1. Appendix A
      2. Groundwater Monitoring Guidance
      3. TABLE OF CONTENTS
      4. APPENDIX A: GROUNDWATER MONITORING GUIDANCE
      5. A. Overview
      6. 1. Introduction
      7. 2. References
      8. B. Monitoring Well Types and Construction
      9. 1. Objectives of Monitoring Wells
      10. 2. Types of Groundwater Monitoring Systems
      11. Figure A-1
      12. Recommended Construction of an Open Borehole Well
      13. Figure A-2
      14. Recommended Construction of a Single-Screened Well
      15. Figure A-3
      16. Example of a Well Cluster
      17. 3. Choice of Monitoring System
      18. 4. Minimum Construction Standards
      19. Figure A-4
      20. Examples of Target Zones
      21. Figure A-5
      22. a) Materials
      23. b) Assembly and Installation
      24. c) Well Development
      25. d) Recordkeeping and Reporting
      26. 5. Direct Push Technology
      27. a) Advantages of DPT
      28. b) Disadvantages of DPT
      29. 6. References
      30. C. Locations and Depths of Monitoring Wells
      31. 1. Importance
      32. 2. Approach to Determining Monitoring Locations and Depths
      33. a) Background Monitoring
      34. b) Site Characterization Monitoring
      35. c) Attainment and Post-remedial Monitoring
      36. 3. Factors in Determining Target Zones for Monitoring
      37. a) Groundwater Movement
      38. i) Geologic Factors
      39. ii) Groundwater Barriers
      40. Figure A-6
      41. Effect of Fractures on the Spread of Contamination
      42. iii) Karst Terrane
      43. Figure A-7
      44. Ineffective Monitoring Wells in a Carbonate Aquifer
      45. iv) Deep-Mined Areas
      46. b) Contaminant Distribution
      47. 4. Areal Placement of Wells
      48. 5. Well Depths, Screen Lengths, and Open Intervals
      49. 6. Number of Wells
      50. 7. Well Yield
      51. a) Fractured Rock
      52. b) Heterogeneous Unconsolidated Formations
      53. c) Areas of Uniformly Low Yield
      54. 8. References
      55. D. Groundwater Sampling Techniques
      56. 1. Importance of Sampling Technique
      57. 2. Sample Collection Devices
      58. 3. Sample Collection Procedures
      59. a) Protective Clothing
      60. b) Water Levels
      61. c) Field Measurements
      62. d) Purging
      63. Table A-1
      64. Advantages and Disadvantages of Different Sampling Devices
      65. ADVANTAGES DISADVANTAGES
      66. ADVANTAGES DISADVANTAGES
      67. i) Criteria Based on the Number of Bore Volumes
      68. ii) Criteria Based on Stabilization of Indicator Parameters
      69. iii) Low Flow Purging
      70. iv) Special Problems of Low-Yielding Wells
      71. v) No-Purge Methods
      72. vi) Summary on Purging
      73. e) Management of Purge Water
      74. f) Private Wells
      75. g) Filtering
      76. Table A-2
      77. Procedure for the Management of Well Purge Water from Groundwater Sampling
      78. TYPE OF
      79. GROUNDWATER
      80. ACTION
      81. h) Sample Preservation
      82. i) Decontamination of Sampling Devices
      83. j) Field Sampling Logbook
      84. k) Chain-of-Custody
      85. References
      86. E. Well Decommission Procedures
      87. 1. Introduction
      88. 2. Well Characterization
      89. 3. Well Preparation
      90. 4. Materials and Methods
      91. a) Aggregate
      92. b) Sealants
      93. c) Bridge Seals
      94. 5. Recommendations
      95. a) Casing Seal
      96. b) Wells in Unconfined or Semi-Confined Conditions
      97. c) Wells at Contaminated Sites
      98. d) Flowing Wells
      99. e) Wells with Complicating Factors at Contaminated Sites
      100. f) Monitoring Wells
      101. Figure A-8
      102. Summary of Procedures for Well Decommissioning
      103. 6. Existing Regulations and Standards
      104. 7. Reporting
      105. 8. References
      106. F. Quality Assurance/Quality Control Requirements
      107. 1. Purpose
      108. 2. Design
      109. 3. Elements
      110. 4. References

261-0300-101 / DRAFT December 16, 2017 / Page A-i
Appendix A
Groundwater Monitoring Guidance

261-0300-101 / DRAFT December 16, 2017 / Page A-ii
TABLE OF CONTENTS
APPENDIX A: GROUNDWATER MONITORING GUIDANCE ................................................ A-1
A.
Overview..................................................................................................................................... A-1
1.
Introduction..................................................................................................................... A-1
2.
References....................................................................................................................... A-2
B.
Monitoring Well Types and Construction .................................................................................. A-3
1.
Objectives of Monitoring Wells...................................................................................... A-3
2.
Types of Groundwater Monitoring Systems................................................................... A-3
3.
Choice of Monitoring System......................................................................................... A-7
4.
Minimum Construction Standards .................................................................................. A-7
a)
Materials ............................................................................................................. A-9
b)
Assembly and Installation................................................................................... A-9
c)
Well Development ............................................................................................ A-10
d)
Recordkeeping and Reporting........................................................................... A-11
5.
Direct Push Technology................................................................................................ A-12
a)
Advantages of DPT........................................................................................... A-12
b)
Disadvantages of DPT ...................................................................................... A-12
6.
References..................................................................................................................... A-13
C.
Locations and Depths of Monitoring Wells.............................................................................. A-15
1.
Importance .................................................................................................................... A-15
2.
Approach to Determining Monitoring Locations and Depths ...................................... A-15
a)
Background Monitoring.................................................................................... A-16
b)
Site Characterization Monitoring...................................................................... A-16
c)
Attainment and Post-remedial Monitoring ....................................................... A-16
3.
Factors in Determining Target Zones for Monitoring .................................................. A-16
a)
Groundwater Movement ................................................................................... A-17
i)
Geologic Factors ................................................................................... A-17
ii)
Groundwater Barriers............................................................................ A-18
iii)
Karst Terrane ........................................................................................ A-20
iv)
Deep-Mined Areas ................................................................................ A-23
b)
Contaminant Distribution.................................................................................. A-23
4.
Areal Placement of Wells ............................................................................................. A-23
5.
Well Depths, Screen Lengths, and Open Intervals ....................................................... A-24
6.
Number of Wells........................................................................................................... A-26
7.
Well Yield..................................................................................................................... A-26
a)
Fractured Rock.................................................................................................. A-27
b)
Heterogeneous Unconsolidated Formations ..................................................... A-27
c)
Areas of Uniformly Low Yield......................................................................... A-27
8.
References..................................................................................................................... A-28
D.
Groundwater Sampling Techniques.......................................................................................... A-30
1.
Importance of Sampling Technique.............................................................................. A-30
2.
Sample Collection Devices ........................................................................................... A-32
3.
Sample Collection Procedures ...................................................................................... A-32
a)
Protective Clothing ........................................................................................... A-32
b)
Water Levels ..................................................................................................... A-32
c)
Field Measurements .......................................................................................... A-32
d)
Purging.............................................................................................................. A-33

261-0300-101 / DRAFT December 16, 2017 / Page A-iii
i)
Criteria Based on the Number of Bore Volumes .................................. A-35
ii)
Criteria Based on Stabilization of Indicator Parameters....................... A-36
iii)
Low Flow Purging ................................................................................ A-36
iv)
Special Problems of Low-Yielding Wells ............................................ A-37
v)
No-Purge Methods ................................................................................ A-38
vi)
Summary on Purging ............................................................................ A-39
e)
Management of Purge Water ............................................................................ A-40
f)
Private Wells..................................................................................................... A-41
g)
Filtering............................................................................................................. A-41
h)
Sample Preservation.......................................................................................... A-42
i)
Decontamination of Sampling Devices ............................................................ A-43
j)
Field Sampling Logbook................................................................................... A-44
k)
Chain-of-Custody.............................................................................................. A-45
4.
References..................................................................................................................... A-45
E.
Well Decommission Procedures ............................................................................................... A-47
1.
Introduction................................................................................................................... A-47
2.
Well Characterization ................................................................................................... A-47
3.
Well Preparation ........................................................................................................... A-48
4.
Materials and Methods.................................................................................................. A-48
a)
Aggregate.......................................................................................................... A-48
b)
Sealants ............................................................................................................. A-49
c)
Bridge Seals ...................................................................................................... A-50
5.
Recommendations......................................................................................................... A-50
a)
Casing Seal........................................................................................................ A-50
b)
Wells in Unconfined or Semi-Confined Conditions......................................... A-51
c)
Wells at Contaminated Sites ............................................................................. A-51
d)
Flowing Wells................................................................................................... A-51
e)
Wells with Complicating Factors at Contaminated Sites ................................. A-52
f)
Monitoring Wells .............................................................................................. A-52
6.
Existing Regulations and Standards.............................................................................. A-54
7.
Reporting....................................................................................................................... A-54
8.
References..................................................................................................................... A-54
F.
Quality Assurance/Quality Control Requirements ................................................................... A-55
1.
Purpose.......................................................................................................................... A-55
2.
Design ........................................................................................................................... A-55
3.
Elements........................................................................................................................ A-55
4.
References..................................................................................................................... A-58

261-0300-101 / DRAFT December 16, 2017 / Page A-1
APPENDIX A: GROUNDWATER MONITORING GUIDANCE
When groundwater is an affected medium, monitoring it is an extremely important part of site
characterization, fate and transport assessment, and ultimately, demonstrating attainment of a cleanup
standard at Act 2 sites. Taking this under consideration, the Groundwater Monitoring Guidance
identifies technical considerations for performing detailed yet concise hydrogeologic investigations and
groundwater monitoring programs at Act 2 sites. The purpose of this guidance is to ensure consistency
within the Department and to inform the regulated community of DEP’s technical recommendations and
the bases for them.
The methods and practices described in this guidance are not intended to be the only methods and
practices available to a remediator for attaining compliance with Act 2 regulations. The procedures used
to meet requirements should be tailored to the specific needs of the individual site and Act 2 project and
based on the history, logistics, and unique circumstances of those sites. The guidance is not intended to
be a rigid step-by-step approach that is utilized in all situations. The Department recommends that site
remediators consult with DEP Regional Office staff for assistance in evaluating and understanding site
characterization information for a more efficient Act 2 cleanup.
A.
Overview
1.
Introduction
Monitoring of groundwater quality is an important component in the application of and
compliance with Act 2 of 1995, the Land Recycling and Environmental Remediation
Standards Act (Act 2, 35 P.S. §§ 6026.101-2026.908). The goal for monitoring
groundwater quality is to obtain reliable data and information that is representative of
aquifer characteristics, groundwater flow direction, and physical and chemical
characteristics of the groundwater.
Before beginning a hydrogeologic investigation at an Act 2 site, a conceptual site model
(CSM) should be developed based on site geology and hydrogeology and the
characteristics of the release. The CSM should estimate distribution of predominant
geologic units, flow conditions, location of aquifers and aquitards (if known), water table
surface and other pertinent hydrogeologic factors present at the site. Coupled with
hydrogeologic properties at the Act 2 site, the CSM should consider the type of
contaminant which has been released and its physical properties (e.g., petroleum-based or
solvent-based, weathered vs. fresh, etc.), the manner of release to the environment, and
the volume of the release as can best be determined.
Typical groundwater quality monitoring at Act 2 sites may include:
Background monitoring: relating to determination of background conditions in
accordance with the Act 2 background cleanup standard (e.g. establishing if a
groundwater contaminant is naturally occurring, an areawide problem typically
resulting from historic, areawide releases, or from an upgradient source). The
results of background groundwater monitoring will form a basis against which
future monitoring results will be compared to established background values for
specific regulated substances of concern, develop groundwater quality trend

261-0300-101 / DRAFT December 16, 2017 / Page A-2
analyses, or remediation effectiveness under Act 2 when the background cleanup
standard is selected.
Site Characterization: During site characterization, groundwater monitoring wells
may be installed and sampled at an Act 2 site throughout the area(s) of
contamination, as well as in areas not affected by the release of any regulated
substance. Some of the data collected at the monitoring well locations may
include groundwater elevations, which are then used to calculate groundwater
flow direction and hydraulic gradient, permeability of aquifer materials, porosity
of the aquifer, the types of regulated substances present and their concentrations,
and the spatial variation in concentration, both horizontally and vertically. A fate
and transport assessment most likely should be implemented during this phase of
the Act 2 investigation.
Attainment monitoring: Attainment monitoring of groundwater is performed to
demonstrate that the selected Act 2 cleanup standard has been attained at the Point
of Compliance (POC). Refer to Section II.B of this guidance for additional
information on this concept. Attainment monitoring is also utilized to determine
the effectiveness of groundwater cleanup activities.
Postremedial monitoring: Postclosure monitoring is conducted to determine any
changes in groundwater quality after the cessation of a regulated activity or
activities. This monitoring may also be part of a postremedial care plan, such as
periodic monitoring of sentinel wells. Analytes most likely to be included are
those which were monitored during site characterization and/or attainment
monitoring.
2.
References
ALASKA DEPARTMENT OF ENVIRONMENTAL CONSERVATION,
September 2013, Division of Spill Prevention and Response Contamination Sites
Program, Monitoring Well Guidance.

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B.
Monitoring Well Types and Construction
1.
Objectives of Monitoring Wells
Monitoring wells should be located and constructed to provide the controlled access
necessary to characterize the groundwater at an Act 2 site. Wells should be constructed
by a driller who is licensed by the Commonwealth of Pennsylvania (Act 610 of 1956,
32 P.S. § 645.12, and 17 Pa. Code Chapter 47). Drillers do not need to be licensed to
install piezometers, temporary well points, or in-situ sampling probes.
Monitoring wells should effectively achieve one or more of the following objectives:
Provide access to the groundwater system for collection of water samples.
Measure the hydraulic head at a specific location in the groundwater flow system.
Provide access for conducting tests or collecting information necessary to
characterize the chemical properties of aquifer materials or their hydrologic
properties.
While achieving these objectives, the groundwater monitoring system should also
preserve the conditions of the subsurface that is penetrated, but not monitored. For
example, a well designed to monitor a bedrock aquifer should be designed and installed
with minimal or no impact to the flow system in the unconsolidated material overlying
the bedrock.
Although monitoring (or observation) wells may be used to measure water levels and
then determine the configuration of the water table, or other potentiometric surface, the
focus of this appendix is groundwater quality monitoring. Specifically, this appendix
provides guidance for the monitoring of groundwater at Act 2 sites.
2.
Types of Groundwater Monitoring Systems
Groundwater monitoring systems range from the simple to the complex. Each system has
its own value and use in the monitoring environment. Various types of groundwater
monitoring systems are described below. General recommendations for the construction
of single-screened wells and open boreholes are shown in Figures A-1 and A-2. Site-
specific circumstances may require modifications to the recommended construction
details.
Open boreholes - These boreholes are typically drilled into competent bedrock with the
casing extending completely through the overburden (unconsolidated material) and into
the competent rock below. Note that a vertical conduit is created which may intercept
active groundwater flow zones (controlled by primary porosity and secondary porosity;
i.e. fractures, bedding planes, solution cavities) previously not in contact with each other,
potentially resulting in cross contamination. Recommended installation details are shown
in Figure A-1.

