After-The-Fact Underground Storage Tank (UST) Closure and Tier 1 Investigation –
Muskingum County, Ohio

STONE was contracted by an owner who was being required by the Bureau of Underground Storage Tank Regulations (BUSTR) to conduct an “after the fact closure” for two diesel USTs that had been removed but never documented over 15 years prior. In order to prepare the BUSTR Closure Assessment, STONE installed three soil borings, screened them in the field using a photoionization detector (PID), and collected samples to be analyzed by a certified laboratory for benzene, toluene, ethylbenzene, xylene (BTEX), methyl tertiary butyl ether (MTBE), polynuclear aromatic hydrocarbons (PAHs), and total petroleum hydrocarbons (TPH) diesel range organics (DRO). Each soil boring was then converted to a groundwater monitoring well, and groundwater samples were collected. The analytical results indicated the presence of PAHs in groundwater above the BUSTR action limits for the

Groundwater Ingestion pathway. Based on the reported results, BUSTR required completion of a Tier 1 Delineation to define the vertical and horizontal extent of PAHs in groundwater.

STONE installed an additional four monitoring wells and submitted soil and groundwater samples for laboratory analysis. Fraction of organic carbon analysis was also conducted, as was geotechnical analysis of a Shelby tube sample to classify soils for subsequent Tier II modeling calculations. The Tier 1 Investigation report summarized the investigations at the site and requested no further action (NFA) status.

Upon review the Tier 1 Investigation report, BUSTR determined all soil and groundwater sample results were below the action levels, but requested an additional groundwater sample to confirm that PAH levels remained below the action levels. STONE discussions with the BUSTR Site Coordinator clarified that NFA status would be granted if the analytical results from the additional groundwater sampling were below the BUSTR action levels. Within a month, STONE arranged for the groundwater to be sampled and analyzed and submitted the results and the request for NFA to BUSTR, concurrently keeping BUSTR apprised of the progress and results. As a result, NFA was granted within 2 days of the submittal.