40 C.F.R. § 435.13
Except as provided in 40 CFR 125.30-32 , any existing point source subject to this subpart must achieve the following effluent limitations representing the degree of effluent reduction attainable by the application of the best available technology economically achievable (BAT):
BAT Effluent Limitations
| Waste source | Pollutant parameter | BAT effluent limitation |
| Produced water | Oil & grease | The maximum for any one day shall not exceed 42 mg/l; the average of daily values for 30 consecutive days shall not exceed 29 mg/l. |
| Drilling fluids and drill cuttings: | ||
| (A) For facilities located within 3 miles from shore | No discharge.1 | |
| (B) For facilities located beyond 3 miles from shore: | ||
| Water-based drilling fluids and associated drill cuttings | SPP Toxicity | Minimum 96-hour LC50. of the SPP Toxicity Test2 shall be 3% by volume. |
| Free oil | No discharge.3 | |
| Diesel oil | No discharge. | |
| Mercury | 1 mg/kg dry weight maximum in the stock barite. | |
| Cadmium | 3 mg/kg dry weight maximum in the stock barite. | |
| Non-aqueous drilling fluids (NAFs) | No discharge. | |
| Drill cuttings associated with non-aqueous drilling fluids: | ||
| Stock Limitations (C16-C18 internal olefin) | Mercury | 1 mg/kg dry weight maximum in the stock barite. |
| Cadmium | 3 mg/kg dry weight maximum in the stock barite. | |
| Polynuclear Aromatic Hydrocarbons (PAH) | PAH mass ratio5 shall not exceed 1 * 10-5. | |
| Sediment toxicity | Base fluid sediment toxicity ratio6 shall not exceed 1.0. | |
| Biodegradation rate | Biodegradation rate ratio7 shall not exceed 1.0. | |
| Discharge Limitations | Diesel oil | No discharge. |
| SPP Toxicity | Minimum 96-hour LC50. of the SPP Toxicity Test2 shall be 3% by volume. | |
| Sediment toxicity | Drilling fluid sediment toxicity ratio8 shall not exceed 1.0. | |
| Formation Oil | No discharge.9 | |
| Base fluid retained on cuttings | For NAFs that meet the stock limitations (C16-C18 internal olefin) in this table, the maximum weighted mass ratio averaged over all NAF well sections shall be 6.9 g-NAF base fluid/100 g-wet drill cuttings.10 For NAFs that meet the C12-C14 ester or C8 ester stock limitations in footnote 11 of this table, the maximum weighted mass ratio averaged over all NAF well sections shall be 9.4 g-NAF base fluid/100 g-wet drill cuttings. | |
| Well treatment, completion, and workover fluids | Oil and grease | The maximum for any one day shall not exceed 42 mg/l; the average of daily values for 30 consecutive days shall not exceed 29 mg/l. |
| Deck drainage | Free oil | No discharge.4 |
| Produced sand | No discharge. | |
| Domestic Waste | Foam | No discharge. |
1 All Alaskan facilities are subject to the drilling fluids and drill cuttings discharge limitations for facilities located beyond 3 miles offshore.
2 As determined by the suspended particulate phase (SPP) toxicity test. See § 435.11(gg) .
3 As determined by the static sheen test. See § 435.11(hh) .
4 As determined by the presence of a film or sheen upon or a discoloration of the surface of the receiving water (visual sheen).
5 PAH mass ratio = Mass (g) of PAH (as phenanthrene)/Mass (g) of stock base fluid as determined by EPA Method 1654, Revision A, [specified at § 435.11(u) ] entitled "PAH Content of Oil by HPLC/UV," December 1992, which is published as an appendix to subpart A of this part and in "Analytic Methods for the Oil and Gas Extraction Point Source Category," EPA-821-R-11-004. See § 435.11(uu) .
6 Base fluid sediment toxicity ratio = 10-day LC5. of C16-C18 internal olefin/10-day LC5. of stock base fluid as determined by EPA Method 1644: "Method for Conducting a Sediment Toxicity Test with Leptocheirus plumulosus and Non-Aqueous Drilling Fluids or Synthetic-Based Drilling Muds" after preparing the sediment according to the procedure specified in EPA Method 1646, which are published as appendices to subpart A of this part and in "Analytic Methods for the Oil and Gas Extraction Point Source Category," EPA-821-R-11-004. See § 435.11(ee) and (uu) .
7 Biodegradation rate ratio = Cumulative headspace gas production (ml) of C16-C18 internal olefin/Cumulative headspace gas production (ml) of stock base fluid, both at 275 days as determined by EPA Method 1647, which is published as an appendix to subpart A of this part and in "Analytic Methods for the Oil and Gas Extraction Point Source Category," EPA-821-R-11-004. See § 435.11(e) and (uu) .
8 Drilling fluid sediment toxicity ratio = 4-day LC5. of C16-C18 internal olefin drilling fluid/4-day LC5. of drilling fluid removed from drill cuttings at the solids control equipment as determined by EPA Method 1644: "Method for Conducting a Sediment Toxicity Test with Leptocheirus plumulosus and Non-Aqueous Drilling Fluids or Synthetic-Based Drilling Muds" after sediment preparation procedures specified in EPA Method 1646, which are published as appendices to subpart A of this part and in "Analytic Methods for the Oil and Gas Extraction Point Source Category," EPA-821-R-11-004. See § 435.11(ee) and (uu) .
9 As determined before drilling fluids are shipped offshore by the GC/MS compliance assurance method (EPA Method 1655), and as determined prior to discharge by the RPE method (EPA Method 1670) applied to drilling fluid removed from drill cuttings. If the operator wishes to confirm the results of the RPE method (EPA Method 1670), the operator may use the GC/MS compliance assurance method (EPA Method 1655). Results from the GC/MS compliance assurance method (EPA Method 1655) shall supersede the results of the RPE method (EPA Method 1670). EPA Method 1655 and 1670 are published as appendices to subpart A of this part and in "Analytic Methods for the Oil and Gas Extraction Point Source Category," EPA-821-R-11-004. See § 435.11(uu) .
10 Maximum permissible retention of non-aqueous drilling fluid (NAF) base fluid on wet drill cuttings averaged over drilling intervals using NAFs as determined by EPA Method 1674, which is published as an appendix to subpart A of this part and in "Analytic Methods for the Oil and Gas Extraction Point Source Category," EPA-821-R-11-004. See § 435.11(uu) . This limitation is applicable for NAF base fluids that meet the base fluid sediment toxicity ratio (Footnote 6), biodegradation rate ratio (Footnote 7), PAH, mercury, and cadmium stock limitations (C16-C18 internal olefin) defined above in this table.
11 Maximum permissible retention of non-aqueous drilling fluid (NAF) base fluid on wet drill cuttings average over drilling intervals using NAFs as determined by EPA Method 1674, which is published as an appendix to subpart A of this part and in "Analytic Methods for the Oil and Gas Extraction Point Source Category," EPA-821-R-11-004. See § 435.11(uu) . This limitation is applicable for NAF base fluids that meet the ester base fluid sediment toxicity ratio and ester biodegradation rate ratio stock limitations defined as:
40 C.F.R. §435.13