9204_Sorrell_MSWLF_Nov2017CoverInspectionReport_DIN28694_20171113

S&ME, Inc. | 3201 Spring Forest Road | Raleigh, NC 27616 | p 919.872.2660 | www.smeinc.com

November 13, 2017
Ms. Jackie Drummond via email: [e-mail]
Division of Waste Management
217 West Jones Street
Raleigh, North Carolina 27603

Mr. James Easthom via email: [e-mail]
Kennon, Craver, Belo, Craig & McKee, PLLC
P.O. Box 51579
Durham, North Carolina, 27717
Reference: Landfill Cover Inspection - November 2017
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Dear Ms. Drummond and Mr. Easthom:
On November 7, 2017, 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, the S&ME’s
memorandum 2017 – Landfill Cover Maintenance Cost Estimate, dated March 16, 2017, and the NCDEQ
memorandum Authorization to Conduct the 2017 Landfill Cover Maintenance at the Closed Sorrell MSW Landfill,
Wake County, Solid Waste Permit Number 92-04, dated March 20, 2017.
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
Landfill Cover Inspection - November 2017
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

November 13, 2017 2
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 November 7, 2017 landfill cover inspection was limited to an evaluation of two areas of compliance:
1. Observation of the items noted by the Facility Compliance Inspection Report issued by the Solid Waste
Section (Section) on February 15, 2016.
2. 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 October 31, 2017 – November 3,
2017 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
1. A slope failure was observed on the upper portion of the steep slope on northwestern portion of the
landfill property (photographs 1a-1b). The slope failure was reported in the last three cover inspections
S&ME performed for the site.
2. Several areas of subsidence on the landfill cap appear to collect surface water after large rain events
(photograph 2). One of these areas is an area north of Slope Drain No. 2 and has been described in
previous reports as being adjacent to where grading was previously adjusted to increase water drainage
in front of Slope Drain No. 2. This area has been under observation for the last several evaluation periods
and has consistently been seen to store water after significant rain events.
3. Corrugated flexible high-density polyethylene (HDPE) 6’’ pipe in mid-section of Slope Drain No. 2 has
become disconnected (photograph 3a-3b).
4. Standing water was observed on the landfill cap adjacent to landfill gas vents GV-13 and VT-13 in the
northeastern portion of the landfill (photographs 4). This area has been under observation for the last
several evaluation periods and is consistently ponding water, including during periods of drought.
Minor Functional Issues
5. Standing water was observed on the landfill cap north of slope drain no. 1, which has previously been
regraded to increase drainage (photograph 5). This area was noted for the first time in the previous
inspection (June 2017) and is still holding water. This area should be monitored moving forward to
determine if the standing water continues to be an issue.
Landfill Cover Inspection - November 2017
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

November 13, 2017 3
6. 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 6).
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 7). The disconnected areas within the pipe
should be monitored for erosion and scouring which could impact the integrity of the road above.
8. 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 8).
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 9a-9b).
10. 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 10). The depression behind the berm is preventing
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 deep.
11. A small depression has formed in diagonal water bar no. 1 (photograph 11). 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 deep.
12. Vegetation on the northern edge of the ditch along the southern edge of the landfill has become
overgrown (photograph 12). While the ditch is still functional, vegetation on the northern side above the
ditch could infiltrate the ditch and cause functionality issues in the future.

Functional Items
13. A depression which had formed adjacent to the berm of the landfill cap was repaired during the October
31, 2017 – November 3, 2017 maintenance event, and is now functional (photograph 13). The depression
formed on the southwest portion of the landfill cap adjacent to the berm where an access road connects
the landfill cap to the southern access road along the southern border of the landfill. Contractors used
gravel and regrading techniques to repair the depression.
14. A depression adjacent to the southern edge of the landfill cap between landfill gas vents GV-2 and GV-3
was repaired, during the October 31, 2017 – November 3, 2017 maintenance event, by filling with gravel
and regrading (photograph 14). This area had been degraded by vehicle traffic while the soil was
saturated.
15. 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 15a-15b).
16. The vegetation growing on the western hill slope of the landfill cap has been mowed and removed from
the slope (photographs 16a-d).
Landfill Cover Inspection - November 2017
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

November 13, 2017 4
17. The vegetation growing in and clogging the drainage ditch running parallel to the landfill along the
southern access road has been removed and treated. The ditch is functioning as designed (photograph
17).
18. The vegetation growing in and clogging slope drain inlets 1 and 2 and their associated headwalls has
been cut and removed. As previously identified (Item #3), one of the pipes for slope drain 2 was
disconnected. However, the slope drains for slope drain 1 has remained straight. The slope drain inlets
and their associated headwalls are functioning as designed (photographs 18a-c).
19. 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 19a-b). The soil slope
below water diversion bar #2, which was previously repaired for erosion, is growing vegetation and is
currently stable.
20. The access roads along the landfill have been mowed to remove excess vegetation (photographs 20a-b).

