HomeMy WebLinkAboutNC0026913_speculative limits_19870721DIVISION OF ENVIRONMENTAL MANAGEMENT
July 21, 1987
MEMORANDUM
TO: Dan Blaisdell
FROM: Randy Dodd -e
THROUGH: Trevor Clem-nts
Steve Tedde
SUBJECT: Town of Sparta Fecal Coliform Limit
I have reviewed information relating to the need for a fecal coliform
limit for the Town of Sparta. The town discharges to the Little River ("C"
waters, 7Q10=18 cfs, average flow=68 cfs), with a permitted flow of 0.25 MGD.
During permit review in 1982, a fecal limit was not included. Rather, an
instream monitoring requirement was included to assess the impact of the dis-
charge (memo attached). Subsequently, instream monitoring data were collected
during 1985 (attached). While a substantial impact is not apparent because of
the discharge, few conclusions can be reached because of the distance to the
downstream station (5.1 miles), the lack of flow data, sampling effluent and
instream sites on different days and the variability in effluent concentra-
tions.
Effluent levels required to maintain a mix count of 1000/100 ml can be
calculated at 7Q10, based on several assumptions of background fecal levels:
Background Effluent Level Required to
0/100 ml) Meet 1000/100 ml instream
0 47,500
200 38,200
500 24,200
1000 1,000
Sparta's monitoring data indicates that daily effluent levels have
reached 480,000/100 ml, and are frequently elevated. Therefore, there is
potential for standard exceedance.
Wasteload allocation procedures require the inclusion of fecal limits
when dilution ratios are less than 67 to 1. The dilution ratio [(permitted
flow + 7Q10)/permitted flow] for Sparta is 47 to 1.
Recommendations
For consistency with wasteload allocation procedures, and in the absence
of conclusive evidence indicating that the Sparta WWTP does not impact the
Little River, it is recommended that a fecal coliform limit (1000/100 ml) be
included in the subject permit.
Please advise if questions.
Sparta Fecal Coliform Data (##/100 ml)
Effluent 100 ft. Downstream
Date Geom. Mean Range Upstream (SR-1425)
1/85 316,800 - 265 1900
2/85 28,200 - 55 49
3/85 <2 - 320 235
4/85 326,000 - 120 735
5/85 <2 - 1285 1845
6/85 <2 - 945 650
7/85 25,000 - 648 450
8/85 <2 - 2365 145
9/85 14,919 <2-480,000 700 2
10/85 <2 200 480
11/85 20 - 1450 930
12/85 <2
1/86 <2 -
2/86 35 <2-695
3/86 <2 <2
4/86 295 <2-43,300
5/86 537 <2-142,400
6/86 I29,1-62 -
7/86 7,694 -
8/86 56 -
9/86 769 -
10/86 111 -
11/86 130 -
12/86 290 -
1/87 6,220 -
2/87 34,467
3/87 316
4/87 2
5/87 5,810 -
RD:ps
cc: Steve Mauney
DIVISION OF ENVIRONMENTAL MANAGEMENT
July 21, 1982
MEMORANDUM
TO: Reggie Baird
FROM: Mark Lewis
SUBJECT: Wasteload Allocation
Town of Sparta
The Town of Sparta has requested that the fecal coliform limit be
deleted from their present permit which was issued on February 26, 1982.
There is very little data on which to asses the impact of a nondisinfected
effluent on the Little River. The monthly self -monitoring reports
contain no fecal coliform values.
Using the highest range of the upstream 7010 estimate, the requirement
of a fecal coliform limit for Sparta becomes cuestionable. It is not
clear as to whether not water quality violiticns will occur.
It is recommended that at this time the fecal coliform limit be
omitted from the present permit. owever, it is requested that weekly
monitoring of fecal coliform at upstream, downstream and effluent be
included. This additional data will aid us in conauctiuc a future analysis
of the impact that this nondisinfected discharge uas on the Little River.
Attached is a new approval form reflecting the requested change.
ML:cs
Attachment