investigating the scale of heterogeneity and...

INVESTIGATING THE SCALE OF HETEROGENEITY AND IMPLICATIONS

FOR NITRATE TRANSPORT, ABBOTSFORD-SUMAS AQUIFER, BRITISH

COLUMBIA AND WASHINGTON STATE

Romain Chesnaux, Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada Sarah McArthur, Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada Diana Allen, Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada Jacek Scibek, Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada ABSTRACT This study investigates the scale of heterogeneity present in the Abbotsford-Sumas aquifer, BC and WA, through the use of ground penetrating radar (GPR) surveys and borehole geophysical logs, and provides preliminary results on nitrate transport modeling. The borehole logs suggest that there are layered fining-upward sequences within sand and gravel on the scale of 3 to 10m. The GPR cross-sections show layering that extends laterally from

in recent years (Sutherland personal communication), nitrate concentrations in the aquifer have not dropped.

The Abbotsford-Sumas aquifer is 160 km2 in area and is a source of water for approximately 120,000 people. The aquifer is located on a broad outwash plain, which is elevated above the adjacent river floodplains. The uplands are centered on the City of Abbotsford, BC and extend westward through Langley, BC and south to Lynden, WA. The coastal climate is humid and temperate, with 1000 to 2100 mm mean annual rainfall over most of the year. Recharge to the aquifer (900 to 1100 mm) is primarily from direct precipitation, mostly from October to May (Scibek and Allen 2006).

Liebscher et al. (1992) determined that in the southern part of the aquifer, groundwater generally flows from north to south, with local variation. There is minimal vertical flow within the aquifer, except in the near surface through direct recharge. This general flow direction was confirmed through numerical modeling (Scibek and Allen 2005), although heterogeneity of the surficial sediments was observed to redirect groundwater locally, particularly around streams. Groundwater discharge occurs through spring flow and seepage to small streams and rivers. The largest rivers, which are hydraulically connected to the aquifer system, are the Nooksack River and the Sumas River. To the north is Fraser River floodplain, where a small component of groundwater discharge occurs.

Figure 1: Location of the Abbotsford-Sumas aquifer in the Lower Fraser Valley. The PARC site and the gravel pit, and the regional and local model domain boundaries are shown. The aquifer is comprised of coarse-grained sediments of glaciofluvial drift origin (11,000–10,000 B.P.), primarily uncompacted sands and gravels of the Sumas Drift, with lenses of sand, silt, and clay (Armstrong et al. 1965). The hydrostratigraphic units are highly heterogeneous as evidenced by the lithologies encountered and logged during drilling. This heterogeneity can be expected to result in complex groundwater paths both at a regional scale and at a local scale.

The aquifer is known to reach depths of 70 m (Liebscher et al. 1992), and it is thickest in the northeast where glacial terminal moraine deposits are found. Laterally, the valley sediments are confined by the Tertiary bedrock surface, which outcrops as mountains on both sides of Sumas Valley, and as small outcrops south of Nooksack River. The aquifer is underlain by an extensive glaciomarine deposit, the Fort Langley Formation, which outcrops in the uplands to the west. The distribution of unconfined and confined portions of the aquifer will have bearing on the distribution of nitrate contamination as confining units tend to protect underlying units from surface contamination. This study attempts to use a combination of borehole geophysical logging and ground penetrating radar (GPR) surveying, constrained by geological interpretations, to facilitate the interpretation of aquifer architecture heterogeneity, which may influence nitrate transport. Two preliminary modeling studies are then undertaken to investigate how heterogeneity may 1) impact nitrate transport through the vadose zone, and hence, nitrate loading to the aquifer, and 2) impact nitrate transport within the saturated aquifer at a larger scale. 2. GEOPHYSICAL SURVEYING 2.1 Site Description All of the geophysics testing was completed at the PARC site in Abbotsford, BC. The PARC site is approximately 200 m by 400 m, and is used for test crops. As part of its monitoring program, Environment Canada installed 10 piezometers at this facility (Fig. 2); these piezometers range in depth from 19.4 m to 46.4 m, with an average depth of 27.9 m. The site was chosen primarily due to the ease of access, but also because there is increased nitrate contamination within the aquifer in this area (McArthur and Allen 2005). The field work was completed during summer 2005. Water levels in the piezometers were measured during both field work excursions. An abandoned gravel pit, located 200 m to the south of the PARC site (see Fig. 1), was also visited in order to investigate the local geological framework.

Figure 2: Site map showing the locations of the GPR lines and the nested piezometers. The black square on Line 1 indicates the location of the CMP survey midpoint.

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2.2 Borehole Logging Natural-gamma and electrical conductivity logs were completed for all piezometers at the site except for CDA2 (see Fig. 2 for locations). The logs were collected using a Mount Sopris MGX-II portable digital logger, including a 305 m winch, a 2PGA-1000 gamma tool, and a Geonics 2PIA-1000 electromagnetic induction (conductivity) tool. The natural-gamma logs were collected at 2.75 m/min in an upwards direction, with a sampling interval of 0.005 m. The data were filtered using a 21-point moving average filter. The conductivity logs were collected at 2.75 m/min in an upwards direction, with a sampling interval of 0.01 m. No processing was completed for the conductivity logs. Figure 3 shows the gamma logs arranged in profile for piezometers 91-4, 91-5 and 91-7. Gamma counts, ranging between 20 and 50 cps below the soil layer, indicate that there are predominantly sands and gravels around the piezometers, which is consistent with the limited lithology data collected from the boreholes during drilling. Vertical heterogeneity is defined primarily by fining upwards sequences within the sands and gravels, which tend to be repeated on a scale of 3 to 10 m. There are also sudden shifts in the gamma counts (either up or down), suggesting the presence of erosion surfaces or scour and fill features, consistent with the depositional environment (Clague personal communication). Coarsening upwards sequences do appear within the logs, however, they are not as common as fining upwards sequences. Below the water table there is an inverse relationship between conductivity (not shown) and natural-gamma values, suggesting that the coarser-grained sediments conduct electric current more readily.

