c. Formation Waters Characteristics of formation waters and EPA discharge limitations are discussed in Section IV.D.2, Formation Waters. An estimated 160 million barrels of formation waters would be discharged over a production period of 27 years from 4 production platforms within the approximately 20.3 million acres of the proposed lease area (presuming a mean oil resource estimate of 200 million barrels and that 0.8 barrels of formation water are produced for each barrel of crude oil recovered--per Appendix D of 1982 Regional FEIS, Gulf of Mexico). Larger volumes would probably be produced near the end of the reservoir's life and small volumes at the beginning, as usually occurs with formation water production. Discharged formation waters would undergo dispersion similar to that described for fine particulate and liquid drilling discharges whereby they would be rapidly diluted and ultimately lost in the large volume of receiving water. Formation waters have a relatively high density and low oxygen content compared to sea water (see Section IV.D.2). Therefore, if large volumes are discharged near the bottom in deeper areas where bottom turbulence is not strong, highdensity flows of low-oxygen water could result. If formation waters are discharged near the surface, however, they would be rapidly diluted in the water column within a few hundred meters and, therefore, are not considered to have a substantial effect on overall ambient water quality. The nature of dissolved elements and their respective concentrations would depend on formation characteristics. To determine the impact formation water would have on ambient water quality, the specific quantitative and qualitative characteristics need to be known. Trace metals present in discharged formation waters would raise ambient concentrations in the immediate vicinity of platforms. Depending on hydrographic conditions, background levels would be reached within a few hundred meters. A comparison of the estimated concentrations of trace metals in typical California formation waters after 1,000-fold dilution (500 meters from the discharge point) with EPA 24-hour criteria (Table IV.E.1-3) showed all trace metals falling below the EPA criteria "safe" levels. Hydrocarbons are present in formation waters as small droplets or in dissolved form. The hydrocarbon content of discharged formation waters would be within EPA's prescribed effluent limits (the concentration of oil should not exceed 72 mg/1 for any one day nor exceed an average 30-day concentration of 40 mg/1 (40 CFR 435)). Based on a total formation water discharge of 160 million barrels (discussed earlier) and an average petroleum content of 25 ppm in formation water (US EPA, 1976), a total of 4,000 barrels of crude oil in formation water would be discharged within the proposed lease area. Because these discharges would be distributed over a long timeframe and widely spaced over a broad area, only small, incremental increases of hydrocarbons would occur at any given time. Upon discharge, some hydrocarbon components would evaporate, and the remainder disperse and subsequently weather in the surrounding receiving waters or settle onto the bottom sediments where they would degrade at a slower rate (see Section IV.B, Oil Spills in the Mid-Atlantic Marine Environment). Dilution models indicate that the areal extent of elevated hydrocarbon levels around a platform would be 0.1 square miles for concentrations over 10 ppb, and 0.001 square miles for those over 1 ppm (Massachusetts Institute of Technology, 1973). Table IV.E.1-3. Trace Metal Arsenic Cadmium Total Chromium Copper Lead Mercury Nickel Silver Zinc Cyanide Comparison of Estimated Maximum Seawater Concentrations Estimated Maximum Concentration 0.08 0.04 0.116 0.28 0.002 0.29 0.03 3.2 0.004 SOURCE: FEIS for Proposed 1983 California OCS Sale No. 73. EPA 24-hr Criteria (ug/1) 508 4.5 18 4.0 663 0.10 7.1 2.3 58 2 d. Other Discharges or Sources of Pollution Domestic wastes (from sinks, showers, laundries, and galleys) and sanitary (sewage) wastes (from toilets and urinals) will be discharged from drilling rigs and platforms. On the average, approximately 100 gallons/person/ day are discharged from offshore oil and gas facilities. of this total rate, sanitary waste comprises approximately 25 gallons and domestic waste the remaining 75 gallons (Burgbacher, J., Shell Oil Company, New Orleans, LA, personal communication, 1984). It is estimated conservatively that approximately 56 million gallons of sanitary waste and 168 million gallons of domestic waste would be discharged during the 34-year total exploratory and production period for Sale No. 111. Sanitary discharges are subject to EPA NPDES permit regulations (e.g. regarding floating solids and residual chlorine content). Plume models (Massachusetts Institute of Technology, 1973; Mobile Plume Model, 1976) indicate that sanitary waste effluents are rapidly dispersed and diluted in the water column. Impacts on water quality would consist primarily of an increase in suspended solids (organic material) and accompanying BOD, and a decrease in oxygen levels in the In addition, low levels of discharged chlorine could eventually form toxic compounds. Impacts from these discharges, however, would be