HomeMy WebLinkAboutMarshall Plan for Identification of New Discharges Sept 30 2014
Marshall Steam Station Ash Basin
Plan for Identification of New
Discharges
NPDES Permit NC0004987
September 30, 2014
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
REPORT VERIFICATION
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Report Verification
PROJECT: GROUNDWATER MONITORING PROGRAM
MARSHALL STEAM STATION
ASH BASIN
NPDES PERMIT NC0004987
TITLE: PLAN FOR IDENTIFICATION OF NEW DISCHARGES
This document has been reviewed for accuracy and quality commensurate with the intended
application.
Prepared by:______ _______________ Date:____ ______________
Checked by:______ ________________ Date:____ ______________
Approved by:_____ ________________ Date:___________________
Project Manager: Brooke Ahrens, PE
Professional Engineer Seal:
HDR Engineering, Inc. of the Carolinas
440 South Church St., Suite 1000
Charlotte, NC 28202
North Carolina Engineering Firm Number F-0116
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
TABLE OF CONTENTS
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Table of Contents
Page
Report Verification ......................................................................................................................... i
Table of Contents .......................................................................................................................... ii
List of Figures .............................................................................................................................. iii
Section 1 - Introduction ................................................................................................................. 1
Section 2 - Site Description ........................................................................................................... 3
2.1 Plant Description ................................................................................................... 3
2.2 Ash Basin Description ........................................................................................... 3
Section 3 - Site Geology and Hydrogeology ................................................................................. 4
3.1 Site Geologic/Soil Framework ............................................................................... 4
3.2 Site Hydrogeologic Framework ............................................................................. 4
Section 4 - Identification of New Discharges ................................................................................ 6
4.1 Purpose of Inspection ............................................................................................ 6
4.2 Seepage ................................................................................................................ 6
4.3 Areas To Be Inspected for New Discharges.......................................................... 6
4.4 Inspection Procedure ............................................................................................ 6
Section 5 - References ................................................................................................................. 7
Appendices
A – Marshall Station Ash Basin – Inspection for Identification of New Discharges
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
LIST OF FIGURES
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List of Figures
Figure 1 – Site Location Map
Figure 2 – Areas To Be Inspected For Seeps
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
SECTION 1 - INTRODUCTION
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Section 1 - Introduction
The purpose of this document is to address the requirements of North Carolina General Statute
(GS)130A-309.210 (d) Identification and assessment of discharges; correction of unpermitted
discharges, as modified by North Carolina Senate Bill 729, for the Marshall Steam Station
(MSS) ash basin operated under National Pollutant Discharge Elimination System (NPDES)
Permit NC0004987.
The following requirements are contained in General statue 130A-309.210:
d) Identification of New Discharges. – No later than October 1, 2014, the owner of a coal
combustion residuals surface impoundment shall submit a proposed Plan for the
Identification of New Discharges to the Department for its review and approval as provided in
this subsection.
(1) The proposed Plan for the Identification of New Discharges shall include, at a
minimum, all of the following:
a. A procedure for routine inspection of the coal combustion residuals
surface impoundment to identify indicators of potential new discharges, including
toe drain outfalls, seeps, and weeps.
b. A procedure for determining whether a new discharge is actually present.
c. A procedure for notifying the Department when a new discharge is
confirmed.
d. Any other information related to the identification of new discharges required
by the Department.
(2) The Department shall approve the Plan for the Identification of New
Discharges if it determines that the Plan complies with the requirements of this
subsection and will be sufficient to protect public health, safety, and welfare; the
environment; and natural resources.
(3) No later than 30 days from the approval of the Plan for the Identification of New
Discharges, the owner shall begin implementation of the Plan in accordance with the
Plan.
The North Carolina Senate Bill 729 establishes the submittal date of this Plan for Identification
of New Discharges no later than October 1, 2014.
This bill also modified GS 130A to establish the following submittals that are related to this Plan.
