April 2004
04/15/WQPC-WWF
EPA/600/R-04/084
Environmental Technology
Verification Report
Stormwater Source Area
Treatment Device
Arkal Pressurized Stormwater
Filtration System
Prepared by
NSF International
Under a Cooperative Agreement with
U.S. Environmental Protection Agency
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THE 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
SEDIMENT REMOVAL
ARKAL PRESSURIZED STORMWATER FILTRATION
SYSTEM
GREEN BAY, WISCONSIN
ZETA TECHNOLOGY, INC.
416 Flamingo Avenue
Stuart, Florida 34966
http://www.zetatechnology.com
zeta@zetatechnology.com
PHONE: (772)781-7000
FAX: (772)781-7001
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 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.
NSF International (NSF), in cooperation with the EPA, operates the Water Quality Protection Center
(WQPC), one of six centers under ETV. The WQPC recently evaluated the performance of the Arkal
Pressurized Stormwater Filtration System distributed by Zeta Technologies, Inc., a system designed to
remove solids from stormwater runoff. The system was installed at St. Mary's Hospital in Green Bay,
Wisconsin. Earth Tech, Inc. and the United States Geologic Survey (USGS) performed the testing.
04/15/WQPC-WWF
The accompanying notice is an integral part of this verification statement.
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April 2004
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TECHNOLOGY DESCRIPTION
The following description of the Arkal Pressurized Stormwater Filtration (Arkal) System was provided by
the vendor and does not represent verified information.
The key components of the Arkal system are the filtration processes, which are manufactured by Arkal.
Ancillary components not manufactured by Arkal, including a splitter manhole and storage tank, were
combined with the filtration processes to form a system designed to remove suspended solids from
stormwater. Stormwater entered a sump where coarse solids settled and was then diverted either to a
9,200 ft3 storage tank that fed the filtration processes, or an overflow bypass pipe that diverted water
directly to the municipal storm sewer system without additional treatment.
The filtration processes consisted of two pressurized systems operating in series. The first filtration
process consisted of four towers, each containing three "StarFilter" disk filter units designed to remove
particles 50 microns and larger. The second filtration stage consisted of a series of five 48-inch diameter
sealed sand filter tanks, designed to remove particles five microns and larger. Both filtration processes
backwashed automatically when pressure differentials exceeded preset levels. The provision of multiple
filters in each process allowed for filtration and backwash to occur simultaneously. The backwash
wastewater was discharged to the municipal sanitary sewer, while the treated stormwater was discharged
to the municipal storm sewer.
The vendor claims that the treatment system can remove 80 percent of the suspended solids greater than
five microns in the stormwater.
VERIFICATION TESTING DESCRIPTION
Methods and Procedures
The test methods and procedures used during the study are described in the Test Plan for Verification of
the Arkal Filtration Systems, Inc. Pressurized Stormwater Filtration System, St. Mary's Hospital, Green
Bay, WI (Earth Tech, January 2001) (VTP). The Arkal system treats the hospital's 5.49-acre drainage
area, which consists of paved parking areas, the building's roof, and landscaped areas. Green Bay
receives an average of nearly 29 inches of precipitation, approximately 35 percent of which occurs during
the summer months.
Verification testing consisted of collecting data during 15 qualified events that met the following criteria:
• The total rainfall depth for the event, measured at the site, was 0.2 inches (5 mm) or greater
(snow fall and snow melt events do not qualify);
• 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 influent and
effluent 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.
Automated sample monitoring and collection devices were installed and programmed to collect composite
samples from the influent, the treated effluent, and the untreated bypass during qualified flow events.
Samples were analyzed for the following parameters:
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Sediments
Nutrients
Metals
total suspended solids (TSS)
total dissolved solids (TDS)
particle size analysis
suspended sediment concentration (SSC)
total phosphorus
dissolved phosphorus
nitrate and nitrite
total Kjeldahl nitrogen (TKN)
total calcium
total magnesium
total zinc
In addition to the flow and analytical data, operation and maintenance (O&M) data were recorded. Power
consumption costs were calculated based on the manufacturer's rated pump specifications and length of
operation during event periods.
VERIFICATION OF PERFORMANCE
Verification testing of the Arkal system lasted nearly 16 months. No bypassing occurred during the
testing period, so all of the influent entering the system was treated and discharged as treated effluent to
the storm sewer or as backwash filtrate to the sanitary sewer.
Test Results
The precipitation data for the 15 rain events are summarized in Table 1.
Table 1. Rainfall Data Summary
Event
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Start
Date
6/2/01
6/10/01
6/11/01
6/15/01
8/25/01
12/12/01
4/18/02
4/24/02
4/27/02
5/1/02
5/25/02
6/13/02
6/21/02
7/25/02
9/19/02
Start
Time
3:45
12:26
22:38
10:20
2:45
22:18
4:27
15:07
20:15
22:19
8:31
23:48
17:15
17:39
4:48
Rainfall
Depth
(inches)
0.81
0.41
0.20
0.38
0.34
0.39
0.40
0.63
1.13
0.22
1.27
0.31
0.36
0.40
0.23
Rainfall
Duration
(hnmin)
7:24
2:54
1:49
1:50
6:52
2:55
3:32
3:39
10:33
3:12
35:40
14:01
1:05
1:08
2:24
Rainfall
Volume1
(ft3)
16,070
6,307
2,367
5,374
4,467
5,495
4,959
8,044
16,332
2,557
16,114
4,640
4,985
5,728
2,929
1 Rainfall volume was measured at the influent monitoring point.
The monitoring results were evaluated using event mean concentration (EMC) and sum of loads (SOL)
comparisons.
The EMC or efficiency ratio comparison evaluates treatment efficiency on a percentage basis by dividing
the effluent concentration by the influent concentration and multiplying the quotient by 100.
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The accompanying notice is an integral part of this verification statement.
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April 2004
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The efficiency ratio was calculated for each analytical parameter and each individual storm event. In
order for efficiency ratio calculations to show a high treatment percentage, the influent parameter
concentrations needed to be relatively high. This was not always the case because of the inherent
variability of stormwater.
The SOL comparison evaluates the treatment efficiency on a percentage basis by comparing the sum of
the influent and effluent loads (the product of multiplying the parameter concentration by the precipitation
volume) for all 15 storm events. The calculation is made by subtracting the quotient of the total effluent
load divided by the total influent load from one, and multiplying by 100. The analytical data ranges, EMC
range and SOL reduction values are shown in Table 2.
Table 2. Analytical Data, EMC Range, and SOL Reduction Results
TSS
SSC
Total
Total
TKN
Parameter
zinc
phosphorus
Dissolved phosphorus
Nitrate and nitrite
TDS
Total
Total
magnesium
calcium
Units
mg/L
mg/L
ug/L
mg/L as P
mg/L as N
mg/L as P
mg/L as N
mg/L
mg/L
mg/L
Influent
Range
10-
12-
426
340
24-210
0.023
0.32
<0.005
0.29
38-
2.3-
6.5
-0.32
-2.2
-0.17
-1.7
550
-16
-64
Effluent
Range
<2-
2-
61
67
<16-26
<0.
0
<0.
0
005
.35-
005
.67-
190-
3.3-
19-
-0.13
-1.0
-0.12
-2.1
950
-41
77
EMC Range SOL Reduction
(percent) (percent)
47-
>94
32-95
21-82
23-
>96
-47 - 59
-75-
-170-
-1,100
-570
-340-
-50
-3.6
--31
-53
--18
82
82
58
55
26
13
-76
-190
-190
-210
The reductions in TSS and SSC exceeded the vendor's performance claim of 80 percent solids reduction,
based on the SOL evaluation method. Additionally, constituents commonly found in particulate form or
attached to sediment particles, such as phosphorus, TKN, and total zinc, were removed as sediments were
removed. However, dissolved-phase parameters, such as TDS, phosphorus, nitrate, and nitrite, were not
removed by the Arkal system. This is consistent with the vendor's performance claim.
The negative efficiencies for TDS, total calcium, and total magnesium were attributed to groundwater
infiltration into the storm sewer system through cracks or poorly sealed joints. Calculation of the
infiltration dilution effect, however, did not show the infiltration to have an impact on the TSS or SSC
SOL evaluation. The infiltration issue is explained in greater detail in the verification report.
Particle size distribution analysis was conducted on the solids trapped in the sump and in samples when
adequate sample volume was collected. Ninety percent of the particles trapped in the sump were larger
than 250 microns, with 70 percent being larger than 2,000 microns. Twelve of the 15 qualified events had
adequate influent sample volume to complete a sand\silt split (greater or less than 62 microns) analysis.
None of the effluent samples had sufficient volume to complete the visual accumulator and pipette
analyses.
The influent analysis indicated a sand/silt split of 25.8 percent to 74.2 percent, while the effluent had a
sand/silt split of 16.2 percent to 83.8 percent. Furthermore, three events had adequate influent sample
volume to conduct particle size analyses for particles as small as one micron. For these three events, the
influent had a range of 17.3 to 38.9 percent of solids passing a four-micron sieve. In order for the Arkal
system to achieve 82 percent sum of loads efficiency for these three events, it had to treat a portion of the
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The accompanying notice is an integral part of this verification statement.
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April 2004
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solids passing a four-micron sieve. This substantiates the vendor's performance claim of being able to
treat particles five microns or larger.
System Operation
The Arkal system was installed prior to verification testing, so verification of installation procedures on
the system was not documented.
Aside from routine monitoring and maintenance, eight maintenance events were performed during the
testing period. Maintenance typically consisted of cleaning and disinfecting the StarFilter rings, which
would develop microbial growth during long dry periods. A total of 84 hours of staff time and $260 in
direct costs were used in maintaining the system during the testing period. No system downtime occurred
as a result of maintenance activities.
Based on system operating time and equipment horsepower, electrical power consumption was calculated
to be approximately 78 kWh per event.
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 percent 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
Lawrence W. Reiter, Ph. D.
July 27, 2004
Original Signed By
Gordon E. Bellen
Lawrence W. Reiter, Ph.D. Date
Acting Director
National Risk Management Laboratory
Office of Research and Development
United States Environmental Protection Agency
August 4, 2004
Gordon E. Bellen
Vice President
Research
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
04/15/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: http://www.epa.gov/etv (electronic copy)
Appendices are not included in the verification report, but are available from NSF upon request.
04/15/WQPC-WWF
The accompanying notice is an integral part of this verification statement.
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April 2004
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Environmental Technology Verification Report
for
Stormwater Source Area Treatment Device
ARKAL PRESSURIZED STORMWATER FILTRATION SYSTEM
Prepared for:
NSF International
Ann Arbor, Michigan
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
April 2004
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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) on this
verification under a Cooperative Agreement. The Water Quality Protection Center, 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 Arkal Pressurized Stormwater Filtration System was
conducted at St. Mary's Hospital in Green Bay, Wisconsin.
