9204_Sorrell_CoverInspectionReport_DIN26306_20160621

S&ME, Inc. | 3201 Spring Forest Road | Raleigh, NC 27616 | p 919.872.2660 | f 919.876.3958 | www.smeinc.com

June 15, 2016
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 – May 2016
Sorrell Landfill (Permit # 92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

Dear Ms. Drummond and Mr. Easthom:
On June 2, 2016, 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 2016 – Landfill Cover Maintenance Cost Estimate, dated April 4,
2016, and the NCDEQ memorandum Authorization to Conduct the 2016 Landfill Cover Maintenance at the
Closed Sorrell MSW Landfill, Wake County, Solid Waste Permit Number 92-04, dated April 6, 2016.
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
Landfill Cover Inspection – May 2016
Sorrell Landfill (Permit # 92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

June 15, 2016 2
thickness of the cap was insufficient, these locations were 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 2, 2016 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.

S&ME personnel did not inspect the landfill side slopes which are covered by growths of pine trees,
hardwoods and underbrush.

1.0 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 items 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. Slope failure observed on upper portion of steep slope on northwestern portion of property
(photographs 1a-1d).
2. Scouring has increased below the stormwater outfall for the culvert draining the stormwater ditch
parallel to the southern access road. While the ditch appears stable downstream of the outfall, the
outfall itself appears to have experienced increased erosion since the previous inspection
(photographs 2a-b).
3. Several areas on the landfill cap appear to collect standing, and possible subsidence, water after
large rain events (photographs 3a-b, 4a-b, 5a-b). 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 areas has been
under observation for the last several evaluation periods and has consistently been seen to store
water after significant rain events (3a-b). The other areas have not previously been identified as
storing water and are described in greater detail under the minor functional issues section below.

Minor Functional Issues:
1. Bare spots of dead vegetation have developed along the northeast slope, most likely the result of
previously piled grass cuttings and debris impacting the vegetation over time (photographs 6a-b).
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 7). The
disconnected areas within the pipe should be monitored for erosion and scouring which could
Landfill Cover Inspection – May 2016
Sorrell Landfill (Permit # 92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

June 15, 2016 3
impact the integrity of the road above.
3. A small slope failure was noted along the southern slope. The failure was approximately 1.5 feet
deep and 2 feet wide. No trash is visible (photographs 8a-b).
4. As discussed in the deficiencies section above, several areas that have not previously been
identified as areas collecting and storing rainwater were observed to have standing water present.
One of these areas is located adjacent to the southern edge of the landfill cap between landfill
gas vents GV-2 and GV-3 (photographs 4a-b). The other area is adjacent to landfill gas vents GV-
13 and VT-13 in the northeastern portion of the landfill (photographs 5a-b).
5. Minor scouring has been observed in the outfall ditch below the newly installed slope drains at
Diversion Ditches/ Diagonal Water Bars Nos. 1 and 2 (photograph 9).

Functional Items:
1. The landfill cap and access roads have been mowed to remove excess grass and vegetation. This
maintenance item has been completed twice in the past year, improving conditions on site
substantially. The grass and vegetation are currently an acceptable height (photographs 10a-10b).
2. The vegetation growing on the western hill slope of the landfill cap has been mowed and
removed from the slope (photographs 11a-d).
3. 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
(photographs 12a-b).
4. The vegetation growing in and clogging slope drain inlets 1 and 2 and their associated headwalls
has been treated and removed. The slope drains have remained straightened. The slope drain
inlets and their associated headwalls are functioning as designed (photographs 13a-d).
5. The vegetation growing in and clogging the headwall structures at the entrance of the slope
drains at water diversion bars No. 1 and 2 has been treated and removed (photographs 14a-b).
The slope of water diversion bar #2, which was previously repaired for erosion, is growing
vegetation and is currently stabilizing.
6. The access roads along the landfill have been mowed to remove excess vegetation (photographs
15a-b).
7. The culvert located within the stream crossing northeast of MW-6 is functioning as designed
(photograph 16).
8. The sediment ponds along the western edge of the property are functioning as designed
(photographs 17a-c).
9. The trash rack on the outlet for the large sediment pond on the western portion of the site was
replaced during previous maintenance and is functioning as designed (photograph 18).
10. Several landfill gas vents were repaired to prevent them from leaning heavily due to a lack of
support from the previously used rubber couplings (photograph 19).

The approximate location of each of the above items is labeled on the attached Site Plan drawing (Figure
1).
Landfill Cover Inspection – May 2016
Sorrell Landfill (Permit # 92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

June 15, 2016 4
2.0 RECOMMENDED CORRECTIVE MEASURES
S&ME recommends the following corrective measures for each observed item:

Deficiencies:
1. 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.
2. Rip rap had previously been installed within the stormwater outfall where scouring was occurring.
This rip rap has been relocated within the outfall during high flow events and is no longer
preventing scour from destabilizing the sides of the outfall. 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.
3. The area described in the above deficiencies section (north of Slope Drain No.2) has consistently
been observed to collect and store rainwater in consecutive inspections. As a result, this area
should be regraded to encourage water drainage off the landfill cap and stabilized with
vegetation.

