Document aBGLQdRjbpqBBOynZk8yZrX5Y

Areas of Concern 1. The EPA detected hydrocarbon emissions from the storage tanks at the following well pads: x Well Pad #60 x Well Pad #74 x Well Pad #77 x Well Pad #114 x Big Bend 1-5SWD 2. The EPA detected unburned hydrocarbon (UBHC) emissions from operating utility flares at the following well pads: x Well Pad #30 x Well Pad #73 x Well Pad #77 3. The EPA detected visible emissions from a flare at the following well pads: x Well Pad #74 x Well Pad #118 See Table 1 below for more details regarding inspected locations and Tables 2 & 3 for inspection observation details for all pads. A log of images and videos captured during the inspections is provided in Appendix A. General Inspection Information Unannounced well pad inspections were conducted jointly by U.S. EPA and Fort Berthold Indian Reservation (FBIR) Tribal inspectors on November 5-8, 2023, at multiple Slawson facilities located on the FBIR. The EPA evaluated each Slawson well site listed in Table 1 using audio, visual, and olfactory (AVO) inspection methods including the use of an optical gas imaging (OGI) camera and EPA Reference Method 22. At each facility, inspectors scanned the crude and/or water storage tanks, closed vent system and flares onsite for any detectable emissions. Specifically, inspectors scanned storage tank covers and closed vent systems for hydrocarbon emissions to determine compliance with the Clean Air Act, including the Fort Berthold FIP and NSPS OOOOa. Each well pad inspection followed the approach below: 1. Record the entry sign of the well pad when available. Survey the entire well pad with OGI camera. 2. Record the number and type of site process equipment such as well heads, tanks, and emission control devices. 3. Record AVO indications of emissions from the storage tanks, closed vent system to the control devices and control devices. 4. Using the OGI camera, survey each process in infrared modes (auto, manual, and/or highsensitivity modes). Record any uncontrolled emissions with the OGI camera and describe the frequency and magnitude of emissions in the field notebook. 5. Observe control devices (enclosed combustor or utility flare) for visible emissions. If there is visible emissions present, conduct Method 22 and record the observations. Page 2 of 7 devices..." The EPA, using an OGI camera, detected natural gas emissions from production and storage tanks at five out of fifteen facilities evaluated. See Area of Concern #1 above. Utility Flare Requirements [ 49.4165(c)] Per 49.4165(c)(1), "For each enclosed combustor or utility flare, the owner or operator must follow the manufacturer's written operating instructions, procedures and maintenance schedule to ensure good air pollution control practices for minimizing emissions." The EPA noted UBHC emissions indicating poor air pollution control practices from lit flares at three out of fifteen facilities evaluated. See Area of Concern #2 above. Per 49.4165(c)(6)(vii), "The owner or operator must ensure that each enclosed combustor and utility flare is operated with no visible smoke emissions." Per 49.4166(g)(3) and EPA Reference Method 22, the EPA noted black smoke emissions at two out of fifteen well pads evaluated. See Area of Concern #3 above. NSPS OOOOa Applicability Based on well production information reported by Slawson to the NDIC and the date of construction, reconstruction, or modification of the storage vessels, the EPA believes that storage vessels and associated emissions control equipment at seven of the 14 oil and natural gas production facilities identified in Table 1 are subject to requirements for storage vessel affected facilities in NSPS OOOOa: x Well Pad #30 x Well Pad #77 x Well Pad #73 x Well Pad #72 x Well Pad #118 x Well Pad #65 x Well Pad #78 Closed Vent System Equipment Requirements [ 60.5411a(c)] Per 60.5411a(c)(1), owners and operators must "Design the closed vent system to route all gases, vapors, and fumes emitted from the material in the storage vessel to a control device that meets the requirements specified in 60.5412(c) and (d), or to a process." The EPA, using an OGI camera, observed emissions from the closed vent systems at Well Pad #77. See Area of Concern #1 above. Control Device Requirements [ 60.5412a(d) and 60.5413a(e)] Per 60.5413(a)(e)(8), owners and operators must, "Operate each control device following the manufacturer's written operating instructions, procedures and maintenance schedules to ensure good air pollution control practices for minimizing emissions." The EPA noted UBHC emissions indicating poor air pollution control practices from lit flares at Well Pads #30, #73, and #77. See Area of Concern #2 above. Per 60.5412a(d)(1)(iii), owners and operators must, "Operate the combustion control device with no visible emissions, except for periods not to exceed a total of 1 minute during any 15-minute period." The EPA observed black smoke continuously for more than five minutes (per Method 22) at Well Pad #118. See Area of Concern #3 above. Page 4 of 7 Well pad #72 2 Well pad #118 2 Well pad #65 2 Well Pad #60 3 Well Pad #78 2 Well Pad #28 1 Jericho 4-5H 1 Well Pad #26 1 Big Bend 1- 0 5SWD AA 2- Yes, prong, HP 2-prong Yes AA, No, HP Yes AA 2- Yes, prong, HP 2-prong Yes HC, Yes, HC, No, HC No AA 2- Yes, prong, HP 2-prong Yes HC Yes HC Yes HP-LP Yes NA NA No, None Yes No, Yes Yes No, None Yes Yes, None No, No Yes, None Yes No None Yes None Yes None NA NA None Continuous visible emissions for >5 minute per Method 22 on High Pressure flare. None None None None None None NA Downward Downward Downward Downward Downward NA Page 7 of 7