Incident Category
OPA Removal Action

Site Description
The site was used to manufacture valves, camshafts, and cylinder cases between 1926 and 1984. During these processes hydraulic fluids constantly dripped from the milling machines to the concrete floors where the oil collected in concrete pits. Several hydraulic and gasoline tanks were also present. All structures on the property were demolished in 1995.

In June 2010, the city of Flint reported to the United States Environmental Protection Agency (EPA) oil discharging through the channelized concrete river wall into the Flint River from the Chevy in the Hole Parcel A Site. EPA and the city of Flint Fire Department deployed boom to contain the oil.

Between June 2010 and April 2011, U.S. EPA investigated the cause and history of the site. Two rounds of assessment, September 2010 and April 2011, confirmed and delineated a discharge of oil from the site. 

During U.S. EPA’s initial site assessment, oil was detected in 14 of the 18 site monitoring wells. The thickness of oil in the monitoring wells ranged from 0.38 feet to 14.53 feet.  Based on the well gauging, the average oil plume could be as thick as 6 feet across 3 acres; however, capillary action is likely causing oil to accumulate in the wells disproportion to its actual thickness.

As documented by GM, the city of Flint, and U.S. EPA, oil from the Chevy in the Hole Parcel A Site was discharging to the Flint River. The Flint River is a navigable waterway of the United States.


Preliminary Removal Assessment/Removal Site Inspection Results
Site investigation activities were completed with the purpose of providing information and results for removal activities and were conducted in September 2010 and April 2011.

The results of these activities include estimated free product volume and extent, contaminated soil volume and extent, and soil and free product characteristics. The results are detailed in the Site Assessment Report (9-2011) and Data Gaps Assessment Technical Memorandum (5-2011).


Summary of the investigation results
The purpose of the preliminary investigation was to define the vertical and horizontal extent of Nonaqueous-Phase Liquid (NAPL) at the site, estimate aquifer properties, estimate NAPL recovery rates, refine existing volume and cost estimates, and determine the waste characterization of the NAPL, soil and groundwater for treatment and/or disposal.

To determine the horizontal and vertical extent of NAPL, NAPL and soil samples were collected,  ultra-violet optical screen tool (UVOST®)-laser-induced fluorescence (LIF) was conducted at 25 locations, Roto-Sonic soil borings were conducted at 21 locations, OIL-IN-SOIL™ screening test kits were used, and visual observations and instrument results were collected.  The results of the NAPL data were provided to the U.S. EPA ERT and was input into a three-dimensional model and a solid surface representing the possible shape and volume of the NAPL was created.

Two NAPL samples were collected and 24 soil samples were collected, analyzed, and the results were compared to NAPL sample results.  This comparison was used to determine whether NAPL was present at the sampled locations based on constituent similarity and concentrations.  A total of 25 UVOST® LIF borings were advanced on-site. Seven of the 25 UVOST® LIF had a response of greater than 150 percent (% ) reference emitter indicated the potential for NAPL.

The NAPL properties are consistent with mineral oils and hydraulic oils that are stable in high temperature and pressure environments.  The NAPL exists throughout the property in the small pore spaces of the predominant sandy silt and appears at different elevations and locations within these tight formations. 

Ten of the soil boring/UVOST® LIF locations indicated the presence of NAPL.  NAPL appears to be present throughout the site with the greatest extent and thicknesses located in the center to the northwest section of the site.  NAPL thickness ranged between 2 to 5 feet across the Site with the greatest NAPL thickness located near the center of the Site at boring SB28.

A total of eight slug tests, three NAPL recovery tests, a single well pumping test, and a single step-drawdown test were completed as part of this field effort to evaluate removal options involving NAPL recovery and groundwater extraction.  The aquifer testing results indicate that the hydraulic conductivities and transmissivities on-site range from low to very low.  Therefore, NAPL recovery will be slow.

The investigation results show that a zone of higher hydraulic conductivity exists along the northern portion of the site and lower hydraulic conductivity soils are present throughout the rest of the site and to the south as indicated in historical reports.  However, the higher hydraulic conductivity soils to the north are still lower permeability soils consisting of variable sands, gravels, and silts. 

Response Actions to Date

See POLREP #1-5 for previous activities.

LATA-KEMRON submitted a Work Plan in March 2013 to U.S. EPA documenting the field activities to be conducted during Summer 2013 (see documents).

Between August 5 and October 17, 2013, U.S. EPA completed the excavation and disposal of 7,000 tons of oil saturated soil directly surrounding the sanitary sewer vault bypass line; collected and treated 2,000 gallons of oil/water; abandoned and sealed the 48in vault bypass line leading to outfall #70; installed a 6in groundwater relief line running parallel to the Flint River; and finished sealing the flood wall joints.