9204_Wake_Sorrell_MSWLF_LFCoverMaint_FID1324040_20190716

July 16, 2019
Ms. Jackie Drummond
Division of Waste Management
217 West Jones Street
Raleigh, North Carolina 27603
Mr. James Easthom
Kennon, Craver, Belo, Craig & McKee, PLLC
P.O. Box 51579
Durham, North Carolina, 27717
Reference: Landfill Cover Inspection — May 2019
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Dear Ms. Drummond and Mr. Easthom:
via email: [e-mail]
via email:[e-mail]
On May 22, 2019, representatives from S&ME, Inc. (S&ME) performed a visual inspection of the landfill cover and
the storm water/surface water conveyance features at the closed Sorrell Landfill located in Apex, North Carolina.
This letter report is provided to document the findings of our inspection. Services conducted by S&ME were
performed in general accordance with S&ME Proposal No. P4258-07V, dated April 25, 2007, S&ME's
memorandum 2079 — Landfill Cover Maintenance Cost Estimate, dated February 21, 2019, and the NCDEQ
memorandum Authorization to Conduct the Spring 2079 and Fall 2079 Landfill Cover Maintenance Activities Closed
Sorrell MSW Landfill, dated March 5, 2019.
BACKGROUND INFORMATION
Sorrell Grading Company initially operated a construction and demolition (C&D) landfill at this site, which
subsequently also accepted municipal solid wastes (MSW) and similar waste materials. A Closure Plan and a Post -
Closure Plan for the landfill were prepared by Stuart Jones Consulting Engineering, dated June 20, 1996 and
submitted to the Section on behalf of Sorrell Grading Company. The Closure Plan provided criteria for the
construction of a landfill cover consisting of a clay cap over the top 24 acres of the landfill and a vegetative layer
of the top and side slopes of the landfill. The Closure Plan indicated that the side slopes were already largely
constructed at that time and that the cap construction was underway.
A Closure Report, dated September 7, 2001, was prepared by S&ME and submitted to the Section on behalf of
Sorrell. The report detailed S&ME's evaluation of the landfill cover after the landfill had been closed and the clay
cap had been placed on top of the landfill. The Closure Report described testing of the cover on the top and the
side slopes of the landfill, verifying the placement and thickness of the infiltration layer and the erosion layer.
Locations on the side slopes and the top of the landfill were tested. Most of the locations were found to contain
adequate thicknesses of cap material. Where the thickness of the cap was insufficient, these locations were
S&ME, Inc. 13201 Spring Forest Road I Raleigh, NC 276161 p 919.872.2660 1 www.smeinc.com

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Landfill Cover Inspection — May 2019
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
identified and repairs were to be made by the owner. Additional information on the construction and condition of
the landfill cover system was described in S&ME's letter report Response to Notice of Violations, submitted to
NCDENR-DWM on January 26, 2009.
The May 22, 2019 landfill cover inspection was limited to an evaluation of two areas of compliance:
Observation of the items noted by the Facility Compliance Inspection Report issued by the Solid Waste
Section (Section) on February 15, 2016.
A visual inspection of the landfill cap over the top 24 acres of the landfill and the storm water/surface
water conveyance features. Cutting and maintenance was performed May 8-13, 2019 by Carolina
Outdoor Services, LLC, subcontractor to S&ME, under a separate task.
S&ME personnel did not inspect the landfill side slopes which are covered by growths of pine trees, hardwoods
and underbrush.
OBSERVATIONS
Overall, the cap and stormwater conveyance features appear to be in good condition with adequate vegetation.
Three deficiencies in need of corrective measures were observed. The following features were visually identified as
1) deficient and in need of corrective measures, 2) as minor functional issues requiring monitoring or 3) as
functional and not in need of corrective measures. The numbered items below correspond to the numbers on
Figure 1 and to the numbered photos in the photographic log.
Deficiencies
A slope failure was observed on the upper portion of the steep slope on northwestern portion of the
landfill property (photograph 1). The slope failure was reported in the last four cover inspections S&ME
performed for the site.
Minor Functional Issues
Scouring below the stormwater outfall for the culvert draining the stormwater ditch parallel to the
southern access road has been observed in previous inspection reports. While a previous inspection
indicated that the outfall itself had experienced erosion, the outfall appears to be stable despite several
significant rain events since the last inspection (photograph 2).
The stormwater outfall for the pipe draining the stormwater ditch parallel to the southern access road
appears to be functioning based on evidence of water flow. There appears to be an area where the pipe
joints have become disconnected under the road (photograph 3). The disconnected areas within the
pipe should be monitored for erosion and scouring which could impact the integrity of the road above.
4. A small slope subsidence was noted along the southern slope. The subsidence was approximately 1.5
feet deep and 2 feet wide. No trash is visible (photograph 4).
S. Scouring was observed in the outfall ditch below the newly installed slope drains at Diversion Ditches/
Diagonal Water Bars Nos. 1 and 2 (photographs 5a and 5b).
A small depression has formed on the landfill cap adjacent to the berm on the southeastern side of the
landfill where the landfill cap is accessed (photograph 6). The depression behind the berm is preventing
July 16, 2019 2

