NC0000361_Memo_20030822

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DIVISION OF WATER QUALITY
Point Source Branch
NPDES Unit
August 22, 2003
MEMORANDUM
To: Madolyn Dominy
Marshall Hyatt
EPA Region IV
Through: Dave Goodrich
From: Jacquelyn M. Nowell
Subject: North Toe River Mining Dischargers
French Broad River Basin
Mitchell County, North Carolina
Background
There are six feldspar and quartz mines discharging into the North Toe River in the
French Broad River basin (subbasin 040306). The facilities are listed here in order, from
upstream to downstream:
• Unimin- Schoolhouse Facility(NC0000361) —2.16 MGD
• Feldspar Mines (NC0000353) —3.5 MGD
• Unimin-Crystal Facility(NC0084620) —0.36 MGD
• K-T Feldspar Mines (NC0000400) — 1.73 MGD
• Unimin—Quartz Facility(NC0000175) —3.6 MGD
• Unimin—Red Hill Facility(NC0085839) —0.682 MGD
Please see the attached schematic that represents the mine locations on the North Toe
River. Most of these facilities have been discharging since the early 1980's. The
exception is the Red Hill Facility that started discharging in 1995 and is located
approximately 20 miles downstream of the other mines and is not relevant to this
discussion from the standpoint that no interaction occurs between this plant and any
other. Therefore, this discussion will only include the mines above the confluence of the
South Toe River. It should also be noted that the Unimin — Crystal Facility discharges
effluent into the Feldspar Mines facility. There is the possibility of a separate discharge
in the future; therefore the facility has received a fluoride allocation.
The primary area of concern is the discharge of fluoride from these facilities. The North
Carolina water quality standard for fluoride is 1.8 mg/l. The allowable fluoride loading
for the North Toe River was determined in 1986 and has been allocated to these mines as
a group instead of individual allocations. This approach of allocating the total fluoride
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load to a section of the North Toe River is similar to other methods used by the Division,
including nutrient control strategies in the Neuse and Tar-Pamlico River basins. Similar
to a "bubble permit"(used in the Air Quality program), some discharges may cause
localized impacts. However, the overall goal of the allocation method is to protect water
quality while allowing some flexibility for the dischargers to maintain compliance. The
Division and EPA have approved this approach for 17 years.
The total pounds per day of fluoride allocated are 574. The permitted fluoride
allocations for each of the mines is as follows:
F hb:n ide Monthly Average Fluoride Daily Maximu'
acili Name .. . W lbs/da lbs/da „
Unimin-Schoolhouse 109 218
Feldspar Mines 174 348
Unimin-Crystal 50 100
K-T Feldspar 132 264
Unimin-Quartz 109 436
These allocations for the mines have been assigned upon all past permit renewals. This
fluoride loading of 574 lbs/day is based on:
1) a summer 7Q10 flow of 45 cfs in the North Toe River just below Little Bear Creek,
2) the current water quality standard for fluoride of 1.8 mg/1, and
3) a background fluoride concentration of 0.05 mg/1.
The 1985 wasteflows for three of the quartz processing mines were used to develop the
fluoride loading:
1) Feldspar @ 1985 Qw = 3.50 MGD
2) KT Feldspar @ 1985 Qw = 2.02 MGD
3) Unimin-Quartz @ 1985 Qw = 4.32 MGD
9.84 MGD = 15.25 cfs
Fluoride loading = (45 cfs + 15.25 cfs)(1.8 mg/1)— (45 cfs)(0.05 mg/1)
_ (60.25)(1.8) —2.25 cfs.mg/1
= 108.45 —2.25 = 106.2 cfs.mg/1
= 106.2 cfs.mg/1 * 5.39= 572 lbs/day -- 574 lbs/day
(Assume the difference is attributable to rounding)
Water Quality Evaluation
There are no federal effluent guidelines for mines that discharge fluoride. The purpose of
this memorandum is to evaluate water quality as it relates to previous permit decisions
and propose a 2003 permit strategy.
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The Division uses a weight of evidence approach when assessing water quality. That is,
all available data are reviewed and evaluated to determine the appropriateness of certain
actions. There are three categories of information in this case:
• Instream biological assessments
• Whole-effluent toxicity testing
• Instream chemical data
Instream biological data are the most directly reliable measurements of stream health and
are, therefore, given the greatest consideration. Whole-effluent toxicity testing also is
given a lot of weight during deliberations. It is not a direct measurement of stream
conditions, but it is a direct measurement of the interaction between wastewater and
species that inhabit the stream or river. The Division also considers comparison of
physical or chemical measurements to existing water quality standards. In the presence of
all three categories of information, contraventions of water quality standards, although
considered serious, are given the least amount of weight. The reason for this is that
comparisons to numeric criteria (which are based on whole-effluent toxicity testing) are
indirect measurements of the biota in the stream. All of this information is valuable, but
North Carolina chooses to make a comprehensive critical evaluation of all available data.
Use Support
There are no segments of the North Toe River listed on the North Carolina 2003 303(d)
impaired stream list. There are approximately 556 miles of the North Toe River that are
rated fully supporting designated uses including the river reaches receiving effluent from
these mines.
Instream Biological Assessment
The benthic macroinvertebrate data for the North Toe River below all the quartz mines
demonstrate good water quality. The most recent evaluation was in 1997 at State Road
1162 at Penland, Mitchell County. This is located just 0.5 miles downstream of the
Unimin-Quartz discharge. There has been improvement in the biological rating over the
years from a poor rating in August 1988 to a good-fair rating in 1989 and 1992.
