&EPA
United States Environmental
Protection Agency
United States Army
Corps of Engineers
July 1991
Engineering Issue
DATA GAPS IN REMEDIAL DESIGN
John E. Moylan
The Regional Superfund Engineering Forum Is a
group of EPA professionals, representing £PA's
Regional Suparfund 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
?f Engineers (US ACE), Kansas City District,
Geotechnical Branch In cooperation with the EPA
Engineering Forum. Engineering Forum review
and comments were coordinated by Ken Erlckson
(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
•"or use by RPWs 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 toie.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 worn during the RI/FS phase has
typically been considered the province 01
scientists whereas engineers are given me
functional lead during RD/RA. The'engineers
have not always been requested to provide
significant input during Rl/FS. Similarly,-the
scientists have often not been made ava (able
during RD/RA, Consequently, some' ROOs or
settlement agreements have dictated rertiedies
that are only marginally appropriate or net'
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 aspec 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 L sed by
Superfund, The starting point is the Regional
Engineering Forum representative and other
Regional technical specialists, such as th»
Technical Support Sections formed by so Tie
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
Twhnolojjr Snrtwiilpri Qftlci'•:
-------
(under the auspices of the OSWER Technology
Innovation Office 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, 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 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 materials
from a distant borrow pit will added 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 also
should 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.
Geochemical Data collection often can 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 overdesigned, 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 TOC 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.
Geotechnical 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
received 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. Atterberq 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. Excavatability - While there is no one test or
set of tests to define this design parameter,
evaluation and judgements should be made in
the pre-ROD phases concerning excavatability
when excavations of any kind are required in
the remedy. Excavatabilty 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.
Hydrogeological Data are routinely collected
both during the RI/FS and RD phases.
However, several aspects will be discussed that
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 also will 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
suggests in which phase or phases of the
remediation process it is advantages to acquire
the data.
-------
1, Site lor
en
1. Limited in RF/FS in fiD
2. in RD
3. HA
4- During operation and maifii®J"taf»c.e
------- |