£ower /Xiwamish iterway £roup
Port of Seattle / City of Seattle / King County / The Boeing Company
Date
February 22, 2013
To
Allison Hiltner and Karen Keeley, EPA
CC
Andrew Smith and Ron Timm, Ecology
From
Lower Duwamish Waterway Group
Subject
Development of the Final Technology Assignments and Modifications to
Alternative 5C Plus Scenario 5a in Support of EPA's Preferred Alternative
On November 11, 2012, EPA provided comments to LDWG on the Draft Technical
Memorandum: Supplement to the Feasibility Study for the LDW Superfund Site, Approaches
for Addressing Additional Concerns in Alternative 5C and Development of Alternative 5C Plus
Scenarios dated September 17, 2012 (referred to as the "Supplemental Scenarios
Memorandum"). The memorandum was finalized on December 20, 2012 (AECOM 2012a). EPA
requested a version of Scenario 5a with two modifications plus the smoothing out of the GIS-
based technology assignment areas, similar to what was done in the feasibility study (FS)
(AECOM 2012b) to more realistically reflect implementable areas for active remedial
technologies. This memorandum describes how the Scenario 5a footprint was modified and
presents the revised areas, volumes, and costs based on these modifications. Also included in
this memorandum are additional metrics from the FS related to both short- and long-term
effectiveness, such as: long-term spatially-weighted average concentrations (SWACs), post-
construction surface and subsurface sediment exceedances of Washington State Sediment
Management Standards (SMS) criteria, air quality impacts during construction, and subsurface
statistics for remaining PCB contamination in sediment. The modified version of Scenario 5a
was requested to support EPA's development of the preferred alternative and will likely be
called EPA's Preferred Alternative by EPA.1 Modifications to Scenario 5a are based on changes
specified by EPA direction and do not imply any position by LDWG.
Modifications to Scenario 5a
As described in the Supplemental Scenarios Memorandum, Scenario 5a had surface sediment
remedial action levels (RALs) of 2 times sediment quality standards (2xSQS) for SMS
contaminants that had been identified as contaminants of concern (COCs) in the remedial
investigation (with the exclusion of PCBs and arsenic because they are also human health risk
drivers) applied to Recovery Category 2 and 3 areas. For Modified Scenario 5a, EPA has
specified that the surface sediment RAL be modified to 2xSQS or the cleanup screening level
(CSL), whichever value is lower. As shown in Table 1, this change would reduce the RAL for 19
of 39 non-human health SMS COCs from 2xSQS to the CSL. This change in RALs is reflected in
Table 2, which provides all the RALs and upper limits (ULs) for enhanced natural recovery
1 Also referred to as Remedial Alternative 5C Plus.
Page 1
Prepared by mmm
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Memorandum to EPA and Ecology
February 22, 2013
(ENR) for Modified Scenario 5a. The surface sample locations above these RALs are shown in
Figure 1.
The Supplemental Scenarios Memorandum (AECOM 2012a) and the FS (AECOM 2012b) refer
to areas that are not actively remediated (and have surface sediment concentrations below the
SQS) as: (a) the area of potential concern (AOPC) 2 outside of AOPC 1, and (b) the remaining
study area; both of these are also labeled as "institutional controls, site-wide monitoring" in FS
Alternative 5C tables and on figures. For the Proposed Plan, EPA is changing the name of these
areas to "MNR2 Below SQS." For this memorandum, Figure 2 represents Modified Scenario 5a
using the same nomenclature as in the FS Supplemental Scenario Memorandum, and Figure 3
represents the data using the nomenclature preferred by EPA for the Proposed Plan. Other than
labeling and coloring, there is no difference in how the various areas would be managed
between the Supplemental Scenario Memorandum and the Proposed Plan (i.e., in terms of
monitoring density, frequency, and contingency actions for sediment).
The Supplemental Scenarios Memorandum assigned technologies based strictly on mapping
output from GIS. Best professional judgment (BPJ) was not used to smooth-out the small area
and sliver artifacts that often occur during GIS mapping, as was done for all of the FS
alternatives. In this memorandum, the Modified Scenario 5a footprint and its technology
assignments from the GIS output were smoothed out using BPJ as was done for the alternatives
in the FS. Small areas or slivers of technologies were lumped together with nearby technology
assignments to make areas that are more realistic for remediation by dredging, capping, and
ENR technologies and that would be large enough to remediate with normal equipment. The
minimum size was generally set as 100 ft x 100 ft, but smaller technology assignment areas were
used where appropriate, based on the waterway's physical features. For example, if a remedial
area was based only on the exceedance of an intertidal RAL, the area was truncated at the end
of the intertidal area even if the intertidal area was smaller than 100 ft wide. This mapping
process has highlighted the uncertainty in the technology assignments for remedial areas that
are driven by subsurface RALs and core polygons. Technology assignments for individual areas
are likely to be modified as additional data become available during remedial design.
Estimated Areas, Volumes, and Costs
Estimated areas, volumes, and costs are presented in Table 3. The construction time for
Modified Scenario 5a is 7 years, the same when rounded as for Scenario 5a in the Supplemental
Scenarios Memorandum. The dredge acres increased and the MNR acres decreased in Modified
Scenario 5a. This change in acreage occurred for two reasons: performing GIS smoothing3 for
mapping technologies, and decreasing the surface sediment RAL from 2xSQS to the CSL in
Recovery Categories 2 and 3. If the smoothing function was applied to Scenarios 5a and 5b in
the Supplemental Scenarios Memorandum, it would have the same net effect (more
dredging/less MNR in areas currently assigned to MNR). The net difference between Scenario
5a and Modified Scenario 5a is estimated to be only a few acres (assuming the smoothing
2 MNR is monitored natural recovery.
3 GIS smoothing accounts for roughly 90% of the changes in acreages assigned to dredging, partial dredging and capping, capping, ENR, or
MNR. The change in surface sediment RAL accounts for the remaining change in acreages. The RAL change may affect additional acres
when new data are collected.
JJj,ower JUpuwaimlsii f^p»terway ^yroup
Port of Smmtitm / City of S+mtttm f King County / Tim Booing Company
Page 2
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Memorandum to EPA and Ecology
February 22, 2013
function was applied to both) based on the RAL change for non-human health SMS
contaminants and using the FS baseline dataset (although the uncertainty in this estimate is
noted above). The rounded total dredge volume for Modified Scenario 5a remains the same as
for Scenario 5a (790,000 cy), because the increased volume resulting from an increase in
dredging area was offset by decreased contingency volume due to a decrease in MNR area.
The costs for the Modified Scenario 5a, presented as net present value using a 2.3% discount
rate (same as in the FS), are slightly higher than for Scenario 5a in the Supplemental Scenarios
Memorandum. A detailed supporting cost estimate for Modified Scenario 5a (including capital
costs, present value adjustment, contingencies, agency oversight, reporting, and monitoring
costs) is presented in Table 4. In addition, Table 3 provides the estimated net present value costs
developed for FS Alternative 5C, Scenario 5a, and the Modified Scenario 5a using 0% and 7%
discount rates, consistent with the sensitivity analysis presented in the FS.
Comparative CERCLA Evaluation
Table 5 provides the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) threshold and balancing criteria for Modified Scenario 5a, in addition to the
information already provided for the Supplemental Scenarios. Table 5 presents information in
the same format as Table 10-1 in the Final FS and Table 11 in the Supplemental Scenarios
Memorandum.
Like FS Alternative 5C and the other Supplemental Scenarios, Modified Scenario 5a is predicted
to achieve the threshold criterion of overall protection of human health and the environment
through varying combinations of engineering controls, natural recovery, and institutional
controls. Modified Scenario 5a is not expected to fully comply with the Model Toxics Control
Act (MTCA) requirement of natural background preliminary remediation goals (PRGs) (for the
three risk-driver COCs with risk-based goals below natural background) or with applicable or
relevant and appropriate requirements (ARARs) for water quality.
Modified Scenario 5a has only minor changes to total dredge volume and construction time
compared to those for Scenario 5a (see Table 5)4; the bed composition model (BCM) predicts
that this modified scenario achieves similar SWACs for the four human health risk drivers
(PCBs, arsenic, cPAHs, and dioxins/furans) in the same time frames and with equivalent
degrees of uncertainty as Scenario 5a (Table 6).
Modified Scenario 5a is predicted to achieve magnitudes of human health and ecological risks
equivalent to those for Scenario 5a. Therefore, the predicted times to achieve the cleanup
objectives (shown in Table 5) for this modified scenario remain unchanged from those for
Scenario 5a in the Supplemental Scenarios Memorandum (AECOM 2012a). Tables 7a, 7b, and 7c
present the risks associated with: total PCBs for human health seafood consumption (RAO 1),
total PCBs for river otter (RAO 4), and all four risk drivers for human health direct contact
(RAO 2).
4
Modified Scenario 5a has incrementally larger volumes compared to Scenario 5a; however, the differences are not large enough to be
evident after rounding to two significant figures (790,664 cy for Modified Scenario 5a compared to 785,216 cy for Scenario 5a).
JJj,ower JUpuwaimlsii f^p»terway ^yroup
Port of Smmtitm / City of S+mtttm f King County / Tim Booing Company
Page 3
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Memorandum to EPA and Ecology
February 22, 2013
Table 8 shows the predicted post-construction exceedances of SMS criteria for Modified
Scenario 5a. As for Scenario 5a, this modified scenario is predicted to be at or below the SQS
within 5 years after the start of cleanup, and has a few predicted point exceedances for
phthalates located near outfalls. The BCM output, shown in 5-year increments, does not portray
any difference between Scenario 5a and Modified Scenario 5a. However, Modified Scenario 5a
reduces uncertainty in meeting the SQS within 10 years by addressing contamination that
exceeds the CSL where 2xSQS is greater than the CSL.
Table 9 provides the magnitude of residual risks for Modified Scenario 5a presented as post-
construction sediment conditions (long-term effectiveness and permanence criteria). The
magnitude of risks is based on the amount of contamination remaining in the subsurface
sediments after remediation and the potential for exposure of subsurface contamination. The
metrics include: the number of cores remaining in the subsurface, the number of acres of
remaining subsurface sediment contamination that could be disturbed, and PCB concentration
statistics in the upper 2 ft of sediments, which all indicate only small differences compared to
Scenario 5a. Compared to Alternative 5C (Table 10), Modified Scenario 5A reduces the
subsurface concentrations in both Recovery Category 1 and Recovery Categories 2 and 3. In
addition, Modified Scenario 5a has a low potential to expose remaining subsurface sediment
contamination as a result of unanticipated disturbance effects, and has a low potential to affect
long-term SWACs.
Modified Scenario 5a ranks similar to Scenario 5a for monitoring and maintenance, because it
requires long-term monitoring of a large area, seafood consumption advisories, public outreach,
and education programs (Table 5).
