Document
reformatted for the the world wide web
16 February 2001
U.S. Army Corps of
Engineers
Regulatory
Branch
P.O. Box 3755
Seattle, WA 98124
ATTN: Jonathan Freedman, Project Manager
Washington State
Department of Ecology
Shorelands and Environmental Assistance
Program
3190 - 160th Ave. SE
Bellevue, WA 98008
ATTN: Ann
Kenny, Environmental Specialist
Subject: Comments on Seattle Tacoma International
Airport Project
Third Runway – Embankment
Fill and West MSE Wall, and
Industrial Wastewater System
Lagoon #3 Expansion Project
On Second Public Notice
Applicant: Port of Seattle
Reference: 1996-4-02325
GeoSyntec Consultants (GeoSyntec) has
been retained on behalf of the Airport Communities Coalition to provide
a technical review of investigation, analysis and design relating to
construction of the embankment fill and West Mechanically Stabilized
Earth (MSE) Wall elements of the proposed Third Runway Expansion Project
at the Seattle Tacoma International Airport.
This letter summarizes GeoSyntec’s comments on these items.
Additional comments are included in this letter regarding the
proposed expansion of the Industrial Wastewater System Lagoon #3. Our technical review included the documents
listed in Attachment A to this letter.
GeoSyntec
is highly qualified to perform this review.
GeoSyntec’s personnel in charge of the review include Patrick
C. Lucia, Ph.D., P.E., G.E., and Edward Kavazanjian, Jr., Ph.D., P.E.,
G.E.
Dr.
Patrick C. Lucia is a Principal with GeoSyntec Consultants’ Walnut Creek
office, with over 25 years experience in geotechnical engineering. Dr. Lucia has been involved in numerous reinforced
walls and slope projects and has designed reinforced walls and slopes
up to 90 feet high. Dr. Lucia
has served on the faculty at the University of California at Berkeley
and Davis as a Visiting and Senior Lecturer respectively.
He has been an invited speaker at a NATO Conference in Turkey
on technology transfer with former Soviet Union countries and has lectured
at Universities around the United States.
He has also served as a consultant to the Panama Canal Commission
on slope stability problems associated with widening of the canal.
Dr.
Edward Kavazanjian, Jr., is a principal
with the GeoSyntec Consultants’ Huntington Beach office. Dr. Kavazanjian has extensive experience in
research, practice, and education in geotechnical and environmental
engineering, including fifteen years in consulting practice and seven
years on the faculty at Stanford University.
He is widely recognized for his work on the geotechnical aspects
of earthquake engineering. Dr.
Kavazanjian is lead author of the Federal Highway Administration Geotechnical
Engineering Circular Number 3, Design
Guidance: Geotechnical Earthquake Engineering for Highways.
In 1999, he chaired the Transportation
Research Board Workshop on New Approaches to Liquefaction Analysis. He served as principal investigator on the
National Science Foundation sponsored joint GeoSyntec-U.C. Berkeley
research project on performance of landfills in the 1994 Northridge
earthquake. He chaired a session on liquefaction at the Ninth World
Conference on Earthquake Engineering and delivered invited papers on
the seismic design of landfills and waste containment systems at the
Third International Conference of Recent Advances in Geotechnical Earthquake
Engineering and Soil Dynamics and at the Eighth Canadian Conference
on Earthquake Engineering. Dr. Kavazanjian currently serves as chairman of the ASCE Geo Institute
Embankments, Dams, and Slopes Committee and is past chairman of the
ASCE Geotechnical Division Safety and Reliability Committee. He is also a member of the Seismic Risk and
Transportation Committees of the ASCE Technical Council on Lifeline
Earthquake Engineering and of the Committee on Foundations for Bridges
and Other Structures for the Transportation Research Board.
The
GeoSyntec review of the project documents listed in Attachment A has
revealed significant deficiencies in the field and laboratory investigation,
and in the analysis of this project.
The documents we have reviewed do not provide a sufficient basis
for the conclusion that the project as conceived can withstand the static
and seismic loads it will be subject to over its lifetime.
The static and seismic analyses performed are not based on sound
interpretation of either existing foundation conditions or the seismic
conditions at the site. The
analyses have not been performed in a sufficiently thorough manner or
to a sufficient level of detail to deserve the approval of the U.S.
