Ground Water
Sampling Devices

Types

• Open Bailer Grab Type
• Point-Source Bailer Grab Type
• Syringe Grab Type
• Submersible Positive Displacement / Gear-Drive Type
• Submersible Positive Displacement / Bladder Pump Type
• Submersible Positive Displacement / Helical Rotor Type
• Submersible Positive Displacement / Gas-Drive Piston Pump Type
• Submersible Positive Displacement / Centrifugal Pump Type
• In-Situ / Pneumatic Type
• Suction Lift / Peristaltic Type
• Gas Contact / Gas Lift Type
• Gas Contact / Gas Drive Type

OPEN BAILER GRAB TYPE SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: no limit
MINIMUM WELL DIAMETER: 1/2 inch
SAMPLE DELIVERY RATE: variable
RADIOACTIVE: radium
BIOLOGICAL: coliform bacteria
ORGANIC: non-volatile
INORGANIC: EC, major ions, trace metals, nitrate/fluoride

Advantages of the Device

+ Can be made of any rigid or flexible material, including those inert to chemical contaminants.
+ Mechanically simple, easy to operate, clean, and repair.
+ Can take samples from virtually any depth.
+ Requires no external power source, lightweight, highly portable.
+ Flexible materials will allow use in non-plumb boreholes.
+ Can be made for any diameter borehole, and to any length for various sample volumes.
+ Can provide a `cut' of immiscible contaminants.

Disadvantages of the Device

- Borehole evacuation difficult, time- and labor-consuming from deep settings.
- Cross contamination can result from use of non-dedicated, non-contaminating line.
- Aeration, degassing, turbulence can result while lowering bailer and making transfers.
- Person bailing is susceptible to exposure.
- Does not supply continuous flow.
- May be difficult to determine sampling point.
- Check valves may not operate properly.
- Tight fitting bailers can produce `swabbing' effect.

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POINT-SOURCE BAILER GRAB TYPE SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: no limit
MINIMUM WELL DIAMETER: 1/2 inch
SAMPLE DELIVERY RATE: variable
RADIOACTIVE: radium
BIOLOGICAL: coliform bacteria
ORGANIC: non-volatile, volatile, TOC, TOX
INORGANIC: EC, pH, Redox, major ions, trace metals, nitrate/fluoride

Advantages of the Device

+ Can be made of any rigid or flexible material, including those inert to chemical contaminants.
+ Mechanically simple, easy to operate, clean, and repair.
+ Can take samples from virtually any depth.
+ Requires no external power source, lightweight, highly portable.
+ Flexible materials will allow use in non-plumb boreholes.
+ Can be made for any diameter borehole, and to any length for various sample volumes.
+ Can provide a `cut' of immiscible contaminants.

Disadvantages of the Device

- Borehole evacuation difficult, time- and labor-consuming from deep settings.
- Cross contamination can result from use of non-dedicated, non-contaminating line.
- Aeration, degassing, turbulence can result while lowering bailer and making transfers.
- Person bailing is susceptible to exposure.
- Does not supply continuous flow.
- May be difficult to determine sampling point.
- Check valves may not operate properly.
- Tight fitting bailers can produce `swabbing' effect.

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SYRINGE GRAB TYPE SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: no limit
MINIMUM WELL DIAMETER: 1 1/2 inch
SAMPLE DELIVERY RATE: 0.01 - 0.2 gallons
RADIOACTIVE: radium, gross alpha and beta
BIOLOGICAL: coliform bacteria
ORGANIC: non-volatile
INORGANIC: EC, pH, Redox, major ions, trace metals, nitrate/fluoride

Advantages of the Device

+ Sample does not contact atmospheric gases, thus no aeration.
+ Sample subjected to very slight negative pressure, thus no degassing.
+ Samples can be collected at discrete intervals and from any depth in well.
+ Can be used to sample water from slowly recharging wells because they only remove a small volume from well.
+ Are or can be made of inert or nearly inert materials.
+ Not restricted to limits of suction lift.
+ Syringe can be used as sample container.
+ Inexpensive, highly portable, simple to use.

Disadvantages of the Device

- Inefficient for collecting large volume samples.
- Cannot be used to evacuate well.
- Not as readily available as other devices.
- Fabrication materials must be carefully selected to prevent sample contamination.
- Limited to water with low suspended solids content.
- Leakage may occur around plunger when sampling water with high suspended solids levels.
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SUBMERSIBLE POSITIVE DISPLACEMENT / GEAR-DRIVE SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: 200 feet
MINIMUM WELL DIAMETER: 2 inches
SAMPLE DELIVERY RATE: 0 - 0.5 gallons per minute
RADIOACTIVE: unsuitable or untested
BIOLOGICAL: unsuitable or untested
ORGANIC: volatile
INORGANIC: unsuitable or untested

Advantages of the Device

+ Made from inert or nearly inert materials, thus suitable for sampling organics if Teflon discharge line is used.
+ Highly portable and self-contained, except when auxiliary power is used.
+ Provides continuous sample over extended time periods.
+ Easy to operate, clean, and maintain in the field.
+ Replacement parts are inexpensive.
+ For performance delivered, are less expensive than other samplers.