In terms of reductions in mobility, toxicity, and volume (Table 5), Modified Scenario 5a is
equivalent to Scenario 5a because it does not include any ex situ treatment and the areas using in
situ treatment as a component of ENR have not changed from Scenario 5a.
A summary of the short-term effectiveness metrics is presented in Table 11. Estimates of gas
and particulate emissions, energy consumption, landfill capacity consumed, carbon footprint
and depleted natural resources for Modified Scenario 5a vary slightly from those for
Scenario 5a.
Modified Scenario 5a has a period of community exposure (including noise, traffic, air
pollution), worker exposure, ecological disturbance, and elevated fish and shellfish tissue
concentrations from resuspension of contaminated material equal to the estimated dredging
duration of 7 years. For this modified scenario, active remediation would impact the benthic
community within a similar area of intertidal and shallow habitat as Scenario 5a (Table 5).
Modified Scenario 5a takes 15 years to achieve the cleanup objectives, which is the same time
frame as for Scenario 5a in the Supplemental Scenarios Memorandum5 (AECOM 2012a), with a
5
Note that the time to achieve cleanup objectives reported for all alternatives (15 years) is relative to the BCM output, which is generated in 5-
year increments (see Table 6). However, in both the FS and in the Proposed Plan the values are adjusted based on time post-construction.
For example, in the Proposed Plan, both FS Alternative 5C and Modified Scenario 5a are shown as requiring 17 years to achieve cleanup
objectives versus 15 years in this memorandum. This is because the construction time frame of 7 years was rounded to the nearest 5-year
JJj,ower JUpuwaimlsii f^p»terway ^yroup
Port of Smmtitm / City of S+mtttm f King County / Tim Booing Company
Page 4
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Memorandum to EPA and Ecology
February 22, 2013
somewhat lower degree of uncertainty (due to the 16 acres of MNR) compared to Scenario 5a
(27 acres of MNR).
Modified Scenario 5a is technically and administratively implementable during and after
construction, because of its minor need for additional actions after dredging and capping as a
result of its more stringent surface RALs (Table 5). This modified scenario has a lower potential
to require contingency actions in the future than Scenario 5a because it has fewer acres of MNR.
The estimated net present value cost of Modified Scenario 5a is $305 million (Table 4), which is
slightly higher than for Scenario 5a (Table 3). FS Alternative 5C, Supplemental Scenario 5a, and
Modified Scenario 5a are predicted to achieve the total PCB excess cancer risk of 2 x 104 for the
Adult Tribal RME seafood consumption scenario at the end of the construction period.
Although the BCM predicts the same risk outcomes for Scenario 5a and Modified Scenario 5a,
Modified Scenario 5a reduces uncertainty by addressing more contamination through active
remediation rather than relying on natural recovery predictions.
References
AECOM 2012a. Technical Memorandum: Supplement to the Feasibility Study for the LDW
Superfund Site, Approaches for Addressing Additional Concerns in Alternative 5C and
Development of Alternative 5C Plus Scenarios. Prepared for the U.S. Environmental
Protection Agency and Washington State Department of Ecology. Prepared by the
Lower Duwamish Waterway Group. December 20, 2012.
AECOM 2012b. Final Feasibility Study. Lower Duwamish Waterway, Seattle, WA. Prepared for the
U.S. Environmental Protection Agency and Washington State Department of Ecology.
Prepared by the Lower Duwamish Waterway Group. October 31, 2012.
Windward Environmental, LLC 2007a. Baseline Ecological Health Risk Assessment, Lower
Duwamish Waterway. Final. Prepared for Lower Duwamish Waterway Group for
submittal to U.S. Environmental Protection Agency, Seattle, WA and Washington
Department of Ecology, Bellevue, WA. July 31, 2007.
Windward Environmental, LLC 2007b. Baseline Human Health Risk Assessment, Lower Duwamish
Waterway. Final. Prepared for Lower Duwamish Waterway Group for submittal to U.S.
Environmental Protection Agency, Seattle, WA and Washington Department of Ecology,
Bellevue, WA. November 12, 2007.
Windward Environmental, LLC 2010. Lower Duwamish Waterway Remedial Investigation, Remedial
Investigation Report. Final. Prepared for Lower Duwamish Waterway Group for
submittal to U.S. Environmental Protection Agency, Seattle, WA and Washington State
Department of Ecology, Bellevue, WA. July 2010.
increment for purposes of the BCM. The time to achieve cleanup objectives was predicted to be 15 years in the BCM, or 10 years post-
construction. An actual construction time of 7 years plus 10 years post-construction equals 17 years following the beginning of construction.
JJj,ower /^uwamish f^p»terway ^roup Pa e 5
Port of 30*tti# / City of 39*Mm / King County / fA# Boeing Company ®
-------
Memorandum to EPA and Ecology February 22, 2013
Table 1 SMS Criteria and 2xSQS versus CSL Remedial Action Level Analysis for Surface Sediment
SMS Contaminant of Concern
SQS
2xSQS
CSL
Unit
2xSQS greater
than CSL?
Metals
Cadmium
5.1
10.2
6.7
mg/kg dw
Yes
Chromium
260
520
270
mg/kg dw
Yes
Copper
390
780
390
mg/kg dw
Yes
Lead
450
900
530
mg/kg dw
Yes
Mercury
0.41
0.82
0.59
mg/kg dw
Yes
Silver
6.1
12.2
6.1
mg/kg dw
Yes
Zinc
410
820
960
mg/kg dw
No
PAHs
2-Methylnaphthalene
38
76
64
mg/kg oc
Yes
Acenaphthene
16
32
57
mg/kg oc
No
Anthracene
220
440
1,200
mg/kg oc
No
Benzo(a)anthracene
110
220
270
mg/kg oc
No
Benzo(a)pyrene
99
198
210
mg/kg oc
No
Benzo(g,h,i)perylene
31
62
78
mg/kg oc
No
Total benzofluoranthenes
230
460
450
mg/kg oc
Yes
Chrysene
110
220
460
mg/kg oc
No
Dibenzofa, h)anthracene
12
24
33
mg/kg oc
No
Fluoranthene
160
320
1,200
mg/kg oc
No
Fluorene
23
46
79
mg/kg oc
No
lndeno(1,2,3-cd)pyrene
34
68
88
mg/kg oc
No
Naphthalene
99
198
170
mg/kg oc
Yes
Phenanthrene
100
200
480
mg/kg oc
No
Pyrene
1,000
2,000
1,400
mg/kg oc
Yes
Total HPAHs
960
1,920
5,300
mg/kg oc
No
Total LPAHs
370
740
780
mg/kg oc
No
Phthalates
Bis(2-ethylhexyl)phthalate
47
94
78
mg/kg oc
Yes
Butyl benzyl phthalate
4.9
9.8
64
mg/kg oc
No
Dimethyl phthalate
53
106
53
mg/kg oc
Yes
Chlorobenzenes
1,2,4-Trichlorobenzene
0.81
1.62
1.8
mg/kg oc
No
1,2-Dichlorobenzene
2.3
4.6
2.3
mg/kg oc
Yes
1,4-Dichlorobenzene
3.1
6.2
9
mg/kg oc
No
Hexachlorobenzene
0.38
0.76
2.3
mg/kg oc
No
Other SVOCs and COCs
2,4-Dimethylphenol
29
58
29
|jg/kg dw
Yes
4-Methylphenol
670
1,340
670
|jg/kg dw
Yes
Benzoic acid
650
1,300
650
|jg/kg dw
Yes
Benzyl alcohol
57
114
73
|jg/kg dw
Yes
Dibenzofuran
15
30
58
mg/kg oc
No
n-Nitrosodiphenylamine
11
22
11
mg/kg oc
Yes
Pentachlorophenol
360
720
690
|jg/kg dw
Yes
Phenol
420
840
1,200
|jg/kg dw
No
Notes:
1. The SMS contaminants total PCBs and arsenic are not shown because they are also human health risk drivers. The site-wide surface
sediment RALs for these contaminants are the SQS.
2. Five other SMS contaminants (diethyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate, hexachlorobutadiene, and 2-methylphenol) are
not listed because they were not identified as COCs during the remedial investigation.
COC = contaminant of concern; CSL = cleanup screening level; dw = dry weight; HPAH = high-molecular-weight polycyclic aromatic
hydrocarbon; kg = kilogram; LPAH = low-molecular-weight polycyclic aromatic hydrocarbon; |jg = micrograms; mg = milligrams; oc = organic
carbon; PAH = polycyclic aromatic hydrocarbon; PCB = polychlorinated biphenyl; SMS = Sediment Management Standards; SQS = sediment
quality standard; SVOC = semivolatile organic compound
^ower /7uwamish f^/aterway proup
Port of Seattle / City of Seattle / King County / The Boeing Company
Page 6
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Memorandum to EPA and Ecology
Table 2 Remedial Action Levels (RALs) and Upper Limits (ULs) for ENR for Modified Scenario 5a
February 22, 2013
Risk Driver
Units
RAL or UL
for ENR
intertidai sediments
(+11.3 ft MLLW to-4 ft MLLW)
Subtidal Sediments
(-4 ft MLLW and Deeper)
Recovery Category 1 Areas
Recovery Category 2 and 3
Areas
Recovery Category 1 Areas
Recovery Category 2 and 3
Areas
4 in (10 cm)
depth interval
1.5 ft (45 cm)
depth interval
4 in (10 cm)
depth interval
1.5 ft (45 cm)
depth interval
4 in (10 cm)
depth interval
2 ft (60 cm)
depth interval
4 in (10 cm)
depth interval
2 ft (60 cm)
depth interval
(applied only at
potential tug
scour areas)3
PCBs (Total)
m
g/kg oc
RAL
12
12
12
65
12
12
12
195
UL for ENR"
-
-
65
97
-
65
195
cPAH
M9TEQ/k 9 dw
RAL
1,000
900
1,000
900
1,000
1,000
1,000
-
UL for ENRb
-
-
3,000
1,350
-
-
3,000
-
Dioxins/Furans
ng TEQ/kg dw
RAL
25
28
25
28
25
25
25
-
UL for ENRb
-
-
75
42
-
-
75
-
Arsenic (Total)
^ g/kgdw
RAL
57
28
57
28
57
57
57
-
UL for ENRb
-
-
171
42
-
-
171
-
39 SMS
contaminants0
contaminant-
specific
RAL
SQS
SQS
2xSQS not to
exceed CSLd
--
SQS
SQS
2xSQS not to
exceed CSLb
—
UL for ENR"
-
-
3xRAL
-
-
-
3xRAL
Notes:
- = no action level
1. The evaluation depth intervals for sediment are 10 cm, 45 cm, or 60 cm, depending on the location and recovery category.
