**APPLIED PHYSICAL SCIENCES IN MMS**

**Volume I: Why and How MMS Uses the Physical Sciences**

**to Fulfill Its Environmental Goals**

By: Zhen-Gang Ji

Environmental Studies Program

April 2003

**U.S. Department of the Interior**
![](media/image1.png){width="0.7993055555555556in"
height="0.38958333333333334in"}

**Minerals Management Service**

**Branch of Environmental Sciences**

**[Table Of Contents]{.underline}**

[List of Figures iv](#list-of-figures)

[Introduction 1](#introduction)

[Support for MMS Mission 1](#support-for-mms-mission)

[Physical Sciences Research Components
3](#physical-sciences-research-components)

[Physical Oceanography 4](#physical-oceanography-1)

[Studies of Deepwater Processes in the Gulf of Mexico
4](#studies-of-deepwater-processes-in-the-gulf-of-mexico)

[Studies on Sea Ice and Ocean Circulation in Alaska Region
5](#studies-on-sea-ice-and-ocean-circulation-in-the-alaska-region)

[Santa Barbara Channel-Santa Maria Basin Circulation Study in California
5](#santa-barbara-channel-santa-maria-basin-circulation-study-in-california)

[Support for Biological and Ecological Studies
6](#support-for-biological-and-ecological-studies)

[Oil Spill Risk Analyses 6](#oil-spill-risk-analyses)

[OSRA Model 7](#osra-model)

[Oil Spill Risk Analysis in the Gulf of Mexico
8](#oil-spill-risk-analysis-in-the-gulf-of-mexico)

[Atmospheric Sciences 8](#atmospheric-sciences)

[Air Quality Models 9](#air-quality-models)

[Haze and Ozone Modeling Studies 9](#haze-and-ozone-modeling-studies)

[Sand and Gravel Program 10](#sand-and-gravel-program-1)

[Summary and Conclusions 11](#summary-and-conclusions)

[Acknowledgements 12](#acknowledgements)

[Bibliography 12](#bibliography)

# List of Figures

Figure 1. Outer Continental Shelf (OCS) planning areas.

Figure 2. Environmental studies used in decisionmaking.

Figure 3. The uses of Oil-Spill Risk Analysis (OSRA) results.

Figure 4. A sketch of some features in a subsurface plume in deepwater.

Figure 5. The surface current output grid of the Princeton Dynalysis
Ocean Model (PDOM) applied to the Gulf of Mexico. This grid is also the
OSRA model input grid for both ocean currents and winds.

Figure 6. Surface currents and wind stresses on August 25, 1992, used in
OSRA model.

# Introduction

This document explains why and how the Minerals Management Service (MMS)
of the U.S. Department of the Interior uses physical sciences to fulfill
its environmental goals, and provides background information on the role
of physical sciences in decisionmaking for Outer Continental Shelf oil,
gas, and other minerals development.

By linking research endeavors to MMS\'s decisionmaking processes and by
using sample MMS studies, this document also communicates the general
direction of MMS physical sciences research to interested constituents
including industry, State and local governments, and environmental
groups.

This document is not intended to give a comprehensive review on physical
sciences research in MMS. Instead, sample MMS studies are presented to
illustrate why and how MMS uses the physical sciences to fulfill its
environmental goals.

## Support for MMS Mission

The Minerals Mangement Services (MMS) is a bureau of the U.S. Department
of the Interior. The mission of MMS is to manage the mineral resources
on the Nation\'s Outer Continental Shelf (OCS) in an environmentally
sound and safe manner, and to collect, verify, and distribute, in a
timely fashion, mineral revenues generated from Federal (onshore and
offshore) and Indian lands.

The term "Outer Continental Shelf" is a legal term created by Federal
statute and is distinct from the geographic term "continental shelf."
There is no scientific definition for the OCS. Legally, the OCS
comprises that part of the submerged lands, subsoil, and seabed lying
between the seaward extents of State[^1] and of Federal
jurisdictions[^2], which is generally 3 nautical miles seaward from the
State's coastline to about 200-300 nautical miles offshore.

Offshore drilling for oil and gas has been conducted since the early
1900's. Oil and gas under the seabed continue to be an important part of
the energy resources of the United States. The OCS provides
approximately 30 percent of domestically produced crude oil and 25
percent of domestic natural gas. Approximately \$4-6 billion per year in
minerals revenue is collected from offshore and onshore leases. The need
to balance the value of these resources against the potential for
environmental damage is an important concern, and has become
increasingly recognized in Federal laws and national debates over
energy.

