminal within northern Alberta. Through periodic ground inspections and a review of LiDAR and aerial imagery, significant lateral deformation of a lined stormwater pond was identified. The potential for pond overflow and uncontrolled stormwater release into the natural environment due to compromised discharge outlets and liner integrity posed an operational and environmental risk. A fast-tracked review and assessment of both the historical and as-built construction details, a good understanding of the regional geology, and geotechnical investigation and instrumentation were required to identify remedial measures that could be implemented to restore the pond prior to the onset of major storm events. Geotechnical investigation and assessment showed weak zones in the bedrock at shallower depths than were historically encountered at the site. Spatial constraints, uncontrolled fill placement in close proximity to the pond, expansion of the pond following original construction, and compromised subsurface drainage were identified as factors that may have contributed to the failure. Assessment of remedial options considered impacts relative to both local and global factors of safety. The selected remedial option was a combination of slope unloading, shear key construction, and improved drainage with the design and construction occurring within a timeframe of 3 months to minimize the time that the pond was out of service. The paper highlights the challenges associated with the slope unloading and shear key construction that were required to control the ground movements. An approach involving sequential excavation and replacement was adopted to manage the risks associated with shear key construction. In addition, directional drill methods were incorporated to install some of the drainage measures due to the risk associated with an open cut approach. The project was fast-tracked to minimize exposure to high precipitation and limited stormwater storage capacity.

Preliminary surficial geology studies, based on air photo interpretation and limited legacy field data in the Brichta Lake map area, provide an understanding of the distribution and nature of surficial materials, and regional glacial history. The terrain is characterized by extensive glacial and meltwater scouring that has affected bedrock outcrops, and eroded hummocky and streamlined till, till blankets, and till veneers in the southwest regions. Streamlined bedrock and till landforms indicate ice flow towards the northwest and north-northwest during the last glaciation. Subglacial meltwater corridors and broader erosional zones, trending north-northwest, consisting of eskers, washed till veneer, ridged till, and scoured bedrock, result from late-phase ablation of the ice sheet during deglaciation. Glaciomarine and postglacial marine sediments extend discontinuously inland from the Queen Maud Gulf to 200 m a.s.l. elevation, notably up Tingmeak and Ellice rivers and their tributaries. In some eastern parts of the map area below 160 m a.s.l. elevation, thick marine deposits form plains that blanket broad shallow valleys.

A hydrostratigraphic framework has been developed for southern Ontario consisting of 15 hydrostratigraphic units and 3 regional hydrochemical regimes. Using this framework, the 54 layer 3-D lithostratigraphic model has been converted into a 15 layer 3-D hydrostratigraphic model. Layers are expressed as either aquifer or aquitard based principally on hydrogeologic characteristics, in particular the permeability and the occurrence/absence of groundwater when intersected by a water well or petroleum well. Hydrostratigraphic aquifer units are sub-divided into up to three distinct hydrochemical regimes: brines (deep), brackish-saline sulphur water (intermediate), and fresh (shallow). The hydrostratigraphic unit assignment provides a standard nomenclature and definition for regional flow modelling of potable water and deeper fluids. Included in the model are: 1) 3-D hydrostratigraphic units, 2) 3-D hydrochemical fluid zones within aquifers, 3) 3-D representations of oil and natural gas reservoirs which form an integral part of the intermediate to deep groundwater regimes, 4) 3-D fluid level surfaces for deep Cambrian brines, for brines and fresh to sulphurous groundwater in the Guelph Aquifer, and the fresh to sulphurous groundwater of the Bass Islands Aquifer and Lucas-Dundee Aquifer, 5) inferred shallow karst, 6) base of fresh water, 7) Lockport Group TDS, and 8) the 3-D lithostratigraphy. The 3-D hydrostratigraphic model is derived from the lithostratigraphic layers of the published 3-D geological model. It is constructed using Leapfrog Works at 400 m grid scale and is distributed in a proprietary format with free viewer software as well as industry standard formats.

Over six linear miles of shallow acoustic reflection geophysical data were collected in an 800 ft by 300 ft survey region at Ogdensburg Harbor, Ogdensburg, NY. To better accommodate modern commercial vessels and expand the harbor’s capacity, the current navigable depth of -19 ft Low Water Depth (LWD) needs to be increased to -28 ft LWD, and an accurate map of the nature of the riverbed material (e.g., unconsolidated sediment, partially indurated glacial till, or bedrock) is required to effectively plan for removal. A total of 28 boreholes were previously collected to map the stratigraphy, and the effort revealed significant spatial variability in unit thickness and elevation between adjacent boreholes. To accurately map this variable stratigraphy, chirp sub-bottom profiles were collected throughout the region, with an average line spacing of 13 ft. These sub-bottom data, validated and augmented by the borehole data, resulted in high-resolution spatial maps of stratigraphic elevation and thickness for the study area. The data will allow for more accurate assessment of the type and extent of different dredging efforts required to achieve a future uniform depth of -28 ft LWD for the navigable region.

Offshore wind farms typically host tens to hundreds of turbines that are individually sited on foundations or anchored if floating. These are connected by inter-farm cables which feed into one or more marine-based substations, further feeding one or more shore-connected high-voltage cables - all infrastructure that requires knowledge of water depth, metocean conditions, and seabed/subsurface geology. With this industry set to establish itself on the continental shelf of Atlantic Canada, knowledge of the geological conditions from the seabed to tens of metres below will be essential for farm layout and foundation design. Thus, geoscience questions addressing regional geomorphology, Pleistocene glacial retreat and sea-level change, the characteristics of key individual stratigraphic layers, and the magnitude and patterns of sediment mobility are important. In Atlantic Canada, ongoing efforts to address these questions are using legacy data, but new data is required to further our understanding of the shallower portions of the shelf. Examples include: what is the distribution of buried tunnel valleys under offshore banks, and might their complex facies infill affect foundation conditions? How and where would the organic sediments, left by a coastal suite of landforms drowned during transgression, affect foundation or landfalling cable stability? How active is salt diapirism, and could it be considered a geohazard? Are demonstrated sediment mass failures also a risk? What is the current understanding of sediment mobility in shallow waters, and how does that affect infrastructure armouring/depth of burial? What is the variability of the geotechnical properties of our offshore sediments? What is the foundation suitability of offshore Tertiary semi-consolidated bedrock? To conclude, the initial scope of a developing regional foundation suitability model will be presented for the Eastern Scotian Shelf.