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Figure A-1
Recommended Construction of an Open Borehole Well

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Figure A-2
Recommended Construction of a Single-Screened Well

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Figure A-3
Example of a Well Cluster
Single screened wells - These wells consist of a prefabricated screen of polyvinylchloride
plastic, stainless steel, etc., that is inserted into an open borehole. Clean sand or gravel is
placed around the annular space of the screen for the entire vertical distance of the screen
length and slightly higher past the connecting screen and well casing. Recommended
installation details are shown in Figure A-2.
Well clusters - Well clusters, or a well nest, consist of the construction of open boreholes
or screened monitoring wells in a specific location, with each well monitoring a different
depth or zone of groundwater. An example of a well cluster is shown in Figure A-3.
Well points - Well points are usually short lengths (i.e., 1-3 feet) of screen attached to a
hardened metal point so that the entire unit can be driven, pushed, or drilled to the desired
depth for monitoring. (This method is usually limited to shallow, unconsolidated
formations.)

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Piezometers - These are small diameter wells, generally non-pumping, with a very short
well screen or section of slotted pipe at the end that is used to measure the hydraulic head
at a certain point below the water table or other potentiometric surface.
3.
Choice of Monitoring System
The type of monitoring system chosen depends on the objectives of monitoring at the
site. Once the target zones, or areal locations and depths that are the most likely to be
impacted by the release are defined, monitoring is often adequately accomplished by
using open rock boreholes or single-screened wells that monitor the entire saturated
thickness, or a large portion of the target zone.
Where contamination has been detected and definition of vertical contaminant
stratification is desired, wells that monitor more discrete intervals of the target zone, or
individual aquifers, usually need to be constructed. In this case, well clusters such as
shown in Figure A-3 will often be the construction design of choice, although open holes
that monitor a short vertical interval or single water-bearing zone also may have
application. As the flow beneath the site is better understood, the monitoring system
typically will target more specific depths and locations.
Well points, or in-situ sampling probes (direct push technology), can be valuable
reconnaissance tools for preliminary site characterizations, or for determining the
locations of permanent monitoring wells (see EPA, 1993 and ITRC, 2006). However, in-
situ sampling probes can miss a light nonaqueous phase liquid (LNAPL) on the water
table and may have problems penetrating coarse sands and gravel (where contamination
may be located). Other potential problems include very slow fill times in clayey
sediments and significant capture of fines in the sample.
Special well construction will be needed to monitor for certain types of contaminants.
For example, if an LNAPL is a concern, the well screen should be open, bridging the
top of the water table and within the zone of fluctuation, so that the LNAPL
contaminants will not be cased-off.
4.
Minimum Construction Standards
To properly meet the objectives listed in Section B.1, monitoring wells should be
designed and constructed using minimum standards in each of the following categories.
1)
Materials
2)
Assembly and installation
3)
Well development
4)
Recordkeeping and reporting

261-0300-101 / DRAFT December 16, 2017 / Page A-8
Figure A-4
Examples of Target Zones
Figure A-5
Monitoring Well Screens Placed Too Deeply Below the Target Zone to Detect Contamination

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Different standards and practices may be necessary depending upon the monitoring
objectives of an individual site. Monitoring wells constructed to meet multiple objectives
should employ the standards of the most rigorous objective. For instance, a well point
may be suitable for monitoring hydraulic head, but may not be optimum for collecting
samples. Therefore, a well proposed to monitor head and collect water samples should be
designed as a conventional, screened well and not as a well point. In addition,
construction methods, materials, and well development of each point in the plan must not
compromise the objective of other monitoring wells in the well system.
a)
Materials
Materials that are used in construction of a monitoring well should not
contaminate the groundwater being monitored. A list of materials should include,
but not be limited to, the drilling tools and equipment, casing, riser pipe, well
screen, centralizers (if needed), annular sealant, filter pack, and drilling fluids or
additives. All materials should be of adequate size and of competent strength to
meet the objectives of the monitoring point. All materials introduced into the
boring should be free of chemicals or other contaminants that could compromise
the monitoring well or other downgradient wells. Practices must be employed to
minimize the potential for contamination of the materials during storage,
assembly, and installation. Specific cleaning procedures should be employed in
situations where the materials might introduce contaminants to the groundwater
system. Well screens and risers should be coupled using either water-tight flush-
joint threads or thermal welds. Solvent welded couplings are not recommended
for monitoring well construction.
b)
Assembly and Installation
Equipment and techniques should be used that create a stable, open, vertical
borehole of large enough diameter to ensure that the monitoring well can be
installed as designed, while minimizing the impact on the zone(s) being
monitored. When drill cuttings and groundwater removed during construction
will likely be contaminated, procedures commensurate with the type and level of
contamination should be followed for the handling, storage, and disposal of the
contaminated material. Whenever feasible, drilling procedures that do not
introduce water or other liquids into the borehole should be utilized. When the
use of drilling fluids is unavoidable, the fluid should have as little impact on the
constituents of interest as possible. If air or other gas is used as the drilling fluid,
the compressor should be equipped with an oil air filter or an oil trap.
The well screen and riser assembly should be installed using procedures that
ensure the integrity of the assembly. If water or other ballast is used, it should be
of known and compatible chemistry with the water in the boring. Unless designed
otherwise, the assembly should be installed plumb and in the center of the boring.
Centralizers of proper spacing and diameter can be used. Unless otherwise
approved, the riser should extend above grade and be capped to prevent the entry
of foreign material.

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Installation of the filter pack, sealants, or other materials in the annular space
should be done using tremie pipes or other accepted practices. Protective casing
and locking well caps must be installed, and any other necessary measures must
be taken to ensure that the monitoring well is protected from vandalism and
accidental damage. To reduce misidentification, all monitoring wells constructed
in developed areas, or in any location where they may be mistaken for other
structures (such as tank-fill tubes, drains, and breather tubes), should have a
locking cap conspicuously labeled “Monitoring Well” (preferably by the well-cap
manufacturer). In addition, locks for the monitoring wells should use a key
pattern different from locks on other structures at the site. It is also advisable that
the well identification number be placed on both the inside and outside of the
protective casing.
c)
Well Development
After installation, groundwater monitoring wells should be developed to:
Correct damage to the geological formation caused by the drilling process;
Restore the natural water quality of the aquifer in and around the well;
Optimize hydraulic communication between the geologic formation and
the well screen; and
Create an effective filter pack around the well screen.
Well development is necessary to provide groundwater samples that represent
natural undisturbed hydrogeological conditions. When properly developed, a
monitoring well will produce samples of acceptably low turbidity (less than
10 Nephelometric Turbidity Units (NTUs) as recommended by U.S. EPA, 2013).
Low turbidity is desirable as turbidity may interfere with subsequent analyses,
especially for constituents that sorb to fine-grained materials, such as metals
(CEPA, 2014). Well development stresses the formation and filter pack so that
fine-grained materials are mobilized, pulled through the well screen into the well,
and removed by pumping.
Well development should continue until as much of the fine-grained materials
present in the well column have been removed as possible. It is important to
record pumping rates utilized during well development. Purging and sampling
rates should not exceed the maximum pumping rate used during well
development. When it is likely that the water removed during development will
be contaminated, procedures commensurate with the type and level of
contamination should be utilized and documented for the handling, storage, and
disposal of the contaminated material. Development methods should minimize
the introduction of materials that might compromise the objective of the
monitoring. If air is used, the compressor should have an oil air filter or oil trap.

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d)
Recordkeeping and Reporting
Because interpretation of monitoring data from a monitoring well is spatially
dependent on both the activity being monitored and other monitoring wells in the
system, records and samples of the materials used to construct and drill the
monitoring well should be kept. Following construction, accurate horizontal and
vertical surveys should be performed. The surveys should be completed by
personnel knowledgeable in land surveying techniques. A permanent reference
point should be made by notching the riser pipe. Whenever possible, all reference
points should be established in relation to an established National Geodetic
Vertical Datum (NGVD). Monitoring well locations should be surveyed to
1
linear foot, and monitoring well elevations should be to the nearest .01 foot.
Elevations of the protective casing (with the cap off or hinged back), the well
casing, and the ground surface should be surveyed for each monitoring well (see
Nielsen, 1991). DEP-permitted facilities are generally required to record the
latitude and longitude for each monitoring well (this also is recommended for
non-permitted facilities).
A groundwater monitoring network report should be prepared. This report should
include copies of the well boring logs, test pit and exploratory borehole logs;
details on the construction of each monitoring point; maps, air photos or other
information necessary to fully describe the location and spatial relationship of the
points in the monitoring system; and a recommended decommissioning procedure
consistent with the applicable regulatory program and the well decommissioning
procedures recommended in Section E of this appendix.
Monitoring well logs should be prepared and should describe, at a minimum, the
date of construction; the thickness and composition of the geologic units
(identification of stratigraphic units should be completed on the well log using the
Unified Soil Classification System); the location and type of samples collected;
the nature of fractures and other discontinuities encountered; the nature and
occurrence of groundwater encountered during construction, including the depth
and yield of water-bearing zones; headspace of photoionization detector (PID)
readings collected; any observations of contamination (e.g. NAPL); and the static
water level upon completing construction.
A well completion plan should also be included in the monitoring network report.
Each plan should include information on the length, location, slot size, and nature
of filter pack for each screen; type, location and quantity of material used as
annular seals and filler; description of the type and effectiveness of well
development employed; and notes describing how the well, as constructed, differs
from its original design and/or location.
The reports described above do not relieve the driller from the obligation to
submit, for each well drilled, a Water Well Completion Report to the Department
of Conservation and Natural Resources (DCNR), Bureau of Topographic and
Geologic Survey, as required by Act 610 (the Water Well Drillers License Act).

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5.
Direct Push Technology
Direct Push Technology (DPT) devices are investigative tools that drive or ‘push’ small-
diameter rods into the subsurface via hydraulic or percussive methods without the use of
conventional drilling. DPT has been in use in the environmental industry for more than
two decades and its utilization as a tool for performing subsurface investigations in
Pennsylvania and many other states has grown concurrently with its evolving technology.
Monitoring wells installed using DPT could either be field-constructed, similar to
conventionally drilled and installed wells, or installed using pre-packed well screens.
The pre-packed well screen assemblies consist of an inner slotted screen surrounded by a
wire mesh sleeve which acts as a support for filter media (sand). The sand is packed
between the slotted screen and the mesh. It is important to note that only DPT pre-
packed wells are considered suitable for Act 2 sites, due to quality assurance concerns
regarding field-construction and associated problems placing the filter pack around the
screens of small-diameter wells.
a)
Advantages of DPT
Depending on site conditions, DPT offers an attractive alternative to conventional
auger drilling and split spoon sampling. The smaller size of DPT rigs enables
well installation and sampling in areas not accessible to traditional large auger
rigs.
As DPT methods utilize a smaller diameter boring than conventional drilling, less
solid waste is generated. Similarly, less liquid waste will be generated from
smaller diameter monitoring wells. Because less waste is generated, worker
exposures are reduced.
Overall, there is minimal disturbance to the natural formation using DPT in
comparison with auger drilling.
From an economic standpoint, DPT has several advantages versus conventional
drilling. In relation to project schedule and budget, the time-effectiveness of DPT
installation may enable the remediator to investigate more areas of a site than
traditional hollow stem auger (HSA) drilling would allow and in a shorter time.
Fewer well construction materials may enable a remediator to install additional
monitoring points on a limited budget.
Most importantly, short-term and long-term groundwater monitoring studies
conducted by others have produced results demonstrating that water samples
collected from DPT installed wells are comparable in quality to those obtained
from conventionally constructed wells.
b)
Disadvantages of DPT
DPT cannot completely replace the use of conventional drilling/monitoring well
installation as limitations of the technology are evident in certain situations. DPT
is only useful at generally shallow depths (less than 100 feet below surface grade)

261-0300-101 / DRAFT December 16, 2017 / Page A-13
and in unconsolidated formations. DPT is not suitable for formations containing
excessive gravel, cobbles, boulders, etc., or for bedrock drilling due to the
obvious lack of augering capabilities. At sites where the potential for flowing
sands exists, DPT should not be utilized. Each time the string of rods are
removed from the borehole for sampling purposes, the lack of a coherent sand
lens in the strata would cause the borehole to collapse.
DPT is inappropriate for monitoring well installation below confining layers or as
‘nested’ wells. Since DPT does not provide for the advancement of casing to
keep the borehole open and seal off each separate zone of saturation, DPT can
potentially allow for the mixing of separate zones of saturation when the push
rods are withdrawn from the borehole. Therefore, the threat of cross-
contamination from separate zones of saturation above clean zones of saturation is
great.
If large volumes of aqueous sample are required, DPT installed monitoring wells
may not be suitable due to the small diameter of the well screen.
Since DPT causes smearing and compaction of the borehole sides, proper well
development techniques are vital to ensure that natural hydraulic permeabilities
are maintained. Several studies have demonstrated that hydraulic conductivities
can vary by an order of magnitude lower for wells installed by DPT versus wells
installed by conventional HSA. For this reason, DPT-installed wells may not be
suitable for aquifer characteristics testing, nor for efficient groundwater recovery.
Great care needs to be taken to ensure adequate well development when using
DPT for well installations.
6.
References
ALLER, L., and others, 1989, Handbook of Suggested Practices for the Design and
Installation of Ground-Water Monitoring Wells, National Water Well Association (This
publication covers nearly all aspects of design and construction of monitoring wells.
Each of the eight chapters has an extensive reference list.).
AMERICAN SOCIETY FOR TESTING AND MATERIALS, 2010, Standard Practice
for Direct Push Installation of Prepacked Screen Monitoring Wells in Unconsolidated
Aquifers, ASTM-D6725-04.
ANDERSON, K.E., 1993, Ground Water Handbook, National Ground Water Association
(A quick reference containing tables, formulas, techniques and short discussions
covering, among other things, drilling, well design, pipe and casing, and groundwater
flow).
CALIFORNIA ENVIRONMENTAL PROTECTION AGENCY, 2014, Well Design and
Construction for Monitoring Groundwater at Contaminated Sites.
DRISCOLL, F.G., 1986, Groundwater and Wells, Second Edition, Johnson Filtration
Systems, Inc., St. Paul, Minnesota 55112, 1089 pp.

