Stream Dissolved Oxygen Improvement Feasibility Study for the East Branch of the DuPage River%3A Final Report

              DUPAGE RIVER SALT CREEK WORK GROUP
STREAM DISSOLVED OXYGEN
IMPROVEMENT FEASIBILITY STUDY
FOR THE EAST BRANCH OF
THE DUPAGE RIVER
FINAL REPORT
DECEMBER 2008
Prepared by:
HDR Engineering, Inc.
8550 W. Bryn Mawr Ave., Suite 900
Chicago, IL 60603
Job No. 31566
This report was prepared in part using U.S. Environmental Protection Agency funds under
Section 319 of the Clean Water Act distributed through the Illinois Environmental Protection
Agency. The findings and recommendations herein are not necessarily those of the funding
agencies
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TABLE OF CONTENTS
1 EXECUTIVE SUMMARY ......................................................................................................................... 1-1
2 PROJECT BACKGROUND AND GOALS.............................................................................................. 2-1
2.1 PROJECT GOAL .......................................................................................................................................... 2-1
2.2 WATER QUALITY STANDARDS ................................................................................................................... 2-2
3 EXISTING CONDITIONS ......................................................................................................................... 3-2
3.1 GEOMORPHIC ASSESSMENTS ...................................................................................................................... 3-2
3.1.1 Channel Evolution ............................................................................................................................. 3-2
3.1.2 Bank Erosion .................................................................................................................................... 3-2
3.1.3 Sediment Transport........................................................................................................................... 3-2
3.1.4 Geomorphic Disturbances ................................................................................................................. 3-2
3.2 STREAM CHARACTERIZATION .................................................................................................................... 3-2
3.3 FLOW DATA .............................................................................................................................................. 3-2
3.4 REACH DESCRIPTIONS ............................................................................................................................... 3-2
3.5 HABITAT SUMMARY.................................................................................................................................. 3-2
3.6 DAM SITE INVESTIGATIONS....................................................................................................................... 3-2
3.6.1 East Branch DuPage / Prentiss Creek Dams..................................................................................... 3-2
3.6.2 Churchill Woods Dam ....................................................................................................................... 3-2
3.7 SEDIMENT OXYGEN DEMAND (SOD) FIELD MEASUREMENTS.................................................................... 3-2
3.7.1 Findings............................................................................................................................. 3-18
3.8 CONTINUOUS DISSOLVED OXYGEN MONITORING ...................................................................................... 3-2
3.9 SUMMARY ............................................................................................................................................... 3-20
4 WATER QUALITY MODELING............................................................................................................. 4-2
4.1 CONVERSION FROM QUAL2E TO QUAL2K MODEL.................................................................................. 4-2
4.1.1 Model Result Comparisons ................................................................................................................ 4-2
4.1.2 Conclusion ........................................................................................................................................ 4-2
4.2 VALIDATION OF QUAL2K MODEL ............................................................................................................ 4-2
4.2.1 Changes in Model Input..................................................................................................................... 4-2
4.2.2 Comparisons of Model and Observed Data....................................................................................... 4-2
4.2.3 Sensitivity Analysis ............................................................................................................................ 4-2
4.3 MODEL REVISIONS .................................................................................................................................... 4-2
4.4 MODELING DO IMPACTS .............................................................................................................................. 4-2
5 SCREENING FOR DAMS ......................................................................................................................... 5-2
5.1 COMPLETE REMOVAL................................................................................................................................ 5-2
5.2 REMOVAL WITH CONSTRUCTED RIFFLES.................................................................................................... 5-2
5.3 PARTIAL REMOVAL OR BRIDGING .............................................................................................................. 5-2
5.4 ISSUES COMMON TO ALL DAMS ................................................................................................................. 5-2
5.4.1 Permitting ......................................................................................................................................... 5-2
5.4.2 Reservoir Sediment ............................................................................................................................ 5-2
5.4.3 Flood Impact..................................................................................................................................... 5-2
6 SCREENING FOR STREAM AERATION.............................................................................................. 6-2
6.1 AIR-BASED ALTERNATIVES....................................................................................................................... 6-2
6.1.1 Simple Aeration ................................................................................................................................ 6-2
6.1.2 Mechanical Aeration......................................................................................................................... 6-2
6.1.3 Bubble Aeration................................................................................................................................ 6-2
6.2 HIGH-PURITY OXYGEN ALTERNATIVES ..................................................................................................... 6-2
6.2.1 Simple Oxygenation Using High-Purity Oxygen ............................................................................... 6-2
6.2.2 Bubble Oxygenation Using High-Purity Oxygen............................................................................... 6-2
6.3 SIDE-STREAM ALTERNATIVES................................................................................................................... 6-2
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6.4 OVERVIEW OF FEASIBLE ALTERNATIVES ................................................................................................... 6-2
7 EVALUATION........................................................................................................................................... 7-2
7.1 EVALUATION CRITERIA............................................................................................................................. 7-2
7.2 CHURCHILL WOODS DAM .......................................................................................................................... 7-2
7.2.1 Churchill Woods Dam Alternatives ................................................................................................... 7-2
8 IMPLEMATION PLAN ............................................................................................................................. 8-1
8.1 CONCEPT PLAN DEFINITION................................................................................................................... 8-1
8.1.1 Project Conception Development ...................................................................................................... 8-1
8.1.1.1 Dam Removal .......................................................................................................................... 8-1
8.1.1.2 Impoundment Sediment Management ........................................................................8-2
8.1.1.3 Stream Channel Restoration ...................................................................................8-3
8.1.2 Agency and Stakeholder Coordination .................................................................................................... 8-4
8.2 COST ESTIMATING AND FUNDING......................................................................................................... 8-4
8.2.1 Cost Estimates .................................................................................................................................. 8-6
8.2.2 Funding............................................................................................................................................. 8-6
8.2.2.1 State and Federal Programs.................................................................................................... 8-7
8.2.2.2 DuPage County Wetland Mitigation Banking..............................................................8-8
8.2.2.3 Private and Non-Profit Organizations……………………………………………………………….8-8
8.3 DESIGN, PERMITTING, AND CONSTRUCTION ................................................................................ 8-8
8.4 OPERATION AND MONITORING.........................................................................................................8-10
9 SOURCES ................................................................................................................................................... 9-2
LIST OF APPENDICES
A – Dissolved Oxygen Monitoring Results
TABLE OF TABLES
Table 2-1 - IPCB DO standards................................................................................................................................ 2-2
Table 3-1 - Impacts of Urbanization on Channel Stability ........................................................................................ 3-2
Table 3-2 - Point Source Discharges8 ........................................................................................................................ 3-2
Table 3-3 - Published River Flows9 ........................................................................................................................... 3-2
Table 3-4 - SHAP Ratings10 ..................................................................................................................................... 3-2
Table 3-5 - SHAP Scores.......................................................................................................................................... 3-2
Table 3-6 - Qualitative Habitat Evaluation Index11 ................................................................................................... 3-2
Table 3-7 - QHEI Scores by River Mile .................................................................................................................... 3-2
Table 3-8 - River Dam Information.......................................................................................................................... 3-2
Table 3-9 - SOD Survey Locations........................................................................................................................... 3-2
Table 3-10 - DO Monitoring Locations ................................................................................................................. 3-220
Table 6-1 - Aeration Alternatives .............................................................................................................................. 6-2
Table 6-2 - Aeration Alternative Rankings................................................................................................................ 6-2
Table 7-1 - Alternative Evaluation Criteria ............................................................................................................... 7-1
Table 7-2 - Churchill Dam Modification - Complicating Conditions........................................................................ 7-2
Table 7-3 - Churchill Dam Modification - Advantageous Conditions ...................................................................... 7-2
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TABLE OF FIGURES
Figure 3-1 - Channel Evolution Model1 .................................................................................................................... 3-2
Figure 3-2 - Prentiss Creek Dam.............................................................................................................................. 3-2
Figure 3-3 - Churchill Woods Dam........................................................................................................................... 3-2
Figure 3-4 - Water Surface Profile at Churchill Woods Dam.................................................................................... 3-2
Figure 3-5 - Dam Outlet Structure............................................................................................................................ 3-2
Figure 3-6 - Location Map........................................................................................................................................ 3-2
Figure 3-7 - Continuous DO Monitoring Locations 2007 ....................................................................................... 3-19
Figure 4-1 - Water Quality Model Development Steps ............................................................................................. 4-2
Figure 4-2 - Comparison of QUAL2K and QUAL2E DO Results............................................................................ 4-2
Figure 4-3 - Bensenville Rainfall Data for 2005 Period15.......................................................................................... 4-2
Figure 4-4 - Comparison of Observed and Predicted DO – Validation Run (8/20/06).............................................. 4-2
Figure 4-5 – East Branch DuPage – Calibration Resuts .......................................................................................... 4-29
Figure 4-6 – East Branch DuPage – Baseline DO..................................................................................................... 4-2
Figure 5-1 - Dam Removal Example........................................................................................................................ 5-2
Figure 5-2 - Riffle Details......................................................................................................................................... 5-3
Figure 5-3 - Examples of Riffle Usage ...................................................................................................................... 5-2
Figure 6-1 - Mechanical Aeration Display ................................................................................................................ 6-2
Figure 6-2 - Bubble Aeration.................................................................................................................................... 6-2
Figure 6-3 - Low Head Oxygenators ......................................................................................................................... 6-2
Figure 6-4 - Diffuser Used for Bubble Aeration........................................................................................................ 6-2
Figure 6-5 - Side-Stream Aeration Facility ............................................................................................................... 6-2
Figure 7-1 – East Branch DuPage – Future Churchill Woods Dam Removal ......................................................... 7-22
Figure 7-2 - Alternative 1 ....................................................................................................................................... 7-25
Figure 7-3 - Alternative 2 ......................................................................................................................................... 7-2
Figure 7-4 - Churchill Woods................................................................................................................................... 7-2
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1 EXECUTIVE SUMMARY
The East Branch of the DuPage River (East Branch) is listed as an impaired waterway in the
303(d) list. Dissolved oxygen (DO) is listed as one of the causes of impairment. This study was
undertaken to address alternative approaches for improving the DO levels on the East Branch
during lower flow periods.
As an initial step, a DO model was developed. Model development was supported by a DO
monitoring program undertaken by the DuPage River Salt Creek Work Group (DRSCW) and by
sediment oxygen demand measurement collected along the waterway.
The East Branch is an urban stream with low hydraulic gradients and extensive channelization.
Eight municipal wastewater treatment plants discharge to the East Branch, and during low flow
periods comprise a significant portion of the overall flow. In addition, two dams of significance,
the Churchill Woods Dam and Prentiss Creek Dam, are located along the East Branch. The DO
monitoring efforts indicated the Churchill Woods Dam was causing DO levels below 2.0 mg/L
above the dam, while at the Prentiss Creek Dam did not have a significant effect on DO levels.
A QUAL2K model was developed using available data. The model was calibrated using DO
data collected between August 13 and 17, 2006. A validation run was then completed for August
20, 2006, that showed overall good agreement between modeled and observed. For the baseline
model, the highest stream temperatures recorded over the past decade were utilized at the 7-day,
10-year low flows. BOD5 loading from the municipal treatment plants was based on the actual
monthly average levels reported by the individual plants, as opposed to the maximum permitted
concentrations. This approach provided a model that more closely matched actual stream
conditions.
Options for partial and complete dam removal were explored. Options for stream aeration were
also explored. These options included air-based and oxygen-based systems, both instream and
side stream. Oxygen-based systems have a distinct advantage of requiring fewer installations, as
the stream DO can readily be increased to 150 percent of saturation. The shallow conditions that
exist throughout much of the East Branch limits the use of instream air-based technologies to the
deeper pools.
From both the modeling and DO monitoring completed, Churchill Woods was identified as the
most significant cause of low DO levels. The model predicted that with the Churchill Woods
Dam removed, minimum DO levels throughout the East Branch would approach 5 mg/L under
low flow conditions. Continuous DO monitoring further downstream at Hidden Lake in 2006
revealed minimum DO levels between 5 and 6 mg/L, consistent with the model. However, in
2007, minimum DO levels in Hidden Lake fell consistently below 4.0 mg/L. The maximum DO
levels during these same periods were near 14 mg/L, versus 10 to 12 mg/L in 2006, suggesting
more plant/algal activity in 2007. This higher DO flux suggests the calibrated model for the
Hidden Lake reach may understate the photosynthesis /respiration rates for some years.
