April 2005
05/20/WQPC-WWF
EPA 600/R-05/099
Environmental Technology
Verification Report
Stormwater Source Area
Treatment Device
Stormwater Management, Inc.
StormScreen® Treatment System
Prepared by
NSF International
Under a Cooperative Agreement with
U.S. Environmental Protection Agency
-------
Environmental Technology Verification Report
Stormwater Source Area Treatment Device
Stormwater Management, Inc.
StormScreen® Treatment System
Prepared by:
NSF International
Ann Arbor, Michigan 48105
and
Scherger Associates
Ann Arbor, Michigan 48105
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 08837
April 2005
-------
THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
vvEPA
U.S. Environmental Protection Agency
PROGRAM
NSF International
ETV Joint Verification Statement
TECHNOLOGY TYPE:
APPLICATION:
TECHNOLOGY NAME:
TEST LOCATION:
COMPANY:
ADDRESS:
WEBSITE:
EMAIL:
STORMWATER TREATMENT TECHNOLOGY
SUSPENDED SOLIDS AND ROADWAY POLLUTANT
TREATMENT
THE STORMWATER MANAGEMENT STORMSCREEN®
TREATMENT SYSTEM
GRIFFIN, GEORGIA
STORMWATER MANAGEMENT, INC.
12021-B NE Airport Way
Portland, Oregon 97220
http://www.stormwaterinc.com
mail@stormwaterinc.com
PHONE: (800)548-4667
FAX: (503)240-9553
NSF International (NSF), in cooperation with the U.S. Environmental Protection Agency (EPA), operates
the Water Quality Protection Center (WQPC), one of six centers under the Environmental Technology
Verification (ETV) Program. The WQPC recently evaluated the performance of the Stormwater
Management StormScreen® (StormScreen) manufactured by Stormwater Management, Inc. (SMI). The
system was installed in a city-owned right-of-way near downtown Griffin, Georgia. Paragon Consulting
Group (PCG) performed the testing.
EPA created ETV 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.
05/20/WQPC-WWF
The accompanying notice is an integral part of this verification statement.
VS-i
April 2005
-------
TECHNOLOGY DESCRIPTION
The following description of the StormScreen was provided by the vendor and does not represent verified
information.
The StormScreen is a device that removes trash, debris, and large suspended particulates at high flow
rates. The StormScreen consists of an inlet bay, cartridge bay, and outlet bay, housed in a 16-ft by 8-ft
precast concrete vault. The inlet bay serves as a grit chamber and provides for flow transition into the
cartridge bay, where the water is screened and discharged through flumes to the outlet bay and the outlet
pipe.
The StormScreen is equipped with 20 cartridges (four discharge flumes with five cartridges per flume).
The cartridges are equipped with screens with a standard opening size of 2.4 mm. The cartridges screen
water by combining direct screening with many of the hydraulic aspects of the siphonic, radial-flow
cartridge system patented by SMI. Water in the cartridge bay passes through the cartridge screen and into
a tube in the center of the cartridge. When the center tube fills, a float valve opens and a check valve on
top of the cartridge closes, creating a siphon that draws water through the screens. The treated water
drains into the discharge flume to the outlet bay, where it exits the system through the discharge pipe. The
system resets when the cartridge bay is drained and the siphon is broken. Screened solids accumulate in
the debris sump in the cartridge bay. Each cartridge has a design flow capacity of 0.5 cfs (224 gpm), so
the unit as a whole has a design flow capacity of 10 cfs (4,488 gpm).
Flows exceeding the capacity of the StormScreen are diverted by an SMI StormGate™ installed upstream
of the StormScreen. The StormGate™ has a field-adjustable weir in a precast cylindrical concrete vault.
Flows with a depth lower than the weir elevation are diverted to the StormScreen, while flows with a
depth greater than the weir elevation are discharged to a bypass pipe. The weir at this installation was set
at an elevation to direct a 10 cfs flowrate to the StormScreen.
SMI claims that the StormScreen will function at design flow when up to 85 percent occluded, and will
remove all particles greater than 2.4 mm in diameter. The StormScreen performance for pollutant removal
is dependent on site conditions, sediment loading, particle size distribution, and environmental variables.
VERIFICATION TESTING DESCRIPTION
Methods and Procedures
The test methods and procedures used during the study are described in the Test Plan for The Stormwater
Management StormScreen, TEA-21 Project Area, Griffin, Georgia (NSF International and PCG, June
2003) (test plan). The City of Griffin requires that all storm drain systems be sized to pass peak flows
from a 25-yr storm without causing surface flooding. For a 25-yr storm, a 5.42-min time of concentration
was determined for the drainage basin, generating a peak runoff of 46.80 cfs. The rational method was
used to calculate the peak flows for the system.
Verification testing consisted of collecting data during a minimum of fifteen qualified events that met the
following criteria:
• The total rainfall depth for the event, measured at the site, was 0.2 in. (5 mm) or greater;
• Flow through the treatment device was successfully measured and recorded over the duration of
the runoff period;
• There was a minimum of six hours between qualified sampling events; and
• Visual observations were noted for the inlet bay, cartridge chamber, and effluent chamber.
05/20/WQPC-WWF The accompanying notice is an integral part of this verification statement. April 2005
VS-ii
-------
The ETV protocol for stormwater treatment technologies does not include any specific quantitative
measurements for technologies, such as the StormScreen, claiming trash and debris removal. The only
approach for verification of this type of technology is to use visual observations by the testing
organization, documented with photographs and field observations logs. This information along with
basic flow data is the basis for evaluating technologies claiming trash and debris removal.
Automated flow monitoring equipment was installed to measure the total flow entering the StormGate™,
and the treated flow exiting the StormScreen. In addition to the flow data, visual observations of the
inside of the unit and operation and maintenance (O&M) data were recorded.
VERIFICATION OF PERFORMANCE
Verification testing of the StormScreen lasted approximately nine months, and fifteen events were
evaluated.
Test Results
The fifteen events used for this verification test covered a wide range of storms with total rainfall amounts
varying from 0.22 in. to 3.06 in. The storms also varied in peak intensity from 0.12 in./hr to 21.6 in./hr.
Some storms were short and intense, while others were longer and less intense. The precipitation data for
the fifteen rain events are summarized in Table 1.
Table 1. Rainfall and StormScreen Performance Data Summary
Event Start
Number Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
05/21/03
06/03/03
07/03/03
08/12/03
09/04/03
09/22/03
10/07/03
10/26/03
1 1/05/03
11/19/03
1 1/27/03
12/10/03
12/14/03
01/05/04
01/17/04
Start
Time
16:35
05:50
17:10
17:10
13:50
14:45
23:30
10:10
15:45
01:25
15:55
02:20
00:20
13:10
20:35
Rainfall
Amount
(in.)
2.16
0.40
0.45
0.22
0.22
3.06
0.53
0.28
0.74
1.52
0.74
0.54
0.34
0.47
0.44
Rainfall
Duration
(hnmin)
12:25
03:40
00:15
00:10
01:30
06:15
06:10
09:30
01:55
03:20
06:30
04:05
02:20
05:35
04:45
Runoff
Volume
(ft3)1
29,000
3,610
4,210
2,020
2,170
30,800
4,660
2,750
6,350
15,600
9,520
6,200
4,230
4,970
4,290
Volume
Peak Flow Rate Bypassed
(gpm) (Percent of
Inlet Outlet Inlet Flow)
3,780
2,580
1,630
1,590
630
3,730
1,450
890
2,430
5,250
550
430
1,160
1,210
630
320
380
160
360
520
410
340
350
340
590
540
300
140
250
320
20
O2
62
15
O2
69
24
O2
69
74
O2
O2
63
69
0
1 Runoff volume was measured at the inlet monitoring point.
2 Some water may have bypassed. However, the elevation/level data at the inlet indicate bypass did not
occur since the water level did not exceed the weir elevation. Volume differences are most likely due
either to possible outlet meter negative bias or inlet meter positive bias during surcharge conditions.
05/20/WQPC-WWF
The accompanying notice is an integral part of this verification statement.
VS-iii
April 2005
-------
The flow data and observations indicated that the maximum flow through the StormScreen during the
verification testing was considerably lower than the design flow capacity. In at least nine events, some
bypass occurred at runoff flowrates less than the anticipated design capacity of the StormScreen unit. The
flow data from the StormScreen outlet shows that the unit was typically treating between 150 to 250 gpm
when the system was flowing at a steady rate. Each event had a peak discharge rate (typically 300 to 600
gpm) that was higher than the steady rate, but still significantly below the design flow capacity of
4,488 gpm (10 cfs). These peak rates were preceded or followed by periods of time (5 to 30 min) when
the unit was running at a fairly steady rate as it processed the water that had entered and accumulated in
the StormScreen and StormGate™. The StormScreen appeared to process more water when the levels in
the StormGate™ were higher, indicating more water was entering the StormScreen.
An accumulation of trash and debris was observed in the cartridge bay after every event. Furthermore,
sediment and a hydrocarbon sheen were observed in the fore bay and cartridge bay after most events. The
cartridge hoods were covered with sediment and debris, and the estimated sediment depth continued to
increase over the nine months that flow measurements and observations were collected. By the end of the
test, the screens were occluded by a significant quantity of organic detritus and fine clay.
After the verification testing was complete, SMI conducted a test on the StormScreen to try to determine
why the design flowrates were not achieved during the ETV study. The first was conducted at the time the
StormScreen was cleaned out, in the presence of the testing organization (TO) and NSF. It involved
thorough cleaning of cartridges for one of the four discharge flumes, and running potable water into the
cartridge bay. The maximum flowrate through the cleaned discharge flume was approximately 0.8 cfs
(360 gpm), or 3.2 cfs (1,440 gpm) for four discharge flumes. This peak flow rate is greater than any peak
rates measured during verification test, but is significantly lower than SMI's rated peak flow capacity of
10 cfs (4,488 gpm). However, the potable water supply was shut off at the request of the City of Griffin
before the water in the vault reached the maximum elevation where the flume would discharge at its
maximum flowrate.
An additional study was performed by SMI on a StormScreen installed at their Portland, Oregon, facility.
This study was conducted with no oversight by the TO or NSF; therefore, the findings do not represent
ETV-verified data. The study first established a relationship between the discharge rate and the water
elevation in the cartridge bay. Then, clean water was pumped into the StormScreen cartridge bay at the
design flow rate. A detailed description of the testing procedures and results is included in the vendor
comments section of the verification report.
Based on the findings of the ETV test and the vendor's subsequent studies, the occlusion of the cartridge
screens by organic detritus and fine clay apparently resulted in the decrease in the StormScreen's flow
capacity at this installation. SMI concluded that a more frequent maintenance schedule, including
cleaning the cartridge screens, would have been required to achieve a higher flow capacity for this
application.
System Operation
The StormScreen was installed on May 9, 2002, prior to the planned start of ETV verification testing, and
operated for one year prior to the start of verification testing. The StormScreen was cleaned in February
2003 after nine months of operation and prior to the start of the verification test in May 2003. There were
no apparent mechanical problems with the unit.
On May 13, 2004, SMI, under the supervision of PCG, conducted a thorough cleanout of the
StormScreen, including an assessment of all the retained solids. The assessment revealed that 4,020 Ib
(wet weight) were retained. The retained material had a mean moisture content of 71% by weight,
resulting in a calculated dry weight total of 1,160 Ib of retained solids.