a. Potential tug scour areas are defined as subtidal areas above -24 ft MLLW north of 1 st Ave South Bridge, and above -18 ft MLLW south of 1 st Ave South Bridge.
b. ENR is not an option in Recovery Category 1 areas. Upper limits for ENR are therefore shown only for Recovery Category 2 and 3 areas.
c. There are 41 SMS contaminants of concern, but PCBs and arsenic are addressed as human health risk drivers.
d. Surface sediment RAL in Recovery Category 2 and 3 areas is 2 times the SQS or the CSL, whichever is lower for non-human health risk drivers.
cm = centimeter; cPAH = carcinogenic polycyclic aromatic hydrocarbon; CSL = cleanup screening level; dw = dry weight; ENR = enhanced natural recovery; ft = feet; in = inch; kg = kilogram; |jg =
micrograms; mg = milligrams; MLLW = mean lower low water; ng = nanograms; oc = organic carbon; PCB = polychlorinated biphenyl; RAL = remedial action level; SMS = Sediment Management
Standards; SQS = sediment quality standard; TEQ = toxic equivalent; UL = upper limit
J^ower J^uwamlsh J^aterway £yroup
Port of ' City of S+attto / King County / Tho Booing Company
Page 7
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Memorandum to EPA and Ecology
Table 3 FS Alternative 5C, Supplemental Scenario 5a, and Modified Scenario 5a: Estimated Areas, Volumes, Construction Times, and Costs
February 22, 2013
Remedial Scenario
Remedial Technology and Areas
Dredge-cut
Prism
Volume
(cy)d
Performance
Contingency
Volume
(cy )e
Total
Dredge
Volumie
(cy)f
Total Placement
Volume
(Capping, ENR///7 situ,
Dredge Residuals,
Habitat)
(cy)
Construction
Time Frame
(years)a
Cost
($MM Net Present
Value)h
Higi/Low Sensitivity
Costs
($MW undiscounted/7%
discount rate)
EAAs
(acres)
Actively Remediated
Areas without Active Remediation
Total
Active
(acres)
Total not
actively
remediated
(acres)
Total
Study
Area
(acres)
Dredge
(acres)
Partial Dredge
and Cap (acres)
Cap
(acres)
ENR/
in situ
(acres)
MNRa
(acres)
VMb
(acres)
Institutional Controls, Site-
wide Monitoring, & Natural
Recovery
(AOPC 2 and Rest of LDW)C
(acres)
FS Alternative 5C
29
57
23
24
53
0
23
232
157
255
441
640,000
110,000
750,0010
580,000
7
$290
$330/$240
Scenario 5a'J'k''
Subsurface RAL of CSL/ 3xCSL only for
PCBs (intertidal/subtidal), and surface RAL
of 2xSQS for non-HH risk drivers
29
62
16
23
48
27
17
220
148
264
441
650,000
130,000
790,0010
560,000
7
$303
$345/$245
EPA Preferred Alternative (Scenario 5a
modified with technology assignment
smoothing (BPJ) and surface sediment RAL
adjusted to CSL when 2xSQS is greater for
applicable non-human health risk driver SMS
contaminants)
29
64
20
24
48
16
17
223
156
256
1441
670,000
120,000
790,0010
590,000
7
$305
$348 / 247
Notes:
1. Areas are rounded to the nearest acre. Acres for all remedial alternatives add up to the total study area of 441.3 acres; apparent discrepancies in total areas are due only to rounding. Volumes are rounded to two significant figures. Volumes are calculated in a spreadsheet prior to rounding; apparent discrepancies in total volumes are due only to
rounding. Volumes and costs do not include the EAAs.
a. MNR is monitoring to achieve the SQS within 10 years following construction. This is referred to as MNR (Surface Sediment >SQS) in Figure 3.
b. VM areas are included as MNR (Surface Sediment >SQS) in Figure 3.
c. Institutional Controls, Site-wide Monitoring and Natural Recovery (AOPC 2 and the Rest of the LDW) are referred to as MNR (Surface Sediment 100 |jg/kg dw (i.e., -clipped to AOPC 2 boundary). The additional remediation
due to subsurface concentrations in navigation channel shoaling areas was estimated using the maximum concentrations in the upper 2 ft of cores, delimited horizontally using core polygons restricted to areas where the existing bathymetric elevations w/ere above the authorized navigation channel depth. Concentrations >Alteinative 5C RALs
were assigned to partial dredging/capping or dredging based on the technology assignment assumptions in the FS.
j. Scenario 5a and Modified Scenario 5a include an intertidal RAL of the CSL for PCBs to 45 cm depth, applied only to Recovery Category 2 and 3 areas (RALs for Recovery Category 1 areas remain the same as for FS Alternative 5C).
k. Subsurface RAL applies in potential tug scour water depths, defined as -24ftMLLW to -4ftMLLW in Reach 1 (i.e., north of 1st Ave Bridge), and -18 ft MLLW to-4ftMLLW in Reaches 2 and 3 (i.e., south of 1st Ave Bridge).
I. Additional remediation from the subsurface RAL exceedances was estimated using the maximum concentrations in the upper 2 ft of cores, delimited horizontally using core polygons. Scenario 5a and Modified Scenario 5a restrict the core polygons to AOPC 1 (i.e., -areas with surface sediment concentrations >Alt. 5C RALs).
AOPC = area of potential concern; BPJ = best professional judgment; C = combined technology; cm = centimeters; CSL = cleanup screening level; cy = cubic yards; EAA = early action area; ENR = enhanced natural recovery; FS = feasibility study; ft = foott; HH = human health; LDW = Lower Duwamish Waterway; MLLW = mean lower low water; MM
= million; MNR = monitored natural recovery; n/a = not applicable; R = removal emphasis; RAL = remedial action level; SMS = Sediment Management Standards; SQS = sediment quality standard; UL = upper limit; VM = verification monitoring
^ower /7uwamish f^/aterway proup
Port of Seattle / City of Seattle / King County / The Boeing Company
Page 8
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Memorandum to EPA and Ecology February 22, 2013
Table 4 Cost Summary for Modified Scenario 5a (with 2.3% Discount Rate)
UNIT
QUANTITY/
TASK
COST
UNIT
SUBTOTAL
PRECONSTRUCTION
Mobilization, Demobilization and Site Restoration (project)
Mobilization, Demobilization and Site Restoration (seasonal)
Land Lease for Operations and Staging
Contractor Work Plan Submittals
Barge Protection
Subtotal:
$800,000
$120,000
$250,000
$100,000
$80,000
LS
YEAR
YEAR
YEAR
LS
1
8.6
8.6
8.6
1
$4,925,966
PROJECT MANAGEMENT (CONTRACTOR)
Labor and Supervision
Construction Office and Operating Expense
Subtotal:
$62,000
$21,600
MONTH
MONTH
39.0
39.0
$3,262,484
DREDGING
Shift Rate
Gravity Dewatering (on the barge)
Subtotal:
$25,963
$10
DAY
CY
761.0
790,664
$27,664,177
SEDIMENT HANDLING AND DISPOSAL
Transloading Area Setup
Water Management
Transload, Railcar Transport to and Tipping at Subtitle D Landfill
Subtotal:
$1,000,000
$10,000
$60
LS
DAY
TON
1
761.0
1,185,997
$79,769,663
SEDIMENT CAPPING, DREDGE RESIDUALS, DREDGE BACKFILL
Debris Sweep
Shift Rate (12 hours)
Cap material procurement and delivery (sand)
Subtotal:
$30,000
$12,500
$27
ACRE
DAY
CY
2
501.6
534,103
$20,790,501
ENHANCED NATURAL RECOVERY
Debris Sweep
Shift Rate (12 hours)
Material procurement and delivery (sand)
Material procurement and delivery (carbon amended sand)
Subtotal:
$30,000
$12,500
$27
$161
ACRE
DAY
CY
CY
5
46
28,824
28,824
$6,151,246
CONSTRUCTION QA/QC
Construction Monitoring
Subtotal:
$7,925
DAY
761.0
$6,030,995
POST-CONSTRUCTION PERFORMANCE MONITORING
Compliance Testing (Dredging)
Compliance Testing (Capping)
Compliance Testing (ENR)
Subtotal:
alt specific
alt specific
alt specific
PROJECT
PROJECT
PROJECT
$1,202,024
$1,112,168
$1,221,569
$3,535,761
CAPITAL COST (base)
$152,130,792
CAPITAL COST (present value)
$139,743,581
Construction Contingency
Sales Tax
Project Management, Remedial Design and Baseline Monitoring
Construction Management
TOTAL CAPITAL COST (INCLUDING SUM OF ABOVE)
$48,910,253
$13,275,640
$41,923,074
$13,974,358
$257,826,907
AGENCY OVERSIGHT, REPORTING, O&M, & MONITORING COSTS (present value)
Agency Review and Oversight
Reporting
Operations and Maintenance (Dredging)
Operations and Maintenance (Capping)
Operations and Maintenance (ENR)
Operations and Maintenance (MNR >SQS)
Operations and Maintenance (MNR
-------
Memorandum to EPA and Ecology February 22, 2013
Table 5 Comparative Evaluation and Relative Ranking of FS Alternative 5C, Supplemental 5C Plus Scenarios, and Modified Scenario 5a
Evaluation Criteria
Remedial Scenario
FS Alternative 5C
5C Plus Base (and
PCB Intertidal RAL)
Scenario 1:
Scenario 2:
Scenario 3:
Scenario 4:
Scenario 5a:
Scenario 5b:
Modified Scenario 5a:
Overall
Protection of
Human Health
and the
Environment
Summary of Overall Protection of
Human Health and the Environment
Alternative 5C, the Supplemental 5C Plus scenarios, and Modified Scenario 5a achieve overall protection of human health and the environment: in varying time frames and with varying degrees of certainty.
All these remedial scenarios require institutional controls to fully achieve protectiveness. Longer construction periods result in proportionately greater short-term impacts.
Dredging or capping a larger surface area has a lower potential for subsurface contamination to be exposed by natural or mechanical disturbances (e.g., scour, earthquakes).
The potential for subsurface contaminated sediment to be exposed diminishes as more contaminated sediment is dredged.
Comply
with
ARARs
Summary of ARARs
Alternative 5C, the Supplemental 5C Plus scenarios, and Modified Scenario 5a are not expected to comply with all surface water quality standards,
or with all natural background sediment standards required under MTCA (for risk-based RBTCs below background). Surfacee water quality and MTCA ARAR waivers,
the need for which varies among the remedial scenarios, will be required at or before completion of the remedial action.
Achieve Threshold Requirements
Scenariosi ikely require one or more ARAR waivers to meet threshold criteria.
