United States
Environmental Protectior
Agency
Region 6
144^ Ro$$ Ave.
Dallas, n 75202
EPA 906/01-69-003
January 13&n
Environmental Draft
Impact Statement
Freeport Harbor (45-Foot Project)
Ocean Dredged Material
Disposal Site Designation
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION VI
1445 ROSS AVENUE, SUITE 1200
DALLAS, TEXAS 7S202
JAN 2 7 W89
TO INTERESTED AGENCIES, OFFICIALS, PUBLIC GROUPS AND INDIVIDUALS:
Enclosed 1s a copy of the Draft Environmental Impact Statement (EIS)
concerning the Environmental Protection Agency's (EPA's) designation
of two ocean disposal sites for material dredged from the Freeport
Harbor and Jetty Channels 1n conjunction with the Galveston District
Corps of Engineer's 45-Foot Project at Freeport Harbor, Texas.
EPA encourages agency and public participation In the decision-making
process. Written comments on this Draft EIS Mill be considered In the
preparation of the Final EIS. If the required changes are minor, EPA's
Final EIS will Incorporate the Draft EIS by reference and Include only
(1) a revised summary; (2) revisions necessary to the Draft EIS as a
result of agency and public comment; (3) EPA's responses to comments
received on the Draft EIS; and (4) EPA's Proposed Action.
The Final EIS will be sent to those making substantive comments on the
Draft EIS and to those specifically requesting a copy (subject to supply
limits). Written comments or Inquiries regarding this Draft EIS should
be addressed to Norm Thomas, Chief, Federal Activities Branch, at the
above address by the date stamped on the cover sheet following this
letter.
Sincerely yours,
Robert E. Layton Jr., P.E
Regional Administrator
Enclosure
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DRAFT ENVIRONMENTAL IMPACT STATEMENT
FREEPORT HARBOR (45-FOOT PROJECT), TEXAS
OCEAN DREDGED MATERIAL DISPOSAL SITE DESIGNATION
RESPONSIBLE AGENCY: U.S. Environmental Protection Agency, Region 6
ADMINISTRATIVE ACTION: The purpose of the action 1s to comply with the
Marine Protection, Research and Sanctuaries Act of 1972 by providing
environmentally acceptable ocean dredged material disposal sites (ODMDSs)
1n compliance with the Ocean Dumping Regulations (40 CFR Parts 220-229).
EPA CONTACT: Norm Thomas (6E-F)
U.S. Environmental Protection Agency
First Interstate Bank Tower
1445 Ross Avenue
Dallas, Texas 75202-2733
ABSTRACT: The proposed action 1s the designation of two ocean disposal
sites. One site 1s for the one time disposal of 5.1 million cubic yards
(mcy) of construction material; the other site 1s for the disposal of 2.1
mcy of future maintenance material dredged annually from the Freeport
Harbor and Jetty Channels 1n conjunction with the U.S. Army Engineer
District, Galveston, 45-Foot Project at Freeport Harbor, Texas. The
major adverse environmental impact of site designation 1s the burial and
high mortality of the benthlc Infaunal community within the disposal site.
COMMENTS ON THE DRAFT EIS DUE: APR 0 3 1989
RESPONSIBLE OFFICIAL:
Robert E. L*yton Jr/, P.E%
Regional Administrator
11
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SUMMARY
Purpose and Need for the Action
The Environmental Protection Agency (EPA) is mandated by Congress
with the authority to regulate ocean disposal and with the responsibility
for site designation and management. The action for which this document was
prepared is the designation of a site(s) for the ocean disposal of
construction and maintenance material dredged from the Freeport Harbor
Entrance and Jetty Channels in conjunction with the U.S. Army Corps of
Engineers (CE) 15-Foot Project. The purpose of this action is to designate,
based on 10 CFR 228, an ocean disposal site(s) which will provide the most
environmentally acceptable and economically and physically feasible area(s)
for the placement of construction and future maintenance material from the
expanded and relocated Freeport Harbor Entrance and Jetty Channels. This
will produce an anticipated 5.1 million oubic yards (mcy) of virgin, new-
work material, from the Entrance Channel, to be discharged offshore.
Additionally, the CE has a general mandate from the U.S. Congress to
maintain the navigable waters of the United States. Specifically, the
Galveston District of the CE is oharged with maintaining the Freeport Harbor
Entrance and Jetty Channels. This will require the removal of approximately
2.1 mcy of additional maintenance material per year.
Alternatives
The general alternatives examined were the No-Action Alternative;
upland disposal; and ocean disposal, including a Mid-Shelf site, a
Continental Slope site, and a near-shore site, including the historically-
used site. The No-Action Alternative constitutes a fatal flaw for the
project and, therefore, was not considered viable. The Mid-Shelf and
Continental Slope Alternatives were not considered feasible because of
safety and economic considerations, limits on monitoring and surveillanoe,
and the lack of any environmental considerations which would dictate the
need for sites that far offshore.
The specific alternatives are the possible sites which could be
selected for designation. The area wherein viable alternative sites could
be located was generated by determining a Zone of Siting Feasibility (ZSF)
based on limits from (1) the oost of transportation of dredged material, (2)
the feasibility of monitoring and surveillanoe, and (3) political
boundaries. The ZSF thus determined is the ocean area included within and
bounded by the beach line and the loci of points ten statute miles from the
intersection of the Freeport Harbor Jetty Channel with the beach line.
Within the ZSF the following were exoluded from consideration as possible
sites:
iii
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1) All areas northeast of the channel and a line extending two
miles beyond the end of the extended and relocated Entrance
Channel, to prevent material being carried back into the
channel by long-shore drift;
2) Sites of cultural and historic interest;
3) All obstructions, plus navigation channel buffer zones to
prevent up-current transport of material back into the
channel and to provide a buffer between the discharging
dredge and vessels in the channel (the anticipated lack of
mounding precludes the exclusion of the safety fairway);
4) Biologically sensitive areas (a white shrimp breeding area,
a sport and commercial fishing harvest area, two reefs and
the jetties, including 1.9-mile buffer zones for virgin
material and 2.65-mile buffer zones for the maintenance
material) and oil and/or gas platforms;
5) Areas of recreational use (the beach, including a 1.9-mile
buffer zone) and the biologically sensitive areas and
platforms noted above.
The preferred size of the virgin ocean dredged material disposal
site (ODMDS) was determined, based on models of the ocean discharge of
dredged material, to be 5,280 feet in a direction parallel to the Channel
(northwest/southeast) and 11,380 feet in a direction perpendicular to the
Channel (northeast/southwest). The Ocean Dumping Regulations, at
10 CFR 228.5(e), state that preference will be given to historically-used
sites, assuming that they meet all other criteria. However, the interim-
designated ODMDS was in the area excluded by the biologically sensitive area
buffer zone. The selection process determined that, in general, an ODMDS
located nearshore would cause fewer impacts to plankton, due to the natural
turbidity of the nearshore area, and to the benthos, due to the resilient
and hardy organisms which occupy the nearshore area. However, also to
reduce impacts to the benthos, it was determined, from the grain size
distribution of the material to be disposed of that the virgin material,
which was mostly silt and clayballs, is most compatible with the silty-clay
regime which ranges from about the 30-foot isobath to about the 60-foot
isobath. Based on safety considerations associated with expected mounding,
it was determined that the virgin material ODMDS should not be located in
water shallower than 55 feet nor in the safety fairways.
Based on all of the above considerations, including the preferred
size determinations, the preferred site for the virgin material ODMDS was
determined to be bounded by the following coordinates (Figure 1):
28° 51' 22" N, 95° 1*' 25" W; 28° 50' 28" N, 95° 13' 30" W;
28° H8' 58" N, 95° 15' 2M" W; 28° M9' 55" N, 95° 16' 19" W.
iv
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zz
STATUTE MILES
7
ZZ
zz
z
z
z
zzz
Arao of Dlapoiol
Actual
DESIGNATED ^ODMDS
*
INTERIM-
Freeport
£ VIRGIN MATERIA
V •
zz
zz^
zz
Fig. 1
Interim-Designated Site, Preferred
Site and Areas Avoilable for a
Virgin Material ODMDS
v
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The preferred size of the maintenance material ODMDS is
1,500 feet parallel to the Channel and 12,500 feet perpendicular to the
Channel. The Ocean Dumping Regulations, at 40 CFR 228.5(e), state that
preference will be given to historically-used sites, assuming that they
meet all other criteria. However, the interim-designated ODMDS was in the
area excluded by the biologically sensitive area buffer zone. The selection
process determined that, in general, an ODMDS located nearshore would cause
fewer impacts to plankton, due to the natural turbidity of the nearshore
area, and to the benthos, due to the resilient and hardy organisms which
occupy the nearshore area. The maintenance material was most compatible
with the silty-sand nearshore regime, which extends from shore to about the
30-foot isobath or the sand-silt-clay regime which extends offshore from
about the 60-foot isobath. Based on safety considerations, it was
determined that the maintenance material ODMDS should not be located in
water shallower than about 30 feet.
Based on all of the above considerations, including the preferred
size determinations, the preferred site for the maintenance material ODMDS
is bounded by (Figure 2):
28° 5U« 00" N, 95° 15' 49" W; 28° 53' 28" N, 95° 15' 16" W;
28° 52' 00" N, 95 16' 59" W; 28 52' 32" N, 95 17' 32" W.
EPA's preferred alternative is the final designation of the
preferred sites for the one-time disposal of virgin construction material
and for the routine disposal of future maintenance material from the
Freeport Harbor Entrance and Jetty Channels.
Affected Environment
Freeport is situated along the coastline of the Upper Texas
Coastal Plain and is in a semi-tropical marine environment dominated by the
Gulf of Mexico. Average temperature and rainfall for winter (January) are
54 F and 3.4 inches, respectively, and for summer (July) are 83 F and
5.0 inches. There is a 37%, 23f or 7 J chance of a tropical storm, hurricane
or extreme hurricane, respectively, striking a 50-mile strip of the Gulf
Coast centered roughly eight miles northeast of Freeport.
Circulation and mixing in the Gulf of Mexico near Freeport is the
result of a complex interaction of tides, meteorological driving forces,
freshwater inflows, Coriolis acceleration, etc. Maximum bottom currents of
around four knots occur on an average of once every three years and
sustained bottom currents of one knot or greater occur for only several days
per year. The semi-permanent westerly current in the northwestern Gulf of
Mexico dominates the hydrodynamic regime near Freeport, but is strongest in
vi
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1111
STATUTE MILES
z
z
zzz.
z
zz
Aria of Actual Otap
TIIRE MAINTENANCE ODMDS
INTERIM4DESIGNATED />DMDS
*
9
Freeport
Fig. 2
Interim-Designated Site, Preferred
Site and Areas Available for a
Maintenance Material ODMDS
vii
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the fall, winter and spring. This causes sediment transport to the
southwest which, when combined with other sources, causes shoaling at
approximately 1,000,000 cy/yr into the existing Freeport Harbor Entrance
Channel.
Sediment quality and water quality in the area are good. Analysis
of sediment and water samples from the Study Area have indicated no quality
problems which would affect the site selection process.
Phytoplankton standing crops offshore of Freeport are similar to
those of other sections of the Texas and Louisiana outer continental shelf
(0CS). Dominant species, mainly diatoms, were typical of the Galveston Bay
communities. The number of zooplankton taxa were found to be relatively low
at all times of the year. Dominant species were mostly copepods. Overall
abundanoe was relatively low but considerable differences in numbers and
composition were noted between stations.
The benthic infaunal species composition at the interim-
designated 0DMDS was found to be consistent with nearby areas. This
appeared to be due to the fact that the maintenance material had a high silt
content, as does the natural bottom sediment, leaving the benthos
relatively undisturbed.
Ten species of aquatic vertebrates, considered endangered or
threatened by National Marine Pisheries Service (NMFS) may be present in the
Texas marine environment. These Include the humpback whale, the sei whale,
the sperm whale, the right whale, the fin whale, the leatherback sea turtle,
Kemp's rldley sea turtle, the hawksbill sea turtle, the green sea turtle and
the loggerhead sea turtle.
Two reefs, a sport and commercial harvesting area, and a white
shrimp breeding area have been reported in the project area. These and
petroleum platforms are Important to fisheries in the area.
Commercial fisheries at Freeport are typical of the Texas Gulf
Coast and are dominated by penaeid shrimp, although black drum and flounder
are caught in appreciable numbers commercially. The primary recreational
speoies are the same as the commercial species, with the addition of red
drum and spotted sea trout. In 1974 and 1975, respectively, 7.5 million
pounds ($10.9 million) and 8.3 million pounds ($18.3 million) of shrimp
were taken off Freeport.
The Freeport Harbor Channel provides aocess for large vessels to
Freeport and surrounding areas. Total annual tonnage through the Channel
for the period of 1961-1984, ranged from 3.8 x 10 short tons in 1961 to
23.4 x 10 short tons in 1981.
viii
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There are 39 sites of cultural or historic interest in the
project area, 18 of which are clustered near the jetties.
Environmental Consequences
The preferred sites were examined relative to the five general
criteria (40 CFR 226.5) and the eleven specific factors (40 CFR 228.6(a)).
The environmental consequences of the preferred alternative on the
different aspects of the affected environment were also examined. The
primary environmental Impact of site designation is that it will allow
burial and, therefore, high mortality of the benthic infaunal community in
the discharge area of the preferred sites, areas of 1.51 square statute
miles for the virgin material ODMDS and 0.72 square statute miles for the
maintenance material ODMDS.
Preferred Alternative
EPA's preferred alternative is the final designation of the
preferred site for the disposal of virgin material from the construction of
the 45' Project and the preferred site for disposal of maintenance material
from the Freeport Harbor Entrance and Jetty Channels, after construction of
the 45' Project. It was determined that use of the preferred sites should
result in fewer environmental impaots than use of any other appropriately-
sized portions of the non-excluded area in the ZSF for the following
reasons.
The preferred sites are located (1) to avoid impacts to benthos;
i.e., the grain size of sediments at the preferred sites is similar to that
of the materials to be deposited at those sites; (2) to avoid hazards to
navigation, based on the mounding predicted by the models; (3) to avoid
biologically sensitive areas, and (4) to avoid recreationally important
areas.
ix
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TABLE OF CONTENTS
Page
Summary Sheet 11
Summary ill
Table of Contents x
Preface xvlil
Chapter 1 PURPOSE AND NEED FOR THE ACTION 1-1
1.1 LEGISLATIVE BACKGROUND AND PROPOSED ACTION 1-1
1.2 U.S. ARMY CORPS OF ENGINEERS 1-2
1.3 U.S. ENVIRONMENTAL PROTECTION AGENCY 1-3
Chapter 2 ALTERNATIVES 2-1
2.1 NO-ACTION ALTERNATIVE 2-1
2.2 UPLAND DISPOSAL 2-1
2.3 OCEAN DISPOSAL 2-2
2.3.1 Mid-Shelf and Continental Slope Alternatives 2-2
2.3.2 Other Ocean Alternatives 2-1
2.3.3 Methodology 2-1
2.3.3.1 Literature Search 2-1
2.3.3.2 Identification of Alternatives via the 2-5
Screening Procedure
2.3.1 Development of Alternative Sites Using the 2-7
Screening Technique
2.3.1.1 Zone of Siting Feasibility 2-7
2.3.1.1.1 Limits Due to Cost of Transport 2-7
2.3.1.1.2 Limits Due to Feasibility of Monitoring 2-8
and Surveillance
2.3.1.1.3 Limits Due to Political Boundaries 2-8
2.3.1.1.1 Conclusion 2-10
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I
TABLE OF CONTENTS (Cont'd)
Page
2.3.4.2 Modeling Dredged Material Distribution 2-10
2.3*1*2.1 Virgin Material 2-12
2.3•4.2.2 Maintenance Material 2-12
2.3.1*3 Buffer Zone Assignment 2-17
2.3*4*3*1 Biologioally Sensitive Areas 2-17
2.3.4.3.2 Beaches and Recreational Areas 2-20
2.3.4.3.3 Navigation Channel 2-20
2.3Ooeanographic Constraints 2-20
2.3 >5 Cultural and/or Historical Resources 2-22
Constraints
2.3.4»6 Non-Llving Resources Constraints 2-22
2.3>7 Living Resources Constraints 2-22
2.3•I'd Environmental Quality Constraints 2-22
2.3.4.9 Recreational Uses Constraints 2-27
2.3.4.10 Areas Available for an ODMDS 2-27
2.3.5 ODMDS Size Determination 2-27
2.3.5.1 Virgin teterlal 2-27
2.3*5.2 Maintenance Material 2-30
2.3.6 Preferred Sites 2-34
2.3.6.1 Virgin Material 2-34
2.3.6.2 Maintenanoe Material 2-34
2.3.7 Disposal Sequence 2-36
2.3.7.1 Virgin Material 2-36
2.3.7.2 Maintenance Material 2-39
2.4 PREFERRED ALTERNATIVE 2-40
2.4.1 Description 2-40
2.4.2 Monitoring and Surveillance 2-40
2.4.2.1 Virgin Material 2-40
2.4.2.2 Maintenanoe Material 2-41
xi
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TABLE OF CONTENTS (Cont'd)
Page
Chapter 3 AFFECTED ENVIRONMENT 3-1
3.1 INTERIM DESIGNATED SITE CHARACTERISTICS 3-1
3.1.1 Site Location 3-1
3.1.2 Proposed Use of the Site 3-1
3.1.3 Characterization of the Disposal Site 3-1
3. "T. ^ Characterization of the Material Expected 3-5
to be Dredged
3.1.4.1 Virgin Material 3-5
3.1.4.2 Maintenance Material 3-5
3.2 PHYSICAL ENVIRONMENT 3-16
3.2.1 Nearby Areas 3-16
3.2.2 Climatology and Meteorology 3-18
3.2.3 Oceanographic 3-22
3.2.3.1 Bathymetry 3-22
3.2.3.2 Circulation and Mixing 3-22
3.2.4 Water Quality 3-27
3.2.5 Sediments 3-27
3.2.5.1 Sediment Quality and Characteristics 3-27
3.2.5.2 Sediment Transport 3-33
3.3 BIOLOGICAL ENVIRONMENT 3-36
3.3.1 Plankton 3-36
3.3.2 Benthos 3-36
3.3.3 Nekton 3-39
3.3.4 Threatened and Endangered Species 3-40
3.3.5 Marine Sanctuaries and Special Biological 3-42
Resource Areas
3.4 SOCIOECONOMIC ENVIRONMENT 3-42
xii
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TABLE OF CONTENTS (Cont'd)
Page
3-4.1 Commercial and Recreational Fisheries 3-42
3.4.2 Shipping 3-^3
3.4.3 Beachea and Recreational Areaa 3-45
3.4.4 Mineral Extraction and Transport 3-45
3.5 Cultural and Historic Sites 3-45
3.4.6 Military Restrictions 3-46
3.4.7 Political Boundaries 3-46
Chapter 4 ENVIRONMENTAL CONSEQDENCES 4-1
1.1 REGULATORY CHARACTERIZATION 4-1
4.1.1 Five General Criteria 1-1
4. 1.1.1 40 CFR 228.5(a) 4-1
4.1.1.2 40 CFR 228.5(b) 4-1
4.1.1.3 40 CFR 228.5(c) 4-2
4.1.1.4 40 CFR 228.5(d) 4-3
4.1.1.5 40 CFR 228.5(e) 4-3
4.1.2 Eleven Specific Factors 4-3
4.1.2.1 40 CFR 228.6(a)(1) 4-3
4.1.2.2 40 CFR 228.6(a)(2) 4-4
4.1.2.3 40 CFR 228.6(a)(3) 4J4
4.1.2.4 40 CFR 228.6(a)(4) 4-4
4.1.2.5 40 CFR 228.6(a)(5) 4-5
4.1.2.6 40 CFR 228.6(a)(6) 4-5
4.1.2.7 40 CFR 228.6(a)(7) 4-6
4.1.2.8 40 CFR 228.6(a)(8) 4-6
4.1.2.9 40 CFR 228.6(a)(9) 4-6
4.1.2.10 40 CFR 228.6(a)(10) 4-7
xiii
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TABLE OF CONTENTS (Cont'd)
Page
4.1.2.11 40 CFR 228.6(a)(11) 4-7
4.2 ENVIRONMENTAL CHARACTERIZATION 4-7
4.2.1 Physical Environment 4-7
4.2.1.1 Oceanography 4-7
4.2.1.1.1 Bathymetry 4-7
4.2.1.1.2 Circulation and Mixing 4-8
4.2.1.2 Water Quality 4-8
4.2.1.3 Sediment Quality and Characteristics . 4-10
4.2.2 Biological Environment 4-10
4.2.2.1 Plankton 4-10
4.2.2.2 Benthos 4-11
4.2.2.2.1 Virgin Material 4-11
4.2.2.2.2 Maintenance Material 4-11
4.2.2.3 Nekton 4-11
4.2.2.4 Threatened and Endangered Species - 4-12
Determination of Effect
4.2.2.5 Marine Sanctuaries and Special Biological 4-12
Resource Areas
4.2.3 Socioeconomic Environment 4-13
4.2.3*1 Commercial and Recreational Fisheries 4-13
4.2.3.2 Shipping 4-13
4.3 ADVERSE ENVIRONMENTAL IMPACTS WHICH 4-14
CANNOT BE AVOIDED
4.4 THE RELATIONSHIP BETWEEN LOCAL SHORT-TERM 4-14
USES OF THE ENVIRONMENT AND THE MAINTENANCE
AND ENHANCEMENT OF LONG-TERM PRODUCTIVITY
4.5 ANY IRREVERSIBLE OR IRRETRIEVABLE 4-14
COMMITMENT OF RESOURCES
xiv
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TABLE OF CONTENTS (Cont'd)
Page
Chapter 5 COORDINATION 5-1
Chapter 6 LIST OF PREPARERS 6-1
Chapter 7 LITERATURE CITED 7-1
APPENDIX A - Modeling Dredged Material Distribution
LIST OF FIGURES
Figure Page
1 Interim-Designated Site, Preferred Site, and v
Areas Available for a Virgin Material ODMDS
2 Interim-Designated Site, Preferred Site and Areas vii
Available for a Maintenance Material ODMDS
1-1 General Project Map 1-1
2-1 Two-Hundred Meter Isobath 2-3
2-2 ODMDS Selection Approach 2-6
2-3 Bathymetry of the Freeport Harbor Area 2-9
2-11 Area Excluded Outside of the ZSF 2-11
2-5 Seafloor Distribution of Dredged Material 2-15
After Single Discharge, Large Dredge, High Current
2-6 Biologically Sensitive Areas and Buffer Zones 2-18
Exoluded from the ZSF - Virgin Material
2-7 Biologically Sensitive Areas and Buffer Zones 2-19
Excluded from the ZSF - Maintenance Material
2-8 Area Excluded from the ZSF by the Beach Buffer Zone 2-21
2-9 Area Excluded to Prevent Transport of Sediment 2-23
Back into the Channel
2-10 Historic Sites and Recent Shipwreck Obstructions 2-24
Excluded from the ZSF
xv
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TABLE OF CONTENTS (Cont'd)
LIST OF FIGURES (Concluded)
Figure Page
2-11 Obstructions, the Navigation Channel Buffer 2-25
2one and Safety Fairways Excluded from the
ZSF - Virgin Material
2-12 Obstructions and the Navigation Channel Buffer Zone 2-26
Excluded from the ZSF - Maintenance Material
2-13 Areas Available for an ODMDS - Virgin Material 2-28
2-14 Areas Available for an ODMDS - Maintenance Material 2-29
2-15 Preferred Site Configuration - Virgin Material 2-31
2-16 Preferred Site Configuration - Maintenance Material 2-33
2-17 Preferred Sites for Virgin and Maintenance 2-35
Material ODMDSs
2-18 Seafloor Distribution of Dredged Material after 2-36
Multiple Discharges, Large Dredge, High Current
2-19 Monitoring Stations - Virgin Material 2-42
3-1 Monthly Precipitation Normals at Key Stations Along 3-20
Segment Normal to the Coastline at Galveston
3-2 Season Variation of Wind Distribution Statistics 3-21
Over the Year, Galveston, Texas (after NDBC, 1973)
3-3 Bathymetry of the Freeport Harbor Area 3-23
3-4 Surface Currents in the Gulf of Mexico 3-25
3-5 Surface Sediment Distribution in Offshore Waters 3-32
3-6 Historic Sites and Recent Shipwreck Obstructions 3-47
LIST OF TABLES
Table Page
2-1 Hopper Dredge Specifications 2-13
2-2 Virgin Dredged Material Characteristics 2-14
xvi
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TABLE OF CONTENTS (Concluded)
LIST OF TABLES (Concluded)
Table Page
2-3 Results of Computer Analysis of Virgin Material 2-16
Disposal - Single Discharge
2-1 Results of Computer Analysis of Virgin Material 2-32
Disposal - Multiple Discharges
2-5 Monitoring Station Locations 2—13
3-1 Freeport Harbor Jetty and Entrance Channel Historical 3-2
Dredging
3-2 Means of Values for Disposal Area Sediment 3-3
3-3 Range of Values for Channel Virgin Sediment 3-6
3-1 Range of Values for Elutriate Samples with Channel 3-7
Virgin Sediment
3-5 Range of Values for Channel Maintenance Sediment 3-9
3-6 Range of Values for Elutriate Samples with Channel 3-11
Maintenance Sediment
3-7 Grain Size Analyses Summary 3-11
3-8 Summary of Bioassay Data for Maintenance Material 3-15
(% Survival)
3-9 Means of Tissue Concentration from Bioaccumulation 3-17
Studies with Maintenance Sediment
3-10 Range of Values for Water Samples 3-28
3-11 Range of Values for Undisturbed Site Sediment 3-30
3-12 Dominant Phytoplankton Species Collected Offshore of 3-37
Freeport, Texas, During 1973 (from Seadock, 1976)
3-13 Dominant Zooplankton Species Collected Offshore of 3-38
Freeport, Texas, During 1973 (from Seadock, 1976)
3-11 Tonnage Through Freeport Harbor Entrance and Jetty 3—I1*
Channels (Short Tons x 10 )
3-15 Locations of Historical Significance and Recent Shipwrecks 3-18
Near Freeport
xvii
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PREFACE
This Environmental Impact Statement (EIS) was prepared with the
assistance of the U.S. Army Corps of Engineers (CE), Galveston District, and
the CE's contractor, Espey, Huston & Associates, Inc. (EH&A). A list of
persons who helped prepare the Draft EIS is presented in Chapter 6.
xviii
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CHAPTER 1
PURPOSE AND NEED FOR THE ACTION
1.1 LEGISLATIVE BACKGROUND AND PROPOSED ACTION
Ocean disposal of dredged material was not specifically regulated
in the United States until passage of the Marine Protection, Research and
Sanctuaries Act of 1972 (MPRSA). Limited regulation was provided by the
Supervisors' Act of 1888 and the Refuse Act of 1899. Under these acts,
transportation and navigation factors, rather than environmental considera-
tions, guided selection of disposal locations by the U.S. Army Corps of
Engineers (CE) and the issuance of permits for ocean disposal.
