United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
Washington DC 20460
EPA/540/P-91/007
January 1999
OSWER 9360,4-06
Compendium of ERT
Groundwater Sampling
Procedures
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EPA/540/P-91/007
OSWER Directive 9360.4-06
January 1991
COMPENDIUM OF ERT GROUNDWATER
SAMPLING PROCEDURES
Sampling Equipment Decontamination
Groundwater Well Sampling
Soil Gas Sampling
Monitoring Well Installation
Water Level Measurement
Well Development
Controlled Pumping Test
Slug Test
Interim Final
Environmental Response Team
Emergency Response Division
Office of Emergency and Remedial Response
U.S. Environmental Protection Agency
Washington, DC 20460
Printed on Recycled Paper
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Notice
This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved
for publication. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
The policies and procedures established in this document are intended solely for the guidance of government
personnel, for use in the Superfund Removal Program. They are not intended, and cannot be relied upon, to
create any rights, substantive or procedural, enforceable by any party in litigation with the United States. The
Agency reserves the right to act at variance with these policies and procedures and to change them at any time
without public notice.
Depending on circumstances and needs, it may not be possible or appropriate to follow these procedures exactly
in all situations due to site conditions, equipment limitations, and limitations of the standard procedures.
Whenever these procedures cannot be followed as written, they may be used as general guidance with any and
all modifications fully documented in either QA Plans, Sampling Plans, or final reports of results.
Each Standard Operating Procedure in this compendium contains a discussion on quality assurance/quality
control (QA/QC). For more information on QA/QC objectives and requirements, refer to the Quality
Assurance/Quality Control Guidance for Removal Activities, OSWER directive 9360.4-01, EPA/540/G-90/004.
Questions, comments, and recommendations are welcomed regarding the Compendium of ERT Groundwater
Sampling Procedures. Send remarks to:
Mr. William A. Coakley
Removal Program QA Coordinator
U.S. EPA - ERT
Raritan Depot - Building 18, MS-101
2890 Woodbridge Avenue
Edison, NJ 08837-3679
For additional copies of the Compendium of ERT Groundwater Sampling Procedures, please contact:
National Technical Information Service (NTIS)
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4600
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Table of Contents
Section
1.0 SAMPLING EQUIPMENT DECONTAMINATION: SOP #2006
1.1 Scope and Application
1.2 Method Summary
1.3 Sample Preservation, Containers, Handling, and Storage
1.4 Interferences and Potential Problems
1.5 Equipment/Apparatus
1.6 Reagents
1.7 Procedures
9
1.7.1 Decontamination Methods
1.7.2 Field Sampling Equipment Cleaning Procedures
1.8 Calculations
1.9 Quality Assurance/Quality Control
1.10 Data Validation
1.11 Health and Safety
2.0 GROUNDWATER WELL SAMPLING: SOP #2007
2.1 Scope and Application
2.2 Method Summary
2.3 Sample Preservation, Containers, Handling and Storage
2.4 Interferences and Potential Problems
2.4.1 General 5
2.4.2 Purging 5
2.4.3 Material
2.5 Equipment/Apparatus
2.4.3 Materials 6
2.51 General 6
2.52 Bailer 8
2.5.3 Submersible Pump
2.5.4 Non-Gas Contact Bladder Pump 8
2.5.5 Suction Pump
2.5.6 Inertia Pump 8
2.6 Reagents
2.7 Procedures
2.7.1 Preparation
2.7.2 Field Preparation 8
2.7.3 Evacuation of Static Water (Purging)
2.7.4 Sampling
2.7.5 Filtering 13
2.7.6 Post Operation
2.7.7 Special Considerations for VGA Sampling
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Section
2.8 Calculations 14
2.9 Quality Assurance/Quality Control 14
2.10 Data Validation 15
2.11 Health and Safety 15
3.0 SOIL GAS SAMPLING: SOP #2149
3.1 Scope and Application 17
3.2 Method Summary 17
3.3 Sample Preservation, Containers, Handling, and Storage 17
3.3.1 Tedlar Bag 17
3.3.2 Tenax Tube 17
3.3.3 SUMMA Canister 17
3.4 Interferences and Potential Problems 18
3.4.1 HNU Measurements 18
3.4.2 Factors Affecting Organic Concentrations in Soil Gas 18
3.4.3 Soil Probe Clogging 18
3.4.4 Underground Utilities 18
3.5 Equipment/Apparatus
18
3.5.1 Slam Bar Method 18
3.5.2 Power Hammer Method 19
3.6 Reagents 19
3.7 Procedures 19
3.7.1 Soil Gas Well Installation 19
3.7.2 Screening with Field Instruments 20
3.7.3 Tedlar Bag Sampling 20
3.7.4 Tenax Tube Sampling 20
3.7.5 SUMMA Canister Sampling 22
Calculations
22
3.8.1 Field Screening Instruments 22
3.8.2 Photovac GC Analysis 22
3.9 Quality Assurance/Quality Control 22
3.9.1 Field Instrument Calibration 22
3.9.2 Gilian Model HFS113A Air Sampling Pump Calibration 22
3.9.3 Sample Probe Contamination 22
3.9.4 Sample Train Contamination 22
3.9.5 Field Blank 22
3.9.6 Trip Standard 22
3.9.7 Tedlar Bag Check 23
3.9.8 SUMMA Canister Check 23
iv
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Section
3.9.9 Options 23
3.10 Data Validation 23
3.11 Health and Safety 23
4.0 MONITORING WELL INSTALLATION: SOP #2150
4.1 Scope and Application 25
4.2 Method Summary 25
4.2.1 Hollow Stem Augering 25
4.2.2 Cable Tool Drilling 25
4.2.3 Rotary Drilling 25
4.3 Sample Preservation, Containers, Handling, and Storage 25
4.4 Interferences and Potential Problems 26
4.5 Equipment/Apparatus 26
4.6 Reagents 26
4.7 Procedures 26
4.7.1 Preparation 26
4.7.2 Field Preparation 26
4.7.3 Well Construction 28
4.8 Calculations 29
4.9 Quality Assurance/Quality Control 30
4.10 Data Validation 30
4.11 Health and Safety 30
5.0 WATER LEVEL MEASUREMENT: SOP #2151
5.1 Scope and Application 31
5.2 Method Summary 31
5.3 Sample Preservation, Containers, Handling and Storage 31
5.4 Interferences and Potential Problems 31
5.5 Equipment/Apparatus 32
5.6 Reagents 32
^9
5.7 Procedures J/
5.7.1 Preparation 32
O r,
5.7.2 Procedures J/
5.8 Calculations 33
5.9 Quality Assurance/Quality Control 33
5.10 Data Validation 33
5.11 Health and Safety 33
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Section
6.0 WELL DEVELOPMENT: SOP #2156
6.1 Scope and Application 35
6.2 Method Summary 35
6.3 Sample Preservations, Containers, Handling, and Storage 35
6.4 Interferences and Potential Problems 35
6.5 Equipment/Apparatus 35
6.6 Reagents 36
6.7 Procedures 36
6.7.1 Preparation 36
6.7.2 Operation 36
6.7.3 Post Operation 37
6.8 Calculations 37
6.9 Quality Assurance/Quality Control 37
6.10 Data Validation 38
6.11 Health and Safety 38
7.0 CONTROLLED PUMPING TEST: SOP #2157
7.1 Scope and Application 39
7.2 Method Summary 39
7.3 Sample Preservation, Containers, Handling, and Storage 39
7.4 Interferences and Potential Problems 39
7.5 Equipment/Apparatus 39
7.6 Reagents 40
7.7 Procedures 40
7.7.1 Preparation 40
7.7.2 Field Preparation 40
7.7.3 Pre-Test Monitoring 40
7.7.4 Step Test 40
7.7.5 Pump Test 41
7.7.6 Post Operation 42
7.8 Calculations 43
7.9 Quality Assurance/Quality Control 43
7.10 Data Validation 43
7.11 Health and Safety 43
SLUG TEST: SOP #2158
8.1 Scope and Application 4$
8.2 Method Summary 45
8.3 Sample Preservation, Containers, Handling and Storage 4$
8.4 Interferences and Potential Problems 4^
8.5 Equipment/Apparatus 4^
8.6 Reagents 45
8.7 Procedures 4^
vi
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Section Page
8.7.1 Field Procedures 45
8.7.2 Post Operation 47
8.8 Calculations 47
8.9 Quality Assurance/Quality Control 47
8.10 Data Validation 48
8.11 Health and Safety 48
APPENDIX A - Sampling Train Schematic
APPENDIX B - HNU Field Protocol 51
APPENDIX C - Forms 55
REFERENCES 61
vn
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List of Exhibits
Exhibit SOP
Table 1: Recommended Solvent Rinse for Soluble Contaminants #2006
Table 2: Advantages and Disadvantages of Various Groundwater #2007
Sampling Devices
Table 3: Advantages and Disadvantages of Various Drilling #2150
Techniques
Table 4: Time Intervals for Measuring Drawdown in the #2157
Pumped Well
Table 5: Time Intervals for Measuring Drawdown in an #2157
Observation Well
Figure 1: Sampling Train Schematic #2149
Forms: Well Completion Form #2150
Groundwater Level Data Form #2151
Pump/Recovery Test Data Sheet #2157
Slug Test Data Form #2158
Page
4
7
27
41
41
50
56
57
58
60
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Acknowledgments
Preparation of this document was directed by William A. Coakley, the Removal Program QA Coordinator of
the Environmental Response Team, Emergency Response Division. Additional support was provided under U.S.
EPA contract #68-03-3482 and U.S. EPA contract #68-WO-0036.
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1.0 SAMPLING EQUIPMENT DECONTAMINATION: SOP #2006
1.1
SCOPE AND APPLICATION
This Standard Operating Procedure (SOP) describes
methods used for preventing or reducing cross-
contamination, and provides general guidelines for
sampling equipment decontamination procedures at
a hazardous waste site. Preventing or minimizing
cross-contamination in sampled media and in
samples is important for preventing the introduction
of error into sampling results and for protecting the
health and safety of site personnel.
Removing or neutralizing contaminants that have
accumulated on sampling equipment ensures
protection of personnel from permeating substances,
reduces or eliminates transfer of contaminants to
clean areas, prevents the mixing of incompatible
substances, and minimizes the likelihood of sample
cross-contamination.
1.2 METHOD SUMMARY
Contaminants can be physically removed from
equipment, or deactivated by sterilization or
disinfection. Gross contamination of equipment
requires physical decontamination, including
abrasive and non-abrasive methods. These include
the use of brushes, air and wet blasting, and high-
pressure water cleaning, followed by a wash/rinse
process using appropriate cleaning solutions. Use
of a solvent rinse is required when organic
contamination is present.
1.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
This section is not applicable to this SOP.
1.4 INTERFERENCES AND
POTENTIAL PROBLEMS
xx The use of distilled/deionized water
commonly available from commercial
vendors may be acceptable for
decontamination of sampling equipment
provided that it has been verified by
laboratory analysis to be analyte free.
* An untreated potable water supply is not
an acceptable substitute for tap water. Tap
water may be used from any municipal
water treatment system for mixing of
decontamination solutions.
• Acids and solvents utilized in the
decontamination sequence pose the health
and safety risks of inhalation or skin
contact, and raise shipping concerns of
permeation or degradation.
• The site work plan must address disposal
of the spent decontamination solutions.
• Several procedures can be established to
minimize contact with waste and the
potential for contamination. For example:
Stress work practices that
minimize contact with hazardous
substances.
Use remote sampling, handling,
and container-opening techniques
when appropriate.
Cover monitoring and sampling
equipment with protective material
to minimize contamination.
Use disposable outer garments
and disposable sampling
equipment when appropriate.
1.5 EQUIPMENT/APPARATUS
appropriate personal protective clothing
non-phosphate detergent
selected solvents
long-handled brushes
drop cloths/plastic sheeting
trash container
paper towels
galvanized tubs or buckets
tap water
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distilled/deionized water
metal/plastic containers for storage and
disposal of contaminated wash solutions
pressurized sprayers for tap and
deionized/distilled water
sprayers for solvents
trash bags
aluminum foil
safety glasses or splash shield
emergency eyewash bottle
1.6 REAGENTS
In many cases, gross contamination can be removed
by physical means. The physical decontamination
techniques appropriate for equipment
decontamination can be grouped into two
categories: abrasive methods and non-abrasive
methods.
Abrasive Cleaning Methods
Abrasive cleaning methods work by rubbing and
wearing away the top layer of the surface containing
the contaminant. The following abrasive methods
arc available:
There are no reagents used in this procedure aside
from the actual decontamination solutions and
solvents. In general, the following solvents are
utilized for decontamination purposes:
xx 10% nitric acid(J)
x* acetone (pesticide grade)(*)
xx hexane (pesticide grade)(*)
* methanol
(:) Only if sample is to be analyzed for trace metals.
(2) Only if sample is to be analyzed for organics.
1.7 PROCEDURES
As part of the health and safety plan, develop and
set up a decontamination plan before any personnel
or equipment enter the areas of potential exposure.
The equipment decontamination plan should
include:
* the number, location, and layout of
decontamination stations
* which decontamination apparatus is needed
• the appropriate decontamination methods
methods for disposal of contaminated
clothing, apparatus, and solutions
1.7.1 Decontamination Methods
All personnel, samples, and equipment leaving the
contaminated area of a silt must be
decontaminated. Various decontamination methods
will either physically remove contaminants,
inactivate contaminants by disinfection or
sterilization, or do hot h.
xx Mechanical: Mechanical cleaning methods
use brushes of metal or nylon. The
amount and type of contaminants removed
will vary with the hardness of bristles,
length of brushing time, and degree of
brush contact.
* Air Blasting: Air blasting is used for
cleaning large equipment, such as
bulldozers, drilling rigs or auger bits. The
equipment used in air blast cleaning
employs compressed air to force abrasive
material through a nozzle at high velocities.
The distance between the nozzle and the
surface cleaned, as well as the pressure of
air, the time of application, and the angle
at which the abrasive strikes the surface,
determines cleaning efficiency. Air blasting
has several disadvantages: it is unable to
control the amount of material removed, it
can aerate contaminants, and it generates
large amounts of waste.
Wet Blasting: Wet blast cleaning, also
used to clean large equipment, involves use
of a suspended fine abrasive: delivered by
compressed air to the contaminated area.
The amount of materials removed can be
carefully controlled by using wry line
abrasives. This method generates a large
amount of waste.
Non-Abrasive Cleaning Methods
Non-abrasive cleaning methods work by forcing the
contaminant off of a surface with pressure. In
general, less of the equipment surface is removed
using non-ahrasive methods. The following non-
abrasive methods arc available:
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x* High-Pressure Water: This method
consists of a high-pressure pump, an
operator-controlled directional nozzle, and
a high pressure hose. Operating pressure
usually ranges from 340 to 680 atmospheres
(atm) which relates to flow rates of 20 to
140 liters per minute.
xx Ultra-High-Pressure Water: This system
produces a pressurized water jet (from
1,000 to 4,000 atm). The ultra-high-
pressure spray removes tightly-adhered
surface film. The water velocity ranges
from 500 m/sec (1,000 atm) to 900 m/sec
(4,000 atm). Additives can enhance the
method. This method is not applicable for
hand-held sampling equipment.
Disinfection/Rinse Methods
xx Disinfection: Disinfectants are a practical
means of inactivating infectious agents.
xx Sterilization: Standard sterilization
methods involve heating the equipment.
Sterilization is impractical for large
equipment.
xx Rinsing: Rinsing removes contaminants
through dilution, physical attraction, and
solubilization.
1.7.2 Field Sampling Equipment
Cleaning Procedures
Solvent rinses are not necessarily required when
organics are not a contaminant of concern and may
be eliminated from the sequence specified below.
Similarly, an acid rinse is not required if analysis
does not include inorganics.
1. Where applicable, follow physical removal
procedures specified in section 1.7.1.
2. Wash equipment with a non-phosphate
detergent solution.
3. Rinse with tap water.
4. Rinse with distilled/deionized water.
5. Rinse with 10% nitric acid if the sample will be
analyzed for trace organics.
6. Rinse with distilled/deionized water.
7. Use a solvent rinse (pesticide grade) if the
sample will be analyzed for organics.
8. Air dry the equipment completely.
9. Rinse again with distilled/deionized water.
Selection of the solvent for use in the
decontamination process is based on the
contaminants present at the site. Use of a solvent
is required when organic contamination is present
on-site. Typical solvents used for removal of
organic contaminants include acetone, hexane, or
water. An acid rinse step is required if metals are
present on-site. If a particular contaminant fraction
is not present at the site, the nine-step
decontamination procedure listed above may be
modified for site specificity. The decontamination
solvent used should not be among the contaminants
of concern at the site.
Table 1 lists solvent rinses which may be required
for elimination of particular chemicals. After each
solvent rinse, the equipment should be air dried and
rinsed with distilled/deionized water.
Sampling equipment that requires the use of plastic
tubing should be disassembled and the tubing
replaced with clean tubing, before commencement
of sampling and between sampling locations.
1.8 CALCULATIONS
This section is not applicable to this SOP.
1.9 QUALITY ASSURANCE/
QUALITY CONTROL
One type of quality control sample specific to the
field decontamination process is the rinsate blank.
