HomeMy WebLinkAbout0403_Chambers_Phase5_Draft_DesignHydroWorkplanReview_DIN27406_201702011
Sugg, William P
From:Sugg, William P
Sent:Wednesday, February 01, 2017 9:21 AM
To:'Stephens, Ed'; Bivins, Nathan
Cc:Wilson, Donna; Mussler, Ed
Subject:RE: Phase 5 Expansion Design Hydrogeologic Investigation Work Plan - Anson Waste Management
Facility - 165-276
Ed/Nathan,
Based on review of the proposed Phase 5 work plan you all submitted and feedback from staff, the Section
offers the following:
General
The proposed Phase 5 area appears to be outside of the previously approved site study/site hydro boundaries
for the facility. This may mean treating the Phase 5 as a new facility under 15A NCAC 13B .1603, rather than
an expansion of the existing landfill. With that, any hydro study would mean meeting requirements of
.1623(a) Site Hydro Report and .1623(b) Design Hydro Report. Regardless that should not be a significant
problem based on adjoining landfill information and proposed work plan approach.
Proposed Design Hydro Work Plan
The primary deviation from .1623(b) in the proposed design hydro work plan is a significant reduction in site
borings required in .1623(b)(1), “an average of one boring for each acre of the area of investigation”. The
proposed footprint of Phase 5 covers approximately 83 acres. The number of borings proposed is 29, or about
one boring for every 3 acres.
The Section’s position is that this proposal for reduced boring density as presented would be inadequate for
providing the more detailed and localized subsurface and hydrogeological data necessary for the basis of site
design and constructability, particularly the vertical separation requirements in .1624(b)(4) and possibly
engineering foundation standards. Uncertainty in subsurface prediction for this area can be expected due to
the following:
•The existing landfill and proposed Phase 5 area lie directly on top of the contact boundary zone
between the Triassic basin and Carolina Slate belt. In addition, hi-angle diabase dikes have been
identified, and can be expected, in the immediate vicinity as well. The exact boundary between the
Triassic and Slate Belt rocks through the site is not known.
•Previous excavation of the existing landfill has revealed unexpected subsurface conditions with
perched water table due to rock lenses or other conditions, resulting for the need to install unplanned
underdrain systems during construction.
•Phase 5 area is sited along a narrow extended ridgeline with steeply sloping side slopes down to the
adjacent floodplain. As such, top of bedrock surface may vary quite dramatically over a short distance.
Conversely, the potentiometric surface could likewise be expected to change somewhat sharply over
short distances as well. Investigative borings spaced too widely would lead to excessive extrapolation
of actual subsurface conditions.
2
Let us know if you need any further assistance with this.
Sincerely,
Perry Sugg, PG
Permitting Hydrogeologist
Division of Waste Management – Solid Waste Section
NC Department of Environmental Quality
Phone: (919) 707.8258
perry.sugg@ncdenr.gov
Physical Address: 217 West Jones St / Raleigh, NC / 27603
Mailing Address: 1646 Mail Service Center / Raleigh, NC / 27699-1646
http://portal.ncdenr.org/web/wm/sw
E-mail correspondence to and from this addresss may be subject to the North Carolina Public Records Law and therefore may be disclosed to third parties.
-i- Work Plan for Phase 5 Hydrogeologic Investigation January 2017
TABLE OF CONTENTS
Page
1.0 INTRODUCTION..............................................................................................................1 1.1 Site Description ....................................................................................................... 1
1.2 Physical Setting ....................................................................................................... 1 1.3 Local Geology/Hydrogeology ................................................................................ 3
2.0 PROPOSED WORK PLAN FOR SITE-SPECIFIC HYDROGEOLOGICAL INVESTIGATION .................................................................5 2.1 Reliance On Previous Data ..................................................................................... 5
2.2 Purpose Of Work Plan ............................................................................................ 5 2.3 Scope Of Work ....................................................................................................... 6
FIGURES
Embedded Figure 3-1 – USGS Topographic Map Attached
Figure 1 – Proposed Phase 5 Boring Location Map
-1- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
1.0 INTRODUCTION
1.1 SITE DESCRIPTION
The Anson Waste Management Facility is situated in the south-central portion of Anson County,
North Carolina. The landfill facility is classified as a municipal solid waste (MSW) landfill and
operates under Permit Number 0403. Development of the landfill facility is progressing
incrementally in five phases with each phase being comprised of smaller cells. The general intent
is to construct a phase incrementally within the landfill when needed. Permits to Construct for
Phase 1 and Phase 2 expansions were issued by NCDEQ in 2000 and 2008, respectively. The
footprint of Phase 1 is approximately 40.38 acres, and Phase 2 consists of 32.78 acres. Both these
existing phases are currently operational. A Permit to Construct Application for Phases 3 and 4
was completed by CEC in November 2016, and has been subsequently submitted to the NC Solid
Waste Section for review and approval. Phases 3 and 4 will include a total of 60 acres, bringing
the total landfill area to 133 acres.
