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Refuges Selected for Study 13 



3. ECOSYSTEMS DESCRIPTIONS 15 



Use of Ecosystems Diagrams 15 



Modeling the Systems 19 



Coastal Uplands 20 



Salt Marsh 32 



Brackish Marsh 36 



Fresh Marsh 42 



Delta Marsh 47 



Levees and Spoil Banks 50 



National Wildlife Refuge Descriptions 55 



Aransas National Wildlife Refuge 57 



Brazoria and San Bernard National Wildlife Refuges 62 



Delta National Wildlife Refuge 68 



Sabine National Wildlife Refuge 72 



4. HYDROCARBON RESOURCE EXTRACTION AND TRANSPORT METHODS 77 



Introduction 77 



Purpose 78 



Overview of Phases of Oil and Gas Activities Found On and 



Off Refuges 78 



Detailed Account of Typical Off-Refuge Oil and Gas Activities . , S3 



Preexploration 84 



Access to the Site 87 



Site Preparation and Operation 93 



Placement and Operation of Production Facilities 101 



Petroleum Transportation Ill 



Oil and Gas Activities on Wildlife Refuges 122 



Aransas National Wildlife Refuge 122 



Brazoria National Wildlife Refuge 126 



Delta National Wildlife Refuge 128 



Sabine National Wildlife Refuge 131 



San Bernard National Wildlife Refuge 135 



Sources of Methods and Standards Required on Refuges 137 



5. OVERVIEW OF IMPACTS ON ECOSYSTEM FUNCTION 138 



Coastal Uplands 138 



Marsh Ecosystems 139 



6. ECOLOGICAL IMPACTS OF OIL AND GAS ACTIVITIES 143 



Use of Ecosystem Diagrams for Impact Assessment 143 



Development Activities 143 



Primary Ecological Alterations 144 



Ecosystems Analysis 146 



Impact Assessment 148 



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