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O O O Q O
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Elements for Effective Management of
Operating Pump and Treat Systems
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This fact sheet summarizes key aspects of effective management for operating pump and treat (P&T)
systems based on lessons learned from conducting optimization evaluations at 20 Superfund-fmanced P&T
systems. The lessons learned, however, are relevant to almost any P&T system. Therefore, the document may
serve as a resource for managers, contractors, or regulators of any P&T system, whether or not that system is
within the Superfund Program. This fact sheet is meant to provide a framework for effective site management, but
is not intended to be a detailed instructional manual.
This fact sheet is not a regulation, and therefore, it does not impose legally binding requirements on EPA,
States, or the regulated community, and may not apply to a particular situation based upon the circumstances. The
document offers technical and policy recommendations to EPA, States and others who manage or regulate Pump
and Treat systems as part of the Superfund or other cleanup programs. EPA and State personnel may use other
approaches, activities and considerations, either on their own or at the suggestion of interested parties. Interested
parties are free to raise questions and objections regarding this document and the appropriateness of using these
recommendations in a particular situation, and EPA will consider whether or not the recommendations are
appropriate in that situation. This fact sheet is a living document and may be revised periodically without public
notice. EPA welcomes public comments on this document at any time and will consider those comments in any
future revision of this guidance document.
TABLE OF CONTENTS
A. INTRODUCTION •... 1
B. SYSTEM GOALS AND EXIT STRATEGY .2
C. EVALUATING PERFORMANCE AND
EFFECTIVENESS OF THE P&T SYSTEM . 3
D. EVALUATING COST-EFFECTIVENESS OF
THE P&t SYSTEM .................. . 12
E. CONTRACTING CONSIDERATIONS .... 16
F. OPTIMIZATION AND CONTINUOUS
IMPROVEMENT 18
G. CITED RESOURCES 18
'Throughout this document, the word "goal" refers to a target or
aim including the following:
• a broad, long-term purpose or intent specified in a decision
document (e.g., cleanup to a specified concentration)
• a performance-based metric or milestone intermediate in
duration (e.g., a 20% decrease in monthly influent
concentrations within 24 months of operation)
• a specific and short-term objective (e.g., demonstration of
plume containment)
Goals, as stated in this document, are not to be confused with
Preliminary Remediation Goals (PRGs) specified in a Superfund
Feasibility Study.
A. INTRODUCTION
The basic components of a P&T system include
ground water extraction, above-ground treatment,
disposal of the treated water, ground water monitoring
in the subsurface, and process monitoring in the
treatment plant. P&T system management includes the
following primary activities:
Setting system goals' and exit strategy - Are the
system goals clearly stated with estimated time frames
for achievement? Are the goals and time frames still
appropriate? Are there measurable performance
standards (i.e., metrics) for evaluating system
performance? Is it clear what is required for some or
all of the P&T system to be discontinued?
Evaluating performance/effectiveness - Do data
indicate that the P&T system is achieving the stated
short-term goals (e.g., preventing plume migration)
and that it will likely achieve the stated long-term
goals (e.g., cleanup to specified levels or continued
containment of the plume)?
Evaluating cost-effectiveness - Can the life-cycle cost
of the P&T system be reduced (while maintaining
effectiveness) by lowering the annual costs of
operations and maintenance (O&M) and/or shortening
the system duration?
Continuous improvement can occur if the above items
are routinely addressed and if modifications to
improve the system are subsequently implemented.
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Skill sets from many disciplines are required for
effective P&T system management:
• policy and regulations
* hydrogeology
• engineering
• risk assessment
• contracting
Site managers may not have expertise in all of these
disciplines, but this fact sheet can be used as a quick
reference guide and checklist for site managers, to
make sure that the key aspects of P&T system
management have been adequately addressed.
B. SYSTEM GOALS AND EXIT STRATEGY
Goals for P&T systems typically involve cleanup
and/or containment of impacted ground water as a
means of protecting human health and the environment.
It is recommended that goals, both short-term or long-
term,
• are clearly stated and prioritized and include a
time frame;
• are appropriate relative to the site-specific
conceptual model;
• include metrics for evaluating system
performance;
• clearly indicate when some or all of the P&T
system can be discontinued; and
• are revised over time as appropriate.
Each of these items is discussed below.
Clearly State and Prioritize Goals
The system goals should be unambiguous, and each
goal should include the expected time frame for
achievement, even if that time frame is subject to
uncertainty. When multiple goals are stated, they
should be prioritized. For instance, ground water
cleanup may be a long-term goal, but plume
containment may be a short-term goal that is critical for
immediate protection of human health and the
environment. In such a case, containment should be
given the higher priority.
Consider Goals Relative to the "Site-Specific
Conceptual Model"
A site-specific conceptual model is a combination of
text and figures that describe the hydrogeologic
system, the cause of the ground water impacts, and the
fate and transport of the ground water contaminants.
// is not a numerical model! The conceptual model
should attempt to explain the items listed in Exhibit 1.
Exhibit 1
A Site-Specific Conceptual Model Should
Identify/Explain the Following Items
historical and continuing sources of ground water
contamination, both above ground and below the
surface
historical growth and/or retreat of the ground water
plume
ground water flow velocity (horizontal and vertical)
and other parameters controlling contaminant fate and
transport
potential human and ecological receptors
anticipated results of remedial actions
If the conceptual model does not adequately identify
or explain all of these items, the data gaps should be
addressed with a focused investigation. This does not
imply a return to the "remedial investigation" phase.
The conceptual model should evolve over time,
including during active remediation, as more
information about the site becomes available.
The goals of the P&T system should be appropriate
relative to the site-specific conceptual model;
otherwise, they may not be achieved. For example, a
P&T system will not likely restore ground water to
cleanup levels in a reasonable time frame if there are
continuing sources of contamination, such as non-
aqeuous phase liquid (NAPL) or soil contamination.
Example 1, on the following page, provides an excerpt
from a conceptual model to demonstrate the type of
data and interpretation that should be included. The
example also highlights potential data gaps in the
conceptual model and related considerations for the
site-wide exit strategy.
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Example 1
Excerpt from a Conceptual Model
.... PCE concentrations in excess of 2,500 ug/L have
persisted in shallow well MW-12S since the remedial
investigation, despite pumping from the underlying but
adjacent deep extraction well EW-2. This persistence
may indicate the possible presence of a continuing PCE
source (NAPL or soil contamination) near MW-12S.
Furthermore, little drawdown is noted at MW-12S,
despite pumping from EW-2. The lack of draw down at
MW-12S due to pumping at EW-2 calls into question the
ability of EW-2 to capture the PCE in the shallow zone in
the vicinity of MW-12S and may indicate that EW-2 is in
a low conductivity zone or that a low conductivity layer
separates EW-2 and MW-12S....
Data Gaps:
• presence of a continuing PCE source
degree of capture near MW-12S
Considerations for the Site-Wide Exit Strategy:
• contain shallow ground water near MW-12S by
pumping (short term)
• characterize and then remove or contain the
continuing PCE source
Include Metrics For Evaluating System Performance
To help determine whether or not the system goals are
achieved, each goal should include metrics (i.e.,
performance standards that can be measured). For
example, a goal of "ground water containment" is
vague unless stated in conjunction with specific metrics
such as gradients, drawdowns, or ground water
elevations ("water levels") that must be achieved at
specific locations. Similarly, metrics for "ground water
cleanup" might include specific milestones for mass
removal, peak concentration reduction, and/or plume
area reduction that must be achieved within specified
time periods or at specified locations.
