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Water Distribution System SCADA Tutorial

Developed by The University of Missouri

Prepared for the

National Institute of Hometown Security

368 N. Hwy 27

Somerset, KY 42503

May 28, 2013

This research was funded through funds provided by the Department of Homeland Security,

administered by the National Institute for Hometown Security Kentucky Critical Infrastructure

Protection program, under OTA # HSHQDC-07-3-00005, Subcontract # 02-10-UK

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Table of Contents

2.1 Supervisory Control and Data Acquisition (SCADA) Systems .......................................... 4 2.1.1 Overview ...................................................................................................................... 4

2.1.2 SCADA Concepts ......................................................................................................... 4

2.1.2A - Data Collection, Data Monitoring, and SCADA ....................................................... 4

2.1.2B - SCADA Function ...................................................................................................... 5

2.1.2C - SCADA Equipment ................................................................................................... 6

Figure 2.1.2C1 - Illustration of four SCADA Equipment Categories ..................................... 6

2.1.3 Sensors and Controls Overview ................................................................................... 7

2.1.4 Interface Devices .......................................................................................................... 9

2.1.4A - Remote Terminal Units ........................................................................................... 10

Figure 2.1.4-A1 - Simplified Illustration of RTU Function in a SCADA System ................ 10

2.1.4B - Programmable Logic Controller (PLC) ................................................................... 10

Figure 2.1.4-B1 - Example PLC photographs ....................................................................... 11

2.1.4C - Intelligent End Device (IED) ................................................................................... 11

Figure 2.1.4-C1 - Simplified Illustration of PLC or IED Function in a SCADA System ..... 12

2.1.5 Potential SCADA Uses in a Water Distribution System ............................................ 12

2.1.6 SCADA System Implementation Process .................................................................. 13

2.2 Communications Network ................................................................................................. 14 2.2.1 General Overview of SCADA Communications ........................................................ 14

Figure 2.2.1-A - Illustration of four SCADA Equipment Categories ................................... 14

2.2.2 Communications Network Options ............................................................................ 15

Table 2.2.2-A – Differences between hard-wired and wireless communication systems. .... 17

2.2.3 Communications Network Features and Considerations ............................................ 18

Figure 2.2.3-A: Typical SCADA Communication Network Configuration ........................ 19

2.2.4 – Communication Security ............................................................................................... 19

2.2.5 – Most Efficient Strategy for Designing and Building the Communication System ....... 20

2.3 Hydraulic Sensors .............................................................................................................. 21 2.3.1 - General Overview of Hydraulic Sensors as Pertinent to Water Distribution Systems .. 21

2.3.2 – Uses of Hydraulic Sensor Data ..................................................................................... 21

2.3.3 – Sensor Equipment Sources ............................................................................................ 22

2.3.4 – Most Efficient Strategy for Obtaining Hydraulic Sensors ............................................ 23

2.3.5 – Hydraulic Sensors Costs and Specifications ................................................................. 23

2.4 Water Quality Sensors ............................................................................................................ 26 2.4.1 - Overview of Water Quality Sensors as Pertinent to Water Distribution Systems ......... 26

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2.4.2 - Sensor Equipment Sources ............................................................................................ 28

2.4.3 - Most Efficient Strategy for Obtaining Water Quality Sensors ...................................... 28

2.4.4 - Water Quality Sensors Costs and Specifications ........................................................... 28

2.5 – Hydraulic and Water Quality Sensor Placement ................................................................. 31

SCADA Sensor Placement Decision-Making Sequence ....................................................... 32

SCADA CWS Sensor Placement Optimization Program Inputs........................................... 33

2.6 Strategies for developing Data Acquisition and SCADA Systems ................................... 34 2.6.1 - Design/Bid/Build Project Delivery Method................................................................... 34

Figure 2.6.1-A – Design-Bid-Build, Owner Equipment Purchase ........................................ 34

Figure 2.6.1-B – Design-Bid-Build, Typical ......................................................................... 35

Figure 2.6.1-C – Design-Bid-Build, Performance Specification........................................... 35

2.6.2 - Engineering, Furnishing, and Installation (EFI) Project Delivery Method ................... 35

Figure 2.6.2-A – EFI Project Delivery .................................................................................. 36

2.6.3 – Considerations for Potential Equipment Suppliers, Engineers and Contractors ........... 36

References ..................................................................................................................................... 39

Appendix A - Listing of Water Related Sensor Manufacturers 2012 ........................................... 42

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2.1 Supervisory Control and Data Acquisition (SCADA) Systems

2.1.1 Overview

In its essence, SCADA is an automated workforce that helps better operate and manage your

water treatment and distribution system. It can perform tasks such as taking water quality

measurements, controlling equipment, monitoring alarms, and data accumulation and

presentation. The benefit of using SCADA to perform these tasks, especially with respect to

security, is that unlike humans, SCADA never takes a day off. The result of the 365 days of

continuous monitoring with respect to virtually any aspect of a water treatment operation equates

to a greater level of security and overall efficiency. This translates into not only peace of mind,

but a better, more consistent product delivered at a substantial cost savings for both the consumer

and the producer. Furthermore, advances in computer modeling and instrumentation have

enabled water system operators greater levels of water system security as well as improved

production and delivery efficiency.

Currently, hydraulic models are calibrated with samples taken manually over a short period of

time. A troublesome aspect to this method is that the model only represents the data from that

particular snapshot of time, without regard to the dynamic conditions that actually exist within

distribution systems. In not accounting for ever changing conditions, such as water demand or

transient pressures, current hydraulic models cannot be expected to be accurate or reliable given

the static calibration conditions (Allen et al. 2011). This can be overcome by supplying the

model with live data from SCADA systems. SCADA in conjunction with hydraulic modeling

software and water quality monitoring equipment has the potential to keep communities safe

from intentional attack by terrorists while simultaneously increasing the efficiency of treatment

and distribution systems.

2.1.2 SCADA Concepts

2.1.2A - Data Collection, Data Monitoring, and SCADA

The term SCADA is often inappropriately used. SCADA by definition includes some level of

control coupled with real-time data collection and monitoring. Many systems only have data

collection, or the “DA” part of SCADA. With data collection only, water system operators log

data from a facility and make any needed changes at the facility based on interrupting that data at

a later date. Obviously this method requires an operator to occasionally visit the facility and this

system is obviously not real-time.

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The next level of complexity builds on data collection and adds real-time monitoring of the data.

However, even though the system is collecting data and an operator is able to monitor the data as

it is collected, if any operational changes need to be made to the system an operator would be

required to visit the facility to make the necessary changes. This level of “SCADA” may be

adequate for many systems, but is still be missing many of the monitoring and control features

that make a SCADA such a desirable system to have.

SCADA in its entirety integrates data collection, real-time monitoring, and facility controls into

one package. When discussing the term SCADA, one must keep in mind that many smaller

systems may only have the data collection aspect of a SCADA, but refer to their system as a

“SCADA”.

While SCADA is a necessary tool in most water systems, as illustrated above it is a broad term

that isn’t always easily defined. Generally speaking, SCADA uses fit into on at least one of the

following six areas: alarms and notifications, energy monitoring/management, equipment and

facilities monitoring/control, data management and record keeping, water chemistry/quality and

hydraulics monitoring/control, and water system/supply security monitoring.

When considering SCADA, there are two general areas to consider; Function and Equipment.

2.1.2B - SCADA Function

SCADA Function categories are:

1. Data Acquisition (Collection)

2. Data Communication (Monitoring)

3. Data Presentation

4. Equipment Control

Note that these SCADA function categories are in a specific order; in other words the second,

third and fourth functions all build on the prior functions. The first three SCADA function

categories deal with data acquisition. Many water systems, especially smaller systems, do not

elect to use supervisory control aspects the SCADA in the daily management of their system.

All SCADA systems must have data acquisition and communication before any supervisory

controls can be implemented; therefore, many industry professionals believe that the “DA” of

SCADA, or data acquisition portion of SCADA, is the most important part of the system.

