HomeMy WebLinkAboutNC0000396_SARP_Rev 0_ Appendix G_20161219Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Asheville Steam Electric Generating Plant Site Analysis and Removal Plan
Revision 0
Appendix G – Post-Closure Operations Maintenance and
Monitoring (OM&M) Plan
POST-CLOSURE OPERATIONS
MAINTENANCE AND MONITORING (OM&M)
PLAN
ASHEVILLE 1982 AND 1964 ASH BASINS
DUKE ENERGY – ASHEVILLE STEAM ELECTRIC
GENERATING PLANT, ARDEN, NORTH CAROLINA
REVISION 0
Prepared for
Duke Energy
550 South Tryon Street
Charlotte, North Carolina 28202
December 2016
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Post-Closure Operations Maintenance and Monitoring Plan, Revision 0
Asheville Steam Electric Generating Plant Site Analysis and Removal Plan
Amec Foster Wheeler Project No. 7810160620
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TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................................................... 1
1.1 Project Information ........................................................................................................................ 1
2. DESCRIPTION OF CLOSURE COMPONENTS ................................................................................... 1
2.1 Compacted Fill .............................................................................................................................. 2
2.2 Geotextiles .................................................................................................................................... 2
2.3 Riprap and Aggregate ................................................................................................................... 2
2.4 Final Soil Layer .............................................................................................................................. 2
2.5 Vegetative Ground Cover .............................................................................................................. 3
2.6 Stormwater Management System ................................................................................................. 3
3. POST-CLOSURE OPERATIONS MAINTENANCE AND MONITORING PLAN ................................. 3
3.1 Monitoring Activities ...................................................................................................................... 3
3.1.1 Groundwater Monitoring ..................................................................................................... 4
3.1.2 Surface Water Monitoring ................................................................................................... 4
3.1.3 Reporting ............................................................................................................................. 4
3.1.4 Modifying Monitoring Requirements ................................................................................... 4
3.2 Maintenance Activities .................................................................................................................. 5
3.2.1 Post-Closure Stormwater Maintenance .............................................................................. 5
3.2.2 Post-Closure Erosion and Sediment Control Maintenance ................................................ 5
3.2.3 Post-Closure Vegetation Maintenance ............................................................................... 6
3.3 Facility Contact Information ........................................................................................................... 7
3.4 Post-Closure Planned Use ............................................................................................................ 7
3.5 Certification ................................................................................................................................... 7
List of Appendices
Appendix I Example Post-Closure Monitoring Form
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1. INTRODUCTION
This Post-Closure Operations Maintenance and Monitoring (OM&M) Plan is being submitted as
part of the Asheville Steam Electric Generating Plant (Plant) Site Analysis and Removal Plan
(Removal Plan), which has been prepared to address removing coal combustion residuals
(CCRs) from the site and to comply with the regulatory requirements of the Federal CCR Rule
§257.102(b)(1)(i-vi) and the North Carolina Coal Ash Management Act (CAMA) for closure of
ash basins / surface impoundments. The information contained in this plan will be used to assist
Duke Energy Progress, LLC (Duke) in the closure of inactive coal ash impoundments and the
maintenance and monitoring required during the post-closure care period.
1.1 Project Information
Duke intends to decommission and remove the 1964 and 1982 Ash Basins on the property of
the Plant. The primary objective of the Removal Plan is to set out the process for closing the
1982 and 1964 Ash Basins at the Plant in accordance with the requirements of CAMA and the
CCR Rule. Excavation of the 1982 Ash Basin was completed on September 30, 2016 . The 1982
Ash Basin was then turned over for dam decommissioning and construction of a natural gas
combined cycle plant.
The CCR materials will also be excavated from the 1964 Ash Basin and removed from the site.
The closure design of the 1964 Ash Basin is planned to include a balanced breach, in which the
impoundment will be excavated to a design elevation. The basin will be backfilled to promote
drainage, resulting in a non-impounding structure. The backfill will also be graded in a way to
allow stormwater flows from the basin to pass through an existing culvert under I-26. The final
long term disposition of the 1964 Ash Basin is still under evaluation.
2. DESCRIPTION OF CLOSURE COMPONENTS
Decommissioning of the CCR facilities at the Plant includes breaching the 1982 Ash Basin Dam
(State ID BUNCO-089) and the 1964 Ash Basin Dam (State ID BUNCO-097). Soil removed from
the dams during excavation and grading activities will be stockpiled and, if suitable, used as fill
material to achieve final grades within the excavation limits of the former CCR facilities. The
proposed closure components are described in the follo wing sections of this report.
