vปEPA
United States
Environmental Protection
Agency
Guidance for Building Online Water
Quality Monitoring Stations
For Source Water and Distribution System Monitoring
Office of Water (MC 140)
EPA 817-B-18-002
May 2018

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Disclaimer
The Water Security Division of the Office of Ground Water and Drinking Water of the EPA has reviewed
and approved this document for publication. This document does not impose legally binding requirements
on any party. The information in this document is intended solely to recommend or suggest and does not
imply any requirements. Neither the United States Government nor any of its employees, contractors, or
their employees make any warranty, expressed or implied, or assumes any legal liability or responsibility
for any third party's use of any information, product, or process discussed in this document, or represents
that its use by such party would not infringe on privately owned rights. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use.
Questions concerning this document should be addressed to WQ SRS@epa.gov or the following
contacts:
Matt Umberg
EPA Water Security Division
26 West Martin Luther King Drive
Mail Code 140
Cincinnati, OH 45268
(513) 569-7357
Umberg.Matt@epa.gov
or
Steve Allgeier
EPA Water Security Division
26 West Martin Luther King Drive
Mail Code 140
Cincinnati, OH 45268
(513) 569-7131
Allgeier.Steve@epa.gov

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Acknowledgements
This document was developed by the EPA Water Security Division, with additional support provided
under EPA contract EP-C-15-012. The following individuals contributed to the development of this
document:
•	Steve Allgeier, EPA, Water Security Division
•	Victoria Berry, CH2M
•	Alan Lai, CH2M
•	Sara Miller, CH2M
•	Kenneth Thompson, CH2M
•	Matt Umberg, EPA, Water Security Division
Peer review of this document was provided by the following individuals:
•	John Hall, EPA, Water Infrastructure Protection Division
•	Johnny Partain, Dallas Water Utilities
•	Ralph Rogers, Philadelphia Water Department
•	David Travers, EPA, Water Security Division

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Table of Contents
List of Figures	iv
List of Tables	v
Abbreviations	vi
Section 1: Introduction	1
Section 2: Station Structure	2
2.1	Wall-Mounted Racks	2
2.2	Free-Standing Racks	4
2.3	Enclosed Stations	6
2.4	Compact Stations	8
2.5	Floating Platforms	9
Section 3: Station Equipment	12
3.1	Basic Equipment	12
3.2	Station Accessories	15
Section 4: Fabrication and Installation Considerations	20
4.1	Utility Personnel vs. External Contractors	20
4.2	On-Site Construction vs. Prefabricated Stations	20
4.3	Design-Build vs. Design-Bid-Build	21
Resources	23
Glossary	24
Appendix A: Wall-Mounted Rack Schematic	25
Appendix B: Free-Standing Rack Schematic	26
Appendix C: Enclosed Station Schematic	27
Appendix D: Compact Station Schematic	28
Appendix E: Floating Platform Schematic	29

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List of Figures
Figure 2-1. Wall-Mounted Rack Installation	3
Figure 2-2. Wall-Mounted Rack with Protective Cage	4
Figure 2-3. Free-Standing Rack Installation	5
Figure 2-4. Enclosed Station Installations (Prefabricated and NEMA Enclosures)	7
Figure 2-5. Compact Station Installation	9
Figure 2-6. Floating Platform Installation	10
Figure 3-1. Station Power Distribution Configuration	13
Figure 3-2. Lighting Fixture	16
Figure 3-3. Autos amplers	16
Figure 3-4. Calibration Switches	17
Figure 3-5. Door Alarm Switch	17
Figure 3-6. Leak Detection Sensor	17
Figure 3-7. Internet-Protocol Camera	18
Figure 3-8. Panel Interface Connector	18
Figure 3-9. Ethernet Switch	18
Figure 3-10. Personal Safety Materials	18
iv

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List of Tables
Table 2-1. Wall-Mounted Rack Overview	3
Table 2-2. Free-Standing Rack Overview	5
Table 2-3. Enclosed Station Overview	7
Table 2-4. Compact Station Overview	8
Table 2-5. Floating Platform Overview	10
Table 4-1. Design-Build Summary	21
Table 4-2. Design-Bid-Build Summary	22
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Abbreviations
AC
Alternating Current
ANSI
American National Standards Institute
DC
Direct Current
FRP
Fiberglass-Reinforced Plastic
NEMA
National Electrical Manufacturers Association
NSF
National Sanitation Foundation
OWQM
Online Water Quality Monitoring
PVC
Polyvinyl Chloride
SRS
Water Quality Surveillance and Response System
UL
Underwriters Laboratory
UPS
Uninterruptable Power Supply

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Guidance for Building Online Water Quality Monitoring Stations
Section 1: Introduction
A Water Quality Surveillance and Response System1 (SRS) is a framework designed to support
monitoring and management of water quality in drinking water sources and distribution systems. An SRS
consists of one or more components that enhance a drinking water utility's ability to quickly detect and
respond to water quality incidents and provide information that can be used to improve distribution
system operations. An overview of SRSs can be found in the Water Quality Surveillance and Response
System Primer.
Online Water Quality Monitoring (OWQM) is a component of an SRS that involves the use of online
water quality instruments for real-time measurement of water quality at one or more locations in a
source water or distribution system. Refer to the Online Water Quality Monitoring Primer for an
overview of the OWQM component.
The information in this document can be used to design, fabricate, and install OWQM stations at a wide
range of installation sites in a utility's watershed and distribution system. This document is primarily
intended for use by water sector professionals during design and implementation of OWQM stations.
The remaining sections of this document cover the following topics:
•	Section 2 describes common station structures, how they have been used, and lessons learned
from previous deployments.
•	Section 3 covers types of equipment that are required for basic stations, as well as accessories
that can be added to enhance station functionality and reliability.
•	Section 4 covers station fabrication and installation considerations related to station fabricators,
and approaches used to construct and deploy stations.
•	Resources presents a comprehensive list of documents, tools, and other resources cited in this
document that are useful for implementing activities described in this document.
•	Glossary provides definitions of terms used in this document, which are indicated by bold, italic
font at first use in the body of the document.
^ Words in bold italic font are terms defined in the Glossary at the end of this document.
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Guidance for Building Online Water Quality Monitoring Stations
Section 2: Station Structure
OWQM stations are typically constructed using one of five common types of structures: wall-mounted
racks, free-standing racks, enclosed stations, compact stations, or floating platforms. The suitability of a
structure type for a given monitoring application can be determined by evaluating the following station
attributes:
•	Cost. The capital cost to procure a station or purchase materials required for construction. Costs
related to purchasing and maintaining water quality instruments and ancillary equipment, as well
as the cost to maintain a station, are not covered in this document.
•	Fabrication. The ease of procuring or constructing a station.
•	Flexibility. A combination of both the suitability of a station for a range of site conditions and the
potential for station relocation.
•	Footprint. The space required for station installation, operation, and maintenance. Note that
estimates provided in this document assume the most compact arrangement of available
instruments and ancillary equipment that is possible.
•	Installation. The ease of transporting a station, or station materials, to an installation site and
preparing it for operation.
•	Protection. The extent to which a station shelters instruments and ancillary equipment from
installation site conditions (e.g., dust, extreme temperatures, precipitation). This includes only
protection provided by a station itself, not that offered by an installation site (e.g., a building).
•	Security. The protection provided by a station against tampering. This includes only security
provided by a station itself, not that offered by an installation site (e.g., a building).
The following subsections describe the five common structure types, discuss station attributes, and
summarize design considerations for station deployments. This information is based on experience with
previous OWQM projects and vendor estimates.
2.1 Wall-Mounted Racks
Wall-mounted racks consist of water quality instruments and ancillary equipment that are secured to a
mounting panel that is attached to a wall. These racks can be custom made or purchased as pre-plumbed,
pre-wired units. Mounting panels are often made of polyvinyl chloride (PVC), aluminum, or coated-steel
sheets to enhance the durability of a station. Pressure-treated plywood can be used for short-term
installations, but exposure to caustic solutions (e.g., spilling or spraying of reagents, buffers, or acid-
based cleaning solutions during maintenance visits) can erode protective paint and cause deterioration of
plywood, that could result in attraction of mold and other organisms.
Wall-mounted racks often require at least nine square feet of clear wall space. Racks are typically placed
such that instruments and controls are about 5 to 6 feet above the ground, or near eye level, for ease of
viewing and access. A minimum of 3 feet of space should be cleared in front of racks to avoid obstruction
of equipment and maintain compliance with building codes. Supplies and equipment not mounted to a
rack can be stored on shelves located on or near the panel. Refer to Appendix A for a schematic of a
basic wall-mounted rack.
2.1.1 Application
Wall-mounted racks can be used for both source water and distribution system monitoring. They are most
often installed because of the simplicity of their design. This allows these racks to be relatively
inexpensive when compared to other types of structures, and it often enables utility personnel to complete
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Guidance for Building Online Water Quality Monitoring Stations
station fabrication and installation. Table 2-1 provides an overview of station attributes related to wall-
mounted racks.
Table 2-1. Wall-Mounted Rack Overview

