Comments on Roxboro Unnamed East Ash Extension

Duke Energy Comments on Proposed Risk Classification of
"Unnamed Eastern Extension Impoundment" at the Roxboro Steam Plant
NC DEQ proposed a risk classification of "intermediate" for what it termed the
"Unnamed Eastern Extension Impoundment" at Roxboro. The Department based this
classification on what it described as "groundwater uncertainty" with respect to two
issues: (1) the impoundment had only recently been identified, and (2) the location of
the impoundment is in close proximity to potential receptors. Since the narrative was
generated, Duke Energy has reviewed its files and compiled information regarding the
history of that area (hereinafter referred to as the "East Ash Pond Remnant"). As
presented below, the information demonstrates that the area is not a separate coal ash
surface impoundment but a portion of the East Ash Pond that was never used by Duke
Energy to store ponded ash. Based on this review, the East Ash Pond Remnant is
correctly identified in prior submissions to NC DEQ as being outside the site's waste
boundary. The physical configuration and history of the East Ash Pond Remnant
support a conclusion that it does not represent a source of potential groundwater
contamination, does not impact potential receptors, and does not call into question the
water quality analyses previously performed. Because it is not a separate basin, it
should be treated as part of the East Ash Pond and assigned a low-risk classification.
Physical Configuration
As depicted in Attachment A, the East Ash Pond was created by damming a natural
drainage feature immediately south of Units 1 and 2. Sluice water entered the pond
near the dam and discharged through an engineered spillway located approximately
halfway between the dam and the eastern edge of the pond, which then discharged to
the plant's intake canal. There were no divider dikes in the pond preventing sluice
water from flowing directly to the spillway. Water also flowed into the pond upstream,
following the natural course of the drainage channel. The result of this design is that
the spillway was probably the easternmost point in the pond where settled ash
accumulated. Floating cenospheres probably migrated upstream due to wind action,
but other ash fractions would not have migrated in significant quantities past the
spillway.
In the late 1980s, a dry ash landfill was built on top of a portion of the East Ash Pond.
The eastern boundary of the landfill is a separation dike located just west of the
spillway. As illustrated in Attachment B, pond ash on the east of the dike was capped
with soil. Construction of the dike isolated the upstream portion of the East Ash Pond,
leaving the East Ash Pond Remnant at issue here.

The East Ash Pond Remnant never functioned as an independent or stand-alone basin
for receiving ash. It was inundated by the East Ash Pond dam but, because it was
located upstream of the spillway, it did not contribute additional ash storage capacity.
For that reason, it is best described as an unused portion of the permitted
impoundment.
History
The East Ash Pond, which received ash generated from Roxboro Units 1 and 2, began
discharging in 1966. An NPDES permit application was submitted in the early 1970s,
but the first permit was not issued until 1981. By 1983, the East Ash Pond was nearly at
capacity, with approximately 100 acre-feet of the original 3,100 acre-feet remaining. In
1985, the East Ash Pond was removed from service to avoid violations of permit limits
on total suspended solids due to short circuiting and low residence time; however, the
spillway remained open, so water continued to flow out of the pond to the intake canal.
In 1986, Duke Energy's predecessor, CP&L, and the North Carolina Department of
Environmental Management, entered into a Special Order on Consent (SOC) to resolve
selenium issues in Hyco Lake. The SOC required the Roxboro site to convert to dry fly
ash handling, including the construction of the dry ash landfill.
As part of the conversion, flows from the East Ash Pond were routed to the West Ash
Pond, but the Department required continued monitoring of the outfall from the East
Ash Pond until CP&L demonstrated that monitoring was no longer necessary. After
the separation dike was built, CP&L capped the remaining ponded ash on the eastern
side of the dike with soil. In 1991, CP&L requested that monitoring of the outfall be
deleted from the permit, and the Department agreed to the request.
Cnnc,li i si nn
The physical design and history of the East Ash Pond Remnant indicate that the limit of
ponded ash, and thus the waste boundary, is correctly drawn at the eastern edge of the
separation dike of the Roxboro landfill. Accordingly, the East Ash Pond Remnant is
located outside the waste boundary, does not extend the waste boundary, and does not
impact potential receptors. To provide additional direct evidence on the issue, Duke
Energy has arranged to take borings in the East Ash Pond Remnant to confirm de
minimis quantities of ash, which will demonstrate that the East Ash Pond Remnant was
not "designed to hold accumulated coal combustion residuals" and, in fact, was never
used for such purposes. The results of these borings are not yet available but will be
provided to the Department when they are final.
2

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