The majority of OCS activity occurs in the U.S. Gulf of Mexico, off the
coast of southern California, and off the coast of Alaska (see Figure
1). The western and central portions of the northern Gulf of Mexico are
one of the world's major oil and gas production areas, and have been a
steady and reliable source of crude oil and natural gas for more than 50
years.

Until 1969, potential environmental damage from OCS oil and gas
activities was mostly a local concern in the affected States. However,
environmental concerns were brought to national attention by oil-spill
damage from a blowout in the Santa Barbara Channel in January 1969. The
spilled oil covered 660 square miles, including 150 miles of coastline
(Cicin-Sain, 1986).

Established in the 1970\'s, the MMS' Environmental Studies Program (ESP)
is a highly focused marine research program designed to provide the
environmental information necessary for OCS energy and nonenergy
minerals planning and development activities. The program supports
studies in marine biology, physical oceanography, endangered species,
marine chemistry, socioeconomics, and air quality. Figure 2 illustrates
types of environmental studies used in decisionmaking.

The MMS prepares environmental assessments (EA's) and environmental
impact statements (EIS's) to determine any possible environmental
consequences of OCS marine minerals development. An EA is a concise
document that (1) briefly provides sufficient evidence and analysis for
determining whether to prepare an EIS, and (2) determines whether the
proposed action poses a significant environmental risk. An EIS is a
detailed document that thoroughly analyzes the proposed action,
alternatives, and cumulative impacts. An EIS is prepared when MMS has
determined that a major Federal action is being considered and is
environmentally significant in scope and magnitude such that the
potential impacts must be examined in greater detail. The MMS's physical
sciences research provides important information for both EA and EIS
documents.

Environmental assessments, compliance regulations, and study activities
also help MMS meet obligations required by numerous legislative
authorities, such as the Outer Continental Shelf Lands Act, the National
Environmental Policy Act (NEPA), the Endangered Species Act, the Clean
Air Act, and the Oil Pollution Act of 1990. Other examples of applicable
laws include the Marine Mammal Protection Act, the Coastal Zone
Management Act, the Clean Water Act, and the Alaska National Interest
Lands Conservation Act. These legal mandates direct MMS to (1) establish
the information needed for assessment and management of environmental
impacts on the human, marine, and coastal environments of the OCS and
potentially affected coastal areas, and (2) provide the information
needed for balanced decisionmaking.

## Physical Sciences Research Components

Physical sciences are an important part of the ESP and provide
information for EA and EIS documents. The physical sciences research
supported in MMS includes physical oceanography, oil-spill risk analysis
(OSRA), atmospheric sciences, and sand and gravel studies.

### Physical Oceanography

Physical oceanography is the scientific study of ocean movements.
Physical oceanographic research supported by MMS includes field data
collection, analysis, and modeling studies. This research is important
for estimating the transport and fate of any spilled oil and other OCS
discharges. The general strategy is to use field observation and model
results to calculate the circulation for a given area. These
calculations, in turn, provide the basis for OSRA's (see below) and
other assessments.

Although physical oceanographic information is used primarily in the
OSRA model and associated EIS document preparations, it is also used to
support biological and ecological studies and to predict the transport
of drilling muds and water discharges containing petroleum compounds and
other byproducts of oil and gas exploration and production. Variability
in physical oceanographic conditions, for example, may be a cause of
variation in biological communities and may be useful in interpreting
long-term monitoring and cumulative impact studies.

### Oil-Spill Risk Analysis

The OSRA model is used by MMS to estimate the probability of oils spills
occurring in a specific lease area, to calculate hypothetical oil-spill
trajectories from selected spill launch points (i.e., places that a
spill is assumed to occur), and to determine the probability that an
environmental resource or coastline segment might be affected by oil
released from the selected launch points. To date, the results from OSRA
modeling are used in different types of documents: (1) EA and EIS
reports completed by the MMS for OCS oil exploration, development, and
production; (2) oil-spill response plans submitted by industry; (3)
environmental reports submitted by industry, (4) biological opinions for
endangered/threatened species, and (5) other Federal and State agencies'
special reports. Figure 3 shows the uses of OSRA results.

