2013 HAWAII OCEAN DISPOSAL SITE MONITORING
SYNTHESIS REPORT
Prepared by:
Dredging and Sediment Management Team
USEPA Region 9
San Francisco, CA
April 27, 2015
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Table of Contents
Executive Summary 1
I. Introduction and Background 1
II. Summary of Site Monitoring Activities 7
2.1. Sediment Profile Imaging (SPI) and Plan View Photography (PVP) 7
2.2. Sediment Sampling for Chemistry and Benthic Communities 13
2.3. Sub-Bottom Profiling Survey of the South Oahu ODMDS 15
III. Survey Results 17
3.1. SPI-PVP Surveys 17
3.1.1 Dredged Material Footprint Mapping 17
3.1.2 Bioturbation Depth 17
3.1.3 Infaunal Successional Stage 24
3.1.4 PI an-View Photography 27
3.1.5 Discussion: SPI-P VP Surveys 30
3.2. Sediment Physical and Chemical Survey Results 30
3.2.1 Physical Results 31
3.2.2 Chemical Results 31
3.3. Benthic Community Analysis Results 34
3.3.1 Abundance of Infauna 34
3.3.2 Diversity of Infauna 35
3.4. Sub-Bottom Profiling Survey (South Oahu Site Only) 36
3.5. Comparison to 1980 Baseline Information 43
3.5.1 South Oahu Disposal Site 43
3.5.2 Hilo Disposal Site 44
IV. Conclusions and Recommendations 46
V. References 47
Appendix: Summary of Planned vs Actual Survey Activities at Hawaii Ocean Dredged
Material Disposal Sites, 2013 A-l
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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List of Figures
Figure 1. Five ocean dredged material disposal sites serve Hawaii ports and harbors. 3
Figure 2. General location of the South Oahu ocean dredged material disposal site. 4
Figure 3. General location of the Hilo ocean dredged material disposal site. 5
Figure 4. SPI-PVP camera system being deployed from the Hi'ialakai. 8
Figure 5. Schematic of deployment and collection of plan view and sediment profile
photographs. 9
Figure 6. Soft-bottom benthic community response to physical disturbance (top
panel) or organic enrichment (bottom panel). 10
Figure 7. Planned (yellow squares) and actual sample station locations at the South
Oahu ODMDS. 11
Figure 8. Planned and actual sample station locations at the Hilo ODMDS. 12
Figure 9. Double Van Veen sediment sampler deployed from the Hi'ialakai. 13
Figure 10. Subsampling from the Van Veen grab for sediment chemistry. 14
Figure 11. Processing a sediment sub-sample for chemical analysis. 14
Figure 12. Processing a sediment sample for benthic community analysis. 15
Figure 13. Sub-bottom profiler equipment - used only at the South Oahu site. 16
Figure 14. Planned transect lines for the sub-bottom profiling survey around the
South Oahu ODMDS. 16
Figure 15. Profile images from the ambient bottom at the Hilo ODMDS (left,
Station S3) and the South Oahu site (right, Station S6). 18
Figure 16. Plan view images of the dredged material deposit compared to the native
seafloor at South Oahu. 19
Figure 17. Profile images from two Hilo Stations showing a surface layer of disposed
coarse white dredged sand. 20
Figure 18. Dredged material footprint identified at the South Oahu site. 21
Figure 19. Dredged material footprint identified at the Hilo site. 22
Figure 20. Plan view image from the center station of the Hilo ODMDS shows a
high density of small rock and coral rubble. 23
Figure 21. Bioturbation depth at the South Oahu site. 25
Figure 22. Bioturbation depth at the Hilo site. 26
Figure 23. Community structure at the South Oahu site. 28
Figure 24. Community structure at the Hilo site. 29
Figure 25. USGS shaded-relief image showing the boundary of the sub-bottom
survey area around the South Oahu disposal site, as well as major
bedforms in the vicinity. 37
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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List of Figures, cont.
Figure 26. USGS sidescan sonar (backscatter) image showing historic dredged
material deposits around the sub-bottom survey area and the South
Oahu disposal site.
Figure 27. Transect lines occupied for the sub-bottom profiling survey of the South
Oahu site.
Figure 28. Geological (surface) interpretation from the sub-bottom profiling survey
superimposed with the SPI-based dredged material footprint map shown
in Figure 17.
Figure 29. Sub-bottom profile for Diagonal Line 1.
Figure 30. Comparison of South Oahu site dredged material volume estimates.
List of Tables
Table 1. Disposal volumes (cubic yards) at the 5 Hawaii ODMDS following
designation in 1980.
Table 2. Summary of sediment chemistry for the South Oahu Ocean Dredged
Material Disposal Site and vicinity.
Table 3. Summary of sediment chemistry for the Hilo Ocean Dredged Material
Disposal Site and vicinity.
Table 4. Infaunal species abundances at the South Oahu site.
Table 5. Infaunal species abundances at the Hilo site.
Table 6. Average Percent Grain Size - South Oahu Site.
Table 7. Trace Metal Concentrations - South Oahu Site.
Table 8. Percent Abundance - South Oahu Site.
Table 9. Average Percent Grain Size - Hilo Site.
Table 10. Trace Metal Concentrations - Hilo Site.
Table 11. Percent Abundance - Hilo Site.
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
2013 HAWAII OCEAN DISPOSAL SITE MONITORING
SYNTHESIS REPORT
EXECUTIVE SUMMARY
In 1980, the US Environmental Protection Agency (EPA) designated five ocean dredged material
disposal sites (ODMDS) offshore of Hawaiian Island ports and harbors. In 1997, EPA and the US
Army Corps of Engineers (USACE) published a Site Monitoring and Management Plan (SMMP)
covering all five of these disposal sites. But since that time, due to lack of available funding, the
sites have not been comprehensively monitored and the SMMP has not been updated. Therefore,
when funding became available for 2013, EPA identified the Hawaii sites as the highest priority to
monitor of all the disposal sites in Region 9. Since only the South Oahu and Hilo sites had
received any disposal activity since the late 1990s, EPA conducted surveys at only these two sites.
Ship and equipment problems resulted in a reduction in the planned survey scope and in the overall
number of samples collected. However, sufficient sampling was completed to provide an adequate
basis to confirm environmental conditions at these sites and to update the SMMP. Based on
analyses of sub-bottom profiling, sediment profile and plan view imaging, and sediment grain size,
chemistry, and benthic community sampling, it appears that the pre-disposal sediment testing
program has protected these sites and their environs from any adverse contaminant loading. The
bulk of the dredged material disposed in the last decade or more appears to have been deposited
properly within the site boundaries. There are minor and localized physical impacts from dredged
material disposal, as expected, but no significant adverse impacts are apparent to the benthic
environment outside of site boundaries. Continued use of the disposal sites, under an updated
SMMP, is recommended.
I. INTRODUCTION AND BACKGROUND
Ocean dredged material disposal sites (ODMDS) around the nation are designated by the
Environmental Protection Agency (EPA) under authority of the Marine Protection, Research and
Sanctuaries Act (U.S.C. 1401 et seq., 1972) and the Ocean Dumping Regulations at 40 CFR 220-
228. Disposal site locations are chosen to minimize cumulative environmental effects of disposal
to the area or region in which the site is located, and disposal operations must be conducted in a
manner that allows each site to operate without significant adverse impacts to the marine
environment. Many ocean disposal sites are located near major ports, harbors, and marinas and are
very important for maintaining safe navigation for commercial, military, and private vessels.
EPA and the US Army Corps of Engineers (USACE) share responsibility for managing ocean
disposal of dredged sediments. First, there is a pre-disposal sediment testing program that is
jointly administered by the agencies to ensure that only clean (non-toxic) sediments are permitted
for ocean disposal. EPA must concur that sediments meet ocean dumping suitability requirements
before USACE can issue a permit for ocean disposal. Post-disposal site monitoring then allows
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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EPA and USACE to confirm the environmental protectiveness of the pre-disposal testing. The
agencies also jointly manage the ocean disposal sites themselves. All sites are operated under a
site management and monitoring plan (SMMP), and the Agencies cooperate on updating the
SMMPs if needed, based on the results of periodic site monitoring. EPA is also responsible for
enforcement of potential ocean dumping violations at each site.
The site use requirements in SMMPs for each specific ODMDS can be based on any issues of
concern identified in the original site designation environmental impact statement (EIS) or
environment assessment (EA), and/or on the results of subsequent (post-disposal) monitoring.
Each SMMP typically incorporates a compliance monitoring component to ensure that individual
disposal operations are conducted properly at the site, as well as a requirement for periodic
monitoring surveys to confirm that the site is performing as expected and that long term adverse
impacts are not occurring.
EPA designated five ODMDS offshore of Hawaiian Island ports and harbors in 1980 (Figure 1).
With the exception of the South Oahu site, these disposal sites are used infrequently (generally
only every 5-10 years or so) when USACE conducts maintenance dredging of the federal channels
serving each harbor. Baseline surveys were conducted in the 1970s to support the original site
designation action, but only limited monitoring work has occurred since then at most of the sites.
The USGS, while doing other coastal mapping work in 1994 and 1995, conducted acoustic
backscatter surveys at all five sites for EPA, to map dredged material deposits on the sea floor.
They also collected sediment chemistry samples at the South Oahu site. Based on the USGS
survey results, EPA and USACE published an SMMP in 1997 covering all five Hawaii disposal
sites. Since that time, due to lack of available funding, the sites have not been comprehensively
monitored and the SMMP has not been updated. When increased funding became available for
2013, EPA therefore identified the Hawaii sites as the highest priority to monitor of all the disposal
sites in Region 9. However, because only the South Oahu and Hilo sites had received any disposal
at all since 1999 (Table 1), EPA planned comprehensive monitoring at only these two sites.1
The South Oahu site (Figure 2) is located approximately 3 nautical miles offshore of Pearl Harbor
in water depths ranging from about 1,300 to 1,650 feet (400 to 500 meters). It is a rectangular
ocean disposal site 2 kilometers wide (west-east) and 2.6 kilometers long (north-south), and
occupies an area of about 5.2 square kilometers on the sea floor. Although the overall site is
rectangular, all disposal actions must take place within a 1,000 foot (305 meter) radius Surface
Disposal Zone at the center of the site. Its center coordinates are 21 degrees 15.167 minutes North
Latitude, 157 degrees 56.833 minutes West Longitude (NAD 83).
The Hilo site (Figure 3) is located approximately 4 nautical miles offshore of Hilo in water depths
averaging about 1,150 feet (350 meters). It is a circular ocean disposal site with a radius of 3,000
feet (920 meters) and an area of about 2.7 square kilometers on the sea floor. As at South Oahu,
all disposal actions must take place within a 1,000 foot (305 meter) radius Surface Disposal Zone
at the center of the site. The center coordinates of the Hilo site are 19 degrees 48.500 minutes
North Latitude, 154 degrees 58.500 minutes West Longitude (NAD 83).
1 USACE is again planning to dredge and dispose at all five Hawaii ODMDS in 2016. Future monitoring of the other
sites will be addressed in an updated SMMP for all the Hawaii ODMDS, which is currently in preparation.
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2013 South Oahu arid Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 1. Five ocean dredged material disposal sites serve Hawaii ports and harbors.
KAUAI
Port Allen ODMDS
Nawiliwili ODMDS
OAHU
Oahu ODMDS
Kahului ODMDS
V f - MAUI
Hilo ODMDS
HAWAII*
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2013 South Oahu arid Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 2. General location of the South Oahu Ocean Dredged Material Disposal Site, showing overall site (yellow box) and
Surface Disposal Zone (red circle).
South Oahu ODMDS
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2013 South Oahu arid Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 3. General location of the Hilo Ocean Dredged Material Disposal Site, showing overall site (yellow circle) and Surface
Disposal Zone (red circle).