261-0300-101 / DRAFT December 16, 2017 / Page A-14
GABER, M.S., and FISHER, B.O., 1988, Michigan Water Well Grouting Manual,
Michigan Department of Public Health (Very thorough coverage of grout and sealant
formulation, characteristics, handling, and placement.).
INTERSTATE TECHNOLOGY REGULATORY COUNCIL, 2006, The Use of Direct
Push Well Technology for Long-Term Environmental Monitoring in Groundwater
Investigations.
NIELSEN, D.M., (Editor), 1991, Practical Handbook of Ground-Water Monitoring,
NWWA, Lewis Publishers, Inc., Chelsea, Michigan 48118, 717 pp.
OHIO ENVIRONMENTAL PROTECTION AGENCY, 2016, Technical Guidance for
Ground Water Investigations, Chapter 15, Use of Direct Push Technologies for Soil and
Ground Water Sampling, Revision 1.
U.S. ENVIRONMENTAL PROTECTION AGENCY, 1993, Subsurface Characterization
and Monitoring Techniques-A Desk Reference Guide, Volume 1: Solids and Ground
Water (Largely 1 to 2-page thumbnail descriptions of methods and equipment.).
U.S. ENVIRONMENTAL PROTECTION AGENCY, 1997, Expedited Site Assessment
Tools for Underground Storage Tank Sites.
U.S. ENVIRONMENTAL PROTECTION AGENCY, 2005, Groundwater Sampling and
Monitoring with Direct Push Technologies.

261-0300-101 / DRAFT December 16, 2017 / Page A-15
C.
Locations and Depths of Monitoring Wells
1.
Importance
The locations and depths of monitoring wells are the most important aspects of a
groundwater monitoring network. A monitoring point that is misplaced, or not
constructed properly to monitor constituents with unique physical characteristics, is of
little use and may misrepresent the quality of the groundwater migrating to or from a site.
On the other hand, a properly positioned and constructed monitoring well that detects the
earliest occurrence of contamination could save both time and money spent on cleanup of
a site. It is important to note that the placement and construction of a groundwater
monitoring network at an Act 2 site shall be conducted by a professional geologist
licensed in Pennsylvania (25 Pa. Code §§ 250.204(a), 250.312(a), and 250.408(a)).
2.
Approach to Determining Monitoring Locations and Depths
Different approaches and efforts for determining the location and depth of wells may be
necessary based on the type of monitoring to be done. However, before well locations
are chosen for any type of monitoring, the existing data should be evaluated. This can
reduce the costs of implementing the monitoring program and can help to make
appropriate choices for three-dimensional monitoring locations.
The most efficient way to accomplish the location and depth of monitoring wells for an
Act 2 study is to formulate a CSM, or conceptual groundwater flow model. A conceptual
groundwater flow model is the illustrative delineation and formulation of the important
controlling components of groundwater flow and thus contaminant transport from
recharge areas to discharge zones or withdrawal points. Without a proper
conceptualization of groundwater flow, a groundwater model can give spurious results.
On the other hand, a well-developed conceptual model may allow groundwater flow to be
accurately approximated without using computer modeling or complex analytical
procedures. The groundwater conceptual model is an important tool in the study of
groundwater flow on both a local and even larger scale. The goal of the conceptual
model is to represent the controlling aspects of groundwater flow at the site being
investigated. Important controlling components of groundwater flow can include
geological characteristics, geologic structural and stratigraphic relationships, anisotropy,
calculated groundwater flow directions and recharge and discharge relationships.
Information may be obtained through site visits, site records and previous studies,
interviews with present and past workers, aerial photographs, scientific publications on
the local and regional hydrogeology, geophysical surveys, borings, wells, aquifer tests,
etc. If enough information is available, the designer can determine the groundwater flow
paths and design a complete monitoring network. However, actual testing of aquifer
parameters and borehole geophysics provides the best information to evaluate placement
and construction of monitoring wells, especially in newly established sites or facilities
where little site information is available.

261-0300-101 / DRAFT December 16, 2017 / Page A-16
a)
Background Monitoring
The determination of background water quality is paramount in understanding the
effect of an activity or site on groundwater quality. Often, insufficient site
information is available so that initial well locations may depend on casual
observations and assumptions regarding groundwater flow. If subsequent
information shows that monitoring wells are misplaced, new wells should be
installed.
b)
Site Characterization Monitoring
Appropriately placed monitoring wells are necessary to detect groundwater
quality at an Act 2 site. The more that is known about the history of operations at
the site, (potential) contaminant flow paths, and the constituents that may have
been discharged to the environment, the more likely that monitoring wells
installed during the site characterization phase of the investigation will be
optimally placed and constructed to monitor the impact on groundwater quality.
Monitoring well locations should be concentrated in those areas that will most
likely first be impacted by the known discharges on the site, which typically will
be located within or comprise the uppermost aquifer. As groundwater data is
collected, additional monitoring wells may need to be installed to fully
characterize the groundwater contaminant plume(s) present. The greater the
complexity of the hydrogeology and the spread of contamination, the more
monitoring wells that may be necessary to characterize the contamination.
c)
Attainment and Post-remedial Monitoring
Any number of wells, including all installed during the site characterization
phase, may be used for attainment monitoring. These wells will demonstrate
attainment of the chosen cleanup standard at the POC. The impact of any
remediation conducted at the Act 2 site on the groundwater flow paths (e.g.
pumping the aquifer) should be considered for placement of attainment
monitoring wells. Postremedial monitoring would likely be conducted in the
same wells as attainment monitoring to monitor for any residual rebound
occurring in the aquifer after remediation activities have been completed.
3.
Factors in Determining Target Zones for Monitoring
The prime requirement for a successful monitoring system is to determine the “target”
zones - the spatial locations and depths that are the most likely areas to be impacted by
the site being investigated. The dimensions of target zones depend on the vertical and
horizontal components of flow in the aquifers being monitored, the size of the Act 2 site,
the potential contaminants released, and the distance that contamination may have
traveled from the facility since being released. Figure A-4 shows how different target
zones could be formed based on these factors.
Horizontal and vertical components of groundwater flow are best determined by
constructing planar and cross-sectional flow nets based on the measurement of water
levels in piezometers. Where the vertical components of flow are negligible, wells, rather

261-0300-101 / DRAFT December 16, 2017 / Page A-17
than piezometers, drilled into the aquifer to about the same depth, will allow preparation
of a contour map of water levels representing horizontal flow. This should be adequate to
prepare a planar flow net and determine the target zone.
With regard to upgradient wells, target zones (as defined above) do not exist. Upgradient
wells should be drilled to depths that are screened or open to intervals similar to that of
the downgradient wells, or to depths that yield water that is otherwise most representative
of the background quality of the water being monitored by the downgradient wells. In
other words, upgradient wells should be installed within the same hydrogeologic aquifer
to the respective downgradient wells.
The numerous site details to consider when establishing target zones may be grouped into
either groundwater movement or the spatial distribution of contamination.
a)
Groundwater Movement
In what direction is groundwater flowing? If flow paths are not easily
determined, what will influence the direction of groundwater flow? The answers
to these questions are critical to selecting target zones and the optimal locations of
monitoring wells.
Using the groundwater levels from piezometers or wells at the site, the
groundwater flow direction and hydraulic gradient can be determined. At least
three monitoring points are needed to determine the horizontal flow direction and
hydraulic gradient; however, at some sites, knowledge of the vertical component
of flow may be important. This is best accomplished by using well pairs of
“shallow” and “deep” piezometers or short-screened wells.
It may appear to be a simple task to place monitoring wells in downgradient
positions using a map of the groundwater elevation contours, or by anticipating
the flow direction based on topography or discharge points. However, at many
sites, three-dimensional flow zones must be understood to install appropriate
monitoring points (see Section C.5 of this appendix). Figure A-5 shows how a
well can miss the vertical location of contamination at a site. Water level
measurements, piezometer and well construction logs, geologic well logs, and
groundwater flow direction maps should be reviewed carefully when assessing the
dimensions of target zones.
i)
Geologic Factors
The geology of a site can complicate the selection of the target zones for
monitoring. Geologic factors can produce aquifers that are anisotropic. In
an anisotropic aquifer, the hydraulic conductivity is not uniform in all
directions so that groundwater moves faster in one direction than another
and oblique to the hydraulic gradient. Anisotropy can result from various
sedimentary or structural features such as buried channels, bedding planes,
folds, faults, voids, and fractures.

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In Pennsylvania, most of groundwater flow in bedrock is through fractured
rocks. Fracture flow in bedrock (or hardened sediments) requires
additional considerations compared to flow in unconsolidated materials.
Consolidated materials may exhibit small effective porosities and low
hydraulic conductivities that impede groundwater flow. However, the
development of secondary porosity may allow substantial flow of
groundwater through fractures, joints, voids, cleavage planes and
foliations. These features tend to be highly directional, exhibit varying
degrees of interconnection, and may produce local groundwater flow
regimes that are much different from the regional trends.
Geologic factors influence the direction of groundwater flow by
controlling the transmissivity. For example, Figure A-6 shows the effect
of fractures on the spread of contamination. Although the gradient
indicates flow to the north, groundwater also follows the major fractures
and spreads to the northeast. Monitoring wells “1” and “2” located to the
north of the site may detect contamination, but the lack of a monitoring
well to the northeast will miss an important direction of migration.
Common sedimentary bedding planes also could have a similar effect on
groundwater flow.
It is important to identify hydrostratigraphic intervals which may or may
not be interconnected at the site when conducting a groundwater
investigation. Monitoring wells should not be screened across
two intervals as groundwater flow and concentrations of contaminants
may differ significantly in each interval.
ii)
Groundwater Barriers
The presence of hydrogeologic barriers should also be considered when
locating wells in a groundwater monitoring system. A groundwater
barrier is a natural geologic or artificial obstacle to the lateral movement
of groundwater. Groundwater barriers can be characterized by a
noticeable difference in groundwater levels on opposite sides of the
barrier. Geologic faults and dikes along with tight lithologic formations
such as shale and clay layers are common examples. Important types of
barriers include the following:
Geologic faults - Fault planes that contain gouge (soft rock material) or
bring rock bodies of widely differing hydraulic conductivity into
juxtaposition can influence groundwater flow direction and velocity.
Location of downgradient wells across fault zones or planes should not be
approved until the nature of the influence of the fault zone on groundwater
flow has been evaluated. One method of evaluating fault zones is to
conduct pumping tests with wells on either side of the fault plane to
evaluate the degree of hydraulic connection.

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Figure A-6
Effect of Fractures on the Spread of Contamination

261-0300-101 / DRAFT December 16, 2017 / Page A-20
Dikes - Diabase dikes, common in southeastern Pennsylvania, can
function as lithologic barriers to groundwater flow because of their very
low permeability. If a dike lies between a site and a proposed
downgradient well, the role of the dike should be evaluated prior to
approving the well’s location.
Others - Geologically “tight” layers (aquitards) or formations can function
in a similar way: they can create subsurface “dams” that cause
groundwater to flow in unexpected directions. Additional barriers to flow
can include inclined confining beds, groundwater divides, and artesian
aquifers.
iii)
Karst Terrane
Carbonate rock such as limestone and dolomite is susceptible to the
formation of sinkholes, solution channels, and caverns. In Pennsylvania,
almost all carbonate rock will exhibit some degree of karst development.
Resulting flow patterns can be very complicated; flow depends on the
degree of interconnection of the joints, fractures, and solution openings
(small and large), the hydraulic gradient, and geologic barriers. The
resulting anisotropic setting can make it difficult to effectively monitor
and model a site in a karst area. Even a relatively small cavernous
opening with its connecting drainage paths can control a significant
amount of the flow from an area, and may perhaps effectively carry all the
groundwater that discharges from underneath a site. In addition, karst
geology has the potential to rapidly transmit groundwater over a large
distance.
Groundwater flow in a karst terrane can be highly affected by precipitation
events, and groundwater divides can be transient. To determine
monitoring locations in limestone and dolomite areas, the remediator
should investigate the degree to which the rocks are susceptible to
dissolution. The more dissolution features that are recognized, the more
likely that conduit flow will occur. Dissolution features may be identified
through site visits, aerial photographs, geologic well logs, and geophysical
techniques.
Thus, it would seem logical that monitoring locations should be based on
major conduits of flow. However, Figure A-7 shows how a monitoring
well can easily miss a primary conduit. It may be futile to attempt to
establish the locations of such flow zones because they probably represent
only a small fraction of a site. However, several procedures can be used to
increase the odds of monitoring the site of concern. (Note that many of
the procedures discussed here also can be used in other types of fractured
rocks.)

