ANALYSIS OF COLOR CONCENTRATIONS IN THE PIGEON RIVER

JANUARY 31, 2018

AQUAETER, INC.

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SECTION 1.0

INTRODUCTION

Blue Ridge Paper Products Inc. doing business as “Evergreen Packaging” (Evergreen),

operates the Canton pulp and paper mill (“Canton Mill”) in Canton, North Carolina. Since 1988,

the Mill has reduced color loadings to the Pigeon River by more than 90%.

Since 2001 the Canton Mill has sampled and analyzed True and Apparent Color in the

Pigeon River upstream from the Mill's discharge and approximately 0.4-mile downstream at the

Fibreville Bridge.1 In 2009, Evergreen retained AquAeTer to sample and analyze True and

Apparent Color in the Pigeon River and its tributaries. Based on the Mill's data, and that collected

by AquAeTer, “A Comprehensive Assessment and Analysis of Color in the Pigeon River2” was

developed.

PURPOSE OF REPORT

This report supplements the Comprehensive Assessment and Analysis of Color in the

Pigeon River with an analysis of color concentrations in the Pigeon River upstream from the

Canton Mill at Park Street and downstream from the Mill's discharge at the Fibreville Bridge3.

The report compares the color concentrations at Fibreville and the difference in concentration

between the upstream and downstream stations from July 2010 through December 2017. This is

the period that the current NPDES permit and associated effluent limits have been in effect.

CONCLUSIONS

The long-term daily average contribution of the Canton Mill to true color in the Pigeon

River since July 2010, is 23 true color units at flows greater than or equal to the annual 30Q2.4

The long term daily average color concentration at the Fibreville Bridge at flows greater than or

equal to the annual 30Q2 is 34 true color units.5 The difference in the long-term daily average

color concentration at Park Street in Canton (14 true color units), upstream from the Canton Mill

1 NPDES Permit NC 0000272 issued to the Canton Mill by the North Carolina Department of Environmental

Quality requires the sampling. The Canton Mill also samples and analyzes color concentrations at Hepco (26 river

miles downstream) and at Brown’s Bridge in Tennessee, approximately ½ mile downstream from the Duke Energy

Progress Hydro-electric plant. 2 AquAeTer, Inc. (2014). Comprehensive Assessment and Analysis of Color in the Pigeon River. Brentwood:

AquAeTer, Inc. 3 The report will also reference color concentrations at the NC / Tennessee state line and at a similar stream from the

same Ecoregion. 4 Table 5, page 10 5 Table 3, page 8

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discharge, and the long term daily average color concentration at the North Carolina/Tennessee

state line (17 true color units), is 3 true color units.6

METHODOLOGY

AquAeTer has evaluated the color in the Pigeon River upstream from the Canton Mill

discharge and at the Fibreville Bridge. The dataset used for this analysis extends from July 1, 2010

through December 31, 20177, unless otherwise noted. The color data were also evaluated in

conjunction with the flows in the River. In particular, monthly flows were evaluated so that distinct

hydrologic/meteorologic periods that are statistically equivalent, but occur with the varying

background natural color that occurs in the River over the course of the different seasons, would

be analyzed separately but equivalently.

6 Table 4, page 9 and Table 6, page 11. 7 This is the period of the current NPDES Permit.

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SECTION 2.0

ANALYSIS OF STREAM FLOWS

15A N.C.A.C. 2B.0206 (a) (5) specifies that aesthetic standards will be met at flows greater

than or equal to the minimum average flow for a period of 30 consecutive days that has an average

recurrence of once in two years (30Q2). The actual period for the calculation is not specified.

Historically, the period used has been an annual number, so an annual 30Q2 has been calculated

for the analyses in this report. However, the annual 30Q2 event is not reflective of the actual

stream conditions through the year for this stream. The chance for the annual 30Q2 to occur in

any given month for an equivalent 30-day period is much greater than a 2-year return interval,

which is not in keeping with the NC standard. The period that is presented in this report is for a

monthly basis, which more accurately reflects the hydrologic cycle over the course of the year. A

comparison of the monthly 30Q2’s to the annual 30Q2 is presented in Figure 1.

