United States Environmental
Protection Agency
United States Army
Corps of Engineers
July 1991
v>EPA Engineering Issue
DATA GAPS IN REMEDIAL DESIGN
John E. Moylan
The Regional Superfund Engineering Forum is a
group of EPA professionals, representing EPA's
Regional Superfund Offices, committed to the
identification and resolution of engineering issues
impacting the remediation of Superfund sites.
The Forum is supported by and advises the
Superfund Technical Support Project.
This paper was prepared by the U.S. Army Corps
of Engineers (US ACE), Kansas City District,
Geotechnical Branch in cooperation with the EPA
Engineering Forum. Engineering Forum review
and comments were coordinated by Ken Erickson
(Region IX), Forum Co-chair. For further infor-
mation contact John Moylan, at FTS 867-3455 or
Ken Erickson, FTS 484-2324.
Introduction
As the number of Superfund sites in the phases
of Remedial Design (RD) and Remedial Action
(RA) has grown, we have become increasingly
aware of the adverse effects of inadequate or
insufficient design data. This paper is intended
for use by RPMs as a checklist or reminder to
consider certain aspects of RD/RA data needs as
early as possible in the life of a Superfund site.
Most of the items have been gleaned from the
collective memory of EPA and USAGE personnel
who have learned some of the lessons the hard
way.
The items addressed include:
types of data where quality or quantity is most
often found to be-inadequate or have the
greatest effect on successful RD and RA;
examples of why these data are needed;
data needs for particular remediation features;
Many design problems causing schedule slippage
or cost overruns in either RD or RA can be
attributed to site characterization data that are not
sufficient for purposes of design. (No attempt is
made in this paper to address potential
inadequacies in interpretation of the site
characterization data.) These data gaps affect
not only highly technological treatment processes
but also the more mundane aspects of
remediation such as caps and liners.
Technical work during the RI/FS phase has
typically been considered the province of
scientists whereas engineers are given the
functional lead during RD/RA. The engineers
have not always been requested to provide
significant input during RI/FS. Similarly, the
scientists have often not been made available
during RD/RA. Consequently, some RODs or
settlement agreements have dictated remedies
that are only marginally appropriate or not
effective at all, much more costly than
anticipated, or virtually impossible to implement.
The RPM should consider that a broad-spectrum
technical assistance team is a key aspect to
successful management of the site from
beginning to end. Under ideal circumstances,
this team should consist of members from
organizations other than the contractors used by
Superfund. The starting point is the Regional
Engineering Forum representative and other
Regional technical specialists, such as the
Technical Support Sections formed by some
Regions or experienced RPMs, who can
participate in the peer review process. Other
resources include the Technical Support Centers
(under the auspices of the OSWER Technology
U.S. Army Corps of Engineers
Kansas City District
Geotechnical Branch
Technology Innovation Office: : :
Ottfct of Solid Wait* and Emwgency-;
Rwpon»», USEPA, Wwrtilngton, D.C,
Walter W.Kovallck, Jr., Ph.D.
::Director ;:;: '.'.''-:.' '
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Innovation Office Technical Support Project), U.S.
Army Corps of Engineers, U.S. Bureau of
Reclamation, U.S. Bureau of Mines, state
agencies, and so forth.
It should be noted that typically design engineers
are accustomed to working from a clearly defined
problem. Unfortunately, most subsurface and
ground water contamination sites lack the degree
of site characterization needed to clearly define
the design at the beginning of the RD phase.
Therefore, it is important that the scientific
disciplines be available throughout the entire
RD/RA period to further define site conditions and
provide interpretations for the engineer. This will
help assure an expeditious and satisfactory
implementation of the design.
A few examples of problems associated with
incomplete site characterization data follow:
1. Soils properties and handling characteristics
are often poorly evaluated or even ignored when
considering various remediation technologies
which require materials excavation and
processing.
2. Volatile emissions during excavation and
handling of contaminated soils are often not
anticipated.
3. Lack of information on temporal and spatial
variations in contaminant loading in ground water
remediation decisions can lead to inefficient
designs.
4. No pre-ROD consideration of availability of
utilities resulting in underestimation of costs or
schedule.
5. Poor understanding of the permeability of
slurry wall key layer leading to unacceptable
leakage.
6. Ground water treatment processes which
focus on the contaminants of interest but ignore
total ground water chemistry, especially the
anions and cations present, will impact the
effectiveness of the treatment process.