localized near the point of discharge, and pollutants would be greatly diluted and dispersed in the larger volume of receiving water. Routine petroleum discharges associated with deck drainage, ballast water, etc., are also subject to EPA NPDES permit requirements as cited in Section IV.D., Drilling and Production Discharges in the Mid-Atlantic Marine Environment. But, because of the subjective nature of the "no visible oil or sheen" standard for deck drainage, oil in these chronic discharges could cause temporary, localized impacts on water quality in the vicinity of drilling rigs. These impacts are not considered to be substantial because, for the entire proposed sale area, no more than 14 wells (usually less than 5) are expected to be drilled during any single year (deck drainage is primarily associated with drilling rigs, not production platforms), and it is unlikely that all rigs would be concentrated within one particular region. Also, the same forces that would promote the dispersion and degradation of large acute spills would act upon chronic discharges of oil in deck drainage (see Section IV.E.1.a, Oil Spills). A total of 300 miles of pipeline (100 miles of trunk line and 200 miles of gathering line) will be installed to transport gas from the lease sale area to shore. If it is decided to bury part of this pipeline, up to approximately 28,000 cubic yards (21,700 m3) of sediment could be disturbed per mile of pipeline laid (see Section IV.E.2). Disturbance of sediment as a result of pipe burial would cause resuspension of sediment, which in turn would temporarily affect water quality by increasing levels of suspended particles and turbidity. The magnitude and extent of any increase in turbidity would depend on hydrographic factors operating at the time of installation, on the duration of activity, and on the type and grain size of the bottom materials. Suspended sediments would be dispersed and transported in the prevailing current direction as described for general transport in Section IV.D.1, Drilling Muds and Cuttings. Pipeline burial could also resuspend toxic metals, pesticides or other organic or inorganic compounds if a sludge or chemical waste dumpsite (shown in Visual No. 1) were traversed. However, final pipeline route determination would emphasize avoidance of such areas. Overall impacts on water quality from pipeline installation by burial then, if it were to occur, would be temporary and, due to dispersion and/or settling of materials, minor in nature. Breaks or ruptures of gas pipelines could occur, although the probability and frequency at which they may occur are unknown. Gas released into the water column would probably result in increased levels of light molecular weight hydrocarbons (C2 to C5) which would subsequently evaporate into the atmosphere. Areas of up to 25 square miles have been reported to be affected in this manner (Parker, 1974). However, concentrations would return to background levels after the gas flow had been curtailed. The most significant effect of gas blowouts would be the localized disturbance of sediments, resulting in temporary water column turbidity. Therefore, impacts from gas pipeline accidents are considered to be temporary and minor to water quality. In summary, the 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. The probability that the one assumed spill (over 1,000 barrels) from the 4 production platforms or from tanker transportation would reach the shallow, coastal area, where severe and prolonged water quality impacts may result, is only 7 percent. Conclusion: A minor, overall impact on water quality is expected from the proposed action. Cumulative Impacts When the oil (160 MMbbl) and natural gas (2.4 tcf) from the presently leased blocks within Sale No. 111 area are added to the proposed action, the total mean resource estimates increase by approximately 80 percent for oil and 66 percent for gas. This means an increase (less than twofold) in exploration and production facilities (wells, platforms, etc.) and, in turn, a less than twofold increase in the total volume of routine discharges (drilling muds and cuttings, formation waters, low-level oil releases, and domestic/ sanitary wastes). However, the volume of these materials would still be small compared to the large volume of the receiving water. These materials would be rapidly dispersed/diluted within a geographically large area and spaced over a long period of time such that impacts to water quality, due to these discharges, would still be temporary and minor in nature. Consideration of existing leases in the Mid-Atlantic Planning Area and existing leases and proposed sales in the North and South Atlantic Planning areas, in addition to the proposed action, results in a combined resource estimate of approximately 457 million barrels of oil (Table 1, Appendix C). The assumed total number of spills (> 1,000 bbl) is still one, this being the same number as in the proposed action (Alternative 1) (Section IV.B.3). Import of oil by tanker, a non-OCS oil and gas related activity, into or through the mid-Atlantic region is projected to result in 27 oil spills (crude and refined product) greater than 1,000 barrels and 13 spills greater than 10,000 barrels (Table 1, Appendix