34-02_HanesMillRdMSWLF_Commenton WorkPLan_alt_finalcover_pilotstudy_DIN28805_20180409

ROY COOPER
Governor

MICHAEL S. REGAN
Secretary

MICHAEL SCOTT
Director
Solid Waste Section

April 09, 2018

Ms. Jan McHargue, PE
Solid Waste Administrator
City/County Utilities
P.O. Box 2511
Winston-Salem, NC 27102

Re: Comments on Final Permit Modification Application – Alternative Final Cover System
Pilot Project
Hanes Mill Road Municipal Solid Waste Landfill
Forsyth County, North Carolina
Permit No.3402-MSWLF-1997, Document ID No. (DIN) 28805

Dear Ms. McHargue:

The Division of Waste Management (DWM), Solid Waste Section (the SWS) reviewed the
following documents:
• Final Permit Modification Application (the Application)– Alternative Final Cover System
Pilot Project (Pilot Project), Hanes Mill Road Landfill, Winston-Salem, North Carolina.
Prepared by HDR Engineering, Inc. of North Carolina, Charlotte, NC (HDR). Dated June
30, 2017 and received on July 05, 2017. (DIN 28113).
• The June 28, 2017 letter of approval of the modification of sediment basin No. 1 of the
Hanes Mill Road Landfill is received by SWS on July 12, 2017; the approval letter that is
issued by NC Land Quality Section is the portion of the Appendix C of the Application
(DIN 28113).
Based on the reviews, the SWS has some comments on the Application and recommendations or
suggestions on the Pilot Project which are stated below.

I Comments on the Application
Section III – Proposed Closure Area
1. Should the pilot study area include both the top deck/flat portion and the side slope of the
landfill? In addition to considering the impact on exposed geomembrane cover (EGC) by
UV radiation, should other environmental/meteorological factors may be considered in
the project? References indicate that some considerations could be temperature variation
on liner, prevailing wind, moisture or standing water accumulation or stress on liner
material due to total or differential settlements, different liner material -
reinforced/textured (used on steep slope area) and un-reinforced/smooth (used on mild
slope area or top deck of a landfill), etc.
Ms. Jan McHargue, PE
April 09, 2018
DIN 28805
Page 2 of 7

Section VIII – Performance Metrics, A Visual Inspection
2. How to identify if the proposed system is subjected to degradation in a quantitative
manner; is there any guidance/checklist to assist the person, who routinely conducts the
quarterly visual inspection in preparing a consistent inspection report?

Section VIII – Performance Metrics, B Material Sampling
3. The Closure TurfTM consists of three components – LLDPE, synthetic/artificial turf
(synthetic grass blades weaved into the woven geotextile), and infill material.
a. Will the specified material testing on the LLDPE be also applicable to the
synthetic/artificial turf (both grass blades and geotextile)? Please clarify.

b. The synthetic/artificial turf that serves as drainage media and erosion control
measure for the Closure TurfTM is also subject to degradation over time due to
long-term UV radiation (Karidis Arlene, 2017). Will the functions of the drainage
and erosion control measures be diminished by long-term UV exposure? How
will the impact on the synthetic/artificial turf resulting from UV radiation be
tested or measured? Please clarify.

4. Should the following laboratory testing should be included in the test menu? The
recommendations are based on the literature research and available case studies on the
EGC.
a. For UV degradation,
i. Why is Standard OIT (by ASTM D 3895) not selected in the study?
ii. Should the material (HDPE & LLDPE) be tested for oven aging (ASTM D
5721) and UV resistance (ASTM D 7238) in addition to HP OIT testing
(GRI-GM13)?

b. For EGC/60-mil HDPE, the material must be tested for environmental stress crack
resistance by ASTM D 5397 (GRI-GM13 and Erickson R.B et al. 2008).

Section VIII – Performance Metrics, C Reporting
5. The final report of this Pilot Project should include the estimate service life of each
proposed alternative final cover system. The anticipated life expectance or the “half-life”
of each alternative system should be calculated based on a model or models (Hsuan Y.G.
and Koerner R.M. 1998, Suits, L.D. and Hsuan Y.G. 2003, and Hsuan Y.G. et al. 2008)
by using the collected field and laboratory results of this Pilot Project.