The subject proposed Phase 5 expansion area lies adjacent and to the north of Phases 3 and 4. The
preliminary proposed Phase 5 expansion footprint contains approximately 83 acres. A site map is
attached as Figure 1 that depicts the preliminary Phase 5 boundaries and the approximate locations
of soil borings/piezometers proposed for the subject Phase 5 Design Hydrogeologic Investigation.
Further, the detection monitoring wells proposed for the Phase 3 & 4 expansions which are located
within the subject Phase 5 expansion area are also shown on Figure 1.
1.2 PHYSICAL SETTING
The site location is shown on Figure 3-1 below. The facility is located in south-central Anson
County between Polkton and Wadesboro along US 74. The site is bounded on the northwest by
Brown Creek, on the east by Pinch Gut Creek, and on the south by the CSX railroad. The
immediate surrounding area is rural and primarily wooded. There is limited residential
development south of the landfill facility. Site topographic features are shown on the USGS
Polkton, NC 7.5-Minute Topographic Quadrangle Map that is presented in Figure 3-1 below.
-2- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
-3- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
The site consists of a series of rolling hills that reach elevations of ±300 feet above mean sea level
and low-lying areas adjacent to Brown and Pinch Gut Creeks at an elevation low of approximately
240 feet above sea level. Generally, surface drainage from the landfill facility is to the northwest
toward Brown Creek and northeast toward an unnamed tributary of Pinch Gut Creek.
1.3 LOCAL GEOLOGY/HYDROGEOLOGY
The Phase 5 expansion area is predominantly underlain by Carolina Slate Belt lithologies. The
Carolina Slate Belt consists mostly of rocks originally deposited on or near the earth’s surface by
volcanic eruption and sedimentation (NC Geological Survey 1985). This lithologic belt is so
named because low-grade metamorphism has imprinted many of the rocks with a “slaty” cleavage.
The belt is intruded by coarse-grained granites in several places; although, intrusive rocks have
not been reported locally. The previously identified local rocks include primarily argillites
described as light gray to bluish-gray or brown, fine-grained, well-bedded, with pronounced
bedding plane cleavage. Other rocks present include mudstones, silty sandstone, and
conglomerate. High-angle diabase dikes have been mapped in adjacent landfill areas and may
occur in the Phase 5 area.
Surficial rocks have differentially weathered to form an upper “saprolite” zone consisting of
unconsolidated silts and clays transitioning at depth to partially weathered rock (PWR) that is
coarser-grained, often containing boulders, less weathered, and a denser porous residuum. Depths
to PWR vary with the occurring rock type’s resistance to chemical weathering and are typically
shallower in higher areas and deeper in low areas. Underlying rocks are typically fine-grained and
exhibit variable fracture density.
Three basic hydrogeologic units have been characterized at the site by others. The uppermost
hydrogeologic units are two density-based zones within a typical Piedmont unconfined “water
table” aquifer within the saprolite zone, which consists of variably dense silty clayey sand and silt
derived from in-situ weathering of the parent rock. A third hydrogeologic unit is underlying
fractured bedrock within which groundwater occurs under unconfined to partially confined
conditions. The density of bedrock fracturing and fracture apertures tend to decrease with
-4- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
increasing depth such that groundwater flow is significantly restricted within a depth of 200 to 300
feet.
Groundwater recharge largely occurs over broad uplands and gentle slopes. Little recharge occurs
in areas of steeper topography. Typically, groundwater occurrence is localized within a relatively
porous PWR zone, which transitions with depth to bedrock. Groundwater discharge occurs along
area streams (i.e., Brown Creek and Pinch Gut Creek), which converge at the northern corner of
the site.
Based on earlier site hydrogeologic characterization by others, the groundwater flow patterns are
not expected to change significantly due to seasonal climatic variation, except that groundwater
levels in recharge zones are expected to exhibit normal seasonal fluctuation.
