|
Items in cart [4] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 462
DREDGING AND DISPOSAL OF CONTAMINATED MARINE SEDIMENT
,
FOR THE U.S. NAVY CARRIER BATTLEGROUP HOMEPORT PROJECT.
EVERETT WASHINGTON
Edward Lukjanowicz, U. S. Navy
J. Richard Paris, U. S. Navy
Paul F. Fuglevand, Hart Crowser, Inc.
Gregory L. Hartman, Ogden Beeman & Associates, Inc.
ABSTRACT
In April 1984 the U.S. Navy selected the East Waterway
of Port Gardner Bay in Puget Sound as the homeport site for
a carrier batt~egroup. Construction involves dredging over
3.3 million yd of sediment; approximately 928,000 yd
of it is treated as contaminated. The Navy selected and has
received permits to proceed with in-water disposal of the
sediment using a method identified as confined aquatic
disposal (CAD). Using the CAD technique, contaminated sedi-
ment will be deposited in depths of 400 ft and capped with
uncontaminated sediment to isolate contaminants from the
aquatic environment of Puget Sound. This summary case
study, discusses the development of the CAD option and the
stringent environmental monitoring requirements imposed on
this disposal technique by federal and state regulatory
agencies. These requirements are intended to safeguard
ecologically sensitive Puget Sound and gather technical
information on the effectiveness of CAD in deep water.
OVERVIEW
This summary case study draws from the many reports completed for
this project. The primary documents are
draft environmental impact statement (DEIS), November 1984
final environmental impact statement (FEIS), June 1985
sediment testing and disposal alternatives evaluation, June 1986
public notice of Section 404 permit, October 1986
draft supplements to FEIS (DSEIS), July 1986
final supplements to FEIS (FSEIS), November 1986
final dredging and disposal monitoring plan, phase I (Monitoring
Plan), November 1987
plans and specifications, environmental monitoring of
dredge/disposal activities (Monitoring P&S), November 1987
462
OCR for page 463
463
Additional environmental and engineering studies have been undertaken
and completed by the Navy. Some of these studies address the following
topics:
· disposal site bioturbation,
· homeport master plan,
· homeport soils analysis,
· air quality modeling,
· slope enhancement for fisheries,
· seabird survey,
· crab surveys (ten seasonal trawls),
· CAD site benthic analysis,
sediment sampling and analysis,
characterization of East Waterway sediments,
water column chemistry,
physical model of East Waterway,
confined aquatic disposal (CAD) feasibility analysis,
Port Gardner bathymetric survey,-
Port Gardner current measurements
leachate/sediment settlement tests
dump modeling,
navigational plans for accurate sediment placement,
preconstruction/construction/post-cons true tion CAD site
monitoring plan,
· Smith Island Upland-Dredge Disposal Feasibility Study &
Evaluation,
re-characterization of P-lll and P-905 sediment
(clean/contaminated),
· geochemical evaluation of Norton Terminal,
· biological assessment for marine mammals, and
· biological assessment for bald eagles.
Project Development
The proposed project site is located in Puget Sound within the city
of Everett, Washington. The site is located on the east side of Port
Gardner Bay, just wes t of the central downtown area. Deep water for
navigational purposes is available near the site, although dredging of
the East Waterway would be required.
Operation of a carrier battlegroup homeport at the site would
require newly constructed facilities to accommodate 13 ships including
the aircraft carrier U.S.S. Nimitz, plus up to 10 additional small
craft needed for support services. Location of a homeport facility at
the 117-acre site in Everett would require construction of many support
facilities.
it snips ~nclu~lng
~ ~ ~ ~ ~ .
OCR for page 464
464
Dredging and Disposal Preferred Alternative
Dredging of the East Waterway will be completed to depths necessary
to accommodate homeported vessel drafts. All dredging will daylight to
deeper depths into Port Gardner. No dredging or disposal will be done
within designated "fish" windows from December 1 to June 15 of any con-
struction year. Dredged material will be disposed of at the proposed
CAD site, which is located in water depths of approximately 310 to 430
ft in Port Gardner, and which will impact an area of approximately 380
acres (Figure 1~. 3
Total dredging volume is estimated at 3,305,000 yd , including 1
ft of overdepth. Of the total dredged volume, approximately 928,000
yd3 of materials will be treated as contaminated, although only
486,900 yd of in situ contaminated sediments exist. They contain
organics, such as decomposed sawdust and wood chips, oils, grease, and
industrial contaminants, such as polyaromatic hydrocarbons and
polychlorinated biphenols.3 Within the total dredge volume,
approximately 2,377,000 yd are clean native materials and will be
removed from the East Waterway to be used as cap and mound materials at
the CAD site. The dredging volumes presented are estimates based on
data from various studies. Actual dredging volumes may differ slightly
due to minor variations encountered during construction, or any
redefinition by regulatory agencies.
Standard equipment and methods will by used for dredging and dis-
posal. Contaminated material will be dredged and disposed of using
clamshell, tug, and bottom dump scow to ensure minimum induced tur-
bidity and maximum compaction of contaminant mass on the bottom.
Hydraulically dredged, native uncontaminated material will be used as
capping material, the release rate and density of which will be con-
trolled to prevent displacement of the deposited contaminated sediments
through use of a floating pipeline with submerged diffuser.
The sequence and placement of the dredged materials into the CAD
site are shown in Figure 2. The Dredging operation will begin by
removing approximately 500,000 yd of uncontaminated material from
the area of the carrier pier and breakwater. This material will be
dredged by clamshell dredge and disposed of in such a manner as to 3
create a mound (1~. Contaminated material (approximately 97,000 yd ~
will be dredged and disposed of in a similar manner and placed (2) to
the "uphill" side of the mound. Immediately thereafter, this material
will be capped (3) using approximately 239,000 yd of uncontaminated
material. Capping will be by hydraulic pipeline dredge with disposal
by submerged discharge. It is anticipated the cap thickness will be in
excess of 3 ft.