C). The probability for occurrence of one or more spills of 10,000 barrels or greater is very high--greater than 99.9 percent. When the importation of oil is considered together with the proposed action and existing leases, the likelihood of a large spill (from the sum of these actions) occurring or being carried to inside the shelf break and close to shore within 30 days, as measured by "land" contact using the OSRAM model, increases dramatically--becoming 97 percent (Table 12, Appendix C). A large oil spill occurring in the shallower coastal area may cause a severe degradation of ambient water quality. Spilled oil may get dispersed throughout the water column and may get entrained in suspended particles and bottom sediments, subsequently to be re-released into the water column as a result of tide, current or wave action. Thus, existing transportation of oil represents a substantial risk which may result in a large oil spill causing major impact on water quality in the mid-Atlantic region. Preliminary results of analyses conducted by the National Oceanic and Atmospheric Administration (NOAA, 1984) indicates a considerable input of oil into east coast waters from the operational discharges of tank ships. This oil input, resulting from normal ship operations (bilge water pumping and tank cleaning and ballasting), was estimated for the year 1979 to be in excess of 4.3 million gallons for the east coast area 3 to 400 miles offshore (3 to 200 miles offshore-Exclusive Economic Zone, plus additional 200 miles further offshore). It appears that, for most years, the total input into east coast waters (3 to 200 miles offshore) far outweighs that resulting from accidental spills. However, the concentration of surface oil from these operationsal discharges is estimated to be relatively small and not varying substantially among seasons. The greatest concentration of dispersed and weathered oil from operational discharges expected to be found off the east coast (3 to 200 miles offshore) is only slightly greater than one-tenth of a gallon per square mile, and less so within the mid-Atlantic area proper. The focus of concern in regard to these operational discharges is in relation to potential chronic and long-term impacts (NOAA, 1984). Within the Sale No. 111 area, a major activity affecting water quality has been that associated with the disposal of industrial (and some municipal sewage sludge) waste at the 106-Mile Ocean Waste Disposal Site located in the northeast portion of the proposed sale area (Visual No. 1). EPA has now designated two smaller sites (for industrial waste and municipal sludge) within and as a replacement for the 106-Mile Site. Water quality impacts from these two new sites is anticipated to be short-term and limited (Section III.A.5.a). Some nearshore (coastal) areas of the Middle-Atlantic Bight have degraded water quality resulting from pollution inputs associated with ocean dumping and estuary/river outflow (discussed in Section III.A.5.b). The impact on water quality from the 11 dredged-materials dumpsites located nearshore to the Middle-Atlantic Bight is uncertain since 10 of these sites have "interim" status, meaning that environmental studies for determining impact have not been completed. The New York Bight receives considerable pollutant loadings from ocean-dumped wastes and from municipal and industrial discharges through ocean outfalls, from surface and groundwater runoff to the Hudson River-Raritan Bay estuaries, and from atmospheric fallout. Water quality impacts include high BODs, excessive bacterial densities, oil and grease, and high concentrations of heavy metals, PCBs and other potentially toxic concentrations of suspended matter. In summary, cumulative impacts on water quality are considerably greater than that anticipated from the proposed action alone. 011 import by tanker represents a substantial oil spill risk which may cause a major impact to water quality. The water quality of the inner New York Bight area continues to be severely impacted from ocean dumping and contaminated outflows. Conclusion: A major impact on water quality is projected for the cumulative impact scenario. It is predicted that two tension leg platforms, two shallow water platforms, two sub-sea wellhead complexes, and 300 mi (484 km) of pipeline will be used for the Proposed Lease Sale. One hundred mi (161 km) of the pipeline is gas trunk line which may be buried into the bottom to prevent damage from anchors or fishing gear. Trenching out soft soil (sand) to a depth of approximately 2 m disturbs the sediments up to about 9 m on either side of the pipeline (Gowen et al., 1980). Based upon calculations in et Gowen et al., (1980) up to 21,700 m3 of sand per kilometer of buried pipeline would be displaced and 19,000 m2 of sediment surface area per kilometer of pipeline would be directly perturbed. In addition, depending on local current regimes, the benthic community for various distances from the pipeline burial activity would be affected because of direct burial by displaced sediments, or by interference of feeding activity because of the increased sediment load in the water column. It is expected that there will be no measurable impact on plankton resulting from mechanical perturbations. |