WO2016141202A1 - System and method for measuring non-aqueous phase liquid accumulations in monitoring wells at contaminated sites - Google Patents

System and method for measuring non-aqueous phase liquid accumulations in monitoring wells at contaminated sites Download PDF

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Publication number
WO2016141202A1
WO2016141202A1 PCT/US2016/020721 US2016020721W WO2016141202A1 WO 2016141202 A1 WO2016141202 A1 WO 2016141202A1 US 2016020721 W US2016020721 W US 2016020721W WO 2016141202 A1 WO2016141202 A1 WO 2016141202A1
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WIPO (PCT)
Prior art keywords
napl
pressure
air
liquid
well
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PCT/US2016/020721
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French (fr)
Inventor
Andrew Pennington
Jonathon SMITH
Brad KOONS
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ARCADIS Corporate Services, Inc.
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Publication of WO2016141202A1 publication Critical patent/WO2016141202A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F22/00—Methods or apparatus for measuring volume of fluids or fluent solid material, not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09C—RECLAMATION OF CONTAMINATED SOIL
    • B09C1/00—Reclamation of contaminated soil
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/18—Water
    • G01N33/1826—Water organic contamination in water
    • G01N33/1833—Oil in water
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/14—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/14—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of pressure
    • G01F23/18—Indicating, recording or alarm devices actuated electrically
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
    • G01F23/241—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid for discrete levels
    • G01F23/242—Mounting arrangements for electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/20—Controlling water pollution; Waste water treatment

