Influence of pumping operational schedule on solute concentrations at a well in randomly heterogeneous aquifers

Libera, A.; Barros, Felipe P. J. de; Guadagnini, Alberto

doi:10.1016/j.jhydrol.2016.12.022

Cited by 34 publications

(21 citation statements)

References 55 publications

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“…Small pumping rates are associated with uncertain well capture zones because of the small drawdown and vertical gradients they induce on the flow field. These results are consistent with findings from 2‐D and 3‐D stochastic simulations of synthetic aquifers by Libera et al (2017) and Henri and Harter (2019), respectively. de Barros et al (2013) similarly pointed out that it is the most uncertain streamlines that delineate the well capture zones.…”

Section: Resultssupporting

confidence: 92%

Evaluating Domestic Well Vulnerability to Contamination From Unconventional Oil and Gas Development Sites

Soriano

Siegel

Gutchess

et al. 2020

Water Resources Research

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The rapid expansion of unconventional oil and gas development (UD), made possible by horizontal drilling and hydraulic fracturing, has triggered concerns over groundwater contamination and public health risks. To improve our understanding of the risks posed by UD, we develop a physically based, spatially explicit framework for evaluating groundwater well vulnerability to aqueous phase contaminants released from surface spills and leaks at UD well pad locations. The proposed framework utilizes the concept of capture probability and incorporates decision-relevant planning horizons and acceptable risks to support goal-oriented modeling for groundwater protection. We illustrate the approach in northeastern Pennsylvania, where a high intensity of UD activity overlaps with local dependence on domestic groundwater wells. Using two alternative models of the bedrock aquifer and a precautionary paradigm to integrate their results, we found that most domestic wells in the domain had low vulnerability as the extent of their modeled probabilistic capture zones were smaller than distances to the nearest existing UD well pad. We also found that simulated capture probability and vulnerability were most sensitive to the model parameters of matrix hydraulic conductivity, porosity, pumping rate, and the ratio of fracture to matrix conductivity. Our analysis demonstrated the potential inadequacy of current state-mandated setback distances that allow UD within the boundaries of delineated capture zones. The proposed framework, while limited to aqueous phase contamination, emphasizes the need to incorporate information on flow paths and transport timescales into policies aiming to protect groundwater from contamination by UD.

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Section: Resultssupporting

confidence: 92%

Evaluating Domestic Well Vulnerability to Contamination From Unconventional Oil and Gas Development Sites

Soriano

Siegel

Gutchess

et al. 2020

Water Resources Research

View full text Add to dashboard Cite

show abstract

“…Conservative approaches usually assume the worst case scenario, associated with higher recharge rates or higher permeability values to increase the plume mobility. The modeling scenarios investigated in this work, however, call into question the appropriateness of such conservative approaches, in fact the non-trivial trade-offs arising from the interplay between dilution and contaminants' mobilization require the use of more realistic and accurate flow and transport simulations, achieved through proper calibration processes, as well as probabilistic risk assessments (Maxwell et al, 2008;de Barros and Rubin, 2008;Siirila and Maxwell, 2012;Atchley et al, 2013;Libera et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

Climate change impact on residual contaminants under sustainable remediation

Libera

Barros

Faybishenko

et al. 2019

Journal of Contaminant Hydrology

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This study investigates the potential impact of climate change on residual contaminants in vadose zones and groundwater. We assume that the effect of climate changes can be represented by perturbations in the natural recharge through the aquifer system. We perform numerical modeling of unsaturated/saturated flow and transport and consider different performance metrics: contaminant concentrations at observation wells and contaminant export at the site's boundary. We evaluate the effect of increasing and decreasing recharge as well as the impact of potential failure of surface capping structures employed to immobilize vadose zone contaminants. Our approach is demonstrated in a real case study by simulating transport of non-reactive radioactive tritium at the U.S. Department of Energy's Savannah River Site. Results show that recharge changes significantly affect well concentrations: after an initial slight dilution we identify a significant concentration increase at different observation wells some years after t he recharge increase and/or the cap failure, as a consequence of contaminants' mobilization. This effect is generally emphasized and occurs earlier as the recharge increases. Under decreased aquifers' recharge the concentration could slightly increase for some years, due to a decrease of dilution, depending on the magnitude of the negative recharge shift. We identify trigger levels of recharge above which the concentration/export breakthrough curves and the time of exceedance of the Maximum Contaminant Level for tritium are remarkably affected. Moreover, we observe that the contaminant export at the control plane, identified as the risk pathway to the downgradient

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“…A fully screened extracting well, modeled as a vertical line, is pumping water at a constant rate Q . After waiting a sufficient time, the nonuniform mean flow is considered as steady, thereby neglecting the effect of transient flow regime (for the impact of transient pumping effects on transport, see, e.g., Libera et al []). Assuming a cylindrical coordinate system

r = (r, ϕ, z)

, centered at the extracting well, the radial mean velocity U assumes the following expression, resulting from imposing mass conservation:

U (r) = \frac{Q}{2 π n D} r^{- 1},

where n is the effective porosity of the medium, and it is assumed to be constant.…”

Section: Mathematical Frameworkmentioning

confidence: 99%

Radial solute transport in highly heterogeneous aquifers: Modeling and experimental comparison

Dato

Fiori

Barros

et al. 2017

Water Resources Research

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We analyze solute transport in a radially converging 3‐D flow field in a porous medium with spatially heterogeneous hydraulic conductivity (K). The aim of the paper is to analyze the impact of heterogeneity and the mode of injection on BreakThrough Curves (BTCs) detected at a well pumping a contaminated aquifer. The aquifer is conceptualized as an ensemble of blocks of uniform but contrasting K and the analysis makes use of the travel time approach. Despite the approximations introduced, the model reproduces a laboratory experiment without calibration of transport parameters. Our results also show excellent agreement with numerical simulations for different levels of heterogeneity. We focus on the impact on the BTC of both heterogeneity in K and solute release conditions. It is shown that the injection mode matters, and the differences in the BTCs between uniform and flux‐proportional injection increase with the heterogeneity of the K‐field. Furthermore, we study the effect of heterogeneity and mode of injection on early and late arrivals at the well.

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Influence of pumping operational schedule on solute concentrations at a well in randomly heterogeneous aquifers

Cited by 34 publications

References 55 publications

Evaluating Domestic Well Vulnerability to Contamination From Unconventional Oil and Gas Development Sites

Evaluating Domestic Well Vulnerability to Contamination From Unconventional Oil and Gas Development Sites

Climate change impact on residual contaminants under sustainable remediation

Radial solute transport in highly heterogeneous aquifers: Modeling and experimental comparison

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