Although the Fish and Wildlife Coordination Act of 1958 initially
referred to inland tidal waters, it included consideration of the effects of
dredged material on commercially important marine species. This act,
together with subsequent judicial decisions, empowered the CE to refuse
permits if the dredging or filling of a bay or estuary would result in
significant, unavoidable damage to the marine ecosystem.
MPRSA and the Federal Water Pollution Control Act (FWPCA), later
amended by the Clean Water Act of 1977, both passed in 1972 and specifically
addressed waste disposal in the aquatic and the marine environment. The
FWPCA and the Water Quality Improvement Act of 1970 set up specific water-
quality criteria to be used as guidelines in controlling discharges into
marine and aquatic environments. These water quality criteria applied to
disposal of dredged material only in cases where fixed pipelines were used
to transport and discharge dredged material into the environment at dis-
crete points. MPRSA, however, specifically regulates the transport and
ultimate disposal of waste materials in the ocean. Under Title I of MPRSA,
the primary regulatory vehicle of the Act, a permit program for the disposal
of dredged and nondredged materials was established which mandates deter-
mination of impacts and provides for enforcement of permit conditions.
The London Convention on the Prevention of Marine Pollution by
Dumping of Wastes and Other Matter (August 1975) is the principal inter-
national agreement governing ocean dumping. The Convention specifies that
contracting nations will regulate disposal in the marine environment within
their Jurisdiction, disallowing all disposal without permits. Certain
materials are prohibited entirely (e.g., biological and chemical warfare
agents and high-level radioactive matter), while others (e.g., cadmium,
mercury, organohalogens and their compounds, oil, and persistent synthetic
materials that float) are prohibited when present in greater than trace
1-1
-------
amounts. Other materials (e.g., arsenic, lead, copper, zinc, cyanides,
fluorides, organosilicon, and pestioides), while not prohibited from ocean
disposal, require special care. Materials not specifically prohibited are
eligible for ocean disposal only under a permit system. The nature and
quantities of all waste material, and the ciroumstances of disposal must be
periodically reported to the International Maritime Organization (formerly
the Inter-Governmental Maritime Consultative Organization) which admini-
sters the Convention.
In October 1973, the U.S. Environmental Protection Agency (EPA)
issued the final Ocean Dumping Regulations and Criteria (the Regulations or
Ocean Dumping Regulations), revised in January 1977 (EPA, 1977) (40 CFR
Parts 220 to 229). These Regulations established procedures and orlterla
for review of ooean disposal permit applications (Part 227); assessment of
impacts of ocean disposal and alternative disposal methods; enforcement of
permits; and designation and management of ooean disposal sites (Part 228).
They also established procedures by whioh the EPA is authorized to designate
ocean dredged material disposal sites (ODMDSs) and times for ocean disposal
of acceptable materials under Section 102(c) of the MPRSA and the criteria
for site designation, including general and specific criteria for site
selection.
EPA*s action for which this document was prepared is the designa-
tion of a site(s) for the ooean disposal of new work (virgin) material
dredged from the Freeport Harbor Entrance Channel and maintenance material
from the Entrance and Jetty Channels In conjunction with the authorized
Federal 45-foot Project (45' Project). A Final Environmental Impact State-
ment (FEIS) has been generated for the 45* Project, per se, by the U.S.
Army Corps of Engineers (CE, 1978). The purpose of this action Is to
designate, based on 40 CFR 228, an ooean disposal slte(s) which will
provide the most environmentally acoeptable and economically and physically
feasible area for the plaoement of the new work and future maintenance
material from the Freeport Harbor Entranoe and Jetty Channels.
1.2 U.S. ARMY CORPS OF ENGINEERS
The CE is mandated by the U.S. Congress to maintain (i.e., remove
accumulated sediment) the navigable waters of the United States. The
material thus removed (oalntenanoe material) must subsequently be dis-
charged. Section 103 of MPRSA requires the CE to oonsider, in its
evaluation of Federal projeots and Section 103 permit applications, the
effects of ocean disposal of dredged material on human health, welfare,
amenities, the marine environment, ecologioal systems, and economic
potentialities. As part of this evaluation, consideration must be given to
utilizing, to the extent feasible, ooean disposal sites designated by the
EPA pursuant to Section 102(c) of MPRSA. Ezoept for those sites whioh have
1-2
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been finally designated, the CE has, since 1977, used those ocean disposal
site designated by EPA on an interim basis (40 CFR 228.12), including the
interim-designated sites off Freeport. Use of these interim designated
sites for ocean disposal has been an essential element in the CE's
compliance with the requirements of the MPRSA and its ability to carry out
its statutory responsibility for maintaining the nation*s navigable
waterways. To continue to maintain the nation's waterways, the CE considers
it essential that environmentally acceptable ocean disposal sites be
identified, evaluated, and permanently designated for continued use pur-
suant to Seotion 102(c).
The existing Freeport Harbor Project was authorized by the River
and Harbor Aots of May 1950 and July 1958. The acts provided for an
Entrance Channel 38 feet deep and 300 feet wide from the Gulf of Mexico to a
point inside the Jetties and for Inside channels 36 feet deep and 200 feet
wide to and including an upper turning basin. Greater depth and width was
authorized by Congress in 1970 (Section 101 of the River and Harbor Aot of
1970, PL 91-611; House Document 289, 93rd Congress - 2nd Session, 31 Dec
1975) and by the President in 1974. These authorizations were for the Jetty
Channel to be relooated and deepened to 45 feet, widened to 400 feet, and
the North Jetty relocated northward. The relocated Entrance Channel was
authorized to a 400-foot width, to a 47-foot depth, and to extend
approximately 4.6 miles into the Gulf. An FEIS for the project was prepared
by the CE in 1978. In 1978, Seaway Pipeline, Inc., under a Department of
the Army permit, widened the existing Entrance Channel to 400 feet and the
Jetty Channel to 230 feet. The CE maintains the existing authorized project
dimensions.
The 1978 45* Project FEIS proposed to double the size of the
interim-designated ODMDS in the seaward direction in order to accommodate
the virgin and subsequent maintenance material. Since that time, addi-
tional guidance on selecting ODMDSs as well as modeling the fate of dredged
material has been prepared. Consequently, this guidance is used in select-
ing the appropriate ODMDSs for the new work and maintenance material asso-
ciated with the 45' Project. The CE expects to continue to use the interim-
designated site at Freeport until construction of the 45' Project is
completed.
1.3 U.S. ENVIRONMENTAL PROTECTION AGENCY NEED
The EPA is mandated with the authority to regulate ocean dumping
and with the responsibility for site designation, monitoring, and manage-
ment by the Congress as stated specifically in 40 CFR 228.4(e)(1). EPA has
been requested by the CE to designate ocean disposal sites for the placement
of construction and future maintenance material from the 45' Project
(Figure 1-1).
1-3
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•Number indicates miles from
outer end of jetty.
STATUTE MILES
End of Authorized
Ch«wt4 Expansion
-5.3*
itranc* Channtl
INTERIM-DESIGNATED OQmDS
Freeport
Fig. 1-1
General Project Map
1-4
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CHAPTER 2
ALTERNATIVES
2.1 NO-ACTION ALTERNATIVE
The No-Action Alternative entails EPA refraining from designating
an ocean disposal site, or sites, for the disposal of 5.1 mcy of virgin
material, during construction, and 2.1 mcy of maintenance material
annually. As developed later, the interim-designated site is too small to
contain all future virgin and maintenance material. Therefore, without
site designation, the CE would be required to develop an alternative dis-
posal method (e.g., land based) or modify or cancel the project. As noted
below, upland disposal was evaluated and ruled out in the CE's EIS for the
U5' Project. Cancellation or modification of the 15* Project would include
the following impacts: 1) long-term increases in transportation costs to
navigation relative to those that would result from projeot implementation;
2) loss of potential for increased channel usage, since a widened channel
would permit vessel traffic during maintenance dredging; and 3) decreased
recreational benefits to fishermen and other visitors to the Jetties.
Therefore, the No-Action Alternative is not considered viable.
2.2 UPLAND DISPOSAL
Dredged material disposal alternatives were considered by the CE
(1978). Non-ocean disposal alternatives inoluded upland disposal, beach
nourishment, and ocean disposal. Criteria used in the evaluation of these
alternatives included environmental, engineering, and oost considerations.
The use of any one alternative for the disposal of all of the virgin and
maintenance material was not feasible for a variety of reasons and the final
preferred alternative (CEt 1976), was a combination of upland disposal,
beach nourishment, and ocean disposal. Sufficient upland sites were not
available to accommodate both (1) the virgin and maintenance material
resulting from the 45* Project and (2) the CE's routine maintenance
material. Therefore, ocean disposal for 5.1 mcy of construction and
2.1 mcy, annually, of maintenance material is requisite for the 15'
Project.
CE (1978) also evaluated alternate dredging methods including the
use of dipper dredges, ladder dredges and bucket dredges and concluded that
these other methods would result in higher turbidities, hazards to
navigation and higher costs without any significant benefits to the
environment. Therefore, hopper dredging was considered the most practical
and economical means of dredging. A review of the status of the dredging
2-1
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industry to the present confirms that the hopper dredge is still the most
economical and feasible means for dredging at sea. The technology of the
other forms of dredging has not progressed sufficiently to be suitable
alternatives to hopper dredging.
2.3 OCEAN DISPOSAL
Five offshore disposal sites were evaluated including a midshelf
site, a continental slope site and three nearshore sites.
2.3.1 Mid-Shelf and Continental Slope Alternatives
A mid-shelf area would be 30 to 35 miles offshore in 150 to
180 feet of water. The benthos at this depth would rarely be disturbed by
sediment resuspension and therefore would not be expected to be as resilient
as would benthic communities (Oliver, et al. 1977) living in nearshore,
high-energy environments. As is noted later, an analysis by the CE,
Galveston District demonstrated that an increase in transport distance from
two to ten miles increased the cost of dredging, on a per-cubic-yard basis
by a factor of three. EPA (1983) notes an increase of $0.15/cy/mile of
transport distance for disposal at a mid-shelf site off Tampa Bay, Florida.
Additionally, as will be disoussed in more detail in Section 2.3*1*1*1,
safety risks Increase and the feasibility of monitoring and surveillance
are decreased with increasing distance offshore.
The Ocean Dumping Regulations (40 CFR 228.5(e)) state that when-
ever feasible, a site beyond the edge of the continental shelf will be
chosen. The edge of the continental shelf is defined as that area where
there is a significant Increase in the vertical/horizontal gradient, indi-
cating the beginning of the continental slope. In the western Gulf of
Mexico, the 200-meter isobath is fairly indicative of the shelf/slope break
and is plotted on Figure 2-1. At Freeport, the continental shelf/slope
break is approximately 75 miles offshore.
Pequegnat et al. (1976) examined the potential Impacts of deep-
water disposal; e.g., at a site on the slope. They note that the Increased
depth would provide greater volumes of water for dilution and dispersal
before the dredged material Impacts the ocean floor. They also note (1) the
relative paucity of benthos in deeper water and (2) that the value of
organisms from the truly deep ocean floor (greater than 1,000 meters depth)
are not important to world fisheries. However, EPA (1983) cites several
sources for the fact that although there may be fewer organisms in the
deeper waters of a slope site, the relative impact of burial by dredged
material would be much greater than to shallow-water benthic organisms
because deep-water organisms are not adapted to survival under conditions
where temporary burial by resuspended sediments is common. Additionally,
2-2
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M*
Watt
Boy
Lovoeo
(Boy
Son Antonio
Boy "N
Copono
Bof\_
Aronsos
Boffin,
Boy \
2-1
100
Two-Hundred Meter Isobath
MILES
50
100
«r»
2-3
-------
the concerns with cost, safety and monitoring and surveillance, noted in the
previous paragraph, would be greater for a continental-slope site.
There are also no data to indicate that such sites would offer any
environmental benefit over a nearshore site. Therefore, the mid-shelf and
continental slope sites have been eliminated from further alternative
analysis.
2.3.2 Other Ocean Alternatives
Historically, the NCPA approach to alternative analysis has been
to select a preferred alternative and compare It to several other arbi-
trarily chosen, reasonable alternatives or to a suite of generic alter-
natives and to the No-Action Alternative. The approach used in this EIS is
basically the same except in the selection of the other sites. Under this
present approach, presented by Science Applications, Inc. (SAI, 1986),
selection of sites is conducted by selecting a Zone of Siting Feasibility
(ZSF) and then, on the basis of available information, excluding those areas
which would not conform to the five general criteria and the eleven specific
factors for site seleotion given In 40 CFR 228.5 and 10 CFR 226.6(a),
respectively. This selection process is visually displayed by a set of
figures which individually show the areas excluded for a single oriterion or
set of criteria (e.g., areas of biological sensitivity) and colleotlvely
show all excluded, and thus, nonexcluded areas. Therefore, the set of
alternative sites is developed on a logical basis for including all feasible
sites.
After all necessary information, including that from field sur-
veys (1)0 CFR 228.13), has been synthesized and nonexcluded areas have been
delineated, the alternative sites are analyzed relative to the five general
criteria (40 CFR 228.5) and the eleven specific factors (10 CFR 228.6(a)).
First application of the criteria and factors would be to the existing
interim Freeport Harbor ODMDS if it is in the nonexcluded area
(10 CFR 228.5(e)). If the interim site conforms to all criteria and fac-
tors, it would normally be reoommended for final designation unless, during
the course of the evaluation, it is discovered that another nonexcluded site
is much more amenable to ocean discharge.
2-3.3 Methodology
2.3.3.1 Literature Search
Several concurrent approaches were taken in collection of data
relative to the Freeport Harbor area. A computerized literature searoh for
information pertinent to site designation was instituted via bibliographic
information retrieval services. Forms of materials referenced include
2-1
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monographs, journals and other serials, conference and symposia proceed-
ings, theses and dissertations, technical reports, government-sponsored
research reports, and pamphlets. Print-outs of abstracts were examined, if
necessary, and those papers or data reports deemed pertinent were obtained
and used.
Data available from work contracted by the CE to private corpora-
tions and universities, and from CE Environmental Impaot Statements and
work-monitoring data were obtained. The data provided by the CE also
provided (1) information on the characteristics and quantity of the
material previously dredged and deposited at the existing interim site, and
(2) expected characteristics of future dredged material. This information
aided in determining the compatibility of future dredged material with that
already at the existing site and the expected amounts of dredged material.
CE personnel also provided information pertinent to physical and geograph-
ical constraints.
Monitoring studies have been conducted at and near the existing
ODMDS. The results of these studies, conducted by the CE and by Espey,
Huston & Associates, Inc. (EH&A), provided the necessary site-specific data
used to characterize the water and sediments in the Freeport Area. Data
reported in documents developed for the proposed Seadook Project were also
used when pertinent.
All of the information discussed above, plus navigation oharts,
Minerals Management Servioe (MMS) charts, Environmental Impact Statements,
and other documents, were identified and oollected.
The collected data were oompiled, arranged according to the per-
tinent topics and examined. Preparation of overlays was begun. At that
time, any data gaps were noted. None were sufficient to disallow completion
of the seleotion prooess; i.e., sufficient information was available to
apply the exclusion prooess and the five general and eleven specific
criteria.
2.3*3*2 Identification of Alternative Sites via the Screening Procedure
The procedure (Figure 2-2) used to determine which potential site
is the preferable site is basioally a series of eliminations carried out in
sequential order. The order used in the elimination prooess is as follows:
1) elimination of areas outside the Zone of Siting Feasibility;
2) elimination due to ooeanographlc constraints;
3) elimination due to cultural and historic sites;
4) elimination due to non-living resources and conditions such
as sediment drift; oil and gas platforms; oil and gas pipe-
lines, as necessary; etc.;
2-5
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DELINEATE
BOTTOM
AREAS
DEFINE
2SF
EUMMA1E
SENSITIVE
AM)
INCOMPATIBLE
AREAS
PHASE I
Source: EPA/CE.1984
DETERMINE
POTENTIAL FOR
CUMULATIVE
EFFECTS
SELECTION
or MOST
ENVIRONMENTALLY
SUITABLE area(s)
PHASE II
PHASE III
Fig. 2-2
ODMDS Selection Approach
-------
5) elimination due to living resources, including an appro-
priate buffer zone;
6) elimination due to environmental quality constraints; and
7) elimination due to recreational uses, such as beaches or
recreational fishing areas, including appropriate buffer
zones.
2.3.* Development of Alternative Sites Using the Screening Technique
2.3.4.1 Zone of Siting Feasibility
The constraints on a site relative to the Zone of Siting Feasi-
bility (ZSF) are those related more to its feasibility from a utilitarian as
opposed to a regulatory perspective, although there is some overlap. Pri-
mary among the geographical and physical constraints are those which would
restrict the safe and economical use of the site, such as distance from the
dredging area, dangerous structures or currents, interference with or from
other vessels, political boundaries, and logistic constraints on monitoring
and surveillance.
2.3.4.1.1 Limits Due to Cost of Transport
The efficiency of the dredging operation, for the purposes of
this report, only depends on the disposal site location since all other
factors will be relatively constant, no matter where the disposal site is
located. This efficiency can be broken down into several factors:
(1) safety to personnel and dredges, (2) cost of dredging per cubic yard,
(3) the time required for the dredge to complete the dredging operation and
be ready to move to another area, and (4) down-time due to equipment
failure. All of these factors are adversely affected by increasing the
distance of the disposal site from the Channel. The last three of these
factors should be directly correlated to the distance from dredging area to
disposal site, while the first is more complicated and site-specific. Cer-
tainly, however, the safety of personnel and dredges is related to some
measure of the exposure time to potential hazards (i.e., weather, other
vessels/structures, etc.) and increasing exposure time in the offshore area
would have an overall adverse impact on safety considerations. The CE did a
computer analysis based on several straightforward assumptions, such as
transport distance, vessel speed, dumping time, and hopper capacity. They
found that increasing the average distance from the dredging area to the
disposal site (transport distance) from three to ten miles increased the
cost per cubic yard by a factor of two. The CE analysis also indicated that
Increasing the transport distance from three to ten miles would also signif-
icantly Increase the dredging time. The analysis by the CE took into
account the increased cost due to the increased time required for travel
between the dredging area and the disposal site, but it did not include
2-7
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increased costs due to the probable necessity of mobilizing additional
barges to adhere to the required maintenance dredging schedule.
In the EISs for the designation of an ODMDS for (1) routine main-
tenance of entrance channels along the Gulf Coast (49 Federal Register
34485 (Friday, August 31, 1984) and 52 Federal Register 22352 (Thursday,
June 11, 1987)) and (2) the Tampa Bay Harbor (EPA, 1983), it was demon-
strated that neither a mid-shelf site nor one beyond the edge of the conti-
nental shelf was preferable to a nearshore site. Therefore, since no
significant reasons for moving the disposal site further offshore, i.e., to
a midshelf site or to one beyond the edge of the continental slope, have
been demonstrated and since economic and safety reasons discourage it, the
ZSF, based on limits due to cost of transport, will be a ten-mile radius
from the mouth of the Freeport Harbor Channel.
2.3.4.1.2 Limits Due to Feasibility of Monitoring and Surveillance
The geographical constraints on the feasibility of a site for
monitoring and surveillance are three: (1) size, (2) configuration, and
(3) location. Based on historical practice, size and configuration are not
pertinent to the ZSF analysis. The restrictions on location are (1) that
the site be near enough to shore to allow safe and efficient monitoring by
vessels reasonably available, and (2) since benthic Impacts are of primary
concern, that the site be located in water shallow enough to allow efficient
benthic sampling by vessels and equipment reasonably available. The first
restriction is moot since any distance feasible for hopper dredge use will
also be feasible for reasonably-available monitoring and surveillance
vessels. The efficiency of getting good replication benthic sampling due to
anchoring difficulties for vessels reasonably available puts a depth limi-
tation on the site of approximately 100 feet (Pequegnat, 1980). Also, any
increase in depth increases benthic sampling time due to increased winch
time in dropping and retrieving the grab sampler. However, along the
shallow Texas coast near Freeport (see Figure 2-3), depth limitations are
not as restrictive as are the cost factors discussed above. However, a site
well beyond the ZSF would place restrictions on monitoring and surveillance
which would reduce the feasibility of such a site.
2.3.4.1.3 Limits Due to Political Boundaries
There are no international or other political boundaries close
enough to the Freeport Harbor Channel to limit the ZSF, including the
territorial limit of the United States. The gulfward boundary of Texas does
not impact site selection.
2-8
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STATUTE MILES
60 ft.
\
Freeport
10 ft
a
Fig. 2-3
Bathynetry of the
Freeport Harbor Area
2-9
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2.3.4.1.4 Conclusion
Pequegnat (1981) recommends additional criteria for selecting a
site and develops criteria such that all U.S. sites would be essentially
suitable for all situations, i.e., an ideal site. For example, a minimum
water depth of 20 m is recommended to assure that the material would remain
in the disposal area for a relatively long time. Should the dredged
material contain pollutants, strong winter waves would not resuspend it.
Also a minimum size of three square nautical miles is recommended which
would be adequate for 26 to 40 million cubic yards of material annually.
However, when site specific information is available, it is not unrea-
sonable to use that information to determine a site, which is specific for
the area of interest. Indeed, Pequegnat (1984) recommends that where exist-
ing sites are suitable for their areas, they should not be excluded from
consideration just because they do not meet the criteria for an ideal
ODMDS.
In this document (as is noted as a significant possibility in SAI,
(1986), the cost and safety issues involved in the transportation of dredged
material were the limiting factors in determining the ZSP. Especially, a
mid-shelf site (30 to 35 miles offshore) and a site beyond the continental
shelf would not be feasible because of dredging costs, safety, and limits on
monitoring and surveillance. However, the amount and quality of the
material to be dredged, based on past analyses, allowed the selection of the
chosen ZSF since deep water and a larger disposal site were not necessary.
Based primarily on the efficiency of the dredging operation in
terms of time, money, and safety, the ZSF is an area bounded by the loci of
points ten statute miles from the intersection of the Freeport Harbor
Channel with the beach line. This ZSF would include approximately
157 square miles and would allow a maximum hopper dredge transport distance
of 10 miles. All areas outside this area are excluded (Figure 2-1).
2.3.4.2 Modeling Dredged Material Distribution
The disposition of dredged material was simulated (see Appendix A
for greater detail) using an updated version of a 1976 model, Dredged
Material Fate (DMF), developed for the O.S. Army Corps of Engineers through
the Dredged Material Research Program by Tetra Tech., Inc. (Brandsma and
Divoky, 1976). The modifications to this model were made in the mid-1980's
by Dr. Billy H. Johnson of the Waterways Experiment Station (HES) of the
U.S. Army Corps of Engineers.
This program models the initial behavior and final disposition of
dredge material deposited "Instantaneously" at the site of interest through
the doors of a hopper dredge. The DMF model assumes that this procedure may
2-10
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2-11
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be broken into three phases: (1) convective descent, during which the
discharge cloud falls under the influence of gravity; (2) dynamic collapse,
occurring when the descending cloud impacts the bottom or arrives at a level
of neutral buoyancy at which point the descent is retarded and horizontal
spreading dominates; and (3) long-term passive dispersion, commencing when
the material transport and spreading are determined more by ambient cur-
rents and turbulence than by the dynamics of the disposal operation (Johnson
and Holliday, 1978). The model also includes the settling of suspended
solids.
The model was run for three different sizes of hopper dredges, the
specifications of which are shown in Table 2-t.
2.3.H.2.1 Virgin Material
The percentage of the various soil particle types anticipated in
the virgin sediment to be dredged was estimated (Table 2-2) using subsur-
face information from sediment borings done by the CE (CE, 1978).
Output from the DMF model simulates the results of depositing one
load of dredged material on the ooean floor. The mounds of virgin material
were skewed in the current and vessel-heading directions. Aerally, the
mound would form a rounded diamond-shape, elongated in the down-current and
vessel-travel directions. At its thickest, the mound elevation for a single
discharge from the Large Dredge, which provides the largest mound of
material, would be only 0.81 feet or 10.1 inches (Figure 2-5). The lateral
extent of the mound, in the with-current direction to the point where the
mound thickness is reduced to 0.04 feet (0.5 inches or 1.2 cm) would be
6,380 feet, from approximately 1,270 feet up-current of the discharge point
to approximately 5,110 feet down-current of the discharge point (Figure 2-5
and Table 2-3). Cross-current mounding extended 350 feet from the release
point in the direction from which the vessel was traveling and 930 feet from
the release point in the direction of vessel travel, for a total of
1,280 feet.