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Landfill Cover Inspection — May 2019
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
water from draining off the landfill, resulting in saturated soils. The depression has been degraded due
to vehicle traffic while the soil is holding water and the depression has become increasingly deeper.
A small depression has formed in diagonal water bar no. 1 (photograph 7). The depression formed as a
result of vehicular traffic over the water bar has degraded the water bar, allowing water to settle. The
depression has become increasingly degraded due to additional vehicle traffic while the soil is holding
water and has become increasingly deeper.
Evidence of vehicular traffic has been observed on the landfill. These vehicles appear to be accessing the
landfill via an access road from an adjacent natural gas easement (photograph 8).
Functional Items
A depression with standing water was observed to the east of the base of the access road on the
southwestern portion of the landfill cap which connects the landfill cap to the southern access road
along the southern border of the landfill (photograph 9). This depression was holding water several
inches deep and showed signs of having been present for an extended period of time during the
previous inspection in November of 2018, but was not identified as holding water in previous
inspections and was not holding water during this inspection.
A depression on the landfill cap adjacent to landfill gas vents GV-13 and VT-13 in the northeastern
portion of the landfill was repaired during the May 2019 maintenance event (photograph 10a and 10b)
and is now functional.
Trees on the southern landfill slope that were bent or had fallen over in places were removed during the
May 2019 maintenance event (photographs 11 a and 11 b) and no longer pose a risk to the soil cover over
the buried waste.
Vegetation that had been encroaching onto the access road to monitor wells MW-4 and MW-7
(photographs 12a and 12b) was removed during the May 2019 maintenance event.
Vegetation on the northern bank of the ditch along the southern boundary access road had been
clogging the drainage ditch running parallel and encroaching onto the access road. The vegetation was
removed and treated during the May 2019 maintenance event (photograph 13), and is no longer
impeding the flow of water through the ditch or encroaching onto the access road.
14. A depression which had formed north of Slope Drain No. 2 was repaired during the May 20-13, 2018
maintenance event and is now functional (photograph 14). This area had previously been regraded to
increase water drainage to Slope Drain No. 2. Contractors used additional fill material and regrading
techniques to repair the depression and to add several drainage swales to increase drainage toward
Slope Drain No. 2. Some degradation has occurred due to vehicular traffic on the landfill cap.
Several depressions on the landfill cap north of slope drain no. 1, which have previously been observed
to hold water, were repaired during the May 20-23, 2018 maintenance event and are now functional
(photograph 15). Some degradation has occurred due to vehicular traffic on the landfill cap.
16. A depression which had formed adjacent to the berm of the landfill cap was repaired during the fall 2017
maintenance event, and is now functional (photograph 16).
17- A depression adjacent to the southern edge of the landfill cap between landfill gas vents GV-2 and GV-3
was repaired, during the fall 2017 maintenance event, by filling with gravel and regrading (photograph
17). This area had been degraded by vehicle traffic while the soil was saturated. Some degradation has
occurred due to vehicular traffic on the landfill cap.
July 16, 2019 3

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Landfill Cover Inspection — May 2019
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
18. The landfill cap and access roads have been mowed to remove excess grass and vegetation. This
maintenance item has been completed twice a year over the past several years, substantially improving
the vegetative cover at the site. The grass and vegetation are currently an acceptable height
(photographs 18a-18b).
19. The vegetation growing on the western hill slope of the landfill cap has been mowed and removed from
the slope (photographs 19a-19d).
20. The vegetation growing in and clogging slope drain inlets 1 and 2 and their associated headwalls has
been cut and removed. The slope drain inlets and their associated headwalls are functioning as designed
(photographs 21a to 21d).
The vegetation previously growing in and clogging the headwall structures at the entrance of the slope
drains at water diversion bars No. 1 and 2 has been cut and removed (photographs 22a-22b). The soil
slope below water diversion bar #2, which was previously repaired for erosion, is growing vegetation and
is currently stable.
The approximate location of each of the above items is labeled on the attached Site Plan drawing (Figure 1).
RECOMMENDED CORRECTIVE MEASURES
S&ME recommends the following corrective measures for each observed item:
Deficiencies
The slope failure should be evaluated by a qualified professional to determine the cause of the failure
and repaired according to their recommendations to prevent further damage to the landfill cap, soil
erosion, or exposure of waste.
Minor Functional Issues:
Rip rap had previously been installed within the stormwater outfall where scouring was occurring. While
the previous inspections indicated that the rip rap was being relocated within the outfall during high flow
events, there has been no additional scour or rip rap relocation in the outfall since the last inspection.
The outfall should continue to be monitored for any further rip rap displacement or scour below the
outfall. If further damage is observed, larger rip rap should be installed to prevent further degradation of
the outfall and to prevent relocation of the newly installed rip rap during high flow periods.
The disconnected joint in the pipe should be monitored for evidence of scouring or erosion between the
joints. Should the level of erosion or scouring reach levels where it could impact the integrity of the road,
the pipe should be repaired or replaced.
The small slope subsidence should be monitored for an increase in depth or size. If the area increases in
size, it should be filled, graded, and stabilized with vegetation. The subsidence has not increased in size
since the last inspection.
July 16, 2019 4