Army Corps of Engineers or the Washington State Department of Ecology.
The
Department of Ecology has examined the geotechnical engineering aspects
of the West MSE Wall during preliminary stages of the project. In a memorandum to Mr. Tom Luster, Mr. Jerrald
LaVassar of Ecology’s Dam Safety Office stated “Clearly, the considerable
height of the wall dictates that it be founded on a dense, unyielding
foundation or a structural fill that spans between such a stratum and
the base of the wall.” This
is not being done. Instead,
a zone of weak peat and loose, liquefiable sands directly beneath the
wall footprint are proposed to be densified in place, followed by construction
of the tallest MSE wall in the world in a very seismically sensitive
area. Mr. LeVassar acknowledged in his memo that
his remarks were based on limited site specific data. We find it surprising that approval can be considered for a project
of this magnitude on the basis of limited site specific data before
detailed design and construction plans had been prepared. A thorough geotechnical review should be performed by the Department
of Ecology in light of the numerous changes since Mr. LaVassar’s last
examination of the project.
Given
the unprecedented scale of the West MSE Wall, this project demands the
utmost in care in all aspects of investigation, analysis, and design. We are very concerned that this care has not
been taken and that the resulting deficiencies could lead to a design
of the embankment and walls that could ultimately result in damage or
failure of the wall, particularly under the influence of a strong seismic
event in the Seattle area. This
could have dire consequences on both the functionality of the airport
and preservation of the creek and wetlands below.
Several key points and additional concerns
will be made in the discussion that follows. Of these, we wish to highlight the following:
·
there is insufficient laboratory
strength data for proper characterization of foundation soils, and the
limited data is being interpreted incorrectly, and in an unconservative
manner;
·
the extent of the potentially
liquefiable material may have been underestimated, and strength values
being assigned to liquefied materials are unconservative;
·
seismic stability analyses
are being performed incorrectly;
·
seismic design criteria
have not been well established, and thus it is impossible to determine
how the wall is intended to perform during an earthquake; and
·
the FLAC analysis being
performed to assess seismic performance of the wall has not been calibrated
or validated with any real data, and thus it is not possible to interpret
the results it provides.
The net result of these deficiencies is that the project proponent
has yet to demonstrate either that a stable wall can be economically
constructed or that the wall, if constructed, can withstand the seismic
loads to which it may be subjected without large, unacceptable deformations.
Comment 1: The
West MSE Wall should be considered at least 153 ft high.
At
its highest point, which occurs at approximately Station 180+00 in project
documents, the West MSE Wall has a total exposed height of 133.5 ft,
with additional embedment bringing the height of the reinforced structure
to 140.3 ft. An embankment is
planned above the top of the reinforced wall, raising the total height
an additional 20 ft. The combined exposed height of the wall and the
overlying embankment that the wall supports is approximately 153 feet.
To our knowledge, a MSE wall of this height has never previously
been built. Similar walls nearing this height (e.g., Tsing
Yi Island wall in Hong Kong at 131 ft, Shikoku Island wall in Japan
at 125 ft) have never been subjected to strong seismicity. Considering this unprecedented height and considering
the strong seismicity of the Seattle area, this project demands the
utmost level of care and attention to detail throughout.
Comment 2: There is insufficient
laboratory testing data in the vicinity of the West MSE Wall relative
to the scale of the project.
Laboratory testing summarized in the
report titled “Subsurface Conditions Data Report – West MSE Wall – Third
Runway Embankment – Sea-Tac International Airport” (June 2000, Hart
Crowser) indicates that only seven samples have been tested for strength
determination in the vicinity of the West Wall.
Of those seven samples, three were tested under Consolidated
Undrained (CU) conditions and four were tested under Unconsolidated
Undrained conditions. Of these seven tests, three were performed
at depth in the strongest subgrade materials, leaving only four tests
performed in the materials most likely to be critical to slope stability
concerns. Additionally, only one test (from boring HC00-B132)
was performed in the vicinity of the critical wall cross-section where
the wall reaches the previously discussed high point.
