Multi ID#'s_Soil Excavation Endpoint_20150915

September 15, 2015
Tom Reeder
Assistant Secretary for the Environment
North Carolina Department ofEnvironment fkNatural Resources
1Q01Mail Service Center
Raleigh, NC 27699-1601
Duke Energy Soil Excavation Endpoints—AahmNleKC|iffside/DanRiver
Hany K.Sidefis
Senior Vice President
Environmental, Health 8 Safety
526 S. Church St.
Mail Code: BC3XP
NC 28202
(704)o82-4303
Duke Energy is planning for closure ofmultiple coal combustion residuals surface
impoundments ona staged schedule, as required bvthe Coal Ash Management Act uf2U14
.Impoundment closure isone element ofolarger coal ash management program that
also involves replacement of coal generation with natural gas generation, rerouting wastewater
streams, and constructing lined landfills for disposal ofexcavated ash. &svxehave discussed
with you on several occasions, most recently on August 27, 2015, Duke Energy needs to make
near-term decisions kJsupport project p|anning VD three sites where indUe1he} infrastructure will
beplaced inthe footprint Vfa closed impoundment. Specifically, wmare planning a:
v Combined Cycle Plant inthe Asheville Ash Pond footprint following excavation
" Lined Wastewater Retention Basin in the C|Mfeido/Rogere Unit 1 —4 |nmctkxa Basin
footprint following excavation
v Landfill in the area of the Dan River Ash Stacks footprint following excavation
Early identification ofexcavation endpoints for impacted soils located beneath the surface
impoundments atthese three sites kscritical 10our planning process, because the process used
to determine the S0i| [8nnUVa| extent will affect the timetable on which we can begin construction
Relevant Authorities
The two regulatory programs most relevant bothe determination ofexcavation endpointsare.
CAK4A and the Groundwater Rules. For these three sites, we are proposing pre -determined
endpoints designed to protect water quality, combined with deed restrictions established at the
completion ofthe project baoedonthaend-usnofthearea. VVethink this proposal kaconsistent
with the authorities set out hare.

CAMA contains a comprehensive program that speaks both to the generation and management
of coal combustion residuals as well as the closure of surface impoundments. For generation
and management, the law includes deadlines for stopping discharges of stormwater to surface
impoundments and conversion to dry ash disposal or facility retirement. See G.S. 130A-
309.210.
CAMA does not contain much detail on excavation at closure. The law's emphasis is clearly on
protection of groundwater. However, there are several relevant provisions. CAMA addresses
the closure of the four highest priority sites (Dan River, Asheville, Riverbend, and Sutton) in
Section 3(b), which requires three tasks: (1) dewatering; (2) removal of coal combustion
residuals; and (3) corrective action to restore groundwater quality. Notably, Section 3(b)
requires the removal of CCRs but not of soil. Additionally, for high-risk sites, CAMA has two
options: (1) for conversion to industrial landfills, it requires removal of CCRs and contaminated
soils (G.S. 130A-309.214(a)(1)(a)); and (2) for closure, remove all coal combustion residuals
from the impoundment but no mention of soil (G.S. 130A-309.214(a)(1)(b)). For all sites,
regardless of risk classification, G.S. 130A-309.214 states, "If corrective action to restore
groundwater has not been completed pursuant to the requirements of G.S. 130A -309.211(b),
the proposed closure plan shall include provisions for completion of activities to restore
groundwater in conformance with the requirements of Subchapter L of Chapter 2 of Title 15A of
the North Carolina Administrative Code."
CAMA also provides instructions on the information that must be included in a closure plan.
The list of information includes the results of groundwater modeling to be used to predict the
effect of closure activities on groundwater quality (G.S. 130A-309.214(a)(4)(d)), and an
assessment of the need for institutional controls (130A-309.214(a)(4)(n)).
2. Groundwater Rules
The groundwater rules address soil remediation goals under the umbrella of groundwater
corrective action by requiring
[r]emoval, treatment or control of secondary pollution sources which would be
potential continuing sources of pollutants to the groundwaters such as
contaminated soils and non -aqueous phase liquids. Contaminated soils which
threaten the quality of groundwaters must be treated, contained or disposed of in
accordance with applicable rules. The treatment or disposal of contaminated
soils shall be conducted in a manner that will not result in a violation of standards
or North Carolina Hazardous Waste Management rules.
15A NCAC 02L .0106(f)(4). (This section is scheduled for revision, but the proposed changes
should not affect this discussion.)
4