-5- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
2.0 PROPOSED WORK PLAN FOR SITE-SPECIFIC HYDROGEOLOGICAL INVESTIGATION
2.1 RELIANCE ON PREVIOUS DATA
On behalf of the facility owner, CEC recently submitted a Permit to Construct Application for
Phases 3 and 4 to the Solid Waste Section for review and approval. Appendix E includes a Design
Hydrogeologic Investigation Report prepared by SCS Engineers, PC dated October 5, 2015 that
provides a discussion of hydrogeologic data collected at the site since initial site suitability work
was performed by GZA Environmental, Inc. in 1992. A Phase 1 Design Hydrogeologic Report
was prepared by TRC Environmental dated December 1998. This document included the Water
Quality Monitoring Plan and deep coring data. The earlier site studies focused on diabase dikes
and included borings advanced to depths up to 200 feet. The Phase 2 design study was completed
by ESP Associates and Davis Garrett & Associates between 2003 and 2007. This investigation
included 41 soil borings within which 34 piezometers were constructed, including seven nested
pairs. The Phase 2 study included 35 slug tests to determine hydraulic conductivities of the defined
hydrogeologic units.
SCS Engineers, PC prepared the Design Hydrogeologic Investigation Report included in the recent
Permit to Construct Application for Phase 3 and 4. The combined Phase 3 & 4 hydrogeologic
study included 34 new borings that were advanced to auger refusal to characterize the top-of-
bedrock surface. All but four borings encountered the water table such that 30 piezometers were
constructed. Rock was cored at three site locations. Previous available information included rock
core data from eight earlier borings. Like the proposed Phase 5 expansion area, Phase 3 & 4 areas
are predominantly underlain by Slate Belt argillite.
2.2 PURPOSE OF WORK PLAN
CEC will perform a Design Hydrogeologic Investigation for the Anson Waste Management
Facility Phase 5 expansion area. The purpose of the study is to characterize hydrogeological units,
determine approximate top-of-bedrock and seasonal high groundwater table elevations, and collect
representative samples for geotechnical testing to provide landfill design parameters for the Phase
-6- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
5 expansion. This investigation will be performed in general accordance with NC Solid Waste
Management Rule 15A NCAC 13B .1623 (b) Design Hydrogeologic Report.
Prior hydrogeologic investigations have been performed by others in permitting four previous
landfill phases that have provided considerable knowledge of local subsurface conditions. CEC
assumes that additional borings, wells, and/or piezometers will be necessary within the Phase 5
footprint to supplement and confirm work previously performed by others as well as fill gaps in
the project area where data is not available or is limited. The proposed investigation area is
approximately 83 acres. It is CEC’s technical opinion that an adequate design hydrogeologic study
can be completed on the Phase 5 expansion area with an exploration density less than one test
boring per acre as specified by 15A NCAC 13B .1623 (b) (1). A total of twenty-nine (29) boring
sites to be completed as temporary piezometers or permanent monitoring wells are proposed for
the Phase 5 study area that will provide a boring density of approximately 1 per 2.86 acres, which
is adequate based on the apparent uniformity of the previously characterized hydrogeologic units.
In addition, four of these boring sites will include a nested deeper boring/piezometer. It is
anticipated that eight of these proposed borings can be converted to permanent detection
monitoring wells for the Phase 3 & 4 expansion areas. The approximate locations of proposed
borings/piezometers/wells are shown on Figure 1. CEC assumes that the Solid Waste Section will
review our proposed investigation scope and will authorize the proposed alternate exploration
density.
2.3 SCOPE OF WORK
This section outlines the proposed Scope of Work to provide appropriate geotechnical and
hydrogeological evaluations for the Phase 5 Expansion Area.
Field Work
An area hydrogeological investigation (field study) will be conducted to obtain the
geologic/hydrogeologic/geotechnical samples and data needed to evaluate site suitability and for
landfill design purposes. In general, CEC activities as part of this task will include:
-7- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
• NC-licensed geologist to plan the site boring/monitoring well/piezometer program
and data collection approach;
• Field geologist to locate, observe, and log all soil borings and rock cores;
• Collection and preparation of representative samples for geotechnical laboratory
testing;
• Gauge and record water levels in piezometers; and
• A magnetometer survey to identify the location and orientation of potential diabase
dikes in the Phase 5 area, if any.
Test Borings
With the prior approval of the NCDEQ Solid Waste Section, eight (8) soil test borings advanced
in the Phase 5 area will be located at sites previously proposed by others for detection groundwater
monitoring wells MW-13 through MW-20 for Phases 3 and 4 as shown on the attached Figure 1.