Definitions

  • the invention relates to characterization and remediation of contaminated sites.
  • the system and method of the invention relates to systems and methods for measurement of non-aqueous phase liquid accumulations in monitoring wells at contaminated sites.
  • Non-aqueous phase liquids are liquids that are minimally soluble in water and do not mix with water, such as oil, gasoline and other petroleum products. NAPLs are known to contaminate soil and ground waters. Many common ground water contaminants enter the subsurface as non-aqueous phase liquids. Since NAPLs do not mix readily with water, they tend to flow separately from ground water.
  • a dense non-aqueous phase liquid or DNAPL is a contaminant that is denser than water.
  • DNAPLs sink below the water table when spilled in significant quantities and only stop when they reach an impermeable material such as competent bedrock. Their penetration into an aquifer makes them difficult to locate and remediate.
  • DNAPLs include:
  • chlorinated solvents such as trichloroethylene, tetrachloroethene, 1 ,1 , 1 - trichloroethane and carbon tetrachloride;
  • PCBs polychlorinated biphenyl
  • a light non-aqueous phase liquid is a NAPL that has a lower density than water.
  • the vertical movement of an LNAPL after it infiltrates into the ground is limited by the water table because of lower density of the LNAPL makes it buoyant in water.
  • LNAPLs include gasoline, diesel, benzene, toluene, xylene, and other hydrocarbons.
  • NAPL The movement of NAPL through the subsurface is controlled by several processes. Upon release, NAPL moves downward under the influence of gravity. If a small volume of NAPL is released, it will move through the unsaturated zone until its mass is immobilized within soil pores as a result of capillary forces. If a sufficient volume of LNAPL is released, it will migrate until it encounters the water table, where buoyancy forces and increasing water content impede the vertical movement of LNAPL. As a result, the less dense LNAPL will migrate laterally along the water table. In general, LNAPL migration will occur in the direction of the water table gradient, although mounding of LNAPL and radial flow can occur if the rate of LNAPL movement from the surface is greater than the lateral migration. DNAPL will typically continue to migrate downward after encountering the water table; if the volume of DNAPL released is sufficient, it will accumulate at the base of an aquifer, with distribution and further migration controlled by migration controlled by aquifer hydrostratigraphy.
  • NAPL may occur as either residual NAPL or as free-phase NAPL within the subsurface environment.
  • NAPL that is retained by soil capillary forces and that is trapped within pore spaces is relatively immobile and termed residual NAPL.
  • Free- phase NAPL occurs when the NAPL saturation exceeds the residual saturation, and a continuous NAPL phase exists among interconnected pores in the soil matrix.
  • regulations for management of free-phase NAPL have required the removal of NAPL from wells, as defined by its thickness in wells rather than its concentration in an environmental medium (i.e., soil, groundwater, air).
  • the NAPL may be very viscous and coat the oil/water interface probe such that it cannot differentiate between NAPL and water; • manual measurements using an oil/water interface probe cannot be collected rapidly enough to adequately characterize a rapid hydraulic response; and/or
  • Methods for automated NAPL thickness measurement are known.
  • several data logging pressure transducers are configured vertically in a specific manner in order to measure NAPL thicknesses.
  • Another known method uses guided radar waves to detect interface locations based on changes in fluid properties.
  • the invention of the invention comprises a combination of sensors and data recording devices that measure and record NAPL thickness in a well or a tank.
  • the system comprises a liquid-level sensor, a hydrostatic pressure transducer, and a data logging device that applies electrical power to the sensors and records the variable electrical resistance within the sensors produced by changes in liquid elevation.
  • the liquid-level sensor measures the physical location of the air/liquid interface within a well or tank.
  • the pressure transducer measures the hydrostatic pressure above the transducer.
  • the data logging device provides a record of these two values that is used to calculate the thickness of the LNAPL.
  • Figure 1 depicts one embodiment of an equipment configuration used for automated LNAPL measurement.
  • Figure 2 illustrates fluid level data measured using an automated NAPL measurement device.
  • the system and method of the invention improves the rate and efficiency of NAPL thickness measurements during LNAPL transmissivity testing in connection with baildown or manual skimming tests, two of the LNAPL transmissivity tests described in ASTM E2856 - Standard Guide for Estimation of LNAPL Transmissivity, which is a commonly used standard in the environmental industry.
