In recent years, there has been increasing concern about man-made debris discarded from offshore and coastal sources and its impact on the marine environment (e.g. Shomura and Godfrey, 1990; Laist, 1987; Heneman and Center for Environmental Education, 1988). Both entanglement in and ingestion of debris have caused the death or serious injury of individual marine mammals (MMC, 1995). The debris items most often found entangling animals and most likely to result from OCS operations are strapping bands and ropes; however, these may also originate from all types of marine traffic not related to oil and gas operations.

(c) Coastal and Marine Birds

A number of normal OCS activities, such as helicopter and service vessel traffic and construction, may affect marine and coastal birds. The major impact-producing factors include disturbance, displacement, and entanglement/ingestion.

Helicopter and service vessel traffic could disturb feeding, resting, or nesting behavior of birds or cause abandonment of preferred habitat. If the disruption was sufficient, this could contribute to population losses by displacement to areas where birds may experience increased environmental or physiological stress. Disturbance of coastal and marine bird nesting and feeding habitats near pipeline landfalls and onshore construction sites could cause a reduction or desertion of birds that use that habitat. Such displacements could have a considerable effect on a local population for one or two generations. Impacts on regional populations should be considerably less unless the affected area was a key habitat for the species.

Coastal and marine birds can become entangled in or ingest plastic debris which may result in injury or mortality. Such debris may be the result of accidental discharges of such material from service vessels, drill rigs, or platforms. Ingested plastic and styrofoam material may cause internal blockage, resulting in injury or death. Ingested plastic may also impair feeding activity and limit accumulation of fat reserves necessary for reproduction and migration (Ryan, 1990; Sileo et al., 1990a). All such material from OCS operations is normally collected and disposed of onshore.

(d) Fish Resources

Normal OCS oil and gas activities that affect fish resources include seismic surveys, construction, and discharges.

Present seismic surveys use nonexplosive energy sources such as airguns to collect seismic data, as permission to use explosive energy is seldom granted. A 300-cubic-inch airgun, which derives its energy from highly compressed air, has a potential lethal radius of 0.6 to 1.5 meters. Considering the widespread distribution of fish (larvae, eggs, smolt, adults, etc.) and the small potential lethal radius of airguns, seismic surveys should have a negligible effect on fish populations, even on a highly localized basis. Seismic surveys that employ airguns affect fish only in a limited area. Experiments testing the effects of air guns on caged coho salmon smolts found no harmful effects (Weaver and Weinhold, 1972). Air guns had little effect on even the most sensitive fish eggs at distances of 1.5 m from the discharge source, and discharges were not observed to have any effect on larvae at the same distances. The disturbance from the acoustic energy generated during the survey may cause a temporary cessation of feeding (Skalski, Pearson, and Malme, 1992). These impacts probably would occur only during the minutes when the acoustic energy source is strongly perceived by the fish.

The installation and initial presence of offshore structures could initially cause temporary disturbance to or displacement of fish. Normally, however, within a very short period of time invertebrates and macrophytes (seaweeds) will settle onto platform legs. These organisms develop quickly and serve as an attractive food source for fish populations. The structures also provide shelter for fish.

Dredging operations associated with platform siting and pipeline laying could result in short-term (a few weeks), localized (a few acres to a few miles) effects on fish. Bottom disturbances result in resuspension of bottom sediments which may clog the gills of both finfish and shellfish with resultant smothering. Settlement of resuspended sediment may directly smother invertebrates or cover burrows of shellfish. Suspended sediments are mostly deposited near where the disturbance occurs. Fish usually avoid areas of high turbidity but soon return as they are attracted to feeding on benthic species exposed by the sediment turnover.

Lethal effects from dredging can also be caused by the entrainment of adult fish or larvae in the suction head of the dredge. However, adult fish densities are normally low in areas where dredging activities take place because of the noise and resuspended sediments.

The majority of platforms are removed by severing platform pilings with explosives placed 5 m below the mud line. The concussive force is lethal to fish with internal air chambers (swim bladders) and those that are located near the bottom in close proximity of the blast. The fish that used the platform as habitat (shelter, food source, etc.) and survive the platform removal would be without the food source provided by the growth of marine organisms on the platform legs, and subject to additional predation.

(e) Reptiles

The normal offshore OCS oil- and gas-related activities that are most likely to result in adverse impacts to sea turtles are service vessel traffic, pipeline construction, and possibly platform removal.

Potential impacts to turtles from service vessel traffic range from nonlethal, short-term startle reactions through lethal collisions. Measurable impacts on local turtle populations from vessels are not anticipated due to the diving behavior of turtles which places them below the surface approximately 90 percent of the time.

Pipeline construction in winter could result in turtles being injured or killed due to a failure to avoid construction activities resulting from reduced metabolic activity. Such activities should not result in turtle injuries or mortalities during the summer months as trenching and pipelaying activities should displace turtles away from construction areas. In deeper water, where the pipeline would be placed directly on the seafloor, no adverse impacts are anticipated.

