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Regulatory Background of the Region 6 Offshore General Permits
On April 3, 1981 (see 46 FR 20284), EPA published three final general NPDES permits authorizing discharges from facilities in the Offshore Subcategory of the Oil and gas Extraction Point Source Category which were located offshore of Louisiana and Texas. Two of those permits, TX0085651 and LA0060224, authorized discharges from facilities located in the territorial seas off Louisiana and Texas. The third permit, TX0085642, authorized discharges from facilities located seaward of the outer boundary of the territorial seas off Louisiana and Texas, an area commonly known as the Outer Continental Shelf. The Outer Continental Shelf General Permit did not include several facilities located near the Flower Garden Banks, an area with sensitive biological features approximately 120 miles southeast of Galveston, Texas. Twelve facilities in the vicinity of the Flower Garden Banks were authorized to discharge under individual permits. The 1981 general permits implemented "Best Practicable Control Technology Currently Available" (BPT) guidelines for the Offshore Subcategory (see 40 CFR 435). Those permits contained a daily maximum oil and grease limit of 72 mg/l for produced water discharges, a prohibition of the discharge of oil based drilling fluids, a limit of no free oil for drilling fluids, drill cuttings, deck drainage and well treatment fluids, and 1 mg/l residual chlorine for sanitary waste water.
The permits expired April 3, 1983 and were reissued on September 15, 1983 (48 FR 41494) with an expiration date of June 30, 1984. The permits were issued for a short period of time because National Effluent Limitations Guidelines for Best Available Technology Economically Achievable were expected to be promulgated by 1983 and again by 1984. The limitations contained in the permits were unchanged in that reissuance, however, some changes were made for facilities located near the Flower Garden Banks. Lease blocks: North Padre Island 962 and Garden Banks 113 through 132, which were previously excluded from the permit, were authorized to discharge. High Island South block A392 was excluded from the permit because of its potential effects. The Louisiana Territorial Seas General Permit was reissued on November 7, 1997 (62 FR 59687) and renumbered as LAG260000. The Texas Territorial Seas General Permit is presently in the process of being reissued as TXG260000.
The Outer Continental Shelf General Permit was reissued on July 9, 1986 (51 FR 24897). In that action EPA Region 6 issued a joint permit with Region 4 which authorized discharges from facilities located in the Outer Continental Shelf throughout the Gulf of Mexico. The permit, numbered GMG280000, prohibited the discharge of oil based drilling fluids, oil contaminated drilling fluids, drilling fluids containing diesel oil, and drill cuttings generated using oil based drilling fluids. New limits were included in the permit for suspended particulate phase toxicity in drilling fluids, the drilling fluid discharge rate near areas of biological concern, and for free oil in drilling fluids and drill cuttings. That general permit expired on July 1, 1991.
On November 19, 1992, EPA Region 6 reissued the NPDES general permit for the Western Gulf of Mexico Outer Continental Shelf (57 FR 54642) covering operators of lease blocks in the Offshore Subcategory of the Oil and gas Extraction Point Source Category located seaward of the outer boundary of the territorial seas of Texas and Louisiana. As a part of that reissuance, new limits for produced water toxicity were added, as well as new limits for cadmium and mercury in stock barite, and a prohibition on the discharge of drilling fluids to which mineral oil has been added. That general permit was modified on December 3, 1993, to implement Offshore subcategory effluent limitations guidelines which were promulgated March 4, 1993 (58 FR 12504) and to include more accurate calculations of produced water critical dilutions. A general permit covering New Sources in that same area of coverage was issued and combined with the Western Gulf of Mexico Outer Continental Shelf general permit on August 9, 1996 (61 FR 41609). The permit expired on November 19, 1997 and was reissued in two parts on November 2, 1998 (63 FR 58722), and April 19, 1999 (64 FR 19156).
In the 1998/1999 reissuance, EPA Region 6 authorized new discharges of seawater and freshwater to which treatment chemicals, such as biocides and corrosion inhibitors, have been added. The maximum discharge rate limit for produced water was removed and the critical dilutions required to be met for the produced water toxicity limit were updated based on the new discharge rates and more current models. To account for advances in drilling fluid technology, the permit was modified on December 18, 2001 (66 FR 65209) to authorize discharges associated with the use of synthetic based drilling fluids. Additional monitoring requirements were also included at that time to address hydrostatic testing of existing piping and pipelines and those discharges were authorized. That permit expired on November 3, 2003.
Legal Basis for the Offshore General Permits
Section 301(a) of the Clean Water Act (CWA or the Act), 33 USC 1311(a), renders it unlawful to discharge pollutants to waters of the United States in the absence of authorizing permits. CWA section 402, 33 USC 1342, authorizes EPA to issue NPDES permits allowing discharges on condition they will meet certain requirements, including CWA sections 301, 304, 306, 401 and 403. Those statutory provisions require that NPDES permits include effluent limitations requiring that authorized discharges: (1) meet standards reflecting levels of technological capability; (2) comply with EPA-approved state water quality standards; (3) comply with other state requirements adopted under authority retained by states under CWA section 510, 33 USC 1370; and, (4) cause no unreasonable degradation to the territorial seas, waters of the contiguous zone or the oceans.
CWA section 301 requires compliance with BCT and BAT no later than March 31, 1989. CWA section 306 requires compliance with New Source Performance Standards (NSPS) no later than the effective date of such standards. Accordingly, three types of technology-based effluent limitations are included in the proposed permit. With regard to conventional pollutants, i.e., pH, BOD, oil and grease, TSS, and fecal coliform, CWA section 301(b)(1)(E) requires effluent limitations based on "best conventional pollution control technology" (BCT). With regard to nonconventional and toxic pollutants, CWA sections 301(b)(2)(A), (C) and (D) require effluent limitations based on "best available pollution control technology economically achievable" (BAT). For New Sources, CWA section 306 requires effluent limitations based on NSPS. Final effluent guidelines specifying BCT, BAT and NSPS for the Offshore Subcategory of the Oil and Gas Point Source Category (40 CFR 435, Subpart A) were issued January 15, 1993, and were published at 58 FR 12454 on March 4, 1993. Those guidelines were modified on January 22, 2001 (see 66 FR 6850, January 22, 2001), to issue technology based treatment standards for discharges associated with the industry’s use of synthetic based drilling fluids.