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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As shown in Table 1, the South Oahu site has received by far the greatest volume of dredged
material of all 5 Hawaii sites, both historically and more recently. (Table 1 does not include
volume disposed at historic Mamala Bay sites prior to 1980.) This material is generated from
construction and maintenance dredging by the U.S. Navy in Pearl Harbor and maintenance
dredging of the Honolulu Harbor federal channel by US ACE, as well as berth maintenance
dredging by Honolulu Harbor and other minor dredging by private marinas. The Hilo site has
received lesser volumes of dredged material, which in recent years was generated from US Coast
Guard maintenance dredging and from terminal improvement projects in Hilo Harbor.
Table 1. Disposal volumes (cubic yards) at the 5 Hawaii ODMDS following designation in
1980. Source: EPA compliance tracking records and USACE Ocean Disposal Database.
Year
South Oahu
Hilo
Kahului
Nawiliwili
Port Allen
Total All Sites
1981
0
1982
0
1983
313,900
313,900
1984
2,554,600
2,554,600
1985
12,000
12,000
1986
0
1987
111,200
111,200
1988
57,400
57,400
1989
75,000
75,000
1990
1,198,000
80,000
58,000
343,000
1,679,000
1991
134,550
134,550
1992
233,000
233,000
1993
322,400
322,400
1994
0
1995
0
1996
27,800
27,800
1997
0
1998
0
1999
27,500
91,000
114,600
20,900
254,000
2000
0
2001
0
2002
53,500
53,500
2003
183,500
183,500
2004
540,000
540,000
2005
3,000
3,000
2006
160,400
160,400
2007
266,500
266,500
2008
0
2009
126,200
126,200
2010
0
2011
18,260
63,879
82,139
2012
70,981
70,981
2013
506,870
506,870
Total 1981-2013
6,286,280
217,860
149,000
1,093,900
20,900
7,767,940
Average/year
190,493
6,602
4,515
33,148
633
235,392
Total 2000-2013
1,855,230
137,860
0
0
0
1,993,090
Average/year
2000-2013
132,516
9,847
0
0
0
142,363
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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II. SUMMARY OF SITE MONITORING ACTIVITIES
EPA Region 9 developed an overall survey plan and quality assurance project plan (QAPP) for the
South Oahu and Hilo ODMDS monitoring (EPA, 2013); supplemental QAPPs were also written
by sub-contractors. The surveys were conducted in late June and early July 2013. A summary of
the survey design and planned vs actual sampling activities is provided in the Appendix to this
report.
The main objective of site monitoring is to support any necessary updates to the SMMP by
collecting data and samples adequate to determine whether the sites are performing as expected
under existing site management practices. The overall site management goal is that there should
be only minor physical impacts inside the disposal site and no adverse impacts outside the disposal
site. Consequently, the Hawaii site monitoring surveys were designed to:
1. determine the horizontal extent of the dredged material deposit ("footprint") relative to site
boundaries;
2. identify any adverse impacts of disposal of dredged material on or off site; and
3. confirm the protectiveness of pre-disposal sediment testing in avoiding disposal of
contaminated sediments.
Specific survey activities specified in the QAPP included: sediment profile and plan-view imaging
to map the dredged material footprint; sediment sampling and analyses for chemistry and benthic
community structure to identify any chemical or biological effects beyond localized physical
impacts; and a geophysical survey (sub-bottom profiling) to determine wide area distribution of
native sea bed features and deposits of dredged material. EPA contracted with the National
Oceanic and Atmospheric Administration (NOAA) to use its vessel Hi'ialakai, stationed in Pearl
Harbor, for the sediment imaging and sampling surveys at both disposal sites, and with Sea
Engineering for the separate sub-bottom profiling survey.
The surveys conducted from the Hi'ialakai were originally scheduled to occur over 8 days (plus
mobilization and demobilization), but problems associated with readiness of the NOAA ship and
its equipment caused some delays. The surveys were ultimately conducted over a 5-day period
(not including transit between the South Oahu and Hilo sites and the return transit from Hilo to
Pearl Harbor), during which field operations were conducted continuously over a 24-hour period
using two scientific crews working 12-hour shifts. Even though not as many stations were
sampled as originally planned due to the reduced survey time, sufficient sampling was completed
to confirm the performance of each site and to provide an adequate basis to update the SMMP, as
described below.
2.1 Sediment Profile Imaging (SPD and Plan View Photography (PVP)
The SPI-PVP system provides a surface and cross-sectional photographic record of selected
locations on the seafloor to allow a general description of conditions both on and off dredged
material deposits. Detailed methods for the SPI-PVP survey are provided in the supplemental
QAPP prepared by Germano and Associates (2013 a).
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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SPI-PVP surveys (Figures 4 and 5) were conducted for each ODMDS to delineate the horizontal
extent of the dredged material footprint both within and outside the site boundaries, as well as the
status of benthic recolonization on the deposited material. With resolution on the order of
millimeters, the SPI system is more useful than traditional bathymetric or acoustic mapping
approaches for identifying a number of features, including the spatial extent and thickness of the
dredged material footprint over the native sediments of the seabed, and the level of disturbance and
recolonization as indicated by the depth of bioturbation, the apparent depth of the redox
discontinuity, and the presence of certain classes of benthic organisms (Figure 6). PVP is useful
for identifying surface features in the vi cinity of where the SPI photos are taken, thereby providing
important surface context for the vertical profiles at each station. For each station, a minimum of
four SPI photos were taken, coupled with at least a single PVP photo
The SPI-PV camera system was deployed at a total of 86 stations (40 at South Oahu and 46 at
Hilo), compared to the planned 98 (49 at each site). The planned vs actual survey stations around
the South Oahu ODMDS are shown in Figure 7, while the Hilo ODMDS survey stations are shown
in Figure 8. (Specific coordinates for each station are available in the Appendix.)
Figure 4. SPI-PVP camera system being deployed from the Hi'ialakai.
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2013 South Oahu arid Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 5. Schematic of deployment and collection of plan view and sediment profile photographs.
(Germano and Assoc., 2013 b).
/
Plan-view image
Deployed
1-2 meters
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SPI mage"
On the
seafioor
"Down" position
transecting the sediment-
water interface
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2013 South Oahu arid Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 6. Soft-bottom bent hie community response to physical disturbance (top panel) or organic enrichment (bottom panel).
From Rhoads and Germano (1982).
Physical Disturbance Time Normal
Stage 0 I Stage 1 I Stage 2 I Stage 3
Grossly Polluted
Distance
3
Normal
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2013 South Oahu arid Hilo Ocean Disposal Site Monitoring Surveys
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Figure 7. Planned (yellow squares) and actual sample station locations at the South Oahu ODMDS.
(The circle at the east side of the map shows the location of a historic disposal site used before 1980.)
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contributors
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2013 South Oahu arid Hilo Ocean Disposal Site Monitoring Surveys
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Figure 8. Planned (yellow squares) and actual sample station locations at the Hilo ODMDS.
SPI/PV and Sediment Sampling Locations
Hilo ODMDS, Hawaii
June/July 2013
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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2.2 Sediment Sampling for Chemistry and Benthic Communities
Sediment samples were collected from a subset of stations at each disposal site for sediment grain
size, chemistry, and benthic community analysis. Samples were collected using a stainless steel
double Van Veen sediment grab (Figure 9, showing side-by-side configuration) capable of
penetrating a maximum of 20 centimeters below the sediment surface. Detailed methods for
performing the sediment sampling for chemistry and benthic community analyses are described in
the QAPP (EPA, 2013 a).
After each acceptable grab sample was measured for depth of penetration and photographed, a
subsample for chemistry was extracted from one side of the grab sampler with a stainless steel
spoon (Figure 10). This subsample was homogenized and divided into separate jars (Figure 11)
for chemistry analyses (grain size, metals and organics). After the chemistry subsample was
extracted, the entire volume of the other side of the grab was processed to create a benthic
community sample for that station (Figure 12). A 500 micron sieve was used to separate
organisms from the sediment, and the separated organisms were placed into bottles where they
were initially preserved with formalin. A total of 18 sediment grab sample stations were sampled
in the two survey areas combined: 10 at South Oahu, and 8 at Hilo (see Figures 7 and 8,
respectively). Chemistry subsamples were collected from all 18 stations and benthic community
samples were collected at 14 of the 18 stations (the lower number of benthic community samples
was due to some grabs being used for field and laboratory chemistry duplicates, and one station
where QAPP metrics were not met for an acceptable benthic sample).
Figure 9. Double Van Veen sediment sampler deployed from the Hi'ialakai.
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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Figure 10. Subsampling from the Van Veen grab for sediment chemistry.
Figure 11. Processing a sediment sub-sample for chemical analysis.
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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Figure 12. Processing a sediment sample for benthic community analysis.
2.3 Sub-Bottom Profiling Survey of the South Oahu ODMDS
The primary purpose of this survey was to collect cross-sectional images of the native sediment
layers and layers indicative of the dredged material deposit across a wide area in the environs of
the South Oahu ODMDS. (The Hilo site was not surveyed in this manner during this round of
surveys because much smaller volumes of dredged material have been disposed there over time
which may not be detectable in terms of thickness and contrast.)
This type of survey allows EPA to separately estimate the cumulative volume of dredged materi al
disposed at the South Oahu site, compared to volumes permitted for disposal. The survey was sub-
contracted to Sea Engineering, who conducted the work aboard a separate vessel specially rigged
for this type of survey with an acoustic sub-bottom profiler system (Figure 13). Figure 14 shows
the grid of transects surveyed. Detailed methods for the sub-bottom survey are provided in the
supplemental QAPP prepared by Sea Engineering (2013).
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 13. Sub-bottom profiler equipment - used only at the South Oahu site.
Figure 14. Planned transect lines for the sub-bottom profiling survey around the South Oahu
ODMDS (from Sea Engineering, Inc., 2014).
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
III. SURVEY RESULTS
3.1 SPI - PVP Survey Results
3.1.1 Dredged Material Footprint Mapping
The presence and extent of the dredged material footprint was successfully mapped at both Hawaii
disposal sites. SPI images of typical native sediments (outside of any dredged material deposit)
around the South Oahu and Hilo sites are shown in Figure 15. Dredged material is usually evident
because of its unique optical reflectance and/or color relative to the native pre-disposal sediments.
The presence of dredged material layers can be determined from both plan view images (Figure
16) and from SPI images (Figure 17). In most cases, the point of contact between the two layers is
clearly visible as a textural change in sediment composition, facilitating measurement of the
thickness of the newly deposited layer.
Two off-site stations around the South Oahu site had native hard-bottom habitat (N6 and SW5,
Figure 7); otherwise the native sediment was fairly uniformly muddy fine sand. The overall
dredged material footprint extended well beyond the current disposal site boundary (Figure 18;
also see Figure 28). Given the lack of natural fine grained sediment around the South Oahu site,
dredged material would be expected to remain visible on the seafloor for a substantial amount of
time (decadal scale). Similarly, given the proximity of historic disposal sites to the current
designated site in Mamala Bay and the large cumulative volume of disposed sediments over the
years (Table 1), it is not surprising that traces of dredged material are found outside of the current
designated site boundary. However, the thickest off-site deposits were just north (shoreward) of
the site boundary indicating that "short-dumping" (disposal from scows before they reached the
Surface Discharge Zone at the middle of the site) probably occurred in the past. EPA has required
satellite-based tracking of all disposal scows since the early 2000s, and there have been no "short-
dumps" since a single partial mis-dump occurred in 2006. Thus the footprint outside the disposal
site boundary would appear to be relic material deposited more than 10 years ago.
Compared to South Oahu, native sediments around the Hilo site were finer. Two off-site stations
(E5 and SE6, Figure 8) were on rocky lava outcrops. Even though this area is primarily a silty,
very fine to fine sandy bottom, there are periodic lava deposits or rock outcrops creating some
topographic diversity. The substantially smaller cumulative volume of dredged material disposed
at Hilo appeared to be more fully confined within the designated disposal site boundary (Figure
19). Except at the center of the site where rubble has accumulated (Figure 20), dredged material
thickness was only 3 cm or less within the site boundary, and less than 1 cm thick outside the
boundary.