Clearly Indicate When Some or All of the P& T
System Can Be Discontinued
To provide a viable exit strategy for the P&T system or
some of its components, the following details or
metrics should be specified as part of the system goals:
• contaminants of concern (COCs) being
addressed by the P&T system, which may be a
subset of the COCs for the entire site
cleanup levels that must be achieved for each
specific COC addressed by the P&T system
• specific criteria for shutting down individual
extraction wells, including the number of
consecutive monitoring events where cleanup
levels must be achieved for attainment at a
particular well and consideration of potential
contaminant rebound
• process monitoring levels or other milestones
that will indicate when individual components
of the above-ground treatment process can be
removed
Revise Goals Over Time As Appropriate
There are many reasons to consider revising goals of
the P&T system over time, some of which are
highlighted in Exhibit 2.
Because the site-specific conceptual model evolves,
periodic review of system goals should occur on a
regular basis, perhaps once every 5 years. For
Superfund sites, this review of system goals could be
done with the Five Year Review process. In some
federal and state programs, a change in the site
decision document may be needed prior to changing
the goals.
C. EVALUATING PERFORMANCE AND
EFFECTIVENESS OF THE P&T SYSTEM
Evaluation of P&T system performance should
include evaluation of the subsurface performance,
offered by the extraction system, and evaluation of the
above-ground performance, offered by the treatment
Exhibit 2
Some Reasons To Modify Goals of the
P&TSystem
revised regulatory framework:
new treatment technologies or strategies
operating experience suggests existing goals are
unrealistic and will not be met
costs are greater than originally anticipated
changes in plume extent
discovery of additional and/or continuing sources of
contamination, such as soil contamination or NAPL
changes in land use or ground water production near
the system
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system. The following five steps are recommended for
thorough P&T system evaluation:
• evaluating plume capture
• performing and interpreting treatment process
monitoring
* performing and interpreting ground water
monitoring
* evaluating extraction well performance
• if applicable, evaluating injection well
performance
Evaluate Plume Capture
For ground water remedies, protection of human health
and the environment often requires hydraulic
containment ("capture") of a contaminant plume.
Evaluation of containment includes defining an
appropriate target capture zone, interpreting actual
capture, and then demonstrating that the actual capture
zone is consistent with the target capture zone. Care
should be taken to ensure this consistency is present
through various temporal changes, such as seasonal
variations in recharge and/or nearby pumping.
Although the complex hydrogeology at fractured
bedrock or highly heterogeneous sites may prohibit
conclusive results, capture zone analyses should be
attempted at these sites for the following reasons: (1)
the analysis may actually be conclusive, and (2)
valuable insights to site-specific ground water flow and
contaminant transport may be gained.
Define the "Target Capture Zone"
A three-dimensional target capture zone should be
indicated on maps and/or on cross-sections of the site.
It should be based on clearly stated criteria (such as a
specific concentration contour or a site boundary). In
some cases capture of the entire plume may be
required, but in other cases capture of a portion of the
plume may be acceptable (e.g., if natural attenuation of
the remaining portion is viable and can be
demonstrated). If the target capture zone is based on a
specific concentration contour, it may need to be
updated over time as plume boundaries change. If a
variety of contaminants of concern are present, the
target capture zone should consider each of those
contaminants. If a target capture zone is not defined,
then it will be uncertain if actual capture is sufficient.
Interpret Actual Capture Zone Achieved
An actual capture zone is defined as the three-
dimensional zone in which all ground water flow
paths converge to one or more extraction points. The
extent of the capture zone depends on many factors:
• pumping rate
• hydraulic gradient (magnitude and direction)
• hydraulic conductivity
• vertical flow to other aquifers
• spacing of extraction wells
• transient influences (recharge, other pumping)
Accurate interpretation of actual capture is difficult
and is best evaluated with converging lines of
evidence. Some potential lines of evidence are listed
in Exhibit 3 and described below. Generally, capture
is actually achieved if multiple lines of evidence
suggest it; however, capture may not be achieved if
only one or two of the multiple lines of evidence
suggest it. Figure 1, on page 6, illustrates the role of
multiple lines of evidence in a capture zone analysis.
Flow Budget and Analytical Modeling. For idealized
conditions (i.e., one well, no recharge, uniform
saturated thickness, and a homogeneous, isotropic
aquifer), the width of the capture zone some distance
upgradient of the extraction system can be estimated
for specific flow rates with a straightforward
analytical equation (see Exhibit 4). Using the same
Exhibit 3
Potential Lines of Evidence for
Ground Water Capture
calculations of capture zone width based on flow
budget and/or analytical models
interpretation of ground water flow lines from
potentiometric surface maps that are based on
measured ground water elevations from the various
subsurface stratigraphic units
inward flow relative to a compliance boundary, based
on measured ground water elevations at two or more
locations oriented perpendicular to the boundary
concentration trends over time at sentinel wells located
downgradient of the capture zone
particle tracking in conjunction with a numerical
ground water :flo\^ model calibrated/verified by actual
ground water elevations under pumping conditions
implementation and analysis of data from tracer tests
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equation, the pumping rate (Q) required for a desired
width of capture (W) can be estimated. The pumping
rate required for a given capture width must generally
be higher than estimated by this equation to account for
recharge and uncertainties in the other parameters.
Similarly, actual capture width for a specified pumping
rate will typically be less than estimated by this
equation for the same reasons.
This approach for idealized situations can and should
be used as a rudimentary analysis of ground water flow
at a site. However, the simplifying assumptions and
resulting limitations should be understood and
specified. The limitations of this approach strongly
indicate a need for considering additional lines of
evidence for evaluating capture.
Potenfiometric Surface Maps. Ground water elevation
measurements can be used to create potemiometric
surface maps, from which ground water flowlines and
the capture zone can be interpreted. Unfortunately, the
number of ground water elevation measurements
typically available is not sufficient to unambiguously
interpret capture. It is important to exclude ground
water elevation data from active pumping wells when
constructing potentiometric surface maps because they
are influenced by well losses and are not representative
of aquifer conditions. Note that when potentiometric
surface maps indicate capture with respect to horizontal
flow, capture may not be adequate with respect to
Exhibit 4
Width of Capture Zone and flow Budget For
Very Simple Hydrogeologic Systems
Assumptions:
• one well
• single layer of constant thickness
* homogeneous, isptropic aquifer
• no recharge: from above or below : " :
Tjr J^
Cx 5x Kxi
or
Q=
Q = extraction rate (gpm)
C = conversion factor (0,005 1 8 gal/ft3 min/day)
W ~ total width of capture zone upgradient of the
extraction system (ft)
B = saturated thickness (ft)
K - hydraulic conductivity (ft/day)
i = hydraulic gradient (ft/foot)
vertical flow. Thus, information from other lines of
evidence may be required.
