Light Non-aqueous Phase Liquids Recovery Research Articles

A New Toolbox for Managing Sites Impacted by Light Non-Aqueous Phase Liquids (LNAPLs)

The Concawe LNAPL Toolbox is one of the first completely web-based tools for managing and remediating light non-aqueous phase liquids (LNAPL) impacted sites. An off-line downloadable version is also available for users who do not want to access it via the internet. LNAPLs are typically historic hydrocarbons released into soils and groundwater, such as liquid fuels, crude oil, and condensates. The toolbox was developed by Concawe, the Scientific Division of European Fuel Manufacturers Association, with the support of the engineering and environmental science-consulting agency GSI Environmental. The toolbox, written on the R-Shiny platform, was released in 2022 and includes over 20 different tools, such as, for example, infographics, nomographs, calculators, mobility models, videos, and checklists. These tools are organized into three tiers, with Tier 1 offering basic graphics and essential information, Tier 2 providing simple quantitative models and calculators, and Tier 3 featuring access and explanations of more complex tools. The toolbox is designed to address six key questions that are important for environmental consultants and regulators managing LNAPL sites, including determining the amount of LNAPL, estimating LNAPL migration and persistence, assessing LNAPL risk over time, determining the effectiveness of LNAPL recovery, and estimating Natural Source Zone Depletion (NSZD). The Concawe LNAPL Toolbox is accessible free of charge via a webpage on an internet browser or by downloading the toolbox for use on a personal computer.

Transition from active remediation to natural source zone depletion (NSZD) at a LNAPL-impacted site, supported by sustainable remediation appraisal

Natural source zone depletion (NSZD) is increasingly being considered as a risk-management option at sites impacted with light non-aqueous phase liquids (LNAPLs). NSZD can be applied in isolation or in combination with active remediation techniques, depending on site-specific risk-management requirements. A case study of the transition from active remediation to passive NSZD is presented for a petroleum-impacted site in NW Europe. This transition was supported by multiple lines of evidence/management options, including: the introduction of institutional controls on groundwater and land-development restrictions; the results from a residual-NAPL risk assessment; monitoring to establish that the LNAPL plume is reducing in size; a LNAPL transmissivity assessment; a CO 2 equivalent assessment of remediation options; and a LNAPL recovery diminishing returns model. Through application of local sustainable remediation principles consistent with ISO/SuRF-UK sustainable remediation frameworks and tools, regulatory approval was obtained for a partial closeout of the remediation system. By the final year of operation, NSZD rates in the portion of the site on which transition to NSZD has been agreed were over three times greater than active LNAPL recovery rates (12 000 l/ha/a for NSZD; 3800 l/ha/a for active LNAPL recovery). In the remaining active remediation areas total fluids extraction currently outperforms NSZD and will be continued until a comparable point is reached when NSZD removal exceeds active remediation. At that point transition to NSZD alone will be considered as the most sustainable risk-based approach.

Quantifying the benefits of in-time and in-place responses to remediate acute LNAPL release incidents

Acute large volume spills from storage tanks of petroleum hydrocarbons as light non aqueous phase liquids (LNAPLs) can contaminate soil and groundwater and may have the potential to pose explosive and other risks. In consideration of an acute LNAPL release scenario, we explore the value of a rapid remediation response, and the value of installing remediation infrastructure in close proximity to the spill location, in effecting greater recovery of LNAPL mass from the subsurface. For the first time, a verified three-dimensional multi-phase numerical framework and supercomputing resources was applied to explore the significance of in-time and in-place remediation actions. A sand aquifer, two release volumes and a low viscosity LNAPL were considered in key scenarios. The time of commencement of LNAPL remediation activities and the location of recovery wells were assessed requiring asymmetric computational considerations. The volume of LNAPL released considerably affected the depth of LNAPL penetration below the groundwater table, the radius of the plume over time and the recoverable LNAPL mass. The remediation efficiency was almost linearly correlated with the commencement time, but was a non-linear function of the distance of an extraction well from the spill release point. The ratio of the recovered LNAPL in a well located at the centre of the spill/release compared to a well located 5 m away was more than 3.5, for recovery starting only 7 days after the release. Early commencement of remediation with a recovery well located at the centre of the plume was estimated to recover 190 times more LNAPL mass than a one-month delayed commencement through a well 15 m away from the centre of the LNAPL plume. Optimally, nearly 40% of the initially released LNAPL could be recovered within two months of commencing LNAPL recovery actions.