The foregoing will complete the first year's dredging. Second-
year dredging consists of approximately 831,000 yd of contaminated
material and will be dredged by clamshell and disposed of by surface
bottom dump barge (4~. Finally, and in sequenced manner, 1,638,000
yd of uncontaminated material will be hydraulically dredged and
disposed of by pipeline as represented by (5~. It is anticipated the
final minimum capping thickness over contaminated material will be 4.5
ft.
OCR for page 465
465
20 ~
PROJECT |
BOUNDARYj i
V
~ ~ _
ant ~ {:
~ \ ~ BOUNDARIES OF CONTAMINATED / ~ ~ /// l
\ \ \ To AND UP / ~ ~ ~ 1/
\ \ \\ DREDGE DEPOSITS
\ An\ \~PPROXIMATELY~=RES~ ~ ~1/
\\ \ \ ~ / /
\\ \ ,'~-' -_ / ~r
1ST YEAR CONSTI `~ \ \ , / / _ ~ by; `}
BOUNDARIES OF CONTAMINATED \ X / / ~ ~ \ / ~ [A
AND UN~AMINAlED \____ - W~ /
DREDGE Do icy/
-EGG ~~//?
act/
l
SCOTT PAPER
//// OUTFALL
SCALE IN fEET
0 800 1, 600
FIGURE 1 Revised application for deep confined aquatic disposal.
OCR for page 466
466
-310.0~
(a) Uncontaminated Material Mound
Conte~neted Materis'
Uncontarransted Material CaD
(I Contaminated rJlaterial
@) Uncontaminated Material CaD
T4.5
,@
-430.0+
hi,
FIGURE 2 CAD site final consolidated section.
I,
SEDIMENT ASSESSMENT AND EVALUATION
Contaminated Sediment
Section Distorted
Not to Scale
The contaminated sediment consists of the upper layer of sediment
in most areas of the harbor ranging from O to 7 ft in thickness. It is
composed of fine-grained, black to dark brown, odorous surface sediment
including abundant wood fragments, chips and sawdust. The contaminants
include oil and grease, heavy metals, polyaromatic hydrocarbons (PAH),
and polychlorinated biphenyls (PCB).
Although the disposal of dredged materials does not fall within the
purview of the Resource Conservation and Recovery Act (RCRA), the act's
definition of hazardous waste is useful as a basis of comparison.
Extensive laboratory testing (FEIS, DSEIS) has shown that contamination
levels in these sediments are well below the concentration associated
with hazardous waste designation under RCRA or related Washington State
Dangerous Waste Regulations (Chapter 173-303, Washington Administrative
Code). However, certain contaminant levels do exceed background levels
in Port Gardner and, to a lesser extent, biological effects thresholds
observed elsewhere in Puget Sound; therefore, capping of the contami-
nated sediments is proposed as a means to isolate them from surrounding
waters .
OCR for page 467
467
`_ ., ./ . . .
it.
,~\
MAY
SCALE IN YARDS
o
1.000
2.000
D - doing Area
^cA-~c-~ Open Water Sites
Nearshore Sites
~f~ Upland Sites
PORT GARDNER
PSD DEEP LTA
S E ~ CAD SI" -
APPUCAT10
FOR DEEP CAD
SITE
POW GARDNER
DISPOSAL SITE
; _
_~5~"
Her -
an_
~ U;i~1:IL
'=~ 0~- . ~
Bend
,_' .
67~ .
FIGURE 3 Dredging area and alternative disposal s ites .
SNOHOMI:
RIVER DELTA
my' ~
.--.
__ A-.
~ 1:,`~.L~
I _:L
it'
[-(AL,
~11
lit,
1 ~
I ' ~ '- N1\ .-r .~e :~.
!:1 //
Source: NaAA Chan 18443. 1982
OCR for page 468
468
Uncontaminated Soil
The uncontaminated soils are exposed south of the south mole and
underlie the contaminated sediments in the harbor area north of the
south mole and in limited areas east of the carrier pier. They range
in thickness to greater than 50 ft and are composed mainly of native
materials in the form of gray and brown sandy silt. Some organic mater-
ial and wood fragments/chips are present in small amounts in certain
areas. Chemical and biological analyses have shown that these sedi-
ments meet requirements for unconfined open-water disposal in Port
Gardner.
Sediment Chemical Characterization
In June 1984, a contaminated sediments assessment program for the
East Waterway of Everett Harbor was developed by the Seattle District,
Corps of Engineers (COE) in coordination with key federal and state
agencies. Nineteen stations in East Waterway were sampled in July 1984
by the COE using a vibracore sampler. Sediment cores were recovered
for depths up to 15 ft. Sediment horizons were visually characterized
and subsamples taken for chemical analysis. By comparison to the only
Puget Sound sediment criteria in existence at that time, the surface
layer of harbor sediment was judged to be unacceptable for unconfined
open-water disposal. All chemical values of the native sediment layer
were below the reference criteria, and met the chemical guidelines for
open-water disposal.
In June 1985, contaminated sediment samples were collected from 16
stations inside the East Waterway and combined to form 8 yd of com-
posited sample, which was provided to the C8E Waterways Experiment Sta-
tion (WES) for physiochemical testing: ~ yd of native sediment was
also collected for testing. Subsamples of the composite and native
sediments were provided to the Battelle Pacific Northwest Laboratory
(PNL) for separate chemical and biological testing.
Priority pollutant analysis of the composite sediment sample col-
lected in the East Waterway by the COE (Table 1) indicated the presence
of 33 sediment contaminants of concern. These compounds included chro-
mium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead
(Pb), cadmium (Cd), mercury (Hg), polychlorinated biphenols (PCBs),
polynuclear aromatic hydrocarbons (PAHs), and 1- and 2-methylnaptha-
lene.
Chemically Related Dredge Disposal Considerations
CAD Standard
Elutriate tests were conducted by the COE on the previously noted
composite sample of sediments collected from the East Waterway (DSEIS).