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.
Lawrence W. Reiter, Acting Director.
National Risk Management Research Laboratory
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
1.2.6 Verification Testing Site 4
Chapter 2 Technology Description 6
2.1 Ancillary System Components 6
2.1.1 Flow Splitter 6
2.1.2 Holding Tank 6
2.1.3 Mechanical Housing Unit 9
2.2 Filtration Process 9
2.2.1 First-Stage Filtration 9
2.2.2 Second-Stage Filtration 11
2.2.3 Backwash Tank 11
2.3 Technology Application and Limitations 11
2.4 Performance Claim 12
Chapters Test Site Description 13
3.1 Location and Land Use 13
3.2 Contaminant Sources and Site Maintenance 13
3.3 Stormwater Conveyance System 15
3.4 Local Meteorological Conditions 15
Chapter 4 Sampling Procedures and Analytical Methods 16
4.1 Sampling Locations 16
4.1.1 Site 1 -Influent Ahead of Flow Splitter 16
4.1.2 Site 2 - Treated Effluent 16
4.1.3 Site 3 - Overflow Bypass 18
4.1.4 Other Monitoring Locations 18
4.2 Monitoring Equipment 18
4.3 Contaminant Constituents Analyzed 20
in
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4.4 Sampling Schedule 21
4.5 Field Procedures for Sample Handling and Preservation 23
Chapter 5 Monitoring Results and Discussion 24
5.1 Monitoring Results: Performance Parameters 24
5.1.1 Concentration Efficiency Ratio 24
5.1.2 Groundwater Infiltration 26
5.1.3 Sum of Loads 27
5.2 Particle Size Distribution 28
5.3 Monitoring Results: Secondary Parameters 30
Chapter 6 QA/QC Results and Summary 34
6.1 Laboratory/Analytical Data QA/QC 34
6.1.1 Bias (Field Blanks) 34
6.1.2 Replicates (Precision) 35
6.1.3 Accuracy 35
6.1.4 Representativeness 37
6.1.5 Completeness 37
6.2 Flow Measurement Calibration 38
6.2.1 Influent 38
6.2.2 Treated Effluent 38
Chapter 7 Operations and Maintenance Activities 41
7.1 System Operation and Maintenance 41
7.2 System Power Usage 42
Chapter 8 References 43
Glossary 44
Appendices 46
A Event Hydrographs and Rain Distribution 46
B Analytical Data Reports 46
C Verification Test Plan 46
D Operation and Maintenance Log 46
Figures
Figure 2-1. Arkal system plan and profile 7
Figure 2-2. Catch basin flow splitter 8
Figure 2-3. Floor plan of filter house detail and profile 10
Figure 2-4. View inside filter house with equipment 12
Figure 3-1. Aerial photo of drainage area 14
Figure 4-1. View of Monitoring Site 1 16
Figure 4-2. View of sampling equipment for Monitoring Sites 1 and 3 17
Figure 4-3. View of Monitoring Site 2 sampler and datalogger 17
Figure 4-4. View of Monitoring Site 3 (bypass and backflow prevention gate) 18
Figure 4-5. View of site rain gauge 19
IV
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Tables
Table 2-1. Percent of Event Volume Bypassing Treatment System 12
Table 3-1. Drainage Area (Acres) by Land Use 13
Table 4-1. Field Monitoring Equipment 19
Table 4-2. Constituent List for Water Quality Monitoring 20
Table 4-3. Summary of Events Monitored for Verification Testing 22
Table 4-4. Rainfall Summary for Monitored Events 23
Table 5-1. Monitoring Results and Efficiency Ratios for Primary Parameters 25
Table 5-2. Dry Weather (Groundwater) Analytical Results 26
Table 5-3. Sum of Loads 27
Table 5-4. Sand/Silt Split Analysis for 12 Events 29
Table 5-5. Particle Size Distribution for Six Influent Sampling Events 29
Table 5-6. Particle Size Distribution for Material from Flow Splitter Sump 30
Table 5-7. Event Mean Concentration for Secondary Parameters (Nutrients) 31
Table 5-8. Event Mean Concentration for Secondary Parameters (Metals) 32
Table 5-9. Sum of Loads for Secondary Parameters 33
Table 6-1. Field Blank Analytical Data Summary 34
Table 6-2. Duplicate Sample RPD Data Summary 36
Table 6-3. Laboratory MS/MSD Data Summary 36
Table 6-4. Laboratory Control Sample Data Summary 37
Table 6-5. Comparison of Runoff Volumes - Holding Tank Measurements Versus Inlet
Velocity/Stage Meter Calculations 39
Table 7-1. Operation and Maintenance During Verification Testing 41
Table 7-2. Power Costs for Arkal System on an Average Event Basis 42
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Abbreviations and Acronyms
BMP
BPSV
cfs
dia
DQI
EMC
EPA
ETV
ft2
ft3
g
gal
gpm
hp
hr
in
kg
kWh
L
Ib
NRMRL
mg/L
mL
NSF
NIST
O&M
psi
QA
QC
ssc
SOL
SOP
IDS
TKN
TO
TP
TSS
USGS
VA
vo
VTP
WDNR
WSLH
Best Management Practice
Back pressure sustaining valve
Cubic feet per second
Diameter
Data quality indicators
Event mean concentration
U.S. Environmental Protection Agency
Environmental Technology Verification
Square foot (feet)
Cubic feet
Gram
Gallon
Gallon per minute
Horsepower
Hour
Inch(es)
Kilogram
Kilowatt hour
Liters
Pound
National Risk Management Research Laboratory
Microgram per liter (ppb)
Micron
Milligram per liter
Milliliter
NSF International, formerly known as National Sanitation Foundation
National Institute of Standards and Technology
Operations and maintenance
Pounds per square inch
Quality assurance
Quality control
Suspended sediment concentration
Sum of loads
Standard Operating Procedure
Total dissolved solids
Total Kjeldahl nitrogen
Testing Organization
Total phosphorus
Total suspended solids
United States Geological Survey
Visual accumulator
Verification Organization (NSF)
Verification test plan
Wisconsin Department of Natural Resources
Wisconsin State Laboratory of Hygiene
VI
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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; 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 verification tests, 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 Arkal Pressurized Stormwater
Filtration System, a stormwater treatment device designed to remove sediments 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 Arkal Pressurized Filtration System, distributed in the United States by
Zeta Technology, Inc., 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
• Wisconsin State Laboratory of Hygiene
• USGS Sediment Laboratory
• Earth Tech, Inc.
• Zeta Technology, Inc.
The following is a brief description of each ETV participant and their roles and responsibilities.
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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 developing 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 verification test plan (VTP) and this verification report. NSF's responsibilities as
the VO include:
• Review and comment on the VTP;
• 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.
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Key contacts at NSF are:
Mr. Thomas Stevens, Program Manager Mr. Patrick Davison, Project Coordinator
(734) 769-5347 (734)913-5719
email: stevenst@nsf.org email: davi son@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),
which was assisted by the U.S. Geological Service (USGS), located in Middleton, Wisconsin.
USGS provided testing equipment, helped 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 were such that the verification testing could meet its stated
objectives. The TO prepared the VTP; oversaw the testing; and managed, evaluated, interpreted
and reported on the data generated by the testing, as well as evaluating and reporting on the
performance of the technology. TO employees established 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, Inc.:
Mr. Jim Bachhuber, P.H. Mr. Jay Kemp
(608)828-8121 (608)828-8164
email: jim bachhuber@earthtech.com email: jay kemp@earthtech.com
Earth Tech, Inc.
1210 Fourier Drive
Madison, Wisconsin 53717
United States Geologic Survey:
Mr. Steve Corsi Ms. Judy Horwatich
(608) 821-3835 (608) 821 -3 874
email: scorsi@usgs.gov email: iawierl@usgs.gov
-------
USGS
8505 Research Way
Middleton, Wisconsin 53562
1.2.4 Analytical Laboratories
Except for particle size and suspended sediment concentration analysis, the Wisconsin State
Laboratory of Hygiene (WSLH), located in Madison, Wisconsin, analyzed the stormwater
samples for the parameters identified in the VTP. The USGS Sediment Laboratory, located in
Iowa City, Iowa, performed the suspended sediment concentration separations and particle size
analysis.
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
Zeta Technology, Inc. (Zeta) of Stuart, Florida, is the vendor of the Arkal Pressurized
Stormwater Filtration System, and was responsible for supplying a field-ready system. Zeta was
also responsible for providing technical support and was available during the tests to provide
technical assistance as needed.
The key contact for Zeta Technology is:
Mr. Eric Crawford
(772)781-7000
email: zetatech@bellsouth.net
Zeta Technology, Inc.
416 Flamingo Avenue
Stuart, Florida 34966
1.2.6 Verification Testing Site
The verification testing was performed at St. Mary's Hospital in Green Bay, Wisconsin. Hospital
personnel were responsible for providing site access and were the liaison for overall system and
day-to-day activities.
-------
The key contact for St. Mary's Hospital is:
Mr. David Behrendt
(920) 613-3747
email: dbehrend@stmgb.org
St. Mary's Hospital
1726 Shawano Avenue
Green Bay, Wisconsin 54606
-------
Chapter 2
Technology Description
The combination of the Arkal Pressurized Stormwater Filter devices and ancillary components
(the flow splitter, storage tank, and mechanical housing unit were not manufactured by Arkal)
form a system designed to remove sediments from stormwater. Each component of the system is
described in this section, and a schematic diagram and profile for the St. Mary's Hospital
installation is shown in Figure 2-1.
Additional equipment specifications, test site descriptions, testing requirements, sampling
procedures, and analytical methods were detailed in the Test Plan for the Verification of Arkal
Filtration Systems, Inc. Pressurized Stormwater Filtration System, St. Mary's Hospital, Green
Bay, WI (January 2, 2001). The Verification Test Plan (VTP) is included in Appendix C.
2.1 Ancillary System Components
2.7.7 Flow Splitter
Stormwater falling on the hospital's paved parking lot was diverted by drains to a manhole. Two
pipes were installed in the manhole. A 15-inch pipe diverted low volume wet-weather flows to
the Arkal treatment system, while an 18-inch pipe bypassed high volume wet-weather flows. A
sump was installed in the manhole below the 15-inch pipe to provide for retention of coarse
solids.
The 15-inch pipe discharged to an underground concrete holding tank that supplied water for the
Arkal system. The pipe was designed with a flow capacity to carry a two-year, 30-minute
duration event having a calculated peak flow of 7.74 cfs. Based on the long-term precipitation
data for the area, the system, as designed, would treat approximately 76 percent of the annual
average runoff volume. During construction, the 15-inch pipe was found to surcharge and was
subsequently re-installed at a slope slightly steeper than designed to alleviate the situation. This
design modification increased the maximum flow of the pipe to approximately 15 cfs, nearly
twice the original design capacity.
