7304_UpperPiedmontMSWLF_Phase4DesignHydrogeoReportAppr_FID1829414_20240208

February 8th, 2024

Sent via Email – [e-mail]

Mr. Matt Einsmann, P.E.
Republic Services of North Carolina, LLC
Environmental Manager
2240 Whitehall Park Drive
Charlotte, NC 28273-3552

Re: Design Hydrogeologic Report – Phase 4 (Cells No. 7-10)
Upper Piedmont Regional Landfill
Permit# 7304-MSWLF-1997
FID 1829414

Dear Mr. Einsmann,

The Division of Waste Management, Solid Waste Section (Section) has reviewed the Design Hydrogeologic
Report – Phase 4 (Cells No. 7-10) (FID 1810481) for the facility submitted by Bunnell Lammons Engineering,
Inc. (BLE) on behalf of Republic Services of North Carolina, LLC (Republic). The proposed Phase 4 will be
comprised of approximately 46 acres and is adjacent to the southern boundaries of Cells 1A and 1B.

The hydrogeologic investigation was conducted using data from 11 pre-existing exploration borings in
addition to 40 borings constructed during the design study. During construction of the historic and recent
borings, three distinct geological zones (residual soils, partially, weathered rock, and bedrock) were
observed. The upper component of the residual soil profile ranged in thickness from 3 to 27 feet below
ground surface with an average thickness of 6.7 feet. The lower component of the residual soil profile
ranged in thickness from 2.5 to 22.5 feet with an average thickness of 7.5 feet. The partially weathered
rock profile was observed to have a thickness ranging from 3 to 22 feet with an average thickness of 10.6
feet. The upper bedrock profile was observed to be fractured and severely to slightly weathered. The
depth where auger refusal was encountered at competent bedrock ranged from 4 to 53 feet below ground
surface. Fracture trace analysis conducted during the hydrogeologic investigation indicated that local and
regional prevailing fracture trends are northeast and northwest. Based on the cross sections presented
in Figure 5B, the vertical separation between the proposed base grade and top of bedrock elevations
ranged from approximately 13 to 18 feet.

Forty-five piezometers were utilized to evaluate hydrogeological conditions in the Phase 4 study area. Six
piezometers were installed with screened intervals in saprolitic soils, 33 were installed with screened
intervals in partially weathered rock, and five were screened within the bedrock zone. Groundwater in
the Phase 4 study area flows to the south and east with hydraulic gradients ranging from 0.028 ft/ft near

the southwestern portion to 0.088 ft/ft near the northwestern portion of the study area. Hydraulic
conductivity values were calculated for the saprolitic soil, partially weathered rock, and fractured bedrock
units with values ranging from 2.8 x 10-7 cm/sec to 3.9 x10-5 cm/sec. Depth of groundwater measurements
were collected from each piezometer monthly from February 2021 to February 2022. An estimated long
term seasonal high groundwater contour map was generated using site specific maximum groundwater
elevation measurements for pre-existing monitor wells and newly installed piezometers between
September 2006 and February 2022. Based on the cross sections presented in Figure 5B, the vertical
separation between the proposed base grade and long term seasonal high groundwater elevation ranged
from approximately 5 to 19 feet.

Based on the results of the Design Hydrogeologic report, proposed Phase 4 fulfills the requirements
specified in 15A NCAC 13B .1623 and is suitable for expansion. Please contact me at [phone] or by
e-mail at [e-mail] if you have any questions or concerns regarding this letter. Thank you
in advance for your cooperation in this matter.

Sincerely,

Ervin Lane
Hydrogeologist
Solid Waste Section

Cc: Perry Sugg, P.E. – SWS Environmental Compliance Branch Head
Sherri Stanley – SWS Permitting Branch Head
Tim Davis – SWS Environmental Senior Specialist
Riley Blais, G.I.T., – Bunnell Lammons Engineering, Inc.
Tyler Moody, P.E. – Bunnell Lammons Engineering, Inc.
T.J. Daniel, P.G., – Bunnell Lammons Engineering, Inc.