Closely tied to the data acquisition, is the communications and data logging/presentation aspects

to the SCADA

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Although this report focuses on the entire SCADA system, it can also be used as a reference if a

system is examining the possibility of using only the data acquisition, logging and presentation.

2.1.2C - SCADA Equipment

All of the SCADA Functions are carried out by SCADA Equipment. There are four SCADA

equipment categories that are illustrated in Figure 1:

1. Sensors and Controllers - Sensors (either digital or analog) and control relays directly

interface with the managed system.

2. SCADA Interface Units - Remote Terminal Units (RTUs), Programmable Logic

Controllers (PLCs), and Intelligent End Devices (IEDs) are small computerized units

deployed in the field at the specific sites and locations where sensors and equipment

controllers are utilized. RTUs, PLCs, and IEDs serve as local collection points for

gathering status from sensors and delivering commands to control relays.

3. Communications Network - The data and control command transmission network that

connects the SCADA master unit to the RTUs in the field.

4. SCADA Master - These are larger computer consoles that serve as the central processor

for the SCADA system. Master units provide a human interface to the system and

automatically regulate the managed system in response to sensor inputs.

Remote Terminal

Unit (RTU),

Programmable Logic Controller (PLC) or

Intelligent End

Device (IED)

SCADA Master with

User Interface

RTUs, PLCs or IEDs Communications Network SCADA Master

Water Levels

Hydraulic Pressure

Motor Speed/Temp

Pump Station Ambient Humidity /

Temperature

Motion Detection

Pump on/off Control

SENSORS/CONTROLS

Figure 2.1.2C1 - Illustration of four SCADA Equipment Categories

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2.1.3 Sensors and Controls Overview

Before we begin on sensors and controls, we need to cover the two basic types of these devices.

The first type is referred to as discrete, or also called digital. A discrete sensor is a sensor that

only senses two positions; “on” or “off”. It cannot sense anything in between these two

positions. Some consultants will refer to discrete sensors as digital sensors, because in the world

of digital devices, either a “I” or “O” is used, which is why some people still refer to these

devices as “I/O devices”. The second type of sensor is an analog sensor. Analog sensors can

sense and report back specific values in any given range of values. For example, if we wanted to

sense temperature. A discrete sensor could tell the user if the temperature is freezing (32˚F) or if

the temperature is boiling (212˚F). In the same example, an analog temperature sensor can

report back any temperature in a broad range, say any temperature between 32˚F to 212˚F.

Another example is a simple motor. A discrete sensor could tell the user if the motor was on or

off, while an analog sensor could tell the user not only if it was on or off, but even how fast it

was running.

To recap, discrete is simply “on” or “off”, “open” or “closed”, and so on, while analog can report

back specific “how much” values in a pre-programed range.

At the time of this report, the top ten SCADA sensors currently in use, based on sales, are:

1. Temperature Sensors - The most basic way to monitor temperature is a discrete threshold

sensor. This is very similar to a simple home thermostat. You set a high-point threshold

or a low-point threshold (one per sensor). When these presets are exceeded, you get a

contact closure alarm, which translates to a basic high or low temperature alarm. The

downside to this type of alarm is that if your threshold was set to 80°F, you could be at

81°F or 181°F - and you wouldn’t be able to tell the difference! More advanced

temperature sensors output analog values. Analog monitoring allows you to monitor

fluctuating sensor levels at your remote sites. With the right SCADA system, you can use

your analog readings to send alarms based on configurable thresholds. You can have

different thresholds for low, critically low, high, and critically high.

2. Humidity Sensors -Often, humidity monitoring is overlooked, but it is one of the key

environmental conditions to monitor in every unmanned remote site. Looking at both

internal and external humidity ranges, it’s very important to monitor what conditions

your equipment is operating in. If your environmental control unit failed and you didn’t

have adequate monitoring of the humidity at your site, you would be completely unaware

of the damage and would be too late in preventing equipment failure. Humidity can be

monitored with both discrete and analog sensors, much like temperature. Where possible,

look for a sensor that monitors both temperature and humidity.

3. Motion Sensors -The most critical element of physical site security is being able to detect

intruders and receive an immediate alert. Motion sensors provide you with the instant

information you need to react to an intruder before the real damage is done. Discrete

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motion sensors can even turn on a light and send an immediate intrusion notification

when movement is detected in its field of vision. It’s very important to consider

placement when installing motion sensors. Windows and other possible intrusion points

should be protected by motion sensors.

4. Water (or any liquid) Level Sensors - Water level sensors can be used to monitor water

towers, ground storage tanks and clearwells. This makes them especially useful for alarm

circuits that may tell a motor when to turn on in order to keep a tower full. With a

discrete liquid level sensor, you can configure the sensor to latch a contact closure when

your liquid level has fallen below a critical line. This allows you to receive a notification

when your water tanks are low. With analog sensors, they can be set up to measure any

water level in the tank, rather than just the high and low levels.

5. Water Flow Sensors- Using water flow sensors gives you an accurate picture of your

water flow rates and direction. Most flow sensors can monitor water with an internal

flow meter or a flow data logging device. At a water treatment plant, water flow is one

item on a long list of data that must be collected during the treatment process. It’s

important to find a reliable water flow sensor that produces accurate flow results and

allows you to make quick decisions based on that data. Water flow direction is also very

important to water system managers to determine if “water racing” is occurring. Water

racing is a phenomenon where water in a distribution system “races” around in circles. If

this occurs, it is a huge waste of energy.

6. Smoke Sensors - Smoke sensors are critical safety devices needed in every remote

facility site. There are many possible reasons a fire could break out at a site. Overheated

equipment, electrical short, wildfire . . . the list goes on. In order to save your equipment,

you need to know right away if smoke or fire is present at a remote site. Fires can cause

irreparable damage, and smoke sensors are a good first line of defense.

7. Door and Window Sensors - Whether or not you’ve already experienced theft or

vandalism in your network, your unmanned sites are vulnerable. While you might expect

this type of criminal activity from strangers, an alarming amount of damage is done by

employees, ex-employees, and outside contractors. Door and window sensors keep your

equipment secure. You’ll know the moment someone tries to gain unauthorized access to

one of your remote sites, or if an employee enters when they’re not supposed to. Without

the protection of a door sensor, an unknowing technician could walk into a dangerous

situation. Door and window sensors provide a warning, “Hey, nobody’s supposed to be

there at 3 a.m.!”

8. Power Failure Sensors - The primary damage caused by a power outage is obvious: If

commercial power fails and you don’t have a reliable backup power supply, that site will

eventually go dark. Dark sites mean network downtime, frustrated customers, and lost

revenue. A power failure sensor will send an alarm when power is disrupted. This is a

discrete sensor that outputs a contact closure when power is not detected for a user-

defined amount of time. Most users want to receive a critical alarm after any failure

lasting more than a few seconds.

9. Current Sensors - You must always know whether your battery chargers, backup

generators, and other power sources are outputting power. Analog current sensors tell you

way more than, “They’re outputting power”. You also need to know the current draw.

Measuring AC/DC currents, current sensors isolate the sensor output from the conductor.

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These types of sensors are highly useful for motor drives, UPS systems, and battery

supplies.

10. Propane Tank Sensors – Another sensor that fall in the category of “not thought of, but

very popular” is a propane tank level monitor. Monitoring your propane tanks can save

you from running out of fuel or notify you of theft. Some propane sensors send an

audible alert when they’re running low. At sites where propane is the only fuel source,

you may need advanced sensors that track gas usage rates and report back to an on-site

RTU with the exact amount left. These types of analog sensors will allow you to order

more propane for your tank - before it runs empty.

