September, 2007
07/31/WQPC-WWF
EPA/600/R-07/121
Environmental Technology
Verification Report
Stormwater Source Area Treatment
Device
Hydro International
Downstream Defender®
Prepared by
NSF International
Under a Cooperative Agreement with
U.S. Environmental Protection Agency
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ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
U.S. Environmental Protection Agency
NSF International
ETV Joint Verification Statement
TECHNOLOGY TYPE:
APPLICATION:
TECHNOLOGY NAME:
TEST LOCATION:
COMPANY:
ADDRESS:
WEB SITE:
EMAIL:
STORMWATER TREATMENT TECHNOLOGY
SUSPENDED SOLIDS TREATMENT
DOWNSTREAM DEFENDER®, 6-ft DIAMETER
MADISON, WISCONSIN
HYDRO INTERNATIONAL
94 Hutchins Drive
Portland, Maine 04102
http://www.hydrointernational.biz/us/
stormwaterinquiries@hil-tech.com
PHONE: (207)756-6200
FAX: (207)756-6212
NSF International (NSF), in cooperation with the U.S. Environmental Protection Agency (EPA), operates
the Water Quality Protection Center (WQPC), one of six centers under the Environmental Technology
Verification (ETV) Program. The WQPC recently evaluated the performance of a 6-ft Downstream
Defender®, manufactured by Hydro International. The Downstream Defender® was installed at the
Madison Water Utility in Madison, Wisconsin. Earth Tech, Inc. and the United States Geologic Survey
(USGS) performed the testing.
EPA created ETV to facilitate the deployment of innovative or improved environmental technologies
through performance verification and dissemination of information. The ETV program's goal is to further
environmental protection by accelerating the acceptance and use of improved and more cost-effective
technologies. ETV seeks to achieve this goal by providing high quality, peer-reviewed data on technology
performance to those involved in the design, distribution, permitting, purchase, and use of environmental
technologies.
ETV works in partnership with recognized standards and testing organizations; stakeholder groups, which
consist of buyers, vendor organizations, and permitters; and with the full participation of individual
technology developers. The program evaluates the performance of innovative technologies by developing
test plans that are responsive to the needs of stakeholders, conducting field or laboratory tests (as
appropriate), collecting and analyzing data, and preparing peer-reviewed reports. All evaluations are
conducted in accordance with rigorous quality assurance protocols to ensure that data of known and
adequate quality are generated and that the results are defensible.
07/31/WQPC-WWF
The accompanying notice is an integral part of this verification statement.
VS-i
September 2007
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TECHNOLOGY DESCRIPTION
The following description of the Downstream Defender® was provided by the vendor and does not
represent verified information.
The Downstream Defender® is a hydrodynamic vortex separator designed to remove settleable solids (and
their associated pollutants), oil, and floatables from stormwater runoff. It consists of a cylindrical
concrete vessel, with plastic internal components and a 304 stainless steel support frame and connecting
hardware. The concrete vessel is a standard pre-cast cylindrical manhole with a tangential inlet pipe
installed below ground. Two ports at ground level provide access for inspection and clean out of stored
floatables and sediment. The internal components consist of two concentric hollow cylinders (the dip
plate and center shaft), an inverted cone (the center cone), a benching skirt, and a floatables lid.
The Downstream Defender® is self-activating, and operates on simple fluid dynamics. The geometry of
the internal components and placement of the inlet and outlet pipes are designed to direct the flow in a
pre-determined path through the vessel. Stormwater is introduced tangentially into the side of the vessel,
initially spiraling around the perimeter in the outer annular space between the dip plate cylinder and
manhole wall. Oil and floatables rise to the water surface and are trapped by the dip plate in the outer
annular space. As the flow continues to rotate about the vertical axis, it travels down towards the bottom
of the dip plate. Low energy vortex motion directs sediment toward the center and base of the vessel.
Flow passes under the dip plate and up through the inner annular space, between the dip plate and center
shaft, as a narrower spiraling column rotating at a slower velocity than the outer downward flow. The
outlet of the Downstream Defender® is a single central discharge from the top water level in the inner
annulus.
Performance of the Downstream Defender®, in terms of sediment removals, depends on the incoming
flow rate, particle size distribution, specific gravity, and runoff temperature. According to Hydro
International, for runoff at 15 C°, the Downstream Defender® will remove over 80% of settleable solids
with a specific gravity of 2.65 and a particle size distribution similar to Maine DOT road sand at flow
rates up to 3 cfs. Flows exceeding the design capacity (3 cfs for the tested system) would be bypassed by
a weir system installed upstream of the Downstream Defender®.
VERIFICATION TESTING DESCRIPTION
Methods and Procedures
The test methods and procedures used during the study are described in the Test Plan for the Verification
of. Downstream Defender® "Madison Water Utility Administration Building Site" Madison, Wisconsin
September 30, 2005. The Downstream Defender® was installed to treat runoff collected from a paved
parking area at the Madison Water Utility in Madison, Wisconsin. Madison receives an average annual
precipitation of nearly 33 in., with an average snowfall of 44 in.
Verification testing consisted of collecting data during a minimum of 15 qualified events that met the
following criteria:
• The total rainfall depth for the event, measured at the site, was 0.2 in. (5 mm) or greater;
• Flow through the treatment device was successfully measured and recorded over the duration of
the runoff period;
• A flow-proportional composite sample was successfully collected for both the inlet and the outlet
over the duration of the runoff event;
• Each composite sample was comprised of a minimum of five aliquots, including at least two
aliquots on the rising limb of the runoff hydrograph, at least one aliquot near the peak, and at least
two aliquots on the falling limb of the runoff hydrograph; and
• There was a minimum of six hours between qualified sampling events.
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Automated sample monitoring and collection devices were installed and programmed to collect composite
samples from the inlet, system outlet, bypass, and combined discharge (system plus bypass) during
qualified flow events. In addition to the flow and analytical data, operation and maintenance (O&M) data
were recorded. Samples were analyzed for total suspended solids (TSS), suspended sediment
concentration (SSC), total dissolved solids (TDS), volatile suspended solids (VSS), and particle size
distribution. The TSS analytical method was modified for samples with a heavy settleable sediment load
using a procedure developed by USGS. The adjusted TSS method was designed to provide an improved
methodology for measuring large, dense sediment particles in samples. Refer to the verification report for
additional details about the modified TSS method.
VERIFICATION OF PERFORMANCE
Verification testing of the Downstream Defender® lasted approximately 17 months, and coincided with
testing conducted by USGS and the Wisconsin Department of Natural Resources. A total of 20 storm
events were sampled.
Test Results
The precipitation data for the rain events are summarized in Table 1. Peak flow rates exceeded the rated
treatment capacity of the Downstream Defender® during events 5, 6, 19 and 20. These events were large
and intense, and it appeared that runoff from an adjacent drainage area may have contributed additional
flow and organic solids loading to the unit during these events.
The monitoring results were evaluated using event mean concentration (EMC) and sum of loads (SOL)
comparisons. The EMC evaluates treatment efficiency on a percentage basis by dividing the outlet
concentration by the inlet concentration and multiplying the quotient by 100. The EMC was calculated
for each analytical parameter and each storm event. The SOL comparison evaluates the treatment
efficiency on a percentage basis by comparing the sum of the inlet and outlet loads (the parameter
concentration multiplied by the runoff volume) for all storm events. The calculation is made by
subtracting from one the quotient of the total outlet load divided by the total inlet load, and multiplying by
100. SOL results can be summarized on an overall basis since the loading calculation takes into account
both the concentration and volume of runoff from each event. The analytical data ranges, EMC range,
and SOL reduction values are shown in Table 2.
The ratio of organic sediment to total sediment was measured by evaluating the ratio of VSS to TSS or
SSC. This ratio showed a median organic sediment loading of 21% over all events, with a range of 4.7%
to 67% during individual events. Organic materials, which include grass or leaf debris, are less dense
than inorganic sediments, such as soil. The vendor claims that the Downstream Defender® is not as
effective at removing lower-density organic solids from runoff.
A particle size gradation was conducted to quantify percentage (by weight) of particles ranging from
>500 um to <2 um, and the SOL was recalculated based on particle sizes. The particle size distribution of
the sediments encountered at this site was significantly finer than the Maine DOT road sand and F-110
Silica Sand which formed the basis of product claims. For the range of solids encountered at this site, the
Downstream Defender® removed 90% of particles larger than 250 um on a cumulative basis. As shown in
Table 3, the Downstream Defender® removed 78% of the particles greater than 125 um and 67% of the
particles greater than 63 um on a cumulative basis.
System Operation
The Downstream Defender® was installed prior to verification, so verification of installation procedures
on the system was not documented. It was thoroughly cleaned prior to the start of verification testing.
The Downstream Defender® was inspected periodically during verification, and no significant issues were
noted. By the end of the verification test, the sediment chamber contained sediment at an approximate
average depth of 0.35 ft. A particle size distribution analysis conducted on the retained solids showed
07/31 /WQPC-WWF The accompanying notice is an integral part of this verification statement. September 2007
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that approximately 93% of the retained solids were 125 um or larger. No specific gravity analysis was
conducted for the captured solids; however, visual inspections suggested significant organic content. The
dry weight of the retained solids was 416 pounds.
Table 1. Rainfall Data Summary
Rainfall Rainfall Runoff
Event Start Amount Duration Volume
Number Date Time (in.) (hr:min)
1.
2.
3.
4.
1 3/8/06 18:03 0.71 4:36
2 3/12/06 18:34 0.43 9:25
3 4/2/06 20:41 1.01 10:01
4 4/12/06 5:07 0.37 2:56
51 4/16/06 4:15 1.13 12:44
6 4/29/06 17:18 1.65 25:38
7 5/1/06 21:16 0.25 0:26
8 5/9/06 12:01 0.37 6:50
9 5/11/06 6:59 0.86 23:55
10 5/17/06 15:36 0.23 2:02
11 6/25/06 17:34 0.79 15:41
12 7/9/06 19:45 0.36 0:08
13 7/11/06 8:44 1.87 8:51
14 7/19/06 21:43 0.96 9:44
15 7/22/06 16:51 0.36 0:30
161 7/27/06 12:27 2.16 1:30
17 8/6/06 6:53 0.71 5:08
18 8/17/06 16:27 0.29 1:45
191 8/23/06 23:06 1.60 8:17
201 8/24/06 13:30 1.35 2:13
(ft3)2
1,880
1,370
5,910
1,980
6,230
8,480
1,570
2,090
5,040
1,310
4,250
1,430
10,990
4,680
1,860
7,150
3,630
1,300
13,450
17,180
Peak Flow
Rate (cfs) 2
1.0
0.42
0.38
0.63
5.81
0.66
2.0
0.35
0.18
0.85
0.67
2.6
1.5
2.5
1.9
6.51
0.50
1.3
4.41
4.61
Water
Temp.
(°C)
3.5
4.6
15.5
3
3
3
3
15.44
10.54
14.84
19.04
24.84
20.74
22.84
23.04
24.04
23.44
22.44
22.44
22.84
Peak flow capacity was exceeded and bypass flows were sampled.
Runoff volume and peak discharge rate measured at the inlet
report for further details.
Temperature not recorded due to equipment malfunction.
Water temperature recorded at a nearby stormwater sampling
Department of Natural Resources.
monitoring point. See the verification
site monitored by Wisconsin
Table 2. Analytical Data, EMC Range, and SOL Reduction Results
SOL SOL reduction
Inlet Outlet reduction all events inc.
range range EMC range w/o bypass bypass
Parameter (mg/L) (mg/L) (%) (%) (%)
TSS
ssc
TDS
vss
23 - 700
22 - 904
<50 - 260
9-76
19-584
21-662
<50 - 238
10-76
-51-62
-47 - 70
-163-55
-82 - 19
27
42
1
-7
22
33
1
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07/31/WQPC-WWF
The accompanying notice is an integral part of this verification statement.
VS-iv
September 2007
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Table 3. Sediment Sum of Load Results by Particle Size Category
Individual
Particle Size Load
DD System
Cumulative
Particle Size Load
DD System
Particle Size
Category (um)
>500
250-500
125-250
63-125
32-63
14-32
DD Inlet
Ob)
453
449
150
128
122
517
DD Outlet
Ob)
39
49
146
156
122
550
Bypass
Ob)
32
58
49
56
31
164
Efficiency
91
89
3
-2
0
-6
Efficiency
85
79
2
-15
0
-5
Efficiency
91
90
78
67
61
42
Efficiency
85
82
69
58
52
34
Quality Assurance/Quality Control
NSF personnel completed a technical systems audit during testing to ensure that the testing was in
compliance with the test plan. NSF also completed a data quality audit of at least 10% of the test data to
ensure that the reported data represented the data generated during testing. In addition to QA/QC audits
performed by NSF, EPA personnel conducted an audit of NSF's QA Management Program.
Original signed by
Sally Gutierrez
October 15, 2007
Sally Gutierrez Date
Director
National Risk Management Research Laboratory
Office of Research and Development
United States Environmental Protection Agency
Original signed by
Robert Ferguson
October 3, 2007
Robert Ferguson
Vice President
Water Systems
NSF International
Date
NOTICE: Verifications are based on an evaluation of technology performance under specific,
predetermined criteria and the appropriate quality assurance procedures. EPA and NSF make no expressed
or implied warranties as to the performance of the technology and do not certify that a technology will
always operate as verified. The end user is solely responsible for complying with any and all applicable
federal, state, and local requirements. Mention of corporate names, trade names, or commercial products
does not constitute endorsement or recommendation for use of specific products. This report is not an NSF
Certification of the specific product mentioned herein.
Availability of Supporting Documents
Copies of the ETV Verification Protocol, Stormwater Source Area Treatment Technologies Draft
4.1, March 2002, the verification statement, and the verification report (NSF Report Number
07/31/WQPC-WWF) are available from:
ETV Water Quality Protection Center Program Manager (hard copy)
NSF International
P.O. Box 130140
Ann Arbor, Michigan 48113-0140
NSF website: http://www.nsf.org/etv (electronic copy)
EPA website: https://www.epa.gov/etv (electronic copy)
Appendices are not included in the verification report, but are available from NSF upon request.