261-0300-101 / DRAFT December 16, 2017 / Page A-21
Figure A-7
Ineffective Monitoring Wells in a Carbonate Aquifer
Tracer tests - Tracer tests offer the best possibility of determining where
groundwater is flowing and discharging. They are conducted to establish
a hydraulic connection between a downgradient monitoring point and the
facility of concern. Tracer tests should be combined with a thorough
inspection for the presence of local and regional springs, surface streams,
and dry stream channels that could serve as discharge points for
groundwater at the site. It also could be possible that groundwater beneath
a site could discharge to several features, or that the flow directions could
be different during flood or high groundwater stages. A determination of
the point of regional base flow should also be made and possibly included
as a monitoring point when possible.
It is important to understand the potential chemical and physical behavior
of the tracer in groundwater. The objective is to use a tracer that travels
with the same velocity and direction as the water and does not interact
with solid material. It should be easily detected and be present in
concentrations well above natural background quality. The tracer should
not modify the hydraulic conductivity or other properties of the medium
being studied. Investigations using tracers should have the approval of
local authorities and the Department, and local citizens should be
informed of the tracer injections.
Various types of tracers are used including water temperature, solid
particles, ions, organic acids, and dyes. Fluorescent dyes are the most
common type of tracer used in karst areas. These dyes are used because
they are readily available, are generally the most practical and convenient
tracers, and they can be adsorbed onto activated coconut charcoal or
unbleached cotton. Fluorescent dyes can be detected at concentrations

261-0300-101 / DRAFT December 16, 2017 / Page A-22
ranging from one to three orders of magnitude less than those required for
visual detection of non-fluorescent dyes. This helps to prevent the
aesthetically unpleasant result of discoloring a private or public water
supply.
Fluorescein (CI Acid Yellow 73 - C
20
H
10
O
5
Na
2
) is one of the most widely
used water-tracers in karst terrane studies because of its safety,
availability, and ready adsorption onto activated coconut charcoal. It is a
reddish-brown powder that turns vivid yellow-green in water, is
photochemically unstable, and loses fluorescence in water with pH less
than 5.5.
Rhodamine WT is another commonly used dye tracer. Rhodamine WT is
a conservative dye and generally efficient tracer because it is water
soluble, highly detectable (strongly fluorescent), fluorescent in a part of
the spectrum not common to materials generally found in water, thereby
reducing the problem of background fluorescence, harmless in low
concentrations, inexpensive, and reasonably stable in a normal water
environment (U.S. EPA 2013).
The toxicity of the dyes should also be considered, especially when there
is a chance of private or public water supplies being affected. Smart
(1984) presents a review of the toxicity of 12 fluorescent dyes. Other
excellent references include U.S. EPA and the USGS (1988) and Davis
and others (1985).
The mapping of outcrops and associated joints and faults can distinguish
directional trends that groundwater might follow. Fracture trace analysis
using aerial photographs can detect local and regional trends in fractures,
closed depressions, sinkholes, stream alignments, and discharge areas.
However, tracer tests are still recommended to verify where groundwater
is flowing.
Additional site investigation techniques may be helpful in determining
flow paths. Geophysical methods such as self-potential (a surface
electromagnetic method) and ground penetrating radar can enhance the
understanding of karst systems.
Effort should be made to monitor at or near the site of concern rather than
depend on springs that discharge away from the site. Wells sited on
fracture traces or other structural trends can be tested with tracers to see if
they intercept groundwater flowing from the site. A monitoring network
should not be solely dependent on water levels to establish the locations of
monitoring wells in such fractured rock settings. These uncertainties and
the potential traveling distances may cause monitoring in karst areas to be
involved and expensive.
For more information regarding tracer tests, please refer to the USGS
website on tracer studies.

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iv)
Deep-Mined Areas
When designing a groundwater monitoring program for a site in which
coal or noncoal deep mining has occurred, it is important to consider the
effect of the underlying mine on the hydrologic system.
Because of the mine workings and the associated subsidence fractures, the
deep mine often acts as a large drain for the overlying water-bearing
zones. Groundwater monitoring of this zone may be considered on a case-
by-case basis.
Saturated zones within deep mines may be characterized as a mine pool,
which is a body of water at a relatively stable elevation, or it may be a
pathway for channelized water. Because of these special problems, a
drilling plan should be devised that includes provisions for drilling
through the coal pillar, mine void or collapsed structures. Several
attempts should be made at each well location to intercept the pool,
saturated zone and/or mine void.
Well construction requires the placement of a grout basket or plug
attached to the riser pipe that is placed above the zone to be monitored.
This helps to seal the bentonite grout.
b)
Contaminant Distribution
In addition to normal groundwater flow (advection), the distribution of
contamination is critical to the correct placement of monitoring points. This
distribution is based on 1) the chemical and physical characteristics of
groundwater and contaminants present that affect the migration of the monitored
contaminant, and 2) its occurrence or source at the site. For example, the density
of a contaminant is one of the most important factors in its distribution in the
aquifer, and especially for determining the depth of a target zone (see Section C.5
of this appendix). Petroleum hydrocarbons tend to remain in shallow
groundwater. Chlorinated VOCs tend to migrate deeper into the aquifer,
sometimes following structural features that may be contrary to groundwater flow
direction. These factors are extremely important to consider when designing a
groundwater monitoring network.
Isoconcentration maps can be useful in plume interpretation and for placement of
groundwater recovery wells. Also, the remediator should keep in mind the
relationship of the flow lines with the activity’s location or potential sources of
contamination.
4.
Areal Placement of Wells
For establishing the target zones, the remediator should consider the topics of
groundwater movement and contaminant distribution that were discussed above. For the
initial placement of wells at a site where little information is available, the downgradient

261-0300-101 / DRAFT December 16, 2017 / Page A-24
well positions are typically assumed to be downslope. In apparent flat-lying sites,
drainage patterns can be used to estimate the flow direction. The site boundary that is
closest to a body of water is a likely choice for downgradient well locations. An
upgradient well is typically placed upslope.
As more information is obtained about the site, groundwater gradients will be more
accurately defined. Upgradient and downgradient monitoring points may need to be
added or moved. However, even well-defined groundwater flow direction maps should
be evaluated carefully when choosing the target zones for upgradient and downgradient
wells. Because of structural controls in fracture flow described in Section C.3.a,
groundwater can move obliquely to the regional gradient. Some monitoring points may
need to be moved as target zones are refined.
In general, when comparing sites, intervals between monitoring wells probably should be
closer for a site that has:
a small area
complicated geology such as folding, faulting, closely spaced fractures, or
solution channels
heterogeneous lithology and hydraulic conductivities
steep or variable hydraulic gradient
high seepage velocity
had liquid contaminants
buried pipes, trenches, etc.
low dispersivity potential
Sites without these features may have well interval distances that are greater. See also
Section C.6 on the number of wells.
Reconnaissance tools and screening techniques such as surface geophysical techniques
and soil gas studies can help to locate plumes before wells are drilled and thus help to
determine optimal well locations. Methods for selecting sample locations range from
random yet logical picks to probability sampling (such as a grid pattern). Random
sampling is very inefficient. When selecting many monitoring points in an area where
little is known, such monitoring points should be placed in a grid or herringbone pattern.
5.
Well Depths, Screen Lengths, and Open Intervals
The first zone of saturation is typically an unconfined or water-table aquifer, which is
recharged from direct infiltration of precipitation. Impacts to the aquifer under
unconfined conditions are more easily evaluated than under confined or semi-confined

261-0300-101 / DRAFT December 16, 2017 / Page A-25
conditions. The shallowest aquifer should be the target zone for chemicals and
substances that are less dense than water.
Sites with confined aquifers that have the potential to be impacted will need to be
evaluated in combination with the unconfined aquifer. Such a situation would require
more detailed vertical and discrete zone monitoring.
Once the subsurface geometry of the monitoring target zone is determined, decisions can
be made with respect to the depth and screen lengths of individual wells that will be used.
Groundwater monitoring networks should monitor the entire saturated thickness of the
target zone, or a very large percentage of it. If large vertical intervals of the target zone
are unmonitored, chances are dramatically increased that groundwater contamination may
go undetected, or be underestimated if detected.
Choosing the length of the open interval in a monitoring well is in many respects a
balancing act. Shorter open intervals or screen lengths provide better accuracy in
determining hydraulic head at a specific point in the flow system. If a sufficient number
of shorter well screens or open intervals are stacked or clustered vertically so that the
entire saturated thickness of the target zone is adequately monitored, they will, when
taken together, provide better resolution of the vertical distribution of any contamination
that may be detected. In addition, the possibility of cross-contamination is minimized.
Disadvantages of shorter intervals include reduced water volume from each well and the
increased cost of installing, sampling, analyzing, and interpreting the data from the more
numerous sampling points, which can be considerable.
Some disadvantages also are likely for longer screen lengths or open intervals.
Resolution of hydraulic head distribution in the aquifer decreases, contamination entering
the well at a specific point may be diluted by other less contaminated water, and there is
less certainty regarding where water is entering the well.
It would be preferable from a strictly technical point of view to monitor the entire
saturated thickness of any target zone with a number of individual, shorter-screened wells
drilled to different depths that, together, monitor the entire target zone. However, the
remediator/hydrogeologist designing the project must decide if the increased cost over
single, longer-screened wells is justified for background and compliance monitoring.
The goal is to establish screens and open intervals that will detect any contamination
emanating from any portion of the site as quickly as possible. A Pennsylvania-licensed
professional geologist should make all decisions related to the construction of monitoring
wells at Act 2 sites.
Care should be taken when monitoring target zones in bedrock formations. In this case,
by geologic necessity, the portion of the target zone which is monitored will be
determined by the location and number of water-producing fractures that are intercepted
by the well. Care must be taken not to drill wells too deeply below the target zone in
search of a water-producing fracture.
Where multiple aquifers exist, such as an unconsolidated aquifer overlying a bedrock
aquifer, or where two permeable aquifers are separated by a confining layer, the target
zones within each aquifer should be monitored separately.

261-0300-101 / DRAFT December 16, 2017 / Page A-26
The specific gravity of a contaminant and whether it will most likely be introduced to the
environment as a free phase or in a dissolved phase also will influence how a well is
constructed. In conducting monitoring for an LNAPL or a petroleum-based dissolved
contaminant, such as gasoline, wells should be constructed with screens, or open
intervals, that intercept the water table surface at all times of the year during periods of
both high and low water table elevations. LNAPL can then accumulate into a distinct
layer and flow into the monitoring well. For materials that exhibit specific gravities
greater than water (such as many chlorinated solvents), it is desirable, though not always
possible, to locate subsurface boundaries on which such contaminants might accumulate
if released to the environment in a free phase.
6.
Number of Wells
The number of wells needed depends on site-specific factors. In general, the spacing of
background or upgradient wells should be adequate to account for any spatial variability
in the groundwater quality. Downgradient wells should be positioned to adequately
monitor the activity and any other variability of the groundwater quality. Compliance
wells should be considered downgradient wells and positioned as close to the
downgradient boundary of the site. The estimate of the separation distance will depend
on the extent and type of activity, the geology, and the potential contaminants (see also
Section C.4 on the Areal Placement of Wells).
7.
Well Yield
Monitoring wells should produce yields that are representative of the formation in which
they are drilled. Wells located in anomalously low-yielding zones are undesirable for
several reasons. First, flow lines tend to flow around low-permeability areas rather than
through them. In effect, this results in potential contaminants bypassing low-
permeability areas, consequently not being detected in representative concentrations. In
addition, by the time a potential contaminant shows up in a very low-yielding well that is
unrepresentative of the formation, other potential contamination may have traveled
extensively downgradient beyond the monitoring well. Therefore, in settings where well
yields are variable, the best monitoring wells will be those that are open to the highest
permeability flow lines that are potentially more likely to be contaminated by the site.
The best information regarding representative yield for the target zones selected for any
site should come from the wells and borings used in the investigation to characterize the
groundwater flow system for the site. Borehole geophysics can be a valuable tool for
determining the location of higher-yielding zones and the presence of contaminants. For
more detailed descriptions of borehole geophysical techniques and devices, see EPA
(1993) Chapter 3 - Geophysical Logging of Boreholes, and Nielsen (1991). Additional
regional hydrogeologic information may be obtained from:
The Pennsylvania Bureau of Topographic and Geologic Survey (BTGS)
The United States Geological Survey (USGS)

261-0300-101 / DRAFT December 16, 2017 / Page A-27
Water Resource Reports have been published by the USGS and BTGS for select counties
and areas in Pennsylvania. Many of these reports are available electronically on their
respective websites.
In Pennsylvania, there are three general hydrogeologic settings that merit special
discussion from a well-yield perspective.
a)
Fractured Rock
In aquifers composed of fractured bedrock, groundwater flow is generally
restricted primarily to the fractures. If a well fails to intersect any fractures or a
very few small fractures in this setting, the well will not detect potential
contamination, or it will be inefficient in detecting potential contamination. For
this reason, wells that fail to intersect fractures in the target zone that are
representative of the formation should be approved with caution, and wells that
are essentially dry are not acceptable. Such wells should be relocated nearby and
another attempt made to obtain a better yield when it is determined that it is likely
that more representative yields can be obtained. Likewise, wells drilled below the
proper target zone, strictly to increase yield, are not reliable for site
characterization purposes.
b)
Heterogeneous Unconsolidated Formations
Low permeability, clay-rich formations with interbedded or lenticular, higher
permeability sand or gravel units can present a significant challenge to designers
and installers of monitoring wells. Wells need to be located so that they are open
to any high permeability zones within the target zone that are hydraulically
connected to the site being monitored. These wells will produce a higher yield
than wells drilled exclusively into the clay-rich portions of the site.
c)
Areas of Uniformly Low Yield
Certain geologic formations and hydrogeologic settings are characterized by
exhibiting naturally low yield over a wide area. Other geologic formations may
exhibit low yield locally in certain settings such as ridge tops, steeply dipping
strata, or slopes. In these settings, a permanent or seasonal perched water table or
shallow flow system may develop on the relatively impermeable bedrock that
may or may not be hydraulically connected to the bedrock system. Depending on
the permeability of the soils and unconsolidated material overlying the solid, less
permeable bedrock, the shallow groundwater flow can express itself as a rather
rapid “subsurface storm flow” or a more sluggish, longer-lasting condition in
poorly drained soils.
It is important to be sure that the shallow systems are part of the target zone of the
site being monitored. In these cases, the shallow system may constitute the most
sensitive target zone for monitoring a facility. While wells drilled into the
bedrock system may be needed to monitor for vertical flow of contaminants, the
importance of sampling monitoring wells or springs in the shallow intermittent
flow system should not be underestimated, although the usual periodic monitoring

261-0300-101 / DRAFT December 16, 2017 / Page A-28
schedules may not always be necessary in these settings. If the systems are
intermittent, one must be aware of when they are active (e.g. in Spring or after
significant or extended precipitation events) and be prepared to monitor the
systems at that time. Monitoring can be conducted in wells, springs that are
properly developed, or in some cases, by sampling man-made underdrain systems
that are constructed to collect the shallow flow system in some cases.
8.
References
DAVIS, S.N. and others, 1985, Ground Water Tracers, through the U.S. EPA.
Cooperative Agreement CR-810036.
DOBRIN, M.B., 1965, Introduction to Geophysical Prospecting, 3rd ed., McGraw-Hill,
New York, 583 pp.
EVERETT, L.G., 1980, Groundwater Monitoring, General Electric Company, 440 pp.
[Note Section 2 (“Groundwater Monitoring Methodology”) and Section 4 (“Monitoring
in the Zone of Saturation”)].
FERGUSON, COLIN, June 1992, The Statistical Basis for Spatial Sampling of
Contaminated Land, Ground Engineering, pp. 34-38.
FETTER, C.W. Jr., Fall 1981, Determination of the Direction of Ground Water Flow,
Ground Water Monitoring Review, pp. 28-31 (Discusses anisotropy in groundwater
flow.).
GIDDINGS, TODD and SHOSKY, D.J. Jr, Spring 1987, Forum - What is an Adequate
Screen Length for Monitoring Wells? Ground Water Monitoring Review, pp. 96-103
(Pros and cons of screen lengths.).
GRANT, F.S. AND WEST, G.F., 1965, Interpretation Theory in Applied Geophysics,
McGraw-Hill, New York, 583 pp.
INTERSTATE TECHNOLOGY REGULATORY COUNCIL, April 2015, Integrated
DNAPL Site Characterization and Tools Selection.
KURTZ, DAVID and PARIZEK, R., 1986, “Complexity of Contaminant Dispersal in a
Karst Geological System,” in Evaluation of Pesticides in Ground Water, American
Chemical Society, Symposium Series, vol. 315, pp. 256-281.
NIELSEN, D.M., (Editor), 1991, Practical Handbook of Ground-Water Monitoring,
NWWA, Lewis Publishers, Inc., Chelsea, Michigan 48118, 717 pp (Note especially
Chapter 2 on “Ground-Water Monitoring System Design” by Martin Sara.).
OHIO ENVIRONMENTAL PROTECTION AGENCY, 2015, Technical Guidance
Manual for Groundwater Investigations, Chapter 3, April 2015.