### Atmospheric Sciences and Air Quality Modeling

Oil and gas production may alter the composition of the marine
atmosphere and may affect air quality over populated and other protected
areas. Atmospheric sciences studies are used by MMS to develop air
quality impact analyses. Atmospheric sciences research focuses on air
quality modeling and field data collection. Initially, field studies in
the MMS Pacific Region were important in developing air quality models.
Currently, the studies emphasize Gulf of Mexico issues. This is due to
the continued rapid growth in the oil/gas-related activities in the Gulf
as well as new regulatory standards that are being implemented by the
Environmental Protection Agency (EPA).

### Sand and Gravel Program

In addition to offshore oil and gas, the MMS has legal and
jurisdictional authority over other mineral resources on the OCS. This
includes sand and gravel deposits, many of which are suitable as beach
nourishment or wetlands restoration material, or as a source of coarse
material for construction aggregate. In recent years, there has been
increasing interest in the sand and gravel resources of the OCS, and the
MMS has responsibilities with respect to the potential environmental
impacts of these resources and must fulfill its NEPA responsibilities by
addressing biological and physical environmental questions concerning
sand extraction from the Federal OCS.

# Physical Oceanography

The U.S. continental margins are divided into four regions: the Alaska
Coast, the Pacific Coast, the Gulf of Mexico, and the Atlantic Coast.
These four regions have fundamental differences in geology, topography,
and bathymetry and in the processes that control the circulation of
shelf waters. Although some characteristics, such as the response of
currents to wind forcing, are common to many continental shelves, the
relative importance of various physical processes in influencing the
shelf flows varies from region to region. All of these features could
influence the transport and dispersion of any spilled oil or OCS
discharges. The following studies illustrate how physical oceanography
research is used in EA and EIS documents.

## Studies of Deepwater Processes in the Gulf of Mexico

With the passage of the Deepwater Royalty Relief Act and the development
of technologies that allow for more cost-effective development beyond
the continental shelf, oil and gas activities in deep water (areas
deeper than 1,000 feet) have proceeded at an unprecedented rate. If
predictions of even larger reservoirs in deepwater areas are proven
true, then the Gulf of Mexico will experience a profound change in the
pattern of development during the next 8-10 years.

Development in deepwater has led to concerns about oil released by
accidents near the seafloor. Figure 4 is a sketch of some physical
features in a subsurface plume. Oil spill experts have realized that oil
and natural gas releases in deep water behave much differently than in
shallow water. This is primarily because of the density stratification,
high pressures, and low temperatures in deep water. Preliminary
calculations suggest that a plume of gas and/or oil could travel beneath
the surface for many kilometers and surface many hours after release.
Some physical and chemical changes that occur in this deepwater
environment, such as the formation of frozen gas hydrates from gas
bubbles, could significantly reduce the buoyancy of the plume and keep
large amounts of the oil submerged for an extended time. This has
significant implications for environmental impact assessment, oil-spill
cleanup, contingency planning, and source tracing.

Recently, it has been shown that there are strong currents at water
depths between 1,000 and 2,000 meters. These strong flows affect oil and
gas operations and MMS assessments of subsurface spills.

The interactions between eddies and the continental slope are also being
modeled to study the dynamics of three-dimensional, physical and
oceanographic processes. The MMS also participated in studies to
evaluate observations made during controlled subsea oil-spill
experiments. Ultimately, this information will be used to build a model
to assist in the development of deepwater oil-spill response plans.

## Studies on Sea Ice and Ocean Circulation in the Alaska Region

Ice conditions are highly influential in determining the movement and
final disposition of spilled oil. Under calm conditions, the primary
processes affecting the oil are spreading, advection, and evaporation.
Under rough water conditions, dispersion and emulsification also become
important to oil movement. Even at 0 °C, evaporation occurs, with
estimates of up to 30-percent evaporation in 48 hours and up to
40-percent evaporation over a 2-week period. Such weathering results in
greater density of the remaining oil, which in turn causes increased
thickness of the oil by increasing its viscosity. The low temperatures
in the Arctic further increase the viscosity and the oil's equilibrium
film thickness. The oiled ice can be transported for a considerable
distance before melting occurs and the oil is released.

Understanding under-ice currents is also necessary for estimating the
potential effects on environmental resources from oil spills. A study of
under-ice currents by MMS indicated that under-ice oil spills could move
and pose risk to offsite and, in particular, shoreward resources. The
MMS continues to develop and improve a model of sea-ice formation and
ocean circulation. Results of this study will include details of ice
motion and ocean currents that will be used in oil spill risk analysis.