The 18-inch diameter pipe was installed in the manhole to allow for bypass to the municipal
storm sewer during high volume storm events. The invert of the bypass pipe was set 1.8 feet
higher in the manhole than the 15-inch pipe, and was equipped with a backflow prevention gate.
The profile for the manhole is shown in Figure 2-2.
2.7.2 Holding Tank
The 15-inch pipe discharged to a 9,200 ft3 (dimensions 56.8 ft x 20 ft x 8 ft) subsurface concrete
holding tank. The tank was sized to completely hold the runoff from two-year, 30-minute event,
taking into account the pumping rate to the filtration system (approximately 450 gpm, or 1 cfs).
-------
|| MONITORING SITE 2\\-
45A BEND—
fc
TAP INTO TOP Ol
STORM SEWER
FIELD VERIFY
INV. EL.
FILTER
HOUSE
VI ,?
y— ACCESS MANHOLE
/ J MANHOLE j MA
_[ L> O
-eOMMON WALL
-rmnrnrAiN HOLDING TANK
4" TANK DRAIN s,"j
?& &S
(L
ANI
18" STORM SEWER
FROM6.3ACRE DRAINAGEAREA
-PRECAST SANITARY MANHOLE
I1 SAND FILTER
OUTLET INV. EL. 127.87
-15" STORM SEWER
18" STORM SEWER
(BYPASS)
SHAWANO AVENUE
-INV. EL. = 119.67
Figure 2-1. Arkal system plan and profile.
-------
APPROXIMATE GRA
EL. 133.00
PRECAST CONCREfE-
ADJUSTING RINGS
12" MAX.
CATCH BASIN FRAME
AND GRATING
NEENAH R-2501
18" STORM SEWER
FROM DRAINAGE AREA,
k,
15" OUTLET
(TO FILTER SYSTEM
18" STORM SEWER
(HIGH FLOW BYPASS)
CATCH BASIN/FLOW SPLITTER -C AST-IN-PLACE
Figure 2-2. Catch basin flow splitter.
-------
The stormwater in the holding tank was pumped to the filtration system by a self-priming solids-
handling pump. The pump was activated by float switches. A high float switch set approximately
18 inches above the base of the tank turned the pump on; and a low float switch set
approximately six inches above the base of the tank turned the pump off. In the event of pump
failure during a wet-weather event, the system was designed so that the tank would fill to
capacity and additional runoff would bypass the system through the flow splitter and discharge to
the storm sewer system.
The tank was manually inspected periodically to check for solids accumulation. During the
course of verification testing, the tank did not have sediment buildup sufficient to interfere with
the system's operation.
2.7.3 Mechanical Housing Unit
The solids-handling pump, backwash booster pump, two-phase filtration system, backwash tank,
and the Arkal Filtration System's control panel were housed in the mechanical housing unit. The
300 ft2 unit was located approximately four feet below grade, and had electrical power,
municipal water, and a sanitary discharge hookup (for backwash water). A plan view showing
the location of the system components in the housing unit is shown in Figure 2-3.
2.2 Filtration Process
The stormwater treatment process consisted of two pressurized filtration systems, in series. The
first stage was designed to remove particles greater than 50 microns, while the second stage was
designed to remove particles down to five microns. The treated stormwater was discharged back
to the storm sewer system, while backwash residuals were discharged to a sanitary sewer.
2.2.1 First-Stage Filtration
The first-stage filtration process consisted of four "towers" of disk filters manufactured by Arkal
Filtration Systems. Each tower contained three "StarFilter" disk filter units, with sets of grooved
rings within each disk filter. According to the vendor, the size of the grooves determines the
particle size removed from the stormwater. The rings can be sized to filter particles down to 25
microns. The disk filters at the test site were equipped with 50-micron rings.
The disk filter units operate in a pressurized mode, with flow from outside the disk filter to
inside. A backwash cycle was automatically initiated when the pressure differential across the
filter rings exceeded 15 psi. A separate booster pump was used to increase the system pressure
during backwash, while a pressure-sustaining valve closed down to throttle the system output.
The system design allowed for simultaneous filtration with three towers while the fourth tower
was in a backwash mode. When the pressure differential was actuated, the towers were
backwashed in sequence. The system was set up so that only one disk filter backwashed at any
one time. The pressurized filtrate was the source of the backwash water. This configuration
allowed the system's filtration process to continue during the backwash cycle. The backwash
water was temporarily stored in a backwash tank and then discharged to a sanitary sewer at the
end of the runoff period. The pre-filtered stormwater was sent to a second filtration stage.
-------
FLOOR PLAN OF FILTER HOUSE
Figure 2-3. Floor plan of filter house detail and profile.
10
-------
2.2.2 Second-Stage Filtration
The second-stage filtration process consisted of a series of five 48-inch diameter sealed sand
filter tanks, also manufactured by Arkal Filtration Systems. According to the vendor, the sand
filters are designed to remove particles five microns and larger from the stormwater. The tanks
were sealed to maintain pressurized flow. The five sand filter tanks received filtered water from
the disk filters through a manifold distribution system. The sand filter tanks had an automatic
backwash cycle, which initiated when the pressure differential across the sand filter exceeded
15 psi. The five tanks in series created a redundant system so four tanks could operate while the
fifth tank backwashed.
The second-stage backwash cycle was initiated independently of the first-stage backwash cycle,
but was controlled by the Arkal system's control panel to prevent the first- and second-stage
filtration systems from backwashing simultaneously.
2.2.3 Backwash Tank
Backwash water for both filtration processes was stored in a backwash tank that had a volume of
approximately 113 ft3 (dimensions 6 ft diameter x 4 ft tall). The backwash tank was designed to
capture, concentrate, and discharge the solids to the sanitary sewer. The tank was designed to
create a vortex action, which directed solids to the bottom of the tank from which they were
discharged to the sanitary sewer.
If the backwash flow exceeded the storage capacity and discharged to sanitary sewer, the tank's
overflow outlet discharged back to the concrete storage tank. This water was subsequently
re-pumped through the filtration system.
The total volume of backwash water discharged from both filter systems to the sanitary sewer for
each storm event was about 200 ft3 (1,500 gallons), or about 1.5 percent of the total volume from
a two-year, 30-minute event. Figure 2-4 is a photo of the two filtration systems in the mechanical
housing unit.
2.3 Technology Application and Limitations
Arkal filtration systems are flexible in terms of the flow they can treat. By varying the holding
tank size, pump rate, or number of filtration pods, the treatment capacity can be modified to
accommodate runoff from various size watersheds.
The filtration system at St. Mary's Hospital was designed to bypass stormwater under high flow
conditions. Based on hydrologic modeling of the drainage area, storm sewer system, holding
tank size, and pumping rate, calculations were made to predict events that would result in bypass
conditions. Table 2-1 summarizes the outcome of the bypass modeling.
11
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2.4 Performance Claim
The vendor claims that the Arkal Filtration System will remove 80 percent of the suspended
solids greater than five microns (5 ^im) in the stormwater treated by the system.
Figure 2-4. View inside filter house with equipment.
Table 2-1. Percent of Event Volume Bypassing Treatment System
Rainfall Duration
Percent Bypass as Function of Rainfall
(hours)
0.5
1
6
12
24
0.5 in
0
0
0
0
0
lin
37
33
0
0
0
1.5 in
56
54
10
0
0
2 in
65
64
33
6
0
2.5 in
70
69
44
22
<1
12
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Chapter 3
Test Site Description
3.1 Location and Land Use
The area draining to the Arkal system is located on the property owned by St. Mary's Hospital.
The hospital grounds cover about 21 acres, with a variety of land uses. Figure 3-1 provides an
aerial view of St. Mary's property, showing the site conditions, including the drainage area and
storm sewer collection system. Table 3-1 summarizes the area for each land use within the
drainage area.
Table 3-1. Drainage Area (Acres) by Land Use
Area (acres)
Parking Lot
& Driveways
3.42
Roof
1.35
Landscape1
0.72
Total Area
5.49
1 Includes ground cover, such as Kentucky bluegrass, ornamental shrubs, and annual flowerbeds.
The total drainage area tributary to the filtration system is 5.49 acres, which is 0.81 acres less
than indicated in the VTP. Inspections of the drainage area conducted during rain events in 2001
refined the drainage boundaries to those shown in Figure 3-1.
3.2 Contaminant Sources and Site Maintenance
The main contaminant contributions within the drainage area were from automobile traffic, snow
removal storage, parking lot surfaces, and rooftop drainage. There were no trash receptacles or
solid waste collection sites within the drainage area.
Hospital staff and visitor parking for approximately 225 cars was provided within the drainage
area. Automobile traffic counts for the parking lots and roadways were not available. The
roadways and parking lots were swept two or three times per year, including at least one cleanup
in the spring. Sand and salting operations occurred in winter as needed.
A private landscaping firm maintained the lawn areas, applying fertilizers and pesticides to the
lawns in spring and fall. Hospital maintenance staff maintained the flower and shrub areas. No
vehicle maintenance or cleaning occurred on the hospital grounds.
Except for the flow splitter manhole, the storm sewer catch basins did not have sumps. There
were no other stormwater treatment devices within the drainage area.
13
-------
Figure 3-1. Aerial photo of drainage area.
14
-------
3.3 Stormwater Conveyance System
The drainage area was totally drained by a subsurface storm sewer collection system. Before
installation of the Arkal system, the site drained to a municipally-owned storm sewer without
treatment. With the installation of the flow splitter, the initial runoff was diverted to the
treatment system. Higher flows bypass the system and continue to discharge to the storm sewer
without treatment.
The treated Stormwater from the Arkal system is discharged to the municipal storm sewer system
on Shawano Avenue, approximately 150 feet west (upstream) of the point where the bypass pipe
enters the municipal storm pipe. Soon after installation of the Arkal system, it was discovered
that under certain flow conditions the treated discharge flowing in the public storm pipe could
cause Stormwater to flow from the city pipe back into the hospital's storm sewer at the bypass
location. This backwater problem was solved with a backflow prevention valve installed in the
bypass pipe. The valve was installed before ETV verification monitoring began.
3.4 Local Meteorological Conditions
The VTP (Appendix C) includes summary temperature and precipitation data from the National
Weather Service station at the Green Bay Airport and the statistical rainfalls for a series of
recurrence and duration precipitation events (Huff et a/., 1992). The climate of Green Bay is
typically continental with some modification created by Lake Michigan and Lake Superior.
Green Bay experiences cold, snowy winters, and warm to hot summers. Average annual
precipitation is nearly 29 inches, with an average annual snowfall of 48.5 inches. Approximately
35 percent of the annual precipitation occurs during the summer months.
15
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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 VTP, which is included as
Appendix C.
4.1 Sampling Locations
Three locations in the test site storm sewer system were selected as sampling and monitoring
sites to determine the treatment capability of the Arkal Pressurized Stormwater Filtration
System. The locations are shown in Figure 2-1.