05/20/WQPC-WWF The accompanying notice is an integral part of this verification statement. April 2005
VS-iv
-------
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 100% 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 Original signed by
Sally Gutierrez September 2, 2005 Thomas Stevens September 7, 2005
Sally Gutierrez Date Thomas G. Stevens, P.E. Date
Director Program Manager
National Risk Management Laboratory ETV Water Quality Protection Center
Office of Research and Development NSF International
United States Environmental Protection Agency
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
05/20/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.
05/20/WQPC-WWF The accompanying notice is an integral part of this verification statement. April 2005
VS-v
-------
Notice
The U.S. Environmental Protection Agency (EPA) through its Office of Research and
Development has financially supported and collaborated with NSF International (NSF) under a
Cooperative Agreement. The Water Quality Protection Center (WQPC), operating under the
Environmental Technology Verification (ETV) Program, supported this verification effort. This
document has been peer reviewed, 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.
-------
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 Stormwater Management, Inc. StormScreen® Treatment
System was conducted at a testing site in Griffin, Georgia, maintained by the City of Griffin
Public Works and Stormwater Department.
The 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 groundwater; prevention and control
of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public and
private sector partners to foster technologies that reduce the cost of compliance and to anticipate
emerging problems. NRMRL's research provides solutions to environmental problems by:
developing and promoting technologies that protect and improve the environment; advancing
scientific and engineering information to support regulatory and policy decisions; and providing
the technical support and information transfer to ensure implementation of environmental
regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan.
It is published and made available by EPA's Office of Research and Development to assist the
user community and to link researchers with their clients.
11
-------
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 City of Griffin—Verification Testing Site 5
Chapter 2 Technology Description 6
2.1 Treatment System Description 6
2.1.1 StormGate 7
2.2 Screening Process 8
2.3 Product Specifications 9
2.4 Operation and Maintenance 10
2.5 Technology Application and Limitations 10
2.6 Performance Claim 10
Chapters Test Site Description 11
3.1 Location and Land Use 11
3.2 Stormwater Conveyance System and Receiving Water 14
3.3 Rainfall and Peak Flow Calculations 14
3.4 StormGate and StormScreen Installation 15
Chapter 4 Sampling Procedures and Analytical Methods 16
4.1 Introduction 16
4.2 Sampling Events and Qualification Criteria 17
4.3 Constituent Selection 17
4.4 Visual Observations 17
4.5 Flow Measurement 17
4.6 Precipitation Measurement 18
4.6.1 Methods 18
4.6.2 Field Procedures 18
4.7 Operation and Maintenance Parameters 18
Chapter 5 Monitoring Results and Discussion 20
5.1 Monitoring Results—Flow and Rainfall Data 20
5.1.1 Flow Verification 27
5.2 Observations of StormScreen Performance—Trash and Debris Removal 28
5.3 Operation and Maintenance 37
5.4 Trash, Debris, and Solids Removal 38
in
-------
5.4.1 Weight of Solids Removed 38
5.4.2 TCLP Results 40
Chapter 6 QA/QC Results and Summary 42
6.1 Laboratory Data QA/QC 42
6.1.1 Precision 42
6.1.2 Accuracy 43
6.2 Field Flow Measurements 44
6.3 Quality Assurance Reports 44
Chapter 7 Vendor-Supplied Information 45
7.1 Testing Equipment 45
7.2 Stage/Discharge Relationship Test without Float Valves 47
7.2.1 Procedure 47
7.2.2 Results 48
7.3 Stage/Discharge Relationship Test with Float Valves 49
7.3.1 Procedure 49
7.3.2 Results 49
7.4 Conclusion 50
Chapter 8 References 51
Glossary 52
Appendices 54
A SMI Design and O&M Guidelines 54
B Verification Test Plan 54
C Standard Operating Procedure for Solids Cleanout 54
D Event Hydrographs and Rain Distribution 54
E Observation Forms and Photographs 54
F Analytical Data Reports with QC 54
Figures
Figure 2-1. Schematic of a StormScreen Treatment System 6
Figure 2-2. Schematic of the StormGate 8
Figure 2-3. StormScreen cartridge 9
Figure 3-1. Drainage basin map with contours for StormScreen 12
Figure 3-2. As-built drawing of StormScreen and storm drain system 13
Figure 5-1. Inlet and StormScreen outlet hydrographs, May 21-22, 2003 23
Figure 5-2. Inlet and StormScreen outlet hydrographs, September 4, 2003 24
Figure 5-3. Inlet and StormScreen outlet hydrographs, December 10, 2003 25
Figure 5-4. Photographs from flow test 28
Figure 5-5. Example StormScreen field observation form 31
Figure 5-6. StormScreen photographs, May through August 2003 32
Figure 5-7. StormScreen photographs, August through September 2003 33
Figure 5-8. StormScreen photographs, September through October 2003 34
Figure 5-9. StormScreen photographs, November 2003 35
Figure 5-10. StormScreen photographs, January 2004 36
Figure 7-1. StormScreen testing and demonstration system 46
IV
-------
Figure 7-2. Electrically actuated control valve and in-line flowmeter 46
Figure 7-3. Effluent bay of StormScreen testing vault, showing rectangular discharge flume and
8-in return pipe to reservoir 47
Figure 7-4. StormScreen stage versus flow relationship without float valves 48
Figure 7-5. StormScreen stage versus flow relationship with float valves 50
Tables
Table 3-1. Rainfall Amount (in.) 14
Table 3-2. Rainfall Intensities (in/hr) 14
Table 3-3. Calculated Peak Flowrates (cfs) 15
Table 3-4. Calculated Peak Flowrates (cfs) Using Time of Concentration 15
Table 4-1. Testing Method, Detection Limit, and Holding Time for TCLP and Metals 19
Table 5-1. Rainfall Summary for Monitored Events 20
Table 5-2. Runoff and Treated Water Volume Summary 21
Table 5-3. Event Maximum Flowrate and Maximum Level 22
Table 5-4. Summary of Field Observations 30
Table 5-5. Percent Solids of Solids Removed from StormScreen 40
Table 5-6. TCLP Results for Cleanout Solids 41
Table 6-1. Analytical Precision Summary 43
Table 6-2. Summary of Replicate Percent Solids Results 43
Table 6-3. Laboratory Control Sample Results 44
-------
Abbreviations and Acronyms
AST
BMP
cfs
EPA
ETV
ft2
ft3
gal
gpm
hr
in.
kg
L
Ib
NRMRL
mg/L
mm
NSF
O&M
PCG
QA
QC
SMI
SOP
TCLP
TO
VO
WQPC
Analytical Services, Inc.
Best Management Practice
Cubic feet per second
U.S. Environmental Protection Agency
Environmental Technology Verification
Square feet
Cubic feet
Gallon
Gallon per minute
Hour
Inch
Kilogram
Liter
Pound
National Risk Management Research Laboratory
Milligram per liter
Millimeter
NSF International
Operations and maintenance
Paragon Consulting Group
Quality assurance
Quality control
Stormwater Management, Inc.
Standard Operating Procedure
Toxicity Characteristics Leaching Procedure
Testing Organization
Verification Organization (NSF)
Water Quality Protection Center
VI
-------
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 field or laboratory testing (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). The WQPC evaluated the performance of the Stormwater Management, Inc.
StormScreen® Treatment System (StormScreen), a Stormwater treatment system designed to
remove trash, debris, and large particulates 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 StormScreen was a cooperative effort among the following participants:
• U.S. Environmental Protection Agency
• NSF International
• Paragon Consulting Group, Inc. (PCG)
• Analytical Services, Inc. (ASI)
• Stormwater Management, Inc. (SMI)
• City of Griffin, Georgia
The following is a brief description of the ETV participants and their roles and responsibilities.
-------
7.2.7 U.S. Environmental Protection Agency
The EPA Office of Research and Development, through the Urban Watershed Branch, Water
Supply and Water Resources Division, National Risk Management Research Laboratory
(NRMRL), provides administrative, technical, and quality assurance guidance and oversight on
all ETV WQPC activities. In addition, EPA provides financial support for operation of the
Center and partial support for the cost of testing for this verification.
EPA was responsible for the following:
• Review and approval of the verification test plan;
• Review and approval of the verification report;
• Review and approval of the verification statement; and
• Post the verification report and statement on the EPA website.
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 the development of consensus standards for the protection of public
health and the environment. NSF also provides testing and certification services to ensure that
products bearing the NSF name, logo and/or Mark meet those standards.
NSF personnel provided technical oversight of the verification process. NSF provided review of
the test plan and was responsible for the preparation of the verification report. NSF contracted
with Scherger Associates to provide technical advice during the project and assist with
preparation of the verification report. NSF's responsibilities as the VO include:
• Review and comment on the test plan;
• Review quality systems of all parties involved with the TO, and qualify the TO;
• Oversee TO activities related to the technology evaluation and associated laboratory
testing;
• Conduct an onsite audit of test procedures;
-------
• Provide quality assurance/quality control (QA/QC) review and support for the TO;
• Oversee the development of the verification report and verification statement; and
• Coordinate with EPA to approve the verification report and verification statement.
Key contacts at NSF are:
Mr. Thomas Stevens, Program Manager Mr. Patrick Davison, Project Coordinator
(734) 769-5347 (734)913-5719
email: stevenst@nsf.org email: davison@nsf.org
NSF International
789 North Dixboro Road
Ann Arbor, Michigan 48105
(734) 769-8010
Mr. Dale A. Scherger, P.E., Technical Consultant
(734)213-8150
email: daleres@aol.com
Scherger Associates
3017 Rumsey Drive
Ann Arbor, Michigan 48105
1.2.3 Testing Organization
The TO for the verification testing was Paragon Consulting Group, Inc. (PCG) of Griffin,
Georgia. The TO was responsible for ensuring that the testing location and conditions allowed
for the verification testing to meet its stated objectives. The TO prepared the test plan; oversaw
the testing; and managed and reported on the data generated by the testing. TO employees set
test conditions, and measured and recorded data during the testing. The TO's Project Manager
provided project oversight and reviewed the draft verification report.
PCG had primary responsibility for all verification testing, including:
• Coordinate all testing and observations of the StormScreen in accordance with the test
plan;
• Contract with the analytical laboratory and any other subcontractors necessary for
implementation of the test plan;
• Provide needed logistical support to the subcontractors, as well as establish a
communication network, and schedule and coordinate the activities for the verification
testing;
• Manage, evaluate, interpret, and report on data generated during the verification testing;
and
• Review the draft verification report.
-------
The key personnel and contacts for the TO are:
Ms. Courtney Nolan, Project Manager
(770)412-7700
email: cnol an@pcgeng. com
Mr. Brian DeLony, Project Engineer
(770)412-7700
email: bdelony@pcgeng.com
Paragon Consulting Group
118 North Expressway
Griffin, Georgia 30223
1.2.4 Analytical Laboratories
Analytical Services, Inc. (AST), located in Norcross, Georgia, analyzed the sediment samples
collected during the system cleanout at the end of the verification test.
The key analytical laboratory contact is:
Ms. Christin Ford
(770) 734-4200
email: cford@ASI.com
Analytical Services, Inc.