Given the critical nature of the project
for the well being of both the airport and Miller Creek and surrounding
wetlands, and the unprecedented scale of the project, which will result
in construction of likely the highest MSE wall in the world, relying
on this minimal level of testing is dangerous and completely inadequate. Additional borings must be performed with targeted
high-quality sample collection for an expanded laboratory testing program
that should focus not only on increasing the spatial distribution of
testing, but should also include sufficient tests within any given soil
layer to provide redundancy in the testing results and confidence in
the ultimately selected strength values.
This testing should additionally be used to calibrate measured
strength with the results of the five cone penetration tests performed
at the site in order to expand the applicability of the testing program.
It should also be pointed out that while
the preceding level of testing is specific to the West MSE Wall, it
is equally likely that additional testing is required for the other
two MSE walls.
Comment
3:
Laboratory strength test data is being interpreted in a manner
resulting in higher strengths than would typically be used in engineering
practice.
Results
of laboratory strength tests by Hart Crowser are included in Appendix
B of the “Subsurface Conditions Data Report – West MSE Wall” report
(June 2000). Examination of the included CU and UU test
results indicates that they are being carried out to strains on the
order of 20%. Several of the
materials tested do not reach a visible peak deviator stress by the
end of the test, and the resulting strengths are being interpreted at
the highest recorded stress, which occurs at the end of the test, at
20% strain. In conventional
engineering practice, a limiting strain of 10% to 15% is normally used
for interpretation of strength from laboratory results, due both to
the assumptions inherent in calculation of stresses from triaxial tests
(i.e. use of constant cross-sectional sample area), and to field considerations,
where 10% to 15% strain in the field would typically represent a failed
condition anyway. It is recommended
that the testing data be reevaluated with a limit of 10% strain used
for interpretation of material strengths.
This will result in a reduction in the interpreted strengths
for many of the tests. These
reduced strengths will likely lead to lower computed factors of safety
against failure (see Attachment B for a discussion of “factor of safety”),
and more deformation of the wall. It
is recommended that a complete reevaluation of the laboratory test data
for the Third Runway project be performed, as it is likely that the
deficiencies pointed out here are not specific to the West MSE Wall
alone.
Comment 4: Potentially unconservative
strength values are being used in stability analysis.
In addition to the potentially high strengths
discussed in Comment 3, the interpreted strengths are being applied
in stability analyses under stress conditions that are much greater
than those tested in the laboratory.
CU tests were performed in the laboratory under a maximum consolidation
pressure of 12,000 pounds per square foot (psf).
After placement of 160 ft or more of fill at the project site,
which weighs an estimated 135 to 140 pounds per cubic foot (pcf), these
materials will in fact be subjected to on the order of 24,000 psf, double
the laboratory conditions. It is in fact quite common for soils to exhibit
a decrease in friction angle under higher confinement, in which case
the foundation soils may not be as strong as Hart Crowser is representing
them, resulting in serious implications on the stability of the wall.
The ramifications of the limited test
data on the stability analysis can be significant in situations where
there is not much room between the computed factor of safety and the
required factor of safety (see Attachment B for a discussion of “factor
of safety”). For example, if a liquefaction analysis results
in a factor of safety of 1.15, and the required factor of safety is
1.1, it is theoretically stable. However,
if this analysis is based on a friction angle of 35 degrees in medium
dense sand, while the actual friction angle at high confinement is closer
to 33 degrees, the available strength in this material decreases by
approximately 1200 psf, which may be sufficient to drop the factor of
safety below 1.1. Such a decrease
in factor of safety would indicate that the wall is not being designed
with a sufficient margin of safety, which could result in excessive
deformations or failure of the wall, particularly during a strong seismic
event.
Given the unprecedented scale and the
critical nature of the project, it is important that testing be performed
to properly account for the true field conditions.
Comment
5: Flaws in the liquefaction analysis of foundation
soils render the conclusion that the wall will not fail due to liquefaction
invalid. Because of these flaws,
the extent of potential liquefaction of the subgrade beneath the West
MSE Wall and the rest of the Third Runway project may have been underestimated.
The
liquefaction analysis described in the September 7, 2000 Hart Crowser
memo appears to have been done primarily by statistical analysis, with
little spatial analysis. The
database was split up into gross subdivisions based on geometry (e.g.,
the West Wall, the 2H:1V embankment) but there was no evidence of further
spatial analysis, e.g., looking for weak seams at a consistent elevation.