Minor Functional Issues:
1. Bare areas on the northeastern slope should be monitored to see if vegetation growth continues
to be inhibited during the summer growing season. If vegetation does not fill in, th ebare spots
may need to be re-seeded.
2. 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.
3. The small slope failure 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.
4. The newly identified areas that were observed to be storing water should be monitored to
determine whether this is a regular occurrence. Should the continued storage of water on the cap
be observed, these areas should be regraded to encourage water drainage off the landfill cap and
stabilized with vegetation.
5. 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.
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.

Landfill Cover Inspection – May 2016
Sorrell Landfill (Permit # 92-04)
Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251

June 15, 2016 5
3.0 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 Steele Samuel P. Watts, P.G.
Staff Scientist Senior Project Manager
[e-mail] [e-mail]

Attachments:
Attachment I - Facility Compliance Inspection Report, dated February 15, 2016
Attachment II - Photographic Log
Attachment III - Figure 1 – Cover Inspection Site Map

Attachment I
Facility Compliance Inspection Report, dated July 7, 2015

Attachment II
Photographic Log

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
1

1a View of small portion of slope failure on the northwestern
slope looking uphill (south).
1b Close up view of small portion of slope failure on the
northwestern slope looking uphill (south).

1c View of small portion of slope failure on the northwestern
slope looking uphill (south).
1d Close up view of small portion of slope failure on the
northwestern slope looking uphill (south).

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
2

2a View of displaced rip rap and increased erosion within
outfall of the culvert draining the stormwater ditch parallel
to the southern access road.
2b View of displaced rip rap and increased erosion within
outfall of the culvert draining the stormwater ditch parallel
to the southern access road.

3a View of area on landfill cap that has been observed to
consistently collect and store water north of Slope Drain
No. 2.

3b View of area on landfill cap that has been observed to
consistently collect and store water north of Slope Drain
No. 2.

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
3

4a View of area on landfill cap that is storing water between
landfill gas vents GV-2 and GV-3 (looking northeast).

4b View of area on landfill cap that is storing water between
landfill gas vents GV-2 and GV-3 (looking northeast).

5a View of area on landfill cap that is storing water adjacent
to landfill gas vents GV-13 and VT-13 (looking northeast).

5b View of area on landfill cap that is storing water adjacent
to landfill gas vents GV-13 and VT-13 (looking northeast).

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
4

6a View of bare patches on northwestern slope looking north. 6b View of bare patches on northwestern slope looking
south.

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).
8a View of small slope failure in landfill cap on southern slope
just north of MW-8 (looking north).

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
5

8b View of small slope failure in landfill cap on southern slope
just north of MW-8 (looking north).
9 View of scouring at outfall of slope drains installed within
Diversion Ditch/ Diagonal Water Bar no. 2.

10a Overall view of recently mowed grass and vegetation
across the landfill cap (looking west).
10b Overall view of recently mowed grass and vegetation
across the landfill cap (looking east).

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
6

11a View of the recently mowed back (western) slope of the
landfill cap looking downhill from the top of the cap.
11b View of the recently mowed back (western) slope of the
landfill cap looking uphill from the access road.

11c View of the recently mowed back (western) slope of the
landfill cap looking uphill from the access road.
11d View of the recently mowed back (western) slope of the
landfill cap looking uphill from the access road.

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
7

12a View of ditch along the southern base of the landfill
looking east.
12b View of access road and rip-rap drainage ditch located
along the southern base of the landfill that has recently
been clear-cut (looking east).

13a View of Slope Drain #1 Inlet/ Headwall, which has recently
had the woody vegetation removed (looking south).
13b View of flexible slope drains from Slope Drain Inlet #1
(looking northwest).

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
8

13c View of Slope Drain #2 Inlet/ Headwall, which has recently
had the woody vegetation removed (looking south).
13d View of flexible slope drains from Slope Drain Inlet #2
(looking north).

14a View of Diversional Ditch/ Diagonal Water Bar #1 (looking
south).
14b View of Diversional Ditch/ Diagonal Water Bar #2 (looking
south).

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
9

15a View of recently mowed access road to monitoring well 4
(looking east).
15b View of mowed access road to monitoring well 7 (looking
north).

16 View of culvert located within stream crossing northeast of
MW-6. The culvert is functioning as designed (looking
southwest).
17a View of sediment pond inlet. The sediment pond is
functioning properly (looking south).

Evaluation of Landfill Cap
Sorrell Landfill, Apex, Wake County, North Carolina
S&ME Project No. 1054-07-251
Taken by: A. Steele Date Taken: 6/2/2016
10

17b View of sediment pond and sediment pond outlet. The
outlet and trash rack are functioning properly (looking
north).
17c View of outlet for small sediment pond along the western
edge of the property and of pond (looking east).

18 View of sediment pond inlet and trash rack. The sediment
pond is functioning properly (looking south).
19 View of landfill cap and landfill gas vents which have been
repaired.

Attachment III
Figure 1 – Cover Inspection Site Map
PROJECT NUMBER:
DATE:F
I
G
U
R
E

N
O
.
SCALE:
DRAWN BY:
CHECKED BY:DRAWING NUMBER:WWW.SMEINC.COM
3201 SPRING FOREST RD, RALEIGH, NC 27616
NC ENGINEER LICENSE #F-0176
1
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