Ground Water Elevation Pairs. In some cases, pairs
of ground water elevation measurements on either side
of a boundary can be used to demonstrate inward flow
relative to that boundary. An example might be
ground water elevation measurements on either side of
property boundary or on either side of a slurry wall.
Another example would be stage measured in a creek
relative to the ground water elevation in the aquifer
immediately adjacent to the creek. A higher creek
stage indicates no discharge from the aquifer to the
creek. Because flow between the creek and aquifer can
change magnitude and even direction with changes in
precipitation and recharge, frequent measurements
from these locations may be required. Ground water
elevation pairs from different levels of the aquifer can
also be used to verify vertical gradients that are
indicative of capture. Generally, it is important to
exclude ground water elevations from active pumping
wells and to consider recent recharge events.
Sentinel Wells. If capture is adequate, monitoring
wells downgradient of the extraction system (i.e.,
sentinel wells) can be monitored over time as follows:
Sentinel wells that are not currently impacted
by contaminants should remain without
impacts over time.
• Sentinel wells that are currently impacted by
contaminants should reach background levels
over time. If concentrations decrease in these
wells but remain over regulatory standards,
capture provided by the extraction system is
likely inadequate.
Because ground water flow is slow, impacts at sentinel
wells may take years to appear, and concentration
measurements over time at sentinel wells can become
very costly. Interpretation may be ambiguous if the
sentinel wells are actually located within the zone of
capture or if they are not in the correct locations to
detect uncaptured portions of a plume. Also, if the
plume is not well delineated, portions of the plume
may have previously migrated beyond the capture
zone and the sentinel wells. These limitations of
sentinel wells emphasize the importance of using
multiple lines of evidence. For sites with fractured
bedrock and/or highly heterogeneous conditions a
greater density of sentinel monitoring points may be
merited due to the increased potential for preferential
pathways of contaminant migration. In addition, for
sites with multiple layers or stratigraphic units with
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Figure1
Converging Lines of Evidence for Evaluating Horizontal Capture
(evaluating vertical capture requires additional analysis)
* E> TRACTION WELL
* MONITORING WELL
,«. WATSR ELEVATION
"'•"{FT)
TARCET CAPTURE I
ZONE '
IFSTIMATHD PLUMS
6CUNOAKV
i. GROUNDVVATER FLOW
*" DRECTiO-J
iiNVVARDFLQ'A'l
0 150 300 ng.2
"" &CAL6 !N FEET
Data:
Hydraulic conductivity
• K = 10 ft/day
• relatively homogeneous
Pumping
• EW-l&2 = 3gpmeach
• EW-3 & 4 = 4 gpm each
* fully penetrating wells
Aquifer thickness
• B = 20 ft
• unconfined aquifer
Target capture zone width
(north to soutril
• W = 600ft
Hydraulic gradient
• i = 0.006 ft/foot
Background:
• barrier wall, plus wells EW-1 and EW-2, act to contain the contaminant source
• EW-3 and EW-4 address the downgradient plume
• target capture zone is a specified concentration contour based on risk assessment,
natural attenuation addresses plume fringe
• plume delineated by monitoring to the north and south
Potential Evidence for Capture:
• ground water flow budget (Exhibit 4) consistent with target capture zone
* (Q>4 gpm required based on simple calculation, actual Q=8 gpm)
• water levels demonstrate "inward flow" across barrier wall
• potentiometric surface indicates flow in the direction of EW-3 & 4, but resolution is
insufficient to confirm capture
• sentinel wells downgradient to the east show decreasing concentrations, provides
increased confidence that capture is occurring
Next Steps:
• delineate on a map the interpreted capture zone and compare it to target capture zone
• consider seasonal variation in ground water flow and plume
• consider additional piezometers in vicinity of EW-3 and EW-4
• consider use of ground water flow model and particle tracking
• continue to monitor sentinel wells (concentrations should decrease to clean up levels)
• ensure vertical capture
potential impacts, sentinel wells would likely be
required in each unit of concern,
Particle Tracking in Conjunction with Ground Water
Modeling. Particle tracking in conjunction with a
ground water flow model can indicate if all model cells
within a target capture zone are captured by a simulated
extraction system. A three-dimensional model can be
particularly helpful in evaluating capture at sites where
vertical heterogeneity and/or migration greatly affect
contaminant fate and transport. However, the
reliability of this line of evidence for interpreting actual
capture depends on the reliability of the model.
Predictions from models are subject to uncertainty
based on the presence of heterogeneity in natural
systems that can be difficult to characterize and
represent in the model. Ideally, the numerical model
can be "verified" by reproducing measured drawdown
responses to various pumping scenarios, increasing
confidence in the model's ability to accurately predict
capture.
Tracer Tests. Demonstrating capture of a tracer
injected into the contaminant plume can increase the
confidence that capture of the plume has been
achieved. Valuable data can be obtained from
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monitoring tracer concentrations in sentinel wells and
tracer mass recovery in extraction wells over time. The
presence of the tracer in sentinel wells indicates a lack
of capture, and a high mass recovery rate in extraction
wells indicates a high degree of capture. The following
are some advantages of tracer tests:
• In fractured bedrock environments, tracers may
indicate flow along bedding planes and the
connectivity of fractures between monitoring
points.
• A known mass of a tracer can be injected at a
specified location and time, allowing mass
removal efficiency to be quantified.
• Data from tracer tests can be used to calibrate
ground water flow and contaminant transport
models.
• Depending on the tracer, sampling and analysis
can be relatively straightforward and low in
cost if the proper sensors are available.
However, tracer tests have the following disadvantages:
• Because the tracer is likely injected only at
select locations, demonstrating capture of the
tracer does not confirm capture of the entire
contaminant plume.
• Injecting tracers may require obtaining an
Underground Injection Control permit.
• Due to the relatively slow movement of most
ground water, tracer tests may take months or
years to yield useful information.
Perform/Interpret Process Monitoring
Process monitoring refers to measurements of
concentrations in treatment plant influent and effluent,
and in some cases at intermediate points in the
treatment process.
Verify that Discharge Standards are Being Achieved
Treated water from a P&T system must generally meet
appropriate standards prior to discharge. Fortunately,
most implemented treatment technologies have been
proven reliable through years of use in a variety of
conditions, and treatment plants regularly meet the
discharge criteria. Nevertheless, sampling of plant
effluent is recommended if not otherwise required, and
the resulting data should be scrutinized by both the site
manager and the site contractor. For facilitated
review, the effluent sampling results should be
presented alongside the discharge criteria.
Exceedances should be highlighted and technical
explanations for the causes of the exceedances and the
planned corrective action should be provided.
Compare Design Parameters and Actual Parameters
for Treatment System
Because site conditions change overtime and these
changes can have implications on the cost and
effectiveness of a remedy, P&T managers and their
contractors should routinely compare design values
versus actual values for the following treatment
process parameters:
• influent flow rate to the treatment plant
• influent concentrations for each contaminant
of concern
• contaminant mass loading to the treatment
system (see Exhibit 5)
• removal rates for the treatment system
(influent mass minus effluent mass, or effluent
concentration divided by influent
concentration)
• air to water ratio for an air stripper
• pressure drop across granular activated carbon
(GAC) units or filtration media
Addressing discrepancies between design and actual
parameters can lead to changes that improve
effectiveness and/or reduce O&M costs. Some
examples are provided in a later section of this fact
sheet ("Modify Inefficient System Components").