Furthermore, Hart Crowser appears to have incorrectly applied
the screening criteria used to identify nonliquefiable soils.
These criteria are intended to identify material that is potentially
liquefiable. Inverting them
to identify soils that are not liquefiable is not appropriate. Hart Crowser states, “if any one of these criteria was not met,
the soil was deemed nonliquefiable.” [underlining added for emphasis]
The four screening criteria are:
1. (Fraction of fines finer than 0.005 mm – 5%)
< 15%;
2. (Liquid limit + 1%) < 35%;
3. (Natural water content + 2%) > 0.9 LL; and
4. Liquidity index ≤ 0.75.
This is not the correct manner in which
to apply these criteria. These
criteria were developed for evaluation of materials that are potentially
liquefiable, not for identification of materials that are not liquefiable. For instance, while soils with fines content
of less than 15 percent (Criterion 1) must always be considered liquefiable,
not all soils with fines content greater than 15 percent are non-liquefiable.
This criterion is of particular importance in Seattle, where
glacial soils may have a large percentage of “non-plastic” fines.
Such soils could easily have a fines content greater than 15
percent and yet still be liquefiable, contrary to the Hart Crowser screening
analysis. This inappropriate application of the screening
criteria means that potentially liquefiable soils may have been identified
as nonliquefiable by Hart Crowser.
Comment
6: Inappropriate selection of residual shear
strength values means that the conclusion that the wall will not slide
on its foundation in the aftermath of a major earthquake is not valid. The selection of residual strength values to
represent conditions after a seismic event is unconservative and some
values are based upon extrapolation beyond the range of past experience.
Residual shear strengths are taken from the Seed and Harder plot
as a function of SPT blow count. The
mid-range of the bands drawn by Seed and Harder are used.
This is not consistent with current practice, wherein the lower
third to lower quartile of the band is generally used.
We recommend the lower quartile.
Furthermore, residual shear strength is extrapolated to blow
counts of 24, well beyond the range of the Seed and Harder plot, and
to values in excess of 1000 psf. The
greatest observed residual shear strength on the Seed and Harder plot
is 600 psf. Hart Crowser reports extrapolated values of
over twice that amount, up to 1300 psf.
By using values that are higher than the accepted engineering
standards and outside of the range of an already limited Seed and Harder
data set, the designers are taking a dangerous design step without any
theoretical or experimental evidence supporting their interpretation.
Comment
7: The methodology used in performing pseudo-static
(seismic) stability analysis is incorrect and may seriously underestimate the ability of
the wall to withstand seismic loads.
According to Hart Crowser, “We typically apply the seismic coefficient
to the most critical failure surface identified in the steady-state
condition.” No justification is given for using this methodology,
and it is in fact incorrect as the critical static (steady-state) and
seismic failure surfaces are frequently very different. Under pseudo-static conditions, a horizontal
acceleration is applied to the entire failure mass, which acts as a
destabilizing force. The computed
critical failure surfaces for the seismic case tend to be longer, extending
further back into the slope in order to collect more driving mass. The critical surface for the seismic case will
also frequently extend along a weak material interface, such as the
existing peat layer, or through the liquefied sand deposit.
A proper pseudo-static slope stability
analysis should be performed to search for the critical failure surface
independently of the static analysis.
Additionally, “sliding block” failure surfaces that propagate
along the weak seams should be examined, rather than just circular surfaces
that cut across them. The Slope/W
program that Hart Crowser is using is well suited to explore these alternate
failure surfaces, and to search carefully for an independent critical
pseudo-static failure surface. This
analysis will likely result in a reduced factor of safety and may lead
to requirements for additional ground improvement.
Figure 1 shows
a conceptual sketch of a representative failure surface under pseudo-static
conditions, extending through the weak peat layer far back into the
fill (and potentially beyond the limits of the modeled cross-section). As currently analyzed and designed only the
weak soils directly below the wall are being improved. If the critical seismic failure surface extends
along the weak peat layer or liquefied zone farther back into the embankment
than the static surface, the areas for ground improvement will also
need to extend further back in order to remove the threat of these weak
soils under a strong earthquake.
