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Uwharrie Regional MSW Landfill
Design Hydrogeologic Report, Phase 4
LIST OF APPENDICES
-MN o rle
May 15, 2008
BLE Project Number J07-1002-74
Appendix
A. Drilling and Sampling Procedures
B. Field Logs of Borings
C. Soil Test Boring/Rock Coring Records and Well Diagrams
D. Piezometer Installation Procedures
E. Precipitation and Groundwater Level Data & Charts
F. Slug Test Procedures and Results
G. Soil Laboratory Test Procedures
H. Soil Laboratory Test Results
I. Fracture Trace Analysis Data
J. Surface Geophysical Methods and Data
v

IRLE C.
Uwharrie Regional MSW Landfill May 15, 2008
Design Hydrogeologic Report, Phase 4 BLE Project Number J07-1002-74
REPORT CROSS-REFERENCE INDEX OF
APPLICABLE NORTH CAROLINA STATE REGULATIONS
15A NCAC 13B .1623 (b) Design Hydrogeologic Report Requirements
STATE
REGULATIONS
LOCATION IN REPORT
b 1 A
Sections 3.5.2.1, 3.6.3; Table 2; Figures 7, 10; Appendix E
(b) (1) (B)
Section 3.5; Tables 2, 3, 6, 7; Figures 6, 9, 10, 11; Appendices D, E,
F
(b) (2 A
From 15A NCAC 13B .1623(a
(a) (4) (A)
Sections 2.1, 3.4.1; Appendices A, B, C
(a) (4) (B)
Sections 2.3, 3.4.4; Tables 4, 5; Appendices G, H
a (4) (C)
Sections 3.4.1, 3.4.4; Tables 4, 5; Appendices B, C, H
(a) (4) (D)
Sections 3.4; Tables 4, 5; Appendices B, C
(a) (4) (E)
Sections 3.4.4, 3.5.5; Tables 3, 4, 7; Appendices F, H
a 5
Sections 2.4, 2.5, 3.4.2, 3.4.3; Figure 8; Appendices I, J
(a) (6)
Figure 6
a 7 (A)
Table 2
(a) (7) (B)
Table 2; Appendix E
a) (7) (C)
Section 3.5.2.2; Table 2; Figure 11; Appendix E
(a) (7) (D)
Sections 3.2, 3.5.2, 3.5.3, 3.5.4
(a) (8)
Sections 3.5.5, 3.5.6; Tables 3, 6, 7; Figures 6, 9; Appendix F
a (9)
Figures 9, 10, 11
(a) (10
Figure 5
(a) (11)
Appendices B, C
(a) (12)
Sections 3.3, 3.4.2, 3.4.3; Figure 8; Appendices I, J
b 2 (B)
Sections 3.4, 3.5, 4. 1; Tables 2, 3, 6, 7; Figures 6, 7, 8, 9, 10
(b) (2) (C)
Sections 3.0, 4.1.2; Tables 2, 3, 6, 7; Figures 6, 7, 8, 9, 10
(b) (2) (D)
Sections 2.1, 3.4.1.3, 3.4.2; Figure 7; Appendices B, C, I
b (2) (E
Figure 11
(b) (2) F)
Figure 7
(b) (2) (G)
Figure 6
b 2 H
Section 3.5; Tables 2, 3, 6, 7; Figures 6, 8, 9, 10
(b) 2) (1)
Section 2.2
(b) (3 (A)
Section 4.1, 4.3; Figure 5
b (3) (B
Section 4.2, 4.3; Figure 5
(b) (3) (C)
I
Signature page
vi

NIL VG.
Uwharrie Regional MSW Landfill
Design Hydrogeologic Report, Phase 4
May 15, 2008
BLE Project Number J07-1002-74
The vertical gradients observed at the site are typical for unconfined aquifers in the Piedmont.
Groundwater recharge occurs in the upland areas in Phase 4, as well as west and south of Phase 4.
Discharge occurs to Rocky Creek located north of Proposed Cell No. 14, and to the drainage
feature east of Proposed Cell No. 13.
3.6 GEOTECHNICAL CONSIDERATIONS
An evaluation of the potential impact from faults, seismic zones and unstable areas, as required by
15A NCAC 13B.1622, was previously prepared for the current landfill site and documented as part
of the Site Hydrogeologic Report dated September 9, 1993 (LAW Job Number 2490472802).
These items are briefly reviewed below to provide a background for our geotechnical evaluation.
3.6.1 Fault Areas
No Holocene faults are located within 200 feet of the subject site (Horton and Zullo, 1991).
3.6.2 Seismic Impact Zones
According to the definition of seismic impact zones in 15A NCAC 13B.1622 (5), this site is in a
seismic impact zone. The maximum horizontal acceleration expressed as a percentage of the
earth's gravity (g) in rock is 0.13g with a 2% probability of being exceeded in 50 years (equal to
10% probability in 250 years; Frankel and others, 2002). Design of the landfill should consider the
seismic conditions; however, the magnitude of acceleration should not significantly impact the
planned construction. In addition, BLE will perform seismic stability analysis for the design of
Cells No. 13 and 14 at a later date once design grades have been prepared.
