20190752 Ver 6_401 Monitoring Plan Addendum Updated_20220915

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NORTH CAROLINA
Envlronm¢ntcl Qvofiry
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Chemours Fayetteville Works Barrier Wall Project
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401 Monitoring Plan Addendum Updated - 2022-09-
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comments:
Geosyntec has updated this submitted monitoring plan addendum pursuant to NCDEQ requests.Below are a
summary of the changes, with a note about the W1-A groundwater gauge transect.
• The addendum lists a revision date of September 15, 2022.
• The figures have been updated to include (i) the location of the seep flow through cells, (ii) the seep
catchments, (iii) the planned barrier wall remedy infrastructure, and (iv) the repositioned groundwater gauge
transect W2-B described below.
• Groundwater gauge text in addendum now says: "A performance monitoring line of evidence for wetland
conditions will be groundwater gauge data meeting a minimum of 5% hydroperiod (12.15 consecutive days)
each year during the growing season indicated by groundwater within 12 inches (") of soil surface to meet the
primary hydrology indicator for high water table. Note, annual reports will document the longest consecutive
time period where groundwater levels were higher than 12" below soil surface for each groundwater gauge,
and document for each gauge the cumulative time groundwater levels were higher than 12" from soil surface
during the growing season."
• Groundwater gauge W4-A is replaced with Groundwater gauge W2-B proximal to the location indicated by
DEQ. Text in the document has been updated to note gauges will be placed in wetlands 1, 2, 3 and 6.
• Upon field inspection groundwater gauge W1-A could not be moved. This wetland was originally delineated
prior to installation of the Seep D flow -through cell. The now installed seep D flow -through cell has impounded
water creating a stilling basin which covers the extent of the previously delineated wetland. Therefore, this
groundwater gauge location could not be moved.
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Geosyntec °
consultants
Geosyntec Consultants of NC. P.C.
NC License No.: C-3500 and C-295
Memorandum
Date: September 8, 2022, Revised September 15, 2022
To: The Chemours Company, FC, LLC
From: Geosyntec Consultants of NC, P.C.
2501 Blue Ridge Road, Suite 430
Raleigh, NC 27607
PH 919.870.0576
FAX [phone]
www.geosyntec.com
Subject: Wetland Monitoring Plan: Addendum — Updated September 15, 2022
Chemours Fayetteville Works Project
Bladen/Cumberland County, North Carolina
DWR # 20190752v6; USACE Aid # SAW-2019-00296
INTRODUCTION
This updated Wetland Monitoring Plan Addendum ("Addendum") has been prepared by
Geosyntec Consultants of NC, P.C. (Geosyntec) for The Chemours Company FC, LLC
(Chemours). On August 13, 2021 the Wetland Monitoring Plan ("Monitoring Plan") was
submitted to the North Carolina Depaitiuent of Environmental Quality (NCDEQ) along with a
Section 404 permit modification request (SAW-2019-00296) through the United States Corps of
Engineers (USACE). This addendum to the previously submitted plan is based on comments by
the North Carolina Department of Environmental Quality (NCDEQ) via email on August 25, 2022.
This document first presents a summary of the stream and wetland monitoring scope described in
both the Monitoring Plan and this Addendum, and then presents the Addendum monitoring scope
additions based on comments and recommendations received from NCDEQ.
SUMMARY OF MONITORING SCOPE
The table on the following page summarizes the monitoring scopes to be implemented based on
both the Monitoring Plan and this Addendum.
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Wetland Monitoring Plan: Addendum
September 15, 2022
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Table 1 Summary of Monitoring Scope
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Geosyntec Gmsulla nle of NC, P.C.
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Scope / Item
Described in
Document
Duration and Frequency
Location
Performance
Standards
Groundwater
Gauges
USACE
Datapoints
NCWAM Forms
DWR Stream
Form
Wetland
Delineation
Reports
Monitoring Plan
and Addendum
Addendum
Monitoring Plan
and Addendum
Addendum
Addendum
Annual, 5 years
Continuous, 5 years
Annual, 5 years
Annual, 5 years
Semi-annual (early and late
growing season), 5 years
Monitoring Plan
Pre -construction: 2020
Post Construction: 2027
Addendum
Annual, 5 years
Wetland Study Area
Wetlands 1, 2, 3, and 6
Wetland and Upland
(Figure 1)
Central Area of Each
Wetland
Stream reaches above and
below barrier wall
Wetland Study Area
N/A
Notes:
USACE: United States Army Corps of Engineers
DWR: North Carolina Department of Environmental Quality, Division of Water Resources
NCWAM: North Carolina Wetland Assessment Method
MONITORING PLAN ADDENDUM
This section presents first comments received from NCDEQ on August 25, 2022 in italicized text
followed by responses in plain text. Responses are provided for comments numbered 5.a.i through
5.d.i in the DEQ comment letter. These responses describe additions and modifications to the
monitoring scope and serve as an addendum supplement to the existing Monitoring Plan. Wetlands
referenced in this addendum are described in Section 3.1.1. of the Waters of the US Findings
Report and detailed in Figure 1(a-c).