110 Technology Parkway
Norcross, Georgia 30092
7.2.5 Vendor
Storm water Management, Inc. (SMI) of Portland, Oregon, is the vendor of the Storm Screen, and
was responsible for supplying a field-ready system. Vendor responsibilities include:
• Provide the technology and ancillary equipment required for the verification testing;
• Provide technical support during the installation and operation of the technology,
including the designation of a representative to conduct onsite inspections during
monitoring to ensure the technology is functioning as intended;
• Provide descriptive details about the capabilities and intended function of the technology;
• Review and approve the test plan; and
• Review and comment on the draft verification report and draft verification statement.
-------
The key contact for SMI is:
Mr. James Lenhart
(800)561-1271
email: jiml@stormwaterinc.com
Storm water Management, Inc.
12021-B NE Airport Way
Portland, Oregon 97220
1.2.6 City of Griffin—Verification Testing Site
Verification of the StormScreen was completed in conjunction with a Georgia Department of
Transportation TEA-21 project. Installation of the system and flow meters used in the
verification was provided by the TEA-21 project. The StormScreen was located within the right-
of-way on the west side of Fifth Street in Griffin, Georgia. A private contractor, Site
Engineering, Inc, installed the system.
The key contact for City of Griffin Public Works and Stormwater Department is:
Mr. Brant Keller, Director
(770) 229-6424
email: bkeller@citvofgriffm.com
Public Works and Stormwater Department
City of Griffin
134 North Hill Street
Griffin, Georgia 30224
-------
Chapter 2
Technology Description
The following technology description was supplied by the vendor and does not represent verified
information.
2.1 Treatment System Description
The components installed at this testing site included a StormScreen and a StormGate™
Separator (StormGate). The StormGate was installed upstream of the StormScreen and included
a field-adjustable weir, which was set to divert flows up to 10 cubic feet per second (cfs) to the
StormScreen. Flows greater than 10 cfs would bypass the StormScreen and discharge to the
overflow pipe that reconnected with the storm sewer system downstream of the StormScreen.
The performance of the StormGate was not included as part of this verification. Additional
technical information on the StormGate is provided in Section 2.2.1.
The StormScreen is a structural system that removes trash, debris, and larger suspended
particulate at high flow rates by combining direct screening with many of the hydraulic aspects
of the patented siphonic, radial-flow cartridge system. This particular system configuration
consists of 20 cartridges, each designed to treat a peak flow of 0.5 cfs (225 gallons per minute),
providing a total system treatment capacity of 10 cfs. A schematic of a typical StormScreen is
shown in Figure 2-1. The StormScreen consisted of an inlet bay, cartridge bay, and outlet bay,
housed in a 16-foot by 8-foot precast concrete vault. The inlet bay serves as a grit chamber and
provides for flow transition into the cartridge bay, where the water is screened through the screen
cartridges and discharged through flumes to the outlet bay and the outlet pipe.
MANHOLE COVER
ACCESS LADDER
STEPS CAST
INTO WAI I
INLET PIPE
DEWATERING PIPE
DEBRIS SUMP
CARTRIDGE PORTS
OUTLET BAY
STORMSCRFFN
CARTRIDGES
PRECAST WALL WITH
BEAM PASS THROUGH HOLES
PRECAST WALL
WITH BEAM POCKET:
ELEVATED DISCHARGE FLUME
Figure 2-1. Schematic of a StormScreen Treatment System.
-------
A primary feature of the StormScreen is that the use of a screen allows for a much higher
treatment rate per cartridge. The StormScreen provides treatment by direct screening through the
StormScreen cartridges and by settling within the concrete vault. The standard cartridge screen
has a pore opening of 2.4 mm (2,400 microns), which ensures the capture of all solids of greater
size. Settling provides some removal of particles smaller than 2.4 mm.
All captured solids are collected in a large sump area on the floor of the vault, located below an
elevated discharge flume that supports the cartridges. This sump may be equipped with a
dewatering mechanism to provide for ease of maintenance.
The modular design of the StormScreen allows for a variety of system configurations. The
system may be designed with a high-flow diversion system (such as the StormGate described
above) or, in some special cases, the system may be placed directly on the stormwater
conveyance line.
It is also possible to combine the StormScreen with the Stormwater Management StormFilter®
for a two-stage treatment system, offering higher end treatment of suspended sediments and
dissolved pollutants at lower flows, and trash and debris removal at higher flows.
2.1.1 StormGate
The StormGate is a system installed upstream of the StormScreen. It is designed to bypass high-
energy flows that exceed the StormScreen, or a similar treatment system's, design capacity. A
schematic of a typical StormGate is shown in Figure 2-2.
High flows can reduce the effectiveness of water quality facilities by resuspending sediments and
flushing captured floatables, which causes a concentrated pulse of pollutants to be sent to
downstream waterways. To minimize the occurrence of pulsing, a high-flow bypass can be
installed upstream of water quality or pretreatment facilities to direct the high flow away from
the treatment system. The StormGate uses a field-adjustable weir to direct polluted low flows to
stormwater treatment systems, while allowing extreme flows to bypass the systems. The
StormGate provides tighter control over system hydraulics than other high-flow bypass methods,
as changes can be made to the weir elevation once actual field elevations are established or if
future design flows change.
The StormGate is provided as a complete manhole or vault unit that installs directly into an
existing sewer system. The StormGate installed at the test site on the west side of Fifth Street in
Griffin, Georgia, is a standard 48-inch diameter manhole unit connected to the existing 36-inch
diameter pipe. SMI provides information on the sizing, construction, and operation of the
StormGate in a technical bulletin. This information is presented in Appendix A.
-------
STEPS
HIGH FLOW OUTLET PIPE
FIELD-ADJUSTABLE WEIR
LOW FLOW OUTLET PIPE
STORMGATE HIGH FLOW BYPASS
Figure 2-2. Schematic of the StormGate.
2.2 Screening Process
The StormScreen's screening process works by passing stormwater through 22 gage stainless
steel screens having 2.4 mm pore openings and 42 pores per square inch. Each cartridge has a
surface area of 7.5 square feet. A diagram identifying the cartridge screen components is shown
in Figure 2-3.
Stormwater enters the cartridge bay through the flow spreader, where it ponds. Air in the
cartridge is displaced by the water and purged from within the cartridge hood through the one-
way check valve located on top of the cap. The water infiltrates through the screen assembly and
into the center tube. Once the center tube fills with water, a float valve opens and the water in the
center tube flows into the under-drain manifold, located beneath the cartridge. This causes the
check valve to close, initiating a siphon that draws stormwater through the cartridge and screen.
The siphon continues until the water surface elevation drops to the elevation of the hood's
scrubbing regulators. When the water drains, the float valve closes and the system resets.
-------
CHECK VALVE
CAP
CENTER TUBE
SCRUBBING RECiUlATORS
STAINLESS STEEL
M:HI IN ASSEMBLY
LOW FLOW
OUTLET
ELEVATED DISCHARGE FLUME
Figure 2-3. StormScreen cartridge.
2.3 Product Specifications
StormScreen:
• Housing - Precast concrete vault
• Dimensions - 16 feet long x 8 feet wide
• Number of Screen Cartridges - 20
• Peak Hydraulic Treatment Capacity - 10 cfs
• Sediment Storage - 5.6 cubic yards
• Sediment Chamber Size - 16 feet by 8 feet
Warranty-All merchandise is warranted against any defect in materials or workmanship
provided by SMI, providing a claim is made in writing within one year from the date of delivery
of merchandise to the purchaser. SMFs obligation on any claim is limited to replacement or
repair of the defective materials at SMFs premises. Except as noted above, SMI is not liable for
any loss, injury, or damages to persons or property resulting from failure or defective operation
of any merchandise furnished.
-------
2.4 Operation and Maintenance
According to SMI, the StormScreen should be cleaned if approximately one foot of trash and
debris or sediment is observed in the debris sump. The large, loose debris and trash can be
removed using a pole with a grapple or net on the end. Water and accumulated sediment can be
removed with mobile vactor (vacuum) equipment. The cartridges should be checked for
abnormalities on the cartridge screen at this time. SMI recommends regular inspections of the
system to ensure that the system is operating properly.
The drainage structures and systems upstream of the treatment system should also be maintained
to ensure they are functioning properly. An Operation and Maintenance (O&M) Guideline is
available from SMI and is presented in Appendix A. The O&M Guideline also provides a written
procedure for cleaning the system on an annual basis, however, the vendor has recently changed
this recommendation to cleaning on a quarterly basis.
2.5 Technology Application and Limitations
The StormScreen is flexible in terms of the flow it can treat. By varying the holding tank size
and number of cartridges, the treatment capacity can be modified to accommodate runoff from
various size watersheds. The StormScreen can be used to treat stormwater runoff in a wide
variety of sites throughout the United States. For jurisdictional authorities, the system offers high
levels of solids and debris removal and improved water quality. The StormScreen may be used
for development, roadways, and specialized applications. Typical development applications
include parking lots, commercial and industrial sites, and high-density and single-family
housing. Typical development applications also include maintenance, transportation, and port
facilities.
All screening systems are effective as a gross pollutant trap. Gross pollutant traps are utilized to
capture litter, trash, debris, coarse sediments, and some oils. These gross pollutants, typically
removed by physical separation, are transported by conveyance systems as bed load, suspended
load, or floatables. Screening systems are not recommended for the removal of fine sediments,
although finer particles attached to larger particles will be found and thus removed. Screening
systems do not contain a soluble pollutant removal mechanism (such as cation exchange), and
thus are not recommended for the removal of soluble metals. Additionally, absorbent inserts
should be considered for the capture of petroleum hydrocarbons that are entrained.
2.6 Performance Claim
SMI claims that the StormScreen will function at design flow when up to 85 percent occluded,
and will remove all particles greater than 2.4 mm in diameter. The StormScreen performance for
pollutant removal is dependent on site conditions, sediment loading, particle size distribution,
and environmental variables.
10
-------
Chapter 3
Test Site Description
3.1 Location and Land Use
The StormScreen was located on the western side of Fifth Street at 33° 14' 51.5400" latitude/
84° 15' 38.2680" longitude. The system was installed on property located within the public
right-of-way.
Figure 3-1 identifies the drainage basin area, the location of the system, and the contours of the
area. The drainage area for the StormScreen consists of approximately 7.3 acres, approximately
330 feet of storm drain lines, and five storm inlets. No detention areas are located within the
drainage basin, and there are no open ditches upstream of the installation location. The majority
of the drainage basin area consists of paved roadways, parking areas, and buildings. Retail
businesses, school facilities, a bank, and an automotive service station are located in the drainage
area. Small portions of the drainage area are landscaped or lawn. Taylor Street has moderate to
heavy traffic volume and Fifth Street has moderate traffic volume. Aside from service station
material, no major storage or use of hazardous materials or chemicals exist in the area. Figure
3-2 is an as-built drawing of the StormScreen and ancillary equipment.
The main contaminant sources within the drainage area are created by vehicular traffic, typical
urban commercial land use, and atmospheric deposition. Trash and debris accumulate on the
surface and enter the stormwater conveyance system through large openings in the street inlets,
sized to accommodate the large storm flows that can occur in this part of Georgia.
No planned or ongoing maintenance activities (street sweeping or catch basin cleaning) are
routinely completed for the installation location. City personnel stated that maintenance activities
are typically performed only in emergencies. No street cleaning or other conveyance system
maintenance was performed during the verification test period. There are no other stormwater
best management practices (BMPs) within the drainage area.
11
-------
150
Figure 3-1. Drainage basin map with contours for StormScreen.