3.6.3 Unstable Areas
An unstable area according to 15A NCAC 13B.1622 (6) is defined as a location that is susceptible
to natural or human induced events or forces capable of impairing the integrity of some or all of the
landfill structural components responsible for preventing releases from a landfill. Unstable areas
could include poor foundation conditions, areas susceptible to mass movements, and karst terrains.
Site and subsurface data obtained was evaluated to determine if unstable site areas exist. The site
is not in a karst area. No unstable conditions were present. Subgrade settlements resulting from
the proposed landfill loading will be well within tolerable limits. BLE will evaluate specific
settlement and slope stability conditions for the Cells No. 13 and 14 area at a later date once
landfill design grades have been prepared.
3.6.4 Permeability of Potential On -Site Soils for Liner and Cover Construction
The permeability of selected potential on -site borrow soils were determined as indicated in Section
3.4.4.2 titled Laboratory Testing Results. Five bag samples of near surface soil were collected.
The samples were compacted at varying percents of the Standard Proctor maximum dry density,
and at varying moisture contents of the Standard Proctor optimum moisture content. Hydraulic
conductivity values ranged from 7.4 x 10-8 to 4.6 x 10-7 cm/sec.
The near surface soils at the site consist of three general soil types based on topographic position.
The near surface soils in the higher elevation areas, including the upper portions of the hill side-
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IBLE ,
Uwharrie Regional MSW Landfill May 15, 2008
Design Hydrogeologic Report, Phase 4 BLE Project Number A7-1002-74
slopes, consist of reddish -brown silty clay and clayey silt. These soils generally transition to light
brown clayey silt along the lower elevations of the hill side -slopes. In the lowest elevations of the
site, along the surface water drainage features, the aforementioned soils transition into gray sandy
silt to silty sand.
The red -brown silty clay and clayey silts along the higher portions of the site present the most
favorable materials for use as compacted clay liner, soil liner, or closure cap soils. The plasticity of
these soils fall generally along the "A" line. The silty clay soils are found immediately below the
topsoil in limited quantity. More abundant clayey silts lie below the clay. Where encountered,
these soils range in thickness from three to eighteen feet. Therefore, soils that could be used as
compacted soil liner can be found over the majority of the site exclusive of the drainage fractures
and lower elevation portions. During site clearing and stripping activities, these soils should be
carefully delineated and stockpiled for later use.
The in situ moistures of the silty clay will vary based on recent rainfall; however, they should be
found at moisture contents within a few points of the standard Proctor optimum moisture content.
Some modification of moisture will be required during soil liner or cap construction.
3.6.5 Excavation
Excavation of the residual soils can be accomplished using conventional earth moving equipment.
Historical excavation of the site has typically employed track excavators, dozers, and trucks. Some
excavation has been performed using tractor scrapers. An estimated top of rock (auger refusal)
contour map was developed as Figure 7 which is based on auger refusal depths in the soil borings
drilled at this site. Materials sufficiently hard to cause refusal to the mechanical drill augers may
result from continuous bedrock, boulders, lenses, ledges, or layers of relatively hard rock or
residual soil. Coring was performed at five locations in the Phase 4 area where refusal to augering
occurred. Continuous rock was found with varying recovery and Rock Quality Designation (RQD)
as discussed above in Section 3.4.1.3. Due to its typically varying surface, the actual occurrence of
hard rock during site grading may vary somewhat from that presented in Figure 7.
There is usually no sharp distinction between soil and rock in residual soil areas as at this site.
Typically, the degree of weathering simply decreases with greater depth until solid rock is
eventually reached. The partially weathered rock, as well as the soil above, may also contain
boulders, lenses or ledges of hard rock. The presence of scattered cobble size rock material in the
residual surface soils was noted in the cleared fields. The mechanical auger used in this
exploration could penetrate some of the partially weathered rock of the transitional zone. The ease
of excavation will depend on the geologic structure of the material itself, such as the direction of
bedding, planes or weakness and spacing between discontinuities. Weathered rock or rock that
cannot be penetrated by the mechanical drill auger will likely require heavy excavating equipment
with ripping tools or other methods for removal, if desired.
3.6.6 Engineered Fill
The residual soils that will be excavated from the cell areas to achieve the design subgrade
elevations are suitable for use as structural fill. Some moisture modification (wetting or drying)
may be required depending on the particular area of excavation. Conventional compaction
equipment and methods should be appropriate.
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IRLE C.
Uwharrie Regional MSW Landfill May 15, 2008
Design Hydrogeologic Report, Phase 4 BLE Project Number J07-1002-74
Fill used for raising site grades should be uniformly compacted to at least 95 percent of the
standard Proctor maximum dry density (ASTM D 698).