261-0300-101 / DRAFT December 16, 2017 / Page A-29
PFANNKUCH, H.O., Winter 1982, Problems of Monitoring Network Design to Detect
Unanticipated Contamination, Ground Water Monitoring Review, pp. 67-76 (Discusses
contamination release, propagation, and monitoring stages of unexpected releases.).
QUINLAN, J.F., 1990, Special problems of ground-water monitoring in karst terranes:
Ground Water and Vadose Zone Monitoring, ASTM Special Technical Paper 1053,
pp. 275-304.
QUINLAN, J.F., 1989, Ground-Water Monitoring in karst terranes: Recommended
protocols and implicit assumptions: US EPA, EPA/600/X-89/050, 78-pp.
SAINES, M., Spring 1981, Errors in Interpretation of Ground Water Level Data, Ground
Water Monitoring Review, pp. 56-61 (Identifies common errors.).
SMART, D.L., 1984, A review of the toxicity of twelve fluorescent dyes used for water
tracing: National Speleological Society Bulletin, v. 46, no. 2, pp. 21-33.
U.S. EPA, September 1986, RCRA Ground Water Monitoring Technical Enforcement
Guidance Document (Note Chapter 2, “Placement of Detection Monitoring Wells.”).
U.S. EPA and the USGS, October 1988, Application of Dye-Tracing Techniques for
Determining Solute-Transport Characteristics of Ground Water in Karst Terranes,
EPA 904/6-88-001 (Note especially Chapter 2: “Hydrogeology of Karst Terrane.”).
U.S. EPA, May 1993, Subsurface Characterization and Monitoring Techniques - A Desk
Reference Guide, Volume 1: Solids and Ground Water. EPA/625/R-93/003a (Complete
description of geophysical techniques and their advantages and disadvantages is included.
Also, aquifer tests and sampling methods are presented.).
U.S. EPA, Science and Ecosystem Support Division, May 2013, Dye Tracer
Measurements. SESDPROC-514-R1.
U.S. GEOLOGICAL SURVEY, 1997, Guidelines and standard procedures for studies of
ground-water quality: Selection and installation of wells, and supporting documentation,
Water-Resources Investigations Report 96-4233.
WILSON, C.R., EINBERGER, C.M., JACKSON, R.L., and MERCER, R.B., 1992,
Design of Ground-Water Monitoring Networks Using the Monitoring Efficiency Model
(MEMO), Ground Water, v.30, No.6, pp. 965-970.

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D.
Groundwater Sampling Techniques
1.
Importance of Sampling Technique
Proper sampling procedures which result in a representative measure of groundwater
quality are critical to any monitoring program. The accuracy of the sample analysis in
the laboratory is dependent upon the sampling methodology in the field. A laboratory
cannot generate reliable data if the sample was collected improperly. Therefore, taking
precautions and selecting the correct sampling methods are imperative to produce
accurate and representative analyses.
Some of the reasons groundwater samples may not be representative of aquifer conditions
include the following:
The sample was taken from stagnant water in the well. Water standing in a well
and exposed to the atmosphere may undergo a gas exchange (oxygen and carbon
dioxide), allowing chemical reactions to occur. Biological organisms capable of
driving reactions might also be introduced. Obviously, such altered waters will
no longer be representative of the water within the aquifer and therefore should be
purged prior to sample collection.
The sample was not collected at the appropriate time. The sample should be
collected as soon as possible after purging is completed. This reduces the
possibility of chemical reactions occurring because of gas exchange and
temperature variations. In addition, if the well is pumped too long, the sample
may be comprised of water far from the well site and not be representative of
groundwater chemistry for the site being monitored.
The sample contained suspended or settleable solids. Groundwater is generally
free of suspended solids because of the natural filtering action and slow velocity
of most aquifers. However, even properly constructed monitoring wells will often
fail to produce samples that are free of sediment or settleable solids (turbidity).
When samples containing suspended solids are analyzed for metals, this sediment
is digested (dissolved) in the laboratory prior to performing the analysis.
Consequently, any of the metals present in the sediment (primarily iron,
manganese, and aluminum) will be included in the results of the analysis of the
water that includes these metals. The analysis of the water samples containing
sediment will result in certain analytes, such as these metals, being reported at
higher levels than the actual levels in groundwater.
In addition to common metals, other metals such as lead, chromium, arsenic, and
cadmium, which occur naturally in trace amounts may also show up in the analysis.
Additionally, the sediment content of the monitoring wells will often vary across a site,
so that samples collected from the same well at different times can vary in sediment
content. This problem can make analysis of monitoring well data for metals where
samples have not been filtered to remove turbidity an almost futile exercise.
Release of carbon dioxide during pumping increased the pH, allowing many
metallic ions to come out of solution (i.e. iron, manganese, magnesium, cadmium,

261-0300-101 / DRAFT December 16, 2017 / Page A-31
arsenic, selenium, and boron). Pumping can also cause volatilization of VOCs.
This emphasizes the importance of conducting field measurements such as pH,
specific conductance, temperature, etc., within the well before the sample is
brought to the surface.
Chemical changes occurred from oxidation of the sample during sampling.
Dissolved oxygen is usually very limited within aquifers. Bringing the sample to
the surface allows oxygen to dissolve within the water sample. Oxidation also
can occur in the pump, or it can be caused by water cascading into a well installed
in “tight” formations. Depending on the chemical makeup of the sample, the
addition of dissolved oxygen may allow chemical reactions to occur. Some of the
changes that can be expected include oxidation of: 1) organics, 2) sulfide to
sulfate, 3) ferrous iron and precipitation of ferric hydroxide, 4) ammonium ion to
nitrate, and 5) manganese and precipitation of manganese dioxide or similar
hydrous oxide. In cases where oxidation would be expected to impact chemical
quality, precautions should be employed to reduce oxidation potential (e.g.
minimize agitation during purging and sample collection, minimize the length of
time the sample is exposed to air, fill the sample container completely to the top,
and promptly chill the sample).
The sample was not preserved correctly. Increases in temperature will allow
certain chemical reactions to occur. Certain metals, especially iron, may coat the
inside of the sample container. If the sample is not properly preserved for
shipment to the laboratory, the sample arriving at the lab may be quite different
chemically from the sample which was collected in the field.
The sample was contaminated by residues in sampling equipment. Residues may
cling to the sampling equipment if it is not properly cleaned or decontaminated.
Those residues may become mobile in successive samples, yielding unreliable
results. This becomes critical when the analytes being sampled are in the parts
per billion or parts per trillion range. As a result, all sample pumps, tubing, and
other associated materials should be properly decontaminated prior to sampling at
each monitoring well location.
The sample was contaminated by the mishandling of bottleware. Care should be
taken to avoid contamination by mishandling bottleware, whether in the field or
during transport. All sample bottleware and coolers should be stored and
transported in clean environments to avoid potential contamination. In addition,
care should be taken when storing and transporting bottleware that already
contains a preservative. For example, the preservative may leak from a sample
bottle or be altered by extreme heat or cold.
The sample was contaminated by residuals on the hands of the sampler. To avoid
contamination that may result from bare skin, protective sampling gloves should
be worn during sample collection. New gloves should be worn for each well
location.
DEP recommends utilizing a consistent sampling methodology throughout the
monitoring program.

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2.
Sample Collection Devices
The most common devices available for the collection of water from monitoring wells
include bailers, suction-lift pumps, air-lift samplers, bladder pumps, submersible
centrifugal pumps, and passive samplers. Each has its advantages and disadvantages, as
shown in Table A-1, and should be considered before selecting the sample collection
device.
3.
Sample Collection Procedures
The following are general procedures that should serve as a framework for sampling
groundwater. These procedures should be modified as necessary for each situation
encountered in the field and to conform to monitoring objectives. In addition,
appropriate health and safety measures should always be taken before, during, and after
sampling.
a)
Protective Clothing
Protective clothing should be worn as dictated by the nature of the contaminants.
Different types of protective clothing are appropriate for different contaminants.
Protective sampling gloves should always be worn during sample collection to
ensure a representative sample and to protect the sampler.
b)
Water Levels
Every effort should be made to determine and record the static water level of the
well prior to purging. Static water levels should be recorded in each well prior to
any well purging when part or all of a groundwater monitoring network is
sampled in one event. Water level measurements should also be measured and
recorded during well purging to document associated drawdown.
c)
Field Measurements
In most cases, field measurements should be taken before and during the sampling
to gauge the purging of the well and to measure any changes between the time the
sample is collected compared to when it is analyzed in the laboratory.
Measurements in the field also provide a record of actual, onsite conditions that
may be useful for data analysis. The following measurements and observations
are often determined in the field:
pH
Eh
water level (static and purged)
temperature

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specific conductance
dissolved oxygen
acidity/turbidity
climatic conditions
The specific techniques for obtaining each of these measurements depend upon
the instruments used. The operator should carefully read and follow the
manufacturer’s instructions, including those for equipment maintenance and
calibration. A record of the calibration and maintenance checks should be kept.
Field measurements should always be made with properly calibrated
instrumentation.
d)
Purging
The purpose of purging a well prior to sampling is to remove stagnant water from
the well bore and assure that the sample is representative of the groundwater in
the geologic formation. Stagnant water in the well bore results from the water’s
contact with the casing and atmosphere between sampling events. What might
seem to be a relatively simple and straightforward procedure, purging technique
has been the subject of considerable scientific investigation and discussion.
There are two basic approaches to purging a well. The first is to use dedicated
equipment in which the water is pumped from a fixed position in the well. This
technique eliminates the possibility of cross-contamination, but tends to purge
only the well section, or screen section opposite of the purge pump. (This is
especially a concern when purge rates are much lower than the yield of the water-
bearing zone supplying water to the purge pump.)
The second basic approach is to use a transportable pump and purge from the
water surface, or preferably by gradually lowering the pump in the well as
stagnant water is evacuated. This technique is considered as being more reliable
in terms of evacuating the entire well bore. However, the disadvantage is that the
equipment must be decontaminated between wells, which in turn increases the
potential for cross-contamination.
It is important to recognize the impact of equipment location in relation to the
well and other sampling equipment. Often purging and sampling equipment
require the use of generators to power pumps and other equipment. The engines
of vehicles and generators produce exhausts which contain VOCs as well as
various metals and particulates. If engines or generators need to be operating
while sampling, they should be located upwind from the well and sampling
equipment since water contacting these exhausts has been shown to contaminate
samples with various compounds.

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Table A-1
Advantages and Disadvantages of Different Sampling Devices
ADVANTAGES
DISADVANTAGES
Bailer
Portable
Simple to use
No need for an electrical source
Difficult to ascertain where within the water
column the sample is collected
Allows for oxidation of the sample
Disturbance of the water column by the
sampler
Impractical for removing large volumes of
water
Suction-lift
Pump
Allows sample to contact only
Teflon (less decontamination)
Very portable
Simple to use for shallow
applications
Flow rates easily controllable
Limited to shallow groundwater conditions
(approximately 30 feet)
Causes sample mixing, oxidation, and allows
for degassing
Not ideal for collection of gas-sensitive
parameters
Air-lift
Sampler
Suited for small diameter wells
Causes extreme agitation
Significant redox, pH, and specie
transformations
Plastic tubing source of potential
contamination
Bladder
Pump
Provide a reliable means for
highly representative sample
Mixing and degassing
minimized
Portable
Noted by EPA as an excellent
sampling device for inorganic
and organic constituents
Somewhat more complex than other samplers
Turbid water may damage the inner bladder
Water with high suspended solids may
damage check valves

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ADVANTAGES
DISADVANTAGES
Submersible
Centrifugal
Pump
Higher extraction rates
Considerable agitation and turbulent flow
Potential to introduce trace metals from the
pump materials
Passive Samplers Low cost
Easily deployed
Minimal purging and water
disposal
Able to monitor a variety of
analytes
Some devices are incompatible with certain
analytes.
May have sample volume limitations.
Results may differ from conventional
methods.
An excellent summary of purging methods and techniques is given by Herzog
et al. (in Nielsen, 1991). The following discussion is based in part on that
summary. Four techniques for determining the volume of water to be purged
from a well are discussed. These techniques include criteria based on:
Numbers of well bore volumes
Stabilization of indicator parameters
Hydraulic and chemical parameters
Special problems with low-yielding wells
By far, the most common choices have been to base the purging volume on either
a certain number of well volumes, or stabilization of chemical and physical
parameters, or some combination of these two.
An alternative approach, also described below, eliminates purging the well
altogether by using passive sampling devices.
i)
Criteria Based on the Number of Bore Volumes
The purging of three well volumes was universally accepted at one time
and ingrained in monitoring practice. However, Herzog et al., provides
references from numerous studies which conclude that anywhere from less
than one to more than 20 bore volumes might variously be purged from
wells prior to being acceptable for sampling. Herzog, et al. conclude:
“It is obvious that it is not possible to recommend that a specific number
of bore volumes be removed from monitoring wells during purging. The

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range of suggested volumes is too large and the cost of improper purging
is too great to permit such a recommendation.”
DEP recommends that if the borehole volume technique is going to be
used, the number of borehole volumes required for each well should have
a technical or scientific basis, such as stabilization of indicator parameters
(see following section) conducted at least once for each well during initial
sampling events, rather than being based on some arbitrary criterion such
as “three well volumes.”
When purging is based on some set number of borehole volumes, the
borehole volume calculation should take into account the entire original
borehole diameter, corrected for the porosity of any sand or filter pack,
and not be based just on the innermost casing diameter.
ii)
Criteria Based on Stabilization of Indicator Parameters
Stagnant water in a well bore differs from formation water with respect to
many parameters. Field measurement of indicator parameters such as
temperature, pH, specific conductance, dissolved oxygen, and Eh has been
used as the criteria for determining the amount of water to purge and when
to sample a well. These parameters are measured in the purge water
during purging until they reasonably stabilize. DEP encourages the use of
this method.
DEP recommends that all of the above indicators be measured during the
initial and first few sampling events for the monitoring well. The data
should then be reviewed to determine which indicator parameters are the
most sensitive indicator that stagnant water has been evacuated from the
well. The most sensitive parameters will be those showing the greatest
changes and longest times to achieve stabilization. During the initial
sampling, the purging time should be extended beyond what initially
appears to be stabilization as a check to ensure that the parameter stability
is maintained.
iii)
Low Flow Purging
Another purge method using the stabilization of indicator parameters is
low-flow (minimal drawdown) well purging. This technique is based
upon placing the pump intake at the screened interval, or in the case of
fractured rock, the water-bearing zone of interest. The well is pumped at a
very low rate, commonly less than 0.5 liters per minute, while producing
less than 0.1 meters of drawdown. Pumping continues until various
indicator parameters stabilize. The objective is to produce minimal
drawdown and less stress upon the aquifer while obtaining a sample from
the aquifer interval of interest. Lack of definitive well construction or
water-producing interval information negates the use of this purge method.

