gas plants, as with any gas plant, will depend on the composition of the gas that must be processed. Dry, low sulfur gas would need virtually no dehydration, processing, and treatment prior to entrance into the existing transmission system. Wet, high sulfur gas may require extensive dehydration, processing, and treatment. Although no information on these characteristics is currently available, it has been assumed, for the sake of impact analysis, that some degree of dehydration, processing, and treatment will be necessary before any of the OCS gas production may enter the existing transmission system. Facilities employed in the scenario have been identified accordingly. Operational Support Bases

Based on the size of the region and previous activity in the area, it is felt that two support bases would be needed to support the exploration and production of oil and gas associated with Sale No. 111 and currently leased blocks in the area. The currently operating support base at Davisville, Rhode Island would be used to support exploration and production activity in the northern half of the sale area. A second support base in Hampton Roads, Virginia would support exploration and production activity in the southern half of the sale area. These ports meet the principal requirement for a support base: proximity to the lease area, a draft at low tide of 15 to 20 ft, 200 ft of marginal wharf space for each rig or platform, and access to industrial infrastructure such as railroad lines or highways, a favorable public attitude, and warehouse space. The capacity of facilities at both sites is adequate to support the level of activity expected from the proposed action.

Approximately 16 service vessels would be required in the mean case scenario in the peak years of 1995 (27 if currently leased blocks are considered). Round trip distances between the assumed support bases and the offshore structures could range from 100 to 400 mi depending on where in the planning area the leased blocks are located.

Helicopter Support Base

Both Hampton Roads, Virginia and Davisville, Rhode Island have area airports which could serve as helicopter support bases. However, it is more likely that the helicopter support bases would be located at the airport nearest the area of exploration and production. Currently the helicopter support base for exploration in the area is located at the Cape May, New Jersey airport.

Other Infrastructure Compressor Stations

Because of the long distances the pipelines must span, and the assumed gas characteristics, it has been assumed that compressor stations could be necessary to ensure efficient transportation within the pipeline. It has been assumed that these compressor stations would be located along the pipeline route at a depth suitable for a conventional bottom-founded platform (see section on resources and production systems).

Pipecoating Yards

Though pipe coating could occur at a variety of mid-Atlantic coastal locations, the expected quantity of work generated by proposed Sale No. 111, as well as the ability of existing yards to meet the required delivery

schedule of the oil and gas industry assumed for this sale, imply that pipecoating activity could be accommodated by existing yards. Numerous suitable facilities are located in the Gulf of Mexico region. From there the coated pipe would be transported to either the operations support base or the offshore site.

Platform Fabrication

It has been assumed that platform fabrication and subsea complex construction for proposed Sale No. 111 would occur at existing yards in the Gulf of Mexico region or other areas outside of the mid-Atlantic area. From here they would be shipped to the mid-Atlantic offshore area. This assumption was based on 1) the fact that there are no existing platform fabrication yards or subsea complex construction areas on the east coast, nor any active proposals to set up either, and 2) the MMS estimates of the schedule of production expected and cost required imply that it may be more feasible to ship these platforms and subsea completion units from existing yards than to set up new ones. The establishment of new construction facilities involves the consideration of many factors such as overall worldwide demand for platforms and subsea complexes, existing capacities for construction, competitive position of individual companies, and the pace of OCS development on the Atlantic coast.

Table II.B.1-1. Index of Activities for Alternative Development
Scenarios

The leasing of blocks under proposed Sale No. 111 may result in 1 oil spill greater than 1,000 barrels in size over the life of the field. Spills occurring in the proposed lease area have less chance of contacting nearshore or onshore vulnerable resources than those spills occurring along transportation routes.

Impacts on offshore water quality would be minor (see impact level definitions in Section II.B.6) as a result of the proposed action. Routine discharges (drilling muds and cuttings, formation waters, sanitary/domestic rig waters, and low-level oil releases) would result in localized and relatively minor water quality perturbations, while impacts of gas pipeline burial and possible rupture would be characteristically temporary and local in nature. Although a large (greater than 1,000 barrels) oil spill could cause a severe alteration of ambient water quality, this is likely to be temporary.