6. Based on the estimate “half-life” of each alternative system and Pilot Project results, the
City/County Utility should provide the following in the final report.
Ms. Jan McHargue, PE
April 09, 2018
DIN 28805
Page 3 of 7

a. Which alternative cover system is selected as the final cover system to be used for the
closure of the active Hanes Mill Road MSWLF? The detail information and data to
support the decision should include in the report.

b. Financial assurance (FA) mechanism and potential payment scheme should be
discussed in the report. Each alternative final cover system will eventually require
total or partial replacement because the deterioration of the geosynthetic material
resulting from long-term exposure to environmental factors such as UV radiation. A
life-cycle-cost analysis, based on the Pilot Project results and/or references from the
similar projects, should be provided in the report, and the costs for either total or
partial replacement of the selected alternative cover system should be provided in the
report. The long-term FA mechanism for the selected alternative final cover system
could include costs for:
i. Maintenance, inspection, and monitoring requirements for the rule-required
30-year post-closure period, and
ii. Total replacement of the selected alternative final cover system with a
prescribed landfill cover system approved at that time, or
iii. Total or partial replacement of the selected alternative final cover system for
the remaining life-spam estimated from this pilot study report, or
iv. Installation of the remaining components of the current prescribed final cover
system – compacted clay liner or geosynthetic clay liner, geo-composite
drainage layer, and vegetative & erosion layer.

Appendix A - Drawings
7. (Detail 1B on Sheet 00C-03) According to the Technical Specification Section 33 47 18 -
Engineered TurfTM, three types infill materials – sand infill, polymer emulsion
component for sand fill or cementitious infill will be placed between geotextile and the
synthetic turf. In addition to sand infill, please add polymer emulsion component for
sand fill or cementitious infill to the Detail 1B.

Appendix D - Technical Specifications
8. (Technical Section 33 47 14 - HDPE) The technical specification is prepared for the
HDPE liner used for the landfill baseliner system; therefore, please modify the
specification for the application of both EGC final cover system (Rowe R.K. and Sangam
H.P., 2002 and Lodi et al. 2014) and the traditional/prescribed final cover system.
a. (Paragraph 1.3.A.1.d) A melt index testing and the specified value (less than 1.0g/10
min) on polyethylene resin by ASTM D 1238.
b. (Paragraph 2.2– Material) The specification must describe the geomembrane surface
characteristics – smooth or textured on single or double sides.
c. (Paragraph 2.2.A.8) please add the following test items to the menu per GRI-GM-13:
Ms. Jan McHargue, PE
April 09, 2018
DIN 28805
Page 4 of 7

i. Stress Crack Resistance (ASTM D 5397) and the specified value.
ii. Oven Aging at 85oC (ASTM D 5721) for both Standard OIT (ASTM D 3895)
and High Pressure OIT (ASTM D 5885) and the specified values.
iii. UV Resistance (ASTMM D 7238) for High Pressure OIT (ASTM D 5885)
and the specified value.
d. (Paragraph 2.3 – Interface Friction Tests) The specification must specify the
minimum interface angle between the compacted soil liner and HDPE, HDPE and
geocomposite drainage material (GDM), & GDM and vegetative layer. This is only
applicable for the traditional/prescribed cover system. The specified interface friction
angles must be greater than or equal to the value (s) concluded from the veneer slope
stability analyses, which should be appended to the Application.
e. (Paragraph 2.4) Please add ASTM methods to vacuum box and air pressure test.

9. (Technical Section 33 47 17 - LLDPE)
a. Please provide the specifications for MQA and MQC submittals and submitted testing
items.
b. (Paragraph 2.2.A.4) please add the following test items to the menu per GRI-GM-17:
i. Maximum 2% Modulus (ASTM D 5323) and the specified value.
ii. Minimum Axi-Symmetric Break Resistance Strain (ASTM D 517) and the
specified value.
iii. Oven Aging at 85oC (ASTM D 5721) for both Standard OIT (ASTM D 3895) and
High Pressure OIT (ASTM D 5885) and the specified values.
iv. UV Resistance (ASTMM D 7238) for High Pressure OIT (ASTM D 5885) and
the specified value.

