Aboveground/Underground Storage Tanks

UST Removal

Federal Emergency Management Administration (FEMA), Region 6

Denton, Texas

dse provided project management and oversight of the in-place closure of part of the UST system at the FEMA Region VI Site. TCEQ considered the site to have three separate source areas: a pipechase, a fuel dispenser island and the tankhold. The system consisted of a fuel island with two dispensers, two day tanks ASTs, four USTs in a common tankhold and associated below ground piping. The four USTs included two 20,000-gallon diesel USTs, which dse closed in-place. One 20,000-gallon water tank and one 5,000-gallon hydro-pneumatic tank were to remain in use. The two day tanks, located within Site buildings and their associated above ground piping were also removed. dse conducted document review, correspondence and submitted various closure, registration and permit documents with the TCEQ.

dse personnel coordinated with FEMA and collected a groundwater sample from the previously installed tankhold observation well prior to the UST closure in order to provide a baseline. Fourteen soil samples along the pipechases and one soil sample beneath each dispenser island were collected and analyzed to close the fuel lines in-place and close out the dispenser islands. In order to close the two diesel USTs in-place, a series of soil samples were collected from the native soils outside the tankhold perimeter. One sampling point was converted to a monitor well, which was developed, purged and sampled using low-flow methods. Both diesel USTs were emptied, triple rinsed, purged, and then filled with a flowable fill material consisting of a lightweight concrete and sand mix. Emergency generator equipment, ASTs, associated piping and monitoring equipment were removed from three equipment rooms at the Site and the piping was capped. All samples were analyzed for BTEX/MTBE and TPH with PAH analyses for the sample with the highest detectable concentration.