2.3.1.2.2 Maintenance Material
The DMF model program was also run on the maintenance material for
the worst case conditions, i.e., large dredge, high current velocity. The
results are that (1) the maximum mound thickness for a single discharge
would be 0.28 feet, (2) at roughly 7,000 ft down current of the discharge
point the mound height would be less than 0.01 feet (0.12 inches), (3) the
maximum up-current extent of detectable mound thickness is less than
500 feet, and (4) the maximum cross-current extent of detectable mound
thickness is 250 feet on either side of the discharge point. The mound
height was taken to 0.01 feet for the maintenance material, as opposed to
2-12
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TABLE 2-1
HOPPER DREDGE SPECIFICATIOHS
Dradaa
ParaMtar
Capacity (ey)
TJTP*
Bop par Laoctb (ft)
Boppar Width (ft)
Door Vldtb (ft)
TIm to aapty ...
bopptr (alnutaa)
Loaded Draft (ft)<#)
Unloaded Draft (ft)
Daptb of Dradgad
MUrUl (ft)
(f)
Saall
(NUnUTTER ISLAND)
3,600
Spilt bull
150
41
16 (*ax); typloally 7-4
* (MX)
19.4
12
27 (aax)
17 (for aaad)
Hadlua .
(EAGLE 1)°
6,400
Split bull
137
10
For aaad - 16.5
For aluab - 7
Sand - 54
Sluab - 1-1/2 to 2
22.«
9.5 bow
15.0 atarn
3«.5 (aax)
Larsa
(3TU7VESART)
9,160
Bottoa door
153
<0 12 x 12 doora
(all oan opan at
onoa)
2-3
29
11.4 bow
20.5 atari!
39 (mx)
Valoelty I Dlaoharga (kt) 1
3-5
(a) Horth iMrloao Tralliac Coapany
(b) Baaa Dradflng Corporation
(c) Stuyvaaant Dredging Coapaay
(d) Dapanda on typa of aatarlal (aaa Hadlua Dradfa).
(a) taxiaua allowad by BSCG.
(f) Dapanda on aaoont of fVial.
2-13
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TABLE 2-2
VIRGIN DREDGED MATERIAL CHARACTERISTICS
*
of
Fall
Density
Concentration
Solids
Velocity
Voids
Description
(gm/cc)
(vol/vol)
(wt)
(ft/sec)
Ratio
Clayballs
1.700
0.101
72.0
2.20
0.75
Old Shell
2.500
0.008
2.0
0.180
0.70
Fine Sand
2.650
0.016
1.5
0.0166
0.80
Silt
2.700
0.017
13.5
0.00256
1.0
Slurry
2.750
0.028
8.0
0.00256
1.5
Fluid
1.022
0.500
N/A
N/A
N/A
BULK DENSITY
1.16
AGGREGATE
VOIDS RATIO
0.81
2-11
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DlW
rig. 2-5
Seafloor Distribution of
Dredged Material after a
Single Discbarge, Large Dredge,
High Current
-------
TABLE 2-3
RESULTS OF COMPUTER ANALYSIS OF
DREDGED MATERIAL
DISPOSAL
- SINGLE
DISCHARGE
Dredge
Small
Medium
Virgin
Large
Maintenance
Single Discharge
Maximum Height (ft)
0.32
0.59
0.84
0.28
Mound width (ft)
J 0.1 kt
957
1280
1280
—
§ 0.65 kt
1400
1020
1280
500
Mound length (ft)
€ 0.1 kt
1470
1470
1530
—
S 0.65 kt
3440
5360
6380
7000
2-16
-------
0.01 for the virgin material, since the discharge of maintenance material is
not a one-time event.
2.3.^.3 Buffer Zone Assignment
The computer model (discussed in detail in Appendix A) for short-
term sediment dispersion, was used to determine the expected distribution
of the construction and maintenance material on the ocean floor. The
information gained from the model runs, by consistently using conservative
scenarios, allowed the determination of (1) the buffer zones discussed
below and (2) the appropriate size for the ODMDS. This model is for short-
term sediment transport after disposal and provides information concerning
maximum mounding of the disposed material.
2.3.1.3.1 Biologically Sensitive Areas
Based on the information in the above-cited documents, at a depth
of 60 feet, which is appropriate for the ZSF (Figure 2-3), a mound of
material (Figure 2-5) will form from the impact of the dredged material with
the bottom as noted previously.
For the virgin construction material, the thickest mound eleva-
tion from a single discharge would be only 10.1 Inches. The lateral extent
of the mound, in the with-current direction to the point where the mound
thickness is reduced to 0.04 feet (0.5 inches or 1.2 cm), would be from
approximately 1,270 feet up-current of the discharge point to approximately
5,110 feet down-current of the discharge point. [Solid phase bioassay
testing according to EPA/CG (1978), which is based on the EPA Ocean Dumping
Regulations (10 CFR 220-229), uses approximately 0.6 inches of sediment to
test the effects of dredged material disposal at the edge of an ODMDS.]
Doubling the figure (5,110 ft) would provide a buffer zone, for virgin
material, of approximately 1.9 miles around areas of biological sensitivity
(Figure 2-6). The maximum width of detectable accumulation is approxi-
mately 1,280 feet so that if the area of biological concern was cross-
current to the ODMDS, additional protection for the area would be provided
by this buffer zone. The development of this buffer zone is based on the
fact that bathymetric surveys of ODMDSs and other studies (Moherek, 1978)
indicate that long-term accumulation of material in offshore dredged dis-
posal sites along the Texas coast does not appear to occur. A buffer zone
was not Included for lighted platforms because they are temporary.
For maintenance material, the lateral extent of the mound, in the
with-current direction to the 0.01-foot thickness (see Section 2.3.4.2.2),
is 7,000 feet. Doubling this figure would provide a biological buffer zone
of 2.65 miles (Figure 2-7). Again, this would obviously be overly protec-
tive for a biologically sensitive area cross-current from the ODMDS.
2-17
-------
STATUTE MILES
///A Sport fishing* Commercial Harvest Area
White Shrimp BrMOin
Lighted Plat
Source:
USFWS (1982
\
\
OOMDS
DESIGN A "ED
INTERIM
Freeport
?
Fig. 2-6
Biologically Sensitive Areas and
Buffer Zones Excluded from the ZSF
Virgin Material
2-18
-------
STATUTE MILES
///A Sport flahins & Commercial Harvest Area
• Lighted/Platform
Source:
liSFWS («P2
\
RIM DESIGN A tD OOMDS
Freeport
?
Fig. 2-7
Biologically Sensitive Areas and
Buffer Zones Excluded from the ZSF
Maintenance Material
2-19
-------
2.3.4.3.2 Beaches and Recreational Areas
The above-derived buffer zones are for the movement of material
along the bottom of the sea floor. For amenities such as beaches and other
recreational areas where aesthetics govern, the fine material (plume) which
stays suspended in the water column is the determining factor. According to
model calculations, the silt fraction takes longer to settle out than do
other sediment fractions, but either the silt had settled to the bottom by
50 minutes (3>000 seconds) after discharge or it was so dispersed as to be
negligible in the water column. This was true for both the virgin and
maintenance materials. According to Seadock (1976), the currents at
Galveston (which Seadock used to approximate those at Freeport) are
onshore, at one knot or greater, only 1.3% of the year. Therefore, for a
"worst-case scenario", the following assumptions were made: (1) a sus-
tained current of one knot, directly toward shore; (2) the discharged
material was all silt; and (3) the material stayed at the surface (e.g.,
visible) until it impacted the bottom, 3,000 seconds after discharge. At
one knot, or 1.7 feet per second, the plume would travel approximately
5,060 feet or 0.95 mile as a visible plume. Doubling of this figure would
provide an adequate buffer zone (1.9 miles) for beaches and similar amenity
areas from either virgin or maintenance material (Figure 2-8).
2.3.1.3.3 Navigation Channel
The up-current edge of detectable mounding for the virgin
material is roughly 1,270 feet upcurrent of the discharge point. Since the
location of the disposal site will Inevitably be downcurrent of the channel
(see Section 2.3.4.4), doubling of the 1,270 feet should provide an
adequate buffer zone to prevent significant material from being carried
back into the channel. This buffer zone also keeps the dredge well out of
the navigation channel when it is discharging. Thus the navigation channel
buffer zone for virgin material is 2,540 feet (0.48 miles) (Figure 2-11).
For the maintenance material, up-current travel is less than 500 feet which
leads to a navigation channel buffer zone, for maintenance material, of
1,000 feet (Figure 2-12).
2.3.4.4 Oceanographic Constraints
Based on continuing bathymetric surveys of ODMDSs and other
studies (Moherek, 1978), long-term accumulation of maintenance material in
offshore dredged material disposal sites along the Texas coast does not
appear to occur. Additionally, with time, the mounding from the construc-
tion material will erode and be carried downcurrent. Since the longshore
drift is predominantly northeast to southwest along the Gulf coast at Free-
port, placing the disposal area to the northeast of the channel would ensure
that the dredged material would be carried back into the channel. There
2-20
-------
STATUTE MILES
OOMDS
DESIGN
Freeport
Fig. 2-8
Areas Excluded from the ZSF
by the Beach Buffer Zone
2-21
-------
fore, all areas northeast of the channel and two miles beyond the end of the
extended channel are excluded from consideration (Figure 2-9).
2.3>4.5 Cultural and/or Historical Resources Constraints
For buried sites of archaeological or historic interest, no buf-
fer zone is suggested for the following reason. There is no long-term
accumulation of material and short-term accumulation outside the Interim
ODMDS is small. Therefore, should exploration or excavation be undertaken,
as long as the ODMDS did not include a site of historic interest, or if the
site was close to the edge of the ODMDS so that the site could be avoided by
the dredger, there should be no significant impact on the site. However,
for added protection, these sites themselves and any cluster of sites,
discussed in Section 3.4.5, are excluded from site selection (Figure 2-10).
2.3*4.6 Non-Living Resources Constraints
All obstructions including oil platforms; the Navigation Channel
Buffer Zone; and the Navigation Fairways, for safety reasons due to expected
mounding, are excluded in Figure 2-11 for virgin material. The
obstructions and Navigation Channel Buffer Zone are excluded in Figure 2-12
for maintenance material. Four small (less than 20 inch) and one large
(greater than 20 inch) gas pipelines are located in the ZSF (DOI/MMS, 1986)
but since disposal of dredged material should not impact these lines, they
are not excluded.
2.3.4.7 Living Resources Constraints
At the southwest border of the ZSF, there is a white shrimp
breeding area, a sport and commercial fishing harvest area, and a reef area
which are excluded, including the 1.9-nile buffer zone (Figure 2-8) or the
2.65-mile buffer zone (Figure 2-7). At the northeast border, there is a
small collection of coral heads (reefs), providing habitat which improves
fishing. These areas and the jetties, including buffer zones, are excluded.
Additionally, there are lighted platforms which improve fishing as do non-
submerged shipwrecks. As noted in Section 3.3.5, brown shrimp spawn in
deeper water than is Included in the ZSF.
2.3.4.8 Environmental Quality Constraints
As noted in the Sections concerned with characterization of the
material to be dredged, with water quality in the ZSF and with the quality
and characteristics of sediment in the ZSF, there are no environmental
quality constraints on the site selection except for those included in the
buffer zone development. However, comparisons of the breakdown of the
virgin material (Table 2-2) and that of the maintenance material
(Table 3-7) with Figure 3-5, demonstrate that, if possible, the virgin
2-22
-------
STATUTE MILES
\
Freeport
\
INTERIM DESIGN
AO
ODMDS
*»•
*o-
ng. 2-9
Atm Excluded to Pmvtnt Transport
of Sadlmcnt Sack Into th« Channel
2-23
-------
STATUTE MILES
EftIM DESIGNATED jOOMDS
Freepor
Fig. 2-10
Historic Sites ond Recent Shipwreck
Obstructions Excluded from the ZSF
2-211
-------
w* *r
t CO
STATUTE MILES
Gos Pipeline
Freeport
Go« Pipelln
Fig. 2-11
Obstructions, the Navigation
Channel Buffer Zone, ana Safety
Fairways Excluded from the ZSF
Virgin Material
2-25
-------
STATUTE MILES
Gas Pipeline
, Gas Pipeline
*0-
Fig. 2-12
Obstructions and the
Navigation Channel Buffer Zone
Excluded from the ZSF
Maintenance Materiol
2-26
-------
material should be placed in the silty-clay regime and that the maintenance
material should be placed in the nearshore, silty-sand regime or the
offshore, sand/silt/clay regime.
2.3*4.9 Recreational Uses Constraints
Areas of reoreational use whioh will impact the site selection
process are excluded by the beach buffer zone (Figure 2-8) and by the
biologically-sensitive area buffer zones (Figures 2-6 and 2-7), which pro-
tect the fishing areas.
2.3.4.10 Areas Available for an ODMDS
Figure 2-13 displays the areas available for the Virgin Material
ODMDS, by combining Figures 2-4, 2-6 and 2-8 through 2-11. For the virgin
material, a large area is available southwest, south and southeast of the
Interim-Designated Site, which is itself mostly excluded by the Biological
Buffer Zone and beoause it is all in the silty-sand regime. For the
maintenance material (Figure 2-14: a combination of Figures 2-4, 2-7, 2-8,
2-9, 2-10, and 2-12), the interim-designated site is excluded by the
Biological Buffer Zone around the Jetties. However, even with the larger
Biological Buffer Zones, a large area south and southeast of the Interim-
Designated ODMDS is available for the Maintenance Material ODMDS. A smaller
area is available northeast of the ohannel for both ODMDSs.
2.3.5 ODMDS Size Determination
2.3*5.1 Virgin Material
The same ooeanographic considerations that applied to the
development of the buffer zones applies to the determination of necessary
size of the disposal site. That is, the site must be designed so that any
mounding which ooours will not endanger shipping, and so that sediment and
water column parameters will be at background levels outside of the disposal
site. In Section 2.3.4.2, using worst-oase soenarlos, it was determined
that detectable mounding can be expected to ooour 1,270 feet up-ourrent and
5,110 feet down-current from the disoharge point. The oomputer results
indicated a maximum cross-ourrent distance of deteotable mounding of
1,260 feet, the edge of whioh was 930 feet from the point of disoharge in
the direction of vessel travel. The model assumes an instantaneous dis-
oharge which approximates an actual hopper disoharge.
Six scenarios were examined with the computer model to provide
information which would enable the size of the buffer zones and the ODMDS to
be determined. It was found that if a single series of discharges was made,
in a seven-by-eight array at 1,000-foot intervals, followed by multiple
2-27
-------
X
STATUTE MILES
V.
z
z
X
z
z
z
\
z
Freeport
Z
DESIGNATED
Z
Z
Fig. 2-13
Areas Available
for an ODMDS
Virgin Material
2-28
-------
z
%
STATUTE MILES
%
Z
Z
Z
z
z
z
z
zz
\
Freeport
?*¦
DESIGNATED
Fig. 2-14
Areas Available
for an ODMDS
Maintenance Material
2-29
-------
discharges inside the original array (Figure 2-15), the 5.1 mcy of con-
struction material oould be contained in mounds which would not accumulate
to more than 0.86-feet above the ocean floor, for the exterior mounds, and
10.5 feet for the seaward interior mounds and 9.7 feet for the landward
interior mounds (Table 2-4). Only the number of interior discharges varied
significantly among the three dredges. As a result of these analyses, the
area of discharge is 6000 feet by 7000 feet. Applying the necessary
boundary conditions for the edges of the 0DMDS by using the distance to the
edge of the mounding and using worst-case scenarios from the computer
analysis (i.e., 5,110 feet in the down-current direction, 1,270 feet in the
up-current direction, 930 or 350 feet in the cross-ourrent directions)
yields an 0DMDS which is 13,380 feet (1270 + 7000 + 5110) or 2.53 statute
miles (2.20 nautical miles) long (with-current) and 7,280 feet (350 +
6000 + 930) or 1.38 statute miles (1.20 nautioal miles) wide (cross-
current) .
Based on this analysis, the Freeport Harbor Virgin Material ODMDS
should be 7,280 feet in a direction parallel to the Channel (northwest/
southeast) and 13,380 feet in a direction perpendicular to the Channel
(northeast/southwest). Of this area, only a 6000 x 7000 ft section will be
used for actual discharging (Figure 2-15).
2.3.5.2 Maintenance Material
As noted previously, 2.1 moy of maintenance material is expeoted
to be disposed of during each maintenance cycle. Using analysis similar to
that discussed above, it was found that this amount of material could be
accommodated in a 5 x 6 Exterior Station array, using the number of dis-
charges per station given in Table 2-4. The maximum mound height for the
multiple discharges of maintenance material would be 0.87 feet for the
exterior stations, 3.1 feet for the seaward interior stations and 2.6 feet
for the landward interior stations. Therefore, the area of discharge is
4000 ft by 5000 ft. Again, applying boundry oonditions (i.e., 7,000 feet
in the down-current direction, 500 feet in the up-current direction,
250 feet in the cross-current directions) yields an ODMDS which is
12,500 feet (500 + 5000 + 7000) or 2.37 statute miles (2.06 nautioal miles)
long (with-current) and 4,500 feet (250 * 4000 + 250) or 0.85 statute miles
(0.74 nautical miles) wide (cross-ourrent).
Based on this analysis, the Freeport Harbor Maintenance Material
ODMDS should be 4,500 feet in a direction parallel to the Channel (north
west/southeast) and 12,500 feet in a direction perpendicular to the Channel
(northeast/southwest). Of this area, only a 4000 x 5000 ft section will be
used for actual discharging (Figure 2-16).
2-30
-------
IS)
I
u>
13,380 FEET
UJ
o
00
CM
-in rr | 11 n-\
A a A a AO A a A A A I
•n *n •>« • • • • • • • •
~ D»
7
939 rr
+
mm rr
1
IMS
>017
kD4
39* FT
DIRECTION or LONGSHORE CURRENTS
a EXTERNAL MOUNDS (E1 - E21)
• INTERNAL MOUNDS (11 - 1143)
DIRECTION OF
DISPOSAL VESSEL
TRAVEL
Fig. 2-15
Preferred Site Configuration
Virgin Material
-------
TABLE 2-4
RESULTS OF COMPUTER ANALYSIS OF
DREDGED MATERIAL DISPOSAL - MULTIPLE DISCHARGES
Dredge
Large
Small Medium Virgin Maintenance
Multiple Discharge
Maximum Height (ft)
Exterior mounds
Interior mounds
Seaward
Landward
Number of discharges/mound
Exterior mounds
Interior mounds
Seaward
Landward
2-32
0.69 0.62
12.4
9.2
11.6
9.7
23
17
12
10
0.86
0.87
10.5
9.2
3.1
2.6
8
7
7
6
-------
12,500 FT
| tow n |
hH
Act
ACt
*0
*(4
AO
AO
no rr
T
*11
<4 t
* ~
«| s
*1 •
*1 T
*»•
*1 •
1
ioo« n
|
*1 1*
*1 IT
*» IS
*1 14
*1 1)
*i n
Ml 11
*• tt
A*7
1
*1 t»
*1 »
*1 «f
* n
H| O
*1 u
*i t>
«| «
*1 f?
oorr
—
*1 »
*!•»
*
-------
2.3.6
Preferred Sites
2.3.6.1 Virgin Material
As noted previously, the virgin material is predominately silt
and clay whioh would make the sllty-elay regime the preferable bottom type
upon which to dispose of the virgin material. The necessity for at least
55' of water depth at the ODMDS, at the initiation of dredged material
disposal, is conducive to the use of this bottom province, although the site
may extend slightly into the sand/siIt/clay regime. Therefore, the pre-
ferred location for the virgin material ODMDS is that shown in Figure 2-17,
i.e., with the northwest corner of the site located at the intersection of
the safety fairway and the 55-foot isobath. This plaoes the site mostly in
the sllty-clay regime and as near to the ohannel as safety considerations
will allow. The interim-designated site is almost completely excluded by
the Biological Buffer Zone around the jetties and is in an inappropriate
grain-size regime.
Therefore, the preferred site for the Freeport Harbor 45' Project
virgin material ODMDS is bounded by:
28® 51' 22" N, 95° 14' 25" W; 28® 50* 28n N, 95° 13' 30" W;
28° 48* 58" N, 95 15' 21" W; 28° 491 55" N, 95 16' 19" W.
It has an area of 3*19 square statute miles (2.64 square nautical miles).
Note that the preferred site includes the smaller area where actual disposal
ooours (fine hatching) as well as the large area for boundary conditions
(coarse hatching).
2.3.6.2 Maintenance Material
As noted previously, the maintenance material is most nearly akin
to the silty-sand, nearshore regime or the sand/siIt/clay offshore regime.
Since there is no reason, for safety or other environmental considerations,
to place the site offshore in the sand/silt/clay regime, and since such a
location would lnorease the oost of maintenance dredging, the site should be
placed as near to the silty-sand regime as is possible. If the northwest
oorner of the maintenance material ODMDS is plaoed at the intersection of
the Biological Buffer Zone with the Navigation Channel Buffer Zone, the
resultant site would Include a biologioally sensitive area downcurrent from
the discharge area. To avoid this situation, the site oan be moved 763 feet
shoreward, whioh will also place it nearer the silty-sand sediment regime.
While this will encroach, to a small extent, on the Biologioal Buffer Zone
around the Jetties, it should be noted that the preferred site is cross-
ourrent from the Jetties. In Seotion 2.3.4.3.1, it was stated that the
Biological Buffer Zone was overly protective for an area whioh was cross-
2-34
-------
STATUTE MILES
Areas of Actual
Disposal
0* FUTURE MAINTENANCE ODWDS >
1 /
V 2n. VIRGIN MATERIAL ODM
Freeport
Fig. 2-17
Preferred Sites for Virgin and
Maintenance Material ODMDSs
2-35
-------
current to a discharge, which is the case here. The site is still over
2.5 miles from the Jetties. Even with the site noved shoreward, sufficient
water depth (minimum of 29 feet) should be maintained in the discharge area
such that even a large dredge would be able to navigate the area with a full
load and be able to open the hopper doors without concern. Additionally, if
a Notice to Mariners is posted, no hazard should result from the mounds.
Therefore, the preferred site for the Freeport Harbor maintenance
material ODMDS (see Figure 2-17) is bounded by:
28° 54• 00" N, 95° 15' 49" W; 28° 53* 28" N, 95° 15' 16" W;
28° 52• 00" N, 95° 16* 59" W; 28° 52» 32" N, 95 17* 32" W.
It has an area of 2.02 square statute miles (1.53 square nautical miles).
Again, note the actual discharge area versus the larger area for boundary
conditions.
2.3*7 Disposal Sequence
2.3*7.1 Virgin Material
A cumulative pattern of deposited material from multiple dis-
charges was simulated by overlaying the single disoharge profiles at vari-
able intervals in a grid pattern. The grid intervals for hopper dumps were
adjusted to distribute the discharged material uniformly at easily deter-
mineable intervals. A cumulative height, dredge material profile, and
total area covered were thus obtained for 5.1 mcy of virgin dredged material
for each of the three hopper size simulations.
Specifically, the cumulative height profile was achieved as
follows. An array was established at 1,000-foot intervals (see
Figure 2-15) with Exterior Stations (i.e., Stations E1-E26) . Interior
Stations were established (i.e., 11-1143), separated by only one-half the
distance between the Exterior Stations. By use of a spreadsheet, the
results of a single disoharge at eaoh station were superimposed. Additional
discharges were superimposed on all Interior Stations, allowing for 10%
compaction at eaoh overlain station, until the 5.1 mcy of virgin material
was discharged. If the number of discharges was not an even multiple of the
number of Interior Stations, the final discharges were superimposed on the
deeper, or seaward, stations. At that time, the height of the highest mound
was determined. If the height of the highest mound was incompatible with
water depth vs. safety considerations, the size of the array was increased
and the prooess repeated. Distances of 500, 1,000, and 1,500 feet, for the
Exterior Station separation distance interval were tried, with 1,000 feet
being the most satisfactory. The original 3x3 array was lteratively
2-36
-------
expanded to a 7 x 8 array, with 143 Interior Stations, to meet all require-
ments.
The final results of the process for the virgin material are given
on Figure 2-15, and on Table 2-3 and 2-4, which provide the following infor-
mation:
1. Maximum height of a single discharge from each vessel size
(see Table 2-1 for vessel specifications).
2. The maximum width (i.e., cross-current direction) of the
mound formed by a single discharge, both at a current velo-
city of 0.1 kt and 0.65 kt.
3. The maximum length (i.e., with-current direction) of the
mound formed by a single disoharge at both current
velocities.
1. The maximum height of the mound at any Exterior Station
after 5.1 moy of material has been discharged at the site,
using multiple discharges at the Interior Stations. The
maximum height of the exterior mounds is thus the height of
the single disoharge at that station plus the accumulation
from all other discharges. Note that for the Small Dredge,
two discharges are allowed at each Exterior Station.
5. The maximum height of the mound at any Interior Station.
Note that sinoe some of the seaward, or deeper, Interior
Stations are to receive an extra disoharge relative to the
landward, or shallow, stations, their maximum height is
greater than that for the landward Interior Stations.
6. The number of discharges per station, both Exterior and
Interior.