These borings will be subsequently converted to permanent monitoring wells constructed in
accordance with 15A NCAC 2C guidelines. Up to twenty-one (21) additional soil test borings
(PZ5-1 through PZ5-21) will be advanced at the approximate locations shown on the attached
Figure 1. The latter soil borings will be converted to temporary shallow piezometers. Also, four
(4) additional piezometers (PZ5-6D, PZ5-7D, PZ5-8D, and PZ5-11D) will be nested with four
shallow piezometers (PZ5-6, PZ5-7, PZ5-8, and PZ5-11) to provide head data to evaluate vertical
hydraulic gradients.
Soil test borings will be advanced by an ATV-mounted drill rig using hollow-stem augers to a
depth of auger refusal. Standard penetration tests (SPT) will be performed at a minimum of five-
foot intervals in accordance with ASTM D 1586-84 (continuous SPT over the bottom ten feet of
each boring) to evaluate relative density and soil strength. Split-spoon samples collected while
performing SPT will be visually classified in the field and representative samples will be retained
for geotechnical classification via the Unified Soil Classification System (USCS) and other
geotechnical testing. Select undisturbed representative samples will be collected for geotechnical
testing by advancing up to ten (10) thin-walled Shelby tubes in the bottom ten feet of several
borings.
-8- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
Rock Cores
Rock cores will be obtained at five (5) boring locations by advancing at least NQ-size core barrels
for wireline recovery. Preferred rock coring locations are those borings which are targeted for
conversion to deep piezometers and/or borings advanced to auger refusal prior to reaching the local
water table. Rock cores will be obtained at a minimum from the upper ten (10) feet of bedrock in
each test boring. The rock cores will be observed for rock classification and structural features,
core recovery values, and Rock Quality Designation (RQD) values.
Permanent Monitoring Wells
Permanent monitoring wells will be installed in borings MW-13 through MW-20 as shown on
Figure 1. Each soil boring will be extended to auger refusal at which depth the bottom of the well
screen will be placed. Each well will be constructed of two-inch Schedule 40 PVC riser and 0.010-
inch slotted PVC well screen. Each well screen interval will be selected in the field based on
existing site conditions. Well installations will be performed under the direction of a qualified
geologist. Permanent monitoring wells will be constructed in accordance with 15A NCAC 2C
guidelines.
Temporary Piezometers
The remaining soil test borings to be converted to shallow piezometers will also be advanced to
auger refusal. A temporary piezometer will be installed in each boring such that the bottom of the
well screen is coincident with the depth of auger refusal. Borings for deeper piezometers will
likely be advanced into bedrock. A temporary piezometer will be installed in each boring such
that the well screen is screened in the bedrock unit. Each piezometer will be constructed of two-
inch Schedule 40 PVC riser and 0.010-inch slotted PVC well screen. Each piezometer screen
interval will be selected in the field based on existing site conditions. Piezometer installations will
be performed under the direction of a qualified geologist.
Monitoring Well/Piezometer Gauging
The monitoring wells and piezometers that will be installed in the Phase 5 expansion will be
gauged for water levels at the time of boring, 24 hours after installation, and following stabilization
of water levels. Stabilized water level elevations will be compared with hydrographs of area wells,
-9- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
meteorological/climatological data, and other available information to estimate a long-tern
seasonal high water table.
Groundwater flow directions, rates, and gradients will be estimated from existing and newly obtain
hydrogeological data.
Note: In-situ permeability tests were performed in 24 piezometers during the previous design
hydrogeologic investigation for Phases 3 and 4. CEC assumes that the available permeability test
data will be representative of similar subsurface materials that will be encountered in the Phase 5
expansion. Existing data will be used to estimate geometric mean permeability for the identified
hydrogeologic units.
Magnetometer Survey
CEC will conduct a proton-procession magnetometer survey of the Phase 5 area for the purpose
of mapping potential diabase dikes. Whereas previous mapped dikes in the area of the landfill
facility have a roughly north-south orientation, four perpendicular east-west traverses will be
performed over the Phase 5 area. Should a magnetic anomaly be detected, additional localized
traverses will be performed to determine its extent.