Based on the modeling and monitoring, removal of the Churchill Woods Dam is the project that
will have the greatest benefit in providing higher DO levels to the East Branch. Sediment
management is a critical component to dam and is likely to be the most costly part of such a
project. Complete sediment removal is estimated to have a total projected cost between $5 and
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$8 million, depending on how the sediment is managed. If only 50% of the sediment is removed,
the cost would decline by approximately half, or $2.5 to $4.0 million. Sediment characterization
is on-going by the EB/SCWG that will allow for a more definitive cost estimate.
Based on the modeling and monitoring, there will likely be at least one area (Hidden Lake),
where DO levels of 5.0 mg/L may not be achieved every year. It is recommended that the
Churchill Woods Dam removal be completed, and subsequent monitoring be completed before
proceeding with any additional project to address low flow DO levels. The location of the
minimum DO may shift somewhat once Churchill Woods Dam is removed.
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2 PROJECT BACKGROUND AND GOALS
Between 1992 and 1998, the East Branch of the DuPage River (East Branch) was listed on the Section
303(d) List of Impaired Waters by the Illinois Environmental Protection Agency (IEPA) as impaired for a
number of water-borne pollutants including nutrients, low dissolved oxygen, and chlorides. In October
2004, Total Maximum Daily Loadings (TMDLs) for this stream were completed by the Illinois
Environmental Protection Agency and approved by the United States Environmental Protection Agency
(EPA). The TMDL report developed for the East Branch includes a discussion of the potential for
improving stream dissolved oxygen (DO) by removing existing dams and/or by constructing and
operating an in-stream aeration program. Two principle dams exist on the East Branch of the DuPage
River. One dam is at Crescent Boulevard, known as Churchill Woods Dam, and the second structure is
located at the confluence of Prentiss Creek and the East Branch.
Since the publication of the TMDL reports, a group of communities, publicly owned treatment works
(POTWs), and environmental organizations formed the DuPage River Salt Creek Workgroup (DRSCW)
to better understand the causes of degraded water quality and, in particular, to find ways to improve DO
levels in the East Branch.
2.1 Project Goal
The goal of this study is to evaluate alternatives available to meet the dissolved oxygen water quality
standard on the East Branch of the DuPage River. Preferred alternatives will be those that will have the
greatest stream benefit and can be readily implemented.
This study was initiated to identify:
1. Criteria for selecting technologies appropriate for various sites where stream aeration could be
used to improve DO levels during low flow conditions.
2. The impact the two dams are having on DO, and where significant, identify appropriate project(s)
for specific dam sites, i.e., complete removal, ‘bridging,’ or some other modification that meets
project goals while addressing applicable concerns.
3. Potential sites where stream aeration equipment would provide an opportunity to raise stream DO
to levels where water quality standards would be achieved during low flow periods.
4. Applicability of alternative technologies available to provide stream aeration, such as mechanical,
diffused air, side-stream elevated pool aeration (SEPA), and high purity oxygen injection (either
in-stream or side-stream).
5. Permitting authorities, required permits, and regulatory issues.
6. Environmental impact on water quality and stream habitat, in addition to secondary impacts and
other community issues such as adjacent land use.
7. Financial impacts, including project capital costs (including sediment removal and disposal costs),
operation and maintenance needs, and costs associated with stream improvement projects (life
cycle depreciation costs).
8. Dam owners and nearby landowners affected by stream improvement projects, along with their
interest in accommodating such a project, and a description of the social impacts of stream
improvement projects.
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9. Adjacent associated construction needed as part of stream improvement projects (e.g., upstream
and downstream stream bank improvements that would be necessary due to altered water levels,
adjacent equipment, electrical feed, and equipment access for maintenance).
10. Potential sources of funding for projects, including federal, state, local and private entities.
11. Other aspects of stream improvement projects that may impact the feasibility of such a project.
2.2 Water Quality Standards
On January 24, 2008, the Illinois Pollution Control Board (IPCB) adopted a revised DO water quality
standard for general use waterways. This standard is summarized in Table 2-1.
Low DO levels occur in the East Branch during prolonged hot, dry low-flow periods.1 As the water
temperature rises, the minimum daily DO values typically fall. From a practical perspective, any solution
must take into account the prolonged hot, dry periods that can occur in June and July when more
restrictive (higher) water quality DO standards apply. Based on in-stream monitoring, the minimum DO
of 5.0 mg/L, as set by the IPCB, will be more difficult to achieve than the 6.0 mg/L daily mean, as
photosynthesis will increase DO levels during the daylight hours well above 6.0 mg/L. Therefore, for the
purposes of this report, the minimum DO of 5.0 mg/L will be the basis for evaluating alternative
approaches of dissolved oxygen improvements on the East Branch.
Table 2-1 - IPCB DO Standards
DO Water Quality Standard
Measurement Interval
August – February March – July
At any time 3.5 mg/L 5.0 mg/L
7 day average
4.0 mg/L Daily Min
Average
6.0 mg/L Daily
Mean
30 day average 5.5 mg/L Daily Mean n/a
1 This study is limited to low flow periods. Low DO levels have also been noted during high flow periods.
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3 EXISTING CONDITIONS
Before evaluating alternatives for improving the DO on the East Branch of the DuPage River, it
is important to understand the existing stream characteristics. Factors such as stream depth,
canopy cover, sediment accumulation, stream bank erosion, riparian zone composition, wetlands,
stream slope, bank heights, point source inputs, and flow data are all important during the
alternative development and evaluation process, and are defined in this section.
3.1 Geomorphic Assessments
Streams are in constant dynamic equilibrium. Although it can be imperceptible over years or
even decades, a stream in equilibrium moves within its floodplain both laterally and vertically
over long periods of time. A channel can be in balance with the hydrologic and sediment
influences or can be in rapid transition as a result of changes in the watershed or within the
stream corridor.
Urban river systems are often in various states of disequilibrium. The development of Chicago
area watersheds has significantly increased the intensity of land use. The impact of urbanization
on stream systems is well documented and includes changes in the hydrology, water quality,
sediment supply, and ecology. Other impacts include isolation from and reduction of, available
floodplain capacity, and installation of road crossings and other lateral and vertical controls.
Urbanization can significantly increase stream instability, as shown in Table 3-1.
Table 3-1 - Impacts of Urbanization on Channel Stability
Instability Description Probable Cause
Increase in erosive energy of stream
Channel Straightening – sinuous and low
gradient streams become straight and steeper
Increase in velocity
Larger discharge rates due to impervious
cover, culverts, drain tiles, and storm sewers
Decrease in in-stream channel
roughness
Removal of riparian vegetation and in-stream
woody debris
Decrease in amount and character of
incoming bed load
There is more energy to move bed material
than there is available bed material due to
impervious cover and channel armoring
Change in geotechnical loading
characteristics of the banks
Alteration of baseflow, as well as periods,
levels, and timing of saturation
Change in riparian management Deforestation and turf grass changes
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3.1.1 Channel Evolution
Schumm (1984) describes the evolution of degraded channels in arid and central plains streams,
and these basic principles apply to urban channels as well. The Schumm system classifies
streams by their place along a continuum of channel evolution, typically initiated by channel
incision (Figure 3-1), a process commonly occurring in urban and agricultural areas following
channelization. As a stream’s slope is increased through straightening (Stage II), the increased
shear forces cause bed material to displace and a small nickpoint or waterfall develops at the
downstream end of the reach. This nickpoint travels upstream until a stable, lower grade is
reached. This process is followed by lateral bank erosion and formation of a new, inset
floodplain (Stages III-IV). The former floodplain is abandoned during runoff events and flow is
confined to the new channel and floodplain. The old floodplain surface becomes an upland
terrace. The stream achieves ultimate stability at a new channel elevation (Stage V).
Figure 3-1 - Channel Evolution Model (Schumm 1984)
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3.1.2 Bank Erosion
Bank erosion is part of the natural processes within a stable stream and is balanced by deposition
of sediment on floodplains and bars. Erosion provides the needed bed material, allows
recruitment of large woody debris, and encourages channel variability. However, ‘excess’ bank
failure associated with unstable riverine systems and massive failures that threaten existing
infrastructure can cause unacceptable environmental impacts and consequences to private and
public resources. Bank failure can generally be attributed to three basic processes: subarial
wasting, hydraulic scour, and mass failure. (Thorne, et al., 1997). Subarial wasting is not
considered to be the major driving force for Midwestern urban streambank instability and is not
discussed further.
The common result of urbanization is a significant increase in bank erosion due to hydraulic
scour of the channel bed and toe of the bank. When changes in land use result in increased water
velocity, streams begin to erode their bed and banks beyond the point of equilibrium. Excess
hydraulic scour generally can be addressed in two ways, either by reducing channel velocity and
thereby reducing erosive force, or by armoring the channel to resist the erosive force. Reduction
of channel velocity can be accomplished either by increasing the cross-sectional area of the
channel, increasing the capacity of the channel and/or floodplain, decreasing flow rates, or
modifying slope through the use of grade controls. Following incision, as noted in the Schumm
(1984) model above, hydraulic scour combined with mass failure can lead to extreme bank
erosion.
Mass failure of the streambank is often the result of increased hydraulic scour, and/or a change in
riparian vegetation management associated with urbanization. There are numerous bank failure
mechanisms due to various loading and resistant conditions, including differences in soil
characteristics and vegetative reinforcement. Streambank soils can vary both vertically and
horizontally, and can generally be classified as cohesive, non-cohesive, and composite (banks
with layers of soil that have significantly different characteristics). Each of these types of
streambank soils presents different engineering challenges and different solutions. The
equilibrium processes of scouring and deposition of soil layers within an alluvial valley can
provide significant variability in the soil conditions within the valley. Hence, the type of bank
material can change significantly along a stream length as the stream passes through different
depositional eras.
Common measures to address mass failure of streambanks include decreasing the load by
reducing bank height, reducing bank slope, providing subsurface drainage or planting stabilizing
vegetation (to reduce pore pressure), and/or increasing the resistance to failure by geosynthetic
reinforcement with revegetation.
3.1.3 Sediment Transport
Understanding sediment transport characteristics of a stream is very important in understanding
stream stability and characteristics. Alluvial streams within urbanizing watersheds frequently
experience rapid channel enlargement. Channel response to urbanization has been described by
Leopold (1964), Hammer (1972), and numerous others. During the initial wave of construction
in a basin, sediment loads reaching the stream from the watershed may increase 10 to 100 times,
resulting in attendant destabilization, and sometimes flooding damages. Typically, high
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sediment yields during the construction phase are followed by reduced yields once infrastructure
and storm sewer systems are fully constructed (Kondolf and Keller, 1991). However, as the
percentage of the watershed covered by impervious materials increases, flow peaks become
sharper, higher, and more frequent, while the sediment load reaching the channel declines.
In the absence of bed control (e.g. bedrock outcrops in natural channels or hardened stream
crossings in urbanized areas), channels typically respond by incising. When bank heights exceed
a critical threshold for geotechnical stability, mass failure ensues and explosive channel
widening occurs. Sediment supply is altered by local and upstream bank failure, and upstream
modifications. Transport capacity is altered by channel widening, meander cutoffs, and
construction of additional crossings. These changes can make a reach aggrading, in equilibrium,
and degrading over time.
Sediment transport continuity describes the ability of a stream reach to transport the sediment
that it receives from upstream sources. A stream reach is considered to be in equilibrium if it can
transport the sediment it receives within the reach and from upstream sources to downstream
reaches. A reach is considered to be degrading if its transport capacity exceeds the sediment
supply and aggrading if the supply exceeds the transport capacity.