These studies are helpful for simulating arctic circulation, improving
oil-spill trajectory modeling applied to Alaskan waters, and enhancing
MMS's environmental impact evaluations.

## Santa Barbara Channel-Santa Maria Basin Circulation Study in California

The MMS, through a cooperative agreement with the Scripps Institution of
Oceanography, is conducting the Santa Barbara Channel-Santa Maria Basin
(SBC-SMB) Circulation Study. This decade-long study is providing
information and understanding of circulations needed to support
postlease decisions, such as reviews of oil-spill response plans

The MMS continues to develop a numerical model of currents in the Santa
Barbara Channel and Santa Maria Basin area. Once completed, the model
will aid in the primary form of risk assessment, which is the assessment
of probable paths and fates of any spilled oil. The model is useful for
determining the frequency and short-term variability of the major
circulation processes important to postlease activities. All of these
time and spatially varying flow processes also affect variations of the
biological characteristics in the area, such as the transport of
nutrients, fish larvae, plankton, and other biota.

These studies directly support MMS management decisions for southern
California. The study is useful for oil-spill trajectory analyses, mud
discharge estimates, and produced water dispersion estimates for review
of development and production plans, and oil-spill contingency plans. An
accurate understanding of the time and spatial variability of the flow
processes is important to support: (1) the development of flow fields
appropriate for the MMS's oil spill risk analysis; (2) MMS biological
research; and (3) oil-spill response efforts conducted by local, State,
and Federal Agencies, and industry.

## Support for Biological and Ecological Studies

Although physical oceanographic information has been used primarily as
input to the OSRA model and to prepare associated EA and EIS documents,
it is also used to support biological and ecological studies. The
GulfCet Program (Davis et al., 2000) is one example.

There has been much concern about how various aspects of oil and gas
exploration and development might affect whales and dolphins
(cetaceans). The purposes of GulfCet were to determine the distribution
and abundance of cetaceans along the continental slope in the northern
Gulf of Mexico and to help MMS assess the potential effects of deepwater
oil and gas exploration and production on these marine mammals.

Whales and dolphins do not occur randomly in the Gulf. The GulfCet
Program has shown that sperm whales and other cetaceans are found in
conjunction with areas of upwelling and nutrient enrichment that enhance
productivity and prey abundance. Cetaceans in the northern Gulf of
Mexico concentrate along the continental slope in or near cyclones
(upwelling waters) and the confluence of cyclone-anticyclone eddy pairs.
Cyclones also show the greatest diversity of seabird species. High
numbers of zooplankton, lanternfish, and squid were found inside cyclone
and confluence areas. As the physical oceanographic features move and
change, prey distribution changes and moves, and so will the presence
and movements of whales and dolphins.

# Oil-Spill Risk Analyses

The MMS assesses oil-spill risks associated with offshore oil and gas
activities. Analyzing the risk of oil spills contacting coastal and
marine resources is part of the EIS process. This analysis addresses the
likelihood of spill occurrence, the transport and fate of spilled oil,
and the environmental impacts that might occur as a result of the spill.
The MMS produces OSRA reports for proposed OCS oil and gas lease sales
and developmental activities. These analyses estimate the potential oil
spill risks that may be associated with offshore activities that occur
once leases are awarded. The OSRA results are also used by other Federal
Agencies (such as by the Fish and Wildlife Service for endangered
species analysis), State agencies (such as for coastal zone consistency
determination), and the oil industry (such as for oil-spill response
plans and for environmental reports).

One focus of MMS's Environmental Studies Program is to develop
supporting environmental data sets for the OSRA model. The OSRA model's
supporting environmental data are among the most comprehensive for all
oil-spill trajectory models and include the best available current and
wind fields from national and international sources. In addition to the
driving wind and ocean current fields, the model uses data on the
geographical extents of biological and commercial resources, such as
seagrass beds, native subsistence areas, coastal habitats, and
recreational beaches.

## OSRA Model

The OSRA model was developed in 1975 by the Department of the Interior,
U.S. Geological Survey, for the analysis of possible oil-spill impacts
from offshore oil and gas operations (Smith et al., 1982). The OSRA
model produces probabilistic estimates of oil-spill occurrence and
contact to biological and economic resources using historical records of
oil spills, winds, and ocean currents. The model initiates thousands of
oil-spill simulations at hundreds to thousands of hypothetical spill
locations to generate an ensemble of oil-spill trajectories, which can
statistically characterize oil-spill risk over a large area. The spill
locations are in areas of prospective drilling and production, and along
projected pipeline and tanker routes.