The various components to be used for the closure of the CCR facilities will consist of the
following:
Compacted fill (including soil materials excavated from onsite) placed on subgrades
Geotextiles placed according to decommissioning plan specifications
Riprap and aggregate placed according to decommissioning plan specifications
Final soil layer placed on final grades
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Vegetative ground cover including seed, mulch and soil amendments applied to
prepared soil surfaces on final grades
A temporary soil layer and vegetation will be installed and maintained during the construction
work to manage erosion and sedimentation. Riprap and geotextiles will be utilized in temporary
and permanent stormwater management structures. Aggregate will be utilized for site access
and temporary haul roads during the construction work. Stormwater management structures will
collect surface water runoff according to the decommissioning plan. The final ground cover for
areas disturbed during the dam decom missioning and CCR removal activities will be vegetated
and maintained with grasses.
2.1 Compacted Fill
Compacted fill to be used in the closure of the CCR facilities will be soil from excavation or
grading activities. Soil materials used for compacted fill may classify as sand (SW, SP, SM, and
SC), silt (ML), or clay (CL) under the unified soil classification system . Note that any fill
classified as peat (PT), high plasticity silt or clay (MH or CH), or organic silt or clay (OL or OH)
shall not be accepted as compacted fill for the project.
2.2 Geotextiles
Woven and non-woven geotextile fabrics to be used in the closure of the CCR facilities will
consist of polypropylene material resistant to biological degradation and naturally occurring
chemicals, alkalis, and acids. Applicable ASTM and AASHTO standards for geotextile properties
as well as delivery, storage and handling requirements are provided in the specifications
included with the decommissioning plan.
2.3 Riprap and Aggregate
Riprap to be used in the closure of the CCR facilities at the Plant may consist of imported Class
A, B, C and Class 1 and 2 rock from a commercial quarry meeting the requirements of Section
1042 RIP RAP Materials in the NCDOT “Standard Specifications for Roads and Structures,”
2012 Edition and additional requirements provided in the specifications included with the
decommissioning plan for riprap. Note that demolished concrete shall not be accepted as
imported riprap for the project.
2.4 Final Soil Layer
The final soil layer to be used in the closure of the CCR facilities at the Plant will consist of
topsoil or soil appropriately amended to support vegetation growth. The topsoil shall be spread
3 inches thick on final grades prior to application of seed, mulch and soil amendments and will
be capable of sustaining vegetation to prevent erosion.
Soil preparation will be implemented according to the procedures included in the technical
specification of the decommissioning plan. Finished grade surfaces will be prepared to promote
positive drainage and support either a grass vegetative cover or future construction projects.
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2.5 Vegetative Ground Cover
The vegetative ground cover to be used in the closure of the CCR facilities will consist of
permanent and temporary seed mixes, nurse crops, mulch, and soil amendments. Unless
directly superseded by the plans and specifications, preparation of subgrade and seeding shall
be performed in accordance with the requirements of the North Carolina Department of
Environmental Quality (NCDEQ) “Erosion and Sediment Control Planning and Design Manual”
dated May 2013, or latest revision. Prior to seeding, soil surfaces receiving seed shall be
scarified to a depth of two to four inches to aid seed germination and reduce loss of seed during
stormwater runoff events. However, the vegetative soil layer will not be subjected to compaction
requirements.
2.6 Stormwater Management System
The proposed closure of the CCR facilities is designed with a network of stormwater
conveyances accounting for ash basin dam decommissioning, CCR removal and final closure
conditions. Stormwater that does not come in contact with CCR materials during the closure will
be treated as non-contact water. Non-contact water will be managed separately from water
within the Ash Basins or that contacts CCR materials. Non-contact water may be used for dust
control or other operational purposes during construction.
Upon final closure, stormwater will be directed across either vegetated finished grades or future
construction projects and into riprap channels before discharging into stormwater culverts
and/or wetland areas that ultimately discharge to the French Broad River. Final grading plans
and details illustrating the stormwater management system are provided in the
decommissioning plan drawings.
3. POST-CLOSURE OPERATIONS MAINTENANCE AND MONITORING PLAN
The Post-Closure OM&M Plan outlines the operations, monitoring, and maintenance activities
required to be performed during the post-closure care period. During the post-closure period,
the re-graded and vegetated areas of the former CCR facilities at the Plant will be monitored
and maintained to sustain their integrity and effectiveness until permanent vegetation is
established.
3.1 Monitoring Activities
Post-closure monitoring events will be conducted quarterly for the first two years and semi-
annually thereafter until permanent vegetation is established on the former CCR facilities area,
where applicable. Post-closure monitoring will include a review of the following:
The condition of site security features such as gates and/or fencing
Evidence of erosion, settlement, ruts, burrows and/or other disturbances within the
closure areas
Type and quality of vegetation within the closure areas
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Evidence of erosion and integrity of stormwater conveyance features
Example forms that may be used to document the monitoring events are included in Appendix I.