The rinsate blank provides information on the
effectiveness of the decontamination process
employed in the field. When used in conjunction
with field blanks and trip blanks, a rinsate blank can
detect contamination during sample handling,
storage and sample transportation to the laboratory.
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Table 1: Recommended Solvent Rinse for Soluble Contaminants
SOLVENT
SOLUBLE CONTAMINANTS
Water
Low-chain hydrocarbons
Inorganic compounds
salts
Some organic acids and other polar compounds
Dilute Acids
xx Basic (caustic) compounds
x* Amines
xx Hydrazines
Dilute Bases — for example, detergent
and soap
Metals
Acidic compounds
Phenol
Thiols
Some nitro and sulfonic compounds
Organic Solvents^) - for example,
alcohols, ethers, ketones, aromatics,
straight-chain alkanes (e.g., hexane), and
common petroleum products (e.g., fuel,
oil, kerosene)
Nonpolar compounds (e.g., some organic compounds)
(:) - WARNING: Some organic solvents can permeate and/or degrade protective clothing.
A rinsate blank consists of a sample of analyte-free
(i.e, deionized) water which is passed over and
through a field decontaminated sampling device and
placed in a clean sample container.
Rinsate blanks should be run for all parameters of
interest at a rate of 1 per 20 for each parameter,
even if samples are not shipped that day. Rinsate
blanks are not required if dedicated sampling
equipment is used.
1.10 DATA VALIDATION
This section is not applicable to this SOP.
1.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA and specific health and
safety procedures.
Decontamination can pose hazards under certain
circumstances even though performed to protect
health and safety. Hazardous substances may be
incompatible with decontamination methods. For
example, the decontamination solution or solvent
may react with contaminants to produce heat,
explosion, or toxic products. Decontamination
methods may be incompatible with clothing or
equipment; some solvents can permeate or degrade
protective clothing. Also, decontamination solutions
and solvents may pose a direct health hazard to
workers through inhalation or skin contact, or if
they combust.
The decontamination solutions and solvents must be
determined to be compatible before use. Any
method that permeates, degrades, or damages
personal protective equipment should not be used.
If decontamination methods pose a direct health
hazard, measures should be taken to protect
personnel or the methods should be modified to
eliminate the hazard.
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2.0 GROUNDWATER WELL SAMPLING: SOP #2007
2.1
SCOPE AND APPLICATION
The objective of this Standard Operating Procedure
(SOP) is to provide general reference information
on sampling of groundwater wells. This guideline is
primarily concerned with the collection of water
samples from the saturated zone of the subsurface.
Every effort must be made to ensure that the
sample is representative of the particular zone of
water being sampled. These procedures are
designed to be used in conjunction with analyses for
the most common types °f groundwater
contaminants (e.g., volatile and semi-volatile organic
compounds, pesticides, metals, biological
parameters).
2.2 METHOD SUMMARY
Prior to sampling a monitoring well, the well must
be purged. This may be done with a number of
instruments. The most common of these are the
bailer, submersible pump, non-gas contact bladder
pump and inertia pump. At a minimum, three well
volumes should be purged, if possible. Equipment
must be decontaminated prior to use and between
wells. Once purging is completed and the correct
laboratory-cleaned sample containers have been
prepared, sampling may proceed. Sampling may be
conducted with any of the above instruments, and
need not be the same as the device used for
purging. Care should be taken when choosing the
sampling device as some will affect the integrity of
the sample. Sampling equipment must also be
decontaminated. Sampling should occur in a
progression from the least to most contaminated
well, if this information is known.
2.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
The type of analysis for which a sample is being
collected determines the type of bottle, preservative,
holding time, and filtering requirements. Samples
should be collected directly from the sampling
device into appropriate laboratory-cleaned
containers. Check that a Teflon liner is present in
the cap, if required. Attach a sample identification
label. Complete a field data sheet, a chain of
custody form and record all pertinent data in the
site logbook.
Samples shall be appropriately preserved, labelled,
logged, and placed in a cooler to be maintained at
4°C. Samples must be shipped well before the
holding time is over and ideally should be shipped
within 24 hours of sample collection. It is
imperative that these samples be shipped or
delivered daily to the analytical laboratory in order
to maximize the time available for the laboratory to
perform the analysis. The bottles should be shipped
with adequate packing and cooling to ensure that
they arrive intact.
Certain conditions may require special handling
techniques. For example, treatment of a sample for
volatile organic (WA) analysis with sodium
thiosulfate preservative is required if there is
residual chlorine in the water (such as public water
supply) that could cause free radical chlorination
and change the identity of the original contaminants.
However, sodium thiosulfate should not be used if
chlorine is not present in the water. Special
requirements must be determined prior to
conducting fieldwork.
2.4 INTERFERENCES AND
POTENTIAL PROBLEMS
2.4.1 General
The primary goal of groundwater sampling is to
obtain a representative sample of the groundwater
body. Analysis can be compromised by field
personnel in two primary ways: (1) taking an
unrepresentative sample, or (2) by incorrect
handling of the sample. There are numerous ways
of introducing foreign contaminants into a sample,
and these must be avoided by following strict
sampling procedures and only utilizing trained field
personnel.
2.4.2 Purging
In a non-pumping well, there will be little or no
vertical mixing of the water, and stratification will
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occur. The well water in the screened section will
mix with the groundwater due to normal flow
patterns, but the well water above the screened
section will remain isolated, become stagnant and
lack the VOAs representative of the groundwater.
Sampling personnel should realize that stagnant
water may contain foreign material inadvertently or
deliberately introduced from the surface, resulting
in an unrepresentative sample. To safeguard
against collecting nonrepresentative stagnant water,
follow these guidelines during sampling:
xx As a general rule, all monitoring wells
should be pumped or bailed prior to
sampling. Purge water should be
containerized on site or handled as
specified in the site-specific project plan.
Evacuation of a minimum of one volume of
water in the well casing, and preferably
three to five volumes, is recommended for
a representative sample. In a high-yielding
ground water formation and where there is
no stagnant water in the well above the
screened section, evacuation prior to
sample withdrawal is not as critical.
However, in all cases where the monitoring
data is to be used for enforcement actions,
evacuation is recommended.
x For wells that can be pumped or bailed to
dryness with the equipment being used, the
well should be evacuated and allowed to
recover prior to sample withdrawal. If the
recovery rate is fairly rapid and the
schedule allows, evacuation of more than
one volume of water is preferred. If
recovery is slow, sample the well upon
recovery after one evacuation.
x A nonrepresentative sample can also result
from excessive pre-pumping of the
monitoring well. Stratification of the
leachate concentration in the groundwater
formation may occur, or heavier-than-water
compounds may sink to the lower portions
of the aquifer. Excessive pumping can
dilute or increase the contaminant
concentrations from what is representative
of the sampling point of interest.
2.4.3 Materials
Samplers and evacuation equipment (bladders,
pumps, bailers, tubing, etc.) should be limited to
those made with stainless steel, Teflon, and glass in
areas where concentrations are expected to be at or
near the detection limit. The tendency of organics
to leach into and out of many materials make the
selection of materials critical for trace analyses.
The use of plastics, such as PVC or polyethylene,
should be avoided when analyzing for organics.
However, PVC may be used for evacuation
equipment as it will not come in contact with the
sample.
Table 2 on page 7 discusses the advantages and
disadvantages of certain equipment.
2.5 EQUIPMENT/APPARATUS
2.5.1 General
water level indicator
- electric sounder
- steel tape
- transducer
- reflection sounder
- airline
depth sounder
appropriate keys for well cap locks
steel brush
HNU or OVA (whichever is most
appropriate)
logbook
calculator
field data sheets
chain of custody forms
forms and seals
sample containers
Engineer's rule
sharp knife (locking blade)
tool box (to include at least: screwdrivers,
pliers, hacksaw, hammer, flashlight,
adjustable wrench)
leather work gloves
appropriate health and safety gear
5-gallon pail
plastic sheeting
shipping containers
packing materials
bolt cutters
Ziploc plastic bags
containers for evacuation of liquids
decontamination solutions
tap water
non-phosphate soap
several brushes
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Table 2: Advantages and Disadvantages
of Various Groundwater Sampling Devices
Device
Advantages
Disadvantages
Bailer
MS* The only practical limitations are size and
materials
x* No power source needed
xx Portable
xx Inexpensive; it can be dedicated and hung in a
well reducing the chances of cross-
contamination
xx Minimal outgassing of volatile organics while
sample is in bailer
xx Readily available
xx Removes stagnant water first
xx Rapid, simple method for removing small
volumes of purge water
Time consuming, especially for large wells
Transfer of sample may cause aeration
Submersible
Pump
xx Portable; can be used on an unlimited number
of wells
xx Relatively high pumping rate (dependent on
depth and size of pump)
xx Generally very reliable; does not require
priming
xx Potential for effects on analysis of trace
organics
xx Heavy and cumbersome, particularly in
deeper wells
xx Expensive
xx Power source needed
xx Susceptible to damage from silt or sediment
xx Impractical in low yielding or shallow wells
Non-Gas Contact
Bladder Pump
! Maintains integrity of sample
fEasy to use
f Difficult to clean although dedicated tubing
and bladder may be used
< Only useful to approximately 100 feet in
depth
f Supply of gas for operation (bottled gas
and/or compressor) is difficult to obtain
and is cumbersome
Suction Pump
: Portable, inexpensive, and readily available
xx Only useful to approximately 25 feet or less
in depth
xx Vacuum can cause loss of dissolved gases
and volatile organics
xx Pump must be primed and vacuum is often
difficult to maintain
xx May cause pH modification
Inertia Pump
xx Portable, inexpensive, and readily available
xx Rapid method for purging relatively shallow
wells
xx Only useful to approximately 70 feet or less
in depth
xx May be time consuming to use
xx Labor intensive
xx WaTerra pump is only effective in 2-inch
diameter wells
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• pails or tubs
• aluminum foil
• garden sprayer
• preservatives
• distilled or deionized water
2.5.2 Bailer
• clean, decontaminated bailer(s) of
appropriate size and construction material
• nylon line, enough to dedicate to each well
• Teflon-coated bailer wire
• sharp knife
• aluminum foil (to wrap clean bailers)
• 5-gallon bucket
2.5.3 Submersible Pump
pump(s)
generator (110, 120, or 240 volt) or 12-volt
battery if inaccessible to field vehicle
1-inch black PVC coil pipe -- enough to
dedicate to each well
hose clamps
safety cable
tool box supplement
- pipe wrenches, 2
- wire strippers
- electrical tape
- heat shrink
- hose connectors
- Teflon tape
winch or pulley
gasoline for generator
flow meter with gate valve
1-inch nipples and various plumbing (i.e.,
pipe connectors)
2.5.4 Non-Gas Contact Bladder Pump
non-gas contact bladder pump
compressor or nitrogen gas tank
batteries and charger
Teflon tubing — enough to dedicate to each
well
Swagelock fitting
toolbox supplements -- same as
submersible pump
2.5.5 Suction Pump
• gasoline ~ if required
• toolbox
xx plumbing fittings
* flow meter with gate valve
pump
black coil tubing — enough to dedicate to
each well
2.5.6 Inertia Pump
xx pump assembly (WaTerra pump, piston
Pump)
xx 5-gallon bucket
2.6 REAGENTS
Reagents will be utilized for preservation of samples
and for decontamination of sampling equipment.
The preservation required is specified by the
analysis to be performed. Decontamination
solutions are specified in ERT SOP #2006,
Sampling Equipment Decontamination.
2.7 PROCEDURES
2.7.1 Preparation
1. Determine the extent of the sampling effort,
the sampling methods to be employed, and
which equipment and supplies are needed.
2. Obtain necessary sampling and monitoring
equipment.
3. Decontaminate or preclean equipment, and
ensure that it is in working order.
4. Prepare scheduling and coordinate with staff,
clients, and regulatory agency, if appropriate.
5. Perform a general site survey prior to site entry
in accordance with the site-specific health and
safety plan.
6. Identify and mark all sampling locations.
2.7.2 Field Preparation
1. Start at the least contaminated well, if known.
2. Lay plastic sheeting around the well to
minimize likelihood of contamination of
equipment from soil adjacent to the well.
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3. Remove locking well cap, note location, time of
day, and date in field notebook or an
appropriate log form.
4. Remove well casing cap.
5. Screen headspace of well with an appropriate
monitoring instrument to determine the
presence of volatile organic compounds and
record in site logbook.
6. Lower water level measuring device or
equivalent (i.e., permanently installed
transducers or airline) into well until water
surface is encountered.
However, monitoring for defining a contaminant
plume requires a representative sample of a small
volume of the aquifer. These circumstances require
that the well be pumped enough to remove the
stagnant water but not enough to induce flow from
other areas. Generally, three well volumes are
considered effective, or calculations can be made to
determine, on the basis of the aquifer parameters
and well dimensions, the appropriate volume to
remove prior to sampling.
During purging, water level measurements may be
taken regularly at 15- to 30-second intervals. This
data may be used to compute aquifer transmissivity
and other hydraulic characteristics.
7. Measure distance from water surface to
reference measuring point on well casing or
protective barrier post and record in site
logbook. Alternatively, if there is no reference
point, note that water level measurement is
from top of steel casing, top of PVC riser pipe,
from ground surface, or some other position on
the well head.
8. Measure total depth of well (do this at least
twice to confirm measurement) and record in
site logbook or on log form.
9. Calculate the volume of water in the well and
the volume to be purged using the calculations
in Section 2.8.
10. Select the appropriate purging and sampling
equipment.
2.7.3 Evacuation of Static Water
(Purging)
The amount of flushing a well receives prior to
sample collection depends on the intent of the
monitoring program as well as the hydrogeologic
conditions. Programs where overall quality
determination of water resources are involved may
require long pumping periods to obtain a sample
that is representative of a large volume of that
aquifer. The pumped volume can be determined
prior to sampling so that the sample is a composite
of known volume of the aquifer, or the well can be
pumped until the stabilization of parameters such as
temperature, electrical conductance, or pH has
occurred.
The following well evacuation devices are most
commonly used. Other evacuation devices are
available, but have been omitted in this discussion
due to their limited use.
Bailer
Bailers are the simplest purging device used and
have many advantages. They generally consist of a
rigid length of tube, usually with a ball check-valve
at the bottom. A line is used to lower the bailer
into the well and retrieve a volume of water. The
three most common types of bailer are PVC,
Teflon, and stainless steel.
This manual method of purging is best suited to
shallow or narrow diameter wells. For deep, larger
diameter wells which require evacuation of large
volumes of water, other mechanical devices may be
more appropriate.
Bailing equipment includes a clean decontaminated
bailer, Teflon or nylon line, a sharp knife, and
plastic sheeting.
1. Determine the volume of water to be purged as
described in Section 2.7.2, Field Preparation.
2. Lay plastic sheeting around the well to prevent
contamination of the bailer line with foreign
materials.
3. Attach the line to the bailer and lower until the
bailer is completely submerged.
4. Pull bailer out ensuring that the line either falls
onto a clean area of plastic sheeting or never
touches the ground.
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5. Empty the bailer into a pail until full to
determine the number of bails necessary to
achieve the required purge volume.
6. Thereafter, pour the water into a container and
dispose of purge waters as specified in the site-
specific project plan.
Submersible Pump
Submersible pumps are generally constructed of
plastic, rubber, and metal parts which may affect the
analysis of samples for certain trace organics and
inorganics. As a consequence, submersible pumps
may not be appropriate for investigations requiring
analyses of samples for trace contaminants.
However, they are still useful for pre-sample
purging. However, the pump must have a check
valve to prevent water in the pump and the pipe
from rushing back into the well.
Submersible pumps generally use one of two types
of power supplies, either electric or compressed gas.
Electric pumps can be powered by a 12-volt DC
rechargeable battery, or a 110- or 220-volt AC
power supply. Those units powered by compressed
gas normally use a small electric compressor which
also needs 12-volt DC or 110-volt AC power. They
may also utilize compressed gas from bottles.
Pumps differ according to the depth and diameter
of the monitoring wells.
1. Determine the volume of water to be purged as
described in section 2.7.2, Field Preparation.
2. Lay plastic sheeting around the well to prevent
contamination of pumps, hoses or lines with
foreign materials.
3. Assemble pump, hoses and safety cable, and
lower the pump into the well. Make sure the
pump is deep enough so that purging does not
evacuate all the water. (Running the pump
without water may cause damage.)
4. Attach flow meter to the outlet hose to
measure the volume of water purged.
5. Attach power supply, and purge well until
specified volume of water has been evacuated
(or until field parameters, such as temperature,
pH, conductivity, etc. have stabilized). Do not
allow the pump to run dry. If the pumping rate
exceeds the well recharge rate, lower the pump
further into the well, and continue pumping.
6. Collect and dispose of purge waters as specified
in the site-specific project plan.
Non-Contact Gas Bladder Pump
For this procedure, an all stainless-steel and Teflon
Middleburg-squeeze bladder pump (e.g., IEA,
TIMCO, Well Wizard, Geoguard, and others) is
used to provide the least amount of material
interference to the sample (Barcelona, 1985).
Water comes into contact with the inside of the
bladder (Teflon) and the sample tubing, also Teflon,
that may be dedicated to each well. Some wells
may have permanently installed bladder pumps (i.e.,
Well Wizard, Geoguard), that will be used to
sample for all parameters.
1. Assemble Teflon tubing, pump and charged
control box.
2. Use the same procedure for purging with a
bladder pump as for a submersible pump.