Figure 3: Natural gamma logs from piezometers 91-7, 91-5 and 91-4. Layers are often characterized as fining upwards on a scale of 3 to 10m. Layers are laterally correlated at a scale of approximately 10m. Based on the cross-section (Fig. 3), heterogeneity also exists laterally, on a scale of up to 10 m, the limit imposed by the piezometer separation. To investigate whether this heterogeneity can be extended beyond the nested

piezometers and across the site, GPR surveys were conducted. 2.3 Ground Penetrating Radar The GPR data were collected using a Sensors & Software pulseEKKO 100 GPR unit with 100 MHz and 50 MHz antennas. The GPR lines were oriented such that they passed by the wells as closely as possible, but due to rows of raspberry bushes, they were generally restricted to the grass roadways between the test plots (see Fig. 2). Both common-offset and common-midpoint data were collected. A common-midpoint survey was conducted first along Line 1 at both 100 MHz and 50 MHz antenna frequencies. The initial separation between the antennas was 0.2 m, with an increase in separation of 0.2 m for each subsequent measurement. Common offset surveys were conducted at both 100 MHz and 50 MHz antenna frequencies along 7 lines. The lines formed a grid, and line spacing was variable, but up to 190 m apart. The antenna separation was 1 m (based on the results of the CMP survey), with a station spacing of 0.2 m for the 100 MHz antennas. For the 50 MHz antennas, the separation was 2 m, with a station spacing of 0.4 m. The data were processed using the software ReflexW (Sandmeier 2005). Figure 4 shows a 165m long section corresponding to Line 2. The top section shows the 50 MHz data, and the bottom section, the 100 MHz data. All of the GPR sections show a very strong reflector between 320 and 370 ns, which is interpreted to coincide with the water table, based on measured water table elevations at the site at the time of the survey. This provides a velocity of 0.105 m/ns for the unsaturated aquifer material, which is typical of partially saturated sands. This velocity is similar to the unsaturated zone velocity determined by Irving and Knight (2003).

Figure 4: GPR data collected along Line 2. a) 50 MHz, b) 100 MHz. Some of the visible reflectors are indicated by white arrows. WT is water table reflector. Piezometer locations from Figure 3 also shown. The GPR sections also show the same types of reflectors. These are generally hummocky to chaotic in

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nature, with diffractions occurring predominantly close to the ground surface (Beres and Haeni 1991). The hummocky configuration is dominant, suggesting that the formation is comprised of bedded sands and gravels. In areas where it is more chaotic in nature, sand and gravel cross-bedding is likely present, with diffractions caused by boulders, as seen in the gravel pit (Fig. 5). The hummocky reflectors are generally horizontal and parallel to sub-parallel. The majority of the reflectors are not laterally extensive, extending no more than 10 m to 15 m along the cross-section. Other reflectors are much longer, extending up to a few hundred meters. Two shaded areas are shown on Figure 4, which represent the layering identified at the piezometer scale (see Fig. 3). The photo from the gravel pit (Fig. 5) similarly shows distinct layers of coarser and finer material. The thickness of the sand and gravel units ranges from 20 cm to approximately 3 m. These layers are laterally continuous, from several meters up to greater than the extent of the photo. Overall, the scale of the heterogeneity present vertically and laterally at this gravel pit is consistent with the results of the borehole geophysics and the GPR surveying. Where the borehole geophysics is able to resolve the finer-scale vertical heterogeneity, only broad layering can be detected using GPR. 2.4 Implications for Nitrate Transport In the borehole logs, vertical heterogeneity is present as repeating fining upward sequences on the order of 3 to 10 m. Some of the fining upward sequences appear to be laterally continuous from one piezometer to the next over a distance of 10 m, and the GPR surveys indicate that bedding extends from a few meters to several hundred meters; well within the scale of the site. Therefore, at a site scale (less than a few hundred metres) the lateral continuity of coarser beds should reasonably be taken into account, as these may provide permeable pathways for nitrate transport. However, the ability of the GPR to resolve these units at this particular site was limited.

Figure 5: Photo from gravel pit excavation showing layers of coarse sand and gravel (1), medium to coarse sand (2), bedded gravel with sand and large cobbles (3), medium sand (4), talus (5). At a larger scale, extending perhaps several hundred meters to kilometres beyond the site, it is unlikely that these sequences are laterally continuous, nor resolvable. Therefore, for transport modeling, it is unlikely that the bed scale heterogeneity could be represented. The most appropriate approach to modeling, therefore, is to consider the aquifer media homogenous (and perhaps anisotropic), and to represent the aquifer with bulk hydraulic properties, recognizing that model calibration to

observed nitrate concentrations may be somewhat poor due to local heterogeneity effects. In order to model nitrate transport, it is necessary to consider both the vadose zone and the saturated zone. In the vadose zone, water and dissolved nitrate infiltrates slowly, and moves in a predominantly vertical (downward) direction. The rate at which the groundwater infiltrates is dependent largely on the hydraulic conductivity of the sediments. Clearly, the nature of the layering within the vadose zone, as defined by the fining upwards sequences and the respective hydraulic properties, cannot be characterized spatially across the aquifer. In areas of relatively shallow water table depth, it might be anticipated that only one, or perhaps two, of these sequences would be encountered, offering a range of grain size. As the water table deepens, additional sequences would be encountered. Therefore, groundwater flow and nitrate transport could be potentially quite variable depending on the water table depth and the range of grain size of the vadose zone sediments. A series of simulations were thus carried out to investigate the effect of grain size range and water table depth. This paper focuses on the grain size results. In the saturated zone, groundwater flow is in a predominantly horizontal direction (note that there is a substantial horizontal gradient in most areas of this aquifer), and the effects of vertical heterogeneity will be less pronounced in comparison to the lateral continuity of any heterogeneities. For example, groundwater can be anticipated to move quickly though coarser grained horizons, with these possibly acting as permeable pathways for nitrate transport. Similarly, the finer grained lithologies will result in slower transport. Therefore, in undertaking nitrate transport simulations within the saturated zone, the presence of laterally continuous geologic units should be taken into account if the scale of the heterogeneity is appropriate to the scale of the model. For example, for a site scale model, it may be possible to resolve the layering and capture this in the model. In contrast, for regional and local scale models, capturing this heterogeneity is problematic because the beds cannot be tracked any further than a few hundred metres. One possible way to overcome this problem is to invoke anisotropy, in an attempt to simulate the effect of the layering. Thus, a series of simulations were undertaken to assess the effect of vertical anisotropy on transport times, and compare the results to ages of the groundwater determined from 3H/3He age dating. 3. VADOSE ZONE MODELLING 3.1 Background The growing season occurs mainly in spring and summer, i.e., from April to September. This period also corresponds to the dry season when the evapotranspiration rate is greater than the precipitation rate. This situation means there is no infiltration, and even a water content depletion in the soil and the upper part of the vadose zone. In contrast, the fall and winter rains are

