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 ------- £PA c<>3o-$,- ni-bbi/- S&A/TSB-12 C~f i 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- FIGURE 2 Average TSS Concentration vs Arkansas River Miles ARKANSAS RIVER MILES DOWNSTREAM FROM THE UPSTREAM DIVERSION DAM 6 ------- 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 ------- 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 ------- 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. ------- 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 ------- 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. 11 ------- 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. 12 ------- APPENDIX 13 ------- 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 ------- |