Other popular water system sensors include:

The following are just a few examples of items that can be monitored by your SCADA:

Suction and/or Discharge pump pressure

Distribution system line pressure

Stream or lake level monitoring

Equipment Temperature

Water detector alarm (to indicate leaks)

Well head pressure monitoring

Well water drawdown level monitoring

Wet well water level monitoring

Pump on/off/fail status

Valve positions

And various water quality parameters, including:

o Free/Total Chlorine

o pH

o Temperature

o Turbidity

o Or just about anything else you can think of.

2.1.4 Interface Devices

There are two primary types of systems to consider when designing telemetry and

communication systems. In a uni-directional system, remote terminal units report data to a

central location, but do not accept remote command and control instructions. Remote telemetry

is truly bi-directional in nature, reporting both statistics and accepting instructions from a central

computer or controller. In most cases, it is worth remembering that in a uni-directional system,

terminal units only send data, the managing system requires a bi-directional link; the link itself

can usually both send and receive information.

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2.1.4A - Remote Terminal Units

Before any data collection or remote sensing can be achieved, information needs to be passed

between the sensors and the communications system in a form that is compatible with the

language of the SCADA system. To accomplish this, a field interface unit required. The most

basic of these units are known as Remote Terminal Units, or RTUs. RTUs are used to convert

electronic signals received from field sensors into machine language, known as protocol, and

transmit data over the communications network to the SCADA Master, where a human will then

use and manage that information. RTUs by themselves are not typically used to control

equipment but rather to collect and transmit data to a controller, where controls are then

exercised. When in the field, the RTU appears as a small box-like device (or several, depending

on how many sensors are being utilized) within a panel. When examining an RTU on a sensor or

in a panel, try to keep the simplified illustration shown in Figure 2.1.4-A1 in your mind.

2.1.4B - Programmable Logic Controller (PLC)

A Programmable Logic Controller, PLC or Programmable Controller, is a digital computer used

to monitor and control certain aspects of equipment, such as motor speed, valve actuation, and

other functions. Typically, a PLC has a range of functions, based on the electrical signal it

receives from the sensor. For example, if the pressure drops 10psi from optimum level in a

distribution system, the PLC may “tell” the variable frequency drive (VFD) on the electric motor

to turn the pump motor faster, which would drive the pump to produce an extra 25 GPM.

Similarly, if the pressure in the same system drops by 20psi, the PLC may drive the pump to

produce an extra 50 GPM in order to make up for the increased “demand” being sensed. This

programming is referred to as “ladder logic” and there are limits to this system. In this example,

keep in mind that all these pump speed changes are occurring on-site, without supervisory

control, all because the PLC has been pre-programed to react to a certain condition.

Although PLCs are intended to control equipment, if a condition comes up that is “outside” the

PLCs programming, then supervisory control would need to be exercised.

Sensor RTU Communications

Network

SCADA

Master

Figure 2.1.4-A1 - Simplified Illustration of RTU Function in a SCADA System

Note 1-way arrow, indicating

data transmission ONLY

1-way arrow, indicating

data transmission

ONLY

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Figure 2.1.4-B1 shows two photographs of open SCADA PLC panels. The PLCs in the first

photo appear in the center of the panel, while the PLCs in the second panel appear in the upper

portion of the panel. A key to identifying the PLC is to identify the wires coming from the

sensor(s), and the wires going to the communications network, by default, the PLC is in between

these two features.

2.1.4C - Intelligent End Device (IED)

Similar to a PLC, and Intelligent End Device (IED) can establish communication between

remote sensors and controllers and the communications network. An IED differs from a PLC in

that a single IED can control several different aspects to a piece of equipment, so that the entire

piece of equipment works in harmony with the rest of the needs of the system and within

established design parameters. IED is a relatively new term and has come about in part because

of confusion between Remote Telemetry Units, with the acronym (RTU) and Remote Terminal

Unit, also with the acronym RTU. To help solve this issue, the industry has begun to call these

more sophisticated interface and controller units, IEDs.

A key difference between the Remote Terminal Unit (RTU) and the PLC or IED is illustrated in

Figure 2.1.4-C1. In this figure, note that the machine language, and hence the data, moves in

both directions, thus allowing for not only data acquisition, but also control.

Typical PLCs

Figure 2.1.4-B1 - Example PLC photographs

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It is important to note that specific instruction for equipment automation is stored locally, in the

PLC or the IED. This is usually due to the fact that over most Communication Networks, there

is a limited bandwidth, thus limiting the actual control to that which is “pre-programed” into the

PLC or IED. As communication networks and the technology that SCADA is based on

continues to improve in leaps, there will no doubt be a day when true, unlimited control can be

exerted from the SCADA Master to the desired equipment. (Bentley, 2004)

2.1.5 Potential SCADA Uses in a Water Distribution System

A SCADA system is a widely distributed computerized system primarily used to remotely

control and monitor the condition of field-based assets from a central location. Field-based

assets include wells, pump stations, valves, treatment plants, tanks, and reservoirs (Bentley,

2004).

Generic uses of SCADA in distribution systems include:

Security monitoring

Energy management

Monitor equipment operations to forecast maintenance, repair, and replacement

Sub-metering utility usage

Identifying alarm conditions

For water distribution, the operational and managerial uses of a SCADA system include the

following:

Monitor the system

Exercise control over the system and ensure that required performance is continuously

achieved

Reduce operational staffing levels through automation or by operating the system from a

central location

Monitor and store data of a system’s behavior, and use the data to achieve full

compliance with regulatory reporting requirements

Controller IED or

PLC

Communications

Network

SCADA

Master

Figure 2.1.4-C1 - Simplified Illustration of PLC or IED Function in a SCADA System

Note 2-way arrows, indicating

data transmission and reception

ote 2-way arrows,

indicating data

transmission and

reception

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Obtain information on the performance of the system and establish effective asset

management procedures for the system

Establish efficient operation of the system by minimizing the need for routine visits to

remote sites.

Potentially reduce power consumption during pumping operations through operational

optimization

Provide a control system that will enable operating objectives to be set and achieved

Provide an alarm system that will allow faults to be diagnosed from a central location,

thus allowing field repair trips to be made by suitably qualified staff to correct the given

fault condition and to avoid incidents that may be damaging to the environment.

Monitor system operations to identify excursions of operating equipment from normal

operating conditions/ranges.

Monitor equipment operations to forecast maintenance, repair and replacement.

Use SCADA data to verify hydraulic and water quality models.

Use SCADA data to identify intrusions, leakages, and other variations from normal

system, operations.

2.1.6 SCADA System Implementation Process

When considering a SCADA system, there are traditionally two methods that are utilized for

implementation. These methods are:

Design-Bid-Build Method

EFI (Engineer, Furnish and Install) Method

These methods are discussed in more detail Section 2.6 of this document.

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2.2 Communications Network

2.2.1 General Overview of SCADA Communications

Without a properly designed communication network system, a SCADA system cannot exist.

All supervisory control and data acquisition aspects of the SCADA system rely entirely on the

communication system to provide a conduit for flow of data between the supervisory controls,

the data acquisition units, and any controllers that may be linked to the system. The purpose of a

communications network within a SCADA system is to connect the Remote Terminal Units

(RTUs) with the SCADA Master.

Referring to Figure 2.2.1-A, we will now discuss the Communications Network of SCADA

Equipment.

Remote Terminal Unit (RTU),

Programmable Logic

Controller (PLC) or Intelligent End

Device (IED)

SCADA Master with

User Interface

RTUs, PLCs or IEDs Communications Network SCADA Master

Water Levels

Hydraulic Pressure

Motor Speed/Temp

Pump Station

Ambient Humidity / Temperature

Motion Detection

Pump on/off Control

SENSORS/CONTROLS

Figure 2.2.1-A - Illustration of four SCADA Equipment Categories

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2.2.2 Communications Network Options

The data can be transmitted through a variety of different communications platforms such as:

Ethernet - A system for connecting a number of computer systems to form a local area network,

with protocols to control the passing of information

Telephone Line - A system that utilizes electrical signals in order to transmit data over a distance

using a single pair of copper (traditionally) wires.