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vigorous within the Lower Mainland, and growth of raspberry plants is very slow to dormant. This means that all nitrates available in the fall will likely be flushed down into the aquifer and, by spring, will no longer be present in the surface soil profile. The common thinking has been that the nitrate flushes right through the unsaturated zone and into the saturated zone each year, thereby contributing to groundwater contamination. A study by Chipperfield (1992) has verified the downward movement of soil nitrate as the fall rains increase in October. Although a detailed recharge analysis has been undertaken for the Abbotsford-Sumas aquifer (Scibek and Allen 2006), a simple water balance approach has been used here. The climate data were extracted from measurements of precipitation and evapotranspitration at the Environment Canada Climate Station situated at the Abbotsford International Airport (www.farmwest.com). The monthly values are an average for years 2000 to 2003. Infiltration (Fig. 6) was determined as the difference between precipitation and evapotranspiration, which assumes there is no runoff, a reasonable assumption for this aquifer. Figure 6 shows that the infiltration from precipitation occurs only during the fall/winter season. It also illustrates that irrigation is necessary during the spring/winter season (May to September) to avoid a depletion of water in the soil.

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Figure 6: Annual infiltration rates for the AB-S aquifer 3.1.1 Residual Nitrate Concentration Most growers use split fertilization of inorganic nitrogen. The Berry Production Guide (BPG) recommends that growers apply nitrogen in early April and again in early May with 50% of the total applied each time. The growers use manure and fertilizer. The raspberry growers use a total of 80 to 100 kg of applied N (Mouritzen 2000; 2001; 2002; 2003), even though this is the high range that is recommended by the Berry Production Guide (BCMAFF 2002/2003). A survey of residual soil nitrate in raspberry fields (Mouritzen, 2000; 2001; 2002; 2003) has consisted of measuring the residual nitrate concentrations in the soil (first meter of soil) after the growing season, and before the significant rainfall of October for the years 2000 to 2003. The reports show that an average of 40 ppm (mg/L) of NO3-N can be considered for the 4 surveyed years

when taking into account both manure and fertilizer practices. 3.2 The Approach The premise for this study is that fertilization occurs primarily at the beginning of the growing season, and that plant uptake occurs during the growing season, leaving some finite residual amount of nitrate in the soil. Residual nitrate concentrations obtained at the end of the growing season (in September), which are thought to be representative of the area, are generally available for the area. Over the balance of the year (October to March), this residual nitrate is available for leaching into the vadose zone. This fall / winter period has intense precipitation and, consequently, infiltration, thereby increasing the nitrate leaching. Considering the fact that nitrate leaching is thought to occur mainly after the growing season, and because of the lack of data for irrigation and plant uptake during the growing season, the approach used in this preliminary study considers only nitrate transport during the fall /winter season. Therefore, knowing the residual nitrate concentrations in the soil, as a first approximation, the nitrate mobility following the growing season can be investigated. Possible limitations to this approach are that it does not account for: 1) leaching of nitrate during the summer months due either to natural precipitation (here assumed to be in deficit over the summer), 2) the potential role of irrigation during the summer, which may act to mobilize nitrate below the root zone, and 3) continued nitrate uptake by the plants in the fall (which is likely not a factor). The codes used for this study are SEEP/W for water seepage and CTRAN/W for contaminant transport (Geo-slope International 2002a; 2002b). CTRAN/W is coupled with SEEP/W. The robustness of the flow model (SEEP/W) has already been assessed by a number of researchers and practitioners. The conceptual model is a vadose zone, which consists of two homogeneous layers (the soil and the vadose zone of the aquifer). The water table is considered to be at elevation zero. The material consists of sand and gravel of porosity 40%. Grain size was measured on samples collected during drilling of a well close to the PARC site. The maximum (Kmax = 4.46×10-2 m/s) and minimum (Kmin = 6.20×10-4 m/s) saturated hydraulic conductivity, predicted from a grain size analysis, were used for each of two the simulations to illustrate the effect of grain size on nitrate leaching. The volumetric water content and hydraulic conductivity curves of the aquifer are computed directly within SEEP/W. A first boundary condition consists of applying, at the soil surface, a recharge function as a flux (calculated from Fig. 6), which corresponds to a monthly precipitation rate expressed per day for October to April. A second boundary condition is the water table, which is defined as a surface where the water pressure is zero. For these simulations, a water table depth of 5m was used.

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However, additional simulations have been undertaken for different water table depths. The initial condition is taken as a situation where the volumetric water content profile is at equilibrium. A constant concentration of 40 ppm is applied within the upper 1m of soil as an initial condition. Longitudinal and transversal dispersivities are defined at 10 cm and 1 cm, respectively. The diffusion is considered negligible. No decay and no adsorption of nitrate have been considered. 3.3 Modelling Results Figures 7 and 8 show the nitrate profiles (versus time and depth) simulated with Kmax and Kmin, respectively, for a 5 m deep water table. In both cases, it appears that nitrate is flushed to the water table during fall. For the Kmax case, the maximum concentration arriving at the water table is 11.4 ppm after two weeks of leaching (Fig. 7), whereas for the Kmin case, the maximum concentration arriving at the water table is 8.4 ppm (after 6 weeks of leaching). Thus, even in unsaturated conditions, the material remains so permeable that complete leaching rapidly occurs. Note that the time for leaching depends on the depth of the water table (not shown). However, even with the water table at a depth of 30 m, the entire amount of nitrate is leached within the fall/winter seasons.