07/31/WQPC-WWF
The accompanying notice is an integral part of this verification statement.
VS-v
September 2007
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Environmental Technology Verification Report
Stormwater Source Area Treatment Device
Hydro International.
Downstream Defender®
Prepared for:
NSF International
Ann Arbor, MI 48105
Prepared by:
Earth Tech Inc.
Madison, Wisconsin
With assistance from:
United States Geologic Survey (Wisconsin Division)
Wisconsin Department of Natural Resources
Under a cooperative agreement with the U.S. Environmental Protection Agency
Raymond Frederick, Project Officer
ETV Water Quality Protection Center
National Risk Management Research Laboratory
Water Supply and Water Resources Division
U.S. Environmental Protection Agency
Edison, New Jersey
September, 2007
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Notice
The U.S. Environmental Protection Agency (EPA) through its Office of Research and
Development has financially supported and collaborated with NSF International (NSF) under a
Cooperative Agreement. The Water Quality Protection Center (WQPC), operating under the
Environmental Technology Verification (ETV) Program, supported this verification effort. This
document has been peer reviewed and reviewed by NSF and EPA and recommended for public
release. Mention of trade names or commercial products does not constitute endorsement or
recommendation by the EPA for use.
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Foreword
The following is the final report on an Environmental Technology Verification (ETV) test
performed for NSF International (NSF) and the United States Environmental Protection Agency
(EPA). The verification test for the Downstream Defender® was conducted at a testing site in
Madison Wisconsin, owned and operated by the City of Madison Water Utility.
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage our
ecological resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for
investigation of technological and management approaches for preventing and reducing risks
from pollution that threaten human health and the environment. The focus of the Laboratory's
research program is on methods and their cost-effectiveness for prevention and control of
pollution to air, land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites, sediments and ground water; prevention and control
of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public
and private sector partners to foster technologies that reduce the cost of compliance and to
anticipate emerging problems. NRMRL's research provides solutions to environmental
problems by: developing and promoting technologies that protect and improve the environment;
advancing scientific and engineering information to support regulatory and policy decisions; and
providing the technical support and information transfer to ensure implementation of
environmental regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan.
It is published and made available by EPA's Office of Research and Development to assist the
user community and to link researchers with their clients.
11
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Contents
Verification Statement VS-i
Notice i
Foreword ii
Contents iii
Figures iv
Tables v
Abbreviations and Acronyms vi
Chapter 1 Introduction 1
1.1 ETV Purpose and Program Operation 1
1.2 Testing Participants and Responsibilities 1
1.2.1 U.S. Environmental Protection Agency 2
1.2.2 Verification Organization 2
1.2.3 Testing Organization 3
1.2.4 Analytical Laboratories 4
1.2.5 Vendor 4
1.3 System Owner/Operator 5
Chapter 2 Technology Description 6
2.1 Treatment System Description 6
2.2 Technology Description (site specific) 9
2.3 Maintenance 14
2.4 Performance Claim 15
2.4.1 Total Suspended Solids 15
2.4.2 Metals and Nutrients 17
2.4.3 Hydrocarbons 17
2.4.4 Floatables 17
Chapters Test Site Description 18
3.1 Location and Land Use 18
3.2 Pollutant Sources and Site Maintenance 21
3.3 Stormwater Conveyance System 21
3.4 Water Quality /Water Resources 22
3.5 Local Meteorological Conditions 22
Chapter 4 Sampling Procedures and Analytical Methods 23
4.1 Sampling Locations 23
4.2 Other Monitoring Locations 24
4.3 Monitoring Equipment 24
4.4 Contaminant Constituents Analyzed 25
4.5 Sampling Schedule 25
4.6 Field Procedures for Sample Handling and Preservation 29
Chapter 5 Monitoring Results and Discussion 30
5.1 Monitoring Results: Performance Parameters 30
5.1.1 Concentration Efficiency Ratio 30
5.1.2 Sum of Loads 34
5.2 Particle Size Distribution 36
Chapter 6 QA/QC Results and Summary 41
6.1 Laboratory/Analytical Data QA/QC 41
in
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6.1.1 Bias (Field Blanks) 41
6.1.2 Replicates (Precision) 41
6.1.3 Accuracy 43
6.1.4 Representativeness 43
6.1.5 Completeness 44
6.2 Flow Measurement Calibration 44
6.2.1 Gauge Height Calibration 44
6.2.2 Flow Calibrations 45
6.2.3 Comparison of Runoff Volumes: Rainfall Depth vs. Flow Measurements .. 48
6.3 Other Monitoring Complications 49
Chapter 7 Operations and Maintenance Activities 51
7.1 System Operation and Maintenance 51
7.2 Description of Post Monitoring Cleanout and Results 52
7.2.1 Background 52
Chapter 8 Vendor Comments 55
Chapter 9 References 56
Glossary 58
Appendices 60
A Adjusted TSS Analysis Discussion 60
B Test Plan 60
C Event Hydrographs and Rain Distribution 60
D Analytical Data Reports with QC 60
Figures
Figure 2-1. Downstream Defender® interior view (generic depiction) 7
Figure 2-2. Downstream Defender® submerged inlet and isolated pollutant storage locations.... 8
Figure 2-3. Downstream Defender® - internal components 9
Figure 2-4. Elevation view of the Downstream Defender® 11
Figure 2-5. General arrangement of the Downstream Defender®, Madison, WI 12
Figure 2-6. Plan view of the Downstream Defender®, Madison, WI 13
Figure 2-7. Particle size distribution for ME DOT road sand and F-l 10 silica sand 16
Figure 2-8. Removal efficiencies for differing sediment gradations at 15 °C 16
Figure 3-1. Site location 19
Figure 3-2. Site map and drainage area 20
Figure 3-3. (a) Diversion between test site and adjacent side (b) evidence of overtopping after
runoff event 21
Figure 4-1. Monitoring equipment for sites B and C 23
Figure 4-2. Monitoring equipment for sites D and E 24
Figure 5-1. Average and maximum influent particle size distribution compared to vendor's
performance claim based on F-110 silica sand 39
Figure 6-1. Flow calibration plots comparing dye dilution flow to inlet discharge meter for event
occurring May 9, 2006 46
Figure 6-2. Flow calibration plots comparing dye dilution flow to inlet discharge meter for event
occurring May 16, 2006 46
Figure 6-3. System outlet flow rating curve as a function of inlet discharges 47
Figure 7-1. Graphical representation of retained solids particle size distribution range 54
IV
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Figure 8-1. Estimated removal efficiencies for ME DOT road sand, F-110 silica sand, and test
site sediment at 15 °C 55
Tables
Table 2-1. Downstream Defender® Pollutant Storage Capacities and Maximum Clean-out
Depths 15
Table 3-1. Drainage Area Land Use 18
Table 4-1. Monitoring Equipment 25
Table 4-2. Constituent List for Water Quality Monitoring 26
Table 4-3. Summary of Events Monitored for Verification Testing 27
Table 4-4. Rainfall Summary for Monitored Events 28
Table 5-1. Monitoring Results and Efficiency Ratios for Sediment Parameters 31
Table 5-2. Adjusted TSS Calculations for Downstream Defender® Inlet 32
Table 5-3. Adjusted TSS Calculations for Downstream Defender® Outlet 32
Table 5-4. Adjusted TSS Calculations for System Outlet 32
Table 5-5. Ratio of Organic Sediment Concentrations to Total Sediment Concentrations 33
Table 5-6. Sediment Sum of Loads Results (adjusted TSS and SSC) 36
Table 5-7. Sediment Sum of Loads Results (TDS and VSS) 37
Table 5-8. Particle Size Distribution Analysis Results 38
Table 5-9. Sediment Sum of Load Results by Particle Size Category - Individual Particle Size
Load 39
Table 5-10. Sediment Sum of Load Results by Particle Size Category - Cumulative Particle Size
Load 40
Table 6-1. Field Blank Analytical Data Summary 41
Table 6-2. Field Duplicate Relative Percent Difference Data Summary 42
Table 6-3. Laboratory Duplicate Sample Relative Percent Difference Data Summary 43
Table 6-4. Laboratory Control Sample Data Summary 43
Table 6-5. Comparison of Calculated vs. Metered Runoff Volumes 49
Table 7-1. Operation and Maintenance During Verification Testing 51
Table 7-2. Field Measurements During Post-Monitoring Cleanout Activities 53
Table 7-3. Retained Solids Particle Size Distribution Analysis 54
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Abbreviations and Acronyms
ASTM
BMP
cfs
DD
DOT
EMC
EPA
ETV
ft
ft2
ft3
g
gal
gpm
hr
in.
kg
L
L/min
Ib
LOD
LOQ
MH
mm
NRMRL
mg/L
min
MS/MSD
NSF
NIST
O&M
QA
QAPP
QC
RPD
ssc
SOL
SOP
Std. Dev.
IDS
TO
TSS
USGS
VO
American Society for Testing and Materials
Best Management Practice
Cubic feet per second
Hydro International's Downstream Defender®
Department of Transportation (reference to Maine DOT)
Event mean concentration
U.S. Environmental Protection Agency
Environmental Technology Verification
Foot or feet
Square feet
Cubic feet
Gram
Gallon
Gallon per minute
Hour
Inch
Kilogram
Liters
Liters per minute
Pound
Limit of detection
Limit of quantification
Manhole
Millimeter
National Risk Management Research Laboratory
Micron
Milligram per liter
Minute
Matrix spike/matrix spike duplicate
NSF International, formerly known as National Sanitation Foundation
National Institute of Standards and Technology
Operations and maintenance
Quality assurance
Quality Assurance Project Plan
Quality control
Relative percent difference
Suspended sediment concentration
Sum of loads
Standard operating procedure
Standard deviation
Total dissolved solids
Testing Organization
Total suspended solids
United States Geological Survey
Verification Organization (NSF)
VI
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VSS Volatile suspended solids
WDNR Wisconsin Department of Natural Resources
WQPC Water Quality Protection Center
WisDOT Wisconsin Department of Transportation
WSLH Wisconsin State Laboratory of Hygiene
vn
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Chapter 1
Introduction
1.1 ETV Purpose and Program Operation
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification (ETV) Program to facilitate the deployment of innovative or improved
environmental technologies through performance verification and dissemination of information.
The goal of the ETV program is to further environmental protection by substantially accelerating
the acceptance and use of improved and more cost-effective technologies. ETV seeks to achieve
this goal by providing high quality, peer reviewed data on technology performance to those
involved in the design, distribution, permitting, purchase, and use of environmental technologies.
ETV works in partnership with recognized standards and testing organizations; stakeholders
groups, which consist of buyers, vendor organizations, and permitters; and with the full
participation of individual technology developers. The program evaluates the performance of
innovative technologies by developing test plans that are responsive to the needs of stakeholders,
conducting field or laboratory (as appropriate) testing, collecting and analyzing data, and
preparing peer reviewed reports. All evaluations are conducted in accordance with rigorous
quality assurance protocols to ensure that data of known and adequate quality are generated and
that the results are defensible.
NSF International (NSF), in cooperation with the EPA, operates the Water Quality Protection
Center (WQPC). The WQPC evaluated the performance of the Downstream Defender®, a
stormwater treatment device designed to remove suspended solids, and other stormwater
pollutants from wet weather runoff.
It is important to note that verification of the equipment does not mean that the equipment is
"certified" by NSF or "accepted" by EPA. Rather, it recognizes that the performance of the
equipment has been determined and verified by these organizations for those conditions tested by
the Testing Organization (TO).
1.2 Testing Participants and Responsibilities
The ETV testing of the Downstream Defender® was a cooperative effort among the following
participants:
• U.S. Environmental Protection Agency
• NSF International
• U.S. Geologic Survey (USGS)
• Wisconsin Department of Natural Resources (WDNR)
• Wisconsin State Laboratory of Hygiene (WSLH)
• USGS Sediment Laboratory
• Earth Tech, Inc.
• Hydro International
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The following is a brief description of each ETV participant and their roles and responsibilities.
7.2.7 U.S. Environmental Protection Agency
The EPA Office of Research and Development, through the Urban Watershed Branch, Water
Supply and Water Resources Division, National Risk Management Research Laboratory
(NRMRL), provides administrative, technical, and quality assurance guidance and oversight on
all ETV Water Quality Protection Center activities. In addition, EPA provides financial support
for operation of the Center and partial support for the cost of testing for this verification.
The key EPA contact for this program is:
Mr. Ray Frederick, ETV WQPC Project Officer
(732)321-6627
email: Frederick.Ray@epamail.epa.gov
U.S. EPA, NRMRL
Urban Watershed Management Research Laboratory
2890 Woodbridge Avenue (MS-104)
Edison, New Jersey 08837-3679
7.2.2 Verification Organization
NSF is the verification organization (VO) administering the WQPC in partnership with EPA.
NSF is a not-for-profit testing and certification organization dedicated to public health, safety,
and protection of the environment. Founded in 1946 and located in Ann Arbor, Michigan, NSF
has been instrumental in development of consensus standards for the protection of public health
and the environment. NSF also provides testing and certification services to ensure that products
bearing the NSF name, logo and/or mark meet those standards.
NSF personnel provided technical oversight of the verification process. NSF also provided
review of the test plan and this verification report. NSF's responsibilities as the VO include:
• Review and comment on the test plan;
• Review quality systems of all parties involved with the TO, and qualify the TO;
• Oversee TO activities related to the technology evaluation and associated laboratory
testing;
• Conduct an on-site audit of test procedures;
• Provide quality assurance/quality control (QA/QC) review and support for the TO;
• Oversee the development of the verification report and verification statement; and
• Coordinate with EPA to approve the verification report and verification statement.