10. (Technical Section 33 47 18 – Engineered Turf) Please provide required clarification or
information.
a. Please provide Specifications 01 33 00 and 01 65 50 which are mentioned in this
Section but are not available in Appendix D.
b. In Paragraph 2.2D the minimum compressive strength of the cementitious infill is
5000 psi at the 28th day. But there are no specified requirements for sample
collection pre- and after deployment, testing frequency, how to replace deployed infill
if the testing result fails to meet the specified compressive strength.
c. The maximum thickness in-fill sand (0.75 inches) specified in Paragraph 3.2L is
different from that (1 inch) shown on Detail 1B on Sheet 00C-03. Please clarify.
d. (Paragraph 3.2L) Will a as-built drawing be prepared by a surveyor registered in the
State of North Carolina for reporting the final infill thickness according to the
specified approaches in items 3 and 6.f? Please clarify.

Ms. Jan McHargue, PE
April 09, 2018
DIN 28805
Page 5 of 7

11. The technical specification of the emergency gas vent should be included in the
Appendix D. The specification should include the requirements of the material,
installation, operation, and maintenance.
a. Will the vent always open to atmosphere? Or it opens when the threshold of gas
pressure is reached. Pleas clarify.
b. If the vent always opens to atmosphere, what is a mechanism(s) or design in the vent
to prevent the surface runoff/precipitation into the underlain landfill waste or into the
interface between liner and bedding soil material? Please clarify.

Appendix E- CQA Plan
12. (Section 3. Geomembrane Liner Construction Quality Assurance)
a. (Section 3.2.2 Earthwork, the second paragraph) In addition to the compacted soil
liner layer, the intermediate soil/bedding soil cover will be used in the proposed
exposed liner systems; would the timely coverage requirement stated in this
paragraph be also applicable to the intermediate soil/bedding soil cover? Please
clarify.
b. (Section 3.2.2.2) What about the soil anchor system? Should this section describe the
requirements for the assurance of the proper installation of soil anchor(s).

II Recommendations/Suggestions
According to the Application, duration for this Pilot Project is two (2) years which corresponds
to the time-frame for a similar study conducted in South Carolina. Should the project potentially
be longer, if that area is not ready for final cover? Some considerations for a longer period
include:
1. The alternative final cover system being used as an intermediate cover system may be
approved by the SWS and, so the City/County Utility can have most benefits described in
the Application and the articles (Tarnowski, C. and Baldauf S. 2006 (?), Koerner R.M.
2012 and Townsend T.G. et al. 2016, and Hullings D. 2017). For example, the landfill
can gain additional air space for disposal due to wastes, enhance the capture of landfill
gas, eliminate costs for mowing grass, increase storm-water quality, reduce leachate
treatment costs, etc.

2. Recent study reports (Nathan Ivy 2002, Adams M.W. 2005, Islam M.Z. et al. 2011, and
Ramsey Boyd 2014) showed that the exposed liners used as the landfill covers in other
states for more than a decade to decades are still in the Stage A - depletion time of
antioxidation, one of three stages defining the lifespan of a geomembrane (Koerner R.M.
et al. 2011). But Rowe R. K. et al. (2003) reported opposite conclusions based on
investigation and testing on a 14-year-long-exposed portion of geomembrane in a retired
lagoon; they concluded the exposed liner portion endured significant degradation
Ms. Jan McHargue, PE
April 09, 2018
DIN 28805
Page 6 of 7

compared to the liner portion submerged inside the leachate. It is reasonable to assume
that the proposed two-year pilot study at this landfill may generate inclusive results.

3. A long-term Pilot Project will help the City/County Utility to better understand the costs
associated with repair, maintenance/inspection, and other pertaining costs associated with
the selected alternative final cover system; in turn, the City/County Utility could produce
a more accurate and persuasive FA mechanism (Hadlock M. et al. 2015) based on the
collection of long-term performance data.