Numerical Modeling of Multiphase Extraction (MPE) Aiming at LNAPL Recovery in Tropical Soils

Subsurface contamination by light non-aqueous phase liquids (LNAPL) is a widespread global problem that requires appropriate techniques to remediate soil and groundwater. In this paper, the subsurface transport over multiple phases (STOMP) model was used to simulate LNAPL multiphase flow and transport during multiphase extraction (MPE) application in two Brazilian tropical soils (silty sand and oxisol) contaminated by diesel. The model was applied to a hypothetical contamination site, with the initial LNAPL thickness observed in well extraction. The first part consisted of the MPE system sensitivity analysis, varying the applied vacuum and tip tube position. The Van Genuchten α parameter and hydraulic conductivity were the properties that most affected LNAPL saturation and fluid extraction volumes. Suitable applied vacuum and tip tube position parametrization was imperative for the efficiency of LNAPL extraction. After the definition of an appropriate MPE system configuration, simulations demonstrated that the immobile LNAPL saturation affected fluid extraction and diesel oil concentrations in aqueous and gas saturation. The model applied is able to predict LNAPL contaminant behavior in porous media during MPE technique application.

Toward Optimizing LNAPL Remediation

AbstractOptimizing the remediation of light nonaqueous phase liquids (LNAPLs) to achieve an acceptable endpoint status for a site is not trivial. Recently, Sookhak Lari, Johnston, et al. (2018, https://doi.org/10.1016/j.jhazmat.2017.11.006), Sookhak Lari, Rayner, and Davis (2018, https://doi.org/10.1016/j.jenvman.2018.07.041) conducted three‐dimensional multiphase, multicomponent simulations to address LNAPL remediation endpoints for a single recovery well. However, optimized LNAPL remediation for multiple wells is not addressed in the literature. In the first part of this paper, we establish a matrix of 10 simulation scenarios to show the sensitivity of the remedial endpoint (i.e., what is feasibly achieved) to several parameters including viscosity and partitioning attributes of the LNAPL, heterogeneity of the formation, and the location and number of the recovery wells. While this addresses the variability of LNAPL removal from the subsurface and is valuable in its own right, it does not address the optimal removal of LNAPL. We address this in the second part of the paper by linking a genetic algorithm to TMVOC‐MP to allow, for example, the assessment of the optimal number and location of LNAPL recovery wells in a field‐scale problem. Using supercomputing facilities and within 49 genetic algorithm generations, each including 150 members, highly optimized answers to different objective functions were obtained. For the first time, such a multiphase, multicomponent optimization tool promises the possibility of optimizing LNAPL remediation at field scale to achieve practicable endpoint conditions, within computational affordability.

Light non-aqueous phase liquids simulation using artificial intelligence models: Esmaeilabad aquifer case study

One of the most important pollutants in the aquifers adjacent to oil facilities is LNAPL (Light non-aqueous phase liquids). LNAPL recovery from the aquifer is one of the fastest and most convenient methods for aquifer cleanup. Identifying LNAPL thickness and fluctuations is very important to determine the LNAPL recovering method and maximizing the recovery. The feasibility of two artificial intelligence models including gene expression programming (GEP), adaptive neuro-fuzzy inference system (ANFIS) and classical multivariate linear regression (MLR) techniques are investigated in this study for LNAPL level forecasting. Discharge rate of LNAPL and groundwater level fluctuations were used as input attributes for the developed GEP, ANFIS and MLR models. Based on the comparison of three methods, it was found that the GEP could be successfully utilized in forecasting LNAPL level fluctuations in recovery process. Also, the GEP models can identify the relationship between dependent and independent variables and provide an equation. The identified equation based on GEP can be useful for planning the recovery method and algorithms. The results indicate that there is a high degree of agreement between the predicted values of the GEP based equation and the actual values.