-------
Key contacts at NSF are:
Mr. Thomas Stevens, P.E. Mr. Patrick Davison
Program Manager Project Coordinator
(734) 769-5347 (734) 913-5719
email: stevenst@nsf.org email: davison@nsf.org
NSF International
789 North Dixboro Road
Ann Arbor, Michigan 48105
1.2.3 Testing Organization
The TO for the verification testing was Earth Tech, Inc. of Madison, Wisconsin (Earth Tech),
with assistance from USGS in Middleton, Wisconsin. USGS provided testing equipment, helped
to define field procedures, conducted the field testing, coordinated with the analytical
laboratories, and conducted initial data analyses.
The TO provided all needed logistical support, established a communications network, and
scheduled and coordinated activities of all participants. The TO was responsible for ensuring
that the testing location and conditions allowed for the verification testing to meet its stated
objectives. The TO prepared the test plan; oversaw the testing; and managed, evaluated,
interpreted and reported on the data generated during the testing, as well as evaluated and
reported on the performance of the technology. TO employees set test conditions, and measured
and recorded data during the testing. The TO's Project Manager provided project oversight.
The key personnel and contacts for the TO are:
Earth Tech:
Mr. Jim Bachhuber, P.H.
(608)828-8121
email: jim_bachhuber@earthtech. com
Earth Tech, Inc.
1210 Fourier Drive
Madison, Wisconsin 53717
USGS:
Ms. Judy Horwatich
(608) 821-3874
email: jahorwat@usgs.gov
-------
USGS
8505 Research Way
Middleton, Wisconsin 53562
1.2.4 Analytical Laboratories
The WSLH, located in Madison, Wisconsin, analyzed the stormwater samples for the parameters
identified in the test plan. The USGS Sediment Laboratory, located in Iowa City, Iowa,
performed the particle size analysis on the material removed from the Downstream Defender®
sump at the end of the monitoring period. All other suspended sediment concentration
separations and particle size analyses were conducted by WSLH.
The key analytical laboratory contacts are:
Mr. George Bowman Ms. Pam Smith
(608) 224-6279 (319) 358-3602
email: gtb@mail.slh.wisc.edu email: pksmith@usgs.gov
WSLH USGS Sediment Laboratory
2601 Agriculture Drive Federal Building Room 269
Madison, Wisconsin 53718 400 South Clinton Street
Iowa City, Iowa 52240
7.2.5 Vendor
The Downstream Defender® is designed by Hydro International, US headquartered in Portland,
Maine. Hydro International was responsible for providing technical support, and was available
during the tests to provide technical assistance as needed.
The key contact for Hydro International is:
Mr. Kwabena Osei
(207) 756-6200
kosei@hil-tech.com
Hydro International
94 Hutchins Drive
Portland, ME 04102
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1.3 System Owner/Operator
®
A 6-ft diameter Downstream Defender was installed at the Madison Water Utility at 119 East
Olin Avenue, Madison Wisconsin.
The key contact for the Madison Water Utility is:
Mr. Alan Larson
608-266-4651
allarson@madisonwater.org
Madison Water Utility
119 East Olin Avenue
Madison, WI 53713
Bureau of Environment
Wisconsin Department of Transportation
4802 Sheboygan Avenue, Room 451
Madison, Wisconsin 53707
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Chapter 2
Technology Description
The following technology description data was supplied by the vendor and does not represent
verified information.
2.1 Treatment System Description
The information provided in this section was provided by the vendor and has not been verified
by the TO. The information is a generic description of the product being tested and is not
specific to the Madison Water Utility site.
The Downstream Defender® is an advanced hydrodynamic vortex separator designed to remove
settleable solids (and their associated pollutants), oil, and floatables from stormwater runoff. Its
flow-modifying internal components have been developed from extensive full-scale testing,
computational fluid dynamics modeling and over thirty years of hydrodynamic separation
experience in wastewater, combined sewer, and stormwater applications. The internal
components distinguish the Downstream Defender® from simple swirl-type devices and
conventional oil/grit separators by minimizing turbulence and headlosses, enhancing separation,
and preventing re-suspension of previously stored pollutants.
The Downstream Defender® has no moving parts and no external power requirements. It
consists of a cylindrical concrete vessel, with plastic internal components and a 304 stainless
steel support frame and connecting hardware. The concrete vessel is a standard pre-cast
cylindrical manhole with a tangential inlet pipe installed below ground. Two ports at ground
level provide access for inspection and clean out of stored floatables and sediment. The internal
components consist of two concentric hollow cylinders (the dip plate and center shaft), an
inverted cone (the center cone), a benching skirt, and a floatables lid. The Downstream
Defender's® key components are illustrated in Figure 2-1.
The Downstream Defender® is self-activating, and operates on simple fluid dynamics. The
geometry of the internal components and placement of the inlet and outlet pipes are designed to
direct the flow in a pre-determined path through the vessel.
Stormwater is introduced tangentially into the side of the vessel, initially spiraling around the
perimeter in the outer annular space between the dip plate cylinder and manhole wall. Oil and
floatables rise to the water surface and are trapped by the dip plate in the outer annular space. As
the flow continues to rotate about the vertical axis, it travels down towards the bottom of the dip
plate. Low energy vortex motion directs sediment toward the center and base of the vessel.
Flow passes under the dip plate and up through the inner annular space, between the dip plate
and center shaft, as a narrower spiraling column rotating at a slower velocity than the outer
downward flow.
-------
Access Ports
Support Frame
Dip Plate
Tangential Inlet
Center Shaft
Center Cone
Benching Skirt
Floatables Lid
Outlet Pipe
Pipe Coupling
Floatables Storage
Sediment Storage
Concrete Manhole
Figure 2-1. Downstream Defender" interior view (generic depiction).
The outlet of the Downstream Defender® is a single central discharge from the top water level in
the inner annulus. Discharging from the inner annulus forces each fluid element to pass through
a long spiral path from the inlet, downward through the outer annulus, then upward through the
inner annulus before it can be released. This increases the retention time for the separation of
settleable solids and floatables.
The Downstream Defender® is designed to collect accumulated pollutants outside the treatment
flow path. This prevents re-entrainment into the effluent during major storms or surcharge
conditions. Furthermore, removal and retention efficiencies are maintained because pollutants
such as sediment, floatables, and oils accumulate between clean-outs and are collected and stored
in isolated storage zones over a period of several months.
A section view of the Downstream Defender® is shown in Figure 2-2 to illustrate isolated
pollutant storage locations and the purpose of the offset inlet and outlet inverts. The
Downstream Defender® is designed with a submerged inlet. The crown of the inlet pipe where it
connects to the unit is at the same elevation as the invert of the outlet pipe. The outlet pipe invert
is placed on the hydraulic profile to maintain a static water level in the Downstream Defender®
equal to the invert elevation of the outlet pipe. During a storm event, the submerged inlet
introduces flow below the unit's static water surface, forcing floatables to rise into the outer
annular region between the dip plate and concrete manhole. Submerging the inlet aids in
stabilizing the flow regime over the unit's entire flow range. This enhances the removal
efficiency and prevents re-suspension and washout (re-entrainment) of previously stored
pollutants.
-------
Headlosses of the Downstream Defender® are primarily a function of the inlet pipe diameter. The
larger the inlet pipe diameter, the lower the headlosses. Headlosses can be decreased by
increasing the inlet pipe diameter up to the diameter of the outlet pipe.
Isolated Oil Storage
Isolated Sediment Storage Su
Figure 2-2.
locations.
Downstream Defender" submerged inlet and isolated pollutant storage
As the rotating flow spirals downward in the outer annular space, the benching skirt directs
sediment toward the center and base of the vessel where it is collected in the sediment storage
facility, beneath the vortex chamber. The center cone protects stored sediment and redirects the
main flow upwards and inwards under the dip plate into the inner annular space. The dip plate is
located at the shear zone (the interface between the outer downward circulation and the inner
upward circulation where a marked difference in velocities encourages solids separation). A
floatables lid covers the effluent area in the inner annular space between the dip plate and center
shaft to keep oil and floatables stored in the outer annulus separate from the treated effluent.
Figure 2-3 summarizes how the internal components of the Downstream Defender® address
storing pollutants within the same vessel without compromising removal efficiencies due to re-
suspension and/or washout (re-entrainment).
-------
the floatables lid
the dip plate cylinder
the center cone redirects the main flow upward into the
inner annular space and prevents re-suspension of
sediment by sheltering the sediment storage sump
below.
the benching skirt
Figure 2-3. Downstream Defender" - internal components.
The Downstream Defender can be used in the following applications:
• New developments and retrofits;
• Construction sites;
• Streets and roadways;
• Parking lots;
• Vehicle maintenance wash-down yards;
• Industrial and commercial facilities;
• Wetlands protection; and
• Pre-treatment for filter and other polishing systems.
The unit should be installed in a location that is easily accessible for a maintenance vehicle,
preferably in a flat area close to a roadway or parking area.
2.2 Technology Description (site specific)
Specific information on the Downstream Defender® installed at the test site is presented in this
section. All pipe sizes were measured by Earth Tech and USGS during an inspection trip on
June 22, 2005. All pipe diameters are inside diameters. The field measured pipe diameters do
not always match the sizes shown on Figures 2-4, 2-5, and 2-6. These differences may be for the
following reasons:
• Some field measurements were very difficult to obtain because of the location of the
pipe. The field measurements should be considered ±0.5 in.;
-------
• The pipes' shapes may be deflected during the construction process and round pipes are
now slightly different in shape; or
• The size pipe installed was not the same as the pipe size shown in the drawings.
A 6-ft diameter Downstream Defender® was installed at the Madison Water Utility site in the fall
of 2004. Two clean out/access ports at grade level are located above the Downstream
Defender®. A flow diversion structure is located approximately 13 ft north of the Downstream
Defender®. Flow from the drainage area is received to the diversion structure through a 13.5-in.
PVC inlet pipe. The Downstream Defender® has a 12-in. PVC inlet pipe and a 16.5-in. PVC
outlet pipe. A weir in the diversion manhole has a crest elevation approximately 14 in. above the
invert of the inlet pipe. The outlet pipe from the diversion manhole to the site's wet detention
pond is 13 in. in diameter.
Figures 2-4, 2-5, and 2-6 detail the planned design for the Downstream Defender® at the
Madison Water Utility site. The pipe diameters shown on the drawings are not consistent with
diameters measured in the field. Elevations on the device and the inlet and outlet pipes that have
been field verified (based on a survey conducted by Earth Tech in September, 2005) are indicted
on Figure 2-4.
Additional equipment specifications, test site descriptions, testing requirements, sampling
procedures, and analytical methods were detailed in the Test Plan for the Verification of
Downstream Defender "Madison Water Utility Administration Building Site" Madison,
Wisconsin (September 30, 2005). The test plan is included in Appendix B.
10
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12
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Flow Monitoring at B, C, D
Water Quality Sampling at B, C, E
FROM CWiH f I
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2.3 Maintenance
Hydro International provided the following guidance and information on the operation and
maintenance of the system.
The Downstream Defender® operates on simple fluid hydraulics. It is self-activating, has no
moving parts, no external power requirement and is fabricated with durable non-corrosive
components. Therefore, no procedures are required to operate the unit and maintenance is
limited to monitoring accumulations of stored pollutants and periodic clean-outs. The
Downstream Defender® has been designed to allow for easy and safe access for
inspection/monitoring and clean-out procedures. Entry into the unit or removal of the internal
components is not necessary for maintenance so that safety concerns related to confmed-space-
entry are avoided.
The internal components of the Downstream Defender® have been designed to protect the oil,
floatables and sediment storage volumes so that treatment capacities are not reduced as
pollutants accumulate between clean-outs. Additionally, the Downstream Defender® is designed
and installed into the storm drain system so that the vessel remains wet between storm events.
Oil and floatables are stored on the water surface in the outer annulus separate from the sediment
storage volume in the sump of the unit providing the option for separate oil immobilization,
removal and disposal (such as the use of absorbent pads). Since the oil/floatables and sediment
storage volumes are isolated from the active separation region, the potential for re-suspension
and washout of stored pollutants between clean-outs is minimized.
Keeping the unit wet also prevents stored sediment from solidifying in the base of the unit. The
clean-out procedure becomes much more difficult and labor intensive if a stormwater treatment
system allows fine sediment to dry-out and consolidate. When this occurs, clean-out crews must
enter the chamber and manually remove the sediment; a labor intensive operation in a potentially
hazardous environment.
A sump-vacuum is used to remove captured sediment and floatables. Access ports are located in
the top of the manhole. The floatables access port is above the area between the concrete
manhole wall and the dip plate. The sediment removal access port is located directly over the
hollow center shaft. The frequency of the sump vacuum procedure is determined in the field
after installation. During the first year of operation, the unit should be inspected every six
months to determine the rate of sediment and floatables accumulation. A simple probe can be
used to determine the level of solids in the sediment storage facility. This information can be
recorded in maintenance logs to establish a routine maintenance schedule. Maximum pollutant
storage capacities are provided in Table 2-1. To prevent floatables and oils from entering the
sediment sump storage volume, it is recommended that oil and floatables are removed prior to
removing sediment.
14
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Table 2-1. Downstream Defender" Pollutant Storage Capacities and Maximum Clean-out
Depths
Unit
Diameter
(ft)
4
6
8
10
Total Oil
Storage
(gal)
70
230
525
1,050
Oil Clean-
Out Depth
(in.)
< 16
<23
<33
<42
Total Sediment
Storage
(gal)
141
424
939
1,760
Sediment Clean-
Out Depth
(in.)
<18
<24
<30
<36
Total Volume
Removed
(gal)
384
1,240
2,890
5,550
Maintenance records were maintained during testing and are included in Chapter 7.
2.4 Performance Claim
This section was prepared by Hydro International.
The following are performance claims made by Hydro International regarding the Downstream
Defender® stormwater quality treatment unit installed at the Madison Water Utility
Administration Building Site in Madison, WI.
The Downstream Defender® is designed to remove and prevent washout (re-entrainment) of
settleable solids and floatables from stormwater runoff. In addition, with proper maintenance,
treatment capacities are not reduced as pollutants accumulate between clean-outs.
