NCG030504_ROS Request_20240304

N cc 0305at� - FZ { e +
SWSG Stormwater Services Group, LLC
8916 Oregon Inlet Court
Raleigh, North Carolina 27603
Phone: [phone]
Fax: [phone]
March 1, 2024
Mike Lawyer
NCDEQ/DEMLR
1612 MSC
Raleigh NC 27699-1612
RE: Flowserve US Inc
NPDES General Permit NCGO30504
Elimination of Outfalls from Monitoring
Dear Mr. Lawyer:
We are requesting that outfalls we have designated as SDO-ALT and SDO-001 be eliminated
from future monitoring effective I"Quarter 2024. Our reasons for this request are as follows:
1. SDO-ALT collects off-site flow from commercial property and S. Saunders St (US 401)
upstream of SDO-001 and north of the facility.
2. SDO-001 collects runoff from SDO-ALT and on-site areas that include an employee
parking lot,roof drainage, exposed metal stock storage, and an access road. There is also
a covered dust collector and an enclosed welding shop within the SDO-001 drainage area.
3. SDO-001 consists of multiple smaller pipe connections and catch basins which could be
interpreted as additional outfalls if we were to isolate Flowserve's runoff at SDO-001
from the off-site runoff at SDO-ALT.
4. A decision was made in the mid 2000s to sample at both SDO-ALT and SDO-001 with
the assumption that the difference in the measured parameter values would be the
contribution from SDO-ALT.
5. A review of past sampling data shows that in most cases, an exceedence of Benchmark
Values at SDO-001 can be contributed to the flow from SDO-ALT. See Table 1
enclosed.
6. With the installation of inlet inserts to capture TSS and metals in the runoff, there will be
no access points within the SDO-001 pipe network where a sample can be collected
safely or representative of the on-site industrial activities.
7. We believe that outfalls SDO-002 and SDO-003 will suffice to represent the industrial
activities at this facility and we will continue analytical and qualitative monitoring at
these two outfalls in accordance with General Permit NCG030000.
Sincerely,
o a SEl:vlces GROUP, LLC
amen D. Frei
Project Manager
Enclosures. cc: File

i
i
,fir x�
r.
a>
Figure 3—SDO-ALT after recent Rain Storm Figure 1 -Sediment Deposit in SDO-ALT
Sample is collected from flow in concrete flume. Sediment source is off-site.
T:
t�
i
Figure 4 -SDO-001 @ End of Pipe Figure 2—SDO-001 at Low Water Level
Sample is collected from channel close to end of Pipe. Flow is right to left.

Table 1 -Recent Sampling Data
SDO-ALT SDO-001
TSS Cu Zn TSS Cu Zn
Benchmark Value 100 0.010 0.126 100 0.010 0.126
O1/06/2024 24.0 0.0095 0.0647 14.9 0.0103 0.0829
10/14/2023 336 0.669 0.0733 148 0.0026 <0.010
08/26/2023 3330 0.0277 0.0196 324 0.0039 0.0107
04/30/2023 30.2 0.315 0.0461 51.5 0.0105 0.0121
11/30/2022 19.3 0.0082 0.0464 152 0.0069 0.0644
09/30/2022 427 1 0.355 0.0482 169 0.0026 <0.020
06/27/2022 52.0 0.0449 0.236 25.6 0.0250 0.374
03/24/2022 - 0.0096 0.049 11.5 0.0075 0.045
11/04/2021 158 0.054 0.012 69.3 0.065 <0.010
O1/25/2021 5.6 0.015 0.058 3.5 0.0084 0.14
04/19/2020 45.9 0.018 0.12 14.6 0.013 0.23
12/23/2019 47.5 0.069 0.016 195 0.34 0.24
07/23/2019 103 0.024 O.l 36.4 1 0.019 1 0.36