3. Be sure to adjust flow rate to prevent violent
jolting of the hose as sample is drawn in.
Suction Pump
There are many different types of suction pumps.
They include: centrifugal, peristaltic and diaphragm.
Diaphragm pumps can be used for well evacuation
at a fast pumping rate and sampling at a low
pumping rate. The peristaltic pump is a low-volume
pump that uses rollers to squeeze the flexible
tubing, thereby creating suction. This tubing can be
dedicated to a well to prevent cross-contamination.
Peristaltic pumps, however, require a power source.
1. Assemble the pump, tubing, and power source
if necessary.
2. To purge with a suction pump, follow the exact
procedures outlined for the submersible pump.
Inertia Pump
Inertia pumps, such as the WaTerra pump and
piston pump, are manually operated. They are
appropriate to use when wells are too deep to bail
by hand, but are not inaccessible enough to warrant
an automatic (submersible, etc.) pump. These
10
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pumps are made of plastic and may be either
decontaminated or discarded, after use.
1. Determine the volume of water to be purged as
described in Section 2.7.2, Field Preparation.
2. Lay plastic sheeting around the well to prevent
contamination of pumps or hoses with foreign
materials.
3. Assemble pump, and lower to the appropriate
depth in the well.
4. Begin pumping manually, discharging water into
a 5-gallon bucket (or other graduated vessel).
Purge until specified volume of water has been
evacuated (or until field parameters such as
temperature, pH, conductivity, etc. have
stabilized).
5. Collect and dispose of purge waters as specified
in the site-specific project plan.
2.7.4 Sampling
Sample withdrawal methods require the use of
pumps, compressed air, bailers, and samplers.
Ideally, purging and sample withdrawal equipment
should be completely inert, economical to use, easily
cleaned, sterilized, reusable, able to operate at
remote sites in the absence of power resources, and
capable of delivering variable rates for sample
collection.
There are several factors to take into consideration
when choosing a sampling device. Care should be
taken when reviewing the advantages or
disadvantages of any one device. It may be
appropriate to use a different device to sample than
that which was used to purge. The most common
example of this is the use of a submersible pump to
purge and a bailer to sample.
Bailer
The positive-displacement volatile sampling bailer
(by GPI) is perhaps the most appropriate for
collection of water samples for volatile analysis.
Other bailer types (messenger, bottom fill, etc.) are
less desirable, but may be mandated by cost and site
conditions. Generally, bailers can provide an
acceptable sample, providing that sampling
personnel use extra care in the collection process.
1. Surround the monitoring well with clean plastic
sheeting.
2. Attach a line to the bailer. If a bailer was used
for purging, the same bailer and line may be
used for sampling.
3. Lower the bailer slowly and gently into the
well, taking care not to shake the casing sides
or to splash the bailer into the water. Stop
lowering at a point adjacent to the screen.
4. Allow bailer to fill and then slowly and gently
retrieve the bailer from the well, avoiding
contact with the casing, so as not to knock
flakes of rust or other foreign materials into
the bailer.
5. Remove the cap from the sample container and
place it on the plastic sheet or in a location
where it will not become contaminated. See
Section 2.7.7 for special considerations on VOA
samples.
6. Begin pouring slowly from the bailer.
7. Filter and preserve samples as required by
sampling plan.
8. Cap the sample container tightly and place pre-
labeled sample container in a carrier.
9. Replace the well cap.
10. Log all samples in the site logbook and on field
data sheets and label all samples.
11. Package samples and complete necessary
paperwork.
12. Transport sample to decontamination zone to
prepare it for transport to analytical laboratory.
Submersible Pump
Although it is recommended that samples not be
collected with a submersible pump due to the
reasons stated in Section 2.4, there are some
situations where they may be used.
1. Allow the monitoring well to recharge after
purging, keeping the pump just above the
screened section,
11
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2. Attach gate valve to hose (if not already fitted),
and reduce flow of water to a manageable
sampling rate.
3. Assemble the appropriate bottles.
4. If no gate valve is available, run the water down
the side of a clean jar and fill the sample
bottles from the jar.
5. Cap the sample container tightly and place pre-
labeled sample container in a carrier.
6. Replace the wel 1 cap.
7. Log all samples in the site logbook and on the
field data sheets and label all samples.
8. Package samples and complete necessary
paperwork.
9. Transport sample to decontamination zone for
preparation for transport to analytical
laboratory.
10. Upon completion, remove pump and assembly
and fully decontaminate prior to setting into the
next sample well. Dedicate the tubing to the
hole.
Non-Gas Contact Bladder Pump
The use of a non-gas contact positive displacement
bladder pump is often mandated by the use of
dedicated pumps installed in wells. These pumps
are also suitable for shallow (less than 100 feet)
wells. They are somewhat difficult to clean, but
may be used with dedicated sample tubing to avoid
cleaning. These pumps require a power supply and
a compressed gas supply (or compressor). They
may be operated at variable flow and pressure rates
making them ideal for both purging and sampling.
Barcelona (1984) and Nielsen (1985) report that the
non-gas contact positive displacement pumps cause
the least amount of alteration in sample integrity as
compared to other sample retrieval methods.
1. Allow well to recharge after purging.
2. Assemble the appropriate bottles.
3. Turn pump on, increase the cycle time and
reduce the pressure to the minimum that will
allow the sample to come to the surface.
4. Cap the sample container tightly and place pre-
labeled sample container in a carrier.
5. Replace the well cap.
6. Log all samples in the site logbook and on field
data sheets and label all samples.
7. Package samples and complete necessary
paperwork.
8. Transport sample to decontamination zone for
preparation for transport to analytical
laboratory.
9. On completion, remove the tubing from the
well and either replace the Teflon tubing and
bladder with new dedicated tubing and bladder
or rigorously decontaminate the existing
materials.
10. Collect non-filtered samples directly from the
outlet tubing into the sample bottle.
11. For filtered samples, connect the pump outlet
tubing directly to the filter unit. The pump
pressure should remain decreased so that the
pressure build-up on the filter does not blow
out the pump bladder or displace the filter.
For the Geotech barrel filter, no actual
connections are necessary so this is not a
concern.
Suction Pump
In view of the limitations of suction pumps, they are
not recommended for sampling purposes.
Inertia Pump
Inertia pumps may be used to collect samples. It is
more common, however, to purge with these pumps
and sample with a bailer.
1. Following well evacuation, allow the well to
recharge.
2. Assemble the appropriate bottles.
12
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3. Since these pumps are manually operated, the
flow rate may be regulated by the sampler.
The sample may be discharged from the pump
outlet directly into the appropriate sample
container.
4. Cap the sample container tightly and place pre-
labeled sample container in a carrier.
5. Replace the well cap.
6. Log all samples in the site logbook and on field
data sheets and label all samples.
7. Package samples and complete necessary
paperwork.
8. Transport sample to decontamination zone for
preparation for transport to analytical
laboratory.
9. Upon completion, remove pump and
decontaminate or discard, as appropriate.
2.7.5 Filtering
For samples that require filtering, such as samples
which will be analyzed for total metals, the filter
must be decontaminated prior to use and between
uses. Filters work by two methods. A barrel filter
such as the " Geotech" filter works with a bicycle
pump, which is used to build up positive pressure in
the chamber containing the sample. The sample is
then forced through the filter paper (minimum size
0.45u) into a jar placed underneath. The barrel
itself is filled manually from the bailer or directly
via the hose of the sampling pump. The pressure
must be maintained up to 30 psi by periodic
pumping.
A vacuum type filter involves two chambers, the
upper chamber contains the sample and a filter
(minimum size 0.45|i ) divides the chambers.
Using a hand pump or a Gilian type pump, air is
withdrawn from the lower chamber, creating a
vacuum and thus causing the sample to move
through the filter into the lower chamber where it
is drained into a sample jar, repeated pumping may
be required to drain all the sample into the lower
chamber. If preservation of the sample is necessary,
this should be done after filtering.
2.7.6 Post Operation
After all samples are collected and preserved, the
sampling equipment should be decontaminated prior
to sampling another well. This will prevent
cross-contamination of equipment and monitoring
wells between locations.
1. Decontaminate all equipment.
2. Replace sampling equipment in storage
containers.
3. Prepare and transport water samples to the
laboratory. Check sample documentation and
make sure samples are properly packed for
shipment.
2.7.7 Special Considerations for VOA
Sampling
The proper collection of a sample for volatile
organics requires minimal disturbance of the sample
to limit volatilization and therefore a loss of
volatiles from the sample.
Sample retrieval systems suitable for the valid
collection of volatile organic samples are: positive
displacement bladder pumps, gear driven
submersible pumps, syringe samplers and bailers
(Barcelona, 1984; Nielsen, 1985). Field conditions
and other constraints will limit the choice of
appropriate systems. The focus of concern must be
to provide a valid sample for analysis, one which has
been subjected to the least amount of turbulence
possible.
The following procedures should be followed:
1. Open the vial, set cap in a clean place, and
collect the sample during the middle of the
cycle. When collecting duplicates, collect both
samples at the same time.
2. Fill the vial to just overflowing. Do not rinse
the vial, nor excessively overfill it. There
should be a convex meniscus on the top of the
vial.
3. Check that the cap has not been contaminated
(splashed) and carefully cap the vial. Place the
cap directly over the top and screw down
firmly. Do not overtighten and break the cap.
13
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4 Invert the vial and tap gently. Observe vial for
at least 10 seconds. If an air bubble appears,
discard the sample and begin again. It is
imperative that no entrapped air is in the
sample vial.
5. Immediately place the vial in the protective
foam sleeve and place into the cooler, oriented
so that it is lying on its side, not straight up.
6. The holding time for VOAs is 7 days. Samples
should be shipped or delivered to the laboratory
daily so as not to exceed the holding time.
Ensure that the samples remain at 4°C, but do
not allow them to freeze.
2.8 CALCULATIONS
There are no calculations necessary to implement
this procedure. However, if it is necessary to
calculate the volume of the well, utilize the
following equation:
Well volume = nr2h (cf) [Equation 1]
where:
n
r =
cf =
radius of monitoring well (feet)
height of the water column (feet)
[This may be determined by
subtracting the depth to water
from the total depth of the well as
measured from the same reference
point.]
conversion factor (gal/ft3) = 7.48
gal/ft3 [In this equation, 7.48
gal/ft3 is the necessary conversion
factor.]
Monitoring wells are typically 2, 3, 4, or 6 inches in
diameter. If you know the diameter of the
monitoring well, there are a number of standard
conversion factors which can be used to simplify the
equation above.
The volume, in gallons per linear foot, for various
standard monitoring well diameters can be
calculated as follows:
v = nr2 (cf) [Equation 2)
where:
v = volume in gallons per linear foot
n = pi
= radius of monitoring well (feet)
cf = conversion factor (7.48 gal/ft3)
For a 2-inch diameter well, the volume in gallons
per linear foot can be calculated as follows:
v = nr2 (cf) [Equation 2)
= 3.14 (1/12 ft)2 7.48 gal/ft3
= 0.1632 gal/ft
Remember that if you have a 2-inch diameter, well
you must convert this to the radius in feet to be
able to use the equation.
The volume in gallons per linear foot for the
common size monitoring wells are as follows:
Well Diameter
2 inches
3 inches
4 inches
6 inches
v (volume in gal/ft.')
0.1632
0.3672
0.6528
1.4688
If you utilize the conversion factors above, Equation
1 should be modified as follows:
Well volume = (h)(v) [Equation 3)
where:
h = height of water column (feet)
v = volume in gallons per linear foot as
calculated from Equation 2
2.9 QUALITY ASSURANCE/
QUALITY CONTROL
There are no specific quality assurance activities
which apply to the implementation of these
procedures. However, the following general QA
procedures apply:
* All data must be documented on field data
sheets or within site logbooks.
xx All instrumentation must be operated in
accordance with operating instructions as
supplied by the manufacturer, unless
14
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otherwise specified in the work plan.
Equipment checkout and calibration
activities must occur prior to
sampling/operation and they must be
documented.
2.10 DATA VALIDATION
This section is not applicable to this SOP.
2.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA and specific health and
safety procedures. More specifically, depending
upon the site-specific contaminants, various
protective programs must be implemented prior to
sampling the first well. The site health and safety
plan should be reviewed with specific emphasis
placed on the protection program planned for the
well sampling tasks. Standard safe operating
practices should be followed such as minimizing
contact with potential contaminants in both the
vapor phase and liquid matrix through the use of
respirators and disposable clothing.
For volatile organic contaminants:
,s Avoid breathing constituents venting from
the well.
xx Pre-survey the well head-space with an
FID/PID prior to sampling.
xx If monitoring results indicate organic
constituents, sampling activities may be
conducted in Level C protection. At a
minimum, skin protection will be afforded
by disposable protective clothing.
Physical hazards associated with well sampling are:
x Lifting injuries associated with pump and
bailer retrieval; moving equipment.
x Use of pocket knives for cutting discharge
hose.
x Heat/cold stress as a result of exposure to
extreme temperatures (may be heightened
by protective clothing).
xx Slip, trip, fall conditions as a result of
pump discharge.
x Restricted mobility due to the wearing of
protective clothing.
15
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3.0 SOIL GAS SAMPLING: SOP #2149
3.1 SCOPE AND APPLICATION
Soil gas monitoring provides a quick means of waste
site evaluation. Using this method, underground
contamination can be identified, and the source,
extent, and movement of the pollutants can be
traced.
This Standard Operating Procedure (SOP) outlines
the methods used by EPA/ERT in installing soil gas
wells; measuring organic levels in the soil gas using
an HNU PI 101 Portable Photoionization Analyzer
and/or other air monitoring devices; and sampling
the soil gas using Tedlar bags, Tenax sorbent tubes,
and SUMMA canisters.
3.2 METHOD SUMMARY
A 3/8-inch diameter hole is driven into the ground
to a depth of 4 to 5 feet using a commercially
available "slam bar". (Soil gas can also be sampled
at other depths by the use of a longer bar or bar
attachments.) A I/Cinch O.D. stainless steel probe
is inserted into the hole. The hole is then sealed at
the top around the probe using modeling clay. The
gas contained in the interstitial spaces of the soil is
sampled by pulling the sample through the probe
using an air sampling pump. The sample may be
stored in Tedlar bags, drawn through sorbent
cartridges, or analyzed directly using a direct
reading instrument.
The air sampling pump is not used for SUMMA
canister sampling of soil gas. Sampling is achieved
by soil gas equilibration with the evacuated
SUMMA canister. Other field air monitoring
devices, such as the combustible gas indicator (MSA
CGI/02 Meter, Model 260) and the organic vapor
analyzer (Foxboro OVA, Model 128), can also be
used depending on specific site conditions.
Measurement of soil temperature using a
temperature probe may also be desirable. Bagged
samples are usually analyzed in a field laboratory
using a portable Photovac GC.
Power driven sampling probes may be utilized when
soil conditions make sampling by hand unfeasible
(i.e., frozen ground, very dense clays, pavement,
etc.). Commercially available soil gas sampling
probes (hollow, l/2inch O.D. steel probes) can be
driven to the desired depth using a power hammer
(e.g., Bosch Demolition Hammer). Samples can be
drawn through the probe itself, or through Teflon
tubing inserted through the probe and attached to
the probe point. Samples are collected and
analyzed as described above.
3.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
3.3.1 Tedlar Bag
Soil gas samples are generally contained in 1-L
Tedlar bags. Bagged samples are best stored in
coolers to protect the bags from any damage that
may occur in the field or in transit. In addition,
coolers ensure the integrity of the samples by
keeping them at a cool temperature and out of
direct sunlight. Samples should be analyzed as soon
as possible, preferably within 24 to 48 hours.
3.3.2 Tenax Tube
Bagged samples can also be drawn into Tenax or
other sorbent tubes to undergo lab GC/MS analysis.
If Tenax tubes are to be utilized, special care must
be taken to avoid contamination. Handling of the
tubes should be kept to a minimum, and samplers
must wear nylon or other lint-free gloves. After
sampling, each tube should be stored in a clean,
sealed culture tube; the ends packed with clean
glass wool to protect the sorbent tube from
breakage. The culture tubes should be kept cool
and wrapped in aluminum foil to prevent any
photodegradation of samples (see Section 3.7.4.).
3.3.3 SUMMA Canister
The SUMMA canisters used for soil gas sampling
have a 6-L sample capacity and are certified clean
by GC/MS analysis before being utilized in the
field. After sampling is completed, they are stored
and shipped in travel cases.
17
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3.4 INTERFERENCES AND
POTENTIAL PROBLEMS
3.4.1 HNU Measurements
A number of factors can affect the response of the
HNU PI 101. High humidity can cause lamp
fogging and decreased sensitivity. This can be
significant when soil moisture levels are high, or
when a soil gas well is actually in groundwater.
High concentrations of methane can cause a
downscale deflection of the meter. High and low
temperature, electrical fields, FM radio
transmission, and naturally occurring compounds,
such as terpenes in wooded areas, will also affect
instrument response.
Other field screening instruments can be affected by
interferences. Consult the manufacturers' manuals.
3.4.2 Factors Affecting Organic
Concentrations in Soil Gas
Concentrations in soil gas are affected by
dissolution, adsorption, and partitioning.
Partitioning refers to the ratio of component found
in a saturated vapor above an aqueous solution to
the amount in the solution; this can, in theory, be
calculated using the Henry's Law constants.
