5103_JohnstonCoMSW_LeachateAssmtRptResp_DIN28636_20171115

November 15, 2017

Sent Via Email – [e-mail]

Mr. Rick Proctor
Johnston County
Department of Solid Waste
680 County Home Road
Smithfield, NC 27577

Re: Leachate Release Response Results
Johnston County Landfill
Solid Waste Permit Number 5103
DIN 28636

Dear Mr. Proctor:

The Solid Waste Section (Section) has completed a review of the Leachate Release Response
Results report (DIN 23635) submitted on behalf of Johnston County by Smith Gardner Inc. (S+G)
for the Johnston County Landfill, Solid Waste Permit Number 5103. The assessment was
conducted in response to a release that was reported to the Section on August 29, 2017. The
leachate release was caused by a faulty pipe coupling located approximately 30 feet east of the
CDLF dewatering manhole. Leachate flowed an approximate distance of 85 feet adjacent to an
access road toward a drain located underneath the road. S+G personnel did not observe
evidence of leachate entering the drain underneath the road. The coupling was subsequently
repaired and approximately 100 cubic yards of soil in the area of leachate impact was excavated
and placed into the MSW landfill.

S+G personnel mobilized to the site on September 14, 2017 to conduct a soil assessment in
accordance with the approved plan (DIN 28457). A total of three discrete soil samples and one
surface water sample was collected during the assessment. Two soil samples (SS-1 and SS-2)
were collected from the release area and a background soil sample (SS-3) was collected from an
area upgradient of the release. The surface water sample (SWPT-2) was collected from a stream
downgradient of the release.

The samples were analyzed for the constituents listed in 40 CFR 258 Appendix I in addition to
nitrate as N, sulfate, and phosphorus. Analytical results for SS-1 and SS-2 were compared to the
background soil sample analytical results and the Inactive Hazardous Sites Branch Preliminary
Soil Remediation Goals (PSRGs). Acetone, methyl ethyl ketone, and methyl isobutyl ketone were

the only volatile organic compounds (VOCs) reported at concentrations above laboratory
detection limits in all three soil samples. The VOC concentrations were below the PSRGs and
their presence in the background soil sample led S+G to conclude that laboratory contamination
was the contributing factor. Arsenic, cobalt, and vanadium were reported at concentrations
exceeding the PSRGs in samples SS-1 and SS-2. Since those constituents were also detected in
the background sample, S+G attributed their presence to natural variability. In addition, there
were no constituents reported at concentrations exceeding the surface water standards
established in 15A NCAC 2B .0100 in SWPT-2.

Based on the results of the assessment, S+G concluded that there is no impact from the release
in remaining soils and surface water. The Section concurs with S+G’s conclusion and Johnston
County is not required to conduct additional assessment or corrective action related to the
August 2017 leachate release at this time. If you have any questions or concerns regarding this
letter, please feel free to contact me by email at [e-mail] or by phone at
919.707.8288. Thank you for your cooperation with this matter.

Sincerely,

Ervin Lane
Compliance Hydrogeologist
Solid Waste Section, Division of Waste Management

Madeline German, P.G., Smith Gardner, Inc.
Jason Watkins, Field Operations Branch Head
Andrew Hammonds, Western District Supervisor
Liz Patterson, Environmental Senior Specialist