4.1.1 Site 1 - Influent Ahead of Flow Splitter
This sampling and monitoring site was selected to characterize the untreated Stormwater from the
entire drainage area. A velocity meter and sampler suction tubing were located in the influent
pipe, approximately two feet upstream from the flow splitter manhole. The arrangement of the
velocity/stage meter and sampler tubing is shown in Figure 4-1. The site and test equipment are
shown in Figure 4-2.
Figure 4-1. View of Monitoring Site 1.
4.1.2 Site 2 - Treated Effluent
This sampling and monitoring site was selected to characterize the Stormwater treated by the
Arkal Pressurized Stormwater Filtration System. A velocity meter and sampler suction tubing
were located in an eight-inch diameter plastic pipe in the filter house downstream from all
16
-------
filtering equipment. The treated effluent outlet point was always pressurized and was under full-
pipe conditions at discharge times. The site and test equipment are shown in Figure 4-3.
ISCO Samplers (Sites 1 & 3)
Figure 4-2. View of sampling equipment for Monitoring Sites 1 and 3.
Datalogger & phone
hookup
Figure 4-3. View of Monitoring Site 2 sampler and datalogger.
17
-------
4.1.3 Site 3 - Overflow Bypass
This sampling and monitoring site was selected to characterize the stormwater that bypassed the
treatment system during larger runoff events. A velocity meter and sampler suction tubing were
located in the 18-inch diameter concrete storm sewer pipe, approximately two feet downstream
from the flow splitter manhole. The site and test equipment are shown in Figures 4-2 and 4-4.
Backflow
prevention gate
Figure 4-4. View of Monitoring Site 3 (bypass and backflow prevention gate).
4.1.4 Other Monitoring Locations
In addition to the three sampling and monitoring sites, a recording water-level measurement
device was installed in the concrete holding tank described in Section 2.1.2. The data from this
device were used to verify the filtration system's flow rate. A rain gauge was located adjacent to
the drainage area to monitor the volume 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.
The rain gauge is shown in Figure 4-5.
4.2 Monitoring Equipment
The specific equipment used for monitoring flow, sampling water quality, and measuring rainfall
is listed in Table 4-1.
18
-------
Figure 4-5. View of site rain gauge.
Table 4-1. Field Monitoring Equipment
Equipment
Water Quality
Sampler
Flow
Measurement
Stage Meter
Datalogger
Sitel
ISCO 6700
refrigerated
automatic
sampler (4,
10 L sample
bottles)
Marsh-
McBirney
Velocity
Meter
Model 270
Accubar
PS2
Pressure
Transducer
Campbell
Scientific
Inc. CR10X
datalogger
Site 2
ISCO 3700
refrigerated
automatic
sampler (4,
10 L sample
bottles)
Dynasonics
M3-902
Doppler
Meter
Campbell
Scientific
Inc. CR10X
datalogger
SiteS
ISCO 6700
refrigerated
automatic
sampler (4,
10 L sample
bottles)
Marsh-
McBirney
Velocity
Meter Model
270
Campbell
Scientific
Inc. CR10X
datalogger
Rain Gauge Holding Tank
Accubar PS2
Pressure
Transducer
Campbell Campbell
Scientific Scientific Inc.
Inc. CR10X CR10X
datalogger datalogger
Rain Gauge
Sierra Misco
19
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4.3 Contaminant Constituents Analyzed
The list of constituents analyzed in the stormwater samples is shown in Table 4-2. The vendor's
performance claim addresses only the ability to remove sediments from the runoff water. Total
suspended solids (TSS) and total dissolved solids (TDS) analyses were the primary testing
parameters to evaluate the vendor's performance claim.
Suspended sediment concentration (SSC) analysis was added to the constituent list, though it was
not specified in the VTP. The requirement for SSC analysis was added to the ETV Verification
Protocol Stormwater Source Area Treatment Technologies, Version 4.1 (March 2002) after the
VTP was prepared.
The vendor's claims do not include the ability to remove nutrients or metals from runoff water.
With the vendor's agreement, additional (secondary) constituents, including nutrients and metals,
were added to the constituent list to provide information for stormwater assessments.
Table 4-2. Constituent List for Water Quality Monitoring
Parameter
TDS
TSS
SSC
Total Kjeldahl nitrogen
Nitrate and nitrite
Total phosphorus
Dissolved phosphorus
Total calcium1
Total magnesium1
Total zinc1
Sand-silt split
Five point sedigraph
Sand fractionation
Reporting
Units
mg/L
mg/L
mg/L
mg/L
mg/L as N
mg/L as P
mg/L as P
mg/L
mg/L
Hg/L
NA
NA
NA
Limit of
Detection
7
5
0.1
0.14
0.01
0.005
0.002
0.02
0.02
0.008
NA
NA
NA
Limit of
Quantification
NA
NA
0.5
0.4
0.031
0.016
0.006
0.05
0.05
0.028
NA
NA
NA
Method
SM2540C
EPA 160.2
ASTMD3977-97
EPA 35 1.2
EPA 3 53. 2
EPA 365.1
EPA 365.1
EPA 200.7
EPA 200.7
EPA 200.7
Fishman et al.
Fishman et al.
Fishman et al.
Samples for the first four events were analyzed by Method SW846, 6010B; in the spring of 2001, WSLH changed
to EPA Method 200.7.
20
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4.4 Sampling Schedule
USGS personnel installed the monitoring equipment under a contract with the WDNR. Earth
Tech provided support and assistance on the operation of the system, property access, safety
issues, and landowner relations.
The monitoring equipment was installed in the spring of 2001. In April and May 2001, several
trial events were monitored and the equipment tested and calibrated. Verification testing began in
June 2001, and ended in September 2002 after verification data from 15 qualified storm events
were collected from the system. Table 4-3 summarizes the sample collection data from the 15
storm events. These storm events met the requirements of a "qualified event," as defined in the
VTP:
1. The total rainfall depth for the event, measured at the site rain gauge, was 0.2 inches
(5 mm) or greater (snow fall and snow melt events did not qualify).
2. Flow through the treatment device was successfully measured and recorded over the
duration of the runoff period.
3. A flow-proportional composite sample was successfully collected for both the influent
and effluent over the duration of the runoff event.
4. 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.
5. There was a minimum of six hours between qualified sampling events.
Table 4-4 summarizes the storm 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 A.
The sample collection starting times for the influent and effluent samples, as well as the number
of sample aliquots collected, varied from event to event. The influent sampler was activated
when the influent velocity meter sensed flow in the pipe. Effluent flow would not occur until
water in the holding tank reached a certain level, which initiated the pumps for the filtration
process. The effluent sampler was activated when the filtration process discharged treated
effluent.
21
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Table 4-3. Summary of Events Monitored for Verification Testing
Influent Sampling Point (Site 1) Effluent Sampling Point (Site 2)
r . Start
Event „ ,
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
6/2/01
6/10/01
6/11/01
6/15/01
8/25/01
12/12/01
4/18/02
4/24/02
4/27/02
5/1/02
5/25/02
6/13/02
6/21/02
7/25/02
9/19/02
Start
Time
3:45
12:26
22:38
10:20
2:45
22:18
4:27
15:07
20:15
22:19
8:31
23:48
17:15
17:39
4:48
End
Date
6/2/01
6/10/01
6/12/01
6/15/01
8/25/01
12/13/01
4/18/02
4/24/02
4/28/02
5/2/02
5/27/02
6/14/02
6/21/02
7/25/02
9/19/02
End No. of Start
Time Aliquots Date
11:23
15:36
00:27
12:36
10:47
01:33
08:43
19:04
08:07
01:00
08:08
11:33
18:57
19:56
07:46
11
8
5
19
16
13
21
13
19
5
37
11
13
24
9
6/2/01
6/10/01
6/11/01
6/15/01
8/25/01
12/12/01
4/18/02
4/24/02
4/27/02
5/1/02
5/25/02
6/13/02
6/21/02
7/25/02
9/19/02
Start
Time
4:18
13:18
23:00
11:18
7:31
22:49
6:12
17:24
18:26
23:20
9:24
23:12
17:56
17:26
5:45
End
Date
6/2/01
6/10/01
6/12/01
6/15/01
8/25/01
12/13/01
4/18/02
4/24/02
4/28/02
5/2/02
5/27/02
6/14/02
6/21/02
7/25/02
9/19/02
End No. of
Time Aliquots
12:15
17:18
1:05
14:30
19:00
1:31
8:35
20:58
7:29
0:28
8:42
11:25
21:09
21:21
7:57
22
10
5
17
33
18
11
20
31
8
29
20
29
15
15
22
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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
Start Date
6/2/2001
6/10/2001
6/11/2001
6/15/2001
8/25/2001
12/12/2001
4/18/2002
4/24/2002
4/27/2002
5/1/2002
5/25/2002
6/13/2002
6/21/2002
7/25/2002
9/19/2002
Start
Time
03:42
12:16
22:13
10:13
02:42
21:54
04:14
14:53
20:02
21:55
08:11
20:45
17:14
17:29
04:48
End Date
6/2/2001
6/10/2001
6/12/2001
6/15/2001
8/25/2001
12/13/2001
4/18/2002
4/24/2002
4/28/2002
5/2/2002
5/27/2002
6/14/2002
6/21/2002
7/25/2002
9/19/2002
End
Time
11:08
15:10
00:02
12:03
09:34
00:49
07:46
18:32
07:35
01:07
07:51
10:46
18:19
18:37
07:12
Rainfall
Amount
(inches)
0.81
0.41
0.20
0.38
0.34
0.39
0.40
0.63
1.13
0.22
1.27
0.31
0.36
0.40
0.23
Rainfall
Duration
(hr:min)
7:24
2:54
1:49
1:50
6:52
2:55
3:32
3:39
11:33
3:12
35:40
14:01
1:05
1:08
2:24
Rainfall
Volume1
(ft3)
16,070
6,307
2,367
5,374
4,467
5,495
4,959
8,044
16,332
2,557
16,114
4,640
4,985
5,728
2,929
1 Rainfall volume measured at the inlet monitoring point.
4.5 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 a qualified event occurred.
Water samples were collected with ISCO automatic samplers. A peristaltic pump on 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-liter sample collection bottles. Samples were capped and removed from the sampler, placed
on ice in coolers, and chain of custody forms were completed. The samples were then
transported to the USGS field office in Madison, Wisconsin, where they were split into multiple
aliquots using a 20-liter Teflon-lined churn splitter. The analytical laboratories provided sample
bottles. Samples were preserved per method requirements and analyzed within the holding times
allowed by the methods. Particle size and SSC samples were shipped to the USGS sediment
laboratory in Iowa City, Iowa. All other samples were hand-delivered to the Wisconsin State
Laboratory of Hygiene in Madison, Wisconsin. Chain of custody forms accompanied the sample
bottles to their final destinations.
