2015-10-08 Mayo CSA Comments to DEQ

SOUTHERN ENVIRONMENTAL LAW CENTER
Telephone [phone] WEST ROSEMARY STREET, SUITE 220 Facsimile 919-929-9421
CHAPEL HILL, NC 27516-2356
October 8, 2015
VIA EMAIL AND U.S. MAIL
Mr. Donald R. van der Vaart, Secretary
North Carolina Department of Environmental Quality
1601 Mail Service Center
Raleigh, North Carolina 27699-1601
Re: Comments on Mayo Steam Station Comprehensive Site Assessment
Dear Mr. van der Vaart:
At a recent hearing before the North Carolina Superior Court regarding alleged contamination at
Duke Energy's ("Duke") coal ash ponds, counsel for the Department of Environmental Quality
("DEQ") invited the public to comment on Duke's Comprehensive Site Assessments ("CSAs")
for its coal ash ponds. On behalf of the Roanoke River Basin Association, the Southern
Environmental Law Center submits the following first set of comments on Duke's CSA for its
Mayo Steam Station in Roxboro, N.C.
The Mayo CSA is inconsistent. It contains contradictory depictions of the waste boundary for the
Mayo ash basin, and in one figure it shows groundwater flowing into the basin while another
figure shows groundwater at the same location flowing out of the ash basin. Consequently, the
Mayo CSA fails to document the extent of the pollution at the site and its likely impacts to public
waters, including Mayo Lake.
Section 6.1, Site Geology and Hydrogeology — Site-specific geology on the east side of the ash
basin near the Flue Gas Desulfurization (FGD) ponds is inadequately defined. The Site Layout
Map (Figure 2-1) and Water Level Map (Figure 6-9) each show the FGD ponds located inside
the waste boundary, apparently indicating that the FGD ponds were constructed over disposed
ash. However, cross-sections identified as C -C' (Figures 6-3, 6-6, 8-3, 11 -lb, 11-2b. 11-3b, 11-
4b, 11-5b, 11-6b, 11-7b, 11-8b, 11-9b, and 11- l Ob) each show coal ash waste boundary stopping
short of the FGD ponds. Instead, the FGD ponds are shown in these figures as being located
above soil/fill, rather than coal ash. The accurate location of the waste boundary must be
determined and figures must be consistent throughout the report. This is important for at least
two reasons.
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First, it appears that coal ash extends underneath the FGD ponds and is saturated by
groundwater. Any closure plan must account for how to separate this coal ash from the
groundwater so it does not continue to be a source of contamination.
Second, the location of the waste boundary is important in evaluating the hydraulic gradient and
groundwater flow velocity between the ash basin and Mayo Lake. As shown in the cross-
sections, groundwater will remain level across the extent of the ash deposits before sloping
downward to the lake, so if the waste boundary extends closer to the lake, the gradient will be
steeper and the velocity of groundwater flow will be greater. It appears this groundwater flow
may carry contaminants from the edge of the FGD ponds east-southeast to Mayo Lake.
Section 6.3.1, Groundwater Flow Direction - The direction of groundwater flow in the vicinity
of the FGD ponds is inadequately defined. The CSA report describes Mayo Lake as acting as a
groundwater discharge area on the east side of the Plant. Each of the C -C' cross-sections (listed
previously) show the water table declining to the east between the ash basin and wells CW -1/1D
with flow toward the east beneath the area of the FGD ponds. But the Water Level Map (Figure
6-9) shows the hydraulic gradient flowing toward the north from a high beneath the electric plant
toward the ash basin in this same location. In other words, one set of figures shows groundwater
flowing into the ash basin, and another shows the groundwater flowing out of the ash basin in the
same location. An additional well cluster located just to the north-east of the FGD ponds, in the
rectangular open area between the FGD ponds and the discharge canal, is needed to provide
additional information on geology and groundwater flow direction, velocity and chemistry in the
area of the FGD ponds. Again, it appears contaminated groundwater may be flowing from the
coal ash basin to Mayo Lake in this location.
Section 6.4, Hydrogeologic Site Conceptual Model — The CSA report (p. 38) states that "there
are no substantive differences in water level among wells completed in the different flow zones."
However, an examination of water level data provided on the Water Level Map (Figure 6-9)
shows the following water level differences at clustered well locations:
Wells (Water Elevation)
Water Level Elevation Difference and Vertical
Gradient Direction
MW -08S (437.02)
MW-08BR (432.54)
4.48 ft. Downward
MW -07D (444.46)
MW- 07BR (445.94)
1.48 ft. Upward
MW -16S (366.92)
MW-16BR 365.41
1.51 ft. Downward
CW -05 501.53)
MW-05BR 501.94
0.41 ft. Upward
ABMW-02 (481.56)
ABMW-02BR (482.75)
1.19 ft. Upward
ABMW-04 (485.11)
ABMW-04BR (483.42)
1.69 ft. Downward
Based on these data, it is inappropriate for the conceptual site model to indicate that there are no
significant differences in water level between the different flow zones. The data show that
significant water level differences are present and variable in direction. The conceptual site
model must indicate that bedrock discharges into overlying units in some locations and is
recharged from overlying units in other locations. The amount of groundwater that discharges
into overlying units from bedrock or from overlying units to bedrock must be accurately
incorporated into any valid groundwater model for Duke Energy's upcoming corrective action
plan, and will likely become a critical component of any subsequent evaluation of remediation

strategy. DENR must require Duke Energy to incorporate the vertical components of
groundwater flow into its current and future analyses.
Section 11.2 Hydrostratigraphic Layer Properties —Cross-sections (Figures 11-1a through
11-10b) presented in this section show concentration contours for various constituents based on
concentrations detected in monitoring wells. Many of these figures are misleading because they
do not incorporate the probability that contaminants have migrated downgradient beneath the ash
basin. Concentrations of boron, manganese and vanadium have been detected in ash basin water
in concentrations above the 2L standard. Infiltration of this water through the underlying ash and
into the saprolite and bedrock will undoubtedly result in elevated contaminant levels below the
impounded water. The cross-sections should incorporate the surface water data contained in the
CSA and should indicate that the extent of contamination for extends downgradient beneath the
ash basin, as appropriate.
These flaws in the Mayo CSA must be corrected in order to ensure an accurate analysis of the
extent of the coal ash and groundwater continuation at the site. We ask that you require Duke
Energy to correct these flaws in the CSA and subsequent reports.
Thank you for your consideration of these comments.
Sincerely,
Frank S. Holleman III
Nicholas S. Torrey
cc: Stanley (Jay) Zimmerman, Director, Division of Water Resources, Central Office
Jane Bernard, DEQ Raleigh Regional Office
Harry Sideris, Senior Vice President of Environmental, Health & Safety, Duke Energy