GS130A-309.210(a) was modified to require:
(2) No later than December 31, 2014, the owner of a coal combustion residuals surface
impoundment shall submit a topographic map that identifies the location of all (i) outfalls from
engineered channels designed or improved for the purpose of collecting water from the toe of
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
SECTION 1 - INTRODUCTION
2
the impoundment and (ii) seeps and weeps discharging from the impoundment that are not
captured by engineered channels designed or improved for the purpose of collecting water
from the toe of the impoundment to the Department. The topographic map shall comply with all
of the following:
a. Be at a scale as required by the Department.
b. Specify the latitude and longitude of each toe drain outfall, seep, and weep.
c. Specify whether the discharge from each toe drain outfall, seep, and weep is
continuous or intermittent.
d. Provide an average flow measurement of the discharge from each toe drain
outfall, seep, and weep including a description of the method used to measure average
flow.
e. Specify whether the discharge from each toe drain outfall, seep, and weep
identified reaches the surface waters of the State. If the discharge from a toe drain
outfall, seep, or weep reaches the surface waters of the State, the map shall specify the
latitude and longitude of where the discharge reaches the surface waters of the State.
f. Include any other information related to the topographic map required by the
Department.
The inspection procedures presented in this plan, developed to satisfy the requirements of
GS130A-309.210(d), will be used as the basis for developing the topographic map required by
GS130A-309.210(a)(2).
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
SECTION 2 - SITE DESCRIPTION
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Section 2 - Site Description
2.1 Plant Description
MSS is a four-unit, coal-fired electric generating plant with a capacity of 2,090 megawatts
located in Catawba County, North Carolina, near the community of Terrell. The site is located
north of NC Hwy 150, east of Sherrills Ford Road and south of Island Point Road, and the
surrounding area generally consists of residential properties, undeveloped land, and Lake
Norman (Figure 1).
The ash basin is situated between the MSS to the south, primarily residences to the west,
residences and undeveloped land to the north, and undeveloped land and Lake Norman to the
east. A topographical divide is located along Sherrills Ford Road to the west and along Island
Ford Road to the north. The topography at the site generally slopes downward from those
divides toward Lake Norman.
2.2 Ash Basin Description
The ash basin system consists of a single cell impounded by an earthen dike located on the
southeast end of the ash basin. The ash basin system was constructed in 1965 and is located
approximately 2,000 feet northeast of the power plant. The area contained within the ash basin
waste boundary is approximately 382 acres in area.
The full pond elevation for the MSS ash basin is approximately 790 feet. The normal pond
elevation of Lake Norman is approximately 760 feet.
The ash basin is operated as an integral part of the station’s wastewater treatment system and
receives inflows from the ash removal system, coal pile runoff, landfill leachate, flue-gas
desulfurization (FGD) wastewater, the station yard drain sump, stormwater flows, and station
wastewater. Due to variability in station operations and weather, inflows to the ash basin are
highly variable. Inflows from the station to the ash basin are discharged into the northwest
portion of the ash basin.
The discharge from the ash basin is through a concrete discharge tower located in the eastern
portion of the ash basin. The concrete discharge tower drains through a 30-inch-diameter slip-
lined corrugated metal pipe which discharges into Lake Norman. The ash basin pond elevation
is controlled by the use of concrete stop logs in the discharge tower.
There are six permitted landfill areas and one structural fill area located adjacent to the ash
basin. Two ash landfills (Permit No. 1804) are located adjacent to the east and northeast
portions of the ash basin. The demolition landfill (Permit No. 1804), asbestos landfill (Permit
No. 1804), and industrial landfill (Permit No. 1812) are located adjacent to the northern portion
of the ash basin. The FGD landfill (Permit No. 1809) is located southwest of the ash basin. The
structural fill area is located adjacent to and partially on top of the western most portion of the
ash basin. The approximate boundary of these landfill/structural fill areas and existing
groundwater monitoring wells associated with the ash landfills and the FGD landfill are shown
on Figure 2.
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
SECTION 3 - SITE GEOLOGY AND HYDROGEOLOGY
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Section 3 - Site Geology and Hydrogeology
3.1 Site Geologic/Soil Framework
MSS and its associated ash basin system are located in the Kings Mountain Belt of the
Piedmont physiographic province of North Carolina (Piedmont). The rocks of the Kings
Mountain Belt were formed during the late Proterozoic to Early Paleozoic era. The Kings
Mountain Belt bedrock consists of metasedimentary and metavolcanic rocks including schist,
phyllite, marble, metavolcanic rock, quartzite, and gneiss (North Carolina Geologic Survey
1996).