Comment 8: There are inconsistencies
in the results of the Probabilistic Seismic Hazard Analysis (PSHA) performed
by Hart Crowser that cast doubt on the validity of the analysis.
The primary inconsistency in the PSHA is with respect to the
magnitude of earthquake assigned to the various probability levels addressed
in the analysis. Unless these
inconsistencies are resolved, we cannot determine whether or not the
design earthquake has been properly characterized.
The earthquake magnitudes assigned by
Hart Crowser to the various probability levels are inconsistent with
results from the United States Geological Survey (USGS) National Seismic
Hazard Mapping Project and with results from analyses GeoSyntec and
others have conducted for projects in the same vicinity.
The progressively higher peak horizontal ground acceleration
(PHGA) values associated with the progressively smaller probability
levels are attributed by Hart Crowser to progressively larger magnitude
“subduction zone” (offshore) earthquakes, while our work and the USGS
information indicates that these higher accelerations should be associated
with the local “crustal” faults (e.g., the Seattle fault).
This inconsistency casts suspicion on the entire analysis. This suspicion is heightened by the observation that the Hart Crowser
acceleration response spectra (curves derived from the PSHA) agree remarkably
well with the USGS values, despite the fact that these curves depend
primarily on earthquake magnitude.
It is hard to say without further study exactly what the source
of the discrepancies is. However,
unless it is resolved we must consider that the seismic environment
at the project site has not been properly characterized.
Comment 9: The single time history
used to analyze the seismic performance of the wall does not provide
an appropriate basis for the conclusion that the wall can withstand
the design earthquake.
It appears that a single time history
was used to characterize the design ground motions. This time history is a synthetic time history that is attributed
to Steve Kramer at the University of Washington. The acceleration response spectrum for this time history is not
provided. However, visual inspection
indicates that this time history represents a long period (or low frequency)
motion (a long, “rolling” motion) and does not contain a lot of energy
at shorter periods or higher frequencies (i.e., does not contain enough
“punch”). This is an important
point because our analysis indicates the resonant frequency of the high
wall (i.e., wall sections over 100-ft (30-m) high) is in the same relatively
short frequency range where the design motion is deficient. In other words, the earthquake time history used in the analysis
does not have enough energy in the range in which the wall is most sensitive
to vibrations. This means that
the time history used in the design analyses does not truly “test” the
wall to the level of seismic force expected in the design earthquake.
Even without the above-cited frequency
deficiency, we do not believe it is appropriate to use only one time
history to evaluate the adequacy of the design.
Given the uncertainty and variability associated with earthquake
ground motions, the seismic analysis should be based on a suite of at
least three or more time-histories that envelop the design acceleration
response spectra.
Comment 10: Seismic design
ground motion criteria have not been established and there do not appear
to be any established seismic performance criteria for the wall.
The designers remain non-committal on
what the seismic design ground motion level is, i.e., on the level of
probability that will be used for design.
While initial reports discussed ground motions with 50, 10, 5,
and 2 percent probabilities of being exceeded in 50 years, later reports
have discussed primarily the 10 percent (475-year return period) and
5 percent (975-year return period) probability levels.
Hart Crowser has stated, “we understand the Port of Seattle used
the 475-year event for design of the South Terminal Expansion and for
analysis of deepening the berths at the Terminal 5 Wharf” (April 10,
2000, Hart Crowser Memo). We
do not believe the 475-year event is adequate for this project.
The 475-year event (a 10 percent in 50 year design level) is
the Uniform Building Code requirement for ordinary buildings, e.g. for
residential construction. This
project is far more important than typical residential construction.
We recommend that the “performance based
design” approach be employed. In performance based design, the performance
of a structure under seismic loads is defined over a broad spectrum
of levels, from the load level at which no damage will occur to the
load level at total collapse. Once
these levels and their associated probabilities are defined, an informed
decision can be made on the adequacy of the design.
The earthquake engineering profession, in general, is moving
towards this method of design, having recognized that this type of analysis
is necessary to truly understand the adequacy of a design in a complex
and uncertain seismic environment.
The designers also remain non-committal
on the seismic performance criteria. The level of calculated seismic deformation in the MSE wall that
is considered acceptable is never stated.