12
-------
DWCB F-1
TOP MH 941,48
INV OUT 936,38
JB D-1
TOP 943.55
INV 937/17
R0X1 MATE LOCATION
PLOW PROBE
2
42.92
JT 934.12
9-34.54 LINE D
934.1 B LINE A
3
45,18
LIT 936,06
UT 939,BE
45.14
939.S4
CONCRETE
PAD
STORM SCREEN
TOP 945,91
INV OUT 937.11
STORM SCREEN
TOP 945.91
INV IN 939.66
INV BTM BOX 937
STORM SCEEN
STORM GATE ELEV. 942,68
JB A-5
TOP 948.60
INV IN 945.20
INV OUT 941.07
A-4
H 948,31
941,09
DO
Figure 3-2. As-built drawing of StormScreen and storm drain system.
13
-------
3.2 Stormwater Conveyance System and Receiving Water
The entire drainage area is served by an underground storm sewer collection system. The water
is collected from the surface through standard inlet structures and is conveyed via 36- and 48-
inch pipes in an easterly direction. The 36-inch pipe is connected to the StormGate. None of the
Stormwater runoff from the drainage basin area is treated prior to the StormScreen. Downstream
from the StormScreen outlet and the bypass from the StormGate the pipe size increases to 48
inches. The combined flow, plus new incoming Stormwater, then flows approximately 800 feet
and enters a detention pond. The water then exits the pond to a storm pipe, where it ultimately
flows into Grape Creek, approximately two-thirds of a mile from the StormScreen site.
3.3 Rainfall and Peak Flow Calculations
The rainfall amounts for the one-, two-, ten-, and twenty-five-year storms for the drainage area
are presented in Table 3-1. Table 3-2 presents the intensities, in inches per hour, calculated for
the given rainfall amounts. These data were utilized to generate the peak flowrates shown in
Table 3-3. Table 3-4 presents the peak flow calculated using the time of concentration for the
drainage basin. The City of Griffin requires that all storm drain systems be designed to
accommodate the 25-year storm. A 5.42-minute time of concentration was determined for the
basin, generating a peak runoff of 46.80 cfs for the 25-year storm event. The rational method was
used to calculate the peak flows for the system.
Table 3-1. Rainfall Amount (in.)
Duration
30 minutes
1 hour
2 hours
12 hours
24 hours
1-year
0.99
1.36
1.68
2.67
2.87
2-year
1.19
1.61
2.00
3.12
3.36
10-year
1.58
2.10
2.62
3.96
4.32
25-year
1.81
2.40
2.98
4.44
4.80
Source: National Oceanographic and Atmospheric Administration, 2000
Table 3-2. Rainfall Intensities (in/hr)
Duration
30 minutes
1 hour
2 hours
12 hours
24 hours
1-year
1.98
1.36
0.84
0.22
0.12
2-year
2.38
1.61
1.00
0.26
0.14
10-year
3.16
2.10
1.31
0.33
0.18
25-year
3.61
2.40
1.49
0.37
0.20
14
-------
Table 3-3. Calculated Peak Flowrates (cfs)
Duration 1-year 2-year 10-year 25-year
30 minutes
1 hour
2 hours
12 hours
24 hours
12.19
8.33
5.16
1.36
0.73
14.59
9.87
6.13
1.59
0.86
19.37
12.87
8.03
2.02
1.10
22.12
14.71
9.13
2.27
1.23
Table 3-4. Calculated Peak Flowrates (cfs) Using Time of Concentration
Duration 1-year 2-year 10-year 25-year
5.42 minutes 25.56 30.26 40.47 46.80
3.4 StormGate and StormScreen Installation
The StormGate and StormScreen were installed in May 2002. The StormGate was connected
directly to the existing 36-inch storm sewer pipe under the roadway. The StormScreen was
installed next to the roadway in the right-of-way. An 18-inch pipe was used to connect the two
systems. The StormGate low-flow outlet pipe was placed at a slope of 0.07 ft/ft, and sized to
more than handle the 10-cfs maximum design flow of the StormScreen. The overflow (bypass)
from the StormGate was a 54-inch pipe that connected to a downstream manhole where treated
water from the StormScreen was combined with any bypass water. The flow-control weir height
was set by SMI after installation was complete. The discharge from the StormScreen (treated
water) entered an 18-inch pipe that reconnected with the existing stormwater sewer system at a
newly installed manhole. An as-built drawing showing all inlet and outlet elevations is presented
in Appendix A. Based on the system elevations and the weir elevation, bypass would occur when
water level reached approximately 32 inches of depth at the exit point of the 36-inch inlet pipe to
the StormGate. Based on the diameter and slope of the two StormGate outlet pipes (low flow to
treatment [18-inch], high flow to bypass [54-inch]) and the StormScreen outlet pipe (18-inch), all
installed pipes were oversized compared to the anticipated design treatment capacity (10 cfs) of
the 20-cartridge StormScreen.
15
-------
Chapter 4
Sampling Procedures and Analytical Methods
4.1 Introduction
Performance of a stormwater treatment technology is characterized by how effective it is in
removing targeted stormwater runoff constituents, pollutants, and contaminants. Most of the
ETV testing programs under the WQPC include the collection of water samples from the inlet
and outlet of treatment technologies and the analysis for chemical constituents. These data are
then used to evaluate the performance of the technology by comparing the concentrations of
various constituents before and after treatment. Further, the wet-weather protocols usually
include summing the loads over fifteen or more events and evaluating the overall reduction in
pollutant loads for all sampling events. The selection of constituents, such as suspended solids,
metals, nutrients, and petroleum hydrocarbons, is based on the specific performance claims made
by the vendor.
In the case of the StormScreen, the primary claim is the removal of trash, debris, and particles
greater than 2.4 mm in diameter. The ETV Technology Panel discussed various methods to
quantify trash and debris removal, but after many hours of discussion concluded that there are
currently no acceptable standard methods for quantitatively measuring trash, debris, and very
large particle removal performance. Therefore, the ETV protocol for stormwater treatment
technologies does not include any specific quantitative measurements for technologies claiming
trash and debris removal. The only approach for verification of this type of technology is to use
visual observations by the testing organization, documented with photographs and field
observations logs. This information along with basic flow data is the basis for evaluating
technologies claiming trash and debris removal.
Given the history of the protocol development and input from the ETV Technology Panel, the
verification test for the StormScreen consisted of observing and documenting that trash and
debris are removed from the influent to the StormScreen. The observations were designed to
determine if trash, debris, and large particles are captured in the system, and to verify that the
system continues to operate properly after several storms have occurred, and trash, debris, and
large solids have accumulated within the vault. At the end of the verification test, as described
herein, the StormScreen was cleaned and the weight of the accumulated residuals was measured.
This quantitative data was collected to provide an estimate of the amounts of materials that were
collected using this type of system in this application.
The verification test plan presents the details on the approach used to verify the StormScreen.
This plan, Environmental Technology Verification Test Plan For Stormwater Management, Inc.,
StormScreen, TEA-21 Project Area, City of Griffin, Spalding County, Georgia, NSF, June 2003,
is presented in Appendix B along with all attachments. An overview of the key procedures used
for this verification is presented below.
16
-------
4.2 Sampling Events and Qualification Criteria
Fifteen qualified sampling events were observed and documented for this verification test. An
event is deemed qualified when it meets the following criteria:
• The total rainfall depth for the event, measured at the site, is 0.2 inches (5 mm) or greater;
• Flow is successfully measured and recorded over the duration of the runoff period;
• Visual observations are noted in the fore bay, cartridge chamber, and effluent chamber; and
• There must be a minimum of six hours between qualified sampling events; that is, there will
be a minimum of six hours between the termination of measured effluent flow during one
event and the start of measured influent to the stormwater technology during the subsequent
rainfall event.
4.3 Constituent Selection
SMI requested that the system be evaluated based on the removal of trash, debris, and large
particles greater than 2.4 mm in diameter. Therefore, as discussed in Section 4.1, no influent and
effluent stormwater samples were collected or analyzed. All results were based on visual
observation of the system. At the end of the verification test, the residuals that accumulated in
the system were collected and tested for percent moisture and teachable heavy metals.
4.4 Visual Observations
Visual observations were conducted at the fore bay, cartridge bay, and effluent bay of the
StormScreen. Photographs were taken of the fore bay area and cartridge chamber and of the
effluent chamber to evaluate the removal capabilities of the system. A StormScreen observation
form was completed for each qualified rain event. The TO field personnel did not physically
enter the vault after rain events, so all measurements shown on the observation form are
estimated measurements made from the surface.
4.5 Flow Measurement
Total flow measurements were taken in the main 36-inch storm sewer upstream of the Storm Gate
using an American Sigma 950 flowmeter. Flow measurements were also taken downstream of
the StormScreen utilizing another American Sigma 950 flowmeter. This effluent flow monitoring
location was prior to the manhole where the bypass flow and treated effluent water combine.
Both flowmeters were equipped with an American Sigma Submerged Level/Velocity Sensor.
Flows were measured at five-minute intervals over the duration of an event. The flow monitoring
equipment was installed, maintained, and calibrated according to the manufacturer's
specifications. Attachment F of the test plan includes this information. PCG personnel were
responsible for inspection and maintenance of the flowmeter equipment.
17
-------
4.6 Precipitation Measurement
4.6.1 Methods
An automatic, electronic recording rain gauge was used to record rainfall depths at intervals of
five minutes. The gauge, which utilized a tipping bucket for rainfall measurement, was
connected to the automated sampler, which recorded rainfall depths in increments of 0.01 inch.
This data was recorded in real time.
4.6.2 Field Procedures
The rain gauge was located within ten feet of the StormScreen. The gauge was calibrated in
accordance with the manufacturer's instructions, and was inspected and cleared of any debris
between events. The rainfall data was downloaded with a data transfer unit (DTU II) and
transferred to a digital file for project use.
4.7 Operation and Maintenance Parameters
PCG maintained a record of activities associated with operating and maintaining the
StormScreen during the testing period. A visual inspection of the system was made following
each storm event. PCG technicians completed an inspection log, and noted any changes that
appeared to occur in the operation of the system. In accordance with the recommended
inspection schedule in the StormScreen O&M Guidelines (Appendix A), PCG inspected the
StormScreen at least once every two to three months. No maintenance of the system was
performed during the verification test. Sediment and trash did accumulate in the system, but did
not exceed the one-foot depth that would trigger a cleanout, as specified in the O&M Guidelines.
At the end of the verification test, the trash, debris, and sediment were removed using shovels
and buckets. This material was allowed to drain of freestanding water, and then an estimate of
the volume of recovered material was made. The material was weighed to provide an estimate of
the total weight of accumulated trash, debris, and sediment. A detailed Standard Operating
Procedure (SOP), included in Appendix C, was prepared for this task.
A sample of the sediment collected from the bottom of the vault was obtained and sent to the
laboratory for analysis. The analyses included percent solids and Toxicity Characteristic
Leachate Procedure (TCLP) metals. Table 4-1 shows the parameter list and the QA/QC
objectives.
18
-------
Table 4-1. Testing Method, Detection Limit, and Holding Time for TCLP and Metals
Parameter
Method
Laboratory
Reporting Limit
(mg/L)
Bottle Type
Maximum
Holding Time
TCLP 1311
Metals on Leachate from TCLP:
NA
Glass/polyethylene 6 months
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
6010 B
6010 B
6010 B
6010 B
6010 B
7470 A
6010 B
601 OB
0.2
0.5
0.01
0.1
0.1
0.002
0.2
0.1
Polyethylene
Polyethylene
Polyethylene
Polyethylene
Polyethylene
Polyethylene
Polyethylene
Polyethylene
6 months
6 months
6 months
6 months
6 months
6 months
6 months
6 months
Note: Sediment/solids are leached in the TCLP test. Metals are run on the leachate generated from the TCLP.
