Report on the Review of the "Permit Writers' Guidance Manual for the Location of Hazardous Waste Land Treatment, Storage and Disposal Facilities Phase II"


SAB-EEC-86-016
Report
on the review of the
"PERMIT WRITERS' GUIDANCE MANUAL
FOR THE LOCATION OF
HAZARDOUS WASTE LAND TREATMENT, STORAGE AND DISPOSAL FACILITIES
PHASE II"
by the
Environmental Engineering Committee
Science Advisory Board
U. S. Environmental Protection Agency
June 1986

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EPA NOTICE
This report has been prepared as a part of the activities of the Science
Advisory Board, a public advisory group providing extramural scientific
information and advice to the Administrator and other officials of the
Environmental Protection Agency. The Board is structured to provide a
balanced expert assessment of scientific matters related to problems
facing the Agency. This report has not been reviewed for approval by the
Agency, and hence the contents of this report do not necessarily represent
the views and policies of the Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.

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TABLE OF CONTENTS
I. Principal Findings and Recommendations	4
II. Introduction
Background	6
Committee Review Procedure	6
III. Detailed Review Comments
General	8
Time-of-Travel Concept	9
Technical Validity of Selected Time Frames (10/100 years)	10
Adequacy of 100-Foot Flow Line	11
Additional Factors to be Considered	11
Specific Page-by-Page Comments	12
Appendix A (Committee Roster)
Appendix B (Memorandum From OSW)

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SECTION I
PRINCIPAL FINDINGS AND RECOMMENDATIONS
On December 6, 1985, Marcia E. Williams, Director, Office of Solid Waste,
(OSW) requested that the Science Advisory Board initiate a review of a draft
document entitled "Permit Writers' Guidance Manual for the Location of Hazardous
Waste Land Treatment, Storage and Disposal (TSD) Facilities (Phase II)." This
guidance was prepared by OSW in response to a requirement in Section 3004(o)(7)
of RCRA, which requires the Agency to publish "guidance criteria" for identi-
fying areas of vulnerable hydrogeology and to promulgate regulations specifying
criteria for the acceptable location of new and existing RCRA facilities.
The Environmental Engineering Committee was assigned the review, which has
now been completed. The Committee concentrated on four technical issues raised
by OSW in their request for SAB assistance (see Appendix B), but also commented
on other issues they felt were important. A summary of the Committee's princi-
pal findings and recommendations follows. More detailed comments will be found
in Section III.
General
A.	The Phase II Location Guidance is a clear and logical presentation of
criteria to be used in evaluating "vulnerable" hydrogeology.
B.	The methodology described in the Guidance is suitable for use with well-
prepared existing permit application data (though the Committee notes
that only a small fraction of the Part B's actually have enough infor-
mation for making time-of-travel calculations).
C.	The methodology is not detailed enough to make a complete site-specific
determination, but is an appropriate method for "triggering" a more de-
tailed analysis.
Time-of-Travel Concept
D.	Although simplistic, the time-of-travel (TOT) concept is technically
sound, and integrates various aspects of hydrogeology into a single
measure reflecting the potential for pollutant migration and exposure.
E.	The TOT concept depends heavily on the determination of effective poro-
sity, hydraulic gradient and hydraulic conductivity, and the guidance
should be more explicit in how data should be collected and used to
make these determinations.
The	permit applications (Part B) frequently do not have enough informa-
tion for	making these determinations (one study in which an SAB consultant was
involved	found that only about one application in ten had sufficient data), and
specific	guidance on what is needed and how it is to be collected must be pro-
vided.

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10/100 Year Time Frames
F.	The technical analyses in Appendix D and the Case Studies	do not ade-
quately support the time frames specified in the proposed	criteria (10
years for treatment and storage facilities, 100 years for	disposal
facilities). Other studies should be conducted.
While the case studies are useful, they may provide a false sense of
"proof" of adequate protection when site data indicates that the TOT criterion
has been met. It would be preferable to determine a TOT that would have been
estimated had hazardous chemicals not been disposed of at the site, since this
would provide a fairer evaluation of "false-positive" and "false-negative"
rates for applications of the criteria (a more extensive discussion of this
point will be found in Section III).
Adequacy of the 100-foot Flow Line Distance
G.	The selection of a 100-foot flow line distance is adequate for the
purposes of the guidance, which should be to trigger further analysis,
but will not accurately define hydrogeologic conditions at a specific,
site.
The 100-foot flow line is a conservative, practical engineering criterion,
and as such is adequate for the purposes of the guidance, but it cannot be jus-
tified on the basis of hydrogeologic homogeneity or flow pattern predictability.
Additional Factors to be Considered
H.	The guidance should include some means of evaluating the e~",cts of
seasonal variation on hydraulic gradient, as well as the effects on
TOT calculations of the physical and kinetic characteristics of the
toxic substances (such as partitioning or decay).
While the Guidance offers logical arguments for not including chemical
factors in the TOT calculation, the Committee feels that the Guidance could be
strengthened by a discussion of how the TOT would be affected if pollutant
transport and transformation were included in the analysis.

