WI0800219_Other Agency Documents_20110901

DIVISION OF WATER QUALITY
AQUIFER PROTECTION SECTION
August 23, 2024
PERMIT ISSUANCE MEMO
TO: Debra Watts
THROUGH: Thomas Slusser
FROM: David Goodrich
RE: Modification to the Existing Permit to Inject RegenOx and ORC-A
Marine Corps Base Camp Lejeune SWMU 350
I recommend that the requested modification, received on August 22, 2011, to modify Permit Number
WI0800219 (issued on March 28, 2011) be issued to Marine Corps Base Camp Lejeune to inject RegenOx and
ORC-A to remediate soils and groundwater contaminated with petroleum hydrocarbons and chlorinated organic
solvents. The modification involves constructing and utilizing 54 permanent injection wells (instead of 101 push
points) for the injection of RegenOx and ORC-A, and decreasing the concentration of the ORC-A injectant
solution from 30% to 5% ORC-A composition.
PROPOSED INJECTION
What was initially proposed: The applicant proposes to use RegenOx for an initial tracer event in a single
push point to confirm groundwater flow direction and injection well radius of influence, and then at 75 injection
push points for in situ chemical oxidation at a depth interval of 20 to 35 feet in the most highly contaminated
area. This event will be followed by another injection event using ORC-A at 26 push points (13 in each of two
other areas that are downgradient) at a depth interval of 20 to 35 feet for enhanced aerobic bioremediation. The
remedial injection events (involving 101 injection push points) may be repeated after ten months, pending the
results of the initial injection effort. The total injection volume of the RegenOx solution will be 21,300 gallons
per event, and the ORC-A solution will be 858 gallons per event. Assuming that the shallow aquifer zone has an
effective porosity of 10% and an average saturated thickness of 40 feet, the injection volume total for both
injectants would occupy an aquifer volume of approximately 29,400 cubic feet, or an area of approximately 27
feet squared. The shallow aquifer has a contaminated volume estimated to be approximately 800,000 cubic feet,
and the injectant volume is approximately 4% of this.
What has been accomplished: The initial tracer event in a single push point has been completed, and its results
have indicated that injection and remediation will be more effective if they are performed through permanent
injection wells instead of push points.
What changes are being proposed: Push points will not be used for the injection activities. Instead, 40
permanent injection wells will be installed in a tightly -spaced pattern over the area of most concentrated
contamination for the injection of the same mass of RegenOx compound over a screened depth interval of 20 to
35 feet. The injection of the ORC-A oxygenation compound will be performed by installing 14 similarly -
constructed permanent injection wells in a pattern of two parallel lines, downgradient of the area of most
concentrated contamination. The concentration of the ORC-A in the injection fluid will now be 5% instead of
30%. The total volumes for each injection will now be 21,600 gallons per injection event for RegenOx and
9,100 gallons per injection event for ORC-A. A second injection event may be required, and this would bring
the total volume of injection fluids to 61,400 gallons, which is less than 2% of the estimated total impacted fluid
volume of the shallow aquifer.
REGIONAL OFFICE COMMENTS Charles Stehman of the Wilmington Regional Office recommends issuance
of this modified permit.