Partially weathered rock may be mixed with the soil borrow materials provided it can be broken
down by the excavation and compaction equipment into particles with a maximum dimension of 6
inches. Larger boulders or rock pieces may be used in the lower portions of the deeper fills if the
boulders are placed individually and soil compacted around and over each boulder. Sufficient
quantities of soil should be mixed with the partially weathered rock so that voids do not result
between the pieces of partially weathered rock and the fill meets the compaction requirements.
Before filling operations begin, representative samples of each proposed fill materials should be
collected and tested to determine the compaction and classification characteristics. The maximum
dry density and optimum moisture content should be determined. Once compaction begins, a
sufficient number of density tests should be performed to measure the degree of compaction being
obtained.
Earthwork cut or fill slopes can be constructed as steep as 2H:1 V (horizontal:vertical). Structural
fill slopes at the 2H:1 V inclination should initially be constructed at two to three feet beyond the
design slope due to difficulty of compacting the edge of slopes, then trimmed to final grade leaving
the exposed face well compacted. Relatively flat slopes, on the order of 3H:1 V or flatter, can be
compacted in place without overfilling. Cut and fill slope surfaces outside the cell area should be
protected from erosion by grassing or other means. Where the cell embankment is to be
constructed on natural slopes steeper than 4H:1 V, we recommend that the fill soils be keyed into
the slopes using horizontal benches to facilitate placement and compaction of structural fill and to
prevent formation of a potential slip surface.
The surface of compacted subgrade soils can deteriorate and lose its support capabilities when
exposed to environmental changes and construction activity. Deterioration can occur in the form of
freezing, formation of erosion gullies, extreme drying, exposure for a long period of time, or rutting
by construction traffic. We recommend that if the fill soils within the cell become deteriorated or
softened, they be proofrolled, scarified and recompacted (and additional fill placed, if necessary)
prior to construction of the compacted soil liner. Additionally, any excavations through the cell
embankments (such as leachate collection line trenches) should be properly backfilled in
compacted lifts. Recompaction of subgrade surfaces and compaction of backfll should be checked
with a sufficient number of density tests to determine if adequate compaction is being achieved.
3-15

NILE_
Uwharrie Regional MSW Landfill May 15, 2008
Design Hydrogeologic Report, Phase 4 BLE Project Number J07-1002-74
5.0 CONCLUSIONS
The proposed Phase 4 landfill cell locations (Cells No. 13 and 14) are on the upland and
intermediate elevation areas west and south of existing Phase 3. The Phase 4 area's subsurface
geology and hydrogeology are typical of Piedmont terrain in North Carolina. No unusual or
unexpected geologic features were observed in the Phase 4 area.
Groundwater flow in the Phase 4 area is northward and eastward. The northward flow discharges to
Rocky Creek, and the eastward flow discharges to a tributary of Rocky Creek. Other than these
natural features, there are no groundwater receptors to this landfill phase.
New and existing groundwater and surface water sampling locations were selected to effectively
monitor the existing Phases (1, 2, and 3) and proposed Phase 4 cell areas. Two existing (GW-18
and GW-19) and one proposed well (GW-21) locations downgradient of Phase 4 were selected
based on the location of landfill sumps and areas of convergent groundwater flow. New
monitoring well GW-21 will be installed in association with Cell No. 13 construction in Phase 4.
Once GW-21 is constructed, the landfill's water quality monitoring system will include nineteen
groundwater monitoring wells and three surface water sampling locations.
The site is favorable for landfill development considering geotechnical aspects. The site is in a
seismic impact zone, but the landfill structural components can be designed using conventional
construction to resist the seismic magnitude. The existing residuum will form a stable foundation
for the landfill. Anticipated subgrade total and differential settlements of the completed waste cells
are expected to be well within acceptable limits of the structural components and leachate
collection system of a MSW landfill. The on -site residual soils are suitable for use as structural fill.
The residual soils and the planned new engineered fill will form stable slopes and provide
acceptable base liner interface friction. Low permeability surficial soils that could be used to
construct a base soil liner or final cover cap (K 5 1.0 x 10-5 cm/sec) are present on site in limited
quantities. Careful selection and use of these clayey soils will be required during waste cell
development. BLE will evaluate settlement and slope stability conditions for the Cells No. 13 and
14 area at a later date once landfill design grades have been prepared.
This Design Hydrogeologic Report was prepared to satisfy the requirements specified in the North
Carolina Title 15A NCAC 13B .1623 (b). Based on the results of field and laboratory testing, it is
our opinion that the study area is geologically, hydrogeologically, and geotechnically suitable for
municipal solid waste landfill cell development. This Design Hydrogeologic Report, while
specifically addressing Phase 4, also considers the potential expanded landfill footprint and grades
shown in the Facility Plan. The final top of clay grades in each cell will be developed at a later
time.
•0•
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