Long-term Effectiveness and Permanence
Magnitude of Residual Risk
(Contaminated sediment remaining in the subsurface)
Total dredge area outside of EAAs (acres)
57
72
80
82
73
66
62
55
64
Total cap, partial dredge/cap
47
49
69
69
53
51
39
38
44
Total ENRtin situ area (in Category
1/Categories 2 & 3 combined; acres)3'b
0/53
0/51
0/45
0/44
0/48
0/50
0/48
0/47
0/48
MNR area (in Category 1/Categories 2 & 3
combined; acres)b
0/0
0/0
0/0
0/0
0/0
0/0
0/27
0/28
0/16
Total VM and AOPC 2 area (in Category
1/Categories 2 & 3 combined; acres)b
23/122
23/110
19/100
19/100
23/108
23/115
23/108c
23/115
23/110
Post-construction number of core stations
remaining >CSL at any depth in the FS
dataset (under caps/ all other locations)11
20/22
21/17
25/13
27/11
22/16
22/19
19/22
19/22
19/23
Potential for Exposing Remaining
Subsurface Contamination
Alternative 5C and all the scenarios have a low potential for exposure due to unanticipated disturbance effects.
Modeling results range from 22 acres disturbed (FS Alternative 5C) up to 49 acres disturbed (Scenario 1) needed to produce a 25% increase in the long-term SWAC.
Adequacy and Reliability of
Controlse
Relative amount of monitoring and
maintenance required (based on total cap,
partial dredge/cap, ENRtin situ, and MNR
areas; acres)
Large area
(100)
Large area
(100)
Large area
(114)
Large area
(113)
Large area
(101)
Large area
(101)
Large area
(114)
Large area
(113)
Large area
(108)
Magnitude and
Duration of
Institutional Controls
Monitoring and notification of
waterway users (based on
total cap, partial dredge/cap,
EHRIinsitu, and MNR
areas)f
Similar requirements for monitoring and maintenance as Alternative 5C.
Seafood consumption
advisories, public outreach,
and education
Similar seafood consumption advisories, public outreach, and education are required for Alternative 5C ;and all the scenarios.
Summary
Scenarios 1 and 2 leave the least area with subsurface contaminated sediments and therefore rank higher in long-term effectiveness and permanence than Alternative 5C and Scenario 5b. All others leave an intermediate amount of sediments,
including Modified Scenario 5a. For comparison purposes, Alternative 4R dredges 93 acres, Alternative 6C dredges 108 acres and Alternative 5R dredges 143 acres (AEC(OM 2012b). The scenarios also have similar monitoring and maintenance requirements to
Alternative 5C.
^ower /)uwamish J^aterway proup
Por/ Seattle / C/
-------
Memorandum to EPA and Ecology February 22, 2013
Table 5 Comparative Evaluation and Relative Ranking of Alternative 5C, Supplemental 5C Plus Scenarios, and Modified Scenario 5a (continued)
Remedial Scenario
Evaluation Criteria
Alternative 5C
5C Plus Base (and
PCB Intertidal RAL)
Scenario 1:
Scenario 2:
Scenario 3:
Scenario 4:
Scenario 5a:
Scenario 5b:
Modified Scenario 5a:
Reduction of
Toxicity, Mobility,
or Volume through
Treatment
£>rs/Mreatment of dredged material
None
None
None
None
None
None
None
None
None
in situ treatment (Area in acres
potentially treated in situ is assumed to
be 50% of total ENR and in situ
treatment area)
26.5
25.5
22.5
22
24
25
24
23.5
24
c
o
~o
"go
Period of community exposure
(including noise), worker exposure,
ecological disturbance and
resuspension of contaminated material
from dredging (years of construction^
7
8
9
9
9
8
7
6
7
o
O
CD
Dredge-cut prism volume/
Performance contingency (cy)
640,000/
750,000
780,000/
880,000
860,000/
950,000
870,000/
960,000
790,000/
890,000
740,000/
840,000
650,000/
790,000
600,000/
740,000
670,000/
790,000h
"O
c
o
~o
_CD
~o
Air quality impacts
(normalized to Alt 5C [divided by
Alt. 5C impacts for a relative score])
1
1.17
1.27
1.28
1.19
1.12
1.05
0.99
1.05
Q_
Ecological - Habitat area shallower
than -10 ft MLLW disturbed (dredging
and capping)
39
48
56
58
50
42
41c
33
43
Short-term Effectiveness
c
o
~o
RAO 1:10-4 magnitude PCB risk
(Adult Tribal RME)i
7
8
9
9
9
8
7
6
7
CD
C/5
C/5
o ro
Q_ S>
RAO 1: Predicted time for total PCBs
and dioxins/furans to reach long-term
model-predicted concentration range
in surface sediment)
15
15
15
15
15
15
15
15
15
E -
'
CD
RAO 2: Individual risk from cPAHs
<1 x 10"6 in all areas except Beach 3
3
3
3
3
3
3
3
3
3
.C
O
CO
RAO 3: Benthic invertebrates (SOS)'
6
6
6
6
6
6
6
6
6
CD
E
i—
RAO 4: Ecological - river otters
(HQ<1)'
7
8
9
9
9
8
7
6
7
Summary of short-term effectiveness
Impacts from construction
similar to Alt 3R and
higher than Alt 2, 3C, and
4C and lower than Alt 5R,
6C and 6R. Construction
time of 7 yrs to reduce
contaminant
concentrations. Very low
uncertainty (no MNR).
Impacts are 20% higher
than Alt 5C. Construction
time of 9 years. No MNR.
Impacts are 30% higher
than Alt 5C. Construction
time of 9 years. No MNR.
Impacts are 30% higher
than Alt 5C. Construction
time of 9 years. No MNR.
Impacts are
20% higher than Alt 5C.
Construction time of 9 years.
No MNR.
Impacts are
10% higher than Alt 5C.
Construction time of 8
years. No MNR.
Impacts are similar to
Altt 5C. Construction time of 7
years.
27 acres MNR.
Impacts are similar to
Alt 5C. Construction time of 6
years.
28 acres MNR.
lmpa:ts are similar to
Alt 5C. Construction time of 7
years.
16 acres MNR.
/.ower /^uwamish f^aterway ^roup
Port of SomtHo / City of 3o*ttto / County / TA* Booing Company
Page 11
-------
Memorandum to EPA and Ecology February 22, 2013
Table 5 Comparative Evaluation and Relative Ranking of Alternative 5C, Supplemental 5C Plus Scenarios, and Modified Scenario 5a (continued)
Remedial Scenario
Evaluation Criteria
Alternative 5C
5C Plus Base (and
PCB Intertidal RAL)
Scenario 1:
Scenario 2:
Scenario 3:
Scenario 4:
Scenario 5a:
Scenario 5b:
Modified Scenario 5a:
>.
3
CO
Technical and administrative implementability during
construction
Construction period
longer than Alt 2, 3 and
4C, and shorter than Alt
4R, 5R and 6. Low
potential for difficulties
and delays.
Longer construction period
than 5C. Greater potential
for construction delays.
Longer construction period
than 5C. Greater potential
for construction delays.
Longer construction period
than 5C. Greater potential
for construction delays.
Longer construction period
than 5C. Greater potential for
construction delays.
Longer construction
period than 5C. Greater
potential for
construction delays.
Same construction period as
5C.
Lower construction period
than 5C.
Same construction period as
5C.
£Z
03
E
03
Q.
E
Technical and administrative implementability after
construction
Additional actions may be
needed after dredging to
meet low RALs. Low
potential for additional
actions in ENR areas.
Additional actions may be
needed after dredging to
meet low RALs. Low
potential for additional
actions in ENR areas.
Additional actions may be
needed after dredging to
meet low RALs. Low
potential for additional
actions in ENR areas.
Additional actions may be
needed after dredging to
meet low RALs. Low
potential for additional
actions in ENR areas.
Additional actions may be
needed after dredging to
meet low RALs. Low
potential for additional
actions in ENR areas.
Additional actions may
be needed after
dredging to meet low
RALs. Low potential for
additional actions in
ENR areas.
Less need for additional
actions after dredging
because of higher surface
RALs. Higher potential for
additional actions than
Alternative 5C due to MNR
areas.
Less need for additional
actions after dredging
because of higher surface
RALs. Higher potential for
additional actions than
Alternative 5C due to MNR
areas.
Less need for additional
actions after dredging
because of higher surface
RALs. Higher potential for
additional actions than
Alternafve 5C due to MNR
areas.
Costs
Total Net Present Value (MM$)n
290
331
357
358
333
319
303
289
305
Notes:
a. The proportion of ENR with or without in s/?f/treatment is assumed to be 50°/cV50% for Alternative 5C and all the scenarios.
b. Recovery categories: Category 1 - recovery presumed to be limited; Category 2 - recovery less certain than Category 3; Category 3 - recovery predicted to occur. The acres shown in Recovery Category 1 are "verification monitoring" acres, which are predicted to be below the Alt 5C RALS when remedial design data are
collected.
c. Two values have been revised from Table 11 in the Supplemental Scenarios Memo (AECOM 2012a) as a result of QC checks. For Scenario 5a, the area of VM and AOPC 2 in Recovery Categories 2 and 3 was revised from 114 to 1108 acres. Also for Scenario 5a, the habitat area (shallower than -10 ftMLLW) disturbed
by dredging or capping was revised from 36 to 41 acres.
d. Remaining cores grouped by those located under caps and those located anywhere else within the LDW after construction.
e. This analysis evaluates the reliability of controls after RAOs are achieved. The construction periods differ (see Short-term Effectiveness) and various controls will also be required during construction.
f. Increased sediment monitoring in areas not actively remediated (AOPC 2 and the rest of the LDW) was assumed for the Supplemental Scenarios. Monitoring frequency changed to 1 sample/acre in natural recovery areas and ICs, amd long-term monitoring areas.
g. Construction period rounded to nearest year. Additional time beyond construction would be required for ecologically sensitive areas to recover. Also, fish and shellfish tissue contaminant concentrations may require additional time aftter construction to recover.
h. Modified Scenario 5a has incrementally larger volumes compared to Scenario 5a; however, the differences are not large enough to be evident after rounding to two significant figures (790,664 cy for Modified Scenario 5a compared to 785,216 cy for Scenario 5a).
i. The predicted time to achieve cleanup objectives is calculated from the start of construction.
j. No remedial scenario achieves RAO 1 PRGs. All remedial scenarios achieve protectiveness with some combination of active and passive remediation and ICs. Two time frames are provided for purposes of comparing the scenarios: 1) the point at which the remedial scenario reduces the Adult Tribal RME seafood
consumption risk to 10", and 2) the predicted time for risk-driver concentrations to achieve long-term model-predicted concentration ranges. The latter are based on achieving a site-wide total PCB SWAC within 25% (< 49 [jg/kg dw)) of the 45-yr FS Alternative 6R total PCB SWAC of 39 [jg/kg dw, and a site-wide
dioxin/furan SWAC within 25% (< 5.4 ng TEQ/kg dw) of the 45-yr FS Alternative 6R dioxin/furan SWAC of 4.3 ng TEQ/kg dw. The time is from the beginning of construction (see Table 6). Fish and shellfish tissue concentrations are expected to remain elevated during construction as a result of resuspension and release
of total PCBs into the water column. Note that the time to achieve cleanup objectives reported for all alternatives (15 years) is relative to the BCM output, which is generated in 5-year increments (see Table 6). However, in both the F'Sand in the Proposed Plan the values are adjusted based on time post-construction. For
example, in the Proposed Plan, both FS Alternative 5C and Modified Scenario 5a are shown as requiring 17 years to achieve cleanup objectives versus 15 years in this memorandum. This is because the construction time frame of T years was rounded to the nearest 5-year increment for purposes of the BCM. The time to
achieve cleanup objectives was predicted to be 15 years in the BCM, or 10 years post-construction. An actual construction time of 7 years plus 10 years post-construction equals 17 years following the beginning of construction.
k. Alternative 3C of the FS specifically addresses direct contact risks and achieves the total and individual direct contact risk metrics defined in FS Section 9.1.2.3 (AECOM 2012b) at the end of construction for all direct contact exposure scenarios. FS Alternative 5C, the Supplemental 5C Plus scenarios, and Modified
Scenario 5a are expected to have similar risk results.