Field-scale multi-phase LNAPL remediation: Validating a new computational framework against sequential field pilot trials

Remediation of subsurface systems, including groundwater, soil and soil gas, contaminated with light non-aqueous phase liquids (LNAPLs) is challenging. Field-scale pilot trials of multi-phase remediation were undertaken at a site to determine the effectiveness of recovery options. Sequential LNAPL skimming and vacuum-enhanced skimming, with and without water table drawdown were trialled over 78days; in total extracting over 5m3 of LNAPL. For the first time, a multi-component simulation framework (including the multi-phase multi-component code TMVOC-MP and processing codes) was developed and applied to simulate the broad range of multi-phase remediation and recovery methods used in the field trials. This framework was validated against the sequential pilot trials by comparing predicted and measured LNAPL mass removal rates and compositional changes. The framework was tested on both a Cray supercomputer and a cluster. Simulations mimicked trends in LNAPL recovery rates (from 0.14 to 3mL/s) across all remediation techniques each operating over periods of 4–14days over the 78day trial. The code also approximated order of magnitude compositional changes of hazardous chemical concentrations in extracted gas during vacuum-enhanced recovery. The verified framework enables longer term prediction of the effectiveness of remediation approaches allowing better determination of remediation endpoints and long-term risks.

Effect of precipitation on LNAPL recovery performance: An integration of laboratory and field results

The recovery rate of light-non-aqueous-phase-liquids (LNAPLs) in an unconfined aquifer was affected by precipitation and the rise and fall of the water table at the 322.5K site in Taiwan. The field performance of LNAPL recovery can be generated in the laboratory waterflood experiments using undisturbed soil samples taken from the 322.5K site. A log–log type-curve-matching method was developed in this paper to compare the laboratory waterflood results with the performance of LNAPL recovery observed on the 322.5K site. Laboratory-observed LNAPL recovery can be scaled up to predict field performance of LNAPL recovery through the log–log type-curve.

An analytical model for predicting LNAPL distribution and recovery from multi-layered soils

An analytical model was developed for estimating the distribution and recovery of light nonaqueous phase liquids (LNAPL) in heterogeneous aquifers. Various scenarios of LNAPL recovery may be simulated using LDRM for LNAPL recovery systems such as skimmer wells, water-enhanced wells, air-enhanced wells, and trenches from heterogeneous aquifers. LDRM uses multiple horizontal soil layers to model a heterogeneous aquifer. Up to three soil layers may be configured with unique soil properties for each layer. Simulation results suggest that LNAPL distribution and its recovery volume are highly affected by soil properties. In sandy soils LNAPL can be highly mobile and the recovery efficiency can be high. In contrast, even at high LNAPL saturations, LNAPL mobility is typically low in fine-grained soils. This characteristic of LNAPL with respect to soil texture has to be carefully accounted for in the model to better predict the recovery of LNAPL from heterogeneous soils. The impact of vertical hydraulic gradient in fine grain zone was assessed. A sensitivity analysis suggests that the formation LNAPL volume can be significantly affected by a downward vertical hydraulic gradient if the magnitude is near a critical amount (=ρr-1). Sensitivity of input parameters with respect to LNAPL formation in soils and LNAPL recovery volume were identified through a sensitivity analysis. The performance of LDRM on predicting the distribution and recovery of LNAP was reasonably accurate for a short-term analysis as demonstrated in a case study. However, further validation is needed to ascertain the model's performance in long-term simulations.

Multi-objective optimization for free-phase LNAPL recovery using evolutionary computation algorithms

A nonlinear, multi-objective optimization methodology is presented that seeks to maximize free product recovery of light non-aqueous phase liquids (LNAPLs) while minimizing operation cost, by introducing the novel concept of optimal alternating pumping and resting periods. This process allows more oil to flow towards the extraction wells, ensuring maximum free product removal at the end of the remediation period with minimum groundwater extraction. The methodology presented here combines FEHM (Finite Element Heat and Mass transfer code), a multiphase groundwater model that simulates LNAPL transport, with three evolutionary algorithms: the genetic algorithm (GA), the differential evolution (DE) algorithm and the particle swarm optimization (PSO) algorithm. The proposed optimal free-phase recovery strategy was tested using data from a field site, located near Athens, Greece. The PSO and DE solutions were very similar, while that provided by the GA was inferior, although the computation time was roughly the same for all algorithms. One of the most efficient algorithms (PSO) was chosen to approximate the optimal Pareto front, a method that provides multiple options to decision makers. When the optimal strategy is implemented, although a significant amount of LNAPL free product is captured, a spreading of the LNAPL plume occurs. Editor Z.W. Kundzewicz; Associate editor L. See Citation Dokou, Z. and Karatzas, G.P., 2013. Multi-objective optimization for free-phase LNAPL recovery using evolutionary computation algorithms. Hydrological Sciences Journal, 58 (3), 671–685.