3.1.4 Geomorphic Disturbances
Almost all geomorphic disturbances in urban streams can be attributed to human causes. The
human-induced impacts to the East Branch include: tributary manipulation (piping, ditching),
channelization, hard armoring, dams, road crossings, berms, direct discharge/hydrologic change,
floodplain filling, riparian canopy removal, impervious surface coverage, and floodplain pond
construction.
3.2 Stream Characterization
In general, the East Branch can be characterized as an urban stream with low gradients and
extensive channelization. Canopy cover in the assessed stretches is limited due to development,
resulting in higher summer stream temperatures and establishment of rooted vegetation within
the stream bed. Contributions from point sources, including municipal wastewater treatment
plant effluents are also significant, contributing phosphorus which may contribute to plant
growth2, but also provide higher flows during low flow and overall cooler temperatures.
The IEPA has assessed the East Branch as partial support (the water body is supporting some,
but not all of its designated uses) for four of the five segments (GBL 05, GBL 10, GBL 08, and
GBL 11) used to evaluate the East Branch (IEPA, 2004). Segment GBL 02 has been assessed as
full support and is the last segment of the East Branch before the confluence with the West
Branch. Identified causes of the less than full use support assessment include dissolved oxygen,
chlorides, total nitrogen, habitat and flow alterations, suspended solids, phosphorous,
sedimentation/siltation, algal growth, and fecal coliform. The sources contributing to
impairment include municipal point sources, runoff and storm sewers, development, stream
modifications, and upstream impoundments.
2 Even without the phosphorus contribution from the POTWs, phosphorus levels within the East Branch would be
sufficient such that it would not be the limiting factor in plant growth. Additional phosphorus reductions would be
necessary from other sources.
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To describe the existing stream conditions, various data were collected, including point source
discharges, stream flow data, stream habitat components, and reach characteristics.
3.3 Flow Data
The East Branch originates near Bloomingdale, Illinois. The East Branch flows approximately
25 miles through DuPage County and the north part of Will County before merging with the
West Branch of the DuPage River (West Branch) (Healy, R. 1979). The stream becomes the
DuPage River at the confluence in Bolingbrook, Illinois. The East Branch drainage area is
approximately 79 square miles (CH2MHill, 2004).
Eight sewage treatment plants (STPs) and two industrial user discharges into the East Branch.
These point source dischargers are presented in Table 3-2. Lombard maintains three combined
sewer overflows (CSOs) within the watershed. Selected stream flows from the East Branch are
listed in Table 3-3.
Table 3-2 - Point Source Discharges
Discharger
River Mile
From
Confluence
with
West Branch
Elmhurst Chicago Stone Not Provided
Illinois-American #2 Sewage Treatment Plant 2.8
Quarry discharge 6.4
Bolingbrook Sewage Treatment Plant #1 5.5
DuPage County Woodridge Sewage Treatment Plant 7.5
Downers Grove Sanitary District Wastewater Treatment Plant 11.5
Glenbard Wastewater Authority - Glenbard 15.9
Glenbard Wastewater Authority - Lombard 18.8
Glendale Heights Sewage Treatment Plant (Armitage Creek) 21.2
Bloomingdale-Reeves Water Reclamation Facility 23.7
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Table 3-3 - Published River Flows (Singh, and Ramanurthy, 1991)
Location
7-Day 10-Year
Low Flow (cfs)
Harmonic Mean
Flow (cfs)
Crescent Boulevard 4.0 13
Above Glenbard Wastewater Authority - Glenbard 3.6 33
Below Downers Grove Sanitary District 23.6 54
Above Woodridge 25.6 61
Before confluence 38.0 78
3.4 Reach Descriptions
To identify East Branch segments with DO impairment, results from previously conducted
dissolved oxygen sampling were reviewed. Data collected from the Lisle sampling station
during a DO study in June and September, 1997 indicated low DO beginning at approximately
RM 8 and extending to RM 24. Based on this information, a field reconnaissance beginning at
St. Charles Road (RM 19.9) and ending at RM 5.7, where a public boat access was available,
was conducted on October 14, 2005.
The IEPA Qualitative Stream Habitat Assessment Procedure (SHAP) was utilized to describe
each stream segment based on the observations collected during the reconnaissance. The SHAP
index includes factors for bottom substrate, deposition, substrate stability, in-stream cover, pool
substrate characterization, pool quality, pool variability, canopy cover, bank vegetation, top of
bank land use, flow-related refugia, channel alteration and sinuosity, width/depth ratio, and
hydrologic diversity. Table 3-4 presents the relative ratings of the possible SHAP scores.
Based on the subjective evaluation for the aforementioned factors, a SHAP score was
determined.
Table 3-4 - SHAP Ratings (IEPA, 1994)
Rating SHAP Score
Excellent > 142
Good 141 to 100
Fair 99 to 59
Poor < 59
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Channelization, lack of canopy cover, sediment oxygen demands, effluent dominated low flows,
nutrient loading, and other factors can all contribute to the vegetative growth and subsequently
lower early morning DO levels.
Generally, the East Branch has been highly channelized through developed areas of DuPage
County. The stream banks are approximately three to six feet high for most of the stream length,
with the exception of the few areas where the channel flows into a detention pond or wide stream
reach. Stream flow velocity is generally slow moving with a few sections where the flow is
restricted due to structures. A description of the stream reaches, specific information for the
observed segments, and SHAP scores are presented below.
St. Charles Road (RM 19.9) to Crescent Boulevard (RM 18.8)
This 1.1-mile segment is located in Churchill Woods, an area owned and managed by the Forest
Preserve District of DuPage County. The stream overbank areas are generally undeveloped with
the exception of the picnic areas and parking within the forest preserve. The Churchill Woods
Forest Preserve segment of the East Branch is an impoundment area created by the spillway of
the Churchill Woods Dam at Crescent Boulevard.
The East Branch within the Churchill Woods Forest Preserve is approximately 500 feet wide and
has created a series of islands within the center of the flow pattern. Water depths range from one
to four feet with the deeper portions immediately upstream of the impoundment. The stream
channel substrate leading to the open water habitat is silty sand which turns to soft sediment in
the open water areas. The depth of the soft sediment is greater than two feet in most areas.
Streambank stabilization has been conducted in several areas along the banks in the Forest
Preserve area. There is good riparian habitat in this area. The combined SHAP score for this
segment and the next segment is 90 indicating a fair habitat quality. Mallards and shorebirds
were observed in this area as were recreational fisherman.
Crescent Boulevard (RM 18.8) to Illinois Route 53 (RM 17.4)
This segment of the East Branch is immediately downstream of the impoundment area in the
Churchill Woods Forest Preserve. Similar to most of the East Branch, this segment is
channelized, with Interstate Route 355 on the east side and a golf course and residential
development on the west side. There is poor streambank riparian habitat with little canopy
cover. The SHAP score for this segment was developed with the previous 1.1 mile segment of
the East Branch and is 89 indicating a fair habitat quality.
The water depth in this segment ranged from six inches to two feet. Two rock dams were
observed near the upstream end of this segment with a riffle area downstream of the second rock
dam. A second riffle area was observed at the downstream end of this segment near Illinois
Route 53. The substrate was generally silty/sandy gravel with cobbles and boulders in the riffle
areas.
The Glenbard Wastewater Authority Sewage Treatment Plant discharges to the East Branch at
RM 18.8, just on the south side of Crescent Boulevard. Immediately downstream of the plant
outfall is a concrete-lined channel which outlets to the East Branch from the east. Vegetation is
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growing through cracks in the concrete. A sewer outlet was also observed at RM 17.8
originating from under Roslyn Road on the west side of the East Branch.
Illinois Route 53 (RM 17.4) to Illinois Route 56 (RM 14.8)
This 2.6-mile segment of the East Branch has residential development on both the east and west
side. Interstate Route 355 is east of and parallel to the stream at the north side of the segment.
The Western Springs Golf Course is located north of Illinois Route 56 at the south end of the
segment.
Five wet detention basins have been constructed along this segment of the East Branch. Due to
the proximity of the ponds to the East Branch channel, the East Branch stream flow has created a
direct hydraulic connection between the stream channel and some of the ponds. The main stream
flow now travels through the detention pond immediately north of Illinois Route 38, as well as
the detention pond between RM 16.3 and RM 16.5.
Water depth in this segment varies between less than 6 inches deep to 4 feet deep. The deeper
portions are within the detention ponds and immediately downstream of the log jam located in
the channel just north of Illinois Route 38 (RM 16.9). Beaver activity was noted along this
segment. Water depths were shallow in the channel areas partially abandoned due to the flow
alteration into the detention ponds. Substrate consisted of sand and gravel with some silt for
most of the channel areas. The pond areas consisted of soft sediment up to 1.5 feet deep.
The SHAP score for this segment is 90 indicating fair quality. Poor canopy cover along the
segment reduces the score as does the level of stream channelization. Beaver activity was
observed along with mallards and a kingfisher.
A structure which blocks approximately half the stream channel was encountered at RM 16.6.
The center portion of the structure had collapsed allowing the stream flow to continue. A riffle
area was observed immediately downstream of the structure and near Illinois Route 56. The
Glenbard Wastewater Authority – Glenbard Sewage Treatment Plant is located along this
segment at RM 15.9.
Illinois Route 56 (RM 14.8) to Interstate Route 88 (RM 12.3)
This 2.5-mile segment of the East Branch includes residential development west of the East
Branch and the undeveloped areas of the Morton Arboretum. Illinois Route 53 parallels the East
Branch on the west from Illinois Route 56 (RM 14.8) to Illinois Route 53 (RM 13.0). The East
Branch channel is within the Morton Arboretum property for most of this segment.
South of Illinois Route 56 the East Branch becomes wider as it passes through the Hidden Lake
Forest Preserve. This stretch includes a poorly defined channel and is approximately 300 to 400
feet wide in some areas. Water depth is less than six inches in most places with up to eighteen
inches of soft sediment. Mussels were observed in this area of the stream. Downstream, the
stream has been channelized with fair canopy cover. Water depth varied between six inches and
four feet with substrate consisting of sandy silt and gravel.
The SHAP score is 83 indicating fair habitat. Trash and debris were noted throughout the
segment in proximity to Illinois Route 53. A large log jam was encountered at approximately
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RM 13.8. Several riffles occurred just upstream of Interstate Route 88. A great blue heron was
observed along this segment.
Interstate Route 88 (RM 12.3) to Maple Avenue (RM 10.8)
This 1.5-mile segment of the East Branch is a combination of residential areas and open space,
mainly the Lisle Community Park. Downstream of Interstate Route 88 is a rock dam with water
depths of three feet to four feet on either side of the dam. The remainder of the segment ranges
in depth from six inches to two feet. The substrate is generally sand, gravel and cobble. An
outfall pipe was observed on the downstream side of the railroad bridge at RM 11.4 on the east
bank.
The SHAP score for this segment is 81 indicating fair habitat quality. There is poor canopy
cover due to stream width and development along the stream banks.
Maple Avenue (RM 10.8) to Hobson Road (RM 8.7)
This 2.1-mile segment of the East Branch has been developed residentially and includes the
River Bend Golf Course and the Seven Bridges Golf Course. Water depths range from six
inches to four feet deep near the downstream end of the segment near where Prentiss Creek
enters the East Branch. The Prentiss Creek dam is located on the East Branch and also spans the
mouth of Prentiss Creek. Substrate is sand and gravel with silt. An old bridge structure is
located on the upstream side of the Hobson Road bridge, which restricts flow in this area.
The SHAP score for this segment is 89 indicating fair habitat quality. Very little canopy was
observed. Riffles had been created in the segment within the Seven Bridges Golf Course and
several large boulders were placed within the stream. Mussels were observed downstream of the
riffles.
Hobson Road (RM 8.7) to Access Point (RM 5.7)
This three mile segment of the East Branch is generally undeveloped and is within the Greene
Valley Forest Preserve. A large amount of trash was observed in this segment, especially near
the bridges. Water depths range from six inches to four feet with substrate consisting of fine
sediment and gravel. A log jam was encountered at RM 7.2.
The DuPage County Woodridge STP is located at RM 7.5 and discharges to a side stream of the
East Branch. A quarry operation is also located near the downstream end of this segment from
approximately RM 6.7 to RM 4.1. Two outlet pipes with no flow and a submerged inlet pipe to
the quarry were observed near RM 6.4.