I. The FS assumes the time to achieve cleanup objectives for RAO 3 to be when at least 98% of FS surface sediment dataset stations are predicted to comply with the SMS and more than 98% of the LDW surface area is predicted to comply with the SMS. This is not intended as a compliance metric. EPA and Ecology will
determine the appropriate metric for SMS compliance.
m. The time to achieve cleanup objectives for RAO 4 is when wildlife seafood consumption HQ <1 is achieved based on the site-wide total PCB SWAC at the end of construction.
n. Net present value costs are calculated using a discount rate of 2.3%. The costs for 5C Plus Base and Scenarios 1 through 3 have the highest uncertainties because of uncertainties in the volume of subsurface sediment above PCB iintertidal RAL of the SOS (cost estimated at $16 MM but could be as high as $40 MM).
AOPC = area of potential concern; ARAR = applicable or relevant and appropriate requirement; C = combined-technology alternative; cPAH = carcinogenic polycyclic aromatic hydrocarbon; CSL = cleanup screening level; cy = cubic yards; dw = dry weight; ENR = enhanced natural recovery; FS = feasibility stud/; HQ = hazard
quotient; IC = institutional control; kg = kilograms; |jg = micrograms; mg = milligrams; MLLW = mean lower low water; MM = million; MNR = monitored natural recovery; n/a = not applicable; ng = nanograms; O&M = operation and monitoring; PCB = polychlorinated biphenyl; PRG = preliminary remediation goal; R = removal-
emphasis alternative; RAL = remedial action level; RAO = remedial action objective; RME = reasonable maximum exposure; SMS = Sediment Management Standards; SQS = sediment quality standard; SWAC = spatially-weighted average concentration; TEQ = toxic equivalent; VM = verification monitoring
JT©w©r /^uwamish J^aterway {^roup
Port of SomtHo / City of 3o*ttto / Ittfetjf County / Tim Booing Company
Page 12
-------
Table 6 Effectiveness Evaluation of Alternative 5C, Supplemental 5C Plus Scenarios, and Modified Scenario 5a - Predicted Post-Construction Arsenic, Total PCB, cPAH, and Dioxin/Furan Concentrations (SWACs)
Arsenic (mg/kg dw) (RAO 2)
Scenario
Active Area
in FS Study
Area (acres)
Construc-
tion Period
(years)
Netfishing Direct Contact
Baseline = 16
10"6 RBTC = 3.7
PRG = Background = 7.0
Tribal Clamming Direct Contact
Baseline = 13
10"6 RBTC = 1.3
PRG = Background = 7.0
Beach Play Direct Contact
Baseline = 9.1
10"6 RBTC = 2.8
PRG = Background = 7.0
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
Alternative 5C
157
7
16
10
9.6
9
9
9
9
9
9
9
13
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
9.1
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
5C Plus Baseb
172
8
16
10
9.5
9.3
9.2
9.2
9.2
9.1
9.1
9.1
13
9.6
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.1
9.1
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Scenario 1
193
9
16
10
9.5
9.3
9.2
9.2
9.2
9.1
9.1
9.1
13
9.6
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.1
9.1
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Scenario 2
195
9
16
10
9.5
9.3
9.2
9.2
9.2
9.1
9.1
9.1
13
9.6
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.1
9.1
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Scenario 3
175
9
16
10
9.5
9.3
9.2
9.2
9.2
9.1
9.1
9.1
13
9.6
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.1
9.1
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Scenario 4
167
8
16
10
9.6
9.4
9.2
9.2
9.2
9.1
9.1
9.1
13
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
9.1
9.6
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Scenario 5a
148
7
16
10
9.6
9.4
9.2
9.2
9.2
9.1
9.1
9.1
13
9.5
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.1
9.1
9.5
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Scenario 5b
139
6
16
10
9.6
9.4
9.2
9.2
9.2
9.1
9.1
9.1
13
9.5
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.2
9.1
9.5
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Modified Scenario 5a
156
7
16
10
9.6
9.4
9.2
9.2
9.2
9.1
9.1
9.1
13
9.5
9.4
9.3
9.2
9.2
9.2
9.2
9.2
9.1
9.1
9.5
9.3
9.3
9.2
9.2
9.2
9.2
9.2
9.2
Total PCBs (|jg/kg dw) (RAOs 1,2, and 4)
Scenario
Active Area
in FS Study
Area (acres)
Construc-
tion Period
(years)
Site-wide
Baseline = 346
Netfishing Direct Contact: PRG = 10~6 RBTC = 1,300
Seafood Consumption - Human: PRG = Background = 2
Seafood Consumption - Ecological (otter): PRG =128-159
Tribal Clamming Direct Contact
Baseline = 540
10"6 RBTC = 500
PRG = 500
Beach Play Direct Contact
Baseline = 286
10"6 RBTC = 1,700
PRG = 1,700
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
Alternative 5C
157
7
178
70
56
48
46
44
44
43
43
41
195
59
52
48
46
45
45
44
44
43
275
54
49
45
44
44
45
44
44
42
5C Plus Baseb
172
8
178
70
53
47
45
44
44
43
42
41
195
59
48
46
44
44
44
43
43
42
275
54
47
45
44
44
45
44
44
42
Scenario 1
193
9
178
70
52
47
45
43
43
42
42
41
195
59
48
46
44
44
44
43
43
42
275
54
47
45
44
44
45
44
44
42
Scenario 2
195
9
178
70
51
47
45
44
43
42
42
41
195
59
48
46
44
44
44
43
43
42
275
54
47
45
44
44
45
44
44
42
Scenario 3
175
9
178
70
53
47
45
44
44
43
42
41
195
59
48
46
44
44
44
43
43
42
275
54
47
45
44
44
45
44
44
42
Scenario 4
167
8
178
70
54
48
46
44
44
43
43
41
195
59
51
48
46
45
45
44
44
43
275
54
49
45
44
44
45
44
44
42
Scenario 5a
148
7
178
70
55
48
46
44
44
43
42
41
195
59
49
46
45
44
44
43
43
42
275
54
48
45
44
44
45
44
44
42
Scenario 5b
139
6
178
70
55
48
46
44
44
43
43
41
195
59
52
48
46
45
45
44
44
43
275
54
49
45
44
44
45
44
44
42
Modified Scenario 5a
156
7
178
70
55
48
46
44
44
43
43
41
195
57
51
47
45
44
45
43
44
42
275
55
50
46
44
44
45
44
44
42
cPAHs (|jg TEQ/kg dw
(RAO 2)
Scenario
Active Area
in FS Study
Area (acres)
Construc-
tion Period
(years)
Netfishing Direct Contact
Baseline = 390
10"6 RBTC = 380
PRG = 380
Tribal Clamming Direct Contact
Baseline = 380
10"6 RBTC = 150
PRG = 150
Beach Play Direct Contact
Baseline = 331
10"6 RBTC = 90
PRG = 90
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
Alternative 5C
157
7
358
156
129
110
105
103
105
103
103
96
296
131
118
107
106
105
107
104
105
99
308
140
129
116
118
118
124
117
119
109
5C Plus Baseb
172
8
358
156
127
109
104
102
105
103
103
96
296
131
116
106
106
105
107
103
105
99
308
140
128
116
118
118
124
117
119
109
Scenario 1
193
9
358
156
126
108
104
102
105
103
103
96
296
131
116
106
106
105
107
103
105
99
308
140
128
116
118
118
124
117
119
109
Scenario 2
195
9
358
156
126
108
104
102
105
103
103
96
296
131
116
106
106
105
107
103
105
99
308
140
128
116
118
118
124
117
119
109
Scenario 3
175
9
358
156
127
109
104
102
105
103
103
96
296
131
116
106
106
105
107
103
105
99
308
140
128
116
118
118
124
117
119
109
Scenario 4
167
8
358
156
128
109
105
103
105
103
103
96
296
131
117
107
106
105
107
104
105
99
308
140
128
116
118
118
124
117
119
109
Scenario 5a
148
7
358
158
130
110
105
103
105
103
103
96
296
130
117
107
106
105
106
103
105
99
308
139
129
116
118
118
124
117
119
109
Scenario 5b
139
6
358
160
131
111
105
103
105
103
103
96
296
130
118
107
106
105
106
103
105
99
308
139
129
116
118
118
123
117
119
109
Modified Scenario 5a
156
7
358
158
129
110
105
103
105
103
103
96
296
129
117
107
106
105
107
103
105
99
308
138
128
116
118
118
124
117
119
109
2/22/2013
port of Seattfe I City of Seattle I KntJ Comity I Tho Bueiil( CorH&Btty Modified Scenario 5a Memo 1 of 2
-------
Table 6 Effectiveness Evaluation of Alternative 5C, Supplemental 5C Plus Scenarios, and Modified Scenario 5a - Predicted Post-Construction Arsenic, Total PCB, cPAH, and Dioxin/Furan Concentrations (SWACs)
Dioxins/Furans (ng TEQ/kg dw) (RAOs 1 and 2)
Site-wide
Tribal Clamming Direct Contact
Beach Play Direct Contact
Baseline = 26
Baseline = 32
Baseline = 18
Netfishing Direct Contact: PRG = 10~6 RBTC =
37
10"6 RBTC = 13
10"6 RBTC = 28
Active Area
in FS Study
Construc-
tion Period
Seafood Consumption - Human
:PRG = 2
PRG
= 13
PRG
= 28
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
Scenario
Area (acres)
(years)
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
0a
5
10
15
20
25
30
35
40
45
Alternative 5C
157
7
24
4.9
4.7
4.4
4.4
4.4
4.4
4.4
4.4
4.3
30
4.9
4.7
4.4
4.4
4.4
4.4
4.3
4.4
4.3
14
4.7
4.7
4.5
4.5
4.5
4.6
4.6
4.6
4.5
5C Plus Baseb
172
8
24
4.9
4.6
4.4
4.4
4.3
4.4
4.4
4.4
4.3
30
4.9
4.6
4.4
4.4
4.3
4.3
4.3
4.3
4.3
14
4.7
4.6
4.5
4.5
4.5
4.6
4.6
4.6
4.5
Scenario 1
193
9
24
4.9
4.5
4.3
4.3
4.3
4.4
4.4
4.4
4.3
30
4.9
4.6
4.4
4.3
4.3
4.3
4.3
4.3
4.3
14
4.7
4.6
4.5
4.5
4.5
4.6
4.6
4.6
4.5
Scenario 2
195
9
24
4.9
4.5
4.3
4.3
4.3
4.4
4.4
4.4
4.3
30
4.9
4.6
4.4
4.3
4.3
4.3
4.3
4.3
4.3
14
4.7
4.6
4.5
4.5
4.5
4.6
4.6
4.6
4.5
Scenario 3
175
9
24
4.9
4.6
4.4
4.4
4.3
4.4
4.4
4.4
4.3
30
4.9
4.6
4.4
4.4
4.3
4.3
4.3
4.3
4.3
14
4.7
4.6
4.5
4.5
4.5
4.6
4.6
4.6
4.5
Scenario 4
167
8
24
4.9
4.6
4.4
4.4
4.4
4.4
4.4
4.4
4.3
30
4.9
4.7
4.4
4.4
4.4
4.4
4.3
4.4
4.3
14
4.7
4.7
4.5
4.5
4.5
4.6
4.6
4.6
4.5
Scenario 5a
148
7
24
5.0
4.7
4.4
4.4
4.4
4.4
4.4
4.4
4.3
30
4.9
4.7
4.4
4.4
4.3
4.4
4.3
4.3
4.3
14
4.7
4.7
4.5
4.5
4.5
4.6
4.6
4.6
4.5
Scenario 5b
139
6
24
5.0
4.7
4.4
4.4
4.4
4.4
4.4
4.4
4.3
30
5.0
4.8
4.5
4.4
4.4
4.4
4.3
4.4
4.3
14
4.8
4.7
4.5
4.6
4.6
4.6
4.6
4.6
4.5
Modified Scenario 5a
156
7
24
4.9
4.7
4.4
4.4
4.4
4.4
4.4
4.4
4.3
30
4.9
4.6
4.4
4.4
4.3
4.4
4.3
4.3
4.3
14
4.7
4.6
4.5
4.5
4.5
4.6
4.6
4.6
4.5
Notes:
1. BCM predictions use base case STM outputs revised June 2010 (Appendix C) and FS dataset.
2. Arsenic BCM inputs (mg/kg dw): upstream 9, lateral 13, and post-remedy bed sediment replacement value 10 (AOPC 1) and 9 (AOPC 2).
3. Total PCB BCM inputs (|jg/kg dw): upstream 35, lateral 300, and post-remedy bed sediment replacement value 60 (AOPC 1) and 20 (AOPC 2).
4. cPAH BCM inputs (|jg TEQ/kg dw): upstream 70, lateral 1,400, and post-remedy bed sediment replacement value 140 (AOPC 1) and 100 (AOPC 2).
5. Dioxin/furan BCM inputs (ng TEQ/kg dw): upstream 4, lateral 20, and post-remedy bed sediment replacement value 4 (AOPC 1).
6. BCM model area = 430 acres and FS study area = 441 acres
a. The 5-year model-predicted intervals associated with the BCM SWAC output are indexed to the start of construction for Alternative 5C and all scenarios.
b. Alternative 5C Plus Base includes the common base elements and PCB intertidal RAL of the SQS.
BCM output used as approximation (estimate) of concentrations after construction.
AOPC = area of potential concern
BCM = bed composition model
cPAH = carcinogenic polycyclic aromatic hydrocarbon
dw = dry weight
EAA = early action area
FS = feasibility study
kg = kilogram
ng = microgram
mg = milligram
ng = nanogram
PCB = polychlorinated biphenyl
PRG = preliminary remediation goal
RAL = remedial action level
RAO = remedial action objective
RBTC = risk-based threshold concentration
SQS = sediment quality standard
STM = sediment transport model
SWAC = spatially-weighted average concentration
TEQ = toxic equivalent
2/22/2013
Modified Scenario 5a Memo 2 of 2
-------
Table 7a Excess Cancer Risks for RME Seafood Consumption Scenarios Associated with Residual Surface Sediment Total PCB SWACs Over Time
Remedial Scenario
Active Area in
FS Study Area
(acres)
Construc-
tion Period
(years)
Adult Tribal RME (Tulalip data)
Baseline HHRA Risk = 2 x 103
Child Tribal RME (Tulalip data)
Baseline HHRA = 3 x 104
Adult API RME
Baseline HHRA Risk = 5 x 104
Time from Be
ginning of Construction (years)3
Time from Be
yinning of Construction (years)3
Time from Be
ginning of Construction (years)3
0b
5
10
15
20
25
30
35
40
45
0b
5
10
15
20
25
30
35
40
45
0b
5
10
15
20
25
30
35
40
45
Alternative 5C
157
7
5 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
1 x 104
4x10s
4x10s
4 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
2 x 104
7 x10 s
6 x10 s
6 x10 s
6 x10 s
5 x10 s
5 x10 s
5 x10 s
5 x10 s
5 x10 s
Scenario 5a
148
7
5 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
1 x 104
4x10s
4 x10 s
4 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
2 x 104
7 x10 s
6 x10 s
6 x10 s
6 x10 s
5 x10 s
5 x10 s
5 x10 s
5 x10 s
5 x10 s
Modified Scenario 5a
156
7
5 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
2 x 104
1 x 104
4x10s
4 x10 s
4 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
3 x10 s
2 x 104
7 x10 s
6 x10 s
6 x10 s
6 x10 s
5 x10 s
5 x10 s
5 x10 s
5 x10 s
5 x10 s
Notes:
1. Excess cancer risks estimated using tissue concentrations predicted by the FWM (Windward 2010) with alternative-specific total PCB SWACs in surface sediment (Table 6) and assumed surface water dissolved total PCB concentrations of 0.6 ng/l
^^K^Wcan^guPers^a%r-I r Colored cells indicate residual non-cancer hazard quotient.
HQ <1 J
BCM Input Values (mid)
Contaminant
Post-remedy Bed Sediment Replacement
Lateral
Upstream
PCB (|jg/kg dw)
60 (AO PC 1) / 20 (AO PC 2)
300
35
^owe r JJuwamlsh j^^ntcrway ^jroup
Modified Scenario 5a Memo
2/22/2013
1 of 2
-------
Table 7c Total Excess Cancer Risks for Direct Contact Based on Predicted SWACs
Receptor Group
Baseline Riskd
Direct Contact Risk for Remedial Scenarios
Alternative 5 Combined (7 years6)
Scenario 5a (7 years6)
Modified Scenario 5a (7 years6)
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
Time from Beginning of Construction (years)
0C
5
10
15
20
25
30
35
40
45
0C
5
10
15
20
25
30
35
40
45
0C
5
10
15
20
25
30
35
40
45
Site-wide Netfishing
3 x 106
6 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
6 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
6 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
3 x 106
Tribal Clamming
2x10"
1 x 10 s
9 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
1 x 10 s
9 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
1 x 10 s
9 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
8 x 10b
Beach 1
9 x 106
9 x 106
4 x 106
5 x 106
5 x 106
5 x 106
5 x 10b
5 x 10b
5 x 106
5 x 10b
5 x 106
9 x 106
4 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
9 x 106
4 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
Beach 2
9 x 106
9 x 106
6 x 106
5 x 106
5 x 106
5 x 10b
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
9 x 106
6 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
9 x 106
6 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
Beach 3
1 x 105
8 x 106
7 x 106
7 x 106
6 x 106
6 x 10b
6 x 10b
7 x 106
6 x 106
6 x 10b
6 x 10b
8 x 106
7 x 106
7 x 106
6 x 106
6 x 106
6 x 106
7 x 106
6 x 106
6 x 106
6 x 106
8 x 106
7 x 106
7 x 106
6 x 106
6 x 106
6 x 106
7 x 106
6 x 106
6 x 106
6 x 106
Beach 4
6 x 104
6 x 104
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 10b
5 x 106
5 x 10b
6 x 104
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
6 x 104
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
Beach 5
3 x 106
3 x 106
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
3 x 106
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
3 x 106
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
Beach 6
1 x 104
1 x 104
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
1 x 104
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
1 x 104
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
4 x 106
Beach 7
4 x 106
4 x 106
4 x 106
5 x 106
4 x 106
5 x 10b
5 x 10b
5 x 106
5 x 10b
5 x 106
4 x 106
4 x 106
4 x 106
5 x 106
4 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
4 x 106
4 x 106
4 x 106
5 x 106
4 x 106
5 x 106
5 x 106
5 x 106
5 x 106
5 x 106
4 x 106
Beach 8
6 x 10b
6 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
6 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
X
o
X
o
X
o
4 x 10b
6 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
4 x 10b
Notes:
1. Total excess cancer risks include only the risk drivers (total PCBs, arsenic, cPAHs, and dioxins/furans).
2. Significant figures are displayed in accordance with the conventions established in the HHRA (windward 2007b).
3. The BCM input values used in the predicted future concentrations after start of construction are as follows:
Contaminant
Unit
Upstream
Lateral
Post-remedy Bed Sediment
Replacement Value
Total PCBs
[jg/kg dw
35
300
60 (AOPC 1), 20 (AOPC 2)
Arsenic
mg/kg dw
9
13
10 (AOPC 1), 9 (AOPC 2)
cPAHs
|jg TEQ /kg dw
70
1,400
140 (AOPC 1), 100 (AOPC 2)
Dioxins/Furans
ng TEQ /kg dw
4
20
4
4. Baseline risks are used as the post-EAA risk at time 0 for the beaches (with the exception of beach 3).
Footnotes:
a. The 5-year model-predicted intervals associated with the BCM SWAC output (for risk estimation) are indexed to the start of construction for all remedial scenario:
b. Risk estimates for time 0 (post-EAA) use the BCM-predicted SWACs after constructions of the EAAs. While baseline HHRA seafood consumption risks were based on tissue data collected from the LDW, seafood consumption risks at time 0 (post-
Mtii^lf«^ffi£f^M^^PMward 2007a)
d. Baseline risks for the direct contact scenarios are reported in FS Section 3 (Table 3-6a for netfishing and tribal clamming scenarios, and Table 3-6b for beach play scenarios: AECOM 2012b)
e. Construction period.
