S&A-TSB-12
INVESTIGATION OF THE EFFECTS OF THE
WASTE DISCHARGES FROM THE NORTHSIDE AND SOUTHSIDE
WATER TREATMENT PLANT RESERVOIRS
AT PUEBLO, COLORADO
ON WATER QUALITY AND BENTHIC ORGANISM
CONDITIONS IN THE ARKANSAS RIVER
OCTOBER 10-12, 1972
TECHNICAL SUPPORT BRANCH
SURVEILLANCE AND ANALYSIS DIVISION
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
DECEMBER, 1972

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S&A/TSB-12
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INVESTIGATION OF THE EFFECTS OF THE
WASTE DISCHARGES FROM THE NORTHSIDE AND SOUTHSIDE
WATER TREATMENT PLANT RESERVOIRS
AT PUEBLO, COLORADO
ON WATER QUALITY AND BENTHIC ORGANISM
CONDITIONS IN THE ARKANSAS RIVER
OCTOBER 10-12, .1.972
U.S.EPA REGION 8 ,
Technical Library 80C-L
999 18th street, Suite 500
Denver, CO 80202
v1'	AGENCT
' ' • ' . • ' ' \ >
: ••.	^v.103
TECHNICAL SUPPORT BRANCH
SURVEILLANCE AND ANALYSIS DIVISION
U. S. ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
December 1972

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TABLE OF CONTENTS
Page
I. Introduction 	 1
II. Study Description 	 1
III. Chemical Survey	4
A.	Methods	4
B.	Results and Discussion 	 4
IV. Biological Survey	7
-A. Methods	7
B. Results and Discussion	10
V. Conclusions and Recommendations	11
VI. References	12
VII. Appendix	13
i

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LIST OF FIGURES
Number	Page
1.	Map of Arkansas River Survey Area 	 2
2.	Average TSS Concentration vs Arkansas 	 6
River Miles
LIST OF TABLES
1.	Sample Station Locations for Chemical Sampling.	.	.3
2.	Average Chemical Data for Arkansas River Survey.	.	.5
3.	Sample Station Locations for Biological Sampling	.	.8
4.	Summary of Benthic Organisms Found in Arkansas .	.	.9
LIST OF TABLES
River Survey Area
i i

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INTRODUCTION
The Arkansas River originates near the Continental Divide in
Central Colorado and then flows eastward through the city of Pueblo
and on across the plains. As the river passes through the city of
Pueblo it is diverted for various industrial and irrigation uses and,
in return, it receives discharges from several sources. Two of the
major sources of waste discharges are the Northside and Southside Water
Treatment Plants. Each of these plants has large settling ponds used to
contain the sludges produced during the chemical treatment of river water
for potable use. Once each year during a two to three week period these
plants dispose of the accumulated solids by flushing them directly into
the Arkansas River.
Disposal of solid waste materials in this manner is not consistent
with the Colorado Water Quality Standards of September, 1971 (Ref. 1).
Although the standards do not list specific numerical limits for total
dissolved solids (TDS) or total suspended solids (TSS) in this stream
reach, there are several narrative standards which relate to solids
concentrations in all waters of the State. These standards state that
all wastes must be "free from substances that will form objectionable
bottom deposits" and "free from substances sufficient to be harmful to
human life or animal life."
STUDY DESCRIPTION
In order to assess the impact of these two water treatment plant
discharges on the Arkansas River, the Technical Support Branch of the
Regional EPA office conducted a study on October 10-12, 1972, during
the period of pond discharge. The basic objective was to determine
whether the solids in the discharges were of sufficient magnitude to
cause benthic organism and water quality degradation in violation of
the Colorado Water Quality Standards.
The study included chemical and biological sampling conducted at
four river stations in a three mile stream reach in the area of the
water treatment plants. The two pond discharges were also sampled for
chemical analysis. The map in Figure 1 shows the general survey loca-
tion and the sample stations. A description of the locations for chemical
sampling are presented in Table 1, while the biological sample locations,
which differed slightly from the water quality sampling stations, are
described in Table 3. All stations are numbered consecutively from the
upstream control station to downstream stations.
1