Disadvantages of the Device

- No control over flow rates, thus can not adjust from high evacuation rate to lower sampling rate.
- Sampling of water with high levels of suspended solids may require frequent gear replacement.
- Potential for pressure changes (cavitation) exists at the drive mechanism.

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SUBMERSIBLE POSITIVE DISPLACEMENT / BLADDER PUMP SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: 400 feet
MINIMUM WELL DIAMETER: 1 1/2 inch
SAMPLE DELIVERY RATE: 0 - 2 gallons per minute
RADIOACTIVE: radium, gross alpha and beta
BIOLOGICAL: coliform bacteria
ORGANIC: non-volatile, volatile, TOC, TOX
INORGANIC: EC, pH, Redox, major ions, trace metals, nitrate/fluoride, dissolved gases

Advantages of the Device

+ Most designed to sample for low levels of contaminants.
+ Can be made of inert or nearly inert materials.
+ Driving gas does not contact sample directly, thus aeration and stripping are minimized.
+ Portable, although accessories can be cumbersome.
+ Allows well evacuation and large sample volumes.
+ Pumping rates can be adjusted for high volume.
+ Easy to disassemble and repair.

Disadvantages of the Device

- Deep sampling requires large volumes of gas and longer cycles, thus increasing operating time and expense and reducing portability.
- Check valves may fail in water with high suspended solids content.
- Generally expensive, prices highly variable.
- Minimum rate of sample discharge may be higher than ideal for sampling volatile compounds.

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SUBMERSIBLE POSITIVE DISPLACEMENT / HELICAL ROTOR SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: 160 feet
MINIMUM WELL DIAMETER: 2 inches
SAMPLE DELIVERY RATE: 0 - 1.2 gallons per minute
RADIOACTIVE: radium, gross alpha and beta
BIOLOGICAL: unsuitable or untested
ORGANIC: non-volatile, volatile, TOC, TOX
INORGANIC: EC, pH, Redox, major ions, trace metals, nitrate/fluoride, dissolved gases

Advantages of the Device

+ Portable, relatively easy to transport.
+ Relatively high pumping rates possible, can be used for evacuation.
+ Specifically designed for monitoring use.

Disadvantages of the Device

- Sample chemistry may be altered from turbulence caused by high pumping rates.
- Pump moderately difficult to assemble, making field service difficult.
- High suspended solids content can cause problems.
- Expensive compared to other devices offering similar performance.
- Must be cycled on/off about every 20 minutes to prevent overheating of motor.
- Flow rate can not be controlled.

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SUBMERSIBLE POSITIVE DISPLACEMENT / GAS-DRIVE PISTON PUMP SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: 500 feet
MINIMUM WELL DIAMETER: 1 1/2 inch
SAMPLE DELIVERY RATE: 0 - 0.5 gallons per minute
RADIOACTIVE: radium, gross alpha and beta
BIOLOGICAL: unsuitable or untested
ORGANIC: non-volatile
INORGANIC: EC, major ions, trace metals, nitrate/fluoride

Advantages of the Device

+ No aeration of sample due to isolation from driving gas.
+ Easy to operate, clean and maintain.
+ Provides continuous sample over extended time periods.
+ Uses compressed gas economically.
+ Flow rates easily controlled by varying driving gas pressure.
+ Is or can be made of inert or nearly inert materials.
+ Moderately high pumping rate at great depths allows for collection of large volumes of sample in relatively short time.

Disadvantages of the Device

- Relatively expensive in relation to other sampling devices.
- Unless pump intake is filtered, particulate matter may damage pump's intricate valving mechanism.
- Valving mechanism may cause series of pressure drops in sample leading to sample degassing and pH changes.
- Not highly portable, usually vehicle mounted.
- Fixed-length tubing bundles may be inconvenient for shallow, low-yield monitoring wells.
- Tubing bundles may be difficult to clean in order to avoid cross- contamination.

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SUBMERSIBLE POSITIVE DISPLACEMENT / CENTRIFUGUAL SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: variable
MINIMUM WELL DIAMETER: 3 inches
SAMPLE DELIVERY RATE: variable
RADIOACTIVE: radium, gross alpha and beta
BIOLOGICAL: unsuitable or untested
ORGANIC: unsuitable or untested
INORGANIC: EC, major ions, nitrate/fluoride

Advantages of the Device

+ Flow rate is easily controlled.
+ Portable and readily available.
+ Can sometimes be used in non-plumb wells.

