NCG020330_Letter RE Discharge_20231213

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Science. 3M Pittsboro
3M
4191 Hwy 87 South
Applied to Life. M Moncure, NC 27559
3M.com
11/09/2023
Sent via email
North Carolina Department of Environmental Quality
Raleigh Regional Office
3800 Barrett Drive
Raleigh, NC 27609
919-791-4200
Subject: Notification of Process Wastewater Discharges and Outfall 002 Designation to Wastewater
(CDC No. NCG020330)
To whom it may concern,
This letter is being submitted to notify the North Carolina Department of Environmental Quality(DEQ)of
process wastewater discharges not previously disclosed during the most recent NCG020000 renewal and
to change Outfall 002 from a stormwater only outfall to a combined process wastewater and
stormwater outfall.
During a recent file review,3M discovered that certain process wastewaters are generated but we were
not able to locate in our file corresponding documentation on past NOIs that documented these
discharges have been adequately disclosed. Part G-1(a)of permit NCG020000 states that"all proposed
wastewater discharges shall be specifically listed in the Notice of Intent".Therefore, 3M is submitting
this letter to update 3M's and NCDEQ's records.As a result, Outfall 002 will become a commingled
stormwater and wastewater outfall.3M will immediately begin sampling Outfall 002 as a process
wastewater outfall. Flow will be estimated until a continuous flow meter can be installed at Outfall 002.
An updated site map is attached for your reference.
Table 1 below summarize the process waters described in this letter.
Table 1: Process Wastewater Summary
Downstream Basins Final Outfall
1 Reclaim water Basins 1, 2, or 3 Outfall 002
2 Potable water Basins 1, 2, or 3 Outfall 002
3 Water used to clean out crushed rock buildup from Closed-loop process No Discharge
conveyors,crushers, and screens water ponds
4 Dust suppression water(quarry dewatering water) used All No Discharge
on access roads
5 Pu mill wet fines pile discharge Basin 3 -> Basin 2 Outfall 002
6 Pu mill washing Basin 3 -> Basin 2 Outfall 002
The information provided below describes each of the above listed process waters in greater detail.

To:North Carolina Department of Environmental quality
Re:Notification of Process Wastewater Discharges and Outfall 002 Designation to Wastewater(CDC No.N00020330)
Date:1110912023
Page:2 of 4
1. Reclaim Water:
3M Pittsboro operates a wastewater treatment plan which produces reclaim water for use in pugmills
and evaporative coolers. 3M Pittsboro treats domestic wastewater from the plant before use in the
process.The Reclaim water may enter stormwater through the pugmill discharges(noted in items 5 and
6 below),through system upsets at the wastewater treatment facility,or any leaking piping connections
(which would be corrected as soon as possible).3M operates the reclaimed water treatment plant
under Permit No.W00020808 issued by the NCDEQ Division of Water Resources. Discharge of this
activity is an allowable non-stormwater discharge under Part G-1 (e); discharges that are authorized by a
non-stormwater NPDES permit.
2. Potable Water Received from the Town of Pittsboro:
3M Pittsboro also receives potable water from Chatham County.The potable water is generally used for
domestic purposes within the plant and then is treated at the wastewater treatment plant before being
re-used as reclaim water(see item 1,above). Potable water is used in certain process operations such as
the mix pots,and may also be used in the pugmill if there is not enough reclaim water. Potable water
may enter the stormwater through the pugmill discharges (noted in items 5 and 6 below),any washing
or hosing activities,fire hydrant testing,or any water line leaks(which would be corrected as soon as
possible). Discharge of this activity is an allowable non-stormwater discharge under Part G-1 (e);
uncontaminated potable water.
3. Water Used by the Mining Contractor for Washing Rock and Equipment:
3M uses a contractor for quarrying operations and primary crushing activities.The mining contractor
crushes,screens,and stockpiles quarried material which is either sold for aggregate or used in 3M's
processing plant.Water is used to wash rock conveyors, crushers,and screens in the mining contractor's
quarry plant area.This activity is covered under permit Part G-3 (washing of mined material); however,
this water is directed to a series of unlined closed-loop process water ponds.The water in these ponds is
reused in the process,creating a closed loop with no direct discharge to an outfall.
4. Dust Suppression Water:
Stormwater accumulated in the pit(pit dewatering water) is applied as dust suppression water to access
roads and haul roads throughout the site.The water is not sprayed in excess resulting in flow to an
outfall. No chemicals are used in the dust suppression water.Therefore,there are no designated
process wastewater outfalls associated with dust suppression water. Dust control is noted as a process
wastewater activity under permit Part G-3; however, NCDEQ's"guidance for determination of NPDES
regulatory status of various discharges on a mine site" published on June 3,2016,specifies that this only
applies if spraying is excessive enough to cause sustained flow or discharge to surface waters.

