NCD003162542_Badin Business Park_Corrective Action_20230530

Badin Business Park LLC 201 Isabella Street Suite 500 Pittsburgh, PA 15212-5858 USA Tel: [phone]
May 30, 2023
Robert C. McDaniel Hazardous Waste Section North Carolina Department of Environmental Quality 217 West Jones Street
Raleigh, NC 27699
Re: Response to Comments on the Alcoa/Badin Landfill Baseline Ecological Risk Assessment
Work Plan Badin Business Park (NCD 003 162 542) Badin, Stanly County, North Carolina

Dear Mr. McDaniel,

Badin Business Park, LLC (BBP) is in receipt of the comments provided by the North Carolina
Department of Environmental Quality (NCDEQ) in the letter dated April 27, 2023 regarding the
“Alcoa/Badin Landfill Baseline Ecological Risk Assessment (BERA) Work Plan” transmitted from
BBP to NCDEQ on January 31, 2023. The comments were prepared by Toeroek Associates, Inc.,
the environmental contractor for USEPA Region 4.
Further commentary resolving specific comments made in the April 27, 2023 letter are provided
below. Items raised by NCDEQ are presented in italic text with responses provided thereafter in
regular text.

RESPONSES TO THE APRIL 27, 2023 CORRESPONDENCE
1. Landfill leachate is a primary source contaminant of potential environmental concern entering
the groundwater and surface water on and near the Alcoa/Badin Landfill. The landfill was used
as both an industrial landfill to accept Alcoa–Badin Works waste streams and municipal solid
waste (MSW) streams. This dual purpose expands the potential contaminants of interest based on
the wide variety of wastes generally associated with a MSW stream. This leachate impact to
groundwater is notable in sampling results collected at groundwater monitoring well ABL–
MW005; however, the sampling effort does not consider volatile organic compounds (VOCs) or
emerging contaminants such as 1,4–dioxane, perfluorooctane sulfonate (PFOS),
perfluorooctanoic acid (PFOA) and other per- and polyfluoroalkyl substances (PFAS). These
contaminants are typically associated with MSW and are likely to be in the leachate not being
captured in infiltrating downward from the unlined landfill to groundwater. Therefore, the
contaminants should be assessed as part of the ecological risk assessment. Please include in the
sampling suite for the groundwater monitoring wells (MW–1, MW–2, MW–3, MW–4, MW–5, and
MW–6) at the Alcoa/Badin Landfill (and leachate monitoring from the leachate sump or POTW
discharge point) annual sampling for VOCs, PFOA, PFOS, and other PFAS–related compounds,
Robert C. McDaniel, Hazardous Waste Section Response to Comments on the Alcoa/Badin Landfill BERA Work Plan
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and update the ecological risk assessment as necessary to consider these MSW contaminants of
interest. Alcoa must include a workplan to collect the groundwater samples including the sampling
methodology and procedures, for the groundwater monitoring wells at the Alcoa/Badin Landfill.

The Groundwater Sampling Plan developed by Civil & Environmental Consultants, Inc. (CEC)
and submitted to the NCDEQ on May 11, 2023 (CEC, 2023) outlines the scope of work and the
relevant constituents (i.e., constituents of potential concern or COPCs) as supported by multiple
previous investigations. At this time, insufficient evidence exists to support the inclusion of
additional MSW parameters in the investigation as the scope of relevant parameters were
established through the Screening-Level Ecological Risk Assessment (SLERA) and BERA Work
Plan process. The current proposed supplemental BERA investigation will be useful in
understanding whether complete exposure pathways exist and refine the conceptual exposure
model for the ABL. Inclusion of additional parameters may be considered following detailed
evaluation of known landfill-related constituents and identified exposure areas in Little Mountain
Creek.