Macroinvertebrate data for the most upstream station above the quartz mines, North Toe
River at US 19E at Ingalls, Avery County, indicate a rating of excellent water quality as of
July 1997. The table below indicates North Toe River biological monitoring stations and
their biological ratings during the 10 year period between 1987 and 1997.
Biological Ratings
Station location 1987 1988_ 1989 1992 1997
North Toe R.,US 19E Good Good Good Good Excellent
at Ingalls
North Toe R., Fair Poor Good Good Good
SR 1162, Penland —Fair -Fair
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Bioclassification Use Support Rating
Excellent Fully Supporting
Good Fully Supporting
Good-Fair Fully Supporting
Fair Partially Supporting
Poor Not Supporting
Whole Effluent Toxicity Testing
All the quartz mines have quarterly whole effluent toxicity tests based on the potential for
toxic effects on the receiving stream. (Please note that Unimin-Crystal has a toxicity
limit, however because it discharges into the Feldspar Mines WWTP, they do not conduct
individual toxicity tests.) Since 1998, there have been 91 tests conducted by the five
quartz mines with a 93% passing rate. There have only been 6 failures of all the tests
conducted in the past four years. The majority of the failures occurred at the same
facility. The Unimin-Schoolhouse plant accounted for four of the six failures. The cause
of this toxicity is unknown. However, it should be noted that Unimin-Schoolhouse been
compliant since August 2001.
;` Number of Number of
Facility Name Toxicity Limit Toxicity Tests Failures
since 1998
Unimin-Schoolhouse 10% 26 4
Feldspar Mines 11% 24 0
Unimin-Crystal 1.3% - -
K-T Feldspar 6% 19 1
Unimin-Quartz 11% 22 1
Instream Chemical Monitoring by Facilities
All the facilities conduct instream self-monitoring for turbidity, fluoride and pH, both
upstream and downstream of their outfalls. This is to help determine the effect of the
discharges on the water quality in the North Toe River. Instream fluoride data from the
time period of January 1999 to August 2002 were reviewed for the preceding five
facilities. During this time period, the monthly averages for instream fluoride have
shown no exceedances of the water quality standard either upstream or downstream of the
Unimin-Schoolhouse and Feldspar facilities. The average upstream value for the
Schoolhouse facility was 0.15 mg/1 and the average downstream value was 0.26 mg/1.
The average upstream value for the Feldspar facility was 1.29 mg/1 and the average
downstream value was 1.2 mg/1.
There were a total of 327 fluoride observations in the stream among these five
dischargers with 30 values >1.8 mg/l. This was 9% of the total monthly observations
with 91% within the standard. Most of the instream fluoride values > 1.8 mg/1 standard
occurred upstream and downstream of the K-T Feldspar discharge. This, more than
likely, occurred as a result of the proximity of the Feldspar Mines discharge which is only
0.6 miles above the K-T Feldspar Mines discharge. The breakdown of instream
observations of values > 1.8 mg/1 are:
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Monitoring Locations Number of Obs. values > 1.8 mg/1
Above Unimin Schoolhouse 43 0 0
Franklintown Bridge 43 0 0
Above Feldspar 37 0 0
Below Feldspar 38 0 0
Above K-T Feldspar 41 7 17%
Below K-T Feldspar 42 15 36%
Above Unimin-Quartz 42 5 12%
SR 1162 at Penland Bridge 42 3 7%
327 30 9%
Ambient Monitoring Data
The Division conducts ambient monitoring in the North Toe River at two sites. The first
station is at US Highway 19E near Ingalls, NC nearly 1 mile above the Unimin-
Schoolhouse Quartz mine. The second station is at State Road 1162 at Penland
approximately 0.8 miles below the Unimin-Quartz outfall. These stations are above the
most upstream mine and below the most downstream mine. Since January 1999, there
have been 30 samples of fluoride taken. There have been only 3 values > 1.8 mg/1 and
these occurred in February 2000, February 2001 and June 2001. This indicates that 90%
of the ambient samples in the past 4 years have been< 1.8 mg/l.
Discussion of Water Quality Information
An overall view of water quality in this segment of the North Toe River indicates that the
biological assessment shows improving water quality conditions. The toxicity data
indicates that the discharges are not toxic or causing toxicity instream. There is greater
than 90% compliance with the toxicity limits. Self monitoring instream data conducted
by the discharges does demonstrate that some instream fluoride standard exceedances
occur. The majority are below K-T Feldspar, and it is concluded that these occur because
the two dischargers are in such close proximity and North Carolina (with EPA approval)
has used a"bubble" permitting approach, which allows some localized impacts by design.
However, the average instream fluoride values collected between January 1999 and
August 2002 show that upstream and downstream of all the dischargers, the instream
fluoride average is below the standard of 1.8 mg/1.
DWO Recommendation
The Division recommends that the allocations for the North Toe River dischargers remain
the same. Water quality data show that there is no impairment in the stream, there have
been minimal toxicity problems, and the numeric water quality standard is being
protected > 90% of the time. It recommended that all the feldspar and quartz mines have
their permits reissued at the existing fluoride allocations.
Attachments
cc: Forrest Westall
Mike Parker
Matt Matthews
NPDES Files: NC0000175 NC0000353 NC0000361
NC0000400 NC0084620 NC0085839
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