Each of the monthly 30Q2

flows plotted in Figure 1 is

statistically equivalent to the other

months meaning they have the

same statistical probability of

occurring. However, the annual

30Q2 is not statistically likely to

occur in four months, and

represents a greater than a two-

year return interval in the other

eight months. The actual

calculated flows are provided in

Table 1. This demonstrates that

while the annual 30Q2 may

statistically have a 50% chance of

occurring in any given year, the

actual chance of the annual 30Q2

flow occurring in any given month is much less.

The United States Environmental Protection Agency (USEPA) also recognizes that, in

some cases, streams need to and can be evaluated on a monthly basis8 due to the variable

hydrologic conditions found. This analysis is and has been applied in many southern states as well

8 US EPA. (1997). Technical Guidance Manual for Performing Wasteload Allocations, Book II: Streams and Rivers

- Part 1: Biochemical Oxygen Demand/Dissolved Oxygen and Nutrients/Eutrophication. Washington, DC: US EPA.

Table 1. 30Q2 Monthly and Yearly Flows and

Recurrence Intervals

MONTH 30Q2

Chance of Annual Flow

Occurring

(cfs) (1 in __ Yrs) (%)

January 390 57.1 1.8

February 420 >88 <1.1

March 457 >88 <1.1

April 419 >88 <1.1

May 288 >88 <1.1

June 207 57.9 1.7

July 149 15.1 6.6

August 127 4.4 22.8

September 133 4.5 22.3

October 172 4.2 23.9

November 207 9.7 10.3

December 285 44.0 2.3

Annual 90.5 2 50

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as in some northern states and was originally proposed by the old U.S. Public Health Service, or

pre-USEPA.9

9 There are multiple NPDES Permits in the southeast which use monthly flow limits (DS Smith Riceboro on the

North Newport River and Georgia Pacific’s Brunswick Mill on the Turtle River (Ga.)), (Georgia Pacific mill in

Naheola, Alabama on the Tombigbee River and West Rock Mill on the Tombigbee (Alabama)) and (Domtar Mill at

Ashdown, Arkansas).

Figure 1. Comparison of Annual and Monthly 30Q2 Low Flows

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SECTION 3.0

ANALYSIS OF COLOR CONCENTRATIONS

The Canton Mill has been collecting in-stream color data since 2001. AquAeTer collected

samples from 2009 through 2011 in the stream and in the tributaries. There are 1,601 days with

measurements collected at Fibreville since January 1, 2001. This report focuses on the period

beginning July 1, 2010, the effective date of the most recent NPDES Permit.10

The analyses presented evaluate True Color in the River in various ways. The first is an

analysis of the samples collected at Fibreville. This location is approximately 0.4-mile

downstream from the Mill’s outfall, and has been considered the compliance point or edge of

mixing zone.

The dataset for the period July 1, 2010 through December 31, 2017, as well as the entire

period of record was evaluated. The Comprehensive Assessment and Analysis of Color detailed

that concentration in the River is not related to flow, but the color loading or pounds per day can

be reasonably predicted based on the flow. The predicted mass loading can then be converted back

to a concentration in order to predict a concentration. However, the analysis in this report focuses

on measured concentration data.

EVALUATION OF DATA

The first evaluation is the proper identification of an average. The arithmetic mean is a

common way to calculate an average. An arithmetic mean is simply the sum of the individual

values divided by the number of values, or mathematically:

= 1

The arithmetic mean is strongly influenced by both large and small values. When a dataset

is normally distributed, the arithmetic mean is appropriate. However, when a dataset is skewed,

the arithmetic mean will no longer represent the central tendency of the dataset. Another average

is the median value.

10 This report presents an analysis of color concentrations for the period July 1, 2010 – December 31, 2017. The

specified term of the current NPDES Permit is July 1, 201 - June 30, 2015. However, Evergreen timely submitted its

renewal application on December 31 2014. As such, the current permit is administratively continued pursuant to N.C.

Gen. Stats. 150B-3 pending final action by NCDEQ on the permit.