In fact, the designers never even explicitly state that the MSE
wall deformation that they calculate in the design event (on the order
of 8 to 10 in. (200 to 250 mm)) is acceptable.
The seismic performance criteria (e.g., the acceptable level
of seismic deformation) for the MSE wall should be clearly stated and
should be substantiated based upon the observed performance of MSE walls
in earthquakes.
Comment 11: To our knowledge,
the computer program FLAC used to evaluate the seismic performance of
the wall in the design earthquake has never been demonstrated to reliably
predict seismic deformations of earth structures. Therefore, the FLAC analyses do not provide an appropriate basis
from which to conclude that the wall can withstand the design earthquake. We have additional concerns about the method
of performing the analysis relating to seismic input, method of dealing
with liquefaction, and residual strengths that are not properly documented
in the material available for review.
FLAC was used to estimate the deformation
of the MSE wall subjected to the design earthquake ground motion (the
ground motion time history addressed in Comment 9). For the purpose of seismic deformation analysis
of MSE structures, FLAC is at best described as unverified, and therefore
unreliable. In fact, to our
knowledge, there has been no demonstration of the program’s ability
to properly predict the seismic deformation of any type of earth structure. This type of demonstration is typically conducted
by comparison of predictions made using the computer program to well-documented
field observations or model tests. This deficiency is significant for conventional earth structures
(e.g., soil embankments or dams) and becomes even more critical when
computer modeling a reinforced earth structure due to the intricacies
of modeling the reinforcement (e.g., modeling the interface elements
and their behavior under cyclic loads).
Certainly, for a project of this unprecedented magnitude and
scope, some type of calibration exercise (e.g., comparison with centrifuge
model tests) is necessary if the FLAC computer program is to be the
basis for the conclusion that the wall is seismically stable.
The FLAC analyses themselves require
much more documentation, even after the program is properly verified. The documentation provided to date leaves us
with numerous unanswered technical questions with significant bearing
on the results of the analysis. FLAC
allows the user to input his own constitutive models and elements. Was this done, or were the constitutive models
and elements supplied with the program used? The size of the cross-section is very small for a seismic response
analysis – were transmitting boundaries used or were the boundaries
rigid? Was the design motion applied directly to the
base of the cross-section or was it treated as a surface motion for
a “half-space” and deconvolved. How
was the liquefaction deformation analysis done?
When was the residual shear strength applied – at the start of
the motion or sometime during the motion?
Was the residual strength only applied to the soil elements that
reach full liquefaction, or were elements with low factors of safety
against liquefaction assumed to also mobilize their residual strength. What is the “composite” strength approach discussed
in the briefing to the Technical Review Board? Was the shear strength of the sand layer simply
weighted by the residual shear strength of liquefiable soils? What about the potential for continuous weak
seams? Without these details,
we cannot properly assess the validity of the analyses, even after the
program is verified. Therefore,
without these details, any conclusion that the wall can withstand the
design earthquake with acceptable deformation is not valid.
Additional Concerns
Comment 12: Very “select”
backfill was assumed for the wall design, with a friction angle of 37
degrees. The plan for assuring
that materials selected for backfill meet the design criteria is not
provided.
Design of the West MSE Wall assumes a
friction angle of 37 degrees for the “select” backfill. The Hart Crowser / Reinforced Earth Company
(RECo) design team state that this corresponds to a material that is
“less than 5 percent fines, well compacted, and relatively well graded”
(August 21, 2000, Hart Crowser Memo).
As several borrow source areas to be used for the project have
apparently already been explored (September 24, 1999 Hart Crowser report),
it is considered prudent to test representative samples of these materials
to ensure that gradation, compaction, strength and other appropriate
backfill requirements can indeed be met prior to relying on the high
strength value used in design. If they do not meet the design strength of 37 degrees, alternate
material sources will have to be identified and tested. A plan should be provided describing the required
testing of potential backfill material, as well as the construction
quality assurance plan describing testing in the field during construction
to ensure that the required strengths and gradations are obtained.
Comment 13: The use of Hollow
Stem Auger drilling techniques for obtaining blow counts in sandy soils
below the water table is not appropriate and can lead to erroneous results,
particularly in loose soils (e.g. liquefiable sands).
