SIDESTREAM ELEVATED POOL AERATION (SEPA) STATIONS: EFFECTS ON IN-STREAM DISSOLVED OXYGEN by Thomas A. Butts, Dana B. Shackleford, and Thomas R. Bergerhouse Illinois Department of Natural Resources Illinois State Water Survey 2204 Griffith Drive Champaign, Illinois 61820-7495 ABSTRACT As a result of increased pollutant loading and low in-stream velocities, dissolved oxygen (DO) levels in the Chicago waterways historically have been low. In 1984 the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) issued a feasibility report on a new concept of artificial aeration referred to as sidestream elevated pool aeration (SEPA). The SEPA station concept involves pumping a portion of water from a stream into an elevated pool. The water is then aerated by flowing over a series of cascades or waterfalls, returning to the stream. The MWRDGC proceeded with design criteria for SEPA stations as a result of experimental work performed by the Illinois State Water Survey (ISWS). Five SEPA stations were constructed and placed in operation along the Calumet River, Little Calumet River, and the Cal-Sag Channel waterway. In 1995 the ISWS returned to conduct research to evaluate the reaeration efficiencies and their effects on in-stream DO. Continuous monitoring of DO, temperature, pH, and conductivity was performed at 14 locations along the Calumet and Little Calumet Rivers, Cal-Sag Channel, and Chicago Sanitary and Ship Canal to evaluate the effectiveness of the SEPA stations on maintaining in-stream DO concentrations. Also, supplemental cross-sectional measurements were made at the 14 locations and at an additional seven locations. Comparisons of mass balance, completely mixed, in-stream mean DO concentrations at the SEPA station outfalls and those measured at cross-sectional stations immediately downstream of each SEPA station were made. Results showed that each SEPA station has an immediate positive impact on in-stream DO concentrations. At SEPA stations 1 and 2, where the impacts are small, the positive effects can best be demonstrated using completely mixed values. Two important conclusions can be made. One is that the SEPA stations, particularly stations 3, 4, and 5, are fulfilling the intended function of maintaining stream DO standards in the Calumet and Little Calumet Rivers and the Cal-Sag Channel. The second is that DO concentrations less than the DO standard are still observed in the Chicago Sanitary and Ship Canal in the reach beginning above its juncture with the Cal- Sag Channel to the Lockport Lock and Dam. Over the entire study period, DO concentrations were maintained above the standard 98.6 percent of the time from the SEPA station 3 outfall to the intake of SEPA station 4 and 97.5 percent of the time from the outfall of SEPA station 4 to the intake of EPA station 5. Significant improvements in DO concentrations were also achieved for at least 4 miles downstream of SEPA station 5 in the Chicago Sanitary and Ship Canal. ii i iv CONTENTS Page INTRODUCTION...............................................................................................................1 Background......................................................................................................................1 Study Objectives..............................................................................................................2 Acknowledgments............................................................................................................3 METHODS AND PROCEDURES.....................................................................................4 Study Area........................................................................................................................4 Station Locations.............................................................................................................4 Monitor Installation Designs............................................................................................5 Study Period.....................................................................................................................7 Field Operations...............................................................................................................9 Monitor Exchanges.......................................................................................................9 Cross-sectional DO/Temperature Measurements.......................................................10 Nitrogen Sampling......................................................................................................12 Laboratory Operations and QA/QC Procedures.............................................................12 Monitor Preparation and Use......................................................................................12 Quality Assurance/Quality Control............................................................................14 Data Reduction and Analyses........................................................................................15 Probability Analyses...................................................................................................15 Comparative Analyses................................................................................................18 RESULTS..........................................................................................................................20 Continuous