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Low-flow purging often creates much less purge water. Some purge water
contains various substances which cannot be disposed of on the ground
necessitating disposal. In these cases, low-flow purging can greatly
reduce the costs of disposal. In addition, purge time is often substantially
less. Set-up is usually more complex, and costs may therefore be higher
than when using other purge methods.
Indicator parameters typically include temperature, pH, redox potential,
conductivity, dissolved oxygen (DO), and turbidity. These common
stabilization parameters are often used to indicate that the water coming
from the pumped interval is aquifer water. Although often not very
sensitive to changes between borehole and aquifer water, temperature and
pH are usually included because they are easy to measure, and the data is
commonly used for other field analysis reasons. The minimum number of
parameters to measure should include pH, conductivity, and dissolved
oxygen. Stabilization is indicated after three successive readings taken at
3- to 5-minute intervals. Indicator parameters should show a change of
less than ± 0.1 for pH, ± 3% for conductivity, ± 10% mv for redox
potential, and ± 10% for turbidity and dissolved oxygen. The stabilization
rates put forth are a guideline. Experience may dictate the need for more
or less tolerance in particular wells or situations.
If a well has a history of water quality data produced using a different well
purging method, the result should be compared with the new low-flow
purge results. Significant variation in data will require justification of
continued use of the low-flow purge method. Depending upon the
situation, purge methods may need to return to the original method.
iv)
Special Problems of Low-Yielding Wells
Low-yield wells present a special problem for the sampler in that they may
take hours, or even days, to recover after purging so that there is enough
water to sample. This waiting period not only increases the cost of
sampling, but also allows changes in water quality to occur between the
time the sample water enters the casing and the time it is collected. This is
especially problematic when sampling volatile constituents.
In practice, very low-yield wells are commonly pumped dry and sampled
the following day if necessary. This practice is believed to result in water
being sampled that is not representative of the aquifer being sampled from
the well due to the loss of volatiles and oxygenation of the water during
the waiting period. This results from pumping the well dry and exposing
the formation to the atmosphere. While there does not appear to be any
method uniformly agreed upon to eliminate these concerns, the following
considerations are suggested:
Purge in such a way that the water level does not fall below the
well screen.

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Evaluate the use of larger diameter wells that may deliver the
required amount of sample water more quickly than small diameter
wells.
If full recovery cannot be achieved within two hours, collect the
required amount of water as it becomes available, collecting
samples for parameters in order of decreasing volatility.
v)
No-Purge Methods
Passive samplers offer an alternative to traditional purge methods.
Commonly used technologies include polyethylene (or passive) diffusion
bags (PDBs) and HydraSleeves
TM
. Some sampler types operate through
diffusion of contaminants into the device; others collect a discrete grab
sample. A key advantage of passive samplers is that no purge water is
generated that requires treatment or disposal. Other advantages include
reduction of field sampling time and potentially less variability in sample
results. The selected method should be capable of accurately determining
contaminant concentrations. Passive methods that are used to detect only
the presence or absence of contaminants are not suitable for
characterization or attainment sampling.
Some important limitations should be evaluated when considering the use
of passive samplers. The well construction, hydraulic properties of the
aquifer, and contaminant type and distribution should be known and
discussed with DEP prior to engaging in a full-scale sampling program
(see the references for further information).
No-purge sampling methods rely on adequate groundwater flow
through the well screen. If the seepage velocity is low or the
screen is fouled, then the exchange rate of water in the well could
be slow, the water may be stagnant, and the sample may not be
representative of groundwater in the formation.
Some devices are incompatible with certain analytes. For
example, most VOCs readily diffuse through polyethylene, but
some (such as MTBE) do not. Polyethylene diffusion bags cannot
be used to sample semi-volatile organic compounds (SVOCs) or
inorganics.
Because passive samplers collect from a discrete interval, results
may be sensitive to the depth at which the device is placed. If flow
is stratified in the formation or localized at bedrock fractures, or if
the contaminant is density-stratified in the water column, then
deployment depth is important. Some sampler types allow
multiple devices to be arrayed vertically on a tether, allowing the
remediator to better determine an optimal depth.

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Passive samplers will not necessarily produce results equivalent to purge
methods. Ideally, a consistent purge and sampling methodology will be
used for all wells in the site network from the beginning of
characterization until the end of attainment. If a change in the sampling
method is being proposed midway through a monitoring program, then
sufficient side-by-side testing with the current approach should be
performed and discussed with DEP to determine if the change in method is
appropriate.
vi)
Summary on Purging
The following general statements can be made with respect to purging:
Every groundwater monitoring plan should contain a section
discussing how wells will be purged.
It is often desirable to use the same device for sampling that was
used for purging. In this case the purge pump can be set within the
screened section of the well or across from the yielding zone being
monitored.
If different devices are used for purging and sampling, purging
should begin at the static water surface and the device should be
lowered down the well at a rate proportional to water stored in the
well bore. Because of the better mixing of water in wells with
multiple yielding zones, this technique is considered preferable for
sampling wells with multiple yielding zones where a composite
sample of water in the yielding zones is desired (see Section C.5
on Well Depths, Screen Lengths, and Open Intervals).
Where the same device is used to sample and purge a well, it
should be established that the sampling device will not change the
quality of the groundwater it contacts.
In sampling for some analytes, such as volatile organics, it is
critical that the discharge be reduced to approximately
100 ml/minute to minimize degassing and aeration (Barcelona et
al., 1984). Flow control should be achieved by means of an
electric current using a rheostat rather than by valving or other
flow restrictors.
Purging should be completed without lowering the water level in
the well below the well screen or water-bearing zone being
sampled.
Never purge a well at a rate or in a way that causes water to cascade into
the well bore, resulting in increased degassing and volatilization.

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e)
Management of Purge Water
The first step in the management of monitoring well purge water is to minimize
its generation. Consideration should be given to techniques that minimize the
amount of purge water produced, such as low-flow or low-volume purging, or a
no-purge method. Purge water should be handled in a way that is
environmentally compatible with the volume generated, the type and
concentration of confirmed or suspected contaminants, and the specific site
conditions. A procedure that can be used is outlined in Table A-2. The procedure
is designed to ensure that potentially contaminated purge water is disposed
properly without contaminating other environmental media.
The following items should be considered when handling purge water:
Purge water should be containerized until it is characterized by laboratory
analysis. Containers with purge water comingled from multiple wells
should use the highest concentration seen in any one of the wells from
which the comingled purge water was produced, unless the comingled
purge water is sampled.
Purge water that has been characterized with no detections (i.e., with
analytical results less than method detection limits (MDLs)) may be
handled as uncontaminated groundwater under Table A-2.
Purge water that has been characterized with detections of constituents
that do not exceed the Act 2 Residential, Used Aquifer Groundwater
MSCs may utilize any of the actions described in the contaminated
groundwater section of Table A-2. Discharging to the ground surface to
return water to the impacted groundwater plume (re-infiltration) under
action (d) is an option if it does not create runoff. Discharge to a surface
water, wetland, storm drain or paved surface that drains to a channel or
stormwater conveyance requires a permit or other appropriate regulatory
authorization.
Purge water that has been characterized with detections of constituents
that exceed the residential used aquifer MSCs should be managed as
contaminated groundwater utilizing one of the actions described in (a), (b),
(d), or (e) of Table A-2. If action (e) is utilized, one of the approved
methods is as follows (for organic constituents only):
?
Place up to 20 gallons/well of contaminated purge water onto the
ground surface of the site in a controlled manner for re-infiltration
after treatment with portable engineered carbon adsorption units
designed and operated to remove the organic contaminants to
levels below residential used aquifer MSCs according to the
following:

261-0300-101 / DRAFT December 16, 2017 / Page A-41
?
Re-infiltration may only occur within the area of
groundwater contamination exceeding Act 2 residential,
used aquifer MSCs;
?
Placement on site should not create runoff that will enter
surface water, wetlands, storm drains or other water
conveyances to surface water;
?
All contaminants should be capable of being treated by
carbon adsorption;
?
Carbon adsorption units should be designed to provide
contact time for the amount of carbon at the expected levels
of raw water contamination to reach residential used
aquifer MSCs;
?
A sample should be collected to demonstrate the unit has
functioned as intended. Samples should be collected at the
beginning and end of the filtration cycle; and
?
Purge water should contain no free product.
f)
Private Wells
If a well is a private water supply, sample as close to the well as physically
practical and prior to any treatment or filtering devices if possible and practical.
If sample collection must be from a holding tank, allow water to flow long
enough to flush the tank and the lines; when the pump in the well is triggered and
turned on, verification of tank flushing is provided. If a sample that passes
through a treatment tank must be taken, the type, size, and purpose of the unit
should be noted on the sample data sheet and in the field log book.
g)
Filtering
When possible, avoid collecting samples which are turbid, colored, cloudy or
contain significant suspended matter. Exceptions to this include when the sample
site has been pumped and flushed or has been naturally flowing for a sufficient
time to confirm that these conditions are representative of the aquifer conditions.
Unless analysis of unfiltered samples for “total metals” is specifically required by
program regulation or guidance, all samples for metals analysis should be field-
filtered through a 0.45-micron filter prior to analysis.

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Table A-2
Procedure for the Management of Well Purge Water from Groundwater Sampling
TYPE OF
GROUNDWATER
ACTION
Purge Water – Shown to not
exceed the Act 2 residential,
used aquifer groundwater
standards contained in
Tables A-1 and A-2 of
25 Pa. Code Chapter 250.
Purge water may be placed on the ground surface (onsite) provided
precautions are in place to avoid erosion or runoff. Discharge to a
surface water, wetland, storm drain or paved surface is prohibited
without a permit or other appropriate regulatory authorization.
Purge Water – Shown to
exceed the Act 2 residential,
used aquifer groundwater
standards contained in
Tables A-1 and A-2 of
25 Pa. Code Chapter 250.
Management of purge water may proceed as follows:
Convey directly into an on-site treatment plant or leachate collection
system for final treatment.
Transport to off-site treatment facility.
Place in a temporary storage unit onsite for analysis to determine the
final disposition.
De minimis quantities may be treated and placed on the ground
surface onsite provided the type and concentration of contamination(s)
will not adversely impact surface water or wetlands, or further
contaminate soil or groundwater. The treatment unit must be rated to
remove the identified contaminants and must be operated and
maintained to ensure contaminant removal to Act 2 residential used
aquifer standards.
Other methods approved by DEP (may require a permit for specific
site conditions).
Purge Water where water
quality is not determined
Purge water that is not characterized needs to be containerized until
laboratory analysis is complete. Containers with purge water
comingled from multiple wells should use the highest concentration
seen in any one of the wells from which the comingled purge water
was produced, unless the comingled purge water is sampled.
Following analysis of purge water, it may be treated as one of the
two categories above.
h)
Sample Preservation
Perform sample preservation techniques onsite as soon as possible after the
sample is collected. Complete preservation of samples is a practical
impossibility. Regardless of the nature of the sample, complete stability for every
constituent can never be achieved. For this reason, samples should be analyzed as

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soon as possible. However, chemical and biological changes occurring in the
sample may be slowed significantly by proper preservation techniques.
Chemical changes generally happen because of a shift in the physical conditions
of the sample. Under a fluctuation in reducing or oxidizing conditions, the
valence number of the cations or anions may change; other analytes may
volatilize or dissolve; metal cations may form complexes or precipitate as
hydroxides, or they may adsorb onto surfaces.
Biological changes can also alter the valence of a constituent. Organic processes
may bind soluble material into the cell structure, or cell material may be released
into solution.
Methods of preservation are relatively limited and are generally intended to:
1) retard biological activity, 2) retard hydrolysis of chemical compounds and
complexes, 3) reduce the volatility of constituents, and 4) reduce sorption effects.
Preservation methods are generally limited to pH control, chemical addition,
refrigeration, freezing, and selecting the type of material used to contain the
sample.
The best overall preservation technique is refrigeration at, or about, 4?C.
Refrigeration primarily helps to inhibit bacteria. However, this method is not
always applicable to all types of samples.
Acids such as HNO
3
and H
2
SO
4
can be used to prevent precipitation and inhibit
the growth of bacteria. Preservation methods for any specific analysis should be
discussed with the accredited laboratory that is analyzing the samples.
i)
Decontamination of Sampling Devices
All non-disposable and non-dedicated equipment that is submerged in a
monitoring well or contacts groundwater will need to be cleaned between
sampling additional wells to prevent cross-contamination. Generally, the level of
decontamination is dependent on the level and type of suspected or known
contaminants. Extreme care should be taken to avoid any decontamination
product from being introduced into a groundwater sample.
The decontamination area should be established upwind of sampling activities and
implemented on a layer of polyethylene sheeting to prevent surface soils from
contacting the equipment. The following steps summarize recommended
decontamination procedures for an Act 2 site:
Wash with non-phosphate detergent and potable water. Use bristle brush
made from inert material to help remove visible soil;
Rinse with potable water - pressure spray is recommended;
If collecting samples for metals analysis, rinsing with 10% hydrochloric or
nitric acid;

261-0300-101 / DRAFT December 16, 2017 / Page A-44
Rinse liberally with deionized/distilled water –pressure spray is
recommended;
If collecting samples for organics analysis, rinsing with solvent-grade
isopropanol, acetone, or methanol (should not be a solvent of potential
interest to the investigation);
Rinse liberally with deionized/distilled water – pressure spray is
recommended;
Air-dry;
Wrap with inert material (such as aluminum foil) if equipment is not being
used promptly.
j)
Field Sampling Logbook
A field logbook or field sampling forms should be completed and maintained for
all sampling events. The following list provides some examples of pertinent
information that should be documented:
date/time of sample collection for each well
well identification
well depth
presence of immiscible layers and detection method (i.e., an interface
probe)
thickness of immiscible layers, if applicable
estimated well yield (high, moderate, or low)
purging device, purge volume, and pumping rate
duration of well purging
measured field parameters (see 4.3.3)
sample appearance
description on any abnormalities around the wellhead (standing/ponded
water, evidence of vandalization, etc.)
description of any wellhead materials that were or need to be replaced
(sanitary well cap, well lid or well lid bolts, locking devices, etc.)