The selected drilling technique for the
majority of the field exploration program was a hollow auger with a
plug at the base that prevents soil from rising up within the auger
while drilling. The plug is
removed prior to collection of samples and performance of standard penetration
testing to determine blow counts. In
many soils, and particularly in weak or loose soils (such as liquefiable
sands) upon removal of the plug, the differential in water levels around
the auger and inside the auger can cause soil to rise up inside the
now open stem. This can lead to disturbance of the soil near
the auger tip, and result in collection of disturbed samples and erroneous
blow count readings. Use of
a drilling technique with known limitations on such a critical project
raises concerns and casts suspicion on the field investigation program
and its results.
Comment 14: Plans for construction of the West MSE Wall
should include instrumentation for monitoring potential deformations
and stresses.
Given
the unprecedented height of the West MSE Wall, it is considered prudent
to plan for installation of instrumentation behind the wall face and
in the backfill to monitor for deformations both during construction
and at repeated intervals during the lifetime of the wall.
Additional instrumentation should be considered to monitor stresses
within the reinforcement strips and at the connections between these
strips and facing elements. This
would serve to verify the functionality of the wall both during normal
operations and after any significant seismic event, providing a comparison
between the theoretical and actual performance.
This point has in fact been made to the
Department of Ecology previously. In
a memo from Jerald LaVassar of Ecology’s Dam Safety Section to Tom Luster,
Mr. LaVassar states: “All parties should recognize that a wall of this
height is rare. Thus, the inclusion
of various monitoring devices in the wall and backfill would provide
valuable confirmation that the wall is deflecting and performing in
the manner anticipated by the designers both during construction and
over a long and protracted service life.”
Comment 15: Use of the HELP model for the estimation of groundwater and creek recharge after construction
of the runway embankment may result in underestimation of subdrain capacity,
leading to a potentially destabilizing buildup of water in the subdrain.
Use of the HELP model is noted briefly
in the presentation to the Technical Review Board (Hart Crowser, November
16-17, 2000). The Hydrologic
Evaluation of Landfill Performance (HELP) model was designed to determine
leachate generation in municipal solid waste landfills.
It has been shown to perform poorly in predicting maximum infiltration
rates through soil covers for landfills (e.g., in predicting the performance
of evapotranspirative soil covers) and thus would not be expected to
provide satisfactory predictions of infiltration through a soil berm
and into a drainage system.
Comment
16: The proposed Industrial Wastewater System (IWS) Lagoon #3 expansion
project may need further review by the Washington State Department of
Ecology Dam Safety Office.
The IWS Lagoon
#3 expansion project has apparently been reviewed and approved by the
Department of Ecology’s Dam Safety Office.
However, only limited documentation exists of the extent of the
review. Among the documents
provided, only one relates to review of geotechnical engineering assumptions
and analyses. This document
is a two page handwritten “Geotech Review” dated May 30, 2000 with initials
JML. The review ends with the following statement:
Will need to complete our independent analysis
in future. But, by inspection
the current design is suitably conservative.
Time constraints presently do not allow doing the full blown
analysis. Again, this will be
done! The project of actual
building the containment berm is scheduled in 2001.
The question remaining is whether this “full blown” analysis
was in fact performed prior to approval of the plans, or whether the
project was approved “by inspection” alone.
No additional documentation has been provided which might clarify
this matter.
Comment 17: The Port of Seattle
must assess the impact of the Third Runway and infrastructure construction
on the fate and transport of contaminants in the Airport Operations
and Maintenance Area.
In
the vicinity of the Airport Operations and Maintenance Area, known contamination
exceeds MTCA cleanup levels. To
our knowledge, there has been no evaluation of the impact of installation
of underdrain systems and utility corridors for the Third Runway project
and infrastructure construction on the fate and transport of contaminated
groundwater from these existing airport operations. The general groundwater gradient leads from the vicinity of existing
contamination towards the new project area and the potentially impacted
creek and wetlands. Evaluation
must be performed to assess the impact of new construction activities
on the potential for adverse impacts on water resources including the
effects of existing contamination.