All methods referenced are EPA methods from SW-846, third revision. Laboratory accuracy target for all
metals is 75-125 percent. Laboratory precision target for all metals is 25 percent.
19
-------
Chapter 5
Monitoring Results and Discussion
The StormScreen is designed to remove trash, debris, and some large particulates from wet-
weather flows. The test plan requires that photographs and visual observations be collected,
rainfall amounts and flowrates monitored, and solids accumulation at the end of the verification
test evaluated as part of the verification test. The results from these observations and
measurements are presented in this section.
5.1 Monitoring Results—Flow and Rainfall Data
A recording rain gauge was located at the upstream monitoring location to record rainfall over
the duration of storm events in five-minute increments. The fifteen events used for this
verification test covered a wide range of storms, with total rainfall amounts varying from 0.22
inches to 3.06 inches. The storms also varied in intensity from 0.12 inches per hour (0.01 inches
per five minutes) to 21.6 inches per hour (0.36 inches in five minutes). Some storms were short
and intense, while others were of longer duration and lower intensity. Table 5-1 shows the
rainfall amounts, duration, and volume of runoff measured for each of the fifteen events.
Table 5-1. Rainfall Summary for Monitored Events
Event
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Start Date
05/21/03
06/03/03
07/03/03
08/12/03
09/04/03
09/22/03
10/07/03
10/26/03
1 1/05/03
11/19/03
1 1/27/03
12/10/03
12/14/03
01/05/04
01/17/04
Start Time End Date End Time
16:35
05:50
17:10
17:10
13:50
14:45
23:30
10:10
15:45
01:25
15:55
02:20
00:20
13:10
20:35
05/22/03
06/03/03
07/03/03
08/12/03
09/04/03
09/22/03
10/08/03
10/26/03
1 1/05/03
11/19/03
1 1/27/03
12/10/03
12/14/03
01/05/04
01/18/04
05:00
09:30
17:25
17:20
15:20
21:00
05:40
19:40
17:40
04:45
22:25
06:25
02:40
18:45
01:20
Rainfall
Amount
(in.)
2.16
0.40
0.45
0.22
0.22
3.06
0.53
0.28
0.74
1.52
0.74
0.54
0.34
0.47
0.44
Rainfall
Duration
(hr:min)
12:25
03:40
00:15
00:10
01:30
06:15
06:10
09:30
01:55
03:20
06:30
04:05
02:20
05:35
04:45
Runoff
Volume
(ft3)1
29,000
3,610
4,210
2,020
2,170
30,800
4,660
2,750
6,350
15,600
9,520
6,200
4,230
4,970
4,290
Runoff volume measured at the inlet monitoring point.
Flowrates were recorded in five-minute increments at the upstream station, the inlet to the
StormGate, to monitor the flowrate and total runoff volume entering the storm sewer conveyance
20
-------
system. A second monitoring station was located in the outlet line from the StormScreen to
measure the flowrates and total volume of water treated. Table 5-2 shows the results of the flow
monitoring for each event. Event hydrographs have been prepared for each event and are
presented in Appendix D. Representative hydrographs from several selected events are shown in
Figures 5-1, 5-2, and 5-3.
Table 5-2. Runoff and Treated Water Volume Summary
Peak Flow Calculated
Rainfall Rate (gpm) Bypass
Date (in.) Inlet Outlet (gal)
05/21/03
06/03/03
07/03/03
08/12/03
09/04/03
09/22/03
10/07/03
10/26/03
11/05/03
11/19/03
11/27/03
12/10/03
12/14/03
01/05/04
01/17/04
2.16
0.40
0.45
0.22
0.22
3.06
0.53
0.28
0.74
1.52
0.74
0.54
0.34
0.47
0.44
3,780
2,580
1,630
1,590
630
3,730
1,450
890
2,430
5,250
550
430
1,160
1,210
630
320
380
160
360
520
410
340
350
340
590
540
300
140
250
320
45,000
0
19,700
2,300
O2
161,000
8,500
O2
32,800
87,100
O2
O2
20,200
25,600
O2
Percent
Bypassed
20
0
62
15
O2
69
24
O2
69
74
O2
O2
63
69
O2
Runoff
Coefficient
at Inlet1
0.37
0.25
0.26
0.25
0.27
0.28
0.24
0.27
0.24
0.28
0.35
0.32
0.34
0.29
0.27
1 Total volume of runoff at the inlet divided by the total volume of water on the falling the drainage area.
2 Some water may have bypassed. However, the elevation/level data at the inlet indicate bypass did not occur,
as level did not exceed the weir height. The volume difference is most likely due either to possible outlet
meter negative bias or inlet meter positive bias during surcharge conditions.
Monitoring the flowrates and volumes at the inlet to the StormGate and the outlet of the
StormScreen provides information to estimate the amount of water that bypassed the treatment
system. Table 5-2 shows the estimated bypass flow for each event, based on the volumes
recorded at the inlet and outlet flowmeters. The outlet volumes have been corrected to account
for the initial filling of the vault. This is necessary since after a storm event ends the vault slowly
releases water until all has been drained from the system. This volume of water is discharged at a
slow flowrate that is not accounted for by the downstream flowmeter.
The data shows that for at least nine of the monitored events, bypass occurred at runoff flowrates
less than the anticipated design capacity of the StormScreen. These results indicate that the
treatment system, as configured, was not routinely capable of handling the design peak flowrates
of 10 cfs (4,488 gpm). The typical peak flowrates measured at the outlet of the StormScreen
range from 350 to 600 gpm, as shown in Table 5-3.
21
-------
Table 5-3. Event Maximum Flowrate and Maximum Level
Peak Flowrate (gpm)
Peak Level (in.)
Date
05/21/03
06/03/03
07/03/03
08/12/03
09/04/03
09/22/03
10/07/03
10/26/03
1 1/05/03
11/19/03
1 1/27/03
12/10/03
12/14/03
01/05/04
01/17/04
Rainfall
(in.)
2.16
0.40
0.45
0.22
0.22
3.06
0.53
0.28
0.74
1.52
0.74
0.54
0.34
0.47
0.44
Inlet
3,780
2,580
1,630
1,590
630
3,730
1,450
890
2,430
5,250
550
430
1,160
1,210
630
\»r /
Outlet
320
380
160
360
520
410
340
350
340
590
540
300
140
250
320
Inlet
36
32
35
33
9.6
37
34
13
34
38
13
24
31
33
24
— y ^
Outlet
2.2
2.5
1.4
2.4
3.0
2.6
2.3
2.4
2.3
3.2
2.9
2.0
1.2
1.8
2.1
22
-------
StormScreen Upstream 999 Event: 5/22/03
40
35 -
Velocity (fps)
'Level (in)
Rainfall (in x 100)
-Flow(gpm)
4000
3500
5/21/0316:25 5/21/0319:25 5/21/0322:25 5/22/031:25 5/22/034:25 5/22/037:25 5/22/0310:25 5/22/0313:25
Time
StormScreen Downstream May 22, 2003
5/21/0316:23
350
300
Velocity (fps)
Level (in)
Rainfall (in x 100)
Flow (gpm)
5/21/0321:11
5/22/031:59 5/22/036:47
Time
50
5/22/0311:35 5/22/0316:23
Figure 5-1. Inlet and StormScreen outlet hydrographs, May 21-22, 2003.
23
-------
StormScreen Upstream September 4, 2003
Velocity (fps)
'Level (in)
Rainfall (in x 100)
-Flow(gpm)
-- 600
-- 500
700
9/4/0313:45 9/4/0314:05 9/4/0314:25 9/4/0314:45 9/4/0315:05 9/4/0315:25 9/4/0315:45 9/4/0316:05
Time
StormScreen Downstream September 4, 2003
- Velocity (fps)
• 'Level (in)
Rainfall (in x 100)
^FIow(gpm)
-- 500
-- 400
600
9/4/0313:45 9/4/0314:05 9/4/0314:25 9/4/0314:45 9/4/0315:05 9/4/0315:25 9/4/0315:45 9/4/0316:05
Time
Figure 5-2. Inlet and StormScreen outlet hydrographs, September 4, 2003.
24
-------
StormScreen Upstream December 10, 2003
25
20
500
Velocity (fps)
'Level (in)
Rainfall (in x 100)
-Flow(gpm)
12/10/032:15
- 450
400
12/10/033:15
12/10/034:15 12/10/035:15
Time
12/10/036:15
12/10/037:'
StormScreen Downstream December 10, 2003
12/10/032:50
12/10/033:50
12/10/034:50
Time
12/10/035:50
12/10/036:50
350
300
50
Figure 5-3. Inlet and StormScreen outlet hydrographs, December 10, 2003.
25
-------
According to the specifications, the StormGate weir was set to divert all of the flow up to 10 cfs
(4,488 gpm) to the StormScreen for treatment and bypass any higher flowrates over the weir to
the bypass pipe. As flowrates began to exceed the maximum flow that could be treated in the
StormScreen, water would begin to back up in the StormGate and the water level would rise.
When the water level reached the top of the weir, excess water bypassed the StormScreen and
entered the downstream storm sewer.
For this installation, the rising water level in the StormGate also caused the water level in the
inlet pipe to rise at the location where the inlet level and velocity monitor was located. Thus, the
water level in the inlet storm sewer pipe provided an indication of the water level in the
StormGate and whether bypass water could flow over the weir. When the water level in the inlet
pipe reached approximately 32 inches (2.67 ft), water would overflow the weir and bypass the
system. Table 5-3 shows the peak flowrates for the inlet and outlet locations, and the peak level
of water in the inlet and outlet pipes. The data shows that water levels exceeded 30 inches at the
inlet station for ten storm events, with nine of the events showing evidence that some amount of
bypass occurred. The five other events had water levels in the inlet pipe in the 9.6- to 24-inch
range. For these five events, it does not appear that bypass occurred, given the fixed weir height
and visual confirmation that the weir was intact, solid, and not leaking water. For three events,
the flow balance was within 20 percent, which is within typical measurement error between
flowmeters in this type of nonideal flow monitoring locations. For the two events that showed a
large difference between the inlet and outlet total volume (11/27/03 and 12/10/03), it appears that
a combination of the surcharged condition at the inlet monitoring locations (yielding possible
positive bias at lower flows) and the high-velocity outlet location (yielding possible negative bias
at low water levels, but high velocity) is the most likely source of the total volume difference.
The peak flowrate from the StormScreen was similar to other events and the system should have
been able to handle the flowrates for these events, even with the apparent reduced capacity from
the original design capacity.
The flow data from the StormScreen outlet shows that the system was typically treating between
150 to 250 gallons per minute when the system was flowing at a steady rate. Each event had a
peak discharge rate (typically 300 to 600 gpm) that was higher than the base rate. These peak
rates were preceded or followed by periods of time (5 to 30 minutes) when the system was
running at a fairly steady rate as it processed the water that had entered and accumulated in the
cartridge bay, fore bay, and StormGate. The StormScreen did appear to process somewhat more
water when the levels in the StormGate were higher, indicating more water was entering the
StormScreen, possibly due to there being more head on the system.