5a.i "Please sped the `additional information' that will be gathered as part of the baseline
characterization. Specifically what data will be collected and how will it be collected? In
Section 3.1.1. of the Waters of the US Findings Report seven distinct wetland areas were identified
based on initial observations. Please expand the baseline assessment for the seven wetland areas
to include characterization of landscape, soils, vegetation, and hydrology. The Division
recommends NC Wetland Assessment Methodology (NCWAM) forms completed for each of the
seven wetland areas identified to document baseline conditions of these wetland systems. Ideally,
a licensed soil scientist should conduct the soils assessments."
Geosyntec will collect NCWAM forms within the center of each of the seven wetlands during
2022 data collection field effort, prior to barrier wall construction. Additionally, NCWAM forms
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Wetland Monitoring Plan: Addendum
September 15, 2022
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will be completed at the same locations for each subsequent year of the monitoring period.
NCWAM forms will be completed by an experienced biologist who has completed Wetland
Delineation training for USACE methodology, including soil identification and characterization.
Additionally, a licensed soil scientist will conduct the soils assessments during the baseline
characterization effort planned for September 2022.
5a. ii "The initial wetland determination sample points focus on wetland/upland edges which is
appropriate for a delineation effort. However, the Division believes that plan should focus on
systemwide functional monitoring of the resources. Therefore, please add additional data
collection points in the central areas of wetlands W2, W3, and W6."
In an effort to better characterize the wetland form and function as a whole, and not just along the
delineated boundaries, Geosyntec established nine additional data points during a 2021
preliminary baseline assessment within the central areas of the wetlands. Data points appended
with a "U" (upgradient of the original datapoint) or "D" (downgradient of the original data point)
are additional datapoints sampled in 2021 to supplement the original data points (Table 2). The
locations of the original and additional data points are provided in Figure 1 of the addendum. These
additional data points already established by Geosyntec are consistent with NCDEQs' request for
additional data points.
Table 2 Wetlands and Associated Datapoints
Wetland
Additional Data Points
Wetland 1 (WI)
Wetland 2 (W2)
Wetland 3 (W3)
Wetland 4 (W4)
Wetland 6 (W6)
Wetland 6 (W6)
Wetland 7 (W7)
5a.iii "At least 4
PFO
PFO
PFO
PFO
PEM
PFO
PFO
1, 2
3, 4
5, 6
7, 8
9, 10
11, 12
14
1U
3U
5U, 5U2, 5U3
N/A
N/A
9U, 11D
13D, 13, 13U
epresentative baseline groundwater gauges should be installed before
construction to document pre -construction data such as the existing hydroperiod and be used in
postconstruction monitoring."
At the request of NCDEQ five transects with representative baseline groundwater gauges will be
installed within wetlands 1, 2, 3, and 6. Five pairs of upland/wetland gauges will be installed in
the wetlands and adjacent upland areas along a transect perpendicular to the wetland
boundary (Figure 1); and remain in place throughout the course of the monitoring period. The
gauges will be installed to a minimum depth of 15 inches below surface using USACE technical
specifications outlined in the June 2005 Technical Standard for Water -Table Monitoring of
Potential Wetland Sites, ERDC TN-WRAP-05-2. The gauges are anticipated to be
installed during mid -September 2022 prior to barrier wall installation to establish baseline
conditions.
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September 15, 2022
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NC F.ioense Nu.: G35tl9 and C-2.95
5a.iv "For any stream segments left as `non -impacted' on the western side of the proposed wall,
please propose a baseline assessment. The Division recommends conducting DWR Stream Forms
assessments pursuant to the North Carolina Methodology for Identification of Intermittent and
Perennial Streams and their Origins, Version 4.11 for all stream proposed to be `nonimpacted. "'
Geosyntec will conduct baseline assessment west of the barrier wall for the four non -impacted
areas of the streams above the barrier wall using the DWR stream form identified by NCDEQ.