Rating

Attributes
• = Positive
O = Neutral
o = Negative
Details
Cost
•
Cost of construction materials starts at about $100 for stations that use a PVC
mounting panel and at about $500 for stations that use a coated-steel panel.
Fabrication
•
Utility personnel can often complete fabrication.
Flexibility
Q
Requires an indoor site that has a suitable wall for mounting; these stations are
often easy to relocate within the same site or move to a different site.
Footprint
•
Requires at least 9 square feet of clear wall space for installation; a minimum of 3
feet of space should be cleared in front of stations.
Installation
•
Utility personnel can often complete installation.
Protection
O
Does not offer protection against site conditions.
Security
O
Does not provide security against tampering.
Wall-mounted racks are readily accessible and open to the surrounding environment, so they are most
often installed inside utility-owned facilities. Figure 2-1 shows a wall-mounted rack installation.
Figure 2-1. Wall-Mounted Rack Installation
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Guidance for Building Online Water Quality Monitoring Stations
2.1.2 Design Considerations
The following is a list of design considerations for wall-mounted racks:
•	Select secure installation sites to prevent tampering. If such a site is available, instruct building
occupants not to access stations for any reason. If a secure site is not available, it may be possible
to install a protective cage like that shown in Figure 2-2 to provide security for a station.
Additionally, post signage to discourage occupants from accessing stations.
•	Place racks in sites free of dirt, dust, debris, and extreme temperatures to ensure proper equipment
operation.
•	Confirm that walls can support the weight of stations prior to installation.
•	Consider building shelves or installing a non-corrosive storage cabinet on or near stations to store
reagents, manuals, spare parts, and equipment not secured to mounting panels.
Figure 2-2. Wall-Mounted Rack with Protective Cage
2.2 Free-Standing Racks
Free-standing racks consist of water quality instruments and ancillary equipment that are secured to a
mounting panel that is attached to an open, structural frame. Structural frames are often made of coated
steel (e.g., Unistrutฎ) framing members, and mounting panels can be made of aluminum, coated steel, or
PVC
Free-standing racks often require at least 8 square feet of floor space. These racks are typically about
6 feet in height to allow for relatively narrow designs. This also places instruments and controls near eye
level and provides sufficient head clearance under a station's top crossbar for personnel to access
equipment. These racks require up to 3 feet of clear space in front of and behind the stations to prevent
obstruction of equipment. Wheels or casters can be added to the bottom of a rack to increase station
mobility. Supplies and equipment not mounted to a rack can be stored on shelves located on or near the
station. Refer to Appendix B for a schematic of a basic free-standing rack.
2.2.1 Application
Free-standing racks can be used for both source water and distribution system monitoring. They can be
effective if a station must be mobile or if a site lacks sufficient wall space or stability to support a wall-
mounted rack. These racks also allow equipment to be mounted and accessed from both sides of a
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Guidance for Building Online Water Quality Monitoring Stations
mounting panel, which can reduce the station footprint. Table 2-2 provides an overview of station
attributes related to free-standing racks.
Table 2-2. Free-Standing Rack Overview

Rating

Attributes
• = Positive
Q = Neutral
O = Negative
Details
Cost
0
Cost of construction materials starts at about $2,000 for stations where
instruments and ancillary equipment are mounted directly to framing members.
Fabrication
O
Can be custom made or procured as a prefabricated unit from vendors or
manufacturers.
Flexibility
o
Requires an indoor site; these stations are often easy to relocate within the same
installation site, but they can be difficult to move to a different site.
Footprint
o
Requires at least 8 square feet of floor space for installation; stations are often
about 6 feet in height and require up to 3 feet of clear space in front of and behind
racks.
Installation
Q
Utility personnel can often complete installation; stations can be difficult to hoist or
lift during installation.
Protection
O
Does not offer protection against site conditions.
Security
o
Does not provide security against tampering.
Free-standing racks are similar to wall-mounted racks in that they are readily accessible and open to the
surrounding environment. Therefore, they are most often installed mside utility-owned facilities or in
secure areas of other types of protected buildings (e.g., fire stations, police departments, hospitals).
Figure 2-3 shows a free-standing rack installation.
Figure 2-3. Free-Standing Rack Installation
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Guidance for Building Online Water Quality Monitoring Stations
2.2.2 Design Considerations
The following is a list of design considerations for free-standing racks:
•	Select a secure installation site to prevent tampering. If such a site is available, instruct building
occupants not to access stations for any reason. If a secure site is not available, it may be possible
to install a protective cage. Additionally, post signage to discourage occupants from accessing
stations.
•	Place racks in sites free of dust, debris, and extreme temperatures to ensure proper equipment
operation.
•	Consider building shelves or installing a non-corrosive storage cabinet on or near stations to store
reagents, manuals, spare parts, and equipment not secured to mounting panels.
2.3 Enclosed Stations
Enclosed stations consist of water quality instruments and ancillary equipment that are housed inside a
custom-made, or prefabricated enclosure. Custom-made enclosures can be made of a wide range of
materials and can often be built by utility personnel or contractors. Some prefabricated enclosures (e.g.,
cabinets, sheds) can be made of metal or plastic and can be purchased at local hardware stores. Others are
fabricated according to National Electrical Manufacturers Association (NEMA) standards for enclosures
that contain electrical equipment (https://www.nema.org/Standards/Pages/Enclosures-for-Electrical-
Equipment.aspx). NEMA enclosures can be made of aluminum, epoxy-painted steel, fiberglass-reinforced
plastic (FRP), or stainless steel, and can be procured from qualified panel fabrication shops.
Enclosed stations often require a footprint of at least 8 square feet. Stations are often about 6 feet in height
to allow for relatively narrow designs. This also places instruments and controls near eye level to allow
for easy access. These stations require enough clear space to allow their doors to open completely.
Supplies and equipment can be stored inside the station, which provides protection against tampering,
theft, and site conditions. Refer to Appendix C for a schematic of a basic enclosed station.
2.3.1 Application
Enclosed stations can be used for both source water and distribution system monitoring. They are most
often installed because of the security and protection they provide for equipment. The benefits provided
by this type of a station are dependent on the type of enclosure selected. Custom-made and prefabricated
enclosures can be built or purchased to satisfy station requirements. NEMA enclosures are designed and
fabricated to accommodate a range of monitoring applications and site conditions. NEMA 12 enclosures
can be used for indoor installations to provide protection against dust, dirt, and non-corrosive liquids.
NEMA 3R enclosures can be used for outdoor installations to vent moisture and provide protection
against rain intrusion and ice formation. NEMA 4X enclosures, which are often more expensive than
NEMA 3R and NEMA 12 enclosures, can be used for indoor and outdoor locations to provide protection
against pressurized sprays and corrosive environments. Note that NEMA 4X enclosures do not include
vents, so heat and condensation buildup can be a concern. More information on these types of NEMA
enclosures can be found at https://www.nemaenclosures.com/enclosure-ratings/nema-rated-
enclosures.html. Table 2-3 provides an overview of station attributes related to enclosed stations.
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Table 2-3. Enclosed Station Overview