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
1. The slope failure should continue to 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.
2. The area of subsidence collecting surface water (north of Slope Drain No.2) has consistently been
observed to have standing water in consecutive inspections. To minimize water ponding on the landfill
cap above the buried waste, this area should be regraded to promote water drainage off the landfill cap
and stabilized with vegetation.
3. The 6’’ HDPE pipe on Slope Drain No. 2 should be reconnected or replaced.
4. The area of subsidence collecting surface water (adjacent to landfill gas vents GV-13 and VT-13) has
consistently been observed to have standing water in consecutive inspections. To minimize water
ponding on the landfill cap above the buried waste, this area should be regraded to promote water
drainage off the landfill cap and stabilized with vegetation.

Minor Functional Issues:
5. The area with standing water, adjacent to gas vents GV-13 and VT-13, should be monitored to determine
whether this is a regular occurrence. Should the standing of water continue to be observed on the cap,
this area should be graded so water will drain off the landfill cap.
6. 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
Landfill Cover Inspection - November 2017
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

November 13, 2017 5
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.
7. 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.
8. 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 first observed.
9. 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.
10. 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.
11. 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.
12. Vegetation on the northern side of the ditch along the southern access road should be trimmed
periodically to reduce the likelihood of any potential future issues within the ditch.
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.

Landfill Cover Inspection - November 2017
Sorrell Landfill (Permit #92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

November 13, 2017 6
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 Samuel P. Watts, P.G.
Staff Scientist Senior Project Manager
[e-mail] [e-mail]

Attachments:
Attachment I - Photographic Log
Attachment II - Figure 1 – Cover Inspection Site Map

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

1a View of a portion of slope failure on the northwestern slope
looking across the hill (east). 1b Additional view of a portion of slope failure on the northwestern slope looking across the hill (east).

2 View of area on landfill cap north of Slope Drain No. 2 observed
to have standing water (looking north).

3a View of 6’’ corrugated HDPE pipe, in flexible slope drain no. 2,
which has become disconnected in several locations.

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

3b View of 6’’ corrugated HDPE pipe in mid-section of slope drain
no. 2 which has become disconnected in several locations
(looking south).
4 View of area with standing water observed between landfill gas vents GV-13 and VT-13 looking north.

5 View of area with standing water observed between north of
slope drain no. 1, looking north. 6 View of displaced rip rap and increased erosion within outfall of
the culvert draining the stormwater ditch parallel to the southern
access road.

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

7 View of the pipe connecting the ditch north of the southern
access road to the ditch south of the access road along the
southern property boundary (looking southwest).
8 View of small slope subsidence in landfill cap on southern slope just north of MW-8 (looking north).

9a View of scouring at outfall of slope drains installed within
Diversion Ditch/ Diagonal Water Bar no. 1. 9b View of scouring at outfall of slope drains installed within
Diversion Ditch/ Diagonal Water Bar no. 2.

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

10 Small depression developing at edge of landfill cap along berm
where the landfill cap is accessed on the southeastern edge
looking southeast.
11 A small depression has developed within diagonal water bar no.1 where vehicular traffic has degraded the water bar, allow

12 Vegetation on north side of ditch along the southern boundary
of the landfill has started to become overgrown.

13 A depression on the landfill cap adjacent to the berm on the
southwest portion of the landfill was repaired using gravel and regrading techniques.

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

14a The depression between landfill gas vents GV-2 and GV-3 was
repaired using gravel and regrading techniques (looking east). 14b Another view of the depression between landfill gas vents GV-2 and GV-3 which was repaired using gravel and regrading techniques (looking west).

15a Overall view of recently mowed grass and vegetation across the
landfill cap (looking west). 15b Overall view of recently mowed grass and vegetation across the
landfill cap (looking east).

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

16a View of the recently mowed back (western) slope of the landfill
cap looking downhill from the top of the cap. 16b View of the recently mowed back (western) slope of the landfill cap looking downhill from the top of the cap.

16c View of the recently mowed back (western) slope of the landfill
cap looking uphill from the access road. 16d View of the recently mowed back (western) slope of the landfill
cap looking uphill from the access road.

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

17 View of ditch along the southern base of the landfill looking east. 18a View of Slope Drain #1 Inlet/ Headwall, which has recently had the woody vegetation removed (looking south).

18b View of flexible slope drains from Slope Drain Inlet #1 (looking
northwest).

18c View of Slope Drain #2 Inlet/ Headwall, which has recently had
the woody vegetation removed (looking south).

Landfill Cover Inspection
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Bentz Date Taken: 11/7/2017

19a View of Diversional Ditch/ Diagonal Water Bar #1 (looking
south). 19b View of Diversional Ditch/ Diagonal Water Bar #2 (looking southeast).

20a View of recently mowed access road to monitoring well 4
(looking east). 20b View of mowed access road to monitoring well 7 (looking north).
PROJECT NUMBER:
DATE:FIGURE NO.SCALE:
DRAWN BY:
CHECKED BY:DRAWING NUMBER:WWW.SMEINC.COM
3201 SPRING FOREST RD, RALEIGH, NC 27616
NC ENGINEER LICENSE #F-01761 BTR1054-07-251
DEC. 20121" = 200'
SORRELL LANDFILL
APEX, NORTH CAROLINA
SITE MAP
B-2054
S:\PROJECTS\2007\07-251 Sorrell Landfill\CAD\B2054.dwg, FIG1, 12/18/2012 2:02:06 PM, 1:1