This-information was then used to estimate the potential for dissolved
contaminant release to the water column during open-water placement of
OCR for page 469
469
dredged materials (CAD alternative). Elutriate testing indicated that
only 7 of 33 contaminants of concern were detected in the elutriate
water: copper (Cu), mercury (Hg), cadmium (Cd), lead (Pb), chromium
(Cr), nickel (Ni), and PCB-12S4. Of these, only the latter five ex-
ceeded Port Gardner background levels. Dissolved concentrations of
nickel, lead, and PCB-1254 exceeded EPA water quality criteria.
The standard elutriate procedure was modified to obtain estimates
of total contaminant concentrations associated with mass release to the
water column during dredging and open-water disposal (CAD) of East
Waterway sediments. Results of these tests revealed that concentra-
tions of total Ni and Pb slightly exceeded the measured dissolved con-
centrations of these metals (i.e., IS ~g/liter dissolved versus 17
g/liter total for Ni, and 28 ~g/liter dissolved versus 30
g/liter total for Pb). Thus undiluted, the effluent concentration
of these two metals would exceed EPA water quality criteria. The total
concentration of PCB 1254 was observed to be less than the dissolved
concentration (i.e., 0.3 versus 0.4 ~g/liter, respectively).
Based on these tests, potential water quality impacts during open-
water placement of contaminated sediments (CAD site) appear to be
limited to these three pollutants. In this regard, the concentration
of Ni in the elutriate was shown to exceed chronic criteria, but was
well below the acute exposure value. Because Port Gardner water
samples collected by the COE and identified as background or reference
waters equal the chronic criteria value for nickel, dilution of the
elutriate with this water would not reduce the elutriate concentration
below the chronic level. In the case of Pb, a dilution factor of 1
would result in water concentrations below the chronic criteria concen-
tration for the elutriate: for PCB 1254 a dilution factor of approxi-
mately 13 would be necessary.
Upland or Intertidal Disposal
Modified elutriate tests were conducted by the COE to estimate
contaminant concentrations in effluent discharged from dredge disposal
sites located in intertidal or upland areas (DSEIS). These tests were
designed to estimate dissolved and particulate-associated contaminant
concentrations in the effluent generated during the placement of
hydraulically dredged sediments. Results of the modified elutriate
test procedure indicates that undiluted discharge of effluent would
significantly degrade the local water quality.
The concentration of chromium (Cr) and PCB 1254 were observed to
exceed the dissolved concentrations. Total concentrations of PCB 1254
would exceed the EPA's saltwater quality criterion and would require a
dilution factor of > 20 to meet the criterion, assuming such effluent
was discharged to salt water. If discharged to fresh water (i.e., the
Snohomish River) the criteria for Cs, Cr. and PCB 1254 would be
exceeded. Dilution factors of 17, 28, and 43 respectively would be
necessary to reduce the total concentration of these contaminants to
below the acceptable water quality criteria. Obtaining such a dilution
could require a diffuser system for the discharge line.
OCR for page 470
c
o
·~t
c
t
U ~
C '
O t
C) ~
Sit
Pa
Co
.,'
O t,
C-)
VO
,1
U]
.,,
In
o
Q.
o
C)
o
h
.
o
. -
In sit
U) a:
C: ~
~ O to
at: c)
r.
.,,
U]
X
m sir
En P.
470
V V V V V V V V V V V
n~
P. C
_ ~
h
S
a
c~ ~ ~ S
~ ~ ~ ~ a
(1,) N ~ a) ~ h ~ ~ ~ S ~ C ~ O
a~=
C ~ ~S ~ ~ ~ ~ - ^ ~S^~S
N 5> 04 N ~ 0)·~1 fa ~ ~ P. C :^ ~ ~ ~ ~ ~ ~ a
) ~ ~ s"
~ ~ ~ ~ S ~ ~ ~ ~ ~ ~ N
52 0 ~ ~ ~ S ~ ~ S ~ ~ ~ ~ S ~ ~ ~ ~ ~ ~ 1 V ~ ~ ~ ~
O~ ~O aC~ ~ ~= `~ ~ ~ ~ S ~ ~= ~ ~ Om'- O^~^ -
h S V ~ ~ ~ ~ ~ ~ S ~ ~ ~ ~ ~ · - ~ ~ S ~ ~ ~ ~ ~ ~ 3 ~ ~ ~ O
O ~ O O ~ ~ O O `~ S ~ ~ S O ~ ~ ~ ~ ~ ``
_~ ·~1 ~1 I ~ ~ h ~ S ~ S ~ ~ ~ O ~ ~ ~ S N S S ~ ~ tD ~ ~ ~ ~ ~
S ~ O S ~ O O O ~ ~ == O O ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~ ^ S
~ E- U ~ h ~= :~ 0 = I" ~ 0 ~ O < a ~ C ~ u mo ~; o ~: ~ ~
. - I =~ - S O S S 04= ~ ~ ~ O ~ ~ ~ ~ ~ ~ `= O ~ ~ O O N
a ~ u c~ ~ ~ V U ~ ~ s 0 ·t _~ V h ~ ~ h C O ~ ~ ~ h ~ I O ~ ~ O ~ O O ~
I tt5 I S S ~ ~ ~ ~ ~ h ~ S ~ 0~ - ~ S ~ N ~ ~O ~Z N ~ ~ N ~ N N
a) rz a) m ~ C) X 3 Z ~ ~ h C ~ ~ ~ ~ ~ I C ~ ~ ~ ~ ~ ~ ~
~) ~ 1 ~ ~ o.~- - 1 U 1 ~ ~ 1 S ~ ~ a- - =~ - ~ S. - ~ ~ O ~ - ~ ~ O
5 ~ z ~ ~ x ~ a a ~ ~ ~ 5 ~ z ~ ~ ~ m a m m ~ c~ a m ~ E~ m a m m
Ln ~ ~ ~ ~ ~ ~ ~ ~ ~ u, ~n In ~ ~ ~n ~ ~ u, ~ u, ~ u, ~ u, u,
c~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ u, ~ In ~
oo oo ooooooooooooooooooooo~ om o
- ~ -
v v v ~ v v v v v v v v v v v v ~ v v v v v v v v v v v v v v v v v v v v v v v ~ v
v v
o ~ ~
s s ~ o ~
~ C ~ h
O C
h O ~ ~ ~ ~ O S ~ . - O S ~
~J ~ _~ C: t: ~ S h ~ ~ h h ) S
~ - - 0 a, ~ ·t
C h ~ SSS ~ - O O - - 0 0
- - O ~ ~ ~ ~ ~ ~ S h ~ S S ~ h
~ ~ a ~s~ ~ ~ ~ O U O ~ U U ~ O O
O ~ ~ I ~ S ~ ~ O O O he~ ~ O ~ - S ~ ~
iD C: ~ O h h ~ h O C]S h h a ~ S O
~ S ~ ~ h O O O O _1 1 U O ~ ~ I ~ U ~ ~
S ~ eC ~ S ~ O ~ ~ ~ ~ ~ ~~ - ~ ~ ~ ~ 0~ - ~ S ~ ~ ~ O
=~~ I ~ C - SSSS U hS O h h h h U I I 0 -
~ ~V ~
~ S . - ~
to O ~l ~ ~ S
e1 C
~S ~ ~ 0
O O ~ ~ ~ ~ .