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The difference between the maximum concentrations obtained for the two cases illustrates the effect of grain size on nitrate leaching within the vadose zone. The finer the material, the higher will be its capability to retain water. Therefore, the nitrate dilution in the front of infiltration will be greater when encountering pore water during leaching. 4. SATURATED ZONE TRANSPORT Previous research led to the development of a regional scale three dimensional groundwater flow model for the Abbotsford-Sumas region (see Fig. 1 for regional model boundary). The model domain boundary was approximated from regional surface water divides and bedrock boundaries. Surface water features, such as streams, lakes and the gravel pit, were represented by either specified head or drain boundary conditions. Recharge was mapped spatially. A comprehensive study was undertaken to determine the hydrostratigraphy for the model using geologic maps and reports, geophysical data, scientific papers, and lithologic data from two water well databases comprising several thousand well records, thus capturing a considerable degree of heterogeneity in the various geologic units. Details concerning model construction and calibration can be found elsewhere (Scibek and Allen 2005). As part of this study, a local model was developed to specifically examine the area surrounding the PARC site. The boundary for the model (see Fig. 1) was based on groundwater divides and equipotential lines from the regional model. All other model parameters remained the same as in the regional model. The calibration of the model was also verified. 4.1 Sensitivity Analysis Although some degree of vertical anisotropy was captured in the original regional scale model, it was uncertain how sensitive the model was to anisotropy and heterogeneity, particularly in regard to nitrate transport. In order to determine the sensitivity of the model to the conductivity anisotropy and heterogeneity, a sensitivity analysis was completed. As a first step, this involved varying the hydraulic properties of the various aquifer units and determining their effect on the model calibration. Sixteen different conductivity configurations were examined. For each, MODFLOW and Zone Budget were run, providing both normalized root mean squared error (NRMS) and water balance (WB) computations. Several of the calibration scenarios produced NRMS values that are marginally lower than in the calibrated scenario (NRMS=9.635, WB= -2.66%). These all occur in scenarios where the hydraulic conductivities become either increasingly isotropic or homogeneous, or both. However, in many of these scenarios the water budget was very poor. Based on the complexity of the geology in this aquifer, it is unreasonable to expect that an increasingly isotropic and homogeneous model provides a realistic representation of the hydrostratigraphy.

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The best scenario (based on NRMS and WB) corresponded to the case where the Kz value of the sand and gravel units had an anisotropy factor of 20× (Khoriz/Kvert). The glaciomarine clays, which outcrop to the east of the glacial outwash and underlie the outwash, had small to no anistropy. This resulted in a very small increase in both the NRMS and the WB. In effect, this anisotropy ratio is thought to reasonably represent the range of particle sizes observed in the fining upwards sequences. 4.2 Particle Tracking For each scenario, particle tracking was completed to determine the effect of changing Kz on the travel length, time and velocity of particles placed within the model. The particles were placed around piezometers for which isotopic ages had been determined (Wassenaar et al. 2006), so that these ages could be compared with travel times determined from the numerical modeling. Eleven piezometers were identified within the model area that had isotopic ages (Fig. 9). A circle of 10 particles was placed at a 1 m radius around the piezometers at the average screen depth for each piezometer. There are 4 different sets of clustered piezometers, with either 2 or 3 piezometers within a cluster.

Figure 9: Location of piezometers with particles and pathlines. MODPATH was run for each of the scenarios with backwards tracking particles to determine the lateral path distances and minimum velocities (thus, age) for all of the particles. The particle pathways for the best scenario are shown in Figure 9. In general, for the shallow wells (less than 5 m below the water table) changing the anisotropy had little affect on the travel time or length of the particle pathway. For particles placed at the deeper wells, there was a substantial change in the travel time and path length when the anisotropy was increased. The resulting particle velocities in these scenarios showed substantial decrease as the anisotropy increased. When the

anisotropy was decreased, there was little change in the travel time; however, the pathway lengths generally increased, resulting in an increase in the velocity of the particles. 4.3 Comparison of Model Ages to Isotopic Ages For each model scenario, the ages of the particles were plotted against isotopic ages determined by Wassenaar et al. (2006) using 3H/3He dating techniques (Fig. 10). The points with high isotopic ages (open circles), correspond to particles tracking back from the piezometers at the western edge of the model and that prematurely terminate at the model boundary. Thus, these particles were excluded from the trend line.

Figure 10: Graph of model age and isotopic age for best scenario. In all 17 scenarios that were run, there was a consistent underestimation of the age of the water particles, as compared with the isotopic ages. The model ages were generally between 60 and 80% of the isotopic ages. This discrepancy may be explained by the fact that the model is unable to account for tortuous pathlines. 5. CONCLUSIONS The borehole logging data show evidence of fining upwards sequences, occasional fining downward sequences, and abrupt changes in grain sizes. Some of the fining upward sequences appear to be laterally continuous from one piezometer to the next, over a distance of 10 m. The fining upwards sequences repeat vertically on a scale of about 3 m to 10 m. The GPR surveys indicate that there are bedded sands and gravels present at the PARC site, with the bedding extending from a few meters to several hundred meters. Photos from a nearby gravel pit indicate that layering is present on a vertical scale even smaller than indicated by the geophysics, with layers 10’s of centimeters thick, but consistent with the heterogeneity suggested by the natural-gamma logs. The small scale nature of the heterogeneity observed at the PARC site will be an important control over vertical groundwater flow and nitrate transport in the unsaturated

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zone. At a site scale, the lateral continuity of layers may be significant as they may contribute to permeable pathways for nitrate migration. However, at a larger scale, it is unlikely that these sequences are laterally continuous, therefore, for transport modeling, it is unlikely that the heterogeneity could be reasonably represented. Preliminary simulation results for nitrate leaching in the vadose zone of the Abbotsford-Sumas aquifer for two cases of hydraulic conductivity suggest that nitrate concentrations arriving at the water table depend strongly on grain size. A sensitivity analysis conducted on a local scale model suggests that an anisotropy factor of 20X (Khoriz/Kvert) provides the best calibration for particle pathlengths (ages) in comparison to 3H/3He age dates, while not adversely affecting the normalized RMS and the water balance. However, model age dates, based on particle tracking are underestimated. 6. ACKNOWLEDGEMENTS The authors wish to acknowledge the financial contributions by the NSERC, Environment Canada and the BC Ministry of Environment. Chaim Kempler at Agriculture and Agri-Food Canada granted permission for the field work to be conducted at the PARC site. Field assistance was provided by Reid Staples, Megan Surrette and Michael Toews. Basil Hii from Environment Canada provided access to the EC piezometers at the site, along with the lithological data for the wells. Gwyn Graham (BC Ministry of Environment) and Kim Sutherland (BC Ministry of Agriculture) are also acknowledged for contributing local insight. Dr. John Clague from SFU allowed us to christen his new GPR system, and provided insight into the depositional history of the area. Rob Luzitano (Golder Associates Ltd.) for geophysical field and data processing assistance. References Armstrong, J.E., Crandell, D.R., Easterbrook, D.J., and

Noble, J.B. 1965. Late Pleistocene stratigraphy and chronology in southwestern British Columbia and northwestern Washington: Geological Society of America Bulletin 76: pp. 321-330.