  • the invention can also be used for long-term, automated monitoring of LNAPL thicknesses in wells and tanks, and could be used to measure DNAPL thickness in a monitoring well for monitoring or aquifer testing purposes.
  • a combination of sensors and data recording devices are used to measure and record NAPL thickness.
  • the system comprises a liquid-level sensor, a hydrostatic pressure transducer, and a data logging device that applies electrical power to the sensors and records the variable electrical resistance within the sensors produced by changes in liquid elevation.
  • the liquid-level sensor measures the physical location of the air/liquid interface within a well or tank.
  • the pressure transducer measures the hydrostatic pressure above the transducer.
  • the data logging device provides a record of these two values that is used to calculate the thickness of the LNAPL using a measured LNAPL density and a common mathematic expression, as follows:
  • bn LNAPL thickness
  • ZALI elevation of the air-liquid interface
  • ZPSE elevation of the potentiometric surface (corresponding to the hydrostatic pressure measured by the pressure transducer)
  • p r ratio of measured LNAPL density to the density of water.
  • Figure 1 depicts one embodiment of the system and method of the invention as used at an environmental site where LNAPL was measured using the following assembly 100:
  • a liquid level sensor 1 1 0 (such as a 24-inch measurement range chemical eTapeTM manufactured by Milone Technologies, Inc.) comprising a pressure-sensitive tape having a printed-circuit configuration that functions as a variable electrical resistor in response to liquid immersion;
  • a datalogging pressure transducer 1 20 such as the Level TROLL® manufactured by In-Situ Inc., the Levellogger® manufactured by Solinst Canada Ltd., or the DiverTM manufactured by Schlumberger);
  • a microcontroller or miniature computer 1 30 such as the chicken Uno (manufactured under license from chicken) or Raspberry Pi (manufactured by the Raspberry Pi Foundation) that measures the resistance of the eTapeTM sensor using a voltage divider circuit;
  • Zener diode barriers 140 (such as the Z-series passive barriers manufactured by Pepperl-Fuchs Industries) installed to render the down-well portion of the voltage divider circuit (i.e., the eTapeTM and related wiring) intrinsically safe; a datalogging "shield” or add-on to the microcontroller 150 that records voltage measurements collected by the microcontroller to an SD memory card 155; and • a "hanger” assembly 160 comprising a plurality of threaded steel rods and a brass plate used to mount the eTapeTM within the well at a fixed depth.
  • the eTapeTM 1 10 was suspended in a monitoring well 105 so that the air- LNAPL interface 1 15 within the well 105 lay within the measurement range of the eTapeTM 1 10 throughout the measurement period.
  • the hanger assembly 160 for assembly 1 00 comprised a wire or steel cable 165 from an attachment point 170 at the top of the well casing 105.
  • the pressure transducer 120 was placed in the well 1 05 below the lowest anticipated location of the LNAPL-water interface 125 during the measurement period. Readings for the eTapeTM 1 10 and transducer 120 were recorded at similar intervals (approximately once per second).
  • Figure 2 illustrates fluid level data measured using the automated NAPL measurement device described in the Example as compared to use of a known oil/water interface probe used according to known methods.
  • the prior art probe used to collect the benchmark data in this field test was a Solinst model 1 22 oil/water interface probe, available from Solinst Canada Ltd. of Georgetown, Ontario, Canada.
  • the probe was lowered into the monitoring well, and the user was alerted to the presence of non-aqueous phase liquids by a light and tone generator.
  • the operator used markings on the PVDF flat-tape to measure the depth from a reference point at the surface to the fluid levels in the subsurface.
  • system of the invention may include the following equipment configuration:
  • the eTapeTM as previously described in the Example, providing 32 inches of measurement range rather than 24 inches; • an outer flexible envelope of polytetrafluoroethylene (PTFE) or similar flexible material, longer than the eTapeTM, to enclose and protect it in the event that fluid reaches the top of the eTapeTM sensor;
  • PTFE polytetrafluoroethylene
  • DI-710 manufactured by DATAQ
  • DI-710 a data acquisition device with higher resolution for voltage readings and built-in SD card datalogging and Ethernet networking functions, as compared to the microcontroller or miniature computer plus datalogging shield as previously described in the Example;
  • a pressure transducer (AST 451 0, manufactured by American Sensor Technologies) providing a 1 -5 V signal to the data acquisition device, bearing intrinsically safe approval under the entity concept, and a corresponding Zener diode barrier;
  • a wireless router functioning as an access point, connected via Ethernet cable to the data acquisition device.