The OSRA depends on the meteorological and geographical conditions of
the study area, the environmental resources that are at risk, and the
estimated volumes of oil resources that are assumed to be discovered,
produced, and transported. The MMS works closely with State and other
Federal Agencies to obtain the best available geographic information on
natural resources and the shoreline, represented by one or more
equal-distant partitions called land segments.

The analysis is usually conducted in three parts corresponding to
different aspects of the overall problem:

-   The first part addresses the probability of oil-spill occurrence
    (Anderson and LaBelle, 1994, 2001).

-   The second part addresses the trajectories of oil spills from
    hypothetical spill locations to various environmental resources
    (LaBelle and Anderson, 1985).

-   The third part combines results of the first two to estimate the
    overall oil-spill risk if there is oil development.

    Projection of potential oil-spill impacts is based on results
    generated by the OSRA model. The OSRA results provide information
    for imposing stipulations or deleting certain tracts from leasing
    where there is a high probability that any oil spilled would affect
    particularly sensitive areas and valuable resources. Because
    potential risks are principally evaluated through OSRA modeling, the
    MMS has used physical oceanographic information primarily to support
    the OSRA model and to prepare associated EIS's.

The OSRA model has been used successfully to hindcast several documented
oil-spill incidents including the Argo Merchant incident (off Nantucket
Island, 1976), the Santa Barbara Channel blowout (1969), and the IXTOC-I
spill (1979-1980). The spill trajectories generated by the OSRA model
closely matched the observed movement of the spilled oil during these
incidents. To provide information for EA and EIS documents, the OSRA
model has been applied also to the U.S. continental coasts and off
Alaska. A recent OSRA application for the Gulf of Mexico is presented in
the following section.

## Oil-Spill Risk Analysis in the Gulf of Mexico

The Federal Government proposed multiple OCS lease sales in the Western
and Central Gulf of Mexico Planning Areas during the 5-year time period,
1998 through 2002. Because oil spills may occur from activities
associated with offshore oil development, MMS conducted formal risk
assessments prior to the proposed lease sales (Ji et al., 2002a, 2002b).

When applied to the Gulf of Mexico, the OSRA model uses 3-hourly ocean
currents over a 9-year period (1986-1994), which are generated by the
Princeton Dynalysis Ocean Model (PDOM) (Herring et al., 1999). The PDOM
is driven by wind, heat flux, and river flows. The wind data are from
the European Center for Medium Range Weather Forecasting Center and are
enhanced by observations from meteorological buoys (Berger et al. 1996).
Figure 5 shows the stretched, curvilinear computational grid of the
PDOM, which illustrates that the PDOM has high spatial resolution of a
few kilometers off the Texas-Louisiana coast and is able to resolve the
dynamic processes in the entire Gulf. Figure 6 presents the surface
currents and wind stresses on August 25, 1992, which are used in the
OSRA model.

Among the observations used for model verification is a set of current
measurements from over 800 satellite-tracked surface drifters deployed
in the Gulf. The drifter deployments constitute one of the most
extensive synoptic surveys of mesoscale and larger-scale surface
circulation and, together with other observations, facilitated a
thorough verification of the model-derived surface currents. The model
current field produced very realistic mesoscale eddies and Loop Current
variations and was, therefore, accepted as a realistic representation of
the surface currents in the Gulf.

# Atmospheric Sciences

Oil and gas production may alter the composition of the marine
atmosphere and may affect air quality over populated and other protected
areas. To address how OCS oil and gas activities are affecting air
quality, it is necessary to have information regarding air emissions
(i.e., types and amounts) as well as an understanding of the transport
and dispersion of these emissions.

The MMS has air quality jurisdiction in the Gulf of Mexico in all OCS
waters west of 87.5^o^ W. longitude, in which most of the oil/gas
development activity takes place. The EPA has jurisdiction in all other
areas (the Eastern Gulf, Atlantic, Pacific, and Alaska). Under the
authority of the Clean Air Act, EPA carries out a rigorous program
designed to improve the Nation's air quality. The MMS works with EPA and
the States to assure that air emissions on the OCS do not hinder this
effort. Through the ESP, the MMS provides much of the scientific data
needed in support of these coordination efforts. The results of
atmospheric sciences studies are ultimately used in EA and EIS
documents.