Modelling of the system for cleaning up free oil products with the application of the MARS simulator

The objective of the conducted computer simulations is the analysis of the LNAPL (Light Non Aqueous Phase Liquids) recovery by wells and piezometers with installed skimmers. The mathematical model calculations were conducted using the MARS programme (Multiple Areal Remediation Simulator) of the Drapen Aden Environmental Modelling, Inc. The programme solves the multiphase filtration equations by the finite elements method [2]. It permits conducting the calculations in an heterogeneous and anisotropic filtration field in transient conditions. The MARS simulator performs the flow calculations for a lighter-thanwater, free oil product appearing on the water table – LNAPL (Light NonAqueous Phase Liquids). It estimates the volume of the free and residual LNAPL. The recovery level of the remaining LNAPL is forecast. It is also possible to estimate the volume of the free and the residual oil and to periodically forecast the recovery level of the free LNAPL to be found in the ground and water environment.

Impact of the water table fluctuations on the apparent thickness of light non-aqueous phase liquids

The light non-aqueous phase liquids (LNAPLs) percolating into the subsurface from damaged underground storage tanks, pipelines cisterns and from the unsealed landfills present a threat to soil and groundwater. If a layer of LNAPL floats on the groundwater table the initial step of remediation should be its recovery. In order to a proper design of LNAPL recovery an assessment of the mobile LNAPL volume is required. This volume can be determined on the base of a thickness of LNAPL layer in the porous medium (the actual thickness) or on the base of LNAPL specific volume. Then the LNAPL actual thickness and specific volume are estimated on the base of the LNAPL thickness measured in the monitoring well (the apparent thickness). Unfortunately, the actual LNAPL thickness is always different from the apparent LNAPL thickness. This difference depends on the properties of soil and the amount and properties of LNAPL. Additional factors influencing significantly the difference between apparent and actual thicknesses are the fluctuations of the water table level (the hydraulic head fluctuations). The major objectives of this study became to investigate the impact of hydraulic head fluctuations on the measured apparent and actual LNAPL thicknesses. Obtained results show that when the hydraulic head diminishes, the apparent thickness of LNAPL increases and the actual thickness decreases. Instead, when the hydraulic head again rises, the apparent thickness decreases, and the actual thickness increases. When the hydraulic head rises considerably it can take place that the free product don’t be present in the observation well. The results affirm that hydraulic head fluctuations complicate considerably the estimation of the actual thickness and the mobile volume of LNAPL on the base of the apparent LNAPL thickness measured in the observation well.

Identification and Assessment of Confined and Perched LNAPL Conditions

Although confined and perched light nonaqueous phase liquids (LNAPLs) have previously been recognized, the majority of technical LNAPL literature focuses on unconfined LNAPL. Little information exists regarding the appropriate use of LNAPL distribution and transmissivity data to distinguish between confined, perched, and unconfined LNAPL hydrogeological scenarios. This paper describes three case histories that illustrate how the observed behavior of LNAPL can be used to identify the hydrogeologic condition of LNAPL at a given site and improved methods for calculating LNAPL drawdown based on these hydrogeologic conditions. The assessment methodology uses routinely available data such as fluid gauging, boring lo, laser-induced fluorescence, visual observations of soil cores, and LNAPL baildown testing. Identification of the correct LNAPL hydrogeologic condition results in more accurate LNAPL conceptual site models, improved estimates of LNAPL recovery rates and volumes, more appropriate technology applications, and improved accuracy of LNAPL remediation metrics such as LNAPL transmissivity.

Measurement of LNAPL Flux Using Single-Well Intermittent Mixing Tracer Dilution Tests

The stability of subsurface Light Nonaqueous Phase Liquids (LNAPLs) is a key factor driving expectations for remedial measures at LNAPL sites. The conventional approach to resolving LNAPL stability has been to apply Darcy's Equation. This paper explores an alternative approach wherein single-well tracer dilution tests with intermittent mixing are used to resolve LNAPL stability. As a first step, an implicit solution for single-well intermittent mixing tracer dilution tests is derived. This includes key assumptions and limits on the allowable time between intermittent mixing events. Second, single-well tracer dilution tests with intermittent mixing are conducted under conditions of known LNAPL flux. This includes a laboratory sand tank study and two field tests at active LNAPL recovery wells. Results from the sand tank studies indicate that LNAPL fluxes in wells can be transformed into formation fluxes using corrections for (1) LNAPL thicknesses in the well and formation and (2) convergence of flow to the well. Using the apparent convergence factor from the sand tank experiment, the average error between the known and measured LNAPL fluxes is 4%. Results from the field studies show nearly identical known and measured LNAPL fluxes at one well. At the second well the measured fluxes appear to exceed the known value by a factor of two. Agreement between the known and measured LNAPL fluxes, within a factor of two, indicates that single-well tracer dilution tests with intermittent mixing can be a viable means of resolving LNAPL stability.