The reason the cartridges were not capable of processing the design flowrate is not known. There
would appear to be two possible explanations: either the cartridge design does not allow the
screens to achieve full design discharge flowrate or rapid occlusion of the cartridges (possibly
due to a heavy load of clay or organic material). The system was cleaned in February 2003 and
the test started in May 2003. If occlusion was a contributing cause, it would have occurred
between February and May. The peak flowrates during the verification test did not indicate
additional deterioration of peak discharge rate as trash, debris, and other material accumulated in
the cartridge bay.
26
-------
There is no evidence that the reduced capacity of the cartridges was caused by hydraulic
conditions upstream or downstream of the StormScreen. On the inlet side of the system, there
was no apparent restriction in the 18-inch inlet pipe. Based on visual observations after each
event, water elevations in the cartridge bay reached 60 to 75 inches, which is at least one foot
above the top of the inlet pipe where it enters the StormScreen. The 18-inch discharge pipe did
not have any apparent flow restriction that might cause water to back up into the vault. The
maximum water elevation observed at the discharge pipe was five inches, indicating that water
did not surcharge in the discharge pipe and back up into the outlet bay.
5.1.1 Flow Verification
The flow capacity data was reviewed with SMI, and they hypothesized that the reduction in the
flow capacity through the system was the result of the cartridge screens becoming occluded. To
test this theory, SMI sent a two-person crew, supervised by PCG and NSF personnel, to the site
on December 2, 2004, to conduct additional testing.
The StormScreen is designed so that the cartridges discharge screened water into one of four
flumes, which drains into the outlet bay. One series of cartridges that discharge to the same
flume was thoroughly cleaned by removing the hoods and hand-scraping sediments from the
screens. The vendor noted that the screens were occluded with a mat of organic detritus and clay.
The cartridges were reassembled after cleaning. The vendor installed an area-velocity flow probe
(ISCO 4150 flow logger with low profile) in the effluent pipe, and calibrated the depth probe
prior to testing.
With permission from the city, PCG personnel attached a fire hose to a nearby hydrant, which
was used to fill the StormScreen vault with water. The manhole covers were removed to observe
the water in the vault. As the water elevation in the vault crested the discharge flumes, a baseline
trickle flow passed through all four flumes. The area-velocity flow probe recorded this flow at
0.31 cfs (140 gpm), which was consistent with the background flowrate noted during most of the
verified storm events.
The City of Griffin instructed PCG to shut off hydrant flow with between two and three inches
left to reach design water elevation in the vault. As the water level in the vault dropped, the head
differential within the cartridges with the cleaned screens caused the floats in the cartridges to
rise, and a brief period of high flow occurred, peaking at 1.12 cfs (500 gpm) and lasting
approximately 10 seconds. Unfortunately, the data storage interval of the flow monitor was set
too high to register this peak in the hydrograph; however, the vendor photographed the high-flow
discharge, shown in Figure 5-4. Because the driving head across the system never achieved
design capacity, this test could not conclusively prove that the StormScreen could discharge at
design flow. The observed peak and attached photos do, however, indicate that when the screens
were cleared of debris, they were capable of discharging more water than the flows measured
throughout the testing period.
This short test suggests that a clean system could discharge at least 0.8 cfs per flume or 3.2 cfs
for the four-flume system used in the verification test, versus the maximum flowrate of 1.3 cfs
27
-------
measured during the verification test. It would appear that the system did experience significant
occlusion that reduced maximum flow capacity. However, it is also not clear that a completely
clean system would achieve the maximum design capacity stated by SMI. Based on the apparent
finding of rapid occlusion in the screens, SMI recommends that StormScreen applications with
heavy leaf and organic loads have a frequent maintenance cycle. The maintenance cycle would
be based on actual field observations.
(a) Flumes at trickle flow
(approximately 0.08 cfs each)
(b) Cleaned flume discharging at
approximately 0.8 cfs
Figure 5-4. Photographs from flow test.
5.2 Observations of StormScreen Performance—Trash and Debris Removal
As described in Section 4.1, there are limited options for quantitative measurement of trash and
debris removal. The primary method for evaluating the performance of the StormScreen was by
documenting visual observations following each event and taking photographs. The observation
forms provided guidance regarding the types of material present and on the water depths that
occurred in the system. Figure 5-5 shows an example of the observation form used for all events.
A complete set of observation forms for all events is provided in Appendix E. Table 5-4 presents
a summary of some of the key observations noted on the forms.
28
-------
The StormScreen was effective in trapping and removing trash and debris that reached the
system. Floating debris, leaves, and general trash (cups, paper, etc.) were clearly present in the
system after each event, as shown in Figures 5-6, 5-7, and 5-8. The design of the vault and
cartridges provided an effective barrier and these large materials were retained in the vault.
The StormScreen also collected large sediment particles and retained some oil and grease, based
on visual observations. A sheen of oil was present in the fore bay and cartridge bay after most
events, and the sediment in the fore bay and the cartridge bay slowly built up over time. As
shown in Table 5-4, the estimated depth of sediment continued to increase over the nine months
that observations and flow measurements were collected. More quantitative information is
provided in Section 5.4 describing the cleanout performed at the end of the verification test.
In addition to the observation forms presented for all events, Appendix E includes photographs
taken from each event. Field observations and photographs indicate StormScreen performed in
accordance with the claim that it can remove trash, debris, and some large solids. There was no
direct physical inspection performed of the screen condition under the hoods during the
verification test, only visual inspection from the surface. Trash, debris, and solids were noted
after all events, while the effluent bay was clear of trash and debris and only showed a slight
buildup of sediment.
The accumulation of sediment and debris on the cartridges and in the sump does not appear to
have resulted in a decrease in flow capacity over the course of the verification test. The data in
Table 5-3 and the hydrographs show that the peak flowrates remained steady throughout the test
period, so the decreased flow capacity does not appear to be related to the accumulation of solids
during the verification test. The postverification test cleanout in May 2004 and the additional
system flow check performed in December 2004 indicate that the cartridge screens had a
significant accumulation of organic detritus and clay. The rate at which the organic detritus and
clay accumulated on the screens is not known. It appears that the initial accumulation of material
caused a significant loss of peak flowrate capacity, but the flow capacity decreased to a steady
state where additional debris accumulation did not cause the flow to further decrease.
29
-------
Table 5-4. Summary of Field Observations
Date
Debris Description
Fore Bay
Debris Description
Cartridge Bay
Sediment
Depth in
Fore Bay (in.)
Sediment
Depth in
Cartridge Bay
(in.)
High Water
Mark in
Fore Bay
(in.)
High Water
Mark in
Cartridge Bay
(in.)
05/21/03
06/03/03
07/03/03
08/12/03
09/04/03
09/22/03
10/07/03
10/26/03
11/05/03
11/19/03
11/27/03
12/10/03
12/14/03
01/05/04
01/17/04
Mud, sand, leaves, misc.
debris
Mud, sand, leaves
Organic, misc. debris
Light leaves and bark
Slight amount of debris
Leaves, little debris
Some debris, leaves and
decaying organics
Average debris, leaves and
organics
Heavy debris, leaves and
organics
Heavy debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
Mud, sand, leaves, misc.
debris
Mud, sand, leaves
Organic, misc. debris
Light leaves and bark
Little debris
Leaves, little debris
Some debris, leaves and
decaying organics
Average debris, leaves and
organics
Heavy debris, leaves and
organics
Heavy debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
Average debris, leaves and
organics
<0.25
0.25
<0.25
0.5
0.5
0.5
0.5
>0.5
>0.5
>0.5
>0.5
10
10
5
10
<0.25
>0.25
<0.25
0.5
0.5
0.5
0.5
>0.5
>0.5
>0.5
>0.5
>0.75
>0.75
0.5
0.5
75
75
60
75
60
60
60
60
75
75
75
75
75
75
75
75
75
60
75
60
60
60
60
75
75
75
75
75
75
75
Note: Miscellaneous debris, such as soda cans, cigarette butts, plastic cups, were present in all observations of the fore bay and cartridge bay.
30
-------
StormScreen Observation Form
Site: Location:
StormScreen 3r<1 St.
Total System Estimated Average Influent (gal):
31,475
Fore Bay Notes / Measurements
Oil sheen presence and degree of:
Slight oil sheen
Debris presence and description of:
Organic (0.25" on wall & steps)
Structural condition (leaks, cracks, etc.):
Good
Current water depth (in.):
20 in.
High water mark (in.):
60 in.
Sediment depth (in.):
<0.25 in.
Additional notes:
Date and Time: Total Rainfall Depth (in.):
7/3/03 0.45
Estimated Average Bypass (gal):
24,280
Cartridge Bay Notes / Measurements
Oil sheen presence and degree of:
Slight
Debris presence and description of:
Organic (0.25" on filters)
Structural condition (leaks, cracks, etc.):
Good
Current water depth (in.):
20 in.
High water mark (in.):
60 in.
Sediment deposition degree on cartridge hoods:
< 0.25 in.
Additional notes:
Average Duration of Storm (hr:mm):
2:40 (inlet and outlet)
Estimated Average Treated (gal):
7,195
Outlet Bay Notes / Measurements
Oil sheen presence and degree of:
None
Debris presence and description of:
None
Structural condition (leaks, cracks, etc.):
Good
Current water depth (in.):
9 in.
High water mark (in.):
33 in.
Sediment depth (in.):
< 0.25 in.
Additional notes:
Figure 5-5. Example StormScreen field observation form.
31
-------
(a) StormScreen vault, June 4, 2003
(b) StormScreen outlet bay, June 4, 2003
(c) StormScreen vault, August 12, 2003
(d) StormScreen vault, May 22, 2003
Figure 5-6. StormScreen photographs, May through August 2003.
32
-------
(a) StormScreen inlet, September 4, 2003
W- sa
(b) StormScreen vault, September 4, 2003
(c) StormScreen vault, August 12, 2003
Figure 5-7. StormScreen photographs, August through September 2003.
33
(d) StormScreen vault, September 24, 2003
-------
(a) StormScreen outlet bay, September 24, 2003
(b) StormScreen vault, September 24, 2003
(c) StormScreen outlet bay, October 26, 2003
(d) StormScreen vault, October 8, 2003
Figure 5-8. StormScreen photographs, September through October 2003.
34
-------
(a) StormScreen vault, November 5, 2003
(b) StormScreen vault, November 5, 2003
(c) StormScreen vault, November 5, 2003
(d) StormScreen vault, November 5, 2003
Figure 5-9. StormScreen photographs, November 2003.
35
-------
(a) StormScreen outlet bay, January 7, 2004
(b) StormScreen vault, January 7, 2004
(c) StormScreen vault, January 17, 2004
(d) StormScreen vault, January 17, 2004
Figure 5-10. StormScreen photographs, January 2004.
36
-------
5.3 Operation and Maintenance
The StormScreen was installed on May 9, 2002. It operated for one year prior to the start of the
verification test and through the nine months of verification test without any apparent
mechanical problems with the cartridges or any special maintenance requirements. Based on
visual observation from the surface, the screens appeared to continue to function normally even
when the cartridge hoods and vault contained debris and solids. No maintenance was performed
during the verification test. The StormScreen and the screens in the cartridges were cleaned in
February 2003 (after nine months of operation) prior to the start of the verification test, and again
after the verification test in May 2004 (15 months of operation). The system design appears to be
robust and capable of withstanding the environment presented by stormwater and stormwater
conveyance systems. As discussed in Section 5.1, the system did not achieve the design flowrate
of 10 cfs, but based on visual observations this did not appear to be caused by a buildup of trash
and debris clogging the screens. Based on the post verification flow test (December 2004), it
appears that screen performance was probably impacted by buildup of organic and clay materials
between the February 2003 cleaning and the start of the test in May 2003.
