HomeMy WebLinkAbout7607_GreatOakSubgradeCell1ASouthwest_DIN26824_20160909 SCS Engineers, P.C.
Environmental Consultants 2520 Whitehall Park Drive 704 504-3107
and Contractors Suite 450 FAX 704 504-3174
Charlotte, NC 28273-3557 www.scsengineers.com
Offices Nationwide
File No. 02215305.02
September 9, 2016
Ms. Christine Ritter
North Carolina Department of Environmental Quality
Division of Waste Management
1646 Mail Service Center
Raleigh, NC 27699-1601
Re: Report of Subgrade Inspection and Vertical Separation Certification
Phase I, Cell 1A, Southwest and Southeast Slopes
Great Oak Landfill
Randleman, North Carolina
Dear Ms. Ritter:
SCS Engineers, PC (SCS), on behalf of Waste Management, Inc., is pleased to present the
following findings of the subgrade inspection performed at the Great Oak Landfill (Landfill) on
July 26, August 16, and September 8, 2016. Mr. Michael Cobb, a licensed geologist, performed
the inspections in accordance with the Landfill’s Permit to Construct, No. 7607-MSWLF-2015,
Part I, Condition 7.
The following document, prepared by S&ME, Inc., of Charlotte, NC, and dated February 2015,
was reviewed by SCS: Design Hydrogeologic Study, Great Oak Landfill – Phase 1. This
document contains information on the geology and hydrogeology of the Facility.
This Report of Subgrade Inspection and Vertical Separation Certification is limited to the 5.8
acres of the western portion of Cell 1A, as depicted in the attached Figure 1. Forthcoming
reports will cover the remainder of Cell 1A and the entirety of Cell 1B.
Subgrade Inspection
The following is a summary of the geologic field observations from the July 26, 2016 site
inspection:
Contractor excavation has revealed rock formations along southwestern slope of Cell 1A.
Contractor has completed some blasting in this area.
Cambrian Age slate (meta-mudstone) was observed to overlay quartzite.
Large quartz veins were observed near the top of the slope, and remnant pieces of quartz,
varying in size from pebbles an inch in length to boulders several feet in length, were
visible in areas in which blasting has occurred.
Material observed in areas in which no blasting had occurred included residuum and
saprolite consistent with the Uwharrie Formation of the Carolina Slate Belt.
Groundwater was not observed in the subject cell.
Ms. Christine Ritter
September 9, 2016
Page 2
The geology of the area of the cell inspected on July 26, 2016, appears to be consistent with the
observations and geologic evaluations documented in the S&ME report cited above.
During the August 16, 2016, site inspection blasting had been completed on the 5.8 acres
covered by this report. The only material observed in the subject area was residuum of the slate
and quartzite formations overlying quartzite formations. The contractor was in the process of
clearing the residuum in preparation of placing structural fill.
During the September 8, 2016, site inspection, the structural fill was largely in place, with the
contractor conducting fine grading the toe of the slope. Minor amounts of residuum of the
quartzite formation and quartz veins were observed; such material was flagged for the contractor
to remove prior to liner being placed.
No rock outcrops jutting above the existing grade established by the contractor were visible
during the August 16 or September 8 site inspections. It is SCS’s opinion that the remaining
geologic features in this portion of Cell 1A (that is, the bedrock remaining after blasting
conducted by the contractor), will have no impact on the construction or operation of the Facility
beyond the vertical separation requirements discussed below.
Vertical Separation Certification
Per 15A NCAC 13B.1624(b)(4), for municipal solid waste landfills, the bottom elevation of the
base liner system must have a minimum vertical separation of four (4) feet above bedrock.
Upon completion of blasting and clearing by the contractor, SCS coordinated with Charlie
Morgan Surveying, PLLC (Morgan), to survey points along the exposed bedrock in the 5.8 acres
of Cell 1A covered by this report. The data provided by Morgan was used to develop an exposed
bedrock map, attached as Figure 1. This map shows that exposed bedrock was present in
approximately 1.44 acres of the portion of Cell 1A covered by this report. Upon completion of
structural fill placement, Morgan surveyed this same set of points to establish the base grade of
this portion of Cell 1A.
The elevations from the surveying were used to prepare Table 1, which shows the amount of
separation at each surveyed point.
Ms. Christine Ritter
September 9, 2016
Page 3
Table 1 – Vertical Separation
Point Northing Easting
Subgrade
Elevation
Top of
Rock
Elevation Separation
PT2008 727077.2252 1775900.948 658.982 654.841 4.141
PT2009 727079.5828 1775857.983 665.037 660.412 4.625
PT2010 727127.8895 1775869.856 668.039 663.401 4.638
PT2011 727170.5857 1775842.072 677.196 672.467 4.729
PT2028 727428.2088 1776070.87 683.509 679.406 4.103
PT2029 727391.0842 1776036.852 682.9 678.842 4.058
PT2030 727352.6718 1776007.858 680.93 676.949 4.131
PT2031 727313.2466 1775976.539 678.675 674.521 4.154
PT2032 727291.4425 1775958.177 677.992 675.239 4.921
PT2033 727265.4457 1775936.488 676.977 672.8 4.177
PT2034 727235.7463 1775911.052 676.124 671.17 4.954
PT2035 727208.3209 1775890.53 674.571 669.03 5.541
PT2036 727180.0545 1775870.547 673.097 669 4.097
PT2037 727151.7807 1775900.642 666.027 661.795 4.232
PT2038 727175.8715 1775922.926 665.339 658.81 6.529
PT2039 727198.9901 1775945.295 664.624 660.2 4.424
PT2040 727221.9835 1775966.871 664.918 660.881 4.037
PT2041 727246.4484 1775991.847 664.581 660.375 4.206
PT2042 727280.3011 1776021.445 663.363 658.849 4.514
PT2043 727317.5493 1776052.295 661.935 658.07 4.319
PT2044 727352.5359 1776084.226 662.588 657.641 4.947
PT2050 727189.5857 1776025.882 654.008 649.937 4.071
PT2053 727104.9392 1775902.023 661.888 657.875 4.013
PT2439 727062.9534 1775786.558 677.904 673.34 4.564
As shown above, the points of exposed bedrock within the 5.8 acres of Cell 1A covered by this
report show a minimum vertical separation of four (4) feet.
Due to changes in the proposed base grade in the northwest corner of Cell 1A necessitated by the
presence of a guy wire support belonging to Duke Energy in this area, an additional four (4) to
eight (8) feet of structural fill was added. As such, the minimum vertical separation requirement
of four (4) feet is satisfied in this area.
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SCS ENGINEERS, PC
2520 WHITEHALL PARK DRIVE, SUITE 450
CHARLOTTE, NORTH CAROLINA 28273
PHONE: (704) 504-3107 FAX: (704) 504-3174
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SUBGRADE/BASEGRADE
POINT IDENTIFICATION PLAN
GREAT OAK LANDFILL
WASTE MANAGEMENT OF CAROLINAS, INC.CELL 1A & 1B
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