9204_Wake_Sorrell_MSWLF_LFCoverMaint_FID1418366_20200710

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July 6, 2020
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 — June 2020
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 June 5, 2020, 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 2020 — Landfill Cover Maintenance Cost Estimate, dated March 13, 2020, and the NCDEQ
memorandum Authorization to Conduct the Spring 2020 and Fall 2020 Landfill Cover Maintenance Activities Closed
Sorrell MSW Landfill, dated March 18, 2020.
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 — June 2020
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 June 5, 2020 landfill cover inspection was limited to an evaluation of one area of compliance:
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 18 to 20, 2020 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 five cover inspections S&ME
performed for the site.
Minor Functional Issues
An area within the access road to monitor well MW-7 was observed to have a small hole. It appears
surface water has been flowing into the hole. The soil inside the hole is being washed away and is
creating a cavity (photographs 2A and 213).
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. This depression appears to
be settling and some ponded water was observed during the June 2020 inspection (photograph 3).
A depression 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). During an inspection in November of 2018, this depression was holding water
several inches deep and showed signs of standing water having been present for an extended period.
No evidence of standing water was observed in the 2019 inspections. During the June 2020 inspection,
standing water was again observed (photograph 4).
A depression between landfill gas vents GV-2 and GV-3 that was repaired during the fall of 2017 appears
to be settling and some ponded water was observed during the June 2020 inspection (photograph 5).
A depression on the southeast corner of the landfill was observed containing standing water during this
inspection (photograph 6). This depression has not been identified during previous monitoring events.
July 8, 2020

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Landfill Cover Inspection — June 2020
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
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 7).
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 8). The disconnected areas within the
pipe should be monitored for erosion and scouring which could impact the integrity of the road above.
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 9).
Scouring was observed in the outfall ditch below the newly installed slope drains at Diversion Ditches/
Diagonal Water Bars Nos. 1 and 2 (photographs 10A and 10B).
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, to the west (photograph 11).
Functional Items
A small depression that had formed on the landfill cap adjacent to the berm on the southeastern side of
the landfill where the landfill cap is accessed (photograph 12) was repaired and is now functional.
13. A small depression has formed in diagonal water bar no. 1 (photograph 13) was repaired and is now
functional.
14. 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 14A-14D).
The vegetation growing on the western hill slope of the landfill cap has been mowed and removed from
the slope (photographs 15A to 15B).
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 16A to 16D).
17. 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 17A and 17B).
18. The vegetation growing in and clogging the drainage ditch running parallel to the landfill along the
southern access road has been removed and treated (photograph 18).
When the maintenance contractor arrive on site on May 18, 2020, the lock and chain were missing from
the gated entrance, to the east off Smith Road. S&ME personnel purchased and installed a new chain
and a new lock with a shrouded shackle to reduce the likelihood of the lock being cut.
The approximate location of each of the above items is labeled on the attached Site Plan drawing (Figure 1).
July 8, 2020

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RECOMMENDED CORRECTIVE MEASURES
Landfill Cover Inspection — June 2020
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
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:
The cavity beneath the access road to monitor well MW-7 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 depression should be monitored to determine whether standing water is a regular occurrence in this
area. Should the standing of water continue to be observed on the cap, these areas should be graded to
promote surface water draining off the landfill cap.
4. The depression should be monitored to determine whether standing water is a regular occurrence in this
area. Should the standing of water continue to be observed on the cap, these areas should be graded to
promote surface water draining off the landfill cap.
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 depression should be monitored to determine whether standing water is a regular occurrence in this
area. Should the standing of water continue to be observed on the cap, these areas should be graded to
promote surface water draining off the landfill cap.
The depression should be monitored to determine whether standing water is a regular occurrence in this
area. Should the standing of water continue to be observed on the cap, these areas should be graded to
promote surface water draining off the landfill cap.
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.
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.
11. Measures should be taken to prevent vehicular traffic from accessing the landfill via the adjacent natural
gas easement, to the west.
July 8, 2020 4

