The Louisiana oil spill Geographic Information System
Jay Arnold
3001, Inc., 3655 SW 2ndAvenue, Suite 3C Gainesville, Florida 32607 David Gisclair Louisiana Oil Spill Coordinator's Office 1885 Wooddale Boulevard, 12ti Floor Baton Rouge, LA 70803 Introduction The first oil well in Louisiana was drilled in 1901. To date, about 209,000 wells have been drilled on land and offshore across Louisiana, and approximately 20% of the United States domestic oil supply is produced in Louisiana. In the last 15 years, the Louisiana Offshore Oil Port (LOOP) offloaded 3.5 billion barrels of foreign crude oil from 3350 tankers. These tankers and barges traverse Louisiana rivers and other waterways daily transporting the world's oil. Today, it is nearly impossible to travel across Louisiana without seeing oil-related activity. There is no question that Louisiana's oil is crucial to the state's economy. Unfortunately, oil spills can be both environmentally and economically disastrous. When the 1990 Oil Pollution Act (OPA 90) was passed as a direct response by our nation's government to Alaska's Exxon Valdez disaster, Louisiana had the foresight to create the Louisiana Oil Spill Coordinator's Office (LOSCO). In conjunction with OPA 90, Louisiana's Legislature passed ACT 740, the Louisiana Oil Spill Prevention and Response Act, to set state regulations that complement and extend OPA 90 regulations. ACT 740 mandates the development of a statewide oil spill contingency plan to prepare Louisiana for the ever-present possibility of oil spills. Specifically, ACT 740 states that "an environmental baseline inventory shall be developed and maintained in such a manner that it will provide the coordinator with the technical data regarding the coastal waters before, during, and after an unauthorized discharge of oil." Because geographic location of physical and cultural features is extremely important for oil spill planning and response, LOSCO determined that a geographic information system (GIS) is the best method for compiling, storing, retrieving, and analyzing the data required for this mandate. Study Area The project study area is the coastal waters of Louisiana, defined in state law R.S. 30:2454(2) as "the water and bed of the Gulf of Mexico within the jurisdiction of the State of Louisiana, including the arms of the Gulf of Mexico subject to tidal influence, estuaries, and any other waters within the state if such other waters are navigated by vessels with a capacity to carry ten thousand gallons or more of oil as fiel or cargo." The major navigable waterways included in the study area are the Mississippi River, the Atchafalaya Navigation Channel, the Red River, and the Ouachita/Black River. However, oil spills can occur throughout the state, not just these coastal waters. Therefore, LOSCO's contractor is creating new data sets and incorporating existing data sets that address the entire state where applicable. Major Logis Data Sets LOGIS provides relevant information for oil spill planning, response, and natural resource damage assessment. As a result, it is proving to be a comprehensive database housing for the first time a vast array of information in a single location. But the task wasn't easy. The challenge was this: to gather multitudes of scattered data, create multitudes of nonexistent data, organize all of it, and make it available to LOSCO twenty-four hours a day, seven days a week. Much of the information needed existed, but it was scattered across the state and in different sources. Therefore, data had to be accessed and organized in a form readily accessible by LOSCO. As well, any required data not already in existence had to be collected. The GIS data sets required for LOGIS fell under ten categories:
Orthophotography Quarter Quadrangles and feature locations; location of monitoring points, including baseline sampling and analysis; and potential oil spill locations, including pit and barge studies. Color Infrared Digital OrthoPhotography Quarter Ouadrandes As a detailed basemap to an existing Landsat Thematic Mapper satellite image mosaic, the contractor is producing statewide USGS color infrared (CIR) Digital Orthophotography Quarter Quadrangles (DOQQS). Unprecedented methods and cutting edge technology are being used to accomplish this task while at the same time saving LOSCO time and money. The DOQQS are being created through an innovative partnering agreement with the U.S. Geological Survey (USGS). The first step upon establishing the agreement was to fly the entire state according to National Aerial Photography Program (NAPP) standards for CIR DOQQS. This is the first time DOQQS have been produced statewide by a single year's flight. To accomplish this flight during the short Louisiana flying season, the USGS -NAPP contractor Northwest Group was hired to provide the statewide photography. Three pressurized twin-engine aircrafl equipped with Wild