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NORTHSIDE
RESERVOIR
SOUTHSIDE
RESERVOIRS
LEGEND
/4TH ST. BRIDGE
/ \aR-4
LOW HEAD DAM
~ BIOLOGICAL SAMPLING STATIONS
@ CHEMICAL SAMPLING STATIONS
FIGURE 1 Map of Arkansas River Survey Area

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TABLE 1
Sample Station Locations for Chemical Sampling
Station Number 	Description	
AR-1	Arkansas River upstream from the effluent from the two
plants at the low head dam near the Southside Plant
Water Intake.
SSP-1	Effluent from the Southside Water Treatment Plant in
drainage ditch about 100 feet above confluence with the
Arkansas River.
AR-2	Arkansas River approximately 30 feet downstream from the
Southside Plant discharge to the river.
NSP-1	Effluent from the Northside Water Treatment Plant in
drainage ditch about 50 feet above confluence with the
Arkansas River.
AR-3	Arkansas River approximately 30 feet downstream from
the Northside Plant discharge to the river.
AR-4	Arkansas River downstream from the two water plants at
the low head dam near the 4th Street Bridge.
3

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CHEMICAL SURVEY
Methods
The collection of water samples for chemical analysis was conducted
at the six locations described in Table 1. At each location a one-liter
sample was collected for laboratory analysis for total dissolved solids
(TDS), total suspended solids (TSS), volatile suspended solids (VSS),
and pH. In addition, a 300 ml dissolved oxygen (DO) sample was col-
lected and preserved for later analysis in the laboratory. At the same
time various field measurements were made. They included the following:
PH
Conductivity
Temperature
DO (one day only)
Results and Discussion
The complete chemical results are presented in Table 1 in the Appendix.
These results are presented as average values for each parameter in Table
2. It is of interest to compare the results from the downstream station
(AR-4) with the results from the upstream control station (AR-1). These
two stations are located about three miles apart and bracket the pond
discharges. Results at these stations will, therefore, reflect the change
in water quality of the Arkansas River due to the pond discharges.
Several significant changes in water quality are evident from Table
2. The average dissolved oxygen content in the stream dropped from 9.2
mg/1 to 7.2mg/1 within the three mile reach "separating the^upstream and,down-
stream stations, representing a decrease of about 22%. This decrease can be
partially attributed to the relatively lower DO values observed in the
two discharges at SSP-1 and NSP-1. These average values were 6.8 mg/1
and 7.2 mg/1, respectively. However, it should be pointed out that the
DO in the river at all sample stations exceeded the minimum recommended
limit (>3 mg/1) specified in the existing stream standard (Class C) for
this reach of river.
A second significant change in water quality is related to the vastly
increased TSS concentrations observed at the downstream station (AR-4).
Table 2 shows that the average TSS value increased from 21 mg/1 at AR-1
to 150 mg/1 at AR-4. This increase is also depicted in Figure 2. The
increase in TSS can be directly related to the Southside and Northside
Plant discharges, which averaged 5900 mg/1 and 36,300 mg/1 TSS, respec-
tively. It should be pointed out that the TSS and VSS concentrations
4

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TABLE 2
Average Chemical Data for Arkansas River Survey




Parameter Average Value for
3 Measurements

Station
Ri ver
Temp
dH

00
Conduc.
TDS
TSS
VSS

Mi les
•c
Field
Lab
mg/l
^tmhos/cm
mg/l
mg/1
mg/l
AR-1
0
14.5
8.5
8.2
9.2
790
520
21
2
SSP-1
1-A
15.0
8.4
7.7
""6.8
870
570
5900
460
AR-2
1 .4
15.0
8.5
8.0
8.8
845
560
760
60
NSP-1
1.8
15.5
8.0
7.3
"7.2
750
520
36300
2650
AR-3
1.8
16.0
8.2
7.6
"8.6
815
535
8520
550
AR-4
2.9
16.0
7.7
7.9
7.2
820
560
150
15
* One Measurement
** Two Measurements

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FIGURE 2
Average TSS Concentration vs Arkansas River Miles
ARKANSAS RIVER MILES DOWNSTREAM FROM THE UPSTREAM DIVERSION DAM
6

