{
  "name": "Technical and Regulatory Comparison of EPA UIC Well Classes",
  "description": "Comparative matrix of United States EPA Underground Injection Control (UIC) well classes, target geological depths, typical injection pressures, barrier standards, and regulatory mechanical integrity test (MIT) cycles compiled from 40 CFR Parts 144-146 and GWPC national data.",
  "page": "https://casrai.org/guides/injection-well",
  "publisher": "CASRAI",
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "dateModified": "2026-11-14T00:54:03Z",
  "temporalCoverage": "2024/2026",
  "spatialCoverage": "United States",
  "columns": [
    {
      "name": "UIC Well Class",
      "unit": "",
      "description": "EPA Underground Injection Control statutory category"
    },
    {
      "name": "Primary Injected Fluid",
      "unit": "",
      "description": "Authorized fluid types and chemical characteristics"
    },
    {
      "name": "Typical Depth Range",
      "unit": "ft",
      "description": "Representative injection zone depth interval below ground surface"
    },
    {
      "name": "Maximum Injection Gradient",
      "unit": "psi/ft",
      "description": "Regulatory fracture pressure gradient threshold limit"
    },
    {
      "name": "Primary Barrier Requirements",
      "unit": "",
      "description": "Casing, cementing, and downhole completion mechanical requirements"
    },
    {
      "name": "Internal MIT Frequency",
      "unit": "years",
      "description": "Statutory interval for Standard Annulus Pressure Test (SAPT) re-testing"
    },
    {
      "name": "Active U.S. Well Inventory",
      "unit": "",
      "description": "Approximate active operational well count according to EPA and GWPC reports"
    }
  ],
  "rows": [
    {
      "UIC Well Class": "Class I (Deep Industrial & Hazardous)",
      "Primary Injected Fluid": "Hazardous industrial waste, municipal wastewater, chemical effluents",
      "Typical Depth Range": "1700 to 10000",
      "Maximum Injection Gradient": 0.75,
      "Primary Barrier Requirements": "Continuous cement to surface, double-string casing, tubing with packer",
      "Internal MIT Frequency": 1,
      "Active U.S. Well Inventory": "800"
    },
    {
      "UIC Well Class": "Class II-R (Enhanced Oil Recovery)",
      "Primary Injected Fluid": "Produced brine, fresh water, steam, polymer solutions, supercritical CO2",
      "Typical Depth Range": "2000 to 14000",
      "Maximum Injection Gradient": 0.65,
      "Primary Barrier Requirements": "Surface casing cemented across USDW, long-string cemented casing, tubing and packer",
      "Internal MIT Frequency": 5,
      "Active U.S. Well Inventory": "145000"
    },
    {
      "UIC Well Class": "Class II-D (Saltwater Disposal)",
      "Primary Injected Fluid": "Produced water from extraction, drilling brine, hydraulic fracturing flowback",
      "Typical Depth Range": "2500 to 12000",
      "Maximum Injection Gradient": 0.6,
      "Primary Barrier Requirements": "Surface casing to base of deepest USDW, cemented long string, packer isolated from casing",
      "Internal MIT Frequency": 5,
      "Active U.S. Well Inventory": "35000"
    },
    {
      "UIC Well Class": "Class II-H (Hydrocarbon Storage)",
      "Primary Injected Fluid": "Liquid hydrocarbons, liquefied petroleum gas (LPG), crude petroleum",
      "Typical Depth Range": "1500 to 6000",
      "Maximum Injection Gradient": 0.8,
      "Primary Barrier Requirements": "Solution-mined salt caverns, multiple cemented casing strings, automated safety shutoff valves",
      "Internal MIT Frequency": 5,
      "Active U.S. Well Inventory": "100"
    },
    {
      "UIC Well Class": "Class III (Solution Mining)",
      "Primary Injected Fluid": "Mining leachates, hot water for sulfur extraction, sodium/potassium salts",
      "Typical Depth Range": "500 to 4000",
      "Maximum Injection Gradient": 0.65,
      "Primary Barrier Requirements": "Corrosion-resistant casing cemented above mineral bed, multi-string concentric tubing",
      "Internal MIT Frequency": 5,
      "Active U.S. Well Inventory": "18500"
    },
    {
      "UIC Well Class": "Class V (Shallow Non-Hazardous)",
      "Primary Injected Fluid": "Stormwater runoff, geothermal return water, septic discharge, experimental remediation",
      "Typical Depth Range": "10 to 500",
      "Maximum Injection Gradient": 0.45,
      "Primary Barrier Requirements": "Gravity drainage or low-pressure discharge, shallow perforated casing or dry well design",
      "Internal MIT Frequency": 0,
      "Active U.S. Well Inventory": "650000"
    },
    {
      "UIC Well Class": "Class VI (Geologic Carbon Sequestration)",
      "Primary Injected Fluid": "Supercritical carbon dioxide (CO2) streams for permanent storage",
      "Typical Depth Range": "3000 to 13000",
      "Maximum Injection Gradient": 0.7,
      "Primary Barrier Requirements": "Corrosion-resistant alloys, CO2-resistant cement, extensive multi-tier monitoring array",
      "Internal MIT Frequency": 1,
      "Active U.S. Well Inventory": "150"
    }
  ],
  "sources": [
    {
      "title": "EPA Underground Injection Control (UIC) Regulations, 40 CFR Parts 144 and 146",
      "url": "https://www.ecfr.gov/current/title-40/chapter-I/subchapter-D/part-144",
      "accessed": "2026-11-13"
    },
    {
      "title": "Ground Water Protection Council (GWPC) National UIC and Produced Water Report",
      "url": "https://www.gwpc.org/uic-information/",
      "accessed": "2026-11-13"
    },
    {
      "title": "U.S. EPA Class II Oil and Natural Gas Management Regulations",
      "url": "https://www.epa.gov/uic/class-ii-oil-and-gas-related-injection-wells",
      "accessed": "2026-11-13"
    }
  ]
}