Free-product plume distribution and recovery modeling prediction in a diesel-contaminated volcanic aquifer

Light non-aqueous phase liquids (LNAPL) represent one of the most serious problems in aquifers contaminated with petroleum hydrocarbons liquids. To design an appropriate remediation strategy it is essential to understand the behavior of the plume. The aim of this paper is threefold: (1) to characterize the fluid distribution of an LNAPL plume detected in a volcanic low-conductivity aquifer (∼0.4m/day from slug tests interpretation), (2) to simulate the recovery processes of the free-product contamination and (3) to evaluate the primary recovery efficiency of the following alternatives: skimming, dual-phase extraction, Bioslurping and multi-phase extraction wells. The API/Charbeneau analytical model was used to investigate the recovery feasibility based on the geological properties and hydrogeological conditions with a multi-phase (water, air, LNAPL) transport approach in the vadose zone. The modeling performed in this research, in terms of LNAPL distribution in the subsurface, show that oil saturation is 7% in the air–oil interface, with a maximum value of 70% in the capillary fringe. Equilibrium between water and LNAPL phases is reached at a depth of 1.80m from the air–oil interface. On the other hand, the LNAPL recovery model results suggest a remarkable enhancement of the free-product recovery when simultaneous extra-phase extraction was simulated from wells, in addition to the LNAPL lens. Recovery efficiencies were 27%, 65%, 66% and 67% for skimming, dual-phase extraction, Bioslurping and multi-phase extraction, respectively. During a 3-year simulation, skimmer wells and multi-phase extraction showed the lowest and highest LNAPL recovery rates, with expected values from 207 to 163 and 2305 to 707l-LNAPL/day, respectively. At a field level we are proposing a well distribution arrangement that alternates pairs of dual-phase well-Bioslurping well. This not only improves the recovery of the free-product plume, but also pumps the dissolve plume and enhances in situ biodegradation in the vadose zone. Thus, aquifer and soil remediation can be achieved at a shorter time. Rough calculations suggest that LNAPL can be recovered at an approximate cost of $6–$10/l.

Enhancing Remediation of LNAPL Recovery through a Response-Surface-Based Optimization Approach

Cost-efficient design for remediation of light nonaqueous phase liquids (LNAPL) from subsurface has become an essential task for site managers in North America. Although many related studies were conducted, there was still lack of efficient and computationally attractive method in such an area. In this study, a response-surface-based optimization approach was developed for enhancing remediation of LNAPL recovery. A two-dimensional numerical model was provided to simulate LNAPL transport during remediation. A dual response regression model was proposed for establishing a linkage between remediation actions and system responses. A nonlinear VFPR management model was then established for generating desired operating conditions. A petroleum-contaminated site in western Canada was used to demonstrate the applicability of the proposed method. The results demonstrated that the DRS model could be used as an effective proxy for simulation models and the optimal solutions from management model led to better cost-ef...

A field trial to assess the performance of CO 2-supersaturated water injection for residual volatile LNAPL recovery

A pilot scale field trial was conducted to evaluate the recovery of volatile, light non-aqueous phase liquids (LNAPLs) using a novel remediation method termed supersaturated water injection (SWI). SWI uses a patented technology to efficiently dissolve high concentrations of CO 2 into water at elevated pressures. This water is injected into the subsurface resulting in the nucleation of CO 2 bubbles at and away from the injection point. The nucleating bubbles coalesce, rise and volatilize residual LNAPL ganglia. In this study, an LNAPL composed of 103 kg of volatile pentane and hexane, and 30 kg of non-volatile Soltrol was emplaced below the water table at residual saturation. The SWI technology removed 78% of the pentane and 50% of the less volatile hexane. Contaminant mass was still being removed when the system was shut down for practical reasons. The mass removed is comparable to that expected for air sparging but a much smaller volume of gas was injected using the SWI system.