Optical Fiber Line- Similar to the traditional copper telephone lines, but differs by utilizing

optical fibers made of glass or plastic and uses light to transmit the data, with is faster and has

less losses as compared to copper wires.

Radio/Wireless - A system that uses radio transmitters and receivers to send data over short

distances. Typically requires line of sight for best application.

Cellular - Based on the cellular phone technology to transmit data, regardless of distance, but

dependent on cellular signal coverage.

Satellite - Similar to the cellular phone platform, but utilizing satellites instead of ground-based

cellular towers.

Wi-Fi - A technology increasing in popularity that allows an electronic device to exchange data

wirelessly (using radio waves) over a computer network, including high-speed internet

connections. Earlier generation Wi-Fi systems can be notoriously insecure; Wireless Equivalent

Privacy [WEP] is relatively easy to compromise, so care must be taken when selecting Wi-Fi

equipment to ensure that it supports robust security. WPA2 is present in almost all currently

available equipment, and its use should be mandated.

Microwave – A system for providing long-range connectivity between two sites, utilizing either

inexpensive public frequencies or FCC-licensed spectrum. Some microwave units are an

extension of Wi-Fi – but for long range (20+ miles), others use proprietary protocols.

To meet security and performance specifications, it is important to consider the endpoint of each

connection. Point-to-point connections (such as Ethernet, Fiber, and Microwave) typically

terminate at a central system management facility. Cellular systems may provide an Internet

connection requiring additional security, and phone-line systems must be protected against

security breaches through the standard land-line, twisted-pair copper wire network.

It is also important to consider the privacy offered by a solution; wireless solutions in particular

need to pay attention to the possibility of a nearby device eavesdropping on an otherwise secure

conversation. This can have profound implications if private data such as passwords are included

in the gathered data.

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Finally, it is important to remember that these technologies are not mutually exclusive. A site can

readily use a combination of Wi-Fi and Ethernet locally, and transmit the entirety of the site’s

data to a central point through fiber, microwave or other longer-range technology.

All of these communications methods fall under either hardwire or wireless category. Hardwire

communication options include dedicated hardwire (i.e. Ethernet cable), fiber optic (i.e. light

pipe), telephone wire (i.e. copper pair), or coaxial cable. Options for wireless data transmission

include but are not limited to include satellite, radio, cellular, and Wi-Fi. Current industry trends

suggest that wireless communication systems will continue to gain a larger market sector of the

SCADA communication platforms, especially for large distributed networks such as water

distribution systems where there is a need for a vast coverage area, perhaps in remote locations

not readily accessible to existing hardwires. The same industry trends indicate that Ethernet is

becoming the preferred communications standard for local area SCADAs, such as a water

treatment plant. (Ritchie, 2011)

Wireless and hardwire options can be used alone or in tandem depending on the size and nature

of the system. Factors to consider in selecting communication options include:

Coverage area of SCADA system. For example, is the SCADA for only for the local water

plant, or does it include an entire, widely dispersed distribution system, as well as the water

plant.

If a system-wide SCADA, then consideration of the size and terrain of the distribution system.

For example, wireless may be a less expensive option, but the communications system would

require adequate line of sight between the radio transmitters/receivers.

Local availability of infrastructure and its proximity to the system feature that will require a

SCADA sensor. For example, if an there is an existing telephone line to a particular site where a

sensor needs to be installed, then that telephone line may be the best option in that case.

Growth of the community could affect the SCADA system performance and future

expandability.

Ability to upgrade the system easily, and

Budget for the system.

Some of the more significant advantages and disadvantages are summarized in Table 2.2.2-A.

Most modern SCADA systems use a variety of communication options within one system to

meet their needs. Typically, there is not a one size fits all solution for SCADA communications

and should be tailor made to fit a utility’s needs.

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Hardwired

Advantages Disadvantages

Telephone Line May already exist to site(s). Very

mature technology.

May be monthly lease charge(s). Consider who

is responsible for fixing problems on the line and

if it is a third party, what is their track record for

repair responses. Typically slow and limited

data transmission.

Ethernet Good application for local site, such as

a water treatment plant.

Limited application range. Cannot be utilized

over distances greater than 1000’ without

boosting signal. Can be prone to lightning

damage without significant protection measures.

Fiber Optic Best direct connection with the fastest

data transmission. Large bandwidth

allows for video applications (i.e.

security cameras) to part of the SCADA

system.

May be significant monthly lease charge(s). If

the fiber does not already exist, the capital costs

for the initial project could have a very high.

Fiber is also typically very expensive to repair.

Coaxial Cable May already exist to the site(s). Very

mature technology. Better data

bandwidth than a telephone line.

May be monthly lease charge(s). Depending on

the setting, this type of hardwire is less common

than a telephone line.

Wireless

Advantages Disadvantages

UHF and VHF

Voice Radio

Generally very low maintenance and

can usually be repaired by a local radio

shop.

FCC license required, along with periodic fees

and renewals.

900Mhz spread

spectrum and

2.4Ghz Data Radio

No FCC license necessary and transmit

data at a higher rate.

Requires line of sight for best application. Some

900Mhz require FCC license.

Wi-Fi Potentially very good option for a local

site application, such as a water

treatment plant.

Very limited ranges (typically 300 ft or less), and

the signal can be significantly diminished by

structures. Wi-Fi requires careful security

assessment.

Microwave Potentially very good option for linking

sites with good elevation, such as water

towers.

Requires expert assistance with installation.

Some frequencies require FCC licensing.

Cellular Quickly gaining in popularity,

especially as pricing continues to

decline and for areas that may not have

strong radio signals or line-of-sight

conditions.

The area for coverage should have good,

consistent cellular coverage.

Satellite Good application where there is no, or

unreliable cell coverage, such as

extreme terrains, very remote locations,

etc.

May become a viable option in the future, but is

currently not cost-effective except in the most

extreme cases.

Table 2.2.2-A – Differences between hard-wired and wireless communication

systems.

18

2.2.3 Communications Network Features and Considerations

When selecting a communications system for plant operations it is common to use only hardwire

to connect remote equipment to the SCADA Master, given the short distances involved. When

using hardwired lines to communicate with remote sites in the distribution system, distance,

reliability and time responses are all limiting factors in the design process. New construction of

hardwire communication networks are not practical when trying to connect to distant system

components, such as a pump station on the other side town. In situations where it is not

economically feasible to run an independent hardwire for each remote site, one may elect to tap

into existing infrastructure or elect to use a form of wireless communication. If a utility elects to

use pre-existing infrastructure several options are available including dial-up or leased telephone

lines or fiber networks. The type of platform selected often depends on the bandwidth required

to perform remote operations such as pumping, or the polling frequency (e.g. how often do you

need to collect data).

Inaccessible sites or lack of “wire” type of infrastructure may necessitate the use of wireless

communications systems, but regardless of terrain, distance, or accessibility, current trends

suggest a growing affinity to use wireless options to replace hardwire systems. Wireless

communication provides utilities with the following benefits versus traditional hardwire systems:

scalability, deployment speed, reduced network and construction costs, and reduced maintenance

and repair of hard wires. The scalability (or ability to quickly expand as the system grows) of a

wireless network is a great advantage over wired systems. Increasing SCADA system coverage

can be achieved without running wire or other costly labor items and can be installed in a

relatively short period of time which offers savings over hardwire systems. Wireless systems

can also expand independent of existing infrastructure to meet the needs of a growing

community. The advantages of wireless can be seen by studying Figure 2.2.3-A. Consider the

image in this figure spread out over a twenty square mile area and the relative costs of a wireless

system versus a hardwire system. Now consider the replacement costs after 20 years of

technological innovation. The ability to upgrade remote sites on an individual basis versus

system wide is a clear advantage and provides a degree of assurance as land lines become phased

out. Existing hardwire systems may also be supplemented with wireless systems on a per unit

level as new operations come on-line. For cellular systems reliability and availability of service

should be taken in to consideration.