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Landfill Cover Inspection — May 2019
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
The scouring below the outfalls for the slope drains in the Diversion Ditches/ Diagonal Water Bar Nos. 1
and 2 should be monitored for further erosion. Should further erosion be observed, efforts should be
undertaken to stabilize the eroded areas. No further erosion has been observed since the last inspection.
The depression behind the berm, within the access road, holding water, should be stabilized by filling the
depression with soil or gravel to prevent the depression from increasing in size when vehicles drive
through this location when soil is saturated.
The depression behind diagonal water bar No. 1, holding water, should be stabilized by filling the
depression with soil to prevent the depression from increasing in size when vehicles drive through this
location when soil is saturated.
Measures should be taken to prevent vehicular traffic from accessing the landfill via the adjacent natural
gas easement.
The depression should be monitored during future monitoring events to determine if the depression is
consistently holding water between monitoring events. If the depression continues to hold water, it
should be regraded to improve drainage.
Functional Issues:
S&ME recommends that the landfill cap continue to receive regular, bi-annual mowing of the landfill cap in the
spring and fall to promote the health of the vegetative cover. Areas of settlement, and depressions, holding water
should continue to be identified, monitored and repaired to promote water draining off the landfill cap and
minimize standing water above waste.
CLOSING
S&ME appreciates the opportunity to provide these services and hopes that you find this report to be complete
and informative. We would appreciate an opportunity to discuss our findings and recommendations with you.
Please call us at [phone] if you have any questions or comments, or if we can be of further assistance.
Sincerely,
S&ME, Inc.
Ashley Bentz
Staff Scientist
[e-mail]
Attachments:
Samuel P. Watts, P.G.
Senior Project Manager
[e-mail]
Attachment I - Photographic Log
Attachment II - Figure 1 — Cover Inspection Site Map
July 16, 2019

Attachments

S&ME Project No. 1054-07-251
Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

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5a View of scouring at outfall of slope drains installed within
Diversion Ditch/ Diagonal Water Bar no. 1.
I
Small depression developing at edge of landfill cap along berm
where the landfill cap is accessed on the southeastern edge
looking southeast.
17
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5b iew of scouring at outfall of slope drains installed within
Diversion Ditch/ Diagonal Water Bar no. 2.
ai-
small depression has developed within diagonal water bar no.1
-iere vehicular traffic has degraded the water bar.
S&ME Project No. 1054-07-251
Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

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8 iew of access road where vehicles appear to be entering the
perimeter road and landfill footprint from an adjacent natural
gas easement.
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10a A depression north of landfill gas vents GV-13 and VT- 13 2 was
repaired in May 2019 maintenance event using fill material and
�rearaclina techni ues and is functional.
0 S&ME Project No. 1054-07-251
III _= Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

iew of vegetation which had bent or fallen over and has been
11 b removed during the May 2019 maintenance event.
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12b iew of the access road to monitor well MW-7, looking north.
egetation that had been encroaching onto the access road was
0 S&ME Project No. 1054-07-251
III _= Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

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13
Vegetation forming a canopy along the northern edge of the
ditch along the southern edge of the landfill was removed.
1
depression on the landfill cap north of slope drain no. 1 was
repaired in 2017 using fill material and regrading techniques and
depression north of Slope Drain No. 2 was repaired in 2017
using
14 fill material and regrading techniques and is continuing to
unction.
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16 depression on the landfill cap adjacent to the berm on the
southwest portion of the landfill was repaired during a previous
S&ME Project No. 1054-07-251
Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

17 he depression between landfill gas vents GV-2 and GV-3 was
repaired during a previous maintenance event (fall 2017) using
18bOverall view of recently mowed grass and vegetation across the
landfill cap (looking east).
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18a Overall view of recently mowed grass and vegetation across the
landfill cap (looking west).
19a iew of the recently mowed back (western) slope of the landfill
cap looking downhill from the top of the cap.
0 S&ME Project No. 1054-07-251
III _= Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

S&ME Project No. 1054-07-251
Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

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20d iew of flexible slope drains from Slope Drain Inlet #2 (looking
south).
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�iew of Diversional Ditch/ Diagonal Water Bar #2 (looking
21 b southeast).
0 S&ME Project No. 1054-07-251
III _ Landfill Cover Inspection Taken by: A. Bentz Date Taken: 5/22/19
Sorrell Landfill, Apex, Wake County, North Carolina

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