Duke Energy Proposal for Soil Excavation Endpoints
�
QUk �
^^/�/Uy proposing anapproach that, consistent with the above au0lor0ee (a) removes
ro8| combustion residuals bve��ovebon` /b) pn�k��a groundwater removing `
soils eeaamuond - ` ' -' �mn�ooDtroUinQ
thnouQh�oon1binoryumuro�ofpoUubon.and(c)pro18ntuhunnonhea|ihbynlinirn|zingexpo8una
ononcfphysical barriers and institutional controls (i'e.,land use naethobona).
Specifically, soil contamination will beaddressed by excavation of all ash to a point determined
by visual observation. Duke Energy has considered several options for determining the outt
e//
of excavation. Our preferred method ioboremove all visible ash and then remove an additional
1 -ft depth ofsoil unless itioimpossible tVremove the additional 1 -ft soil layer due tothe depth
ofrock (which ielikely tobe the case a1the AohoViU\a�i��.Visible ash vviUdetermined by
inspection inthe field conducted bvatechnician ewpmhen`edinsoil classification.
�8oUa left in place vvoukJ be sampled (with urn|nhnunl of 1 soil�,–
'^" collected foreech a
c
re of
excavation) '---for —�~'~~Um��UQ�PAKeth000SVlU/hU2O' The data would bo
used to eva|uatethe impact ofany remaining constituents of concern, using agroundwater
model, toassist inthe determination ofgroundwater corrective acU»»' The evaluation Of
potential impacts togroundwater would beperformed usin0 the groundwater models developed
for the groundwater corrective action plans in combinationththeend-uogeuenahoap|an
ned
for these three sites.
Groundwater corrective action will be designed in part based on estimates of remaining soil
constituents and effects ofland use (e.g,low pern1eabUh»cape,rerouted site
vegetation). The remnmm�ofirnpactmdsoil vNUreduce the
'conthbu�onof~~"'="'�u�`
/constituents oyconcern
togrouDdmater.Ginoe1heashbma/nehavninpactad8noundvator' they will "e subject mu
continued groundwater monitoring and will besubject bothe corrective action developed as a
result of the comprehensive site assessments.The corrective action plan would consider the
potential impacts Dmthe site groundwater conditions from any impacted soil that may remain
after completion of site excavation. Human exposure to remaining soils will be minimized by
immediate construction of new facilities, addition of clean cover soil over areas not covered
nf�vfaoi|iUeo,and byuse ofappropriate land use restrictions tailored husite conditions.
by
This approach would ensure protection of both human health and the environment while
allowing excavation with a known plan that defines axcavatonendpoints based onh�n
y
field | i
instead of more time consuming laboratory analysis. Inthecontext of much larger program
ue
that will affodvek/eliminate coal ash oaanenvironmental �--'aueinNortCarolina, Duke Energy
be/�nnaatha1eXpmd�inAU)mexo8vebonproceasbmotthegoa|oof(�AK�A'andig
consistent with CA&4,�'a requirements to remove(�<�Ra'andachieves–
gnoUnd««aierrn»de||inQand considers innUtuhmna|controls.
bui|d�c|»aunmP/an�hmtino|uden
3

` In summary, Duke Energy is requesting approval of this proposal described above to
*
�onoveaUvisib|eashandonadditkzna|1-ftofaoi/ba|ovtheouh/ayer/`u
n|ema@dd0ona|ooUnanoVa/kanottechnicoUvpuaaib|eduetothadaofhof rock.m Perform soil sampling and laboratory analysisafter completion cdexcavation, an
d use
the analytical results to evaluate groundwater/mpmotaandmek8 any necessary tothe groundwater corrective action plan.
w Expeditiously implement physical site controls to minimize contact between remaining
soils and surface and groundwater (e.g., caps, rerouted site drainage, vegetation).
VVeare requesting approval for the proposal described above ononk/Ulesethree sites tn
enable pu�autplanning tobaadvanced for a: ~
• Combined Cycle Plant in the Asheville Ash Pond footprint Lined Wastewater Retention Basin inthe [dfoiOe/Uognn;footprint Unit 1 —4/n
a<tivmBaainfoUomingaxcovation
o Landfill in the area of the Dan River Ash Stacks footprint following excavation
Although vveexpect site closure plans for other Duke Energy sites where excavation i
performed tnpropose similar approaches for the extent ofsoil rmmuva| we would n Pnopooethmt
the o�ent0fsoil rennova|for those sites tobeevaluated through the review of closure plans.
IZ2
Duke Energy, Senior Vice President
Environmental, Health & Safety
N