The soils that overlie the bedrock in the area have generally formed from the in-place
weathering of the parent bedrock. The fractured bedrock is overlain by a mantle of
unconsolidated material known as regolith. The regolith, where present, includes the soil zone;
a zone of weathered, decomposed bedrock known as saprolite; and alluvium. Saprolite, the
product of chemical and mechanical weathering of the underlying bedrock, is typically
composed of clay and coarser granular material up to boulder size and may reflect the texture of
the rock from which it was formed (LeGrand 2004).
3.2 Site Hydrogeologic Framework
Piedmont topography is characterized by gently rounded sloped hills and valleys. Recharge
typically occurs on upland areas and slopes while groundwater discharge is concentrated in
surface water bodies and lowland areas. LeGrand’ s (1988, 2004) conceptual model of the
groundwater setting in the Piedmont incorporates the above two medium systems into an entity
that is useful for the description of groundwater conditions. That entity is the surface drainage
basin that contains a perennial stream or river (LeGrand 1988). Each basin is similar to
adjacent basins and the conditions are generally repetitive from basin to basin. Within a basin,
movement of groundwater is generally restricted to the area extending from the drainage divides
to a perennial stream or river (Slope-Aquifer System; LeGrand 1988, 2004). Rarely does
groundwater move beneath a perennial stream or river to another more distant stream (LeGrand
2004).
Therefore, in most cases in the Piedmont, the groundwater system is a two-medium system
(LeGrand 1988) restricted to the local drainage basin. The groundwater occurs in a system
composed of two interconnected layers: residuum/saprolite and weathered rock overlying
fractured crystalline rock separated by the transition zone. Typically, the residuum/saprolite is
partly saturated and the water table fluctuates within it. Water movement is generally through
the fractured bedrock. The near-surface fractured crystalline rocks can form extensive aquifers.
The character of such aquifers results from the combined effects of the rock type, fracture
system, topography, and weathering. Topography exerts an influence on both weathering and
the opening of fractures while the weathering of the crystalline rock modifies both transmissive
and storage characteristics.
The aquifer system in the Piedmont typically exists in an unconfined or semi-confined condition
in the bedrock zone. Under natural conditions, the general direction of groundwater flow can be
approximated from the surface topography. Groundwater moves both vertically down through
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
SECTION 3 - SITE GEOLOGY AND HYDROGEOLOGY
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the regolith and parallel to the bedrock surface to areas where groundwater discharges as
seepage into streams, lakes, or other surface water bodies.
A surface water divide is located to the west of the MSS ash basin approximately along Sherrills
Ford Road to the west of the ash basin (Figure 2). A surface water divide is also located
approximately along Island Ford Road to the north of the ash basin. Lake Norman is located to
the southeast of the ash basin. The geology/groundwater conditions at the site are expected to
be generally consistent with the characteristics of the conceptual groundwater model developed
by LeGrand for the Piedmont region.
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
SECTION 4 - IDENTIFICATION OF NEW DISCHARGES
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Section 4 - Identification of New Discharges
4.1 Purpose of Inspection
The purpose of the inspection is to identify indicators of potential new discharges, including toe
drain outfalls, seeps, and weeps associated with the coal combustion residuals surface
impoundment (ash basin).
4.2 Seepage
Seepage is considered to be the movement of wastewater from the ash basin through the ash
basin embankment, the embankment foundation, the embankment abutments, or through
residual material in areas adjacent to the ash basin. A seep is defined in this document as an
expression of seepage at the ground surface. A weep is understood to have the same meaning
as a seep.
Indicators of seepage include areas where water is observed on the ground surface and/or
where vegetation suggests the presence of seepage. Seepage can emerge anywhere on the
downstream face, beyond the toe, or on the downstream abutments at elevations below normal
pool. Seepage may vary in appearance from a "soft," wet area to a flowing "spring." Seepage
may show up first as only an area where the vegetation is lusher and darker green than
surrounding vegetation. Cattails, reeds, mosses, and other marsh vegetation often become
established in a seepage area.1 However, in many instances, indicators of seeps do not
necessarily indicate the presence of seeps.