19

2.2.4 – Communication Security

Security is an important consideration when designing a SCADA network. Many existing

SCADA systems have been found wanting in this regard, leaving essential systems vulnerable to

outside influence.

Security should be considered on three levels:

Perimeter Security, limiting access to systems and network equipment from

unauthorized sources.

Interior Security, requiring at the very least a login to access important infrastructure.

Transport Security, ensuring that it is difficult to illicitly access a network segment in

an attempt to gain control.

Additionally, a cohesive security plan requires the following components:

Authentication, answering the question “who are you?” This is typically handled with a

login requirement (user’s name and password), although more secure systems are

possible. Ideally, a system should be compatible with a centralized login security system,

Figure 2.2.3-A: Typical SCADA Communication Network Configuration

20

preventing the need to visit each device in order to revoke authorization whenever

personnel changes.

Authorization, answering the question “what are you allowed to do?” This dove-tails

with authentication. Again, an ideal system will centralize this authority permitting rapid

revocation of authorization in the event of personnel changes or a security breach.

Accounting, answering the question “who did what?” In essence, this is an audit-trail,

allowing you to see which user performed what operation, and when they did it. This can

be an essential element of understanding an incident after it occurs, or catching it as it

begins.

2.2.5 – Most Efficient Strategy for Designing and Building the Communication System

When considering a SCADA system, there are traditionally two methods that are utilized for

implementation. These methods are:

Design-Bid-Build Method

EFI (Engineer, Furnish and Install) Method

These methods are discussed in more detail Section 2.6 of this document.

21

www.directindustry.com

www.onicon.com

www.watts.com

www.flowmaxx.com

2.3 Hydraulic Sensors

2.3.1 - General Overview of Hydraulic Sensors as Pertinent to Water Distribution Systems

Hydraulic sensors are common place in most modern water distribution systems. By far, the two

most common hydraulic sensors found in a water distribution system are:

Pressure Sensors – A manual read-out pressure sensor is commonly referred to as a

pressure gage. Pressure gages have been around for several centuries

and are proven accurate and reliable. Pressure gages were one of the

first sensors integrated to meet our digital needs. In modern SCADA

systems, pressure sensors are simply pressure gages

that are connected to a 4-20 mAmp analog signal

and calibrated over a specific pressure range. For

example, if you wanted to measure system pressure

on a scale from 0 to 100 psi. One would simply

calibrate the 4 to 20 mAmp signal over the 0 to 100 psi range on the

pressure sensor. This would translate a 4 mAmp signal to a

corresponding pressure of 0 psi, and a 20 mAmp signal to 100 psi.

Similarly, 50 psi would indicate that there was a 10 mAmp signal

in this example. Pressure can be a function of static water

pressure or dynamic pressure. An example of static water pressure is measuring the

water level in a storage tank, and an example of dynamic water pressure is measuring the

water pressure in a water line in the distribution system, in order to monitor transient

pressures or pipe bursts.

Flow Sensors – Methods to measure flow rates have also been around

for many centuries. Some of the earliest methods are

still in use today, such as pitot tubes, venturi systems

that measure differential pressure, microturbins, or

pressure sensitive probes that measure the bending

force on the sensors tip to measure water velocity, and

thus a corresponding flow rate. More modern flow

meters utilize electromagnetics, vortex swirl

measurement, or Coriolis mass measurement

methods. Similar to the pressure sensors, the

output is analog in nature and is calibrated over the 4-20 mAmp signal

to provide a flow output.

2.3.2 – Uses of Hydraulic Sensor Data

For many system applications flow and pressure sensors give an adequate sense of the current

operating conditions of water distribution systems. A properly designed hydraulic monitoring

system can provide valuable information to water system managers that can be used to analyze

current and historical demand, detect pipe bursts, identify illegal connections, optimize system

efficiency, and a variety of other uses. In addition to operations, hydraulic sensors have the

22

capacity to detect unauthorized intrusions and can be a valuable security tool when combined

with the proper software. When used in tandem with a modern SCADA system these sensors

become the eyes and ears of system managers, providing real time actionable information that

can be used to maintain and optimize a water distribution system.

The typical suite of hydraulic sensors includes flow and pressure. These sensors are used in

conjunction with a SCADA system, hydraulic computer model, or both which provides a means

to analyze the real time or forecasted hydraulic parameters within a water distribution system.

The hydraulic sensors connect to an RTU/PLC via hardwire or wireless connection and stream

hydraulic data through the communication network on demand or at set time intervals. This data

ultimately ends up at the HMI and/or SCADA Master where it is presented to the end user for

analysis, or compiled in a historian (database system) where it can be accessed for forecasting

demand patterns, evaluating system efficiency, and analyzing system hydraulic head

deficiencies.

Hydraulic sensor data plays an important role in distribution system management. Uses of the

data include but are not limited to: 1) assure adequate flow of water for supply and fire-fighting

to industries, schools, and other critical users or locations in the system; 2) identify water

turnover in ground and elevated water storage tanks; 3) detect major water loss incidents; 4)

plan hydrant flushing; 5) verify distribution system hydraulic modeling; 6) verify distribution

system water quality modeling; 7) identify distribution system valve problems; 8) provide data

that is used as a component of a contaminant warning system (DWS), 9) provide an

understanding of flows and pressures in the distribution system to analyze water quality issues,

assure adequate fire flows and system pressures, etc.

In a number of situations, it may be of value to have both hydraulic and water quality sensor data

from the same location in the distribution system for decision making. It should be expected that

combining both types of sensors in the same location will be less costly than having two

monitoring stations. Making this decision must be on a case-by-case basis.

2.3.3 – Sensor Equipment Sources

Several sources for hydraulic sensors are:

ABB, abb.com

Ashcroft, ashcroft.com

Holykell, holykell.com

Honeywell, honeywell.com

Keyence, keyence.com

Truck, truck-usa.com

23

This is a brief list of manufacturers. A more complete list is included in Appendix A.

2.3.4 – Most Efficient Strategy for Obtaining Hydraulic Sensors

When considering a SCADA system, there are traditionally two methods that are utilized for

implementation. These methods are:

Design-Bid-Build Method, described in section 2.1.3.A

EFI (Engineer, Furnish and Install) Method, described in section 2.1.3.B

These methods are discussed in more detail Section 2.6 of this document.

2.3.5 – Hydraulic Sensors Costs and Specifications

A variety of cost components are involved in the installed cost of sensors in a distribution

system. These include land purchase, construction of the vault in which the sensors and

connections to the distribution piping will be located, installation of the sensor, supplying power

to the site, installing the communications equipment, and upgrading/installing equipment at the

central control room (Berry 2005). Other costs include design and bidding the construction and

installation work, access to the site, and security fencing and lighting. Obviously, the more

remote and/or less accessible the location of the sensors, the higher the installed costs will be.

Combining hydraulic and water quality sensors in the same locations should yield lower installed

costs for all the sensors in the system. However, the efficacy of combined installations with

respect to the management, operations, and/or future design decisions needs to be considered.

The authors’ collective experience has shown that some distribution systems have long-standing

water quality problems associated with excess water residence time in some areas in distribution

systems that are a considerable distance from the water treatment. This is especially true of

water supplies that purchase their treated water from other utilities. Because the sensors

themselves are such a small portion of the total installed costs, it appears to be prudent to

optimize the number of locations by carefully deciding the combinations of sensors at each RTU.

Pricing surveys conducted at the time of this report showed as much as two orders of magnitude

cost differences on sensor that appear to be equivalent in nature. Determination of value

(relative to price) is a process that you should rely on your design consultant to help you with.

However, some considerations to try to stay aware of include:

Product customer service and technical support: Customer service is a series of activities

designed to enhance the level of customer satisfaction – that is, the feeling that a product

24

or service has met the customer expectation. Customer service includes providing

technical support in an easy to understand and effective manner.