Discrepancies between design and actual parameters
should be discussed with site contractors and
potentially with other technical assistance resources.
Evaluate Treatment System Components
The performance of the treatment system and its
components can be evaluated by determining the mass
loading and removal rates. Especially during start up,
determining the mass loading and removal rates for
the individual treatment components may be merited.
After system startup, however, these components
should be operating reliably and evaluation of the
treatment system as a whole (i.e., influent and effluent
monitoring) should suffice.
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Perform/Interpret Ground Water Monitoring
continue with the current P&T system
Long-term ground water monitoring programs typically
involve quarterly, semi-annual, or annual monitoring of
ground water quality and elevations. The data from
this monitoring should be managed electronically to
facilitate analysis, reduce time, and reduce the
possibility of entry errors. The data should be used to
monitor the effectiveness of the subsurface remedy and
update or calibrate site ground water flow and
contaminant transport models, if they exist. New data
should be interpreted and compared to historical data
on a regular basis. Though not always necessary,
statistical analysis may be helpful in interpreting the
data. Based on trends from these data, site managers
should periodically consider the following options
(perhaps every 2-3 years as part of a comprehensive
performance evaluation such as the Five Year Review
for Superfund sites):
increase capacity of the current P&T system
and/or modify extraction well locations
investigate and characterize potential
additional contaminant sources
apply an aggressive source removal
technology
switch to another remedial technology or
implement an additional technology
consider alternate goals
focus extraction on specific areas
reduce the extent and frequency of monitoring
as a clear pattern develops
Exhibit 5
Calculating Contaminant Mass Loading and Removal Rates
Contaminant mass loading and removal rates can be calculated with the same basic equation. However, the units
and conversion factors are different for air than they are for water.
* QHl
Hl0
For Water:
3.785 L 1440 min. 2.2 Ibs.
gallon day 10* ug
For Air:
0.0283 m3
ft3
1440 mm. 2.2 Ibs.
day X 10s mg
= mass loading, removal rate in wato (Ibs /day)
= flow rate in water (gpm) ••.;: ;:•:•.•:
~ contaminant concentration (ug/Uppb)
Qar
= mass loading, removal rate in air (Ibs / day)
= flow rate in air (cfin) ; :
Ca> = contaminant concentration (mg/rh3)
For air calculations, C^ in mg/m3 (with:moiecular weight, MWX, in grams per mole) can be obtained at 7Q°F and a
pressure of 1 atmosphere from parts per million by volume (ppmv) by the following steps:
Conc(ppmv) 1 mole air
Note: The conversion factor (I mole air)/(24J L) varies with both temperature and pressure. At a pressure of 1
atmosphere and a temperature ofSTF (0"C), the conversion is (i mole air)/(22. 4 L).
Approximate Molecular Weights (MW) in grams/mole of Common Volatile Organic Compounds (VOCs)
Benzene: 78
Carbon tetrachloride: 154
Chlorobenzene: 113
DCA: 99
DCE:97
Mylbenzene: 106
PCE: 166
TCA: 133
TCE: 131
Toluene: 92
Vinyl chloride: 62.5
Xylene:106
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Collect and Report Accurate and Reliable Data
Accurate data is crucial for making well-informed
decisions about site operations and strategy. It can also
represent a significant portion of O&M cost. As a
result, a number of considerations should be applied to
collection and management of ground water elevations
(Exhibit 6) and water quality data (Exhibit 7, on the
following page).
Update Plume Maps. Potentiometric Surfaces, and
Trend Analyses
Plume maps, potentiometric surfaces, interpreted flow
directions and magnitudes, and data trend plots are
fundamental to data interpretation and are useful for
site decision making, tracking the progress of
remediation, determining target capture zones, and
interpreting success or failure of actual capture (see
previous Section "Evaluate Plume Capture").
Processing data and generating and reviewing these
plots for each monitoring event ensures data quality
because errors, inconsistencies, or data gaps can be
addressed before subsequent events. Electronic data
management, spreadsheets, and plotting software
allow these plots to be updated with minimal level of
effort and low cost. Thus, if practical, the plots should
be generated after each monitoring event. Consistent
contouring methods or software should be used for
developing the plots for a given site, and the method
or software used should be noted.
Exhibit 6
Considerations for Collecting and Recording Ground Water Elevation Measurements ;
Measure depths to ground water in each well or piezometer two or three times to avoid false readings, and measure
depths to water at all locations on the same day, if possible. Include water levels from surface water bodies that may
influence ground water elevations.
Have on hand historical data when measuring depths to ground water to confirm that current measurements are consistent
with the historical ones. If there is a significant discrepancy, determine if a similar discrepancy exists for each sampling
location. If the discrepancy appears to be an anomaly (exists at only one or two wells), note the discrepancy in the field
log book and in the O&M reports.
Note piezometer and monitoring well integrity and conditioa Routine redevelopment or cleaning may be necessary.
Always measure depths to ground water from a clearly visible surveyor's elevation mark on the well.
The location of each piezometer and well should be accurately surveyed to within 0.1 feet horizontally, and the reference
mark should be accurately surveyed to within 0.01 feet vertically.
Re-survey wells and piezometers if changes in easing elevation are suspected due to settling, frost heaves, or other
damage to wells. ; v: ".:\ '"'.•"....
Maintain surveyor's mark to prevent fading.
In reports, clearly distinguish the difference between the depth to ground water and the ground water elevation (i.e.,
"water level"). Specify the reference points and units for each measurement (i.e., "feet below ground surface" for depth
to ground water and "feet above mean sea lever' for ground water elevation).
Report new ground water elevations alongside previously recorded ground water elevations in tables so that trends can be
easily noticed by the reader.
Interpret each round of ground water elevation measurements with respect to the site conceptual model and site goals.
Reconsider the frequency of measurement events if the amount of data and interpretation are either insufficient or
excessive with respect to the system goals. The monitoring frequency for water levels and water quality need not be the
same.
Obtain ground water elevations from clusters of wells or piezometers with various elevations if vertical flow is an
important aspect of the site conceptual model.
Note: Inaccurate or insufficient data can lead to poor management decisions, and excessive data are not cost-effective.
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Exhibit 7
Considerations for Ground Water Quality Sampling and Analysis
Select sampling locations, sampling techniques, analytical methods, and sampled constituents based on the goals of the
system (e.g., sampling from the body of the plume may not be required if plume containment is the only system goal).
Note piezometer and monitoring well integrity and condition. Routine redevelopment or cleaning may be necessary.
Use consistent sampling techniques and analytical methods; report any inconsistencies if they do occur
Select sampling techniques that are appropriate for the site:
» Consider dedicated sampling equipment when cost-effective and appropriate.
> Utilize low-flow sampling when appropriate (e.g., reduced sampling time, more accurate measure of dissolved metals
concentrations, less purge water, etc.).
» Consider traditional purge and sample techniques if parameters, such as turbidity, do not stabilize in a reasonable time
frame during low-flow sampling.