7. Solvent extraction of explosives from soil is
feasible, however, the unrecognized instability of
the residue can be disastrous.
8. Cap designs which utilize the cost-
effectiveness of geosynthetics but require slopes
on which geosynthetics are not. stable or caps
which require the use of low permeability clays
but don't evaluate the availability of suitable clay
borrow material can be impractical to construct or
very costly.
9. Excavation limits may be defined based on
chemical analysis of bore hole samples and not
account for contaminant migration along
secondary pathways, e.g:, root holes. Trenching
and careful inspection and sampling may alleviate
this problem.
10. The presence of debris or boulders may not
be recognized or fully appreciated during the
analysis of remedial alternatives if bore holes
alone are used to investigate the limits of waste.
The term geochemical is used rather than the
more narrow chemical term in order to emphasize
the importance of understanding the chemical
processes operating in the geological
environment in order to implement effective
remediations. The importance of quality
analytical chemistry is already well understood
and appreciated, however, our understanding of
ongoing chemical processes needs improvement.
The following paragraphs identify some
commonly overlooked data requirements and
include examples of problems resulting from the
data gaps.
Site Data needs are often overlooked in the
pre-ROD/consent decree phase and even well
into design. Unforeseen cost increases, time
delays, and contract modifications can and do
result. Some common data needs include:
1. Topographic Surveys - The need should be
readily apparent, however, this aspect is often
overlooked. In some instances, available general
topographic mapping is used without verification.
Consequently during RA, excavation or fill
overruns or underruns or impossible site drainage
are discovered which require contract
modifications. Property boundary surveys and
adequate horizontal and vertical controls are also
included in this category.
2. Utility Availability - Water, gas, power, and
sewer services required for remedy
implementation must be identified. In addition,
leaking industrial sewer lines might be
contamination sources and previously unidentified
utility lines crossing a remediation site can cause
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contract shutdown pending their relocation or
protection.
3. Borrow Availability - In most cases, site
remediation which includes earthwork, e.g., liners,
caps, slurry walls, etc., require the utilization of
earth materials to effect the remediation. When
those materials are not available from required
on-site excavation, they must be obtained
elsewhere and are referred to as borrow. In
some areas suitable borrow is scarce. The costs
of trucking suitable material from a distant borrow
pit will add significant cost and transportation
problems if not recognized. As an example, a
5-acre cap with an average thickness of 3 feet of
soil, requires almost 25,000 cubic yards or
approximately 1,400 truckloads of suitable earth
borrow material. The availability of admixtures
such as fly ash, cement, and lime for stabilization
should also be considered in this category.
4. Transportation Network - The proximity of
suitable roadways and/or rail lines is important to
remedies requiring the transportation of heavy
equipment and earth materials into the site or
contaminated or treated wastes from the site.
Local opposition to frequent heavy truck traffic
and damage to streets and roads, especially
through residential areas, must be anticipated.
Geochemlcal Data collection can often be
improved to more confidently select effective
remedies and better effect quality RD and RA.
Some examples include:
1. Multiple Sampling Rounds - In too many
cases, remediation decisions are made which
are based on single or poorly timed, multiple
ground water sampling rounds. Time allowed for
RD often doesn't provide for seasonal sampling.
As a result, chemical loading may exceed
treatment plant capability, the plant may be over-
designed, or the operating plan is not optimized
to accommodate variations in loading.
2. Anion/Cation Analysis - These analyses are
inexpensive, yet if they are overlooked in ROD
preparation, the designed treatment train may be
either more expensive than anticipated or
ineffective if not detected during RD. Eh, pH, and
TOG are other chemical parameters that must be
considered for effective RD.
In addition, caution should be exercised when
unusually high metals analyses are obtained from
turbid ground water samples. If these analyses
are used for treatment plant design, the design
and cost estimates can be unrealistic. Total
chemistry also impacts well design. Anion and
cation precipitates will prematurely clog injection
wells if not recognized and treated.
Geotechnlcal Data must be gathered for many
types of remedies, both for purposes directly
related to the remedial process and for design
auxiliary to the actual remedial process, such as
building foundation design or excavations.
1. Soil Moisture Content - The natural moisture
content of site soils, especially fine-grained soils,
is valuable information both in the pre-ROD and
RD phases. As examples, the moisture content
of contaminated soil that will receive thermal
treatment affects fuel consumption and the
moisture content of a fine-grained foundation soil
can be an indicator of the soils strength and
consolidation characteristics.
