3402_HanesMillRdMSWLF_MSE_Comment_Samplingplan_FID1286108_20190311

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Chao, Ming-tai
From:Chao, Ming-tai
Sent:Monday, March 11, 2019 9:29 AM
To:Jan McHargue
Cc:Stanley, Sherri; Heim, Susan A; Plummer, Michael; Mussler, Ed
Subject:Re: [External] RE: MSE wall, Hanes Mill Road MSWLF, 34-02
Hi Jan:

On Friday afternoon, 03/08/19 the Solid Waste Section (the SWS) received a subsurface investigation and
sampling plan (the plan), which was prepared by HDR on behalf of City of Winston-Salem & City/County
Utilities Commission (the permittee). The plan provides a drawing of soil boring layout and a laboratory soil
testing program for the proposed mechanically stabilized earth wall (MSEW) along the east and west side of the
active lined Hanes Mill Road MSWLF, Permit No. 3402-MSWLF-1997 (the Landfill). According to the plan
the drilling activities will start in the week of 03/11/19, the SWS is not given sufficient time to review the plan,
consequently, only the limited inputs and assistance can be provide to you and the permittee at this time.

After conducting a review of the plan, the SWS has several questions/comments/concerns of the plan which are
stated below.
1. The 03/08/2019 e-mail message stated the plan was developed between Tensar and HDR in order to gain
adequate subsurface information to finalize the design of MSEW.
a. The SWS wants to understand the relationship and responsibilities among the permittee, Tensar, &
HDR associated with this MSEW project at the landfill.

b. According to the email message, the submitted plan was prepared, reviewed and approved by the
permittee, Tensar & HDR. Please include the representative from Tensar in charge of this MSEW
project to the communication.

Sampling Program
2. The plan and the drawing must be signed and sealed by a professional engineer registered in the State of
North Carolina which may be considered as a certified record to be filed in a local government authority
according the North Carolina Building Codes.

3. Describe the procedures of borehole advancement and drilling machine & equipment for this project (for
example, hollow stem auger, rotary coring, wash-boring/percussion with drilling fluid or water
etc.). Will any casing or drilling fluid be used to protect opening of a borehole from caving in or
collapse while advancing soil boring or sampling.

4. Provide ASTM standards for STP testing and Shelby tube sampling (thin-wall tube sampling).

a. For STP testing, the weight of hammer, the drop distance, operations (manual or automatic) and
calculation of STP-N value must be specified for the sampling activities.
b. For thin-wall tube sampling please specify the approved methods for penetration to selected soil
stratifications and the criterion of sample recovery.

c. The compensation requirements must be specified should the sample is lost (zero recovery) or the
sample length fails to meet the specified the criterion of sample recovery.
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5. The ASTM D5434 – “Field Logging of Subsurface Explorations of Soil and Rock” shall be used for
preparing a field log. ASTM D2488 is used for describing and identifying of soil types in filed by visual
and other manual tools. The typical boing log should be appended to the plan.

6. The plan proposes that STP blow counts will be obtained at 5-feet depth intervals along with split-spoon
soil samples. This sampling protocol should also be conducted at or near the interface when the soil
strata change.

7. The plan proposes to collect Ten (10) Shelby tube samples from soil borings which will be sent to a
HDR soil lab for testing.
a. What are the acceptable dimensions of the sampler?

b. Specify the minimum length of a sample is required for specified soil testing.

c. Where is the location of the HDR soil lab to receive and test collected soil samples? If samples
will be shipped to a lab via a long-distance travel, are there measures to protect the "relatively
undisturbed" samples from any unnecessary disturbance and to preserve sample natural moisture
while shipping.

d. Please explain why 10 samples are adequate for design of approximately 5,300 linear-feet
MSEW. What guidance is used for supporting this sampling strategy?

e. Who will decide the location or depth for collecting a Shelby tube sample? Is there a
guidance/rationale to select the Shelby tube samples at the specific location or depth and for
specific testing – shear strength & consolidation?

f. The unit weight of each soil sample should also be tested.

8. It is likely that clayey soil material (aka marginal material), rather than free-drained granular soil
material will be used as the reinforced fill of the proposed MSEW; therefore, the CU test should
measure the pore water pressure during the stage of the sample being sheared to failure, and the report
must provide both total and effective shear strengths for different field conditions.

9. If advancement of soil boring would be terminated prior to reaching the planned termination depth,
should the termination depth of the soil boring be also decided by the SPT counts, rather than
considering auger refusal as only option?

10. Please provide the guidance to manage the condition when advancing soil boring is disrupted (not
encounter hardpan or rock layer) prior to reaching the planned terminated depth.

11. Considering/identifying the existence of perched water table, measurement/document of groundwater
depths in the boring log during a boring advancement is a standard practice; therefore, it is imperative to
measure the depths of groundwater table inside the borehole at the time of advancing soil boring, the
beginning of each day after groundwater was encountered and if drilling is not yet terminated, and 24-
hours after boring is terminated.