O ~ ~ ~ 0= 0 ~ ~ ~ X ~ ~
~ O F. ~. h o4 ~ a) N O ~ N
S: h- ~ ~ I S ~ ~ S
V O ~S O ~ ~ ~ ~ -
_~ _t ~ U) (U ~ I ~ O ~ ~ O ~
= ^~ ~ - - ~ ~ ~ ~ ~ O O~ O
U S O h (1)~~ ~ · ~ O h h O
n). - ~ ~ O N h I ~ ~ ~ ~ h O O h O
_~ '~ ~ O N O N ~ ~ ~1
O ~ ~ ~ ~ ~ S ~ ~ ~ Ue~ ~ ~ V ~ ~ O ~ O O ~ ~ ~ ~ S ~eS ~ ~ ~ O ~ O ~ h ~ U ~ ~eS ~
h 0 ~5 :^ E~ U ·~-~- - ~5 1 1 · - O C I ~ I ~ ~ ~ O U ~ ~ I O O h ~ h ~ 0~ - 1 · - =- -
~ h h S O ~q~ _~ a a a 0 tn ~ a h O tn S t~ O O Q) ~ _1_ tt5 <1) _1 ~ L~ ~ ~ O S a a ~ a~-
·^ O O ~ ~ S ~ ~ I I I ~ ~ O ~ ~ U ~ h N I S h ~ OO `- - `~ - h ~ I I I N I
~ ~ O ~ C: ~ ~ ~ ~ O ~ ~ ~ ~ h ~e~ O ~ ~ ~ ~ V ~ ~ h ~ ~ h Z S Z ~ O ~ ~ 0
I S S I h ~ ~ - h h S ~ h h he~ ~ . - 1 0 O Ue~ S U I ~ I . - 0
~r c~ v ~ m ~ ~ ~ ~ ~ ~ m h _1 _1 V V E~ E~ -1 m a m ~ ~ ~ ~ h <: m ~ ’5 z ~ Z z ~ ~ ~ m ~ m
h ~
S . -
_ ~ `:
:^
:- Q,
~ O
O ~ ~
h O4 :^
O4 1 S
O ~ ~
rn nl n~ I ~`
N
O 0 0 0 0 ~ 0 0 0 0 0 0 0 0 0 0 0 ~ ~ ~ ~ r~
~? O O O O O O O O O O O O O O O O O O O O O O U, O O O O
t~ ~ ~ ~ O O O O O O O O O O O O O O O O O O O O ~ O O O O
1D ~ _~ t~ Ct) OC~ cn 0 ~ 0 t~ 0 a~ 0 0 1 - 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ~ ~ ~ i O
V ~ V CO V V ~ V V V V V V V V V V V V V V V V V V V V V V V V V V V
CO
tn c
S"
O O
S
U) ' -
O Z
~ t,1 S ~ ~ ~1
V ~ ~ ~ ~ ~ ~ ~ ' -
h ~i 3 · ~ ~ ~ · ~ h 3
I:: ~ ~^ ~ 3 .- ~O CO ~a~ 0
~ ~= ~ ~5 V 0 ~ ~ s" m:e ~ ~ ~ 0 I: o a ~ 0
0 ~v~ ~ ~ s~ s~ o~ c:m~mm em~a
S~ 0- - ~ ~- - S ~ ~ ~ ~ 1 0 1 1 ~ 1 S ~- -
#;: Cd Z C) ~ N V :~: H ~S ~ ~ E~ ~S a ~: m v ~ a ~
~ x
~ o
~ cL
c
~ 1:5 h ~
- - O O
o
_I
O ~C O ~
:^ ~ ~ ~ O
S ~ O
S~ ~ ~ ~
O O ~=
O £ _/ _1
~ 1 ^= ~ ~ O
(1) t~ S V S O h
a) (~ 1 ~)- ~~
o ~ o -
3 _ ~ ~ _ _ . . _
~n tn s s ~ ~ ~ ~ ~ ~ ~ ~ ° ~ ~ ~ ~ ~ ~
O C: O ~ V ~ ~ ~ ~ ~ o ~ ~ S ~ O - - - 1 0-~- -
W~--E-~-- ~ m-~- =~ - oa~-aa
a c: s~a c: s-~= I I I I I I I m~-s ~ I s I
a ~ ~ a ~ n:5 ~ ~ m m m m m m m x z
`14 1 ~ ~ 1 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0 1 1 S 1
~ <: ~ ~ m ~ :s: z c4 ~ ~ 04 ~ ~ ~ E~ ~ ~ ~ ~ ~ ~ ~ ~
OCR for page 471
471
Surface Runoff Impact
Tests were conducted by the COE to estimate the potential impacts
to receiving water quality as a result of surface water runoff from a
confined upland or nearshore dredge disposal site. A rainfall
simulatory-lysimeter was utilized to predict the quality of surface-
water runoff from such a disposal site.