Monitoring DO...........................................................................................20 Temporal (Station) Profiles........................................................................................21 Longitudinal Profiles..................................................................................................21 Other Parameters........................................................................................................22 Cross-sectional DO/Temperature...................................................................................22 DO Probability Distributions.........................................................................................25 DISCUSSION...................................................................................................................27 CONCLUSIONS...............................................................................................................39 REFERENCES..................................................................................................................44 TABLES............................................................................................................................45 FIGURES..........................................................................................................................78 Appendix A. YSI Model 6000 121 UPG........................................................................................................................... Appendix B. Continuous, Hourly DO Measurements.....................................................129 Appendix C. Summary of Continuous Monitoring for pH and Specific Conductance and Manually Collected Nitrogen Data...............................................147 Appendix D. Ten Most Variable Cross-sectional DO Patterns Shown with Delimiting Isopleths..................................................................................................153 Appendix E. Hourly DO Probability Curves for Each Monitoring Station by Period....165 Appendix F. Daily Mean Probability Curves for Each Monitoring Station by Period....199 v SIDESTREAM ELEVATED POOL AERATION (SEPA) STATIONS: EFFECTS ON IN-STREAM DISSOLVED OXYGEN by Thomas A. Butts, Dana B. Shackleford, and Thomas R. Bergerhouse INTRODUCTION As a result of increased pollutant loading and low in-stream velocities, dissolved oxygen (DO) levels in the Chicago waterway historically have been low. During the 1970s, water quality modeling was performed by the Metropolitan Water Reclamation District of Greater Chicago (District) to evaluate the effectiveness of tertiary treatment on reducing the occurrence of low DO levels. The results were not encouraging. The construction of advanced waste treatment facilities at each of the three major District plants would result in the expenditure of hundreds of millions of dollars while producing questionable results. Consequently, the District began investigating in-stream aeration as an alternative for increasing waterway DO concentrations. Background During the late 1960s the District considered four in-stream aeration approaches: barge-mounted aeration devices, in-stream mounted mechanical aerators, U-tubes at head-loss structures, and diffused air systems using ambient air blowers or molecular oxygen. The in-stream mechanical system, although the most cost-effective, could not be used because of navigational considerations. The District evaluated the barge-mounted system in Chicago area waterways, but it did not prove to be practical. The U-tubes are not applicable at most locations at which chronic low DO concentrations occur in the Chicago area waterways because such installations require large instantaneous head losses to operate. By default, diffused aeration was selected by the District for supplementing waterway DO at ten locations, and two diffused aeration stations were built. In 1979, the Devon Avenue station was completed on the North Shore Channel. A second aeration station was constructed at Webster Street on the North Branch of the Chicago River and became operational in 1980. These diffused aeration stations experienced operational and maintenance problems. Prior to building eight additional aeration stations, the United States Environmental Protection Agency (USEPA) deferred on its demands for the District to build advanced wastewater treatment plants while, in turn, endorsing the use of in-stream aeration. This reversal in opinion prompted an immediate search for an improved technological approach to aerating the waterways. In 1984, the District (Macaitis et al., 1 1984) issued a feasibility report on a new concept of artificial aeration referred to as sidestream elevated pool aeration (SEPA). The SEPA station concept involves pumping a portion of the water from the stream into an elevated pool. The water is then aerated by flowing over a cascade or waterfall that returns the aerated water to the stream. Over the next several years, modifications were made to the SEPA station design originally proposed by Macaitis et al. (1984). In particular, Tom Butts, with the Illinois State Water Survey (ISWS), suggested using a stepped-weir system in place of a continuous cascade or one large waterfall. As a result, research scientists from the ISWS and the District’s Research and Development Department cooperated in conducting full- scale testing of a sharp-crested weir