Data validation is a methodical process of checking precision, accuracy, and completeness of laboratory data quality and
utility. Such validation is merited during initial investigations and at other decision points of the remedy but should be
avoided for most routine sampling events during O&M, ;
Interpret ground: water samples from each event with respect to the site conceptual model and site goals.
Sample for appropriate natural attenuation parameters if natural attenuation is or will be considered as a site remedy.
Reconsider sampling frequency and locations if current amount of data and interpretation is either insufficient or
excessive with respect to the system goals and site conceptual model. The monitoring frequency for water levels and
water quality need not be the same.
Note: Inaccurate or insufficient data can lead to poor management decisions, and excessive data are not cost-effective.
New plume maps, potentiometric surfaces, and data
trend plots do not always require immediate submission
in individual reports. In some cases, it may be more
appropriate to collect data and generate plots for
several events prior to interpreting the combined results
in a single O&M report (e.g., generating an annual
report that discusses four quarters of ground water
monitoring).
The frequencies of monitoring events, data analysis,
and reporting should each be commensurate with the
time frame for site decision making and consistent with
appropriate regulations. Relatively new systems, where
the system and the site conditions are in a state of flux,
may require more frequent monitoring, data processing,
and reporting than relatively mature, stable systems. A
review of historical trends in the data may help a site
team determine if a change in monitoring frequency is
merited.
Evaluate Concentration Trends At Monitor Wells
The trends in concentrations at each monitoring well
and groups of monitoring wells should also be studied.
Increased or constant concentrations, or even
decreased concentrations that remain above the site
standards, in downgradient or sentinel wells may
indicate inadequate capture by the extraction system.
In such cases, the capture zone should be analyzed,
and the extraction system may require augmentation.
Increases or constant, but elevated, concentrations in a
well may indicate the presence of a continuing source
of contamination from the vadose zone or from NAPL.
If such sources are not addressed, the P&T system will
likely operate indefinitely.
Decreases in contaminant concentrations at wells may
indicate success of the remedy, but they may also
indicate dispersion or contaminant transport to
downgradient areas. Reviewing water quality data at
other locations or ground water flow patterns may
help confirm which of the above is occurring.
Contaminant levels may also decrease and then
plateau above cleanup levels or may rebound after
pumping has stopped.
10
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Evaluate Extraction Well Performance
Extraction wells should be monitored to determine if
they are in the most effective location, given potential
changes in the contaminant plume, and also to
determine if they are performing as expected.
Evaluate Concentration Trends at Extraction Wells
As contaminant mass is extracted from the subsurface,
the contaminant concentrations in extraction wells
should decrease unless a continuing source of
contaminant exists or contaminant levels have reached
a plateau. If the contaminant concentration in an
extraction well, or nearby monitoring wells, has
decreased to low levels, then it may be more effective
to shut down that extraction well, relocate it, or
reallocate ground water extraction to other wells.
However, shutting down a well may not be possible if
that well is required for capture of the contaminant
plume. If a well is shut down, monitoring should
continue for some period of time to ensure that
concentrations do not "rebound" due to desorption of
contaminants from soil to ground water, diffusion of
contaminants from tighter portions of the formation, or
additional dissolved contamination from continuing
sources. Monitoring ground water concentrations in
individual extraction wells on an annual or semi-annual
basis is likely sufficient for the above analyses.
Pumping Rates and/or Specific Capacity Versus Time
Bacterial growth and chemical deposits can lead to
fouling of extraction wells. If addressed properly
through a well-maintenance or well-rehabilitation
program, fouling can usually be mitigated. If well
fouling is left unattended, however, it may reach a
point where well rehabilitation is infeasible and the
well will need to be reinstalled.
In general, fouling blocks die well screen and provides
resistance to water entering the well. As a result, the
water level in the well decreases until there is a
sufficient hydraulic gradient directing water into the
well to balance that being extracted by the pump or
until the water level in the well drops below the pump.
Fouling may therefore occur with no noticeable change
in the extraction rate until the pump shuts down.
The best indicator of well fouling is the specific
capacity of the well, which is the extraction rate
divided by the drawdown (note that the ground water
elevation under both static and pumping conditions is
required to calculate drawdown). A baseline level of
specific capacity should be recorded when the well first
becomes operational. Specific capacity should then be
measured regularly and a trend line plotted. The
average extraction rate should also be compared to the
design extraction rate. If a decrease in specific
capacity or the extraction rate of more than 10% is
noted, well-rehabilitation is likely required. In some
cases, a well-maintenance program may need to be
implemented. Note that for a well operating at a
constant rate, drawdown trends provide the same
information as specific capacity trends. For wells
where ground water elevations cannot be measured
due to restrictions in access, measurement of the
extraction rates will have to suffice (i.e., decreasing
rate over time may indicate fouling).
Regional changes in the ground water elevations due
to drought, recharge, or off-site pumping should be
considered by reviewing ground water elevation trends
in nearby monitoring wells. Regional increases in
ground water elevations could mask a decrease in
specific capacity, and regional decreases in ground
water elevations could falsely suggest a decrease in
specific capacity.
A general guide to well maintenance developed by the
U.S. Army Corps of Engineers (USAGE) can be found
in USAGE Engineering Pamphlet EP 1110-1-27.
If Applicable, Evaluate Injection Well or Infiltration
Gallery Performance
If a system discharges treated water to the subsurface
through injection wells or an infiltration gallery, the
performance of these points should be monitored to
ensure fouling does not limit the discharge capacity,
and therefore the capacity of the entire P&T system.
Many of the same procedures for monitoring
extraction wells can be used to monitoring injection
points. The discharge rate and the increase in ground
water elevation within the wells or galleries are
measured rather than the extraction rate and the
drawdown.
Increases in the water levels within the reinjection
points, given a constant discharge, indicate either
regional increases in ground water elevation or fouling
of the injection wells. Regional increases in the
ground water elevation can be confirmed or rejected
by reviewing ground water elevation trends in nearby
monitoring wells. If increases are not due to regional
influences a rehabilitation program may need to be
implemented, and the treatment system should be
reviewed for options to minimize solids in the
effluent.
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D. EVALUATING COST-EFFECTIVENESS
OF THE P&T SYSTEM
An evaluation of system cost-effectiveness should
consider life-cycle costs because life-cycle costs
account for up-front capital expenditures, annual costs,
the time frame for system O&M, and costs for
replacing or updating the system. For example, by
considering life-cycle costs, a site manager can better
evaluate if up-front expenditures for more efficient
equipment or for making modifications will result in
overall savings to the project. Because it may be
difficult to calculate life-cycle costs due to the
uncertainty of a remedy time frame, best estimates
should be used. Depending on the organization
funding the remedy, life-cycle costs may need to be
expressed in net present value, which considers the
effects of inflation and the rate of investment returns on
future expenditures. Most commonly used spreadsheet
software applications can calculate net present value
when provided with a remedy time frame, adjustment
or discount rate, and system costs.
Identify Significant Cost Items
For an operating system, generally the first step in
evaluating the cost-effectiveness of a P&T system is to
identify the significant cost items. A table of average
annual costs, similar to the one presented in Example 2,
should be developed for the site based on previous
invoices and/or contracts. Using annual rather than
monthly costs will account for costs that vary monthly
or that are incurred on a quarterly, annual, or irregular
basis. The areas of highest costs will likely be the
areas where the greatest savings can be realized.