Platform removal could result in the death of a few animals if turtles attracted to these structures are not displaced and explosives are used. Explosive platform removals can cause capillary damage, disorientation, and loss of motor control in marine turtles. Although marine turtles far from the site may suffer only disorientation, those nearby can sustain fatal injuries. Lethal impacts are most likely to occur at platforms sited in relatively shallow water owing to the primarily inshore or coastal distribution of most species. Pelagic leatherback turtles are an exception. Juvenile sea turtles are not expected to be routinely found near platforms during the migratory stage of their early development.

OCS-related debris is a source of mortality and debilitation for marine turtles. They are attracted to floating plastic debris because it resembles their preferred food, the jellyfish. Ingestion of plastic and styrofoam materials can result in drowning, lacerations, digestive disorders or blockage, and reduced mobility resulting

in starvation (Carr, 1987; USDOC, NOAA, 1988d; Heneman and the Center for Environmental Education, 1988; USDOI, MMS, 1989). The MMS prohibits the disposal of such debris from oil and gas facilities into the marine environment.

Offshore and onshore biological habitats can be affected to varying degrees by normal OCS oil and gas activities. These activities include construction, anchoring, emplacement of offshore structures (platforms and pipelines), dredging, discharges, and platform removal.

WETLANDS AND ESTUARIES: Wetlands occur as tidal marshes and swamps and the loss of these habitats is a major problem. Impact-producing factors resulting from OCS oil and gas activities that could adversely affect wetlands include pipeline placement, dredging navigation channels, and construction of facilities in wetland areas.

Pipeline emplacement in wetlands and estuaries can convert the habitat to open water (canal) and spoil areas and result in secondary effects related to the hydrologic changes associated with the canal. Generally, onshore pipeline projects are backfilled which minimizes or eliminates spoil banks and reduces secondary impacts. After backfilling, a pipeline right-of-way re-vegetates or remains as a shallow water body (Tabberer et al., 1985: Turner and Cahoon, 1987: Wicker et al., 1989). Turner and Cahoon (1987) determined that 77 percent of all existing OCS-related pipeline canals in the Gulf of Mexico coastal plains were backfilled, partially filling the canal. In areas where soils have high organic content (such as a marsh or swamp), a canal is not usually filled completely after backfilling. In areas with soils containing low organic content, most of the canal length is usually filled and naturally re-vegetates after backfilling. Damage to wetlands includes temporary die back of the above ground vegetation, some complete plant mortality, and accelerated rates of land loss (the conversion of wetlands to open water).

Modern installation methods and planning procedures have reduced the levels of impacts from pipeline construction in wetlands. Directional boring under sensitive surface features eliminates adverse impacts as the pipeline is driven through the soft subsurface material without disturbing the surface.

Dredging of new navigation channels and maintenance dredging of existing channels encourages salt water intrusion. Disposal of dredge material can cover adjacent wetland areas and aggravate the damming effect of the spoil banks on marsh surface drainage. If wetlands occur along navigation channels, waves generated by OCS-related vessels in the channel can cause bank erosion and wetland loss. Channels that have high navigational usage widen about 1.5 m/yr more rapidly than channels that have little navigational usage.

Onshore support facilities located in wetlands could damage or destroy the habitat. It is highly unlikely that permission to construct facilities would be granted in wetlands. Should permission be given, the clearing of native vegetation, filling of flood prone areas, and altering of local drainage regimes are likely to affect swampy or marshy areas within and near the site.

BARRIER BEACHES: Coastal barrier beaches occur adjacent to a large portion of the OCS, especially in the Gulf of Mexico and Atlantic Regions. The primary impact-producing factors that could affect barrier beaches are pipeline landfalls and navigation channels.

Where buried pipelines come ashore, the landfall through a barrier beach may be dredged, or the pipe may be directionally bored through the beach with no surface disturbance. Where dredged, replacement of beach material usually results in the landfall returning to its natural state within a short time.

Pipeline landfall sites on barrier islands have been identified as potential causes of accelerated beach erosion and island breaching. Little or no impact to barrier beaches occurs as a result of modern techniques for pipeline crossings (Wicker et al., 1989; LeBlanc, 1985; Mendelssohn and Hester, 1988).

The construction of new navigational channels or the deepening of existing ones through barrier beaches and barrier passes could result in interruptions in the littoral transport system and deprive beaches located downdrift from the channels of needed sediments. Some localized erosion is expected in the vicinity of navigation channel dredging. Jetties designed to reduce shoaling in channels and maintenance dredging and stabilization of bar channels could affect the stability of adjacent barrier landforms if jetties or the bar channel serve as sediment sinks that intercept sediment from longshore drift. Material from maintenance dredging of bar and pass channels is typically discharged to nearby, ocean dump sites, which usually remove the sediment from the littoral sediment drift, or routes it around the beach immediately downdrift of the involved channel. Placement of dredged material in shallow coastal waters sometimes forms sand bars that impair coastal navigation by shallow water vessels.