The SHAP score for this segment is 96 indicating fair habitat quality. There is poor canopy
cover along this segment of the East Branch and several areas of bank erosion were observed.
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3.5 Habitat Summary
The SHAP scores and the habitat conditions for each segment are summarized in Table 3-5,
beginning at St. Charles Road and proceeding south.
Table 3-5 - SHAP Scores
Stream Reach
Assessment
Score
SHAP
Limiting Habitat
Conditions
St Charles Road to Crescent Boulevard
RM 19.9 – RM 18.8
90 (Fair) -
Crescent Boulevard to Illinois Route 53
RM 18.8 – RM 17.4
89 (Fair)
Lack of canopy (over
channelized)
Illinois Route 53 to Illinois Route 56
RM 17.4 – RM 14.8
90 (Fair)
Poor riparian area/canopy
(over channelized)
Illinois Route 56 to Interstate 88
RM 14.8 – RM 12.3
83 (Fair) Channelized
Interstate 88 to Maple Avenue
RM 12.3 – RM 10.8
81 (Fair)
Poor riparian area,
canopy cover
Maple Avenue to Hobson Road
RM 10.8 – RM 8.7
89 (Fair) Poor canopy cover
Hobson Road to Access Point
RM 8.7 – RM 5.7
96 (Fair)
Poor canopy cover/stream
bank stabilization
In addition, the qualitative habitat evaluation index (QHEI) was determined at eight locations on
the East Branch. The QHEI provides a quantitative assessment of physical characteristics of a
stream and represents a measure of in-stream geography. The maximum total QHEI score is
100, and is broken down in Table 3-6. The East Branch QHEI scores by river mile are shown in
Table 3-7.
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Table 3-6 - Qualitative Habitat Evaluation Index (Rankin, 1989)
QHEI Component Point Value
Substrate type and quality 20
In-stream cover type and amount 20
Channel morphology – sinuosity, development, channelization stability 20
Riparian zone – width, quality, bank erosion 10
Pool quality – maximum depth, morphology, current 12
Riffle quality – depth, substrate stability, substrate embeddedness 8
Map gradient 10
Table 3-7 - QHEI Scores by River Mile
River Mile Location QHEI Score
22.00 6385 ft downstream of Army Trail Road 43.0
20.50 1936 ft downstream of North Avenue 35.0
17.30 471 ft downstream of IL-53 48.0
11.85 119 ft upstream of Lacey Avenue 35.0
11.10 88 ft downstream of Short Street 39.0
8.46 1484 ft downstream of Hobson Road 46.0
5.15 3138 ft downstream of Royce Road (Will
County)
43.0
2.60 4908 ft upstream of Naperville Road (Will
County)
56.5
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3.6 Dam Site Investigations
Removal or reconfiguration of dams has the potential to increase dissolved oxygen in waterways.
The two dams were investigated to gain an understanding of their characteristics. The names,
locations, and river miles (based on the GIS model) of the two dams on the East Branch are
listed in Table 3-8.
Table 3-8 - River Dam Information
Bounding Bridges
Name
Year
Built
River Mile
Upstream Downstream
Nearest
Town
Churchill Woods
Dam
~1930 18.9
St. Charles
Road
Crescent
Boulevard
Lombard
Prentiss Creek / EB
DuPage Dam(s)
1989 8.75
Summerhill
Drive
Hobson Road Woodridge
3.6.1 East Branch DuPage / Prentiss Creek Dams
The Prentiss Creek Dams are owned by the Village of Woodridge and were constructed in 1989
as stormwater storage and mitigation for the Seven Bridges Development. The system includes a
dam across the East Branch, and another across the mouth of Prentiss Creek. Further up Prentiss
Creek, three grade control weirs provide additional stormwater storage up to the intersection of
Illinois Route 53. The dams are gravity structures consisting of rock-filled gabions covered by a
concrete cap. The structure within the East Branch is 20 ft. wide at a weir elevation of 643.5 ft.
while the Prentiss Creek structure is 10.1 ft. wide at an elevation of 646.0 ft. There is no
upstream control mechanism for regulating upstream pool elevations.
There is little sediment being deposited within the East Branch DuPage River upstream of the
dam: however, there is fair amount of fine material that has settled upstream of the Prentiss Creek
structure. A total of seven cross sections were evaluated through the Prentiss Creek backwaters.
Hydraulic Impacts: The project was designed to provide regional stormwater storage and
compensatory mitigation for the associated development. The impact at a range of flood events is
unknown.
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Figure 3-2 - Prentiss Creek Dam
3.6.2 Churchill Woods Dam
The Churchill Woods Dam is located just upstream of Crescent Avenue and is owned by the
Forest Preserve District of DuPage County. Little historical documentation could be found
relating to this dam. Residents in the area mentioned it was built during the Works Progress
Administration (WPA) in the 1930’s as a flood control project. Significant improvements were
made to the structure as part of the Crescent Boulevard reconstruction in 1983.
The Churchill Woods Dam is a concrete gravity dam about 3.5 feet high with a 50-feet wide weir
crest. The dam appears to be in good condition, as do the associated four box culvert structures
that take water under Crescent Boulevard. The spillway and apron are in good condition and
show signs of normal weathering and associated maintenance. There is a dewatering gate on the
west end of the spillway. The dam is depicted in Figure 3-3.
The Churchill Woods Dam reservoir contains a large amount of sediment largely due to the low
gradient and wide, shallow channel path. The profile shown in Figure 3-4 indicates nearly four
feet of material consistently blanketing the bed of the reservoir. A number of areas have as much
as eight feet of deposited material. The sediment is mostly composed of fine material (silts and
clays) and is fairly consolidated in areas where it is greater than three feet in depth. Coarse
(small gravel) depositional features were found approximately 1,000 feet upstream of the St.
Charles Road Bridge, indicating this may be the extent of the delta formed as a result of the
impoundment.
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Figure 3-3 - Churchill Woods Dam
The hydraulic impact of the Churchill Woods structure is likely minimal, especially for larger
flows. More interesting from a hydraulic perspective is the existing configuration of the dam,
the four culverts under Crescent Boulevard, and the two stone arches under the railroad.
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Figure 3-4 - Water Surface Profile at Churchill Woods Dam
Figure 3-5 - Dam Outlet Structure
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3.7 Sediment Oxygen Demand (SOD) Field Measurements
Field data were collected in the summer of 2006 to provide an estimate of the sediment oxygen
demand (SOD) in the East Branch of the DuPage River. These data provided independent,
empirical estimates of the SOD that were being modeled for dissolved oxygen as described in
Section 4. It was concluded during the modeling analysis of stream DO improvement
alternatives, that more SOD data in the vicinity of dams were needed to better understand the
effects of potential dam removals. The survey was conducted at SOD stations at the locations
described in Table 3-9. The field surveys were performed concurrently with the continuous DO
monitoring. As water temperature affects SOD, the SOD survey period was completed during
higher water temperatures to minimize temperature adjustments. The locations of the SOD sites
and of the DO probes can be viewed in Figure 3-6.
Table 3-9 - SOD Survey Locations
Station ID River Mile Location
EB1 19.9 Upstream of St. Charles Road
EB2 19.1 Churchill Woods Dam
EB3 18.9 Churchill Woods at Crescent Boulevard
EB4 16.9 Just north of Route 38 (Roosevelt Road)
EB5 16.3 At outflow of detention pond, downstream of Route 38
EB6 14.8 300 feet upstream (north) of Butterfield Road (on east side of stream)
EB7 14.7 50 feet south of Butterfield Road
EB8 8.8 At Hobson Road
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Figure 3-6 – SOD Location Map
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3.7.1 FINDINGS
The SOD measured at ambient temperature in the East Branch ranged from a minimum of 0.67
g/m2/day to a maximum of 9.53 g/m2/day. Station-averaged 20oC-temperature adjusted SOD
values were in the range of 1.13 to 3.61 g/m2/day. The temperature standardized 20oC SOD rates
used in the preliminary QUAL2K modeling were in the range from 1.0 to 2.5 g/m2/day.
The results of the SOD survey were used to examine the model calibration/verification
particularly in the reaches adjacent to the dams. The refined model was then used to evaluate the
DO improvement alternatives.
3.8 Continuous Dissolved Oxygen Monitoring
Continuous monitoring for dissolved oxygen values in the East Branch has been performed by
the DRSCW and IEPA during 2006 and 2007. Stream monitoring data have been collected at
six locations on the East Branch from April to October. Parameters included dissolved oxygen,
temperature, pH, and conductivity.
All DO data was collected according to the Quality Assurance Project Plan (QAPP) agreed upon
by the IEPA and the DRSCW. Calibration of the probes for the other parameters listed was
carried out according to the manufacturerer’s recommendations and the QAPP.
One site (EBSC) was abandoned in early 2007 after a build up of debris around the protective
housing caused the sonde to be exposed to air. A new site (East Branch Churchill Woods
(EBCW) was opened up just downstream of the abandoned site. The EBCW sampling location
is within the impoundment of the Churchill Woods Dam just upstream of Crescent Boulevard.
No data were produced meeting the outlined QAPP standards for the EBSC site. Table 3-10
catalogs the monitoring locations and Figure 3-7 displays the monitoring locations.
Appendix A includes a summary of the continuous DO data collected in 2006 and 2007. At the
sites monitored both years, 2007 showed a greater DO flux (maximum minus minimum DO),
suggesting more algal or rooted plant activity in that year. At Hidden Lake (RM 14.2),
minimum DO in 2007 during a low flow period averaged 4.0 mg/L, compared to 5.9 mg/L the
previous year.
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Table 3-10 - DO Monitoring Locations
3.9 SUMMARY
The East Branch DuPage River is characterized in the upper reaches as being channelized and
incised, having long stable ditched sections that are aggraded, having long reaches impounded by
dams, having floodplains that are heavily encroached upon by residential development, golf
courses, and detention pond storage. The channelization affects a large percentage of the East
Branch. For example, the river is nearly completely straight from RM 7.0 to RM 14.0. Of the 25
miles assessed in this project, only the downstream 4.0 miles have any significant meanders
remaining.
The East Branch of the DuPage River is a highly disturbed urban stream with low channel
gradients and extensive channelization. Floodplains for the tributary stream and main channel
were either filled in or separated from waterways by large berms that concentrate flood flows
into a deep narrow channel. Floodplain and drainage surfaces are covered by pavement, and
water is now directed into sewers and pipes that discharge directly into the creek. Point sources,
including municipal wastewater treatment plant effluents, result in higher base flow during low
flow periods and higher total phosphorus and total nitrogen. Canopy cover in general is limited,
resulting in higher summer stream temperatures and promoting establishment of rooted
vegetation. All of these attributes contribute to the low DO levels.
Station Location Crossroad Steward Parameters
EBAT
Unincorporated
Bloomingdale
Army Trail Road Bloomingdale
DO,
Temperature
pH,
Conductivity
EBCW Glen Ellyn Crescent Blvd Glenbard WWA
DO
Temperature,
pH,
Conductivity
EBBR
Unincorporated
Downers Grove
Butterfield Road
Downers Grove
Sanitary District
DO,
Temperature,
pH,
Conductivity
EBHL
Unincorporated
Downers Grove
Hidden Lake
Forest Preserve
DuPage County
Wastewater
DO,
Temperature,
pH,
Conductivity
EBHR
Unincorporated
Woodridge
Hobson Road
Downers Grove
Sanitary District
DO,
Temperature,
pH,
Conductivity
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Downstream of RM 8.7, the river is channelized and bordered by either forest, reed canary grass
wetland, or abandoned quarry pits. Excellent opportunities for channel restoration exist
downstream of RM 8.7, and between RM 20 to RM 23. Remnant meanders exist throughout the
Arboretum property, and restoration of a meandering channel could also be completed anywhere
along portions between RM 12.0 to RM 19.0.