Contaminants can also be adsorbed onto inorganic
soil components or "dissolved" in organic
components. These factors can result in a lowering
of the partitioning coefficient.
Soil "tightness" or amount of void space in the soil
matrix, will affect the rate of recharging of gas into
the soil gas well.
Existence of a high, or perched, water table, or of
an impermeable underlying layer (such as a clay
lens or layer of buried slag) may interfere with
sampling of the soil gas. Knowledge of site geology
is useful in such situations, and can prevent
inaccurate sampling.
3.4.3 Soil Probe Clogging
A common problem with this sampling method is
soil probe clogging. A clogged probe can be
identified by using an in-line vacuum gauge or by
listening for the sound of the pump laboring. This
problem can usually be eliminated by using a wire
cable to clear the probe (see procedure #3 in
Section 3.7.1).
3.4.4 Underground Utilities
Prior to selecting sample locations, an underground
utility search is recommended. The local utility
companies can be contacted and requested to mark
the locations of their underground lines. Sampling
plans can then be drawn up accordingly. Each
sample location should also be screened with a
metal detector or magnetometer to verify that no
underground pipes or drums exist.
3.5 EQUIPMENT/APPARATUS
3.5.1 Slam Bar Method
• slam bar (one per sampling team)
• soil gas probes, stainless steel tubing, 1/4-
inch O.D., 5 foot length
• flexible wire or cable used for clearing the
tubing during insertion into the well
• "quick connect" fittings to connect sampling
probe tubing, monitoring instruments, and
Gilian pumps to appropriate fittings on
vacuum box
• modeling clay
• vacuum box for drawing a vacuum around
Tedlar bag for sample collection (one per
sampling team)
• Gilian pump Model HFS113A adjusted to
approximately 3.0 L/min (one to two per
sampling team)
• 1/4-inch Teflon tubing, 2 to 3 foot lengths,
for replacement of contaminated sample
line
• Tedlar bags, 1 liter, at least one bag per
sample point
• soil gas sampling labels, field data sheets,
logbook, etc.
• HNU Model PI 101, or other field air
monitoring devices, (one per sampling
team)
• ice chest, for carrying equipment and for
protection of samples (two per sampling
team)
• metal detector or magnetometer, for
detecting underground utilities/
pipes/drums (one per sampling team)
• Photovac GC, for field-lab analysis of
bagged samples
• SUMMA canisters (plus their shipping
cases) for sample, storage and
transportation
18
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3.5.2 Power Hammer Method
Bosch demolition hammer
l/2inch O.D. steel probes, extensions, and
points
dedicated aluminum sampling points
Teflon tubing, I/Cinch O.D.
"quick connect" fittings to connect sampling
probe tubing, monitoring instruments, and
Gilian pumps to appropriate fittings on
vacuum box
modeling clay
vacuum box for drawing a vacuum around
Tedlar bag for sample collection (one per
sampling team)
Gilian pump Model HFS113A adjusted to
approximately 3.0 L/min (one to two per
sampling team)
1/4-inch Teflon tubing, 2 to 3 foot lengths,
for replacement of contaminated sample
line
Tedlar bags, 1 liter, at least one bag per
sample point
soil gas sampling labels, field data sheets,
logbook, etc.
HNU Model PI 101, or other field air
monitoring devices, (one per sampling
team)
ice chest, for carrying equipment and for
protection of samples (two per sampling
team)
metal detector or magnetometer, for
detecting underground utilities/
pipes/drums (one per sampling team)
Photovac GC, for field-lab analysis of
bagged samples
SUMMA canisters (plus their shipping
cases) for sample, storage and
transportation
generator with extension cords
high lift jack assembly for removing probes
3.6 REAGENTS
• HNU Systems Inc. Calibration Gas for
HNU Model PI 101, and/or calibration gas
for other field air monitoring devices
* deionized organic-free water, for
decontamination
• methanol, HPLC grade, for
decontamination
* ultra-zero grade compressed air, for field
blanks
standard gas preparations for Photovac GC
calibration and Tedlar bag spikes
3.7 PROCEDURES
3.7.1 Soil Gas Well Installation
1. Initially, make a hole slightly deeper than the
desired depth. For sampling up to 5 feet, use
a 5-foot single piston slam bar. For deeper
depths, use a piston slam bar with threaded 4-
foot-long extensions. Other techniques can be
used, so long as holes are of narrow diameter
and no contamination is introduced.
2. After the hole is made, carefully withdraw the
slam bar to prevent collapse of the walls of the
hole. Then insert the soil gas probe.
3. It is necessary to prevent plugging of the probe,
especially for deeper holes. Place a metal wire
or cable, slightly longer than the probe, into the
probe prior to inserting into the hole. Insert
the probe to full depth, then pull it up 3 to 6
inches, then clear it by moving the cable up and
down. The cable is removed before sampling.
4. Seal the top of the sample hole at the surface
against ambient air infiltration by using
modeling clay molded around the probe at the
surface of the hole.
5. If conditions preclude hand installation of the
soil gas wells, the power driven system may be
employed. Use the generator-powered
demolition hammer to drive the probe to the
desired depth (up to 12 feet may be attained
with extensions). Pull the probe up 1 to 3
inches if the retractable point is used. No clay
is needed to seal the hole. After sampling,
retrieve the probe using the high lift jack
assembly.
6. If semi-permanent soil gas wells are required,
use the dedicated aluminum probe points.
Insert these points into the bottom of the
power-driven probe and attach it to the Teflon
tubing. Insert the probe as in step 5. When
the probe is removed, the point and Teflon
tube remain in the hole, which may be scaled
by backfilling with sand, bentonite, or soil.
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3.7.2 Screening with Field
Instruments
1. The well volume must be evacuated prior to
sampling. Connect the Gilian pump, adjusted
to 3.0 L/min, to the sample probe using a
section of Teflon tubing as a connector. Turn
the pump on, and a vacuum is pulled through
the probe for approximately 15 seconds. A
longer time is required for sample wells of
greater depths.
2. After evacuation, connect the monitoring
instrument(s) to the probe using a Teflon
connector. When the reading is stable, or
peaks, record the reading. For detailed
procedures on HNU field protocol, see
appendix B, and refer to the manufacturer's
instructions.
3. Some readings may be above or below the
range set on the field instruments. The range
may be reset, or the response recorded as a
figure greater than or less than the range.
Consider the recharge rate of the well with soil
gas when sampling at a different range setting.
3.7.3 Tedlar Bag Sampling
1. Follow step 1 in section 3.7.2 to evacuate well
volume. If air monitoring instrument screening
was performed prior to sampling, evacuation is
not necessary.
2. Use the vacuum box and sampling train (Figure
3 in Appendix A) to take the sample. The
sampling train is designed to minimize the
introduction of contaminants and losses due to
adsorption. All wetted parts are either Teflon
or stainless steel. The vacuum is drawn
indirectly to avoid contamination from sample
pumps.
3. Place the Tedlar bag inside the vacuum box,
and attach it to the sampling port. Attach the
sample probe to the sampling port via Teflon
tubing and a "quick connect" fitting.
4. Draw a vacuum around the outside of the bag,
using a Gilian pump connected to the vacuum
box evacuation port, via Tygon tubing and a
"quick connect" fitting. The vacuum causes the
bag to inflate, drawing the sample.
5. Break the vacuum by removing the Tygon line
from the pump. Remove the bagged sample
from the box and close valve. Label bag,
record data on data sheets or in logbooks.
Record the date, time, sample location ID, and
the HNU, or other instrument reading(s) on
sample bag label.
CAUTION: Labels should not be pasted directly
onto the bags, nor should bags be labeled directly
using a marker or pen. Inks and adhesive may
diffuse through the bag material, contaminating the
sample. Place labels on the edge of the bags, or tie
the labels to the metal eyelets provided on the bags.
Markers with inks containing volatile organics (i.e.,
permanent ink markers) should not be used.
3.7.4 Tenax Tube Sampling
Samples collected in Tedlar bags may be sorbed
onto Tenax tubes for further analysis by GC/MS.
Additional Apparatus
x* Syringe with a luer-lock tip capable of
drawing a soil gas or air sample from a
Tedlar bag onto a Tenax/CMS sorbent
tube. The syringe capacity is dependent
upon the volume of sample being drawn
onto the sorbent tube.
xx Adapters for fitting the sorbent tube
between the Tedlar bag and the sampling
syringe. The adapter attaching the Tedlar
bag to the sorbent tube consists of a
reducing union (I/Cinch to 1/16-inch O.D.
-- Swagelok cat. # SS-400-6-ILV or
equivalent) with a length of 1/4 inch O.D.
Teflon tubing replacing the nut on the 1/6-
inch (Tedlar bag) side. A I/Cinch I.D.
silicone O-ring replaces the ferrules in the
nut on the I/Cinch (sorbent tube) side of
the union.
The adapter attaching the sampling syringe
to the sorbent tube consists of a reducing
union (I/Cinch to 1/16-inch O.D. --
Swagelok Cat. # SS-4OO-6-ILV or
equivalent) with a I/Cinch I.D. silicone
O-ring replacing the ferrules in the nut on
the 1/4 inch (sorbent tube) side and the
needle of a luer-lock syringe needle
inserted into the I/16-inch side (held in
place with a 1/16-inch ferrule). The
20
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luer-lock end of the needle can be attached
to the sampling syringe. It is useful to have
a luer-lock on/off valve situated between
the syringe and the needle.
«« Two-stage glass sampling cartridge (1/4-
inch O.D. x l/&inch I.D. x 5 1/8 inch)
contained in a flame-sealed tube
(manufactured by Supelco Custom
Tenax/Spherocarb Tubes or equivalent)
containing two sorbent sections retained by
glass wool:
Front section: 150 mg of Tenax-GC
Back section: 150 mg of CMS
(Carbonized Molecular Sieve)
Sorbent tubes may also be prepared in the
lab and stored in either Teflon-capped
culture tubes or stainless steel tube
containers. Sorbent tubes stored in this
manner should not be kept more than 2
weeks without reconditioning. (See SOP
#2052 for Tenax/CMS sorbent tube
preparation).
** Teflon-capped culture tubes or stainless
steel tube containers for sorbent tube
storage. These containers should be
conditioned by baking at 120°C for at least
2 hours. The culture tubes should contain
a glass wool plug to prevent sorbent tube
breakage during transport. Reconditioning
of the containers should occur between
usage or after extended periods of disuse
(i.e., 2 weeks or more).
** Nylon gloves or lint-free cloth. (Hewlett
Packard Part # 8650-0030 or equivalent.)
Sample Collection
1. Handle sorbent tubes with care, using nylon
gloves (or other lint-free material) to avoid
contamination.
2. Immediately before sampling, break one end of
the sealed tube and remove the Tenax
cartridge. For in-house prepared tubes, remove
cartridge from its container.
3. Connect the valve on the Tedlar bag to the
sorbent tube adapter. Connect the sorbent tube
to the sorbent tube adapter with the Tenax
(white granular) side of the tube facing the
Tedlar bag.
4. Connect the sampling syringe assembly to the
CMS (black) side of the sorbent tube. Fittings
on the adapters should be very tight.
5. Open the valve on the Tedlar bag.
6. Open the on/off valve of the sampling syringe.
7. Draw a predetermined volume of sample onto
the sorbent tube. (This may require closing the
syringe valve, emptying the syringe and then
repeating the procedure, depending upon the
syringe capacity and volume of sample
required.)
8. After sampling, remove the tube from the
sampling train with gloves or a clean cloth. Do
not label or write on the Tenax/CMS tube.
9. Place the sorbent tube in a conditioned
stainless steel tube holder or culture tube.
Culture tube caps should be sealed with Teflon
tape.
Sample Labeling
Each sample tube container (not tube) must be
labeled with the site name, sample station number,
sample date, and sample volume.
Chain of custody forms must accompany all samples
to the laboratory.
Quality Assurance
Before field use, a QA check should be performed
on each batch of sorbent tubes by analyzing a tube
with thermal desorption/cryogenic trapping
GC/MS.
At least one blank sample must be submitted with
each set of samples collected at a site. This trip
blank must be treated the same as the sample tubes
except no sample will be drawn through the tube.
Sample tubes should be stored out of UV light (i.e.,
sunlight) and kept on ice until analysis.
Samples should be taken in duplicate, when
possible.
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3.7.5 SUMMA Canister Sampling
1. Follow item 1 in step 3.7.2 to evacuate well
volume. If HNU analysis was performed prior
to taking a sample, evacuation is not necessary.
2. Attach a certified clean, evacuated 6-L
SUMMA canister via the 1/4-inch Teflon
tubing.
3. Open the valve on SUMMA canister. The soil
gas sample is drawn into the canister by
pressure equilibration. The approximate
sampling time for a 6-L canister is 20 minutes.
4. Site name, sample location, number, and date
must be recorded on a chain of custody form
and on a blank tag attached to the canister.
3.8 CALCULATIONS
3.8.1 Field Screening Instruments
Instrument readings are usually read directly from
the meter. In some cases, the background level at
the soil gas station may be subtracted:
Final Reading =
Sample Reading -
Background
3.8.2 Photovac GC Analysis
Calculations used to determine concentrations of
individual components by Photovac GC analysis are
beyond the scope of this SOP and are covered in
ERT SOP #2109, Photovac GC Analysis for Soil,
Water and Air/Soil Gas.
3.9 QUALITY ASSURANCE/
QUALITY CONTROL
3.9.1 Field Instrument Calibration
Consult the manufacturers' manuals for correct use
and calibration of all instrumentation. The HNU
should be calibrated at least once a day.
3.9.2 Gilian Model HFS113A Air
Sampling Pump Calibration
Flow should be set at approximately 3.0 L/min;
accurate flow adjustment is not necessary. Pumps
should be calibrated prior to bringing into the field.
3.9.3 Sample Probe Contamination
Sample probe contamination is checked between
each sample by drawing ambient air through the
probe via a Gilian pump and checking the response
of the HNU PI 101. If HNU readings are higher
than background, replacement or decontamination
is necessary.
Sample probes may be decontaminated simply by
drawing ambient air through the probe until the
HNU reading is at background. More persistent
contamination can be washed out using methanol
and water, then air drying. Having more than one
probe per sample team will reduce lag times
between sample stations while probes are
decontaminated.
3.9.4 Sample Train Contamination
The Teflon line forming the sample train from the
probe to the Tedlar bag should be changed on a
daily basis. If visible contamination (soil or water)
is drawn into the sampling train, it should be
changed immediately. When sampling in highly
contaminated areas, the sampling train should be
purged with ambient air, via a Gilian pump, for
approximately 30 seconds between each sample.
After purging, the sampling train can be checked
using an HNU, or other field monitoring device, to
establish the cleanliness of the Teflon line.
3.9.5 Field Blank
Each cooler containing samples should also contain
one Tedlar bag of ultra-zero grade air, acting as a
field blank. The field blank should accompany the
samples in the field (while being collected) and
when they are delivered for analysis. A fresh blank
must be provided to be placed in the empty cooler
pending additional sample collection. One new field
blank per cooler of samples is required. A chain of
custody form must accompany each cooler of
samples and should include the blank that is
dedicated to that group of samples.
3.9.6 Trip Standard
Each cooler containing samples should contain a
Tedlar bag of standard gas to calibrate the
22
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analytical instruments (Photovac GC, etc.). This
trip standard will be used to determine any changes
in concentrations of the target compounds during
the course of the sampling day (e.g., migration
through the sample bag, degradation, or
adsorption). A fresh trip standard must be provided
and placed in each cooler pending additional sample
collection. A chain of custody form should
accompany each cooler of samples and should
include the trip standard that is dedicated to that
group of samples.
3.9.7 Tedlar Bag Check
Prior to use, one bag should be removed from each
lot (case of 100) of Tedlar bags to be used for
sampling and checked for possible contamination as
follows: the test bag should be tilled with ultra-zero
grade air; a sample should be drawn from the bag
and analyzed via Photovac GC or whatever method
is to be used for sample analysis. This procedure
will ensure sample container cleanliness prior to the
start of the sampling effort.
3.9.8 SUMMA Canister Check
From each lot of four cleaned SUMMA canisters,
one is to be removed for a GC/MS certification
check. If the canister passes certification, then it is
re-evacuated and all four canisters from that lot are
available for sampling.
If the chosen canister is contaminated, then the
entire lot of four SUMMA canisters must be
recleaned, and a single canister is re-analyzed by
GC/MS for certification.
3.9.9 Options
Duplicate Samples
A minimum of 5% of all samples should be
collected in duplicate (i.e., if a total of 100 samples
arc to be collected, five samples should be
duplicated). In choosing which samples to
duplicate, the following criterion applies: if, after
filling the first Tedlar bag, and, evacuating the well
for 15 seconds, the second HNU (or other field
monitoring device being used) reading matches or
is close to (within 50%) the first reading, a
duplicate sample may be taken.
Spikes
A Tedlar bag spike and Tenax tube spike may be
desirable in situations where high concentrations of
contaminants other than the target compounds are
found to exist (landfills, etc.). The additional level
of QA/QC attained by this practice can be useful in
determining the effects of interferences caused by
these non-target compounds. SUMMA canisters
containing samples are not spiked.
