8401_CityofAlbemarle_MetalsASDResp_DIN28285_20170803

August 3, 2017

Sent Via Email – [e-mail]

Ms. Nina Underwood
City of Albemarle
40592B Stony Gap Road
Albemarle, NC 28001

Re: Appendix I Inorganic Constituent Exceedances
City of Albemarle Landfill
Solid Waste Permit Number 8401-MSWLF-1999
DIN 28285

Dear Ms. Underwood:

The Solid Waste Section (Section) has completed a review of the Alternate Source Demonstration (DIN
27404) submitted on behalf of the City of Albemarle by Shield Engineering, Inc. (Shield) for the City of
Albemarle Landfill, Solid Waste Permit Number 8401. The report was submitted in response to
correspondence from the Section titled Appendix I Inorganic Constituent Exceedances dated August 8,
2016 (DIN 26556) and in accordance with 15A NCAC 13B .1633.

The facility consists of an active CDLF on top of a closed unlined MSWLF and a Subtitle D Lined MSWLF.
The groundwater monitoring network consists of 17 wells for the C&D over unlined MSWLF and 10
additional wells for the Subtitle D landfill. Shield conducted a historical groundwater data review that
indicated inorganic constituents were reported at higher concentrations during the early sampling years.
The initial elevated inorganic concentrations were attributed to the presence of excessive sediment in
samples collected from recently installed wells. The data review did not indicate an upward trend in
inorganic constituent concentrations. Shield also presented published information from various sources
outlining how groundwater quality in the region is influenced by chemical characteristics of water from
recharge areas, lithologic composition of crystalline bedrock, rate of groundwater flow, and Redox
conditions.

A second line of evidence explored by Shield was the comparison between total and dissolved metals
concentrations following the July 2016 groundwater monitoring event. Results of the total and dissolved
sample analysis indicated that 91% of the dissolved concentrations were lower than the associated total
concentrations. Total metals analysis indicated exceedances of arsenic, cadmium, chromium, cobalt, iron,
lead, manganese, thallium, and vanadium at the CDLF over MSWLF site. Arsenic, chromium, cobalt,
thallium, and vanadium were reported at elevated concentrations at the MSWLF site. Detectable
concentrations of cobalt, manganese, thallium, and vanadium were reported in the dissolved
groundwater samples and in a few cases, the dissolved concentration was greater than its associated total

concentration. The primary constituents that exhibited higher dissolved than total concentrations were
manganese and thallium at both the CDLF over MSWLF and lined MSWLF.

Shield performed a statistical analysis using groundwater analytical results from both the CDLF over
MSWLF and the Subtitle D Landfill. The analysis indicated that manganese reported the largest number
of exceedances but was statistically significant at the 1% significance level when compared to the
background wells at the CDLF over MSWLF site. The remaining inorganic constituents with the highest
percentages of exceedances at the CDLF over MSWLF site were iron, vanadium, arsenic, chromium, lead,
thallium, and cadmium. Most of those exceedances were reported at the 5% significance level. Cobalt,
vanadium, and arsenic were the constituents with the highest percentages of exceedances reported at
the lined MSWLF facility. Vanadium exceedances occurred at the 1% significance level while cobalt and
arsenic occurred at the 5% significance level.

Based on the results of the ASD, it appears that the metals reported in groundwater samples at this time
are naturally occurring and turbidity may be impacting analytical results. The City of Albemarle should
determine if modification to sample collection methodology and/or establishing a monitoring well re-
development schedule is necessary to reduce the impact of suspended sediment. Statistical background
concentrations should be calculated for the constituents of concern, arsenic, cadmium, chromium, cobalt,
iron, lead, manganese, thallium, and vanadium in accordance with 15A NCAC 13B .1634 (g)(5) to
determine if any future elevated concentrations are a result of landfill impact. Analytical data from
background monitor well MW-8D should only be used to calculate a statistical background concentration
for monitor wells screened in similar lithology.

Since turbidity may have impacted groundwater analytical results, statistical background concentrations
should not be calculated using previous monitoring data unless field notes indicate that turbidity values
were less than 10 Nephelometric Turbidity Units (NTUs). Statistical background concentrations derived
from turbid samples may not accurately reflect background conditions, therefore, the City of Albemarle
should calculate statistical background concentrations using analytical data from a minimum of ten
groundwater samples with turbidity values less than 10 NTUs. If there is an insufficient number of
previous background samples with turbidity values less than 10 NTUs or no field notes to verify the
turbidity values, the City of Albemarle should establish a temporary groundwater monitoring schedule to
collect the required number of non-turbid samples from the background well(s) within a two-year period.
If a temporary monitoring schedule is necessary, the City of Albemarle should submit the schedule to the
Section within 90 days of receiving this letter. Turbidity values should be recorded and submitted to the
Section during the temporary monitoring period. If the City of Albemarle declines to calculate statistical
background concentrations, additional assessment activities may be necessary.

Additional guidelines for calculating statistical background concentrations are listed below:
• If previous data is deemed suitable for use, the outliers identified and excluded from the statistical
analysis in the alternate source demonstration should not be included in the statistical
background calculations.
• If utilizing Upper Tolerance Limits, determine the new groundwater protection standards for the
metals of concern by the distribution hierarchy normal, gamma, lognormal, and nonparametric;

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 continued cooperation with this
matter.

Sincerely,

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

cc sent via email: Ellen Lorscheider, Solid Waste Section Chief
Jason Watkins, Field Operations Branch Head
Deb Aja, Western District Supervisor
Teresa Bradford, Environmental Senior Specialist
Ed Mussler, P.E., Permitting Branch Head
Perry Sugg, P.G., Permitting Hydrogeologist
Ming Chao, P.E., Permitting Engineer
J. David Wallace, P.E., Shield Engineering, Inc.