Rating

Attributes
• = Positive
ฉ= Neutral
o= Negative
Details
Cost
ฉ
Cost of materials to construct custom-made enclosures can vary significantly;
prefabricated enclosures start at about $250, and NEMA enclosures start at
about $5,000.
Fabrication
ฉ
Generally takes longer to fabricate due to custom designs;
NEMA enclosures must be procured from qualified panel fabrication shops.
Flexibility
ฉ
Suitable for indoor and outdoor sites, but stations are often difficult to relocate
within a site or move to a different site.
Footprint
O
Requires at least 8 square feet of floor space for installation; stations are often
about 6 feet in height and require enough clear space to allow their doors to
open completely.
Installation
O
Can be difficult to hoist or lift during installation; establishing connections through
an enclosure to distribution system water, drain, power, and communications
can add to the complexity of the installation.
Protection
•
Offers significant protection against site conditions.
Security
•
Provides an increased level of security; typically lockable to prevent tampering.
Enclosed stations both protect and conceal instalments and equipment, so they are most often installed
outdoors (e.g., in parks, public areas, watersheds) or inside unsecured facilities (e.g., city-owned
facilities). Figure 2-4 shows enclosed station installations that use prefabricated and NEMA enclosures.
Figure 2-4. Enclosed Station Installations (Prefabricated and NEMA Enclosures)
2.3.2 Design Considerations
The following is a list of design considerations for enclosed stations:
•	For sites that lack a smooth, flat section of pavement to support a station, consider constructing a
dedicated concrete pad to serve as a base.
•	Install door locks to prevent unauthorized access.
•	Include passive air vents to the exterior of enclosures to remove heat and moisture from stations.
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Guidance for Building Online Water Quality Monitoring Stations
•	Depending on a site's climate and the temperature rating of a station's equipment, consider
installing a small heater, air conditioning unit, or exhaust fan to regulate the temperature inside
the enclosure. Additionally, placing a station under a shade structure can limit temperature
increases in warm climates.
•	Attach heat trace cable to sample lines to prevent sample water from freezing.
•	For sites that lack surrounding infrastructure, consider using wireless communications and solar
power with batteries.
2.4 Compact Stations
Compact stations are smaller versions of enclosed stations. They are often designed around a limited
number of reagentless water quality instruments due to their relatively small footprint, although reagent-
based instruments can be used in some cases. These stations are typically built using NEMA 4X
enclosures. Enclosures can be made of aluminum, epoxy-painted steel, FRP, or stainless steel, and can be
procured from qualified panel fabrication shops.
Compact stations often require a footprint of at least 1.5 square feet. These stations are typically a
maximum of 3 feet in height and require enough clear space to allow their doors to open completely.
Supplies and equipment are often stored offsite due to the limited space inside these stations. Refer to
Appendix D for a schematic of a basic compact station.
2.4.1 Application
Compact stations can be used for both source water and distribution system monitoring. They are most
often installed because of their small footprint. Similar to enclosed stations, the benefits provided by this
type of station are dependent on the type of enclosure selected. Refer to Section 2.3 for information on the
benefits provided by various types of NEMA enclosures. Table 2-4 provides an overview of station
attributes related to compact stations.
Table 2-4. Compact Station Overview
Attributes
Rating
• = Positive
O = Neutral
o = Negative
Details
Cost
e
Cost of NEMA enclosures starts at about $1,500.
Fabrication
o
Generally takes longer to fabricate due to custom, tight designs; NEMA
enclosures must be procured from a qualified panel fabrication shop.
Flexibility
•
Suitable for indoor and outdoor sites; these stations are often easier to relocate
than enclosed stations.
Footprint
•
Requires at least 1.5 square feet of floor space for installation; stations are a
maximum of 3 feet in height and require enough clear space to allow their doors
to open completely.
Installation
e
Connections through an enclosure to distribution system water, drain, power, and
communications can add to the complexity of installation.
Protection
•
Offers significant protection against site conditions.
Security
•
Provides an increased level of security; typically lockableto prevent tampering.
Compact stations have a small footprint and can both protect and conceal equipment, so they are most
often installed outdoors at sites where deployment of larger enclosed enclosures is not feasible (e.g., in
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Guidance for Building Online Water Quality Monitoring Stations
public rights-of-way, parking lots, parks) or inside buildings where space is limited. Figure 2-5 shows an
example of a compact station that was designed and fabricated by the Philadelphia Water Department.
Philadelphia Water Department's Compact Stations
Figure 2-5. Philadelphia Water
Department Compact Station
The Philadelphia Water Department has
designed and fabricated "rapid deployment
modules," which are examples of compact
stations. These stations, which are about the
size of a briefcase, can monitor chlorine
residual, pH, conductivity, turbidity, and
temperature.
These stations have been used for short-term,
distribution system monitoring applications,
such as monitoring during high-profile events,
during changes in distribution system
operations, and to support investigations into
customer complaints related to water quality.
2.4.2 Design Considerations
Design considerations for compact station deployment are largely the same as those listed for enclosed
stations in Section 2.3, with the following additions:
•	Consider both the size and performance of instruments to add to these stations, as space is very
limited.
•	Design stations such that personnel can easily access instruments despite space limitations; add
removable panels or a system that allows equipment to slide on rails to allow for easier access.
•	Note that inclusion of station accessories, which are covered in Section 3.3, is often not feasible
for compact designs due to space limitations.
2.5 Floating Platforms
Floating platforms consist of one or more NEMA 4X enclosures, containing water quality instruments
and ancillary equipment, which are mounted to a flotation system (e.g., a navigation buoy, custom-made
pontoon system). These stations can be custom made or purchased as complete units. A platform's
flotation element is often made of synthetic foam; structural members are often made of aluminum or
stainless steel. Reagentless instalments must be used with these stations due to the lack of infrastructure
available to discharge waste streams that contain reagents. This type of station should include an anchor
to keep it in a fixed location. These stations should also have a warning light to prevent collisions with
recreational watercraft and allow utility personnel to locate the stations at night, if needed.
Floating platforms often require a footprint of at least 25 square feet and are at least 3 feet in height.
Supplies and equipment are typically stored offsite due to the limited space available on the stations.
Refer to Appendix E for a schematic of a basic floating platform.
2.5.1 Application
Floating platforms are used for source water monitoring only. They are most often deployed when
installation of other types of structures on the bank of a waterbody is either infeasible or incapable of
providing a water sample that is representative of the waterbody. Deployment of these stations may
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Guidance for Building Online Water Quality Monitoring Stations
require the use of boats and, for large stations, cranes. Table 2-5 provides an overview of station
attributes related to floating platforms.
Table 2-5. Floating Platform Overview
Attributes
Rating
• = Positive
ฉ= Neutral
o= Negative
Details
Cost
O
Cost of basic navigation buoy system starts at about $5,000,
Fabrication
O
Floating platforms generally take longer to fabricate due to custom designs
and multiple station elements.
Flexibility
•
Can be easy to relocate within the same waterbody, but they can be difficult to
move to other waterbodies.
Footprint
N/A*
Requires at least 25 square feet of space for installation; stations are at least 3
feet in height.
Installation
e
Deployment may require the use of boats and cranes.
Protection
•
NEMA enclosures used on a platform offer significant protection for electronics
and communications equipment against site conditions.
Security
•
Stations are often accessible by boat only; NEMA enclosures provide an
increased level of security for electronics and communications equipment.
•Rating is not applicable because floating platforms are deployed on large waterbodies.
Floating platforms can be placed anywhere on the surface of a waterbody. Identifying potential
monitoring sites requires an understanding of navigation routes and public recreational areas to minimize
the likelihood of collisions with recreational watercraft and tampering. Figure 2-6 shows a floating
platform installation.
Figure 2-5. Floating Platform Installation
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Guidance for Building Online Water Quality Monitoring Stations
2.5.2 Design Considerations
The following is a list of design considerations for floating platforms:
•	When designing stations, consider the waterbody to be monitored and site conditions (e.g., wave
height).
•	Prioritize instrument accessibility in station designs, as utility personnel typically access stations
from a boat.
•	Select instruments that can operate when immersed directly into a waterbody to avoid the need
for pumps to collect sample water.
•	Due to the lack of surrounding infrastructure, consider using wireless communications and solar
power with batteries.
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Guidance for Building Online Water Quality Monitoring Stations
Section 3: Station Equipment
The types of equipment that are incorporated into a station impact its functionality and reliability.
Equipment should be appropriate for its intended monitoring application and able to operate properly in
its intended monitoring environment.
This section covers basic types of equipment that are necessary for all stations as well as accessories that
can be added. The section is divided into subsections that cover the following topics:
•	Basic equipment
•	Station accessories
3.1 Basic Equipment
Every station must be furnished with a basic set of equipment to carry out the primary OWQM functions
of generating water quality data and transmitting it to a utility's control center.
The types of basic equipment discussed in this section include these:
•	Control panels
•	Uninterruptible power supplies
•	Water supply manifolds
•	Water quality instruments, computing elements, and flow-cells
•	Drain assemblies
Refer to Appendices A through E for schematics that depict how basic equipment can be incorporated
into each of the station structures discussed in Section 2.
Note that this document does not cover equipment that is external to a station (e.g., power sources,
distribution system water sources, waste drains). This equipment must be present at an installation site
prior to station deployment.
3.1.1 Control Panels
A control panel distributes power throughout a station and facilitates communication within a station and
between it and a control center. A control panel is often housed inside a dedicated NEMA 4X enclosure
and contains circuit breakers (or fuses), a receptacle, a surge suppressor, and a communications system.
Most stations accept power in 120 volts AC, although 24 volts DC is also possible (e.g., for solar-
powered stations). Figure 3-1 shows a typical power distribution configuration for a station. Control
panels typically require Underwriters Laboratory (UL) 508 certification (most qualified panel fabrication
shops are UL-certified). UL 508 requirements include industry-standard practices and methods for safe
electrical construction of an enclosure with energized equipment.
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CONTROL PANEL
COMPUTING
ELEMENTS
UNINTERRUPTABLE
POWER SUPPLY
POWER COMMUh
CONVERTER ~~ SYSTEM
COMMUNICATIONS
SURGE
SUPPRESSOR
ฉ
POWER
SOURCE
dt
(tub
LEGEND
€
120VAC PLUG
CIRCUIT
BREAKER
POWER CABLE
120VAC RECEPTACLE
POWER WIRING IN
CONDUIT OR
WIREWAY
STATION
RECEPTACLE
Figure 3-1. Station Power Distribution Configuration
Circuit breakers or fuses provide overcurrent protection for a station's energized equipment. Each piece
of equipment should be hard-wired into one of these devices to prevent the entire station from losing
power if a single piece of equipment experiences an electrical issue. For stations located at non-utility
facilities, it can be helpful to install emergency power disconnects at power sources to allow utility
personnel to cut power to a circuit without having to contact the facility owner.
A receptacle that has a built-in ground fault circuit interrupter minimizes the risk of electrical shock
because of inadvertent water spills at a station.
A surge suppressor protects energized equipment from power spikes, or transients, that come from
external sources. In most cases, a single surge suppressor, installed immediately downstream of a control
panel's power supply, can provide protection for an entire station.
A communications system facilitates the transfer of water quality data from a station to a control center.
Both wired and wireless communications systems can be effective for OWQM stations. Note that, if a
wireless system is installed inside an enclosed or compact station, the enclosure must be made of a non-
metallic material (e.g., FRP, polyester, polycarbonate) or the system's antenna must either protrude
through the enclosure or be remotely mounted to transmit a signal. If an antenna is exposed to the outside
environment, the antenna cable may need to be connected to a dedicated surge suppressor inside the
control panel box prior to connecting to a station's communications system (e.g., cellular modem). Also,
if the wireless signal is poor at a site (e.g., in a basement), a communications system may have to be
installed in a separate location (e.g., a top floor) and connected to the station. For more information on
deploying communications systems, refer to Guidance for Designing Communications Systems for Water
Qualify Surveillance and Response Systems.
3.1.2 Uninterruptable Power Supplies
An uninterruptable power supply (UPS) can provide a station with a temporary power source if the
primary source fails. UPSs used for OWQM often provide 1,000 to 1,500 volt-amperes of power and
13