2.4.1 Total Suspended Solids
The 6-ft Downstream Defender® installed at the Madison Water Utility Administration Building
Site is designed to remove settleable solids from stormwater runoff. Generally, the removal
efficiency of the Downstream Defender® decreases with increasing flow rates, finer particles and
cooler water temperatures. For runoff at 15 C°, the Downstream Defender® will remove over
80% of settleable solids with a specific gravity of 2.65 with a particle size distribution similar to
Maine DOT road sand (see Figure 2-7) at flow rates up to 3 cfs (see Figure 2-8). Hydro
International defines "settleable sediment" as particles greater than 62 jim in size.
Performance of the Downstream Defender®, in terms of sediment removals, depends on the
incoming flow rate, particle size distribution, specific gravity and runoff temperature. Figure 2-7
shows two example particle size distributions (for Maine DOT road sand and F-l 10 silica sand).
The range of removals for each particle size distribution based on flow are shown in Figure 2.8
(assuming a water temperature of 15° C).
15
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100% -i
LU
100
1000
10000
PARTICLE SIZE (MICRONS)
100000
Figure 2-7. Particle size distribution for ME DOT road sand and F-110 silica sand.
100%
o
LU
o
ce
80% -
60% -
40% -
20% -
0%
FLOW RATE (cfs)
Figure 2-8. Removal efficiencies for differing sediment gradations at 15 °C.
16
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2. 4. 2 Metals and Nutrients
Significant levels of metals and nutrients have been detected in the sediment removed by the
Downstream Defender® during tests conducted at other locations. Removal of metals and
nutrients depends on the portion of these contaminants that are attached to the particulates.
Therefore, no specific removal claims are made.
2. 4. 3 Hydrocarbons
®
Even though the Downstream Defender is designed to treat petroleum hydrocarbons in
stormwater, Hydro International did not make specific performance claims for petroleum
hydrocarbons to be verified by ETV testing, and this test plan will not include provisions to
verify the Downstream Defender® hydrocarbon treatment capability.
2.4.4 Floatables
Up to 100% floatables removal has been observed visually in the Downstream Defender®.
However, the ETV protocol has no provisions for monitoring floatables. Therefore, no specific
performance claims are made.
17
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Chapter 3
Test Site Description
3.1 Location and Land Use
The Downstream Defender is located in the parking lot at the Madison Water Utility
Administration Building at 119 East Olin Avenue in Madison, Wisconsin. The latitude and
longitude coordinates are 43° 3'9" N and 89° 22'55" W. The device receives direct stormwater
runoff from the parking lot and rooftops through a storm sewer collection system. Figure 3-1
shows the location of the test site.
The Madison Water Utility Building grounds cover about 5.5 acres. Figure 3-2 shows the site
conditions with the drainage area and storm sewer collection system delineated. Based on the
analysis conducted during the Test Plan development, the drainage area tributary to the device
was 1.9 acres in size. Table 3-1 shows a breakout of the land uses within the drainage area.
based on that analysis.
Table 3-1. Drainage Area Land Use
Area (acres)
Walkways/
Sidewalks
0.08
Parking
Lot/ Road
1.05
Building
(Roof)
0.49
Landscape
0.29
Total Area
1.91
The property adjacent to the Madison Water Utility (to the west) is a City of Madison recycling
facility with outside storage of yard and brush waste. Visual inspection (during the Test Plan
development phase) indicated that some runoff from this property could enter the monitored
area. The City of Madison constructed a speed bump diversion (shown in Figure 3-3) to keep
this runoff from entering the monitored area.
During the monitoring phase, evidence indicated that during certain larger events, runoff from
the recycling facility may have overtopped the speed bump (see Figure 3-3), contributing
additional runoff to the monitored drainage area, especially during large storm events. Based on
a site inspection conducted by Earth Tech and the WDNR, the extent of the additional drainage
area size could be as much as four acres. It cannot be precisely determined how much additional
runoff is contributed to the monitored area for the following reasons: 1) various intensities and
rain depths will likely jump the installed "speed bump"; 2) a depressed inlet to the south of the
driveway between the two properties was intermittently clogged and a certain portion of the
runoff would be stored at this location before additional runoff would enter into the monitored
drainage area. See Section 6.2.3 of this report for further discussion of this issue.
18
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Madison Water Utility
Downstream Defender Site
Madison, . ..^
" EarthTech
Figure 3-1. Site location.
19
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Data from Survey on 9/22/2005
Structure
Inlet 11
Inlet 10
Inlet 9
Inlet 6
Inlets
Inlet 4
Inlets
Outlet
Rim Elevation
852.83
853.31
853.15
853.98
853.82
853.76
853.78
na
Invert Elevation'
850.73
85066
850.28
850.06
849.77
84959
849.00
848.75
Invertof outlet pipe from manhole.
July 2005
Site Map and Drainage Area
Madison Water Utility
Downstream Defender Site
Madison, Wl
© EarthTecni
ir^w^DMiiM-^Mnl
Figure 3-2. Site map and drainage area.
20
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(a)
(b)
Figure 3-3. (a) Diversion between test site and adjacent side (b) evidence of overtopping
after runoff event.
3.2 Pollutant Sources and Site Maintenance
The main pollutant sources within the drainage area are created by vehicular traffic, rooftop
drainage, atmospheric deposition, and, winter sand or rock salt that is applied as conditions
require.
The storm sewer catch basins do not have sumps. There are no other stormwater best
management practice (BMP) devices within the drainage area.
3.3 Stormwater Conveyance System
The site is drained by a storm sewer collection system. The storm sewer system within the
monitored drainage system consists of 12- and 15-in. diameter concrete pipe. The storm sewer
collects stormwater from the buildings and parking lot and conveys it to the Downstream
Defender®. From the Downstream Defender®, the treated stormwater (and bypass flow) enters a
wet detention pond (located at the Water Utility property) and subsequently to the city's storm
sewer system.
The storm sewer collection system that conveys stormwater to the Downstream Defender® and
the bypass structure, was surveyed on September 22, 2005 by Earth Tech. Surface elevations
and pipe invert elevations for the inlets were measured. Measurements were also taken at the
flow diversion manhole of the Downstream Defender®. The City of Madison provided
benchmark elevations on the site. The benchmark used for the survey was located on the top of
the fire hydrant on the west edge of the site and it has an elevation of 856.47 ft. The survey
results for the storm sewer system are shown on Figure 3-2.
Based on the survey results there was a concern that backwater from the detention pond could
create a tailwater effect on the bypass structure's outlet pipe (location D on Figure 2-6). To
reduce the potential for this occurrence the pond's low flow outlet opening was enlarged in the
21
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fall of 2005 (for the monitoring period). There were no issues noted with any of the runoff
events resulting from the modification to the outlet pipe.
An 18 in. storm sewer along the north edge of the site, collects runoff from part of the main
building, parking lot and landscaped areas, and discharges directly to Wingra Creek. This
system does not discharge runoff to the monitored drainage area.
3.4 Water Quality/Water Resources
The receiving water of the site's runoff is Wingra Creek, which is a tributary to Lake Monona.
Wingra Creek is on the WDNR 303(d) impaired waters list. Wingra Creek's impairments are
aquatic toxicity and contaminated sediment.
Most of the urban communities within the Yahara watershed including the City of Madison are
under the State of Wisconsin storm water permitting program (NR 216). This program meets or
exceeds the requirements of EPA's Phase I stormwater regulations.
3.5 Local Meteorological Conditions
Madison, Wisconsin has the typical continental climate of interior North America with a large
annual temperature range and with frequent short period temperature changes. Madison
experiences cold snowy winters, and warm to hot summers. Average annual precipitation is
approximately 33 in., with an average annual snowfall of 44 in. Additional details on
temperature and precipitation records are included in the Test Plan.
22
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Chapter 4
Sampling Procedures and Analytical Methods
Descriptions of the sampling locations and methods used during verification testing are
summarized in this section. Additional detail may be found in the test plan.
4.1 Sampling Locations
The detailed locations of the flow and water quality sampling locations are shown in Figure 2.6.
Below is a description of each site identified in Figure 2.6:
Site A: This site conveys all of the raw stormwater from the drainage area to the flow splitting
device. No flow or water quality monitoring occurred at this site.
Site B: This is the inlet to the Downstream Defender®. At this site both a velocity/stage sensor
and a water quality sampling line were established.
Site C: This is the outlet from the Downstream Defender®. At this site both a velocity/stage
sensor and a water quality sampling line were established.
SiteD: This is the system outlet site. All stormwater both treated and untreated (overflow
bypass at Site E) pass out this pipe. At this location a velocity / stage sensor is located.
Site E: This is the high-flow bypass weir. Discharge greater than 3 cfs (the design flow for the
treatment system) is bypassed over the weir. At this site a water quality sampling line
was established. The sampling line was fixed at the top of the weir wall and samples
were only taken when flow overtopped the weir elevation.
SiteB
Figure 4-1. Monitoring equipment for sites B and C.
SiteC
23
-------
SiteD
Figure 4-2. Monitoring equipment for sites D and E.
SiteE
4.2 Other Monitoring Locations
A rain gauge was located adjacent to the drainage area to monitor the depth and intensity of
precipitation from storm events. The data were used to characterize the events to determine if
they met the requirements for a qualified storm event.
4.3 Monitoring Equipment
The specific equipment used for monitoring flow, sampling water quality, and measuring rainfall
for the upstream and downstream monitoring points are listed in Table 4-1.
24
-------
Table 4-1. Monitoring Equipment
Location
SiteB
SiteC
SiteD
Velocity /
Stage
ISCO2150
flow meter
ISCO2150
flow meter
ISCO2150
flow meter
Water Quality
Sampling Other
ISCO 3700 with 3/4 in.
Teflon™ sample tube
ISCO 3700 with 3/4 in.
Teflon™ sample tube
SiteE
Flow
Splitter
Chamber
Sampling
Station
Rain Gauge
ISCO 3700 with 3/4 in.
Teflon™ sample tube
Stage & Temperature: Design Analysis
H-310 Pressure Transducer &
Temperature Probe
ISCO 3700 Data Logger: Campbell Scientific, Inc.
refrigerated automatic CR10X
samplers (3) Modem: Campbell Scientific COM 200
Design Analysis H340SPI tipping bucket
rain gauge
4.4 Contaminant Constituents Analyzed
The list of constituents analyzed in the stormwater samples is shown in Table 4-2. The vendor's
performance claim addresses reductions of inorganic sediments from the runoff water.
The TSS analytical method utilized for this project was modified using a process developed by
USGS (Selbig, 2007). The modification is intended to more accurately quantify the
concentration of larger sediment particles in a sample. An explanation of the modified method is
found in Appendix A. For the purposes of this report, the TSS concentrations are reported as
"adjusted TSS" concentrations to reflect the possible differences in concentrations between the
USGS method and the strict adherence to the USEPA method 160.2.
4.5 Sampling Schedule
USGS personnel installed the monitoring equipment under a contract with the WDNR. The
monitoring equipment was installed in September, 2005. Several trial events were monitored
and equipment was tested in the Fall of 2005. The first qualified event was successfully
25
-------
monitored in April, 2006. The last qualified event was monitored in August of 2006. Table 4-3
summarizes the sample collection data from the storm events.
Table 4-2. Constituent List for Water Quality Monitoring
Parameter
Total dissolved solids (TDS)
Total suspended solids (TSS)2
Volatile suspended solids (VSS)
Suspended sediment
concentration (SSC)
Sand-silt split
Five point sedigraph
Sand fractionation
Reporting
Units
mg/L
mg/L
mg/L
mg/L
NA
NA
NA
Limit of
Detection
50
2
0.1
NA
NA
NA
Limit of
Quantification
167
7
0.5
NA
NA
NA
Method1
SM 2540C
EPA 160.2
ASTMD3977-97
Fishman etal.
Fishman etal.
Fishman etal.
1 EPA: EPA Methods and Guidance for the Analysis of Water procedures; SM: Standard Methods for the Examination of
Water and Wastewater (19th edition) procedures; ASTM: American Society of Testing and Materials procedures;
Fishman et al.: Approved Inorganic and Organic Methods for the Analysis of Water and Fluvial Sediment procedures.
2 Explanation of TSS Analysis: In Chapter 5 of this document all TSS results are reported as "Adjusted TSS" values. A
full explanation of the procedures and reasoning for the adjustments is provided in Appendix A.
The 20 storm events listed in Table 4-3 met the requirements of a "qualified event," as defined in
the test plan:
• The total rainfall depth for the event, measured at the site rain gauge, was 0.2 in. (5 mm)
or greater;
• Flow through the treatment device was successfully measured and recorded over the
duration of the runoff period;
• A flow-proportional composite sample was successfully collected for both the inlet and
outlet (and bypass if applicable) over the duration of the runoff event;
• Each composite sample collected was comprised of a minimum of five aliquots,
including at least two aliquots on the rising limb of the runoff hydrograph, at least one
aliquot near the peak, and at least two aliquots on the falling limb of the runoff
hydrograph; and
• There was a minimum of six hours between qualified sampling events.