3.1.2 Bioturbation Depth
The depth to which sediments are biologically mixed is an important indicator of the status of
recovery of the infaunal community following disturbance (e.g., by dredged material disposal).
Biogenic particle mixing depths can be estimated by measuring the depths of imaged feeding voids
in the sediment column. This parameter represents the particle mixing depths of head-down
feeders, mainly polychaetes. This depth is also related to the apparent redox potential
discontinuity (aRPD) depth. In the absence of bioturbating organisms, the aRPD (in muds) will
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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Figure 15. Profile images from the ambient bottom at the Hilo ODMDS (left, Station S3) and the South Oahu site
(right, Station S6). The ambient seafloor at Hilo has a higher silt-clay content, allowing greater camera
penetration than at South Oahu. Scale: width of each profile image = 14.4 cm. (Germano & Assoc., 2013)
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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Figure 16. Plan view images of the dredged material deposit compared to the native
seafloor at South Oahu. Station CI on dredged material (top) shows the visual
difference in both sediment color and surface texture/features of dredged
material compared to the ambient bottom at Station NW6 (bottom). Scale: width
of each PV image is approximately 4 m. (Germano & Assoc., 2013)
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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Figure 17. Profile images from two Hilo Stations showing a surface layer of disposed coarse white dredged
sand that thins from NW1 (left) near the center of the disposal site to only trace amounts at NW3 (right).
Scale: width of each profile image = 14.4 cm. (Germano & Assoc., 2013)
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
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Figure 18. Dredged material footprint identified at the South Oahu site.
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IND
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f SO-N5
1033
\ SO-N4
15.44
S0^3
SO-NE6
0.00
7\
SO-NE4
it 6.24
15.94
SO-NW2
*
11538
$0-W2
1930
SO-W1
SO-N2
3635
I O
: SO-N1
' 9.67 J
4.33 |
SO-NE2 l
I 1(1
(I
• •
SO-SW3
0.00 ,
SO-SW1 i
1633
SO-SW2
IND
SO-C
9.00
SO-E1
9.46
SO}-E2
432'
> SO-S1
7.87
SO-S2
531
SO-SE2
trace
SO-SW4
0.00
SO-E3
7.11
SO-E4
0X)0
SO-E5
0.00
SO-E6
0.00
SO-SW5
0.00
SO-SW6
0.00
f SO-S3
4.84
SO-S4
0.00
SO-S5
aoo
SO-SE4
0.00
SO-SE0
0.00
Station Average
Dredged Material
Thickness (cm)
o.o
trace
# 0 .1 -1.0 cm
# 1.1-10.0 cm
# >10.0 cm
O Indeterminate (IND)
Dredged material
exceeded penetration?
Oyes
Dump site boundary
SO-S6
0.00 Sources: Esri. GEBCO. NOAA. National Geographic. DeLorme. NAVTEQ. Geonames.org. and other contributors
21
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 19. Dredged material footprint identified at the Hilo site.
SPl^V and S«d»m#nt Sampling Location*
Hilo OOMOS. Hawa-
June/July 2013
Station Average
Dredged Material
Thickness (cm)
00
trace
9 0.1 -10cm
• 1.1-10.0 cm
• >10 0 cm
Dredged material
exceeded penetration?
o
yes
» Dump site
K-SW8
000
H-N6
000
H-NWG
000
H-NW5
0.00
H-N4
000
M-NE6
000
H-NW4
Tr»c«
K-NC5
000
H-NW3
o.so
H-NC4
000
H-N2
1.00
H-NE3
000
H-NW2
aw .
• \H-NE2
\
h-wo
000
H-W5
000
H-W4
0.00
H-W3
0.00
H-SW3
000
H-NW11
306 1
H-W2 H-W1
\ 2.08
\M-SW1 |
\ 1.46
Jh-c
*>11.61
KSW2
0-64
• H-NE1
130
H-SE1
I -S3
H-E2
OSS
H-E4
000
H-E5
000
H-SI
1.44
K-SW4
000
H-SW3
000
H-S2
Tr*e
H-S3
0,00
K-SE2
0.63
H-SE3
Tttc*
M-SW6
000
H-SE4
000
K-SW7
000
H-S4
000
H-S5
0J00
K-SE5
0.00
K-SE6
000
H-se
ooo
H-SW6
OOO
Sourctv Evi GEBCO. NOAA Nafconai G+ograptuc. D#t.o*m* NAVTEQ. G^e
: arvo o^coobnttifcL
22
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 20. Plan view image from the center station of the Hilo ODMDS shows a high density of small rock and coral rubble.
Rubble falls rapidly through the water column with minimal dispersal, and thus has accumulated only at the center of the site.
Scale: width of PV image is approximately 4 m. (Germano & Assoc., 2013)
23
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
typically reach only 2 mm below the sediment-water interface (Rhoads 1974). However, it is quite
common in profile images to see evidence of biological activity (burrows, voids, or actual animals)
well below the mean aRPD (Germano and Assoc., 2013 b).
At the South Oahu site, the maximum bioturbation depths (>15 cm) were generally found at the
stations that also had the thickest deposits of dredged material (including the off-site stations to the
north with relic dredged material deposits) (Figure 21). A similar pattern was seen for average
feeding void depth, and for the aRPD depth (see Germano and Assoc., 2013 b). This is to be
expected, since dredged material is generally finer, less consolidated, and therefore more
conducive to supporting a richer community of burrowing organisms compared to the native,
consolidated fine sand around the disposal site. Stations with a native fine sand substrate exhibited
lower camera penetration, shallower aRPD depths, and shallower average feeding void depths.
At the Hilo site, where much less dredged material has been discharged and where the native
seafloor is more heterogenous, the pattern was different (Figure 22). Although dredged material
was thickest at the center of the site, a high concentration of gravel and coral rubble prevented full
camera penetration there, so that bioturbation depth and aRPD could not be determined fully.
Other on-site stations showed fairly uniform bioturbation depths of 7-10 cm. Many off-site
stations also had bioturbation depths in this range, although bioturbation depths of 10-18 cm were
also common. Since the native seafloor around the Hilo site is finer-grained than around the South
Oahu site, greater bioturbation depths, and less difference between on-site and off-site stations,
would be expected.
3.1.3 Infaunal Successional Stage
The mapping of infaunal successional stages is readily accomplished with SPI technology.
Mapping of successional stages is based on the theory that organism-sediment interactions in fine-
grained sediments follow a predictable sequence after a major seafloor perturbation (Germano and
Assoc., 2013). This continuum of change in animal communities after a disturbance (primary
succession) has been divided subjectively into four stages: Stage 0, indicative of a sediment
column that is largely devoid of macrofauna, occurs immediately following a physical disturbance
or in close proximity to an organic enrichment source; Stage 1 is the initial community of tiny,
densely populated polychaete assemblages; Stage 2 is the start of the transition to head-down
deposit feeders; and Stage 3 is the mature, equilibrium community of deep-dwelling, head-down
deposit feeders (see Figure 6).
After an area of bottom is disturbed by natural or anthropogenic events, the first invertebrate
assemblage (Stage 1) appears within days after the disturbance. Stage 1 consists of assemblages of
tiny tube-dwelling marine polychaetes that reach population densities of 104to 106 individuals per
m2 These animals feed at or near the sediment-water interface and physically stabilize or bind the
sediment surface by producing a mucous "glue" that they use to build their tubes.
If there are no repeated disturbances to the newly colonized area, then these initial tube dwelling
suspension or surface-deposit feeding taxa are followed by burrowing, head-down deposit feeders
that rework the sediment deeper and deeper over time and mix oxygen from the overlying water
into the sediment. The animals in these later-appearing communities (Stage 2 or 3) are larger, have
lower overall population densities (10 to 100 individuals per m2), and can rework the sediments to
depths of 3 to 20 cm or more.
24
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 21. Bioturbation depth at the South Oahu site - deeper values here are reflective of an active benthic community
reworking deposited dredged material. (Germano & Assoc., 2013)
so-Nwe
o.oo 1
SO-NW4
1156
IND
so-we
IND
SO-W5
4.98
SO-W4
6.62
SO-W3
SO-N6
IND
SO-N5
14.42
SO-N4
18.23
l_SO-N3 _
19.55~~
18.54
SO-NW2
tn
SO-N2
825
5.61 '
SO-NE2 i
SO-NE8
IND
'64
SO-NE4
7.87
i r. i
M5.88
$0-W2
21.09
SO-W1
SO-N1
10.76!
6? >
E (I ij
SPL/PV and Sediment Sampling Locations
South Oahu ODMDS. Hawaii
June 2013
Station Maximum
Bioturbation Depth (cm)
# 0.0 -1.0 cm
# 11 -5.0 cm
5.1 -10.0 cm
# 10.0 -15.0 cm
# > 15.0 cm
O Indeterminate (IND)
Dump site boundary
SO-SW3
10J09 ,
SO-SW1 i
17.81
SO-SW2
5.95
SO-SW4
127
SO-SW5
IND
SO-SW6
573
SO-E1 SOj-E2 SO-E3 SO-E4 SO-E5 SO-E0
1059 5.66
• SO-S1
8.67
SO-S2
7.66
SO-SE2
IND
1353
SO-S3
8.02
SO-S4
3.44
SO-S5
IND
SO-SE4
IND
SO-SE6
IND
so-se
IND Sources: Esri. GEBCO. NOAA. National Geographic, DeLomne. NAVTEQ. Geonames.org. and other contributors
25
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 22. Bioturbation depth at the Hilo site: on-site and off-site stations show similar depths (much less material has
been disposed here than at South Oahu). (Germano & Assoc., 2013)
SPI/PV and Sediment Sampling Locations
Hilo ODMDS. Hawaii
June/ July 2013
H-N6
4.45
N
Station Maximum
Bioturbation Depth (cm)
•
0 0- 1.0 cm
•
1.1 -5.0 cm
5.1 -10.0 cm
•
10.0 -15.0 cm
•
> 15.0 cm
t *
1
Dump site
H-NW6
13.01
H-NW5
13.81
H-N4
8.45
H-NE6
3.59
H-NW4
8.93
H-NE5
3.88
H-NW3
8.47
H-NE4
4.56
H-NW2
9.15 ,
H-W6
18.63
H-W5
13.90
H-W4
16.12
H-W3
929
H-SW3
10.19
H-W2
9.81 '
H-SW2
9.65
H-NW1
7.82
H-W1
8.62
;H-SW1
\ 831
H-N2
10.09
I H-C
000
H-NE3
6.64
• \ H-NE2
\ 8.04
H-NE1
6.91
H-E2
209
H-SE1
7.29
H-E4
3.35
H-E5
0.00
H-SW4
10.64
H-S1
7.82
H-S2
8.69
H-SE2
7.13
H-SW5
11.87
H-SE3
7.94
H-SW6
11.38
H-SW7 |
1&78 '
H-S3
9.12
H-S4
1264
H-SE4
7.94
H-SE5
7.94
H-SW8
8.44
H-S5
9.56
H-S0
929
H-SE8
0.00
H-SW0
18.54
Sources: Esri. GEBCO. NOAA. National Geographic. DeLorme. NAVTEQ. Geon3rne>.qrg.andidther
26
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Various combinations of these basic successional stages are possible. For example, secondary
succession can occur (Horn, 1974) in response to additional labile carbon input to surface
sediments, with surface-dwelling Stage 1 or 2 organisms co-existing at the same time and place
with Stage 3, resulting in the assignment of a "Stage 1 on 3" or "Stage 2 on 3" designation
The distribution of successional stages in the context of the mapped disturbance gradients is one of
the most sensitive indicators of the ecological quality of the seafloor (Rhoads and Germano 1986).
The presence of Stage 3 equilibrium taxa (mapped from subsurface feeding voids as observed in
profile images) can be a good indication of relatively high benthic habitat stability and quality. A
Stage 3 assemblage indicates that the sediment surrounding these organisms has not been disturbed
severely in the recent past and that the inventory of bioavailable contaminants is relatively small.