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Functional Issues:
Landfill Cover Inspection — June 2020
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
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. S&ME personnel purchased and installed a new chain and a new lock with
a shrouded shackle, on the gated entrance to the east off Smith Road.
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, P.W.S Samuel P. Watts, P.G.
Project Scientist Senior Project Manager
[e-mail] [e-mail]
Attachments: Photographic Log
Figure 1 — Cover Inspection Site Map
July 8, 2020

Attachments

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iew of a portion of slope failure on the northwestern slope
looking across the hill (looking east).
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26 View of cavity forming under access road to monitoring well
MW-7.
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iew of small hole at entrance of cavity in the access road to
monitoring well MW-7.
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3View
of depression forming on the landfill cap adjacent to
landfill gas vents GV-13 and VT-13. The repair appears to have
settled slightly and is ponding water.
Site Photographs S&ME Project No. 1054-07-251
Sorrell Landfill Taken by: A. Bentz Date Taken: 6/5/2020
Apex, Wake County, North Carolina

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of the pipe connecting the ditch north of the southern
s road to the ditch south of the access road along the
DA View of scouring at outfall of slope drains installed within
Diversion Ditch/ Diagonal Water Bar no. 1.
iew of small slope subsidence in landfill cap on southern slope
ist north of MW-8 (looking north).
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AV
of scouring at outfall of slope drains installed within
1OB �iew
iversion Ditch/ Diagonal Water Bar no. 2.
Site Photographs S&ME Project No. 1054-07-251
Sorrell Landfill Taken by: A. Bentz Date Taken: 6/5/2020
Apex, Wake County, North Carolina

1 of access road where vehicles appear to be entering the
�iew
erimeter road and landfill footprint from an adjacent natural
12 iew of depression adjacent to the berm on the southeastern
side of the landfill where the landfill cap is accessed which has
been repaired.
14A Overall view of recently mowed grass and vegetation across the
landfill cap (looking west).
0 Site Photographs S&ME Project No. 1054-07-251
III _= Sorrell Landfill Taken by: A. Bentz Date Taken: 6/5/2020
Apex, Wake County, North Carolina

�1 B View of the access road to monitor well MW-4, looking east.
egetation that had been encroaching onto the access road was
14D iew of the access road to monitor well MW-7, looking south.
egetation that had been encroaching onto the access road was
removed.
14C Overall view of recently mowed grass and vegetation across the
landfill cap (looking east).
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15A iew of the recently mowed back (western) slope of the landfill
cap looking uphill from the access road.
kb
Site Photographs S&ME Project No. 1054-07-251
Sorrell Landfill Taken by: A. Bentz Date Taken: 6/5/2020
Apex, Wake County, North Carolina

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56 iew of the recently mowed back (western) slope of the landfill
cap looking uphill from the access road.
6B riew of flexible slope drains from Slope Drain Inlet #1 (looking
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16Aiew
of Slope Drain #1 Inlet/ Headwall, which has recently had
he woody vegetation removed (looking south).
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16C
iew of Slope Drain #2 Inlet/ Headwall, which has recently had
he woody vegetation removed (looking west).
0 Site Photographs S&ME Project No. 1054-07-251
III _= Sorrell Landfill Taken by: A. Bentz Date Taken: 6/5/2020
Apex, Wake County, North Carolina

17A (View of Diversional Ditch/ Diagonal Water Bar #1 (looking
18 egetation growing in and clogging the drainage ditch along
southern landfill boundary has been removed and treated.
0 Site Photographs S&ME Project No. 1054-07-251
III _= Sorrell Landfill Taken by: A. Bentz Date Taken: 6/5/2020
Apex, Wake County, North Carolina

9 71ockLith
ersonnel purchased and installed a new chain and a new
a shrouded shackle, on the gated entrance off Smith
0 Site Photographs S&ME Project No. 1054-07-251
III _= Sorrell Landfill Taken by: A. Bentz Date Taken: 6/5/2020
Apex, Wake County, North Carolina

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