26
-------
Table 4-3. Summary of Events Monitored for Verification Testing
System Inlet Sampling Point (Site B)
Event Start Start End End
Number Date Time1 Date Time1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
3/8/06
3/12/06
4/2/06
4/12/06
4/16/06
4/29/06
5/1/06
5/9/06
5/11/06
5/17/06
6/25/06
7/9/06
7/11/06
7/19/02
7/22/06
7/27/06
8/6/06
8/17/06
8/23/06
8/24/06
18:03
18:34
20:41
5:07
4:15
17:18
21:16
12:01
6:59
15:36
17:34
19:45
8:44
21:43
16:51
12:27
6:53
16:27
23:06
13:30
3/9/06
3/13/06
4/3/06
4/12/06
4/16/06
4/30/06
5/1/06
5/9/06
5/12/06
5/17/06
6/26/06
7/9/06
7/11/06
7/20/02
7/22/06
7/27/06
8/6/06
8/17/06
8/24/06
8/25/06
0:45
4:23
6:47
8:01
16:33
17:11
22:05
18:01
5:40
17:14
8:15
20:55
14:47
7:11
17:40
14:37
11:05
17:26
7:26
6:27
Unit Outlet
No. of Start Start
Aliquots Date Time1
18
12
22
19
39
43
15
20
31
10
26
11
40
23
11
30
20
8
30
29
3/8/06
3/12/06
4/2/06
4/12/06
4/16/06
4/29/06
5/1/06
5/9/06
5/11/06
5/17/06
6/25/06
7/9/06
7/11/06
7/20/02
7/22/06
7/27/06
8/6/06
8/17/06
8/23/06
8/24/06
18:09
22:29
20:43
5:11
4:23
16:51
21:17
14:25
7:11
15:38
17:47
19:45
8:48
2:50
16:51
12:29
6:59
16:30
23:07
13:29
Sampling Point (Site C) System Outlet Sampling Point (Site E)
End End No. of Start Start End End No. of
Date Time1 Aliquots Date Time1 Date Time1 Aliquots
3/8/06
3/13/06
4/3/06
4/12/06
4/16/06
4/30/06
5/1/06
5/9/06
5/12/06
5/17/06
6/26/06
7/9/06
7/11/06
7/20/02
7/22/06
7/27/06
8/6/06
8/17/06
8/24/06
8/25/06
22:51
3:40
6:58
8:38
16:24
10:50
22:18
20:00
2:02
16:38
7:47
20:26
13:47
7:25
17:41
13:20
11:22
17:11
6:58
7:20
40
16
22
19
39 4/16/06 13:04 4/16/06 13:20
42
14
16
27
10
25
12
40
24
12
30 7/27/06 12:32 7/27/06 13:23
21
8
30 8/24/06 3:37 8/24/06 3:45
33 8/24/06 13:31 8/25/06 15:07
8
34
10
32
1. Time of first and last water quality sample from the event.
27
-------
Table 4-4 summarizes the rainfall data for the qualified events. Detailed information on each
storm's runoff hydrograph and the rain depth distribution over the event period are included in
Appendix C.
Table 4-4. Rainfall Summary for Monitored Events
Event
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Rainfall
Depth
(in.)
0.71
0.43
1.01
0.37
1.13
1.65
0.25
0.37
0.86
0.23
0.79
0.36
1.87
0.96
0.36
2.16
0.71
0.29
1.60
1.35
Rainfall
Duration
(hr:min)
4:36
9:25
10:01
2:56
12:44
25:38
0:26
6:50
23:55
2:02
15:41
0:08
8:51
9:44
0:30
1:30
5:08
1:45
8:17
2:13
Runoff Volume (ft3)
Site B Site E
1,880
1,370
5,910
1,980
6,230 1,240
8,480
1,570
2,090
5,040
1,310
4,250
1,430
10,990
4,680
1,860
7,150 7,720
3,630
1,300
13,450 1,220
17,180 3,720
Peak Flow Rate4
(cfs)
1.0
0.42
0.38
0.63
5.81
0.66
2.0
0.35
0.18
0.85
0.67
2.6
1.5
2.5
1.9
6.51
0.50
1.3
4.41
4.61
Temp
(°C)
3.5
4.6
15.5
0
-)
2
2
15.43
10.53
14.83
19.03
24.83
20.73
22.83
23.03
24. 03
23.43
22.43
22.43
22. 83
1. Peak design flow rate exceeded during event.
2. Temperature not recorded because of equipment malfunction.
3. Temperature readings were recorded from a nearby stormwater monitoring site. See Section 6.3 for
details.
4. Peak flow rate as measured at the system outlet pipe (Site D)
The Downstream Defender® was sized to treat a maximum flow rate of 3 cfs. The high-flow
weir elevation within the flow-splitter structure was set so that flow rates in excess of 3 cfs was
diverted over the weir and bypassed the Downstream Defender®. When flow exceeded
approximately 3 cfs, the sampling line at location E was activated and flow-weighted water
quality samples of the bypass water were collected.
28
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4.6 Field Procedures for Sample Handling and Preservation
Data gathered by the on-site datalogger were accessible to USGS personnel by means of a
modem and phone-line hookup. USGS personnel collected samples and performed a system
inspection after storm events.
Water samples were collected with ISCO automatic samplers programmed to collect 1-L aliquots
during each sample cycle. A peristaltic pump in the sampler pumped water from the sampling
location through Teflon™-lined sample tubing to the pump head where water passed through
approximately three feet of silicone tubing and into one of four 10-L sample collection bottles.
Samples were capped and removed from the sampler after the event by the USGS personnel.
The samples were then transported to the USGS field office in Middleton Wisconsin, where they
were split into multiple aliquots using a 20-L Teflon™-lined churn splitter. When more than
20 L (two 10-L sample collection bottles) of sample were collected by the autosamplers, the
contents of the two full sample containers would be poured into the churn, a portion of the
sample in the churn would be discarded, and a proportional volume from the third or fourth
sample container would be poured into the churn. The analytical laboratories provided sample
bottles. Samples were preserved per method requirements and analyzed within the holding times
allowed by the methods.
The samples were maintained in the custody of the sample collectors, delivered directly to the
laboratory, and relinquished to the laboratory sample custodian(s). Custody was maintained
according to the laboratory's sample handling procedures. To establish the necessary
documentation to trace sample possession from the time of collection, field forms and lab forms
(see Appendix B of the test plan) were completed and accompanied each sample.
29
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Chapter 5
Monitoring Results and Discussion
The verification testing results related to contaminant reduction are reported in two formats:
1. Efficiency ratio comparison, which evaluates the effectiveness of the system for each
qualified storm event on an event mean concentration (EMC) basis.
2. Sum of loads (SOL) comparison, which evaluates the effectiveness of the system for
all qualified storm events on a constituent mass (concentration times volume) basis.
The test plan required that only various forms of solids, be evaluated to test the vendor's
performance claim.
5.1 Monitoring Results: Performance Parameters
5.1.1 Concentration Efficiency Ratio
The concentration efficiency ratio reflects the treatment capability of the device using the event
mean concentration (EMC) data obtained for each runoff event. The concentration efficiency
ratios are calculated by:
Efficiency ratio = 100 x (l-[EMCoutiet/EMCiniet]) (5-1)
The inlet and outlet sample concentrations and calculated efficiency ratios are summarized by
analytical parameter categories.
The inlet, outlet, and bypass sample concentrations and calculated efficiency ratios for sediment
parameters are summarized in Table 5-1. As noted in Section 4.4, the TSS method utilized for
this project was based on a procedure developed by USGS (Selbig, 2007) and intended to
provide a more accurate methodology for quantification of larger sediment particles. For the
purposes of this report, these values are reported as "adjusted TSS" values. The raw data used to
calculate the adjusted TSS concentrations are summarized in Tables 5-3, 5-4, and 5-5. The
adjusted TSS inlet concentrations ranged from 23 to 700 mg/L, the outlet concentrations ranged
from 19 to 584 mg/L, and the efficiency ratio ranged from -51 to 62%. The SSC inlet
concentrations ranged 22 to 904 mg/L, the outlet concentrations ranged from 21 to 662 mg/L,
and the efficiency ratio ranged from -47 to 70%.
The TDS inlet concentrations ranged from <50 to 260 mg/L, the outlet concentrations ranged
from <50 to 238 mg/L, and the efficiency ratio ranged from -163 to 55%. The highest TDS inlet
and outlet concentrations occurred during events 1 and 2 in the spring. The high concentrations
may be the result of residual road salt being washed off the pavement.
30
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Table 5-1. Monitoring Results and Efficiency Ratios for Sediment Parameters
Event
No.
1
2
o
J
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
DD
Inlet
(mg/L)
126
62
59
121
227
35
144
23
24
159
106
395
35
81
103
700
51
544
447
483
TSS (adjusted)
DD System
Outlet Outlet
(mg/L) (mg/L)
147
52
36
97
188
30
217
24
19
153
105
584
38
120
119
425
37
207
348
292
NA
NA
NA
NA
675
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
534
NA
NA
401
424
Reduction
(%)'
-17
16
39
20
17
14
-51
-4
21
4
1
-48
-9
-49
-16
41
27
62
22
39
DD
Inlet
(mg/L)
127
64
58
120
270
35
165
22
25
156
104
450
57
128
116
904
59
705
527
624
ssc
DD System
Outlet Outlet
(mg/L) (mg/L)
166
52
36
95
190
30
202
21
22
143
104
662
37
137
127
418
37
211
327
285
NA
NA
NA
NA
1006
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
610
NA
NA
476
494
Reduction
(%)'
-31
19
38
21
30
14
-22
5
12
8
0
-47
35
-7
-9
54
37
70
38
54
DD
Inlet
(mg/L)
260
192
96
74
62
54
<50
74
88
58
60
80
<50
52
<50
96
<50
78
136
226
TDS
DD System
Outlet Outlet
(mg/L) (mg/L)
238
86
84
86
94
56
64
52
60
66
52
72
<50
<50
<50
82
58
98
112
222
NA
NA
NA
NA
<50
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
94
NA
NA
90
170
Reduction
(o/o)1
8
55
13
-16
-52
-4
<-28
30
32
-14
13
10
~
>4
~
15
<-16
-26
18
2
DD
Inlet
(mg/L)
26
13
NA
20
28
22
47
12
16
70
52
49
9
20
21
33
26
46
58
76
vss
DD System
Outlet Outlet
(mg/L) (mg/L)
38
15
NA
19
45
18
69
11
13
61
49
72
10
30
24
37
18
73
61
76
NA
NA
NA
NA
65
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
46
NA
NA
66
67
Reduction
(o/o)1
-46
-15
~
5
-61
18
-47
8
19
13
6
-47
-11
-50
-14
-12
31
-59
-5
0
1. Percent reduction values based on difference of DD Inlet and DD Outlet.
31
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Table 5-2. Adjusted TSS Calculations for Downstream Defender® Inlet
Sieved Sediments (mg/L)
Sieve Size (Contribution to Sum)
Event
No.1
2
5
12
16
18
19
20
500 urn
(70%)
0.5
0.5
0.5
472
502
225
0.5
250 urn
(55%)
1.1
92
94
101
21.3
18.8
291
125 um
(60%)
4.5
30
44.0
54.3
26.3
29.7
56.6
Adjusted TSS Concentration (mg/L)
Sum Product
of Sieved
Concentration
3.7
69
78.6
419
379
186
195
Aqueous
Concentration
58
158
316
281
165
261
288
Sieved +
Aqueous
Concentration
62
227
395
700
544
447
483
1. Events listed are limited to those where the adjusted TSS method was utilized.
Table 5-3. Adjusted TSS Calculations for Downstream Defender® Outlet
Event
No.
12
16
19
Sieved Sediments (mg/L)
Sieve Size (Contribution to Sum)
500 urn 250 urn 125 um
(70%) (55%) (60%)
0.5 71.3 178
54.5 20.7 61.6
7.2 8.6 48.9
Adjusted TSS Concentration (mg/L)
Sum Product of Sieved +
Sieved Aqueous Aqueous
Concentration Concentration Concentration
146 438 584
86.5 338 425
39.1 310 349
1. Events listed are limited to those where the adjusted TSS method was utilized.
Table 5-4. Adjusted TSS Calculations for System Outlet
Event
No.
5
16
19
20
Sieved Sediments (mg/L)
Sieve Size (Contribution to Sum)
500 fim 250 um 125 um
(70%) (55%) (60%)
1 133 124
185 73 58
62 24 52
115 45 29
Adjusted TSS Concentration (mg/L)
Sum Product of
Sieved
Concentration
148
205
87
123
Aqueous
Concentration
527
329
314
301
Sieved +
Aqueous
Concentration
675
534
401
424
1. Events listed are limited to those where system outlet samples were collected and the adjusted TSS
method was utilized.
The VSS inlet concentrations ranged from 9 to 76 mg/L, the outlet concentrations ranged from
11 to 76 mg/L, and the efficiency ratio ranged from -59 to 19%. VSS is a measure of organic
material, such as leaves or grass clippings, which generally have a specific gravity lower than
inorganic sediments. Both organic and inorganic sediments are measured as part of the TSS or
SSC analytical methods. A comparison of VSS to TSS or SSC gives an approximate percentage
of organic sediments as part of the total sediment concentrations or loadings.
32
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The Downstream Defender® operates as a hydrodynamic separator. Particles with a
comparatively higher density or specific gravity are retained by the unit, while particles with a
lower density or specific gravity tend to pass through the unit. Table 5-5 shows the ratio of VSS
concentrations to adjusted TSS and SSC concentrations for the inlet and outlet concentrations for
each event (except event 3, in which VSS samples were not analyzed). The contribution of
organic sediments would reduce the sediment specific gravity, and thus the effectiveness of the
Downstream Defender® to remove sediments.
Table 5-5. Ratio of Organic Sediment Concentrations to Total Sediment Concentrations
Event No.
1
2
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Median
Minimum
Maximum
Inlet
VSS/TSS
(%)
21
21
17
12
63
33
52
67
44
49
12
26
25
20
4.7
51
8.5
13
16
21
4.7
67
Ratios
vss/ssc
(%)
20
20
17
10
63
28
55
64
45
50
11
16
16
18
3.7
44
6.5
11
12
18
3.7
64
Outlet
VSS/TSS
(%)
26
29
20
24
60
32
46
68
40
47
12
26
25
20
8.9
49
35
18
26
26
8.9
68
Ratios
VSS/SSC
(%)
23
29
20
24
60
34
52
59
43
47
11
27
22
19
8.9
49
35
19
27
27
8.9
60
33
-------
5.1.2 Sum of Loads
The sum of loads (SOL) is the sum of the percent load reduction efficiencies for all the events,
and provides a measure of the overall performance efficiency for the events sampled during the
monitoring period. The load reduction efficiency is calculated using the following equation:
% Load Reduction Efficiency = 100x(l-(A/B)) (5-2)
where:
A = Sum of Outlet Load = (Outlet EMCi)(Flow Volumei) +
(Outlet EMC2)(Flow Volume2) + (Outlet EMCn)(Flow Volumen)
B = Sum of Inlet Load = (Inlet EMCi)(Flow Volumei) +
(Outlet EMC2)(Flow Volume2) + (Outlet EMCn)( Flow Volumen)
n= number of qualified sampling events
Flow was monitored in the Downstream Defender® inlet (site B), Downstream Defender® outlet
(site C), and the system outlet (site D). For the purposes of SOL calculations, the inlet flow data
was used to calculate both the Downstream Defender® inlet and Downstream Defender® outlet
SOL values. Flow at site D was used to calculate SOL values of the overall system as further
described below.