BCMAFF. Berry production guide for commercial growers 2002/2003. B.C. Ministry of Agriculture and Food and the Lower Mainland Horticultural Improvement Association, Abbotsford, BC.

Beres, M. Jr., and Haeni, F.P. 1991. Application of ground-penetrating-radar methods in hydrogeologic studies. Groundwater 29(3), pp. 375-386.

Chipperfield, K. 1992. Raspberry field soil nitrate survey. Sustainable Poultry farming Group and Canada-BC. Soil Conservation Program.

Clague, J. 2006. Personal Communication. Department of Earth Sciences, Simon Fraser University, Burnaby, BC.

Geo-slope International Ltd., 2002a. SEEP/W for finite element seepage analysis, version 5: User’s guide. Calgary, Canada.

Geo-slope International Ltd., 2002b. CTRAN/W for finite element contaminant transport analysis, version 5: User’s guide. Calgary, Canada.

Irving, J., and Knight, R. 2003. Saturation-dependent velocity anisotropy in borehole radar data. In Proceedings of the Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP 2003), San Antonio, TX, April 6-10.

Liebscher, H., Hii, B., and McNaughton, D. 1992. Nitrates and Pesticides in the Abbotsford Aquifer, Southwestern British Columbia. Inland Waters Directorate, Environment Canada, North Vancouver, BC. 83pp.

McArthur, S., and Allen, D.M. 2005. Abbotsford-Sumas Aquifer - Compilation of a Groundwater Chemistry Database with Analysis of Temporal Variations and Spatial Distributions of Nitrate Contamination. BC Ministry of Water, Land and Air Protection, Climate Change Branch. 24pp.

Mouritzen, C. 2000. A survey of residual soil nitrate in raspberry fields locates on the Abbotsford-Sumas aquifer. Southwestern Crop Consulting, Chilliwack, BC.

Mouritzen, C. 2001. A survey of residual soil nitrate in raspberry fields locates on the Abbotsford-Sumas aquifer (year 2). Southwestern Crop Consulting, Chilliwack, BC.



Sandmeier, K.J. 2005. ReflexW: Windows 9x/NT/200/XP-program for the processing of seismic, acoustic or electromagnetic reflection, refraction and transmission data. Version 3.5. Karlsruhe, Germany.

Scibek, J., and Allen, D.M. 2005. Numerical Groundwater Flow Model of the Abbotsford-Sumas Aquifer, Central Fraser Lowland of BC, Canada, and Washington State, US. Report to Environment Canada.

Scibek, J. and D.M. Allen. 2006. Comparing the responses of two high permeability, unconfined aquifers to predicted climate change. Global and Planetary Change XX, pp. CC-CC.

Sutherland, K. Personal Communication. BC Ministry of Agriculture.

Wassenaar, L.I., M.J. Hendry and N. Harrington. 2006. Decadal Geochemical and Isotopic Trends for Nitrate in the Transboundary Abbotsford-Sumas Aquifer and Implications for Beneficial Agricultural Management Practices. Environment Canada. 32pp.

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Pages1345-1459.pdfPaper 274.pdfINTRODUCTIONLIMESTONE HYDROGEOLOGY AND QUARRYING IN THE EAST MENDIPSGIS DEVELOPMENTConceptMethodology

RESULTSGeographical Information SystemLocal Planning ToolSystem Publication

CONCLUSIONSACKNOWLEDGEMENTS

Paper 313.pdfINTRODUCTIONPROJECT OVERVIEWAFLRP PROJECT COMPONENTSAvailable Reclaimed WaterReclaimed Water Storage Credits and Recovery

GROUNDWATER MODELINGPrevious Infiltration Impact AssessmentsGroundwater Model DevelopmentNo-Action ScenarioInitial AFLRP ProjectionsRevised AFLRP Projections

AREA OF HYDROLOGIC IMPACTCONCLUSIONS

Paper 214.pdfINTRODUCTIONDESCRIPTION OF THE STUDY AREAGEOLOGYBedrock geologyWolfville FormationBlomidon FormationNorth Mountain Formation

Surficial deposits

FIELDWORKWater level surveyDrilling and installation of piezometersWater and soil samplingHydraulic testsSeepage and flowmeter measurementsBorehole geophysicsFuture work

ANALYSES AND INTERPRETATIONBedrock resultsSurficial deposits and soil resultsConceptual modelSurface water results

COUPLED MODELINGCONCLUSIONACKNOWLEDGEMENTS

Paper 250.pdfINTRODUCTIONMATERIALS AND METHODSDescription of the studied watershedThe AGRIFLUX modelThe PHYSITEL/HYDROTEL modelThe MODFLOW model

RESULTS AND DISCUSSIONInfiltration and recharge using AGRIFLUXSurface flow using PHYSITEL/HYDROTELGroundwater flow using MODFLOW

CONCLUSIONACKNOWLEDGEMENTS

Paper 258.pdfINTRODUCTIONDATAClimate DataHistoric Climate DataGlobal Climate Model Data

Spatial Data

METHODSClimate GenerationFuture Predicted Climate ChangeDownscaling Using SDSMRaw GCM Data

Recharge Model

RESULTSCONCLUSIONS

Paper 213.pdfINTRODUCTIONSITE DESCRIPTIONMETHODOLOGYPiezometersRunoff and Pond Water LevelsMeteorological Stations and Soil TemperatureChloride extraction

RESULTSSpring Melt 2003Snowmelt and runoffSoil thawing and pond infiltrationGroundwater