Warranty: No piece of hardware can be warrantied forever. However, the longer the

warranty the better the indication that the sensor is made from quality materials and

quality components.

Sensor replacement availability: This is an important question that needs to be

considered. If the sensor you plan to install in your system is not readily available, then

perhaps a different sensor or manufacturer should be considered.

Ease of maintenance and testing: A water system operator understands that all equipment

needs to be regularly maintained and/or tested needs to be easily accessible. However,

not all equipment manufacturers understand that the equipment being maintained and/or

tested equally needs to be operator-friendly. Be sure to take into account how easily

regular maintenance and testing can be performed on the sensor.

Compatibility with the rest of the SCADA system: If you have an existing system, new

sensor compatibility is an absolute requirement, or else you are essentially buying a new

stand-alone piece of equipment.

The cost of the sensors is frequently a very small portion of the cost of the sensor installation.

(Berry et al, 2005) Site specific installation cost projections need to be developed. Typical cost

components that will be included in the total cost of a sensor installation at each potential

location.

Land purchase

Construction of the vault in which the sensors and connections to the distribution piping

will be located

Installation of the sensors and RTU

Supplying power to the site

Installing the communications equipment and upgrading/installing equipment at the

central control room

Design and bidding the construction and installation work

Access to site

Security fencing and lighting

There are two generic types of SCADA and sensor specifications. These are the Use

Requirements Specification and the Detailed Technical Specification type. Either type of

specifications should include a complete explanation of the intended uses of the sensor data, and

details of existing SCADA components (system architecture) with which the sensor system will

must be integrated, and require operator training associated with the sensors and sensor data

management.

The Use Requirement Specification identifies the data to be sensed and the uses of the data. It

leaves the technical details up to the suppliers and contractors. In general, this type of

25

specification takes less time and cost to develop that the Detailed Technical Specification. It

may also allow greater competition from bidders. However, it does reduce the ability of the

Utility to control who bids on the project, if that is of interest for any reason.

The Detailed Technical Specification includes detailed specifications for each item in the system

to be constructed/installed. The specifications are usually provided by the supplier who assists

the designer in the design of the sensor system. Detailed specifications are often used to reduce

the number of bidders, or to try to exclude certain products, types of products, or bidders.

However, when federal funds are used to pay a portion of the cost of the

construction/installation, these specifications are required to include multiple supplier names

and/or an “or equal” statement. A potential pitfall to using a Detailed Technical Specification is

not including the specification for one or more of the components of the system.

Technical specifications and costs are impacted by 1. measurement sensitivity, 2. monitoring

range, 3. measurement accuracy, 4. measurement response time, 5. measurement interferences, 6.

installation location restrictions (e.g., turbulence interference), 7. routine maintenance required,

8. sensor life expectancy, 9. calibration methods and frequency, 10. materials of construction, 11.

installation methods, and 12. other technical requirements that are based on the experience of the

distribution system SCADA technical experts. This information should be included in either the

Use Requirement Specification or the Detailed Technical Specification.

26

2.4 Water Quality Sensors

2.4.1 - Overview of Water Quality Sensors as Pertinent to Water Distribution Systems

There is a variety of reasons to employ water quality sensors in water distribution systems.

Contamination by cross-connections with non-potable water, contaminated water entering the

distribution system through leaking pipes in area of low pressure, or microbial growth in the

distribution system pipes is always a management concern (EPA 817-R-07-002). Nationally

recognized water security experts have identified distribution systems as very vulnerable to

attack because of the physical characteristics of the piping systems and the lack of monitoring

and surveillance of the systems (WaterSentinal). Identifiable threats or indications of possible

contamination is a management concern (EPA 817-R-07-002).

Water quality sensor data is used for decision-making on a variety of management issues. These

include but are not limited to: 1) identifying compliance with regulatory water quality

requirements; 2) identifying non-regulatory water quality for critical users (e.g., at industries

requiring certain process water chemistry) and at other important locations throughout the

system; 3) verifying water quality modeling; 4) planning hydrant flushing; and 5) implementing

a contamination warning system (CWS).

A CWS is a proactive operation to generate distribution systems water quality data and combine

that with a variety of other information to continuously monitor for the presence of unexpected

contaminants in the system (Contamination Warning System CIPAC 2012). The intent of a

CWS is to minimize the number of people who are negatively impacted by a contamination

event in a distribution system. The location of the sensors for a CWS is critical to accomplishing

a minimizing of people impacted. A number of computer programs exists that are used to

optimize the location of water quality sensors for a CWS. WaterSentinel is a federal program to

advance the knowledge and use of CWS in water utilities ( see

http://water.epa.gov/infrastructure/watersecurity/index.cfm). Threat Ensemble Vulnerability

Assessment Sensor Placement Optimization Tool (TEVA SPOT) is software that optimizes the

locations of water quality sensors in a distribution system when they are to be used as

components of a CWS (see https://software.sandia.gov/trac/spot).

The chemical, physical and biological conditions of water combined form its quality. Even

minute changes in these characteristics can impact the people and industries that depend on

water. To preserve its quality, monitoring water parameters such as conductivity, pH, salinity,

temperature, dissolved oxygen, chlorine residual and turbidity is crucial. For the same reason,

water quality sensors have become common in most modern distribution systems.

Water quality sensors are employed using one of two main approaches. They are either used to

directly measure constituents of interest (chemical concentrations, solids, etc.) in the water, or tp

measure surrogates. Surrogates are chemical concentrations or solids that may indicate the

presence of unanticipated contaminants in the water.

27

www.veoliawaterst.com

www.geinstruments.com

www.directindustry.com

www2.emmersonprocess.com

Many types of water quality sensors are available in market based on what one wants to measure,

below is the list of most common ones in use and some of their details.

Chlorine Residual Sensor - Measuring chlorine residual in drinking water treatment

plant and distribution systems is a common process and has been necessary as long

as chlorine has been used in water treatment. Chlorine is the most widely used

disinfectant which can be attributed to its efficiency and economical aspects.

Chlorine sensors measure free chlorine, monochloramine, and total chlorine. The

primary application is drinking water disinfection, although total chlorine is often

measured in treated wastewater, including reclaimed wastewater.

TOC Sensor - Total Organic Carbon (TOC) is an important parameter for water

quality analysis. It is used as a direct indicator and a surrogate for many

water quality purposes. There are two different TOC measurements

devices available in the market: TOC analyzers and TOC sensors. If the

intended TOC device use is for regulatory reporting, managing an

important process control variable, real-time release, or other critical-to-

quality product attributes, instrument accuracy is essential. If the intended

use is for general TOC monitoring—not for making critical quality

decisions—then other characteristics may be more important than

accuracy. Sensors are typically used to monitor a process and the data

collected from them is used for information only.

Turbidity Sensor - Turbidity sensors measure suspended solids in water, typically by measuring

the amount of light transmitted through the water. They are used in river and stream gaging,

wastewater and effluent measurement, drinking water treatment process and control, control

instrumentation for settling ponds, sediment transport research, and laboratory measurements.

Conductivity Sensor -Conductivity measurements are carried out in industrial processes

primarily to obtain information on total ionic concentrations (e.g. dissolved compounds)

in aqueous solutions. Widely used applications are water purification, clean in place

(CIP) control, and the measurement of concentration levels in solutions. The measuring

system consists of an appropriate inline sensor directly inserted or in a housing, a cable

connected to a transmitter converting the received signals to a measurement result or

forwarding it to a DCS

pH Sensor - In the process world, pH is an important parameter to be measured

and controlled. The pH of a solution indicates how acidic or basic (alkaline) it is.

pH sensor components are usually combined into one device called a combination

pH electrode. The measuring electrode is frequently glass and quite fragile. Recent developments

have replaced the glass with more durable solid-state sensors. The analyzer or

transmitter has a man machine interface for calibrating the sensor and

configuring outputs and alarms, if pH control is being done.