III References
1. Adams M.W., 2005. Forensic Study of a HDPE liner after 10 years of exposure. TP-237.
GSE Lining Technology, Inc.
2. Erickson R.B., Thiel R.S., and Peters J., 2008. The Ongoing Quality Issues Regarding
Polyethylene Geomembrane Material Manufacturing & Installation. The First Pan
American Geosynthetics Conference & Exhibition.
3. Hadlock M., Woolsey J., Laux S., Davis, D. 2015. The Future of Landfill Closures:
Exposed Geomembrane Covers. MSW Management Magazine.
4. Hsuan Y.G. and Koerner R.M. 1998. Antioxidant Depletion Lifetime in HDPE
Geomembrane, Journal of Geotechnical and Geoenvironmental Engineering ASCE, 532-
541.
5. Hsuan Y.G., Schroeder H.F., Rowe K., Muller W., Greenwood J., Cazzuffi D., and
Koerner R.M. 2008. Long-term Performance and Lifetime Prediction of Geosynthetics.
EuroGeo4 Keynote Paper.
6. Hullings D. 2017. The Benefits of Exposed Geomembrane Covers for Intermediate
Applications at Landfills. ASCE – Geotechnical Frontiers 2017.
7. Islam M.Z., Gross B.A. and Rowe R.K., 2011. Degradation of Exposed LLDPE and
HDPE Geomembranes: Review. ASCE – Geotechnical Frontiers 2011.
8. Karidis Arlene, 2017. SWANA Analyzes Post Closure Cover Choices – A Recent Report
Examines the Efficiency of Exposed Geomembranes and Engineered Turf Covers.
Waste360.
9. Koerner R.M., Hsuan Y.G., and Koerner G.R., 2011. GRI White Paper #6 on
Geomembrane lifetime prediction: unexposed and exposed conditions. Geosynthetic
Institute.
10. Koerner R.M., 2012. Traditional vs Exposed Geomembrane Landfill Covers – Cost and
Sustainability Perspectives. Geosynthetics Magazine.
11. Lodi, P.C, Bueno, B.S., and Zornberg J.G. 2014. Considerations About Weathering
Exposure and UV Degradation of Polymeric Geomembranes. Minerva.
12. Nathan Ivy, 2002. HDPE Geomembrane After 20 years of Service. GFR.
13. Ramsey Boyd., 2014. Technical Note. A 13-year Study of an exposed green
geomembrane cover. GSE Environmental.
Ms. Jan McHargue, PE
April 09, 2018
DIN 28805
Page 7 of 7

14. Rowe R.K. and Sangam H.P., 2002. Durability of HDPE Geomembranes. Geotextiles
and Geomembranes 20. PP 77-95. Elsevier Science Ltd.
15. Rowe R.K., Sangam H.P. and Lake C.B. 2003. Evaluation of an HDPE Geomembrane
after 14 Years as a Leachate Lagoon Liner. Canadian Geotechnic Journal 40:536-550
(2003).
16. Suits, L.D. and Hsuan Y.G. 2003. Assessing the Photo-degradation of Geosynthetics by
Outdoor Exposure and Laboratory Weatherometer. Geotextile and Geomembrane, Vol.
21, 111-122.
17. Tarnowski, C. and Baldauf S. 2006(?) Aging Resistance of HDPE-Geomembranes -
Evaluation of Long-Term Behavior Under Consideration of Project Experience. GSE
World.Com
18. Townsend T.G., Jain P., Smith J., 2016. Exposed Geomembranes as a Sustainable
Practice for Landfill Design and Operation. Geosynthetics, Forging a Path to Bona Fide
Engineering Materials. ASCE-GSP 275.

The SWS is available for a meeting to further discuss this letter and parameters of a pilot project.
Let us know of times and dates if you are interested and we can arrange a conference room iin
Raleigh, or we can meet on site if you would prefer. If you have any questions you may contact
me at 919-707-8251 [e-mail].

Sincerely,

Ming-Tai Chao, P.E.
Environmental Engineer
Division of Waste Management, NCDEQ

cc:
Edward Gibson, P.E., City/County Utilities Michael Plummer, P.E., HDR
Thomas M. Yanoschak, P.E., HDR Ed Mussler, P.E, Permitting Branch Supervisor
Susan Heim, DWM Deb Aja, DWM
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