Spring Melt 2004Snowmelt and runoffGroundwater

Post-snowmelt 2004Recharge by rainfall eventControlled flooding of C24

Chloride balance

DISCUSSIONPrecipitationRunoffSnowmeltInfiltrationDepression-focused recharge


Paper 544.pdf1. BACKGROUNDThere was an extraordinary coincidence of events in 1973 with B.C. Hydro’s initiation of the Revelstoke Dam Project. These eve1.3 B.C. Hydro’s Project ManagementThe project management of B. C. Hydro (Hydro) was critical to the successful outcome of the slide investigation. Hydro ensure

The ideal modular monitoring array probably needs to be made up of two or more compatible modular subsystems:

Firstly, a modular borehole completion casing system that can be used to hydraulically isolate monitoring zones by means of seSecondly, a modular data acquisition and control system that can be used inside the casing system for data collection. This sy3.2 Calibration and Maintenance RequirementsThe ideal borehole monitoring system should have the capability for essential QA tests to be conducted on all components immed3.3 Requirements for Multilevel Borehole Seals3.5 Other Useful CapabilitiesAlthough fluid pressure is the key parameter in any slide study, it would be helpful in other geotechnical and hydrogeologic s4.2. Adverse Drilling ConditionsDrilling conditions were extremely adverse in comparison with typical geotechnical environments. Boreholes were lost or unabl5. INSTRUMENTATION SOLUTIONS ADOPTEDIt was recognized that no geotechnical instruments were available to handle the combination of depth, fluid pressure, placemen5.1. First Solution – Multiple StandpipesHydro had previous experience placing small-diameter standpipes inside HQ and NQ sized boreholes. They continued to develop thThe fluid levels in the standpipes were monitored for piezometric level fluctuations. Frequently, in any one borehole there wThe multilevel piezometer system is a borehole completion casing that has a number of components including external casing pacBecause slide movements can deform the borehole, the instrument system had to be flexible. As a result, telescopic casing seg

7.2 Dutchman’s Ridge Slope Stability StudyIn the period 1986 to 1988, B. C. Hydro undertook the first full deployment of the multilevel piezometer system for the slope 8. CONCLUSIONSThe serious engineering problem posed by the existence of the Downie Slide along the side of the proposed Revelstoke Dam reserWhile the fluid–pressure data utilized for the Downie Slide studies were largely provided by the use of multiple standpipe pieAn early version of the resulting system was installed late in the Downie Slide investigations. But, it was not until after thWithout the stimulus provided by the Downie Slide investigations and the creative environment associated with the project, the

9. ACKNOWLEDGEMENTSHubbert, M. K. (1940) The theory of ground-water motion, Jour. Geology, 48: 8: 785-944Imrie, A. and Bourne, D. R. (1981) Engineering geology of the Mica and Revelstoke Dams, Field Guides to Geology and Mineral DePatton, F.D. and Deere, D.U. (1971a) Significant geological factors in rock slope stability Proc. Int. Conf. on Planning Open Patton, F. D. (1983) The role of instrumentation in the analysis of the stability of rock slopes, Int. Sym. on Field MeasuremePatton, F. D. (1990) The concept of quality in geologic and hydrogeologic investigations, Proc. 5th Int. Sym. on Landslides, L

Patton, F. D., Black, W. H. and Larssen (1991) D. A modular subsurface data acquisition system (MOSDAX) for real-time multi-leTatchell, G. E. (1991) Automated data acquisition systems for monitoring dams and landslides, Proc 3rd Int. Sym. on Field Meas

Paper 147.pdfINTRODUCTIONSTRATIGRAPHYINSTUMENTATIONGROUNDWATER SYSTEM MODELINGSTABLITY MODELINGCONCLUSIONSACKNOWLEDGEMENTS

Paper 391.pdfDevelopment of flushable adaptorDetermination of grout propertiesPore pressure response testPiezometer selectionInstallation Procedure

Paper 364.pdfINTRODUCTIONINSTRUMENTATION SYSTEMSETTLEMENT OF THE DAMUpstream ShellDownstream ShellClay Core

NUMERICAL MODELLINGBack Analysis


Paper 566.pdfINTRODUCTION2.HAZARD3.EARTHQUAKE MAGNITUDE FOR USE IN LIQUEFACTION ASSESSMENTSELECTION OF EARTHQUAKE RECORDSCHARACTERISTIC EARTHQUAKE DISTANCE

Paper 558.pdfINTRODUCTIONREAL FRACTURES AND FRACTURE NETWORKSDISCRETE FRACTURE NETWORK TECHNOLOGYIntroductionDerivation of DFN Parameters

DFN BLOCK ANALYSISDFN SLOPE STABILITY EXAMPLEDFN MODELS AND GROUNDWATER FLOWWELL TESTS AND FRACTURE FLOWDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES

Pages1460-1583.pdfPaper 267.pdfPaper 267.pdfINTRODUCTIONOBJECTIVES AND SCOPEPHASE 3 ANALYTICAL STUDYDatabase Development and InterpretationConceptual Hydrogeologic ModelGroundwater ModelSlope Stability Analyses

RESULTS AND CONCLUSIONSCritical Moraine SlopesMoraine Hydrogeology Modeling ResultsStability of Critical SlopesConsequences of FailuresStability Risk Assessment

RECOMMENDATIONSRemedial MeasuresReservoir Operations

ACKNOWLEDGMENTS

Paper 416.pdf3. PHYSICAL CHARACTERISTICS OF THE AQUIFERAGRICULTURE PROGRAMS AND RESULTS5.1 Stewardship Programs by the Raspberry Industry

6. TRENDS IN GROUNDWATER QUALITY7. SOURCE AND MECHANISM OF CONTAMINATION7.1 Effectiveness of Nutrient Management Planning as Source Control Tool7.2 Additional Sources of N7.3 Mechanism of Contamination

8. FURTHERING OUR UNDERSTANDING8.1 Advanced Hydrogeological Research8.1.1 Modeling8.1.2 Direct Testing of Recommended BMP’s8.1.2 In-Situ Remediation8.2 Improvement of Monitoring

Paper 265.pdfINTRODUCTIONPHASE 1 - DATA COMPILATIONPHASE 2 – CONCEPTUAL MODELPHASE 3 – NUMERICAL MODELModel DevelopmentWell Capture ZonesAquifer Water Balance