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SECTION II
INTRODUCTION
Background
In a December 6, 1985 memorandum (see Appendix B), Marcia E. Williams,
Director, Office of Solid Waste, requested that the Science Advisory Board re-
view a draft of guidance prepared by OSW on the definition of ground water vul-
nerability for RCRA facilities, a central facet of the OSW RCRA ground water
policy (and very much related to other RCRA provisions, including alternate
concentration limits, double-liner variances and waste-ban petitions). In the
December 6 memorandum, Ms. Williams asked that the SAB focus its review on the
following issues:
A.	Whether the time-of-travel (TOT) concept is technically adequate within
the context of its use with existing permft. application data.
B.	Whether the technical analyses of risk associated with the case studies
and theoretical modeling presented in Appendix D (of the Guidance) adequately
support the specified time frames.
C.	Whether the 100-foot flow line distance accurately samples local hydro-
geologic conditions (does it identify important influences on flow patterns
such as fractures and stratigraphic variations).
D.	Whether EPA should consider additional factors to enhance the accuracy
of the TOT tests, and if so, how the additional factors should be incorpor-
ated into the calculation.
The Phase II Location Guidance has two purposes. It proposes the "guidance
criteria" for identifying vulnerable hydrogeology required in Section 3004(o)(7)
of RCRA, and sets forth the basis for one of the "criteria for the acceptable
location" of hazardous waste land treatment, storage and disposal facilities
(Phase I of the Guidance dealt with the other four criteria). Appendices to
the Guidance also provide more detailed technical explanations of such things
as flow net/flow line determinations, TOT calculation in the unsaturated zone,
and risk-based justification of the TOT criteria.
Committee Review Procedures
A Subcommittee of the Environmental Engineering Committee was formed to
conduct the review (see roster, Appendix A). Several consultants were added to
assist with the review. Because of the extremely tight deadlines imposed by
OSW, the decision was made to send copies of the draft guidance to the Subcom-
mittee members well in advance of a meeting. This was done, and on February
12, 1986, an open public meeting was held in Washington, D.C. to receive a
briefing on the draft Guidance, and to complete the reveiw. At the conclusion
of the meeting, Subcommittee members agreed to prepare individual comments on

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the draft. These were then forwarded to Mr. Torno, Executive Secretary of the
Environmental Engineering Committee, who assembled all of the comments into a
coherent report. This report was then circulated by mail, and Mr. Torno re-
ceived further comments which were incorporated into this final version for
submission to the Agency. While it was not possible to prepare a completed
written report for the Agency by the end of February as requested, the Com-
mittee was able, at its February 12 meeting, to convey the essence of its
review to Agency staff.