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A skewed dataset may follow a log-normal distribution. For these datasets, the mean and

median are calculated using the formulas:

, =+ 2 ∗ ∑ + ∑ − ∗ ∑ − − 12

2

, = 3

Determination of Dataset Distribution

The evaluation of the full dataset that extends from January 1, 2001 to the present indicates

that most months follow a log-normal distribution. The goodness of fit results using the Anderson-

Darling (A-D) test for both normal and log-normal distributions for the full dataset and the most

recent dataset are presented in Table 2. When the result presented in the table is greater than 0.05,

relating to a 95% probability, the dataset fit the specified distribution. The best fit distribution for

each case is highlighted in Table 2. The appropriate calculations will be used for calculating the

monthly averages.

Table 2. Goodness of Fit for a 95% Probability for Dataset at Fibreville

MONTH Normal Distribution Log-Normal Distribution

Full Dataset

July 1, 2010 –

Present Full Dataset

July 1, 2010 -

Present

January 0.00 0.03 0.23 0.16

February 0.00 0.00 0.20 0.34

March 0.02 0.20 0.12 0.22

April 0.00 0.00 0.40 0.10

May 0.00 0.00 0.08 0.29

June 0.00 0.00 0.22 0.37

July 0.00 0.90 0.19 0.01

August 0.00 0.00 0.21 0.24

September 0.00 0.00 0.00* 0.00*

October 0.00 0.00 0.25 0.60

November 0.00 0.01* 0.00* 0.00

December 0.00 0.04* 0.04* 0.01

Note: * = Value does not pass A-D test, but this distribution was used.

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EVALUATION OF IN-STREAM COLOR AVERAGES

Long-term Daily Average for each Month for In-Stream Color Concentrations Measured at

Fibreville

The long-term average of the daily concentration values for each month for the period from

July 1, 2010 through December 31, 2017 is presented in Table 3. This table demonstrates that the

color concentration measurements at Fibreville are less than or equal to 40 color units on a long-

term average for each month when flows are greater than or equal to the monthly 30Q2. The 90th

percentile column is presented since that method is used and accepted by EPA to determine if a

set of data for a pollutant parameter is meeting a numerical water quality standard. The table

shows that one month is as high as 61 color units at the 90th percentile, while the remaining months

are 53 color units or less. Though there is no North Carolina numerical water quality standard for

color, discussions of acceptable target values for the Pigeon River in the range of 50 to 100 have

been considered in the past. All of the values in Table 3 fall within or below this range.

Table 3. Long-term Daily Average Color Concentration for each Month for In-Stream

Measurements at Fibreville for July 1, 2010 through December 31, 2017

MONTH

DISTRI-

BUTION

TOTAL

NUMBER OF

VALUES

LONG-TERM

DAILY AVG.

WHEN FLOWS

>=A30Q2

(mg/L)

LONG-TERM

DAILY AVG.

WHEN FLOWS

>=M30Q2

(mg/L)

LONG-TERM

90th PER-

CENTILE

WHEN FLOWS

>=M30Q2

(mg/L)

Jan. LN 61 27 18 29

Feb. LN 57 27 19 30

Mar. LN 64 26 19 27

Apr. LN 60 22 20 29

May LN 62 26 23 34

Jun. LN 54 43 31 45

Jul. N 70 48 30 40

Aug. LN 72 46 40 61

Sep. LN 70 51 39 53

Oct. LN 70 45 35 51

Nov. N 71 49 31 46

Dec. N 71 36 25 38

Annual LN 782 34 27 41

Note: LN = Log Normal

A30Q2 = Annual 30Q2 Condition

M30Q2 = Monthly 30Q2 Condition

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The values in Table 3 do not represent a separation of background color and color

contributed by the Mill. The long-term daily average Park Street measurements for each month

are presented in Table 4.

Table 4. Long-Term Daily Average Color Concentration at Park Street Upstream for

July 1, 2010 through December 31, 2017

MONTH

DISTRI-

BUTION

TOTAL

NUMBER OF

VALUES

LONG-TERM

DAILY AVG.

WHEN FLOWS

>=A30Q2

(mg/L)

LONG-TERM

DAILY AVG.