Paper 152.pdfINTRODUCTIONGEOPHYSICAL SURVEYINGSite DescriptionBorehole LoggingGround Penetrating RadarImplications for Nitrate Transport

VADOSE ZONE MODELLINGBackgroundResidual Nitrate Concentration

The ApproachModelling Results

SATURATED ZONE TRANSPORTSensitivity AnalysisParticle TrackingComparison of Model Ages to Isotopic Ages


Paper 359.pdf1. INTRODUCTION 2. HYDROGEOLOGY 3. METHODS 6. ACKNOWLEDGEMENTS

Paper 377.pdfINTRODUCTIONSTUDY AREALocation and Geologic SettingHydrogeology

SALINITY DISTRIBUTIONTRANSPORT MODELLINGDISCUSSIONEstuarine AreasInland and Delta Front Areas

CONCLUSIONS

Paper 401.pdfINTRODUCTIONPHYSIOGRAPHIC AND GENERAL GEOLOGICAL SETTINGGeneral Stratigraphy

EXISTING GROUNDWATER USAGESTRATIGRAPHIC INTERPRETATION FOR GROUNDWATER DEVELOPMENTSemiahmoo Outwash SandWestlynn Outwash

APPLICATION OF THE SURREY STRATIGRAPHIC MODEL TO GROUNDWATER EXPLORATION AND DEVELOPMENTSurrey Test Well Drilling Program

CONCLUSIONS

Paper 121.pdfINTRODUCTIONPHYSIOGRAPHY AND HYDROGEOLOGYFRACTURE COLLECTION AND ANALYSISField Data CollectionStatistical AnalysisStochastic ModelingDiscrete Fracture NetworksParameter Estimation

VERTICAL PERMEABILITY RESULTSCLIMATE AND RECHARGE MODELLINGClimateRechargeRecharge Modelling

RECHARGE DISTRIBUTIONCONCLUSIONSACKNOWLEDGEMENTS

Paper 316.pdfINTRODUCTIONHYDROGEOLOGYVancouver IslandGulf Islands

AQUIFER CLASSIFICATIONSOBSERVATION WELL NETWORKLONG-TERM TRENDS IN WATER LEVELSSite 1 – North-Central Saanich AquiferSite 2 – Gabriola Island

6.SUMMARY7. ACKNOWLEDGEMENTS

Paper 417.pdfINTRODUCTIONSTUDY REGION AND GEOLOGIC SETTINGFRACTURED BEDROCK AQUIFERS AND WELL YIELDSdrilling. In some instances, involving low-producing wells, some well drillers would also drill a few extra metres below the INVESTIGATORY APPROACHRESULTSArea “A” (Aquifer 608 at Ardmore)

Figure 4. Extension fractures (tension joints) occurring between shear zones striking east-west and dipping towards the north,Area “B” (Aquifer 681 at Willis Point)Area “C” (Aquifer 680, Highlands-Lone Tree Hill)

Figure 10. Curvilinear low angle shear fracture and intersecting open tension fractures in rocks of West Coast Crystalline ComCONCLUSIONSREFERENCES

Paper 350.pdfINTRODUCTIONStudy Area

METHODSEstimated Well YieldWell Head Location, Elevation and SlopeLineaments

RESULTS AND DISCUSSIONEstimated YieldWell DepthElevation at the Well HeadSlopeBedrock TypeDistance Between Well and Closest LineamentDistance between Well and Closest Lineament IntersectionSources of Error

CONCLUSIONS & RECOMMENDATIONSACKNOWLEDGEMENTS

Paper 188.pdfINTRODUCTIONSTUDY AREAMETHODOLOGYFIELD DATANUMERICAL MODELMODEL DESIGN

RESULTS AND DISCUSSIONSteady state calibrationTransient state simulation

CONCLUSIONACKNOWLEDGEMENTS

Pages1584-1680.pdfPaper 234.pdfELEVATED FLUORIDE AND BORON LEVELS IN GROUNDWATER FROM THE NANAIMO GROUP, VANCOUVER ISLAND, CANADASteven Earle, Geology Dept., Malaspina University-College, Nanaimo, British Columbia, CanadaErik Krogh, Applied Environmental Research Laboratories, Chemistry Dept., Malaspina University-College, Nanaimo, British Colum1. INTRODUCTION1.1 Study area

FormationLithologyGabriolaMedium- to coarse-grained submarine fan feldspathic sandstone (average 15% matrix), with mudstone interbedsSpraySubmarine fan mudstone and siltstone with turbidites, and with sandstone interbedsGeoffreyMedium- to coarse-grained submarine fan feldspathic sandstone (average 15% matrix) interbedded with conglomerateNorthum-berlandSubmarine fan mudstone and siltstone with sandstone interbedsDe CourcyMedium- to coarse-grained submarine fan feldspathic sandstone (average 15% matrix), with mudstone interbedsCedar DistrictSubmarine fan mudstone and siltstone with turbidites, and with sandstone interbeds2. METHODS3.1 Major element water geochemistryAs shown on Figure 4a, the majority of the groundwaters that we sampled are dominated by bicarbonate, although a few have chloThe major-element characteristics of the Yellow Point and Gabriola groundwaters, as described above, are generally very simila3.2 Trace element water geochemistry3.3 Rock geochemistry

Paper 286.pdfHydrogeological Study of the Cold Lake Air Weapon Range, Alberta

Paper 327.pdf3.2.Second exemple, |a| < 2, éqs. [20-21]Chapuis, R.P. 2002. Solution analytique de l’écoulement en régime permanent dans un aquifère incliné à nappe libre, et compara

Paper 237.pdfHYDROGEOLOGIC INVESTIGATIONS IN THE CANADIAN NORTH1.INTRODUCTION2.ACCESS, CLIMATE, AND DRILLING3.PERMAFROST4.POST-GLACIAL GEOLOGY

Paper 240.pdf1.INTRODUCTION

Paper 118.pdfINTRODUCTIONTHE INTERFACIAL FLOW METER DESIGNCalibrationInstallation of piezometer and stream gauge clusters.Measuring water flow across the sediment-water boundary

RESULTS AND DISCUSSIONTemporal and spatial variation of hydraulic headWater flow across the sediment-water boundaryVertical hydraulic conductivity