Site managers should keep in mind that reducing
annual costs may require capital expenditures and that
cost-effective modifications are those that result in
overall savings to the project. Typically, a site
manager should expect the savings in annual costs
expressed in net present value to pay for the capital
expenditures in less than 5 years, though the acceptable
time frame for payoff is highly dependent on the
expected duration of the remedy.
Maintain and Clean Equipment as Appropriate
Proper maintenance of system components can help
maximize the efficiency of the treatment plant. All
system components should be maintained and cleaned
as needed, especially if biological or chemical fouling
is a concern. Even relatively passive treatment
Example 2
Hypothetical Annual Costs for P&T O&M
Category
Labor
• PM &. reporting
• O&M operator
• sampling labor
Utilities
• electricity
• gas
• public water
• phones
Materials
• GAC
• chemicals
• filters
Chemical analysis
Disposal costs
Total
Annual
Cost
$30,000
$49,200
$28,800
$54,000
$9,600
N/A
$2,400
$12,000
$30,000
$2,400
$36,000
$24,000
$278,400
% of Total
Annual Cost
39%
23.5%
16%
13%
8.5%
100%
components, such as clarifiers in metals removal
systems, may require cleaning to effectively reduce
solids in the process water. However, a cost-benefit
analysis should be conducted and discharge
requirements should be considered to determine the
appropriate frequency for maintenance and cleaning
for a P&T system.
Modify Inefficient System Components
Modifying inefficient system components can yield
significant savings, especially in the use of utilities
and materials. Four common examples of inefficient
system components are described below.
Oversized Motors
Pumps, blowers, air compressors, and other equipment
have motors that have different power requirements,
measured in horsepower (hp), depending on the
amount of air or water they must move and against
what head they must move it. In many cases,
oversized motors are being used and the valves are
throttled back to reduce the flow. However, this
approach does not reduce power usage and may also
decrease the motor's life span.
12
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The following steps should be taken on a regular basis
to reduce the use of oversized motors:
• inventory all pumps, blowers, and air
compressors
• note their power requirements (in horsepower)
• use their manuals and O&M data to compare
their specifications to the actual task
• conduct a cost-benefit analysis of replacing
oversized equipment with new equipment or
installing a variable speed drive that will allow
an operator to control its power usage
• replace equipment that demonstrate significant
cost savings (i.e., can pay off cost of
replacement in a few years)
In general, assuming 75% motor efficiency and
$0.10/kilowatt-hour (kWh),
1 horsepower = $70/month
The cost savings of replacing a large blower for a
smaller, more efficient one is shown in Example 3.
Example 3
Figure 2
Savings from Replacing a 50-hp Blower with;
15-hp Blower
50 hp x $70/monlh/hp
15 hp x $70/month/hp
$3,500/month
- $l,050/month
Savings $2,450/month
Payoff tone: Less than one year assuming a capital
cost of $25,000 to replace the blower.
Over-designed Treatment Components
Individual components of the treatment system may be
over-designed with respect to the operational
parameters of die system, such as pumping rate or
influent concentration. Figure 2 illustrates why some
systems may be over-designed.
Comparing design parameters and actual parameters for
a treatment system and its components will help
Maxi
A
«J 4 -
1
2 -
0 -
mum RI Concentrations Overestimate
ctual Concentrations During P&T
I — _ _a I |"-- R |
concentration |— ,
Blended influent to
tre a tm e n t p la n t fro m
extraction we Us
/
/
Rl Design & O&M O&M O&M
Installation Yr. 1 Yr 3 Yr. 5
Tim e (years)
The concentration of PCE is measured during the
remedial investigation and then during O&M. Due to
pumping and the blending of water from different
extraction wells and overall mass reduction in ground
water, the influent concentration to the treatment plant
during O&M is often much lower than the maximum RI
concentration observed in the aquifer.
determine if components are oversized. As shown in
Example 4, conducting a cost-benefit analyses will
help determine if it is cost-effective to eliminate or
replace oversized components.
Example 4
Evaluating Over-design of Treatment for Air
Stripper Offgas
Operational Parameters
• 36 Ibs of VOCs per day in plant influent
• 0 Ibs of VOCs per day in plant effluent
• 36 Ibs of VOCs per day in air stripper offgas
Offgas Treatment (Thermal Oxidizer) Parameters
• designed for 160 Ibs of VOCs per hour
• requires $22/)00/month for natural gas
• requires $3,000/month for electricity
Solution: Replace thermal oxidizer with an onsite
carbon regeneration system.
• designed for over 50 Ibs of VOCs per day
• capital costs for implementation: $370,000
* utility costs of $2,000 per month
• estimated annual cost savings: $276,000 per year
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Ineffective Filtration Media
Filters are often included in treatment trains to remove
solids and metal precipitates. Filters help the treatment
plant meet discharge criteria for solids and metals.
They also protect the other treatment components, such
as GAC units, that might otherwise become fouled.
For instance, if filters are ineffective, the GAC units
may require more frequent replacement due to fouling
than would otherwise be required due to chemical
loading alone. Because costs of GAC replacement
substantially exceed the cost of properly maintaining a
filtration unit, ineffective filtration may result in
increased O&M costs.
Premature fouling of carbon or decreased reduction in
total suspended solids are indications of ineffective
filtration units.
Inefficient Air Strippers
Removal of volatile organic compounds (VOCs) is
often most effectively achieved with air stripping.
Packed towers and tray aerators are two types of
systems that, when properly designed, effectively strip
VOCs.
In some cases, typically in systems that at one point
utilized biotreatment, air stripping is achieved by
diffused air strippers (i.e., large storage tanks that use
large blowers to diffuse air through process water).
Such an approach typically uses a 20- horsepower
blower and results in 80% removal of VOCs whereas a
well-designed tray aerator may use a 5-horseblower
blower and achieve 99% removal of VOCs. Thus,
switching to a well-designed air stripper from a
diffused air stripper might reduce power costs
substantially and allow for removal of a GAC polishing
step due to improved removal efficiency.
Remove Redundant or Unnecessary Components
Eliminating unnecessary components that stem from
over-design or changing site conditions may result in
substantial savings. Three common examples of
redundant or unnecessary components are provided.
Metals Removal Systems
Metals removal is a common treatment component that
may be unnecessary shortly after a system becomes
operational and functional, at some other point before
site closure, or with proper filtering. Because elevated
metals concentrations in extracted water may be due to
suspended solids, proper filtering of process water can
often eliminate the need for a metals removal system.
Metals concentrations in extracted water may also
decrease over time because the mobility of metals is
sensitive to their oxidation states. Metals such as iron,
manganese, and arsenic become relatively immobile
when oxidized and relatively mobile when reduced.
Ground water with elevated levels of organic
contaminants may initially have highly reducing
conditions, making these metals more mobile. Once
pumping begins, however, the reducing conditions
may diminish due to mixing and/or contaminant
removal. Therefore, as remediation progresses, the
extracted water may have significantly lower metals
concentrations than anticipated from remedial
investigation data. In some cases, metals
concentrations may fall below the discharge criteria,
rendering metals treatment unnecessary.