The continuous DO monitoring results from 2006 and 2007 (Appendix A) indicate that upstream
of Churchill Woods (EBCW) DO levels drop to below 2.0 mg/L. This area has the lowest DO
monitored on the East Branch of the DuPage River. At River Mile 14.2, Hidden Lake appears to
also have DO levels below 4.0 mg/L during some dry weather periods (2007, but not observed in
2006).
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4 WATER QUALITY MODELING
To develop the TMDLs for those constituents bound by water quality standards (i.e., DO and
chlorides), IEPA used a regulatory water quality model called QUAL2E to analyze two stretches
of the East Branch. The analyses were conducted to allocate allowable wasteloads for each
pollutant discharger along the stream.
Since those analyses, the QUAL2E model has been updated with a more user-friendly interface
and convenient post-processing tools. The updated version of QUAL2E is called QUAL2K and
was developed for the USEPA by Steve Chapra, et al., at Tufts University (2005). Model theory,
equations, and parameters are described completely in the QUAL2K Users Manual.
The goals of the water quality modeling for this study are to perform a model conversion from
QUAL2E to QUAL2K, to validate the new modeling tool, to identify locations where low DO is
expected or observed, and to quantitatively evaluate the effects of alternatives to potentially
improve DO. These alternatives may include removal and/or bridging of dams, as well as
aeration (mechanical, diffused air, side stream elevated pool, and pure oxygen).
Figure 4-1 shows the steps in developing and utilizing a water quality model to evaluate
alternatives.
Figure 4-1 - Water Quality Model Development Steps
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4.1 Conversion from QUAL2E to QUAL2K Model
Dissolved oxygen is a key indicator of water quality in streams and is of main interest to this
project. As pollutant constituents in wastewater discharges demand oxygen through decay
reactions, the DO concentration in the stream is consumed. Sediment oxygen demand and
respiration of abundant algal life also consume oxygen. DO is restored through reaeration as
well as plant photosynthesis during daylight hours. (For a full description of the mechanisms
affecting DO, refer to Chapra 2005, Thomann and Mueller 1987, or Chapra 1997.)
The fundamental utility of QUAL2E and QUAL2K is essentially the same; they are one-dimensional,
steady-state models to predict DO and associated water quality constituents in
rivers and streams. However, QUAL2K has more refined features such as the capability of
diurnally varying headwater/meteorological input data and a full sediment diagnosis model to
compute SOD and nutrient fluxes from the bottom sediment to the water column. In addition,
the QUAL2K model offers more options for decay functions of water quality constituents,
reaeration rate equations, heat exchange, and photo-synthetically available solar-radiation
calculations.
As the fundamental theoretical underpinnings of both models are similar, the objective of this
subtask was to use the input data previously used in QUAL2E and produce QUAL2K outputs
that are similar to the results found in the TMDL reports. Since QUAL2E input data files were
not available, the listings of input data in the appendices of the TMDL reports were used to
prepare the input to QUAL2K. The QUAL2E model set-up was closely followed to reproduce
those results by applying QUAL2K instead of QUAL2E. The more refined features in the
QUAL2K, described above, were not utilized, at least initially, to adhere to the QUAL2E
modeling. Subsequently, independent evaluation of the selection of model formulations and
functions and parameter evaluations for the East Branch was conducted.
4.1.1 Model Result Comparisons
The TMDL reports were reviewed to identify sets of input and output data that could be used for
comparisons of QUAL2E and QUAL2K. QUAL2E model outputs of DO, CBOD5, and NH3-N
were listed in the East Branch TMDL report. These QUAL2E results are compared against
QUAL2K outputs. As presented in Figure 4-2, the QUAL2K model reproduced the general
trend of DO profiles generated previously with QUAL2E. QUAL2K showed a jump in DO
immediately downstream of each of the dams. QUAL2E, which has the same dam re-aeration
equation as QUAL2K, did not show an increase in DO at the Churchill Woods dam; this does not
appear to be an accurate depiction of what actually occurs, therefore, it was investigated further.
Differences between the two models were investigated to check that the relevant model
equations were the same and the model parameter values were equal. A subtle difference
between the QUAL2E and QUAL2K formulations of the SOD term in the DO equation was
found, and input to the latter was adjusted to accommodate this difference. The values of SOD
at 20oC were input into QUAL2E and adjusted by the model calculations to ambient temperature
based on a temperature correction factor. In contrast to this, the “prescribed SOD” input to
QUAL2K is not temperature corrected internally, so the factor was applied external to the model
to adjust the SOD input to the ambient temperature. The models differed slightly in the input
relating to the height of water falling at a dam; QUAL2K input was adjusted to yield the same
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value as QUAL2E for the dams. The coefficients in the dam re-aeration equation in QUAL2K
are set by the model developers whereas these coefficients can be specified as input in QUAL2E.
Although there was a difference in the values of one of these two coefficients, it does not appear
to substantially affect the calculated increase in DO at any of the dams being modeled.
The CBOD5 and nitrate results from QUAL2K show trends that are generally consistent with the
QUAL2E results. Certain results from QUAL2E appeared to be anomalous, such as the minimal
decrease in BOD at the Churchill Woods dam. In general, QUAL2K results appeared to
conform more to expectations than the QUAL2E results. It should be noted that the
computerized input files for QUAL2E were not made available for this project. As a result, the
It has been assumed that the documentation of input data and output in the TMDL reports is
completely correct, yet inconsistencies between the actual model and the TMDL report
documentation cannot be eliminated as an explanation of the discrepancies between the two
models.
Figure 4-2 - Comparison of QUAL2K and QUAL2E DO Results
4.1.2 Conclusion
Overall, the QUAL2K model reproduced the general trends in water quality constituents with
distance along the project study extents of the East Branch as reported in the TMDLs. Therefore,
the next step was to validate the QUAL2K model with continuous DO measurements.
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4.2 Validation of QUAL2K Model
After converting the QUAL2E model to QUAL2K, recent DO measurement data were used to
validate the QUAL2K model. The DO in the East Branch was measured by DuPage County
during several days starting on July 25, 2005 and ending on August 9, 2005. The field data
consisted of date, time, station number, cross-section position (left, middle, right) sample depth
and DO. It is important to note that these measurements were performed during daylight only so
that the cyclically low DO due to respiration of phytoplankton during the night time was not
captured.
There were also spreadsheets provided with DO data for a station on the East Branch
downstream of the DuPage County WWTP (approximately RM 7.5). Hourly measurements for
24-hour periods during July 29-30, 2003 and August 14-15, 2003 were reviewed but not
graphically compared to the model because the model validation period is in 2005.
River mile (RM) points of reaches were modified in QUAL2K based on more recent GIS data
collected as part of this project as opposed to USGS RM information used in QUAL2E.
Differences in RM between USGS and GIS data for East Branch were minimal.
All of the DO data were plotted against river mile to show the range in DO and provide an
approximate basis for comparing QUAL2K results. As QUAL2K is a steady-state model, it
assumes that stream conditions, such as flow, point source discharge, and loadings are constant
in time. Sampling to collect data for comparison to a steady-state model is normally performed
during periods when flow and other conditions are relatively constant. However, the DO data
may not reflect steady-state conditions because of the variability in flow, meteorology, point
source loadings, and headwater conditions during the 32 day sampling period. Since river flow
data and point source data for July and August 2005 were not available, it was not possible to
ascertain whether relatively constant conditions prevailed.
It should be noted that stormwater runoff and combined sewer overflow (CSO) discharges are
assumed to be zero in the model and their effects, if any, would contribute to differences between
the field measurements and the model. Daily precipitation recorded at Bensenville, IL for the
sampling period was obtained and are presented on Figure 4-3 to provide an indication of
potential stormwater/CSO discharges.
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Figure 4-3 - Bensenville Rainfall Data for 2005 Period15
4.2.1 Changes in Model Input
This section describes the model input changes made to simulate the period of DO data
collection (July - August 2005), as well as changes to the hydraulic characteristics (i.e., stream
slope, depth and width data) necessary to reflect findings obtained during the field data
collections (see Section 2.0, Existing Conditions for more details) and other recent sources of
data. Reaction rate coefficients that depend on stream depth and velocity, such as the reaeration
rate coefficient and the BOD oxidation coefficient, were also changed to reflect the changes in
the hydraulic data. Other model parameter values from QUAL2E were also changed in
QUAL2K in an attempt to improve its ability to simulate conditions in East Branch DuPage
River as explained below.
Headwater flows were changed using historical USGS flow data for 20 years or more. Monthly
average flows for July and August for the period of record were averaged. Flows from point
sources were accounted for in calculating flows with distance upstream of the gaging stations.
Water quality measurements at the headwaters during July - August, 2005 would have been
ideal, but they were not available at this time. For the East Branch, a diurnal variation was used
with an adjustment factor equal to the ratio of the average DO measured at the East Branch
headwater to the average DO at JFK Boulevard. The DO, CBOD5, and ammonia concentrations
of the tributaries were assumed to be the same as those in the QUAL2E model.
Main channel slopes were revised using the FEQ model input of the East Branch DuPage River
developed by DuPage County. In addition, impoundment areas, where there are occurrences of
Rainfall Data at Bensenville, IL
(Data Source: AccuWeather.com)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
7/8
7/9
7/10
7/11
7/12
7/13
7/14
7/15
7/16
7/17
7/18
7/19
7/20
7/21
7/22
7/23
7/24
7/25
7/26
7/27
7/28
7/29
7/30
7/31
8/1
8/2
8/3
8/4
8/5
8/6
8/7
8/8
8/9
8/10
Date
Daily Total Precipitation (in.)
M M M M M M M M M M
Note: "M" stands for dates of DO measurenets.
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hydraulic backup and sedimentation due to the presence of dams, were delineated as a
refinement in QUAL2K. This was done by subdividing the appropriate QUAL2E model reach
into two reaches for QUAL2K, a free-flowing reach and an impounded reach. Water depth
information was taken from field reconnaissance. These changes of channel slope, depth, and
velocity in impounded areas would potentially change re-aeration rates and BOD deoxygenation
rates as explained under “decay rates” below.
Air and dew point temperatures were changed to represent a more reasonable local effect of
weather for a period with which model validation was compared. Other meteorological inputs
such as wind speed, cloud cover, and shades were set to 0m/s, 30%, and 0%, respectively. As
the model does not simulate rainfall related inflows, precipitation data (shown previously) are
not included as input.
As stated, changes to the stream geometry indicated that reaction rate coefficients would also
change. CBOD, nitrification, and settling rates of various water quality constituents were
changed using stream characteristics and a more reasonable range based on Chapra (1997) and
Thomann and Mueller (1987). Velocity and depth are generally calculated by QUAL2K except
for impounded reaches, where these data are taken from the Existing Conditions section and
directly input to the model.
The model lacks absorption and back scatter of light by particulates because total suspended
solids (TSS) was not simulated. This was accounted for by using a higher background light
extinction rate compared to QUAL2E inputs.
Because DMR data for the period (July - August, 2005) were not available, monthly DMR data
for July and August 2003, which is the last year of available data, were averaged to set discharge
flows, CBOD5, and NH4 concentrations. Other effluent data, such as organic nitrogen, nitrate,
phosphorus, and DO concentrations, were not available in the DMR data; therefore, the previous
QUAL2E inputs were used. Thus, it should be recognized that this hypothetical set of point
source data may not represent the period of model validation.
The SOD rates in the QUAL2E model input listings (0 for East Branch Scenario 1) were lower
than expected for the existing conditions. (Note that no calibration data were reported for the
East Branch DuPage River). SOD rates for the summer 2005 were set based on stream
characteristics such as bottom sediment substrates, water depth, and impoundment as provided in
Section 3.0, Existing Conditions. When a reach segment is characterized as “with silty/soft
bottom” or “pool water depth greater than 5 ft”, higher SOD rates (2.5 g/m2/d at 20oC) were used
because the reach was expected to have relatively heavy sedimentation with organic matter.
Ammonia flux from the bottom sediments was set to zero because there was no information to
support any other value.
4.2.2 Comparisons of Model and Observed Data
In the model, point source discharges in the East Branch account for the entire increase in flow
between the headwaters and the model’s downstream boundary. Hence, the East Branch is
substantially influenced by effluent in this simulation of summer 2005 conditions.