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Results and Discussion continued
measured in the pond discharges varied over a wide range. For example,
Table 1 in the Appendix shows that the TSS concentration in the North-
side discharge varied from a low of 640 mg/1 on 10/12 to 73,400 mg/1 on
10/10. This variation is primarily due to the time of sample collection
in relation to the pond flushing operation. The nature of the pond
flushing operation is variable in itself, due to the fact that it con-
sists simply of men with high pressure water hoses scouring the pond
bottom free of accumulated solids. It is thought, however, that the
samples collected are fairly representative of the normal discharge
during the flushing operation.
The values for TSS and VSS in Table 2 for Stations AR-2 and AR-3
are much higher than at the downstream Station (AR-4). The reason for
this is because samples at Stations AR-2 and AR-3 were collected a short
distance downstream from the Southside and Northside discharges, respec-
tively, at which point the solids had not been uniformly diluted withl
the full river flow. The physical condition of the stream at these two
points consisted of an extremely turbid flow of water and extensive
mud-sludge deposits along the river bank. Several dead fish were also
observed at these two stations.
In addition to the relatively large DO and TSS changes observed in
the Arkansas River, a slight (10%) reduction ip pH also occurred in the
three mile study area. This reduction is shown in Table 2 for field
pH values, while for the lab pH values, a smaller decrease is noted. In
general, the pH value measured in the laboratory was about 6% lower than
pH values measured in the field. This difference is likely due to bio-
logical and chemical changes occurring in the sample during transporta-
tion and storage at the Laboratory.
BIOLOGICAL SURVEY
Methods
The benthic organism survey was conducted on October 10, 1972, and
covered about the same stream reach as the chemical survey. However, the
sample locations were displaced slightly downstream from the chemical
sample stations in order to find more suitable sampling sites. A descrip-
tion of the biological sample stations is presented in Table 3.
An earlier benthic organism survey was undertaken on August 3, 1972,
in this same stream reach. At that time high water flow precluded finding
7

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TABLE 3
Sample Station Locations for Biological Sampling
Station Number		Description	
1	Arkansas River about 50-100 yards downstream from
low head dam near the Southside Water Treatment
Plant.
2	Arkansas River about 300 yards downstream from
Southside water reservoir discharge point.
3	Arkansas River about 100 yards downstream from
Northside water reservoir discharge point.
4	Arkansas River about 50 yards downstream from
lowhead dam near the 4th Street Bridge.
suitable quantitative sampling sites. Therefore, qualitative samples
were collected about 30 feet downstream from both the Northside and
Southside reservoir discharges. In the October survey the river flow
had diminished to the extent that suitable sites for quantitative
sampling were found at all stations.
One qualitative sample and two square foot Surber samples were
collected at each station. Qualitative samples were collected with
dip nets and by picking organisms from rocks with forceps. The samples
were preserved in 10% formalin and transmitted to the EPA laboratory
for processing. In the laboratory, samples were sorted and organisms
classified to the lowest taxonomic level possible. These data are re-
corded in Table IV.
8

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TABLE IV
Sunmary of Benthic Organisms Found in Arkansas River Survey Area
Organism
Station #
1	2
Plecoptera (Stoneflies)
Neophascjanophora sp.
Ephemeropt.era (Mayflies)
Baetis sp.
Rithrogena sp.
TrTcorythcdes sp.
Heptageriia sp.
Centroptijun sp.
EpTienierFlYa""sp.
Stenonema "sp,
Trichoptera (Caddis flies)
Hydropsyche sp.
Lrachycentrus sp.
Amphipcda (scuds)
Gammarus sp.
H?miptera (vater bugs)
Aptvit j au i> .
Decapoda (crayfish)
Astacidae
Cdonata
Ophiogonphus sp. (dragon flies)
Agriomoe (damsel flies)
h'etaerina sp. (damsel flies)
Diptera
Chirononiidae (midges)
Tipulidae (crane flies)
Tabanidae (Horse flies)
Simulidae (Black flies)
Annelida
Oligochaeta (sludge worms)
6
Q
1
99
1
2
1
65
1
1
3
Q
Q
Q
Q
30
1
2
1
1
1
Q
Q
26
Q
Q
Q
Q
27
Total Number of Organisms/sq.ft.
Total Number of kinds
179
14
66
15
29
5
Q - Organism not collected in quantitative sample, arbitrarily assigned a value
of "1" for computing number of kinds.