23
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Chapter 5
Monitoring Results and Discussion
The monitoring results related to contaminant reduction over the 15 events are reported in two
formats:
1. Efficiency ratio comparison, which evaluates the effectiveness of the system on an event
mean concentration (EMC) basis.
2. Sum of loads comparison, which evaluates the effectiveness of the system on a
constituent mass (concentration times volume) basis.
The Arkal system is designed to remove suspended solids from wet-weather flows. The VTP
required that a suite of analytical parameters, including solids, metals, and nutrients, also be
evaluated because stormwater management assessments often require evaluating the potential
reduction of other constituents commonly found in stormwater. The data obtained during the
verification testing are presented in two sections: the primary parameter section, which evaluates
the sediment data and addresses the vendor's claim of suspended solids removal; and the
secondary parameter section, which evaluates metals and nutrient data, of interest for water
quality purposes but not part of 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 (ER) = 100 x (l-[EMCeffluent/EMCinflUent]) (5-1)
The mean concentrations for influent and effluent samples, along with the efficiency ratios
calculated from the analytical data, are summarized in Table 5-1.
The mean influent TSS concentration for the 15 events was 72 mg/L, and the mean effluent
concentration was approximately 13 mg/L. The efficiency ratio for TSS reduction for the
individual events ranged from 47 percent to greater than 94 percent. The volume of sample
collected for events was not always sufficient to complete all of the required analyses and the
SSC, so there were two influent and three effluent events where the SSC was not determined. For
the events where the SSC was determined, the mean influent SSC concentration was 82 mg/L
and the mean effluent concentration was 14 mg/L. The efficiency ratio for SSC ranged from a
low of 32 percent to a high of 95 percent. The wide fluctuations of reductions from event to
event can make the data difficult to interpret. For example, the low percent reductions in EMC
generally occur when the runoff water concentrations are low (relatively "clean" runoff). It is
more difficult to obtain a high percentile reduction in TSS or SSC when the influent water has
low concentrations of TSS or SSC.
24
-------
Table 5-1. Monitoring Results and Efficiency Ratios for Primary Parameters
Total Suspended Solids
Suspended Sediment1
Total Dissolved Solids
Event
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Rainfall
(in)
0.81
0.41
0.20
0.38
0.34
0.39
0.40
0.63
1.13
0.22
1.27
0.31
0.36
0.40
0.23
Influent
(mg/L)
10
38
20
23
32
17
150
430
25
15
14
19
88
180
21
Effluent
(mg/L)
<3
7
<2
4
<2
3
45
61
9
8
4
3
8
25
6
Efficiency
Ratio
>70
82
>90
83
>94
82
71
86
64
47
71
84
91
86
71
Influent
(mg/L)
12
47
~
25
31
14
140
340
28
~
13
16
122
240
43
Effluent
(mg/L)
~
4
~
4
2
3
43
67
19
~
5
4
7
12
2
Efficiency
Ratio
~
91
~
84
94
79
70
80
32
~
62
75
94
95
95
Influent
(mg/L)
38
62
110
74
160
54
280
550
170
200
120
190
120
68
210
Effluent
(mg/L)
190
610
500
370
250
380
650
770
450
950
280
340
570
810
560
Efficiency
Ratio
-400
-880
-370
-400
-56
-600
-130
-40
-170
-380
-130
-80
-380
-1100
-170
Captured water volume not always sufficient to conduct the SSC analysis.
25
-------
5.1.2 Groundwater Infiltration
The TDS data showed a higher effluent concentration of dissolved solids than the influent. The
likely reason for this is the infiltration of groundwater with elevated TDS concentrations into the
storm sewer system through cracks and poorly sealed joints. This is supported by the observation
of water flowing in the storm sewer collection system during dry-weather periods. Also, during
the installation of the system's holding tank, groundwater and mottled soil were encountered at
depths of approximately five to six feet below grade, the same depth as the storm sewer pipes.
Finally, before testing began, all possible non-storm water connections (cooling water, air
conditioner condensate, etc.) were identified and eliminated from the storm sewer network.
Samples of the non-stormwater flow were collected and analyzed for TDS, total calcium, and
total magnesium during a dry weather period (August 8, 2001). The results are shown in
Table 5-2.
Table 5-2. Dry Weather (Groundwater) Analytical Results
Time
1445
1514
1620
1520
Sample
No./Location
1 (Holding Tank)
2 (Site 1)
3 (Holding Tank)
4 (Site 3)
Mean
TDS
(mg/L)
774
836
780
782
793
Total Calcium
(mg/L)
81.5
73.2
78.0
80.9
78.4
Total Magnesium
(mg/L)
49.0
47.9
46.2
48.0
47.7
Average TDS concentrations in the dry-weather flow (793 mg/L) were considerably higher than
average influent concentrations observed during the 15 qualified events (161 mg/L). Water
flowing into the system entered the holding tank during dry-weather periods, which prompted the
pump cycle to initiate every 2 to 21/2 days. This occurrence was monitored by the stage meter
located inside the holding tank and the effluent flow meter, and was recorded by the TO's
monitoring equipment operated by USGS. This pattern appears consistently throughout the
monitoring period. Based on this time interval and the volume of the tank, which is drained
during one pump cycle (approximately 8,500 gal), the system was experiencing infiltration at a
rate of approximately two to three gpm. During storm events, runoff water with lower TDS
concentrations would mix with the high TDS ground water in the holding tank. The combined
water was then pumped through the system, resulting in TDS concentrations in the treated
effluent that were higher than in the influent.
Assuming the infiltration into the storm sewer occurred at the same rate during the 15 monitored
events, the groundwater volume was not sufficient to impact the influent mass loadings to a
mathematical or statistical significance.
26
-------
5.1.3 Sum of Loads
The Sum of Loads (SOL) calculation provides a measure of the efficiency of Arkal system
performance. SOL results reflect the mass pollutant load (concentration times event volume) of a
constituent for all 15 captured events, and is calculated using the following equation:
SOL = 100 x (l-[SOLeffluent/SOLmfluent]) (5-2)
The SOL data for sediments is summarized in Table 5-3.
Table 5-3. Sum of Loads
Event
No.
1
2
O
4
5
6
7
8
9
10
11
12
13
14
15
Total
SOL
Inlet
10
15
O
7.7
8.9
5.8
47.4
214
26
2.4
14.1
5.5
27.4
62.9
3.8
453.8
TSS
(Ib)
Outlet
1.5
2.8
0.1
1.3
0.3
1
13.9
30.6
9.3
1.3
4
0.9
2.5
8.9
1.1
79.7
82
Inlet
12
18.5
0
8.4
8.6
4.8
43.7
171
29.1
0
13.1
4.6
38
85.1
7.9
444.5
SSC
(Ib)
Outlet
0
1.6
0
1.3
0.6
1
13.3
33.6
19.7
0
5
1.2
2.2
2.2
0.4
82.1
82
Inlet
38
24
16
25
45
19
87
274
176
33
123
55
38
24
38
1,019
TDS
(Ib)
Outlet
187
240
74
123
70
130
200
386
465
152
284
100
179
289
102
2,980
-192
The SOL analyses indicate sediment (TSS and SSC) reductions slightly better than the vendor's
claim of 80 percent sediment reduction. As discussed in Section 5.1.2, the TDS data showed a
negative efficiency.
The effluent flow measurements were not considered to be reliable (see Section 6.2.2), so the
influent flow volumes were used to calculate the SOL values. During the monitored events, the
27
-------
stormwater entering the system was discharged either as treated effluent to the storm sewer or
untreated backwash to the sanitary sewer. Since backwashing occurred during each event, the
treated effluent volume was less than the influent volume. Substitution of the higher influent
volume for the effluent volume in Equation 5-2 decreases the SOL values. The result is that the
calculated SOL values presented in Table 5-3 are conservative values.
5.2 Particle Size Distribution
Particle size distribution analysis was conducted in three different ways:
1. A "sand/silt split" analysis determined the percentage of sediment (by weight) larger than
62 |im (defined as sand) and less than 62 jim (defined as silt).
2. A Visual Accumulator (VA) tube analysis (Fishman et. al., 1994) defined the percent of
sediment (by weight) sized less than 1000, 500, 250, 125, and 62 |im.
3. A pipette analysis (Fishman et al., 1994) was conducted to further define the silt portion
of a sample as the percent of sediment (by weight) sized less than 31, 16, 8, 4, and 2 jam.
The autosamplers did not always collect an adequate volume of sample to conduct the full suite
of particle size analyses. Influent and effluent samples from 12 of the 15 qualified events were
analyzed for sand/silt split (Table 5-4). Of the 12 events, six influent samples had sufficient
sediment content and sample volume to conduct the VA tube analysis, and three samples also
had sufficient sediment content to conduct the pipette analysis to provide a full definition of the
particle size distribution (Table 5-5). No effluent samples contained sufficient sediment content
and sample volume for the VA tube and pipette analyses.
28
-------
Table 5-4. Sand/Silt Split Analysis for 12 Events
Event
Number Date
Inlet (percent)
>62 (urn) <62 (urn)
Outlet (percent)
>62 (urn) <62 (urn)
2
4
5
6
7
8
9
11
12
13
14
15
6/10/2001
6/15/2001
8/25/2001
12/12/2001
4/18/2002
4/24/2002
4/27/2002
5/25/2002
6/13/2002
6/21/2002
7/25/2002
9/19/2002
44
23
.0
.8
32.9
Table 5-5. Particle Size Distribution
9.
1.
0.
19
10
18
42
37
67
7
9
9
.4
.0
.5
.5
.9
.9
56
76
67
.0
.2
.1
90.3
98
99
80
90
81
57
62
32
for Six Influent
.1
.1
.6
.0
.5
.5
.1
.1
Sampling
29
21
54
20
2.
8.
7.
1.
24
17
3.
2.
.1
.7
.8
.6
3
8
6
4
.7
.7
0
4
70.9
78.3
45.2
79.4
97.7
91.2
92.4
98.6
75.3
82.3
97.0
97.6
Events
Sieve Passage Rate (Percent)
Sieve Size
(um)
<1000
<500
<250
<125
<62
<31
<16
<8
<4
<2
Event 7
4/18/02
100
100
99.6
98.7
98.1
94.4
81.4
58.9
35.3
17.9
Event 8
4/24/02
100
100
100
99.8
99.1
95.5
78.8
56.4
38.9
23.9
Event 9
4/27/02
87.6
86.8
82.2
80.8
80.6
N/A
N/A
N/A
N/A
N/A
Event 13
6/21/02
79.0
72.2
60.4
57.5
57.5
N/A
N/A
N/A
N/A
N/A
Event 14
7/25/02
94.3
85.1
75.2
68.8
62.1
44.4
32.6
25.2
17.3
13.5
Event 15
9/19/02
40.2
40.2
36.0
32.5
32.1
N/A
N/A
N/A
N/A
N/A
The flow splitter catch basin had a three-foot deep sump that trapped coarse material, preventing
it from entering the holding tank. For the purposes of this verification, the sump was considered
to be part of the Arkal system's treatment process at this installation. The sump was emptied
prior to the verification monitoring period (May 2001). At the end of the verification monitoring
29
-------
period (November 2002), the volume of sediment trapped in the sump was evaluated and core
samples were collected. The sediment depths varied from 14 inches near the inlet to one inch on
the opposite side of the inlet. As shown in Table 5-6, the sediment trapped in the flow splitter
sump was primarily large and coarse. Three composite samples were collected and analyzed for
the particle size distribution analyses. These data are summarized in Table 5-6.