Impacts on benthic organisms due to mechanical disturbance because of rig and pipeline emplacement would be localized; plankton is not expected to be affected from mechanical perturbations. Drilling muds and cuttings may have a severe impact in the immediate vicinity of the discharge site but regional populations of benthic organisms and plankton are not expected to be affected measurably. Formation waters will have a minor and extremely localized impact on plankton communities in the immediate vicinity of the discharge pipe. If formation waters are shunted to the bottom, localized impacts on benthic organisms can be expected. Oil spills would have their greatest impacts in nearshore, shallow waters. Benthic organisms are especially vulnerable to the effects of oil whereas planktonic species are expected to be affected to a lesser degree. Bioaccumulation of metals from drilling fluids poses a temporary problem for benthic organisms. Considering all impact-producing factors resulting from the proposed action, moderate impacts on benthic organisms and minor impacts on plankton can be expected.

Marine and coastal birds could be exposed to several adverse impacts from OCS oil and gas exploration and development associated with proposed Sale No. 111. These impacts can be broken down into direct and indirect effects. Direct include contact with a spill causing matting of plumage which can reduce flying and swimming ability, loss of buoyancy which prevents resting and sleeping on the water, and loss of insulation resulting in death by exhaustion. Oil ingestion and accumulation of toxic petroleum hydrocarbons can lead to reproductive failure and increased physiological stress which can reduce an animal's ability to survive. During the nesting season, oiled adults can transfer oil from their plumage to unhatched eggs or chicks, thereby reducing hatching and fledging success. Indirect effects include impacts that can alter a species' habitat, prey availability, or cause a disruption of essential activities. The incorporation of crude oil into the sediments of a shallow bay, estuary, or wetland could contaminate that habitat and depress populations of prey species (primarily shellfish) for several years. Construction activities, service vessel and helicopter traffic, and platform noises

could disturb nesting, migrating, feeding or resting birds. But due to the low probability of an oil spill occurring as a result of this proposal, impacts on marine and coastal birds and their habitats are considered to be minor.

Coastal habitats are potentially very vulnerable to impacts from oil spills, pipeline emplacement, and construction of onshore facilities. However, due to the low probability of an oil spill resulting from the proposal, there should be a negligible impact on sensitive coastal habitats.

Endangered birds (bald eagle, peregrine falcon, brown pelican, and Bermuda petrel) could be adversely affected by spilled oil, either by direct contact or oiled prey. The shortnosed sturgeon is not expected to be affected by this proposal. Due to the low number of expected oil spills from the proposal, impacts on endangered birds and coastal species are considered minor.

Endangered sea turtles could be adversely affected by spilled oil by contact and/or ingestion. Collision by support vessels in the vicinity of rigs and platforms could cause injury or death. However, the low number of expected oil spills and numbers of platforms resulting from this proposal indicates that only a minor impact on sea turtles is to be expected. Marine mammals (whales, dolphins, and porpoises) are vulnerable to adverse effects stemming from contact with spilled oil such as skin and eye irritation, inhalation and ingestion of oil, and baleen fouling. Disruption of feeding and migratory behavior due to the presence of oil in the water also adversely affects these animals. Cetaceans may be startled by low frequency sounds associated with activities on rigs and platforms and geophysical surveys. A minor level of impact on the sperm and sei whales is expected. However, if production activities are concentrated in the deeper (slope) waters of the lease area, these two species could experience somewhat greater impacts. Humpback and fin whales may have a minor level of impact. Activities associated with the proposed action could have a moderate impact on right whales.

Impacts on the mid-Atlantic fish resources would be a result of spilled oil contacting vulnerable egg and larval stages. This will cause a minor impact with individual populations experiencing local declines in abundance and changes in distribution. Recovery to pre-impact levels is expected,

however, within 1 year.

Adverse impacts on commercial and sport fishing are primarily due to oil spills and preclusion of fishing space by OCS facilities. However, the expected number of oil spills and OCS structures to be built as a result of this proposal will produce minor impacts on the mid-Atlantic commercial and sport fishery. Economic losses are expected to be less than 10 percent with secondary employment not affected.

Coastal recreation areas may experience a moderate impact on a local scale as a result of an oil spill contact. However, the overall regional expected impact level is negligible.

Since all proposed activities and facility siting and construction are expected to occur in generally compatible areas and since detailed siting approval and procedural requirements are expected to reduce impacts where unavoidable, it is expected that impacts on land use will be minor.