The example disposal sequence, outlined above, is discussed in
detail below. Figure 2-18 provides an idea of the three-dimensional
profile of the mounds by depicting the height of the outer three mounds in
the wlth-ourrent direction (e.g., Stations 115, 114, and E9) and in the
oross-current direction (e.g., Stations 115, 112, and E7). A small mound at
Station E8 oan also be seen.
The final disposal station array, for virgin material, Is pre-
sented in Figure 2-15. The latitude and longitude of Stations E1, E8, E14,
and E21 are, respectively,
2-37
-------
M
U>
CD
\0*
Fig. 2-18
Seafloor Distribution of
Dredged Material alter
Multiple Discharges, l»ar?e Dredge,
High Current
-------
28° 50' 27.0n N, 95° 13' 48.0" W; 28° 49* 39.6" N, 95° 14» 46.8" W;
28° 50' 25.2" N, 95° 15' 31.8" W; 28° 51' 11.3" N, 95° 14' 33.0" W.
Since the stations are located in a regular array and each station is either
500 ft or 1,000 ft from its nearest neighbor, in any row or oolumn, all
other station locations can be calculated by a competent mariner.
It is important that the disposal method used meets the criteria
of the Regulations; i.e., no impacts outside of the designated site and
maintenance of proper safeguards for navigational safety. The example
disposal sequence given below accomplishes these items and provides a good
method for determining the movement of material via the computer model, but
is obviously not the only possible disposal method which would be satisfac-
tory. However, because the Exterior Stations aot as a barrier to dredged
material migration after multiple discharges at Interior Stations have
ooourred and beoause the following sequenoe will allow for maximum oompao-
tion, it is important that the following example sequenoe, or an equivalent
method, be utilized.
The example sequence is as follows:
1. One discharge at all Exterior Stations (two in the case of
the small dredge).
2. One discharge at each of the Interior Stations in a given
sequenoe.
3. Repeat Step "2" until the allowed number of discharges for
landward Interior Stations have been oompleted.
4. One discharge (two in the case of the small dredge) at
Station 11, 12, etc. until dredging is complete.
2.3.7.2 Maintenance Material
The disposal sequenoe for future maintenance material is the same
as that described above exoept the number of stations (or area) at which
discharge occurs is slightly smaller. The locations of Stations E1, E6, E10
and E15 (Figure 2-16), for the maintenance material site area are, respec-
tively;
28® 53' 54.6" N, 95° 15' 51.7" W; 28° 53' 26.0" N, 95° 15' 22.2" W;
28° 52' 47.0" N, 95 16' 07.5" W; 28° 531 15.6" N, 95 16» 37.0" W.
Again, an equivalent disposal sequence or method whioh would satisfy envi-
ronmental and safety considerations would be acceptable.
2-39
-------
2.4 PREFERRED ALTERNATIVE
2.4.1 Description
Alternatives examined were the No-Action Alternative, upland dis-
posal, and offshore disposal at various looations. Preferred offshore
sites were developed for the virgin and maintenance materials by excluding
those areas which would not be acceptable for ocean disposal of dredged
material and then selecting the apparent environmentally-preferable,
suitably-sized disposal sites. EPA's Preferred Alternative is the final
designation of (1) the preferred site as the Virgin Material ODMDS for the
one-time disposal of virgin material from the dredging of the 45' Project
and (2) the preferred site as the Maintenance Material ODMDS for the
material from the future routine maintenance of the Preeport Harbor
Entrance and Jetty Channels.
2.4.2 Monitoring and Surveillance
While mention is made of the possibility and likely desirability
of monitoring, the Ocean Dumping Regulations (40 CFR 220-229) do not
require monitoring of designated sites. However, the consensus in the
regulatory oomsunlty seems to be that a monitoring program should be
developed as a part of the site designation prooess; e.g., "The final
designation of a marine dredged material disposal site carries with it the
strong probability that the District Engineer will find it advantageous to
monitor the site at appropriate intervals to ensure that unexpected deteri-
oration of the site environ's is not occurring. Monitoring efforts will be
searching for unfavorable trends" (Pequegnat et al., 1981).
There are two approaches whloh may be applied to determining
unfavorable trends. One Is to conduct monitoring surveys on the eoosystem
at and near the ODMDS at regular Intervals. The other approach is to
determine the quality of the material to the discharged at the site, from a
ohemloal and blologioal perspective, and thereby, to determine expected
Impacts.
2.4.2.1 Virgin Material
While the literature on maintenance material disposal on the Gulf
Coast indicates only minor short-term and negligible long-term mounding
from disposal activities, the virgin material ODMDS was sized based on
significant expeoted mounding. Additionally, construction disposal is
expected to last for only a period of two years or less and more frequent
monitoring would be expected than would be necessary for the periodic, but
short-term disposal whioh occurs with maintenance dredging. Finally, there
is a no-Impact history for the discharge of maintenance material, but not
2-40
-------
for virgin material since there has been no periodio testing of the latter.
Therefore, the following monitoring and surveillanoe program is proposed
for the 451 Project ODMDS during construction.
1. A major consideration in sizing the ODMDS was the looation
of the dredge when each discharge ocours. To prevent exces-
sive mounding, it is necessary that a method be utilized to
record the looation of each discharge relative to the
sequence given in Section 2.3*7*1« if the example disoharge
locations given in that section are used.
2. Routine bathymetric scans should be oonducted, with any dis-
posal methodology, to allow the prevention of excessive
mounding and so that a Notice to Mariners oan be posted
relative to any mounding whioh does occur.
3. Monitoring stations (Figure 2-19 and Table 2-5), Including a
control station, stations located immediately outside the
ODMDS and stations located some distance down current from
the site should be sampled, for the items noted in the fol-
lowing paragraph, to determine if impacts are ocourring out-
side of the ODMDS. Two stations on eaoh side of the ODMDS,
roughly 300 feet from the ODMDS edges (Stations B1 through
B6); a control site located southeast of the ODMDS and two
stations located 10,000 ft down current (southwest) of the
down-current edge of the ODMDS are proposed (Stations B9 and
B10).
These stations should be sampled periodioally during construction
and for one year after the cessation of discharge of virgin material at the
site. Duration and frequenoy of monitoring will be decided by the EPA, in
oooperation with the CE prior to oonstruotlon. Samples should be colleoted
for (1) grain-size analysis, (2) ohemioal characterization of sediments,
and (3) maorobenthic invertebrates (in triplioate).
2.4.2.2 Maintenance Material
The periodic CE dredged material examination program requires an
examination of the maintenance material in terms of sediment chemistry;
elutriate ohemistry; grain size analysis; liquid, suspended partioulate and
solid phase bioassays; and bioaocumulation studies. Additionally, ohannel
station and disposal site water chemistry; disposal site sediment
ohemistry; and referenoe station solid phase bioassays and bioaooumulation
studies are oonduoted. Thus the material to be dlsoharged at the ODMDS is
thoroughly examined, ohemioally and toxicologioally and the ODMDS sediment
is examined ohemioally.
2-41
-------
STATUTE MILES
VIRGIN MATERIAL ODMDS
87
B2
* Control Station
INTERTWvDESIGNATED ODMOS
BIO
Fig. 2-19
Monitoring Stations
Virgin Material
-------
TABLE 2-5
MONITORING STATION LOCATIONS
Station Latitude (N) Longitude (W)
B1
28° 49'
55.8"
95°
14*
05.4"
B2
28° 49'
25.8"
95°
14'
42.0"
B3
28° 49'
13.8"
95°
15*
44.4"
B4
28° 49'
30.6"
95°
16'
03.0"
B5
28° 50'
25.8"
95°
15'
44.4"
B6
28° 50'
54.0"
95°
15*
06.6"
B7
28° 51'
06.0"
95°
14'
04.2"
B8
28° 50'
49.2"
95°
13*
45.6"
B9
GO
O
CO
49.2"
95°
17'
46.2"
B10
28° 47*
53.4"
95°
16'
47.4"
Control
28° 511
23"
95°
18'
14"
2-43
-------
Considering the characterization of the material to be dredged
and the quality and characteristics of sediment in the ZSP, there appears to
be no reason why future maintenance material would not be expected to meet
the criteria for ocean disposal. Short-term iapaots will ooour in the site,
but the size of the site should limit these short-term impacts to the ODMDS.
If no long-term impacts are occurring within the disposal site, none would
be expected outside the site and it is the area outside the ODMDS which the
Ocean Dumping Regulations are designed to protect (Pequegnat et al., 1981).
Since, based on historic data, long-term detrimental impacts out-
side the disposal site are not expected, an intense monitoring program is
not warranted. It is proposed that the monitoring and surveillance program
for future maintenance material should consist of:
1. Assessment of channel sediment quality (sediment and
elutriate chemistry; bioassays and bioaoououlation studies)
to insure that polluted material will not be discharged into
the ODMDS;
2. Assessment of water column and sediment quality of the ODMDS
(sediment and elutriate chemistry, grain-size analysis) to
determine if the quality of water and sediment in the site is
deteriorating with time; and
3. Assessment of the health of the biological community of the
ODMDS and Immediately down current from the ODMDS;
4. Elutriate testing of the disposal sediment; and
5. Three replicates each for macrobenthos at three stations: a
oontrol station; an ODMDS station (1-32), as is customarily
used in the CE program; and a station 300 feet from the
oenter of the southwestern boundary of the ODMDS
(28° 52• 59.6" N, 95° 16* 26.3" W).
Additionally, it is proposed that these stations be sampled shortly before
maintenance disposal begins.
2-44
-------
CHAPTER 3
AFFECTED ENVIRONMENT
This section provides a brief description of the area comprising
the land and ocean areas near Freeport, ranging from Pass Cavallo to the
southwest, Galveston to the northeast, and offshore for roughly 30 miles.
This is the Freeport Area as the term is used in this section. Thus, this
section provides more information than that pertaining to the existing site
or even the Zone of Siting Feasibility. More specific information, as the
Ocean Dumping Regulations apply to the preferred alternative, are presented
in Section 1.1.
3.1 INTERIM-DESIGNATED SITE CHARACTERISTICS
3.1.1 Site Location
The existing interim-designated ODMDS contains approximately
0.58 square statute miles and is bounded by 28 51' 12" N, 95 17* 38" W;
28° 51' 03" N, 95° 16' 54" W; 28° 53' 18" N, 95° 17* 27" W; and
28° 51' 21" N, 95° 18' 03" W. Water depth ranges from 26 ft to 31 ft and
the site is 1.11 miles from shore at its closest point. The area of the
site equals 0.58 square statute miles.
3.1.2 Proposed Use of the Site
Predominantly southward longshore transport has caused shoaling
of the existing channel at a rate of approximately 1,000,000 cy/yr. This
requires that the CE, Galveston District conduct maintenance dredging of
the existing Freeport Harbor Entranoe and Jetty Channels at approximately
10-month intervals. The environmental consequences of the maintenance
dredging are covered in the CE EIS for maintaining the Freeport Harbor
Channel (CE, 1975).
3.1.3 Characterization of the Disposal Site
Based on Information provided by the CE, Table 3-1 provides
dredging dates and volumes dredged from the Freeport Harbor Entrance and
Jetty Channels from 1961 through 1983* The average time between the begin-
ning of dredging operations is approximately ten months and the average
amount of maintenance material dredged is approximately one million cy/yr.
Chemical data were collected on disposal site sediments by the CE
in 1971, 1975, and 1982-1987 and by EH4A in 1980. Those data are presented
in Table 3-2. Other samples at the disposal site were collected by the CE
3-1
-------
I
TABLE 3-1
FFEEPORT HARBOR JETTY AND ENTRANCE
CHANNEL HISTORICAL DREDGING
Dredging Dates Material Excavated (CY)
13 Jul
86
18
Aug
86
925,709
19 Aug
85
-
30
Sep
85
1,000,000
05 Oct
84
-
29
Nov
84
1,186,000
09 Jun
83
-
07
Nov
83
1,438,004
18 Jun
82
-
05
Aug
82
1,388,226
1 *1 Aug
80
-
02
Jan
81
1,098,920
08 Dec
79
mm
02
Feb
80
1,101,208
01 Feb
78
•
01
Mar
78;
966,648
30 Aug
78
-
04
Oct
78
04 Nov
76
-
07
Dec
76
667,707
24 Sep
75
-
21
Jan
76
1,427,865
20 Nov
74
-
27
Dec
74
1,010,361
08 Sep
73
-
22
Jan
74
1,089,540
30 Apr
73
-
27
May
73
452,767
16 Nov
72
-
10
Dec
72
415,773
17 Apr
72
-
14
May
72
854,558
29 Oct
71
-
28
Nov
71
306,657
22 Feb
71
m
16
May
71
988,436
03 Nov
70
-
27
Dec
70
626,000
18 May
70
-
07
Jun
70
529,262
01 Dec
69
-
30
Dec
69
629,818
14 Apr
69
-
11
May
69
571,000
07 Oct
68
-
11
Nov
68
694,300
05 Jun
67
-
11
Jun
67
320,000
02 Aug
66
-
18
Sep
66
664,909
26 Jun
66
a»
30
Jun
66
50,000
24 Oct
65
-
19
Nov
65
965,200
05 Oct
64
-
15
Nov
64
806,689
Maintenance Qycle: 10 months.
Shoaling Rate: 1,007,980 cy/yr.
3-2
-------
TABLE 3-2
MEANS OP fALOES POD DISPOSAL AREA SEDIMENT
Y
u>
Parameter
197*, 1975*
1980b
1982°
1983°
198*°
1985d
1985°
1986°
1967°
(total («A|)
Arson io
3.0
< 1
< 1.0
12.5
2.5
*.7
*.8
1.1
2.2
Cadalua
< 0.62
< 0.5
o.*
< 0.5
0.9
< 0.5
< 0.5
0.3
0.1
Chroalua
12
19
2.7
33
7.1
8.9
o
V
20.2
10.3
Copper
8.0
6
3-7
13.2
5.7
7.0
< 5.0
11.8
5.2
Lead
9.6
8
13.5
< 5.0
9.6
< 5
8.9
**.6
9.3
Msrcurjr
< 0.1
< 0.1
< 0.1
< 0.1
0.2
< 0.1
< 0.1
<
0.1
< 0.1
Nickel
11.*
7
13.0
17.1
9-9
10.0
6.2
<
1.0
17.2
Zlne
36
23
27.1
*2.5
26.9
27.1
78.3
<
1.0
29.1
Nitrogen (n/ks)
Aannli
< 0.01
7
63
5.0
1
55
29.*
—
—
Total KjeMahl
1,000
268
338
80
< 1
1
90
—
—
Oil 1 Grease (m/kg)
17*
193
125
37.1
< 5
93
775
361
299
PC8a (ug/kg)
Total
—
8
< 10
< 10
< 10
10
< 10
<
5.0
< 5.0
Peatloldes (w/ki)
Aldrln
—
< 0.2
< 0.2
< 0.2
< 0.2
< 0.2
<
0.2
~
Cklordine
< 0.18
< 1.0
< 1.0
< 1.0
< 1.0
< 1.0
<
0.2
< 0.2
p.p'-DDD
—
< 0.11
< 0.5
< 0.5
< 0.5
< 0.5
< 0.02
—
—
1
4
-------
TABLE 3-2 (Concluded)
Parameter 197*. 1975* 1980b 1982° 1983° 198<° I985d 1985° 1986® 1987°
Paatloldaa (ug/kg) (Concluded)
p.p'-DOC
< 0.09
< 0.5
< 0.5
< 0.5
<
0.5
<
0.5
<
0.2
—
p.p'-DOT
< 0.21
< 0.5
< 4.8
< 0.5
<
0.5
<
0.5
<
0.2
< 0.2
Dleldrln
< 0.09
< 0.5
< 0.5
< 0.5
<
0.5
<
0.5
<
0.2
—
Baptaotilor
< 0.09
< 0.5
< 0.5
< 0.5
<
0.5
<
0.5
<
CM
•
O
—
Lindane
< 0.11
< 0.5
< 0.5
< 0.5
<
0.5
<
0.5
<
0.2
~
Taxaphana
< 0.29
< 10
< 10
< 10
<
10
<
10
<
5.0
< 5.0
* C8 (1978).
b BMA (1980).
0 Onpobliehad CB data (1982.1987).
* BMA (1985).
-------
for a before-, during-, and after-dredging study in 1975 and 1976. These
data are best presented in Section 3.1.4.2 as part of the discussion of that
study.
3.1.4 Characterization of the Material Expected to Be Dredged
3.1.4.1 Virgin Material
Two studies have been conducted, one in 1971 and the other in
1976, which provide information on the virgin sediments of the area (CE,
1978). These studies included sediment and elutriate analyses with
sediments collected from the Freeport Entrance and Jetty Channels. These
data are presented in Table 3-3 (sediment) and Table 3-4 (elutriate).
The concentration of no parameter in the elutriates exceeds the
EPA Hater Quality Criteria (Table 2-2), except perhaps copper. The
concentration of copper (<10 ug/1) may exceed the Hater Quality Criterion
but since the detection limit is higher than the Criterion, this cannot be
determined.
Bioassay and bioaccumulation studies have not been conducted on
the virgin construction material from Freeport, but have been on virgin
sediments from the nearby Galveston Channel. These were found acceptable
for ocean disposal (CE, 1979). Additionally, virgin material at other sites
along the Texas Gulf Coast has been tested and found acceptable
(Brownsville, CE, 1982; Corpus Christi, EPA, 1987), and there is no reason
to expect virgin sediment at Freeport to fail to meet the standards of
40 CFR 227.
3.1.4.2 Maintenance Material
The CE, as a part of the data collection for the FEIS (CE, 1978)
for the channel improvements discussed in Section 1.1, conducted two
monitoring programs (September/October 1975 and December 1975/January 1976)
of the dredging of the Freeport Harbor Channel. The results are similar.
However, some samples were contaminated in the first study and only the
latter will be discussed in detail.
The study consisted of water and sediment samples taken before
the 2 December 1975 and after the 28 January 1976 dredging at four channel
stations, an undisturbed station north of the channel, and a disposal site
station. Hater samples were also taken during (22 December 1975) the
dredging operation: (1) up-current and down-current of a channel station
where dredging was occurring and (2) at the disposal area, pre- and post-
discharge. Parameters for which tests were conducted are turbidity,
dissolved oxygen, pH, salinity, temperature, total solids, total volatile
3-5
-------
TABLE 3-3
RANGE OF VALUES FOR CHANNEL VIRGIN SEDIMENT
Parameter 1971*8 1976a
Metals (og/kg)
Arsenic 2.1 - *1.9 2.2 - 11.0
Cadmium 0.3 - 2.5 0.33 - 1.19
Chromium 38 - 85 11 - 27
Copper 12-26 7-19
Lead 19 - 23 14 - 32
Mercury 0.13 - 1.0 < 0.1
Selenium < 0.1 - 0.48
Nickel 38 - 85 14 - 33
Zinc 56 - 64 28-108
Nitrogen (og/kg)
Ammonia 90 - 230 1 - 248
Total KJeldahl 510 - 1,200 118 - 643
Oil 4 Grease (mg/kg)
140 - 540 100 - 181
a CE (1978).
-------
TABLE 3-H
RANGE OF VALUES FOR ELUTRIATE SAMPLES WITH
CHANNEL VIRGIN SEDIMENT
Parameter
Hater*
Quality
Criteria
1974®
1976a
Metal (ug/1)
Arsenic
69
—
<0.1 - 4
Cadmium
i»3
< 1
<2-3
Chromium
1,100
—
<10-20
Copper
2.9
—
< 10
Lead
110
10 - 20
Mercury
2.1
0.36 - 0.73
Nickel
140
40 - 130
10 - 20
Selenium
410
< 0.1 - 1.9
Zinc
170
—
10 - 20
Nitrogen (or/1)
Ammonia
—
0.52 - 15.2
Total Kjeldahl
1,000
0.80
0.56 - 15.8
• EPA (1986).
a CE (1978).
3-7
-------
solids, total KJeldahl nitrogen, oil and grease, chemical oxygen demand,
chlorides, arsenic, cadmium, total chromium, copper, lead, mercury, nickel
and zinc.
As would be expected, the before and after water column condi-
tions were unaffected by the disposal operation, as determined by comparing
the late January data to the early December data. The only sediment para-
meter which was elevated in the disposal area post-dredging samples rela-
tive to the pre-dredging sample, without a concomitant increase in the
undisturbed and channel area samples, was oil and grease, which Increased
from 246 ppm to 500 ppm, an increase of 252 ppm. However, since the oil and
grease content of the pre-dredging channel sediment was not as high as that
in the post-dredging disposal area sample, the increase at the disposal site
may not have been from the disposal operation. Indeed, an examination of
the pre-dredging sediment data reveals no parameter which was consistently
higher in the channel sediments relative to the disposal area sediments or
the undisturbed area sediments. Therefore, a tracer of channel sediment
presence in the disposal area was not available.
Only turbidity and perhaps chemical oxygen demand (COD) in water
column samples indicate that dredging and disposal were occurring on
22 December 1975. Turbidity was higher at all three down-current (vs. up-
current) sampling times during channel dredging. The COD was higher at the
first two down-current samplings than was the up-current value, but was
lower than the up-current value at the final down-current sampling time.
Turbidity (60 FTU) was higher in disposal area water immediately after the
discharge than before (20 FTU), but then decreased to 15 FTU and remained
there. The COD was 31 mg/1 in disposal area water before the discharge,
rose to 51 mg/1 immediately after the discharge, and to 72 mg/1 20 minutes
later. For the following two hours, it ranged from 61 mg/1 to 67 mg/1.
However, on 2 December 1975, in the pre-dredging sampling, the COD value for
the disposal area was 93 mg/1 and 165 mg/1 at the undisturbed area site. In
summary, the monitoring of the dredging of the Freeport Harbor and asso-
ciated disposal operation indicates that only minor, short-term impacts to
water and sediment quality are experienced near the channel and at the
disposal area.
Four studies to satisfy the requirements of the Ocean Dumping
Regulations, using the requirements of EPA/CE (1976), have been conducted
for the CE: two by NUS Corporation and two by Espey, Huston & Associates,
Inc. (NUS 1976a, b; EH&A 1960, 1965). These include bioassays and bioac-
cumulation studies and, for EH&A (1960, 1965), extensive chemical analyses
(earlier regulations only required analysis of cadmium and mercury). The
CE also collected samples in 1974 and 1962-1987 (CE, 1978; unpublished CE
data 1962-1987) for channel sediment analyses and channel elutriate
analyses. The results of these studies are presented in Tables 3-5 and 3-6
3-8
-------
TABLE 3-5
RANDS Of TALOES TOR CHARREL MAIRTERARC8 SEDIMENT
Firmttr
197*, 1975*
1980b
1982°
1983°
198*°
1985*
1985°
1986°
1987°
~totals («/kg)
Araanlo
< 3.0 - 9.0
< 1
< 1.0
3-13
<1-1.2
2.3 - 13.0
2.9 - *.0
< 1.0 - 3.3
2.8 - *.1
Cadalua
0.37 - 1
< 0.5
0.4 - 0.6
< 0.5
< 0.5 - 1.1
< 0.5
< 0.5
< 0.1
< 0.1
Chroalua
9-29
8-17
6-15
13 - 30
<5-10
5.8 - 120
< 5.0 - 6.*
6.5 - 26.3
6.1 - 13.5
Coppar
* - 17
6-7
9.3 - 12.0
5.1 - 12.5
<5-6.8
< 0.5 - 7.*
< 5.0 - 21.*
*.3 - 13.1
5.7 - 10.9
Laad
8-28
9-11
20 - 27
< 5
7-10
< 0.5
5.9 - 7.9
1*.6 - 31.3
*.3 - 9.6
Haroury
< 0.1
0.1 - 2.1
0.1 - 0.2
< 0.1
0.3 - 0.5
< 0.1
< 0.1
< 0.1
* 0.1
Rlekal
9-28
7-9
17 - 28
8-16
5-10
< 5 - 11.5
5.1 - 7.9
13.6 - 29.3
6.9 - 35.6
Zlno
28 - 86
30 - 37
28 - 5*
32 - <5
2* - 30
26.7 - 33.7
13.8 - 23.2
23.0 - 57.6
27.3 - 32.2
Rltrogan («/ki)
Aaaonla
58 - 1*0
17 - 36
63 - 125
21 - 37
< 1
67 - 230
22.8 - 36.5
—
—
Total KJaldahl
190 - 1,011
**7 - 821
80 - 150
279 - 553
<1-620
322 - «7*
-------
TABLE 3-5 (Conelud«d)
Faraaetar 197*. t975* 1960b 1982° 1963* 198«° I985d 1985* 1986° 1987°
Fotteldw ((ug/kg) (Conoludad)
p,p* DDE
0.28 . 1.05
< 0.5
<0.5
<0.5
<0.5
< 0.5
<0.2
—
p,p' DDT
< 0.21
< 0.5
< 0.5 - 6.9
<0.5
<0.5
<0.5
< 0.2
< 0.2
Dleldrln
< 0.9
< 0.5
<0.5
<0.5
<0.5
<0.5
<0.2
—
Raptaohlor
< 0.9
< 0.5
<0.5
<0.5
<0.5
< 0.5
<0.2
—
Lindane
<0.11
< 0.5
<0.5
<0.5
<0.5
<0.5
<0.2
—
ToxapK«n«
<0.29
< 10
< 10
< 10
< 10
< 10
<5.0
< 5.0
" CK (1978).
b ma (1980).
c Pnpub Halted CS data (1982.1987).
d EttA (1985).