2. The cover of the Alcoa/Badin Landfill is an item directly influencing the Alcoa/Badin Landfill
Baseline Ecological Risk Assessment Work Plan as it is a contributor to human health and
environmental risk. The landfill cap is described as consisting of a non–typical cover comprised
of a 12–inch soil layer of compacted silty clay with a 6–inch vegetative layer. Soil only landfill
caps are generally constructed in accordance with guidance for evapotranspiration covers which,
depending on soil type, typically have a minimum of 2.5 feet of soil along with a vegetative layer.
The Plan discusses heavy leachate generation and flow after heavy precipitation events. This
leachate generation scenario provides evidence that supports the likelihood that infiltration is
occurring through this thin landfill cover. It is recommended that a more traditional landfill cap
design that includes modeling of infiltration potential using the free EPA Hydrologic Evaluation
of Landfill Performance (HELP) model. This information should be used to assess further
enhancing the landfill cap design to promote a reduction of meteoric water infiltration and
leachate generation to better protect human health and the environment from contaminants of
concern generated by the industrial and municipal solid wastes contained by the landfill. A more
robust cap will reduce leachate generation to more manageable volumes and prevent excessive
leachate generation. Developing a landfill cap more typical of industry practice, in conjunction
with existing leachate control practices, will result in fewer, or no, impacts to the environment
from landfill leachate.
Information regarding the design and upgrades to the landfill were reviewed as part of the phases
of the Corrective Measures studies completed by Environeering, Inc. (Environeering, 2009a;
Environeering, 2009b; Environeering, 2012; Environeering, 2013) along with the discussion of
fate and transport pathways in the ABL BERA Work Plan (EHS Support, 2023) and
Hydrogeological Conceptual Site Model (HCSM) Update (EHS Support, 2022). It is unclear where
in the ABL BERA Work Plan or in the HCSM the processes of “heavy leachate generation” and
Robert C. McDaniel, Hazardous Waste Section Response to Comments on the Alcoa/Badin Landfill BERA Work Plan
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“flow after heavy precipitation events” are discussed. The ABL BERA Work Plan considered the
following primary constituent transport pathways:
1. Groundwater migration and discharge to surface water;
2. Overland stormwater runoff associated with precipitation events; and,
3. Direct discharges of stormwater via stormwater conveyances.”
The BERA process as outlined by the Work Plan will be used to understand whether potential for
unacceptable adverse effects to biota exists in the Floodplain or Little Mountain Creek exposure
areas (EHS Support, 2023). Risk-based decision making (at scientific management decision
points) will be employed to assess whether further consideration to the landfill cover configuration
is warranted.

3. NC DEQ Specific Comment 1: Section 3.1.5.1 – Direct Contact, page 35
The fifth sentence of the first paragraph states that dermal contact exposure routes to birds and
mammals are not considered significant exposure routes due to feathers, fur, and scales on
reptiles that mitigate direct dermal exposure in accordance with the EPA Guidance for
Developing Ecological Soil Screening Levels. Attachment 1–3 of the EPA guidance document
entitled Guidance for Developing Ecological Soil Screening Levels (Eco–SSLs) states in Section
1.1 (Dermal Contact with Contaminated Soils) that the data necessary to estimate dermal
exposures for wildlife is generally not available and while feathers, fur, and scales are
“believed” to reduce dermal exposure studies assessing the toxicity of dermal exposures for
wildlife species is limited. Please update this sentence in Section 3.1.5.1 to represent the
guidance language more accurately (i.e., that is the data necessary to estimate dermal exposures
is not available).

The fifth sentence of the first paragraph within Section 3.1.5.1 – Direct Contact has been revised
to state:

“There is limited data to constrain dermal contact exposure routes to birds, reptiles, and
mammals, however this pathway is not considered as a significant exposure route due to the
presence of fur on mammals, feathers on birds, and scales on reptiles that are believed to mitigate
direct dermal exposure (USEPA, 2005b). USEPA (2005b) found dermal exposure to contribute
less than one percent to 11 percent of the total risk compared to oral exposure.”

4. NC DEQ Specific Comment 2: Section 2.3.2.2 – Site Hydrogeological Units, Figure 2–5 (ABL
Cross–Section), page 15.
Figure 2–5 provides a cross–section (A to A’) but does not include a map view of the cross–
section. Please provide a map–view showing the cross-sectional line A to A’.
Figure 2-5 has been revised into Figures 2-5a, as illustrated below, and the original Figure 2-5
retained as Figure 2-5b.
Robert C. McDaniel, Hazardous Waste Section Response to Comments on the Alcoa/Badin Landfill BERA Work Plan
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5. NC DEQ General Comment 3: Section 3.2.1.1.1 – Surface Water, page 46.
The seventh sentence of paragraph three references a surface water collection location as
“downgradient” of Highway 740. We recommend the use of the term “downstream” for surface
waters as opposed to the term downgradient which is typically used for groundwater
consideration.
The sentence has been modified as follows:
“Station ABL-SW008, located downstream of State Highway 740…”