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SECTION III
DETAILED REVIEW COMMENTS
General
The Permit Writers' Guidance Manual - Phase II is a clear and logical pre-
sentation of the criteria to be used in evaluating "vulnerable" hydrogeology.
The manual reflects the background and experience of the EPA and the consultants,
who played significant roles in its preparation - e.g. the firm of Geraghty and
Miller. The classification of ground waters into 3 types is a sound basis for
evaluation, comparable to previously established classifications of surface
waters. This manual is directed to Class II ground waters, which are defined
as current or potential sources of drinking water or other beneficial uses, as
contrasted to the special value of Class I and limited use of Class III.
The TOT^qq concept provides a good basis for integrating various aspects of
hydrogeology into a single informative measure. It reflects the potential for
pollutant migration and eventual exposure, and seems to be consistent with
generally held views of aquifer vulnerability. The guidance for computing the
TOTiqq appears appropriate. In particular, Appendix B on flow net construction
is well written and informative.
There is a need, however, for clarification of the intended use of the
TOTioo criteria. The proper use of the information in this guidance document
is to: (a) identify hydrogeology that may cause ground water to be vulnerable
to contamination when the site is used for a hazardous waste TSD facility and
(b) serve as a trigger or "red flag" when a particular site may be identified
as having possibly vulnerable hydrogeology. The Committee recommends that a
succinct, explicit statement about the intended use of the document and guidance
be included in the Executive Summary and the Introduction to the manual. That
statement should indicate that the document is for guidance and the approach is
intended to trigger the subsequent careful review of the site and the evaluation
of mitigation techniques to assure that groundwater contamination does not
occur.
The document indicates (page ES-4), that the purpose of the guidance
manual is to define "conditions of vulnerability that would make the site un-
acceptable for the siting of a hazardous waste facility in the absence of spe-
cial controls." This definition seems to infer that if a site "fails" the
vulnerability test, special controls will be necessary. The Committee does not
believe that the approach will indicate that special controls are necessary.
As indicated above, the approach is better used to trigger the need for more
detailed evaluations. Only after these detailed evaluations will the need for
special controls become clear.
The stated belief (page ES-4) also appears inconsistent with the statement
on page ES-8 that EPA "recognizes that the vulnerable hydrogeology criteria
cannot be the sole determining factor in making decisions on banning certain
locations for the purpose of facility siting or in denying permits to existing
facilities." An evaluation of this possible inconsistency and clarification
(if needed) is suggested.

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The statement that: (a) this document is not intended to apply to land
treatment units (page ES-9) and (b) the criteria are not intended to be the
sole determining factor in making banning decisions or denying permits should .
be included in the first paragraph of the Introduction (page 1-1) so as to make
these important caveats obvious to the reader.
Case studies can be very helpful in any Guidance document to more clearly
identify how an indicated approach is to be applied. For each case study,
there should be a clear opening statement that identifies what the reader should
learn from the case study and how the information in each case study may be
used in other situations. It also is recommended that an overall summary of
all the case studies be included in the manual. The overall summary should
indicate why the particular case studies are included and what the reader is
expected to learn from the studies. It is important that any case studies add
light and clarity to guidance in addition to bulk.
Time-of-Travel (TOT) Concept
The TOT concept is technically adequate within the context of its use with
respect to the ground water hydrology and aquifer characteristics, and provides
a good basis for integrating various aspects of hydrogeology into a single in-
formative measure. The concept lends itself to a more consistent, quantitative
means of evaluating the vulnerability of ground water at a site than does the
use of traditional risk analyses, i.e. determine exposure and compare with
effects. It takes into account the significant features of the aquifer and the
pertinent parameters to define the flow velocity, reflects the potential for
pollutant migration and eventual exposure, and seems to be consistent with
generally held views of aquifer vulnerability. The guidance for computing the
TOTiqo appears appropriate. In particular, Appendix B on flow net construction
is well written and informative.
In the TOT concept the determination of hydraulic conductivity (K), gra-
dient, and effective porosity are of utmost importance. Consequently, the
methods employed to identify these parameters will be under close scrutiny.
This document could provide a more clear direction for field investigation
programs and laboratory testing. For example, laboratory tests for hydraulic
conductivity could be eliminated and more emphasis could be placed on in-situ
tests which are more reliable.
The TOT calculation should be based on more than a single set of hydrogeo-
logic conditions. The effects of seasonal fluctuations on water levels, gra-
dients and transient flow conditions should be considered.
A thorough analysis of the sensitivity of the TOT calculation to uncer-
tainties associated with the input parameters should be provided in the guidance
manual. The permit applicant should also provide a similar analysis in his/her
application so that the confidence associated with the actual result can be
estimated by the permit writer.