The SOL values are calculated for:
1. The load change between site B and site C. This represents the actual sediment changes
for the stormwater that only entered and exited the Downstream Defender®;
2. The load change between site A and site D. This represents the sediment load changes of
the overall system (total raw stormwater runoff);
3. The SOL was also calculated by particle size (sand/silt split). Since all events were
analyzed by SSC, and a particle distribution was conducted for each event, the analysis
could be conducted, (see Table 5-3 for these results).
Sediment: Tables 5-6 and 5-7 summarizes results for the SOL calculations for each sediment
analyte (adjusted TSS, SSC, TDS, and VSS).
Hydro International's performance claim is repeated below:
"For runoff at 15 C°, the Downstream Defender® will remove over 80% of
settleable solids with a specific gravity of 2.65 with a particle size distribution
similar to Maine DOT road sand at flow rates up to 3 cfs. Hydro International
defines "settleable sediment" as particles greater than 62 jim in size."
Each of the conditions mentioned in the performance claim are summarized below:
34
-------
• Water Temperature: Based on the temperature data shown in Table 4-4, the water
temperature of all except for events 1, 2, and 9 were at or above 15 C°.
• Specific Gravity: Specific gravity of the sediment captured in the sampler was not
required, based on the test plan. However, the test plan required that specific gravity of
the sediment samples captured in the sump of the Downstream Defender® be measured.
However, based on the data presented in Table 5-2, the contribution of organic sediments
to the total sediment load would reduce the specific gravity of the captured sediments.
The measured specific gravity of sediment samples from the Downstream Defender®
sump was less than 2.0. Typical inorganic sediments have a specific gravity ranging
from 2.5 to 3.0. This finding would indicate the presence of lighter organic sediments
retained in the sump.
• Flow: The data in Table 4-4 show that bypass occurred only in events where the peak
flow exceeded 3 cfs. This indicates that the weir wall elevation was properly set to
bypass flows greater than 3 cfs around the Downstream Defender® . The maximum peak
recorded flow was 5.61 cfs. The average observed peak flow for all events was 1.9 cfs.
• Particle Size Distribution: Particle size distribution was measured for each event. The
results of this analysis are shown in Table 5-8. The particle size distribution was also
used to summarize the SOL results by particle size in Table 5-9. This table shows how
much load was captured by the Downstream Defender® for each particle size and for the
"cumulative" particle size. For example, based the results shown in Table 5-10; the
Downstream Defender® captured 67% of the sediment particles greater than 63 jim (of
the loading that actually entered the Downstream Defender®) and 58% of the sediment
particles greater than 63 jim (of the loading that entered the flow splitter).
35
-------
Table 5-6. Sediment Sum of Loads Results (adjusted TSS and SSC)
Event
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Inlet
Runoff
Volume
(ft3)
1,880
1,370
5,910
1,980
6,230
8,480
1,570
2,090
5,040
1,310
4,250
1,430
10,990
4,680
1,860
7,150
3,630
1,300
13,450
17,180
Sum of Loads
DD
Inlet
Ob)
15
5
22
15
89
19
14
3
8
13
28
35
24
24
12
315
12
44
378
521
1,596
Reduction
efficiency (%)
Adjusted TSS
DD DD
Outlet bypass
Ob) (lb)
17
4
13
12
74
16
21
o
3
6
13
28
53
26
35
14
191
8
17
295
315
1,163
27%1
52
259
31
99
441
System
Outlet
(lb)
15
5
22
15
141
19
14
3
8
13
28
35
24
24
12
574
12
44
409
620
2,037
DD
Inlet
(lb)
15
6
22
15
106
19
16
3
8
13
28
40
39
38
14
406
13
58
446
674
1,977
22%2
DD
Outlet
(lb)
20
4
13
12
74
16
20
3
7
12
28
60
26
40
15
188
8
17
276
308
1,147
42%1
SSC
DD System
bypass Outlet
(lb) (lb)
15
6
22
15
77 183
19
16
3
8
13
28
40
39
38
14
296 702
13
58
37 482
116 789
525 2,502
33%2
1. Reduction efficiency only for load entering and exiting the Downstream Defender® (does not account for
bypass).
2. Reduction efficiency for entire load entering the bypass chamber and exiting the bypass chamber (accounts
for bypass).
5.2 Particle Size Distribution
Particle size distribution analysis was completed on all events. In order to produce particle size
distribution data, USGS sieved each sample with a 500 um, 250 um, and 125 um sieve from a
known volume of sample. The retained sediment was dried and weighed from a known volume
of water (sample volume). The dried sediment weight and sample volume was used to calculate
a sediment concentration at these three particle sizes. WSLH conducted a similar sieve analysis
on the aqueous sample received from the USGS except that the WSLH sieved at 500 um, 250
um, 125 um, 63 um, and 32 um size. A laser particle counter was used for particle size
distribution smaller than 32 um. The USGS and WSLH results are combined to report the final
particle size concentrations and distributions for each event. Each particle size concentration is
multiplied by the event volume to get an event load by particle size.
36
-------
The particle size distribution results are summarized in Table 5-8. In each event, the outlet
samples had a higher percentage of particles in the silt category (<62.5 um) than the equivalent
inlet sample. This is a result of the separation treatment mechanism of the Downstream
Defender® removing a higher percentage of the larger, heavier sediment particles.
Figure 5-1 is a comparison of the average inlet particle size distribution presented in Table 5-8 to
the particle size distribution related to the vendor's performance claim, which was based on
F-110 graded silica sand (see Figure 2-7). This comparison shows that the Downstream
Defender® encountered a proportion of fine material greater than the anticipated material in their
performance claim. For particles approximately 105 um and smaller, the Downstream
Defender® exceeded its performance claim.
Table 5-7. Sediment Sum of Loads Results (TDS and VSS)
Event
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Inlet
Runoff
Volume
(ft3)
1,880
1,370
5,910
1,980
6,230
8,480
1,570
2,090
5,040
1,310
4,250
1,430
10,990
4,680
1,860
7,150
3,630
1,300
13,450
17,180
Sum of Loads
TDS
DD
Inlet
Ob)
31
17
36
9
24
29
2
10
28
5
16
7
17
15
3
43
6
6
115
244
663
Reduction
efficiency (%)
DD
Outlet
(Ib)
28
7
31
11
37
30
6
7
19
5
14
6
17
40
3
37
13
8
95
240
655
P/o1
DD System
Bypass Outlet
(Ib) Ob)
31
17
36
9
2 26
29
2
10
28
5
16
7
~
15
~
46 89
-
6
7 122
40 284
731
1%2
DD
Inlet
(Ib)
3
1
-
2
11
12
5
2
5
6
14
4
6
6
2
15
6
4
49
82
235
-7%
VSS
DD
Outlet
(Ib)
4
1
-
2
18
10
7
1
4
5
13
6
7
9
3
17
4
6
52
82
251
i
DD System
Bypass Outlet
(Ib) (Ib)
3
1
-
2
5 16
12
5
2
5
6
14
4
6
6
2
22 37
6
4
5 54
16 98
283
-6%2
1. Reduction efficiency only for load entering and exiting the Downstream Defender® (does not
account for bypass)
2. Reduction efficiency for entire load entering the bypass chamber and exiting the bypass chamber
(accounts for bypass)
37
-------
Table 5-8. Particle Size Distribution Analysis Results
Event
No.
1
1
2
2
3
3
4
4
5
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
13
13
14
14
15
15
15
16
16
17
17
18
18
19
19
19
20
20
20
Percent Less Than Particle Size (um)
Location
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
System Outlet (site E)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
System Outlet (site E)
Unit Outlet
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
Outlet (site C)
Inlet (site B)
System Outlet (site E)
Unit Outlet (site C)
Inlet (site B)
System Outlet (site E)
Unit Outlet (site C)
<500
100
100
99
99
99
99
100
99
100
100
100
98
98
100
98
97
97
93
98
87
94
93
97
100
100
93
95
100
94
89
69
89
46
87
85
98
27
100
55
86
98
100
74
100
<250
99
97
98
98
98
98
97
98
64
81
94
84
87
94
91
95
92
81
77
74
89
80
85
76
88
89
91
56
90
86
57
83
34
81
73
91
24
92
51
80
95
49
64
96
<125
95
96
91
96
96
95
94
94
53
64
83
66
66
79
71
77
70
66
62
61
68
61
67
65
58
81
84
44
80
79
47
62
28
66
53
74
20
73
45
68
80
39
57
86
<62.5
93
93
90
92
88
92
79
83
42
43
57
41
39
50
52
55
48
55
47
43
49
39
36
44
40
56
61
28
59
54
35
40
23
51
39
52
16
54
38
55
69
34
51
74
<31
88
88
81
86
79
86
70
71
34
31
44
28
28
36
34
44
37
46
36
32
37
29
27
27
24
37
40
18
39
36
30
29
20
45
30
38
13
44
29
38
56
29
45
63
<16
74
70
59
76
57
66
50
50
24
20
29
21
20
23
23
33
31
40
31
22
25
25
24
25
19
29
37
14
33
35
29
29
19
43
28
34
12
36
27
36
53
27
42
61
<8
65
59
49
63
47
56
39
40
19
15
24
19
18
17
19
29
27
37
29
18
20
21
19
16
11
22
33
12
24
32
25
26
16
37
27
31
10
27
23
32
45
22
32
51
<4
48
42
35
46
32
40
28
29
15
10
17
16
15
12
13
24
22
33
24
13
14
17
15
12
7
16
28
11
18
26
19
22
12
28
26
29
8
21
21
29
37
14
20
35
<2
17
9
11
12
9
12
7
7
4
2
5
6
8
4
3
8
10
15
9
4
3
8
7
6
3
9
19
8
9
13
10
9
6
13
24
23
5
14
16
26
26
5
7
13
38
-------
100
10 100
Particle size (microns)
1000
Figure 5-1. Average and maximum influent particle size distribution compared to vendor's
performance claim based on F-110 silica sand.
The SOL can be recalculated for SSC concentrations and "sand/silt split" data to determine the
proportion of sand and silt removed during treatment. This evaluation, summarized in Tables
5-9 and 5-10, shows that the Downstream Defender® was most effective in removing the larger
particles. Particle size distribution is affected by such things as site conditions and land use,
maintenance (e.g. street sweeping), and weather.
Table 5-9. Sediment Sum of Load Results by Particle Size Category - Individual Particle
Size Load
Particle Size
Category
(um)
>500
250-500
125-250
63-125
32-63
32-14
DD Inlet
(Ib)
453
449
150
128
122
517
DD Outlet
(Ib)
39
49
146
156
122
550
Bypass
(Ib)
32
58
49
56
31
164
DD
Efficiency
(%)
91
89
3
-2
0
-6
System
Efficiency
(%)
85
79
2
-15
0
-5
39
-------
Table 5-10. Sediment Sum of Load Results by Particle Size Category - Cumulative
Particle Size Load
Particle Size
Category
(urn)
>500
250-500
125-250
63-125
32-63
32-14
DD Inlet
Ob)
453
902
1,052
1,181
1,303
1,820
DD Outlet
Ob)
39
87
233
389
512
1,060
Bypass
Ob)
32
90
139
195
226
391
DD
Efficiency
(%)
91
90
78
67
61
42
System
Efficiency
(%)
85
82
69
58
52
34
40
-------
Chapter 6
QA/QC Results and Summary
The Quality Assurance Project Plan (QAPP) in the test plan identified critical measurements and
established several QA/QC objectives. The verification test procedures and data collection
followed the QAPP. QA/QC summary results are reported in this section, and the full laboratory
QA/QC results and supporting documents are presented in Appendix D.
6.1 Laboratory/Analytical Data QA/QC
6,1.1 Bias (Field Blanks)
Field blanks were collected at both the inlet and outlet samplers on two separate occasions to
evaluate the potential for sample contamination through the entire sampling process, including
automatic sampler, sample-collection bottles, splitters, and filtering devices. "Milli-Q" reagent
water was pumped through the automatic sampler, and collected samples were processed and
analyzed in the same manner as event samples. The first field blank was collected on October 4,
2005 (before event sample began). The second field blank was collected on May 8, 2006
(between events 7 and 8).
Results for the field blanks are shown in Table 6-1. All analyses were below the limits of
detection (LOD). These results show a good level of contaminant control in the field procedures
was achieved.
Table 6-1. Field Blank Analytical Data Summary
Blank 1 (10/04/05)
Parameter
TSS
ssc
TDS
vss
Units
mg/L
mg/L
mg/L
mg/L
Inlet
<2
<2
<50
<2
Unit
Outlet
<2
<2
<50
<2
System
Outlet
<2
<2
<50
<2
Blank 2 (5/08/06)
Inlet
<2
<2
<50
<2
Unit
Outlet
<2
<2
<50
<2
System
Outlet
<2
<2
<50
<2
LOD
2
2
50
2
LOQ
7
7
167
7
6.1.2 Replicates (Precision)
Precision measurements were performed by the collection and analysis of duplicate samples.