3.10 DATA VALIDATION
For each target compound, the level of
concentration found in the sample must be greater
than three times the level (for that compound)
found in the field blank which accompanied that
sample to be considered valid. The same criteria
apply to target compounds detected in the Tedlar
bag pre-sampling contamination check.
3.11 HEALTH AND SAFETY
Because the sample is being drawn from
underground, and no contamination is introduced
into the breathing zone, soil gas sampling usually
occurs in Level D, unless the sampling location is
within the hot zone of a site, which requires Level
B or Level C protection. However, to ensure that
the proper level of protection is utilized, constantly
monitor the ambient air using the HNU PI 101 to
obtain background readings during the sampling
procedure. As long as the levels in ambient air do
not rise above background, no upgrade of the level
of protection is needed.
Also, perform an underground utility search prior to
sampling (see section 3.4.4). When working with
potentially hazardous materials, follow U.S. EPA,
OSHA, and specific health and safely procedures.
23
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Page Intentionally Blank
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4.0 MONITORING WELL INSTALLATION: SOP #2150
4.1 SCOPE AND APPLICATION
The purpose of this Standard Operating Procedure
(SOP) is to provide an overview of the methods
used for monitoring well installation. Monitoring
well installation creates a permanent access for the
collection of samples to determine groundwater
quality and the hydrogeologic properties of the
aquifer in which the contaminants exist. Such wells
should not alter the medium which is being
monitored.
The most commonly used drilling methods are: (1)
hollow-stem augers, (2) cable tool drills, and (3)
rotary drills. Rotary drilling can be divided into a
mud rotary or air rotary method.
4.2 METHOD SUMMARY
There is no ideal monitoring well installation
method for all conditions; therefore, hydrogeologic
conditions at the site and project objectives must be
considered before deciding which drilling method to
use.
4.2.1 Hollow-Stem Augering
Hollow-stem augering is fast and relatively less
expensive than cable tool or rotary drilling methods.
It is possible to drill several hundred feet of
borehole per day in unconsolidated formations.
4.2.2 Cable Tool Drilling
Cable tool drilling method involves lifting and
dropping a heavy, solid chisel-shaped bit, suspended
on a steel cable. This bit pounds a hole through
soil and rock. Temporary steel casing is used while
drilling to keep the hole open and to isolate strata.
The temporary casing is equipped with a drive shoe,
which is attached to the lower end, and which aids
the advancement of the casing by drilling out a
slightly larger diameter borehole than the hole
made by the drill bit alone.
Water is sometimes used when drilling above the
saturated zone to reduce dust and to form a slurry
with the loosened material. This facilitates removal
of cuttings using a bailer or a sand pump. Potable
water or distilled/deionized water should be used to
prevent the introduction of contamination into the
borehole.
4.2.3 Rotary Drilling
Mud Rotary Method
In the mud rotary method, the borehole is advanced
by rapid rotation of the drill bit, which cuts and
breaks the material at the bottom of the hole into
smaller pieces. Cuttings are removed by pumping
drilling fluid (water, or water mixed with bentonite)
down through the drill rods and bit, and up the
armulus between the borehole and the drill rods.
The drilling fluid also serves to cool the drill bit and
prevent the borehole from collapsing in
unconsolidated formations.
Air Rotary Method
The air rotary method is the same as the mud
rotary except that compressed air is pumped down
the drill rods and returns with the drill cuttings up
through the annulus. Air rotary method is generally
limited to consolidated and semi-consolidated
formations. Casing is sometimes used to prevent
cavings in semi-consolidated formations. The air
must be filtered to prevent introduction of
contamination into the borehole.
4.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
Often, a primary object of the drilling program is to
obtain representative lithologic or environmental
samples. Lithologic samples are taken in order to
determine the geologic or hydrogeologic regime at
a site. The most common techniques for retrieving
lithologic samples in unconsolidated formations are
described below.
«* Split spoon sampling, carried out
continuously or at discrete intervals during
drilling, is used to make a field description
of the sample and create a log of each
boring.
25
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xx Shelby tube sampling, is used when an
undisturbed sample is required from clayey
or silty soils, especially for geotechnical
evaluation or chemical analysis.
.* Cuttings description is used when a general
lithologic description and approximate
depths are sufficient.
The most common techniques for retrieving
lithologic sampling in consolidated formations are
described below.
* Rock coring is carried out continuously or
at discrete intervals during drilling and
enables the geologist to write a field
description of the sample, create a log of
each boring, and map occurrences and
orientation of fractures.
^ Cuttings description is used when a general
lithologic description and approximate
depths are sufficient.
4.4 INTERFERENCES AND
POTENTIAL PROBLEMS
Table 3 on page 27 displays the advantages and
disadvantages of the various drilling techniques.
4.5 EQUIPMENT/APPARATUS
The drilling contractor will provide all operational
equipment for the drilling program which is
outlined. The geologist should bring:
• well log sheets
* metal case (container for well logs)
' ruler
xx depth sounder
* water level indicator
* all required health and safety gear
* sample collection jars
xx trowels
x description aids (Munsell, grain size charts,
etc.)
4.6 REAGENTS
No chemical reagents are used in this procedure.
Decontamination of drilling equipment should
follow ERT SOP #2006, Sampling Equipment
Decontamination and the site-specific work plan.
4.7 PROCEDURES
4.7.1 Preparation
The planning, selection and implementation of any
monitoring well installation program should include
the following steps.
1. Review existing data on site geology and
hydrogeology including publications, air photos,
water quality data, and existing maps. These
may be obtained from local, state, or federal
agencies.
2. Visit the site to observe field geology and
potential access problems for drill rig, to
establish water supply, and drill equipment and
materials storage area.
3. Prepare site safety plan.
4. Define project objectives; select drilling, well
development, and sampling methods.
5. Select well construction materials including well
construction specifications (i.e., casing and
screen materials, casing and screen diameter,
screen length and screen interval, filter pack
and screen size).
6. Determine need for containing drill
cuttings/fluids and their disposal.
7. Prepare work plan including all of the above.
8. Prepare and execute the drilling contract.
9. Implement the drilling program.
10. Prepare the final report, including background
data, project objective, field procedure, well
construction data including well logs and well
construction.
All drilling and well installation programs must be
planned and supervised by a professional
geologist/hydrogeologist.
4.7.2 Field Preparation
1. Prior to the mobilization of the drill rig,
26
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Table 3: Advantages and Disadvantages of Various Drilling Techniques
Drilling Type
Advantages
Disadvantages
Auger
Allows sampling from different strata
during drilling.
Less potential for cross-contamination
between strata than in other
techniques.
Large diameter borehole may be
drilled for multiple-well completion.
Less well development is generally needed
than in mud rotary because of the
relatively large diameter borehole, the
ability to emplace a large and effective
gravel pack, and because no drilling fluids
are introduced into the borehole.
^Very slow or impossible in coarse
materials such as cobbles and boulders.
Cannot drill hard rock formations and is
generally not suited for wells deeper than
100 feet.
,fNot good in caving formations.
* Potential for disturbing large volume of
subsurface materials around the borehole;
therefore affecting local permeabilities
and creating annular channels for
contaminant movement between different
strata.
Cable Tool
** Allows for easy and accurate detection of
the water table.
** Driven casing seals off formation,
minimizing the threat of cross-
contamination in pollution investigation.
^Especially successful for drilling in glacial
till.
Extremely slow rate of drilling.
lose casing in deep wells.
Mud Rotary
«Quite fast, more than 100 feet of borehole
advancement per day is possible.
t Geophysical logs such as resistivity (which
must be run in an uncased borehole) can
be run before well construction.
Potential cross-contamination of strata
exposed to the circulating drilling fluid
during drilling.
Difficulty in removing mud residues
during well development.
Drilling mud may alter the groundwater
chemistry by binding metals, sorbing
organic compounds and by altering pH,
cation exchange capacity and chemical
oxidation demand of native fluids.
Drilling mud may change local
permeability of the formation.
Air Rotary
*Like mud rotary method, more than 100
feet of borehole advancement a day is
possible.
< Sampling different strata during drilling is
possible if temporary casing is advanced.
Jn contaminated formations, the use of
high pressure air may pose a significant
hazard to the drill crew due to rapid
transport of contaminated material up the
borehole during drilling.
Introduction of air to ground water could
reduce concentration of volatile organic
compounds locally.
27
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thoroughly decontaminate the rig and all
associated equipment to remove all oil, grease,
mud, etc.
2. Before drilling each boring, steam-clean and
rinse all the "down-the-hole" drill equipment
with potable water to minimize cross-
contamination. Special attention should be
given to the thread section of the casings, and
to the drill rods. All drilling equipment should
be steam-cleaned at completion of the project
to ensure that no contamination is transported
to or from the sampling site.
3. Record lithologic descriptions and all field
measurements and comments on the well log
form (Appendix C). Include well construction
diagrams on the well log form for each well
installed. At a minimum, the well construction
information should show depth from surface
grade, the bottom of the boring, the screened
interval, casing material, casing diameter, gravel
pack location, grout seal and height of riser
pipe above the ground. Also record the actual
compositions of the grout and seal on the well
log form.
4.7.3 Well Construction
The most commonly used casing materials include
stainless steel, polyvinyl chloride (PVC) and Teflon.
Monitoring wells are constructed with casings and
materials that are resistant to the subsurface
environment. The selection of well construction
material is based on the material's long-term
interaction with the contaminated groundwater.
Construction materials should not cause an
analytical bias in the interpretation of the chemical
analysis of the water samples.
Well casing material should also be judged from a
structural standpoint. Material should be rigid and
nonporous, with a low surface-area-to-water ratio in
the wellbore relative to the formation materials
(U.S. EPA, 1987).
1. Fill the annular space between the well screen
and the boring with a uniform gravel/sand pack
to serve as a filter media. For wells deeper
than approximately 50 feet, or when
recommended by the site geologist, emplace the
sand pack using a tremie pipe (normally
consisting of a 1.25inch PVC or steel pipe).
Pump sand slurry composed of sand and
potable water through the tremie pipe into the
annulus throughout the entire screened interval,
and over the top of the screen. It is necessary
to pump sufficient sand/gravel slurry to cover
the screen after the sand/gravel pack has
settled and become dense.
2. Determine the depth of the top of the sand
using the tremie pipe, thus verifying the
thickness of the sand pack. Add more sand to
bring the top of the sand pack to approximately
2-3 feet above the top of the well screen.
Under no circumstances should the sand pack
extend into any aquifer other than the one to
be monitored. In most cases, the well design
can be modified to allow for a sufficient sand
pack without threat of crossflow between
producing zones through the sand pack.
3. In materials that will not maintain an open
hole, withdraw the temporary or outer casing
gradually during placement of sand pack/grout
to the extent practical.
For example, after filling 2 feet with sand pack,
the outer casing should be withdrawn 2 feet.
This step of placing more gravel and
withdrawing the outer casing should be
repeated until the level of the sand pack is
approximately 3 feet above the top of the well
screen. This ensures that there is no locking of
the permanent (inner) casing in the outer
casing.
4. Emplace a bentonite seal, composed of pellets,
between the sand pack and grout to prevent
infiltration of cement into the filter pack and
the well screen.
These pellets should have a minimum purity of
90% montmorillonite clay, and a minimum dry
bulk density of 75 lb/ft3 for 1A inch pellets, as
provided by American Colloid, or equivalent.
Bentonite pellets shall be poured directly down
the annulus.
Care must be taken to avoid introducing pellets
into the well bore. A cap placed over the top
of the well casing before pouring the bentonite
pellets from the bucket will prevent this. To
ensure even application, pour the pellets from
different points around the casing. To avoid
bridging of pellets, they should not be
introduced at a rate faster than they can settle.
A tremie pipe may be used to redistribute and
28
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level out the top of the seal,
5. If using a slurry of bentonite as an annular seal,
prepare it by mixing powdered or granular
bentonite with potable water. The slurry must
be of sufficiently high specific gravity and
viscosity to prevent its displacement by the
grout to be emplaced above it. As a
precaution, regardless of depth, and depending
on fluid viscosity, add a few handfuls of
bentonite pellets to solidify the bentonite slurry
surface.
6. Place a mixture of cement and bentonite grout
from the top of the bentonite seal to the
ground surface.
Only Type I or II cement without accelerator
additives may be used. An approved source of
potable water must be used for mixing grouting
materials. The following mixes are acceptable:
MS Neat cement, a maximum of 6 gallons of
water per 94-pound bag of cement
MS MS Granular bentonite, 1.5 pounds
bentonite per 1 gallon of water
of
MSMS Cement-bentonite, 5 pounds of pure
bentonite per 94-pound bag of cement with
7-8 gallons of water; 13-14 pounds weight,
if dry mixed
MS Cement-bentonite, 6 to 8 pounds of pure
bentonite per 94-pound bag of cement with
8-10 gallons of water, if water mixed
** Non-expandable cement, mixed at 7.5
gallons of water to 1/2 teaspoon of
aluminum hydroxide, 94 pounds of neat
cement (Type I) and 4 pounds of bentonite
MS Non-expandable cement, mixed at 7 gallons
of water to 1/2 teaspoon of aluminum
hydroxide, 94 pounds of neat cement (Type
I and Type II)
7. Pump grout through a tremie pipe to the
bottom of the open annulus until undiluted
grout flows from the annulus at the ground
surface.
8. In materials that will not maintain an open
hole, the temporary steel casing should be
withdrawn in a manner that prevents the level
of grout from dropping below the bottom of
the casing.
9. Additional grout may be added to compensate
for the removal of the temporary casing and
the tremie pipe to ensure that the top of the
grout is at or above ground surface.
10. Place the protective casing. Protective casings
should be installed around all monitoring wells.
Exceptions are on a case-by-case basis. The
minimum elements in the protection design
include:
^ A protective steel cap to keep precipitation
out of the protective casing, secured to the
casing by padlocks.
^ A 5-foot-minimum length of black iron or
galvanized pipe, extending about 1.5 to 3
feet above the ground surface, and set in
cement grout. The pipe diameter should
be 8 inches for 4-inch wells, and 6 inches
for 2-inch wells (depending on approved
borehole size). A 0.5-inch drain hole near
ground level is permitted.
« The installation of guard posts in addition
to the protective casing, in areas where
vehicular traffic may pose a hazard. These
guard posts consist of 3-inch diameter steel
posts or tee-bar driven steel posts. Groups
of three are radially located 4 feet around
each well 2 feet below and 4 feet above
ground surface, with flagging in areas of
high vegetation. Each post is cemented in-
place.
MSMS A flush mount of protective casing may
also be used in areas of high traffic or
where access to other areas would be
limited by a well with stickup.
After the grout sets (about 48 hours), fill any
depression due to settlement with a grout mix
similar to that described above.
4.0 CALCULATIONS
To maintain an open borehole using sand or water
rotary drilling, the drilling fluid must exert a
pressure greater than the formation pore pressure.
Typical pore pressure for an unconfined aquifer is
29
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0.433 psi/ft and for a confined aquifer is 0.465
psi/ft.
The calculation for determining the hydrostatic
pressure of the drilling fluid is:
Hydrostatic Pressure (psi) = Fluid Density
(Ib/gal) x Height of Fluid Column (ft) x 0.052
The minimum grout volume necessary to grout a
well can be calculated using:
Grout Vol (ft3) = Vol of Borehole (f3) -
Vol of Casing (ft3)
r - r
where:
rB = radius of boring (ft)
rc = radius of casing (ft)
L = length of borehole to be grouted (ft)
4.9 QUALITY ASSURANCE/
QUALITY CONTROL
There are no specific quality assurance activities
which apply to the implementation of these
procedures.
However, the following general QA procedures
apply:
* All data must be documented on standard
well completion forms, field data sheets or
within field/site logbooks.
• All instrumentation must be operated in
accordance with operating instructions as
supplied by the manufacturer, unless
otherwise specified in the work plan.
Equipment checkout and calibration
activities must occur prior to
sampling/operation and they must be
documented.
4.10 DATA VALIDATION
This section is not applicable to this SOP.
4.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA, and specific health and
safety procedures.
30
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5.0 WATER LEVEL MEASUREMENT: SOP #2151
5.1 SCOPE AND APPLICATION
The purpose of this Standard Operating Procedure
(SOP) is to set guidelines for the determination of
the depth to water in an open borehole, cased
borehole, monitoring well or piezometer.
Generally, water level measurements from
boreholes, piezometers, or monitoring wells are
used to construct water table or potentiometric
surface maps. Therefore, all water level
measurements at a given site should be collected
within a 24-hour period. Certain situations may
necessitate that all water level measurements be
taken within a shorter time interval. These
situations may include:
• the magnitude of the observed changes
between wells appears too large
• atmospheric pressure changes
• aquifers which are tidally influenced
• aquifers affected by river stage,
impoundments, and/or unlined ditches
* aquifers stressed by intermittent pumping
of production wells
* aquifers being actively recharged due to
precipitation events
5.2 METHOD SUMMARY
A survey mark should be placed on the casing for
use as a reference point for measurement. Many
times the lip of the riser pipe is not flat. Another
measuring reference should be located on the grout
apron. The measuring point should be documented
in the site logbook and on the groundwater level
data form (see Appendix C).
Water levels in piezometers and monitoring wells
should be allowed to stabilize for a minimum of 24
hours after well construction and development, prior
to measurement. In low yield situations, recovery
may take longer.
Working with decontaminated equipment, proceed
from the least to the most contaminated wells.