RC-30 cameras, onboard flight management, and airborne GPS were used. All photography was captured from January through February 1998, in spite of the record El Nino weather pattern. For airborne GPS control, five GPS Continuous Operation Reference Stations (CORS) were used around the state. Using airborne GPS during the flight greatly reduced the need for field survey control, which is typically established with ground-based GPS. A total of 15,000 line miles of aerial photography, including cross-strips to augment aerotriangulation, were used. These NAPP photos were flown 20,000 feet above ground level at a scale of 1:40,000. As the next step, the USGS office in Reston, Virginia reviewed the processed film. Two additional time and money saving aspects of the DOQQ initiative also are being used. The first is the use of automated aerotriangulation to extend photogrammetric control. This technique greatly reduces the technician time required for bridging over standard Fully Analytical Aerotriangulation (FAAT) methods. The second is a Zeiss SCAI single-pass, roll-feed scanner. This scanner requires only a single pass for all three colors, cutting scan time by two-thirds. In addition, the scanner has the capability for roll-feed scanning, eliminating the need to feed the photographs in individual frames. Through an agreement with EROS Data Center, dodged duplicate film rolls are being scanned instead of the original. This provides a high quality image without the need for film diapositives. Standard USGS Level II Digital Elevation Models (DEMs) are being used in the orthorectification process. While some Level II DEMs exist, others are being created using raster-to-vector data conversion from Mylar contour separates of the standard USGS 1:24,000 quadrangle maps. To ensure the highest level of applicability for LOSCO and other interests, CIR photography was chosen for the DOQQS. CIR photography, as opposed to black-and-white or standard color photography, greatly improves one's ability to identify the land-water interface. It also has enhanced capabilities for soil type and wetness delineation, vegetation delineation, assessment of vegetation health and quality, and identification of cultural versus natural features. Other Gulf States with needs similar to Louisiana are developing projects using CIR orthophotography as well. Specifically, Texas and Florida are creating CIR digital orthophotographs for oil spill contingency planning, land use and land cover studies, environmental assessment, and GIS support. They are wise. DOQQS provide a proven method for creating high-resolution imagery with well-defined costs. Feature Location Surface features must be located in each LOGIS category for natural resources and oil-related facilities throughout the study area. LOSCO identified four possibilities for data sources, ranging from existing data that is directly usable to non-existing data that must be provided through new mapping and GIS analysis. Because many GIS and mapping projects have similar data requirements, one of the main challenges is to prevent duplication of effort when locating data and assessing its usability. To collect existing information, data sets were first located and incorporated. Primary criteria for all existing data include: spatial and content accuracy, age of the data set, update cycle, distribution format, and general availability. New mapping is performed for the required LOGIS layers when data do not meet this criteria. But there is so much new data to be acquired that mapping by traditional field techniques would be cost-prohibitive. Therefore, the mapping plan calls for using the CIR DOQQS the contractor is producing. Through photo interpretation, natural resources and oil-related facilities are identified on the imagery. Traditionally, field crews mapping oil-related facilities are guided by standard topographic maps and permits. However, mapping features through photo interpretation using the CIR DOQQS in an all-digital environment bypasses these traditional methods of location. Using photo interpretation methods, CIR DOQQS are displayed on a computer screen in-house. Because of their one-meter resolution, the images reveal many oil facilities to in-house interpreters. If there is a question about the site, field crews are then sent to a known, pinpointed location to verify the map accuracy. This innovative method not only saves LOSCO time and money, but it is also highly effective and thorough. Moreover, the creation of CIR DOQQS and their use for mapping features answer, with a single solution, LOSCO'S need for high resolution imagery and surface feature location. Baseline Samdin~ and Analvsis Study Another major component of the LOGIS database is the Baseline Sampling and Analysis (BSA) study. This new product provided a means to evaluate the current petroleum hydrocarbon concentrations in Louisiana's coastal zone sediments where an oil spill could occur. Over a three-year period, four contractors are performing sampling to provide Global Positioning System (GPS) coordinates and laboratory analysis of samples taken throughout the study area. First year field work for the sampling component included pinpointing monitoring points by GPS on land and in water and performing sample collection and analysis. Years two and three involve re-sampling the points established during year one. The sampling study concentrates on areas exhibiting a high probability for oil spills. LOSCO ranked areas in terms of probability as follows:
To assist field crews with their sampling, LOSCO and the contractor developed a Microsoft Access database. Using laptop computers, field crews are able to input field data directly into a digital format, including Latitude and Longitude with corresponding UTM coordinates from the GPS. As the study progresses, each contractor's database shows the cumulative samples collected. Sampling progress is monitored by displaying the sample coordinates stored in the database as an ArcView GIS theme superimposed on the system base map. The ability to quickly display this type of geospatial information has proven to be an invaluable asset for project management. This ability allows management to observe differences between actual and proposed sample locations, monitor sampling progress visually, and evaluate projected completion for sampling operations. Pit and Barge Studies Two specific studies identify oil sites that pose a threat. They are the pit and barge studies. The purpose of the first effort, the pit study, is to identifi and locate abandoned oil production facilities and apparatus that pose a potential threat for creating an oil spill through either natural or accidental causes. Erosion and other problems frequently expose oil production elements in the coastal waters, including oilfield waste pits, pipelines, manifold headers, and tank batteries, that were formerly buried or on land. Additionally, the cribbing around a well may decay or fall away, leaving the well exposed. These exposed elements also are susceptible to damage by boat traffic. Contractors for LOSCO noted all apparatus and pits in the field with this potential and determined the positions of these features with GPS. The observable data recorded for each location includes feature type, observations on the feature, and in some cases, photographs or site plans. The total number of sites inventoried to date is approximately 16,200, all cataloged in the working LOGIS database. The purpose of the second study, the barge study, is to inventory abandoned vessels and barges in Louisiana's coastal waters. The inventory located containers of oil waste (primarily abandoned vessels) requiring immediate attention and potential containers for oil waste which could become a hazard. Such containers may hold oil or other hazardous wastes that could be released into the environment or are potential repositories for future illegal hazardous waste dumping. The inventory allows LOSCO to access various data including location of the vessel, identification of the vessel and its owner (if determinable), and a priority based on hazard potential. The inventory includes 802 vessels located in three zones of the project study area. Data was converted from an existing Microsoft Access database of barge and pit locations into a standard framework for direct integration with ArcView. Progress is monitored by the display the pit and barge coordinates stored in the database as an ArcView theme superimposed on the system base map. Conclusion The LOGIS database has already proven to be a tool with many applications. The next challenge will be distributing and maintaining such a large volume of data. LOSCO and its contractor already are planning for distributing the system over the Internet. However, serving more than a terabyte of data via FTP or through a Web browser currently is not feasible. The team now is evaluating its data set priorities and researching new data compression techniques so they will be prepared when it becomes time to distribute the data. With a broad range of data incorporated into the system, LOSCO is able to meet all its needs from oil spill planning to response to damage assessment. Therefore, while the tankers and barges continue to carry oil into and out of the Bayou State, the people of Louisiana can let the good times roll. Through preparation for the worst, LOSCO is preventing it. As a result, LOSCO is protecting the best resources the state harbors: its people and its environment. Acknowledgements LOSCO would like to thank all private entities and government agencies that have contributed to and supported the LOGIS effort. The LOGIS project would not be successful without cooperation from both government and the private sector. | ||
| © GISdevelopment.net. All rights reserved. |