## Air Quality Models

Based on an EPA regulatory model, MMS developed the Offshore and Coastal
Dispersion (OCD) model in the 1980's. The OCD Model is used to evaluate
air quality impacts from emission sources located on the OCS. The MMS
applies the OCD model to air quality analyses for lease sale EIS
documents.

There is a continuing need for air quality modeling, particularly in the
Gulf of Mexico, to assist analysts in developing air quality impact
analyses for NEPA documents. The EPA has developed what is called
third-generation air quality models for regulatory applications. These
models incorporate more realistic atmospheric processes. The MMS is
developing a new-generation air quality model based on the EPA model.
The model will incorporate the most current knowledge of dispersion
modeling and will be versatile enough to be used spatially in
short-range as well as long-range applications. The complete model
package will consist of (1) preprocessors for generating land use and
terrain data, (2) meteorological data preprocessor, (3) a meteorological
model, (4) an air quality model, and (5) postprocessors for model result
analysis and presentation.

Recently, EPA promulgated revised standards for ozone, particulate
matter, and regional haze. These required the collection of additional
data, further studies, and increased cooperation with other Federal and
State agencies. To evaluate possible degradation of air quality in
sensitive areas, MMS pursued cooperative efforts to conduct field
sampling and data collections. The information generated was used to
determine if any actions were needed to minimize the degradation.
Emissions, air quality, and meteorological data were collected from both
onshore and offshore areas.

Predictive models are incorporated with measured data to quantify the
pollution levels over the area and their changes over time. Results are
used to determine if there has been degradation that exceeds the limits
allowed under the Clean Air Act. Appropriate action may then be taken to
remedy any significant degradation.

## Haze and Ozone Modeling Studies

The EPA has promulgated new regulatory programs to address regional haze
and ozone. Emissions of air pollutants over the OCS, including carbon
monoxide, sulfur dioxide, nitrogen oxides, particulate matter, and
hydrocarbon compounds, influence the ambient concentrations of ozone and
haze material. State agencies, therefore, must assess how air emissions
in the Gulf of Mexico contribute to ozone and haze material over coastal
regions. The MMS supports the States by providing emissions data
regarding OCS oil and gas activities, so these agencies can interpret
and control regional concentrations of ozone and haze material. For
completeness, MMS may also collect and provide emissions data for other
activities such as recreational boating and commercial shipping.

These studies also support EA and EIS documents. The information
obtained supports cumulative impact analyses for NEPA documents. These
studies develop a framework for making decisions about where and which
emissions should be targeted for controls to reduce current or
foreseeable significant impacts.

There is a continuing need to improve the science and gather additional
data, especially as conditions change and new issues arise. The MMS is
augmenting its existing meteorological monitoring programs to get a
better understanding of the atmospheric conditions that affect the
movement and spread of air pollutants. This knowledge is important for
improving the predictive models that are used to estimate what the
pollutant levels will be and which areas will be affected.

# Sand and Gravel Program

In addition to offshore oil and gas, MMS has legal and jurisdictional
authority over other mineral resources on the OCS. These include sand
and gravel deposits, which maybe suitable as beach nourishment or
wetlands restoration material, or as a source of coarse material for
construction aggregate.

Dredging significant volumes of sand from OCS sites could potentially
alter the bottom topography. An important physical impact issue is
whether the dredging will have any measurable influence on the nearshore
wave regime and local littoral sediment budget. Prior to any dredging
activity at identified borrow sites, the potential for adverse changes
in the local wave and current patterns must be assessed. The MMS
conducts site-specific studies to evaluate the possible physical effects
associated with extraction of sand and gravel material from OCS. These
studies:

> • compile and analyze existing oceanographic literature and data sets
> to develop an understanding of existing environmental conditions and
> the ramifications of dredging operations at selected sand borrow
> sites;
>
> • use physical processes field data sets and wave climate simulations
> to predict wave transformation under natural conditions and in the
> presence of proposed dredging activities;
>
> • determine existing coastal and nearshore sediment transport patterns
> using historical data sets, and predict future changes resulting from
> proposed sand dredging operations;
>
> • evaluate the potential cumulative environmental effects of multiple
> dredging scenarios.