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Guidance for Building Online Water Quality Monitoring Stations
typically provide 2 to 8 hours of run time in the event of a power failure (the exact time depends on the
power consumption of UPS-connected devices). To maximize run time during a power outage, UPSs
should only be connected to critical devices, such as water quality instruments and communications
equipment. UPSs should be compatible with the temperature, humidity, and vibration typically present at
a site, as unfavorable conditions can reduce the useful life of a UPS battery. Note that UPSs often use gel,
cell-type batteries, which can expel hydrogen and oxygen gas through battery valves when overcharged.
Therefore, air vents should be installed for enclosed or compact stations to allow for sufficient diffusion
and ventilation if this type of battery is used.
3.1.3 Water Supply Manifolds
A water supply manifold is an apparatus that distributes sample water throughout a station. Manifolds are
typically made of copper piping and brass fittings. All connections must be sealed with Teflon tape, as
opposed to Teflon pipe dope that can seep into the water and potentially interfere with water quality
instrument operation and measurement. Manifolds often include the following features:
•	Supply bulkhead. A fitting that allows a distribution system water source (e.g., a hose or tubing)
to connect to a manifold.
•	Backflow prevention device. A device that prevents
sample water from returning to the distribution system
once it enters a manifold. These devices should be
included in every station.
•	Strainer/filter. "Y" strainers are common devices that
remove unwanted debris (e.g., displaced sediment) from
sample water prior to contact with water quality sensors.
These strainers are typically 100 microns in size and do
not act as pre-filters that could impact water quality
parameters, such as turbidity. In cases where sensitive
instruments require additional protection, 50-micron
strainers have been used without impacting measured
values. In-line traps are devices that can control
microbubble formation, as needed.
•	Flow gauge/sensor. Devices that measure the flow of sample water that enters a manifold.
Gauges typically indicate current values on the devices themselves, while sensors can often
display current values at the station and transmit data to a control center.
•	Pressure regulator. A device that reduces the pressure of sample water in a manifold from
distribution system levels to levels that meet instrument specifications.
•	Isolation valve(s). A device that enables the flow of sample water to water quality sensors.
•	Sampling port(s). A device that allows for the collection of water samples for field or laboratory
analysis.
•	Pressure gauge/sensor. Devices that measure the water pressure inside a manifold. Gauges
typically indicate current values on the devices themselves, while sensors can often display
current values at the station and transmit data to a control center. These devices can be placed
upstream of a pressure regulator to monitor distribution system pressure and potentially identify
water quality incident (e.g., main breaks). They can also be placed downstream of a regulator to
ensure that pressure levels within a station are consistent with operating ranges listed in
instrument specifications.
•	Drain valve. A mechanism that allows for rapid purging of unwanted debris. This is particularly
useful during initial start-up and after maintenance on upstream water supply lines.
ill	'
Compliance with NSF/ANSI
Standards
Station materials that contact
sample water upstream of a
backflow prevention device
should comply with NSF/ANSI
61: Drinking Water System
Components. In cases where
sample water is pumped back
into a distribution system, all
station materials that contact
sample water should comply
with this standard.
v
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Guidance for Building Online Water Quality Monitoring Stations
Refer to Appendices A through D for schematic details that show basic manifold configurations. Note that
manifolds are not needed for floating platform stations if water quality sensors are immersed directly into
a waterbody.
3.1.4	Water Quality Instruments, Computing Elements, and Flow-Cells
Water quality instruments measure OWQM parameters in the sample water that flows through a station.
The selection of parameters to monitor and instruments to install significantly impacts the benefits that
can be realized from OWQM. For information on OWQM parameters and the benefits they can provide
as part of source water monitoring and distribution system monitoring systems, refer to Online Source
Water Quality Monitoring for Water Quality Surveillance and Response Systems and Online Distribution
System Water Quality Monitoring for Water Quality Surveillance and Response Systems, respectively.
For information on types of technologies that are available to monitor parameters and additional
considerations for selecting instruments, refer to Guidance for Selecting Online Water Quality Monitoring
Instruments for Source Water and Distribution System Monitoring. For a list of available instruments that
includes general information about each instrument, refer to List of Available Online Water Quality
Monitoring Instruments.
Each station must include one or more local computing elements, which is typically a proprietary
instrument controller (e.g., Hach SC1000, s::can con::cube, YSIIG SensorNet). However, in some cases
an instrument controller is an industrial computer that can provide more complex and flexible processing
capabilities.
Some instruments require the use of a flow-cell to control the pressure or flow rate of sample water that
contacts water quality sensors. In this case, sensors can be inserted directly into a flow-cell. Flow-cells
can enhance instrument performance and improve the quality of the data that is generated.
3.1.5	Drain Assemblies
A drain assembly collects and directs a station's waste streams, which consist of sample water that has
been analyzed by water quality instruments, to a suitable outlet for disposal. A drain assembly often
consists of a plastic funnel connected to PVC piping that extends to an outlet. The funnel is a critical
feature of a drain assembly because it creates an air gap, or unobstructed vertical space between waste
stream tubing and an assembly, which provides backflow protection for a station. The height of an air gap
should be at least twice the diameter of waste stream tubing.
For most indoor installations, assemblies can direct waste streams to a floor drain for disposal into a
public sewer system. For most outdoor, land-based installations, assemblies can direct waste streams to a
sewer pipeline; if a sewer pipeline is not available, waste streams can be directed to a dry pit. If a dry pit
is used, hazardous solutions (e.g., calibration standards, buffers, reagents) should be collected in a large
container, such as a carboy, and transported to a sanitary drain for disposal. For floating platforms that use
reagentless instruments, assemblies can return waste streams to the waterbody. In all cases, state and local
discharge requirements should be considered to ensure proper disposal of waste streams.
3.2 Station Accessories
Station accessories can be added to enhance the reliability and functionality of a station. These
accessories often interface with a station's control panel. The feasibility of including accessories in a
design typically depends on a utility's capital budget for procurement, annual operating budget,
availability of personnel for maintenance, desired functionality of a station, and installation site
conditions.
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Guidance for Building Online Water Quality Monitoring Stations
The types of station accessories discussed in this section include these:
•	Lighting fixtures
•	Autosamplers
•	Calibration switches
•	Door switches
•	Leak detection sensors
•	Internet protocol cameras
•	Panel interface connectors
•	Ethernet switches
•	Personal safety materials
3.2.1 Lighting Fixtures
Lighting fixtures can supplement the external light typically
present at a site. These fixtures allow utility personnel to safely
access stations at night and at sites that lack sufficient lighting.
Fixtures are often mounted to the top of wall-mounted and free-
standing racks, or to the ceiling of enclosed and compact stations.
They are typically not included on floating platforms. LED lights
are particularly effective for remote installations as they consume a
relatively low amount of power and require less frequent bulb
replacement.
3.2.2 Autosamplers
If a station contains a computing element that allows for remote
control of the station, autosamplers allow utility personnel to
trigger the collection of water samples at a station immediately
after a water quality anomaly is detected. This enables personnel
to retrieve and analyze samples that are present at the time of an
alert, as opposed to samples that are manually collected after that
water has passed through the station.
Autosampler bottles often sit on the ground beneath wall-mounted
and free-standing racks, or on the floors of enclosed and compact
stations. They can be installed on floating platforms if sufficient
space is available and a pump is provided to collect sample water
from a waterbody. Autosamplers often collect samples in 5-gallon
bottles made of plastic or glass (glass is needed for samples that are analyzed for organic compounds).
The tap for the tubing leading to the sample bottles is typically placed downstream of the in-line pressure
reducer on a station's water supply manifold. A solenoid valve should be placed at the sample port and
connected to the station's computing element to allow for remote actuation of the sample tap.
The sample bottle is usually capped to prevent contamination prior to sample collection. The cap should
be fitted with an inlet for sample collection and a check valve to allow air to escape as the sample bottle
fills. The check valve can include a filter to remove particulates and organics from air purged from the
bottle during sample collection. Personnel should program the station's computing element so the sample
tap stays open long enough to fill the sample bottle without overfilling it. Two sample bottles with
independent sampling solenoids can be installed to allow for collection of multiple samples. In most