-------
TIM 3-6
uni or nuns rot n.*mm mhtus
wm cwuma. Mimataci aniMn
ktar'
9aa lit)
it*r Oltcrli
m»* 19T6b,e I960* 1962* t9#3* 196** 1965r ,9#5* "86* ,987"
H.UI (of/l)
Irnnio
<9
1 . 1
—
<3
<2-3
12-20
< 2
2.2 - 5.4
2.9 - 3.5
<2.0 - 33.6
< 2.0
CiMut
*3
2 - 3
5.0
<5-9
< 2
< 2.0
< 2
<2-3
< 2
< 2.0
< 2.0
Otroalu*
1,100
<10 - 10
—
< 50 -1T0
<10
< 10
< 10
<10 - 26
<10
< 10
< 10
Coppar
2.9
10
—
<2-2*
1* - 25
< 1.0
<1-17
<1-17
< 1
< 1.0 - o.«
< 1
LnO
i»o
R
1
O
—
< IB - 20
< 10
< 10.0
< 10
< 10
< 10
< 5.0
< 5.0
H»rcury
2.1
<0.1 - 0.6*
< 0.1 - 0.20
< 0.1
<0.8
< 0.1
< 0.1
<0.1
<0.1
< 0.2 - 0.*
< 0.2
1*0
10
—
< 0.1
<20
< 20
< 20
< 20
<20
<5.0 - 11.*
< 5.0
Zlrvo .
170
10 . 20
—
< » - 40
<20-33
< 20
< 20
< 33-65
<20
19.6 - 50.2
<5.0 - 237
Hltrciwn (««/l)
Aaaonla
—
—
—
0.20 - 0.42
< 0.05
< 0.05 - O.tO
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-------
respectively, as ranges of values for the various parameters for which
analyses were conduoted. Also presented (Table 3-7) are the results of the
grain size analyses conducted by the CE and by EH&A (1985).
An analysis of data from the elutriates (Table 3-6) made with
channel samples shows no cause for concern except for perhaps copper in
1974, 1980, 1982, 1984 and 1985, and toxaphene, in all years but 1980. In
the case of copper, the EPA Water Quality Criteria has been lowered from
50 vg/1 (EPA, 1976) to 23 yg/1 (EPA, 1981) to 2.9 Vg/1 (EPA, 1986). The
proposed EPA Criterion for copper (Mills et al., 1985) was 23 Ug/1 and the
human health standard is 1,300 yg/1. For toxaphene, the detection limit is
greater than the Hater Quality Criterion. However, in either Instance,
calculation of Initial mixing (EH&A, 1980) would reduce all copper and
toxaphene levels to well below the Criteria. As will be noted in the next
paragraph, additional data from bioassays conducted on Freeport Harbor
Channel sediments have shown no indication of acute toxicity or bioaccumu-
lation potential.
Bioassay data were generated by NUS (1978a, b) and EH&A (1980,
1985). The results of these studies are summarized in Table 3-8. An
examination of Table 3-8 indicates that in all but two tests, survival of
organisms exposed to the liquid phase (LP) and suspended particulate phase
(SPP) of sediments from the Freeport Harbor Channel was greater than 50*.
Therefore, no 96-hour LC^q (that concentration of a substance which is
lethal to 50t of test organisms after a continuous exposure time of
96 hours) could be calculated. Since all sediment from a discharge can be
expected to settle out of the water oolumn in a time frame measured in
minutes, as opposed to hours or days (Bokunlewlcz et al., 1978), 96 hours
should provide a conservative test for acute toxicity. In the two cases
(designated by a super-script "c" on Table 3-8), where a 96-hour LC^q calcu-
lation oould be performed, calculation of expected dilution values indi-
cated that at no time oould the water concentration of sediments be expected
to be equal to or greater than 0.01 times the lower 95t confidence limit of
the LC^q (NUS, 1976a and b).
For all solid phase (SP) bioassays (Table 3-8) with Freeport Har-
bor Channel sediment, survival In the tests was not significantly less (at
the 95* confidence level) than control survival. Both field and laboratory
bloaccumulatlon studies were oonducted. Field studies by NUS (1978a)
examined the concentration of mercury and cadmium in the sea pansy (Renilia
muellerl). while those by NUS (1978b) examined mercury and oadmium in the
polyohaete (Dlopatra ouprea) and the blue crab (Calllnectes saoldus). In
all Instances, the tissue concentration of disposal site organisms was not
significantly different (p * 0.05) from that in control organisms. NUS
(1978a) used the clam (Ranjgla cuneata) to look for bioacoumulation of mer-
cury and cadmium in a laboratory study. Also In a laboratory study, EH&A
3-13
-------
TABLE 3-7
GRAIN SIZE ANALYSES STMURT
Oraln
Six*
Slava
CE
CHANNEL STATIONS
(ua)
Claaalfloation
No.
60*00
55*00
50*00
*5*46
*0*00
30*00 25*00
20*00
10*00
5*00
0*46
-S*6o
*.760
Coaraa Sand
*
100*
100
100
100
100
100 100
100
100
100
100
100
2,000
10
100
100
100
100
100
100 100
100
100
100
100
100
s«o
Hadlua Sand
20
100
100
99
100
100
100 100
100
100
100
99
100
*20
*0
99
100
99
100
100
100 100
100
100
100
99
100
297
50
9S
100
99
100
99
99 100
99
100
99
98
99
210
Plna Sand
70
95
99
98
99
98
99 100
99
100
98
97
98
1*9
100
92
99
96
98
95
97 99
98
100
97
97
97
105
1*0
B*
97
89
89
80
81 93
90
87
85
83
8*
7*
200
7*
9*
78
7*
4*
61 86
59
7*
6*
66
6*
53
270
65
86
69
59
11
51 80
*0
65
*8
58
5*
37
Silt
*00
60
80
60
52
9
*2 7*
35
59
*3
50
48
10
*6
63
*6
38
5
27 5*
26
*0
32
3*
37
5
38
5*
36
32
4
23 *5
23
3*
28
26
3*
3
Clay
3*
*8
30
30
2
20 39
21
29
25
20
31
1
26
32
18
21
2
13 30
16
20
20
16
25
< 1
Colloidal
2*
22
17
20
2
12 29
16
19
19
15
24
Oraln
Slaa
3 lava
CE CJUKNEL STATIONS
(ua)
Claaairieatlon
¦o.
•18*00
-30*00
-40*00
-I5*M
-50*6
-66*60
•70*00
40*00
-90*00
-110*00
Araraga
*.760
Coaraa Sand
*
100
100
100
100
100
100
100
100
100
100
100
2,000
10
1O0
100
100
100
99
100
100
100
100
100
99.9
8*0
Hadlua Sand
20
100
100
100
100
98
100
100
100
100
100
99.8
*20
*0
100
100
100
100
97
100
100
100
100
100
99.7
297
50
99
100
100
100
96
100
100
100
100
100
99.3
2t0
Plna Sand
70
99
100
99
100
96
100
100
99
100
100
98.8
1*9
100
98
100
98
100
95
100
100
99
100
99
97.9
105
1*0
86
100
97
99
89
98
100
98
99
98
91.2
7*
200
68
100
96
96
76
9*
100
9*
97
95
79.8
53
270
52
93
91
87
61
87
8*
8*
92
91
68.6
3T
Silt
*00
*3
88
8*
78
*8
77
76
7*
88
8*
61.5
10
31
70
6*
57
3*
50
57
56
65
58
*5.0
5
28
6*
56
50
27
42
52
50
5*
50
38.6
3
Clay
25
56
50
**
25
37
*5
46
67
40
3*.7
1
20
*1
38
33
13
29
35
35
37
26
24.8
< 1
Colloidal
20
*0
37
32
12
28
3*
3*
36
2S
23.5
All data froa unpubllabad CE data (1971-1987) and/or EMA 1985.
* Eaeh motor rapraaanta tha paroant of partlolaa Nbioh ara flnar than tha train aisa llatad oppoalta it in tha flrat ooli
-------
TABLE 3-8
SOMlAn OF BIQASSA? DATA FOU MAINTENANCE MATERIAL (* SURVIVAL)
F-1 (30*00) F-2 (-60*00) P-3 (-110*00) M1
Date Organlaa TF 5F W TP IFF 5F LP SPP » T? Iff »
1978
(Apr.) HyaldopaH ilgri' 87 80 100 83 23° 87 53 17c
Hanldla barylllna 100 87 100 100 97 100 100 100
M. alwra6 93 90 93 93 97 90 100 90
Total Organlaaad 86 85 90 80
1978
(Oct.) M. alwra 100 100 87 70 87 80 70 93
1980
1985
M. barylllna 87 93 100 67 90 93 100 93
K. alayrmb 80 97 56 83 93 52 93 100 35e 93 70 6«
Haroanarla —roanarla 99 98 98 97
Dlopatra oupraa 9* 91 99 97
M. banrlllna 97 100 97 83 97 100
K. alayrab 97 100 100 100 90 100
Palaaaoaataa pmlo 100 100 93 100 93 96 100 93 98
K. aareaaarla 100 100 99
Marala Tirana 9* 95 87
Cyprlnodon varlagatua 100 77 100 100 100 100
Hyaldopala bahla 93 83 90 90 70 77
P. puglo 97 100 97 100 100 98 93 100 99
K. aaroaaarla 100. 100 100
N. Tirana 89 8* 91
* adult ajralda.
b post-larral vyslda.
0 aurrlral laas than 509.
d organlaaa Mara Rangla ounaata. iaanthaa aranaoaodantata. Hraldopala alanrra.
• Station P-A la looatad 2 allaa aaaward of tba aaa baojr, on a lloa with tba Praaport Entraaoa Cbaanal.
>15
-------
(1980, 1985; see Table 3-9) examined the quahog clan (Mercenaria
mercenaria) and the polychaete (Nereis virens) for accumulation of arsenic;
cadmium; chromium; copper; lead; mercury; nickel; zinc; total PCBs; aldrin;
chlordane; p,p'-DDD; p,p'-DDE; p,p'-DDT; dieldrin; heptachlor; lindane; and
toxaphene. As with the field studies, no significant (p = 0.05) indication
of bioaccumulation was exhibited by these test organsims.
The results of both the chemical and biological analyses noted
above on the Preeport Harbor Channel maintenance sediment, and elutriates
made from those sediments, indicate that there are no particular pollution
or toxicological problems associated with these sediments and that they are
acceptable for ooean disposal under 40 CFR 227. Therefore, there is no
indication that these sediments would require a special location, or any
special precautions, for their disposal.
3.2 PHYSICAL ENVIRONMENT
3.2.1 Nearby Areas
In 1881, the construction of the Freeport Jetties was begun by
private interests and was oompleted in 1889 by the CE (Seadock, 1976). The
original channel was dredged as an improvement to the natural mouth of the
Brazos River. In 1929, the Brazos River was diverted to the south, with a
new opening into the Gulf of Mexioo approximately 6.5 miles south of the
natural mouth. At the same time, a levee was built across the old river
channel to complete the diversion.
The existing Freeport Harbor Project was authorized by the River
and Harbor Acts of May 1950 and July 1958. The acts provided for an
Entrance Channel 38 feet deep and 300 feet wide from the Gulf of Mexico to a
point inside the Jetties and for Inside channels 36 feet deep and 200 feet
wide to and Including an upper turning basin. The project also provides for
maintenance of a channel and basin of 30 foot depth extending from the
36-foot deep portion of the waterway to the Brazos Harbor Turning Basin.
Greater depth and width was authorized by Congress in 1970 (Sec-
tion 101 of the River and Harbor Act of 1970, PL 91-611; House Document 289,
93rd Congress - 2nd Session, 31 Dec 1975) and by the President in 1974.
These authorizations were for the Jetty Channel to be relocated and deepened
to 45 feet, widened to 400 feet, and the North Jetty relocated northward.
The relocated Entrance Channel was authorized to a 400-foot width and a
47-foot depth and will extend approximately 4.6 miles into the Gulf. The
authorization also provided for deepening of the inside channels and basins
to 45 feet. An FEIS for the project was prepared by the CE in 1978. In
1978, Seaway Pipeline, Inc., under a Department of the Army permit, widened
the existing Entranoe Channel to 400 feet and the Jetty Channel to 230 feet.
The CE maintains the existing authorized project dimensions.
3-16
-------
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-------
The 1978 45' Project FEIS proposed to double the size of the
interim-designated ODMDS in the seaward direction in order to accommodate
the virgin and subsequent maintenance material. Since that time, addi-
tional guidance on selecting ODMDSs as well as modeling the fate of dredged
material has been prepared. Consequently, this guidance is used in select-
ing the appropriate ODMDSs for the new work and maintenance material asso-
ciated with the 45' Project. The CE expects to continue to use the interim-
designated site at Freeport until construction of the 45' Project is
completed.
The Freeport Harbor Channel provides access for large vessels to
the town of Freeport and nearby areas. The Freeport area is somewhat unique
in that, as opposed to 90f of the Texas shoreline, it is not separated from
the Gulf by a barrier island, but extends to the Gulf through the old Brazos
River Delta. In addition to the old and new Brazos River channels, the
Freeport area is cut by Oyster Creek to the northeast and the San Bernard
River and Jones Creek to the southwest. The Gulf Intracoastal Waterway runs
southwest/northeast through the area, about 3,000-4,000 feet inland from
the Gulf. Freeport is located in the eastern portion of the Colorado-Brazos
deltaic plain, and like most of the the Gulf Coastal Plain, has a gentle
verticalrhorizontal gradient of 1:1,000 to 2:1,000. The only prominent
natural features are surface expressions of salt domes. The relative sea
level reached its present position around 4,500 years ago. Local subsi-
dence in the area, between 1943 and 1973, was between 0.5 and 1.5 feet
(Gabrysch and Bonnet, 1974).
3.2.2 Climatology and Meteorology
Freeport is situated along the coastline of the upper Texas
Coastal Plain and within the contiguous waters of the Gulf of Mexico.
Detailed discussions of various aspects of Texas climate may be found in
Orton (1964), Portig (1962), Jehn (1974), United States Weather Bureau
(USWB, 1961), and the many publications of the National Climatic Center of
NOAA, particularly the climatography series. Much of the material in this
section is drawn from Ward (1977).
Freeport is in a marine environment dominated by the Gulf of
Mexico. The dominating influenoe of the Gulf arises chiefly from (1) the
large area of the Gulf and long residence time of overlying air whloh
enables the Gulf to function as an airmass source region and (2) the persis-
tent onshore flow that transports Gulf air deep into the State. The onshore
flow is interrupted by weather disturbances carried in the belt of prevail-
ing westerlies, but these interruptions occur primarily in winter, when the
belt of westerlies is displaced southward to the middle latitudes of the
U.S., the Bermuda High weakens considerably, and frontal passages over the
project area become much more frequent.
3-18
-------
In late summer, when the westerlies have retreated into Canada,
the south Texas and Gulf coast areas fall under the Influence of the tropi-
cal easterlies, which, like the westerlies, carry disturbances. These
tropical systems, easterly waves, depressions, and sometimes hurricanes,
enter the State from the east and southeast and move westward. The peak
month of this tropical activity is September. According to Henry and
McCormack (1975), there is a 37 J, 23J, or 7% chance of a tropical storm,
hurricane, or extreme hurricane, respectively, striking a fifty-mile strip
of the Gulf Coast centered approximately eight miles northeast of Freeport.
The average temperatures in the Freeport Area for winter
(January) and summer (July) are 54 r and 83°F, respectively (all means and
normals refer to the current 1941-70 cllmatologlcal norm unless stated
otherwise). These average temperatures are, of course, the statistical
expression of a complex of meteorological systems within the respective
months over many years. Average monthly rainfalls in the Freeport Area for
months representative of the four seasons are as follows: 3.4 in.
(January), 3*7 in. (May), 5.0 in. (July), and 6.5 in. (September).
In general, the annual onset of rainfall in the upper Gulf coast
is bimodal with maxima in the late spring and early fall. Figure 3-1
displays a segment normal to the coastline at Galveston, consisting of
Conroe, Houston and Galveston, and illustrates this march of rainfall. The
first maximum is indicative of the effects of spring frontal passages inter-
acting with the increasing moisture supply from the Gulf of Mexico.
Although both Conroe and Houston display such a maximum, this maximum is
absent in Galveston, an indication of the Increasing marine influence
(hence, limited Influence of frontal passages) within even the short dis-
tance from Houston to Galveston. (Jehn, 1971, among others, has pointed out
the significant cllmatologlcal ohanges that occur within a thin strip —
about 5 to 10 miles — of the coastline.)
A general impression of the typical wind variations may be
obtained from the wind roses in Figure 3-2. These wind roses, from National
Data Buoy Center (NDBC, 1973), display the seasonal variation of wind dis-
tribution statistics over the year. The influence of prevailing southeas-
terly flow is evident particularly in the summer months. The prevailing
direction shifts to the south-southeast in winter, with the weakening and
southward movement of the Bermuda High, and frontal northerly winds com-
prise a greater proportion of the observations.
From the hydrographlc point of view, the most significant cllma-
tologlcal effects are due to seasonal precipitation distributions and to
the forcing of circulations and wave motions by wind systems. With respect
to the latter, the phenomenon of the frontal passage is of particular
importance. Bays along the Texas coast are extremely responsive to meteoro-
3-19
-------
itr
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TIME ((Malta)
Fig. 3-1 Monthly Precipitation Normals at Key Stations
Along Segment Normal to the Coastline at Galveston
3-20
-------
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
KNOTS
* "
«.IO H-lf tT4T
o m m m
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PVMtwrMK ffKOMNCT KALI
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DEC
Fig. 3-2 Season Variation of Wind Distribution Statistics
Over the Year, Galveston, Texas (after NDBC, 1973)
-------
logical forcing. Although the characteristics and morphology of frontal
systems are highly variable, a general scenario may be sketched as follows.
As a polar outbreak enters Texas, low-level convergence in the frontal zone
enhanoes the normal southerly flow. The resultant onshore winds elevate
water levels in the upper parts of the bays and along the northwest Gulf
coast, forcing a volume of water through the passes. With the passage of
the front, pressure increases inland and the wind turns to the north,
depressing water levels in the upper bays and in the northwest Gulf, thus
discharging volumes of water through the passes into the Gulf.
3.2.3 Ooeanographlc
3.2.3.1 Bathymetry
The bathymetry of the Freeport Area is essentially the same as for
any other section of the Texas Gulf coast. From the beach to approximately
3,300 feet from shore, the vertical to horizontal gradient is approximately
5:1,000. Beyond this, the true Gulf Continental Shelf begins with a
gradual vertical to horizontal gradient of 5:10,000. As can be seen from
Figure 3-3, the water depth in the area ranges to approximately 70 feet.
There is no relief of any consequence in the project area.
3.2.3*2 Circulation and Mixing
The hydrodynamic regime of the northwestern Gulf of Mexico is the
result of the oooplex interaction of tides, meteorological driving forces
(i.e., wind and atmospheric pressure gradients), freshwater inflows,
Corlolis acceleration, eto. Both local conditions and the overall Gulf
circulation pattern affeot the hydrodynamics of the study area. In addi-
tion, major meteorological events such as hurricanes and tropical storms
can have profound influence on waves, tides, and currents. However, these
events are relatively rare and of short duration. For example, EPA (1982)
states that within approximately 40 miles of the northeastern Texas Gulf
coast, bottom ourrents will reach a maximum velooity of around 3*92 knots
every three years and sustain velocities of 1 knot or greater for several
days onoe a year.
Astronomioal tides are generally small in the Gulf of Mexico.
They vary from diurnal to semidiurnal as a Amotion of the moon's dedica-
tion, with a typioal diurnal range of 2 to 1 feet along the coast. Spring
tides are generally higher, but sinoe the range is so small, meteorological
effects (i.e., wind or storms) oan completely obscure tidal fluctuations
(BLM, 1979). A more detailed disoussion of tides in the Gulf of Mexico can
be found in Manner (195t).
A major feature whioh dominates oiroulation in the eastern Gulf
of Mexioo is the Loop Current, a continuation of the Yucatan Current which
3-22
-------
STATUTE MILES
10 ft.
20 ft
30 ft.
60 ft
10 At.
\
Freeport
20 ft.
30 ft.
Fig. 3—3
Bathymetry of the
Freeport Harbor Area
10 ft.
3-23
-------
enters the Gulf through the Yucatan Straits. There are two important semi-
permanent currents difluent from the Loop Current: one circulating clock-
wise in the southwestern Gulf, the other circulating counterclockwise in
the northwestern Gulf (Curray, 1960). The general surface circulation in
the Gulf of Mexioo is depicted in Figure 3-1*
As a result of this semi-permanent counterclockwise circulation
pattern in the northwesten Gulf, a net surface current component to the
south prevails in the project area (Curray, 1960; Nowlin, 1971). The
existence of a semi-permanent olockwise circulation pattern in the south-
western Gulf is also indicated in the same figure. The zone of convergence
of these two circulation patterns occurs well to the southwest of Freeport
during the winter, and, in general, the stronger and more persistent
westerly currents prevail during the winter in the study area. During the
summer, this zone of convergence migrates northward as a result of strong
south to southeast winds which normally occur from May through August, but
the zone of convergence still remains southwest of the study area. However,
the westerly current becomes feebler and less persistent during the summer
months as the zone of convergence moves nearer to Freeport. A shift to more
easterly winds and more frequent frontal northerlies beginning in September
moves the zone of convergence southward, and the westerly currents once
again become more dominant and increase in speed.
This general surface circulation pattern is verified by recent
ship drift measurements as compiled by the Naval Oceanographic Offices
(1978) which indicate prevailing currents off Galveston Island to the west
or west-northwest at 0.7 to 1.0 knots. The lower velocities were more
prevalent in the late summer months. Further compilation of surface current
data was reported by Seadock (1976). They found that, except for June and
July, surface currents were to the southwest; in June and July, weak
northeast surface currents occurred.
Few scientific studies have been conducted that report either
surface or bottom currents specifically for the Gulf of Mexico in the
nearshore area off Freeport. Two papers reporting the results of a sediment
transport study in the Galveston Island area indicate high variability in
flow direction and magnitude, though a net southwesterly current was mea-
sured. Both Hall (1976) and Estes and Scrudato (1977) present bottom
current data (1 m off bottom) taken in or near the hopper dredge disposal
area approximately 4 km southeast of Galveston with continuous recording
meters. The data Indicate a complex interaction of the semi-permanent
westerly ourrent with diurnal and semi-diurnal tidal currents and the
resulting water movement into and out of Galveston Bay through Bolivar
Roads. However, the occurrence of southwesterly flow currents greatly
exceed those flowing to the northeast. Measured bottom currents ranged from
0.0 to 1.2 knots. During the various sampling periods, median bottom velo-
3-2^
-------
»0*
8
f
Source: Nowlin, 1971
(Currents in knots)
Figure 3-4
Surface Currents
in the Gulf of Mexico
3-25
-------
cities ranged from 0.35 knots to 0.75 knots. Current profiles from Hall
(1976), taken at several depths at selected sites, indicated greater velo-
cities near the surface and a diminishing of magnitude with depth, though
current direction was nearly uniform in the water column. However, current
profiles reported in Estes and Scrudato (1977) indicate that current direc-
tion reversals with depth do occur.
Other available current data exist for the area of the Gulf con-
taining the Buccaneer Field, the oil and gas production field which is
located 32 mi south of Galveston. Although this region is southeast of
Freeport, results from the Buccaneer Field are probably relevant at
offshore locations in the Freeport Area where tidal currents from Galveston
Bay are greatly diminished. Harper (1977) reported aurface and bottom
currents as recorded with current meters. The surface currents were
predominantly westward in March through June and easterly in July through
September for the study period October 1971 through August 1974 in the
Buccaneer Field. Easterly bottom currents prevailed in July, August,
November, and December. The July and August currents exceeded 0.5 knots Moj
of the time and 1.0 knots \5% of the time. The strongest westerly bottom
currents occurred in April with speeds greater than 0.5 knots 20% of the
time. Also, surface currents 180 out of phase with bottom currents were
often recorded. Martin (1977), utilizing drogues and ballasted drift
bottles, reported currents in the Buccaneer Field for various months from
May 1976 through February 1977. The results of the drift bottle releases
indicated a predominantly westward current, though occasionally bottles
drifted to the northeast, particularly in May and July 1976. (Due to a poor
recovery rate on the drift bottles, this data as reported must be used with
discretion.) Drogues set at the surface and at a depth of 10 m followed the
general seasonal pattern previously discussed above. In July 1976, the
drogues moved easterly part of the time and westerly the remainder of the
time. All other monthly studies, August 1976 through February 1977, indi-
cated a southwest current movement at both the surface and the 10 m depth.
In conclusion, it appears that the semi-permanent westerly cur-
rent of the northwestern Gulf of Mexico dominates the hydrodynamic regime
near Freeport. However, variations in current speed and direction occur
frequently in season and throughout the water column. The westerly current
is strongest in the fall, winter and spring. During the summer, easterly
currents become more frequent and may, at times, dominate. Surface currents
in the projeot area averaged 0.5 knots (Seadock, 1976), though with con-
siderable variation. The ourrents diminish with depth, so that bottom
currents (1 m above the bed) are in the general range of one-half the
surface velocity. Changes in current direction with depth do occur, and
bottom currents may at times be directed in the opposite direction from
surface currents.
3-26
-------
3.2.11 Water Quality
A sampling program was undertaken in 1973 (Seadock, 1976) to
determine background information of the nearshore water quality from
Galveston to Pass Cavallo. This included 18 offshore stations. The CE, in
June 1976, collected samples for chemical analyses from the Freeport
Harbor, the disposal site, and an undisturbed area to the northeast of the
channel. EH&A (1980, 1985), under contract to the CE, reported concentra-
tions of various water quality parameters. The results of those three
reports are included in the Table 3-10. Also included in the table are the
EPA Water Quality Criteria for the parameters for which criteria have been
developed. Copper appears to exceed the Water Quality Criteria in four
different years (1973 * 1976, 1980, 1984). However, as discussed in Sec-
tion 3.1.4.2 initial mixing calculations would reduce the copper, and toxa-
phene, levels to below the Criteria for these constituents. A further
review of Table 3-10 indicates no water quality problems in the Freeport
Area.