At the South Oahu site, infaunal community successional stage was readily apparent on the
dredged material deposit, but was generally unmeasurable (indeterminate) on the native sandy
sediments off-site (Figure 23). Successional stage on the dredged material mound, including the
relic off-site material to the north, was fairly uniformly Stage 1 on 3. While this indicates relatively
rapid recolonization and a well-established infaunal community in the finer, more carbon-rich
dredged sediments, it is clearly a different community than would be supported by the native fine
sand at this location in the absence of dredged material disposal.
At the Hilo site, differences between stations with and without dredged material were less apparent
(Figure 24). Since far less dredged material has been discharged at this site than at the South Oahu
site, less disturbance to the native sediments around the site has occurred. Both on-site and off-site
stations were dominated by Stage 1 on 3 communities, but more heterogenous communities were
present to the east and northeast of the site as well. These stations had either no apparent dredged
material, or only trace thicknesses of dredged material; therefore the different community structure
at these stations may reflect natural heterogeneity of benthic habitat types in this area rather than
any particular effect from dredged material deposition.
3.1.4 Plan-View Photography
Unusual surface sediment textures or structures detected in any of the sediment profile images can
be interpreted in light of the larger context of surface sediment features (for example, is a surface
layer or topographic feature a regularly occurring feature and typical of the bottom in this general
vicinity or just an isolated anomaly?). The scale information provided by the underwater lasers
allows accurate density counts (number per square meter) of attached epifaunal colonies, sediment
burrow openings, or larger macrofauna or fish which may be missed in the sediment profile cross-
sections.
Except for the two stations on hard bottom, the native seafloor around the South Oahu site is a
muddy carbonate sand with rippled bedforms and relatively low abundance of epifauna. Other
than the occasional hermit crab or other decapods such as shrimp or Brachyurans, the presence and
abundance of epifauna was directly proportional to the amount of rock/rubble/outcrop present on
the flat sandy bottom. Anything that provided a hard surface or additional vertical relief for
niche/topographic diversity became a suitable substratum to which organisms could attach
(tunicates, cnidarians, bryozoans) or hide within (echinoderms), which subsequently attracted more
fish to that particular location.
27
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 23. Community structure at the South Oahu site: presence of Stage 3 organisms is indicative of healthy
benthic community. (Germano & Assoc., 2013)
©s
©
~
764
.SO-NE4
SP1/PV and Sediment Sampling Locations
South Oahu ODMDS. Hawaii
June 2013
Infaunal Successional Stages
rep 1
Stage 2 — 3
^3 0"" ® Stage 3
^p2 ® Stage I on 3
O Indeterminate
Dump site boundary
SO-NE2
SO-W6 SO-W5 SO-W4 SO-W3 io-W2 SO-W1
© © © ©
lso-si
©
©
so-swi/y\ ^
m r"fe
Q SO-S4
© SO-S5
41 a
^ s © ©
SO-E1 SOj-E2 SO-E3 SO-E4 SO-€5 SO-E6
©'
©S
©¦
Sources: Esri. GEBCO. NOAA. National Geographic. DeLorme. NAVTEQ. Geonames.org. and other contributors
28
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 24. Community structure at the Hilo site: presence of Stage 3 organisms is indicative of healthy benthic community.
(Germano & Assoc., 2013)
SPl/PV SwnpJmj l«JWx»
Hrto OOMDS Hmu
Amm/Jul? 2013
Into una I Successlonal Stages
O Stage 2
to i O Stage I on 2
lnv2 ©Stage2-3
# Stage I on 3
O Indeterminate
-*>3©
H-NWO
J V/r / , ,
O
H-NW4 ©
©'
h L
1H*2 X
H-NW2 I
©-
©
©
©
M-NE4
K-NE3
K-NE2
I H-KE1 »
/ r
H-WC
K-WS
H-W4
# _«r ©« @
M-W3 H-W2 « H-W1
H-E2
H-SWS J
\H.SWll • /V~\
^(y)v7Hs£i
H-SW2 (V) h-s"
•e ®
©
H-E4
M-SC2
V H-SE3
IH-SE4
H-SWO |
r /
K-SW8
©
H-S4I
H-S9I
0'
M-SES
©~
__
H-se i
Evt GEBCO, NOAA. G«ogrAphie. NAVTEQ 3
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
In contrast, the native Hilo sediments had a higher percentage of fine sediments (attracting higher
densities of small prey, evidenced by burrow holes in plan view images) along with more frequent
occurrence of rocky outcrops (creating habitat heterogeneity) both inside and outside the site
boundaries. These characteristics attracted a generally more abundant and varied epifauna and fish
assemblage. Unlike the South Oahu site, the areas of the highest accumulation of dredged material
(near the site center where the surface was a continuous cover of rubble) appeared to have the
lowest faunal attractiveness. But higher densities of fish and anthozoans as well as more frequent
evidence of burrowing infauna were seen throughout the area as a whole, compared to South Oahu.
3.1.5 Discussion: SPI-PVP Surveys
Minor and localized physical impacts are expected within the site as a result of disposal operations.
However, historical and more recent disposal activity appear to have had little lasting adverse
impact on benthic infauna, or epibenthic organisms, at either site. With the exception of the center
station at the Hilo site where an accumulation of disposed rubble has most likely altered the
resident infaunal community on a localized scale, the disposal of dredged material, in general, has
not impeded benthic recolonization or the re-establishment of mature successional stages. At the
South Oahu site, it appears the larger cumulative volume of fine grained, higher carbon content
dredged material deposited over the native coarser grain carbonate sands may have actually
enhanced the secondary benthic production by promoting the settlement and persistence of
subsurface deposit feeders that would not normally exist in the native carbonate sand bottom here.
The prediction in the original EIS (EPA 1980) that disposal of dredged material at both the Hilo
and South Oahu ODMDS will have no lasting adverse impact on the benthic community inside or
outside of site boundaries is supported by the results of the SPI-PVP survey. Stage 3 taxa have
successfully recolonized all but the center station at the Hilo ODMDS, and secondary production
appears to be enhanced at the South Oahu ODMDS within the dredged material footprint. Also
epifauna, in general, are similar on-site and off-site (though different between South Oahu and
Hilo overall.
Based on the results of the SPI-PVP surveys, the authors predicted that the traditional benthic
sampling results would also show a higher species diversity and infaunal abundance in samples
from the Hilo site versus those from the South Oahu site, because of the increased amount of fines
and evidence of increased subsurface burrowing in the images from the Hilo site. (See discussion
of Benthic Community Analysis Results, below.)
3.2 Sediment Physical and Chemical Survey Results
Full physical and chemical analytical results are provided in ALS Environmental (2013) and EPA
(2013 b). Due to vessel and equipment problems, less than half the originally-targeted benthic grab
stations were sampled. But by using the SPI survey results to help select the chemistry (and
benthic community) stations at each site, a sufficient number of samples were collected within and
outside of site boundaries and the dredged material footprints to characterize the native (ambient)
seafloor compared to seafloor areas physically impacted by dredged material disposal.
Nevertheless, only qualitative (vs statistical) analysis of the physical and chemical results was
conducted given that only four "on site" and five "offsite" stations were ultimately sampled at
South Oahu, and only three "on site" and four "offsite" stations were sampled at Hilo.
30
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
3.2.1 Physical Results
Minor and localized physical impacts are expected within the site boundary as a result of disposal
operations. Tables 2 (South Oahu) and 3 (Hilo) compare areas within the disposal sites that have
dredged material deposits (indicated as "Inside") and off site areas without any dredged material
deposits (indicated as "Outside"). Physical on-site differences are most apparent at the South
Oahu site, which has received an order of magnitude more dredged material over the years than the
Hilo site. At South Oahu (Table 2), "inside" stations have substantially more gravel, more fines
(silt and clay), and higher organic carbon content than the "outside" stations that represent ambient
or native seafloor conditions. This reflects the character of dredged material typically disposed at
this site, which often includes grave-size coral rubble, and fines from land-side runoff that settles
in harbors, berths, and navigation channels. In contrast, native sediments around the South Oahu
site are uniformly sandier, with lower carbon. These on-site physical changes are expected to be
persistent, but are not considered to be a significant or adverse impact.
Physical characteristics of the off-site ambient or native sediments around the Hilo site are more
variable (Table 3) reflecting the more heterogeneous nature of the seafloor in the area, which
includes a mixture of hard bottom features (submerged reef and terraces) coupled with areas of
accumulated finer grained sediments (USGS, 2000). The dredged material disposed at the Hilo
site has not substantially altered the physical nature of the disposal site in part due to this natural
variability, and in part because only a relatively small volume of material has been disposed at
Hilo (especially compared to disposal volumes at South Oahu).
3.2.2 Chemical Results
Although physical differences are expected as a result of disposal operations, pre-disposal
sediment testing is intended to minimize any degradation to the site which might be caused by
introduction of contaminants which are bioavailable and/or pose a toxicity risk to the marine
environment. The bulk chemistry data show low but variable concentrations of most chemical
constituents at both sites (Tables 2 and 3). At both "inside" and "outside" stations, four to six
metals were at concentrations above NOAA's effects-based 10th percentile screening value (ER-L),
below which adverse effect are predicted to rarely occur (NOAA, 2008). Of these metals, only
chromium, copper, and mercury were slightly higher at "inside" stations compared to "outside"
stations, and only at the South Oahu site. At Hilo, the metals concentrations were virtually
indistinguishable between "inside" and "outside" stations.
Only nickel exceeded its 50th percentile screening value (ER-M), above which adverse effects are
expected to frequently occur (NOAA, 2008). It was most elevated at Hilo, but was at similar
elevated concentrations at both "inside" and "outside" stations there. Nickel is often naturally
elevated in certain sediments, including volcanic sediments.
Organic constituents were also low at both sites. Only two constituents exceeded NOAA ER-L
screening levels, and again only at the South Oahu site. PCBs and DDTs each slightly exceeded
their respective ER-Ls at one "inside" station and one "outside" station. PCBs were generally
higher at the "inside" stations, even when not exceeding the ER-L. There were no exceedances of
ER-Ls for organics at either "inside" or "outside" stations at the Hilo site.
31
-------
2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Table 2. Summary of sediment chemistry for the South Oahu Ocean Dredged Material Disposal site and vicinity.
Survey Station:
South Oahu site
"
nside"
"Outside"
NOAA Screening
Analyte
Units (dw)
SO-N1
SO-N1 dup*
SO-N2
SO-SW1
SO-W1
SO-SE4**
SO-W5
SO-S6
SO-E6
SO-E4
ER-L
ER-M
Gravel
%
21
3
69
3
12
1
1
0
1
11
-
-
Sand
%
43
53
29
47
50
78
79
82
83
64
—
—
Silt
%
21
24
11
25
24
16
12
12
10
20
--
--
Clay
%
14
17
4
15
11
5
4
5
5
7
—
--
Total Organic Carbon
%
1.25
1.78
1.25
1.02
1.48
0.58
0.53
0.43
0.41
0.81
--
--
Arsenic
mg/kg
20
13
24
33
19
40
39
27
30
27
8.2
70
Cadmium
mg/kg
0.6
0.69
0.39
ND
0.43
ND
0.42
ND
ND
ND
1.2
9.6
Chromium
mg/kg
100
160
100
110
120
68
100
47
45
73
81
370
Copper
mg/kg
65
84
47
43
56
22
36
11
13
37
34
270
Lead
mg/kg
25
31
22
15
95
19
37
10
15
23
46.7
218
Mercury
mg/kg
0.2
0.13
0.13
0.1
0.38
0.09
0.1
0.02
0.05
0.19
0.15
0.71
Nickel
mg/kg
68
140
68
71
92
37
63
24
30
53
20.9
51.6
Selenium
mg/kg
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
—
-
Silver
mg/kg
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
1
3.7
Zinc
mg/kg
78
130
76
75
86
52
79
34
35
69
150
410
Dioxins - Total TEQ
ng/kg
6.33
3.88
4.49
1.27
4.12
1.06
0.91
0.07
0.95
4.01
-
-
Total DDTs
ug/kg
ND
2.1
ND
ND
ND
ND
ND
ND
ND
2.6
1.58
46.1
Total Organotins
ug/kg
1.73
4.67
4
1.46
2.21
0.71
5.83
ND
4.1
2.09
—
—
Total PAHs
ug/kg
741
264
274
182
160
344
153.8
ND
263
1501
4022
44792
Total PCB Congeners
ug/kg
21.43
17.49
35.98
8.87
14.11
6.07
7.16
0.09
2.7
23.15
22.7
180
"Inside" stations are both within the disposal site boundary AND on the dredged material deposit as determined by the SPI-PVP survey.