The relative percent difference (RPD) recorded from the sample analyses was calculated to
evaluate precision. RPD is calculated using the following formula:
%RPD = (Jfi^fi) x 100o/0 (6-D
\ x J
41
-------
where:
xi = Concentration of compound in sample
x_2 = Concentration of compound in duplicate
x = Mean value of xi and X2
Field precision: Field duplicates were collected to monitor the overall precision of the sample
collection procedures. Duplicate inlet and outlet samples were collected during two different
storm events to evaluate precision in the sampling process and analysis. A third field duplicate
sampling was inadvertently missed. The duplicate samples were processed, delivered to the
laboratory, and analyzed in the same manner as the regular samples. Summaries of the field
duplicate data are presented in Table 6-2.
Overall, the results show very good field precision. The following section is a discussion on the
results from selected parameters.
TSS, SSC, TDS, and VSS: Results were within targeted limits. Both inlet and outlet samples
showed equally good precision, except for the outlet sample on 6/25/06 which had a 14% relative
difference. This is still well within the precision objective of 30% (Table 6-1 of the Test Plan).
Table 6-2. Field Duplicate Relative Percent Difference Data Summary
4/12/06 6/25/06
Parameter Units
TDS
TSS
SSC
VSS
mg/L
mg/L
mg/L
mg/L
Inlet
Outlet
Inlet
Outlet
Inlet
Outlet
Inlet
Outlet
Rep la
74
86
121
97
120
95
20
19
Replb
76
84
119
98
120
94
20
19
RPD (%)
3
2
2
1
0
1
0
0
Rep la
60
52
106
105
104
104
52
49
Replb
56
56
105
105
105
102
52
51
RPD (%)
7
7
~
0
1
2
0
4
Laboratory precision: WSLH analyzed duplicate samples from aliquots drawn from the same
sample container as part of their QA/QC program. Summaries of the laboratory duplicate data
are presented in Table 6-3.
42
-------
Table 6-3. Laboratory Duplicate Sample Relative Percent Difference Data Summary
Mean Maximum Minimum Std. Dev.
Parameter1 Count2 (%)
TSS
TDS
vss
22
12
16
9.9
2.1
1.8
57
8
5.8
0
0
0
17
2.2
1.8
1 Laboratory precision may also be evaluated based on absolute difference between duplicate
measurements when concentrations are low. For data quality objective purposes, the absolute
difference may not be larger than twice the method detection limit.
2 Analyses where both samples were below detection limits were omitted from this evaluation.
6.1.3 Accuracy
Method accuracy was determined and monitored using laboratory control samples (known
concentration in blank water). The laboratory control data were evaluated by calculating the
absolute value of deviation from the laboratory control concentration. Accuracy was in control
throughout the verification test. Tables 6-4 and 6-5 summarize the matrix spikes and lab control
sample recovery data, respectively.
Table 6-4. Laboratory Control Sample Data Summary
Mean Maximum Minimum Std. Dev.
Parameter Count (%) (%) (%) (%)
ssc
TSS
TDS
9
20
13
2.8
6.7
5.1
4.9
21
14
0.29
0
0
1.3
5.7
4.3
The balance used for solids (TSS, TDS, and total solids) analyses was calibrated routinely with
weights that were NIST traceable. The laboratory maintained calibration records. The
temperature of the drying oven was also monitored using a thermometer that was calibrated with
a NIST traceable thermometer.
6.1.4 Representativeness
The field procedures were designed to ensure that representative samples were collected of both
inlet and outlet stormwater. Field duplicate samples and supervisor oversight provided assurance
that procedures were being followed. The challenge in sampling stormwater is obtaining
representative samples. The data indicated that while individual sample variability might occur,
the long-term trend in the data was representative of the concentrations in the stormwater.
43
-------
The laboratories used standard analytical methods, with written SOPs for each method, to
provide a consistent approach to all analyses. Sample handling, storage, and analytical
methodology were reviewed to verify that standard procedures were being followed. The use of
standard methodology, supported by proper quality control information and audits, ensured that
the analytical data were representative of actual stormwater conditions.
Regarding flow (velocity and stage) measurements, representativeness is achieved in three ways:
1. The meter was installed by experienced USGS field monitoring personnel familiar with
the equipment, in accordance with the manufacturer's instructions;
2. The meter's individual area and velocity measurements were converted to a
representation of the flow area using manufacturer's conversion procedures (see ISCO
2150 Area Velocity Flow Meter O&M Manual available from NSF International or Earth
Tech);
3. The flow calculated from the velocity/stage measurements was calibrated using the
procedure described in Section 6.2.
To obtain representativeness of the sub-samples (aliquots) necessary to analyze the various
parameters from the event sample, a churn splitter was used. As noted in Radtke, et al. (1999),
the churn splitter is the industry standard for splitting water samples into sub-samples. However,
inconsistencies have been noted in the sub-samples, especially when the sample contained high
concentrations of large-sized sediments. The even distribution of the larger particulates becomes
problematic, even with the agitation action of the churn within the splitter. The issue of the
potential for uneven distribution of particulates was addressed through the pre-analysis sieving
process described in Appendix A
6.1.5 Completeness
The flow data and analytical records for the verification study are 100% complete. There were
instances of velocity "dropouts" during some events. A discussion of the calibration procedures
for flow data (velocity and stage measurements), including how velocity dropouts were
addressed, is provided in Section 6.2.
6.2 Flow Measurement Calibration
6.2.1 Gauge Height Calibration
On October 4, 2005 and May 10, 2006, full pipe static gage height calibrations were completed.
Calibration procedures consisted of inflating balls in pipes A and B (see Figure 3-6 of the test
plan) to seal off a catchment area upstream of the device. The inlet, unit outlet, and system
outlet flow meters were calibrated simultaneously by moving all three meters into the catchment
area. Using a garden hose, the water level inside the catchment area were increased by
increments of 0.1 to 0.15 ft. Ten to 15 water surface level taped readings were taken for each
44
-------
flow meter. These measurements were then compared to what was recorded by the respective
flow meters.
Gage height measurements were also checked periodically under low flow or standing water
conditions. Offsets were applied directly to the meters on March 31, 2006 (after event 2 and
before event 3) to account for the standing water conditions. Before this date, corrections were
made to the stored stage data. Gage height calibration on May 10, 2006 concluded all meters
were recording correct water levels and that no stage corrections were necessary.
The pressure transducer probe was used to initiate the bypass sampling routine when a given
stage threshold was reached. It is located at on the upstream side of site E. It was calibrated on
May 10, 2006. The design of the probe prevented stage from being recorded until water reached
a height of 0.58 feet. The stage was offset by 0.84 ft.
6.2.2 Flow Calibrations
Met (Site A) Flows
In April of 2006, an automatic dye dilution system was installed to calibrate flow. The injection
site for known dye concentrations was located in site A, 10 ft upstream of the weir wall (see
Figure 2-6). The location for drawing a sample mixture of stormwater and diluted dye to the
fluorometer was at the inlet meter, (a fluorometer measures the concentration of dye
fluorescence). A separate gage house for sampling dye and recording data was located adjacent
to the sampling gage houses. A dye-dilution event occurred when a given stage threshold was
reached at the inlet area/velocity meter.
The equation to convert dye recordings to flow is:
Q = q*C/c (6-2)
where:
Q = flow being measured (L/min)
q = injection rate (mg/L)
C = concentration of injected dye (mg/L)
c = concentration of dye measured (mg/L)
Storms from May 9 and 16, 2006 produced over 650 sample points of calibration at the inlet
meter. Comparison of the inlet area/velocity flow and the dye dilution flow yielded ±8%
difference per storm, as shown in Figures 6-1 and 6-2. Results from these storms concluded the
meter was recording flow accurately.
The device outlet and system outlet meters could not be calibrated by dye dilution because it was
unclear how the dye would mix inside of the bypass structure.
45
-------
5/16/06 17:00 5/16/06 17:11 5/16/06 17:23 5/16/06 17:34 5/16/06 17:46 5/16/06 17:57
Date and Time
Figure 6-1. Flow calibration plots comparing dye dilution flow to inlet discharge meter for
event occurring May 9, 2006.
o 0.25
5/9/0613:00 5/9/0613:28 5/9/0613:57 5/9/0614:26 5/9/0614:55 5/9/0615:24 5/9/0615:52
Date and Time
Figure 6-2. Flow calibration plots comparing dye dilution flow to inlet discharge meter for
event occurring May 16, 2006.
46
-------
System (Site D) Outlet Flows
Four of the twenty events sampled recorded bypassing. To predict the amount of water flowing
over the weir to the system outlet meter, a relationship correlating flow between the calibrated
inlet meter and the system outlet meter was established. The system outlet meter is located at
Site D (see Figure 2-6). This relationship is based on four assumptions:
1. No time delay from the inlet and system outlet;
2. The hydrograph rise was the only data used, to eliminate inaccuracy with meters due to
possible backwater from the detention pond;
3. Flows in which bypass was recorded were not included in the calibration; and,
4. Events 1 and 2 were not used, because they had a different stage discharge relationship
than the dye dilution test because of the shift in stage.
A scatter plot of bypass structure outlet flow to device bypass structure inlet flow indicated that
the outlet flows were low (Figure 6-2). The regression line of y = 1.1557x + 0.0326 for a stage
above 0.05 was used to correct the system outlet flow inaccuracies. Several other regressions
fitted the higher flow regime, but results produced larger errors for overall storm accuracies. For
storms without bypassing, the average difference between the inlet and system outlet was -10%.
1 1.25 1.5
System Flow(cfs)
Figure 6-3. System outlet flow rating curve as a function of inlet discharges.
Device (Site C) Outlet Flows
Flows from the device outlet area/velocity meter were not used to calculate loadings for three
reasons:
47
-------
1. Inlet and device outlet flows should be equal and the inlet meter was calibrated;
2. The device outlet flows were over-calculating inlet flow; and,
3. Bypass conditions would affect the device outlet.
6.2.3 Comparison of Runoff Volumes: Rainfall Depth vs. Flow Measurements
A final comparison of instrument measurements was to compare the measured rainfall depth
over the drainage area to the runoff volume calculated at the site B or site D flow meter. The
rational method was used to convert rainfall depth to runoff volume, using the following
equation:
Q = CIA (6-3)
where:
Q = calculated runoff volume (ft3)
C = runoff coefficient (unitless)
I = rainfall depth (ft)
A = drainage area (ft2)
For this study, a runoff area of 1.91 acres (83,200 ft2) and a runoff coefficient of 1 (i.e. no
infiltration or evaporation) was used. The runoff data is summarized in Table 6-6. The
calculated runoff was then compared to the flow meter readings as another means to verify
accuracy. The flow meter at site B was proven to be the most accurate measurement based on
the dye testing, however, this meter does not account for the bypass events where water flowed
over the weir. For those four events, the flow at site D was used for the volume calculations.
The comparison shows that calculations for 11 of the 20 events are within ±30% of each other,
and the median difference was 26%. The highest deviations occurred during events 1 and 2,
prior to the stage offset input, as discussed in Section 6.2.1. The calculated runoff volume was
higher than the metered runoff volume for all events except events 19 and 20, which would be
expected, since the calculated runoff does not account for evaporation, infiltration, or other forms
of non-runoff precipitation. There are several possibilities for differences in these readings
including:
• Inherent accuracy of each instrument (rain gauge and velocity meter);
• Accuracy of the drainage area delineation (This issue is explained in Chapter 3. It would
appear that this phenomena is a factor for runoff events 5, 16, 19 and 20); and,
• Inlet capacity may also affect the volume of rainfall entering the storm sewer system.
48
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Table 6-5. Comparison of Calculated vs. Metered Runoff Volumes
Event No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Rainfall
Depth
(in.)
0.71
0.43
1.01
0.37
1.13
1.65
0.25
0.37
0.86
0.23
0.79
0.36
1.87
0.96
0.36
2.16
0.71
0.29
1.60
1.35
Calculated Runoff
Volume
(ft3)
4,930
2,995
6,989
2,558
7,862
11,440
1,733
2,558
5,990
1,560
5,491
2,510
12,972
6,656
2,496
14,976
4,923
2,011
11,093
9,360
Metered Runoff
Volume
(ft3)
1,884
1,374
5,910
1,979
7,448
8,484
1,572
2,091
5,037
1,313
4,251
1,426
10,990
4,683
1,866
14,869
3,663
1,305
14,671
20,896
Difference
(%)
-62
-54
-15
-23
-5
-26
-9
-18
-16
-16
-23
-43
-15
-30
-25
-1
-26
-35
32
123
After reviewing the data and the site conditions, it appears that the adjacent recycling center
property provided runoff to the monitoring area during storm events with large rainfall depths,
resulting in flows greater than the Downstream Defender® design capacity. Figure 3-4 shows
evidence that runoff from the recycling center property (north of the Water Utility property) may
cross over the speed bump diversion located on the boundary between the two properties. An
estimation of the contribution of runoff from the adjacent property, based on the runoff data and
visual observations at the site, indicate that the contribution from the adjacent property during
large storms could have increased the drainage area size to 5.7 acres (an addition of 3.8 acres
above the original 1.91 acres). This estimate will vary by rain depth, intensity, and the capacity
of the ground inlet at the driveway between the properties.
6.3 Other Monitoring Complications
After the unit was installed, but before the first event was sampled, an observation that
stormwater was taking several hours to drain out of the device was noted. This caused standing
water at the system outlet pipe and may affect the performance of the device. The bypass
structure outlet pipe drains into a detention pond where the elevations of the pond are controlled
by a standpipe. The pond's standpipe controlled the elevation of the pond to be less than 1 ft
below the bypass outlet pipe elevation. During some events, this likely caused standing water at
the bypass structure outlet pipe. In January 2006, a larger opening in the standpipe was created
49
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to lower pond elevation and reduce the potential backwater effect of the pond. The drainage
issue was not observed during the test period.
A few storms during the summer of 2006 were missed due to power failures with the samplers.
High summer temperatures increased the power needs of the refrigerators. When the sampler
tried to take a sample, there was not enough power to run the pumps, resulting in power failures.
Adding an extra battery was added to the system alleviated this problem.