Test results showed that if dredged sediments placed in upland or
nearshore sites are not capped and are allowed to dry, physiochemical
changes will occur. Under such conditions, runoff water from rainfall
would potentially carry dissolved contaminants from the site. Studies
conducted with East Waterway sediments indicate that under these condi-
tions the.concentration of dissolved Cd would substantially exceed EPA
water quality criteria.
Leachate Testing
The potential for generation of leachate from an upland disposal
site was studied using experimental laboratory testing procedures for
sediments collected from the East Waterway. Leachate contaminant
levels from these sediments were quantified using batch and column
testing techniques.
Based on these leachate tests, the geochemical changes associated
with aerobic disposal on land would result in mobilization of a large
fraction of some of the contaminants. If the material could be placed
below the water table at a given site (usually more of an option for
nearshore/intertidal disposal), such mobilization would be signifi-
cantly reduced. The leaching tests indicated that mobility of metals
and organic contaminants is low under anaerobic conditions. Under
aerobic conditions, some of the metals were mobilized in large quan-
tities. The fraction of metals that was resistant to anaerobic leach-
ing was generally greater than 90 percent of the bulk sediment concen-
tration. Under aerobic conditions, over 85, 65, and 49 percent of the
Zn, Ni, and Cd, respectively, was mobilized in the tests. The higher
metal release observed in aerobic testing is related to the pH (i.e.,
the pH in aerobic testing was lower than the pH in anaerobic testing).
DREDGING AND DISPOSAL ALTERNATIVES
Dredging Equipment Consideration
Based on dissolved contaminants and mass releases, both hydraulic
and mechanical dredges appear equally viable. Contaminants associated
with East Waterway sediments appear to be strongly bonded to those sed-
iments as long as they remain saturated. Mechanical dredging to remove
the contaminated layer is preferred for confined aquatic disposal since
the lower in situ water content would encourage clumping of the mate-
rial. Hydraulic dredging of the native material would assist in maxi-
mizing spread for cap placement. Either dredging method could be
OCR for page 472
472
employed for nearshore confined disposal, although hydraulic dredging
appears to be most efficient. Mechanical dredging would require double
handling of the material to place it in the site. As water quality
problems would not be markedly different from conventional operations,
use of specialized dredging equipment is not recommended.
General Disposal Alternatives
A number of disposal methods and site alternatives were considered
for the removed sediments. The preferred method is CAD, to dispose of
the contaminated sediments at a deepwater site and then cap them with
the clean native sediments. The preferred disposal alternative, Re-
vised Application Deep (RAD) CAD, was developed in response to public
comments concerning potential significant impacts to the Dungeness crab
(Cancer magister) resource of Port Gardner. The RAD CAD site is
deep enough to minimize short-term and avoid long-term impacts to
Dungeness crabs.
A second alternative involved placing either all of the removed
sediments or just the contaminated sediments in an intertidal site on
the Snohomish River. If only the contaminated sediments were placed
there, the clean sediments would be taken to the Port Gardner aquatic
disposal site. A third disposal method involves placement of the
contaminated sediments on an upland site on Smith Island. With this
alternative, clean sediments not required for cover could be disposed
of at a deep-water site in Port Gardner. These sites together with
other alternative sites are shown on Figure 3.
As part of the evaluation methodology for contaminated materials,
seven criteria were used to assess each of the different sites. Cri-
teria included contaminant availability, potential contaminant mobi-
l~ty, site environmental conditions, erosion potential, institutional
constraints, site capacity, relative cost, and monitoring capability.
A criteria evaluation matrix is given in Table 2. For clean dredged
material, five criteria, including site environmental considerations,
availability for capping, institutional constraints, site capacity, and
relative cost were applied.
Open-Water Capped Disposal Site Considerations
A detailed locational analysis was undertaken within Port Gardner
to identify potential site alternatives for disposal of dredged
material by the CAD method. An initial step in the site identification
process was a bathymetric survey conducted of much of Port Gardner,
focusing on areas shallower than 400 ft. Subsequently, core samples
were taken throughout the area and a map of sediment types was pre-
pared. Areas of potential geotechnical risk, as indicated by recent
slumping and other factors, were identified as well. Other significant
characteristics, such as the location of outfalls, were also mapped.
The key siting criteria, based on engineering and construction
reliability, used to select potential sites included the following:
OCR for page 473
473
Potential for subsequent natural deposition. The site should be
in a zone of accretion. That is, natural deposition of
sediments that could add to the thickness of the capping
material was considered to be beneficial. Conversely, areas of
potential erosion that could remove cap material were to be
avoided.
Geotechnical stability. The site should be in an area with no
evidence of slope movement. Areas where slumping was identified
or where there was a high potential for slumping (in particular,
steep slopes) were to be avoided.
Site configuration. The site should be relatively flat so that
the deposited dredge materials would stay in place. An upwardly
sloping terrain on one side of the site was considered benefi-
cial, because the slope would function as a natural berm. The
natural berm would help confine the cap material and allow a
thicker cap to be constructed.
Site size. The overall size of the disposal sites is governed
primarily by the total amount of material being deposited, sedi-
ment bulking factors, stable side slope characteristics of the
sediments, and existing bottom topography and consolidation char-
acteristics of both the bed and the dredged material. The ini-
tial area of deposition for both the barge and hydraulic dredge
methods can be expected to increase with increasing depth. For
the depth range identified in the general CAD disposal vicinity,
the increased depths will not increase initial areas of deposi-
tion enough to significantly increase overall site size.
Other factors. Facilities already in place, such as outfalls,
were to be avoided so that there would be no interference with
their operation. Dredge disposal sites that have experienced
permitting difficulties were considered less desirable. Other
potential disposal sites were also avoided because other future
disposal activities could potentially violate the integrity of
the CAD cap.
Much of the study area was considered unsuitable for a CAD site
because of steep slopes or evidence of unstable geotechnical condi-
tions. The RAD CAD site was selected as the preferred alternative,
meeting the above criteria and minimizing potential impacts on biol-
ogical resources (Table 21.