Disadvantages of the Device

- Sampling limited to situations in which the potentiometric level is less than 25 feet below the surface.
- Drop in pressure due to application of pressure causes degassing of sample and loss of volatiles.
- Gasoline motor power source used for most centrifugals provides potential hydrocarbon contamination of samples.
- May have to be primed, providing a source for possible sample contamination.

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IN SITU / PNEUMATIC SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: no limit
MINIMUM WELL DIAMETER: not applicable
SAMPLE DELIVERY RATE: 0.01 - 0.13 gallons
RADIOACTIVE: radium, gross alpha and beta
BIOLOGICAL: coliform bacteria
ORGANIC: non-volatile
INORGANIC: EC, pH, Redox, major ions, trace metals, nitrate/fluoride

About the Device

In situ devices generally utilize the same operating principles as syringe samplers: a pressurized or evacuated sample container is lowered to the sampling port and opened, allowing the sample to enter. Materials may include PVC, stainless steel, polypropylene, and Teflon.

SUCTION LIFT / PERISTALTIC SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: 26 feet
MINIMUM WELL DIAMETER: 1/2 inch
SAMPLE DELIVERY RATE: 0.01 - 0.3 gallons per minute
RADIOACTIVE: radium
BIOLOGICAL: coliform bacteria
ORGANIC: non-volatile
INORGANIC: EC, major ions, nitrate/fluoride

Advantages of the Device

+ Flow rate is easily controlled.
+ Highly portable and readily available.
+ Inexpensive compared to other sampling devices.
+ Does not contact sample, only the tubing of the peristaltic pump must be cleaned.
+ Can be used in wells of any diameter and in non-plumb wells.

Disadvantages of the Device

- Sampling limited to situations where potentiometric level is less than 25 feet below the surface.
- Drop in pressure due to application of strong negative pressure (suction) causes degassing of sample and loss of volatiles.
- Electric power source required.
- Low pumping rates make it difficult to evacuate the well bore in a reasonable amount of time.
- Where sample comes into contact with tubing, the choice of appropriate materials for flexible pump-head tubing may be restrictive.

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GAS CONTACT / GAS LIFT SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: variable
MINIMUM WELL DIAMETER: 1-inch
SAMPLE DELIVERY RATE: variable
RADIOACTIVE: unsuitable or untested
BIOLOGICAL: unsuitable or untested
ORGANIC: unsuitable or untested
INORGANIC: unsuitable or untested

Advantages of the Device

+ Highly portable and inexpensive.
+ Discrete sampling depth possible.
+ Can provide sample at controlled, near continuous rate.
+ Use of inert driving gas minimizes sample oxidation and other sample chemical alteration.
+ Can be installed permanently in uncased borehole.
+ Multiple installations possible.
+ Can be constructed entirely of inert materials.
+ Sampling depth limited only by burst strength of construction materials.

Disadvantages of the Device

- If air or oxygen used as driving gas, oxidation may occur (causing precipitation of metals, gas stripping of volatiles, thus may not be appropriate for many chemically-sensitive parameters.
- Portability constrained by need for compressor or tanks.
- Excessive air pressure can rupture gas entry or discharge tubing.
- Permanently installed devices difficult to retrieve for service; proper installation and operation may be difficult to ensure.

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GAS CONTACT / GAS-DRIVE SAMPLERS

Performance Specifications

MAXIMUM SAMPLE DEPTH: 150 feet
MINIMUM WELL DIAMETER: 1-inch
SAMPLE DELIVERY RATE: 0.2 gallons per minute
RADIOACTIVE: radium
BIOLOGICAL: unsuitable or untested
ORGANIC: non-volatile
INORGANIC: EC, major ions, nitrate/fluoride

Advantages of the Device

+ Highly portable and inexpensive.
+ Discrete sampling depth possible.
+ Can provide sample at controlled, near continuous rate.
+ Use of inert driving gas minimizes sample oxidation and other sample chemical alteration.
+ Can be installed permanently in uncased borehole.
+ Multiple installations possible.
+ Can be constructed entirely of inert materials.
+ Sampling depth limited only by burst strength of construction materials.

Disadvantages of the Device

- If air or oxygen used as driving gas, oxidation may occur (causing precipitation of metals, gas stripping of volatiles, thus may not be appropriate for many chemically-sensitive parameters.
- Portability constrained by need for compressor or tanks.
- Excessive air pressure can rupture gas entry or discharge tubing.
- Permanently installed devices difficult to retrieve for service; proper installation and operation may be difficult to ensure.

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