The property previously operated as Northside Motor Exchange beginning in 1975. The facility included three gasoline underground storage tanks (USTs) on the east, central, and southern portions of the property associated with an automotive filling and repair station. The former USTs were removed in May 2021. Historical use of the property includes automotive sales, repair, and service dating back to 1921. Surrounding land use includes residential, retail, and industrial properties.  The following is a case study presenting the investigation and remediation activities conducted during the course of this project.

Investigation

Leaaf personnel performed a Phase I Environmental Site Assessment (ESA) in conformance with the scope identified in ASTM E 1527-13 and all appropriate inquiries (AAI).  The property was vacant commercial at the time of the Phase I ESA; however, former operations consisted of a filling station, auto sale and service, and auto repair.  Leaaf identified an oil/water separator, hydraulic lift, aboveground storage tanks (ASTs) associated with the former auto parts and engine wash operations, and USTs associated with the former filling station.  Further investigation was recommended to evaluate if former operations had negatively impacted the site.

Leaaf was engaged by the owner in August 2020 to perform site investigations and Risk Evaluation / Corrective Action Program (RECAP) Management Option (MO)-1 Evaluation to evaluate whether constituents of concern (COCs) associated with historic operations were present at concentrations that may pose risk to human health or the environment at the site.

The RECAP evaluation was further evaluated for surface soil and enclosed space (should future development include structures).  Groundwater was not encountered during the soil evaluation and was determined not to be present for the purposes of this investigation.  For this investigation, the groundwater classification, GW3A was based on a slug test at a nearby former Exxon Service Station located approximately 2,000 feet north of the site.  Groundwater flow direction was unknown and the nearest surface water body was Capitol Lake, approximately 4,000 feet to the northwest.  Aquifer thickness (Sd) was unknown; an Sd of 10 feet was assumed based on the Sd at the Exxon Service Station.  A Dilution Factor 3 (DF3) was used in accordance with RECAP Appendix H.

Remediation

Leaaf prepared a Corrective Action Plan (CAP) pursuant to the owners proposed redevelopment plans that included mixed use commercial and residential units.  The purpose of the CAP was to summarize the goals and procedures to remediate surface soil. The CAP also detailed actions to address any additional environmental concerns that may arise during construction. The focus of this corrective action is surface soil only; groundwater was not encountered during sampling to depths of up to 40 feet below ground surface (ft bgs).  Additionally, the soil to groundwater exposure pathway has previously been eliminated by acceptable leach test results.  Corrective action and sampling activities will be performed in accordance with Appendix B of the RECAP Guidance Document.

Approximately 65 tons of contaminated soil were removed in May 2021. The soil contained residual concentrations of Aliphatics >C8-C10 at levels that exceeded the limiting MO-1 enclosed structure RECAP standards (RS). Post-excavation confirmation soil sampling indicated no concentrations present that exceeded any MO-I RS.

An inspection of the site was performed on August 25, 2023, confirming that no investigation-derived waste (IDW) remains on site.

Soil removed from the Area of Investigation (AOI) shall comply with Louisiana Administrative Code (LAC) 33 Chapter 11, Solid Waste Beneficial Use and Soil Reuse, or shall be disposed at a permitted disposal facility.

The Louisiana Department of Environmental Quality (LDEQ) issued a No Further Action (NFA) Letter on February 26, 2024.

Summary of Project Results

Concentrations of Aliphatics >C8-C10 in surface soil above RECAP Standards were observed in the Phase II ESA.  Based on future development plans, a remedial approach (soil excavation) was developed to reduce concentrations to below limiting MO-1 non-industrial enclosed structure RECAP standards.   The remedial approach proved to be effective as the remaining COC concentrations were below their respective RECAP Standards.  LDEQ issued an NFA letter for the site on February 26, 2024.  This allowed the owner to redevelop the site without the need for environmental institutional or engineering controls for soil.

During redevelopment efforts, three USTs and nine hydraulic cylinders presumed to be from historical hydraulic lifts were discovered by the contractor.  Leaaf successfully closed and removed the three USTs and hydraulic cylinders per LDEQ’s UST Closure Guidance Document.

Leaaf’s management of the project offered tremendous value to the owner.  Since the Phase II ESA was performed prior to the UST Closure, the need for soil corrective action was identified prior to mobilizing heavy equipment.  The corrective action was performed in conjunction with the UST Closure and hydraulic lift removal, which eliminated the need for a second mobilization of labor and equipment.  Additionally, the use of field screening to determine the horizontal and vertical limits of excavation eliminated the need for an additional investigation with a drill rig to define the excavation limits.

Issues Encountered

Future development included proposed mixed use commercial and residential units; however, no structures were currently located at the site.  Leaaf prepared the CAP to remediate elevated concentrations of Aliphatics >C8-C10 in the surface soil and also to address any additional environmental concerns that may arise during construction.  The goal of the effort was to remediate the impacted soil in the vicinity of B1 to below the RECAP MO-1 Standard for non-industrial enclosed structures.  B1 was strategically placed based on the locations of structures in the future development plans.  This allowed for unrestricted redevelopment of the site and negated the need for environmental institutional or engineering controls for soil.

During construction efforts to redevelop the site, the contractor discovered a 1,000-gallon gasoline/diesel steel UST and two 1,000-gallon used oil USTs from a former service station located at the site.  Leaaf’s UST certified worker mobilized to the site to close the USTs.  Backfill and closure samples were collected per the May 2010 LDEQ Closure/Change-In- Service Guidance Document.  All COCs in the collected soils were below their respective RECAP limiting screening standards (LSS).

In addition to the three UST closures, nine 55-gallon hydraulic cylinders were found onsite during redevelopment efforts.  The hydraulic cylinders were presumed to be from historical hydraulic lifts.  Leaaf cleaned, removed, and transported the cylinders for disposal/recycling.

Current Site Status

LDEQ issued a No Further Action Letter on February 26, 2024.  The USTs and hydraulic cylinders have been removed and the site was able to be developed by the client.