{"data":{"id":"us/40-cfr-421.254","jurisdiction":"us","citation":"40 CFR 421.254","heading":"Standards of performance for new sources.","body":"Any new source subject to this subpart shall achieve the following new source performance standards:\n(a) Smelter wet air pollution control.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of gold and silver smelted\nLead 0.364 0.169\nMercury 0.195 0.078\nSilver 0.377 0.156\nZinc 1.326 0.546\nGold 0.130\nOil and Grease 13.000 13.000\nTotal suspended solids 19.500 15.600\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(b) Silver chloride reduction spent solution.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver reduced in solution\nLead 0.112 0.052\nMercury 0.060 0.024\nSilver 0.116 0.048\nZinc 0.408 0.168\nGold 0.040\nOil and Grease 4.000 4.000\nTotal suspended solids 6.000 4.800\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(c) Electrolytic cells wet air pollution control.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of gold refined electrolytically\nLead 5.544 2.574\nMercury 2.970 1.188\nSilver 5.742 2.376\nZinc 20.200 8.316\nGold 1.980\nOil and Grease 198.000 198.000\nTotal suspended solids 297.000 237.600\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(d) Electrolyte preparation wet air pollution control.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/troy ounce of silver in electrolyte produced\nLead 0.014 0.007\nMercury 0.008 0.003\nSilver 0.015 0.006\nZinc 0.051 0.021\nGold 0.005\nOil and Grease 0.500 0.500\nTotal suspended solids 0.750 0.600\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(e) Calciner wet air pollution control.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 6.160 2.860\nMercury 3.300 1.320\nSilver 6.380 2.640\nZinc 22.440 9.240\nGold 2.200\nOil and Grease 220.000 220.000\nTotal suspended solids 330.000 264.000\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(f) Calcine quench water.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 4.928 2.288\nMercury 2.640 1.056\nSilver 5.104 2.112\nZinc 17.950 7.392\nGold 1.760\nOil and Grease 176.000 176.000\nTotal suspended solids 264.000 211.200\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(g) Calciner stack gas contract cooling water.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) or mercury condensed\nLead 1.162 0.540\nMercury 0.623 0.249\nSilver 1.204 0.498\nZinc 4.233 1.743\nGold 0.415\nOil and Grease 41.500 41.500\nTotal suspended solids 62.250 49.800\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(h) Condenser blowdown.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of mercury condensed\nLead 3.864 1.794\nMercury 2.070 0.828\nSilver 4.002 1.656\nZinc 14.080 5.796\nGold 1.380\nOil and Grease 138.000 138.000\nTotal suspended solids 207.000 165.600\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.\n(i) Mercury cleaning bath water.\nNSPS for the Primary Precious Metals and Mercury Subcategory\nPollutant or pollutant property Maximum for any 1 day Maximum for monthly average\nmg/kg (pounds per million pounds) of Mercury condensed\nLead 0.392 0.182\nMercury 0.210 0.084\nSilver 0.406 0.168\nZinc 1.428 0.588\nGold 0.140\nOil and Grease 14.000 14.000\nTotal suspended solids 21.000 16.800\npH (1) (1)\n1 Within the range of 7.5 to 10.0 at all times.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER N—EFFLUENT GUIDELINES AND STANDARDS","PART 421—NONFERROUS METALS MANUFACTURING POINT SOURCE CATEGORY","Subpart W—Primary Precious Metals and Mercury Subcategory"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"66b078fab086b53c2decdea436c8a75a64d8b0fd1f933f27bf91016345e4f7bb","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-421.253","next":"us/40-cfr-421.255"},"notice":"GroundRules: Original legal text. Not legal advice."}