To:North Carolina Department of Environmental Quality
Re:Notification of Process Wastewater Discharges and Outfoll 002 Designation to Wastewater(CDC No.NCG020330)
Date:1110912023
Page:3 of 4
5. Pugmill Wet Fines Pile Discharge:
The pugmill is a process where fines materials are mixed with water to create a slurry in preparation for
stockpiling and transferring the material to the mining refuse area for deposition.The pugmill discharges
a wet fines pile consisting of baghouse fines,fine dust from screening, process water, potable water,
recycled water,and/or reclaim water.Water runs off or seeps from the base of the pile and enters basin
3. Basin 3 flows to basin 2 and eventually outfall 002. 3M is seeking clarification that this is considered a
wastewater point source discharge from "like industrial activities deemed by the Division to be similar to
permitted operations in the process,or the discharges, or the exposure of raw materials, intermediate
products, by-products,final products,or waste products".3M will immediately begin sampling Outfall
002 according to the process wastewater requirements in Part H of Permit No. NCG020000.
6. Pugmill Washing:
The pugmill and associated conveyors must be regularly washed to prevent clogging.The pugmill water
may contain residual colorants,oils,silicone, reclaim water, etc.The water from the pugmill discharges
to a pond north of 3M's processing plant called"the pugmill pond".3M attempts to re-use the pugmill
pond water in the process per the correspondence between Carie Mathison(3M) and Rick Riddle
(NCDEQ) dated March 26,2018. However,during rain events or when the pugmill pond water is not able
to be reused,the pond overflows to basin 3 and eventually basin 2/Outfall 002.
3M recently completed sampling of the pugmill pond.The analytical results are attached and the results
for metals are summarized in Table 2, below. Please note that the samples are representative of the
water in the pugmill pond and not Outfall 002.
Table 2—Pu mill Pond Anaiytical Results (u /L)
Sample ID 4/10/2023 8/17/2023
Pugmill Pond Pugmill Pond
Arsenic <10.0 <10.0
Beryllium <4.0 <4.0
Cadmium* <1.0 <1.0
Chromium* <5.0 <5.0
Copper* 8.5 23.9
Lead* <10.0 <10.0
Nickel* <5.0 <5.0
Selenium <15.0 <15.0
Silver* <5.0 <5.0
Zinc* 41.9 148
3M has taken samples for metals,oil and grease, hardness, and the permit-required wastewater
parameters at outfall 002 to adequately characterize the discharge from the site and will submit the
results to NCDEQ upon receipt.

To:North Carolina Department of Environmental quality
Re:Notification of Process Wastewater Discharges and Outfall 002 Designation to Wastewater(CDC No.NCG020330)
Date:1110912023
Page:4 of 4
3M is seeking clarification that discharges from the pugmill operations are considered wastewater point
source discharges from "like industrial activities deemed by the Division to be similar to permitted
operations in the process,or the discharges,or the exposure of raw materials, intermediate products,
by-products,final products, or waste products".
Apart from Outfall 002, 3M does not anticipate any of the above discharges to change the current
Representative Outfall Status (ROS)of any outfalls onsite. Outfall 002 was not previously registered as a
wastewater outfall;therefore, 3M would request the DELI update the outfall as having process
wastewater discharge.Thereby, adjusting the DMR sampling parameters.
If any further information or clarification is required regarding the above-listed discharges, please feel
free to contact me at [e-mail]
Sincerely,
Blake Arnett I Plant Director, 3M Pittsboro
Enterprise Supply Chain
4191 Hwy 87 South I Moncure, NC 27559
Mobile: [phone] Office:919 642 4011
[e-mail]