4.3 Areas To Be Inspected for New Discharges
The areas to be inspected for new discharges are the areas of the site where water contained in
the ash basin might infiltrate into the underlying residual material and be expressed as seepage.
This would include the earthen embankment which impounds the ash basin and certain
adjacent areas.
The extent of the area to be inspected was determined based on the generalized LeGrand
conceptual model, the concept of the slope-aquifer system, and the site topography. In this
generalization, flow of water from the ash basin would be expected to be located within the
slope-aquifer compartment and to be below the full basin elevation of the ash basin. The area
to be inspected for new discharges is shown on Figure 2.
4.4 Inspection Procedure
The inspection procedure for identification of new discharges and indicators of potential
discharges associated with the MSS ash basin is provided in Appendix A. In addition to the
specific requirements for the inspection, Appendix A also provides the general requirements, the
frequency of inspections, documentation requirements, and provides a decision flow chart for
determining if the discharge is associated with the ash basin.
1 Dam Operation, Maintenance, and Inspection Manual, North Carolina Department of Environment and
Natural Resources, Division of Land Resources, Land Quality Division, 1985 (Revised 2007).
Duke Energy Carolinas, LLC | Plan for Identification of New Discharges
Marshall Steam Station Ash Basin
SECTION 5 - REFERENCES
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Section 5 - References
North Carolina Geologic Survey. 1996. Generalized Geologic Map of North Carolina, 1991,
Reprinted 1996.
LeGrand, H.E. 1988. Region 21, Piedmont and Blue Ridge, p.201-208, in Black, W.,
Rosenhein, J.S., and Seaber, P.R., eds., Hydrogeology: Geological Society of America,
The Geology of North America, v. O-2, Boulder, Colorado, 524p.
LeGrand, Harry, Sr. 2004. A Master Conceptual Model for Hydrogeological Site
Characterization in the Piedmont and Mountain Region of North Carolina, North Carolina
Department of Environment and Natural Resources.
Figures
SEPTEMBER 30, 2014
Areas to be inspected
A
MARSHALL STEAM
STATION ASH BASIN
INSPECTION FOR
IDENTIFICATION OF
NEW DISCHARGES
Marshall Steam Station Ash Basin
INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES
1
1. Purpose of Inspection
The purpose of the inspection is to identify new discharges and indicators of potential new discharges,
including toe drain outfalls, seeps, and weeps that arise after the initial submittal of maps required by
North Carolina General Statute 130A‐309.210(a)(2)(ii). Seepage is considered to be the movement of
wastewater from the ash basin through the ash basin embankment, the embankment foundation, the
embankment abutments, or through residual material in areas adjacent to the ash basin. Therefore, a
seep is defined in this document as an expression of seepage at the ground surface. A weep is
understood to have the same meaning as a seep. If new discharges or indicators of potential new
discharges are identified, the decision flow chart (see Figure A‐1) will be used to determine if the
potential new discharge is from the ash basin and if notification to the North Carolina Department of
Environment and Natural Resources (NCDENR) Division of Water Resources (DWR) is required.
2. General Inspection Requirements
2.1. Inspections are to be performed on areas that are below the ash basin full pond elevation and
within the area shown on Figure A‐2. The purpose of the inspection is to identify new
discharges and indicators of potential new discharges, including toe drain outfalls, seeps, and
weeps associated with the coal combustion residuals surface impoundment (ash basin).
2.2. If required, a larger scale figure showing the locations of outfalls from engineered channels will
be developed. If a separate figure showing outfalls from engineered channels is not developed,
Figure A‐2 will be revised to show these features.
2.3. Inspections of areas on or adjacent to the ash basin embankments should be performed within
two months after mowing, if possible.
2.4. Inspections should not be performed if the following precipitation amounts have occurred in
the respective time period preceding the planned inspection:
2.4.1. Precipitation of 0.1 inches or greater within 72 hours or
2.4.2. Precipitation of 0.5 inches or greater within 96 hours
2.5. Record the most recent ash basin water surface elevation.
2.6. Review previous Inspection for Identification of New Discharge report(s) prior to performing
inspection.