6. NC DEQ General Comment 4: Section 4.2 – Conceptual BERA Investigation Approach, Table
4–1 (Supplemental BERA Investigation Sampling Program Summary), page 68.
The groundwater sampling objectives consider source characterization using groundwater
samples but does not address leachate sampling to further characterize source. Samples should
be collected from the leachate sump for comparison to groundwater samples. Include in the
conceptual BERA an investigative approach to assess leachate directly to provide a record of
constituents of concern that may be mobilized in the groundwater or impact surficial receptors.
Typically, leachate sampling of a landfill is conducted at least once annually.
The monitoring wells selected as part of the Groundwater Sampling Plan (CEC, 2023) are
considered most representative of conditions within the ABL. The points identified in the ABL
BERA Work Plan are most suitable for the assessment of ecological exposure conditions given the
hydrogeological conceptual site model (EHS Support, 2023) and further leachate characterization
is not necessary given the BERA objectives.

7. NC DEQ Specific Comment 5: Background Characterization, page 75.
This section addresses collection of background data to support robust statistical evaluation to
assess constituents of potential ecological concern from surface water, pore water, and sediments.
Robert C. McDaniel, Hazardous Waste Section Response to Comments on the Alcoa/Badin Landfill BERA Work Plan
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The Plan does not discuss groundwater monitoring background data or provide any evidence of
collecting background groundwater information from the upgradient background study area. The
development of a baseline that represents the quality of groundwater entering the evaluation area
is necessary to ensure remedial efforts do not overlap with any potential contaminant inflow from
non-Site sources or does not attempt to remediate beyond natural background concentrations.
Include in Section 4.2.3 installation of at least one representative background groundwater
monitoring well that includes a regular sampling schedule of at least on sample annually to further
assess the groundwater pathway and any associated plume that could impact a receptor.
The areas upgradient of the landfill will be assessed as part of the groundwater investigation
outlined in the Groundwater Sampling Plan (CEC, 2023). However, understanding background
groundwater concentrations is not a primary objective of the BERA. Screening of downgradient
monitoring wells against ecological screening values (ESVs) will be assessed as the primary
method used to understand constituents of interest, which may have the potential to cause adverse
effects to ecological receptors. Information obtained as part of the Groundwater Sampling Plan
may be considered as part of the BERA assessment.

SUMMARY
In summary, this letter provides the responses addressing the NCDEQ comments. A revised Work
Plan following acceptance of the responses presented herein will be provided upon request. Let us
know if NCDEQ would like to meet virtually to discuss any of the responses provided. If you have
any immediate questions or comments regarding our responses, please contact Jason Mibroda of
Alcoa at [phone] at your convenience.
Thank you,
Ronald M. Morosky
Director, Corporate Remediation and Technology Badin Business Park LLC cc via email:
Adam Ulishney
Kim T. Caulk Brian Bastek Leah H. Davis Maria Arevalo Gonzalez
Sarah Cook
Rose Pruitt Robyn L. Gross Jason Mibroda Ryke Longest
Chandra Taylor-Sawyer
Robert C. McDaniel, Hazardous Waste Section Response to Comments on the Alcoa/Badin Landfill BERA Work Plan
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References:
Civil Environmental Consultants Inc. (CEC). 2023. Groundwater Sampling Plan. Prepared for
Badin Business Park LLC. May.

EHS Support. 2022. Hydrogeological Conceptual Site Model Update. Badin Business Park.
Badin, North Carlina. December 2022.

EHS Support. 2023. Alcoa/Badin Landfill Baseline Ecological Risk Assessment Work Plan.
Badin Business Park. Badin, North Carlina. January 2023.

Environeering. 2009a. Corrective Measures Study – Phase I Report, Alcoa, Inc., Alcoa-Badin
Works Facility, Badin, North Carolina, August.

Alcoa. 2009b. Corrective Measures Study – Phase 2 – Identification of Potential Treatment
Technologies Report, Alcoa, Inc., Alcoa-Badin Works Facility, Badin, North Carolina, October.

Environeering. 2012. Corrective Measures Study – Phase 3 Engineering Data Collection for the
Corrective Measures Study Report, Alcoa, Inc., Alcoa-Badin Works Facility, Badin, North
Carolina, October.

Environeering. 2013. Corrective Measures Study – Phase 4 – Corrective Measures Alternatives
and Phase 5 – Justification and Recommendation of the Selected Corrective Measure
Alternative, Alcoa, Inc., Alcoa-Badin Works Facility, Badin, North Carolina, July.