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To provide a basis for the sensitivity analysis, a method (clearly spe-
cifying test conditions, tracer, column specifications, hydraulic gradient and
flow rate) for the "measurement" of effective porosity should be provided. .At
least the range of median grain size and total porosities, where the gravity
drainable porosity can be substituted for effective porosity, should be provi-
ded (similar considerations apply to measurements of hydraulic conductivity).
Quality assurance and quality control criteria should be stipulated,
including minimum number and type of core samples for effective porosities or
slug tests for K at each point, acceptable replicates and averaging procedures,
and minimum sample coverage per stratigraphic unit or unit length of flow path.
Acceptable units for K (i.e. cm/sec or gal/day/ft^) and I (i.e. cm/m or
ft/ft) should be limited and clearly stated. Extrapolations from regional
transmissivities or odd units should be discouraged in the interest of data
conformity, error minimization and building up a "feel" for the data with the
permit writers.
All data transformations, default decisions or inferred porosities from
soil types should be well documented.
Technical Validity of Selected Time Frames (10/100 years)
The draft Guidance examines how the criterion for vulnerability corre-
sponds to actual facility performance in a wide variety of hydrogeologic set-
tings using case studies and theoretical modeling. The cases presented where
the TOT100 was ^on9 indicate that no contamination is evident. - -/ever, this
does not constitute proof that an a-priori determination of a long TOTiqo (i.e.
prior to waste disposal, based on hydrogeological characterization) ensures pro
tection against contamination. For example, it appears that Example 3.7.4 (pre
sumably Love Canal) may have a-pnori passed the TOTiqq test. Yet severe en-
vironmental problems ensued, due to the "bathtub" effect, where contaminants
entering an aquitard backed up into surface structures. Is this effect rare or
common? 0SW should determine whether there are other cases that illustrate
contamination in spite of site conditions that are conducive to a long TOT.
This will give a perspective on whether the vulnerability test should consi-
der additional hydrogeologic conditions beyond flow field considerations.
Appendix D should contain an explicit caveat that emphasizes the utility
of the TOTIQO test as a factor or "trigger" for further hydrogeologic investi-
gations on a case-by-case basis, and not as a fool-proof test for classifying
a "safe" site. Anything short of an extensive hydrogeologic investigation
cannot serve as a definitive means of proving that a site will be guaranteed
as safe.
Although the TOTioq test encourages siting in aquitards rather than aqui-
fers, permit writers should be more clearly cautioned about the possibility
of channeling ground water through fissures and cracks that can occur in any

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subsurface strata. These features should be stressed as necessary for consi-
deration when evaluating a site using the TOT test. It would be helpful to
include a number of case studies that illustrate what the permit writer should
look for to understand how the TOT^gg test could be misused to misrepresent a
vulnerable location by avoiding to acknowledge the presence of such features.
It would be useful to summarize all the case studies presented in both
Appendix D and the Technical Resource Document (TRD) for evaluating facility
location. A single table indicating aquifer type, computed TOT^qq, and the
degree of contamination found at each site would be informative if included in
Appendix D. A separate brief summary of each case study evaluated in the se-
parate TRD, citing the information above, would make the case studies more use-
ful and more easily distinguishable to the permit writer.
Adequacy of the 100-Foot Flow Line
The use of the 100-foot flow line distance as a measure of vulnerable
hydrogeology is adequate for the purposes of the Guidance, but cannot ade-
quately characterize local hydrogeologic conditions.
The range of hydrogeologic conditions in near-surface aquifers is quite
wide and diverse. Given the fact that the land has (or will have) been dis-
turbed in the vicinity of these sites, the 100 foot distance probably "samples"
the conditions which may have resulted from the facility. It is questionable,
that the 100 foot flow path can provide a representative sample of large-scale
(i.e. local to regional areas) stratigraphy, fractures or flow patterns. Some
level of effort should be documented in the permit application to interpret the
relative importance of scale-dependent features on the TOT^gg calculation.
Additional Factors to be Considered
As the locations meeting the TOT^gg criteria are likely to be aquitards
with high ground water tables, it would be useful to include an analysis of
how these soil and moisture conditions are likely to influence the likelihood
of developing a leak in the first place. That is, once a leak develops, these
sites may be preferred, but if the soil conditions substantially increase the
likelihood of a leak, some of the advantages may be lost.
The discussion on use of engineered barriers (page 2-15) appears inconsis-
tent with other Office of Solid Waste (0SW) emphases. The assumption on page
2-15 is one of total failure of any liner and leachate collection system and
the ineffectiveness of any caps. In the development of other OSW guidance and
regulations, considerable emphasis is given to the design and use of proper
liners, leachate collection systems and caps. This assumption of total failure
and ineffectiveness is not justified by information included in the draft Gui-
dance, and appears to represent an overly conservative worst case situation.
If liners and caps are designed using the best OSW guidance, it is not likely
that there will be massive failures. It is possible that there may be some
leaks over time but not total failure. Unless the document intends to infer
that liners and caps prepared using other OSW guidance will fail, it is recom-
mended that the use of engineering barriers (liners, caps, leachate collection
systems and related protection approaches) be re-evaluated. This re-evaluation
should consider how the time of travel considerations can be modified to include