DREDGING AND DISPOSAL DESIGN
Performance Goals
Selection of dredging equipment for the contaminated Everett Harbor
sediments was based on the following performance goals:
1. Water entrainment during the dredging operation must be
. · .
mlnlmlzec ,.
2. Dredging equipment must be compatible with the confined aquatic
OCR for page 474
474
,
o · -
'Fit
o
1
~ . -
P:
Hi) 1
C
,4 1
U]
. -
U]
. -
o
o
U)
. -
U]
o
U)
. -
a
o
x
. -
£
A.
En
U
· -
U) O
C
O
In
O ~
P
~ .
.,
c: 1
At) 1
1
1
O ~
1
1
1
At l: 1
U)
- ~ - ~
.,
~ lo_
0 ~ 1
=~
O O 1
P.
it-
,
,
o
()
1
o
.,1
~ a
. -
C;)
U1
eC
In
.-, ~ 0
~ ~s ~
o ~ ~m
s C: ~
o ~ ~ -
u] ~ ~ #’
0 ~
s ~
u]
ca)
~n V1
0 ~
~ s~
o ~
o
3 X
o
V)
O ~
Uo)
C)
~n
0
U)
o
C)
0 0
s~
~S ~
~ O
S~
O~
~- -
O
a~ 0 ~ ~
X :E t/] .-
tn
.. ....
0 ~ ~
· · ~
er ~ (D
o o o
o o o
o o
~ ~ U)
V>~ -
-
_.
a)
_
C)
~n
s ~n
a
~ ~: ~
0 ~ os
I S~
Q a o
Q ’5: ~ ~
aS ts: U~ U]
OCR for page 475
475
disposal alternative under consideration.
3. Dredging equipment must be capable of removing the sediments at
a reasonable cost.
Selection of dredging equipment for the placement of the clean cap
sediments was based on the following performance goals:
1. Cap sediment placement would avoid displacement of the
contaminated sediments.
2. Cap placement could be controlled and monitored.
3. Dredging equipment must be capable of removing the sediments at
a reasonable cost.
Proposed Dredging Equipment
Given the equipment performance goals, a mult'phase dredging
approach for the CAD alternative was identified. Initial dredging of
uncontaminated sediments will be accomplished for purposes of construct-
ing a subaqueous confining mound at the downslope limit of the disposal
site. This dredging would also serve as a test to demonstrate the
acceptability of the final dredge equipment selection and disposal site
design. Depending on the results of the mound construction, the remain-
ing dredging and disposal would be continued as proposed or revised as
appropriate.
Mound construction will be accomplished by clamshell dredging and
bottom dump of the clean surficial sediments to the disposal site. Dur-
ing the second phase, contaminated materials will be dredged by clam-
shell dredge, with haul and dumping by split hull barges of 3,000-yd3
capacity or larger. Uncontaminated capping sediments will then be
dredged in the third phase, using a hydraulic Butterhead pipeline
dredge with discharge below surface through a diffuser unit. The
dredging effort will take place over two years, and the second year
will include a repeat of the contaminated phase and capping phase
accomplished in the first year.
Mound Construction Phase
Mound construction will be the first phase of dredging to be accom-
plished. It was originally planned for completion by pipeline dredge
with controlled placement of sediments by downpipe in the shape of a
confining mound. The intent of this original approach was to control
the placement of the clean sediments in a slurry form by the downpipe
to create a downslope confining structure to prevent loss of contam-
inated sediments during the subsequent dredging phase. It is question-
able that subaqueous confining berms can be constructed with fine-
grained soils to the side slopes proposed using a slurried hydraulic
pipeline discharged material. It was further established that the con-
taminated materials would not require a substantial berm for confine-
ment. It was finally concluded that using clamshelled material for the
OCR for page 476
476
construction of a mound with flatter side slopes--similar to that pro-
posed for the contaminated materials--was advantageous because of the
cohesion and clumping associated with clamshelled sediments. Construc-
tion of a mound section with cohesive clumps is considered less of an
uncertainty, and construction by surface disposal of clamshelled sedi-
ments became a viable option.
The downslope mound still provides a limiting structure for contam-
inated sediment placement and provides a secondary benefit. Because
the sediments are similar in situ to contaminated surficial sediments
and will be dredged and dumped in the same manner and with the same
equipment, a verification of dumping procedures and sediment fate can
be completed in the prototype prior to dredging of the contaminated
sediments. This has become an important factor in the regulatory
agency considerations to approve the disposal permit because it satis-
fied the opportunity to check the dredge and disposal design before
release of the contaminated sediments at the disposal site.
Contaminated Material Placement
Clamshell dredging for the contaminated sediment is considered the
most compatible dredging method for the CAD disposal alternative.
Modeling results indicate that the material will tend to mound if
dredged by clamshell. Placement of the material by double handling
through a submerged discharge such as a vertical downpipe was proposed,
but was discarded as unnecessary and undesirable. Use of a vertical
downpipe would require mechanical or hydraulic dredge rehandling from
the haul barge to the pipe. Based on physical modeling results, the
downpipe tended to cause side shear and Entrain greater amounts of
water in the already reduced 5- to 10-yd clumps of sediment
rehandled from the haul barge. This resulted in a lesser sediment
strength on the bed to support a cap than the surface release of the
barge load.
Disposal of clamshelled material at the surface is a viable option
for the contaminated material. For surface disposal, the cohesion and
clumping normally associated with clamshelled material would be of
benefit in reducing material spread and resuspension and would result
in a contaminated sediment mass with more strength for support of a
cap. Clamshelled material would also entrain less water, thereby
resulting in a smaller subaqueous confined volume.