AOPC = area of potential concern: API = Asian and Pacific Islander: BCM = bed composition model: C = combined: cPAH = carcinogenic polycyclic aromatic hydrocarbon: dw = dry weight: EAA = early action area: ERA = ecological risl
assessment: FS = feasibility study: FWM = Food Web Model: HHRA = human health risk assessment: HQ = hazard quotient: kg = kilogram: L = liter: LDW = Lower Duwamish Waterway: LOAEL = lowest observed adverse effect level: ng
= nanogram: |jg = microgram: PCB = polychlorinated biphenyl; R = removal: RME = reasonable maximum exposure: SWAC = spatially-weighted average concentration.
Modified Scenario 5a Memo
2/22/2013
2 of 2
-------
Table 8 Effectiveness Evaluation of Alternative 5C, Supplemental 5C Plus Scenarios, and Modified Scenario 5a- Predicted Post-Construction Exceedances of SMS Criteria (CSL and SQS) (Addresses RAO 3)
Remaining CSL Chemistry Station Counts; Total Baseline Station Count = 1,395
Time from Beginning of Construction
0yra
5yr
10 yr
15 yr
20yr
25 yr
30yr
Active Area in
Construc-
%of
%of
%of
%of
%of
%of
%of
FS Study
tion Period
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Scenario
Area (acres)
(years)
Stations
< CSL
< CSL
Stations
< CSL
< CSL
Stations
< CSL
< CSL
Stations
< CSL
< CSL
Stations
< CSL
< CSL
Stations
< CSL
< CSL
Stations
< CSL
< CSL
Alternative 5C
157
7
63
95%
96%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
5C Plus Base6
172
8
63
95%
96%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 1
193
9
63
95%
96%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 2
195
9
63
95%
96%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 3
175
9
63
95%
96%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 4
167
8
63
95%
96%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 5a
148
7
63
95%
96%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
Scenario 5b
139
6
63
95%
96%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
Modified Scenario 5a
156
7
63
95%
96%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
Remaining SQS Chemistry Station Counts; PRG =
compliance with SQS; Total Baseline Station Count =
1,395
Time from Beginning of Construction
0yra
5yr
10 yr
15 yr
20 yr
25 yr
CO
O
Active Area in
Construc-
%of
%of
%of
%of
%of
%of
%of
FS Study
tion Period
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Number of
Stations
% of Area
Scenario
Area (acres)
(years)
Stations
< SQS
< SQS
Stations
< SQS
< SQS
Stations
< SQS
< SQS
Stations
< SQS
< SQS
Stations
< SQS
< SQS
Stations
< SQS
< SQS
Stations
< SQS
< SQS
Alternative 5C
157
7
224
84%
82%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
5C Plus Base6
172
8
224
84%
82%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 1
193
9
224
84%
82%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 2
195
9
224
84%
82%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 3
175
9
224
84%
82%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 4
167
8
224
84%
82%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
Scenario 5a
148
7
224
84%
82%
2
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
Scenario 5b
139
6
224
84%
82%
2
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
Modified Scenario 5a
156
7
224
84%
82%
2
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
10 Years Following End of
Construction
%of
Number of
Stations
% of Area
Stations
< CSL
< CSL
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
1
>99%
>99%
1
>99%
>99%
1
>99%
>99%
10 Years Following End of
Construction
%of
Number of
Stations
% of Area
Stations
< SQS
< SQS
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
0
>99%
>99%
3
>99%
>99%
3
>99%
>99%
3
>99%
>99%
= Predicted percentage of baseline stations or LDW surface area below CSL or SQS is > 98%
Notes:
1. FS study area = 441 acres. BCM model area = 430 acres.
2. Contaminant concentration predictions use BCM input parameters for SMS contaminants as described in Section 5 of the Final FS (AECOM 2012)
3. Stations falling within the actively remediated footprint of each remedial scenario are not counted after construction is completed for that scenario. However, recontamination potential analysis shows that 23 STM grid cells (out of >700)
have the potential to recontaminate above the SQS for bis 2-ethylhexyl phthalate (BEHP) 10 years after remedy completion. These counts are not factored into the recontamination potential.
4. In some locations, the BCM predicts point concentrations above the SQS, but recent chemical data and trend analysis suggest sediment concentrations are below the SQS. Therefore, the assignment of remedial technologies may not
be consistent with BCM point-counts. This apparent discrepancy will be resolved during remedy implementation through design sampling, monitoring, and adaptive management.
5. Many of the predicted remaining SQS exceedances are located on the edges of areas to be actively remediated and will likely be recharacterized during remedial design sampling. Other locations are in areas expected to recover
(based on other factors used to define the recovery categories) and were assigned to MNR using best professional judgment.
6. The percent of LDW area below SMS criteria is calculated by dividing the polygon-derived areas associated with predicted exceedances by the total area of the LDW (441 acres).
7. The percent of stations below SMS criteria is calculated by dividing the predicted number of station exceedances by the number of FS baseline surface sediment stations (n = 1,395 points).
8. Station-specific TOC values were used to oc-normalize dry weight concentrations for non-polar organic compounds, with TOC values between 0.5 and 4%. For samples with a TOC outside this range, oc-normalization was not
performed, and the dry weight concentration was compared to the LAET and 2LAET criteria.
9. The convention of 98% stations or LDW surface area below the SMS criteria is used in the FS for point count and area estimation purposes only. It does not represent a standard to be applied to compliance monitorinq.
a. The 5-year model-predicted intervals associated with the BCM output are indexed to the start of construction for FS Alternative 5C and all the scenarios.
b. Alternative 5C Plus Base includes the common base elements and PCB intertidal RAL of the SQS
2LAET = second lowest apparent effects threshold
BCM = bed composition model
CSL = cleanup screening level
D/F = dioxins and furans
EAA = early action area
FS = feasibility study
LAET = lowest apparent effects threshold
LDW = Lower Duwamish Waterway
MNR = monitored natural recovery
oc = organic carbon
PRG = preliminary remediation goal
RAL = remedial action level
RAO = remedial action objective
SMS = Sediment Management Standards
SQS = sediment quality standard
STM = sediment transport model
TOC = total organic carbon
yr = year
Modified Scenario 5a Memo
2/22/2013
lof 1
-------
Table 9 Post-construction Sediment Conditions for Modified Scenario 5a
Number of Core Stations with SMS Chemistry Exceedances and Total PCB Concentrations in Areas Outside the EAA and Dredge Footprint for Modified Scenario 5a
Scenario
Recovery
Category
Located within AOPC 1 and AOPC 2 Outside Dredge and Cap Footprint
Cap / Partial Dredge and Cap
Core Station
Counts
Total PCB Concentration
(M-g/kg dw)
Core Station
Counts
Total PCB Concentration
(jig/kg dw)
0 to 2 ft depth
2 to 4 ft depth
0 to 4 ft depth
> CSL
< CSL,
> SQS
n
Mean
UCL 95
n
Mean
UCL 95
> CSL
< CSL,
> SQS
n
Mean
Modified
Scenario 5a
1
0
3
15
79
193
13
136
420
19
4
27
639
2 and 3
23
20
75
379
660
66
379
508
All
23
23
90
329
569
79
339
585
Surface Areas Outside the EAA and Dredge Footprint Corresponding to Technology Assignment Groups for Modified Scenario 5a
~ Cap / Partial Dredge and Cap
~ ENR / in situ /MNR/VM/ AOPC 2
100 150
Surface Area (acres)
Summary Statistics of Subsurface Total PCB Concentrations Remaining in AOPC 1 and AOPC 2 and Outside the EAA, Dredge and Cap Footprint for Modified Scenario 5a
500 600 700 800 900
Total PCB Concentration (pg/kg dw)
1,000 1,100 1,200 1,300 1,400 1,500
Notes:
1. Recovery Category 1,2, and 3 designations were assigned to any area of the LDW, regardless of AOPC or RAL status, and based on a specific recovery assessment (see FS Section 6). Recovery in Category 1 areas is presumed
to be limited. Recovery in Category 2 areas is less certain. Category 3 areas are predicted to recover.
2. Core counts may be conservative because some of the material at these locations may have been previously dredged. In such cases, it is unconfirmed whether all contamination was removed and, in some instances, whether
dredging actually occurred at these locations. Therefore, all remaining cores were included in the core counts.
3. Modified Scenario 5a includes 64 acres of dredged areas, not shown in center panel. The AOPC 1 and 2 footprints are approximately 180 and 122 acres, respectively.
4. Summary statistics for the 0- to 2-ft and 2- to 4-ft intervals (top table and lower panel) are for the vertically averaged total PCB concentrations in each remaining core station. Summary statistics were calculated with ProUCL 4.1
software; the Pro UCL-re com mended UCL was used as the UCL95 in all cases, with the exception of the H-Statistic UCL, use of which was avoided (per ProUCL warning) and overridden by a non-parametric 95% Chebyshev (Mean,
SD) UCL. No data greater than the 1.5*IQR+75th percentile are shown in the lower panel.
5. The mean PCB concentration for capped and partially dredged/capped areas in the 0- to 4-ft interval (shown in top table) is the vertical average of the combination of clean capping material (0 to 2 ft [with an assumed total PCB
concentration of 40 jog/kg dw]), and the native sediment (0 to 2 ft in areas to be capped, and 2 to 4 ft in areas to be partially dredged/capped [with the total PCB concentration from those intervals in the subsurface FS baseline
dataset]). However, the sediment cap is designed to be 3 ft thick.
6. The mean and UCL95 total PCB concentrations in the 0- to 4-ft interval in the rest of the waterway (110 acres outside of AOPC 2; 52 cores) are 68 and 12(lg/kg dw, respectively.