3.2.5 Sediments
3.2.5.1 Sediment Quality and Characteristics
The range of values for sediment collected at areas which should
be unaffected by dredging and disposal activities northeast of both the
channel and the ODMDS are presented in Table 3-11. The generalized sediment
types of the surficial sediments are presented in Figure 3-5.
During conduct of the bioassays discussed in Section 3*3» bio-
assays and bioaccumulation studies were also conducted on sediments from
the unaffected area northeast of the channel. Survival was high in the
unaffeoted sediment solid phase bioassays and the concentration of para-
meters of interest in the tissues of organisms exposed to the unaffected
area sediment was near or less than that of background organisms. There is
no indication of sediment quality problems in the Freeport Area which would
affect the site selection process.
As an examination of Figure 3-5 reveals, the surficial sediment
provinces tend to parallel the beach with nearshore sand to the northeast
and to the southwest of the Freeport Harbor Channel. The nearshore area at
Quintana, Freeport, and Surfside is silty sand while farther offshore, the
sediment becomes silty clay. In the deeper portions of the study area are
found sand, silt, and clay. As an examination of Tables 2-7 and 2-11 shows,
on the average, the virgin material to be dredged contains 72.OK clayballs,
4.5$ fine sand, 13*5$ silt and 8.Of slurry, while present maintenance
material contains 1% medium sand, 31? fine sand, 30$ silt, 14$ clay and 34$
colloidal material. Due to the high percentages of silt and clay, the
3-27
-------
vaitr
hiwt« oitM-u* »*rr lrrt" i»eo®
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— < 0.01 - 0.3t < 0.1 - o.«
ToUl t>M*kl t.OOO — o.oa - 0.5* < 0.2 - 0.55
Oil I qr~» «¦»/!)
0.3 - 0.9* «t.t.* < 0.09 - 9.11
rat <<*/»
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1965
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< W
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< 0.1
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< 10
<0.1
< 20
< 20
2.1 - *.2
< 2
< 10
< I
< 10
<0.1
< ?0
< to
22.9 - 72.1
< 2
it.i - ij.i
< i - 2.h
<5
< 0.2 - 0.5
< 5.0
19.8 - 100.0
< 2
< 2
< 10
< 1
< 5
< 0.2
< 5.0
7.* - 21.7
< 0.05 0.05 - 0.00 < 0.05 • 0.12 < 0.75 - 0.95 <0.05
< 0.05 0.3S - 0.77 0.05 • 0.35 < 1.0 - 1.2 0.M - 0.90
< 1 - 12.6
< 1.0
2.5 - 15
< 1.0 - 1.1
1.1 - 7.5
< 0.5
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< 0.5
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-------
TABLE 3-11
RANGE OF VALUES FOR UNDISTURBED SITE SEDIMENT
u>
lA>
o
Parameter
1974
1975
1982b
1983b
1985b
1986b
1987b
Metal (mg/kg)
Arsenic
3.7 - 7.2
<1.0
12.8
6.9
3.5
2.1
Cadmium
0.31 - 0.52
0.6
0.5
< 0.5
< 0.1
<0.1
Chromium
11-22
13.1
30
< 5.0
26.1
6.0
Copper
5.0 - 27
12.3
12.5
< 5.0
11.1
5.5
Lead
<5-25
22.5
< 5.0
< 5.0
35.9
1.3
Mercury
< 0.1
0.1
< 0.1
< 0.1
< 0.1
< 0.1
Nickel
12 - 25
29.0
18.1
7.1
26.1
31.0
Zinc
20 - 72
17.3
15.0
22.8
11.9
29.1
Nitrogen (ng/kg)
Ammonia
—
92
6.0
27.6
—
—
Total Kjeldahl
119 - 900
115
158
75.0
—
—
Oil & Grease (mg/kg)
87 - 293
151
10.1
702.0
178
331
PCBs (ug/kg)
Total
< 10.0
< 10.0
< 10.0
< 5.0
<5.0
-------
TABLE 3-11 (Concluded)
1971
Parameter 1975* 1982b 1983b 1985b 1986b 1987b
Pestioldea (ug/kg)
Aldrln
<
0.2
< 0.2
< 0.2
< 0.2
m —
Chlordane
<
1.0
< 1.0
< 1.0
< 0.2
< 0.2
p,p'-DDD
<
0.5
< 0.5
<0.02
—
—
p,p'-DDE
<
0.5
< 0.5
< 0.5
< 0.2
—
p,p *-DDT
<
0.5
<3.30
< 0.5
< 0.2
< 0.2
Dleldrin
<
0.5
< 0.5
< 0.5
< 0.2
—
Heptachlor
<
0.5
< 0.5
< 0.5
< 0.2
—
Lindane
<
0.5
< 0.5
< 0.5
< 0.2
—
Toxaphene
<
10.0
<10.0
<10.0
< 5.0
—
a CE (1978)
b Unpublished CE data (1982, 1983, 1985, 1986, 1987)
-------
STATUTE MILES
Sand
Silty Sand
Silty Clay
Sand Silt Clay
Source: DOI.MMS (1983)
TER1M DESIGNATED
///////
//////
/ / A
/ / / / // /
< t f / /' '
////
/////
Freepor
Rg. 3-5
Surface Sediment Distribution
Offshore Waters
3-32
-------
virgin material is most similar to the silty-clay regime, while the mainte-
nance material is most similar to the silty-sand or sand/silt/clay pro-
vinces. Since biological community composition, in any geographic area,
largely results from the grain size of the sediments (Science Applications,
1984), from a biological perspective, the virgin material ODMDS should be in
the silty-clay regime and the maintenance material ODMDS should be, if
possible, in the silty-sand regime or the sand/siIt/clay regime.
3.2.5.2 Sediment Transport
The Texas shoreline is an ever changing land interface with the
waters of the Gulf of Mexico. When the tides, waves, and currents of the
Gulf Interact with the sediments forming the beach areas, changes in the
alignment and character of the shoreline occur. Similarly, the sediments on
the Gulf floor in the nearshore region (5 to 30 mi seaward) are subject to
various sedimentary processes.
Sedimentation processes result from the interaction between the
winds, waves, currents, tides, and other active agents in the littoral zone.
Shores erode, accrete, or remain stable, depending on the rates at which
sediment is supplied to and removed from the shore. Beaches along the
coast, both north and south of the Freeport Area, are in a general deposi-
tional state (Morton and Pleper, 1975).
Energy for sediment dispersal on the Texas shelf is attributed
primarily to meteorological events (prevailing winds and storms), and
secondarily to astronomic tidal events (Shldeler, 1978). The most effec-
tive normal winds are the persistent southeasterly winds and the short-
lived, Intense northers. The predominant southeasterly winds combined with
the current regime in the northwestern Gulf of Mexioo (Section 3-2.3.2),
generate a net longshore drift in a southwesterly direction at Freeport.
Sediments supplied by this longshore drift are derived from erosion of the
relic deltaic sediments of the inner continental shelf, from rivers dis-
charging into the Gulf and from erosion of the barrier island beaches. Some
sediment is also carried to or along the shoreface by tropical storms and
hurricanes. The northers create strong waves and complicated circulation
patterns, (resulting in resuspension of sediments), strong ebb currents,
and the neutralization of flood currents.
Moherek (1978) studied four different sediment types, containing
different quantities of sand, silt, and clay found near Galveston Bay. The
study was conducted to determine the bottom water velocity necessary to
cause rapid erosion of the bottom sediments; i.e., to cause movement of both
the suspended load and the bed load. He found a critical erosion velocity,
of 0.17 knots, with little variation among the sediment types. As noted in
Section 3*2.3>2, on an annual basis the bottom currents in the Freeport Area
3-33
-------
should have sustained velocities of at least twice the critical erosion
velocity for several consecutive days. This would cause significant sedi-
ment movement. At a bottom water speed of around 1 knots, which can be
expected every three years, massive bed load erosion can be expected.
The astronomic tidal components of the hydraulic regime are most
influential in the sedimentation processes by providing suspended sediment
through coastal tidal inlets. Wind-drift currents are the dominant sedi-
ment transport mechanism compared to the residual wave-drift components.
There is minimal wave-drift sediment transported along the Texas coast
under normal wave conditions, however, storm waves, which possess longer
periods, have substantial influence. In a few hours, hurricane and severe
tropical storms oan produce erosion and deposition equal to the effect of
normal conditions over months or even years. Storm tides are also important
as dispersal agents by intensifying the discharge of sediments from coastal
inlets. Also, rip currents and littoral currents along the coastal zone, in
addition to tidal currents, are important to regional sediment dispersal.
Motion of sediment in the littoral zone is initiated by wind
induced waves which then drive current systems that transport the sediment.
Breaker height is significant in determining the quantity and size of sand
to be set in motion, and breaker angle with the coast is a major factor in
determining the direction and rate of longshore transport. Onshore-off-
shore transport in the littoral zone is dictated by sediment size, wave
steepness, and beach slope. In general, high, steep waves transport
material offshore, while low waves move sediment onshore. Waves may break
and re-form three or four times across the shoreface producing an associated
line of breakers and breaker bars. These shell and sand breaker bars change
size and shift position as determined by the variable wave height. Varia-
tions in the wind direction and wave approach can mean that longshore
transport direction can vary hourly, daily, or seasonally with the wind.
Attempts to determine the fate of dredged material once it is
discharged into open water involve two basic considerations: (1) when and
where does the material reach the sea floor, and (2) once the material is on
the floor, how long will it remain and what percentage will remain in place?
In analyzing the first consideration, computer models have been
developed by the CE Waterways Experiment Station which provide estimates of
the short-term fate of dredge material in ocean disposal operations. The
models were developed from sophisticated numerical solutions to mathem-
atical models of transport and deposition of the material. Two separate
disposal methods have been modeled by the CE, one an instantaneous discharge
(hopper), the other a continuous moving or stationary source (hydraulic-
dredge pipeline). The models were developed by coupling the appropriate
short-term dynamic portions of the Koh-Chang oceanic disposal model (Koh
3-3*
-------
and Chang, 1973) with an extensive modification (originally developed by
Fischer) which predicts the fate of chemical waste in an estuary. The two
models are used to estimate the behavior of discharged material as it reacts
to currents, depth, turbulence, and shear stresses encountered in the
system during the fall to the sea floor. Since hopper dredges are most
likely to be used for construction dredging and future maintenance, the
instantaneous discharge model was used, as is discussed in Section 2.3.1.2.
Detailed technical discussions of both models are contained in Dredge
Material Research Program Technical Reports of the CE Waterways Experiment
Station (Brandsma and Divoky, 1976; Johnson and Holliday, 1978).
The second consideration, the fate of the material after disposal
and initial deposition, is of conoern to the marine environment and to the
engineering aspects of the dredging project. Once the dredged material is
discharged and settles to the bottom, its further movement or laok thereof,
will be a function of the nature of the material itself, as well as the
nature of the near-bottom current regime.
There has been little current data collected in the nearshore
waters of the Texas coast near Freeport. However, what is available has
been discussed in Section 3.2.3.2. Because of the sparseness of available
data, only generalizations as to the long-term fate of dredge material can
be made. However, dredging records from the maintenance of the Channel
indicate an average sediment volume of 1,000,000 cy/yr has been deposited
in the interim-designated disposal area. Estimates for the rate of sediment
transport have been made from dredging disposal records in a study by the CE
Waterways Experiment Station (Bastian, 1971) which addresses the effects of
open-water disposal on the bottom topography along the Texas Gulf ooast.
Contained in this study were dredging dates, volumes of dredged material and
the average elevation of the surveyed ODMDS. The results indicate that
significant mounding does not occur. In fact, a general decrease in eleva-
tion of the disposal sites was occurring and, therefore, removal rates must
approximate or exceed disposal rates. While, on the short-term, extensive
mounding Is expected from the disposal of the virgin material, the mound
will likely disappear in a few years, or sooner if a major storm ocours.
Because of the nature of the available data and the scarcity of
ourrent velocity and direction measurements from the project area, it is
difficult to make specific predictions of the transport rate and direction
of dredged material disposed of offshore. As discussed above, the general
trends are clear; i.e., sediment material erodes and is generally trans-
ported to the southwest. Storms, including hurrloanes, can cause massive
bedload erosion.
3-35
-------
3.3
BIOLOGICAL ENVIRONMENT
3.3.1 Plankton
Seadock (1976) reports quarterly sampling during 1973 of phyto-
plankton in the immediate project area. Diatoms were present in all
quarters and comprised most of the species collected. The dominant species
oollected are listed in Table 3-12. These are very similar to the dominant
species listed for the Galveston Bay System by Copeland and Fruh (1969).
Relatively high densities are maintained even in turbid water. Seadock
(1976) reports primary productivity estimates of 30.9 and 28.1 gm C/m /hr
at 6 and 29 miles off Freeport. They note these values are comparable with
literature reports for Texas and Louisiana waters. Chlorophyll measurement
in the fall generally increased from nearshore to offshore. The report
(Seadock, 1976) Indicates that the area from the nearshore to 30 miles
offshore is generally more productive than open Gulf of Mexico areas.
Plankton blooms were noted both during periods of increasing available
light and higher nutrient loads due to high river flows.
The dominant zooplankton species oollected offshore in the
vicinity of the project are listed in Table 3-13 (Seadock, 1976). The
number of taxa collected were relatively low during all seasons sampled.
Copepods were among the most abundant zooplankters at all stations during
all four quarters. Crustaoean nauplii were the dominant taxa in the winter
and fall samples. Lamelllbranch larvae were abundant during the spring and
fall seasons and were interpreted as indicating the presence of viable
offshore mollusk shell beds in the region. Overall abundance was rela-
tively low and considerable difference in numbers and composition was noted
between stations.
3.3.2 Benthos
Seadock (1976) reported the results of a benthlc sampling program
in which 296 species of organisms were collected at 116 stations. Seventy-
one species were present at ten or more stations. The benthic organisms
collected at the Gulf stations near Freeport, during the study, could be
divided into nearshore and offshore assemblages. Nearshore assemblages
occur within 5 miles of the Gulf shoreline, whereas the offshore
assemblages were found from 5 to 30 miles offshore. Nearshore assemblages
were not dominated by any taxonomic group, but rather several groups
(polyohaeta, ophiurodae, bivalvia, nemertea, gastropoda) were present in
roughly equal numbers. Generally, the nearshore species were similar to
those found in estuarlne assemblages. Offshore assemblages were dominated
by polychaetes. Twenty-seven of 35 species characterizing the offshore
assemblage were polychaetes. The most diverse and abundant samples were
oollected in areas of sand or shell substrate. Within their sampling
3-36
-------
TABLE 3-12
DOMINANT PHYTOPLANKTON SPECIES COLLECTED OFFSHORE
OF FREEPORT, TEXAS, DURING 1973 (FROM SEADOCK, 1976)
Winter
Spring
Chaetoceros didymus
Rhizosolenia alata
Thalasslothrlx dellcatula
Oscillatoria erythreae
Nitzschia pungens
Nitzschia seriata
Summer
Fall
Rhizosolenia calcar avis
Skeletonema costaturn
Rhizosolenia styliformes
Thalassiothrix dellcatula
Rhizosolenia alafca
Nitzschia pungens
Chaetoceras coarctatus
3-37
-------
TABLE 3-13
DOMINANT ZOOPLANKTON TAXA COLLECTED OFFSHORE
OF FREEPORT, TEXAS, DURING 1973 (FROM SEADOCK, 1976)
Winter
Spring
Copepoda
Copepoda
Crustacean nauplii
Lame1libranch larve
Oikopleuridae
Summer
Fall
Copepoda
Crustacean nauplii
Limacinildae
Copepoda
Cladocera
Brachyura zoea
Sagltta sp.
Limaciniidae
Lame1libranch larvae
3-38
-------
program, areas to the south of the proposed Seadock platform (which was to
be looated 31 miles south-southeast of Preeport) and off the mouth of the
Brazos River contained twice as many species and three times the abundance
of individuals as other offshore stations. Only the area off the Brazos
River would be included in the project area. The nearshore assemblages were
less diverse than offshore areas largely due to effects of environmental
fluctuations, primarily freshwater Inflow. Very little seasonal variation
was noted.
In a monitoring program in 1974 (CE, 1978), sampling was con-
ducted at sites up current (approximately 4.3 miles northeast), at, and
down current (approximately 5.3 miles southwest) of the interim-designated
ODMDS. Maoroinvertebrate samples were taken with a Van Veen grab and two
five-minute Otter Trawls. For the grab samples, 11 individuals represent-
ing 3 taxa, 13 individuals representing 5 taxa, and 9 individuals repre-
senting 2 taxa were found at the up-current, ODMDS and down-current sites,
respectively. In the same station sequence, 104 individuals representing
7 taxa, 245 individuals representing 13 taxa, and 82 individuals represent-
ing 8 taxa were found in the trawl samples. This sampling program followed
a dredging operation, oonducted 6 September 1973 through 22 January 1974,
during whloh over 1,000,000 cy of dredged material were discharged into the
disposal area.
Additionally, the CE oollected benthlc infauna1 and eplfaunal
data monthly between April 1976 and February 1977 at four ohannel stations
up-current, at, and down-current from the interim-designated disposal site,
and at two stations further offshore than the interim-designated site (CE,
1978). Organisms were collected on a No. 30 soil sieve (0.59 mm). For the
non-channel stations, the farthest offshore and deepest station (50 ft) had
the fewest total number of benthlc infauna (400) oollected during the
sampling, the lowest monthly maximum number of benthlc infauna (90) and the
lowest total apeoies diversity (Margalef's index, 15.2). The highest total
number of benthlc infauna (720) and the highest diversity (Margalef's
Index, 19.8) were at the down-current station, whloh was also the shallowest
station (22 ft). The highest monthly maximum (260) was at the ODMDS
station. Unfortunately, the unit area of sampling was not given. The trawl
data did not conform to the infaunal data exoept for the highest and lowest
diversity. The highest and lowest total number of organisms were at the up-
ourrent station and at the station Just offshore of the ODMDS, respectively.
The highest and lowest monthly maxima were at the up-current and down-
ourrent stations, respectively. A dredging operation was being oonducted
during November 1976, but the disposal site variation in terms of the number
of organisms and the diversity was not out of line with the variation whioh
occurred at other times or at other stations.
3.3.3 Nekton
The largest fraotion of the marine fishes in the proposed project
area is typloal of the temperate fauna largely dominated by members of the
3-39
-------
croaker family (Seiaenidae). Farther offshore in this region, fishes
typical of the tropical fauna, such as grunts (Pomadasyidae) and mojarras
(Gerreidae), are more adundant (Hoese and Moore, 1977). Young and larvae of
some of the more tropical species often make their way inshore, especially
during the summer. In addition to fishes, numerous crustaceans, especially
penaeid shrimp, utilize the offshore area to varying degrees, depending on
the season and life stages present.
3.3•^ Threatened and Endangered Species
In accordance with Section 7 of the Endangered Species Act, as
amended, the National Marine Fisheries Service (NMFS) has been contacted
concerning the listed and proposed threatened and endangered species within
the project area (see Coordination Section). NMFS identified ten species of
aquatic vertebrates that are considered endangered or threatened and which
may be present in the Texas marine environment: fin whale, humpback whale,
right whale, sel whale, sperm whale, green sea turtle, hawksbill sea turtle,
Kemp's ridley sea turtle, leatherback sea turtle, and loggerhead sea
turtle.
Listed in 50 CFR 17 (as revised 10 April 1987) are eight species
of terrestrial and aquatic vertebrates considered endangered or threatened
by the U.S. Fish and Wildlife Service (USFWS). These include the sperm,
finback, blue, and black right whales; brown pelican; Atlantic leatherback
and Atlantic Ridley turtles; and Caribbean manatee. Additionally, the
Texas Organization of Endangered Species (TOES) lists other species (TOES,
1984). TOES lists the Gulf streambeaked whale, goose-beaked whale, pygmy
sperm whale, dwarf sperm whale, pygmy killer whale, and diamondback
terrapin as threatened species. TOES also lists the loggerhead turtle as
endangered.
There are only a very few records of the whales and manatees
occurring along the Texas Gulf coast. Of eight cetaoeans listed as
threatened or endangered by USFWS, four are known to occur In waters off the
coast of Texas. Records Indicate that of these four species, the giant
sperm whale (Physeter catodon) is the most common along the Texas Coast
(Schmidly and Shane, 1978). Sperm whales apparently prefer deeper waters
and only approach shorelines oharaoterlzed by shelves that drop off rapidly
in depth. The gradual slope of Texas' continental shelf may account for the
fact that only four known stranding records of this species have been
reported for the State, in spite of the fact that sperm whales used to taken
regularly in the eastern Gulf of Mexico by whalers (Sohmidly and Shane,
1976). Of the four strandings on the Texas coast, one occurred near Sabine
Pass, one near the wreck of the Nioaragua on Padre Island, and two in the
vicinity of Port Isabel.
3-JJ0
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The blue whale (Balaenoptera musculus) is confirmed in Texas
waters on the basis of a stranding on the upper Texas Coast, although
several other sightings and strandings are probably attributable to this
species (Schmidly and Shane, 1978). Both of the other endangered ceteacean
species, the black right whale (Eubalaena glaoialls) and the common finback
whale (Balaenoptera physalus), are also known from Texas on the basis of
single records. The single right whale, which washed up in 1972 near
Freeport, Brazoria County, represents the westernmost record for this
species in the Gulf of Mexico (Schmidly and Shane, 1978). The single record
of a finback whale occurred in 1951, near Gilchrist in Chambers County,
Texas (Schmidly and Shane, 1978).
The West Indian manatee (Trichechus manatus) is an extremely rare
visitor to Texas coastal waters. The species has been recorded only four
times on the Texas Coast including one record at the mouth of the Rio Grande
(Davis, 1971). Of the Federally listed species, it is unlikely that any
would occur in the Freeport Area.
Of the five species of sea turtles occurring in Texas coastal
waters, the leatherback (Dermochelys corlacea), Kemp's ridley (Lepidochelys
kempi), and hawksbill (EretmochelysTmbrlcata) are considered endangered,
and the green turtle (Chelonia mydas) and loggerhead (Caretta caretta) are
olassified as threatened (USFWS, 1987).
The loggerhead is by far the most abundant sea turtle in Texas
waters, and the hawksbill the least abundant. According to the Sea Turtle
Stranding and Salvage Network (STSSN, 1981-1986), 528 turtles were washed
ashore on Texas beaches between 1981-1984. Of the 506 that were identified,
301 (59.5$) were loggerheads, 117 (29*) were Kemp's ridleys, 27 (5.3*) were
green turtles, 16 (3.2*) were hawksbills, and 15 (3$) were leatherbacks.
During the first nine months of 1986, 334 turtles were stranded, mainly
Kemp's ridley (57.5*) and the loggerhead (31.7*) (STSSN, 1986). This
increase over previous years is due to a variety of factors Including a more
efficient stranding network and a possibly lnoreased shrimping activity.
In addition, many of the ridley strandings were of head-started turtles
released off the Texas coast by the NMFS. As of January 1, 1987, 10,792
head-started ridleys have been released; 498 (4.6*) of them have been
subsequently recovered, including strandings (Sharon Manzella, NMFS,
Galveston, Texas pers. comm. to D. Green, Espey, Huston & Associates, Inc.
18 February 1987). Few data are available on the frequency of occurrence of
turtles specifically in the Freeport Area. Breeding activities of the
Atlantic ridley turtle have been reported on Padre Island, at least
150 miles southwest of Freeport, although a Mexican beach near Rancho
Nuevo, Mexico is the only known nesting area in the world for this species.
The TOES-listed diamondback terrapin could occur near Freeport, but its
primary habitat would be estuarlne.
3-41
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Brown pelicans, generally found further south, could traverse the
Freeport Area, but it Is unlikely that they would occur offshore near
Freeport.
3.3.5 Marine Sanctuaries and Special Biological Resource Areas
There are no marine sanctuaries near Freeport; however, two un-
named reefs and a fish haven/obstruction have been reported (OSFWS, 1982).
These areas are listed as adult concentration areas and provide sport
fishing for jacks, sheepshead, red snapper, bluefish, cobia, little tunny,
Spanish mackerel, and king mackerel. One area is located approximately
10 miles south and the other about 10 miles southwest of the intersection of
the Freeport Harbor Channel and the beach line. Both areas are in about
60 feet of water. Spawning activity for penaeid (commerical) shrimp,
especially white shrimp, can and does occur in the Freeport Area with a
white shrimp breeding area roughly ten miles southwest of the interim-
designated ODMDS (USFWS, 1982). White shrimp generally spawn exclusively
at depths of 120 feet or less. For white shrimp, spawning occurs at 45 feet
from spring to early fall and at 90-120 feet a few weeks earlier (Ringo,
1965). Brown shrimp generally spawn at 90 feet from March through April and
November through December. However, spawning shrimps are caught routinely
at all times of the year at depths of 150-360 feet (Ringo, 1965). Fischer
(1967) noted oonoentrations of post-larval penaeid shrimp between Cameron,
Louisiana and Freeport, Texas from January through April. This constituted
one of three areas of shrimp concentration along the Louisiana-Texas coast-
line; the other two being off Corpus Christ!, Texas and off Morgan City,
Louisiana. Thus the Freeport Area is located in, or very close to a region
of concentrated brown shrimp spawning, although this spawning primarily
occurs in fairly deep (90-foot) waters.