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something less than massive failure and ineffectiveness.
Specific Page-by-Page Comments
In addition to the more general comments offered above, a number of details
on specific pages of the draft Guidance need to be changed. These include:"
Guidance Manual
Page 2-10: The cornnon use of the term attenuation is very loose. It
would be better if retardation processes or mechanisms were discussed relative
to the transport mechanisms (i.e. advection and dispersion) and the use of the
term attenuation discontinued (see also pages 3-3 and 3-13).
Page 3-2: The "measurement" of effective porosity must be clearly de-
scri bed.
Pages 3-5 to 3-8: It would be useful to encourage the development of a
water level history for each site which could be analyzed for flow gradient
changes over time.
Page 3-13: Mechanical dispersion is identified as an attenuation mechanism.
While it is true that dispersion reduces both steady-state and peak concentra-
tions, it also hastens the arrival of the leading edge of the plume. This re-
duction in travel time for the plume front may be the most important impact of
dispersion and related phenomena (e.g. macropore channeling). Note that TOT's
calculated are for the center of mass of a contaminant pulse, and the contami-
nant front will generally arrive much sooner.
Page 3-13: Sorption should be substituted for absorption, since the for-
mer is a more general term. Mechanical dispersion is a transport mechanism,
and has nothing to do with retardation.
Page 3-15 (Table 3.3-1): The uncertainty associated with the inputs to
the TOT equation and the result should be clearly detailed for the permit
writer if it is to be applied properly.
Page 4-4: The discussion of passive measures to slow waste migration
should be reworded to minimize ground-water flow, since predicting contaminant
transport is not the aim of the TOT concept.
Page 6-2: The differences between storage and disposal rationales must be
more clear than the use of containment vs. immobilization. The words are sy-
nonymous in this context.
Appendix C
Experience indicates that most permits will not have the necessary data
for the unsaturated zone TOT calculation. Also, the theoretical approach
described in this section leaves too much to the discretion of the applicant.

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Page 2-3: The statement in paragraph 3 essentially reverses the sense of
the policy for data reliability stated for the saturated"zone TOT calculation.
Field measurements of moisture content and matrix potential (at least) should
be more reliable than laboratory measurements. Without site-specific data th6'
entire exercise may be futile except for calculating worst- or best-case con-
ditions.
Page 3-7, paragraph 1: The average velocity can only yield mean pore
water velocity and the mean free path of travel, which may be significantly
different from one set of conditions to another.
Page 4-2, paragraph 2: Again, the use of site specific data'is vitally
important if the unsaturated zone TOT calculation is to have any relevance to
actual conditions.
Appendix D
Page 2-5: In interpretation of the ground-water velocity distribution,
the uncertainty in calculated velocities from the many cases may put consider-
ably more than 10-15% of the cases within the 100/10 TOT guideline.
Pages 2-11 and 2-12: "g" is the acceleration due to gravity and units
should be stipulated for the inputs.
Case study D-l, page 2-36: The same value of effective porosity (i.e.
0.1) was used for all formations. This does not seem reasonable.
Case studies D-4, D-5: No mention has been made of the origin of the
data inputs. The source of the data and reliability should be emphasized.
Page 2-88: Equation (1) is incorrect (d^ is missing).
Units for C(x,t) of g/m^ should be g/m^.
Page 2-89: Here again, the general term sorption is preferable to either
adsorption or absorption.
"Page 2-106: The results in Figure 2.4.1 contradict the discussion in the
text. The graph shows a positive relationship between TOT and peak concentra-
tion, not an inverse relationship as the text claims.
Page 3-8: Descriptive case: The units of hydraulic conductivity should
be either cm/sec or gal/day/ft^ to insure data consistency. Transmissivity
values can be most misleading when converted to K's.
Pages 4-3 and 4-4 (Table 4.2): The classification scheme for geologic
settings ignores hydrologic effects such as recharge, humidity, discharge,
pumpage. This would seem to limit its usefulness.

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Appendix E
Page 2-22: The preparation of water level contours should include a
consideration of vertical gradients and the need to use water levels measured
in wells which are screened in the same formation. It would be helpful to
emphasize these aspects to the permit writer.
Page 2-24: Some reference should be given for the statement, that K values
are log-normally distributed.
Page 2-24 (last sentence): Should specify the actual level of confidence
(90%, 95%) implied.

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