The Tulane Shell facility has been operated as a gasoline service with three underground storage tanks (USTs) and four active fuel dispensers. The USTs were installed in April 1982 and registered with the Louisiana Department of Environmental Quality (LDEQ) in May 1986. A historic release was reported to LDEQ in March 2003 following a Minimum Site Assessment conducted by the property owner. Following a Risk Evaluation / Corrective Action Program (RECAP) Management Option (MO)-1 Evaluation, a conveyance notice was filed with the Orleans Parish Clerk of Court limiting the site to industrial use only. A No Further Action (NFA) Notification was issued by LDEQ in May 2012.

On June 28, 2017, there was a confirmed petroleum release of product into the city sewer lines during the installation of new UST piping and dispensers. Approximately 3,900 gallons of fuel and water were removed, including flush water from the sewer lines. A tank tightness test was performed with passing results. The Site was referred to remediation for further investigation for the unknown source of petroleum in the city sewer lines. The Site currently remains in operation.

Subsurface soils were identified and described by Leaaf geologists using the Unified Soil Classification System (USCS) system. In general, stratigraphic lithology consisted of a 4-inch sitewide layer of white concrete. Fill material including gray to black fine-grained sands (SM) and/or soft gray to brownish/black clay with red brick and glass to approximately 1 – 3 feet below ground surface (ft bgs). Native soils below this fill material were generally gray to black soft medium to high plasticity clay (CH) with wood fragments to approximately 4.5 ft to 7.5 ft bgs, with alternating 1 – 5.5 ft beds of gray/brown soft organic-rich clay (OH) and brown peat (PT) from approximately 7.5 ft bgs to total depth (TD) at 12 ft bgs.

Based on the United States Department of Agriculture (USDA) soil survey, all water used for public consumption in the City of New Orleans is taken from the Mississippi River. Groundwater is available from four aquifer systems in Orleans Parish including: The Gramercy 200-foot sand aquifer, the Norco 400-foot sand aquifer, the Gonzales 700-foot sand aquifer, and the 1,200-foot sand aquifer.

The first encountered groundwater during soil boring/monitoring well installation was approximately 3.5 to 5 ft bgs. Groundwater elevation measurements taken from the monitoring wells installed during this site investigation indicate the shallow groundwater flows northeast to northwest.

The nearest downgradient surface water body, the Point of Exposure (POE), is Bayou St. John, located approximately 3,455 feet northeast of the site. Bayou St. John, which is not used for drinking water, flows into Lake Pontchartrain, which is also not classified as a drinking water source per Louisiana Administration Code (LAC) Title 33, Part IX, Subpart 1 Table 3. For these reasons groundwater at the site was classified as GW3 Non-Drinking Water (GW3NDW).

Investigation

Leaaf was contracted by the owner as their Response Action Contractor (RAC) for this release and responded to the LDEQ request for a Site Investigation Work Plan. Leaaf proactively performed a site visit to check the release detection device (RDDs) and submersible turbine pump (STP) sumps prior to submittal of the Work Plan. Approximately 0.04 feet of free phase was measured with an interface probe at the RDD well (northeast portion of the site) using a disposable bailer and interface probe on April 24, 2018. An absorbent sock was installed inside this RDD well that same day. This sock was replaced on May 25 and July 13, 2018, and did show signs of product saturation with no measurable amount of phase detected.

In the Work Plan, Leaaf proposed to advance 11 soil borings and install several monitoring wells to adequately assess site condition, potential define the horizontal and vertical extent of the impact, determine whether constituents of concern (COCs) migrated offsite, and determine potential for airborne exposure at adjacent enclosed structures. Of the eleven soil borings, five of the borings were to be converted to temporary monitoring wells, four were to be converted to permanent monitoring wells, and two were to be installed to investigate a suspected historic tank pad. One geotechnical boring was to be installed in an unimpacted area of the property to collect site specific parameters to be used in the RECAP Evaluation. Additionally, groundwater sampling events and vacuum extraction events were proposed.

The Site Investigation and RECAP Evaluation indicated soil concentrations of benzene exceed the RECAP MO-1 Limiting RECAP Standard (LRS) and the Appendix I MO-2 LRS for non-industrial exposure but are below the Appendix I MO-2 LRS for industrial exposure. All other detected soil concentrations and detection limits are below the RECAP MO-1 LRS for both non-industrial and industrial exposure. All detected groundwater concentrations and detection limits are below the RECAP MO-1 LRS for both non-industrial and industrial exposure.

Corrective Action

Four vacuum extraction events were performed by Leaaf to recover the phase separated hydrocarbons (PSH) present within the tank hold. An interim Corrective Action Plan (ICAP) – Category 5 was submitted by Leaaf to address the PSH that persists at the RDD well. The ICAP was approved for three additional mobile vacuum events and six additional gauging and hand bailing events for product recovery. Additional interim remedial actions involved placement of a passive recovery canister in the RDD and the monthly evacuation to recover PSH. The interim remedial actions proved to be successful as the thickness of PSH within the tank hold was reduced to only a small trace.

A total of seven groundwater sampling events were performed, and the results indicated that COC concentrations in groundwater were consistently below their respective non-industrial RECAP Standards. Leaaf plugged and abandoned the permanent monitoring wells following the seven groundwater sampling events.

Leaaf filed a conveyance notice for the Site in Orleans Parish limiting the use of the property to industrial use only, without addition corrective Action due to COC concentrations above the site-specific non-industrial RECAP Standard but below the industrial RECAP standard.

LDEQ issued a No Further Action Letter on December 14, 2023.

Summary of Project Results

Leaaf successfully managed the remediation of a gasoline service facility with three USTs and four active fuel dispensers. Following a historic release reported in 2003 and a confirmed petroleum release in 2017, Leaaf conducted comprehensive site assessments and limited remediation activities, leading to the issuance of an NFA letter by LDEQ on December 14, 2023.

Proactive measures included early site visits to check release detection devices and submersible turbine pump sumps, ensuring timely identification and management of free phase presence. Leaaf advanced 11 soil borings, installed monitoring wells, and performed multiple vacuum extraction events, significantly reducing the thickness of PSH within the tank hold. These efforts expedited the project’s completion and ensured compliance with regulatory standards, resulting in successful project closure and continued site operation.

Issues Encountered

The thickness of PSH was reduced to a trace after the vacuum events were performed. The last vacuum event appeared to have little impact in removing the trace amount of PSH remaining. Leaaf decided that performing the remaining three budgeted vacuum events was not cost efficient, and a passive PSH recovery approach was more efficient. This decision proved to be correct. The decision also resulted in lower overall costs for PSH recovery.

The depth to product/water was less than one foot below ground surface in the RDDs. Extremely high-water tables can make it difficult to monitor the presence and thickness of PSH, as the PSH can be trapped outside of the well riser. Leaaf’s Geologist intentionally set the screened portion of the monitoring wells as high as possible to allow for monitoring of PSH in the wells. This decision could have potentially saved several thousand dollars in costs if PSH were present in the groundwater monitoring wells, and they needed to be reinstalled to allow for monitoring/recovery of PSH.

Current Site Status

This site received an NFA Letter from LDEQ on December 14, 2023, and remains an active gasoline station.