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Results and Discussion
Pollution sensitive organisms in this report will be defined as
those which are incapable of withstanding adversely high concentrations
of suspended solids in the water. Their morphological adaptations re-
quire clean, sediment-free, rocky substrate to which they can remain
attached. Their gills are delicate and cannot tolerate the scouring
effect of high suspended solids. Organisms of this type include Plecoptera
(stone flies), Ephemeroptera (may flies), and Trichoptera (caddis flies).
Pollution tolerant organisms in this" context are those which can exist
in heavy sediment concentrations in water and in accumulated bottom de-
posits. These organismsare adapted to living in sediment deposits be-
cause of their worm-like anatomy. They are capable of respiration through
the body surface, and therefore do not require gills which are susceptable
to abrasion by sediments. Oligochaeta (sludge worms) are the major members
of this group found in the Arkansas River.
The diversity and number of organisms per square foot of substrate
decreased as one progressed from the upstream control station (Sta 1.)
to the extreme downstream station (Sta 4). At the control station (Sta 1)
the water was clear and the substrate free of any overlying sediments.
Sampling in the riffle areas at this location revealed a diversity of
fourteen different kinds of organisms and a total of 179 organisms per
square foot. There were eight different kinds of pollution sensitive
stoneflies, mayflies, and caddis flies for a total of 108 pollution
sensitive forms per square foot of substrate.
Downstream from the Southside reservoir discharge (Sta 2) was a
long (200 yards) shallow pool with a sediment layer approximately six
to twelve inches deep covering the bottom. Sampling was conducted in
a riffle area immediately downstream from this large pool. The pool
area upstream of this riffle area allowed considerable settling of sedi-
ments, and the swift water flow over the riffle kept the substrate
sparingly free of sediment accumulation. Even though this location
was downstream from the Southside sediment discharge, the conditions
created by the large pool and swift riffle made a suitable sediment-free
substrate for the benthic organisms. Fifteen different kinds of organisms
were found here for a total of 66 per square foot. Seven of the fifteen
kinds of organisms were pollution sensitive mayflies and caddis flies.
These pollution sensitive forms dropped from 108 per square foot at
Sta 1 to 17 per square foot at this location (Sta 2). Thus, even though
the diversities of organisms between stations 1 and 2 were similar the
increased sediment load did greatly deplete the number of pollution
sensitive forms per square foot of substrate. Pollution tolerant sludge
worms numbered 26 per square foot at this location compared to none at
Station 1.
For a distance of 50 yards downstream of the Northside reservoir
discharge (Sta 3) sediments covered the river bottom to a depth of about
six to twelve inches. Sampling was conducted approximately 100 yards
downstream from this discharge to insure thorough sediment mixing with
10