WHEN FLOWS

>=M30Q2

(mg/L)

LONG-TERM

90th PER-

CENTILE

WHEN FLOWS

>=M30Q2

(mg/L)

Jan. LN 61 11 12 22

Feb. LN 57 10 12 21

Mar. LN 64 10 11 19

Apr. LN 60 12 15 28

May LN 62 12 12 18

Jun. LN 61 16 15 27

Jul. LN 70 15 14 21

Aug. LN 72 15 15 25

Sep. LN 69 17 19 29

Oct. LN 70 18 21 31

Nov. LN 70 16 17 25

Dec. LN 71 15 18 33

Annual LN 787 14 15 26

Note: LN = Log Normal

A30Q2 = Annual 30Q2 Condition

M30Q2 = Monthly 30Q2 Condition

Table 4 shows the variable nature of color in the Pigeon River upstream from the Mill. In

some months the expected long term daily average when flows are greater than or equal to the

Monthly 30Q2 are as high as 21 color units. The 90th percentile values in some months are as high

as 33 color units. Background concentrations have been measured as high as 94 mg/L in the Pigeon

River upstream from the Mill.11 This means that no numerical water quality value below this can

be a realistic target even if the Mill were not located on the river.

Determination of In-Stream Color Delta at Fibreville

The Pigeon River coming to the Mill in Canton has been measured for color on a routine

basis. Because of the variability in background color as shown in Table 4, an in-stream delta

between the background and the downstream location is more appropriate to evaluate the Mill’s

contribution to color in the River. Similarly to the in-stream values, the majority of the long-term

11 December 24, 2015 at Park Street Bridge in Canton

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daily average delta concentrations for each month do not fit a normal distribution. The long-term

daily average in-stream delta concentrations for each month are provided in Table 5.

This table demonstrates that for any month, the long term daily average contribution of the

Canton Mill to color at Fibreville when flows are greater than or equal to monthly 30Q2 is 25 true

color units or less. The 90th percentile of color contribution of the Canton Mill does not exceed 43

true color units for any month when flows are greater than or equal to the monthly 30Q2.

Table 5. Long-Term Daily Average In-Stream Delta Color Concentration at Fibreville

Bridge downstream for Each Month for July 1, 2010 through December 31, 2017

MONTH

DISTRI-

BUTION

TOTAL

NUMBER OF

VALUES

LONG-TERM

DAILY AVG.

WHEN FLOWS

>=A30Q2

(mg/L)

LONG-TERM

DAILY AVG.

WHEN FLOWS

>=M30Q2

(mg/L)

LONG-TERM

90th PER-

CENTILE

WHEN FLOWS

>=M30Q2

(mg/L)

Jan. LN 61 16 6 11

Feb. LN 57 17 7 14

Mar. LN 64 16 8 13

Apr. LN 60 10 5 11

May LN 62 14 11 21

Jun. LN 53 28 17 25

Jul. N 70 33 16 29

Aug. LN 72 32 25 43

Sep. N 69 34 21 41

Oct. LN 70 27 14 30

Nov. N 70 32 14 24

Dec. N 71 21 7 17

Annual LN 779 23 13 28

Note: LN = Log Normal

A30Q2 = Annual 30Q2 Condition

M30Q2 = Monthly 30Q2 Condition

Determination of Average Color on the French Broad River and Comparison to the Pigeon

River at or near the North Carolina – Tennessee state line

For comparison purposes, the color measurements collected on the French Broad River

upstream from Newport, Tennessee are also included in Table 6. It is noted that the difference

between the upstream and downstream locations on the French Broad River and on the Pigeon

River are both 3 color units. This is consistent with the general expectation that color increases in

the downstream direction as stream order increases.

The Tennessee Department of Environment and Conservation collects samples on the

Pigeon River near the state line, as well as, on the French Broad River at the Highway 70 Bridge

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(near Del Rio, TN) and at the Highway 321 Bridge (near Newport, TN). There are not enough

data points to calculate long-term daily averages for each month, nor to determine the proper

distribution of the datasets. Overall averages of the three datasets are presented, along with the

number of samples in each calculation.

Table 6. Comparison of Color Concentration for In-Stream Measurements on Pigeon

and French Broad Rivers

PARAMETER

PIGEON RIVER

AT PARK

STREET IN

CANTON

PIGEON RIVER

NEAR NC/TN

STATE LINE

FRENCH

BROAD RIVER

NEAR DEL RIO,

TN

FRENCH

BROAD RIVER

NEAR

NEWPORT, TN

Drainage Area (sq.

mi.) 130 538 1,713 1,858

Number of Samples 787 232 30 24

Samples Collected

by EPI TDEC TDEC TDEC

Average Color,

mg/L 14 17 22 25

Minimum Color,

mg/L 1 5 8 7

Maximum Color,

mg/L 94 43 63 110

Note: Both French Broad TDEC stations are upstream from the confluence of the Pigeon

River and the French Broad River near Newport, Tennessee.