Open the well and monitor headspace with the
appropriate monitoring instrument to determine the
presence of volatile organic compounds. Lower the
water level measurement device into the well until
water surface or bottom of casing is encountered.
Measure distance from water surface to the
reference point on the well casing and record in the
site logbook and/or groundwater level data form.
Remove all downhole equipment, decontaminate as
necessary, and replace well casing cap.
5.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING AND
STORAGE
This section is not applicable to this SOP.
5.4 INTERFERENCES AND
POTENTIAL PROBLEMS
• The chalk used on steel tape may
contaminate the well.
* Cascading water may obscure the water
mark or cause it to be inaccurate.
* Many types of electric sounders use metal
indicators at 5-foot intervals around a
conducting wire. These intervals should be
checked with a surveyor's tape to ensure
accuracy.
* If there is oil present on the water, it can
insulate the contacts of the probe on an
electric sounder or give false readings due
to thickness of the oil. Determining the
thickness and density of the oil layer may
be warranted, in order to determine the
correct water level.
• Turbulence in the well and/or cascading
water can make water level determination
difficult with either an electric sounder or
steel tape.
-------
An airline measures drawdown during
pumping. It is only accurate to 0.5 foot
unless it is
"drawdowns".
calibrated for various
5.5 EQUIPMENT/APPARATUS
There are a number of devices which can be used to
measure water levels, such as steel tape or airlines.
The device should be adequate to attain an accuracy
of 0.01 feet.
The following equipment is needed to measure
water levels:
* air monitoring equipment
* water level measurement device
* electronic water level indicator
* metal tape measure
* airline
* steel tape
* chalk
* ruler
* notebook
* paper towels
* decontamination solution and equipment
*< groundwater level data forms
5.6 REAGENTS
No chemical reagents are used in this procedure,
with the exception of decontamination solutions.
Where decontamination of equipment is required,
refer to ERT SOP #2006, Sampling Equipment
Decontamination and the site-specific work plan.
5.7 PROCEDURES
57.1 Preparation
1. Determine the extent of the sampling effort, the
sampling methods to be employed, and which
equipment and supplies are needed.
2. Obtain necessary sampling and monitoring
equipment.
3. Decontaminate or preclean equipment, and
ensure that it is in working order.
4. Prepare scheduling and coordinate with staff,
clients, and regulatory agency, if appropriate.
5. Perform a general site survey prior to site entry
in accordance with the site-specific health and
safety plan.
6. Identify and mark all sampling locations.
5.7.2 Procedures
1. Make sure water level measuring equipment is
in good operating condition.
2. If possible and where applicable, start at those
wells that are least contaminated and proceed
to those wells that are most contaminated.
3. Clean all equipment entering the well by the
following decontamination procedure:
• Triple rinse equipment with deionized
water.
• Wash equipment with an Alconox solution
followed by a deionized water rinse.
• Rinse with an approved solvent (e.g.,
methanol, isopropyl alcohol, acetone) as
per the work plan, if organic contamination
is suspected.
• Place equipment on clean surface such as
a Teflon or polyethylene sheet.
4. Remove locking well cap, note location, time of
day, and date in site notebook or an
appropriate groundwater level data form.
5. Remove well casing cap.
6. If required by site-specific condition, monitor
headspace of well with PID or PID to
determine presence of volatile organic
compounds and record in site logbook.
7. Lower electric water level measuring device or
equivalent (i.e., permanently installed
tranducers or airline) into the well until water
surface is encountered.
8. Measure the distance from the water surface to
the reference measuring point on the well
casing or protective barrier post and record in
the field logbook. In addition, note that the
32
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water level measurement was from the top of
the steel casing, top of the PVC riser pipe,
from the ground surface, or from some other
position on the well head.
9. The groundwater level data form in Appendix
C should be completed as follows:
' site name
* logger name: person taking field notes
x date: the date when the water levels are
being measured
**s location: monitor well number and
physical location
x time: the military time at which the water
level measurement was recorded
xx depth to water: the water level
measurement in feet, or in tenths or
hundreds of feet, depending on the
equipment used
* comments: any information the field
personnel feels to be applicable
• measuring point: marked measuring point
on PVC riser pipe, protective steel casing
or concrete pad surrounding well casing
from which all water level measurements
for individual wells should be measured.
This provides consistency in future water
level measurements.
10. Measure total depth of well (at least twice to
confirm measurement) and record in site
notebook or on log form.
11. Remove all downhole equipment, replace well
casing cap and lock steel caps.
12. Rinse all downhole equipment and store for
transport to next well.
13. Note any physical changes such as erosion or
cracks in protective concrete pad or variation in
total depth of well in field notebook and on
field data sheets.
5.8 CALCULATIONS
To determine groundwater elevation above mean
sea level, use the following equation:
Ew = E-D
where:
5.9
Ew = Elevation of water above mean sea
level
E = Elevation above sea level at point
of measurement
D = Depth to water
QUALITY ASSURANCE/
QUALITY CONTROL
The following general quality assurance procedures
apply:
• All data must be documented on standard
chain of custody forms, field data sheets or
within personal/site logbooks.
* All instrumentation must be operated in
accordance with operating instructions as
supplied by the manufacturer, unless
otherwise specified in the work plan.
Equipment checkout and calibration
activities must occur prior to
sampling/operation, and they must be
documented.
• Each well should be tested at least twice in
order to compare results.
5.10 DATA VALIDATION
This section is not applicable to this SOP.
5.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA, and specific health and
safety procedures.
14. Decontaminate all equipment as outlined in
Step 3 above.
33
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Page Intentionally Blank
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6.0 WELL DEVELOPMENT: SOP #2156
6.1 SCOPE AND APPLICATION
The purpose of monitoring well development is to
ensure removal of fines from the vicinity of the well
screen. This allows free flow of water from the
formation into the well and also reduces the
turbidity of the water during sampling events. The
most common well development methods are:
surging, jetting, and overpumping.
Surging involves raising and lowering a surge block
or surge plunger inside the well. The resulting
motion surges water into the formation and loosens
sediment to be pulled from the formation into the
well. Occasionally, sediment must be removed from
the well with a sand bailer to prevent sand locking
of the surge block. This method may cause the
sand pack around the screen to be displaced to a
degree that damages its value as a filtering medium.
For example, channels or voids may form near the
screen if the filter pack sloughs away during surging
(Keely and Boateng, 1987).
Jetting involves lowering a small diameter pipe into
the well to a few feet above the well screen, and
injecting water or air through the pipe under
pressure so that sediments at the bottom are
geysered out the top of the well. It is important not
to jet air or water directly across the screen. This
may cause fines in the well to be driven into the
entrance of the screen openings thereby causing
blockages.
Overpumping involves pumping at a rate rapid
enough to draw the water level in the well as low as
possible, and allowing it to recharge. This process
is repeated until sediment-free water is produced.
Overpumping is not as vigorous as surging and
jetting and is probably the most desirable for
monitoring well development.
concern is that the method being used for
development does not interfere with allowing the
grout to set.
Open the monitoring well, take initial measurements
(e.g. head space air monitoring readings, water
level, well depth, pH, temperature, and specific
conductivity) and record results in the site logbook.
Develop the well by the appropriate method (i.e.,
overpumping jetting, or surging) to accommodate
site conditions and project requirements. Continue
until the developed water is clear and free of
sediment. Containerize all discharge water from
known or suspected contaminated areas. Record
final measurements in the logbook. Decontaminate
equipment as appropriate prior to use in the next
well.
6.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
This section is not applicable to this Standard
Operating Procedure (SOP).
6.4 INTERFERENCES AND
POTENTIAL PROBLEMS
The following interferences or problems may occur
during well development:
* The possibility of disturbing the filter pack
increases with surging and jetting well
development methods.
x The introduction of external water or air by
jetting may alter the hydrochemistry of the
aquifer.
6.2 METHOD SUMMARY
Development of a well should occur as soon as
practical after installation, but not sooner than 48
hours after grouting is completed, if a rigorous well
development is being used. If a less rigorous
method, such as bailing, is used for development, it
may be initiated shortly after installation. The main
6.5 EQUIPMENT/APPARATUS
The type of equipment used for well development is
dependent on the diameter of the well. For
example, submersible pumps cannot be used for
well development unless the wells are 4 inches or
greater in diameter, because the smallest
35
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submersible pump has a 3 1/4 inch O.D.
In general, the well should be developed shortly
after it is drilled. Most drilling rigs have air
compressors or pumps that may be used for the
development process.
6.6 REAGENTS
No chemical reagents are used in this procedure
except for decontamination solutions. For
guidelines on equipment decontamination, refer to
ERT SOP #2006, Sampling Equipment
Decontamination and the site-specific work plan.
6.7 PROCEDURES
6.7.1 Preparation
1. Coordinate site access and obtain keys to the
monitoring well security cap locks.
2. Obtain information on each well to be
developed (i.e., drilling, method, well diameter,
depth, screened interval, anticipated
contaminants, etc.).
3. Obtain a water level meter, air monitoring
equipment, materials for decontamination, pH
and electrical conductivity meters, a
thermometer, and a stopwatch.
4. Assemble containers for temporary storage of
water produced during well development.
Containers must be structurally sound,
compatible with anticipated contaminants, and
easy to manage in the field. The use of
truck-mounted tanks may be necessary in some
cases; alternately, a portable water treatment
unit (e.g. activated carbon) may be used to
decontaminate the purge water.
6.7.2 Operation
The development should be performed as soon as
practical after the well is installed, but no sooner
than 48 hours after grouting is completed.
Dispersing agents, acids, or disinfectants should not
be used to enhance development of the well.
1. Assemble necessary equipment on a plastic
sheet around the well.
2. Record pertinent information in field logbook
(personnel, time, location ID, etc.).
3. Open monitoring well, and take air monitoring
readings at the top of casing and in the
breathing zone as appropriate.
4. Measure depth to water and the total depth of
the monitoring well from the same datum
point.
5. Measure the initial pH, temperature, and
specific conductivity of the water and record in
the logbook.
6. Develop the well until the water is clear and
appears to be free of sediment. Note the initial
color, clarity and odor of the water.
7. All water produced by development in
contaminated or suspected contaminated areas
must be containerized or treated. Clearly label
each container with the location ID.
Determination of the appropriate disposal
method will be based on the fast round of
analytical results from each well.
8. No water should be added to the well to assist
development without prior approval by the site
geologist. If a well cannot be cleaned of mud
to produce formation water because the aquifer
yields insufficient water, small amounts of
potable water may be injected to clean up this
poorly yielding well. This may be done by
dumping in buckets of water. When most of
the mud is out, continue development with
formation water only. It is essential that at
least live times the amount of water injected
must be produced back from the well in order
to ensure that all injected water is removed
from the formation.
9. Note the final color, clarity and odor of the
water.
10. Measure the final pH, temperature and specific
conductance of the water and record in the
field logbook.
11. Record the following data in the field logbook:
« well designation (location ID)
« date(s) of well installation
* date(s) and time of well development
* static water level before and after
36
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development
x* quantity of water removed and time of
removal
xx type and size/capacity of pump and/or
bailer used
x description of well development techniques
used
6.7.3 Post Operation
1. Decontaminate all equipment.
2. Store containers of purge water produced
during development in a safe and secure area.
3. After the first round of analytical results have
been received, determine and implement the
appropriate purge water disposal method.
6.8 CALCULATIONS
There are no calculations necessary to implement
this procedure. However, if it is necessary to
calculate the volume of the well, utilize the
following equation:
Well volume = nr2h(cf) [Equation 1]
where:
n
r
h
Pi
radius of monitoring well (feet)
height of the water column (feet)
[This may be determined by
subtracting the depth to water
from the total depth of the well as
measured from the same reference
point.]
cf = conversion factor (gal/ft3) = 1.48
gal/ft3 [In this equation, 7.48
gal/ft3 is the necessary conversion
factor, because 7.48 gallons of
water occupy 1 ft3]
Monitoring wells are typically 2 inches, 3 inches, 4
inches, or 6 inches in diameter. If the diameter of
the monitoring well is known, a number of standard
conversion factors can be used to simplify the
equation above.
The volume, in gallons per linear foot, for various
standard monitoring well diameters can be
calculated as follows:
v
where:
v
n
r
cf =
nr (cf) [Equation 2]
volume in gallons per linear foot
Pi
radius of monitoring well (feet)
conversion factor (7.48 gal/ft3)
For a 2-inch diameter well, the volume per linear
foot can be calculated as follows:
v = nr2(cf) [Equation 21
3.14 (1/12 ft)2 7.48 gal/f?
0.1632 gal/ft
Remember that if you have a 2-inch diameter well,
you must convert this to the radius in feet to be
able to use the equation.
The volume per linear foot for monitoring wells of
common size are as follows:
Well diameter
2-inch
3-inch
4-inch
6-inch
If you utilize the factors above, Equation 1 should
be modified as follows:
Well volume = h(v) [Equation 3]
v (Volume in gal/ft.)
0.1632
0.3672
0.6528
1.4
where:
h =
v
height of water column (feet)
volume in gallons per linear foot
from Equation 2
6.9 QUALITY ASSURANCE/
QUALITY CONTROL
There are no specific quality assurance activities
which apply to the implementation of these
procedures. However, the following general QA
procedures apply:
x All data must be documented on standard
chain of custody forms, field data sheets or
personal/site logbooks.
xx All instrumentation must be operated in
accordance with operating instructions as
37
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supplied by the manufacturer, unless 6.11 HEALTH AND SAFETY
otherwise specified in the work plan.
Equipment checkout and calibration when working with potentially hazardous materials,
activities must occur prior to fouow U.S. EPA, OSHA, and specific health and
sampling/operation and they must be safely procedures.
documented.
6.10 DATA VALIDATION
This section is not applicable to this SOP
38
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7.0 CONTROLLED PUMPING TEST: SOP #2157
7.1 SCOPE AND APPLICATION
The most reliable and commonly used method of
determining aquifer characteristics is by controlled
aquifer pumping tests. Groundwater flow varies in
space and time and depends on the hydraulic
properties of the rocks and the boundary conditions
imposed on the groundwater system. Pumping tests
provide results that are more representative of
aquifer characteristics than those predicted by slug
or bailer tests. Pumping tests require a greater
degree of activity and expense, however, and are not
always justified for all levels of investigation. For
example, slug tests may be acceptable at the
reconnaissance level whereas pumping tests are
usually performed as part of a feasibility study in
support of designs for aquifer remediation.
Aquifer characteristics which may be learned using
pumping tests include hydraulic conductivity (K),
transmissivity (T), specific yield (Sy) for unconfined
aquifers, and storage coefficient (S) for confined
aquifers. These parameters can be determined by
graphical solutions and computerized programs.
This Standard Operating Procedure (SOP) outlines
the protocol for conducting controlled pumping
tests.
7.2 METHOD SUMMARY
It is desirable to monitor pre-test water levels at the
test site for about 1 week prior to performance of
the pump test. This information allows for the
determination of the barometric efficiency of the
aquifer, as well as noting changes in head, due to
recharging or pumping in the area adjacent to the
well. Prior to initiating the long term pump test, a
step test is conducted to estimate the greatest flow
rate that may be sustained by the pump well.
After the pumping well has recovered from the step
test, the long term pumping test begins. At the
beginning of the test, the discharge rate is set as
quickly and accurately as possible. The water levels
in the pumping well and observation wells are
recorded accordingly with a set schedule. Data is
entered on the Pump/Recovery Test Data Sheet
(Appendix C). The duration of the test is
determinated by project needs and aquifer
properties, but rarely goes beyond 3 days or until
water levels become constant.
7.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
This section is not applicable to this SOP.
7.4 INTERFERENCES AND
POTENTIAL PROBLEMS
Interferences and potential problems include:
• atmospheric conditions
• impact of local potable wells
• compression of the aquifer due to trains,
heavy traffic, etc.
7.5 EQUIPMENT/APPARATUS
tape measure (subdivided into tenths of
feet)
submersible pump
water pressure transducer
electric water level indicator
weighted tapes
steel tape (subdivided into tenths of feet)
generator
electronic data-logger (if transducer
method is used)
watch or stopwatch with second hand
semilogarithmic graph paper (if required)
water proof ink pen and logbook
thermometer
appropriate references and calculator
a barometer or recording barograph (for
tests conducted in confined aquifers)
heat shrinks
electrical tape
flashlights and lanterns
pH meter
conductivity meter
discharge pipe
flow meter
39
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7.6 REAGENTS
from the pumping well.
No chemical reagents are used for this procedure;
however, decontamination solutions may be
necessary. If decontamination of equipment is
required, refer to ERT SOP #2006, Sampling
Equipment Decontamination and the site-specific
work plan.
7.7 PROCEDURES
7.7.1 Preparation
1. Determine the extent of the sampling effort, the
sampling methods to be employed, and which
equipment and supplies are needed.
2. Obtain necessary sampling and monitoring
equipment.
3. Decontaminate or preclean equipment, and
ensure that it is in working order.
4. Prepare scheduling and coordinate with staff,
clients, and regulatory agency, if appropriate.
5. Perform a general site survey prior to site entry
in accordance with the site-specific health and
safety plan.
6. Identify and mark all sampling locations.
7.7.2 Field Preparation
1. Review the site work plan and become familiar
with information on the wells to be tested.
2. Check and ensure the proper operation of all
field equipment. Ensure that the electronic
data-logger is fully charged, if appropriate.