cases, preservatives and quenching agents should not be added to sample bottles, as they can be added to
bottles designated for specific analyses during sub-sampling.
Figure 3-2. Lighting Fixture
Figure 3-3. Autosamplers
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Guidance for Building Online Water Quality Monitoring Stations
3.2.3	Calibration Switches
Calibration switches can notify utility personnel when
calibration or maintenance activities are taking place at a
station. Data generated while these switches are activated can
be flagged to indicate that any water quality anomalies detected
during this time are likely the result of work being performed at
the station. These switches are often installed on the face of a
station's control panel for all types of stations. An indicator
light can be added to both signal that a switch has been
activated and remind technicians to return the switch to its
normal setting prior to the end of a visit. If a technician fails to
return a switch to its normal setting, utility personnel can do so
remotely from a control center if the station's computing
element allows for remote control of the station.
3.2.4	Door Alarm Switches
Door alarm switches can generate alerts to notify utility
personnel when a station door has been opened or when a door
has been opened for longer than expected. In the absence of
calibration switches, door alarm switches can indicate when
calibration or maintenance activities are taking place at a
station. Personnel can also use these switches to detect
unauthorized accessing of a station. These switches are often
installed inside enclosed and compact stations such that they are
activated and deactivated when station doors open and close,
respectively. They are not typically used for wall-mounted
racks, free-standing racks, or floating platforms.
3.2.5	Leak Detection Sensors
Sensor environments should be kept consistently dry to avoid
nuisance alerts. Leak detection sensors can be used to generate
alerts to notify utility personnel when plumbing leaks and
sample bottle overflows occur at a station. These sensors can be
mounted to the bottom of wall-mounted and free-standing
racks, or placed on the floor beneath these racks if they have an
open bottom with spill containment. They can also be placed on
the floor of enclosed stations and compact stations, or mside
floating platform control panels. If a leak is detected, personnel
can remotely shut off a station's water supply if the station's
computing element allows for remote control of the station.
Figure 3-4. Calibration Switches
Figure 3-5. Door Alarm Switch
Figure 3-6. Leak Detection Sensor
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Guidance for Building Online Water Quality Monitoring Stations
3.2.6	Internet-Protocol Cameras
Internet-protocol cameras equipped with microphones allow utility
personnel to view a station to examine for leaks, hear audible alarms, and
identify unauthorized access. These cameras typically offer the ability to
pan, tilt, and zoom, and select alternate viewing modes (e.g., low-light,
infrared). Cameras can be installed anywhere at a site that has a clear view
of wall-mounted and free-standing racks. They can be installed inside
enclosed and compact stations in a top comer that has a clear view of the
station. Waterproof and underwater cameras can be installed on floating
platforms above or below the water surface.
3.2.7	Panel Interface Connectors
Panel interface connectors for Ethernet or 120VAC connections
installed on the outside of control panel boxes can allow utility
personnel to plug equipment, such as a notebook PC, into the
panels without having to open the box. Thi s capability is
particularly useful for utilities that do not allow personnel to open
energized panels without an electrical safety permit. These
connectors are typically installed on the face of the control panel
for wall-mounted racks, free-standing racks, enclosed stations, and
compact stations. They are not typically included on floating
platforms. Although these connectors have a cover that is usually
closed, they should be placed above and away from all water tubes
to protect against spraying from system leaks. Installing a lockable
cover on panel interface connectors can provide additional
physical security.
3.2.8	Ethernet Switches
An Ethernet switch is required when the number of computing
elements used to transmit data to a control center is larger than the
number of Ethernet ports available on the communications device
(e.g., cellular modem) present at a station. Ethernet switches are
most often installed inside a station's control panel box for all
types of stations.
3.2.9	Personal Safety Materials
Storing personal safety materials at stations can help to ensure the
safety of personnel who conduct maintenance activities for station
equipment. Examples of such materials may include safety glasses,
latex gloves, disposable ear plugs, hard hats, safety boots, Material
Safety Data Sheets (for any reagents that are used at the stations),
first aid kits, eye wash supplies, and a listing of the nearest medical
centers in case of an emergency.
Redundant Instruments
Installation of multiple water quality instruments that measure the
same parameter at a station ensures constant generation of water
quality data in the event of a sensor malfunction. Also, data precision
can be assessed by comparing data from the two instruments.
Figure 3-7. Internet-
Protocol Camera
Figure 3-8. Panel Interface
Connector
Figure 3-9. Ethernet Switch
Figure 3-10. Personal Safety
Materials
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Guidance for Building Online Water Quality Monitoring Stations
Section 4: Fabrication and Installation Considerations
Several considerations can impact the selection of qualified personnel and approaches used for station
fabrication and installation. The resulting decisions made by utilities can significantly impact the
efficiency of OWQM deployment and performance of stations.
This section covers common station fabrication and installation considerations. The section is divided into
subsections that cover the following topics:
•	Utility personnel vs. external contractors
•	On-site construction vs. prefabricated stations
•	Design-build vs. design-bid-build
4.1	Utility Personnel vs. External Contractors
Following the design of stations, utilities should assess the availability and capability of internal
personnel to complete fabrication and installation activities.
Fabrication activities typically include these:
•	Planning and design of stations
•	Fabrication of stations
o Welding and metal fabrication
o Water quality instrument and control panel wiring
o Plumbing within the stations
Installation activities typically include these:
•	Site modification (e.g., demolition, drain waste vent piping, electrical service connections,
construction of a concrete base)
•	Pipe work (e.g., making municipal water plumbing connections, pipe penetrations)
•	Coordination of equipment delivery to a site
•	Systems integration support
•	Organization of post-installation inspections, start-up, training, and acceptance
If utility personnel have sufficient availability and are both capable and certified to do so, it is often
preferred that they complete the above activities. However, if personnel are unable to complete these
activities, or if a utility would like to leverage the experience of OWQM specialists, external contractors
can be hired to provide assistance. Note that if contractors are involved with station installation at a
privately-owned facility, negotiations may be required to address issues such as legal liability and risk.
It is recommended that utilities engage instrument vendors following station installation to provide on-site
training for operations and maintenance.
4.2	On-Site Construction vs. Prefabricated Stations
Stations can either be constructed at installation sites or delivered to sites as prefabricated units. The ideal
approach for an installation is often determined by the complexity of a station's design and site
conditions.
On-site construction of a station involves the delivery of water quality instruments, ancillary equipment,
and construction materials to a site, and then personnel assembling the station on location. This approach
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Guidance for Building Online Water Quality Monitoring Stations
is most often used when station designs are relatively simple and sites provide sufficient space to
complete assembly. It can also be effective when delivery of an assembled station to a site is infeasible
(e.g., if site access points are narrow).
Prefabricated stations are constructed offsite and delivered to sites as complete units. These stations are
most often used when designs are relatively complex or when sites lack sufficient space for on-site
assembly. They can also be effective when fully assembled stations can be delivered to a site without
difficulty or when security may be an issue at a site. Because these stations are often constructed,
inspected, and tested by the same individuals under controlled conditions, there is a greater likelihood
they are constructed in a consistent, effective manner.
In cases where a prefabricated station is desired but space is limited at installation site access points (e.g.,
a basement that has a narrow staircase for access), a combination of the above approaches can be used.
Separate modules can be fabricated offsite, delivered to a site, and assembled on location. This approach
provides many of the benefits of prefabricated stations, but the separate modules are often easier to
transport to a site.
4.3 Design-Build vs. Design-Bid-Build
The most common approaches used to design and fabricate stations are the design-build and design-bid-
build project delivery methods. The suitability of each method for a given project is often determined by
utility procurement policies, project budgets and schedules, and the desire of utility personnel to
participate in the design and fabrication processes.
The design-build method consists of utilities developing a set of station qualifications for a system
integrator and then procuring services from one or more entities for design, fabrication, startup, and
transfer to the utility. This method is often effective when a utility has a compressed project schedule and
would prefer that a single contractor be responsible for design, fabrication, and installation. Table 4-1