ORP Sensor - ORP sensors measure the Oxygen-Reduction Potential of a

solution. Used in tandem with a pH sensor, the ORP measurement provides

28

insight into the level of oxidation/reduction reactions occurring in the solution. The ORP Sensor

requires a compatible interface and software to collect data.

For many system applications these sensors provide indication of water quality conditions of

water distribution systems. A properly designed water quality monitoring system can provide

valuable information to operators and engineers that can be used to calibrate their hydraulic

models, predict formation of regulated substances, provide compliance data and track the change

in quality over time which in turn helps system operators make important decisions about water

treatment unit processes and operational conditions. When used in tandem with a modern

SCADA system these sensors become eyes and ears of system operators, providing real time

actionable information that can be used to maintain and optimize the water quality in distribution

systems.

2.4.2 - Sensor Equipment Sources

Several sources of water quality sensors are

ABB, abb.com

GE, ge.com

Hach, hach.com

Siemens, siemens.com

Emerson, emersonprocess.com

Yokogawa, yokogawa.com/us

This is a brief list of manufacturers. A more complete list is included in Appendix A.

2.4.3 - Most Efficient Strategy for Obtaining Water Quality Sensors

NOTE: Information in 2.6.3 is generally a repeat of section 2.1.3, but is kept in tack within this

section to maintain the effort to make each section stand alone.

When considering a SCADA system, there are traditionally two methods that are utilized for

implementation. These methods are:

Design-Bid-Build Method

EFI (Engineer, Furnish and Install) Method

These methods are discussed in more detail Section 2.6 of this document.

2.4.4 - Water Quality Sensors Costs and Specifications

29

Site specific installation cost projections need to be developed. Typical cost components that

will be included in the total cost of a sensor installation at each potential location.

Land purchase

Construction of the vault in which the sensors and connections to the distribution piping

will be located

Installation of the sensors and RTU

Supplying power to the site

Installing the communications equipment and upgrading/installing equipment at the

central control room

Design and bidding the construction and installation work

Access to site

Security fencing and lighting

There are two generic types of SCADA and sensor specifications. These are the Use

Requirements Specification and the Detailed Technical Specification type. Either type of

specifications should include a complete explanation of the intended uses of the sensor data, and

details of an existing SCADA components (system architecture) with which the sensor system

will must be integrated, and require operator training associated with the sensors and sensor data

management.

The Use Requirement Specification identifies the data to be sensed and the uses of the data. It

leaves the technical details up to the suppliers and contractors. In general, this type of

specifications takes less time and cost to develop that the Detailed Technical Specification. It

may also allow greater competition from bidders. However, it does reduce the ability of the

Utility to control who bids on the project, if that is of interest for any reason.

The Detailed Technical Specification includes detailed specifications for each item in the system

to be constructed/installed. The specifications are usually provided by the supplier who assists

the designer in the design of the sensor system. Detailed specifications are often used to reduce

the number of bidders, or to try to exclude certain products, types of products, or bidders.

However, when federal funds are used to pay a portion of the cost of the

construction/installation, these specifications are required to include multiple supplier names

and/or an “or equal” statement. A potential pitfall to using a Detailed Technical Specification is

not including the specification for one or more of the components of the system.

Technical specifications and costs are impacted by 1. measurement sensitivity, 2. monitoring

range, 3. measurement accuracy, 4. measurement response time, 5. measurement interferences, 6.

installation location restrictions (e.g., turbulence interference), 7. routine maintenance required,

8. sensor life expectancy, 9. calibration methods and frequency, 10. materials of construction, 11.

30

installation methods, and 12. other technical requirements that are based on the experience of the

distribution system SCADA technical experts. This information should be included in either the

Use Requirement Specification or the Detailed Technical Specification.

31

2.5 – Hydraulic and Water Quality Sensor Placement

Determining locations where either hydraulic and water quality sensors should be installed

should be driven by exactly what information is needed about the distribution system. For

example, if all that is needed is the water level in an elevated storage tank, then obviously

placing a pressure sensor at or near the base of the tower is probably the logical choice.

However, the placement choices become very complicated when the most logical option is not

economical or a physically optimal option. The remoteness of the location and access to such

facilities sometimes pose questions that are hard to answer. The use of computer modeling for

sensor placement is increasing. The USEPA model Threat Ensemble Vulnerability Assessment-

Sensor Placement Optimization Tool (TEVA-SPOT) is one such computer tool available to assist

in sensor location decisions. Hart and Murray (2010) reported on three sensor placement

strategies that are being applied for deployment of DWS: expert opinion, ranking methods, and

optimization (computer modeling). Berry, et al, (2005) reports that tests of the use of sensor

placement modeling and the decisions made by local experts in a water supply system “…

suggest that a collaboration between modelers and those with practical water system expertise

can improve the effectiveness of sensor placement decisions”. Programs like TEVA-SPOT can

assist in finding optimal locations for each sensor in a distribution system for use as a component

of a drinking water system, while the operators and/or managers need to decide which among the

potential alternative locations are optimal to place the sensor for their purposes.

The placement choices can become very complicated if the purpose of the sensor is to determine

model inputs for a hydraulic model, or if the goal is to monitor for maliciously injected

contaminants, which is termed a contaminant warning system (CWS) or detect pipe bursts and

other leakage. (Mounce, S. et. al., 2003 and 2006), (Berry, J. et. al., 2005) Hydraulic sensors are

very useful for modeling water quality in a distribution system, by monitoring flows, and thus

residence times in the system. This use of hydraulic data also has direct application to regulatory

compliance.

Berry, J, et al (2005) identified placement cost budget, contamination public health impacts, and

potential attack scenarios as considerations in sensor placement. The Public Health Security and

Bioterrorism Preparedness and Response Act of 2002 identified physical security of water supply

distribution systems as a major priority for water utilities. So, in addition to combining hydraulic

and water quality sensors in the same location, consideration of the value of data from these

sensors at locations of security sensing (e.g. water storage towers, basins, and pump stations)

may be worthwhile.

SCADA sensor placement decisions made without the use of computer models are frequently

based on the experience of the decision-maker and his/her support group’s experiences.

Following is a list of sensor placement design issues provided in a sequence used by the authors

(Mounce, S. et. al., 2003 and 2006), (Berry, J. et. al., 2005) in the design of SCADA systems.

32

SCADA Sensor Placement Decision-Making Sequence

1. Intended uses of data

A. hydraulic and water quality monitoring

B. security monitoring

C. energy management

D. equipment management including repair and replacement forecasting

E. sub-metering utility usage

F. identifying alarm conditions

G. verifying hydraulic or water quality modeling

H. provide data as a component of a CWS

2. Parameters of interest & to be monitored

3. Locations/areas for which data is desired

A. areas or location of major public health impacts from contamination (schools, health

care facilities, food preparation, elderly living centers, etc.)

B. potential contamination attack scenarios and locations based on physical

characteristics of distribution system

C. areas of known poor water quality in distribution system based on complaints, etcetera

D. locations of regulatory agency required compliance sampling

4. Locations of other types of sensors currently in distribution system

5. Potential locations of other (security, water quality, etc.) sensors to be added to the system

6. Potential locations based on the above

7. Security & accessibility of potential sensor sites

8. Cost components (relative costs) by location

9. Sensor station design & construction budget available

10. Final sensor placement locations

If a water system SCADA is being planned, sensor placement computer programs (e.g., TEVA

SPOT) are available to optimize the locations of the sensors to minimize the impacts of a

contamination incident. To use one of these programs, complete, accurate and calibrated

33

hydraulic and water quality models of the distribution system are necessary to provide inputs to

the sensor placement program. Following is a list of the information/data needed from the

system operators and/or managers for input to these programs.

SCADA CWS Sensor Placement Optimization Program Inputs

1. Complete and calibrated hydraulic and water quality distribution system models.

2. Simulation time – the length of time (number of hours) the program run should simulate.

3. Time of release – the length of time a contaminant is injected into the distribution system.

4. Mass injection rate (mg/min) – the amount of contaminant that is injected into the distribution

system per unit time.

