NC0085812_Crooked Creek Model_20200527

Strickland, Bev
From:
Behm, Pamela
Sent:
Wednesday, May 27, 2020 11:30 AM
To:
Scheller, Roberto
Cc:
Denard, Derek
Subject:
Fw: [External] FW: Rocky River QUAL2K model issues
Attachments:
Q9120000 Dissolved Oxygenjpg;
Crooked Creek QUAL2K Calibration and Corroboration Review.docx
See attached. The memo states that the model was developed correctly.
From: Behm, Pamela
Sent: Friday, September 20, 2019 12:53 PM
To: Grzyb, Julie <[e-mail]>; Banihani, Qais <[e-mail]>; Hill, David A
<[e-mail]>; Basinger, Corey <[e-mail]>
Cc: Hong, Bongghi <[e-mail]>; Kebede, Adugna <[e-mail]>; Baker, Virginia
<[e-mail]>
Subject: FW: Rocky River QUAL2K model issues
All, please see a summary below of the recent permitting requests we are looking at in regards to Rocky River
(Yadkin). Our draft initial look at the Crooked Creek model is also attached, in -stream low DO issues of great
concern. There is a real need for these communities to work together for regional planning for long-term wastewater
needs. Holistically, the Rocky River is stretched pretty thin.
Thanks,
Pam
From: Hong, Bongghi <[e-mail]>
Sent: Friday, September 20, 2019 11:45 AM
To: Behm, Pamela <[e-mail]>; Kebede, Adugna <[e-mail]>
Cc: Painter, Andy <[e-mail]>
Subject: Rocky River QUAL2K model issues
Hi Pam and Adugna,
It looks like there are many requests for new and expanding wastewater plants along Rocky River:
- Mallard Creek WRF from 12 MGD to 16 MGD (first discharges to Mallard Creek)
- Muddy Creek WWTP from 0.3 MGD to 1 MGD
- Grassy Branch WWTP from 0.05 MGD to 0.12 MGD (first discharges to Crooked Creek)
- a new wastewater treatment facility discharging to Crooked Creek (being considered but no official request submitted
yet)
- West Stanly WWTP planning an expansion from 0.9 MGD (discharging to Rocky River near Long Creek confluence)

- City of Locust is currently sending its wastewater to West Stanly WWTP but looking for an alternative (i.e, direct
discharge to Rocky River)
We currently have a QUAL21K model simulating DO in Rocky River, developed for Charlotte Water per Mallard Creek WRF
expansion request. Some relevant river milepoints in the model are (from the downstream end):
- Mallard Creek: 54.6 mi
- Muddy Creek: 30.0 mi
- Crooked Creek: 23.8 mi
- Long Creek: 8.2 mi
- Lane Creek (most downstream tributary): 0.2 mi
Because the model was developed to simulate Mallard Creek WRF expansion scenarios, there appears to be relatively
higher degree of confidence in the upstream areas. Model uncertainty may increase as it gets closer to the downstream
areas. Some factors potentially contributing to the downstream uncertainty are:
-The current model may not include all the wastewater plants in the downstream area. For example, West Stanly WWTP
doesn't seem to be explicitly included in the model.
- The downstream end of the model is not the end of Rocky River (i.e., Rocky River -Pee Dee River confluence). The
model ends at about 0.2 miles downstream from the Lane Creek confluence, where the USGS station 02126000 is
located. At about 2 miles downstream from the Lane Creek confluence, there is an ambient monitoring station
(Q9120000) that is not covered by the current QUAL21K model.
Andy kindly provided a DO plot for this station (attached). There doesn't seem to have been an apparent change in DO
for the last 10 years, and DO stayed above 5 mg/L all the time (except for one occurrence which seems to be an outlier).
Before we meet with City of Locust, I will try and create a map showing Rocky River and the points of interest described
above, including all the wastewater plants discharging to Rocky River, all the way down to its Pee Dee River confluence.
Hopefully we can meet beforehand and discuss the best way to go from here. Perhaps we can ask Stanly County and/or
City of Locust to refine the downstream portion of the model?
Bongghi Hong
Environmental Specialist II
Modeling and Assessment Branch, Planning Section, Division of Water Resources
Department of Environmental Quality
919 707 3691 office
607 793 1778 mobile
bongghi.hongamcdenr.gov
1611 Mail Service Center
Raleigh, NC 27699-1611
Email correspondence to and from this address is subject to the North Carolina Public Records Law and may be disclosed
to third parties.

INTEROFFICE MEMORANDUM
TO: DWR Complex Permitting Branch
FROM: DWR Modeling and Assessment Branch
SUBJECT: Review of Crooked Creek QUAL2K Model Calibration and Corroboration
DATE: September XX, 2019
CC:
The Division of Water Resources (DWR) Modeling and Assessment Branch has completed
review of the Crooked Creek QUAL2K modeling study. Union County Public Works is currently in
the process of submitting an SOC application for the Grassy Branch WWTP located 6.7 miles
upstream of Crooked Creek's confluence with Rocky River (Figure 1). Also, a new wastewater
treatment facility that would discharge to Crooked Creek in the vicinity of Highway 601 was
proposed before, although no official application has been submitted as of yet. Data collected
from three field trips in the summer of 2016 were used for the calibration and corroboration of
the model, along with other sources (DMR, AMS, etc.). The work is generally of high quality.
Most of the parameter choices are backed up by the data or otherwise justified. No
inconsistency was found between the report and model contents.
The reported simulation results suggest, and are supported by field measurements, that
dissolved oxygen may be under severe depletion around and upstream of Beaver Dams area
(Figure 1). It appears safe to assume that there is no or little assimilative capacity left from the
headwaters of North Fork Crooked Creek (upstream of the South Fork confluence) down to the
Highway 601 crossing. Dissolved oxygen in Crooked Creek starts to recover from the Highway
601 area and becomes around 6 mg/L when discharged to Rocky River. Water quality conditior
at the end of Crooked Creek, and its potential impact downstream of Rocky River confluence,
will need to be carefully considered in the subsequent scenario analyses.
Again, these simulations are based on surveys made in the summer of 2016. Critical condition
was not yet assessed in this work, and no model run was made under the permitted (as
opposed to actual) discharges. Simulated flow at the Crooked Creek -Rocky River confluence
was about 4 cfs. Subtracting point source contributions, the natural flow might have been
around 2.5 cfs at the time of field surveys. It represents a low -flow condition, though still higher
than the critical 7Q10 condition (about 0.2 cfs, or as low as 0 cfs, as estimated by USGS).
Also as a reminder, the Complex Permitting Branch asked to include NCO088838 (Radiator
Specialty Company) in the model, a groundwater remediation system permitted at 0.09 MGD
discharging to an unnamed tributary of South Fork Crooked Creek.

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Crooked Creek QUALM Dissolved Oxygen Simulations
(Based on Actual Discharges)
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—Calibration Run (8/24/2016)
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—Corroboration Run (9/14/2016)
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River Mile
Figure 1. Crooked Creek dissolved oxygen simulation results. Wastewater discharges used in the
simulations were obtained from DMR data: Hemby Acres WWTP at 0.09 MGD (permitted at 0.3
MGD); Crooked Creek #2 WWTP at 0.83 MGD (calibration run) or 0.87 MGD (corroboration run)
(permitted at 1.9 MGD); Grassy Branch WWTP at 0.04 MGD (permitted at 0.05 MGD).
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