summarizes the advantages and disadvantages of this method.
Table 4-1. Design-Build Summary
Advantages
Disadvantages
•	Construction typically starts before the design is
completed, which can shorten the project schedule.
•	Construction costs may be fixed and known during
the design process, which places an emphasis on
controlling project costs (progressive design-build
processes will develop costs with a contractor by
the 30% design).
•	Utilities do not need detailed design expertise,
although technical knowledge is required to
develop specifications.
•	Utilities and design-build entities share design and
construction risk.
•	Comprehensive and carefully prepared plans and
specifications may be required during the 30%
design phase.
•	Utilities may incur additional costs if changes are
made to plans and specifications after the 30%
design is locked in.
The design-bid-build method consists of utilities procuring design entities to develop detailed station
specifications, and then using those specifications to procure a contractor to fabricate stations. This
method is often effective when a utility has an extended project schedule or when utility or state policies
do not allow for alternative delivery approaches. Table 4-2 summarizes the advantages and disadvantages
of this method.
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Guidance for Building Online Water Quality Monitoring Stations
Table 4-2. Design-Bid-Build Summary
Advantages
Disadvantages
•	Utilities can work with design entities to ensure that
desired requirements are included in specifications
prior to construction beginning.
•	The process of procuring construction contractors
is typically competitive, which can result in lower
construction costs.
•	Utilities have a better understanding of the
expected cost of a project.
•	Design and construction are performed in series,
which often results in longer project schedules.
•	Construction costs are not locked in until a contract
is awarded (but are typically closely estimated
costs).
•	Utilities must execute separate procurements for
design entities and construction contractors.
•	Utilities or design consultants are financially liable
for design errors that require modifications during
construction.
•	It can be difficult to resolve construction disputes
due to shared responsibility for delivery.
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Guidance for Building Online Water Quality Monitoring Stations
Resources
Guidance for Designing Communications Systems for Water Quality Surveillance and Response
Systems (EPA, 2016)
This document provides guidance and information to help utilities select an appropriate
communications system to support operation of an SRS. It provides rigorous criteria for
evaluation communications system options, evaluates common technologies with respect to these
criteria, describes the process for establishing requirements for a communications system, and
provides guidance on selecting and implementing a system. (EPA 817-B-16-002, September
2016.)
https ://www.epa. gov/sites/production/files/2017-
04/documents/srs communications guidance 081016.pdf
Guidance for Selecting Online Water Quality Monitoring Instruments for Source Water and
Distribution System Monitoring (EPA, in press)
This document provides detailed information about commonly monitored water quality
parameters and guidance on selecting appropriate parameters to monitor for a given application. It
also provides a summary of available technologies for monitoring each parameter.
https://www.epa.gov/waterqualitvsurveillance/online-water-qualitv-monitoring-resources
List of Available Online Water Quality Monitoring Instruments (EPA, 2017)
This spreadsheet provides general information related to OWQM instruments that utilities can use
to identify instruments that are capable of satisfying OWQM system requirements.
https://www.epa.gov/waterqualitvsurveillance/online-water-qualitv-monitoring-resources
Online Distribution System Water Quality Monitoring for Water Quality Surveillance and
Response Systems (EPA, 2017)
This document provides guidance for designing a real-time distribution system water quality
monitoring system to achieve a variety of design goals, including monitoring for contamination
incidents and optimizing distribution system water quality. (EPA 817-B-19-001, April 2018)
https://www.epa.gov/waterqualitvsurveillance/online-water-qualitv-monitoring-resources
Online Source Water Quality Monitoring for Water Quality Surveillance and Response Systems
(EPA, 2016)
This document provides guidance for designing a real-time source water quality monitoring
system to achieve a variety of design goals, including treatment process optimization, detection of
source water contamination incidents, and monitoring threats to long-term source water quality,
https ://www.epa.gov/sites/prodiiction/files/2016-
09/documents/online source water monitoring guidance.pdf
Online Water Quality Monitoring Primer (EPA, 2015)
This document provides an overview of the OWQM component and presents information about
the goals and objectives of OWQM in the context of an SRS. (EPA 817-B-15-002A, May 2015.)
https ://www.epa. gov/sites/production/files/2015-
06/documents/online water quality monitoring primcr.pdf
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Guidance for Building Online Water Quality Monitoring Stations
Water Quality Surveillance and Response System Primer (EPA, 2015)
This document provides an overview of SRSs, and serves as a foundation for the use of technical
guidance and products used to implement an SRS. (EPA 817-B-15-002, May 2015.)
https ://www.epa. gov/sites/production/files/2015-
06/documents/water quality sureveillance and response system primer.pdf
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Guidance for Building Online Water Quality Monitoring Stations
Glossary
alert. An indication from an SRS surveillance component that an anomaly has been detected in a
datastream monitored by that component. Alerts may be visual or audible, and may initiate automatic
notifications such as pager, text, or email messages.
anomaly. A deviation from an established baseline in a monitored datastream. Detection of an anomaly
by an SRS surveillance component generates an alert.
benefit. An outcome associated with the implementation and operation of an SRS that promotes the
welfare of a utility and the community it serves. Benefits can be derived from a reduction in the
consequences of a contamination incident and from improvements to routine utility operations.
control center. A utility facility that houses operators who monitor and control treatment and distribution
system operation, as well as other personnel with monitoring or control responsibilities. Control centers
often receive system alerts related to operations, water quality, security, and some of the SRS surveillance
components.
dry pit. A man-made pit consisting of a rock layer covered by a dirt layer that allows for OWQM station
waste streams to be discharged and naturally treated before percolation. Dry pits are often used when
sewer lines are not available.
installation site. The specific area where an OWQM station is installed (e.g., a utility facility closet or
fire station basement). Installation sites provide the physical space, sample water source, waste stream
outlet, power source, and data communications access required for stations to function.
Online Water Quality Monitoring (OWQM). One of the surveillance components of an SRS. OWQM
utilizes data collected from monitoring stations that are deployed at strategic locations in a source water
or a distribution system. Monitored parameters can include common water quality parameters (e.g., pH,
specific conductance, turbidity) and advanced parameters (e.g., total organic carbon, spectral absorbance).
Data from monitoring stations is transferred to a central location and analyzed.
reagent. A chemical substance used to cause a reaction for the purpose of chemical analysis.
real-time. A mode of operation in which data describing the current state of a system is available in
sufficient time for analysis and subsequent use to support assessment, control, and decision functions
related to the monitored system.
sensor. The part of a water quality instrument that performs the physical measurement of a water quality
parameter in a sample.
sensor malfunction. A condition in which the data produced by a sensor unit does not reflect actual
conditions.
turbidity. The cloudy appearance of water caused by the presence of suspended particles.
water quality incident. An incident that results in an undesirable change in water quality (e.g., low
residual disinfectant, rusty water, taste & odor, etc.). Contamination incidents are a subset of water quality
incidents.
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Guidance for Building Online Water Quality Monitoring Stations
water quality instrument. A unit that includes one or more sensors, electronics, internal plumbing,
displays, and software that is necessary to take a water quality measurement and generate data in a format
that can be communicated, stored, and displayed. Some instruments also include diagnostic tools.
Water Quality Surveillance and Response System (SRS). A system that employs one or more
surveillance components to monitor and manage source water and distribution system water quality in
real time. An SRS utilizes a variety of data analysis techniques to detect water quality anomalies and
generate alerts. Procedures guide the investigation of alerts and the response to validated water quality
incidents that might impact operations, public health, or utility infrastructure.
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Guidance for Building Online Water Quality Monitoring Stations
Appendix A: Wail-Mounted Rack Schematic
CONTROL
PANEL
FROM WATER SUPPLY+
DETAIL OF
DETAIL OF ฉ
(WATER QUALITY INSTRUMENTS, COMPUTING ELEMENTS, AND FLOW-CELL)
(DRAIN ASSEMBLY)
FROM M-
CONTROLT
PANEL
COMPUTING
V. ELEMENT
FROMM-ft-
CONTROLT •
PANEL
FROM
CONTROL'
PANEL
FROM
FLOW-CELL
AND FLOW-
THROUGH
SENSOR
COMPUTING
\ ELEMENT
COMPUTING
\ ELEMENT
FROM
CONTROL'
' PANEL
% COMPUTING I *'
% ELEMENT
SENSORS I	FLOW-
• THROUGH \
SENSOR V
FUNNEL
FLOW-CELL-
MOUNTING
BRACKET
ROTAMETERS
TO DRAIN m+\
TO DRAIN | —ฆ
ASSEMBLY ~ 2
FROM WATER	S
+ SUPPLY MANIFOLD	tp
mi in in hi in in in iii in in iiiiiiii"
j in in in in in in in in in in in in in iiii*x
TO DRAIN
'ASSEMBLY
DETAIL OF @
(WATER SUPPLY MANIFOLD)
TO ROTAMETERS
PRESSURE
GAUGE

