Oil and Gas Well Site – AST Release of Production Fluid

Oil and gas production company

A production fluid (brine) release to soil from an aboveground storage tank (AST) at a rural oil and gas well site was discovered and reported to the PADEP by the landowner. Stressed/dead vegetation was reported around the AST and within an adjacent downward sloping cornfield. The source of the release was determined to be a hole in the bottom of the 50-barrel fiberglass production fluid AST, and likely caused by a groundhog (AST was located immediately above a burrow). The volume of production fluid released was estimated at 210 gallons. Letterle field measurements indicated the area of dead vegetation was approximately 20 feet by 155 feet. The soil remediation strategy involved soil excavation with field screening and soil attainment sampling.

The client chose to remediate the release in accordance with the Alternative Remediation option detailed in the PADEP document, Addressing Spills and Releases at Oil & Gas Sites or Access Roads, dated September 21, 2013 (Document 800-5000-001). In accordance with this approach, attainment of the remediation standards available under Act 2/Land Recycling Program regulations in Chapter 250 of Title 25 of the Pennsylvania Code must be demonstrated, without requirements to provide the public notice, review and fee provisions under Sections 302(e) and/or 303(h), and Section 703.

The targeted goal for the site was attainment of the PADEP Used Aquifer Residential Statewide Health Standard (with a total dissolved solids concentration of less than or equal to 2,500 milligrams per liter) (UARSHS) Medium Specific Concentrations (MSC) as detailed in Act 2 (The Land Recycling and Environmental Remediation Standards Act).

Within one week of the initial discovery, emergency response activities commenced to excavate impacted soil based on visual observations and stressed vegetation. The damaged AST was removed. The excavation area was measured at 20 feet by 178 feet by up to 4-inches in depth, which also included an excavation area below the former AST measuring 8 feet by 8 feet by 2 feet deep.

Subsequently, an initial site visit was completed inclusive of a sensitive receptor survey, soil conductivity screening to assess the effectiveness of the emergency response soil excavation extent and flag areas for further excavation, and an ecological screening.

Approximately three weeks later, further soil excavation was completed in areas previously flagged with high soil conductivity readings. The excavation area was extended deeper as needed up to depths of 10-inches and the portion of the excavation proximal to the former AST was extended to 17 feet by 17 feet by 3 feet deep. Following soil excavation, five biased soil attainment samples were collected at the source area and at four locations with the highest remaining soil conductivity values. The soil samples were submitted for laboratory analysis of metals (aluminum, barium, boron, iron, lithium, manganese, strontium, vanadium, and zinc), selenium, Synthetic Precipitation Leaching Procedure (SPLP) chloride, and total chloride. The total overall volume of soil excavated and transported off-site for proper disposal was approximately 34 tons. No production fluid or surface/groundwater was observed during any site activities; further assessment for groundwater was not warranted. The site was restored to the specifications necessary to resume agricultural activities.

Based on soil excavation extents, soil conductivity field screening results, and post-excavation biased soil attainment sampling results (with no exceedances of the applicable PADEP UARSHS MSCs), soil attainment was demonstrated for selected regulated brine constituents. The attainment demonstration for chloride (which does not have a UARSHS MSC) was conducted using two separate methods: SPLF chlorides and total chlorides. The PADEP reviewed and approved the Site Characterization Report for the response action completed at the site in accordance with the Alternative Remediation provision of Document 800-5000-001. However, the option of completing all remaining Act 2 requirements remains available, which upon approval, would provide a Relief of Liability under Act 2.