In summary, based on our review of the
available documentation, there appear to be critical deficiencies in
both the field and laboratory investigations performed for this project,
as well as in the analysis assumptions and methodologies used. We are very concerned
that these deficiencies could lead to a design of the embankment and
walls that could ultimately result in significant damage or failure
of the wall, particularly under the influence of a strong seismic event
in the Seattle area. As such,
we request on behalf of the Airport Communities Coalition that, prior to
regulatory certification or approval of the proposed Third Runway Project,
the applicant be required to respond to the issues raised in this letter,
and that we be granted the opportunity to provide follow-up review and
comment on that response.
Sincerely,
Patrick C. Lucia, Ph.D.,P.E.,G.E. Edward Kavazanjian, Jr., Ph.D.,P.E.,G.E.
Principal
Principal
Enclosures: List of Documents Reviewed
Discussion of Factor of Safety
vitae
cc: Peter Eglick, Helsell Fetterman LLP
Kimberly Lockard, Airport Communities
Coalition
Attachment A
List of Documents Reviewed
“Evaluation of Retaining Wall/Slope Alternatives
to Reduce Impacts to Miller Creek – Embankment Station 174+00 to 186+00,”
Prepared by HNTB, Hart Crowser, Inc., and Parametrix, (No Date).
“Evaluation of Retaining Wall/Slope Alternatives to Reduce
Impacts to Miller Creek – Embankment Station 174+00 to 186+00,” Memorandum
from Jerald LaVassar (Washington State Dept. of Ecology Dam Safety Office)
to Tom Luster (Washington State Department of Ecology) regarding a review
of the document in the title, (Date Unknown).
“30% Submittal – Third Runway – Embankment Construction –
Phase 4,” HNTB Corporation, (No Date).
“Industrial Wastewater Treatment Engineering Report,” Kennedy/Jenks
Consultants, December 1995 (incomplete).
“Geotechnical Design
Recommendations – Phase 1 Embankment Construction – Third Runway Project
– Sea-Tac International Airport – Seatac, Washington,” Prepared for
HNTB Corporation by AGI Technologies, January 22, 1998.
“Addendum to the IWS
Engineering Report,” Kennedy/Jenks Consultants, April 1998.
“Base Preparation
Stability Analysis (Phase II),” Hart Crowser Memorandum, August 13,
1998.
“Approach to Stability
Assessment,” Hart Crowser Memorandum, August 18, 1998.
“Geotechnical Engineering
Report – 404 Permit Support – Third Runway Embankment – Sea-Tac International
Airport,” Prepared for HNTB Corporation and The Port of Seattle by Hart
Crowser, July 9, 1999.
“Subsurface Conditions
Data Report – 404 Permit Support – Third Runway Embankment,” Prepared
for HNTB Corporation and The Port of Seattle by Hart Crowser, July 1999.
“Subsurface Conditions
Data Report – Borrow Areas 1, 3, and 4 – Sea-Tac Airport Third Runway,”
Prepared for HTNB and the Port of Seattle by Hart Crowser, September
24, 1999.
“Sea-Tac Airport Third
Runway – Probabilistic Seismic Hazard Analysis,” Hart Crowser Memorandum,
October 8, 1999.
“Hydrogeologic Investigation
Report – Industrial Wastewater System – Lagoon #3 Upgrade – Seattle-Tacoma
International Airport,” for the Port of Seattle by Kennedy/Jenks Consultants,
February, 2000.
“Seattle-Tacoma International
Airport – Industrial Wastewater System Lagoon #3 Expansion Project,”
Plan Set, Kennedy/Jenks Consultants, March 13, 2000.
“Project Manual, Including
Specifications, for Industrial Wastewater system Lagoon #3 Expansion
Project,” Port of Seattle, March 16, 2000.
“Seismic Basis of
Design – Third Runway Project,” Hart Crowser Memorandum, April 10, 2000.
“Geotech Review” –
Two page handwritten commentary on ISW Lagoon #3 project geotechnical
engineering report by Zipper Zeman Associates, Inc. by Washington State Department of Ecology Dam Safety Section, Initials
“JML,” Date May 30, 2000.
“Subsurface Conditions
Data Report – West MSE Wall – Third Runway Embankment – Sea-Tac International
Airport,” Prepared for Port of Seattle and HNTB by Hart Crowser, June
2000.
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