Table 5-6. Particle Size Distribution for Material from Flow Splitter Sump
Sieve Size Sieve Passage Rate (percent)
(um)
<2000
<1000
<500
<250
<125
<62
Sample 1
70
51
34
16
6
3
Sample 2
68
49
34
16
7
3
Sample 3
71
54
39
21
8
4
Mean
70
51
36
18
7
3
5.3 Monitoring Results: Secondary Parameters
As previously stated, the vendor's claim is applicable only to TSS and SSC (as reported in
Tables 5-1 and 5-3). However, for the purpose of stormwater management assessment, it is often
necessary to evaluate the potential for reduction of other constituents commonly found in
stormwater. The VTP included secondary parameters such as nutrients (TKN, nitrates and
phosphorus) and metals (magnesium, calcium, and zinc) commonly found in urban runoff, which
are of concern to water resource managers. These data are summarized in Tables 5-7 through
5-9.
The EMC and SOL data on the non-performance parameters indicated that the system removed
phosphorus, TKN, and zinc from the runoff. These constituents commonly attach to sediment
particles and the treatment was likely the result of the constituents attached to treated sediment
particles. Dissolved-phase nutrients and metals passed through the system without treatment.
As discussed in Section 5.1.2, the groundwater infiltration issue also likely affected the calcium
and magnesium analyses (see Table 5-2).
30
-------
Table 5-7. Event Mean Concentration for Secondary Parameters (Nutrients)
1
(mg/L as N)
Event Percent
No. Inlet Outlet Change
1 0.32J
2T 0.51
3 1.0
4 0.62
5 1.3
6 0.42
7 2.1
8 2.2
9 0.33J
10 0.56
11 0.84
12 0.51
13 0.84
14 1.1
15 0.78
0.39J
0.59
0.55
0.57
0.53
0.43
1.71
1.0
0.35J
0.43
0.51
0.75
0.57
0.78
0.46
-22
-16
45
8.1
59
-2.4
19
55
-6.1
23
39
-47
32
29
41
NO2 + NO3asN
(mg/L)
Percent
Inlet Outlet Change
0.286
0.641
0.889
0.557
1.69
0.357
1.34
0.743
0.393
0.697
0.599
0.587
0.623
0.839
0.839
0.674
1.70
1.49
1.10
1.63
0.931
1.80
0.906
0.839
1.88
0.789
0.935
1.34
2.09
1.24
-136
-165
-67.6
-97.5
3.55
-161
-34.3
-21.9
-113
-170
-31.7
-59.3
-115
-149
-47.8
Total Phosphorus Dissolved Phosphorus2
(mg/L as P) (mg/L as P)
Percent Percent
Inlet Outlet Change Inlet Outlet Change
0.023
0.07
0.059
0.061
0.061
0.043
0.17
0.32
0.069
0.053
0.056
0.05
0.11
0.21
0.26
0.015J
0.005
0.028
0.037
0.025
0.033
0.087
0.087
0.051
0.034
0.033
0.032
0.034
0.067
0.13
35
96
53
39
59
23
49
73
26
36
41
36
69
68
50
0.005
0.005
0.005
0.020
0.012
0.021
0.038
0.026
0.022
0.024
0.014J
0.015J
0.016
0.017
0.168
0.005
0.005
0.005
0.014J
0.021
0.025
0.028
0.021
0.021
0.017
0.015J
0.011J
0.0080J
0.025
0.119
50
0.0
0.0
30
-75
-19
26
19
4.5
29
-7.1
27
50
-47
29
One of four field blank results for TKN showed a concentration above the MDL, below the LOQ (inlet sample: 0.24 mg/L);
see Section 6.1.1, Table 6-1.
Dissolved phosphorus for the first four events was analyzed as ortho phosphorus.
Denotes an estimated concentration. Concentration is above the MDL and below the LOQ.
31
-------
Table 5-8. Event Mean Concentration for Secondary Parameters (Metals)
Event
No
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Inlet
24J
50
36J
45J
72
45J
130
210
35J
36J
53
31J
73
130
52
Total Zinc
(Mg/L)
Outlet
19J
20J
24J
25J
19J
<16
56
50
26J
18J
22J
18J
21J
22J
17J
Pet.
Change
21
60
33
44
74
82
58
76
26
50
58
42
71
83
67
Inlet
6.50
11.5
12.8
10.6
21.8
7.70
33.6
63.6
13.2
17.4
12.0
23.8
21.1
34.6
22.5
Total Calcium1
(mg/L)
Outlet
19.2
60.3
48.4
36.9
25.7
41.6
47.2
35.3
33.3
77.2
25.0
34.1
51.9
75.9
47.4
Pet.
Change
-195
-424
-278
-248
-18.0
-440
-40.0
44.0
-152
-344
-108
-43.0
-146
-119
-111
Inlet
2.3
4.3
4.6
4.1
8.5
3.1
12
30
5.4
7.4
4.5
10
9.8
16
11
Total Magnesium1
(mg/L)
Outlet
8.3
29
23
17
11
23
20
14
15
36
11
15
26
41
28
Pet.
Change
-260
-570
-400
-320
-29
-640
-67
53
-180
-390
-140
-50
-170
-160
-160
1 Field blank results for calcium and magnesium showed constituents at concentrations above MDL; see Section 6.1.1,
Table 6-1.
1 Denotes an estimated concentration. Concentration is above the MDL but below the LOQ.
R Denotes duplicate sample.
32
-------
Table 5-9. Sum of Loads for Secondary Parameters
Event
No.
1
2
o
J
4
5
6
7
8
9
10
11
12
13
14
15
Total:
SOL
(Percent):
TKN
(Ib as N)
Inlet Outlet
0.32
0.20
0.15
0.21
0.37
0.14
0.63
1.11
0.33
0.09
0.84
0.15
0.26
0.38
0.14
5.35
0.39
0.23
0.08
0.19
0.15
0.15
0.53
0.52
0.35
0.07
0.51
0.22
0.18
0.28
0.08
3.94
26
NO2 + NO3
(Ib as N)
Inlet Outlet
0.29
0.25
0.13
0.19
0.47
0.12
0.41
0.37
0.40
0.11
0.60
0.17
0.19
0.30
0.15
4.17
0.68
0.67
0.22
0.37
0.45
0.32
0.56
0.45
0.85
0.30
0.79
0.27
0.42
0.75
0.23
7.33
-76
Dissolved
Phosphorus
(Ib as P)
Inlet Outlet
0.005
0.001
0.000
0.007
0.003
0.007
0.012
0.013
0.022
0.004
0.014
0.004
0.005
0.006
0.031
0.135
0.003
0.001
0.000
0.005
0.006
0.009
0.009
0.011
0.021
0.003
0.015
0.003
0.002
0.009
0.022
0.118
13
Total Phosphorus
(Ib as P)
Inlet Outlet
0.023
0.028
0.009
0.020
0.017
0.015
0.051
0.159
0.070
0.008
0.056
0.014
0.035
0.076
0.047
0.629
0.015
0.001
0.004
0.012
0.007
0.011
0.027
0.044
0.052
0.005
0.033
0.009
0.011
0.024
0.025
0.280
55
Total
Inlet
0.02
0.02
0.01
0.02
0.02
0.02
0.04
0.10
0.04
0.04
0.04
0.02
0.01
0.03
0.01
0.42
Zinc (Ib)
Outlet
0.02
0.01
0.00
0.01
0.01
0.00
0.02
0.03
0.03
0.02
0.02
0.01
0.01
0.01
0.00
0.18
58
Total Calcium
Ob)
Inlet Outlet
6.5
11.0
13.0
11.0
21.9
7.7
33.7
63.8
13.2
17.5
12.0
23.9
21.2
34.7
22.6
18.0
19.1
60.2
49.2
37.1
25.8
41.7
47.4
35.4
33.4
77.5
25.1
34.2
52.1
76.1
47.6
51.7
-188
Total
Magnesium
(Ib)
Inlet Outlet
2.3
4.3
4.6
4.1
8.5
3.1
12.0
30.1
5.4
7.4
4.5
10.0
9.8
16.1
11.0
8.0
8.3
29.1
23.1
17.1
11.0
23.1
20.1
14.0
15.0
36.1
11.0
15.0
26.1
41.1
28.1
25.1
-213
NOTE: For purposes of statistical analysis, parameters below detection level were assigned a value of one-half of the detection level.
33
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Chapter 6
QA/QC Results and Summary
The Quality Assurance Project Plan (QAPP) in the VTP 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 B.
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 11/09/00
(before the first event was sampled), allowing the USGS to review the results as early as possible
in the monitoring schedule and to make adjustments. The next field blank was taken on June 25,
2001 (between events 4 and 5). Results for both field blanks are shown in Table 6-1.
Table 6-1. Field Blank Analytical Data Summary
Blank 1 Blank 2
Parameter (mg/L) Inlet Outlet Inlet Outlet
TSS
TDS
TKN
NO2 + NO3
Dissolved phosphorus
Total phosphorus
Total calcium
Total magnesium
Total zinc
<5.0
<7.01
<0.14
<0.01
<0.005
<0.005
0.05
<0.03
<0.019
<5.0
<7.01
<0.14
<0.01
<0.005
<0.005
0.34
1.50
<0.019
<5.0
<20l
0.24
<0.01
<0.005
<0.005
0.22
0.12
<0.019
<5.0
<20l
<0.14
<0.01
<0.005
<0.005
0.05
<0.03
<0.019
1 The WSLH increased TD S detection limits in July of 2001, between the field blank sample dates.
The field blank results show no detectable levels for dissolved solids, suspended solids, and total
and dissolved phosphorus. A low concentration of TKN (0.24 mg/L) was detected in the inlet
sample from the second inlet blank. This concentration was above the MDL, but below the LOQ,
for the method. The possible source of this contamination is not known. The data for TKN,
presented in Table 5-7, has been flagged with a footnote, indicating that the field blank result
34
-------
was positive for one sample. Also, low concentrations of calcium and magnesium were detected
in the field blank samples. The data, presented in Table 5-8, have been flagged with a footnote
indicating that the field blanks showed positive results. Field contamination could contribute a
positive bias to the inlet data, if present during all events, and should be considered when
evaluating the data. The outlet data, apparently influenced by the presence of groundwater
infiltration, showed higher concentration of calcium and magnesium, so any bias due to field
contamination would be lower than for the inlet data.