Sample tubing was replaced at the inlet sampler in June 2006 due to damage from rodents to the
line. This caused an event on June 10, 2006 to be missed.
The temperature probe did not record correctly after May 1, 2006. Temperature reading from
another site stormwater monitoring site, two miles northeast of the Downstream Defender®, was
substituted for the remaining storms. The substitute probe was installed in May, 2006 at a
downtown Madison, Wisconsin parking lot stormwater monitoring site.
50
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Chapter 7
Operations and Maintenance Activities
7.1 System Operation and Maintenance
Hydro International recommends inspecting the system every six months in the first year of
operation to check for accumulated sediment depth in the sump. Hydro International also
recommends that the 6-foot diameter unit be cleaned out if the accumulated sediment reaches 24
inches in depth.
The TO followed the manufacturer's guidelines for maintenance on the Downstream Defender®
during the verification testing. Installation of the Downstream Defender® was completed in the
fall of 2004. In the fall of 2005 the monitoring equipment was installed and initial monitoring
began in spring, 2006. Table 7-1 summarizes O&M activities undertaken by the TO and USGS
once verification testing was initiated.
Table 7-1. Operation and Maintenance During Verification Testing
Date
Activity
Personnel
Time/Cost
10/04/05 Site visit with P. Davison (NSF Int.); L. Glennon (Hydro
Mr.); J. Horwatich (USGS); Jill Kendall (City of Madison)
J. Bachhuber & J. Hurlebaus (Earth Tech. Decided to hold
off pre-monitoring period cleaning until after the final
monitoring instrument checks
Field elevation measurements obtained:
• 5.15 ft from manhole (MH) rim to the bottom of bypass
box downstream of weir;
• 5.16 ft from MH rim to the bottom of the bypass box
upstream of weir;
• Sediment depth was about 2 in.;
• Water surface was 0.91 ft below the invert of the pond
inlet pipe;
• Pond outlet structure has three circular openings. The
lowest one is 0.8 ft diameter and the bottom was at the
water surface elevation on 10/4/05. The middle opening
was 1.4 ft from the water surface elevation and has a 1 ft
diameter. The highest opening is also 1 ft diameter and
the bottom of this opening was 1.65 ft from the water
surface elevation.
6 staff;
approximately 3
hours at the site.
Not directly related
to maintenance
costs
11/09/05 City of Madison Vac-All equipment removed all possible
sediment. Also cleaned flow-splitter box, outer annulus
(floatables area) and main sump area.
2 city staff® 3
hours each = 6 staff
hours
51
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Date
Activity
Personnel
Time/Cost
11/10/05 J. Bachhuber & J. Hurlebaus verified cleanout. Following
measurements were made:
• MH rim to water surface in Downstream Defender® center
shaft: 7.8ft;
• Water depth in Downstream Defender® 3.0 ft;
• No sediment was detected with probe;
• Floatables chamber was clear;
• Small amount of sediment in flow-splitter box corners;
• Less than Vi in. of sediment in flow-splitter box.
2 Earth Tech staff
@ 1 hour each = 2
staff hours.
1/13/06 USGS personnel enlarged the low-flow opening to the
detention pond to reduce the frequency and potential for
backwater effects on the flow-splitter box outlet pipe.
3/1/06 - Routine USGS visits to site to maintain monitoring
9/15/06 equipment. Downstream Defender® checked for backwater
and/or debris clogging operation. No problems found.
09/15/07 Final post-monitoring Downstream Defender® cleanout.
Summary of activity and results provided in Section 7.2.
2 USGS personnel
@ 4 hours each = 8
hours Not directly
related to
maintenance costs
2 USGS, 2 Earth
Tech, & 2 City staff
@ 8 hrs each = 48
staff hours. This
time does not
include the
sediment drying,
measuring and
weighing effort.
7.2 Description of Post Monitoring Cleanout and Results
7. 2. 1 Background
®
On September 15, 2006, the Downstream Defender was cleaned out so that as much of the solid
material as possible from the device could be dried, weighed, and characterized. The weather
was sunny and clear, with temperatures in the mid 70s, and there had been no rain for the
previous two weeks.
52
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The general steps followed were:
1. Measure sediment depth and water depth before starting;
2. Decant standing water from Downstream Defender® to pond with pump;
3. Measure drawdown depth and take TSS samples during process to calculate sediment
mass of decanted water;
4. Use city Vac-All to remove remaining material; and,
5. Transport material in truck to USGS and deposit in large constructed tank for drying,
weighing, and analysis.
7.2.2 Field Measurements
Field measurements and observations are outlined in Table 7-2, and resulted in an estimated
retained materials depth of 0.35 ft.
Table 7-2. Field Measurements During Post-Monitoring Cleanout Activities
No.
1.
2.
O
4.
5.
Measurement Description
Top of water in Downstream Defender to rim of center shaft
Rim to top of retained solids (3 replicates)
Average depth of last two replaces of measurement 2
Rim to bottom of chamber
Calculated retained solids depth (measurement 4 - measurement 3)
Result (ft)
2.00
4.71
5.10
5.10
5.10
5.45
0.35
7.2.3 Measurement Results
Five sub-samples of the retained solids were transported to the USGS Sediment Laboratory in
Iowa City, Iowa for particle size distribution analysis. Table 7-3 summarizes the results of the
material analysis. The term "sediment" is avoided in this analysis, because much of the material
consisted of leaves, trash, and larger debris. The weight did not take into account the larger
debris, which was removed prior to drying and weighing. As shown in Table 7-3, approximately
93% of the sediment retained in the sediment chamber had a particle size of 125 jim or larger.
Figure 7-1 shows that the greatest proportion of sediments were in the 250 to 500 |im range.
The actual total mass of the material removed from the Downstream Defender® had a dry weight
of 416 pounds.
53
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Table 7-3. Retained Solids Particle Size Distribution Analysis
Sieve Size -
(urn)
<16,000
<8,000
<4,000
<2,000
< 1,000
<500
<250
<125
<63
<31
<16
<8
<4
Sample 1
97.2
94.8
89.7
80.0
64.8
41.0
17.4
7.1
3.5
2.2
1.0
0.5
0.3
Sample
100
97.5
93.3
82.7
68.1
42.2
18.0
7.3
3.9
2.7
1.4
0.6
0.5
Sieve Passage Rate (c
2 Sample 3
100
96.3
91.9
84.2
70.2
44.7
17.1
5.8
2.7
2.4
0.9
0.6
0.5
Yo)
Sample 4
100
97.6
94.6
87.4
75.6
50.5
21.9
8.3
4.0
2.5
1.3
0.7
0.6
Sample 5
100
98.2
95.0
87.9
74.9
49.8
20.9
7.4
3.3
2.0
0.9
0.5
0.4
- Mean
99.4
96.9
92.9
84.4
70.7
45.6
19.1
7.2
3.5
2.4
1.1
0.6
0.5
30 -r
a
cs
*!/3
C3
c.
sediments
D <-
'ercent of
| | f f | 1 | 1
<4 4-8 8-16 16-31 31-6363-125 125- 250- 500- 1,000- 2,000- 4,000- 8,000 - >16,000
250 500 1,000 2,000 4,000 8,000 16,000
Particle size range (urn)
Figure 7-1. Graphical representation of retained solids particle size distribution range.
54
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Chapter 8
Vendor Comments
The following evaluation was performed by the vendor, Hydro International, and does not
represent verified data.
Hydro International uses proprietary software to predict the performance of the Downstream
Defender® and its other stormwater source area management products. The software predicts
the sediment removal percentage as a function of particle gradation, flow rates, and water
temperature. This software was used to create the anticipated performance curves for Maine
DOT road sand and F-l 10 silica sand presented in Figure 2.8 as part of the vendor's performance
claims.
Based on the particle size distribution data generated as part of this study, the software was used
to estimate percent sediment removal at flow rates ranging from 0.5 to 3 cfs. This curve is
expressed graphically in Figure 8.1.
100% 1
80% -
o 60% -
c
01
'o
E
HI
ra 40% i
o
Ol
o:
20% -
0%
27% TSS removal at an
average peak flow rate of
1.94 cfs, as measured at
the test site.
ME DOT Road Sand
•F-110 Silica Sand
•ETV Gradation
Flow Rate (cfs)
Figure 8-1. Estimated removal efficiencies for ME DOT road sand, F-110 silica sand, and
test site sediment at 15 °C.
Based on the data recorded during the 20 qualified events, the average peak flow rate was
1.94 cfs and the TSS removal efficiency (as measured by sum of loads) was 27%, which is in
line with the ETV gradation curve predicted by Hydro International's software package.
Therefore, for the particle size gradation encountered at this test site, the Downstream Defender®
performed in line with expectations and in this regard met its performance claim.
55
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Chapter 9
References
1. APHA, AWWA, and WEF. Standard Methods for the Examination of Water and
Wastewater, 19th ed. Washington, DC, 1995.
2. Bannerman, R. Wisconsin Department of Natural Resources; Personnel Communications,
2006
3. Capel, P.D., and SJ. Larson. 1996. Evaluation of selected information on splitting devices
for water samples: Water Resources Investigation Rep. 95-4141. USGS, Washington, DC.
4. Gray, J.R., G.D. Glysson, L.M. Torcios, and G. Schwartz. 2000. Comparability of
suspended-sediment concentration and total suspended solids data. Water Resources
Investigation Rep. 00-4191. USGS, Washington, DC.
5. Fishman, M. J., Raese, J. W., Gerlitz, C. N., Husband, R. A., U.S. Geological Survey.
Approved Inorganic and Organic Methods for the Analysis of Water and Fluvial Sediment.,
1954-94, USGS OFR 94-351, 1994.
6. Horowitz; AJ; Hayes, T.S.; Gray; J.R.; Capel, P.D. Selected Laboratory Evaluations of the
Whole-Water Sample-Splitting Capabilities of A Prototype Fourteen-Liter Teflon* Churn
Splitter, U.S. Geological Survey Office of Water Quality Tech. Memorandum No. 97.06.
USGS, Washington, DC. 1997.
7. Huff, F. A., Angel, J. R. Rainfall Frequency Atlas of the Midwest., Midwestern Climate
Center, National Oceanic and Atmospheric Administration, and Illinois State Water Survey,
Illinois Department of Energy and Natural Resources. Bulletin 71, 1992.
8. NSF International and Earth Tech, Inc. Test Plan for the Verification of. Downstream
Defender* "Madison Water Utility Administration Building Site" Madison, Wisconsin
September 30, 2005.
9. NSF International. ETV Verification Protocol Stormwater Source Area Treatment
Technologies. U.S. EPA Environmental Technology Verification Program; EPA/NSF Wet-
weather Flow Technologies Pilot. March 2002 (v. 4.1).
10. Radtke, D.B. et al., National Field Manual for the Collection of Water-Quality Data, Raw
Samples 5.1. U.S. Geological Survey Techniques of Water-Resources Investigations Book 9,
Chapter A5, pp 24-26, 1999.
11. Selbig W. R., Bannerman R.T., Bowman G.T, Improving the Accuracy of Sediment-
Associated Constituent Concentrations in Whole Storm Water Samples by Wet-Sieving.
Journal of Environmental Quality, 36:226-232, 2007
56
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12. United States Environmental Protection Agency. Methods and Guidance for Analysis of
Water, EPA 821-C-99-008, Office of Water, Washington, DC, 1999.
57
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Glossary
Accuracy - a measure of the closeness of an individual measurement or the average of a number
of measurements to the true value and includes random error and systematic error.
Bias - the systematic or persistent distortion of a measurement process that causes errors in one
direction.
Comparability - a qualitative term that expresses confidence that two data sets can contribute to
a common analysis and interpolation.
Completeness - a quantitative term that expresses confidence that all necessary data have been
included.
Precision - a measure of the agreement between replicate measurements of the same property
made under similar conditions.
Protocol - a written document that clearly states the objectives, goals, scope and procedures for
the study. A protocol shall be used for reference during Vendor participation in the verification
testing program.
Quality Assurance Project Plan - a written document that describes the implementation of
quality assurance and quality control activities during the life cycle of the project.
Residuals - the waste streams, excluding final outlet, which are retained by or discharged from
the technology.
Representativeness - a measure of the degree to which data accurately and precisely represent a
characteristic of a population parameter at a sampling point, a process condition, or
environmental condition.
Wet-Weather Flows Stakeholder Advisory Group - a group of individuals consisting of any
or all of the following: buyers and users of in drain removal and other technologies, developers
and Vendors, consulting engineers, the finance and export communities, and permit writers and
regulators.
Standard Operating Procedure - a written document containing specific procedures and
protocols to ensure that quality assurance requirements are maintained.
Technology Panel - a group of individuals with expertise and knowledge of stormwater
treatment technologies.
Testing Organization - an independent organization qualified by the Verification Organization
to conduct studies and testing of mercury amalgam removal technologies in accordance with
protocols and Test Plans.
Vendor - a business that assembles or sells treatment equipment.
58
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Verification - to establish evidence on the performance of in drain treatment technologies under
specific conditions, following a predetermined study protocol(s) and Test Plan(s).
Verification Organization - an organization qualified by EPA to verify environmental
technologies and to issue Verification Statements and Verification Reports.
Verification Report - a written document containing all raw and analyzed data, all QA/QC data
sheets, descriptions of all collected data, a detailed description of all procedures and methods
used in the verification testing, and all QA/QC results. The Test Plan(s) shall be included as part
of this document.
Verification Statement - a document that summarizes the Verification Report reviewed and
approved and signed by EPA and NSF.
Verification Test Plan - A written document prepared to describe the procedures for conducting
a test or study according to the verification protocol requirements for the application of in drain
treatment technology. At a minimum, the Test Plan shall include detailed instructions for sample
and data collection, sample handling and preservation, precision, accuracy, goals, and quality
assurance and quality control requirements relevant to the technology and application.
59
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Appendices
A Adjusted TSS Analysis Discussion
B Test Plan
C Event Hydrographs and Rain Distribution
D Analytical Data Reports with QC
60
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