SEAFLOOR: OCS oil and gas activities that could affect seafloor habitats are the emplacement of platforms, laying pipelines, platform removal, and anchoring.

The emplacement of platforms and pipelines, removal of platforms, and anchoring result in resuspension of bottom sediments. The resettlement of the sediments could cause smothering of bottom communities. Subtidal soft- and hard-bottom organisms can be crushed by activities such as pipeline dredging and anchoring of drill rigs, pipeline barges and service vessels.

The bottom area disturbed in the emplacement of platforms is about 9 acres per platform. Pipeline placement causes considerably more disruption to the bottom sediments and consequentially benthic communities than platform placement because the disturbance is linear and may extend for many miles. In deeper water the placement of the pipeline on the surface can crush benthic organisms. The dredging of the pipeline trench and placement of dredged material next to it can cover hard-bottom communities. Sediment thrown into suspension by the dredging activity can move down-current to settle on and smother additional areas of hard bottom.

Impacts on hard-bottom benthic communities around platforms could result in the community within a 100 yard radius being destroyed or severely altered. The impacts could come from crushing from the platform itself, anchoring of exploratory drill rigs, anchoring of service vessels, and drill discharges. Recovery could require several years after the platform is removed.

Anchoring can result in scars (trenches and mounds) on the seafloor that could range from 160-1,800 feet in length and could last for 2 to 5 years in fine soft-bottom sediments. Anchor cables could disturb bottom areas for 1,600 feet per anchor and create a 2-foot swath. These scars could serve as traps for fine sediment and organic material. Bottom disturbance could result in temporary changes in species composition on the seafloor. Temporary and local sediment scouring could result in reduced dissolved-oxygen concentrations and interfere with the feeding of suspension feeding benthic species causing alteration of ecological relationships, displacement/reduction of some species or enhancement of the population of others. These impacts could be expected to last 1 or 2 years in soft bottoms. Hard-bottom communities take longer to recover than softbottom communities.

Removal of platforms may cause impacts to the habitats in and near where they are located. The impact of platform removal on benthic communities (both soft and hard bottoms) could include crushing and displacing established organisms during vessel anchoring and the detachment of the platform jacket from its foundation. The effect should be localized and short-term on soft-bottom habitat. In hard-bottom conditions, impacts would also be local, but would probably require more than 5 years to recover. Additionally, the removal of the platform itself would result in removal of the artificial reef platform habitat and the loss of associated organisms on the platform. Platforms act as artificial reefs for fish and macroinvertebrates. The legs and cross-members of platforms provide a hard substrate for the development of hard-bottom communities such as mussels, anemones, barnacles, and crabs. Both explosive and nonexplosive removal operations would disturb the seafloor and resuspend bottom sediments in the water column resulting in turbidity. Deposition of these sediments could result in sessile organisms being smothered.

Maintenance dredging of navigation channels and prop-wash of vessel traffic can also temporarily increase nearshore turbidity levels, which can deleteriously affect shallow-water nearshore- biological communities such as seagrasses.

DEMOGRAPHY AND EMPLOYMENT: Coastal areas have experienced considerable growth in recent decades. Currently, coastal areas have a population density more than four times greater than the national average (USDOC, Bureau of Census, 1990). This expansion is expected to continue. The OCS program may contribute to this growth as it has in the coastal communities in the Gulf of Mexico Region where the offshore oil industry is well-established. The fabrication of oil field equipment, construction and operation of support bases, offshore drilling, and the installation of pipelines and processing facilities are all OCS-related activities which directly or indirectly affect the demography and employment of an area.

Offshore activities require onshore support facilities to maintain an adequate flow of supplies and provisions. Resupply efforts for offshore operations could create jobs for residents of coastal communities. About 45 jobs are created with the development of a temporary support base for exploratory activities. Employment is available on the supply boats and crew boats needed for each rig. During bad weather or if drilling operations are more than 24 km (15 mi) from shore, helicopters are required, providing the potential for additional jobs for aviators and crew. In frontier areas, about three-fourths of the total labor requirements could be filled from the local labor force.

Permanent bases to support field development and production activities are considerably larger than temporary bases and they support a much higher level of activity. Up to 90 workers are required for the construction of the base and 50 to 60 service base jobs are associated with each platform engaged in development drilling. In frontier areas up to half of this employment is likely to come from the local labor source. Worker requirements decline during the production phase with only about 20 jobs associated with each platform. However, most, if not all, of these positions could be filled with local labor.

There would also be employment opportunities on exploratory and development rigs, and production platforms. Total employment requirements may exceed 200 per exploratory rig. Labor sources vary but approximately one third could be local hires in frontier areas, one third will relocate from other regions, and one third will commute home during off-duty periods. Exploration drilling is typically a short-term, temporary activity, with drilling programs lasting between 45 and 120 days per well.