As mentioned earlier, the 2005 DO measurements were performed during daylight hours only so
that cyclically low DO due to respiration of phytoplankton (and the temporary cessation of
photosynthesis) during night times were probably not measured. Therefore, the model may
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underestimate DO compared to the observed data because QUAL2K is a steady state model that
simulates the diurnal variation in water quality as well as the daily average concentrations.
The model validation process was somewhat hampered by the absence of point source DMR
information and stream flow data. Point source flows and effluent concentrations probably had a
significant effect on DO, particularly during the relatively dry summer of 2005. Also, the model
did not generate sharp fluctuations of DO compared to measurement data because average values
of available data were used for diurnal variations, headwater flows, and point source parameters.
Thus, the range of the model predicted DO would be narrow compared to the observed.
4.2.3 Sensitivity Analysis
Due to the interim status of the model validation, only one model sensitivity run was performed
to date. The cloud cover was changed from 30% to 0% at all times in the East Branch DuPage
River. This change resulted in model DO concentrations that were within 0.1 mg/L of the base
case (30% cloud cover) DO. Increasing sunlight at the water surface tends to increase algal
growth, which leads to higher photosynthesis and respiration. These mechanisms would partially
offset each other and yield minimal change in DO.
4.3 Model Revisions
Model input changes were made to simulate the period of DO data collection in August 2006, to
change the characteristics of the Churchill Woods impoundment based on the bathymetric survey
performed in 2006, and to incorporate other data from recent sources. Updated data included
flow and DMRs. Using the updated inputs and stream geometry a calibration and validation run
of the model was carried out and the results compared with observed data gathered by the
continuous DO monitoring program. The results are graphically represented in figures 4-4 and
4-5.
Figure 4-4 shows a validation run of the revised model with computed DO for August 20, 2006
plotted against the continuous DO measurements taken during field sampling for August 20,
2006. The diurnal range of the modeled DO is represented in Figure 4-4 with the minimum and
maximum values being shown.
.
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Figure 4-4 - Comparison of Observed and Predicted DO – Validation Run (8/20/06)
Figure 4-5 depicts the calibration run for August 13 to 17, 2006 versus the model. The diurnal
pattern at Hidden Lake appears to be greater than then model predicted, but otherwise excellent
agreement has been obtained. The green triangles shown along the top of figure 4-5 represent
the locations of POTWs discharging to the East Branch. The relative size of each triangle is
representative of the quantity of discharge supplied by the plant.
4.4 Modeling DO Impacts
Utilizing the average BOD5 and ammonia levels discharged during the summer months, the
seven-day, ten-year low flow for the East Branch, and the maximum stream temperatures
recorded over the past ten years, a baseline model was run. Figure 4-6 depicts the results of this
model, which is intended to reflect worst case conditions low flow conditions. Upstream of the
Churchill Woods Dam, DO minimum levels are predicted to drop to zero mg/L DO. The mean
DO is predicted to decline to 1.5 mg/L. The computed values suggest that other DO deficits
along the East Branch are minor compared to the DO impact from the Churchill Woods Dam.
The green triangles shown along the top of figure 4-6 represent the locations of POTWs
discharging to the East Branch. The relative size of each triangle is representative of the quantity
of discharge supplied by the plant.
0
2
4
6
8
10
12
45 40 35 30 25 20 15 10 5 0
Distance from downstream (km)
DO(mgO2/L) DO (mgO2/L) data DO(mgO2/L) Min DO(mgO2/L) Max
Minimum DO-data Maximum DO-data DO sat
Churchill Woods Dam Prentiss Creek/ EB DuPage Dam
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Figure 4-5
East Branch DuPage - Calibration Results
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Figure 4-6
East Branch DuPage – Baseline DO
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East Branch DuPage River 5.0 Screening for Dams
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5 SCREENING FOR DAMS
Small, low-head dams have been noted to bring multiple problems to streams in the US due to
the shear number that exist today. Dams inhibit the natural linear flow of energy in a stream, be
it in the form of flowing water, sediment transport, fish migration, macroinvertabrate drift, or
downstream nutrient spiraling. Specific to the impact on dissolved oxygen that is being studied
on the East Branch DuPage River, dams create impoundments that concentrate sediment and
organic material upstream which actively respires, removing dissolved oxygen from the water.
In addition, dams slow the velocity of the water, allowing additional time for water to absorb
solar energy and increase in temperature and consume the limited mass of oxygen with the
longer retention time. These effects are further exacerbated when dams increase the width of the
stream through the impoundment, which limits the extent of riparian shade that can counter the
effect of solar heating, and increases surface area for algae
Complete removal or retrofitting of dams is becoming an increasingly utilized tool to eliminate
the disruptive influence that dams create within the fluvial system. The impacts of dams on
sediment, flood conveyance, and aquatic flora and fauna have been documented in the literature:
however, there is little guidance that exists for implementing a dam removal or retrofit.
Questions about the fate of impoundment sediment, mechanisms for de-watering, and short
versus long term impacts to the health of the system dominate any dam removal project and
usually default to the experience of a few individuals for solutions as opposed to documented
methods.
Dam Modification projects like these will have an overall positive effect on the aquatic
environment of the East Branch of the DuPage River. The effect of dams upon rivers and
streams include changing flow regimes, altering physiochemical parameters, promoting increases
in siltation upstream, and scouring substrates below the dams. Dams also can alter fish
assemblages and block fish movement which affects mussel reproduction by limiting availability
of host fish for larvae. Dams can reduce species richness and abundance and increase non-native
species composition.
The proposed project includes the evaluation of dam modifications, restoration of natural flows,
and removal of sediment which has built up behind the dam structure as a result of
impoundment. Strict erosion control will mitigate construction-related impacts to the aquatic
resources. These sort of projects include a Restoration Plan taking into account mitigation for
wetlands, waters, and riparian impacts including vegetation restoration. The stabilization and
improvement of the riparian area will have positive affects on the aquatic resources.
The restoration of a stable, normal flow regime coupled with dam/sediment removal will
improve the aquatic environment. Normal fish movement will be enhanced within this portion
of the East Branch of the DuPage River, and siltation will be minimized as a result of the project.
The project will restore the natural ecological functions and processes of a free-flowing river
segment, and eliminate barriers to fish migration and mussel dispersion upstream leading to an
improved and functional aquatic habitat.
Although a myriad of options exist for any given dam site, the three basic options being
investigated for this study are: complete removal; complete removal with riffles installed
upstream to maintain a given pool elevation, and partial removal or bridging. These options are
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being driven by the primary design objective of improving the DO content of the stream. A
secondary design objective is to re-establish biological connectivity, mainly in the form of faunal
passage, at each site. The three alternatives are discussed in more detail below.
5.1 Complete Removal
Complete dam removal involves the removal of the entire dam structure. The most common
case for removal is to eliminate the legal definition of a dam at a particular site, thereby
removing liability and responsibility from the owner. Usually dams have exceeded their design
life, and the cost of rehabilitation is greater than the cost of removal. Ecological benefits are
significant, but are often a secondary consequence in the removal of the structure.
Complete removal can occur in a number of ways based on site conditions and budget. Dams
with a substantial amount of sediment behind the structure are often drawn down in stages to
minimize the downstream transport of sediment. Sediment in the dewatered impoundment can
be excavated and/or stabilized in place, depending on the type and quality of material (i.e., silt
vs. sand and contaminated vs. non-contaminated).
Depending on the size of the impoundment, varying levels of restoration of the new channel are
required. In large impoundments the effort for restoration is great, while in narrow
impoundments, only slightly wider than the natural channel, the restoration effort may be less
extensive.
There is a broad range of effort that can be dedicated to restoration of the site based on funding,
aesthetics, resource use, aquatic and terrestrial wildlife needs, hydrology, and sediment transport.
A passive approach (minimal effort) to channel rehabilitation might include the excavation of a
fairly straight, perhaps oversized channel through the impoundment. This would allow the
stream to do most of the work of recovery, creating its own path and allowing flood and
groundwater hydrology to dictate the riparian vegetation regime over a prolonged timescale.
Timescales for the completion of this restoration can range from decades to centuries depending
on site conditions. Alternatively, active channel restoration, requiring the largest effort, would
involve the complete construction of a functioning floodplain and sinuous channel similar to
what existed prior to dam construction. The geometry of this channel would emulate the
historical channel but would be designed to function appropriately within the constraints of
modern hydrology and sediment loading. This active restoration option could be constructed
within a few months but for a greater cost. The costs and timescales for these approaches are
drastically different to achieve the same ultimate outcome, the re-establishment of an intact
fluvial system.
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Figure 5-1 - Dam Removal Example
5.2 Removal with Constructed Riffles
Dam removal with constructed riffles to control the water surface elevation is an option that was
not originally identified on the project. However, it has become obvious during the data
collection phase of the project that development has occurred based on the rather constant water
surface elevation provided by the dams. Along certain reaches of stream where the potential
decrease in the pool elevation would have negative impacts, the use of constructed riffles in the
stream can help maintain a constant pool elevation. Dam removal proceeds exactly as described
above, followed by the construction of riffles at a spacing and elevation dictated by site
conditions.
Figure 5-2 – Riffle Details
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The construction of riffles requires careful planning and attention to their location along the
profile of the stream. Due to the urban nature of the stream, little coarse sediment exists for
replenishment, so riffles will need to remain intact in both their form and composition against a
range of flows. Riffles occur naturally in streams at grade breaks along the profile. Constructed
riffles consist of rock placed in the stream with the long tapering tail pointing downstream. The
crest of the riffle is designed to maintain the water surface elevation required, while the long
downstream slope ensures fish passage and provides the added benefit of aeration and interstitial
habitats for macroinvertebrates.
Constructed riffles can be a great means of providing additional habitat and aesthetic value while
maintaining pool elevations upstream. Though not confirmed in the model for the East Branch
DuPage River, literature suggests that providing several areas of aeration along a stream in the
form of riffles (example: four one-foot high riffles) is more advantageous to DO than providing a
single, large riffle at one spot on the stream (example: one four-foot high riffle). The downside
of riffles is the access required for their construction along the stream. In addition, since they are
man-made structures, riffles would likely fall under the “dam” designation by IDNR, though
their hazard classification is expected to be minimal.
Figure 5-3 - Examples of Riffle Usage
Figure 5-3 – Examples of Riffle Usage
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5.3 Partial Removal or Bridging
The final option is partial removal or bridging. The basic concept is to build a ramp of large rock
leading up to the downstream face of the dam. The ramp effectively “bridges” the dam by
providing upstream-downstream fish passage and/or canoe passage. Common variations to this
include partially removing or lowering the dam crest in order to decrease the vertical elevation
that must be made up downstream. In addition, notching the dam crest to concentrate flow in the
center of the channel is also common.
Bridging provides fish passage and aeration as well as some interstitial habitat for
macroinvertebrates. It also preserves existing water surface elevations upstream. Bridging does
not eliminate the concentration of fine sediment and organic material that accumulates upstream
of the dam. In fact, all negative impacts created by the upstream impoundment are still valid
when using the bridging technique, though the extent of impoundment and sediment
accumulation can be decreased if partial removal is done as well. Bridging does not remove the
legal designation of a dam at the site. The State of Illinois’ definition of a dam is “any structure
built to impound or divert water.” Thus the responsibility for maintaining and monitoring the
structure will remain with the dam owner. There is a possibility for the hazard classification of
the structure to be downgraded if partial removal diminishes the hydraulic impact of the
structure.
5.4 Issues Common to All Dams
There are several issues that need to be addressed for project with modifications to existing
dams. Permitting by federal, state, and local agencies, characterization and disposal of sediments
removed from dam impoundments, and impacts of dam removal on flooding must be considered.