6.1.2 Replicates (Precision)
Precision measurements were performed by the collection and analysis of duplicate samples.
Field duplicates were collected to monitor the overall precision of the sample collection and
laboratory analyses. Two duplicate samples from Sites 1 and 2 were collected to evaluate
precision in the sampling process and analysis. No replicates from Site 3 were collected since a
bypass event did not occur. The duplicate samples were obtained on April 7, 2002 (Event 9) and
June 21, 2002 (Event 13). The samples were taken from the composite sample collected at each
site for each event and split into two separate samples. They were processed, delivered to the
laboratory, and analyzed in the same manner as the regular samples. The relative percent
difference (RPD) recorded from the sample analyses was calculated to evaluate precision. JAPD
is calculated using the following formula:
%RPD = ft^l x 100% t6'1)
\ x J
where:
xi = Concentration of compound in sample
X2 = Concentration of compound in duplicate
x = Mean value of xi and X2
Summaries of the field duplicate data are presented in Table 6-2. The duplicate analyses were
within the JAPD limits for all samples with the exception of the TSS outlet sample during the first
replicate sample event. This difference occurred on replicate samples with low TSS
concentrations (13 and 9 mg/1). These concentrations are only two to three times the method
detection limit, which is commonly a measurement range that has lower precision. The field
duplicate precision results for TSS are within the typical range for stormwater or wastewater
samples, particularly at low concentrations.
6.1.3 Accuracy
Method accuracy was determined and monitored using a combination of matrix spike/matrix
spike duplicates (MS/MSD) and laboratory control samples (known concentration in blank
water). The MS/MSD data are evaluated by calculating the deviation from perfect recovery (100
percent), while laboratory control data are evaluated by calculating the deviation from the
laboratory control concentration. Accuracy was in control throughout the verification test. Tables
6-3 and 6-4 summarize the matrix spikes and lab control sample recovery data, respectively.
35
-------
Table 6-2. Duplicate Sample RPD Data Summary
Parameter
TSS
IDS
Nitrates
Dissolved
phosphorus
Total
phosphorus
Total calcium
Total
magnesium
Total zinc
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Influent
Effluent
Rep. la
(mg/L)
25
13
170
470
0.393
0.839
0.022
0.021
0.069
0.051
13.2
33.3
5.4
15
35
26
Rep. Ib
(mg/L)
25
9
174
488
0.386
0.858
0.021
0.021
0.068
0.049
13
32.7
5.2
15
37
25
RPD1
(pet)
0
36
2.3
3.8
1.8
2.2
4.7
0
1.5
4.0
1.5
1.8
3.8
0
5.6
3.9
Rep. 2a
(mg/L)
85
7
110
582
0.623
1.34
0.016
0.008
0.114
0.034
21.1
51.9
9.8
26
73
21
Rep. 2b
(mg/L)
88
8
122
574
0.637
1.36
0.015
0.007
0.114
0.034
17.9
51.5
8
25
69
21
RPD 2
(pet)
3.5
13
10
1.4
2.2
1.5
6.5
13
0
0
16
0.8
20
3.9
5.6
0
Limit
(pet)
30
30
25
20
25
25
25
25
Table 6-3. Laboratory MS/MSD Data Summary
Parameter
Average Maximum Minimum Std. Dev.
Count (percent) (percent) (percent) (percent) Range (Pet)
Total calcium
Total magnesium
Dissolved nitrates
Dissolved phosphorus
TKN
Total phosphorus
Dissolved zinc
Total zinc
14
14
14
13
16
21
6
13
94
95
100
103
99
102
96
94
100
98
107
106
109
105
98
99
89
92
94
99
92
97
93
89
2.75
2.03
3.50
2.02
5.37
2.29
1.65
2.35
85-115
85-115
90-110
90-110
90-110
90-110
85-115
85-115
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
an NIST traceable thermometer.
36
-------
Table 6-4. Laboratory Control Sample Data Summary
Parameter
Total magnesium
Nitrate & nitrite
TSS
Dissolved phosphorus
TDS
TKN
Total phosphorus
SSC
Total zinc
Count
18
13
13
3
15
23
19
13
22
Mean
(percent)
2.5
4.9
9.5
0.3
9.9
2.6
1.0
11
3.2
Minimum
(percent)
0.3
2
3
0.3
0
0.3
0.2
2.2
0.3
Maximum
(percent)
7.4
9.0
20
0.5
22
4.3
3.1
19
6.4
Std. Dev.
(percent)
2.0
2.5
6.5
0.1
8.2
1.4
0.8
5.0
1.8
6.1.4 Representativeness
The field procedures were designed to ensure that representative samples were collected of both
influent and effluent 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 may
occur, the long-term trend in the data was representative of the concentrations in the stormwater,
and redundant methods of evaluating key constituent loadings in the stormwater were utilized to
compensate for the variability of the laboratory data.
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.
6.1.5 Completeness
The flow data and analytical records for the verification study are 100 percent complete.
37
-------
6.2 Flow Measurement Calibration
6.2.1 Influent
Calibration of influent flow (Site 1) was based on stage measurements from the holding tank
during runoff periods. At the inlet, a Marsh-McBirney Model 270 Velocity Meter measured
velocity and stage. Calibration of flow measurement at the inlet was achieved by comparing a
mass balance between the calculated runoff volume at the inlet (using the recording velocity
meter and stage recorder) and the stage/volume measured in the holding tank, before the filter
pump turned on. The two calculated volumes were compared and used as a basis for correction
of inlet flow values. Table 6-5 summarizes the comparisons of the holding tank volumes and the
inlet runoff volumes for 29 events, covering the time frame of this verification. The maximum
absolute difference between methods was 12.4 percent and the average difference over the 29
events was 0.3 percent. Because of the small difference in the average difference, no adjustments
were made to the inlet Marsh-McBirney flow or volume measurements.
6.2.2 Treated Effluent
Calibration of the treated effluent site (Site 2) used a similar approach as the influent. During
non-runoff periods, the known volume of water in the tank (derived from groundwater flow) was
drawn down and the volume of draw down was compared to the measured volume that passed
through the effluent site as calculated by the Doppler velocity meter measurements, assuming a
full-pipe condition. Full-pipe conditions were assumed because the municipal storm sewer
receiving the treated flow was surcharged under small runoff events. This surcharging would
maintain a full-pipe condition at Site 2 during runoff periods. Dry-weather periods were used for
this analysis because inflow to the holding tank was at a minimum during these periods, and the
tank volume draw down rate was not being influenced by inflow.
The evaluation of the Site 2 Doppler velocity meter was conducted throughout the monitoring
period (a total of 54 dry-weather evaluations were conducted). The regression between the tank
volumes and the outlet volumes did not prove to be sufficiently accurate for the purposes of this
study. It is believed the poor regression results were due to one or more of the following:
1. The Doppler velocity meter at Site 2 had difficulties measuring accurate velocities at
times due to the very low suspended solids concentrations in the filtered water. The
principles of operation for the Doppler velocity meter are based on the reflection of an
acoustic signal off the suspended solids. If suspended solids concentrations are low, the
acoustic signal strength can be compromised. Published specifications for the velocity
meter state minimum requirements of 25 mg/L TSS of 30-|im particles, while Table 5-1
shows that the TSS concentrations at Site 2 were less than 25 mg/L for 12 of the 15
events.
2. Back flushing of the system may have occurred during the draw down periods used in the
calibration process and this volume of water was not accounted for (the backwash water
discharges to a sanitary sewer).
38
-------
Table 6-5. Comparison of Runoff Volumes - Holding Tank Measurements Versus Inlet
Velocity/Stage Meter Calculations
Test No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Date
4/11/01
6/1/01
6/10/01
6/15/01
7/20/01
7/28/01
8/25/01
9/7/01
9/19/01
10/10/01
10/13/01
4/12/02
4/18/02
4/24/02
4/27/02
5/6/02
5/25/02
5/27/02
6/3/02
6/10/02
6/1 1/02
6/13/02
6/22/02
6/26/02
7/25/02
8/4/02
8/1 1/02
8/21/02
9/19/02
Tank Volume Inlet Volume
(ft3) (ft3)
910.2
665.8
1117.4
1168.7
270.5
615.5
531.0
3823.9
419.4
549.1
3275.7
288.7
1122.4
197.1
910.2
299.7
473.7
193.1
357.0
3965.7
534.1
2026.6
842.8
432.5
286.6
3082.6
518.0
5679.5
933.3
Maximum
Minimum
941.76
596.16
1140.48
1192.32
276.48
622.08
527.04
3818.88
406.08
578.88
3222.72
267.84
1192.32
172.8
907.2
302.4
466.56
198.72
380.16
3473.28
570.24
1944
846.72
475.2
276.48
2998.08
535.68
5581.44
993.6
Absolute Difference:
Absolute Difference:
Mean Difference:
Difference
(percent)
3.5
-10.5
2.1
2.0
2.2
1.1
-0.8
-0.1
-3.2
5.4
-1.6
-7.2
6.2
-12.3
-0.3
0.9
-1.5
2.9
6.5
-12.4
6.8
-4.1
0.5
9.9
-3.5
-2.7
3.4
-1.7
6.5
12.4
0.1
0.3
39
-------
3. Buildup of biomass on the StarFilter rings resulted in high backwash rates resulting
in low volumes passing the velocity meter and more frequent discharges to the
sanitary sewer than anticipated.
For these reasons, the effluent flow measurements and resulting volume calculations were
considered to be unreliable.
Since the calibrated influent flow values were considered to be sufficiently accurate, the influent
flow volumes were used to calculate both the influent and the effluent constituent loads. Given
that no bypassing occurred (Site 3) during the 15 qualified events reported, the flow entering the
system through the influent must equal the sum of the flows through the effluent and the
backwash to the sanitary sewer. Using the influent flow as the flow through the Arkal system
assumes that the amount of flow discharged to the sanitary sewer is small relative to the treated
flow discharged to the storm sewer. Based on use of the influent flow data as representative of
the effluent flow, loading reduction (SOL) calculations conducted for this report provide a
conservative estimate of the reduction in loads through the stormwater treatment system (actual
loading reductions are greater than reported).
In spite of the accuracy issues encountered with the Site 2 flowmeter, the flowmeter did trigger
the auto sampler in an appropriate manner, which in turn sampled the outlet flow in a flow
proportional manner throughout the discharge period.