SMI provides an Operations and Maintenance (O&M) Guideline Manual, included in Appendix
A, which describes the cleanout procedures for the StormScreen. The procedures are clearly
described and are similar to those used for cleaning the system at the end of the verification test.
The normal cleanout should be easier and faster than the one used for the verification test, as
detailed measurements of the weight of solids accumulated by the system are not normally
needed for routine cleanout. A vactor truck can be used to remove the solids rather than the
shovel and bucket/barrel approach described in Section 5.4.
SMI states that the StormScreen should require annual maintenance in normal service
applications, but that cleaning may be needed six months after initial installation due to soil
erosion on newly constructed sites. SMI also states that site-specific conditions, such as site
activities (commercial, residential, and industrial locations will vary in pollutant loading) and
stormwater pollutant source control practices (sweeping, covered solids storage, etc.) will impact
cleaning frequency. SMI has indicated that based on the findings of this verification test, they
recommend more frequent system checks and cleaning when large amounts of clay and organic
detritus are present in the stormwater being treated by the system.
According to SMI's O&M Guideline, the following should be noted and recorded during
inspection:
1. Visually inspect the inlet bay to make sure debris does not hinder water flow.
2. Inspect the filtration bay with a conventional dipstick to determine the depth of trash, debris,
and sediment in the system. If one foot or more of either is measured, refer to the
"Maintenance Methods" section.
3. Inspect for water. The filtration bay should be completely dewatered. If water has not drained
down, refer to the "Maintenance Methods" section.
4. Inspect the structural integrity of the vault.
37
-------
Based on over one year of observations and verification testing, these general guidelines seem
reasonable for the StormScreen system in applications where large trash and debris are the
primary pollutants present in the stormwater. Regular inspection is needed to ensure that the
system is operating properly. However, while the cartridges and the overall system have a robust
design to handle trash and debris, smaller particles, such as fine debris, clay, and organic matter
trapped in the system appear to have the potential to cause clogging in the cartridges. In
applications where these fine materials are present in large quantities, more frequent inspection
and cleaning may be required. Quarterly or even monthly inspection and cleaning may be
required in some applications. The actual type of material present in any specific location is often
not known in advance. Therefore, in order to assess the actual types of materials present in a
specific location and their impact on inspection and cleaning frequency requirements, it is
recommended that inspection of the cartridges be performed monthly or quarterly during the first
year of operation. The results of the more frequent inspections can then be used to determine the
inspection and cleaning frequency required at a specific location.
It was not possible to challenge the StormScreen (after cleaning one set of screens on one flume)
to maximum design flow (2.5 cfs per set or per flume) in the postverification flow test. This was
because the City of Griffin ordered the water to be shut off before the vault was fully charged.
This flow test did show that after cleaning, peak flowrates on the order of 1.12 cfs could be
obtained from one set of screens. This peak flowrate is still well below the design rate of 2.5 cfs.
Based on the findings of this verification test, it is not possible to verify that the StormScreen
can, in fact, achieve the design flowrate with 85 percent occlusion of the screens. Given the
uncertainty that the screens can achieve the full design flowrate, based on these test results, it is
recommended that users check the design flowrate of the system after the initial installation
when the screens are clean.
5.4 Trash, Debris, and Solids Removal
5.4.1 Weight of Solids Removed
At the end of the verification test, on May 12, 2004, a two-person SMI crew came to the site to
clean the system under the observation of PCG. The work was completed in accordance with a
Standard Operating Procedure (SOP) prepared by SMI (Appendix C). Griffin provided a two-
person team with a vactor truck and a dump truck. The cleanout was somewhat more
complicated than a normal maintenance procedure, as the goal was to collect as much of the
solids as possible in order to determine the weight of solids retained in the system. As described
below, it rained the day before the cleanout began, so it was necessary to dewater the system
with a vactor truck before solids could be shoveled into buckets and raised to the surface.
The field report by the SMI field team on the StormScreen cleanout included the following
observations and detail.
0835 AM: SMI arrived onsite and removed the manhole covers to inspect vault.
Thunderstorms occurring the previous day had filled the vault, and the water level had
drained down to just below the StormScreen flumes (approximately two feet). SMI
38
-------
personnel awaited the arrival of Griffin and PCG personnel prior to proceeding with the
cleanout.
0900 to 0930 AM: PCG arrived onsite. A City of Griffin dump truck arrived to collect
and remove sediment, and a vactor truck came to remove liquid. The vactor crew
removed the standing water by slowly lowering the truck's suction pipe to just below the
standing water level in the cartridge bay and the fore bay. Some solids and floatables
were removed during this process, but care was taken to minimize this loss.
0945 AM: A hired contractor set up forced air ventilation, and SMI tested the vault
atmosphere prior to confined space entry. Initial readings showed high levels of
combustibles, but it was determined that these were due to exhaust from the generator
used to power the ventilation fan. The fan was repositioned away from the generator
exhaust, and subsequent readings were negative.
1000 AM: Solids removal began according to the SOP, with deviations as listed:
• Due to excessive solids loading on the hoods of the StormScreen cartridges, cartridge
inspection was carried out in the vault instead of at the surface as proposed in the
SOP. Solids to be removed at the surface and added to the bulk solids were simply
scraped to the vault floor. The cartridge screens did not appear to be occluded in
excess of 85 percent, so the hoods were not removed. The hoods were agitated by
knocking a shovel handle against them, causing trapped solids to fall out. Solids
accumulation on the flumes and hood exteriors were scraped to the vault floor.
• 30-gallon polypropylene drums were used instead of 55-gallon drums. These were
fitted with a rope and hoisted out of the vault using a forklift.
• The contents of the drum were removed and weighed in five-gallon increments using
buckets.
• Solids were removed by shovel until the vault contents were reduced to 0.25 inch of
slurry across the bottom of both vault bays. This was removed with the vactor truck.
As outlined in the SOP, a representative sample was collected in five-gallon buckets. One shovel
of material was added to each bucket per barrel retrieved, resulting in three five-gallon buckets
of sample. These buckets were mixed in an empty barrel, and split into subsamples for laboratory
analyses. Three one-liter samples were taken for percent solids analysis, and one one-liter sample
was analyzed for TCLP metals. Samples were sent to the analytical laboratory by PCG. An
estimated 10 to 15 gallons of loose trash and debris (mostly soda cans and bottles, which did not
contribute to the mass loading) were removed separately. The majority of the solids mass
consisted of leaves and organic matter.
Rainfall was predicted for the afternoon of May 13, 2004, which would have created a hazardous
work environment in the vault, and spoiled the solids assessment. To expedite the sediment
removal and avoid damaging the polypropylene drums, the drums were removed when they were
about two-thirds full. As a retrieved barrel was being weighed and emptied into the dump truck,
the next barrel was lowered into the vault to be filled. This rapid-fire system allowed for a timely
removal of solids, but prohibited an accurate estimate of volume. An estimated volume of 470
39
-------
gallons or 63 cubic feet of wet sediment was removed during this process. The volume of solids
was estimated by recording the volume of sediments in each container used to transport solids
from the StormScreen to the dump truck. The volume of the weighed solids would have fit in one
vactor truck if normal cleanout procedures had been used.
A total of 4,016 pounds of solids (wet weight basis) were removed during this cleanout. Samples
of the solids were sent to the laboratory for percent solids analysis. The laboratory removed any
excess freestanding water and performed a percent solids test on two different samples. One
sample was split into three samples that were run in duplicate and the other sample was run in
triplicate. The results are shown in Table 5-5. The average percent solid for the samples was 29
percent. Using this average value, it is estimated that approximately 1,160 pounds of solids (dry
weight basis) was removed from the system.
Table 5-5. Percent Solids of Solids Removed from StormScreen
Sample Number Sample Split Number Percent Solids
Sample #1 19
Sample #1 17
Sample #1 23
Sample #1 Mean 20
Sample #2
Sample #2
Sample #2
Sample #2
Sample #2
Sample #2
Sample #2 Mean
Overall Mean
Split #1
Split #1
Split #2
Split #2
Split #3
Split #3
38
36
38
40
38
39
38
29
Sample #1 was ran in triplicate; sample #2 was split into three samples and each
sample ran in duplicate.
5.4.2 TCLP Results
Samples of the solids removed from the vault were sent to the laboratory for TCLP metals
analysis. These results shown in Table 5-6 indicate that any metals present in the solids were not
teachable and the sediment was not hazardous. Therefore, it could be disposed of in a standard
Subtitle D solid waste landfill or other appropriate disposal location. The solids collected in the
StormScreen were taken to the local municipal landfill for disposal.
40
-------
Table 5-6. TCLP Results for Cleanout Solids
Regulatory Hazardous
Parameter TCLP Result (mg/L) Waste Limit (mg/L)
Arsenic <2.5 5.0
Barium 0.5 100
Cadmium <0.01 1.0
Chromium <0.01 5.0
Lead <0.1 5.0
Mercury <0.005 0.2
Selenium <0.5 1.0
Silver <0.01 5.0
41
-------
Chapter 6
QA/QC Results and Summary
QA/QC summary results are reported in this section, and the full laboratory QA/QC results and
supporting documents are presented in Appendix F.
6.1 Laboratory Data QA/QC
The laboratory analyses for this verification test were TCLP analyses and metals testing on
sediment samples, and percent solids analyses. AST followed the QA procedures in the AST
QA/QC manual (Attachment I of Appendix B). The goal for the metals analyses was to achieve
precision of 25 percent and accuracy of 75 to 125 percent for all metals being tested. Sediments
were analyzed using EPA-approved methods as given in SW-846 or equivalent Standard
Methods. Table 4-1 showed the test methods, bottle types, and reporting limits for these
analyses.
6.1.1 Precision
Precision refers to the degree of mutual agreement among individual measurement and provides
an estimate of random error. Analytical precision is a measurement of how far an individual
measurement may deviate from a mean of replicate measurements. Precision is evaluated from
analysis of field and laboratory duplicates and spiked duplicates. The standard deviation (SD),
relative standard deviation (RSD), and/or relative percent difference (RPD) recorded from
sample analyses are methods used to quantify precision.
Precision measurements were performed by the collection and analysis of duplicate samples. The
relative percent difference (RPD) recorded from the sample analyses was calculated to evaluate
precision. RPD is calculated using the following formula:
%RPD = - x 100%
where:
xi = Concentration of compound in sample
x_2 = Concentration of compound in duplicate
x = Mean value of xi and X2
The laboratory analyzed matrix spike duplicates as part of the metals analyses. All of the data for
the one dataset that apply to the test samples were within established limits. Results are shown in
Table 6-1.
42
-------
Table 6-1. Analytical Precision Summary
Parameter
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
Recovery
Matrix Spike
(Percent)
106
99
93
94
97
93
111
112
Recovery
Matrix Spike Duplicate
(Percent)
105
98
92
93
96
94
111
112
RPD
(Percent)
1
1
1
1
1
1
0
0
The percent solids/percent moisture analyses on the cleanout solids samples were performed in
triplicate on sample #1. Sample #2 was split into three samples and each sample analyzed in
duplicate. All results were within the data quality goal of 25 percent. Table 6-2 shows a summary
of the results as reported by the laboratory.