2.7. Review the most recent previous dam inspections.
2.8. Conduct an interview with the Site Environmental Coordinator prior to performing inspection
to inquire about possible changes to site conditions, such as pond elevations, operations,
additions or removal of wastewater discharges to the ash basin, changes to site surface water
drainage, etc.
Marshall Steam Station Ash Basin
INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES
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3. Frequency of Inspections
Inspections will be performed on a semi‐annual basis during the following months: April to May and
October to November.
4. Qualifications
The inspections shall be performed under the direction of a qualified Professional Engineer or
Professional Geologist.
5. Documentation of Inspection
The inspection shall be documented by the individual performing the inspection. The report should
contain observations and descriptions of the seeps observed, changes in observations compared to
previous inspections, estimates of flows quantities, and photographs of seeps and outfalls of engineered
channels designed or improved for collecting water from the impoundment. Photographs are to be
numbered and captioned.
6. Initial Inspection
An initial inspection should be performed to identify features and document baseline conditions
including location, extent (i.e., dimensions of affected area), and flow. Seep locations should be
recorded using a Global Positioning System (GPS) device. Photographs should be taken from vantage
points that can be replicated during subsequent semi‐annual inspections.
7. Inspection For New Seeps at Outfalls From Engineered Channels
Inspect the outfalls from engineered channels designed and/or improved (such as through the
placement of rip‐rap) associated with the ash basin dikes to identify new seeps or indicators of new
seeps.
7.1. Inspect all outfalls from engineered channels designed and/or improved (such as through the
placement of rip‐rap)
7.2. Document the condition of the outfall of the engineered channel with photographs.
Photographs are to be taken from similar direction and scale as photographs taken during the
initial inspection.
7.3. Observe outfall for seepage and for indicators of seeps.
7.4. Compare current seepage location, extent, and flow to seepage photographs and descriptions
from previous inspections.
7.5. Record flow rate if measureable.
Marshall Steam Station Ash Basin
INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES
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9. Inspection For New Seeps Not Captured by Engineered Channels
Inspect areas below the ash basin full pond elevation and within the slope‐aquifer system shown on
Figure A‐2 to identify new seeps or indicators of new seeps. Inspect topographic drainage features that
potentially could contain new seeps that potentially discharge from the ash basin.
9.1. Previously Identified Seeps
a) Inspect previously identified seep locations. Document the condition of the seeps with a
photograph. Photographs are to be taken from similar direction and at a similar scale as the
photograph documenting original photograph of seep. Describe the approximate
dimensions and flow conditions of the seep.
b) If flow measurement device is installed at the outfall, record flow.
c) Observe seep to determine if changes to location, extent, or flows are present. Document
changes to location, extent, and/or flow amount or pattern.
9.2. New Seep or Indicators of Seep
a) Mark the location of new seep or indicators of seep using a GPS device.
b) Document the condition of the seeps or indicators of seeps with a photograph.
c) Describe the approximate dimensions and flow conditions of the seep.
d) Map the location of new seep or indicator of seep using GPS coordinate points collected
during the site visit.
e) If seep or indicator of seep was not caused by changes in surface water drainage and if the
location is below the ash basin pond elevation, utilize the decision flow chart to determine if
the seep represents a discharge from the ash basin and if notification to DWR is required.
10. Update Maps Identifying Seeps
If new seeps are identified during the inspection, Figure A‐2 shall be updated to show the location of the
new seeps. All seeps located below the ash basin full pond elevation and within the slope‐aquifer
system shown are to be shown on Figure A‐2.
11. Decision Flow Chart
The decision flow chart developed to determine whether a new seep discharges from the ash basin is
found on Figure A‐1.
Marshall Steam Station Ash Basin
INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES
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12. Procedure for Notifying NCDENR DWR If New Discharge Is Confirmed
If it is determined that a newly identified seep is present, Duke Energy will notify the DWR Regional
Office by mail within 14 days after the determination.
Marshall Steam Station Ash Basin INSPECTION FOR IDENTIFICATION OF NEW DISCHARGES 5 Notes: 1. If no new seeps are identified, inspection will be documented however no notification to NCDENR DWR is required. 2. If new seeps are identified that do not represent discharge from the ash basin during the same inspection that identifies new seeps that do represent a discharge from the ash basin, a single report will be submitted to NCDENR DWR.
Areas to be inspected