Test the electronic data-logger using a
container of water. Always bring additional
transducers in case of malfunctions.
3. Assemble a sufficient number of field data
forms to complete the field assignment.
4. Develop the pumping well prior to testing, per
ERT SOP #2156, Well Development.
5. Provide an orifice, weir, flow meter, container
or other type of water measuring device to
accurately measure and monitor the discharge
6. Provide sufficient pipe to transport the
discharge from the pumping well to an area
beyond the expected cone of depression.
Conducting a pumping test in contaminated
groundwater may require treatment, special
handling, or a discharge permit before the
water can be discharged.
7. The discharge pipe must have a gate valve to
control the pumping rate.
8. Determine if there is an outlet near the well
head for water quality determination and
sampling.
7.7.3 Pre-Test Monitoring
It is desirable to monitor pretest water levels at the
test site for about 1 week prior to performance of
the test. This can be accomplished by using a
continuous-recording device such as a Stevens
recorder. This information allows the determination
of the barometric efficiency of the aquifer when
barometric records are available. It also helps
determine if the aquifer is experiencing an increase
or decrease in head with time due to recharge or
pumping in the nearby area, or diurnal effects of
evapotranspiration. Changes in barometric pressure
are recorded during the test (preferably with an on-
site barograph) in order to correct water levels for
any possible fluctuations which may occur due to
changing atmospheric conditions. Pretest water
level trends are projected for the duration of the
test. These trends and/or barometric changes are
used to "correct" water levels during the test so they
are representative of the hydraulic response of the
aquifer due to pumping of the test well.
7.7.4 Step Test
Conduct a step test prior to initiating a long term
pumping test. The purpose of a step test is to
estimate the greatest flow rate that may be
sustained during a long term test. The test is
performed by progressively increasing the flow rate
at 1 hour intervals. The generated drawdown versus
time data is plotted on semilogarithmic graph paper,
and the discharge rate is determined from this
graph.
40
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7.7.5 Pump Test
Time Intervals
After the pumping well has fully recovered from the
step test, the long term pumping test may start. At
the beginning of the test, the discharge rate should
be set as quickly and accurately as possible. The
water levels in the pumping well and observation
wells will be recorded according to Tables 4 and 5
below.
Water Level Measurements
Water levels will be measured as specified in ERT
SOP #2151, Well Level Measurement. During the
early part of the test, sufficient personnel should be
available to have at least one person at each
observation well and at the pumping well. After the
first 2 hours, two people are usually sufficient to
continue the test. It is not necessary that readings
at the wells be taken simultaneously. It is very
important that depth to water readings be measured
accurately and readings recorded at the exact time
measured. Alternately, individual pressure
transducers and electronic data-loggers may be used
to reduce the number of field personnel hours
required to complete the pumping test. A typical
aquifer pump test form is shown in Appendix C.
During a pumping test, the following data must be
recorded accurately on the aquifer test data form.
1. Site ID - A number assigned to identity a
specific site.
Table 4: Time Intervals for Measuring
Drawdown in the Pumped Well
Elapsed Time
From Start of Test (Minutes)
0-10
10-15
15-60
60-300
300-1440
1440 - termination
Interval Between Measurements
(Minutes)
0.5 - 1
1
5
30
60
480
Table 5: Time Intervals for Measuring Drawdown
in an Observation Well
Elapsed
Time From Start of Test (Minutes)
O-60
60 - 120
120 - 240
240 - 360
360-1440
1440 - termination
Interval Between Measurements
(Minutes)
2
5
10
30
60
480
41
-------
2. Location - The location of the well in which
water level measurements are being taken.
3. Distance from Pumped Well -- Distance
between the observation well and the pumping
well in feet.
4. Logging Company - The company conducting
the pumping test.
5. Test Start Date - The date when the pumping
test began.
6. Test Start Time ~ Start time, using a 24hour
clock.
7. Static Water Level (Test Start) -- Depth to
water, in feet and tenths of feet, in the
observation well at the beginning of the
pumping test.
8. Test End Date - The date when the pumping
test was completed.
9. Test End Time - End time, using a 24hour
clock.
10. Static Water Level (Test End) -- Depth to
water, in feet and tenths of feet, in the
observation well at the end of the pumping test.
11. Average Pumping Rate - Summation of all
entries recorded in the Pumping Rate (gal/min)
column divided by the total number of Pumping
Rate (gal/min) readings.
12. Measurement Methods ~ Type of instrument
used to measure depth-to-water (this may
include steel tape, electric sounding probes,
Stevens recorders, or pressure transducers).
13. Comments ~ Appropriate observations or
information which have not been recorded
elsewhere, including notes on sampling.
14. Elapsed Time (min) ~ Time of measurement
recorded continuously from start of test (time
00.00).
15. Depth to Water (ft) - Depth to water, in feet
and tenths of feet, in the observation well at the
time of the water level measurement.
16. Pumping Rate (gal/min) ~ Plow rate of pump
measured from an orifice, weir, flow meter,
container or other type of water-measuring
device.
Test Duration
The duration of the test is determined by the needs
of the project and properties of the aquifer. One
simple test for determining adequacy of data is
when the log-time versus drawdown for the most
distant observation well begins to plot as a straight
line on the semilogarithmic graph paper. There are
several exceptions to this simple rule of thumb,
therefore, it should be considered a minimum
criterion. Different hydrogeologic conditions can
produce straight line trends on log-time versus
drawdown plots. In general, longer tests produce
more definitive results. A duration of 1 to 3 days is
desirable, followed by a similar period of monitoring
the recovery of the water level. Unconfined
aquifers and partially penetrating wells may have
shorter test durations. Knowledge of the local
hydrogeology, combined with a clear understanding
of the overall project objectives, is necessary in
interpreting just how long the test should be
conducted. There is no need to continue the test if
the water level becomes constant with time. This
normally indicates that a hydrogeologic source has
been intercepted and that additional useful
information will not be collected by continued
pumping.
7.7.6 Post Operation
1. After completion of water level recovery
measurements, decontaminate and/or dispose
of equipment as per ERT SOP #2006,
Sampling Equipment Decontamination.
2. When using an electronic data-logger, use the
following procedures.
** Stop logging sequence.
^ Print data, or save memory and disconnect
battery at the end of the day's activities.
3. Replace testing equipment in storage
containers.
4. Check sampling equipment and supplies.
Repair or replace all broken or damaged
equipment.
5. Review field forms for completeness.
42
-------
6. Interpret pumping/recovery test field results.
7.8 CALCULATIONS
There are several accepted methods for determining
aquifer properties such as transmissivity, storativity,
and conductivity. However, the method to use is
dependent on the characteristics of the aquifer
being tested (confined, unconfined, leaky confining
layer, etc.). When reviewing pump test data, texts
by Fetter, or Driscoll or Freeze and Cherry may be
used to determine the method most appropriate to
your case. See the reference section on page 69.
7.9 QUALITY ASSURANCE/
QUALITY CONTROL
Calibrate all gauges, transducers, flow meters, and
other equipment used in conducting pumping tests
before use at the site.
Obtain records of the instrument calibration and file
with the test data records. The calibration records
will consist of laboratory measurements. If
necessary, perform any on-site zero adjustment
and/or calibration. Where possible, check all flow
and measurement meters on-site using a container
of measured volume and stopwatch; the accuracy of
the meters must be verified before testing proceeds.
7.10 DATA VALIDATION
This section is not applicable to this SOP.
7.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA, and specific health and
safely procedures.
43
-------
Page Intentionally Blank
-------
8.0 SLUG TEST: SOP #2158
8.1 SCOPE AND APPLICATION
This procedure can determine the horizontal
hydraulic conductivity of distinct geologic horizons
under in situ conditions. The hydraulic conductivity
(K) is an important parameter for modeling the
flow of groundwater in an aquifer.
8.2 METHOD SUMMARY
A slug test involves the instantaneous injection of a
slug (a solid cylinder of known volume) or
withdrawal of a volume of water. A slug displaces
a known volume of water from a well and measures
the artificial fluctuation of the groundwater level.
There are several advantages to using slug tests to
estimate hydraulic conductivities. First, estimates
can be made in situ, thereby avoiding errors
incurred in laboratory testing of disturbed soil
samples. Second, compared with pump tests, slug
tests can be performed quickly and at relatively low
cost, because pumping and observation wells are not
required. And last, the hydraulic conductivity of
small discrete portions of an aquifer can be
estimated (e.g., sand layers in a clay).
8.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
This section is not applicable to this Standard
Operating Procedure (SOP).
8.5 EQUIPMENT/APPARATUS
The following equipment is needed to perform slug
tests. All equipment which comes in contact with
the well should be decontaminated and tested prior
to commencing field activities.
tape measure (subdivided into tenths of
feet)
water pressure transducer
electric water level indicator
weighted tapes
steel tape (subdivided into tenths of feet)
electronic data-logger (if transducer
method is used)
stainless steel slug of a known volume
watch or stopwatch with second hand
semilogarithmic graph paper (if required)
waterproof ink pen and logbook
thermometer
appropriate references and calculator
electrical tape
2IX micrologger
Compaq portable computer or equivalent
with Grapher installed on the hard disk
8.6 REAGENTS
No chemical reagents are used in this procedure;
however, decontamination solvents may be
necessary. When decontaminating the slug or
equipment, refer to ERT SOP #2006, Sampling
Equipment Decontamination, and the site-specific
work plan.
8.4 INTERFERENCES AND
POTENTIAL PROBLEMS
^ Only the hydraulic conductivity of the area
immediately surrounding the well is
estimated, which may not be representative
of the average hydraulic conductivity of the
area.
* The storage coefficient, S, usually cannot
be determined by this method.
8.7 PROCEDURES
8.7.1 Field Procedures
When the slug test is performed using an electronic
data-logger and pressure transducer, all data will be
stored internally or on computer diskettes or tape.
The information will be transferred directly to the
main computer and analyzed. Keep a computer
printout of the data in the files as documentation.
If the slug test data is collected and recorded
manually, the slug test data form (Appendix C) will
45
-------
be used to record observations. The slug test data
form should include the following information:
• site ID — identification number assigned to
the site
xx location ID — identification of location
being tested
xx date — the date when the test data were
collected in this order: year, month, day
(e.g., 900131 for January 31, 1990)
* slug volume (ft) = manufacturer's
specification for the known volume or
displacement of the slug device
x logger — identifies the company or person
responsible for performing the field
measurements
xx test method -- the slug device either is
injected or lowered into the well, or is
withdrawn or pulled-out from the monitor
well. Check the method that is applicable
to the test situation being run.
• comments -- appropriate observations or
information for which no other blanks are
provided.
& elapsed time (minutes) — cumulative time
readings from beginning of test to end of
test, in minutes
xx depth to water (feet) — depth to water
recorded in tenths of feet
The following general procedures may be used to
collect and report slug test data. These procedures
may be modified to reflect site-specific conditions:
1. Decontaminate the transducer and cable.
2. Make initial water level measurements on
monitoring wells in an upgradient-to-
downgradient sequence, if possible, to minimize
the potential for cross-contamination.
3. Before beginning the slug test, record
information into the electronic data-logger.
The type of information may vary depending on
the model used. When using different model,
consult the operator's manual for the proper
data entry sequence to be used.
4. Test wells from least contaminated to most
contaminated, if possible.
5. Determine the static water level in the well by
measuring the depth to water periodically for
several minutes and taking the average of the
readings, (see SOP #2151, Water Level
Measurement).
6. Cover sharp edges of the well casing with duct
tape to protect the transducer cables.
7. Install the transducer and cable in the well to
a depth below the target drawdown estimated
for the test but at least 2 feet from the bottom
of the well. Be sure the depth of submergence
is within the design range stamped on the
transducer. Temporarily tape the transducer
cable to the well to keep the transducer at a
constant depth.
8. Connect the transducer cable to the electronic
data-logger.
9. Enter the initial water level and transducer
design range into the recording device
according to the manufacturer's instructions.
The transducer design range will be stamped
on the side of the transducer. Record the
initial water level on the recording device.
10. "Instantaneously" introduce or remove a known
volume or slug of water to the well. Another
method is to introduce a solid cylinder of
known volume to displace and raise the water
level, allow the water level to restabilize and
remove the cylinder. It is important to remove
or add the volumes as quickly as possible
because the analysis assumes an "instantaneous"
change in volume is created in the well.
11. Consider the moment of volume addition or
removal as time zero. Measure and record the
depth to water and the time at each reading.
Depths should be measured to the nearest 0.01
foot. The number of depth-time measurements
necessary to complete the test is variable. It is
critical to make as many measurements as
possible in the early part of the test. The
number and intervals between measurements
will be determined from previous aquifer tests
or evaluations.
12. Continue measuring and recording depth-time
measurements until the water level returns to
equilibrium conditions or a sufficient number of
readings have been made to clearly show a
trend on a semilogarithmic plot of time versus
depth.
13. Retrieve slug (if applicable).
40
-------
Note: The time required for a slug test to be
completed is a function of the volume of the slug,
the hydraulic conductivity of the formation and the
type of well completion. The slug volume should be
large enough that a sufficient number of water level
measurements can be made before the water level
returns to equilibrium conditions. The length of the
test may range from less than a minute to several
hours. If the well is to be used as a monitoring
well, precautions against contaminating it should be
taken. If water is added to the monitoring well, it
should be from an uncontaminated source and
transported in a clean container. Bailers or
measuring devices should be decontaminated prior
to the test. If tests are performed on more than
one monitoring well, care must be taken to avoid
cross-contamination of the wells.
Slug tests should be conducted on relatively
undisturbed wells. If a test is conducted on a well
that has recently been pumped for water sampling
purposes, the measured water level must be within
0.1 foot of the static water level prior to sampling.
At least 1 week should elapse between the drilling
of a well and the performance of a slug test.
8.7.2 Post Operation
When using an electronic data-logger, use the
following procedure:
1. Stop logging sequence.
2. Print data.
3. Send data to computer by telephone.
4. Save memory and disconnect battery at the end
of the day's activities.
5. Review field forms for completeness.
8.8 CALCULATIONS
The simplest interpretation of piezometer recovery
is that of Hvorslev (1951). The analysis assumes a
homogenous, isotropic medium in which soil and
water are incompressible. Hvorslev's expression for
hydraulic conductivity (K) is:
K=r21n£L/R_L
2LTo
for L/R > 8
where:
K = hydraulic conductivity [feet/second]
= casing radius [feet]
r = length of open screen (or open borehole)
[feet]
R = filter pack (borehole) radius [feet]
To = Basic Time Lag [seconds]; value of t on
semilogarithmic plot of (H-h)/(H-Ho)
vs. t, when (H-h)/(H-Ho) = 0.37
where:
H = initial water level prior to removal of slug
Ho = water level at t = 0
h = recorded water level at t> 0
(Hvorslev, 1951; Freeze and Cherry, 1979)
The Bower and Rice method is also commonly used
for K calculations. However, it is much more time
consuming than the Hvorslev method. Refer to
Freeze and Cherry or Fetter for a discussion of
these methods.
8.9 QUALITY ASSURANCE/
QUALITY CONTROL
The following general quality assurance procedures
apply:
* All data must be documented on standard
chain of custody forms, field data sheets, or
within personal/site logbooks.
xx All instrumentation must be operated in
accordance with operating instructions as
supplied by the manufacturer, unless
otherwise specified in the work plan.
Equipment checkout and calibration
activities must occur prior to
sampling/operation, and they must be
documented.
The following specific quality assurance activity will
apply:
* Each well should be tested at least twice in
order to compare results.
47
-------
8.10 DATA VALIDATION
This section is not applicable to this SOP.
8.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA, and specific health and
safety procedures.
48
-------
APPENDIX A
Sampling Train Schematic
49
-------
Figure 1: Sampling Train Schematic
SOP #2149
VACUUM
BO
1/4" I.D. THIN WALL
TEFLON TUBING /&>
1/4" TEFLON TUBING
I/4" S.S.
SAMPLE PROBE
SAMPLING
PORT
"QUICK CONNECT"
FITTING
MODELING
CLAY
^~r
SAMPLE
WELL
50
-------
Figure 1: Sampling Train Schematic
SOP #2149
VACUUM
BO
1/4" I.D. THIN WALL
TEFLON TUBING /&>
1/4" TEFLON TUBING
I/4" S.S.
SAMPLE PROBE
SAMPLING
PORT
"QUICK CONNECT"
FITTING
MODELING
CLAY
^~r
SAMPLE
WELL
50
-------
APPENDIX A
Sampling Train Schematic
49
-------
8.10 DATA VALIDATION
This section is not applicable to this SOP.
8.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA, and specific health and
safety procedures.
48
-------
8.10 DATA VALIDATION
This section is not applicable to this SOP.
8.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA, and specific health and
safety procedures.
48
-------
Note: The time required for a slug test to be
completed is a function of the volume of the slug,
the hydraulic conductivity of the formation and the
type of well completion. The slug volume should be
large enough that a sufficient number of water level
measurements can be made before the water level
returns to equilibrium conditions. The length of the
test may range from less than a minute to several
hours. If the well is to be used as a monitoring
well, precautions against contaminating it should be
taken. If water is added to the monitoring well, it
should be from an uncontaminated source and
transported in a clean container. Bailers or
measuring devices should be decontaminated prior
to the test. If tests are performed on more than
one monitoring well, care must be taken to avoid
cross-contamination of the wells.