"Outside" stations are both outside the site boundary AND off the dredged material deposit.
* Field duplicate sample from a separate grab taken at a different time at the same station
** This station was chosen for full OTM testing on upcoming dredging project(s) as a possible new reference site for future Hawaii projects.
32
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Table 3. Summary of sediment chemistry for the Hilo Ocean Dredged Material Disposal site and vicinity.
Survey Station:
Hilo site
Units (dw)
"Inside"
"Outside"
NOAA Screening
Analyte
H-Wl
H-Wl dup*
H-Nl
H-SW1
H-SE4
H-NE5
H-SW6
H-W6
ER-L
ER-M
Gravel
%
2
3
2
0
0
0
0
0
—
—
Sand
%
62
61
47
69
72
85
26
14
—
—
Silt
%
25
24
21
26
21
16
61
70
—
—
Clay
%
5
8
7
5
7
5
11
17
-
-
Total Organic Carbon
%
0.83
0.98
0.81
0.81
0.69
0.57
2.43
3.27
—
-
Arsenic
mg/kg
36
36
32
36
26
28
48
55
8.2
70
Cadmium
mg/kg
0.4
ND
0.5
0.6
0.72
0.5
0.71
0.62
1.2
9.6
Chromium
mg/kg
110
120
140
130
140
140
150
160
81
370
Copper
mg/kg
30
35
31
31
30
31
51
56
34
270
Lead
mg/kg
11
11
11
12
9.6
11
19
21
46.7
218
Mercury
mg/kg
0.05
0.06
0.05
0.06
0.04
0.04
0.14
0.17
0.15
0.71
Nickel
mg/kg
160
200
290
230
320
290
88
82
20.9
51.6
Selenium
mg/kg
ND
ND
ND
ND
ND
ND
ND
ND
—
—
Silver
mg/kg
ND
ND
ND
ND
0.75
ND
1.1
1.2
1
3.7
Zinc
mg/kg
70
81
83
78
87
83
91
95
150
410
Dioxins - Total TEQ
ng/kg
3.02
1.99
2.19
1.96
1.58
0.831
4.84
7.65
-
—
Total DDTs
ug/kg
IMD
ND
ND
ND
ND
ND
ND
ND
1.58
46.1
Total Organotins
ug/kg
ND
ND
0.86
ND
ND
ND
ND
ND
—
-
Total PAHs
ug/kg
2.2
2.3
10.2
1.8
ND
ND
3
17.4
4022
44792
Total PCB Congeners
ug/kg
0.3
0.5
ND
ND
ND
ND
0.25
0.28
22.7
180
"Inside" stations are both within the disposal site boundary and ON the dredged material deposit as determined by the SPI-PVP survey.
"Outside" stations are both outside the site boundary and OFF the dredged material deposit.
* Field duplicate sample from a separate grab taken at a different time at the same station
33
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
The screening level exceedances were relatively minor in magnitude and, in many cases, were seen
at both "inside" and "outside" stations. The few constituents that were at higher concentrations
within the disposal sites reflect the contaminant levels in the dredged material approved for
discharge. All sediments discharged at ocean disposal sites are fully characterized before approval
for ocean disposal is granted. Sediments that contain toxic pollutants in toxic amounts, or that
contain elevated levels of compounds that will readily bioaccumulate into tissues of organisms
exposed to them on the seafloor, are prohibited from being discharged. Thus the chemical
concentrations identified are not considered to represent a risk of environmental impacts in and of
themselves; also, these low concentrations indicate that the pre-dredge sediment testing regime is
adequately protecting the environment of the disposal sites by identifying and excluding more
highly contaminated sediments from being disposed.
3.3 Benthic Community Analysis Results
Less than half of the original targeted stations were sampled for sediment grab sampling due to
ship and equipment problems. Nevertheless, by selecting stations based on the results of the SPI-
PVP surveys, sufficient samples were collected within and outside of site boundaries and the
dredged material deposit footprint to provide general characterization of benthic communities
occupying native (ambient) seafloor and seafloor physically impacted by dredged material
disposal.
3.3.1 Abundance of Infauna
As noted earlier, some physical changes (e.g., grain size and organic carbon content) were
apparent at stations with dredged material, especially at the South Oahu site. However, overall
abundances of different organism classes, while low, were not statistically different between
"inside" and "outside" stations at either disposal site (Tables 4 and 5) (EcoAnalysts, Inc., 2014).
At South Oahu, where both disposal volume and physical changes were greatest, crustaceans were
similarly abundant at "inside" and "outside" stations; annelids appeared to be somewhat less
abundant at "inside" stations; while mollusks and other miscellaneous taxa appeared to be
somewhat more abundant at "inside" stations. But considering all infauna classes, overall
abundance was very similar on-site and off-site.
At Hilo, Crustacea appeared to be somewhat more abundant at "inside" stations, but annelids,
mollusks and other miscellaneous taxa appeared to be somewhat more abundant at "outside"
stations. Overall abundance of infaunal organisms appeared to be slightly greater off-site than on-
site but these results were not statistically significant, perhaps due in part to the small sample size.
As predicted from the SPI-PVP survey results, overall infaunal abundance appeared to be slightly
greater at Hilo than at South Oahu.
Dredged material had been fairly recently deposited at both sites, and these infaunal abundance
results are consistent with relatively rapid recolonization following disposal.
34
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Table 4. Infaunal species abundances at the South Oahu site.
"Inside"
"Outside"
Category
SO-N1
SO-N2
SO-W1
SO-SW1
SO-W5
SO-S6
SO-SE4
SO-E4
SO-E6
Annelida
390
540
700
400
1190
120
50
660
670
Annelida
Average
507.5
538
Crustacea
0
10
10
10
20
0
0
10
10
Crustacea
Average
7.5
8
Mollusca
10
40
20
20
0
30
0
10
0
Mollusca
Average
22.5
8
Miscellaneous
Taxa
30
50
130
40
20
10
0
110
60
Miscellaneous
Taxa Average
62.5
40
Totals
430
640
860
470
1230
160
50
790
740
Overall
Averages
600
594
Table 5. Infaunal species abundances at the Hilo site.
"Inside"
"Outside
»
Category
H-Nl
H-SW1
H-NE5
H-SW6
H-SE4
Annelida
900
320
490
930
650
Annelida
610
690
Average
Crustacea
20
20
10
0
10
Crustacea
20
6.7
Average
Mollusca
50
10
10
260
10
Mollusca
30
93.3
Average
Miscellaneous
50
50
50
80
100
Taxa
Miscellaneous
50
76.7
Taxa Average
Totals
1020
400
560
1270
770
Overall
710
866.7
Averages
3.3.2 Diversity of Infauna
Based on species lists and statistics presented in EcoAnalysts, Inc. (2014), the overall benthic
community at the South Oahu site was shown to be different from the assemblage at the Hilo site.
This finding is not surprising given that the Hilo site is located in a relatively heterogeneous area
containing a mixture of hard bottom features (submerged reef and terraces) coupled with areas of
accumulated finer grained sediments (USGS, 2000), while the South Oahu site is located on a
more homogeneous sandy seafloor with some scattered hard bottom features. However, as is
expected of deep-sea benthic habitats overall, both sites have well developed benthic communities
with high diversity and relatively low abundances, and presence of several undescribed taxa.
35
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
For both sites combined, there were 126 taxa found. A total of 85 infaunal taxa were identified
from the South Oahu ODMDS sampled locations and a total of 79 taxa were identified from the
Hilo ODMDS sampled stations. Within the polychaetes identified from both locations, 24 of 89
species were determined to likely be undescribed (EcoAnalysts, Inc., 2014).
At the South Oahu site, diversity was high and abundances tended to be low at all stations.
Stations located inside the disposal site were not statistically different in terms of diversity,
abundances, or species richness when compared to stations located outside the disposal site. Thus
there is no evidence that dredge material is negatively impacting the benthic communities at the
South Oahu ODMDS sites sampled.
Similarly at the Hilo site, there were no significant differences in diversity between inside and
outside stations. As at South Oahu, diversity was high while abundances were relatively low,
which was expected of deep-sea benthic habitats. Based on these results there is no evidence that
dredge material is negatively impacting the benthic communities at the Hilo ODMDS stations
sampled, other than the expected reduction of abundances due to physical impacts from rubble
disposed at the center of the site.
3.4 Sub-Bottom Profile Survey (South Oahu site only)
The survey area, approximately 8 square nautical miles, covered the current designated site and
surrounding abyssal plain seafloor areas, including existing hard bottom features (such as relic
reefs and other outcrops) (Figure 25). The contrast between high reflectance native bottom bed
forms and lower reflectance non-native deposited sediments allowed for identification of dredged
material deposits throughout the study area.
While dredged material was identified within the current disposal site boundary, deposits of
dredged material were still identifiable outside the site boundaries as well (Figure 26), probably
due to past (pre-1980) disposal at historic disposal sites as well as mis-dumping before the 2000's
(when satellite tracking systems began being required to help ensure proper disposal within site
boundaries). Transects lines for the survey are shown on Figure 27. Figure 28 superimposes an
area-wide surface geological map from the sub-bottom profiling survey with the SPI-based
mapping of the dredged material footprint, showing excellent concordance between the two
methods. Sub-surface results for a typical transect are shown on Figure 29, which presents a cross-
section through the center of the disposal site looking down through both the dredged material
deposit and the native sediment underlying it.
The analysis of the full sub-bottom data set (Sea Engineering, Inc., 2014) suggests that the dredged
material deposits in and around the South Oahu site generally vary between 3 and 12 feet (1- 4 m)
in thickness. An order of magnitude approximation of the total amount of dredged material within
the study area was calculated using an average thickness of 6 feet (2 meters). The total volume of
dredged material mapped throughout the entire study area, including historic disposal outside the
current site boundaries, was thus calculated to be 27,885,600 cubic yards (21,320,000 cubic
meters). However, the total volume of dredged material mapped within the current South Oahu
site boundary was calculated to be 1,736,000 cubic yards (1,327,350 cubic meters). This compares
quite favorably with the recorded volume of 1,855,230 cubic yards of material known to have been
disposed from 2000 through 2013 (Table 1, and Figure 30).
36
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 25. USGS shaded-relief image showing the boundary of the sub-bottom survey area around the South Oahu
disposal site, as well as major bedforms in the vicinity (shaded relief imagery from USGS, 2000). (Sea
Engineering, 2014)
G"»*
HQ 4s
Obslri
10
„ « > V'W- ,, " \ \V. '
¦c° --£T"\ * * 3 £"•->. ;A - -TP.
. jT^u1 si Vw 24 7. - V « » ti '*!»