Metals treatment via precipitation involves chemicals
for pH adjustment, significant labor (i.e., one or more
operators full time), and generation and disposal of
filter cake. As a result, metals removal systems are
extremely costly and should be eliminated, shutdown,
or bypassed if they are unnecessary. At some sites
where metals, such as iron and manganese, are not
COCs but frequently cause fouling of other system
components, it may be cost-effective to frequently
clean the P&T system than it is to operate a metals
removal system.
GAC Polishing Steps
Although not always the case, air strippers can often
reduce VOC concentrations in extracted ground water
without a GAC polishing step. If a GAC polishing
step is planned for or is part of a P&T system, efforts
should be made to optimize the air stripper because
the polishing step may not be required. Often,
strippers can be made more effective by increasing the
air/water ratio, changing the packing material (for
packed towers), or adding another tray (for tray
aerators). A second air stripper can also be considered
as a polishing step. A cost benefit analysis should be
conducted to determine which approach is most
appropriate for a specific site.
Parallel Systems or Components
Providing redundancy (e.g., a spare component,
perhaps installed in parallel to the operational
component) for filters or mechanical equipment such
as pumps and blowers is often warranted. However,
splitting the flow of process water into parallel
treatment trains or providing an additional treatment
14
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train as backup is not usually warranted for removal of
VOCs or metals. The components of these treatment
trains require minimal downtime, and because ground
water moves slowly, maintaining and operating parallel
systems to prevent a few days of downtime per year is
not cost-effective. If one train of an operational
parallel system can treat the extracted water, managers
should consider bypassing or eliminating the other train
if savings from labor and maintenance are expected to
exceed the capital cost of the modification.
Consider Alternate Discharge/Disposal Options
The following discharge options are typically available
for treated water:
publicly owned treatment works (POTWs)
• storm sewer and surface water (both regulated
under National or State Pollutant Discharge
Elimination System, NPDES or SPDES,
programs)
• reinjection to the subsurface (regulated by
Underground Injection Control Program)
Each of these options have positives and negatives
associated with them, and these are summarized in
Exhibit 8. Site managers should regularly evaluate
discharge options to determine which is most cost
effective and should consider capital, negotiation, and
sampling costs of the options in this evaluation.
Disposal of filter cake from biotreatment or metals
precipitation can generally be disposed of as non-
hazardous waste if it passes Toxicity Characteristic
Leaching Procedure (TCLP) testing. This costs less
than disposal at a hazardous waste facility. If these
materials are considered "listed" waste because of past
site use, but the wastes pass TCLP testing, then "de-
listing" should be pursued. Savings of up to $200 per
ton could result from a change in disposal practices.
For some sites, this could translate to savings of up to
$4,000 per month in costs associated with
transportation and disposal of such wastes.
Identify Opportunities for System Automation
Common treatment components such as air strippers
and GAC units, when properly designed and installed,
have been proven reliable through years of testing in
the field. As a result, when these systems are installed
with alarms, auto shut-offs for high levels, and auto-
Exhibit 8
Discharge Alternatives for Water from a P&T System
Discharge alternative
Positives
Negatives
Publicly-owned treatment
works (POTWs)
require relatively flexible discharge
standards compared to other alternatives
(typically 2.13 mg/L total toxic
organics)
accept and treat some hard to treat
contaminants (ketones and ammonia)
may refuse to accept treated or
untreated ground water due to dilution
or lack of capacity
require payment (approximately
$0.002 to $0.03 per gallon)
often require pretreatment
Storm sewer and surface
water
typically do not require payment
often readily accessible from treatment
plant
minimal capital costs
for resource conservation, some areas
do not allow discharge of ground water
to surface water
discharge criteria is generally stringent
(e.g., MCLs for naturally occurring
inorganics)
lengthy permitting process
frequent sampling requirements
Reinjection to subsurface
(reinjection wells or
infiltration galleries)
may help with hydraulic control of
plume
relatively easier permitting process
biotoxicity testing not required
may hinder hydraulic control of plume
may require substantial capital cost
potential issues with fouling of wells
requires space for wells or galleries
15
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dialers to remotely contact an "on-call" operator, they
can often run unattended with only weekly or biweekly
checks and maintenance. Metals removal systems may
require more attention man these units, but the
chemicals required for operation may be automatically
dosed and batched thereby reducing operator labor to
40 hours per week. System operators should be local,
(i.e., located within an hour from the system, if
possible) to quickly address potential alarms and to
minimize or eliminate per diem or travel costs. In some
cases, remote access to system data and controls by
modem can further reduce operator labor.
Opportunities for increased system automation and
decreased operator labor can result in significant cost
savings. The table in Exhibit 9 provides general
guidelines, based on information gathered during
reviews of 20 Fund-lead P&T systems, as to the
amount of labor typically required for various types of
treatment plants.
A number of factors can affect these guidelines. For
example, additional labor may be required if substantial
maintenance is required for recurring issues, such as
well or system fouling due to iron bacteria. Very few
systems should require more than 2 full time operators,
and with proper automation, sites should not require a
24-hour presence.
Eliminate Excess Process Monitoring
Process monitoring is generally required to demonstrate
the effectiveness of the treatment plant but can be
costly if laboratory analysis is required. Therefore,
excess process monitoring should be eliminated, and
when possible sensors should be used to determine the
performance of the treatment components. Many
commonly used treatment technologies, such as air
strippers and granular activated carbon, have been used
successfully and reliably for years and minimal
monitoring is necessary to demonstrate their
effectiveness once the system is operating. In many
cases, a metals removal system can be effectively
operated based on sensor readings of total suspended
solids and oxidation-reduction potential, and its
performance can be cost-effectively evaluated by
analyzing samples from the plant effluent for metals.
Process monitoring samples that are collected are
generally most cost-effectively analyzed in off-site
laboratories. Although the use of inexpensive field kits
are often beneficial and cost-effective as screening
level data, the use of staffed on-site laboratories or
sophisticated on-site analytical equipment, such as gas
chromatographs, are often not cost effective over time.
Such laboratories or equipment may have been
Exhibit 9
I
General Guidelines for Labor Typically
tequired for Various Types of Treatment Plants
Treatment Plant
* air stripping
• vapor phase GAC
foroffgas
treatment
• GAC treatment
• metals removal
• filtration
• metals removal
• filtration
• air stripping
'.•;.•; GAC :.,:;..::.:..
Estimated Labor
• weekly checks by local
operator (8- 12
hours/week)
* quarterly checks by
engineer
• weekly checks by local
operator (8- 12
hours/week)
• quarterly checks by
engineer
• one or two operators
full time (1 or 2 x 40
hours/week)
• two operators full time
(2 x 40 hours/week)
included during the design or early in O&M, when
frequent sampling was necessary for system
"shakedown". However, the need for this frequent
sampling may be eliminated when the system reaches
steady-state or continuous operation. Except in rare
cases, a reduced number of samples can be analyzed in
an independent off-site laboratory with a one-week or
even 24-hour turnaround time for a lower cost than the
labor and materials required to maintain and staff an
on-site laboratory or calibrate and operate
sophisticated equipment.