II III III II
ISOLATION
VALVES
SAMPLING
PORTS
PRESSURE
REGULATOR
SUPPLY
BULKHEAD
FROM WATER SUPPLY
J /— BACKFLOW
\y PREVENTION
* ncwioc
DETAIL OF ฉ
(CONTROL PANEL)
TO
ACOMPUTING %ฆ TO COMPUTING ELEMENTS
* ELEMENTS^.
-CIRCUIT
BREAKERS

3OWER
CONVER
COMMUN
CATIONS
%%\\ SYSTEM—v
FROM
EXTEVM
ANTENNA
F ~.:V;ER
SOURCE
CIRCUIT
BREAKER
SURGE
SUPPRESSOR
FROM UPS ฆ
d
TO STATION ฆ
RECEPTACLE ~
LEGEND
ll I IB SAMPLE TUBE 	ANTENNA
lllll WASTE TUBE	CABLE
POWER CABLE •••SIGNAL
	ETHERNET CABLE CABLE
	WATER LINE
UPS = UNINTERRUPTIBLE POWER SUPPLY
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Guidance for Building Online Water Quality Monitoring Stations
Appendix B: Free-Standing Rack Schematic
CONTROL
PANEL
FROM
WATER
SUPPLY
J
FRONT VIEW

RIGHT SIDE VIEW
FROM WATER
SUPPLY
DETAIL OF
(WATER SUPPLY MANIFOLD)
i--^7,	TO ROTAMETERS
PRESSURE -i
Y STKAINcR
REGULATOR
PRESSURE
GAUGES
SAMPLING
SOLATION
PORT
VALVES
-BACKFLOW
PREVENTION
DEVICE
DETAIL OF ฉ
(CONTROL PANEL)
DETAIL OF ฉ
(DRAIN ASSEMBLY)

