Restoration of Heavily Oiled Tidal Flats and Salt Marshes 18 Years After The Gulf War Oil Spill Linos Cotsapas Jason Hale, Christopher Cormack, Thomas Minter, and Jacqueline Michel Research Planning, Inc. and Pandion
Outline Introduction/Restoration Goals Indicators of Stress Remediation Activities Results
The Event and The Program Largest marine spill in history Less than 10% of estimated spill volume recovered UN-sponsored; KSA-implemented program governed by UN-set guidelines
Guiding Principles Decision 258 and F4 panel principles: Avoid techniques that pose unacceptable risks Facilitate natural recovery to the extent possible Rely on proven techniques Utilize adaptive management Be cost effective Consider short- and long-term effects and landscape connectivity Result in more positive than negative results
The Approach Target Ecological Restoration Methods must: Understand and characterize conditions and site Identify stressors Design appropriate remediation activities Test and monitor effects of remediation activities Adaptively manage
Heavily Impacted Tidal Channels Healthy Tidal Channels
Achieving Restoration Goals Promote ecological restoration in contrast to removal of contaminants Ecological structure, what we see Ecological function, the jobs that are done
Achieving Restoration Goals Promote ecological restoration in contrast to removal of contaminants Ecological restoration and natural recovery Remediation activities must promote or accelerate rate of natural recovery Remediation activities must conserve areas exhibiting natural recovery
Achieving Restoration Goals Promote ecological restoration in contrast to removal of contaminants Ecological restoration and natural recovery Removal of contaminants implies oil is the principle stressor But is this the case after 20 years?
Indicators of Stress Ponding of upper marsh and channels at low tide Widespread laminated algal mat Widespread oil residues, surface and sub-surface Tidal channel bank and bottom habitat degradation Limited abundance and distribution of halophytes (annual and perennial) Limited abundance and distribution of key benthic fauna
How to Speed up Recovery Build on proven methods and adaptively manage to local conditions Practical methods that are readily implementable Assess results and adapt
The Setting Salt marshes and tidal flats: Make up over 95% of intertidal habitats between Jubail and Kuwait border Severely impacted by the spill
Salt Marshes Remediation Objectives Re-establish tidal channel function Eliminate ponding - promote drying of part of marsh surface between tidal cycles Reduce total petroleum hydrocarbon levels Remove/till barriers Provide improved channel bank and bottom substrate
Salt Marshes Techniques Channel excavation/refreshment Tilling to break up algal mat and cohesive oiled sediments Removal/disposal of surface and cohesive subsurface oiled layers Microhabitat creation Planting of marsh vegetation
Tidal Flats Remediation Objectives Increase suitable habitat for grazers and burrowing infauna Reduce total petroleum hydrocarbon levels Improve drainage and reduce ponding between tidal cycles Tilling to break up algal mat and cohesive oiled sediments
Tidal Flats Techniques Dry tilling of sediments followed by manual removal of remaining surface oil Wet tilling of sediments within constructed berms while flooded to liberate oil; and recovery by skimming/vacuuming Removal/disposal of surface and cohesive subsurface oiled layers
Excavation of Tidal Channels Routing always follows natural cues Priority - existing channels in salt marsh habitat Additional straight channels added to areas with persistent ponding during low tide and where density was below average Rules of connectivity determined stream order Fixed dimensions for channel types
Excavation of Tidal Channels Before Excavation (line indicates location) After Excavation
Excavation of Tidal Channels
Channel Development
Channel Development
Point Bar Morphology
Point Bar Micro-Habitat
Pool Morphology
Microhabitat Creation
Mangrove Transplants
Tilling and Mixing
Wet Tilling
Oil Liberation and Removal
Results
Project Site Plan
Restoration Progress-Ecology Abundance and distribution of key benthic taxa that perform critical ecosystem functions: Grazing of microalgae substrate to keep channel bottom free from algal mat build-up Bioturbation for nutrient and carbon cycling; continued release/remediation of remaining residues
Restoration Progress-Ecology
Early Colonizers - Channel Bottom Grandidierella amphipod Habitat
Early Colonizers - Channel Bottom Grandidierella amphipod Potamides mud snail Polychaete and other benthic infauna Habitat
Nasima Burrowing Activity
Monitoring Results Robust monitoring program established measuring physical, chemical, and ecological variables Monitoring program data indicate that remediation methods have increased rate of ecological recovery in both salt marshes and tidal flats
CRC1 Colonization Two months post excavation South Channel North Channel Nasima Snails Amphipods
CRC1 Colonization Five months post excavation South Channel North Channel Nasima Snails Amphipods
CRC1 Colonization 30 months post excavation South Channel North Channel Nasima Snails Amphipods
Average TPH Levels Before and After Wet Tilling 14000 12000 TPH (mg/kg) 10000 8000 6000 4000 Before After 2000 0
Number of Burrows present in channel along 10 m transect 350 300 250 200 150 100 50 0 10-May-2010 10-Jun-2010 10-Jul-2010 10-Aug-2010 10-Sep-2010 10-Oct-2010 10-Nov-2010 10-Dec-2010 10-Jan-2011 10-Feb-2011 10-Mar-2011 10-Apr-2011 10-May-2011 10-Jun-2011 10-Jul-2011 10-Aug-2011 10-Sep-2011 10-Oct-2011 10-Nov-2011 10-Dec-2011 10-Jan-2012 10-Feb-2012 10-Mar-2012 10-Apr-2012 Date
Program Achievements Excavated +160 km of existing and new tidal channels Tilled +300 ha of marsh and unvegetated tidal flats Off-site disposal of 110,000 m 3 oil-contaminated substrate On-site re-use of 45,000 m 3 of No or low contaminated substrate as micro-habitat Transplanted 105,000 mangroves Remediated 1,800 ha of salt marsh and tidal flat habitat
Conclusion Even after total devastation, with little if any natural recovery occurring 18 years after the spill, restoration of salt marshes and salt flats by re-establishing hydrological functioning and removal of physical barriers is possible with significant and quantifiable positive effects in the recovery of intertidal habitat functions