•* ^ 2
Co
ODMDS
BEDFORMS
SURVEY LIMIT
SURVEY
LIMIT
HIGH RELIEF
AREA
BEDFORMS
37
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 26. USGS sidescan sonar (backscatter) image showing historic dredged material deposits around the sub-bottom
survey area and the South Oahu disposal site (sidescan imagery from USGS, 2000). (Sea Engineering, 2014)
DREDGED MATERIAL
DEPOSITS
38
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 27. Transect lines for the sub-bottom profiling survey of the South Oahu site. Results for Diagonal line 1
through the center of the disposal site (arrows) are given in Figure 29. (Sea Engineering, 2014)
39
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
Figure 28. Geological (surface) interpretation from the sub-bottom profiling survey superimposed with the SPI-
based dredged material footprint map shown in Figure 17. (DM = dredged material; HSL = hard sand layer;
HR/DM = high-relief terrain with dredged material.) (Sea Engineering, 2014)
SURVEY LIMIT
.S6
A. A
£6
•SE6 J
HSL
SPI.PV aid Sadment Sairiplnj Loutoni
South uaiu OLMQS, Hawai
Juno
Station Average
Dredged Material
Thickness (cm)
Dump site
0.0
lr»C*
0 0 1 -1.0 cm
# 1.1-10 0 cm
0 > 10.0 cm
O lnt)et«rrr\*ia(e (IKD)
Dredged material
excnnded penetration?
40
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 29A. Sub-bottom profile - NE portion of Diagonal Line 1. (Sea Engineering, 2014)
Siity very fine sand with
ODMDS
Match with E
IRREGULAR HIGH-RELIEF
TERRAIN CONSISTENT WITH
LIMESTONE REEF OR BEDFORMS
THIN COVER OF SAND AND DM
THIN SAND (1m)
OVER DM
Discrete sand over silty
sand layering. Debris,
mudclasts, and organism tubes
at SWI.
-"RU-
THIN SAND AND DM (3m) *
OVER HIGH-RELIEF TERRAIN
I LACK OF -
! SUB-BOTTOM FEATURES
I INDICATIVE OF DM
Figure 29B. Sub-bottom profile - SW portion of Diagonal Line 1. (Sea Engineering, 2014)
Match with A
LACK OF SUB-BOTTOM FEATURES
INDICATIVE OF DREDGED MATERIAL (DM)
| O
-*•4
: ro
DM - Discrete deposits, fines at depth
arid winnowed sands at SWI.
LACK OF SUB-BOTTOM FEATURES
INDICATIVE OF OHEOGEO MATERIAL (DM)
DM - Discrete layering,
medium sand over silty
very firie sand & muds.
V)
S
ODMDS
Trace DM - Silty fine to
medium sand with some silt
No DM - Medium sand with
interstitial fines and silt.
5UB-BOTTOM FEATURES
APPEAR WHEN DM THINS OS IS NOT PRESENT
41
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Figure 30. Comparison of South Oahu site dredged material volume estimates: from sub-
bottom mapping versus recorded disposal volumes for 2000-2013 (see Table 1).
Comparison of Disposal Volumes:
Sub-Bottom Profile Survey versus
Disposal Records
Estimated Volume of Dredged Material
Disposed at the South Oahu ODMDS
Based on Sub-Bottom Profile Results:
Volume estimated in overall Study Area:
27,885,600 cy (21,320,000 m^)
Volume estimated within ODMDS limits only:
1,736,000 cy (1,327,350 m3)
Disposal Records:
Year
Cubic Yards
2000
0
2001
0
2002
53,500
2003
183,500
2004
540,000
2005
0
2006
160,400
2007
266,500
2008
0
2009
126,200
2010
0
2011
18,260
2012
0
2013
506,870
Total:
1,855,230
Although the volume of dredged material estimated by the sub-bottom profiling survey to be
within the South Oahu disposal site boundary (1.74 million cy) compares well with the actual
disposal records since 2000 (1.85 million cy), Table 1 shows that a total of 6.3 million cy has
actually been disposed since the site was designated in 1980. It is likely that some substantial
portion of the total 6.3 million cy disposed at the South Oahu site since 1980 is actually
represented within the approximately 26 million cy of historic material estimated to be outside the
site boundaries. Prior to the early 2000s, automatic satellite-based tracking and recording of
disposal scow position was not required 2, and "short-dumping" (resulting in material depositing
outside site boundaries) probably occurred fairly frequently. Still, it is highly likely that much of
the material disposed between 1980 and 2000 was nevertheless deposited on-site, so more than 1.8
million cy should be present. It is to be expected that physical consolidation of any dredged
material deposit would occur over time, reducing its apparent volume compared to disposal
records. For all these reasons, the sub-bottom profiling survey's rough estimate is certainly low.
However, it is also certainly within an order of magnitude, and is an interesting cross-check on
other disposal site monitoring results.
2 The 1997 SMMP (USEPA and USAGE, 1997) required a navigation system capable of 30 m accuracy, but did
not specify that the system show the position of the disposal scow itself (as opposed to the tug or towing
vessel). Similarly, the 1997 SMMP did not require "black box" recording of the actual disposal location, so
independent confirmation that disposal only occurred at the center of the disposal site (as required) was
difficult. But beginning in the 2000s, as both commercial GPS accuracy and vessel sensor technology
advanced, and EPA and USAGE began requiring sophisticated automatic tracking systems as conditions for
all individual project's ocean disposal permits.
42
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
3.5 Comparison to 1980 Baseline Information
EPA Region 9
3.5.1 South Oahu Disposal Site
Comparison of the data contained in the 1980 EIS to the data collected from the 2013 survey
shows that the grain size proportions in the disposal site have shifted to a higher percentage of silt
and clay, as well as higher percentage of sediments coarser than sand (Table 6). This is not
surprising because maintenance dredged material tends to be finer grained in comparison to the
native bottom sediments which contain a higher percentage of sand, as described in the 1980 EIS.
New work (deepening) dredging projects in areas such as Pearl Harbor have likely removed deeper
layers of reef formation material, thus contributing to the gravel-sized fraction. This much coarser
material is expected to sink rapidly to the bottom, without dispersing and drifting outside of the
site boundary, in contrast to fine grained dredged material.
Table 6. Average Percent Grain Size - South Oahu Site
Grain Size
1980 EIS
2013 - Disposal
2013 - Outside of
2013 - Entire
Category
(Pre-Disposal)
Site only
Disposal Site
Survey Area
Gravel
12.0
21.6
2.8
12.2
Sand
75.0
44.4
77.2
60.8
Silt & Clay
13.0
33.2
19.2
26.2
Comparison to baseline sediment chemistry is limited to the trace metal concentrations shown in
the 1980 EIS. When comparing the 1980 trace metal data to the data collected from the 2013
survey, it is apparent that dredged material disposal operations generally have not appreciably
increased contaminant loading on-site, or relative to the surrounding environs, except for copper
(Table 7). The slightly elevated on-site copper concentration is higher than the NOAA ER-L
screening level, but is much lower than the ER-M screening level where toxicity effects are more
likely to occur. As discussed in Section 3.2, all sediments discharged at ocean disposal sites are
fully characterized before approval for ocean disposal is granted. Sediments that contain toxic
pollutants in toxic amounts are prohibited from being discharged. Thus the slightly elevated
concentration of copper compared to the 1980 baseline is not considered to represent a risk of
environmental impact.
Table 7. Trace Metal Concentrations - South Oahu Site
Analyte
1980 EIS
2013 - Disposal
2013 - Outside of
2013-
Entire
ER-L
ER-M
(Pre-Disposal)
Site only
Disposal Site
Survey Area
Range
Ave.
Range
Ave.
Range
Ave.
Range
Ave.
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
Cadmium
4.0-6.3
5.2
0.0-
0.69
0.4
0.0-0.42
0.08
0.0-0.69
0.25
1.2
9.6
Mercury
0.5-0.9
0.7
0.10-
0.38
0.18
0.02-
0.19
0.09
0.02-
0.38
0.14
0.15
0.71
Copper
17.6-
45.5
31.0
43.0-
84.0
59.0
11.0-
37.0
23.8
11.0-
84.0
41.4
34
270
Lead
38.1-
59.0
48.6
15.0-
95.0
37.6
10.0-
37.0
20.8
10.0-
95.0
29.2
46.7
218
43
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
EPA Region 9
The 1980 EIS characterized the benthic community as typical for abyssal depths, with low infaunal
abundance relative to shallow depth communities. Infaunal abundances were similar in the 2013
surveys, although on-site percent abundances of crustaceans and other miscellaneous taxa
appeared to be slightly lower than in 1980 (Table 8). Nevertheless, even these minor differences
are most likely attributable to natural variability across the study area rather than to disposal
activities. This conclusion is supported by abundances of crustaceans and other miscellaneous
taxa in 2013 being greater inside the disposal site compared to outside it.
Table 8. Percent Abundance - South Oahu Site
Taxonomic Group
1980 EIS
2013 - Disposal
2013-Outside of
2013- Entire Survey
(Pre-Disposal)
Site only
Disposal Site
Area
Annelida (includes
82.9
84.6
90.6
87.9
polychaetes)
Crustacea
2.9
1.3
1.3
1.3
Mollusca
0.8
3.8
1.3
2.4
Miscellaneous taxa
13.3
10.4
6.7
8.4
3.5.2 Hilo Disposal Site
Comparison of the data contained in the 1980 EIS to the data collected from the 2013 survey
shows that the grain size character has shifted to a somewhat higher percentage of silt and clay
(Table 9). This is not surprising because maintenance dredged material tends to be finer grained in
comparison to the native bottom sediments which contain a higher percentage of sand, as described
in the 1980 EIS. But these physical changes are less obvious and widespread than at the South
Oahu site, where much more dredged material has been disposed. Also in contrast to the South
Oahu site, new work (deepening) dredging projects have not placed such a high volume of much
coarser reef formation material, and as a result, the gravel-sized fraction has not increased
significantly.
Table 9. Average Percent Grain Size - Hilo Site
Grain Size
1980 EIS
2013 - Disposal
2013 - Outside of
2013- Entire
Category
(Pre-Disposal)
Site only
Disposal Site
Study Area
Gravel
1.0
1.75
0.0
0.9
Sand
77.0
59.8
49.3
54.5
Silt & Clay
22.0
30.3
52.0
41.1
Comparison to baseline sediment chemistry is limited to the trace metal concentrations shown in
the 1980 EIS. When comparing the 1980 trace metal data to the data collected from the 2013
survey, it is apparent that dredged material disposal operations at the Hilo site have not caused any
significant increase in contaminant loading, except for copper (Table 10.). The slightly elevated
copper concentration is higher than the NOAA ER-L screening level, but is much lower than the
ER-M screening level, where toxicity effects are more likely to occur; therefore the slightly
elevated copper is not considered to represent a risk of environmental impact. In addition, the
copper elevation is shoreward and outside the disposal site. Possible explanations include
contaminants from other shore-side source, or historic short-dumping from disposal scows (prior to
the early 2000's, after which "black box" compliance monitoring was required).
44
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys EPA Region 9
Table 10. Trace Metal Concentrations - Hilo Site
Analyte
1980 EIS
2013 - Disposal
2013 - Outside of
2013-
Entire
(Pre-Disposal)
Site only
Disposal Site
Survey Area
ER-L
ER-M
Range
Ave.
Range
Ave.
Range
Ave.
Range
Ave.
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
Cadmium
—
3.4
0.0-0.6
0.4
0.50-
0.72
0.64
0.0-
0.72
0.51
1.2
9.6
Mercury
0.10-
0.59
0.35
0.05-
0.06
0.06
0.04-
0.17
0.10
0.04-
0.17
0.08
0.15
0.71
Copper
33.9-
38.1
36.0
30.0-
35.0
31.8
30.0-
56.0
42.0
30.0-
56.0
36.9
34
270
Lead
19.5-
29.0
24.3
11.0-
12.0
11.2
9.6-
21.0
15.2
9.6-
21.0
13.2
46.7
218
The 1980 EIS characterized the benthic community at the Hilo site as typical for abyssal depths,
with low infaunal abundances relative to shallow depth communities. Compared to data presented
in the site designation EIS, some minor differences in percent abundance appear to have occurred
(Table 10). Mollusks and miscellaneous taxa appear to be very slightly lower on-site compared to
off-site in 2013 (though not statistically significantly so), and miscellaneous taxa appear to be less
abundant in 2013 than they were in 1980. However, in 2013 miscellaneous taxa were lower both
inside and outside the disposal site, while mollusks were more abundant region-wide than in 1980.