2. Atterbero Limits - These parameters define
the plasticity of fine-grained soils, give the
geotechnical designer an early indication of the
strength of that soil, especially when evaluated
with moisture content, and can be an indicator of
contaminated soil handling and processing
characteristics. The test is relatively inexpensive
but the results can be very useful.
3. Soil Strength Parameters - Generally not
needed prior to the RD phase. Some design
features requiring soil strength testing include
structure or building foundations, significant
excavations, dredging, and slurry wall trenches.
Blow counts from Standard Penetration Tests can
be used as an early indication of soil strength.
4. Gradations - Some representative gradations
or particle size distribution analyses done in the
RI/FS phase can be very helpful in estimating
approximate permeability and for designing
efficient monitoring wells. Gradations are
required for the design of such things as
collection drains and withdrawal wells and in
evaluating soils handling and processing
characteristics.
5. Excavatabilitv - While there is no one test or
set of tests to define this design parameter,
evaluations and judgments should be made in the
pre-ROD phase concerning excavatability when
excavations ot any kind are required in the
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remedy. Excavatability includes such factors as
whether the material can be machine excavated,
the necessity for blasting, the existence of
boulders or cobbles, the need for dewatering, etc.
None of the excavatability factors should be
minimized since all of them can greatly impact
the final cost of remediation.
6. Landfill Subsidence - Remediations often
include capping an existing landfill and perhaps
incorporating a gas collection and venting system.
Many such landfills are still subsiding with
attendant surface disruption capable of adversely
impacting the effectiveness of the cap and vent
system. Carefully surveyed settlement data
collected throughout the RI/FS phase are
invaluable for remedy selection and to support
design. Settlement data collection should
continue through RD and RA and into the
operations and maintenance phase if
displacements are continuing and significant.
Hydrogeologlcal Data are routinely collected
both during the RI/FS and RD phases. However,
several aspects will be discussed which are
sometimes slighted but can be very important to
selection of an effective remedy and to proper
design and implementation.
1; Multiple Water Levels - In order to understand
the hydrogeological character of the site in
sufficient detail to select an effective remedy, it is
important that enough water levels be obtained to
define both the vertical and horizontal flow
directions seasonally and as they respond to both
natural and manmade recharge and discharge.
For example at a ground water contamination site
in the Plains States, the regional flow is severely
distorted locally by irrigation pumping during
several months of the year.
2. Detailed Stratigraphy - In too many cases,
stratigraphic detail has not been well developed
due to poor sample recovery often coupled with
too infrequent sampling intervals, lack of
geophysical logs, improper sampler selection,
field geologists poorly trained in logging methods,
or combinations of the above. Even relatively
minor variations in lithology have a strong
influence on contaminant migration and plume
development. This is an important factor during
pre-ROD, RD, RA, and even into the operation
and maintenance phase of both ground water
and vadose zone remediation.
3. Secondary Porosity Features - Joints,
defoliation planes, bedding planes, root holes,
etc., often strongly influence the overall gross
permeability of bedrock materials and
fine-grained soils, especially clays. In too many
cases these features are not targeted during site
exploration or if they are, the vertical features are
difficult to intercept and analyze. Careful
consideration of these features is warranted
during the RI/FS phase and remedy selection for
problems such as contaminated bedrock aquifers,
multiple stacked aquifers, and slurry walls keyed
into an impermeable layer. For sites such as
these, additional characterization will also be
needed during RD.
The various types of site characterization data
discussed in this paper are not needed or at least
not to the same degree for all features of site
remediation. The following remediation features
were considered:
1. Withdrawal & injection wells
2. Internal drains
3. Slurry walls
4. Slurry wall key layer
5. Caps
6. Chemical Stabilization
7. Ground water treatment
8. Landfills
. 9. Thermal treatment
10. Soil washing
11. Excavations
12. Dredging
13. Vapor extraction
Table 1 presents a summary of site
characterization data determined to be useful or
needed for remediation. The table also suggest
in which phase or phases of the remediation
process it is advantageous to acquire the data.
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Table 1. Site Characterization Data needed for Remediation
REMEDIATION FEATURE
DATA
Topographic Surveys
1,3
1,3
1,3
1,3
1,3
1,3
1,3,4
(/) Q
Utility Availability
Borrow Availability
Transportation Network
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