If frequent sampling is required for a treatment plant
during "shakedown", a temporary period of on-site
monitoring could be arranged if cost-effective
compared to sending samples off site. This approach
is generally more cost effective than arranging and
staffing a permanent laboratory.
E. CONTRACTING CONSIDERATIONS
An O&M contract for a P&T system should clearly
outline the responsibilities of the O&M contractor.
However, because of changing site conditions,
progress toward site closure, and optimization
opportunities, the contract should also allow for
reductions in the scope of work.
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Clearly Establish Responsibility For Key Items
Oeratin Procedures and Site Records
Contracts should clearly task the contractor with
development and updates to an O&M manual that
provides fundamental information about the system and
standard operating procedures. The contracts should
also task the O&M contractors with maintaining site
records and providing transition training for future
O&M contractors.
Evaluation of P&T System Performance
O&M of a P&T system requires regular evaluation of
the remedy's effectiveness. These evaluations need to
consider performance of both the above-ground
treatment processes and responses in the subsurface.
Because many parties (site owner, state and federal
regulators, contractors, and possibly subcontractors)
are involved in the O&M of a P&T system, the
responsibility for evaluations should be clearly defined
and tasked to the O&M contractor in the O&M
contract.
Evaluations can be divided into three components:
• data collection
• data analysis and interpretation
• reporting
O&M contracts typically task the responsibility for data
collection and reporting but may assume data analysis
and interpretation is the responsibility of the site
owners or regulators. In such cases, sufficient data
analysis may not occur to monitor system effectiveness.
To avoid such situations, a contract should clearly task,
to the contractor, all data evaluation and analysis.
Further analysis could then be conducted by the site
manager, if necessary.
Key items that should be included in a typical O&M
report are listed in Exhibit 10.
Compare Lump Sum versus Cost Reimbursable
Contracts should clearly delineate financial
responsibility. Example 5, on the following page,
provides summaries of two contracting options for
operation of the same P&T system. It illustrates that
lump sum is most effective for items that are highly
predictable while cost reimbursable is more effective
for items that are more uncertain. Examples of items
that should be cost reimbursable are materials, utilities,
and unexpected or emergency repairs or modifications.
Plan For Reductions in Scope
Due to changing site conditions and progress toward
cleanup, reductions in the scope of work may be
warranted during a contract. Therefore, well-written
contracts should provide for potential reductions in
scope. The following are examples of areas where
scopes may be reduced during a long-term contract.
Process monitoring: Substantial process monitoring
may be required, especially during "shakedown".
However, when stable operation is achieved, process
monitoring can be reduced.
Ground water sampling: During the first few years of
operation, quarterly ground water monitoring may be
Exhibit 10
Key Items to be Included in an O&M Report
Subsurface performance
• ground water quality data and updated plume map(s)
• ground water elevations and updated potentiometric
surfaces)
• extraction well rates and specific capacities
• concentrations at extraction wells
• updated trend analyses
• ; capture zone analysis • ;
Treatment plant performance
* plant influent concentrations presented along side
design influent concentrations
• plant effluent concentrations presented along side
discharge criteria -I'M
• plant flow rate and operational parameters (e.g.,
head differentials across filters, air stripper air to
water ratio, ete.)
system efficiency along side design efficiency
materials and utility use
maintenance items
identification and description of exceedances
system downtime
Interpretation '..••.'..•, :
* are short-term goals being met? ;
* are long-term goals expected to be met?
• evidence of progress toward goals (trends in
concentrations, etc.)
• revised site conceptual model;
Other Significant O&M Activities
* system modifications
• non-routine maintenance and costs (e.g., well-
rehabilitation)
• communication with neighbors or local/State •
authorities
• Other significant site activities
17
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merited at many sites. However, once the plume is
found to be relatively stable, sampling semi-annually,
annually, or at some other frequency may be merited,
and the number of sampling locations and/or
parameters may also be reduced. Provisions in the
contract should exist to reduce the sampling scope of
work accordingly.
Reductions in materials and labor: If a metals removal
system or another treatment component is no longer
necessary because influent concentrations meet
discharge requirements, that system should be removed
and the associated labor eliminated.
Examples
Lump sum versus cost reimbursable
Hypothetical P& T System
* system addresses polyaromatic hydrocarbons (PAHs)
from a former wood treating facility.
• extracted water is pumped through an oil/water
separator and then through large GAC units.
• replacement of GAC units occurs twice every year and
costs $20,000 per replacement
• electricity rates have varied from $0.05 to $0.10 per
kWh over the past 5 years. On average 20,000 kWh
are used per month (240,000 kWh per year).
Contracting option 1: lump sum
Contractor bids $750,000 lump sum for 3 years of O&M
assuming six potential GAC replacements ($120,000), a
possible electrical rate of $0.12 per kWh ($28,800 per
year) to account for uncertainty, and $50,000 for non-
routine maintenance
Contracting option 2: combated lump sum/cost
reimbursable
Contractor receives $495,000 lump sum for labor,
reporting, sampling and analysis for 3 years of O&M. To
remove uncertainty from the lump sum bid, the site owner
pays for GAC replacements, electrical usage, and non-
routine maintenance as required (cost reimbursable).
Scenario:
During 3 years of O&M, improved filtration and
decreasing concentrations reduce frequency of GAC
replacement to once per year (3 total), electrical rates are
approximately $0.06 per kWh, and $25,000 of non-
routine maintenance is required.
Costs for contract 1: $750,000
Costs for contract 2: $623,200
Difference:
$126,800
Lesson: Lump sum is more effective for items that are
highly predictable, and cost reimbursable is more
effective for items that are uncertain.
F. OPTIMIZATION AND CONTINUOUS
IMPROVEMENT
Continuous improvement can occur by periodically
evaluating goals, performance, and cost-effectiveness
and then implementing changes from these
evaluations.
Periodic third-party (or independent) reviews of a
P&T system that include a review of site documents
and discussions with the site stakeholders are
recommended. These reviews, when performed by a
team of experts, can provide the following benefits:
• an unbiased, external review of system
operation and costs
• expertise in hydrogeology and engineering
• specific knowledge and experience with new
or alternative technologies
• experience gained from designing, operating,
or reviewing other systems
• a fresh perspective on the problems at hand
and the current remedy
System improvement, however, will only occur if
recommendations are implemented.
G. CITED RESOURCES
»•»***•**
U.S. Army Corps of Engineers, Engineer Pamphlet
1 1 10-1-27. Available at http://www.uS3ce.army.mil
This document was prepared by GeoTrans, Inc. for U.S.
EPA under Dynamac Contract No. 68-C-99-256,
Subcontract No. 91517, Task AD02-105. Mention of trade
names or commercial products does not constitute
endorsement or recommendation for use.
This document may be downloaded from EPA's Clean Up
Information (CLUIN) System at http://www.clu-in.org.
Hard copy versions are available free of charge from the
National Service Center for Environmental Publications
(NSCEP) at the following address:
U.S.EPANSCEP
P.O. Box 42419
Cincinnati, OH 45242-2419
Phone: (800) 490-9198 or (513) 489-8190
Fax:(513)489-8695 _
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