NC0024112_Wasteload Allocation_19840703

DIVISION OF ENVIRONMENTAL MANAGEMENT
July 3, 1984
MEMORANDUM
TO: Russell Radford
FROM: Trevor Clements 11l
THROUGH: Randy Williams
Steve Tedder
SUBJECT:
Summary
In -Stream Assessment
Thomasville WWTP - Hambys Creek
Davidson County
The Tbwn of Thomasville is seeking permission to add 141,300 gpd
of, domestic wastewater to their effluent. According to self -monitoring
data, the Thomasville WWTP is operating out of compliance with their final
limits for BOD5 and NH3-N. They are, however, within compliance of
their interim limits which apply until June 30th of this year.
A level C Qual-II modeling analysis was performed using both Thomasville's
1983 summer period average wasteflow of 2.455 MGD and the projected flow
of 2.55 MGD. The additional wasteflow did not result in a significant
impact. However, a minimum DO of 2.2 mg/1 was predicted to occur under
each scenario along with a projected degraded zone (D.O. less than 5 mg/1)
of 5.5 miles.
Analysis and Results
Thomasville discharges to Hambys Creek, a class "C" stream, 6.8
miles above its confluence with Rich Fork Creek. Thomasville is permitted
with final limits of:
Summer Winter
Wasteflow 4.0 MGD 4.0 MGD
BOD5 5 mg/1 10 mg/1
NH3-N 2 mg/1 3 mg/1
DO 5 mg/1 5 mg/1
TSS 30 mg/1 30 mg/1
fecal coliform 1000/100 ml 1000/100 ml
pH 6-8.5 SU 6-8.5 SU

Russell Radford
May 14, 1984
- page two -
They do have interim limits of:
BOD5 20 mg/1
NH3-N 12 mg/1
According to self -monitoring data recorded between April and October of
1983, Thomasville's effluent has the following characteristics:
Wasteflow 2.55 MGD
BOD5 15.1 mg/1
NH3-N 2.7 mg/1
DO 7.9 mg/1
TSS 10.7 mg/1
fecal coliform 5/100 ml
These characteristics were input to a Level C Qual-II model. The model
was run at the existing and proposed wasteflow levels.
Under both wasteflows; a DO minimum of 2.2 mg/1 was predicted to
occur 6 miles downstream of the outfall. A degraded zone (DO 5.0 mg/1)
was predicted to occur for a 5.5 mile stretch. Since the downstream
monitoring station for Thomasville is located only 2.1 miles below the
outfall, information obtained there cannot be used to support these
modeling conclusions.
JTC:cs
cc: L. Page Benton, Jr.
Dean Cunningham