3.1 SOCIOECONOMIC ENVIRONMENT
3.^.1 Commercial and Reoreatlonal Fisheries
The most important fishery from poundage and value perspectives
In the project area is the penaeid shrimp fishery. Landings from Gulf of
Mexico grid areas 18 and 19, whioh include offshore areas from east of
Galveston Bay to below Pass Cavallo and, therefore, encompass the project
area, indicate commercial fisheries for black drum, flounder, Atlantic
oroaker, gafftopsail oatfish, sheepshead, whiting, mullet, Florida pompano,
oobia, grouper, snapper, blue orab and squid (Osburn et al., 1986). Of
these, only blaok drum, flounder, cobia, snapper and unclassified food fish
are caught in appreciable numbers comnercially. Most of the fish species
-------
listed above are caught recreationally, with the addition of red drum and
spotted seatrout. From 1977 through 198*1, the finfish catch from grid 18
generally declined whereas that from grid 19 remained similar or increased
slightly. Only red drum and spotted seatrout catch data demonstrated a
consistent downward trend in that time span. These species are no longer
fished commercially in Texas waters. Finfish catch for both grids 18 and 19
Increased in 1985. The exvessel value of the commercial catch (except
shrimp) from grid 18 generally ranged from $65,000 to $270,000 from 1977
through 1985, whereas the grid 19 dollar value was $75,000 to $90,000 per
year, in years with low catches of snapper, and from $137,000 to $470,000 in
years of high snapper catches (Osburn et al., 1986). There are no data to
indicate what fraction of the landings came from the project area. However,
species such as grouper, and snapper would not occur routinely in the
project area. Because grid areas 18 and 19 include offshore areas from east
of Galveston Bay to below Pass Cavallo (Matagorda Bay); it is Impossible to
speculate on the fraction of the landings which may be attributable to the
small project area. However, in 1971 and 1975, respectively, 7.5 million
pounds ($10.9 million) and 8.3 million pounds ($18.3 million) of shrimp
were taken off Preeport (CE, 1978). Grid areas 18 and 19 produced 10.2 and
12.5 million pounds of shrimp, respectively, in 1977 (NMFS, 1979). The
value of these catches were 22.6 and 29.5 million dollars for grids 18 and
19, respectively. Brown shrimp accounted for roughly 80$ of the pounds
caught, and white shrimp oomprised the bulk of the remaining catch.
Grids 16 and 19 historically produced greater catches than the lower Texas
coast grids and roughly equivalent catches with grid 17 to the east which
includes a portion of Louisiana. The dollar values of the catch from
grids 18 and 19 historically rank high compared to the entire Gulf of Hex loo
catch.
3.1.2 Shipping
The major industry in the Freeport area is the manufacture of
basic and intermediate chemicals. Therefore, the major shipping tonnage is
related to the transport of these items, primarily to Dow Chemioal Company
Plant A, Phillips Petroleum Company, Stouffer Chemioal Plant, and Seaway
Pipeline Company. The amount of this commerce increased after plant altera-
tions and expansions in 1966, even though the overall seagoing oommerce
remained fairly stable between 1959 and 1971 (CE, 1978). A steady increase
in total tonnage (see Table 3-14), due mainly to an increase in orude petro-
leum imports/receipts, occurred at Freeport and peaked in 1978 and again in
1981. The peroent of the total tonnage from foreign imports inoreased from
0.2% in 1970 to 69$ in 1978. All of the increases in imports/receipts are
partially due to increased petroleum importation at the Phillips Petroleum
oil terminal and tank farm for transfer to its Sweeney Refinery. Addi-
tionally, dry oargo vessels go up the Brazos Harbor Channel to the port
facilities of the Brazos River Harbor Navigation District. In 1976,
3-43
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TABLE 3-14
TONNAGE THROUGH FREEPORT HARBOR ENTRANCE AND JETTY CHANNELS
(SHORT TONS x 106)
Foreign
laports
For«iprn
Experts
Coastvlao
Receipts
Coastwise
Shipments
Crude
Petroleua
laports/
Reoelpts
Basle
ChMloal
Products
Exports/
Shipaents
Total
Tons
Total
Ton-
Hlles
1961
3.81
1962
*•31
1963
4.29
1964
5.19
1965
4.59
1966
4.36
1967
4.19
1966
4.63
1969
5.86
1970
0.01
1.12
0.12
1.05
—
1.05
5.28
25.1
1971
0.07
1.31
0.12
1.10
0.04
1.52
5.72
26.7
1972
0.27
1.17
0.18
1.29
0.19
1.61
5.98
28.0
1973
2.02
1.40
0.39
1.09
2.04
1.67
7.35
33.5
1974
1.76
1.45
0.77
1.23
2.06
1.74
8.90
41.4
1975
3-12
0.97
0.26
1.11
3.15
1.13
8.19
39.0
1976
4.5«
1.07
0.29
1.11
4.46
1.28
9.71
46.2
1977
10.14
1.28
0.25
1.10
9.98
1.50
15.33
73.8
1978
14.97
1.29
0.97
1.42
15.54
1.58
21.71
104.6
1979
12.81
1.41
1.72
1.15
14.00
1.82
19.98
95.6
1980
13.02
1.30
1.90
1.07
14.24
1.64
20.13
97.0
1981
12.89
1.20
4.41
1.19
16.34
1.45
23.36
110.0
1982
7.59
0.96
3.52
0.94
10.50
1.24
14.99
71.9
1983
8.44
0.68
4.12
0.53
12.21
0.98
15.67
76.00
1984
6.96
0.89
4.46
0.41
10.86
1.14
15.12
73.01
Source: CE (1970-1994).
3-44
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excluding those with less than 19-foot draft, 317 inbound and 339 outbound
tankers and 72 inbound and 87 outbound dry cargo vessels passed through the
Freeport Channel. In 1980, 111,600 tons of ootton, corn, oats, rice, and
wheat were exported from Freeport to foreign countries.
3.4.3 Beaches and Recreational Areas
Quintana is immediately to the southwest of the South Jetty,
Bryan Beach is to the southwest of Quintana Beaches, and Surfside is imme-
diately to the northeast of the North Jetty. Quintana Beach and Surfside
Beach have county amenities on the beaohes to facilitate swimming and boat-
ing in these areas. The beaches in the area are popular for surf fishing;
the Jetties are popular fishing areas. Quintana Beach is in the town of
Quintana, Surfside Beaoh in the town of Surfside, and Bryan Beaoh is managed
by the Texas Parks and Wildlife Department. All have fine-grained sand
beaches although acoess to Bryan Beach is not as good as for the other two.
Freeport also attracts sportfishing enthusiasts from the surrounding coun-
ties and areas, including Houston.
Other fishing spots in the area include the ooral heads and oil
platforms discussed earlier, both of which provide hard substrate for
Improved fishing.
3.4.4 Mineral Extraction and Transport
The only aspect of mineral extraction in the Freeport Area that
impacts the siting of an ODMDS is the presenoe of offshore platforms. There
are, however, four small (less than 20-inoh) gas pipelines whioh landfall in
the projeot area; three a few miles south of the Channel and one north. Two
of these are from a multiwell platform looated four to five miles south of
the Jetties. A large (greater than 20 lnoh) gas pipeline landfalls roughly
a mile and one-haIf north of the Jetties. The platforms are important both
as obstructions and fishery resource areas.
3.4.5 Cultural and Historic Sites
A oultural resources records search was conducted for the project
area. The records of the marine cultural resouroes data bank of the Texas
Antiquities Comnlttee (TAC) were reviewed for the identification of pre-
viously recorded oultural resouroes. These reoords consist of maps and
charts, oard and miscellaneous files, and computerized data. These reoords
were reviewed to identify and desoribe historically significant offshore
locations near Freeport. Historically significant looations were assigned
on the basis of a comparison of oharts prepared by the TAC from both primary
and secondary souroes.
3-^5
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The TAC charts are supported by a computerized data base which
provides the name of the vessel, the date it wrecked, and the State oil and
gas lease block where it is located. The records also provide the location
of untested magnetic anomalies. The computer data is supported by a card
file which provides additional information relating to the location, type
and size of vessel, circumstances of the wreck, and references. Sites
numbered above 1629 have not been entered in the computerized list and their
cards could not be located in the shipwreck files; therefore, some of the
resultant data are incomplete.
The review of the records of the marine cultural resources data
bank of the TAC resulted in the identification of 22 historically signif-
icant (more than 50 years old) locations. These locations were taken from
oharts and are approximate. Further identification of these locations,
along with recent shipwreck obstructions, appears on Figure 3-6 and
Table 3-15.
3.4.6 Military Restrictions
There are no military restrictions which would apply to the Free-
port Harbor ODMDS selection process.
3.4.7 Political Boundaries
There are no political boundaries near Freeport which would
affect site designation although the gulfward boundary of Texas extends out
to three marine leagues or 10.4 miles (Texas Senate Bill 1257, Title 2,
Subtitle A, Chapter 11). Any site suitable for dredged material disposal
would be well within the U.S. territorial sea which extends out to 200 miles
at Freeport.
3-46
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V)
£ £
.•» iS
r oa
x*
0 1 2 3 4 5 6 7
1 I I I I I I I
STATUTE MILES
ZJ
V,
IN
TRIM DCSCNATED
40S
*0'
Fig. 3-6
Historic Sites and Recent
Shipwreck Obstructions
3-47
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TABLE 3-15
LOCATIONS OF HISTORICAL
SIGNIFICANCE AND RECENT SHIPWRECKS
NEAR FREEPORT
Texas Antiquities
Name of
Date of
Committee Number
Vessel
Sinking
9H9
Acadia
102
Admiral Foot
1867
11105
Granfos
1886
11103
Barge #1
1889
112H
Mary Janette
1900
1351
Elizabeth
1835
1352
American
—
212
Dell-D
I960*
118H
Unknown
1969*
1*139
Fair Play
1892
irnn
General C.B.
1913
14113
Traveler
1908
11128
Sport
1898
1182
Billy P.
1969*
1187
Sea Bird
1969*
986
Katie Ross
1875
6H1
Alice
18811
889
Sea Bird
1967*
1073
Unknown
—
252
Unknown
—
1188
Unknown
1969*
1M27
Orlina
1897
3-48
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TABLE 3-15 (Concluded)
Texas Antiquities
Name of
Date of
Committee Number
Vessel
Sinking
883
Lavena
1959*
884
Sunrise
1966*
885
Kokomo
1961*
497
Texas Star
1956*
1550
Marion
1864
161
Captain Pete
1966*
82
America
1835
80
Tamaulipas
—
191
Colonel Rufus Ingalls
1897
625
Granite City
1865
971
Lady Byron
1845
974
Rodney
1840
1384
Aransas 1057
1887
1267
Selma
1868
1387
Mary
1884
1082
Belvadere
1837
596
Obstruction
1955*
* Reoent shipwreck obstructions.
3-49
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CHAPTER 4
ENVIRONMENTAL CONSEQUENCES
The environmental consequenoes of site designation will be dis-
cussed from two perspectives, even though some of the Information may be
repetitive. First, the preferred sites will be examined relative to the
five general criteria and the eleven specific factors (40 CFR 228.5 and
10 CFR 228.6(a), respectively). Then the classic NEPA approach will be
undertaken whioh will examine the environmental oonsequences of the action
on the different aspects of the Affected Environment.
4.1 REGULATORY CHARACTERIZATION
4.1.1 Five General Criteria
4.1.1.1 40 CFR 228.5(a)
The dumping of materials into the ooean will be per-
mitted only at sites or in areas selected to minimize
the interference of disposal activities with other
activities in the marine environment, particularly
avoiding areas of existing fisheries or shellflsheries,
and regions of heavy oonmerclal or reoreational naviga-
tion.
The preferred sites like the other nonexcluded areas, were
selected, including appropriate buffer zones, to avoid sport and commercial
fishing activities, as well as other areas of biological sensitivity. The
excluded areas Include a white shrimp breeding area, a sport and commercial
fishing harvest area, two reef areas and the Jetties, all with buffer zones;
platforms; submerged shipwrecks; and several single oil and/or gas
platforms. The buffer zones were sized on the basis of the physloal
movement of the disposal material, sinoe sediment analysis concluded that
the quality of the material proposed for dlsoharge met the oriterla of
40 CFR 227. The preferred sites are outside the Channel, Including the
navigation ohannel buffer zone, and they avoid known navigational
obs timet ions.
4.1.1.2 40 CFR 228.5(b)
Locations and boundaries of disposal sites will be so
ohosen that temporary perturbations in water quality or
other environmental oondltlons during initial mixing
4-1
-------
caused by disposal operations anywhere within the site
can be expected to be reduced to normal ambient sea-
water levels or to undetectable contaminant
concentrations or effects before reaching any beach,
shoreline, marine sanctuary, or known geographically
limited fishery or shellflshery.
The results of the ohemlcal analyses and toxicity studies
indicate that the material which has been dredged in the past has been
acceptable for ocean disposal under 40 CFR 227. The biota of the ZSF is
healthy. While toxicity tests have not been conducted for the virgin
sediments, there is no evidence to suggest that they would not meet the
criteria of 40 CFR 227 and ohemlcal analysis and experience with other
Texas Gulf Coast areas, including the nearby Qalveston Harbor Channels,
support an expectation that the virgin sediment would be acceptable for
ocean disposal. The appropriate sizes for the buffer zones and for the
preferred sites are based on the sediment transport information and the
physloal oceanographic characterization of the Freeport Area. These,
combined with the information on the expected quality of the material to be
dredged as discussed above, ensure that perturbations oaused by disposal
would be reduced to ambient conditions at the boundaries of the site.
4.1.1.3 40 CFR 228.5(c)
If at any time during or after disposal site evaluation
studies, it is determined that existing disposal sites
presently approved on an interim basis for ocean
dumping do not meet the criteria for site selection set
forth in 228.5-228.6, the use of such sites will be
terminated as soon as suitable alternative disposal
sites can be designated.
Although Included in the General Criteria, this item is not
really a criterion for site designation, and, in fact, the exercise for
which this document was written, is designed to answer the question raised
by 40 CFR 228.5 (c). Additionally, extensive monitoring and surveillance
programs including bathymetrlo soans; water, sediment and elutriate
ohemistry; bloassays; bioaooumulatlon studies; and benthlo infauna1
analyses should provide warning of potential problems. However, the
results of the exclusion analysis indicate that, should the preferred sites
be found, in the future, to be non-suitable and de-designation of the
preferred sites prove desirable, other areas are available and suitable for
use as an ODMDS.
4-2
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4.1.1.4 40 CFR 228.5(d)
The sizes of ocean disposal sites will be limited in
order to localize for identification and oontrol any
immediate adverse impacts and to permit the implementa-
tion of effective monitoring and surveillance programs
to prevent adverse long-range impacts. The size, con-
figuration, and looation of any disposal site will be
determined as a part of the disposal site evaluation or
designation study.
The sizes of the sites are as small as possible to meet reasonably
the oriteria stated at 40 CFR 228.5 and 228.6(a). The determined size for
the virgin material site is 3*49 square statute miles (2.64 square nautical
miles) while that for the future maintenance material site is 2.02 square
statute miles (1.53 square nautical miles) versus 0.53 square statute miles
for the interim-designated site. The monitoring program noted in the
previous section should provide adequate surveillance to prevent adverse
long-range Impacts.
4.1.1.5 40 CFR 228.5(e)
EPA will, wherever feasible, designate ocean dumping
sites beyond the edge of the continental shelf and
other such sites that have been historically used.
Cost, safety and time factors plus difficulties with monitoring
and surveillance dlotate that the distanoe to the edge of the continental
shelf at Freeport precludes the use of any 0DMDS off the shelf. Addition-
ally, the laok of resilience of the deep-ooean benthic community and the
grain size disparity between the material to be discharged and the deep-
ocean sediments off Freeport indicate that an off-shelf disposal site would
cause severe impacts to the off-shelf benthlo community. No advantage to an
off-shelf site was noted. The existing interim-designated ODMDS was in the
excluded area and could not be selected. There are no other historically-
used sites within the ZSF.
4.1.2 Eleven Specific Factors
40 CFR 228.6(a) states that the factors included below as Sec-
tions 4.1.2.1 through 4.1.2.11 will be considered in the selection process
for site designation.
4.1.2.1 40 CFR 228.6(a)(1)
Geographical position, depth of water, bottom topog-
raphy, and distanoe from ooast.
4-3
-------
The preferred site for the virgin material disposal, as deter-
mined in Chapter 2, is bounded by the following coordinates (Figure 2-17):
28° 51* 22" N, 95° 11' 25" W, 28° 50* 28" N, 95° 13' 30" W,
28° 48' 58" N, 95° 15' 24" W, 28° 19' 55" N, 95° 16' 19" W.
The water depth at the preferred site ranges from 51 to 63 feet
(Figure 3-3), the bottom topography is flat and the preferred virgin
material disposal site is approximately 6 miles from the coast at its
closest point.
The preferred maintenance material disposal site is bounded by:
28° 54* 00" N, 95° 15' 49" W; 28° 53' 28" N, 95° 15* 16" W;
28 52' 00" N, 95 16' 59" W; 28 52' 32" N, 95 17' 52" W.
Hater depths range from 31 to 38 feet and the site is approximately three
miles from shore, at its closest point.
4.1.2.2 40 CFR 228.6 (a)(2)
Location in relation to breeding, spawning, nursery,
feeding or passage areas of living resources in adult
or Juvenile phases.
At the southeast border of the ZSF, there is a white shrimp
breeding area, a sport and commercial fishing harvest area, and a reef area,
which are excluded, including buffer zones. At the northeast border, there
is a small collection of coral heads (reefs), providing habitat which
improves fishing. This area and the Jetties, plus buffer zones are
excluded. Also excluded are lighted platforms and non-submerged shipwrecks
which improve fishing.
4.1.2.3 40 CFR 228.6(a)(3)
Location in relation to beaches or other amenity areas.
The preferred sites for virgin and maintenance material disposal
are roughly 6 miles or 2.5 miles, respectively, from beaohes or other
amenity areas.
4.1.2.4 40 CFR 228.6(a)(4)
Types and quantities of wastes proposed to be disposed
of and proposed methods of release, inoluding methods
of paokaglng the waste, If any.
4-4
-------
Virgin construction material (5.1 mcy) only will be discharged
into the virgin material ODMDS. Only maintenance dredged material from the
Freeport Harbor Entrance and Jetty Channels will be disposed in the mainte-
nance material ODMDS. Historically, an average of one million cy/yr is
dredged from the ohannel at roughly ten-month intervals. This material has
historically been transported by hopper dredges but could be transported by
pipeline. With the proposed modifications, it is anticipated that future
maintenance material will equal 2.1 mcy annually. Based on chemical
analyses of both virgin and maintenance and biological toxicity studies of
past maintenance material which indicated no problems with the accept-
ability of these materials for ocean disposal, it was concluded that no
special location or precautions would be necessary for the disposal of the
materials to be dredged except that, based on grain size analyses, the
virgin material was most compatible with the silty-clay regime while the
maintenance material was most compatible with the silty-sand or
sand/silt/clay regimes.
*4.1.2.5 40 CFR 228.6(a)(5)
Feasibility of surveillance and monitoring.
The preferred sites are amenable to surveillance and monitoring.
The proposed monitoring and surveillance program for the virgin material
consists of (1) a method for recording the looation of each discharge;
(2) bathymetric surveys; and (3) grain size analysis, sediment chemistry
characterization and benthic infaunal analysis at selected stations
(Figure 2-19). For future maintenance material, the program consists of
water, sediment and elutriate ohemistry; bioassays; bioaccumulation
studies; and benthic infaunal analyses.
4.1.2.6 40 CFR 228.6(a)(6)
Dispersal, horizontal transport, and vertical mixing
characteristics of the area, including prevailing cur-
rent velocity, if any.
These physical oceanographio parameters were used (1) to develop
the necessary buffer zones for the exclusion analysis and (2) to determine
the minimum size of the preferred site. Predominant longshore currents, and
thus predominant longshore transport, is to the southwest. Long-term
mounding has not historically ocourred. Therefore, steady longshore trans-
port and occasional storms, including hurricanes, remove the disposed
material from the site. Both ODMDSs were sized on the basis of modeling of
short-term transport.
4-5
-------
4.1.2.7 MO CFR 228.6(a)(7)
Existence and effects of current and previous dis-
charges and dumping in the area (including cumulative
effects).
The discussion of the results of chemical and bioassay testing of
past maintenance material and material from the existing ODMDS plus chemi-
cal analyses of water from the area concluded that there were no indications
of water or sediment quality problems in the ZSF, including the preferred
sites. Testing of past maintenance material indicates that it was accept-
able for ocean disposal under 40 CFR 227. Studies of the benthos at the
interim-designated ODMDS and nearby areas have not indicated any signifi-
cant decrease or change in composition of the benthos at the ODMDS.
4.1.2.8 40 CFR 228.6(a)(8)
Interference with shipping, fishing, recreation,
mineral extraction, desalination, fish and shellfish
culture, areas of special scientific importance and
other legitimate uses of the ocean.
The items from the above list which are pertinent to the Freeport
ODMDS are shipping, mineral extraction, commercial and recreational
fishing, recreational areas and historic sites. The preferred sites were
selected so that their use will not interfere with other legitimate uses of
the ocean since the exclusion process was designed to prevent the selection
of sites which would interfere. Disposal operations in the past have not
interfered with other uses.
4.1.2.9 40 CFR 228.6(a)(9)
Existing water quality and ecology of the site as
determined by available data or by trend assessment or
baseline surveys.
Monitoring studies have shown only short-term water column
perturbations of turbidity, and perhaps COD, which resulted from disposal
operations. No short-term sediment quality perturbation oould be direotly
related to disposal operations. In general, the water and sediment quality
is good throughout the ZSF, including the interim-designated ODMDS. This
indicates that there have been no long-term impacts on water and sediment
quality. As noted in the previous section, there also appear to be no long-
term impacts on the benthos at the interim-designated ODMDS. The available
data were used to determine the preferred sites.
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4.1.2.10 HO CFR 228.6(a)(10)
Potentiality for the development or recruitment of
nuisance species in the disposal site.
With a disturbance to any benthic community, initial recoloniza-
tion will be by opportunistic species. However, these species are not
nuisance species in the sense that they would interfere with other legiti-
mate uses of the ocean or that they are human pathogens. The disposal of
virgin or maintenance material in the past has not, and disposal of the
proposed material should not, attract or promote the development or
recruitment of nuisance species.
4.1.2.11 40 CFR 228.6(a)(11)
Existence of or in close proximity to the site of sig-
nificant natural or cultural features of historical
Importance.
A discussion of the location and types of areas and features of
historical importance was presented and these areas are excluded from
consideration. The nearest site of historical importance to the virgin
material preferred site Is approximately 0.5 miles away from the edge of
this site in a cross-current direotion. For the maintenance material site,
the nearest site of historical Importance Is roughly 1.2 miles from the edge
of the site in a cross-current direction. Therefore, use of the preferred
sites would not Impact sites of historical importance.
4.2 ENVIRONMENTAL CHARACTERIZATION
4.2.1 Physical Environment
Of the areas discussed in the Physical Environment Section
(Section 3*2), there will be no Impacts on nearby land areas, climatology,
or meteorology from designation of the preferred sites.
4.2.1.1 Ooeanography
4.2.1.1.1 Bathymetry
There will always be localized and temporary changes in bathy-
metry caused by dredged material disposal. While, on the short term,
extensive mounding is expected from the disposal of the virgin material, the
mounds will likely disappear in a few years, or sooner if a major storm
occurs.
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Because of the nature of the available data and the soarcity of
current velocity and direction measurements from the project area, It is not
realistic to make exact predictions of the transport rate and direction of
dredged material discharged offshore. However, the general trends are
clear; I.e., sediment material erodes and is generally transported to the
southwest. Storms, including hurricanes, can cause massive bedload
erosion.
It is expected that mounding of up to 10.5 feet (virgin material)
and 3*1 feet (maintenance material) may occur. However, studies of the
existing ODMDS Indicate that, over the long term, there is little or no
buildup of materials. The preferred sites were selected so that the tempo-
rary reduction in water depth and long-term transport of material from the
site would oause no adverse impacts.
1.2.1.1.2 Circulation and Mixing
The determined area of both of the preferred sites is small
oompared to the shelf area off Freeport. As noted above, changes in bathy-
metry are small and temporary. Therefore the disposal of dredged material
anywhere in the nonexcluded part of the ZSF would have negligible impact on
the circulation and mixing of shelf waters.
4.2.1.2 Hater Quality
Possible effeots on water quality relative to dissolved oxygen
(DO), biochemical oxygen demand (BOD), oil and grease, heavy metals, pesti-
cides and nutrients are disoussed below.
The DO concentration in the water column at a dredged material
disposal site may temporarily decrease (Brown and Clark, 1968; Pearce,
1972; Hopkins, 1972), not change (Hay, 1973), or increase (Vindom, 1972;
Wakeman, 1971). May (1973) found that although the water column DO did not
change, a temporary decrease was found at the water/sediment interface in
the areas of mud flow. He found little apparent difference in the immediate
oxygen demand between recently deposited sediments from dredged material
disposal and other sediments. May (1973), Jones and Lee (1978), Peddicord
(1979), and Lee (1976) agree that even with sediments which have a high
total oxygen demand, as measured in the laboratory, oxygen depletion upon
disposal is not likely to cause adverse environmental Impacts because only a
small part of the oxygen demand is exerted at disposal.
The most obvious result of dredged material disposal to the water
oolumn Is turbidity whioh has been shown to reduoe primary production in
laboratory studies (Sherk, 1971). Field studies, however, have shown
essentially no biologioal impaots from turbidity (Odum and Wilson, 1962;
4-8
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May, 1973)* May (1973) found that on a still day, the turbidity plume was
detectable, from an aircraft, more than a mile down current. On days when
winds caused natural turbidity in an estuarine system, the plume was not
detectable more than a few hundred yards down current from an active dredge.