5.4.1 Permitting
The permitting climate for dam removal and bridging is somewhat uncertain. Because the
technique, especially removal, is so new, most states, including Illinois, have had little guidance
to craft efficient permitting processes to deal specifically with the technique. Instead, the current
permitting environment that governs classic issues related to construction in and around streams
and wetlands is applied. There are three levels of permitting that will be required for each
project, with variations on each depending on the design method chosen. The Joint Permit
Application Packet is designed to simplify the approval process for the applicant seeking project
authorizations from the U.S. Army Corps of Engineers, the Illinois Department of Natural
Resources Office of Water Resources, and the Illinois Environmental Protection Agency. The
application portion sent to each individual agency should be tailored to that agency’s area of
responsibility, but otherwise provides a fairly seamless entry into the application process.
Federal Level – At the federal level, the Army Corps of Engineers has jurisdiction over any
design that will impact wetlands or waterways. Because DuPage County’s regulations are more
stringent than the Federal Laws, a memorandum of understanding has been in place that allows
much of the permit review for the Federal 401/404 permit to be accomplished by the County.
State Level – Permitting from the State of Illinois involves several agencies, including the IEPA
and the Illinois Department of Natural Resources (IDNR). Within the Joint Permit Application
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process, there are several layers of review that require the approval of various agencies. The
IDNR Office of Water Resources has established requirements for applications for permits to
remove dams, detailed in Section 3702 of the State Administrative Code. The Office of Water
Resources handles aspects mainly related to the construction (removal) process, such as the plan
for dewatering and upstream restoration and the impacts to the flood profile. The IDNR Office
of Realty and Environmental Planning will perform a review of the project to ensure no impacts
to threatened or endangered species. A review will be done by the Illinois Historic Preservation
Agency to ensure no impacts to state historic or archaeological resources.
Additional regulations that may apply depending on the project include Part 3708 – Floodway
Construction in Northeastern Illinois.
The IEPA handles most of the sediment related questions concerning dam removal such as fate
and transport of material and likelihood of contamination.
County Level - DuPage County permitting requirements are more stringent than most State or
Federal requirements. As a result, once the county requirements are met for various items held
in common among both state and federal regulations, the federal and state requirements are also
met by default. It is important to note that this is only for certain items, such as wetland impacts,
that are common among the three levels of permitting. Other items such as dam safety and the
regulations associated therein are not common among the various permitting agencies and so the
responsibility remains with the issuing agency, in this case, IDNR.
The county has a single permit application that covers all work in waterways that will be
proposed on this project. The stormwater permit includes provisions for hydraulic/floodplain
impacts, wetland impacts, and property impacts.
Hydraulic/Floodplain impacts are the most important category to identify prior to taking any
project beyond conceptual design. It is premature to estimate what the impacts of the three
alternatives would be at each of the dam locations. Removal of fixed elevation dams may
increase or decrease the flood elevation depending on location along the profile, the nature of the
impoundment, and the local hydraulics at the site for a range of flood events. Regardless of the
alternative used at the site, it will likely require a Letter of Map Revision (LOMR) through the
Federal Emergency Management Agency (FEMA). The LOMR is needed for both increases and
decreases to the existing base flood elevations. If an increase in the base flood elevation is
needed, easements will have to be secured from adjacent property owners who are affected.
Wetland impacts will be the next important parameter to characterize in the project. Wetland
impacts associated with dam removal are evaluated on a case by case basis. Obviously wetlands
that have been created as a result of dam construction would be impacted by removal. The
quality of these wetlands and the impact to them is weighed against the potential ecological
benefits of the dam removal/modification itself. Mitigation may be required if high quality or
critical wetlands are impacted.
5.4.2 Reservoir Sediment
The correct characterization and understanding of reservoir sediments is the largest factor
governing dam removal. Because dam bridging would have limited impact on upstream
sediment transport, this discussion is mainly pertinent to full removal options. Reservoir
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sediments must first be evaluated for contamination. If material is deemed to be contaminated,
the options for removal are likely limited to those that involve full removal of all contaminated
material after drawdown or suction dredging material prior to dewatering the reservoir. This
situation represents the most costly project scenario. If it is determined that the sediment is not
contaminated, the next concern is transport of the material downstream.
There are no models currently available to accurately predict the movement and transport of
reservoir material following a dam removal. The DREAM model developed by UC-Berkeley
and Stillwater Sciences has made some inroads to model transport following dam removal,
however it has been developed for non-cohesive silt, sand, and gravel situations, which do not
often exist in Midwestern impoundments. HEC-6 has been used in the past to model transport,
but it is incapable of accurately modeling the steep slope that results once the dam is removed
and the nickpoint begins to move upstream (Cui, 2006.).
A decision must be made at this point based on limited information on how much material will
be allowed to move down from the reservoir. This decision affects the cost of the project. A
requirement of no material moving downstream means the sediment must be treated much like it
was contaminated and removed mechanically or stabilized in place, if practicable. The other
extreme is that the amount of material moving downstream is of little concern and the channel
can be allowed to restore itself through a process of incising and widening. Most removals fall
in the middle, where every attempt is made to stabilize material in place and excavate a volume
of material for the new channel which will minimize the majority of transport associated with
nickpoint migration and the ensuing channel widening.
5.4.3 Flood Impact
As mentioned above in the permitting section, quantifying the flood impact of any project on the
dams being studied is of utmost importance. The impact may increase or decrease the floodplain
boundaries as dictated by the Flood Insurance Rate Map (FIRM) from FEMA, and the recent
revisions to the FEQ model done by the County.
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6 SCREENING FOR STREAM AERATION
Numerous aeration technologies have been developed and utilized to increase dissolved oxygen
(DO) in water. The purpose of this section is to introduce the readers to available aeration
technologies and identify a group of technologies that may be feasible for implementation in the
East Branch of the DuPage River. Other approaches for increasing DO concentration, such as
in-stream improvements, may be feasible for this project but will be presented separately.
Feasible technologies, constructability, and efficiencies of alternatives identified in this section
will be further evaluated in Section 7.0 according to site-specific characteristics and project
objectives. Thus, this section will provide general information regarding application,
efficiencies, advantages, and disadvantages for each group of alternatives.
During this discussion, the term aeration will serve to designate the transfer of oxygen gas to the
water column. For this study, aeration will be synonymous with the term reaeration.
Additionally, this discussion designates low dissolved oxygen concentration as concentrations
less than the state water quality standard of 5.0 mg/L minimum (March – July); moderate
concentrations as concentrations from 5.0 mg/L to the point of saturation; and high
concentrations as concentrations at the point of oxygen saturation and above. Operational
effectiveness will be referenced as oxygen transfer efficiency (OTE) or the amount of oxygen
that is absorbed by water during the aeration process divided by the amount of air or oxygen
applied to the water. Efficiencies used in this section are generalized efficiency ranges for the
technology applied to various conditions.
The following discussion incorporates information from scientific journals, government and state
reports, independent research, project case studies, and manufacturer supplied specifications
(where applicable). Available technologies are presented in three major categories: air-based
alternatives, high-purity oxygen alternatives, and side-stream alternatives. Subsections 6.1, 6.2
and 6.3 briefly describe various technologies and subsection 6.4 provides an overview of the
screening process. Table 6-1 provides a summary of the alternatives presented, and Table 6-2
lists the screening criteria and ranks alternatives in terms of general applicability.
6.1 Air-Based Alternatives
Approximately 21% of the earth’s atmosphere is comprised of oxygen. In general, air-based
alternatives are designed to expose as much water volume as possible to the atmosphere in order
to increase dissolved oxygen in the water. As water is exposed to the atmosphere, oxygen
absorbs into the water and dissolves until the pressure of oxygen in the atmosphere and the water
are the same. When this point is reached, the water is at a “saturated state” and dissolved oxygen
has reached the maximum theoretical concentration at ambient pressure and atmospheric
conditions. This subsection outlines alternatives that have been developed to increase or
maintain DO concentrations utilizing only the percentage and pressure of oxygen present in the
atmosphere. The following air-based alternatives are grouped into simple aeration, mechanical
aeration, and bubble aeration.
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6.1.1 Simple Aeration
Often associated with stream elevation changes, simple aeration exposes water to the atmosphere
as it drops and/or splashes into a lower pool. As a result, oxygen is entrained and the DO
concentration is increased in the lower pool. Examples of simple aeration devices include weirs,
inclined corrugated sheets, splashboards, cascade aerators, multiple-tray aerators, towers, and
columns. The existing dams in the East Branch of the DuPage River are also examples of simple
aeration.
Simple aeration devices are appropriate when sufficient changes in elevation are available,
stream sediment loads are small, and low-to-moderate oxygen transfer efficiencies are adequate.
If elevation changes are present, many of these alternatives can be implemented without a power
source due to the force of gravity. If elevation changes are not present, these alternatives will
require pumping to transfer water to the aeration device. In general, implementation may require
site considerations for constructability, a power source if pumping is required, permitting, and
maintenance access. The advantages to simple aeration alternatives include relatively low
operation costs, ease of construction (in some cases), and limited moving parts to service.
Disadvantages include the impediment for fish migration, and limitations due to navigational
impacts. In addition, placement of some simple aeration alternatives, such as weirs, could extend
the pooled conditions presently observed behind the dams on the East Branch of the DuPage
River thus contributing to the upstream sediment accumulation, and lower dissolved oxygen
levels upstream. Oxygen transfer efficiencies for these alternatives are low-to-moderate,
excluding the negative impact from the pooled effects and sediment buildup on the upstream side
of the device. Specific efficiencies are dependent on the height of the elevation drop or the
height of the aeration device, water velocity, and the initial DO concentration.
6.1.2 Mechanical Aeration
Mechanical aeration is achieved with devices that create movement in the water, via splashing or
agitation, or circulation between the top and bottom of the water column. Most mechanical
aerators are designed to operate at or near the surface of the water column and draw water up
into the air, but some aerators may be submerged and function by drawing the oxygenated
surface water to the bottom of the water column. Common examples of mechanical aeration
include paddlewheels, spray aerators, propeller-aspirator aerators, and jet aerators.
Implementation of these devices may require site considerations for constructability, availability
of an electrical source, permitting due to navigational impacts, placement of equipment and
access for maintenance and operation. All mechanical aerators require electrical power and
continuous maintenance on working parts.
Advantageous features of mechanical aeration devices include the ability to be placed in existing
conditions and generally low cost for implementation. Disadvantages of mechanical aeration
include the need for a continuous power source, operational costs for power consumption,
generation of noise during operation, possible safety issues, potential for navigational impacts,
and limitation of placement due to water depths. In general, oxygen transfer efficiencies for
these devices are low-to-moderate and depend on the initial DO concentration and the water
depth.
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Figure 6-1 - Mechanical Aeration Display
6.1.3 Bubble Aeration
Bubble aeration consists of utilizing blowers or air compressors to introduce bubbles into the
water column through air diffusers. The generated air stream is delivered via piping or tubing to
air diffusers at the bottom of the water column. In general air is forced through the diffuser
resulting in a release of small bubbles into the water. Examples of bubble aeration include
aeration cones, and fine and coarse bubble diffusers. In order to install bubble aerators, site
considerations may be required for constructability, availability of an electrical source,
equipment, and periodic access for maintenance and operation, and sufficient depth for efficient
oxygen transfer.
Figure 6-2 - Bubble Aeration
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Advantages of bubble aeration include the ability to be placed in existing conditions with relative
ease, minimal impacts from floating debris, widely serviceable components for repairs, and the
ability to operate in series. Disadvantages of bubble aeration include the need for a continuous
power supply, the need to place the piping/tubing level operational costs to generate an air
source, housing for the generator, clogging, and potential noise associated with blower operation.
Oxygen transfer efficiencies are low in shallow areas, but moderate efficiencies can be obtained
when the water depth is greater than 5 feet. The efficiency of bubble aeration systems is
dependent on the initial DO concentration, the size of bubbles generated, and the water depth.
6.2 High-Purity Oxygen Alternatives
High-purity oxygen alternatives for increasing dissolved oxygen are based on contacting the
water column with a concentrated source of oxygen, with or without pressure above ambient
atmospheric conditions. This concentrated or high-purity oxygen source is generally 90% to
99% oxygen versus the atmospheric percentage of around 21%. High-purity oxygen applications
generally require onsite storage of oxygen in the liquid form or on-site oxygen generation.