As noted earlier, the native benthic environment around the Hilo site is more heterogeneous than
around the South Oahu site to begin with. These minor differences may in infaunal abundances
therefore are at least substantially attributable to natural variability across the study area rather
than to disposal activities.
Table 11. Percent Abundance - Hilo Site
Taxonomic Group
1980 EIS
2013 - Disposal
2013-Outside of
2013- Entire Survey
(Pre-Disposal)
Site only
Disposal Site
Area
Annelida (includes
80.0
85.9
79.6
81.8
polychaetes)
Crustacea
2.2
2.8
1.0
1.5
Mollusca
1.1
4.2
10.8
8.5
Miscellaneous taxa
16.7
7.0
8.8
8.2
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IV. CONCLUSIONS AND RECOMMENDATIONS
Multiple survey activities were conducted in 2013 to assess the condition and performance of the
EPA-designated South Oahu and Hilo ocean dredged material disposal sites. Over the past two
decades, South Oahu and Hilo have been the most heavily used of the five disposal sites that serve
the ports and harbors of the Hawaiian Islands. The survey results are intended to identify whether
any adverse impacts of dredged material disposal are occurring compared to baseline conditions, to
confirm the protectiveness of the pre-disposal sediment testing required by EPA and USACE, and
to serve as a basis for updating the Site Management and Monitoring Plan (SMMP) as appropriate.
The dredged material deposit (footprint) was mapped at each site. Significant deposits of dredged
material are apparent outside the South Oahu site boundaries, but this likely resulted from short-
dumping prior to the early 2000s when EPA and USACE began requiring "black box" tracking
systems. Since that time, virtually all material disposed at South Oahu is documented as having
been discharged properly within the Surface Disposal Zone at the center of the site. At the Hilo
site, almost all of the dredged material footprint is contained within the site boundary.
Sediment sampling confirms that there have been no significant adverse impacts as a result of
dredged material disposal operations at either of the disposal sites monitored. Only minor physical
effects (grain size and organic carbon content changes) have occurred at either site, despite the
order-of-magnitude greater volume that has been disposed at the South Oahu site over the last 15
years. Chemical analysis of both on-site and off-site stations indicated only low concentrations of
chemicals of concern, both on-site and off-site. Benthic community analyses showed that
recolonization occurs after dredged material is deposited, and similar infaunal and epifaunal
communities occupy both on-site and off-site areas. Taken together, these results also provide
support that the pre-disposal sediment testing program is effective in not allowing highly
contaminated sediments to be discharged at either site.
The 2013 monitoring results also indicate a lack of significant adverse impacts compared to 1980
baseline conditions. Only minor and localized physical changes are apparent as a result of disposal
operations at either site.
Overall, these findings suggest that ongoing use of the South Oahu and Hilo ocean dredged
material disposal sites, under testing and management conditions at least as stringent as have been
applied over the past 15 years, should similarly result no significant adverse effects. Permit
conditions should be updated in the revised SMMP, and a more specific site monitoring schedule
should be established for the future. But based on all the monitoring results, no significant
changes to sediment testing or to the overall site management framework appear to be warranted
for these sites.
Continued use of the other three Hawaii ocean dredged material disposal sites that were not
monitored in 2013 is also supported by inference. These sites have received far less frequent
dredged material disposal than South Oahu or even Hilo, and impacts can be expected to be
negligible there as well. Nevertheless, the other Hawaii sites should be considered for
confirmatory monitoring after the next round of disposal operations, currently expected to occur in
2016.
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V. REFERENCES
ALS Environmental, 2013. South Oahu Ocean Sediments. (Analytical chemistry results for grain
size, total solids, TOC, PCBs, Dioxins/Furans, and butyltins.) Prepared under EPA contract
EP-C-09-020 for ERG Inc., Chantilly, VA.
EcoAnalysts, Inc., 2014. Final Report for Benthic Community Analysis for Site Monitoring of
EPA-Designated Ocean Disposal Sites in Region 9: South Oahu and Hilo Sites (EPA
Contract EP-C-09-020, Work Assignment 4-27). Woods Hole, MA.
Germano & Associates, 2013 a. Confirmatory Site Monitoring of the South Oahu and Hilo Ocean
Dredged Material Disposal Sites Utilizing Sediment Profile and Plan View Imaging:
Quality Assurance Project Plan. Prepared under EPA contract EP-C-09-020 for ERG Inc.,
Chantilly, VA.
Germano & Associates, 2013 b. Monitoring Survey of the EPA-Designated South Oahu and Hilo
Ocean Dredged Material Disposal Sites: Sediment Profile & Plan View Imaging Results,
2013 (Project No. 0268.04.027/2, EPA Contract EP-C-09-020, Work Assignment 4-27).
Bellevue, WA.
NOAA, 2008. Sediment Quick Reference Tables (SQuiRT), NOAA OR&R Report 08-1, Office of
Response and Restoration Division, Seattle, WA.
Rhoads, 1974. Organism-sediment relations on the muddy seafloor. Oceanography and Marine
Biology: An Annual Review; 12:263-300.
Rhoads and Germano. 1982. Characterization of benthic processes using sediment profile
imaging: An efficient method of remote ecological monitoring of the seafloor (REMOTS™
System). Mar. Ecol. Prog. Ser. 8:115-128.
Sea Engineering Inc., 2013. Quality Assurance Project Plan: Sub-Bottom Profiler Survey for
Confirmatory Site Monitoring of the South Oahu Ocean Dredged Material Disposal Sites.
Prepared under EPA contract EP-C-09-020 for ERG Inc., Chantilly, VA
Sea Engineering Inc., 2014. South Oahu Ocean Dredged Material Dump Site Sub-Bottom Survey,
Honolulu, HI (EPA Contract No. EP-C-09-020, Work Assignment 4-27; Subcontract
0268.04.027/1). Waimanalo, HI.
Torresan and Gardner, 2000. Acoustic Mapping of the Regional Seafloor Geology in and
Around Hawaiian Dredged Material Disposal Sites (USGS Open File Report 00-124).
USACE. Ocean Disposal Database. http://el.erdc.usace.armv.mil/odd/ODMDSSearch.cfm.
USEPA, 1980. Final Environmental Impact Statement for Hawaii Dredged Material Disposal Site
Designation, US Environmental Protection Agency, Oil and Special Materials Control
Branch, Marine Protection Branch. Washington, D.C.
USEPA, 2013 a. Work Plan QAPP (EPA Contract No. EP-C-09-020, Work Assignment 4-27);
EPA Region 9, San Francisco, CA.
USEPA, 2013 b. Analytical Testing Results, Project R13W07, SDG 13189B. EPA Region 9
Laboratory, Richmond, CA.
USEPA and USACE, 1977. Site Management Plan (SMP) for the Hawaii Ocean Dredged
Material Disposal Sites. Special Joint Public Notice, April 7, 1997.
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APPENDIX
SUMMARY OF PLANNED VS ACTUAL SURVEY ACTIVITIES AT
HAWAII OCEAN DREDGED MATERIAL DISPOSAL SITES, 2013
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APPENDIX
SUMMARY OF PLANNED VS ACTUAL SURVEY ACTIVITIES AT
HAWAII OCEAN DREDGED MATERIAL DISPOSAL SITES, 2013
General Survey Information:
Site Name (Region): South Oahu and Hilo Ocean Dredged Material Disposal Sites (Region 9)
Survey Chief Scientist/Organization: Allan Ota (EPA Region 9)
Telephone: 415-972-3476
E-mail: ota.allan@epa.gov
Other Key Personnel/Organization: Brian Ross (EPA Region 9)
Telephone: 415-972-3475
E-mail: ross.brian@epa.gov
Science Crew/Organization:
Amy Wagner (EPA Region 9)
Leslie Robinson (US Navy, HI)
Sean Hanser (US Navy, HI)
Thomas Smith (USACE, HI)
Robert O'Connor (NO A A, HI)
Joseph Germano (Germano & Assoc., WA)
David Browning (Germano & Assoc., WA)
Christine Smith (ANAMAR, FL)
Schedule of Operations:
Number of survey days: 8 planned, 5 actual (plus 2 for mobilization/demobilization)
Mobilization date (Location): 24-25 June 2013 (Ford Island, Pearl Harbor, Oahu)
Demobilization date (Location): 03 July 2013 (Ford Island, Pearl Harbor, Oahu)
Original Problem Definitions/Task Descriptions (from Quality Assurance Project Plan)
1. Using the Hi'ialakai, collect MBES images to confirm overall bathymetry and identify
any features of interest to adjust sediment sampling locations as appropriate:
a. Is the overall bathymetry different from the standard NOAA charts?
b. Are there unusual or unique features that suggest that adjustment of planned
sampling station locations is necessary to improve interpretation of site
monitoring data?
2. Using the Hi'ialakai, collect SPI and PVP images at up to 49 stations covering each
EPA ODMDS and adjacent areas outside of site boundaries to address the following
management questions:
a. Is the footprint of recently deposited dredged material contained within site
boundaries? Are dredged materials in a single mound feature or contained
in multiple mounds?
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b. Are the sediments within the dredged material deposit footprint visually
similar or dissimilar from ambient bottom sediments?
c. Are there indications of disposal of materials other than dredged materials?
d. Are there indications of an undisturbed or disturbed environment (adverse
impacts)?
3. Using the Hi'ialakai, collect up to 20 sediment grab samples at each EPA ODMDS and
adjacent areas outside of site boundaries to address the following management
questions:
a. Are sediment contamination levels at the sites within the range predicted by
pre-disposal sediment testing of dredged material approved for disposal?
b. Are levels of contaminants at historic disposal sites (>10 years since used)
adjacent to the active South Oahu site similar to or below ambient levels
(undisturbed native sediments - outside of deposit footprint or site
boundaries)?
c. How do the biological communities compare, between within the site and
outside of site boundaries?
d. How do the biological communities compare to what existed when these
permanent sites were designated?
4. Using a contracted (Sea Engineering) vessel, collect high resolution sub-bottom seismic
profiles within selected basin locations to address the following management questions:
a. Based on the acoustic signal contrast between native bottom sediments and
dredged material layer, what is the horizontal extent of the dredged material
deposit footprint relative to the site boundaries? - i.e., does the dredged material
deposit appear to reside mostly or completely within site boundaries, suggesting
site is performing as expected?
b. Based on the acoustic signal contrast between native bottom sediments and
dredged material layer, what is the apparent thickness of the dredged material
deposit footprint? - i.e., does the bulk of the dredged material volume appear to
reside mostly or completely within site boundaries, suggesting site is
performing as expected?
c. How does the calculated volume of the dredged material identified by this
survey compare with dredging records for projects using the site? - i.e.,
comparison of volumes from compiled disposal records to the calculated
volume using information from (a) and (b) above.
Actual Sequence of Tasks/Events
The surveys were originally scheduled to occur over 8 days (plus mobilization and
demobilization), but problems associated with readiness of the NOAA ship and its equipment
caused some delays. The surveys were ultimately conducted over a 5-day period (not including
transit between the South Oahu site and the Hilo site, and the return transit to Pearl Harbor from
the Hilo site). Field operations were conducted continuously over a 24-hour period (two scientific
crews working 12-hour shifts).
The survey sampling objectives were not fully accomplished due to the following problems:
1. Departure was delayed by one day, due to:
a. Hole/rupture in the NOAA ship's bilge tank which had to be repaired.
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b. The original contracted marine winch, which was installed during the previous
week, was not working properly and its hydraulic unit had to be replaced.
2. The replacement winch operated at a slower rate (about 20 meters per minute, instead of
40-60 meters per minute) than what was expected when the survey plan was conceived,
resulting in less than half of the planned sediment grab sampling stations being occupied in
the time remaining for survey work.
3. Hard bottom features were encountered and multiple attempts were needed at several
stations to obtain acceptable samples, as judged by QAPP metrics (i.e., adequate
penetration and undisturbed appearance).