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k)
Chain-of-Custody
A chain-of-custody record provides a legal document that traces sample
procession from time of collection to final laboratory analysis. The document
should account for all samples collected that require laboratory analyses and
provide the following information:
sample identification number
printed name and signature of sample collector(s)
date/time of collection for each sample
sample media type (i.e., groundwater)
thickness of immiscible layers, if applicable
well identification
type and number of containers for each sample
laboratory parameters requested for analyses
type(s) of preservatives used
carrier used, if applicable
printed name and signature of person(s) involved in the chain of
possession
date/time samples were relinquished by the sampler and received by the
laboratory
presence/absence of ice in cooler or other sample holding device
special handling instructions for the laboratory, if applicable
4.
References
BARCELONA, M.J., HELFRICH, J.A., GARSKE, E.E., and GIBB, J.P., 1984, A
Laboratory Evaluation of Groundwater Sampling Mechanisms, Groundwater Monitoring
Review, v.4, No.2, pp. 32-41.
DRISCOLL, F.G., 1986, Groundwater and Wells, Second Edition, Johnson Filtration
Systems, Inc., St. Paul, Minnesota 55112, 1089 pp.

261-0300-101 / DRAFT December 16, 2017 / Page A-46
GIBB, J.P., SCHULLER, R.M., and GRIFFIN, R.A., 1981, Procedures for the Collection
of Representative Water Quality Data from Monitoring Wells, Cooperative Groundwater
Report 7, Illinois State Water Survey and Illinois State Geological Survey, Champaign,
IL.
HERZOG, B., J. Pennino, and G. Nielsen, 1991, Ground-water sampling. In: Practical
Handbook of Ground-Water Monitoring. D. M. Nielsen, ed. Lewis Publishers. Chelsea,
Michigan. pp. 449-499
INTERSTATE TECHNOLOGY REGULATORY COUNCIL, 2004, Technical and
Regulatory Guidance for Using Polyethylene Diffusion Bag Samplers to Monitor Volatile
Organic Compounds in Groundwater.
INTERSTATE TECHNOLOGY REGULATORY COUNCIL, 2006, Technology
Overview of Passive Sampler Technologies.
INTERSTATE TECHNOLOGY REGULATORY COUNCIL, 2007, Protocol for Use of
Five Passive Samplers to Sample for a Variety of Contaminants in Groundwater, 121 pp.
NIELSEN, D.M., (Editor), 1991, Practical Handbook of Ground-Water Monitoring,
NWWA, Lewis Publishers, Inc., Chelsea, Michigan 48118, 717 pp.
NIELSEN, D.M., NIELSEN, G., 2007, The Essential Handbook of Groundwater
Sampling, CRC Press.
OHIO ENVIRONMENTAL PROTECTION AGENCY, 2012, Technical Guidance
Manual for Groundwater Investigations, Chapter 10, Groundwater Sampling.
U.S. ENVIRONMENTAL PROTECTION AGENCY, 2010, Low Stress (Low Flow)
Purging and Sampling Procedure for the Collection of Groundwater Samples from
Monitoring Wells, 30 pp.
U.S. GEOLOGICAL SURVEY, 2001, User’s Guide for Polyethylene-Based Passive
Diffusion Bag Samplers to Obtain Volatile Organic Compound Concentrations in Wells,
Water-Resources Investigations Report 01-4060.
U.S. GEOLOGICAL SURVEY, 2006, Collection of water samples (ver. 2.0): U.S.
Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A4,
September 2006.

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E.
Well Decommission Procedures
1.
Introduction
Unsealed or improperly sealed wells may threaten public health and safety and the
quality of the groundwater resources. Therefore, the proper abandonment
(decommissioning) of a well is a critical final step in its service life.
Act 610, the Water Well Drillers License Act (32 P.S. § 645.1, et seq), includes a
provision for abandonment of wells. This legislation makes it the responsibility of a well
owner to properly seal an abandoned well in accordance with the rules and regulations of
DCNR. In the absence of more stringent regulatory standards, the procedures outlined in
this section represent minimum guidelines for proper decommissioning of wells and
borings. These procedures may be applicable for, but not limited to, public and domestic
water supply wells, monitoring wells, borings or drive points drilled to collect subsurface
information, test borings for groundwater exploration, and dry wells (drains or borings to
the subsurface).
Proper well decommissioning accomplishes the following: 1) eliminates the physical
hazard of the well (the hole in the ground and the wellhead protruding above surface
grade when applicable); 2) eliminates a pathway for the introduction and migration of
contamination; and 3) prevents hydrologic changes in the aquifer system, such as the
changes in hydraulic head and the mixing of water between aquifers. The proper
decommissioning method will depend on both the reason for abandonment and the
condition and construction details of the boring or well and the specific threat of existing
and potential contamination sources near the well bore.
An unused and decommissioned well could be the conduit for spread of contamination.
The lack of well decommissioning and a poorly sealed well could both result in the
spread of contamination into previously uncontaminated areas for which the well owner
or contractor may be responsible.
2.
Well Characterization
Effective decommissioning depends on knowledge of the well construction, site geology,
and hydrogeology. The importance of a full characterization increases as the complexity
of the well construction, site geology, and the risk of aquifer contamination increases.
Construction information for wells drilled since 1966 may be available from the DCNR
BTGS PaGWIS database. Additional well construction data and information describing
the hydrologic characteristics of geologic formations may be available from reports
published by BTGS and the USGS. Site or program records also may exist. The well
should be positively identified before initiating the decommissioning. Field information
should be compared with any existing information.
Water levels and well depths can be measured with a well sounder, weighted tape
measure, or downhole camera. In critical situations, well construction details and
hydrogeology can be determined with borehole geophysics or a downhole camera. For
example, a caliper log, which is used to determine the borehole diameter, can be very
helpful in locating cavernous areas in open hole wells.

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3.
Well Preparation
If possible, the borehole should be cleared of obstructions prior to decommissioning.
Obstructions such as pumps, pipes, wiring, and air lines must be pulled. Well preparation
also may involve “fishing” obstacles out of the borehole. An attempt should be made to
pull the casing when it will not jeopardize the integrity of the borehole. Before the casing
is pulled, the well should be grouted to near the bottom of the casing. This will at least
provide some seal if the well collapses after the casing is pulled.
The presence of nested or telescoped casing strings complicates well decommissioning.
Inner strings should be removed when possible, but only when removal will not
jeopardize the decommissioning of the well. If inner strings cannot be removed and
sealing of the annular space is required, then the inner string should be vertically split
(plastic-cased wells) or cut (metal-cased wells) at intervals necessary to ensure complete
filling of the annular space.
Damaged, poorly constructed or dilapidated wells may need to be re-drilled prior to
application of proper decommissioning techniques. Also, in situations where intermixing
of aquifers is likely, the borehole may need to be re-drilled.
4.
Materials and Methods
a)
Aggregate
Materials that eliminate the physical hazard and open space of the borehole, but
do not prevent the flow of water through the well bore, are categorized as
aggregate. Aggregates consist of sand, crushed stone or similar material that is
used to fill the well. Aggregates should be uncontaminated and of consistent size
to minimize bridging during placement.
Aggregate is usually not placed in wells smaller than two inches in diameter.
Nominal size of the aggregate should be no more than 1/4 of the minimum well
diameter through which it must pass during placement. Because aggregate is
usually poured from the top of the well, care should be taken to prevent bridging
by slowly pouring the aggregate and monitoring the progress with frequent depth
measurements. The volume of aggregate needed should be calculated prior to
placement into the well.
Aggregates may be used in the following circumstances: 1) there is no need to
penetrate or seal fractures, joints or other openings in the interval to be filled; 2) a
watertight seal is not required in the interval to be filled; 3) the hole is caving;
4) the interval does not penetrate a perched or confined aquifer; and 5) the interval
does not penetrate more than one aquifer. If aggregate is used, a casing seal
should be installed (see Section E.5.a). The use of aggregate and a casing seal
should be consistent with the future land use.

261-0300-101 / DRAFT December 16, 2017 / Page A-49
b)
Sealants
Sealants are used in well decommissioning to provide a watertight barrier and
prevent the migration of water in the well bore, in the annular spaces or in
fractures and openings adjacent to the well bore. Sealants usually consist of
Portland cement-based grouts, “bentonite” clay, or combinations of these
substances. Additives are frequently used to enhance or delay specific properties
such as viscosity, setting time, shrinkage, or strength.
Sealing mixtures should be formulated to minimize shrinkage and ensure
compatibility with the chemistry of the groundwater in the well.
To avoid the bridging of sealants in the well, sealing should be performed under
pressure from the bottom upward. A grout pump and tremie pipe are preferred for
delivering grout to the bottom of the well. This method ensures the positive
displacement of the water in the well and will minimize dilution or separation of
the grout.
If aggregate is to be placed above sealant, sufficient curing time should be allotted
before placing the aggregate above the seal. Curing time for grout using Type 1
cement is typically 24-48 hours, and 12 hours for Type III cement.
General types of sealants are defined as follows:
Neat cement grout: Neat cement grout is generally formulated using a ratio of
one 94-pound bag of Portland cement to no more than 6 gallons of water. This
grout is superior for sealing small openings, for penetrating any annular space
outside of the casings, and for filling voids in the surrounding rocks. When
applied under pressure, neat cement grout is strongly favored for sealing artesian
wells or those penetrating more than one aquifer. Neat cement grout is generally
preferred to concrete grout because it avoids the problem of separation of the
aggregate and the cement. Neat cement grout can be susceptible to shrinkage, and
the heat of hydration can possibly damage some plastic casing materials.
Concrete grout: Concrete grout consists of a ratio of not more than six gallons of
water, one 94-pound bag of Portland cement, and an equal volume of sand. This
grout is generally used for filling the upper part of the well above the water-
bearing zone, for plugging short sections of casings, or for filling large-diameter
wells.
Concrete grout, which makes a stronger seal than neat cement, may not
significantly penetrate seams, crevices or interstices. Grout pumps can handle
sand without being immediately damaged. Aggregate particles bigger than this
may damage the pump. If not properly emplaced, the aggregate is apt to separate
from the cement. Concrete grout should generally not be placed below the water
level in a well, unless a tremie pipe and a grout pump are used.
Grout additives: Some bentonite (2 to 8 percent) can be added to neat cement or
concrete grout to decrease the amount of shrinkage. Other additives can be used

261-0300-101 / DRAFT December 16, 2017 / Page A-50
to alter the curing time or the permeability of the grout. For example, calcium
chloride can be used as a curing accelerator.
High-solids sodium bentonite: This type of grout is composed of 15-20 percent
solids content by weight of sodium bentonite when mixed with water. To
determine the percentage content, the weight of bentonite is divided by the weight
of the water plus the weight of the bentonite. For example, if 75 pounds of
powdered bentonite and 250 pounds of granular bentonite were mixed in
150 gallons of water (at 8.34 pounds per gallon), the percentage of high-solids
bentonite is approximately 20 percent [325/(1251+325)]. High-solids bentonite
must be pumped before its viscosity is lowered. Pumping pressures higher than
those used for cement grouts are usually necessary. Hydration of the bentonite
must be delayed until it has been placed down the well. This can be done by:
1) using additives with the dry bentonite or in the water; 2) mixing calcium
bentonite (it expands less) with sodium bentonite; or 3) using granular bentonite,
which has less surface area.
In addition, positive displacement pumps such as piston, gear, and moyno
(progressive cavity) pumps should be used because pumps that shear the grout
(such as centrifugal pumps) will accelerate congealing of the bentonite. A paddle
mixer is typically used to mix the grout. A high-solids bentonite grout is not
made from bentonite that is labeled as drilling fluid or gel.
c)
Bridge Seals
A bridge seal can be used to isolate cavernous sections of a well, to isolate
two producing zones in the well, or to provide the structural integrity necessary to
support overlying materials, and thus protect underlying aggregate or sealants
from excessive compressive force. Bridge seals are usually constructed by
installing an expandable plug made of wood, neoprene, or a pneumatic or other
mechanical packer. Additional aggregate can be placed above the bridge.
5.
Recommendations
The complexity of the decommissioning procedure depends primarily on the site
hydrogeology, geology, well construction, and the groundwater quality. Four principal
complicating factors have been identified, which include: 1) artesian conditions,
2) multiple aquifers, 3) cavernous rocks, and 4) the threat or presence of contamination.
The recommended procedures for abandoning wells will be more rigorous with the
presence of one or more complicating factors. The procedures may vary from a simple
casing seal above aggregate to entirely grouting a well using a tremie pipe after existing
casing has been ripped or perforated. Figure A-8 summarizes the general approach to
well decommissioning.
a)
Casing Seal
The transition from well casing to open borehole is the most suspect zone for
migration of water. To minimize the movement of water (contaminated or
otherwise) from the overlying, less consolidated materials to the lower water-