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the river water. The water at this location was very turbid (high in
TSS as shown in Table 1 in the Appendix), and the substrate had a sedi-
ment overlay approximately h inch in depth. Kinds of organisms dropped
to five with a total of 29 organisms per square foot of substrate being
recorded. In the five kinds of organisms present only two pollution
sensitive caddis flies were present, numbering two per square foot.
The other 27 organisms per square foot were pollution tolerant sludge
worms. This indicates further depletion of organisms from Station 2
due to the sediment load.
Downstream from the low head dam near the 4th Street bridge (Sta 4)
the turbidity of the water had greatly decreased from Station 3 (see
TSS values in Table 1 in the Appendix). Substrate consisted of large
pieces of shale (three by four feet) with some rocky areas in a small
side channel of the river. The number of kinds of organisms recorded
here was seven, with a total number of nine organisms per square foot.
This decline in number of organisms from the previous upstream station
is somewhat misleading. In looking at Table IV it can be seen that at
Station 3, 27 of the 29 organisms per square foot of substrate were
sludge worms. At Station 4 sludge worms were also present at a density
of seven per square foot. However, the substrate was not sedimented
over to the same extent as that at Station 3, which offered a less favor-
able habitat for this particular organism. Even though there was a de-
crease in number of organisms per square foot, there was a slight in-
crease in diversity of organisms from Station 3 to Station 4. This
diversity numbered seven different kinds of organisms at Station 4 com-
pared to five at Station 3. Two of this number were pollution sensitive
mayflies and caddis flies. This would tend to indicate some recovery
from the sediment load being discharged upstream. The recovery is likely
due to the settling out of some of the suspended solids upstream from
the low head dam at Station 4.
CONCLUSIONS AND RECOMMENDATIONS
The data from this three-day survey provides documentation from
which recommendations concerning the two Pueblo water treatment plant
discharges can be made. The conclusions and recommendations related
to the survey are presented below.
1. The discharge of pond sediments from the Northside
and Southside water treatment plants causes a seven-
fold increase in total suspended solids in the Arkansas
River. As a result of these discharges extensive
sludge deposits have built up along the river banks
immediately downstream from the discharges. This con-
dition violates the narrative standards of the Colorado
Water Quality Standards.
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2.	Dissolved oxygen (DO) values decreased by over 20% in
the affected stream reach near the discharges. However,
no existing water quality standards are violated, since
the DO remains above 7 mg/1.
3.	The heavy sediment discharges have a detrimental impact
on the benthic invertebrate organisms for at least two
and a half stream miles. Both the number of organisms
per square foot and the diversity of organisms (with the
exception of Station 3) declined from the upstream con-
trol station to the stations downstream from the discharges.
4.	It is recormiended that the practice of flushing pond sedi-
ments from the Pueblo Northside and Southside Water Treat-
ment Plants into the Arkansas River be discontinued. An
alternative sludge disposal system must be devised by the
city and put into operation. Such a system could include
sludge drying beds similar to those used for sewage sludge
dryi ng.
REFERENCES
1. Colorado Water Quality Standards Summary, Water Pollution
Control Commission, Colorado Department of Health, May 1,
1972.
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APPENDIX
13

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TABLE 1
Summary of Chemical Data for Arkansas River Survey
October 10-12, 1972
Station
Date Time Temp pH
DO, mq/1
Conductivity
TDS
TSS
VSS

UC Field | Lab.
Field Probe Lab Winkler
ymhos/cm
mg/1
mg/1
mg/1

10/10
1040
15.0
8.50
8.2
-
8.9
795
532
20.5
0.5
AR-1
10/11
1212
15.0
8.65
8.3
6.9
9.4
770
506
16.8
1.2

10/12
1020
13.0
8.40
8.0
-
9.2
805
526
24.8
4.0

10/10
1330
18.5
7.30
8.1
_
7.5
860
568
168
18
AR-2
10/11
1002
14.0
7.85
7.9
-
7.2
740
548
158
14

10/12
1230
15.0
7.90
7.8
-
6.8
860
562
124
13

10/10
1235
17.0
8.45
7.5
•
Too Muddy
815
550
8240
520
£ AR-3
10/11
1102
15.0
7.65
7.3
2.3
Too Muddy
805
526
17000
1120

10/12
1200
15.0
8.35
7.9
-
8.6
830
532
319
12

10/10
1125
15.0
9.00
8.1

8.8
850
566
1630
126
AR-4
10/11
1150
15.5
8.10
7.9
7.2
8.8
840
558
418
34

10/12
1100
14.0
8.45
8.0
-
8.8
850
562
228
20

10/10
1110
15.5
8.90
7.5
_
Too Muddy
890
566
15600
1200
SSP-1
10/11
1136
15.5
8.10
7.6
6.0
Jfc 5.7
850
580
1950
180

10/12
1045
14.5
8.25
7.9
-
8.0
870
570
153
10

10/10
1245
17.0
8.65
7.2
•
Too Muddy
635
542
73400
5520
NSP-1
10/11
1050
15.0
7.6
7.1
0.3
Too Muddy
805
496
35000
2400

10/12
1140
15.0
7.9
7.7
-
7.2
820
530
640
24

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