Specialized liquid oxygen vessels store the oxygen under pressure and utilize onsite vaporization
to convert liquid oxygen to gaseous oxygen. As an alternative to liquid storage, on-site oxygen
generators can be utilized to provide a source of high purity oxygen. However, there is more
complexity associated with on-site oxygen generation and the seasonal requirement generally
favors storage.
High-purity oxygen systems differ from atmospheric systems due to a larger pressure and
concentration differential between the oxygen source and the water column. The pressure and
concentration of oxygen in the air limits the mass transfer of oxygen in atmospheric systems. In
high-purity oxygen systems with increased pressure and oxygen concentration, the water can
reach DO concentrations up to 100 mg/L or more than ten-fold higher than with air systems. In
other words, oxygen can be continuously transferred to the water regardless of initial dissolved
oxygen content and partial pressure of the water. Thus, systems that utilize a source of high-purity
oxygen rather than atmospheric oxygen have much higher oxygen transfer efficiencies.
Supersaturated DO conditions in the water will dissipate with time as the water flows further
from the aeration source or as agitation occurs. This subsection outlines alternatives that have
been developed to increase dissolved oxygen concentrations utilizing high-purity oxygen. For
this discussion, alternatives are grouped into simple oxygenation and bubble oxygenation. For
high-purity oxygen, the term oxygenation will replace aeration as an indication of the high purity
versus atmospheric source of oxygen.
6.2.1 Simple Oxygenation Using High-Purity Oxygen
Simple oxygenation devices increase DO concentrations by allowing oxygen-starved water to
contact high-purity oxygen as it flows through a chamber. As water drops from the top of the
chamber to the bottom, a gas/liquid interface is created by contact between the water and the
oxygen source. Low head oxygenators (LHO) and sealed columns are two examples of devices
that can be utilized with high-purity oxygen. These alternatives would typically be applied in a
side-stream setting with pumping due to limitation of sufficient gradient change necessary to
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drive water through the devices, flow requirements, and navigational issues. Installation of these
devices may require site considerations for constructability, maintenance and operation access,
storage of supplies, and storage of liquid oxygen.
Advantages of these alternatives include high oxygen transfer efficiency, ease of construction,
little navigational impact, and low maintenance due to a limited number of working parts.
Disadvantages include potential for debris collection or clogging, placement of storage tanks,
and possible transportation costs.
Figure 6-3 - Low Head Oxygenators with liquid oxygen cylinders
6.2.2 Bubble Oxygenation Using High-Purity Oxygen
Bubble oxygenation devices are similar to bubble aeration devices but differ in respect to the
source of oxygen. Rather than an air stream traveling through an aeration cone or diffuser, high-purity
oxygen is utilized to create small bubbles that float from the bottom to the top of the water
column or oxygenation device. Bubble oxygenation systems include aeration cones, U-tubes,
porous diffusers, and nonporous diffusers. Installation of these devices may require site
considerations for constructability, maintenance and operation access, and storage of supplies
and liquid oxygen.
Advantages to bubble oxygenation devices include low navigational impacts, moderate-to-high
efficiencies due to the ability to supersaturate, adaptability to varying locations and water depths,
and ability to operate in varying water flows. Disadvantages include clogging (in some cases),
and high operational costs oxygen.
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Figure 6-4 - Diffuser Used for Bubble Aeration
6.3 Side-Stream Alternatives
Aeration of side-streams is another technique that can be utilized to increase DO concentrations.
Side stream applications involve partitioning a portion of the total river flow off and increasing
the dissolved oxygen concentration in that portion. Both air-based and high purity based sources
of oxygen can be utilized. The amount of water partitioned is site dependent but typically ranges
from 5% to 40% of the total flow. Higher DO increases are associated with larger volumes of
water contacted with the alternative, particularly with air-based alternatives. Specific side-stream
applications include side-stream elevated pool aeration (SEPA), pressurized side-stream
columns, side-stream channels, and bubble-free aeration; however, all alternatives outlined
above can also be implemented as a side-stream alternative with the construction of a side-stream
channel adjacent to the existing main riverbed. Advantages of the side-stream applications
include potential for community amenity (SEPA has been implemented in the Chicago Metro
area with positive results), a reduced column of water needed for direct addition of air or oxygen,
control over flow conditions, and enhanced ability to supersaturate when utilizing high-purity
oxygen (in some cases). Disadvantages include the need for elevation changes necessitating
pumping (in some cases), fish impingement and entrainment as a result of pumping, and the
required space adjacent to the main river channel. Advantages and disadvantages of specific air-based
and high purity based alternatives listed above would also apply, if chosen for
implementation.
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Figure 6-5 - Side-Stream Aeration Facility
6.4 Overview of Feasible Alternatives
It is possible that multiple strategies could be utilized at varying locations throughout the project
area. The ultimate efficiency and applicability of the technology selected to enhance dissolved
oxygen is site and condition dependent. For this reason, it is important to consider the
technologies that are most applicable for the general conditions in the East Branch DuPage River
as outlined in Section 3.0. Further evaluation of the site specific criteria is necessary. The list of
available alternatives must first be narrowed to those alternatives that have the greatest
opportunity for meeting the project objectives without generating public opposition and without
degrading local environmental conditions.
Using a similar matrix as Table 6-2, a numerical value has been assigned to each of the listed
alternatives. A simple one to three (most desirable to least desirable) ranking system was
implemented for categories classified as general, while a one to five (most desirable to least
desirable) ranking was implemented for categories that are critical for meeting the project
objective (see Table 6-1). Critical categories for this project were the ability to increase DO to
the state standard of 5.0 mg/L, navigation impacts, and efficiency of transfer at shallow depths.
The following descriptions outline ranking criteria for aeration technologies utilized in the initial
screening process:
• Ability to increase DO to the minimum state standard of 5.0 mg/L
Each alternative screened must be capable of increasing the DO to the standard under varying
conditions. This criterion is critical in order to achieve the project objective. Alternatives
that may be capable of meeting the objective but with significant effort and/or low transfer
efficiencies are more likely to receive a high score (least desirable), while alternatives
capable of quickly and efficiently meeting the standard are more capable of receiving a lower
score (most desirable).
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• Navigational impacts
Navigational impacts reflect the likelihood that an alternative will impede progress or
degrade the experience of individuals using the rivers for recreational purposes. This
criterion is considered critical. Alternatives that block recreation or require significant effort
to be avoided are more likely to receive a high score while alternatives that require no effort
to avoid or that do not block navigation are more likely to receive a low score.
• Efficiency of oxygen transfer in shallow water depths
This is critical criterion used to screen the ability of an alternative to meet the project
objective with adequate oxygen transfer efficiencies in shallow water depths present in many
areas of the East Branch of the DuPage River. Alternatives that will not operate or will
operate at greatly reduced efficiencies in shallow water are more likely to receive a high
score, while alternatives that are capable of operation and oxygen transfer in shallow depths
are more likely to receive a low score.
• Ability to increase dissolved oxygen concentration above saturation
This criterion is important for considering the ability of each alternative to create a positive
impact over great horizontal distances, thereby necessitating fewer installations along the
River. Alternatives that will have a localized impact on the DO concentrations are more
likely to receive a high score, while alternatives that are capable of enhancing DO
concentrations for greater horizontal distances are more capable of receiving a low score.
• Constructability complexity and costs
Alternatives that do require major renovations, present engineering and construction
challenges, or have an anticipated high investment cost are more likely to receive a high
score, while alternatives that are easily implemented and generally cost less are more likely
to receive a low score.
• Operation and/or maintenance issues
Considerations are given for frequency of maintenance, required site personnel, and monthly
operational costs. A high score reflects an alternative that is anticipated to be costly to
operate on a monthly basis and/or may require a significant investment in maintenance
dollars and man-hours. Lower scores are associated with alternatives that are relatively
maintenance free or require fewer man-hours.
• Public concerns
This criterion includes aesthetics, noise from equipment, and public safety issues that may be
associated with alternatives. Public perception is an important aspect for a successful
implementation of alternatives. Alternatives that are unsightly, obstruct views, and/or
generate an intolerable noise level are more likely to receive a high score, while alternatives
that remain less visible and are more aesthetically pleasing are more capable of a lower score.
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• Environmental impacts
This criterion screens alternatives that may through either construction or operation be
responsible for a negative impact to the local environment. Considerations are given for
alternatives that may cause species impingement or entrainment, alternatives that negatively
impact any adjacent wildlife, and alternatives that severely disrupt the environment of the
location where the alternative is implemented.
The general existing conditions on the East Branch of the DuPage River in addition to
operational limitations of the alternatives were considered in the ranking. For the screening
purposes of this study, the following scores were used to group items for further evaluation:
• <20 – Represents alternatives that are strong candidates for enhancing DO conditions and
may be applicable to the conditions present in the East Branch of the DuPage River. These
alternatives will be considered in the evaluation phase of this study.
The following alternatives are strong candidates for meeting the project objective: fine
bubble tubing, oxygen diffusers, U-tube, aeration cone (high purity oxygen based), low-head
oxygenator, sealed column, and all side-stream alternatives.
• 21-25 – Represents alternatives that are moderate candidates for enhancing DO. These
alternatives may be applicable only if very specific site and operational conditions are met.
These conditions would include such things as space or elevation change or the need to apply
alternatives in pools above dams.
The following alternatives are moderate candidates for meeting the project objectives:
cascade aerator, packed column, turbine aerators, spray aerators, paddlewheels, aeration
cones and air diffusers.
• >25 – Represents alternatives that are weak candidates and would not provide sufficient
opportunity to enhance DO. These alternatives will not be presented for consideration in the
evaluation phase.
The following alternatives are weak candidates for project objectives: any type of weir
configuration, spray tower, multiple tray aerators, jet aerators (submersible), and aeration
cones when using the atmosphere as a source of oxygen.
As previously outlined, the alternatives most suitable for meeting the project objective will be
more closely evaluated in Section 7.0 on a site specific basis.
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Table 6-1 - Aeration Alternatives
Aeration Alternative
Oxygen
Source
Efficiency
Power
Necessity
Navigational Impact
Operational and/or
Maintenance Issues
Other Comments
Simple Aeration
Weir, Inclined Corrugated Sheet,
Splash Board, Cascade Aerator
Air Low No
Moderate if placed in
main channel
Low maintenance and no
operation required
Requires elevation change; may contribute to localized
flooding and sediment accumulation
Simple Aeration
Spray Tower, Multiple-tray Aerator,
Packed Column
Air Moderate Likely Minimal
May need periodic
maintenance
Requires elevation change or pumping; large water
volumes require multiple units; aerators may become
clogged
Mechanical Aeration Paddlewheels,
Turbine Aerators (Jet Aspirators),
Pumps, Spray Aerators
Air Moderate Yes
Moderate if placed in
main channel
Periodic maintenance
is required
Sediment may accumulate in dead areas; good mixing
capabilities; potentially noisy and disturbing to aquatic
life
Mechanical Aeration Submersible
Aspirators and Jet Aerators
Air Moderate Yes Minimal
Periodic maintenance
is required
Potentially disturbing to aquatic life; difficult to access
for maintenance
Bubble Aeration
Porous and Nonporous Diffusers,
Aeration Cone
Air
Low to
Moderate
Yes None
Requires continuous
maintenance
Subject to clogging ,chemical or biological fouling;
requires good depth for high efficiency, adaptable to
various stream conditions
Bubble Aeration using High-Purity
Oxygen
Paclked or Sealed Column, Low
Head Oxygenator (LHO)
High Pure
O2
Moderate to
High
Yes None to minimal
May need periodic
maintenance
May require pumping; large water volumes require
multiple units; may become clogged or fouled by
organics and particulates
Bubble Aeration using High-Purity
Oxygen
Aeration Cone, U-tube Porous&
Nonporous Diffusers,
High Pure
O2
Moderate Yes None to minimal
Requires continuous
maintenance
Subject to clogging and chemical or biological fouling;
adaptable to various stream conditions
Side Stream Aeration Air Moderate Yes None Low maintenance
Requires stream modification, elevation change and
area adjacent to water body
Side-Stream Aeration
using Air based Alternative
Air Moderate Yes None
Depends on specific
alternativ