These forms will be completed by an experienced biologist or one who has completed the NC
Surface Water Identification Training Certificate program. Geosyntec will resurvey the streams
west (non -impacted) and east (impacted) of the barrier wall semi-annually to occur in the early
growing season and the late growing season. An emphasis of the detailed documentation of
monitored streams' biology (macrobenthics and other biological indicators) will be incorporated
into the development of the forms.
5b. i "Given the permanent drawdown expected from the proposed barrier wall and the connection
between several of the wetlands' primary hydrology to the hillside/upstream seeps, the Division is
concerned that visual observation monitoring is not sufficient to demonstrate a 'no impact'
determination. Therefore, the Division recommends direct hydrologic measurement using multiple
groundwater gauges over a multiyear monitoring period. Groundwater gauges should be installed
per US Army Corps of Engineers (USACE) technical specifications guidance."
As described in response to comment 5a.iii., multiple groundwater gauges will be installed prior
to the construction activities to provide baseline data. These data will be monitored continuously
during the five year monitoring period. These data will offer further understanding of the influence
of the remedy construction on recorded groundwater levels within the wetland study area. This
will also allow specific measurement of hydrological changes of the ground water table in the
wetlands.
5b.ii "The monitoring plan's performance standards need to be more specific and measurable.
For example, groundwater gauges should meet a minimum 5% hydroperiod during the growing
season each year under normal rainfall conditions. Please update the plan to include
specific/measurable performance standards. The growing season start/end dates (and source of
this information) should be specified in the monitoring plan. In addition, the distance from the site
to the rainfall data sources should be provided if there is no on -site rain gauge."
To assess groundwater levels within the wetlands groundwater gauges will be monitored
throughout the requested 5-year monitoring period post -construction. Each gauge will log
groundwater elevation throughout the length of the study.
A performance monitoring line of evidence for wetland conditions will be groundwater gauge data
meeting a minimum of 5% hydroperiod (12.15 consecutive days) each year during the growing
season indicated by groundwater within 12 inches (") of soil surface to meet the primary hydrology
indicator for high water table. Note, annual reports will document the longest consecutive time
period where groundwater levels were higher than 12" below soil surface for each groundwater
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Wetland Monitoring Plan: Addendum
September 15, 2022
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Geosyntec Gmsulla nle of NC, P.C.
NC F.ioense Nu.: G35tl9 and C-2.95
gauge, and document for each gauge the cumulative time groundwater levels were higher than 12"
from soil surface during the growing season. The growing season is 16 March to 14 November
(243 days) based on the Natural Resource Conservation Service (NRCS) Bladen County Soil
Survey, for each year under normal rainfall conditions (a review of NRCS WETS table growing
season data did not yield any available data for Bladen or Cumberland Counties). Normal rainfall
conditions are determined to occur when rainfall values for a typical year. Typical year conditions
will generally be determined by: Normal precipitation conditions based on the three 30-day periods
preceding the observation date. For each period, a weighted condition value is assigned by
determining whether the 30-day precipitation total falls within, above, or below the 70th and 30th
percentiles for totals from the same date range over the preceding 30 years. A determination of
"normal," "wetter than normal," or "drier than normal" is made based on the condition value sum.
The USACE's Antecedent Precipitation Tool will be consulted to assess typical year precipitation
totals. Additional reference rainfall data will be assessed from the Fayetteville Area (PWC)
monitoring station, located approximately 15 miles north of the Site. This station is the closest
station to the Site which includes historical average month -to -date and year-to-date data to use as
a reference for "normal" conditions. Rainfall data may also be augmented using data from
Chemours' Onsite meteorological data station which records data on five minute intervals and the
United States Geological Survey (USGS) W.O. Huske Dam precipitation gauge (station
02105500) which records rainfall data on 15 minute intervals. The Onsite met station is
approximately one mile away from the wetlands and the USGS station is between 100 yards and
one mile away from the wetlands.
5b. iii "In addition to groundwater monitoring, the Division believes that an annual assessment of
vegetation composition and health is important. The proposed monitoring plan does identify good
examples of negative wetland plant stressors (lack of growth/vigor, mortality, upland/pioneer
plant competition). However, the monitoring plan proposes use of USACE wetland data forms as
the assessment tool for identification of the vegetation stressors. These forms were developed as a
delineation tool and not a monitoring/functional assessment tool. Therefore, please expand the
proposed data collection to include information such as tree/shrub species, height, DBH, health,
and wetland indicator status to assess changes in wetland community diversity, density and health.