system during 1987 and 1988. A prototype SEPA station was built along the Chicago Sanitary and Ship Canal at the District’s Stickney Water Reclamation Plant. This experimental work led to the development of SEPA station design criteria by Butts (1988). Information and recommendations in this report (Butts, 1988) were used by District consultants to design five SEPA stations along the Calumet waterway system (figure 1). Figures 2-6 are photographs of all five SEPA stations. Table 1 presents waterway mile locations and basic design features of all five SEPA stations. Study Objectives Additional artificial aeration stations are being planned for future locations along the Chicago waterway system. But, information is needed on the operating characteristics of the SEPA stations and their effects on DO concentrations in the waterways below their discharge. In a November 25, 1994, letter to James Park of the Illinois Environmental Protection Agency (IEPA), the District proposed a two-year study to accomplish five objectives. Three of these objectives were addressed through a two-phase study, conducted between 1995 and 1997, which was designed to: • Determine the actual oxygen transfer rate due to the waterfalls at the SEPA stations. • Determine the actual oxygen transfer rate due to the spiral-lift screw pumps at the SEPA stations. • Determine the effect of the operation of the SEPA stations on the DO levels in the Calumet waterway system. This report presents the results and conclusions relative to the third objective. The first two objectives are addressed in a separate report (Butts et al., 1999). The work tasks to address the third objective were deemed the highest priority by ISWS researchers and were performed first. Therefore, this part of the overall study is designated Phase I. Consequently, the studies associated with the first two objectives were designated Phase II. 2 Acknowledgments This study was funded by the Research and Development (R & D) and Engineering Departments of the District. Irwin Polls R & D project leader and liaison to the ISWS provided scheduling and sampling input. David Tang of the District’s Maintenance and Operations Department provided SEPA station operational data used in this report. Thanks are extended to ISWS personnel Bob Larson and Bill Meyer for their intensive efforts in the field and in the laboratory, which helped make this study successful. Bill Meyer’s role was especially significant in that he was responsible for preparing the monitors/dataloggers for field use, downloading and filing data, and performing quality assurance/quality control (QA/QC) procedures. This report was prepared under the general administration of Derek Winstanley, Chief of the ISWS. The original manuscript was typed by Linda Dexter and edited by Eva Kingston and Agnes Dillon. The views expressed in this report are those of the authors and do not necessarily reflect the views of the sponsor or the Illinois State Water Survey. 3 METHODS AND PROCEDURES The approach used for determining the effects that SEPA stations have on in- stream water quality was to install continuous water quality monitors at critical points along portions of the Calumet and Little Calumet Rivers, the entire Cal-Sag Channel, and the Chicago Sanitary and Ship Canal below its junction with the Cal-Sag Channel. All continuous monitoring data were recorded hourly. Monitors were installed in early spring 1996 and were left in place until late fall 1996. Also, cross-sectional DO readings were made periodically at each monitoring station to generate data for relating mean cross- sectional DO values to the point values generated by the continuous monitors. An ancillary study was performed to determine the extent of in-stream nitrification in the study area waterways. Study Area Figure 1 shows the study area. Monitors were installed in the following waterways: Waterways Evaluated in Study Area Inclusive river Waterway mile designation Calumet River 328.1-326.6 Little Calumet River 326.6-319.8 Cal-Sag Channel 319.8-303.3 Chicago Sanitary and Ship Canal 303.3-291.2 Monitoring was extended to the Lockport Lock and Dam (river mile or RM 291.2) along the Chicago Sanitary and Ship Canal to provide background data for evaluating possible needs for additional aeration below the junction of the Cal-Sag Channel and the Chicago Sanitary and Ship Canal. Station Locations The DO data were generated by using remote continuous water quality monitors/dataloggers and periodically measuring and recording DO and water temperatures manually at selected cross-sectional locations. Cross-sectional measurements were made at all continuous monitoring waterway river mile point locations and at supplemental locations considered essential to the development of well defined longitudinal DO profiles. Temperature measurements were made in concert with all DO measurements. Additionally, pH and conductivity were continuously monitored. 