Table 6-2. Summary of Replicate Percent Solids Results
Parameter
Sample 2-1
Sample 2-2
Sample 2-3
Sample Result
Percent Solids
38
38
38
Duplicate Sample
Percent Solids
36
40
39
RPD
(Percent)
5.4
5.1
2.6
6.1.2 Accuracy
Accuracy is defined for water quality analyses as the difference between the measured value or
calculated sample value and the true value of the sample. Spiking a sample matrix with a known
amount of a constituent and measuring the recovery obtained in the analysis is a method of
determining accuracy. Using laboratory performance samples with a known concentration in a
specific matrix can also monitor the accuracy of an analytical method for measuring a constituent
in a given matrix. Accuracy is usually expressed as the percent recovery of a compound from a
sample. The following equation will be used to calculate percent recovery:
43
-------
Percent Recovery = [(AT-A; ) / As ] x 100% (6-2)
where:
AT = Total amount measured in the spiked sample
A; = Amount measured in the un-spiked sample
As = Spiked amount added to the sample
The laboratory ran a matrix spike and a spike duplicate for the metals sample from the TCLP.
Table 6-3 shows the results of these analyses. All results were within the established data
objective of 75 to 125 percent recovery. The laboratory also analyzed a lab control sample for
accuracy. These results are also shown in Table 6-3 and are within the control limits.
Table 6-3. Laboratory Control Sample Results
Parameter
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
Recovery Lab
Control Sample
(Percent)
106
101
100
99
100
97
113
111
Recovery Lab Control
Duplicate
(Percent)
106
100
99
98
100
88
113
111
RPD
(Percent)
0
1
1
1
0
10
0
0
6.2 Field Flow Measurements
Flow measurement equipment was calibrated and maintained in accordance with the
manufacturer's recommendations. Attachment F of the test plan (Appendix B) provides the
flowmeter and sampler data acquisition operation and maintenance procedures. The flowmeters
were set and checked following the procedures described by American Sigma. The rain gauge
was inspected and cleaned as necessary after each rainfall to ensure proper operation.
6.3 Quality Assurance Reports
The laboratory-provided Quality Assurance Reports were submitted with each data package.
NSF performed a field audit in July 2003 and discussed all of the field procedures with PCG.
The Field Observation Forms and recent photographs were reviewed and found to be complete.
The AST lab manager and project coordinator met with the team at PCG's office and the needs
for QA reports discussed. The laboratory acknowledged that QC reports would be part of the lab
reports submitted at the end of the verification test.
44
-------
Chapter 7
Vendor-Supplied Information
The information and data contained in this section of the report is provided by the technology
vendor, SMI, and has not verified by the Testing Organization or the Verification
Organization.
This chapter summarizes two tests performed by Stormwater Management, Inc. at their Portland,
Oregon headquarters. The purpose of the tests was to quantify the discharge from the
StormScreen treatment system relative to driving head (the height of water above the
StormScreen cartridge discharge point) and to demonstrate the ability to discharge water at the
design flow rate in a full-scale application with clean water.
The tests were conducted to verify whether the diminished flow capacity conditions experienced
during verification testing was a function of a design limitation associated with the StormScreen,
or environmental conditions, such as pollutant loading. The testing procedures and data were not
collected in accordance with the procedures outlined in the protocol or test plan.
7.1 Testing Equipment
Testing was performed at the Stormwater Managment Inc. (SMI) testing and demonstration
facility, located at their Portland, Oregon headquarters. This facility consists of a series of full-
scale models from the SMI product line, a pumping and conveyance system, and a reservoir tank,
which holds approximately 3,800 gallons. The StormScreen model at the facility contains four
standard StormScreen cartridges mounted on a single aluminum discharge flume within a
standard 6-ft by 12-ft concrete vault, as shown in Figure 7-1. Water discharged from the
StormScreen vault through the discharge flume to the outlet bay, shown in Figure 7-3, where it
was piped back to the reservoir tank. Water was pumped to the StormScreen from the reservoir
via an eight-inch steel pipe by a 15-horsepower Berkelely centrifugal pump. Flow was restricted
by a gate valve upstream of the StormScreen inlet pipe which was controlled by a Bray Series 70
electric actuator, as shown in Figure 7-2. Flow was monitored by a Data Industrial 200 Series
impeller gage with a 1500 Series LCD readout. Stage was measured in inches relative to the top
of the discharge flume.
45
-------
Figure 7-1. StormScreen testing and demonstration system.
Figure 7-2. Electrically actuated control valve and in-line flowmeter.
46
-------
Figure 7-3. Effluent bay of StormScreen testing vault, showing rectangular discharge flume
and 8-in return pipe to reservoir.
7.2 Stage/Discharge Relationship Test without Float Valves
The purpose of this test was to quantify the discharge from the StormScreen relative to driving
head in a full-scale application with no pollutant loading. The test data was collected with the
following assumptions:
1. Flow through the StormScreen will be measured at steady state and will not account for
the siphon effect that occurs during normal design applications.
2. Flow measurements will not account for possible backwater conditions caused by the
structural design of the testing facility.
Both of these effects would serve to dampen the discharge through the system and negatively
bias the measurable flow observed in this study. The results will therefore be a conservative
estimate of the system's hydraulic performance capacity.
7.2.1 Procedure
The siphon function of the StormScreen cartridges was disabled by removing the float valves
from the cartridge center tubes and loosening the top caps, opening the cartridges to atmospheric
pressure. This allowed the flow through the system to be held at steady state throughout the
range of water elevations from the base to the top of each cartridge relative to the discharge
47
-------
flume. All screens were cleaned of debris, and trash usually left in the vault for demonstration
purposes was removed.
Water was pumped to the StormScreen, and water elevation (stage) was measured in inches
relative to the top of the discharge flume. Pumping was initiated at a very slow rate until the
water level in the vault remained constant. Flow was then increased slightly in incremental steps
by adjusting the control valve. Steady state was achieved at each step, and flow and stage were
measured in two- to three-minute increments. Flow was increased in this manner until stage
reached 16 inches. At this level, flow and stage were decreased and recorded in the same
stepwise manner until the initial conditions were reached.
7.2.2 Results
The discharge results during rising were reduced to a per-cartridge basis, and compared to the
water elevations in the StormScreen during rising and falling flow conditions. The results are
plotted in Figure 7-4.
18
16
14
Stage Rising
Stage Falling
SeriesS
line (exponential)
y = 4.1422e
Figure 7-4. StormScreen stage versus flow relationship without float valves.
The plot shows that the 0.5 cfs per cartridge design discharge rate is achieved with a driving head
of less than 15 inches. These results were obtained under steady-state conditions without the
48
-------
siphon action created by the floats in the cartridges, and may have been influenced by minor
backwater conditions in the StormScreen effluent bay. As both of these conditions would add
negative bias to the observed results, this data should be viewed as a conservative estimate of the
StormScreen cartridge clean water discharge potential.
7.3 Stage/Discharge Relationship Test with Float Valves
A second test was performed to demonstrate the ability of the StormScreen to discharge water at
the design flow rate with the floats in the StormScreen cartridges. The objective of this test was
to measure stage relative to the discharge flume at steady influent flow rates up to 0.5 cfs per
cartridge (2 cfs for the four cartridges on the manifold). Constant or falling stage readings at the
2 cfs influent flow rate would indicate that water volume was discharging from the StormScreen
at, or greater than, the influent flow rate.
7.3.1 Procedure
Prior to testing, the float valves were reinstalled in the cartridge center tubes and the top caps
were secured. Stage was recorded in one-minute increments using an ISCO 6700-series
automated sampler with a 750-series flow module. A low-profile area-velocity probe was
calibrated and secured to the discharge flume to measure water elevation. Flow was recorded in
two- to three- minute increments throughout the test. The times at which the floats raised were
also noted.
Clean water was pumped into the StormScreen vault at an initial rate of 2-cfs for 20 minutes,
causing the float valves to lift, reset, and lift again. Flow was then dropped to 1.5 cfs for about
ten minutes. After float valves lifted again, flow was further reduced to 1 cfs for an additional 10
minutes. Flow was then increased to 2 cfs, and float valves were observed to lift and reset twice
before flow was increased to 2.14 cfs and returned to 2 cfs over 20 minutes. Following the last
lifting of float valves, flow was terminated.
7.3.2 Results
Results of the testing were plotted, as shown in Figure 7-5. Float valves in the cartridge center
tubes restrict flow through the system until the water elevation relative to the cartridge base
reaches about 19 inches, at which point the float buoyancy causes the float to lift, the valve to
open, and the water discharge rapidly through the discharge flume until float valves reset. The
initial peak stage measurement was understated due to the rapid initial filling of the vault relative
to the one-minute data recording interval. Float reset occurs between approximately 9 and 11
inches. Small peaks seen up to 14:20 are due to noise associated with the calibration of the
area/velocity probe.
49
-------
25
HI
ro
JS
2.5
Stage- - - Influent Q X Cartridge float lifts
1/26/200513:30 1/26/200514:00 1/26/200514:30 1/26/200515:00 1/26/200515:30 1/26/200516:00 1/26/200516:30
Time (date hh:mm)
Figure 1-5. StormScreen stage versus flow relationship with float valves.
Due to slight differences in cartridge installation elevation, not every cartridge float reset to a
closed position after all floats initially lifted. Thus, periods of near steady stage are observed
during which peak flow is maintained by several cartridges while the remaining cartridges
discharge only at the nominal "trickle" rate. Stage slowly rises during these periods until the final
float(s) are lifted, at which point the stage drops rapidly. At no point did stage surpass the top of
the cartridge hood (21 inches), even when the influent flow exceeded 2 cfs over a period of 15
minutes. The rapid stage decrease observed during the separate periods of 2 cfs influent flow
demonstrates that the StormScreen float valves consistently lift and allow discharge in excess of
the influent flow.
7.4 Conclusion
Based on the results of these tests, the four-cartridge StormScreen system was able to discharge
at rates in excess of 0.5-cfs per cartridge. After lifting, floats did not interfere with or diminish
the hydraulic capacity of the system. This is consistent with the results of the previous
stage/discharge study under steady-state conditions and indicates that the StormScreen system,
with no pollutant loading, meets its hydraulic performance claim of 0.5-cfs discharge per
cartridge.
50
-------
Chapter 8
References
1. NSF International and PCG, Inc. Environmental Technology Verification Test Plan For
Stormwater Management, Inc., StormScreen, TEA-21 Project Area, City of Griffin,
Spalding County, Georgia, June 2003.
2. 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).
3. National Oceanic and Atmospheric Association (2000). "Technical Paper No. 40 Rainfall
Frequency Atlas of the United States."
51
-------
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.
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.
Wet-Weather Flows Stakeholder Advisory Group—a group of individuals consisting of any
or all of the following: buyers and users of stormwater treatment 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.
Verification—to establish evidence on the performance of stormwater 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.
52
-------
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 a
stormwater 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.
53
-------
Appendices
A SMI Design and O&M Guidelines
B Verification Test Plan
C Standard Operating Procedure for Solids Cleanout
D Event Hydrographs and Rain Distribution
E Observation Forms and Photographs
F Analytical Data Reports with QC
54
------- |