Announcement:

The Draft Environmental Assessment (EA) and Draft Finding of no Significant Impact (FONSI) will be available here for review and comment from May 17 through June 17, 2024.

Former Aua Fuel Farm

BACKGROUND

In 1991, a Formal Determination of Eligibility for inclusion in the Formerly Used Defense Site Program was issued for the Aua Fuel Farm. In 2016, a second eligibility assessment was performed to reexamine the eligibility of the site based on the existing FDE and to augment the record in ac-cordance with current FUDS and Defense Environmental Restoration Program policies.

THE PAST

Construction of this facility was completed Dec. 31, 1943, and the U.S. Navy operated the fuel farm for bulk fuel oil storage, distribution and a construction battalion camp to support Naval Station Tutuila during World War II.

The FUDS property, formerly known as the Aua Fuel Farm, is located on the northeast side of Pago Pago Harbor on Tutuila Island, American Samoa. The project site encompasses approximately 44 acres in Aua Village (based on the tank farm footprint) and extends from Highway 1 to the base of the axial mountain range.

The U.S. Navy operated the fuel farm for bulk fuel oil storage, distribution and a construction battalion camp to support Naval Station Tutuila during World War II. Aua Fuel Farm consisted of 12 aboveground storage tanks, or ASTs, 13 pump houses, and approximately 7,500 feet of 12-inch-diameter pipeline. No records regarding the final dismantling of the ASTs were found; however, based on observations during various environmental investigations, the tanks were believed to have been crushed, folded and buried under approximately 3 feet of imported fill material. Historical documents indicated the tanks were no longer in the inventory of the U.S. Naval Station Pago Pago as of May 1947.

At the request of the American Samoan government, the Corps' Honolulu District performed multiple investigations and response actions between 1991 and 1999 to address identified petroleum contamination in soil and groundwater, and to remove some of the buried ASTs.

THE WORK

PREVIOUS ONSITE ACTIVITIES

Between September 2018 and February 2019, three tanks were discovered. From August through September 2019, USACE performed a tank removal and petroleum contamination investigation within Aua Village.

  • The objectives of the project were to:
  • Rremove three ASTs that were impeding ongoing munici-pal sewer utility improvements
  • Delineate the extent of the fuel farm and the exact loca-tion of all 12 ASTs
  • Characterize the nature and extent of petroleum-related contamination in subsurface soil, groundwater, soil vapor, and indoor air
  • Assess whether an unacceptable risk was posed to hu-man health and/or the environment from residual petroleum-related contamination at the former Aua Tank Farm

The subsurface investigation identified one or more of the following constituents in subsurface soil at concentrations exceeding the Tropical Pacific environmental screening levels at tanks 1, 2, and 10: total petroleum hydrocarbons (TPH) as diesel-range organics (TPH-DRO), TPH as residualrangeorganics (TPH-RRO), and polycyclic aromatic hydrocarbons (PAHs).

Free product was also observed in subsurface soil at all 12 tank sites. The vertical extent of free product varied by tank site, but generally started at the approximate depth of the former tank remnants and extended down through the vadose zone and into saturated soil. The investigations concluded that subsurface free product was mobile and being transported by groundwater.

Results of the human health risk assessment indicated that no cancer hazards were present; however, noncancer hazards exceeded the U.S. Environmental Protection Agency target hazard index of 1.0 at tanks 2, 4, and 9.

No significant ecological concerns were identified during the screening-level ecological risk assessment: however, discharge of dissolved-phase contamination and/or free product to surface waters was determined to pose a potential hazard to the environment and potentially be a violation of the Oil Pollution Act of 1990 (Title 33 United States Code [U.S.C.] Chapter 401) and American Samoa Water Quality Standards Section (§) 24.0205 (ASEPA, 2013).

CURRENT USACE REMOVAL ACTIONS

During 2021, a removal action was performed to remove tank remnants and PCS from the site. Excavation activities were performed at nine tank sites: 1, 2, 3, 4, 5, 9, 10, 11
and 12. Excavations continued laterally and vertically until no visual or olfactory evidence was present in soil or until one of the following was encountered: a substantial surface
feature that was protected such as a building, grave or large tree, groundwater, or refusal.

Nearly 8,200 cubic yards of PCS were excavated, thermally treated and used as excavation backfill. Two hundred and twenty-five gallons of free product-impacted groundwater were removed and dis-posed of at an offsite facility. Contamination observed on groundwater and/or in the smear zone (approximately 1 to 2 feet above the groundwater table) was addressed by skimming free product and/or introducing an oxygen release compound (ORC Advanced®) into the open excavation to enhance the in-situ aerobic bioremediation of petroleum hydrocarbons. In total, 771.4 pounds of ORC Advanced® were applied.

Portions of the suspected pipeline were encountered at several locations throughout the village, including at tank sites 3, 9 and 11. Free product was observed on groundwater and saturated soil along the pipeline route. Fuel was observed flowing out of pipeline segments that were removed during sewer line installation near tank sites 3, 9 and 11. It is unknown if the fuel conveyance pipeline remains in place throughout the rest of the village or if fuel remains in the pipelines (if present).

USACE is currently working to identify any of the buried fuel pipeline and the removal with treatment of any contaminated soil and water.

 

Questions?

If you have questions regarding the Former Aua Fuel Farm FUDS project, call (808) 835-4091 or send an email to HonoluluDistrictFUDSinfo@usace.army.mil

 

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