40
-------
Chapter 7
Operations and Maintenance Activities
7.1 System Operation and Maintenance
Installation of the Arkal system at St. Mary's Hospital was completed in December 1998. During
1999, the system was placed into operation and adjustments to the system were completed,
including replacement of the backwash booster pump and enlarging the Star Filter backwash
discharge pipe. The sampling equipment for the ETV verification testing was set up by USGS in
October 2000, and final adjustments and preparation of the system for ETV testing were
completed in the spring of 2001. Preparation included replacement of a leaking sand pod and
replacement of the sand media in all pods. The staff time to complete this effort was 48 hours. A
new roof hatch was added to the system and the backwash tank cleaned just prior to the start of
the testing, requiring staff time of 16 hours and a contractor cost of $1,000.
Table 7-1 summarizes the maintenance activities and major activities related to the Arkal system
during the verification testing. The reported staff hours for maintenance activities include those
of St. Mary's Hospital, Earth Tech, and Zeta Technology staff. The maintenance activities were
conducted during dry weather periods and did not result in system downtime.
Table 7-1. Operation and Maintenance During Verification Testing
Date
Activity
Personnel Time/Cost
September 2001
October 2-3, 2001
October 4, 2001
October 25, 2001
November 2, 2001
Decembers, 2001
June 2002
Star filter rings not opening during backwash.
Bacteria/slime growth suspected to cause them to
bind together
Hospital staff removed and cleaned star filter rings
Filter system disinfected with chlorine solution;
water solenoid valve converted to an air-driven
system
Backpressure sustaining valve, star filter valves,
and main pump functions checked
Main pump sheaves changed to improve pumping
rate
Maintenance check completed; pressure gauges
installed; system disinfected with chlorine solution
All nine backwash valves disassembled and
inspected for sediment fouling; none found
None associated with
identification of
problem
16 hours labor
16 hours labor; $260
for air compressor
16 hours labor
12 hours labor
18 hours labor
6 hours labor
41
-------
7.2 System Power Usage
Table 7-2 summarizes the estimate of the Arkal System power usage, measured in kilowatt hours
(kWh), during the monitored events. Based on a statistical evaluation of over 50 years of Green
Bay precipitation records conducted by the USGS, the average length of an event is 5.5 hours,
the same average duration of the 15 qualified events sampled during this verification. Costs are
computed on an average event basis assuming a total runtime averaging 6.5 hours per event
(there is a runoff storage and lag time for each event). The costs shown in Table 7-2 are based on
the average precipitation year and are not based on actual costs incurred during the monitoring
period. The power costs for pumping groundwater infiltration (between events) are not included
in these estimates because this situation may vary greatly from location to location.
Table 7-2. Power Costs for Arkal System on an Average Event Basis
Equipment
15 hp self-priming solids handling pump
5 hp vertical in-line centrifugal process pump
Controllers
5 hp air compressor
Total Costs/Event
Annual Power Costs1
Power (kWh)
70.9
5.9
0.22
0.28
Rate
$0.08
$0.08
$0.08
$0.08
Cost/Event
$5.67
$0.47
$0.11
$0.02
$6.27
$689.70
Assuming average of 110 runoff events per year
42
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Chapter 8
References
1. 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.
2. 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.
3. NSF International; and Earth Tech. Test Plan for the Verification of Arkal Filtration
Systems, Inc. Pressurized Stormwater Filtration System, St. Mary's Hospital, Green Bay,
WI. January 2, 2001.
4. 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).
43
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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 effluent, 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.
44
-------
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 USEPA 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 USEPA 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.
45
-------
Appendices
A Event Hydrographs and Rain Distribution
B Analytical Data Reports
C Verification Test Plan
D Operation and Maintenance Log
46
-------
APPENDIX A
EVENT HYDROGRAPHS AND RAIN DISTRIBUTION
-------
Event:
Flow A Sample Points
•Precipitation
1.8 -,
1.6
T 0.90
0.80
0.00
D
O
e
(ID
O
D
O
Ci
CM
e
(D
O
O
O
e
in
O
D
O
a
(N
e
(D
O
D
O
a
(N
e
(D
D
O
a
(N
e
(D
Date/Time
D
O
e
(Jll
O
D
o
a
(N
e
to
o
D
O
a
CM
e
(D
O
D
O
a
-------
Event: 06/10/01
Flow A Sample Points
•Precipitation
1.8 -,
T 0.45
0.00
D
O
Ci
O
O
O
Ci
O
O
O
Ci
O
(Jll
O
(D
O
CD
O
(D
O
(D
O
(D
O
Date/Time
(D
O
(D
O
(D
O
(D
O
-------
Event: 06/11/01
Flow A Sampling Point;
•Precipitation
1.8 -i
1.6
T 0.25
0.00
(J3
O
(O
o
(O
o
(O
o
(O
o
(O
o
to
o
ID
O
Q
O
Ci
ID
O
Q
O
Ci
ID
O
Date/Time
Q
O
Ci
fN
(3
o
-------
Event: 06/15/01
Flow A Sample Points
•Precipitation
1.8 -,
1.6
T 0.40
-• 0.35
0.00
Q
O
Ci
in
(J3
O
O
O
Ci
in
(J3
O
(ID
O
(O
o
Q
o
Ci
(O
o
o
o
Ci
(O
o
(O
o
ooo
Date/Time
to
o
o
o
Ci
m
to
o
to
o
to
o
(3
o
o
o
Ci
in
(3
o
-------
Event: 08/25/01
Flow A Sample Points
•Precipitation
1.8 -,
1.6
T 0.40
0.35
-• 0.30
4 0.25 ~
'u
Q)
4 0.20 »
-• 0.15
I I
I I
(J
-• 0.10
^- 0.05
^ 0.00
CO
o
CO
o
en
o
en
o
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
08/25/2001
o
o
Ci
m
C!
CO
0
08/25/2001
08/25/2001
1003/93/90
08/25/2001
o
o
in
C!
CO
0
Date/Time
-------
Event: 12/12/01
Flow A Sample Points
•Precipitation
o
o
Q!
CN
Q
O
Ci
CN
CN
CN
Q
o
Q
CN
Q
O
a
CN
O
O
d
CN
CN
Q
O
Q!
CN
Q
O
Ci
CN
CN
CN
CN
CN
CN
CN
Q
O
Ci
CO
Q
O
Q
CO
O r~i
O O
Q| JN
CO CO
CN C"M
CO
CN
Date/Time
-------
Event: 04/18/02
Flow A Sample Points
Precipitation
1.8 -,
1.6
1.4
1.2
S 1
cu
E1
ra
tj °'8
E
0.6
0.4
0.2
0
T 0.45
0.40
0.35
0.30 •?
u
0.25 £
D.
w
0.15
0.10
0.05
'0.00
0
CN
O
O
Ci
CO
0
CN
O
O
C'
CD
0
CN
O
O
CJ
CO
0
CN
O
O
c>
CO
0
CN
O
O
CJ
oo
0
CN
O
O
a
CO
0
CN
O
O
Q
CO
0
CN
O
O
CN
CO
0
CN
O
O
d
CO
0
CN
O
O
QJ
OO
0
CN
O
O
CN
CO
0
CN
O
O
CN
CO
0
CN
O
O
CN
CO
0
CN
O
O
CN
CO
0
CN
O
O
£^
OO
0
CN
O
O
CN
OO
0
CN
O
O
CN
CO
0
CN
O
O
CN
CO
0
CN
O
O
CJ
OO
0
CN
O
O
CN
CO
Date/Time
-------
Event: 04/24/02
Flow A Sample Points
•Precipitation
3.5 -,
-• 0.60
0.00
r-j
o
o
r-j
o
o
^i-
o
^i-
o
*=t
o
*=t
o
*=t
o
*=t
o
*=t
o
*=t
o
*=t
o
d
*=t
o
a
*&
o
a
*&
o
a
^•
o
a
^~
o
a
^~
o
a
^•
o
a
^~
o
a
^•
o
a
^~
o
^~
o
^~
o
^~
o
^~
o
^~
o
Date/Time
-------
Event: 04/27/02
Flow A Sample Points
•Precipitation
1.6 -,
1.4
T 1.20
Date/Time
-------
Event: 05/02/02
Flow A Sample Points
•Precipitation
1.8 -,
1.6
T 0.30
0.00
Date/Time
-------
Event: 05/25/02
Flow A Sample Points
•Precipitation
1.8 n
1.6
1.4
1.2
u
E1
ra
H °'8
E
0.6
0.4
0.2
0
O
r-t
Q
O
LJ-)
O
Oj
O
r-j
o
o
Ci
in
D
O
o
o
CJ
in
C!
in
o
r-j
o
o
C-t
D
O
o
o
Q!
to
o
Oj
o
r-j
o
o
Ci
(D
o o
Date/Time
(D
Ci
to
Ci
kn
o
(D
Q
LD
o
o
o
r-t
Q
o
Q!
in
o
-• 1.20
-• 1.05
-• 0.90
40.75
A
Q.
w
- 0.60 -|
- 0.45 =
-• 0.30
- 0.15
0.00
(D
o
Oj
O
c-t r-t
o o
o o
Ci Ci
S C!
m UT
o o
-------
Event: 06/13/02
1.8 -,
1 R
I .D
1 A -
•i 9 .
5 1
0)
E1
"5 n R -
E
n R -
n A
n 9
u . ^
^
i ft\
!S*\
J \^^..._
i i i
o o o o
CO CO CO CO
CO O 4^ CN
r-j o o o
r-t r-t r-t r-t
o o o o
o o o o
0000
Flow A Sample Points Precipitation
o o o o o
CO ••* ifi CD h-^
00000
r-j r-j r-j r-j c-t
o o o o o
o o o o o
o o o o b
Date/Time
,'i
ii
' !
1 i
i
! i
1 A
A
i \
i
' V
,' V
1 ^ -
• O.GO
• 0.50
• 0.40 t
'u
Q)
CL
0)
• 0.30 -|
n
i
• 0.20 U
• 0.10
' n nn
1 1 ' 1 1 U.UU
o o o o
CO CO CO CO
CO CD O 4^
0 0 T^ T^
r-t r-t c-t r-t
o o o o
o o o o
CD CD CD CD
0000
-------
Event: 06/21/02
Flow A Sample Points
•Precipitation
3.5 -,
T 0.40
-• 0.35
0.00
c-j
o
o
CM
O
O
CM
O
O
CM
O
O
o
o
Ci
o
o
Ci
o
o
Ci
CN
O
O
CN
O
O
C-l
D
O
CD
o
CD
o
co
o
co
o
co
o
CD
o
CD
O
Date/Time
CD
O
CD
O
CD
O
CD
O
CD
O
-------
Event: 07/25/02
Flow A Sample Point
•Precipitation
T 0.45
-• 0.40
t-
o
g
o
Date/Time
o
o
Ci
tn
Q!
i--
o
o
o
Ci
tn
Q!
i--
o
-------
Event: 09/19/02
Flow A Sample Points
•Precipitation
T 0.25
0.00
en
o
en
o
en
o
en
o
en
o
en
o
en
o
en
o
en
o
Date/Time
en
o
en
o
en
o
en
o
en
o
------- |