: FROM
' FLOW-CELL
AND FLOW-
THROUGH
SENSOR
FUNNEL
CAP
MOUNTING
BRACKET
TO DRAIN
LEGEND
IB I IB SAMPLE TUBE 	ANTENNA CABLE
lllll WASTE TUBE
—- POWER CABLE ••• SIGNAL CABLE
	ETHERNET CABLE
	WATER LINE
UPS = UNINTERRUPTIBLE POWER SUPPLY
ANTENNA
COMPUTING
ELEMENTS
CIRCUIT
BREAKERS
POWER
CONVERTER
COMMUNICATIONS
SYSTEM
•MODEM POWER
—1 rm-n SOURCE
TO STATION
RECEPTACLE
SURGE—'
SUPPRESSOR CIRCUIT-'
BREAKER
FROM UPS'
26
ELEMENT
FLOW-THROUGH		*
SENSOR ^ \K
ZZFROM
WATER
V* SUPPLY
MANIFOLD
COMPUTING—'# COMPUTING-/ V
DETAIL OF ฎ
(WATER QUALITY INSTRUMENTS,
COMPUTING ELEMENTS, AND FLOW-CELL)
TO DRAIN
ASSEMBLY
FROM CONTROL PANEL
SENSOR
FLOW-CELL
ROTAMETERS

-------
Guidance for Building Online Water Quality Monitoring Stations
Appendix C: Enclosed Station Schematic
DETAIL OF
(WATER SUPPLY MANIFOLD)
'TO ROTAMETERS
'""i in m„
""a in „i,ti
BACKFLOW
PREVENTION
r DEVICE
CONTROL
PANEL
FROM
WATER
SUPPLY
SAMPLING
PORT
ฆISOLATION
VALVES
"Y" STRAINER
PRESSURE
REGULATOR
•SUPPLY
BULKHEAD
DETAIL OF
(CONTROL PANEL)
ANTENNA
4 TO COMPUTING ELEMENTS
Vj" T	/-CIRCUIT
! • II	/ BREAKERS
FRONT VIEW
RIGHT SIDE VIEW
DETAIL OF (ฐ)
(WATER QUALITY INSTRUMENTS,
COMPUTING ELEMENTS, AND FLOW-CELL)
POWER
CONVERTER
DETAIL OF
(DRAIN ASSEMBLY)
FROM CONTROL PANEL
FROM FLOW-CELL
AND FLOW-THROUGH
SENSOR
. COMMUNICATIONS
.•SYSTEM
FUNNEL
FROM
EXTERNAL
POWER
SOURCE
COMPUTING-' $ COMPUTING J
ELEMENT $ ELEMENT
+ + FLOW-THROUGH
f	SENSOR
MOUNTING
BRACKET
CIRCUIT
BREAKER
ANTENNA
SURGE
SUPPRESSOR
TO DRAIN
FLOW-CELL.
TO STATION
RECEPTACLE
FROM UPS
ROTAMETERS
ANTENNA CABLE
11111 WASTE TUBE
POWER CABLE -
	ETHERNET CABLE
• SIGNAL CABLE
UPS = UNINTERRUPTIBLE POWER SUPPLY
FROM
WATER
SUPPLY
MANIFOLD
TO DRAIN
ASSEMBLY
27

-------
Guidance for Building Online Water Quality Monitoring Stations
Appendix D: Compact Station Schematic
18"
CONTROL
PANEL

fFROM
EXTERNAL
FROM WATER
SUPPLY
POWER
SOURCE
FRONT VIEW	RIGHT SIDE VIEW

(WATER QUALITY INSTRUMENT,
COMPUTING ELEMENT, AND FLOW-CELL)
DETAIL OF ฉ
(DRAIN ASSEMBLY)
CONTROL

COMPUTING
t EMFNT
^'11111111111^*=
^ \-FLOW
CELL
ROTAMETER
FROM
FLOW-CELL
MOUNTING
BRACKET
~ FROM WATER SUPPLY
MAINIFOLD



-4™ TO DRAIN


TO DRAIN ASSEMBLY ฆ ^
DETAIL OF
(WATER SUPPLY MANIFOLD)
TO ROTAMETER
tl
ISOLATION
VALVE
PRESSURE
REGULATOR
GAUGES
J
STRAINER
SUPPLY
BULKHEAD
/— SAMPLING
/ PORT
FROM WATER SUPPLY
ฆ BACKFLOW
PREVENTION
DEVICE
DETAIL OF
(CONTROL PANEL)
TO COMPUTING ELEMENT
CIRCUIT
BREAKERS
POWER
CONVERTER
ฆCOMMUNICATIONS
SYSTEM
ANTENNA SURGE
SUPPRESSOR
FROM UPS
ill ฆฆ SAMPLE TUBE -ฆ
11111 WASTE TUBE
— POWER CABLE m
	ETHERNET CABLE
	WATER LINE
UPS = UNINTERRUPTIBLE POWER SUPPLY
LEGEND
ANTENNA CABLE
SIGNAL CABLE
28

-------
Guidance for
Appendix
Building Online Water Quality Monitoring Stations
E: Floating Platform Schematic
FRONT VIEW
RIGHT SIDE VIEW
TO ANCHOR
TOANCHOR
DETAIL OF
(WATER QUALITY
DETAIL OF
DETAIL OF
INSTRUMENT)	(SOLAR PANELS AND WARNING LIGHT)	(COMPUTING ELEMENTS AND CONTROL PANEL*)
TO
CONTROL
PANEL
WATER—s.
QUALITY ป
INSTRUMENT
WARNING LIGHT
SOLAR PANELS
'O KM/ PA^iF!
ฆ FROM SOLAR
~ PANELS
SURGE
SUPPRESSOR
TO
IMMERSED
SENSOR i
BATTERY
BATTERY
CHARGER/
=>OWER SUPPLY
W...KT s\rJ
V COMPUTING 		
ELEMENT / rr,*,,Di iTiwr-A
COMMUNICATIONS	'	X-.
SYSTEM ELEMENT ~
	T'—
ANTENNA SURGE —' *

TO T
IMMERSQP
SENSOR'
ANTENNA SURGE
SUPPRESSOR
* Battery charger/power supply and battery shown above are often provided
by solar panel manufacturerers,
LEGEND

— POWER CABLE
	ANTENNA CABLE
	ETHERNET CABLE
• ••SIGNAL CABLE
29
CONTROL
PANEL

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