Abstract

A system and method for characterization and remediation of contaminated sites is disclosed. In particular, the system and method of the invention relates to systems and methods for measurement of non-aqueous phase liquid accumulations in monitoring wells at contaminated sites. The invention of the invention comprises a combination of sensors and data recording devices that measure and record NAPL thickness in a well or a tank. The system comprises a liquid-level sensor, a hydrostatic pressure transducer, and a data logging device that applies electrical power to the sensors and records the variable electrical resistance within the sensors produced by changes in liquid elevation.

Description

SYSTEM AND METHOD FOR MEASURING NON-AQUEOUS PHASE LIQUID ACCUMULATIONS IN MONITORING WELLS AT CONTAMINATED SITES
[0001 ] FIELD OF THE INVENTION.
[0002] The invention relates to characterization and remediation of contaminated sites. In particular, the system and method of the invention relates to systems and methods for measurement of non-aqueous phase liquid accumulations in monitoring wells at contaminated sites.
[0003] BACKGROUND OF THE INVENTION.
[0004] Non-aqueous phase liquids, or NAPLs, are liquids that are minimally soluble in water and do not mix with water, such as oil, gasoline and other petroleum products. NAPLs are known to contaminate soil and ground waters. Many common ground water contaminants enter the subsurface as non-aqueous phase liquids. Since NAPLs do not mix readily with water, they tend to flow separately from ground water.
[0005] A dense non-aqueous phase liquid or DNAPL is a contaminant that is denser than water. DNAPLs sink below the water table when spilled in significant quantities and only stop when they reach an impermeable material such as competent bedrock. Their penetration into an aquifer makes them difficult to locate and remediate.
[0006] Examples of DNAPLs include:
• chlorinated solvents, such as trichloroethylene, tetrachloroethene, 1 ,1 , 1 - trichloroethane and carbon tetrachloride;
• coal tar;
• creosote;
• polychlorinated biphenyl (PCBs);
• mercury; and • extra heavy crude oil, with an API gravity of less than 10.
[0007] A light non-aqueous phase liquid (LNAPL) is a NAPL that has a lower density than water. The vertical movement of an LNAPL after it infiltrates into the ground is limited by the water table because of lower density of the LNAPL makes it buoyant in water. Examples of LNAPLs include gasoline, diesel, benzene, toluene, xylene, and other hydrocarbons.
[0008] The movement of NAPL through the subsurface is controlled by several processes. Upon release, NAPL moves downward under the influence of gravity. If a small volume of NAPL is released, it will move through the unsaturated zone until its mass is immobilized within soil pores as a result of capillary forces. If a sufficient volume of LNAPL is released, it will migrate until it encounters the water table, where buoyancy forces and increasing water content impede the vertical movement of LNAPL. As a result, the less dense LNAPL will migrate laterally along the water table. In general, LNAPL migration will occur in the direction of the water table gradient, although mounding of LNAPL and radial flow can occur if the rate of LNAPL movement from the surface is greater than the lateral migration. DNAPL will typically continue to migrate downward after encountering the water table; if the volume of DNAPL released is sufficient, it will accumulate at the base of an aquifer, with distribution and further migration controlled by migration controlled by aquifer hydrostratigraphy.
[0009] NAPL may occur as either residual NAPL or as free-phase NAPL within the subsurface environment. NAPL that is retained by soil capillary forces and that is trapped within pore spaces is relatively immobile and termed residual NAPL. Free- phase NAPL occurs when the NAPL saturation exceeds the residual saturation, and a continuous NAPL phase exists among interconnected pores in the soil matrix. [0010] Historically, regulations for management of free-phase NAPL have required the removal of NAPL from wells, as defined by its thickness in wells rather than its concentration in an environmental medium (i.e., soil, groundwater, air). In practice, the presence of product in wells at a site has been used as both the factor driving remediation and the end-point for evaluating remediation success (i.e., thickness of product in wells). In the US, state regulations typically require that LNAPL be removed to the "maximum extent practicable," and some states also define end-points based on various criteria including the NAPL thickness in a well (3 mm, or 1 /8 inch, Georgia), sheen (Maryland), or any measurable amount of NAPL (Utah).
[001 1 ] The most prevalent current art for measuring NAPL thicknesses at environmental sites is to manually deploy an oil/water interface probe into a well or tank. Since the most common LNAPLs are oils, the upper surface of the LNAPL layer is termed the "air/oil interface" and the lower surface of the oil is termed the "oil/water interface." The upper surface of a DNAPL is termed the water/oil interface. The oil/water interface probe senses a change in optical and dielectric properties and sounds an audible tone, and in some cases an indicator light, to provide the user feedback on whether the probe is in air, immersed in water, or immersed in a NAPL. This approach to measuring NAPL thicknesses can be difficult for some or all of the reasons below:
• the dielectric or optical properties of the NAPL are not compliant with the factory-established setpoints in a typical oil/water interface probe;
• the NAPL may be very viscous and coat the oil/water interface probe such that it cannot differentiate between NAPL and water; • manual measurements using an oil/water interface probe cannot be collected rapidly enough to adequately characterize a rapid hydraulic response; and/or
• manual measurements using an oil/water interface probe introduce human error, incur unnecessary labor cost, and may create a safety risk for the person making the manual measurements.
[0012] Methods for automated NAPL thickness measurement are known. In one known method, several data logging pressure transducers are configured vertically in a specific manner in order to measure NAPL thicknesses. Another known method uses guided radar waves to detect interface locations based on changes in fluid properties.
[0013] SUMMARY OF THE INVENTION.