The proposed grading profiles and final grades showing the limits of disturbance and
stormwater features are presented in the decommissioning plan. As-built drawings will be
prepared after the dam breach and following completion of the final grades on the former CCR
facilities. The as-built drawings will be used to assist with post-closure monitoring. Completed
post-closure forms will be maintained in the facili ty operating record.
3.1.1 Groundwater Monitoring
Post-closure groundwater monitoring requirements will be established in the Groundwater
Monitoring Plan, to be submitted under separate cover. The Comprehensive Site Assessment
(CSA) Report (SynTerra 2015) provides an interim groundwater monitoring plan to bridge the
gap between completion of CSA Report activities and implementation of the pending
Groundwater Monitoring Plan and Corrective Action Plan (CAP).
The Interim Groundwater Monitoring Plan presented in Section 16.0 of the CSA will be
superseded by the updated Interim Monitoring Plan (IMP), and a p ost-closure Effectiveness
Monitoring Program (EMP) described in Section 9.0 of Part 2 of the CAP, if and when the
proposed remedial actions are accepted as proposed in Part 2 of the CAP.
3.1.2 Surface Water Monitoring
Post-closure surface water monitoring will be consistent with the NPDES permit for wastewater
discharges (Permit NC0000396) for the Plant. The discharge permits should be consulted for a
detailed description of the parameters and frequency of surface water monitoring required at the
site. Following completion of the closure activities at the Plant, wastewater and stormwater
discharge NPDES permits will require modification to reflect the discontinuation of certain
discharges. Specifically, flow from the ash basin and dewatering liquids, as well as, several
stormwater pipes and outfalls that will be removed during construction.
3.1.3 Reporting
In addition to the forms, reporting, and record keeping that will be done as part of the
groundwater and surface water monitoring plans, the various notifications, reports, plans, and
amendments associated with closure and post-closure of the CCR facilities will be placed onto
Duke’s CCR website.
3.1.4 Modifying Monitoring Requirements
A request can be made any time during the post-closure care period to reduce the requirements
for groundwater monitoring provided that sufficient justification exists for the periodic reduction.
The request will explain the reason for reducing monitoring with justification from state and
federal CCR rules, and be submitted to NCDEQ for regulatory approval.
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3.2 Maintenance Activities
Maintenance activities will be conducted as soon as practical to address items of concern
identified during monitoring events. Maintenance activities will be performed at the frequencies
defined herein and are anticipated to include the following:
Localized placement of fill to prevent ponding of water caused by settlement , erosion,
ruts, burrows and/or other disturbances
Mowing vegetation
Vegetative cover shall be amended and fertilized as needed to maintain healthy
vegetation
Repair of stormwater conveyance measures
3.2.1 Post-Closure Stormwater Maintenance
Post-closure operations of the former CCR facilities shall not cause the discharge of a non-point
source of pollution to waters of the United States, including wetlands, that violates any
requirements of an area-wide or statewide water quality management plan that has been
approved under Section 208 or 319 of the Clean Water Act, as amended.
Drainage stormwater features (i.e., diversion ditches, berms, dissipaters, re tention ponds,
discharge pipes, etc.) will be inspected at a minimum twice per year, and within 24 hours of
rainfall events of 0.5 inches or greater until permanent vegetation is established. Any signs of
damage, settlement, clogging, silt buildup, or washouts will be documented during these
inspections. If necessary, repairs to stormwater features will be made as soon as possible
following detection of a problem. Any disturbed areas will be seeded and soil amendments
applied as necessary to establish a healthy vegetative cover.
3.2.2 Post-Closure Erosion and Sediment Control Maintenance
Erosion and sediment control during post-closure operations of the former CCR facilities will
consist of monitoring and repairing stormwater features and surface erosion as described
above. It is anticipated that post-closure erosion control measures at the site will include:
Minimizing ground disturbances to the extent possible while mowing and performing
other maintenance
Seeding and mulching of disturbed areas commencing as soon as practically possible
Employing erosion control matting or seeding and mulch on slopes and other erosion
prone areas
Use of earthen berms, wattles, silt fences, riprap, or equivalent devices down gradient of
disturbed areas, and at intervals along g rassed waterways, until such time as permanent
vegetation is established
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Maintaining an adequate vegetative ground cover with a suitable seed mix and soil
amendments
Placement of riprap at the inlets and outlets of stormwater pipes
Adequate erosion control measures will be provided to prevent sediment from leaving the site.
