HomeMy WebLinkAboutNC0004961_RBSS_SARP_Rev0_Appx G_20161219Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Duke Energy Coal Combustion Residuals Management Program
Riverbend Steam Station Site Analysis and Removal Plan
Revision 0
APPENDIX G: RIVERBEND POST-CLOSURE
OPERATIONS MAINTENANCE AND MONITORING
PLAN
POST-CLOSURE OPERATIONS
MAINTENANCE AND MONITORING (OM&M)
PLAN
RIVERBEND STEAM STATION
REVISION 0
Prepared for
Duke Energy
550 South Tryon Street
Charlotte, North Carolina 28202
December 2016
Prepared by
Amec Foster Wheeler Environment & Infrastructure, Inc.
Project No. 7810160625
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Post-Closure Operations Maintenance and Monitoring Plan
Riverbend Steam Station Site Analysis and Removal Plan
Revision 0
i
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 OM&M 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 ................................................................................................................................ 8
List of Appendices
Appendix A Example Post-Closure Monitoring Form
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
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Riverbend Steam Station Site Analysis and Removal Plan
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1. INTRODUCTION
This Post-Closure Operations Maintenance and Monitoring (OM&M) Plan is being submitted as
part of the Riverbend Steam Station 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 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 Carolinas, 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 CCR facilities, specifically the Primary and
Secondary Ash Basins, Dry Ash Stack and Cinder Pit Storage Area, on the property of the
retired Riverbend Steam Station. The primary objective of the Removal Plan is to remove CCR
materials from the site, breach the existing dams that form the ash basins, and to establish fin al
grades to promote drainage. The CCR materials at the Riverbend Steam Station will be
excavated and removed from the site using conventional excavation equipment and transported
using over-the-road trucks and, eventually, transition to railcar after the initial phases of the
project. Upon establishing final grades, the site will be seeded to establish a vegetative ground
cover per approved grading plan drawings and specifications. In addition to establishing
vegetative ground cover, relatively gentle slopes will be established during final grading to
control runoff velocities. The final long term disposition of the site 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.
2. DESCRIPTION OF CLOSURE COMPONENTS
Decommissioning of the CCR facilities at the Riverbend Steam Station includes breaching the
Primary Ash Basin Dam (State ID GASTO-097), the Secondary Ash Basin Dam (State ID
GASTO-098), and the Intermediate Dam (State ID GASTO-099). 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 following 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 decommissioning 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 at Riverbend Steam Station will be
soil from excavation or grading activities. Soil materials used for compacted fill may classify as
sand (SW, SP, SM, SC), silt (ML or MH), or clay (CL or CH) under the unified soil classification
system. Note that any fill classified as peat (PT) 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 at
Riverbend Steam Station 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 Riverbend Steam Station 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. 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 Riverbend Steam Station will
consist of topsoil. 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 soil testing report included in the technical
specification of the decommissioning plan. Finished grade surfaces will be prepared to promote
positive drainage and support a grass vegetative cover.
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2.5 Vegetative Ground Cover
The vegetative ground cover to be used in the closure of the CCR facilities at Riverbend Steam
Station 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 at the Riverbend Steam Station 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 vegetated finished grades and into riprap
energy dissipaters before discharging into stormwater culverts and/or wetland areas that
ultimately discharge to the Catawba River and Mountain Island Lake. Final grading plans and
details illustrating the stormwater management system are provided in the decommissioning
plan drawings.
3. POST-CLOSURE OM&M 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 Riverbend Steam Station
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. 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
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
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Riverbend Steam Station Site Analysis and Removal Plan
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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
A. 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 facility operating record.
3.1.1 Groundwater Monitoring
Post-closure groundwater monitoring requirements will be established in the Groundwater
Monitoring Plan, and submitted under separate cover. The Comprehensive Site Assessment
(CSA) Report (HDR, August 2015a) 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).
Two comprehensive sampling events and two background-only sampling events were
conducted in 2015. There have been two comprehensive sampling events so far in 2016.
The proposed constituents and parameters for the interim groundwater monitoring plan are
presented in Table 16-1 of the CSA Report, and the proposed sampling locations are presented
in Table 16-2 of the CSA Report. The interim groundwater monitoring plan includes sampling
background wells during the additional interim groundwater sampling event in 2015.
3.1.2 Surface Water Monitoring
Post-closure surface water monitoring will be consistent with the NPDES permits for wastewater
discharges (Permit NC0004961) and stormwater discharges (Permit NCS000549) for the
Riverbend Steam Station. 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 Riverbend Steam Station, wastewater and stormwater
discharge NPDES permits will require modification to reflect the discontinuation of certain
discharges. Discontinued discharges include 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 maintained 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 web site.
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.
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
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The request will explain the reason for reducing monitoring with justification, and be submitted
to NCDEQ for regulatory approval.
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 at the Riverbend Steam Station 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.
Stormwater drainage features (i.e., diversion ditches, berms, dissipaters, retention ponds,
discharge pipes, etc.) will be inspected at a minimum of 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 at the
Riverbend Steam Station 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
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Post-Closure Operations Maintenance and Monitoring Plan
Riverbend Steam Station Site Analysis and Removal Plan
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Use of earthen berms, wattles, silt fences, riprap, or equivalent devices down gradient of
disturbed areas, and at intervals along grassed waterways, until such time as permanent
vegetation is established
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 at the
Riverbend Steam Station will consist of periodic mowing at a minimum of 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 mulching 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 revision. Typical
seed mix applications for permanent seeding are as follows:
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Post-Closure Operations Maintenance and Monitoring Plan
Riverbend Steam Station Site Analysis and Removal Plan
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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
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 Riverbend Ash Basins should be directed to:
Duke Energy Carolinas, LLC
Riverbend Steam Station
175 Steam Plant Rd
Mt. Holly, North Carolina 28120
(704) 263-3200
Station Sponsor for Ash Basins Operations or Environmental Professional
The physical address of the proposed Riverbend Ash Basins is the same as above.
3.4 Post-Closure Planned Use
The CCR facilities at the Riverbend Steam Station will be vegetated following closure. Site
access to the public will remain restricted through closure and post-closure care periods. The
final long term disposition of the site has not been determined at this time and there are no
current anticipated post-closure uses for the former Ash Basins, Dry Ash Stack, and Cinder Pit
Area. The short term disposition of the site will be grading the site to drain, establishing the
Amec Foster Wheeler Environment & Infrastructure, Inc. December 2016
Post-Closure Operations Maintenance and Monitoring Plan
Riverbend Steam Station Site Analysis and Removal Plan
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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.
Amec Foster Wheeler Environment & Infrastructure, Inc.December 2016
Post-Closure Operations Maintenance and Monitoring Plan
Riverbend Steam Station Site Analysis and Removal Plan
Revision 0
APPENDIX A
Example Post-Closure Monitoring Form
Date/Time:
Observation Personnel:
Weather/Temperature:
Question No Yes If yes, location Description Corrective Actions
Recommended Date Corrected
Is there evidence of erosion,
settlement, rutting, or potholes?
Is there evidence of vegetative
cover intrusion (ruts, burrows,
excavation or other disturbance)?
Is there evidence of stressed
vegetation or bare spots?
Is there evidence of erosion or
sedimentation in stormwater
channels, pipes, or other
stormwater features?
Is there evidence of regular
maintenance not being
performed?
Is there evidence of human
encroachment (trash, fire pits,
tire/footprints)?
General Notes:
Duke Energy - Riverbend Steam Station
Ash Basin Post-Closure Monitoring Form
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