[0014] The invention of the invention comprises a combination of sensors and data recording devices that measure and record NAPL thickness in a well or a tank. The system comprises a liquid-level sensor, a hydrostatic pressure transducer, and a data logging device that applies electrical power to the sensors and records the variable electrical resistance within the sensors produced by changes in liquid elevation. The liquid-level sensor measures the physical location of the air/liquid interface within a well or tank. The pressure transducer measures the hydrostatic pressure above the transducer. The data logging device provides a record of these two values that is used to calculate the thickness of the LNAPL.
[0015] BRIEF DESCRIPTION OF THE DRAWINGS.
[0016] Figure 1 depicts one embodiment of an equipment configuration used for automated LNAPL measurement. [0017] Figure 2 illustrates fluid level data measured using an automated NAPL measurement device.
[0018] DETAILED DESCRIPTION OF THE INVENTION.
[0019] The system and method of the invention improves the rate and efficiency of NAPL thickness measurements during LNAPL transmissivity testing in connection with baildown or manual skimming tests, two of the LNAPL transmissivity tests described in ASTM E2856 - Standard Guide for Estimation of LNAPL Transmissivity, which is a commonly used standard in the environmental industry. The invention can also be used for long-term, automated monitoring of LNAPL thicknesses in wells and tanks, and could be used to measure DNAPL thickness in a monitoring well for monitoring or aquifer testing purposes.
[0020] According to one embodiment of the invention, a combination of sensors and data recording devices are used to measure and record NAPL thickness. The system comprises a liquid-level sensor, a hydrostatic pressure transducer, and a data logging device that applies electrical power to the sensors and records the variable electrical resistance within the sensors produced by changes in liquid elevation. The liquid-level sensor measures the physical location of the air/liquid interface within a well or tank. The pressure transducer measures the hydrostatic pressure above the transducer. The data logging device provides a record of these two values that is used to calculate the thickness of the LNAPL using a measured LNAPL density and a common mathematic expression, as follows:
, _ ZALI ~ ZpsE
n ~ (1 - Pr)
where bn = LNAPL thickness, ZALI = elevation of the air-liquid interface, ZPSE = elevation of the potentiometric surface (corresponding to the hydrostatic pressure measured by the pressure transducer), and pr = ratio of measured LNAPL density to the density of water.
[0021 ] EXAMPLE
[0022] Turning to the figures, Figure 1 depicts one embodiment of the system and method of the invention as used at an environmental site where LNAPL was measured using the following assembly 100:
a liquid level sensor 1 1 0 (such as a 24-inch measurement range chemical eTape™ manufactured by Milone Technologies, Inc.) comprising a pressure- sensitive tape having a printed-circuit configuration that functions as a variable electrical resistor in response to liquid immersion;
a datalogging pressure transducer 1 20 (such as the Level TROLL® manufactured by In-Situ Inc., the Levellogger® manufactured by Solinst Canada Ltd., or the Diver™ manufactured by Schlumberger);
a microcontroller or miniature computer 1 30 (such as the Arduino Uno (manufactured under license from Arduino) or Raspberry Pi (manufactured by the Raspberry Pi Foundation) that measures the resistance of the eTape™ sensor using a voltage divider circuit;
Zener diode barriers 140 (such as the Z-series passive barriers manufactured by Pepperl-Fuchs Industries) installed to render the down-well portion of the voltage divider circuit (i.e., the eTape™ and related wiring) intrinsically safe; a datalogging "shield" or add-on to the microcontroller 150 that records voltage measurements collected by the microcontroller to an SD memory card 155; and • a "hanger" assembly 160 comprising a plurality of threaded steel rods and a brass plate used to mount the eTape™ within the well at a fixed depth. [0023] The eTape™ 1 10 was suspended in a monitoring well 105 so that the air- LNAPL interface 1 15 within the well 105 lay within the measurement range of the eTape™ 1 10 throughout the measurement period.
[0024] The hanger assembly 160 for assembly 1 00 comprised a wire or steel cable 165 from an attachment point 170 at the top of the well casing 105. The pressure transducer 120 was placed in the well 1 05 below the lowest anticipated location of the LNAPL-water interface 125 during the measurement period. Readings for the eTape™ 1 10 and transducer 120 were recorded at similar intervals (approximately once per second).
[0025] Figure 2 illustrates fluid level data measured using the automated NAPL measurement device described in the Example as compared to use of a known oil/water interface probe used according to known methods. The prior art probe used to collect the benchmark data in this field test was a Solinst model 1 22 oil/water interface probe, available from Solinst Canada Ltd. of Georgetown, Ontario, Canada. The probe was lowered into the monitoring well, and the user was alerted to the presence of non-aqueous phase liquids by a light and tone generator. The operator used markings on the PVDF flat-tape to measure the depth from a reference point at the surface to the fluid levels in the subsurface.
[0026] In another embodiment, the system of the invention may include the following equipment configuration:
the eTape™, as previously described in the Example, providing 32 inches of measurement range rather than 24 inches; • an outer flexible envelope of polytetrafluoroethylene (PTFE) or similar flexible material, longer than the eTape™, to enclose and protect it in the event that fluid reaches the top of the eTape™ sensor;
the voltage divider circuit, as previously described in the Example, with Zener diode barriers for safety of down-well circuits;
a data acquisition device (DI-710, manufactured by DATAQ) with higher resolution for voltage readings and built-in SD card datalogging and Ethernet networking functions, as compared to the microcontroller or miniature computer plus datalogging shield as previously described in the Example;
a pressure transducer (AST 451 0, manufactured by American Sensor Technologies) providing a 1 -5 V signal to the data acquisition device, bearing intrinsically safe approval under the entity concept, and a corresponding Zener diode barrier; and
a wireless router functioning as an access point, connected via Ethernet cable to the data acquisition device.
[0027] These system examples are provided for illustration purposes only. The system can be configured in other ways as will be known to those skilled in the art according to the principles disclosed herein.