The Pigeon River near the state line and the French Broad River near Del Rio are especially suited

for comparison purposes since 1) they both drain the identical ecosystem classification; 2) they are

both level 5 on the Schuler stream classification system (stream order); and 3) the French Broad

near Del Rio has no known large sources of color discharging to it. The comparison shows that

the Pigeon River near the state line actually has less color than the French Broad River near Del

Rio when compared to an equivalent stream system (i.e., same ecosystem and same order stream).

This indicates the Pigeon River at the state line does not have color levels outside of the expected

range for a stream with no large point source of color discharging to it. These data also show the

difference in color at the Park Street Bridge on the Pigeon River and the color at the state line on

the Pigeon River is only 3 color units which is outside the range perceptible by the human eye.

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SECTION 4.0

FINDINGS AND CONCLUSIONS

FINDINGS FOR THE PERIOD JULY 1, 2010 THRU DECEMBER 31, 2017:

The long-term daily average color concentration at the Fibreville Bridge when flows are greater

than or equal to the annual 30Q2 is 34.

The long-term daily average contribution of the Canton Mill to true color in the Pigeon River is

23 true color units when flows are greater than or equal to the annual 30Q2.

Based on a methodology used by and recognized by EPA, 30Q2 values for each month of the year

for the Pigeon River more accurately reflects the hydrologic cycle over the course of the year.

Color concentration measurements at Fibreville are less than or equal to 40 color units on a long-

term average for each month when flows are greater than or equal to the monthly 30Q2.

The 90th percentile of the long-term daily color concentrations at Fibreville when flows are equal

to or greater than the monthly 30Q2, ranged from 27 in March to 61 in August. (90th percentile

was examined from EPA’s guidance on comparing a set of data to a specific water quality standard

i.e. if the 90th percentile is less than a target value, then water quality standards are being met).

The long term daily average color concentration added, i.e., the delta, to the Pigeon River by the

Mill, at flows greater than or equal to the monthly 30Q2, is less than 25 color units for any month

except August. Also, the 90th percentile of the color concentration added by the Mill, at flows

greater than or equal to the monthly 30Q2, is less than 43 color units for any month except August.

The color concentrations in the Pigeon River upstream from the Mill are variable. In some months

the expected long term daily average color concentration, when flows are greater than or equal to

the monthly 30Q2, are as high as 21 color units; and 90th percentile values in some months are as

high as 33 color units. Also, color concentrations upstream from the Mill have been measured as

high as 94 color units. This means that no numerical water quality value below this can be a

realistic target even if the Mill were not located on the river.

OTHER FINDINGS:

Comparison of the French Broad River near Del Rio shows the Pigeon River at the Stateline does

not have color levels outside of the expected range for a stream with no large point source of color

discharging to it.

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The difference in the long-term daily average color concentration at Park Street in Canton,

upstream from the Canton Mill discharge, and the long-term daily average color concentration at

the North Carolina-Tennessee Stateline is 3 true color units.

CONCLUSIONS:

The long term daily average contribution (delta) of the Canton Mill to true color in the Pigeon

River is 23 color units at flows greater than or equal to the annual 30Q2. The long term daily

average color concentration at the Fibreville Bridge at flows greater than or equal to the annual 30

Q2 is 34 true color units. The difference in the long term daily average color concentration at Park

Street in Canton (14 true color units), upstream from the Canton Mill discharge and the long term

daily average color concentration at the North Carolina-Tennessee state line (17 true color units)

is 3 true color units. This difference is minimal and imperceptible to the human eye.

Though there is no North Carolina numerical water quality standard for color, discussions of

acceptable target values for the Pigeon River in the range of 50 to 100 have been considered in the

past. The long-term average and 90th percentile values at Fibreville and the long-term average and

90th percentile contributed by the Mill meet this target range.

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