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UST Inspection Report Dakota Crossing (Buche's) Date of Report: Inspection Date & Time: Weather: Facility Owner: Facility Owner Address: July 1, 2025 May 20, 2025, at 8:15 a.m. Central Daylight Time (CDT) Rainy, 50 degrees Fahrenheit Sisseton Wahpeton Oyate Tribe 12554 BIA Hwy 711 Agency Village, SD 57262 Facility Address: 2410 SD Hwy 10 Sisseton, SD 57262 Facility Representative: EPA Facility ID Number: Reason for Inspection: Inspection Team: 4030063 Routine compliance inspection Marta Grabowski, Inspector, EPA UST Program UST System Description The Dakota Crossing (Buche's) (Facility) is a Tribally-owned gas station and grocery/convenience store located on the Lake Traverse Reservation in Sisseton, South Dakota. The fuel at this Facility is sold to the public. The Environmental Protection Agency's Facility records indicate the Facility has two 15,000gallon, double-walled Elutron underground storage tanks (UST) with three total compartments. The three compartments will be referred to as Tank 1, Tank 2, and Tank 3 for this report. The UST system was installed in 2017. Tank 1 is 15,000 gallons and stores regular unleaded gasoline. Tank 2 is 7,500 gallons and stores diesel fuel. Tank 3 is 7,500 gallons and stores premium gasoline. Piping for all tanks is pressurized, double-walled flex plastic. Inspection Narrative On May 20, 2025, the EPA UST program personnel conducted an inspection at Dakota Crossing (Buche's) in Sisseton, South Dakota. The EPA last inspected the Facility on May 3, 2022, and they selected it for routine re-inspection. Ms. Grabowski, the EPA inspector, emailed the Facility representative on April 16, 2025, and spoke with him on April 30, 2025, to schedule the inspection and provide inspection details (see Attachment A). Ms. Grabowski arrived at the Facility at 8:15 a.m. CDT and informed a staff member of her arrival. and from the Tribal environmental department arrived approximately 25 minutes later. The Facility operator, , also arrived around 8:40 a.m. 4030063-Dakota Crossing Page 1 of 4 5/20/2025 UST Inspection The EPA inspector introduced herself to the Facility operator and presented inspector credentials. Ms. Grabowski proceeded to conduct a physical inspection of the UST system as well as a review of Facility records. Photographs of UST system components taken during the inspection are in Attachment B. Copies of operation and maintenance records are in Attachment C. Tank Leak Detection Tank leak detection is conducted by a Veeder Root TLS 450 Plus automatic tank gauge (ATG), which performs interstitial monitoring via sensors in each tank. The EPA inspector viewed 12 months of sensor status records on the Veeder Root console. All sensors indicated "normal" operation for the past 12 months except for the Tank 1 interstitial sensor (L1), which has been in alarm for at least 12 months. The Facility operator explained that a service provider, Westmor, had been investigating the presence of water in the Tank 1 interstice. During the inspection, Ms. Grabowski spoke with a representative from Westmor to confirm. Annual operability testing for the ATG and tank interstice sensors was last conducted on June 13, 2025, according to records received via email. The ATG passed testing for all tanks. The Tank 2/3 interstice sensor passed, and the Tank 1 interstice sensor was marked "fail" due to the alarm indicating water between the double wall of the tank. Comments on the test form indicate that the Tank 1 sensor itself is passing. Piping Leak Detection Piping leak detection is satisfied by electronic line leak detectors (ELLD) and interstitial monitoring via sensors in each submersible turbine pump (STP) sump and under dispenser containment (UDC) sump. 12 months of sump sensor status records viewed on the ATG console indicated "normal" operation. Annual operability testing for the ELLDs and sump sensors was last conducted and passed on June 13, 2025, according to records received via email. Hydrostatic testing of UDC sumps and STP sumps was conducted on June 13, 2025, according to records received via email. The diesel STP sump failed testing due to water coming by the conduit entry boot. All other sumps passed. Cathodic Protection Cathodic protection (CP) is not required at the Facility. The portion of tanks and piping that are in contact with soil are constructed from non-corrodible materials. Periodic Testing/Inspection of Spill and Overfill Prevention Equipment Triennial testing records for spill buckets and overfill prevention devices (high-level alarm) were not available onsite at the time of inspection; however, EPA records include passing high-level alarm testing dated January 4, 2024, and a spill bucket testing form that is not dated. The EPA inspector provided copies of these records to the Facility operator via email after the inspection. EPA later received spill bucket test results and overfill alarm test results dated June 13, 2025. Tank 1 spill bucket passed, and Tanks 2 and 3 spill buckets failed testing. The overfill alarm passed for all three tanks. Periodic Operation & Maintenance (O&M) Walkthrough Inspections Records of monthly walkthrough inspections were available onsite for the previous 12 months. An annual walkthrough checklist available onsite indicated the last annual walkthrough was conducted on December 31, 2024. 4030063-Dakota Crossing Page 2 of 4 5/20/2025 UST Inspection Operator Training Copies of Class A/B operator training certificates were available onsite at the time of inspection. The Facility representative indicated that there are new employees who still need to be trained as Class C operators. Class C documentation was provided via email to EPA on June 15, 2025. Financial Responsibility In South Dakota, financial coverage for regulated UST systems is provided through the South Dakota Petroleum Release Compensation Fund. Each UST facility is responsible for the deductible. At the time of inspection, a Facility representative provided a copy of the South Dakota Certificate of Financial Assurance for Petroleum Underground Storage Tanks. Physical Observations The EPA inspector viewed the spill buckets/fill pipes, under dispenser containment (UDC) sumps, tank top sumps, high-level alarm enunciator, and the ATG console. It was actively raining during the inspection and the spill buckets each contained a small amount of water. The premium STP sump contained a small amount of fuel. On June 5, 2025, the Facility operator emailed photos of clean, dry spill buckets and premium STP sump to the EPA inspector. At the time of inspection, the fill cap for the diesel tank did not fit securely on the fill pipe. Liquid sensors were present and properly positioned in each UDC sump. The high-level overfill alarm enunciator was tested and confirmed to be operational at the time of inspection. Inspection Conclusions and Recommendations At the end of the inspection, the EPA inspector filled out an Onsite Deficiency Identification Form (see Attachment D), which represents initial compliance recommendations at the time of the inspection. On June 5, 2025, a Facility representative emailed photographs and a service schedule, as mentioned in the above paragraphs. EPA later received test results dated June 13, 2025, as described in the above paragraphs. Prior to departing the Facility, Ms. Grabowski stated that a full inspection report would be forthcoming, which includes the inspection checklist (see Attachment E). Ms. Grabowski provided the Facility representative with the deficiency form and retained a carbon copy for recordkeeping. Inspection Report Attachments A. Record of communication for scheduling the inspection B. Photo log C. Facility O&M Documents D. Onsite Deficiency Identification Form E. Inspection checklist Signature Lead Inspector 4030063-Dakota Crossing Page 3 of 4 5/20/2025 UST Inspection MARTA GRABOWSKI Date: 2025.07.01 14:24:14 -06'00' Digitally signed by MARTA GRABOWSKI Marta Grabowski Date of signature 4030063-Dakota Crossing Page 4 of 4 5/20/2025 UST Inspection