4. The multi-beam echo sounder (MBES) survey initially planned for both sites was not
executed due to the equipment on the NOAA vessel not functioning properly at the
beginning of the first survey leg. As a result, no MBES data was collected at either site. In
the absence of the MBES survey data, the combination of SPI and PVP photography and
analysis of the SPI visual parameters provided information on the horizontal and vertical
extent of the dredged material footprint, and context for the other (sediment) sampling
results.
Survey Activities/Operations Conducted to Address Problem Definitions:
The following are the survey activities executed at both sites:
1. Sediment Profile Imaging (SPI) and Plan View Photography (PVP)
SPI-PVP surveys were conducted for each ODMDS to delineate the horizontal extent
of the dredged material deposit footprint within the site, and outside of site boundaries
if any deposits exist (Figure 2). A total of 86 stations were occupied with the SPI/PV
camera system (40 at South Oahu and 46 at Hilo), compared to the planned 98 (49 at
each site). With optimal resolution on the order of millimeters, the SPI system is
particularly useful for identifying a number of features, including the edges of the
footprint as they overlay native sediments of the seabed, identifying dredged material
layers relative to native sediments, and the level of disturbance as indicated by presence
of certain classes of benthic organisms (Figures 3 and 4). PVP is useful for identifying
surface features where the SPI photos are taken, thereby providing surface context for
the vertical profiles at each station. For each station, a minimum of four SPI photos
were taken, coupled with a single PVP photo.
2. Sediment Sampling for Chemistry and Benthic Communities:
Sediment samples were collected for sediment grain size, chemistry, and benthic
community analysis with a stainless steel double Van Veen sediment grab (Figure 5)
capable of penetrating a maximum of 20 centimeters of depth below the sediment
surface. Sediment grab samples were judged acceptable based on approved QAPP
metrics. After each acceptable grab sample was measured for depth of penetration and
photographed, sufficient volume of chemistry subsample were extracted from one of
the two grabs with a stainless steel spoon for further processing (Figure 6). The
chemistry subsample was then homogenized and divided into the different chemistry
analysis jars (i.e., grain size, metals and organics). After the chemistry subsample was
extracted, the entire volume of the other grab was processed (Figure 7) to create a
benthic community sample for that station. A 500 micron sieve was used to separate
organisms from the sediment, and the separated organisms were then initially preserved
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with formalin. A total of 18 sediment grab sample stations were occupied in the two
survey areas combined, relative to the original targeted 40 locations. 18 chemistry
samples were processed (10 at South Oahu, and 8 at Hilo), 3 of which were field or
laboratory duplicates. A total of 14 benthic community samples were collected; the
lower number than the chemistry samples was due to some grabs being used for field
and laboratory chemistry duplicates, and one station where QAPP metrics were not met
for an acceptable benthic sample (lack of time to re-deploy).
The following survey activity was executed only at the South Oahu site:
3. Collection of high-resolution sub-bottom seismic-reflection profiles:
The primary purpose of this survey was to collect cross-sectional images of the native
sediment layers and identify layers indicative of the dredged material deposit footprint
in the environs of the South Oahu ODMDS. (The Hilo site was not surveyed in this
manner during this round of surveys, primarily due to the much smaller volumes of
dredged material which may not be detectable in terms of thickness and contrast.) The
survey was contracted to Sea Engineering, who conducted the work aboard a separate
vessel specially rigged for this type of survey with an acoustic sub-bottom profiler
system (Figure 8), which was more cost effective than attempting to install the
equipment on the NOAA vessel. The results of this survey allowed EPA to calculate an
estimate of cumulative volume of dredged material in the South Oahu site.
The study areas are depicted in Figures 9 and 10 (South Oahu) and 11, and 12 (Hilo) The target
sampling station coordinates are listed in Tables 2 (South Oahu) and 3 (Hilo).
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
Figure 9. General location of the South Oahu ODMDS
EPA Region 9
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Figure 10. Planned and actual sample station locations at the South Oahu ODMDS:
EPA Region 9
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Table 2. South Oahu ODMDS Sampling Station Coordinates (NAD83). SPI and PVP
photographic samples at all stations; sediment grab samples at highlighted stations.
Station ID
Latitude
Longitude
Sampling Notes
C
21 14.970 N
157 56.670 W
SPI-PV only
N1
21 15.220 N
157 56.670 W
SPI-PV and sediment grab
Nl-A
2115.199 N
157 56.647 W
SPI-PV and sediment grab (field dupe)
N2
21 15.470 N
157 56.670 W
SPI-PV and sediment grab
N3
21 15.720 N
157 56.670 W
SPI-PV only
N4
21 15.965 N
157 56.670 W
SPI-PV only
N5
2116.215 N
157 56.670 W
SPI-PV only
N6
21 16.470 N
157 56.670 W
SPI-PV only
SI
21 14.720 N
157 56.670 W
SPI-PV only
S2
21 14.465 N
157 56.670 W
SPI-PV only
S3
21 14.220 N
157 56.670 W
SPI-PV only
S4
21 13.965 N
157 56.670 W
SPI-PV only
S5
21 13.720 N
157 56.670 W
SPI-PV only
S6
21 13.465 N
157 56.670 W
SPI-PV and sediment grab
W1
21 14.970 N
157 56.940 W
SPI-PV and sediment grab
W2
21 14.970 N
157 57.210 W
SPI-PV only
W3
21 14.970 N
157 57.475 W
SPI-PV only
W4
21 14.970 N
157 57.740 W
SPI-PV only
W5
21 14.970 N
157 58.000 W
SPI-PV and sediment grab
W6
21 14.970 N
157 58.275 W
SPI-PV only
El
21 14.970 N
157 56.400 W
SPI-PV only
E2
21 14.970 N
157 56.135 W
SPI-PV only
E3
21 14.970 N
157 55.870 W
SPI-PV only
E4
21 14.970 N
157 55.600 W
SPI-PV and sediment grab
E5
21 14.970 N
157 55.340 W
SPI-PV only
E6
21 14.970 N
157 55.070 W
SPI-PV and sediment grab
NW1
2115.140 N
157 56.865 W
Station not occupied
NW2
21 15.300 N
157 57.070 W
SPI-PV only
NW3
21 15.470 N
157 57.270 W
Station not occupied
NW4
21 15.650 N
157 57.450 W
SPI-PV only
NW5
21 15.825 N
157 57.635 W
Station not occupied
NW6
2116.010 N
157 57.820 W
SPI-PV only
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Table 2, continued. South Oahu ODMDS Sampling Station Coordinates (NAD83). SPI and PVP
photographic samples at all stations; sediment grab samples at highlighted stations.
NE1
2115.140 N
157 56.480 W
Station not occupied
NE2
21 15.300 N
157 56.280 W
SPI-PV only
NE3
21 15.470 N
157 56.090 W
Station not occupied
NE4
21 15.650 N
157 55.900 W
SPI-PV only
NE5
21 15.825 N
157 55.710 W
Station not occupied
NE6
2116.010 N
157 55.530 W
SPI-PV only
SW1
21 14.790 N
157 56.865 W
SPI-PV only
SW2
21 14.620 N
157 57.050 W
SPI-PV and sediment grab
SW3
21 14.435 N
157 57.225 W
SPI-PV only
SW4
21 14.245 N
157 57.400 W
SPI-PV only
SW5
21 14.070 N
157 57.590 W
SPI-PV only
SW6
21 13.900 N
157 57.785 W
SPI-PV only
SE1
21 14.790 N
157 56.480 W
Station not occupied
SE2
21 14.620 N
157 56.280 W
SPI-PV only
SE3
21 14.435 N
157 56.090 W
Station not occupied
SE4
21 14.245 N
157 55.910 W
SPI-PV and sediment grab
SE5
21 14.070 N
157 55.720 W
Station not occupied
SE6
21 13.900 N
157 55.530 W
SPI-PV only
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Figure 11. General location of the Hilo ODMDS:
EPA Region 9
~ o
°o *
- » <
nhL.
%aMl
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2013 South Oahu and Hilo Ocean Disposal Site Monitoring Surveys
Figure 12. Planned and actual sample station locations at the Hilo ODMDS:
EPA Region 9
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Table 3. Hilo ODMDS Sampling Station Coordinates (NAD83). SPI and PVP photographic
samples at all stations; sediment grab samples at highlighted stations.
Station ID
Latitude
Longitude
Notes
C
19 48.315 N
154 58.340 W
SPI-PV only (grab failed)
N1
19 48.565 N
154 58.320 W
SPI-PV and sediment grab
N2
19 48.815 N
154 58.295 W
SPI-PV only
N3
19 49.065 N
154 58.285 W
Station not occupied
N4
19 49.315 N
154 58.270 W
SPI-PV only
N5
19 49.570 N
154 58.260 W
Station not occupied
N6
19 49.820 N
154 58.245 W
SPI-PV only
SI
19 48.075 N
154 58.365 W
SPI-PV only
S2
19 47.825 N
154 58.395 W
SPI-PV only
S3
19 47.570 N
154 58.425 W
SPI-PV only
S4
19 47.325 N
154 58.450 W
SPI-PV only
S5
19 47.075 N
154 58.475 W
SPI-PV only
S6
19 46.820 N
154 58.500 W
SPI-PV only
W1
19 48.335 N
154 58.600 W
SPI-PV only
W2
19 48.355 N
154 58.870 W
SPI-PV only
W3
19 48.375 N
154 59.125 W
SPI-PV only
W4
19 48.400 N
154 59.385 W
SPI-PV only
W5
19 48.430 N
154 59.655 W
SPI-PV only (grab failed)
W6
19 48.460 N
154 59.920 W
SPI-PV and sediment grab
El
19 48.290 N
154 58.075 W
Station not occupied
E2
19 48.270 N
154 57.810 W
SPI-PV only
E3
19 48.250 N
154 57.545 W
Station not occupied
E4
19 48.230 N
154 57.285 W
SPI-PV only
E5
19 48.210 N
154 57.020 W
SPI-PV only
E6
19 48.190 N
154 56.755 W
Station not occupied
NW1
19 48.490 N
154 58.530 W
SPI-PV only
NW2
19 48.675 N
154 58.700 W
SPI-PV only
NW3
19 48.880 N
154 58.860 W
SPI-PV only
NW4
19 49.060 N
154 59.040 W
SPI-PV only
NW5
19 49.265 N
154 59.200 W
SPI-PV only
NW6
19 49.470 N
154 59.365 W
SPI-PV only
NE1
19 48.480 N
154 58.130 W
SPI-PV only
NE2
19 48.650 N
154 57.935 W
SPI-PV only
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Table 3, continued. Hilo ODMDS Sampling Station Coordinates (NAD83). SPI and PVP
photographic samples at all stations; sediment grab samples at highlighted stations.
NE3
19 48.815 N
154 57.735 W
SPI-PV only
NE4
19 48.975 N
154 57.535 W
SPI-PV only
NE5
19 49.130 N
154 57.330 W
SPI-PV and sediment grab
NE6
19 49.275 N
154 57.110 W
Station not occupied
SW1
19 48.155 N
154 58.540 W
SPI-PV and sediment grab
SW2
19 48.015 N
154 58.760 W
SPI-PV only
SW3
19 47.865 N
154 58.970 W
SPI-PV only
SW4
19 47.720 N
154 59.185 W
SPI-PV only
SW5
19 47.565 N
154 59.385 W
SPI-PV only
SW6
19 47.415 N
154 59.600 W
SPI-PV and sediment grab
SW7
19 47.257 N
154 59.827 W
SPI-PV only (station added in field)
SW8
19 46.989 N
155 00.245 W
SPI-PV only (station added in field)
SW9
19 46.648 N
155 00.587 W
SPI-PV only (station added in field)
SE1
19 48.110 N
154 58.180 W
SPI-PV only
SE2
19 47.925 N
154 58.010 W
SPI-PV only
SE3
19 47.715 N
154 57.850 W
SPI-PV only
SE4
19 47.530 N
154 57.690 W
SPI-PV and sediment grab
SE5
19 47.325 N
154 57.520 W
SPI-PV only
SE6
19 47.135 N
154 57.340 W
SPI-PV only
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