Increased wave action after dredging offshore shoal areas has been noted
in certain coastal areas. A proper and thorough assessment should take
into account the local current regime and the historical wind and wave
climate. Knowledge of the general circulation and bottom-boundary flow
conditions provides a basis for estimating the transport of suspended
materials.

Computer modeling is the primary tool used to evaluate the physical
effects of offshore dredging. A primary advantage of wave modeling is
its ability to simulate multiple scenarios. The model domain can be
modified (e.g., comparison of existing and postdredging scenarios,
different structural configurations, evaluation of varying beach
nourishment templates, etc.) to determine the effects that various
seafloor changes have on the wave climate. Wave input also can be
modified to simulate a wide range of wave conditions (e.g., storm
events, seasonal variations) to determine the impacts on shoreline
response.

# Summary and Conclusions

This document describes why MMS conducts research in physical sciences
and how MMS uses this information to fulfill its environmental goals.
Instead of giving a comprehensive review on physical sciences research
in MMS, sample MMS studies are presented.

The MMS utilizes physical sciences data and analyses throughout the
various phases of 5-year planning, prelease and leasing activities,
exploration, development, production, and decommissioning of offshore
platforms. The MMS designs studies to address the data and analytical
needs arising from these specific phases in the decisionmaking process.

Physical oceanographic studies focus on understanding and verifying
physical processes and features on the OCS. The mechanisms of these
processes and features in the ocean and atmosphere control the transport
of materials and cause the mixing and redistribution of pollutants. The
information obtained through studies in physical oceanography and
meteorology are used in assessing: (1) the transport of spilled oil, (2)
the dispersion of discharge fluids and produced water, (3) the movement
and spread of air pollutants, (4) sand and gravel dredging impacts, and
(5) the effects on the migration of marine mammals, the distribution of
fishes, and other biological resources.

Physical oceanography and meteorological data are required to calculate
the probable trajectories of any spilled oil and, more generally, to
provide background information for environmental impact assessment.
Circulation and trajectory model results are ultimately integrated into
the EIS's used for lease sales. The information is also used by other
investigators (biologists, chemists, and geologists, for example) to
assist them in interpreting and analyzing their data.

Improving the modeling and observations of ocean currents and winds and
modeling their action on spilled oil with time-varying physical
properties are difficult tasks. However, the MMS is committed to
continued improvement of the OSRA estimations and EIS analyses, and it
will use the most recent results of field and modeling studies to
fulfill this commitment. As offshore activity expands into deeper waters
and new geographic areas, MMS modeling results will be applied to risk
assessments and be validated with environmental observations.

This document (Volume 1) summaries why and how MMS uses physical
sciences to fulfill its environmental goals. A companion document
(Volume 2) presents the strategic plan for physical sciences in MMS.

# Acknowledgements

The author would like to thank the following MMS colleagues for their
contributions: Robert LaBelle, Jim Cimato, Walter Johnson, Ron Lai, Jim
Price, Chip Marshal, Dirk Herkhof, and Barry Drucker at the MMS
Headquarters; Elizabeth Pueler, Alexis Lugo-Fernandez, Carole Current,
and Chester Huang at the MMS Gulf of Mexico Region; and Cleveland
Cowles, Dick Prentki, and Caryn Smith at the MMS Alaska Region. The
author would also like to thank James Kendall, who provided valuable
guidance and comments that made this document possible, and Eileen Lear,
who provided her editing skills.

# Bibliography

Anderson, C.M., and R.P. LaBelle. 1994. Comparative Occurrence Rates for
Offshore Oil Spills. Spill Science and Technology Bulletin 1(2):131-141.

Anderson, C.M., and R.P. LaBelle. 2001. Update of Comparative Occurrence
Rates for Offshore Oil Spills. Spill Science and Technology Bulletin
5(5-6):303-321.

Berger, T.J., P. Hamilton, R.R. Leben, G.H. Born, and C.A. Fox. 1996.
Louisiana/Texas Shelf Physical Oceanography Program: Eddy Circulation
Study. Final Synthesis Report. Vol. 1, Technical Report. OCS Study MMS
96-0051. U.S. Department of the Interior. Gulf of Mexico Region, New
Orleans, LA. USA. 294 p. NTIS PB97-126569

Cicin-Sain, B. 1986. Offshore Oil Development in California: Challenges
to Governments and to the Public Interest. Public Affairs Report, Vol.
27, Feb-Apr. 1986. Nos. 1 and 2, University of California, Berkeley, CA,
USA.

