20210929_LQS_comments

From:
Denton, Bill
To:
Miller, David
Cc:
Parr, Adam; Barham, Ivana S
Subject:
68-04 Tony Merritt"s Gravel Pit - RRO modification comments
Date:
Wednesday, September 29, 2021 9:06:54 AM
David,
With thanks and credit to Ivana Barham for her review of the plans for E&SC-related issues, here are
our combined comments for the submittal:
1. The plans clearly show them working in the riparian buffer along the north property line/mine
permit boundary including the installation of a permanent channel (Sheet 4 Dwg S3). I do not
recall if we have ever had a discussion about existing/proposed buffer impacts and the
possible need for DWR 401 approval for these activities. If that has not been previously
resolved, it needs to be addressed now. They need to identify all streams, wetlands, and
buffers (delineate between Zone 1 and Zone 2) on the plan sheets. Identify the permitted
impacts and impact areas on the erosion and sedimentation control plan sheets to
correspond with the USACE and DWR documents. Include any additional measures,
construction specifications, maintenance requirements and construction sequencing as
required by the 404/401/Buffer Determination and Buffer Authorization on the plan sheets.
2. Provide delineations of watersheds flowing to each sediment basin at full scale (small
scale in report shows insufficient level of detail). Provide design for worst case during the
life of mine. Provide narrative explaining the design procedure for the basins. Simply
providing model inputs/results is insufficient. How was the pumping discharge from
dewatering operations factored into the design?
3. Provide calculations for the temporary diversions indicating they will be stable for 10-year
return period design storm. Provide additional liners to ensure they meet this design
standard. If using detail 5 Sheet EC1, toe of slope must be armored with rip rap to
appropriate extents where water flows.
4. Provide 3 baffles on each sediment basin per design criteria specified in the NC Erosion
and Sediment Control Planning and Design Manual.
5. Provide additional measures to ensure water is discharged into the sediment basins in a
manner to prevent erosion. Provide a stable conveyance from diversions into basins (i.e.
rip rap lined channel, slope drain, tarp, etc.) Provide stable conveyance (extend pipe,
provide tarp or other acceptable practice) from outlet of skimmer to perimeter silt
fence/silt fence outlet. Provide construction details as needed for stable conveyance.
6. Provide silt fence and silt fence outlet below the skimmer outlet for both basins.
7. Specify the structure/device that will be sued to dewater temporary basins prior to
removal and/or conversion to a permanent structure. Pumps and silt bags are typically
used for this purpose. Provide a plan detail, construction specifications, and maintenance
requirements for silt bags. Specify pumping rates compatible with silt bag size that is
selected. Construction detail should specify a floating intake located in the skimmer cell.
Include a symbol/icon on the legend for this structure. Detail the use of this device in the

construction sequence. Include the location of the sediment filter bag on the plan sheets.
Specify in the construction sequence that silt bag will be continuously monitored during
operation.
8. Provide the location of emergency spillway for the basins. Emergency spillways must be
located in natural ground to reduce the potential for failure of the embankment.
9. Due to the addition of at least one additional stormwater outfall location, the NCG02 general
permit must be revised as needed to address this change.
10. Sheet 2 Dwg S1: Leader arrow indicates south property line is the southern edge of the 60-ft
right-of-way shared with the property owner to the south. My understanding is that the
property line is actually the centerline of this right-of-way. Please correct this sheet. Other
sheets appear to have it labeled correctly.
11. With regard to existing violations of the mine permit for disturbance of the buffer areas, they
have not finished the work needed to resolve this compliance issue (Operating Condition 9B).
I do not recommend we give them this approval until that work is completed to our
satisfaction.
12. Due to the difficulty we have historically had pinning down this issue, I recommend we
require much more prominent indicators of the extent of the high wall barriers; both fencing
and "safety berms" are proposed. The symbology for fence and safety berms should be
reflected in the legends on sheets where they appear.
13. 1 recommend the engineer confirm whether the location of the well serving the residence
owned by Tony Wayne Merritt (Orange Co. PIN: 9777560215) is outside of 500 feet of the pit.
It may not be a matter of public record, so they may need to conduct a field visit to verify.
14. Provide labels or symbols to differentiate occupied dwelling from other structures. Add
symbol to legend as needed.
15. With reference to Item 1h from the previous ADI letter, I do not see the aboveground storage
tanks located on the plans. Will they be relocated to the covered storage shown on Sheet 2
Dwg S1?
16. Sheet 3 Dwg S2: Sediment Basin 1 discharge pipe and outlet dissipator are installed through
the undisturbed buffer and beyond permit limits. This isn't allowed.
17. Sheet 3 Dwg S2: Locations of temporary diversions and the proposed safety berm are on top
of each other which is physically impossible. Provide construction detail with plan view and
cross-section to show how each of these structures will be located relative to the other. It
should be noted that the base width of the temporary diversion as shown in the construction
detail would be 10 feet and the base width of the safety berm as shown in the detail would be
25 feet assuming a 6 ft height. Proximity to the proposed excavation limits must also be taken
into account.
18. Specify proposed height of safety berm in detail on Sheet 8 Dwg EC3.
19. Given the proximity of the proposed excavation to Damascus Church Road, does the
excavation plan need NCDOT approval? Should we at least make them aware of this plan?
20. Design report/Mining Application Page 1, Section 4.0: They are proposing to add material

processing to the permit. It appears they have been in communication with DAQ on this issue,
but I am unclear where the issue of air quality permitting stands due to my unfamiliarity with
their regulations. With your prior experience with that Division, I'll leave that to you.
21. Design report/Mining Application Page 4, Section 6.0, Item C: Response from the engineer is
inaccurate. The marking of the mine boundaries has mostly been accomplished, but as of our
last inspection some additional markers were still needed.
22. Sheet 7 Dwg EC2, Detail 2 Sediment Basin Cross Section: the rigid extension of pipe from the
riser to the flexible coupling requires additional structural support to prevent excessive
movement and potential damage. How will it be protected during basin clean out?
23. Sheet 8 Dwg EC3, Seeding Schedule: Strongly recommend the removal of sericea lespedeza
from the seeding mix and replacing with appropriate annual seed. Sericea lespedeza is a
perennial which tends to compete successfully with more desirable turfgrass species in
certain growing conditions. Please note that tall fescue will require repeat seeding, watering,
and other maintenance to ensure a stand adequate to restrain erosion. A warm season grass
may be preferred depending upon the desired maintenance input by the owner.
General note: This is a matter for attorneys, not engineers, but it is my understanding that the
mine has the right to use the full width of the shared 60-ft right-of-way for the main access into
the mine. We had discussed with the mine operator a possibly relocation of this road, but that
would be impossible given the proposed excavation plan (Sheet 3 Dwg S2).
That's what we have for this round. Let me know if there are questions or need for clarification on
any of the comments. Have a good day.
Best regards,
Bill
William H. Denton, IV, PE
Regional Engineer — RRO
Division of Energy, Mineral, and Land Resources — Land Quality Section
Department of Environmental Quality
919 791 4200 office
bill.dentonQncdenr.gov
1628 Mail Service Center, Raleigh, North Carolina 27699
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