ACKNOWLEDGEMENTS

Paper 146.pdfINTRODUCTIONDATA ACQIUISITION STRATEGYCompound-Specific Isotope Analysis (CSIA)Signature Metabolite Analysis (SMA)Redox-Sensitive Tapes (RST)

CASE STUDIESCase Study 1 – Creosote-contaminated SiteSite DescriptionSite-specific Data Acquisition StrategyResults

Case Study 2 – Gas Station SiteSite DescriptionSite-specific Data Acquisition Strategy

Results

CONCLUSIONS

Paper 386.pdfINTRODUCTIONSIMULATION OF ADVECTIVE HEAT TRANSPORT IN HETEROGENEOUS ENVIRONMENTSGeneration of Permeability FieldsNumerical Models

RESULTSDISCUSSION AND CONCLUSIONSACKNOWLEDGEMENTS

Paper 144.pdfFINDING BURIED TREASURE – ASSESSING AQUIFER SUITABILITY FOR LARGE OPEN LOOP GEOEXCHANGE APPLICATIONSINTRODUCTIONGENERAL APPROACHRequired Site InformationAcceptance CriteriaIn practical use, many of the above parameters can be estimated or approximated using established methods and the minimum requSuitability Assessment

FLOW CHART FOR SITE SUITABILITY ASSESSMENTCASE EXAMPLECONCLUSIONSACKNOWLEDGEMENTSWater QualityMineral scaling or corrosion of well screens or exchanger platesThermalSpace for required geoexchange well separationSpace for dissipation of thermal plumeInduced temperature change in nearby wells

Paper 550.pdfINTRODUCTIONPRE-MINING CONCEPTUAL MODELS1996 Field Data1996 Conceptual Model 1997 Field Data1998 Conceptual ModelGeochemical Data1998 Numerical Model1999 Field Data1999 Conceptual Model

OBSERVATIONS DURING MININGCONCEPTUAL MODEL 2004DEWEY'S FAULTDISCUSSIONACKNOWLEDGEMENTSREFERENCES

Paper 138.pdfINTRODUCTIONDISCRETE VS MIXED PLUMESSTATISTICAL MEASURES OF SIMILARITY4.APPLICATION TO THE LLAGAS SUBBASINCONCLUSIONSACKNOWLEDGEMENTS7.REFERENCES

Pages1681-1773.pdfPaper 235.pdfPaper 235.pdfINTRODUCTIONGEOLOGICAL SETTINGFigure 2. MERA I and II springs overlayed on the lithology of the SNRB and NNP (based on Okulitch, 2005).LINKING MAJOR IONS AND ISOTOPES TO THE LOCAL GEOLOGYPREDICTING MINERALIZATION TYPES USING TRACE ELEMENT CONCENTRATIONSStatisticsLocal Pluton and Spring Trace Element ComparisonFicklin DiagramLinking Trace Element and Major Ion Geochemistry

CONCLUSIONSACKNOWLEDGEMENTSREFERENCES

Paper 238.pdf1.INTRODUCTION2.HYDROSTRATIGRAPHY2.1Ordovician Sedimentary Rocks2.2Ekwan River and Severn River Formations2.3Attawapiskat Limestone2.4Quaternary Deposits

3.GROUNDWATER FLOW

Paper 251.pdfINTRODUCTIONMETHODSRESULTS AND DISCUSSIONPhase I Data ReviewEarly Historical DataHistorical Data from 1990 to 2001

2002 to 2005 Monitoring ResultsWater Levels2002 Chemistry2004 and 2005 Chemistry

SUMMARY AND CONCLUSIONSACKNOWLEDGEMENTSREFERENCES

Paper 260.pdfINTRODUCTIONSITE HYDROGEOLOGYNUMERICAL HYDROGEOLOGIC MODELEVALUATION OF REMEDIAL ALTERNATIVESOption 1 – Pumping of Mixed Freshwater and SeawaterOption 2 – Pumping of Freshwater with Seawater BarrierOption 3 – Pumping of Freshwater with Barrier WallOption 4 – Pumping of Freshwater Only

IMPLEMENTATION OF GROUNDWATER MANAGEMENT SYSTEM

Paper 279.pdfINTRODUCTIONEXPERIMENTAL OVERVIEW –TRACE-METAL MOBILITY EXPERIMENTSSampling: Aqueous PhaseSampling: Solid Phase

RESULTS AND DISCUSSIONAqueous GeochemistryTrace-Metal Mobility MCCTrace-Metal Mobility MFCC

CONCLUSIONS

Paper 319.pdfINTRODUCTIONWELL INSTALLATIONSDesign of Monitoring Wells

SAMPLING AND TESTINGWater Quality

PRESSURE PROFILESDISCUSSIONACKNOWLEDGEMENTSREFERENCES

Paper 326.pdfINTRODUCTIONMODELLING APPROACHESCONCEPTUAL MODEL 1OverviewSimulation ApproachSimulation Results

CONCEPTUAL MODEL 2OverviewSimulation ApproachSimulation Results

CONCLUSIONSACKNOWLEDGEMENTSREFERENCES

Paper 353.pdfINTRODUCTIONCONCEPTUAL MODELGROUNDWATER FLOW MODELSOLUTION MINING IMPACT ASSESSMENTOperation PeriodPost Operation Period

SUMMARY AND CONCLUSIONSACKNOWLEDGEMENTS

Paper 430.pdfINTRODUCTIONDIVERSION CAPACITY OF INCLINED COVERSBACKGROUND STUDIESSIMULATIONS OF THE YEARLY RESPONSE UNDER HUMID CONDITIONSDISCUSSION AND CONCLUSIONACKNOWLEDGEMENTS

Paper 475.pdfINTRODUCTIONASSESSMENT OF THE TUNNEL PLUGProving that the Plug Test would be safePreparation for the Plug Test and Mine FillingFilling of the Mine and the Plug TestResults of the Mine Filling Experiment

ACKNOWLEDGEMENTS

Paper 525.pdfINTRODUCTIONClimate

POTENTIAL REMEDIAL OPTIONSCONCLUSIONS

Pages1774-1775.pdfEXTENDED ABSTRACT

investigating the scale of heterogeneity and...

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