4 Fourteen continuous monitoring sites were established, and seven supplemental manual sampling locations were selected. Manually recorded point (vertical) measurements were made in the outfalls at all five SEPA stations. Table 2 presents the monitoring and/or sampling station locations and descriptions, including river mile points and type of station. Cross-sectional measurements consisted of selecting a number of horizontal locations on transects and measuring DO/temperature at selected depths on verticals at these horizontal locations. Reference to vertical measurement stations indicates DO/temperature readings were taken at selected depths on only one vertical at a location. Monitor Installation Designs Various monitor housing and restraining riggings were used at the sampling stations. Variables considered in the designs were benthic conditions, commercial navigation, vandalism, accessibility, and representativeness (with respect to cross- sectional water quality). Three basic designs were developed and used; descriptions and figure numbers are: Monitor Rigging Designs Type Description Figure number I Horizontal bottom line, single shroud 7a IA Horizontal bottom line, double shroud 7b II Vertical line off wall, attached shroud 8 IIA Vertical line off wall, 2 attached shrouds 9 IIB Vertical line off wall, fixed shroud 9 III Floating shroud 10 Figures 11-15 are photographs of the three basic systems. Table 2 gives the type of installation used at each of the 14 monitoring stations. Schematic diagrams showing the areal locations and rigging layouts for each station are shown (figures 16a-16n). These rigging designs and transect placements were derived through trial runs conducted during the summer and fall of 1995 and by modifying “permanent” installations used during the 1996 monitoring time period. During 1995, type II installations with monitors were placed at the intakes of SEPA stations 3 (RM 318.08) and 4 (RM 311.55), and type IIA and IIB installations were placed at the Lockport Lock and Dam. Also during 1995, type I or IA riggings were placed at monitoring station 13 (RM 310.70) on the Cal-Sag Channel, the intake of SEPA station 5 (RM 303.63), and monitoring station 17 (RM 302.56) on the Chicago Sanitary and Ship Canal. Monitoring was done at stations 15 and 17 but not at station 13 during this period. Monitoring station 13 is less than 12 feet deep; consequently, the decision not to install a monitor in the rigging for a lengthy trial period was made. This shallow location experiences heavy barge traffic, and a centerline submerged rigging appeared to 5 be vulnerable to entanglement by passing barge tows. This concern, here and at two similar sites, proved to be justified and expensive. All monitoring installations were placed into operation between March 13 and 15, 1996. The shallow, type IA installation at monitoring station 13 had remained in place, unscathed, during fall 1995 and winter 1995-1996. Consequently, such a setup seemed safe and was “permanently” installed at this site and at monitoring stations 7 (RM 320.71) and 10 (RM 317.62), among others. However, the rigs at these three sites, including encased DataSonde I monitors, were quickly lost; lost dates for monitoring stations 7, 10, and 13 were April 17, May 2, and April 18, 1996, respectively. DataSonde I monitors were initially installed at all locations instead of the new YSI 6000 units to minimize the trauma of losing a unit from a barge accident. This obviously proved to be a wise decision. To adjust for these losses, a type I rigging was placed along the left bridge headwall at monitoring station 10 (figure 16f), and type II riggings were placed at monitoring stations 7 and 13 as shown on figures 16d and 16h. These placements remained intact during the remainder of the study. During the 1995 trial run, the type IA rigging placed at the intake of SEPA station 5 was secured with a heavy log chain that eventually was crushed and broken by barges that frequently glide along the wall. Fortunately, the rigging was retrieved undamaged. Consequently, the 1996 permanent installation was provided with a retrieval line secured in the Illinois and Michigan Canal (figure 16j) instead of the chain. Most type I and IA riggings were retrieved using a side-line attached to a downstream light weight that was attached to the bank as shown by figure 17. The use of a sideline at monitoring station 17 (RM 302.56) was eventually abandoned because it was routinely cut during barge fleeting, a frequent occurrence in this area of the Chicago Sanitary and Ship Canal. During the remainder of the study, this rigging was routinely recovered with a grappling hook. The type I rigging at the intake of SEPA station 1 (RM 328.10) also routinely was recovered with a hook in lieu of a sideline. Problems were encountered with the original type IA rigging installed at the inlet area of SEPA station 2 (RM 321.32) because of deep flocculent sediment deposits. The sediment problem was not entirely unforeseen. A type IA system was used to raise the monitor off the bottom and keep the shroud from sinking into the muck. However, the extremely flocculent nature of the sediments had not been recognized fully, and this provision failed. Consequently, the type IA rigging was replaced with a type III floating box, which kept the monitors from contacting the bottom. The installations at the Lockport Lock and Dam are modified versions of the standard type II rigging. The modifications had to be made to accommodate three problems: deep water, extremely variable water levels, and DO stratification. The water depth is normally about 28 feet at monitoring station 21 (figure 16n), but it may drop as low as 15 feet in a few hours when the Lockport Powerhouse releases large amounts of water in anticipation of impending storms. Because of the deep water and high sediment 6