Slug tests should be conducted on relatively
undisturbed wells. If a test is conducted on a well
that has recently been pumped for water sampling
purposes, the measured water level must be within
0.1 foot of the static water level prior to sampling.
At least 1 week should elapse between the drilling
of a well and the performance of a slug test.
8.7.2 Post Operation
When using an electronic data-logger, use the
following procedure:
1. Stop logging sequence.
2. Print data.
3. Send data to computer by telephone.
4. Save memory and disconnect battery at the end
of the day's activities.
5. Review field forms for completeness.
8.8 CALCULATIONS
The simplest interpretation of piezometer recovery
is that of Hvorslev (1951). The analysis assumes a
homogenous, isotropic medium in which soil and
water are incompressible. Hvorslev's expression for
hydraulic conductivity (K) is:
K=r21n£L/R_L
2LTo
for L/R > 8
where:
K = hydraulic conductivity [feet/second]
= casing radius [feet]
r = length of open screen (or open borehole)
[feet]
R = filter pack (borehole) radius [feet]
To = Basic Time Lag [seconds]; value of t on
semilogarithmic plot of (H-h)/(H-Ho)
vs. t, when (H-h)/(H-Ho) = 0.37
where:
H = initial water level prior to removal of slug
Ho = water level at t = 0
h = recorded water level at t> 0
(Hvorslev, 1951; Freeze and Cherry, 1979)
The Bower and Rice method is also commonly used
for K calculations. However, it is much more time
consuming than the Hvorslev method. Refer to
Freeze and Cherry or Fetter for a discussion of
these methods.
8.9 QUALITY ASSURANCE/
QUALITY CONTROL
The following general quality assurance procedures
apply:
* All data must be documented on standard
chain of custody forms, field data sheets, or
within personal/site logbooks.
xx All instrumentation must be operated in
accordance with operating instructions as
supplied by the manufacturer, unless
otherwise specified in the work plan.
Equipment checkout and calibration
activities must occur prior to
sampling/operation, and they must be
documented.
The following specific quality assurance activity will
apply:
* Each well should be tested at least twice in
order to compare results.
47
-------
be used to record observations. The slug test data
form should include the following information:
• site ID — identification number assigned to
the site
xx location ID — identification of location
being tested
xx date — the date when the test data were
collected in this order: year, month, day
(e.g., 900131 for January 31, 1990)
* slug volume (ft) = manufacturer's
specification for the known volume or
displacement of the slug device
x logger — identifies the company or person
responsible for performing the field
measurements
xx test method -- the slug device either is
injected or lowered into the well, or is
withdrawn or pulled-out from the monitor
well. Check the method that is applicable
to the test situation being run.
• comments -- appropriate observations or
information for which no other blanks are
provided.
& elapsed time (minutes) — cumulative time
readings from beginning of test to end of
test, in minutes
xx depth to water (feet) — depth to water
recorded in tenths of feet
The following general procedures may be used to
collect and report slug test data. These procedures
may be modified to reflect site-specific conditions:
1. Decontaminate the transducer and cable.
2. Make initial water level measurements on
monitoring wells in an upgradient-to-
downgradient sequence, if possible, to minimize
the potential for cross-contamination.
3. Before beginning the slug test, record
information into the electronic data-logger.
The type of information may vary depending on
the model used. When using different model,
consult the operator's manual for the proper
data entry sequence to be used.
4. Test wells from least contaminated to most
contaminated, if possible.
5. Determine the static water level in the well by
measuring the depth to water periodically for
several minutes and taking the average of the
readings, (see SOP #2151, Water Level
Measurement).
6. Cover sharp edges of the well casing with duct
tape to protect the transducer cables.
7. Install the transducer and cable in the well to
a depth below the target drawdown estimated
for the test but at least 2 feet from the bottom
of the well. Be sure the depth of submergence
is within the design range stamped on the
transducer. Temporarily tape the transducer
cable to the well to keep the transducer at a
constant depth.
8. Connect the transducer cable to the electronic
data-logger.
9. Enter the initial water level and transducer
design range into the recording device
according to the manufacturer's instructions.
The transducer design range will be stamped
on the side of the transducer. Record the
initial water level on the recording device.
10. "Instantaneously" introduce or remove a known
volume or slug of water to the well. Another
method is to introduce a solid cylinder of
known volume to displace and raise the water
level, allow the water level to restabilize and
remove the cylinder. It is important to remove
or add the volumes as quickly as possible
because the analysis assumes an "instantaneous"
change in volume is created in the well.
11. Consider the moment of volume addition or
removal as time zero. Measure and record the
depth to water and the time at each reading.
Depths should be measured to the nearest 0.01
foot. The number of depth-time measurements
necessary to complete the test is variable. It is
critical to make as many measurements as
possible in the early part of the test. The
number and intervals between measurements
will be determined from previous aquifer tests
or evaluations.
12. Continue measuring and recording depth-time
measurements until the water level returns to
equilibrium conditions or a sufficient number of
readings have been made to clearly show a
trend on a semilogarithmic plot of time versus
depth.
13. Retrieve slug (if applicable).
40
-------
8.0 SLUG TEST: SOP #2158
8.1 SCOPE AND APPLICATION
This procedure can determine the horizontal
hydraulic conductivity of distinct geologic horizons
under in situ conditions. The hydraulic conductivity
(K) is an important parameter for modeling the
flow of groundwater in an aquifer.
8.2 METHOD SUMMARY
A slug test involves the instantaneous injection of a
slug (a solid cylinder of known volume) or
withdrawal of a volume of water. A slug displaces
a known volume of water from a well and measures
the artificial fluctuation of the groundwater level.
There are several advantages to using slug tests to
estimate hydraulic conductivities. First, estimates
can be made in situ, thereby avoiding errors
incurred in laboratory testing of disturbed soil
samples. Second, compared with pump tests, slug
tests can be performed quickly and at relatively low
cost, because pumping and observation wells are not
required. And last, the hydraulic conductivity of
small discrete portions of an aquifer can be
estimated (e.g., sand layers in a clay).
8.3 SAMPLE PRESERVATION,
CONTAINERS, HANDLING, AND
STORAGE
This section is not applicable to this Standard
Operating Procedure (SOP).
8.5 EQUIPMENT/APPARATUS
The following equipment is needed to perform slug
tests. All equipment which comes in contact with
the well should be decontaminated and tested prior
to commencing field activities.
tape measure (subdivided into tenths of
feet)
water pressure transducer
electric water level indicator
weighted tapes
steel tape (subdivided into tenths of feet)
electronic data-logger (if transducer
method is used)
stainless steel slug of a known volume
watch or stopwatch with second hand
semilogarithmic graph paper (if required)
waterproof ink pen and logbook
thermometer
appropriate references and calculator
electrical tape
2IX micrologger
Compaq portable computer or equivalent
with Grapher installed on the hard disk
8.6 REAGENTS
No chemical reagents are used in this procedure;
however, decontamination solvents may be
necessary. When decontaminating the slug or
equipment, refer to ERT SOP #2006, Sampling
Equipment Decontamination, and the site-specific
work plan.
8.4 INTERFERENCES AND
POTENTIAL PROBLEMS
^ Only the hydraulic conductivity of the area
immediately surrounding the well is
estimated, which may not be representative
of the average hydraulic conductivity of the
area.
* The storage coefficient, S, usually cannot
be determined by this method.
8.7 PROCEDURES
8.7.1 Field Procedures
When the slug test is performed using an electronic
data-logger and pressure transducer, all data will be
stored internally or on computer diskettes or tape.
The information will be transferred directly to the
main computer and analyzed. Keep a computer
printout of the data in the files as documentation.
If the slug test data is collected and recorded
manually, the slug test data form (Appendix C) will
45
-------
Page Intentionally Blank
-------
6. Interpret pumping/recovery test field results.
7.8 CALCULATIONS
There are several accepted methods for determining
aquifer properties such as transmissivity, storativity,
and conductivity. However, the method to use is
dependent on the characteristics of the aquifer
being tested (confined, unconfined, leaky confining
layer, etc.). When reviewing pump test data, texts
by Fetter, or Driscoll or Freeze and Cherry may be
used to determine the method most appropriate to
your case. See the reference section on page 69.
7.9 QUALITY ASSURANCE/
QUALITY CONTROL
Calibrate all gauges, transducers, flow meters, and
other equipment used in conducting pumping tests
before use at the site.
Obtain records of the instrument calibration and file
with the test data records. The calibration records
will consist of laboratory measurements. If
necessary, perform any on-site zero adjustment
and/or calibration. Where possible, check all flow
and measurement meters on-site using a container
of measured volume and stopwatch; the accuracy of
the meters must be verified before testing proceeds.
7.10 DATA VALIDATION
This section is not applicable to this SOP.
7.11 HEALTH AND SAFETY
When working with potentially hazardous materials,
follow U.S. EPA, OSHA, and specific health and
safely procedures.
43
-------
2. Location - The location of the well in which
water level measurements are being taken.
3. Distance from Pumped Well -- Distance
between the observation well and the pumping
well in feet.
4. Logging Company - The company conducting
the pumping test.
5. Test Start Date - The date when the pumping
test began.
6. Test Start Time ~ Start time, using a 24hour
clock.
7. Static Water Level (Test Start) -- Depth to
water, in feet and tenths of feet, in the
observation well at the beginning of the
pumping test.
8. Test End Date - The date when the pumping
test was completed.
9. Test End Time - End time, using a 24hour
clock.
10. Static Water Level (Test End) -- Depth to
water, in feet and tenths of feet, in the
observation well at the end of the pumping test.
11. Average Pumping Rate - Summation of all
entries recorded in the Pumping Rate (gal/min)
column divided by the total number of Pumping
Rate (gal/min) readings.
12. Measurement Methods ~ Type of instrument
used to measure depth-to-water (this may
include steel tape, electric sounding probes,
Stevens recorders, or pressure transducers).
13. Comments ~ Appropriate observations or
information which have not been recorded
elsewhere, including notes on sampling.
14. Elapsed Time (min) ~ Time of measurement
recorded continuously from start of test (time
00.00).
15. Depth to Water (ft) - Depth to water, in feet
and tenths of feet, in the observation well at the
time of the water level measurement.
16. Pumping Rate (gal/min) ~ Plow rate of pump
measured from an orifice, weir, flow meter,
container or other type of water-measuring
device.
Test Duration
The duration of the test is determined by the needs
of the project and properties of the aquifer. One
simple test for determining adequacy of data is
when the log-time versus drawdown for the most
distant observation well begins to plot as a straight
line on the semilogarithmic graph paper. There are
several exceptions to this simple rule of thumb,
therefore, it should be considered a minimum
criterion. Different hydrogeologic conditions can
produce straight line trends on log-time versus
drawdown plots. In general, longer tests produce
more definitive results. A duration of 1 to 3 days is
desirable, followed by a similar period of monitoring
the recovery of the water level. Unconfined
aquifers and partially penetrating wells may have
shorter test durations. Knowledge of the local
hydrogeology, combined with a clear understanding
of the overall project objectives, is necessary in
interpreting just how long the test should be
conducted. There is no need to continue the test if
the water level becomes constant with time. This
normally indicates that a hydrogeologic source has
been intercepted and that additional useful
information will not be collected by continued
pumping.
7.7.6 Post Operation
1. After completion of water level recovery
measurements, decontaminate and/or dispose
of equipment as per ERT SOP #2006,
Sampling Equipment Decontamination.
2. When using an electronic data-logger, use the
following procedures.
** Stop logging sequence.
^ Print data, or save memory and disconnect
battery at the end of the day's activities.
3. Replace testing equipment in storage
containers.
4. Check sampling equipment and supplies.
Repair or replace all broken or damaged
equipment.
5. Review field forms for completeness.
42
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APPENDIX B
HNU Field Protocol
51
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Page Intentionally Blank
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HNU Field Protocol
SOP #2149
Startup Procedure
1. Before attaching the probe, check the function
switch on the control panel to ensure that it is
in the 'off position. Attach the probe by
plugging it into the interface on the top of the
readout module. Use care in aligning the
prongs in the probe cord with the plug in; do
not force.
2. Turn the function switch to the battery check
position. The needle on the meter should read
within or above the green area on the scale. If
not, recharge the battery. If the red indicator
light comes on, the battery needs recharging.
3. Turn the function switch to any range setting.
For no more than 2 to 3 seconds look into the
end of the probe to see if the lamp is on. If it
is on, you will see a purple glow. Do not stare
into the probe any longer than three seconds.
Long term exposure to UV light can damage
eyes. Also, listen for the hum of the fan motor.
4. To zero the instrument, turn the function switch
to the standby position and rotate the zero
adjustment until the meter reads zero. A
calibration gas is not needed since this is an
electronic zero adjustment. If the span
adjustment setting is changed after the zero is
set, the zero should be rechecked and adjusted,
if necessary. Wait 15 to 20 seconds to ensure
that the zero reading is stable. If necessary,
readjust the zero.
Operational Check
1. Follow the startup procedure.
2. With the instrument set on the 0-20 range, hold
a solvent-based Magic Marker near the probe
tip. If the meter deflects upscale, the
instrument is working.
Field Calibration Procedure
1. Follow the startup procedure and the
operational check.
2. Set the function switch to the range setting for
the concentration of the calibration gas.
3. Attach a regulator (HNU 101-351) to a
disposable cylinder of isobutylene gas. Connect
the regulator to the probe of the HNU with a
piece of clean Tygon tubing. Turn the valve on
the regulator to the 'on' position.
4. After 15 seconds, adjust the span dial until the
meter reading equals the concentration of the
calibration gas used. The calibration gas is
usually 100 ppm of isobutylene in zero air. The
cylinders are marked in benzene equivalents for
the 10.2 eV probe (approximately 55 ppm
benzene equivalent) and for the 11.7 eV probe
(approximately 65 ppm benzene equivalent).
Be careful to unlock the span dial before
adjusting it. If the span has to be set below 3.0
calibration, the lamp and ion chamber should
be inspected and cleaned as appropriate. For
cleaning of the 11.7 eV probe, only use an
electronic-grade, oil-free freon or similar water-
free, grease-free solvent.
5. Record in the field log: the instrument ID #
(EPA decal or serial number if the instrument
is a rental); the initial and final span settings;
the date and time; concentration and type of
calibration used; and the name of the person
who calibrated the instrument.
Operation
1. Follow the startup procedure, operational
check, and calibration check.
2. Set the function switch to the appropriate
range. If the concentration of gases or vapors
is unknown, set the function switch to the 0-20
ppm range. Adjust it if necessary.
3. While taking care not to permit the HNU to be
exposed to excessive moisture, dirt, or
contamination, monitor the work activity as
specified in the site health and safety plan.
4. When the activity is completed or at the end of
the day, carefully clean the outside of the HNU
with a damp disposable towel to remove any
53
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visible dirt. Return the HNU to a secure area plastic to prevent it from becoming contaminated
and place on charge. and to prevent water from getting inside in the
event of precipitation.
5. With the exception of the probe's inlet and
exhaust, the HNU can be wrapped in clear
54
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APPENDIX C
Forms
55
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Well Completion Form
SOP #2150
PAGE-OF-
Clirnti
Srt*i
Total
Conn*
j:
+*
a
a
a
MONITOR WELL NSTALLATION
Depth
Synbol
Stratigraphy
Sample Description
Conple"tlan Data
56
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Groundwater Level Data Form
SOP #2151
PAGE-OF-
SITE NAME:
LOG DATE: LOGGER NAME:
MEASUREMENT REFERENCE POINT: -TOP OF GROUND -TOP OF CASING
LOCATION
TIME
DEPTH TO
WATER (FT)
COMMENTS
57
-------
Pump/Recovery Test Data Sheet
SOP #2157
PAGE-OF-
SITE ID:
LOCATION:
TEST START
DATE:
TIME:
STATIC WATER LEVEL (FT):
DISTANCE FROM PUMPED WELL (FT):
LOGGER:
TEST END
DATE:
TIME:
STATIC WATER LEVEL (FT):
AVERAGE PUMPING RATE (GAL/MIN):
MEASUREMENT METHODS:
COMMENTS:
ELAPSED
TIME
(MIN)
0.00
PUMP TEST
DEPTH TO
WATER (FT)
PUMPING
RATE
(GAL/MIN)
RECOVERY
TEST ELAPSED
TIME (MIN)
0.00
DEPTH TO
WATER (FT)
58
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Pump/Recovery Test Data Sheet (Continued)
SOP #2157
PAGE-OF-
SITE ID: DATE:
LOCATION: LOGGER:
ELAPSED
TIME
(MIN)
PUMP TEST
DEPTH TO
WATER (FT)
PUMPING
RATE
(GAL/MIN)
RECOVERY
TEST ELAPSED
TIME (MIN)
DEPTH TO
WATER (FT)
59
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Slug Test Data Form
SOP #2158
PAGE-OF-
DATE:
SITE ID:
LOCATION ID:
SLUG VOLUME (FT3):
LOGGER:
TEST METHOD: _ SLUG INJECTION _ SLUG WITHDRAWAL
COMMENTS:
TIME (Begin Test #1):
TIME (End Test #1):
ELAPSED TIME
(MIN)
DEPTH TO WATER
(FT)
TIME (Begin Test #2):
TIME (End Test #2):
ELAPSED TIME
(MIN)
DEPTH TO WATER
(FT)
60
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