Backpulsing fouling control with membrane recovery of light non-aqueous phase liquids

Membrane recovery of light non-aqueous phase liquids (LNAPLs) was studied. Small membrane modules, operated in a sealed end configuration, were pressurized with several LNAPLs in order that membrane permeability and fouling processes might be characterized. The mitigation of membrane fouling via backpulsing was optimized for backpulse amplitude, frequency, and duration. A full-scale LNAPL recovery device was tested in the laboratory. Clean-membrane permeability was determined via single-fiber extraction of 2-propanol, distilled kerosene, commercial kerosene, commercial diesel fuel, and LNAPL obtained from the subsurface of a contaminated refinery site. Membrane fouling occurred during laboratory extraction of commercial kerosene, distilled kerosene, and the refinery fluid, but not for 2-propanol. Filtration experiments showed suspended solids present within the LNAPLs. Scanning electron microscope images of fouled membranes indicated that these solids were deposited upon the membrane surface. The fouling was due to pore blockage, pore constriction, and/or cake layer formation. The use of backpulsing was found to mitigate pore constriction and cake layer formation. Backpulsing improved recovery rates by ∼30% over a 15 h period, but it could not prevent the occurrence of some irreversible fouling. The device designed to fit into a typical recovery well extracted ∼35% of the volume expected for given operating pressures and clean-membrane permeability, under non-fouling conditions. The less than optimal performance was due to crimping of hollow fibers during the potting process, and not fiber–fiber interactions. Under non-fouling conditions, field operation of the device can yield 1–2000 l per day, which is a theoretical range of subsurface LNAPL recharge rates. With the use of backpulsing under fouling conditions, the membrane recovery device can extract up to 50 l per day, but this must be coupled with regular cleaning/replacement of the membranes.

Bioslurping Model for Assessing Light Hydrocarbon Recovery in Contaminated Unconfined Aquifer. II: Optimization Analysis

The bioslurping model was successfully applied to simulate the recovery efficiency of light nonaqueous phase liquids (LNAPLs) in a companion remediation study. This paper carries out an advanced environmental systems analysis for handling the application challenges related to a seamless integration of simulation outputs, regression analyses, and optimization practices to search for the best remediation solution. In view of the inherent complexity of integrating simulation outputs at various scales for building the optimization steps and searching for the ultimate risk-informed and cost-effective solutions, a set of regression submodels describing the system response to water and gas pumping and oil skimming in hydrocarbon recovery are derived and employed to bridge the traditional gap between simulations and optimization studies. The bioslurping model is used to generate regression submodels of the system behavior during remediation operations. To test the robustness of the operational scheme, three planning scenarios based on a common linear programming framework are defined and utilized to assess the optimal control mechanics for LNAPL recovery. These scenarios are designed to shed light on improving the predictive capabilities for environmental decision making to handle a complex multiphase and multimedia remediation program. The research findings indicate that water-pumping volume can be minimized and oil and soil gas recovery can be maximized whether the candidate well locations are fixed beforehand or not. However, flexible choices in well locations in the optimization steps merit substantial examination in the future.

Analytical Solutions for Free‐Hydrocarbon Recovery Using Skimmer and Dual‐Pump wells

AbstractAccidental release of petroleum hydrocarbons to the subsurface may occur through spills around refineries, leaking pipelines, storage tanks, or other sources. If the spill is large, the hydrocarbon liquids may eventually reach a water table and spread laterally in a pancake‐like lens. Hydrocarbons that exist as a separate phase are termed light nonaqueous phase liquids (LNAPLs). The portion of the LNAPL that is mobile, not entrapped as residual saturation, is termed “free product.”This paper presents new analytical solutions for the design of long‐term free‐product recovery from aquifers with skimmer, single‐ and dual‐pump wells. The solutions are for steady‐state flow, based on the assumption of vertical equilibrium, and include the effect of coning of LNAPL, air, and water on flow. The solutions are valid for soils of large hydraulic conductivity where the effect of capillary pressure on coning is small.The results show how to estimate the maximum rate of inflow of LNAPL for skimmer wells, i.e., wells in which LNAPL is recovered with little or no water production. The paper also shows how to calculate the increase in LNAPL recovery when water is pumped by single‐ or dual‐pump wells. A simple equation is given that can be used to adjust the water rate to avoid smearing of the LNAPL below the water table.