Cap Placement
Hydraulic dredging of uncontaminated material for the cap placement
was recommended. The potential for displacement of the soft contami-
nated material or bearing-type failure of the cap would require that
the cap layer thickness be gradually built up. This process could be
accomplished by surface disposal or submerged pipe discharge suspended
some variable distance above the contaminated material surface. Use of
a submerged diffuser (directly connected to the hydraulic pipeline with
OCR for page 477
477
flexible hose) is an option that will be used to avoid any potential
for jetting action causing erosion of the contaminated sediments.
Final Disposal Configuration--Summary
Several final calculated designs of the disposal cross-section and
area spread were accomplished. Since the proposed dredging plan ex-
tends over two dredging seasons, the sequence of disposal operations
was taken into consideration. This sequence includes initial placement
of uncontaminated materials for a mound, then placement of a relatively
small amount of contaminated materials and immediate capping with a
greater amount (relative to the contaminated materials) of uncontam-
inated materials. After approximately nine months, an additional
larger sequence of contaminated and capping materials would be placed
(Figures 1 and 2~.
Quantities used in the design were as follows:
· year 1 uncontaminated mound materials, 580,000 yd3;
· year 1 contaminated materials, 97,000 yd ; 3
· year 1 uncontaminated cap materials, 239,800 yd ;
· year 2 contaminated materials, 831,000 yd ; 3
· year 2 uncontaminated cap materials, 1,638,000 yd .
Sediment consolidation would occur at a geometric rate, with the
greatest amount of consolidation resulting during the first few months
following disposal activities. The final design assumed a conservative
consolidation of 50 percent of the immediate deposition thickness
within three months after placement to establish cap thickness. A
minimum of 1-m thickness was required for CAD alternative acceptance by
regulatory agencies. It is anticipated that final minimum capping
thickness over contaminated materials will be 4.5 ft or more. The
total impacted area, where 3 cm or more of dredged material will be
deposited, is approximately 380 acres.
ENVIRONMENTAL MONITORING
The dredging and disposal monitoring plan, phase I document
outlines a detailed plan for meeting the conditions outlined in the
State Water Quality Certification, and COE Section 10/404 permit of
September 24, 1987.
Monitoring is divided into five phases:
1. baseline,
2. mound construction,
3. contaminated dredging and disposal,
4. capping dredging and disposal, and
5. long-term monitoring.
The monitoring plan is designed to measure physical, chemical, and
OCR for page 478
478
biological characteristics of the revised application for deep confined
aquatic disposal (PAD/CAD) site and to collect data regarding the
effect of project construction on those characteristics. The plan was
prepared considering details of the permit application, COE Section
10/404 permit, results of the Washington State Department of Ecology's
review process, and the project's construction plans and specifications
as they exist. Results of the first-year monitoring and construction
activities will then be applied toward development of the second-year
monitoring plan (phase II).
A listing of the various monitoring activities associated with the
dredging and disposal component of the Navy's Everett Homeport project
follows.
.
.
Electronic Positioning: precise sea-surface positions will be
established to meet the requirement for absolute accuracy of + 3
m. Also, a seabed positioning system will be used to locate the
actual seabed position of the sediment and benthic samples and
sediment profile camera photos.
Bathymetry: precision bathyme try (+ 20 cm accuracy) with lane
spacing of 20 m over the 1150-acre survey area.
Sidescan sonar surveys: information on the surficial characteris-
tics of the seafloor to either side of the survey trackline out
to a range of 500 ft.
Sediment profile camera: during baseline monitoring, 70 SPC
stations will be photographed with three replicates per sta-
tion. Following sediment disposal, additional photos will be
taken to define the limits of the disposed material.
· Sediment cores: sediment box cores at 37 stations will be taken
during baseline, with the upper 2 cm of each analyzed for physi-
cal properties and 79 PSDDA (Puget Sound Dredge Disposal Analy-
sis) "Chemicals of Concern," all run using Puget Sound Estuary
Program (PSEP) protocol. Piston cores will be taken after dis -
posal to identify properties of disposed sediments and thickness
of capped material. 2
Benthic macroinvertebrate assemblages: using a 0.06m box
corer at 37 stations (5 replicate/station), traditional taxon-
omic analysis will assess the characteristics of the Benthic
community. Additionally, complementary Benthic Resource
Assessment Technique (BRAT) will also be performed.
· Bioaccumulation: one epifaunal species (Cancer magister) and
one infaunal species (Mo ~padia) to be collected and investi-
gated at six stations for chemical bioaccumulation in tissue.
Bioturbation randomly located on the disposal site, 35 box core
e
stations will be collected and analyzed for density of macro-
benthic infauna and number and depth of burrows to determine
possible effects on cap material integrity.
· Sea- surface microlaYer: microlayer ~ ~ ess than 100 microns ) water
samples will be collected with a ceramic rotary drum system
prior to and during contaminated sediment disposal.
OCR for page 479
479
.
.
Current measurements: site-specific current conditions will be
collected during mound disposal, during the whole of contami-
nated sediment disposal and during two days of dredging to
determine the current influence on sediment transport. Current
meter stations at the RAD CAD site will include arrays of meters
at discrete depths (i.e., 90, 120, and 220 ft. and near bottom)
as well as an acoustic doppler current profiling meter.
Water column effects (disposal site): three-step procedure using
current drogues and acoustical transponders for plume tracing,
acoustical transponders and transmissometers for plume charac-
terization and state water quality standards monitoring.
Water column effects (dredge site): for dissolved oxygen, per-
cent light transmittance, total suspended solids, and nephelo-
metric turbidity units at various depths and distance from dredg-
ing activities.
Chemical analysis of water samples: conventional parameters will
be measured as well as 69 PSDDA chemicals of concern, all run
us ing PSEP protocol .
Sediment traps: positioned around the disposal site (over 20
locations) will be two pairs of traps on each mooring, one
located 1 to 2 m above the bottom and the other 20 m above the
bottom. Four locations will include turbidity meters on the
moorings as well.
Bioeffects (shellfish/fish): short- and long-term impacts and
changes on density, diversity, and population abundance will be
measured in a statistically significant manner.
Mussel watch: over 2,200 noncontaminated mussels will be
deployed at each of three depths on nine moorings for a 30-day
period during contaminated sediment disposal, after which mussel
tissue chemical concentration analysis will be performed.