The Division recommends using NCWAM forms. "
While use of the USACE methodology can provide adequate data on vegetative conditions by
detailing species composition, dominance, indicator status, etc.; Geosyntec agrees with NCDEQ
that additional data using NCWAM forms will provide even more detail on vegetative community
species composition and condition/health and will supplement the monitoring plan well.
Geosyntec will utilize NCWAM forms within each of the seven wetlands. Each form will be
completed annually for a five year period at the same location within each wetland.
5c. i "To assess potential secondary impacts to surface waters, the Division believes that semi-
annual assessments of surface hydrology indicators is necessary. Please update the monitoring
plan to include conducting DWR Stream Form assessments pursuant to the North Carolina
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Wetland Monitoring Plan: Addendum
September 15, 2022
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NC F.ioense Nu.: G3500 and C-2.95
Methodology for Identification of Intermittent and Perennial Streams and their Origins, Version
4.11 for all stream segments on a semi-annual basis."
DWR Stream Form assessments will be conducted for each stream (Figure 1) by an experienced
biologist or one who has completed the Surface Water Identification Training Certification course.
The form will be completed at the same location semi-annually (early growing season and late
growing season) to monitor for potential changes in surface hydrology and the effects on the
biological community.
5d. i "The Division believes that three years will likely not be a sufficient length of time to visually
assess the extent of stream and wetland function degradation or loss. Therefore, please update the
plan to include five years of monitoring for all elements. After five years, the groundwater data,
surface hydrology indicators and vegetation composition/health should collectively provide
evidence ofwhether the barrier wall is having an impact on adjacent wetlands and surface waters.
This information along with a site re -delineation should allow proper assessment of whether state
wetland and surface water resources have been lost or significantly degraded thereby potentially
requiring mitigation."
At the request of NCDEQ, the monitoring period will be extended from three years to five years
post -construction, while also including the additional monitoring protocol adjustments detailed
above. Reports will be submitted annually to NCDEQ by January 31s1 of the following year.
Encl.
Tables Table 1: Summary of Monitoring Scope
Table 2: Wetlands and Associated Datapoints
Figures Figure 1 a-c: Wetland Monitoring Point Locations
Wetland Monitoring Plan: Addendum DWR # 20190752v6; USACE Aid # SAW-2019-00296
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Figures

Legend
2020 Upland Datapoint
O 2021 Additional Wetland Datapoint
A 2020 Wetland Datapoint
O Stream Monitoring Datapoint
QEx -situ Capture Location
■ Flow -Through Cell
▪ Surficial Aquifer Extraction Well
▪ Black Creek Aquifer Extraction Well
North Forcemain
South Forcemain
■ 1 Barrier Wall Barrier Wall
Site Boundary
Seep
Nearby Tributary to River
Wetlands Investigation Area
Exclusion Areas
Wastewater Treatment Pad
North
Forcemain
AS5' TRIBU
I`
S5-N I
Seep A�
Capture
Groundwater
Treatment
Delineated Feature:
® Ordinary High Water Mark (OHWM)
Palustrine Emergent (herbaceous) Wetland (PEM)
Palustrine Forested Wetland (PFO)
Estimated Catchment to Seep Flow Through Cells
■
a
a
Seep D
Seep A
Seep B
Seep C
Notes:
1. The outline of Cape Fear River is approximate and is based on open data from ArcGIS Online and North Carolina Department of
Environmental Quality Online GIS (MajorHydro shapefile).
2. Basemap sources: NC OneMap (2 9). North Carolina Department of Information Technology, Government Data Analytics Center, Center
for Geographic Information and Analysis. Available at https://www.nconemap.gov.
250125 0 250 Feet
Wetland Monitoring Point Locations
Wetland Monitoring Report - 2021
Chemours Fayetteville Works
Cumberland/Bladen County, North Carolina
Geosyntec r.
consultants
Geosyntec ConsulLants al NC, P.C.
NC License No.: C-3500 and C-295
Figure
Raleigh
September 2022
1
Prgection_ NAD 1983 StatePlane South Carolina FIPS 3900 Feet, Unils in Foot US

0
A
2020 Upland Datapoint
2021 Additional Wetland Datapoint ■ 1
2020 Wetland Datapoint
OStream Monitoring Datapoint
QEx -situ Capture Location
■ Flow -Through Cell
▪ Surficial Aquifer Extraction Well
▪ Black Creek Aquifer Extraction Well
North Forcemain
South Forcemain
Barrier Wall Barrier Wall
Site Boundary
Seep
Nearby Tributary to River
Wetlands Investigation Area
Exclusion Areas
Wastewater Treatment Pad
Delineated Feature:
® Ordinary High Water Mark (OHWM)
Palustrine Emergent (herbaceous) Wetland (PEM)
Palustrine Forested Wetland (PFO)
Estimated Catchment to Seep Flow Through Cells
■ Seep A
aSeep B
aSeep C
Seep D
Notes:
1. The outline of Cape Fear River is approximate and is based on open data from ArcGIS Online and North Carolina Department of
Environmental Quality Online GIS (MajorHydro shapefile).