He also noted that because the small size of the particles, responsible for
an extended turbidity, causes them to behave differently than most of the
disposed material, the turbidity plume has little relationship to dredged
sediment distribution, except near the dredge. Impacts from increased
turbidity would be less nearshore, where higher turbidity is common, than
they would be farther offshore in more pristine water.
May (1973) found that total suspended solids (TSS) was reduced by
92% within 100 feet of the discharge point, by 98? at 200 feet, and that
concentrations above 100 mg/1 were seldom found beyond 400 feet from the
disposal point. Therefore, unless contaminants are released from the dis-
charged sediments, more than short-term, local impacts could not be
expected from the TSS resulting from discharge.
Chemical analyses of elutriates made with past virgin maintenance
material indicate that no significant release of constituents from the
sediment can be expected during dredging and disposal. Additionally, exam-
ination of water at the disposal site yielded no indications of water
quality problems.
DeCoursey and Vernberg (197*0 noted that the concentration of
some constituents in the settling basins of contained disposal material
sites, and the release of these constituents in the effluent from the sites
in concentrations greater than background, would be expected in open-bay
disposal. However, the potential contaminants they noted were nitrogen,
phosphorus, and manganese. Considering the dynamios of most nearshore
areas, localized, short-term increases of phosphorus and nitrogen would not
be expected to be toxic and might offset the potential for reduced primary
productivity caused by associated turbidity (Morton, 1977).
Manganese is the only trace metal found by Jones and Lee (1978) to
be released from sediments in significant amounts, using the elutriate
test. However, in a long-term aerobic leaching study involving 32 dif-
ferent dredged material samples, Brannon et al. (1978) found manganese and
ammonia to be lower in the leaohate that those in the initial disposal site
waters, indicating an active removal of these parameters from the water
column. They also found the elutriate test to be a good prediction of long-
term net release of constituents from sediments under aerobic conditions.
Brannon et al. (1978) state that "worst case evaluations of the potential
effects of contaminant releases, oonducted by comparing results of this
study with the most stringent water quality criteria available, indloated
that sediments used in this study would not be expected to oause significant
long-term water quality problems."
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In sutmnary, water quality Impacts from dredged material disposal
anywhere in the nonexoluded part of the ZSF would be temporary, localized
and equivalent.
4.2.1.3 Sediment Quality and Characteristics
Chemical analyses of virgin sediments from the Preeport Channels,
and of elutriates made from those sediments, Indicate no cause for ooncern.
Bioassays and bioaooumulation studies on sediments from the nearby
Galveston Entrance, Outer Bar, Inner Bar, and Jetty Channels have lndioated
that those sediments were acceptable, under 40 CFR 227, for ocean disposal.
The preferred site for virgin material was plaoed, to the extent possible,
in the silty-clay regime to aatoh the grain size of the bottom sediments,
with that of the virgin material.
Past maintenance material, the quality of whioh was determined by
ohemical analyses and bioassays, was acceptable for ocean disposal under
40 CFR 227. There are no sediment quality problems at the existing ODMDS
nor at surrounding areas. No detrimental iapaots on bottom sediments would
be expected from the disposal of maintenance material from the Freeport
Harbor Channel. The preferred site was plaoed as near to the sllty-sand
regime as possible.
4.2.2 Blologloal Environment
It should be noted that the biologioal impacts whioh are dis-
cussed in this document are the result of dredge disposal, not site designa-
tion per se, especially sinoe non-dredging and non-disposal of dredged
materials are not alternatives to the aotion. The selection prooess used to
determine the preferred site inoluded minimizing impaots to those items
listed at 40 CFR 228.5 and 228.6(a).
4.2.2.1 Plankton
The impact of designation of the preferred sites on phytoplankton
would probably be greater than that associated with designation of more
offshore (i.e., greater than 30 miles) sites sinoe Seadock (1976) found
more productivity within 30 miles of the ooast. There would be both nega-
tive and positive impacts. A localized inorease in turbidity would ocour,
which has been found to decrease phytoplankton production in laboratory
studies (Sherk, 1971). Conversely, the deorease in production, presumably
from deoreased available light, has been found to be offset by increased
nutrient content (Morton, 1977)* In past studies of the lmpaots of dredged
material disposal from turbidity and nutrient release, the effects are both
looalized and temporary (May, 1973; Odum and Wilson, 1962; Brannon et al.,
1978). Thus, due to the reproductive oapacity and natural variation in
4-10
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phytoplankton populations, the impaots of dredged material disposal any-
where within the ZSF are not expected to be significant and, therefore,
Impacts at the preferred sites are not expected to be significantly dif-
ferent from those at any other part of the ZSF.
4.2.2.2 Benthos
1.2.2.2.1 Virgin Material
No constituents were found in the virgin sediments which would
lead to an expectation that toxic impacts to benthos would occur. Addition-
ally, virgin materials from other offshore channels, including the nearby
Galveston Entrance, Outer Bar, Inner Bar and Jetty Channels, have shown no
potential for toxic impacts to the benthos.
1.2.2.2.2 Maintenance Material
There is no apparent difference in the benthic community at the
interim-designated ODMDS and that in the natural bottom sediments near the
existing site (CE, 1978). This is probably due to the fact that the
maintenance material from the Freeport Harbor Channel which has been
disposed of in the ocean does not contain a high sand content (less than
30%, Table 3-7) and, therefore, is similar to normal offshore sediments in
the Freeport Area (Figure 3-5) although it would appear to be slightly
sandier than the silty-clay sediment regime. No detected impact has
oocurred at the interim-designated ODMDS, but, the interim-designated site
is not in the available area. However, the impact of using the preferred
maintenance material site would be expected to be less than or equal to that
at other areas in the nonexcluded portion of the ZSF. Based on the chemical
analysis of, and bioassays conducted with, past maintenance material, no
chronic impacts to the benthos are expected from exposure to contaminants,
whether in the water, at the water-sediment interface or in the disposed
sediments. The Impact from burial would be expected to be slightly less at
a nearshore site since the nearshore area is naturally more turbulent than
the deeper areas of the ZSF and therefore is inhabited by a more resilient,
opportunistic community. The site is as near to shore as is possible.
1.2.2.3 Nekton
Wright (1978) indicates that nekton are not directly affeoted by
dredged material disposal sinoe they oan avoid areas of high turbidity. The
benthos at the site, which would have been used as a food source, will be
lost, but the area of the site Is as small as is feasible and is small
compared to the offshore area near Freeport. The elutriate analyses and
bioassessments with the proposed virgin and maintenance material yield no
1-11
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expectation of short-term toxicity from disposal operations. Therefore, no
significant impacts to the nekton of the area from the proposed disposal
operations are expected.
4.2.2.4 Threatened and Endangered Species - Determination of Effect
In accordance with Section 7 of the Endangered Speoles Act, as
amended, the NMFS has been contacted concerning the proposed project (see
Coordination Section). The following species have been identified as
occurring in the area:
Listed Species
green sea turtle
Kemp's (Atlantic)
ridley sea turtle
leatherbaok sea turtle
loggerhead sea turtle
hawksbill sea turtle
fin whale
humpback whale
right whale
sei whale
sperm whale
Scientific Name
Chelonla mydas
Lepldochelys kempl
Dermochelys corlacea
Caretta caretta
Eretmochelys imbrlcata
Balaenoptera physalus
Megaptera novaeangllae
Eubaleana glacialls
Balaenoptera borealls
Physeter catodon
Status Date Listed
Th 7/28/78
E 12/2/70
E 6/02/70
Th 7/28/78
E 6/02/70
E 12/02/70
E 12/02/70
E 12/02/70
E 12/02/70
E 12/02/70
While rare off Texas, the above listed species of sea turtles are
present in the project area during certain portions of the year. In
addition, these species inhabit inland and shallow water to feed. The
listed whales, in contrast, are found in deep ooeanic water off the conti-
nental slope. The effects of disposing dredged material at the proposed
site inolude: 1) a collision potential from the dredge vessel; 2) the
deposition of dredged material on food souroes, and 3) the possibility of
trash and debris from the dredge operation. Regarding the deposition of
dredged material, significant short-term mounding of oonstruotlon material
may oocur. However, considering the mobility of the species, available food
sources would not seriously be reduced.
Regarding the vessel and trash deposition, it is the oombined
effeot of many marine activities (e.g., oil spills, oil and gas exploration,
oommercial fishing, trash, marine transportation, etc.) that oonstltute a
hazard and not a single activity such as a hopper dredge operation. All of
these activities, combined with natural predation and development on land,
contribute to and result in a cumulative adverse Impact on sea turtles (DOI,
1987). EPA has determined, however, that the proposed site designation does
not oonstltute an adverse Impact on the listed sea turtles. Based on the
shallow-water location of the disposal site and the deep water preferenoe of
4-12
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the whale species, EPA has also determined that no adverse effect to the
listed whale species would result from EPA's proposed action.
4.2.2.5 Marine Sanctuaries and Special Biological Resource Areas
A white shrimp breeding area, a sport and commercial harvest
area, a reef area, the Jetties and other fishing areas were excluded in the
selection process, including, where appropriate, protective buffer zones.
Therefore, any site looated inside the nonexcluded area would not be
expected to impact any special biological resource area. There are no
marine sanctuaries in the ZSF.
4.2.3 Socioeconomic Environment
The selection process used to generate the excluded and non-
excluded areas of the ZSF was oonducted to exclude other features and
amenities. Beaohes are exluded, including appropriate buffer zones. All
known cultural and historic sites were excluded. Accordingly, there should
be no Impacts to other features and amenities from dredged material disposal
anywhere within the nonexcluded portion of the ZSF. The site was selected
to avoid oil and gas production facilities and, therefore, no Impacts on
mineral extraction are expected.
4.2.3.1 Commercial and Recreational Fisheries
Wright (1978) indioates that nekton, including commercial and
recreational species, are not directly affected by dredged material dis-
posal since they oan avoid areas of high turbidity. The benthos at the
sites, which would have been used as a food souroe, will be lost, but the
size of the sites is as small as is feasible. The elutriate analyses and
bioassessments give no indication of short-term toxicity from disposal
operations. The Jetties, two reefs, a sport and commercial fishing harvest
area, and a white shrimp breeding area, including appropriate buffer zones,
and all oil platforms were excluded to proteot reoreational fisheries.
Therefore, no significant Impacts to commercial and reoreational fisheries
are expected should any site in the ZSF be selected for designation.
4.2.3*2 Shipping
Impacts to shipping are not expeoted since the navigation channel
buffer zone was used to help looate the preferred site for maintenance
material. This buffer zone, while developed for non-navigational safety
reasons, does provide 1,000 feet between the toe of the ohannel and the edge
of the site, thus removing the hopper dredge, during disposal, from possible
ship traffic. The virgin material preferred site is outside of navigation
fairways.
4-13
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4.3
ADVERSE ENVIRONMENTAL IMPACTS WHICH CANNOT BE AVOIDED
Ocean disposal cannot legally occur without site designation and,
therefore, there are a number of unavoidable environmental impacts which
result from the disposal of dredged material; e.g., increase in turbidity
and suspended solids; release of minor quantities of heavy metals, oil and
grease and nutrients; a ohange in dissolved oxygen content and smothering of
the benthos. However, these impacts will result from the disposal dredged
material no matter where the disposal site is located. The preferred sites
were selected to minimize impacts to the extent possible. However, certain
impacts will ooour, most notably the temporary loss of most of the benthic
infauna in the actual discharge areas. However, recolonization can be
expected shortly after the disposal of virgin material ceases and between
maintenance dredging intervals, as is the case with the interim-designated
ODMDS. Complete reoovery can be expected at the virgin material site.
tl.il THE RELATIONSHIP BETWEEN LOCAL SHORT-TERM USES OF THE
ENVIRONMENT AND THE MAINTENANCE AND ENHANCEMENT OF
LONG-TERM PRODUCTIVITY
The No-Action Alternative was found not to be viable, therefore,
no disposal is not an alternative to the action. For site designation to
reduce the impact of short-term uses of the environment (e.g., dredged
material disposal) to the long-term productivity of the environment, the
sites which are designated must be the sites whioh have the fewest impacts
on the long-term productivity of the area. As discussed in detail in
Sections 4.1 and >1.2 and summarized in Section 4.2.5, the preferred sites
were selected to fulfill this obligation.
4.5 ANY IRREVERSIBLE OR IRRETRIEVABLE COMMITMENT OF
RESOURCES
Final designation of the preferred sites would commit the benthic
infauna in the disoharge area of the virgin material ODMDS, during oonstruc
tion, and of the maintenance material ODMDS, at roughly one-year Intervals
after initiation of maintenance material disposal. The resources asso-
ciated with the monitoring program; e.g., manpower, dlesel fuel, sampling
gear, and boat-time would be committed during monitoring.
4-14
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5.0 COORDINATION
EPA's Notice of Intent for EIS preparation on this site
designation appeared in the Federal Register dated .
The notice of availability of this Draft EIS in the Federal
Register initiates a 15-day review and comment period. Copies of the Draft
EIS were sent to various federal, state and local agencies and organizations
for review. All substantive comments received on the Draft EIS will be
considered by EPA in preparing the Final EIS. A 30-day review period is
associated with the Final EIS.
Rulemaking Is also required for site designation. In order to
establish an ocean disposal site, EPA oust prepare proposed and final rules
for the project. These rules will be published in the Federal Register.
Significant correspondence for this project is Included on the
following pages.
5-1
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6.0 LIST OF PREPARERS
Principal Authors
Joe Swick (EPA, Region VI)
B.S., Biology
Richard Medina
(CE, Galveston District)
B.S., Oceanography
M.S., Environmental Management
Martin Arhelger (EH&A)
B.S., Chemistry
M.S., Oceanography
Experience
Environmental Impact
Assessment, Ocean Dumping
Site Designation for
Dredged Material
Environmental Impact
Assessment, Ocean Dumping
Site Designation for
Dredged Material
Dredging and Disposal,
Environmental Impact
Assessment
Dredged Material Disposal
Impacts, Environmental
Impact Assessment
Darlene Coulson (EPA, Region VI)
B.S., Biology
George Ward, Ph.D. (EH&A) Oceanography, Coastal
B.A., Mathematics Processes, Meteorology
M.A., Mathematics
Ph.D., Atmospheric Sciences
James Wiersema (EH&A) Fisheries
B.S., Biology
M.S., Biology
Gilbert Ward (EH&A)
B.S., Geology
Coastal Processes
Contribution to EIS
EPA Project Officer
EPA Project Officer
CE Project Manager, Study
Coordination, Cost Analyses
EH&A Project Manager, Report
Preparation, Alternatives
Analysis, Water and Sediment
Quality Impacts Analysis
Sediment Transport, Circulation
and Mixing, Climatology
Biological Environmental Charac
terization and Impacts Analysis
Sediment Transport, Circulation
and Mixing
-------
6.0 LIST OF PREPARERS (Concluded)
Principal Authors Experience
Jack Irion (EH&A) Archaeology, Anthropology
B.A., Anthropology
M.A., Anthropology
David Thonas (EH&A) Aquatic Biology
B.S., Environmental
Management
Patricia McCoy (EH&A) Coastal Ecology
B.A., Earth Science/Education
M.A., Zoology/Marine Science
Contribution to EIS
Cultural and Historic Resources
Biological Environmental Charac-
terization, Report Preparation
Report Preparation
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7.0 LITERATURE CITED
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Program Technioal Report D-78-7, Contraot No. DACW 39-76-C-0105
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Brown, C. L. and R. Clark. 1968. Observations on dredging and dissolved
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Management.
Copeland, B.J. and E.G. Fruh. 1969. Biological-eoological studies of
Galveston Bay. Report to Texas Water Quality Board Control IAC
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DeCoursey, P. J. and W. B. Vernberg. 1974. The effeot of dredging in a
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abundance. Bep., Bur. Coon. Fish., Biol., Lab. Galveston FY 1966,
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Gabrysch, R.K. and Bonnet, C.W. 1974. Land surfaoe subsidence in the area
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Hall, G.L. 1976. Sediment transport processes in the nearshore water
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Harper, D.E., Jr. 1977. Distribution and abundanoe of maorobenthlo and
meiobenthlc organisms, pp. 175-274. In: Environmental assessment of
an active oil field in the northwestern Gulf of Mexico, 1976-1977.
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description and climatology. Texas A&M University. Publ.
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Louisiana and adjaoent waters. Texas A&M University Press. 327 pp.
Hopkins, T. S. 1972. The effeots of physical alteration on water quality
in Mulatto Bayou, Excambia Bay. Quarterly Journal Florida Aoademy of
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Johnson, B.H. and B. W. Holliday. 1978. Evaluation and calibration of the
Tetra Teoh dredged material disposal models based on field data.
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Engineer Waterways Experiment Station, Vioksburg, Miss.
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dredged sediments and environmental Impact of open-water dredged
material disposal. Technloal Report D-78-45, U.S. Arny Waterways
Experiment Station, Vioksburg, Mississippi. 217 pp.
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7-8
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APPENDIX A
MODELING DREDGED MATERIAL DISTRIBUTION
A-1
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APPENDIX A
MODELING DREDGED MATERIAL DISTRIBUTION
The disposition of dredged material was simulated using an
updated version of a 1976 model, Dredged Material Pate (DMP), developed for
the U.S. Army Corps of Engineers through the Dredged Material Research
Program by Tetra Tech., Ino. (Brandsma, et al., 1976). The modifications to
this model were made in the mid-1980's by Dr. Billy H. Johnson of the
Waterways Experiment Station (WES) of the U.S. Army Corps of Engineers.
This program models the initial behavior and final disposition of
dredge material deposited "instantaneously" at the site of interest through
the doors of a hopper dredge. The DMF model assumes that this prooedure may
be broken into three phases: (1) convective descent, during which the
discharge cloud falls under the influence of gravity; (2) dynamic collapse,
ocourring when the descending oloud impacts the bottom or arrives at a level
of neutral buoyancy at whioh point the descent is retarded and horizontal
spreading dominates; and (3) long-term passive dispersion, commencing when
the material transport and spreading are determined more by ambient
currents and turbulence than by the dynamics of the disposal operation
(Johnson and Holliday, 1978).
When modeling oonvective descent of an instantaneous discharge, a
single cloud of hemispherical shape is assumed to be instantaneously
released. Since the solids concentration in the discharge material is
usually fairly low, the cloud is assumed to behave as a dense liquid,
following equations that govern motion, i.e., conservation of mass,
momentum, and vortlcity.
During dynamic collapse, the discharged material cloud grows as a
result of entralnment during the convective descent. When the material
reaches the bottom or attains neutral buoyancy, the vertical motion is
arrested and dynamio horizontal spreading oocurs. In the hopper discharge
model, the cloud Is assumed to take the shape of an oblate spheroid. During
horizontal spreading, the same conservation equations used In convective
descent are applicable to the oblate spheroid, with the exception of
vortlcity, which is assumed to be dissipated by stratification In the
ambient water oolumn. In the oase of collapse on the bottom, an additional
faotor is lnoluded which is a frlctional drag force between the bottom and
the cloud.
The passive dispersion phase of the model is initiated when the
rate of horizontal spreading in the dynamic collapse phase becomes less than
the estimated rate of spreading due to turbulent diffusion, whereupon the
-------
collapse phase is terminated. During the collapse phase, the individual
solid fractions are allowed to settle at their fall velocities, but as they
leave the main body of material, they are stored in Individual clouds
characterized by a uniform concentration, thickness, and position in the
water column. These clouds are allowed to settle and disperse until they
become large enough to be inserted in the long term, two-dimensional passive
dispersion grid positioned in the horizontal plane. Once the small clouds
are allowed to be inserted at a particular grid point, then those grid
points have a concentration, thickness, and top position associated with
them. In addition to the horizontal oonveotion and diffusion of the
material, settling of suspended solids also occurs. Therefore, in addition
to having a concentration associated with each grid point, the amount of
solid material deposited on the bottom and a corresponding thickness are
also calculated in the final output. One important basic assumption in the
model is that, once the material is deposited on the bottom, it remains
there.
Model input may be broken into four categories: the physical
(ooean) environment, the hopper characteristics, and the dredged material
characteristics (discussed below) and the model coefficients (discussed
below).
A. Input relative to the physical environment includes the size
and number of grid steps used to define the area of interest,
the depth at each grid point, the particular slope charac-
teristics of the ooean floor, the ambient water density
profile, and the profile of the horizontal component of
water velocity. For the simulations performed, a oonstant
depth was assumed with the grid area adjusted to include all
sediment deposited on the bottom. Several simulations were
performed at depths from forty to one hundred feet. A
uniform ourrent velocity of 0.1 knot was assumed for low
flow conditions and 0.65 knots in the high velocity case.
B. The user must specify the hopper door width and length, the
vessel location on the grid, time required to empty the
hopper, loaded and unloaded draft of the vessel, depth of
material in the hopper, and the vessel's course and speed,
if moving. The specifications of three different-sized
hopper dredges are shown in Table A-1. Each set of envi-
ronmental conditions was simulated for each of the three
vessel sizes.
C. Input relative to the dredged material includes a listing of
each component of the dredged material (fine sand, old
shells, etc.) along with a listing of their physical charac-
A-3
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TABLE A-1
HOPPER DREW2 SPECIFICATIONS
Dredge
Fimitir
capaoity (or)
Type
Bopper Length (ft)
Bopper Width (ft)
Door Width (ft)
Tlae to «*>ty
hopper (Binutea)
Loaded Draft (ft)(#)
Unloaded Draft (ft)
Depth of Dredged
Material (ft)
(d)
(f)
Saall
(MAKHATTKH ISLAKD)
3,600
Split hull
150
*1
16 (w); typioally 7-fi
< (MS)
19.1
12
27 (aax)
17 (for
Ntdlua h
(IA0LE 1)
6,100
Split bull
137
10
Por aand - 18.5
for aluah - 7
Sand - 5-6
Sluah - 1-1/2 to 2
22.4
9.5 bow
15.0 atern
31.5 (w)
Urge
(STUTVESANT)
9,180
Bottoa door
153
10 12 x 12 doora
(all oan open at
onoe)
2-3
29
11.1 bow
20.5 atern
39 (hu)
Telocity • Discharge (let) 1
3-6
(a) forth Aaerloan Trailing Coapany
(b) Baas Dredging Corporation
(e) 3tuy*aaeiit Dredging Coapaay
(d) Dependa on type of Material (aee Madlua Dredge).
(e) Maxlaua allowed by OSCG.
(f) Dapenda on aaount of fuel.
A-*»
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TABLE A -2
VIRGIN DREDGED MATERIAL CHARACTERISTICS
Description
Density
(gm/co)
Concentration
(vol/vol)
*
of
Solids
(wt)
Pall
Velocity
(ft/sec)
Voids
Ratio
Clayballs
1.700
0.401
72.0
2.20
0.75
Old Shell
2.500
0.008
2.0
0.480
0.70
Pine Sand
2.650
0.016
4.5
0.0466
0.80
Silt
2.700
0.047
13.5
0.00256
1.0
Slurry
2.750
0.026
8.0
0.00256
1.5
Fluid
1.022
0.500
N/A
N/A
N/A
BULK DENSITY 1.46
AGGREGATE VOIDS RATIO 0.81
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teristlcs including solids density, concentration by volume,
fall velocity, and voids ratio. Additionally, the user must
designate bulk density of the initial cloud, voids ratio of
the aggregate solids, and, if a conservative chemical con-
stituent is to be traced, its Initial concentration and
background concentration.
Virgin Material
The percentage of the various soil particle types anticipated in
the virgin sediment to be dredged was estimated using subsurface informa-
tion from sediment borings done by the CE (CE, 1978). The following proce-
dure was used:
The percentages of the various strata encountered in the borings
down to -49 feet MSL were determined. Based on the borings and
the strata descriptions provided by CE, the virgin sediment from
the Entrance Channel was estimated to be approximately 72.0? clay
balls, 2.0? old shell, 4.5? fine sand, 13*5? silt and 8.0? slurry.
The fall velocity for each partiole type was then calculated
using Stokes law. The combination of the soils and water in the
hopper dredge for the 45' Project was estimated using a weighted
average technique. Input data are shown in Table A-2.
The DMF model program oontains default values for the 14 coeffi-
cients neoessary to model an Instantaneous dump. However, for a test case
(Johnson and Holliday, 1978), the entrainment coefficient, collapse drag
coefficient, convectlve desoent coefficient, and bottom friction coeffi-
cient were found to differ significantly from the default values. There-
fore, appropriate values for an instantaneous dump in 60 feet of water off
Freeport were used In the model.
Output from the DMF model simulates the results of depositing one
load of dredged material on the ocean floor. Output includes convection of
the material to the bottom and a grid outlay of the spread of the appro-
priate volume of material on eaoh grid. Height of the material determined
by the model was not used, since the height varied for identical cases with
varying time increments and did not change consistently with depth. This
may be due to the dlsorete step functions used by the model in distributing
material. The dispersion and volume of material over an area for each
simulated case was used to determine smooth three- dimensional profiles of
deposited material. The mounds of virgin material were skewed in the
ourrent and vessel-heading directions. As would be expected, irregulari-
ties in the model output were observed when the water depth was too shallow
to allow completion of the diffusive phase. Since diffusion of sediments,
along with the dynamic collapse, was considered important, a linear regres-
-------
sion was performed over simulations which provided diffusive spreading
results. The regression allowed output to be adjusted for simulations in
water for which the model, beoause of the shallowness of the water, did not
allow diffusive spreading to ocour.
A-7
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