Davis, R.W., W.E. Evans, and B. Würsig, eds. 2000. Cetaceans, Sea
Turtles and Seabirds in the Northern Gulf of Mexico: Distribution,
Abundance and Habitat Associations. Volume I: Executive Summary.
USGS/BRD/CR-1999-0005. U.S. Department of the Interior, U.S. Geological
Survey, Biological Resources Division, Reston, VA, and OCS Study MMS
2000-002, Minerals Management Service, Gulf of Mexico OCS Region, New
Orleans, LA, USA. 27 pp.

Herring, H.J., M. Inoue, G.L. Mellor, C. N.K. Moores, P. P. Niiler,
L.-Y. Oey, R.C. Patchen, F.M. Vukovich, and W.J. Wiseman Jr. 1999.
Coastal Ocean Modelling Program for the Gulf of Mexico. Technical
Report, Dynalysis of Princeton, Princeton, NJ, USA.

Ji, Z.-G., W.R. Johnson, C.F. Marshall, G.B. Rainey, and E.M. Lear.
2002a. Oil-Spill Risk Analysis: Gulf of Mexico Outer Continental Shelf
(OCS) Lease Sales, Central Planning Area and Western Planning Area,
2003-2007, and Gulfwide OCS Program, 2003-2042. OCS Report 2002-032,
Minerals Management Service, Herndon, VA, USA.

Ji, Z.-G., W.R. Johnson, C.F. Marshall, G.B. Rainey, and E.M. Lear.
2002b. Oil-Spill Risk Analysis: Gulf of Mexico Outer Continental Shelf
(OCS) Lease Sales, Eastern Planning Area, 2003-2007, and Gulfwide OCS
Program, 2003-2042. OCS Report 2002-069, Minerals Management Service,
Herndon, VA, USA.

LaBelle, R.P., and C.M. Anderson. 1985 The Application of Oceanography
to Oil-Spill Modeling for the Outer Continental Shelf Oil and Gas
Leasing Program. Marine Technology Society Journal 19(2):19-26.

Smith, R.A., J.R. Slack, T. Wyant, K.J. Lanfear. 1982. The Oilspill Risk
Analysis Model of the U. S. Geological Survey, Geological Survey
Professional Paper 1227, U. S. Geological Survey, Reston, VA, USA.

![](media/image2.png){width="6.447916666666667in"
height="4.510416666666667in"}

> Figure 1. Outer Continental Shelf (OCS) planning areas.

![](media/image3.jpeg){width="6.513888888888889in"
height="4.888888888888889in"}

Figure 2. Environmental studies used in decisionmaking.

![](media/image4.jpeg){width="6.53125in" height="4.875694444444444in"}

Figure 3. The uses of Oil-Spill Risk Analysis (OSRA) results.

![](media/image5.jpeg){width="6.53125in"
height="4.875694444444444in"}Figure 4. A sketch of some features in a
subsurface plume in deepwater.

> ![](media/image6.wmf){width="6.522222222222222in"
> height="4.575in"}Figure 5. The surface current output grid of the PDOM
> applied to the Gulf of Mexico. This grid is also the OSRA model input
> grid for both ocean currents and winds.

![](media/image7.jpeg){width="6.277777777777778in"
height="5.473611111111111in"}

> Figure 6. Surface currents and wind stresses (August 25, 1992) used in
> OSRA model.

[^1]: **[State jurisdiction]{.underline}** is defined as follows:

    Texas and the Gulf coast of Florida are extended 3 marine leagues (1
    marine league = 18,228.3 feet) seaward from the baseline from which
    the breadth of the territorial sea is measured.

    Louisiana is extended 3 imperial nautical miles (1 imperial nautical
    mile = 6,080 feet) seaward of the baseline from which the breadth of
    the territorial sea is measured.

    All other States' seaward limits are extended 3 nautical miles (1
    nautical miles = 6,076 feet) seaward of the baseline from which the
    breadth of the territorial sea is measured.

[^2]: **[Federal jurisdiction]{.underline}** is defined under accepted
    principles of international law. The seaward limit is defined as the
    farthest of 200 nautical miles seaward of the baseline from which
    the breadth of the territorial sea is measured or, if the
    continental shelf can be shown to exceed 200 nautical miles, a
    distance not greater than a line 100 nautical miles from the
    2,500-meter isobath or a line 350 nautical miles from the baseline.