2. Basemap sources: NC OneMap (2 9). North Carolina Department of Information Technology, Government Data Analytics Center, Center
for Geographic Information and Analysis. Available at https://www.nconemap.gov.
250
125
0
250 Feet
Wetland Monitoring Point Locations
Wetland Monitoring Report - 2021
Chemours Fayetteville Works
Cumberland/Bladen County, North Carolina
Geosyntec r.
consultants
Geosyntec ConsulLants al NC, P.C.
NC License No.: C-3500 and C-295
Figure
Raleigh
September 2022
la
Prgection_ NAD 1983 StatePlane South Carolina FIPS 3900 Feet, Unils in Foot US

•
•
2020 Upland Datapoint
2021 Additional Wetland Datapoint ■ 1
2020 Wetland Datapoint
OStream Monitoring Datapoint
QEx -situ Capture Location
■ Flow -Through Cell
▪ Surficial Aquifer Extraction Well
▪ Black Creek Aquifer Extraction Well
North Forcemain
South Forcemain
Barrier Wall Barrier Wall
Site Boundary
Seep
Nearby Tributary to River
Wetlands Investigation Area
Exclusion Areas
Wastewater Treatment Pad
Delineated Feature:
® Ordinary High Water Mark (OHWM)
Palustrine Emergent (herbaceous) Wetland (PEM)
Palustrine Forested Wetland (PFO)
Estimated Catchment to Seep Flow Through Cells
■ Seep A
aSeep B
aSeep C
Seep D
Notes:
1. The outline of Cape Fear River is approximate and is based on open data from ArcGIS Online and North Carolina Department of
Environmental Quality Online GIS (MajorHydro shapefile).
2. Basemap sources: NC OneMap (2 9). North Carolina Department of Information Technology, Government Data Analytics Center, Center
for Geographic Information and Analysis. Available at https://www.nconemap.gov.
250
125
0
250 Feet
Wetland Monitoring Point Locations
Wetland Monitoring Report - 2021
Chemours Fayetteville Works
Cumberland/Bladen County, North Carolina
Geosyntec r.
consultants
Geosyntec ConsulLants al NC, P.C.
NC License No.: C-3500 and C-295
Figure
Raleigh
September 2022
1b
rgection_ NAD 1983 StatePlane South Carolina FIPS 3900 Feet, Unils in Foot US

2020 Upland Datapoint
O 2021 Additional Wetland Datapoint ■ 1
A 2020 Wetland Datapoint
O Stream Monitoring Datapoint
■ Flow -Through Cell
▪ Surficial Aquifer Extraction Well
▪ Black Creek Aquifer Extraction Well
North Forcemain
South Forcemain
Barrier Wall Barrier Wall
Site Boundary
Seep
Nearby Tributary to River
Wetlands Investigation Area
Exclusion Areas
Wastewater Treatment Pad
Delineated Feature:
® Ordinary High Water Mark (OHWM)
Palustrine Emergent (herbaceous) Wetland (PEM)
Palustrine Forested Wetland (PFO)
Estimated Catchment to Seep Flow Through Cells
■ Seep A
aSeep B
aSeep C
Seep D
Notes:
1. The outline of Cape Fear River is approximate and is based on open data from ArcGIS Online and North Carolina Department of
Environmental Quality Online GIS (MajorHydro shapefile).
2. Basemap sources: NC OneMap (2 9). North Carolina Department of Information Technology, Government Data Analytics Center, Center
for Geographic Information and Analysis. Available at https://www.nconemap.gov.
UU
250
125
0
250 Feet
Wetland Monitoring Point Locations
Wetland Monitoring Report - 2021
Chemours Fayetteville Works
Cumberland/Bladen County, North Carolina
Geosyntec r.
consultants
Geosyntec ConsulLants al NC, P.C.
NC License No.: C-3500 and C-295
Figure
Raleigh
September 2022
lc
Prgection_ NAD 1983 StatePlane South Carolina FIPS 3900 Feet, Unils in Foot US