AOPC = area of potential concern; Cat. = recovery category; CSL = cleanup screening level; EAA = early action area; ENR = enhanced natural recovery; FS = feasibility study;
ft = foot; IQR = interquartile range; LDW = Lower Duwamish Waterway; [jg/kg dw = microgram per kilogram dry weight; MNR = monitored natural recovery; n = number of cores; PCB = poly chlorinated bi phenyl;
RAL = remedial action level; SD = standard deviation; SMS = Sediment Management Standards; SOS = sediment quality standard; UCL95 = 95% upper confidence limit on the mean; VM = verification monitoring
w c
Modified Scenario 5a Memo
2/22/2013
-------
Table 10 Post-Construction Sediment Conditions for FS Alternative 5C
Number of Core Stations with SMS Exceedances and Total PCB Concentration in Areas Outside the EAA and Dredge Footprint for FS Alternative 5C
Remedial
Alternative
Recovery
Category
Located within AOPC 1 and AOPC 2 Outside Dredge and Cap Footprint
Cap / Partial Dredge and Cap
Core Station
Counts
Total PCB Concentration
(M-g/kg dw)
Core Station
Counts
Total PCB Concentration
(Hg/kg dw)
0 to 2 ft depth
2 to 4 ft depth
0 to 4 ft depth
> CSL
< CSL,
> SQS
n
Mean
UCL95
n
Mean
UCL95
> CSL
< CSL,
> SQS
n
Mean
5C
1
0
2
16
80
166
14
133
750
20
4
31
610
2 and 3
22
22
75
399
677
66
451
847
All
22
24
91
343
579
80
395
730
Surface Areas Outside the EAA and Dredge Footprint Corresponding to Technology Assignment Groups for FS Alternative 5C
Cat. 1
~ Cap I Partial Dredge and Cap
~ ENR / in situ / MNR / VM / AOPC 2
Cat.2&3
175
50
100 150
Surface Area (acres)
200
250
Summary Statistics of Subsurface Total PCB Concentrations Remaining in AOPC 1 and AOPC 2 and Outside the EAA, Dredge and Cap Footprint for FS
Alternative 5C
Q)
c
O
LO
-O
o
3
>
S
5
ro
c
_o
o
<1)
m
<
CO
Ll_
CNI
O
Cat. 1
Cat. 2 & 3
Cat. 1
Cat. 2 & 3
~
SQS
n=14
n=75
Legend
25th
percentile
50th
percentile
~CSL
75th
percentile
1 O
1.5*IQR+75th UCL95
percentile
100
400 500 600 700 800 900 1,000 1,100 1,200 1,300 1,400 1,500
Total PCB Concentration (pg/kg dw)
Notes:
1. Recovery Category 1,2, and 3 designations were assigned to any area of the LDW (excluding EMs), regardless of AOPC or RAL status, and based on a specific recovery assessment (see FS Section 6).
Recovery in Category 1 areas is presumed to be limited. Recovery in Category 2 areas is less certain. Category 3 areas are predicted to recover.
2. Core counts may be conservative because some of the material at these locations may have been previously dredged. In such cases, it is unconfirmed whether all contamination was removed and, in some
instances, whether dredging actually occurred at these locations. Therefore, all remaining cores were included in the core counts.
3. Areas in the center panel reflect designations made in developing the remedial alternatives and should not be assumed to contain subsurface contaminants at concentrations represented in the table.
4. FS Alternative 5C includes 57 acres of dredged areas, not shown in center panel. The AOPC 1 and 2 footprints are approximately 180 and 122 acres, respectively.
5. Summary statistics for the 0- to 2-ft and 2- to 4-ft intervals (top table and lower panel) are for the vertically averaged total PCB concentrations in each remaining core station. Summary statistics were
calculated with ProUCL 4.1 software; the ProUCL-recommended UCL was used as the UCL95 in all cases, with the exception of the H-Statistic UCL, use of which was avoided (per ProUCL warning) and
overridden by a non-parametric 95% Chebyshev (Mean, SD) UCL. No data greater than the 1,5*IQR+75th percentile are shown in the lower panel.
6. The mean PCB concentration for capped and partially dredged/capped areas in the 0- to 4-ft interval (shown in top table) is the vertical average of the combination of clean capping material (0 to 2 ft [with an
assumed total PCB concentration of 40 |ag/kg dw]), and the native sediment (0 to 2 ft in areas to be capped, and 2 to 4 ft in areas to be partially dredged/capped [with the total PCB concentration from those
intervals in the subsurface FS baseline dataset]). However, a sediment cap is designed to be 3 ft thick.
7. The mean and UCL95 total PCB concentrations in the 0- to 4-ft interval outside of AOPCs 1 and 2 (i.e., rest of the waterway-110 acres) are 68 and 120 |ag/kg dw, respectively (52 cores).
AOPC = area of potential concern; C = combined; Cat. = recovery category; CSL = cleanup screening level; EAA = early action area; ENR = enhanced natural recovery; FS = feasibility study; ft = foot;
IQR = interquartile range; LDW = Lower Duwamish Waterway; (jg/kg dw = microgram per kilogram dry weight; MNR = monitored natural recovery; n = number of cores; PCB = polychlorinated biphenyl;
R = removal; R-T = removal with treatment; RAL = remedial action level; SD = standard deviation; SMS = Sediment Management Standards; SQS = sediment quality standard; UCL95 = 95% upper confidence
limit on the mean; VM = verification monitoring
Modified Scenario 5a Memo
2/22/2013
-------
Memorandum to EPA and Ecology
February 22, 2013
Table 11 Summary of Short-term Effectiveness Metrics for FS Alternative 5C, Supplemental
Scenario 5a, and Modified Scenario 5a
Metric
Remedial Scenario
FS Alternative 5C
Scenario 5a
Modified Scenario 5a
Period of community exposure, worker exposure and
ecological disturbance (years of construction)3
7
7
7
Total PCB mass exported from site as a result of natural
erosion; 45-yr model period (kg)
3.0
2.9
2.9
Total PCB mass exported from site as a result of dredging
(kg)
6.3
6.3
6.3
Transportation (miles)b
Truck
480,000
500,000
510,000
Train
130,000
130,000
130,000
Ecological - Habitat area above -10 ft MLLW disturbed
(dredging/partial dredge and cap/capping; acres)
39
41
43
Gas / Particulate Emissions
Greenhouse gas emissions
(CO2; metric tons)
30,000
31,000
31,000
Other air pollutants
(NOx/SOx; metric tons)
578/14
597/15
605/15
Particulate matter emissions
(PM10; metric tons)
25
25
26
Energy Consumption (MJ)
4.2E+08
4.3E+08
4.3E+08
Landfill Capacity Consumed (1.2 x Dredge Volume)
900,000
940,000
950,000
Carbon Footprint (acre-years)0
7,094
7,290
7,412
Depleted natural resources (sand/gravel for in-water
placement; cy)
580,000
560,000
590,000
Notes:
1. See FS Appendices L and M (AECOM 2012b) for details on basis and assumptions for short-term metric values.
a. Construction period rounded to nearest year. Additional time beyond construction required for ecologically sensitive areas to recover. Also,
fish and shellfish tissue contaminant concentrations may require additional time (1 to 2 years) after construction to recover.
b. Sediment is assumed to be disposed of by trucking from a transloading area to an intermodal station, where it is loaded onto train cars for
transport to a landfill in Eastern Washington or Eastern Oregon. Trucking miles are estimated using an average 28 tons/truck and 12 miles
to the intermodal station. Train miles are estimated assuming 568 miles (round trip) to the landfill and assuming that each train can carry
5,000 tons of dredged material.
c. One acre-year represents the amount of CO2 sequestered by one acre of Douglas fir forest for one year. Carbon footprint in units of acre-
years is an appropriate way to account for the differences in construction periods among the alternatives.
C = combined; CAD = contained aquatic disposal; CO2 = carbon dioxide; cy = cubic yards; kg = kilograms; MJ = megajoule; MLLW = mean low
lower water; NOx = nitrogen oxides; PM = particulate matter; R = removal; R-T = removal with treatment; SOx = sulfur oxides
JJj,ower JUpuwaimlsii f^p»terway ^yroup
Port of Soattto / City mi Soattht f Xing County / Tim Booing Company
Page 20
-------
Note:
1. Locations DR290 and DR292 are not shown on the map because they
have been dredged.
| | AOPC 1 (189 acres)
| | AOPC 2 (116 acres)
~ Early Action Area (29 acres)
200 400
ATCOM
£ow«r /7uwaml»h J^atorway {yroup
p*'t e/M+ttU ' Ctor C*mtfr / r»» h-r—T
I Feet
800
Lower Duwamish Waterway
60150279-9.9
DATE: 02/22/13
DWRN:MVI/sea
Revision: 0
Surface Sediment RAL Exceedances
for EPA's Preferred Alternative
(Alternative 5C Plus)
I FIGURE 1
AOPC= area of potential concern; cPAH= carcinogenic polycyclic
aromatic hydrocarbon; CSL= cleanup screening level; D/F= dioxins and furans;
PCB= polychlorinated biphenyl; RAL= Remedial Action Level;
SMS= Sediment Management Standards; SQS= sediment quality standard.
Surface Sediment Exceedance Location
o Surface Sediment Location >RALs for Human Health Risk Drivers,
and/or >2xSQS or >CSL for SMS Contaminants
Surface Sediment Location >SQS, but <2xSQS and
0
-------
AOPC= area of potential concern; ENR= enhanced natural recovery;
MLLW= mean lower low water; SMS= Sediment Management Standards;
SQS= sediment quality standard.
Shoreline Condition
Armored Slope (10.1 miles)
Exposed Bank (3.7 miles)
Dock Face (4.9 miles)
Vertical Bulkhead (1.0 miles)
Navigation Channel
River Mile Marker
Legend
Technology Assignment
Dredge (64 acres)
Partial Dredge and Cap (20 acres)
Cap (24 acres)
ENR///7 situ (48 acres)
Monitored natural recovery (surface sediment >SQS)(16 acres)
Verification Monitoring (17 acres)
AOPC 2 Outside of AOPC 1 (Institutional Controls and Site-wide
n
200 400
I Feet
800
Monitoring) (116 Acres)
Remaining Study Area (Institutional Controls and
Site-wide Monitoring) (107 acres)
Early Action Area (29 acres)
Overwater Structures
Intertidal Area > -4 ft MLLW
AICOM
£owtr ^uwamish ^jroup
Lower Duwamish Waterway
60150279-9.8
EPA's Preferred Alternative
(Modified Scenario 5a) -
Areas Labeled as in the Feasibility Study
DATE: 02/22/13 | DWRN:MVI/sea I Revision: 0
I FIGURE 2
-------
AOPC= area of potential concern; ENR= enhanced natural recovery;
MLLW= mean lower low water; SMS= Sediment Management Standards;
SQS= sediment quality standard.
I Feet
0 200 400 800
Legend
Technology Assignment
Dredge (64 acres)
Partial Dredge and Cap (20 acres)
Cap (24 acres)
ENR///7 situ (48 acres)
Monitored Natural Recovery (Surface Sediment >SQS)(33 acres)
Monitored Natural Recovery (Surface Sediment -4 ft MLLW
Navigation Channel
River Mile Marker
AICOM
f owm ^uw.imKh |/|/at«rway {jrrc
*V'I rf frtttfr ¦ cttr *> tr-mt* • Mint Ctwnlr ¦ rt— *»¦ i'i>
Lower Duwamish Waterway
60150279-9.8
EPA's Preferred Alternative
(Modified Scenario 5a) -
Areas Labeled as in the Proposed Plan
DATE: 02/22/13 | DWRN:MVI/sea I Revision: 0
I FIGURE 3
------- |