Design Hydrogeologic Report
CEC will provide a narrative to discuss previous published area geology/hydrogeology, design
hydrogeologic investigation methods, data interpretations, and findings to include:
• A report on local and regional geologic and hydrogeology based on
research of available literature for the area. This report will include a
fracture trace analysis and Rose Diagram based on inferred structurally–
controlled lineaments identified on an area topographic map;
• A report on field observations that includes topographic setting, springs,
streams, drainage features, existing or abandoned wells, rock outcrops
(including strike and dip), groundwater discharge features, and other
pertinent features that may affect site suitability;
-10- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
• A groundwater contour map will be generated based on the estimated
seasonal high water table that is superimposed on a topographic map and
includes the location of borings and rock cores and the water table
elevations at each location used to generate the groundwater contours;
• A bedrock contour map of the upper surface of the bedrock that is
superimposed on a topographic map and includes the location of borings
and rock cores and the top-of-rock elevations at each location used to
generate the upper surface of bedrock contours;
• A 3-D groundwater flow net or several hydrogeologic cross-sections that
characterize the vertical groundwater flow regime for this area;
• A report on the groundwater flow regime for the area including flow paths
for both horizontal and vertical components of groundwater flow,
horizontal and vertical hydraulic gradients, flow rates, and recharge and
discharge areas; and
• A certification by a Licensed Geologist that all borings at the site that have
not been converted to permanent monitoring wells will be properly abandoned
in accordance with the procedures for permanent well abandonment as
delineated in 15A NCAC 02C .0113.
Geotechnical Sample Collection and Laboratory Testing
The scope of work includes a geotechnical field-testing program and associated slope stability and
settlement analysis for the Phase 5 expansion in general accordance with 15A NCAC 13B .1624
Construction Requirements and 15A NCAC 13B .1627 Closure and Post Closure Requirements
for MSWLF Facilities.
Geotechnical properties of the soils will be estimated by various geotechnical laboratory tests.
These tests and their estimated number are listed in the table below.
-11- Work Plan for Phase 5 Hydrogeologic Investigation
January 2017
Laboratory Test Est. Number of Tests
Moisture Content 25(1)
Sieve Analysis 25(1)
Hydrometer Analysis 25(1)
United Soil Classification System 25(1)
Atterberg Limits 25(1)
Porosity 25(1)
Shelby Tubes 10(2)
Standard Proctor 5
Permeability (Remolded) 5(3)
One-Dimensional Consolidation (Undisturbed) 2
CU Triaxial (Remolded) 2
CU Triaxial (Undisturbed) 2
Notes:
1. Moisture content, sieve analysis, hydrometer analysis, USCS, Atterberg limits, and porosity will be performed at each boring location to demonstrate soil consistency.
2. Only four tests require undisturbed samples, however, additional Shelby tube samples should be collected and archived for possible future testing requirements. 3. Number of proposed tests assumes soil uniformity in Phase 5 area.
Design Analysis
CEC will perform a slope stability and settlement analysis for the Phase 5 expansion. In addition, CEC will
perform an anchor trench design and a geotextile cushion design for the proposed geotextile-clay liner
system.
FIGURES
B-17
B-23
B-22
8
A
B
34567 12
C
D
E
F
G
H
8 34567 12
A
B
C
D
E
F
G
H
DE
S
C
R
I
P
T
I
O
N
DA
T
E
NO
RE
V
I
S
I
O
N
R
E
C
O
R
D
ww
w
.
c
e
c
i
n
c
.
c
o
m
19
0
0
C
e
n
t
e
r
P
a
r
k
D
r
i
v
e
-
S
u
i
t
e
A
-
C
h
a
r
l
o
t
t
e
,
N
C
2
8
2
1
7
Ph
:
9
8
0
.
2
3
7
.
0
3
7
3
·
F
a
x
:
9
8
0
.
2
3
7
.
0
3
7
2
DA
T
E
:
DW
G
S
C
A
L
E
:
DR
A
W
N
B
Y
:
CH
E
C
K
E
D
B
Y
:
AP
P
R
O
V
E
D
B
Y
:
PR
O
J
E
C
T
N
O
:
SHEET OF
DRAWING NO.:
PR
O
P
O
S
E
D
P
H
A
S
E
5
BO
R
I
N
G
L
O
C
A
T
I
O
N
M
A
P
14
2
-
9
6
2
1"
=
3
0
0
'
JA
N
U
A
R
Y
2
0
1
7
CT
H
NT
B ES
1 1
FIGURE 1
NORTH
REFERENCE
FU
T
U
R
E
P
H
A
S
E
5
E
X
P
A
N
S
I
O
N
AN
S
O
N
C
O
U
N
T
Y
L
A
N
D
F
I
L
L
AN
S
O
N
,
N
O
R
T
H
C
A
R
O
L
I
N
A
DRAFT