Histopathology: will assess any short- or long-term hepatic
pathologic abnormalities in English sole before and after
disposal activities.
Second-Year Monitoring
Second-year environmental monitoring activities are expected to be
similar to the first-year activities just described, although some
adjustments to the monitoring effort will most probably result from a
review of the data collected and "lessons learned."
Long-Term Monitoring
Monitoring of environmental conditions at the disposal site is
required for at least 10 years following completion of the second-year
cap. Monitoring will be conducted at specific intervals, currently
scheduled for years 1, 2, 4, 7, and 10. Monitoring will be conducted
using the same operational procedures described for baseline and/or
disposal monitoring and will minimally include
OCR for page 480
480
electronic positioning,
bathymetry,
sediment cores, and
bioeffects - - shellfish/fish, benthic macroinvertebrates, BRAT,
bioturbation, and histopathology.
CONCLUS IONS
-
includes
sediment ___
additional volume of clean sediments in excess of 2 million Ads, to
construct an engineered CAD site in water depths of 310 to 430 ft. The
work.will be completed in three separate, regulated phases, and the
success of each preceding phase is the prerequisite to continuing with
the next phase. These phases include the clean test mound construc-
tion, phase T contaminated sediment and clean cap disposal, and phase
II contaminated sediment and clean cap disposal.
Since 1984, the prod ect has undergone extensive environmental re-
view ( including 20 public hearings ), culminating in the issuance of a
Washington State conditional use shoreline permit (May 1988) , a COE
Section 10/404 permit (September 1987) and attendant Washington State
water quality certification (March 1987~. The environmental review
process resulted in substantive project design modifications to miti-
gate environmental concerns. Nonetheless, the critical component of
the project has always been and continues to be controversy surrounding
the technical feasibility and environmental impacts of successfully
constructing a CAD site for contaminated marine sediments in a deep-
water environment. The quest for the answers to these questions has
resulted in administrative permit appeals, legal challenges in federal
and state court, repeated schedule revisions and extensions, project
funding constraints attributed to environmental concerns, and unprece-
dented environmental monitoring requirements. As a result, dredging
and disposal activities are currently scheduled to start in the summer
of 1988, more than a year after the original programmed date.
The preferred disposal alternative (CAD) is a direct extension of
existing technology that has been used successfully in other areas of
the United States. The CAD procedure has been the subject of extensive
research both within the United States as well as abroad, and is a tech-
nology sanctioned by the London Dumping Convention scientific group.
The levels of contamination encountered in Everett Harbor sediments are
handled routinely in other areas of the country. Even with this back-
ground to draw upon, regional environmental concern for Puget Sound
necessitated the expenditure of substantial time and money, far beyond
previous experience. Currently, for this project, predisposal
This paper has presented a summary of the sediment evaluation proce-
dures, disposal alternative assessments, design considerations, and
monitoring requirements associated with the dredging and disposal
required for construction of the Navy's Carrier Battlegroup Homeport
Project in Everett, Washington. The preferred disposal alternative
the dredging of approximately 1 million yd of marine
that will be treated as contaminated, together with an
OCR for page 481
481
nonconstruction costs are approximately $3.50/yd3 of contaminated seg-
iment and anticipated environmental monitoring costs exceed $8.00/yd
of contaminated sediment. These Posts can be compared to anticipated
construction costs of $4 to $7/yd of dredged material (Table 3~.
The level of monitoring required for this project is particularly
extensive, and it should be recognized that such costs would likely not
be supportable by smaller projects, privately funded projects, or local
governmental entities. A major benefit of the monitoring for this
project should be the demonstration of the viability of the CAD tech-
nique in deep water. As such, those monitoring activities intended to
verify the CAD concept would not be appropriate for future projects.
like conclusion is applicable to other components of this monitoring
program that do not demonstrate usefulness in documenting compliance
with required levels of environmental performance. Review of the pro-
ject literature reveals that several of the required sediment evalua-
tion procedures produced inconclusive results. Some evaluations demon-
strated poor repeatability and others a potential for significant false
positive results when contrasted with controls. Often these results
served to confuse rather than clarify the evaluation of possible im-
pacts. Specific aspects of this project which have produced or may
produce questionable results include
· mass loss determinations and impacts,
· microtox bioassay,
· standard bioassays,
· sea-surface microlayer,
· chronic toxicity and bioaccumulation,
· plume tracing for water quality impacts, and
· bioturbation.
TABLE 3 Summary of Dredging Costsa
Item
Contaminatedb TotalC
Sediment evaluation
Disposal alternative evaluation
Environmental Monitoring
$ 1.26
2.21
8.27
Total nonconstruction costs 11.74
Total dredging and disposal design costs
Total Construction Costs
0.35
0.62
2.32
3.29
0.21
4.00-7.00
NOTES
aNonconstru~tion costs, expressed as dollars/yd3.
b928, 000 yd
3,305,000 yd
OCR for page 482
482
The data summarized by this preliminary case study supports the
continued need for a strong national research program relating to mar-
ine sediments. The program should be directed at defining appropriate
repeatable procedures for sediment evaluation and monitoring efforts.
In addition, the process should actively eliminate requirements that
demonstrate a significant tendency for inconclusive results. Funding
and prioritization for such research should be established by an inde-
pendent national group and implemented on projects where significant
new information could be developed during construction through coor-
dination with the project proponent. It is generally not in the
national interest to allow uncertainty with regard to environmental
issues to burden a project having significant social or economic bene-
fits. The responsibility of resolving research questions related to
issues of environmental impacts should be jointly shared by the
research community and project components. Also, a national guideline
or standard on the disposal of contaminated dredged sediments should be
promulgated. The guideline should draw from the wealth of regional
experience, such as the homeport project, to minimize the unilateral
research burden on future projects. While the guideline needs to be
sensitive to regional differences and concerns, it must at the same
time maintain reasonable levels of national uniformity.
Representative terms from entire chapter:
east waterway