Claims

CLAIMS What is claimed is:
1 . A method of measuring non-aqueous phase liquid accumulations in monitoring wells, tanks, or other vessels comprising:
deploying, at a fixed depth, a sensor that identifies the location of an air- liquid interface within a well;
placing a pressure transducer in the well below the lowest anticipated location of the NAPL-water interface;
collecting with the transducer measurements of the hydrostatic pressure above the transducer;
measuring the height of the air-liquid interface within the well with the air- liquid interface sensor; and
calculating the thickness of the NAPL in the well using NAPL density measurements.
2. The method of claim 1 , wherein the air-liquid interface comprises an air-NAPL interface.
3. The method of claim 1 , wherein the air-liquid interface comprises an air-water interface.
4. The method of claim 1 , wherein the NAPL density measurements comprise previously collected or known NAPL density measurements.
5. A system for measuring NAPL thickness in monitoring wells, tanks, or other vessels wherein the components of the system comprise: an air-liquid interface sensor comprising a pressure-sensitive tape having a printed-circuit configuration that functions as a variable electrical resistor in response to liquid immersion;
a datalogging pressure transducer;
a microcontroller or a miniature computer that measures the resistance of the pressure-sensitive tape using a voltage divider circuit;
Zener diode barriers installed to render the down-well portion of the voltage divider circuit intrinsically safe;
a datalogging "shield" or an add-on to the microcontroller that records voltage measurements collected by the microcontroller to an SD memory card; and
a mounting assembly used to hold the pressure sensitive tape within the well at a fixed depth.
6. The system of claim 5, wherein the pressure-sensitive tape provides about 24 inches of measurement.
7. The system of claim 5, wherein the pressure-sensitive tape is enclosed in an envelope of a flexible material that extends above the top of the air-liquid interface sensor and electrical connections to the air-liquid interface sensor.
8. The system of claim 7, wherein the flexible material comprises polytetrafluoroethylene.
9. A system for measuring NAPL thickness in monitoring wells, tanks, or other vessels wherein the components of the system comprise: a liquid level sensor comprising a pressure-sensitive tape having a printed- circuit configuration that functions as a variable electrical resistor in response to liquid immersion;
a data acquisition device for obtaining voltage readings, built-in SD card datalogging and Ethernet networking functions;
an intrinsically safe pressure transducer that provides a 1 -5 V signal to the data acquisition device;
a wireless router that allows an operator of the system to connect to the data acquisition device and download data logged by the data acquisition device; and
a mounting assembly used to hold the pressure sensitive tape within a well at a fixed depth and stabilize it against lateral movement.
10. The system of claim 9, wherein the pressure-sensitive tape provides about 32 inches of measurement.
1 1 . The system of claim 9, wherein the wireless router connects to the data acquisition device via Ethernet cable.
12. The system of claim 9, wherein the pressure-sensitive tape is enclosed in an envelope of a flexible material that extends above the top of the liquid level sensor and electrical connections to the liquid level sensor.
13. The system of claim 12, wherein the flexible material comprises polytetrafluoroethylene.
PCT/US2016/020721 2015-03-03 2016-03-03 System and method for measuring non-aqueous phase liquid accumulations in monitoring wells at contaminated sites WO2016141202A1 (en)

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Cited By (4)

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Publication number Priority date Publication date Assignee Title
WO2019178376A1 (en) * 2018-03-16 2019-09-19 Aecom Systems and methods for determining a thickness of a nonaqueous phase liquid layer
KR200491669Y1 (en) * 2019-08-30 2020-05-15 주식회사 다올엔지니어링 Devcie for measuring underground water level and underground subsidence
CN112517632A (en) * 2020-12-18 2021-03-19 苏州精英环保有限公司 Extraction well and heterogeneous extraction system of restoration contaminated site NAPL looks
CN115921511A (en) * 2023-02-27 2023-04-07 宝航环境修复有限公司 Method for accurately detecting, extracting and repairing LNAPL pollution source in underground water

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