261-0300-101 / DRAFT December 16, 2017 / Page A-51
bearing units, this zone should be sealed. Generally, this can be accomplished by
filling at least the upper 10 feet of open borehole and the lower five feet of casing
with sealant. The length of open borehole sealed should be increased if
extenuating circumstances exist. Such circumstances would include a history of
bacterial contamination, saprolitic bedrock, or possibly deep fracture zones.
Water-bearing zones reported in the upper 20 feet or so of open borehole are
indications of fractures and warrant the use of additional sealant. Casing that is
deteriorated should be sealed along its entire length. If the casing is to be pulled,
the sealant used should remain fluid for an adequate time to permit removal of the
casing.
If the casing is to remain, then whenever feasible, it should be cut off below land
surface. After the casing seal discussed above achieves adequate strength, the
open casing should, at a minimum, be filled with aggregate. It is strongly
suggested that a sealant be used in the upper two to five feet of casing.
b)
Wells in Unconfined or Semi-Confined Conditions
These are the most common well types in Pennsylvania. The geology may consist
of either unconsolidated or consolidated materials. When applicable, unconfined
wells in non-contaminated areas may be satisfactorily decommissioned using
aggregate materials up to 10-15 feet below the ground surface. Monitoring wells
located at sites with no known contamination might be decommissioned in this
manner. The casing seal should be installed above the aggregate. A sealant may
be used over the entire depth.
c)
Wells at Contaminated Sites
A decommissioned, contaminated well often mixes contaminated groundwater
with uncontaminated groundwater. Complete and uniform sealing of the well
from the bottom to the surface is required. Therefore, proper well preparation
(Section E.3) should be accomplished before the well is sealed with a proper
sealant (Section E.4.b).
d)
Flowing Wells
The sealing of artesian wells requires special attention. The flow of groundwater
may be sufficient to make sealing by gravity placement of concrete, cement grout,
neat cement, clay or sand impractical. In such wells, large stone aggregate (not
more than 1/4 of the diameter of the hole), or well packers (pneumatic or other)
will be needed to restrict the flow and thereby permit the gravity placement of
sealing material above the zone where water is produced. If plugs are used, they
should be several times longer than the diameter of the well to prevent tilting.
Seals should be designed to withstand the maximum anticipated hydraulic head of
the artesian aquifer.
Because it is very important in wells of this type to prevent circulation between
water yielding zones, or loss of water to the surface or annular spacing outside of

261-0300-101 / DRAFT December 16, 2017 / Page A-52
the casing, it is recommended to pressure grout the well with cement using the
minimum volume of water during mixing that will permit handling.
For wells in which the hydrostatic head producing flow to the surface is low, the
movement of water may be stopped by extending the well casing to an elevation
above the artesian pressure surface.
e)
Wells with Complicating Factors at Contaminated Sites
Wells with one or more of the above complicating factors that are to be
decommissioned in areas with contaminated groundwater, or in areas where the
groundwater is at a high risk for future contamination, require the most rigorous
decommissioning procedures. In general, the entire length of these wells should
be sealed.
When the threat of contamination has been established, the elimination of a
potential flowpath is critical. For example, a contaminated well in a karst terrane
must be carefully sealed to avoid exacerbating the situation. In general, the entire
lengths of these wells should be sealed. In some situations, a bridge seal may
need to be installed, and casing may have to be perforated. In each case, a
prudent method should be selected which will eliminate all potential vertical
flowpaths.
f)
Monitoring Wells
Monitoring wells which are installed for an investigation, cleanup or other
monitoring in a program that has no rules or regulations for decommissioning,
such as the Act 2 program, should be decommissioned in accordance with the
following guidelines.
Monitoring wells that were installed and continue to function as designed can
usually be decommissioned in place after they are no longer needed. Exceptions
would include wells whose design precludes complete and effective placement of
sealant and wells in locations subject to future disturbance that could compromise
the decommissioning. In such instances, all tubing, screens, casings, aggregate,
backfilling, and sealant should be cleaned from the boring and the hole should be
completely filled with an appropriate sealant.
Monitoring wells that are abandoned in place should be completely filled with
sealant. Screened intervals can be backfilled with inert aggregate if sealant may
alter the groundwater chemistry, thereby jeopardizing ongoing monitoring at the
facility. Intervals between screens, and between the last screen and the surface,
must be filled with sealant. Generally, sealant should be emplaced from the
bottom of the interval being sealed to the top of that interval. Protective casings,
riser pipes, tubing, and other appurtenances at the surface which could not be
removed should be cut off below grade after the sealant has properly set. When
decommissioning will be completed below the finished grade, the area of the
boring should be covered with a layer of bentonite, grout, concrete, or other
sealant before backfilling to grade.

261-0300-101 / DRAFT December 16, 2017 / Page A-53
Figure A-8
Summary of Procedures for Well Decommissioning

261-0300-101 / DRAFT December 16, 2017 / Page A-54
6.
Existing Regulations and Standards
17 Pa. Code § 47.8
requires that the owner or consultant who is to abandon the well notify
DCNR’s BTGS of the intent to decommission a well at least 10 days before the well is
sealed or filled.
7.
Reporting
All decommissioned wells shall be reported to BTGS, along with any bureau that requires
a report, on forms required by BTGS (and any other pertinent forms). If available, the
original driller’s log should be included, along with the details of the well
decommissioning procedure. A photograph should be taken of the site, and a reference
map should be made, showing the location of the decommissioned well. It also may be
appropriate to survey the exact location of the well (if not already completed). Licensed
drillers may use the online application WebDriller to complete the well decommissioning
report.
8.
References
AMERICAN WATER WORKS ASSOCIATION, 1990, Abandonment of Test Holes,
partially completed wells and completed wells: AWWA Standard for Water Wells,
pp. 25-26.
DRISCOLL, F.G., 1986, Groundwater and Wells, 2nd ed., Johnson Filtration Systems,
Inc., St. Paul, Minnesota 55112, 1089 pp.
NYE, J.D., September 1987, Abandoned Wells - How One State Deals with Them, Water
Well Journal, pp. 41-46
RENZ, M.E., May 1989, In Situ Decommissioning of Ground Water Monitoring Wells,
Water Well Journal, pp. 58-60.
U.S. ENVIRONMENTAL PROTECTION AGENCY, 1975, Manual of Water Well
Construction Practices, Office of Water Supply, EPA-570/9-75-001.

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F.
Quality Assurance/Quality Control Requirements
1.
Purpose
A Quality Assurance/Quality Control Plan (QA/QC Plan) is a detailed account of
methods and procedures used for data collection (i.e., monitoring) activities. This plan,
when properly developed and implemented, ensures that adequate control and
documentation procedures are utilized, from initiation to completion of the monitoring,
so that the data generated is of the highest quality and can be used for the intended
purpose with confidence. A QA/QC plan is also an effective tool in assessing and
assuring the completeness and adequacy of the basic monitoring plan.
2.
Design
A QA/QC plan should be designed to satisfy the objectives of the monitoring project.
Although the elements of each QA/QC plan described below will be similar, the intended
uses of the collected data will determine the requirements associated with the monitoring
activity. In most cases, there will be sufficient differences within monitoring activities
for each project to require a specific QA/QC plan.
The following paragraphs describe the basic elements of a QA/QC plan. In most cases,
the proper development and adherence to this format will be sufficient to ensure that the
data collection meets the objectives of a project. However, in some cases it may be
necessary to include additional considerations that may be unique to a specific site and/or
project.
3.
Elements
Project Name or Title: Provide the project identification and location.
Project Required by: Provide the reason(s) or requirement(s) for the project.
Date of Requirement: Provide date the project was required, either by legal or
other order.
Date of Project Initiation: Provide date that the project was implemented.
Project Officer(s): Provide name(s) of individual(s) responsible for managing or
overseeing the project.
Quality Assurance Officer(s): Provide name(s) of individual(s) responsible for
development of and adherence to the QA/QC plan.
Project Description: Provide the following: 1) an objective and scope statement
which comprehensively describes the specific objectives and goals of the project,
such as determining treatment technology effectiveness, or remediation
effectiveness for specific parameters; 2) a data usage statement that details how
the monitoring data will be evaluated, including any statistical or other methods;
3) a description of the location of monitoring stations and reasons for the

261-0300-101 / DRAFT December 16, 2017 / Page A-56
locations, including geologic, hydrogeologic or other considerations; and 4) a
description of the monitoring analytes and frequency of sample collection,
including the expected number of samples to be collected for each analyte, the
sample matrix (i.e., water), the exact analytical method, reasons for selection of
analytes, and sample preservation method(s) and holding time(s).
Project Organization and Responsibility: Provide a list of key personnel and their
corresponding responsibilities, including the position and/or individual in charge
of the following functions: field sampling operations, field sampling QA/QC,
laboratory analyses, laboratory analyses QA/QC, data processing activities, data
processing QA/QC and overall project coordination.
Project Fiscal Information: Provide an estimate in work days of the project time
needed for data collection, laboratory support, data input, quality assurance and
report preparation in work days.
Schedule of Tasks and Products: Provide a projected schedule for completing the
various tasks and developing the products associated with the project, such as
sample collections (monthly, quarterly, etc.), data analysis/reports (quarterly,
annual, biennial, etc.).
Data Quality Requirements and Assessments: Provide a description of data
accuracy and precision, data representativeness, data comparability, and data
completeness.
Sampling Procedures: Provide a description of the procedures and
equipment/hardware used to collect samples from monitoring wells or other sites,
including sampling containers and field preservation and transport procedures.
Sampling Plan: A sampling plan should provide necessary guidance for the
number and types of sampling QCs to be used. The following is a list of common
sample QC types and the recommended minimum frequency if used. It is
important to remember that all QC samples should be treated with the same
dechlorination and/or preserving reagents as the associated field samples.
?
Trip Blanks - These are appropriate sample containers filled with
laboratory-quality reagent water that are transported to and from the
sampling site(s) and shipped with the samples to the laboratory for
analysis. The intent of these samples is to determine whether cross
contamination occurred during the shipping process. They are also used to
validate that the sampling containers were clean. Each sampling event
that uses this type of QC should have a minimum of one trip blank for
each container type used.
?
Field Blanks - These are appropriate sample containers that are filled with
laboratory-quality reagent water at the sampling site(s) and shipped with
the samples to the laboratory for analysis. These samples are intended to
determine if cross-contamination occurred during the sampling process
due to ambient conditions. They are also used to validate that the

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sampling containers were clean. Each sampling event that uses this type
of QC should have a minimum of one field blank for each sampling site
and of each container type used. This type of sampling QC is most useful
when sampling for VOC’s.
?
Rinsate Blanks - These are samples of laboratory-quality reagent water
used to rinse the collection device, including filtration devices and filters,
which contact the same surfaces as the sample. The QC samples(s) are
then submitted with the field samples for analysis. This type of QC
sample helps to determine if the sample collection device is contributing
any detectable material to the sample. The minimum number of blanks
needed, if this type of QC is utilized, is dependent upon operational
considerations. A minimum of two rinsate blanks should be submitted
(one before sampling and one after sampling) if multiple samples are
being collected with the same decontaminated collection device. If you
are using disposable sample collection devices or multiple pre-cleaned
devices, then a single representative sample should suffice.
?
Split/Duplicate Samples - This is a single, large sample that has been
homogenized, split into two or more individual samples, with each sample
submitted independently for analysis. This QC determines the amount of
variance in the entire sampling/analysis process. This type of QC is not
recommended for samples analyzed for analytes that would be adversely
affected by the homogenization process (i.e. VOC’s). The minimum
number of this type of sampling QC, if utilized, is one per sampling event,
with a rate of 5 percent to 10 percent commonly used.
?
Replicate Samples - Comprised of two or more samples collected from the
same source, in a very short time frame (i.e., minutes), with each sample
submitted independently for analysis. This QC measure, like the
split/duplicate sample, determines the amount of variance in the entire
sampling/analysis process. The amount of variance determined by this
type of QC may be larger than that of a split/duplicate sample. The use of
this type of QC also presumes that the sample’s materials are already
homogenous. This type of QC is recommended for samples where
analytes could be adversely affected by an external homogenization
process (i.e. volatile organics). The minimum number of this type of
sampling QC, if utilized, is one per sampling event, with a rate of
5 percent to 10 percent commonly used.
?
Known Samples - These are reference materials that have been
characterized as acceptable to the range of values for the analytes of
concern. These materials are available from commercial sources. This
type of QC helps determine if the analytical work is sufficiently accurate.
It must be noted that improper handling or storage of this type of reference
material can invalidate the materials characterization. The minimum
number of this type of QC, if used, is one per subject.

261-0300-101 / DRAFT December 16, 2017 / Page A-58
?
Spiked Samples - These are split/duplicate or replicate samples that have
been fortified with the analytes of concern. This QC is intended to
determine if there have been changes in concentration due to factors
associated with the sample or the shipping and analysis process. This type
of QC is very difficult to use in a field environment and routinely is done
as part of the analysis process. If this type of QC is necessary, the
minimum required is one per project.
Sample Custody Procedures: Provide information which describes accountability
for sample chain-of-custody including sample collector identification, sample
location identification, sample number, date and time of collection, parameters to
be analyzed, preservatives and fixatives, identification of all couriers,
identification of laboratory and receiver, time and date of receipt at laboratory,
laboratory analyzer, and time and date of analysis.
Calibration Procedures and Preventative Maintenance: Equipment maintenance
and calibration should be performed in accordance with manufacturer’s
instructions. Calibration and maintenance sheets should be maintained on file for
all equipment.
Documentation, Data Reduction, and Reporting: Provide discussion on where
field data are recorded, reviewed, and filed.
Data Validation: Provide a discussion and reference to the protocols used for
validation of chemical data and field instrumentation and calibration. Describe
procedure for validating database fields (i.e., through error checking routines,
automatic flagging of data outside of specified ranges, and manual review and
spot checking of data printouts against laboratory analytical results).
Performance and Systems Audits: Provide a description of how field staff
performance is checked and how data files are verified for accuracy and
completeness.
Corrective Action: Provide a discussion on what corrections are made when
errors are found and actions taken to prevent future recurrence of errors.
Reports: Provide a list of the types and frequency of reports to be generated (i.e.,
performance and systems audits, compliance analyses, remediation effectiveness,
etc.).
4.
References
U.S. ENVIRONMENTAL PROTECTION AGENCY, May 1984, Guidance for
Preparation of Combined Work/Quality Assurance Project Plans for Environmental
Monitoring, (OWRS QA-1), US EPA Office of Water Regulations and Standards.
Mueller, D.K., Schertz, T.L., Martin, J.D., and Sandstrom, M.W., 2015, Design, analysis,
and interpretation of field quality-control data for water-sampling projects: U.S.
Geological Survey Techniques and Methods, book 4, chap. C4, 54 p.

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U.S. Geological Survey, 2006, Collection of water samples (ver. 2.0): U.S. Geological
Survey Techniques of Water-Resources Investigations, book 9, chap. A4,
September 2006.

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