12. Bulk soil samples will be collected borrow area is described in the Plan:
a. The potential borrow area for the reinforced fill material to construct MSEW must be shown the
drawing of the plan.
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b. Adding the grain size analysis (ASTM D6913) to the testing menu.
c. The soil from a borrow or borrows that potentially contain harmful chemical properties and have
negative impacts or effects on the geosynthetic material/reinforcement of the MSEW; therefore,
in addition to characterize the engineering property of the soil form a borrow or borrows, the
properties of the soil or chemical compounds inside the soil must be also studied.

Geotechnical Report
13. The contents of the geotechnical report (the report) are too vague to follow. In a minimum, the report
should include, but not limited to, the following info:
a. The report must be signed and sealed by a professional engineer registered in the State of North
Carolina and may be considered as a certified record to be filed in a local government authority
according the North Carolina Building Codes.
b. The slope stability analysis associated for design of a MSEW can be classified as internal and
external stability analyses. Please state what kind stability analyses will be included in the report.
c. Will the report include the following recommendations or conclusions, but not limited to, lateral
pressures exerted on the MSEW, calculations of bearing capacity (assess the allowable soil bearing
pressure underneath the wall), total & differential settlement amount (define the tolerance values or
loadings –types and patterns) & the values of coefficient of consolidation and compression index,
the possibility of the MSEW failure due to overturning, sliding, the long-term performance or
interaction between a geosynthetic reinforcement and selected reinforced fill material.
d. The report should list what data or results will be directly related to MSEW design and construction
including preparing specifications and the CQA plan.
e. The statements of deviations to the plan.

Other concerns associated with the plan
14. The plan proposes not to survey locations of soil borings by a licensed surveyor but to document
locations by using a hand-held GPS device. It shall be noted that the surveyed coordinates and
elevations of soil borings are imperative information/references for generating soil profiles along the
wall alignment. In fact, the permitee may consider to conduct a detail survey along the proposed
MSEW alignment (including some distance affront and back of the wall), this survey data will be used
for wall design, production of cross-sections, profiles that are essential reference for estimating material
quantity (cut and fill), construction control (wall plumb & setback), long-term wall performance and
monitoring & inspection.

15. The plan does not address how to manage investigation derived wastes generated from the proposed
drilling and sampling activities.

16. Safety measures for this field work are not available in the plan. Should the plan, in a minimum, address
the drilling safety and prevention the existing landfill infrastructures / operations (especially leachate
force-main, LFG gas lines, waste disposal activities/ traffic, landfill baseliner system, & etc.) from
interruption by the drilling activities?

The SWS would highly recommend that the permittee puts this drilling activities on-hold till the proper
responses to the above-mentioned questions/comments/concerns, which are incorporated into the final plan.

Ming-Tai, Chao
Environmental Engineer, Solid Waste Section
Division of Waste Management
North Carolina Department of Environmental Quality
919.707-8251 (Office)
[e-mail]
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From: Plummer, Michael <[e-mail]>
Sent: Friday, March 8, 2019 3:01 PM
To: Chao, Ming-tai; Jan McHargue
Cc: Stanley, Sherri; Heim, Susan A
Subject: [External] RE: MSE wall, Hanes Mill Road MSWLF, 34-02

CAUTION: External email. Do not click links or open attachments unless you verify. Send all suspicious email as an attachment to
[e-mail]

Hey Ming,

Attached is the drilling layout and the boring/lab testing plan for the MSE Wall foundation investigation. This plan was
developed between Tensar and HDR in order to gain adequate subsurface information to finalize the design of the MSE
Wall. The drilling crew began the work this week and will likely finish by next week.

Thanks and have a great weekend!

Mike

Michael Plummer, PE
Solid Waste Section Manager

HDR
440 South Church Street, Suite 1000
Charlotte, NC 28202
D [704.338.6843] M [704.578.4031]
[e-mail]
hdrinc.com/follow-us

From: Chao, Ming-tai [mailto:[e-mail]]
Sent: Friday, March 8, 2019 1:05 PM
To: Jan McHargue <[e-mail]>
Cc: Plummer, Michael <[e-mail]>; Stanley, Sherri <[e-mail]>; Heim, Susan A
<[e-mail]>
Subject: MSE wall, Hanes Mill Road MSWLF, 34-02

Hi Jan: Happy Friday.

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I am sending out this e-mail message to check on the status of the proposed MSW wall around the active
MSWLF unit. On 03/05/2019 NC SWANA conference, you, mike and I briefly talked about the MSE wall, and I
recalled that Hanes Mill Road MSWLF planned to conduct a subsurface investigation program along the
proposed wall alignment in the coming weeks. Could you please provide the SWS the tentative schedule for
this investigation program? So I can move my current assignments and open the specific time frame to review
the work plan of this investigation program. Thank you for your help on this matter. Have a wonderful
weekend.

Ming-Tai Chao, P.E.
Environmental Engineer
Permitting Branch, Solid Waste Section
NCDEQ, Division of Waste Management
(Mailing Address)
1646 Mail Service Center
Raleigh, NC 27699-1646
(Street Address)
Green Square, 217 West Jones Street
Raleigh, NC 27603
Tel. [phone]
[e-mail]
http://portal.ncdenr.org/web/wm/sw
NC DEQ: Solid Waste Section
portal.ncdenr.org
Building 217 W Jones Street Raleigh, NC 27603 Phone [phone] Mail 1646 Mail Service Center
Raleigh, NC 27699-1646

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