Stormwater features and slopes within the former CCR facilities will be periodically checked for
erosion and vegetative quality, fertilized, and mowed. Slopes will be observed for erosion,
cracking, sliding, sloughing, and seepage. Slopes identified as needing maintenance will be
repaired as soon as practical and as appropriate to correct deficiencies. Repair activities may
include re-shaping the slope, filling in low areas, and/or seeding.
3.2.3 Post-Closure Vegetation Maintenance
Vegetation maintenance during post-closure operations of the former CCR facilities will consist
of periodic mowing at a minimum twice per year and other maintenance activities as needed
until permanent vegetation is established and, where necessary, to enable access to stormwater
and groundwater monitoring features during the post-closure period.
Post-closure maintenance may also include applying temporary seeding and installation of
temporary erosion controls as required until a permanent ground cover is established. Post-
closure m ulching may be used to stabilize areas where final grade has been reached and/or
vegetation is inadequate. Soil mulch materials may include wood chips, straw, hay, jute matting,
and synthetic fibers. Mulches allow for greater water retention, reduce runoff and improve soil
moisture and temperature conditions. Mulch will also help retain seeds, fertilizer and lime when
it is applied. Steeper slopes (3:1 horizontal to vertical or steeper ) should be protected with
erosion control matting.
Temporary and permanent seeding will be applied as specified in the current Duke Vegetation
Maintenance Implementation Plan (VMIP) using prescribed seasonal seed mixes or over-
seeding mixes. Alternatively, seeding may be applied in accordance with the NCDEQ “Erosion
and Sediment Control Planning and Design Manual” dated May 2013, or latest revis ion. Typical
seed mix applications for permanent seeding are as follows:
Species Pounds per Acre
Kentucky 31 Tall Fescue (Festuca arundinacea)100
Rye Grain (Secale cereale)50
Species Pounds per Acre
German Millet (Setaria italica)50
Table 3.1: Permanent Seeding
Fall to Early Spring - September through April
Spring to Summer - May through August
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Post-closure application of soil amendments including fertilizer and lime may be required to
establish or improve the vegetative ground cover pursuant to soil sampling and testing results.
North Carolina Department of Agriculture soil test(s) may be conducted to assess soil nutrient
requirements. Typical soil amendment applications for permanent seeding are as follows:
Soil Amendment Pounds per Acre
Agricultural limestone 4,000
Fertilizer (10-10-10)1,000
Mulch (straw)4,000
Table 3.2: Permanent Seeding Soil Amendments
3.3 Facility Contact Information
Duke will be responsible for post-closure maintenance and monitoring. Correspondence
regarding the Asheville Ash Basins should be directed to:
Duke Energy Progress, LLC
Asheville Steam Electric Generating Plant
200 CP&L Drive
Arden, North Carolina 28704
(704) 263-3200
Station Sponsor for Ash Basins Operations or Environmental Professional
The physical address of the Asheville Ash Basins is the same as above.
3.4 Post-Closure Planned Use
The CCR facilities at the Plant will be vegetated following closure, except for the areas within
the 1982 Ash Basin that are to be impacted by subsequent construction of the proposed
Combined Cycle Plant. Site access to the public will remain restricted through closure and the
post-closure care periods. The final long term disposition of the 1964 Ash Basin has not been
determined at this time. The short term disposition of the site will be grading the site to drain,
establishing the vegetative cover and maintaining the site in an undeveloped state. Duke
Energy will obtain approval from NCDEQ if a proposed post-closure use is identified.
3.5 Certification
Within 60 days following completion of the post-closure care period, a notification will be
prepared that the post-closure care has been completed. The notification will include the
certification of a qualified professional engineer verifying that the post-closure care has been
completed in accordance with the Removal Plan and the OM&M Plan. The notification will be
placed in the facility Operating Record.
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Appendix I: EXAMPLE POST-CLOSURE MONITORING
FORM
DUKE
ENERGY
Date{Time=
Observation Personnel•
Weather)'Tem perature=
Duke EnegV - fk: heoi Ile. wish Basin Closure
Post -Closure Monit.onng Form
Qu�tlert
No
Yes
Yf yes. locatlalr
Description
Corrective Actions
Corrective
W-i e:L_,,
Recommended
Is there eviderce of eroslort
settlement, rutting, rr pssfficrdes?
Is there evidence of vegetative
cover i ntnasion I ruts, burrows,
excavation or of her dlsturbancel?
Is there evidence of stressed
vegetation or bare spots?
Is diere evidence of erosion o
sedimentation in stormwater
channels, pipes., or other
s-ormwaterfeatures?
Is there evidence of regular
nuintenance not being
performed?
Is there evidence of h un'iar,
encroachment Itrash, fire pt�.
tireJfootprintsj?
,Seneral Notes.
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