5. Contaminant – the contaminant(s) that may be injected into the system.

6. Response time delay – the time between initial detecti9on of a contaminant in the distribution

system and when public warnings are issued.

7. Detection limit – some level of contaminant concentration below the health impact level of a n

injected contaminant; this must be in the range between the upper and lower detection limits of

the sensors.

8. Impact metrics – any of a variety of impacts can be used: the number of people ingesting the

contaminant, length of distribution system piping that is contaminated, number of people with

health effects from the contaminant, etcetera.

9. Sensor placement objective - any of a variety of objectives for the placement of sensors can be

used: minimize the number of public health impacts, minimize the extent of distribution system

contamination, etcetera.

34

2.6 Strategies for developing Data Acquisition and SCADA Systems

2.6.1 - Design/Bid/Build Project Delivery Method

As the name implies, this implementation method consists of three distinct project phases; the

design phase, the bid phase and the build phase. This method of project delivery is most

common in utility and other public sector projects. The owner will typically be dealing with at

least two persons or companies to deliver their completed SCADA system, but sometimes many

more than two. There will always be an engineer or other design professional involved.

Depending on if the owner decides to direct purchase the necessary equipment or let the

contractor be responsible for equipment purchases as part of the contract, there can be either one

or more additional entities that the owner will need to engage.

The design-bid-build method requires a set of plans and specifications to be created by an

engineer or other design professional. Traditionally, these plans and specifications contain every

detail of the proposed project, from what kind of SCADA Master, to exact communications

network specifications, to which general types of RTUs, PLCs, to power supplies, to which

equipment sensors and controls will be installed and even where the sensors will be installed on

the specific piece of equipment. This means that the designer needs to finalize every detail of the

project before the project is put out for bids. After these detailed plans and specifications are

completed, the owner chooses one of two routes: either purchasing all the equipment directly,

then receiving multiple, qualified bids for installation (Figure 2.6.1-A), or more simply (and

typically) receives bids from multiple, qualified contractors that include the equipment and the

installation (Figure 2.6.1-B). Once the project is complete the owner must pay the contractor the

bid amount, plus or minus the net amount of contract change orders. After the owner signs a

contract for a bid-build project, they have minimal input in the remaining part of the project,

unless there are any unforeseen obstacles or problems. These often result in “change orders”,

which tend to be costly and all parties try to avoid. Changes to the system can be made after

project completion, but usually at a higher cost.

Engage a

qualified

engineer or

design

professional

Begin the

design process

for complete

set of plans and

specs

Owner

purchases

equipment

specified in

plans and specs

Obtain bids from

multiple qualified

contractors to

install purchased

equipment

Engage a

contractor

to complete

project

Figure 2.6.1-A – Design-Bid-Build, Owner Equipment Purchase

35

A small twist on the design-bid-build project delivery method is something known as issuing a

“performance specification” (Figure 2.6.1-C). This method accomplishes the same end goal but

in this case the engineer simply issues a ultimate project goal to be met. The engineer can even

require certain equipment, but no detailed plans or specifications are produced in this process,

thus transferring much of the project risk to the prospective contractor to deliver the required

final product. Performance specification projects, though convenient for the design professional,

often produce higher bids because the contractor understands the risk of project success has been

transferred to them as the contractor and away from the design professional. It is much less

probable to realize any change orders in a performance spec type of design-bid-build project,

unless the conditions change or the owner initiates the change.

2.6.2 - Engineering, Furnishing, and Installation (EFI) Project Delivery Method

An EFI is a person or company that provides engineering, furnishes necessary equipment,

installs all equipment and commissions the system. Depending on where you are in the nation,

some companies use the term “design-build” instead of EFI. Compared to the design-bid-build

method, where the owner usually only has input in the design phase of the project, the EFI

method combines the engineer, equipment furnisher, and installer into one entity and shifts the

involvement of the owner to the entire life of the SCADA implementation project. Most major

decisions about the system are made up-front, so that a project budget price can be established;

however, many more decisions are made as the project proceeds, so that the final project is able

to perform the best that it can.

While the owner may have more control over their project in an EFI project delivery method,

they will need to devote more time to the project during the building/implementation processes

and have more opportunity to become very involved with the project. Many of the minor

decisions will be made later in the implementation process and only when they are needed. The

Engage a

qualified

engineer or

design

professional

Begin the

design process

for complete

set of plans and

specs

Obtain bids from

multiple qualified

contractors to build

project per plans and

specs

Engage a

contractor to

complete

project

Figure 2.6.1-B – Design-Bid-Build, Typical

Engage a

qualified

engineer or

design

professional

Produce a

“performance

specification”

design

Obtain bids from

multiple qualified

contractors to build

project per performance

spec

Engage a

contractor to

complete

project

Figure 2.6.1-C – Design-Bid-Build, Performance Specification

36

biggest advantage with the EFI project delivery process is the overall simplicity (Figure 2.6.2-A)

and flexibility to change a certain aspect of a project, which helps when you are entering a

project with little certainty of your expectations. In this form of project execution, the owner and

the contractor work together to reach a desired end result and projects are usually paid by a cost-

plus method, where the owner pays for the cost of the project with the addition of profit and

overhead to the contractor. Other arrangements such as fixed-cost are also common, but in an

EFI method, contractors will try to avoid that arrangement because too much risk is assigned to

the contractor.

Figure 2.6.2-A portrays the EFI method as a simple, one-step process. This is may or may not

necessarily be the case, but compared to the previous examples, the EFI method is indeed more

simplistic. There are certain cautions that the owner should be aware of, the first being that the

EFI method may not be allowed by certain state or federal agencies, if their funding is involved

in the project. This is simply because granting or loaning agencies may require competitive bids

as a requirement of the use of their funds. Although and EFI project delivery method can be set

up to be competed on by multiple EFIs in a competitive manner, it is very difficult to arrange this

because unlike the design-bid-build delivery method, the final scope of work and product is not

exactly known before the bid process occurs.

There are distinct advantages to each delivery process and you should take time to educate

yourself on the pros and cons of each before you select your method of choice.

2.6.3 – Considerations for Potential Equipment Suppliers, Engineers and Contractors

Very often, the owner will have an existing relationship with an engineering or design

consultant. This person/company may actually have the in-house talent necessary to design the

entire SCADA system to meet your needs. If they do not have the necessary talent in-house,

then they probably have a relationship with a fellow consultant/company that does that the

necessary skill sets and capacity.

Designing a practical and reliable SCADA system requires a great deal of expertise and time.

There's physical installation, power supplies, communications network, network connections,

and then the even more difficult phases of configuration and data basing. It can be a daunting

task, especially for most engineers that do not necessarily specialize in these projects. It is very

important that the design professional you select has the depth of expertise necessary for the job.

Engage a qualified EFI

to complete project

Figure 2.6.2-A – EFI Project Delivery

37

Below are several items that should be considered before you decide on a specific engineer or

design professional:

Quality Standard Certifications: Many engineers, design professionals, and equipment

manufacturers adhere to procedures certified by industry standards organizations, such as

ISO 9000 or the telecommunications-specific TL 9000 standard.

Experience and Client Testimonials: As with any business-to-business professional

service, you should check carefully for your engineer’s or design professional's

reputation. Find out how long they or their company has been in business, see if it can

offer testimonials from its clients-and check with their clients to get a real sense of how

they rate the company's services.

Vendor Partnerships: Depending on your situation, pre-existing vendor partnerships may

or may not be of concern to you. However, you as the owner need to be aware of any

existing partnerships so you can be aware that you may be “driven” to a certain platform

or product line. Just because you are outsourcing the project design, you should still

retain control. Check what vendors your engineer prefers or works with. You should be

still able to specify the vendor and equipment you want.

Compare Prices, But Don't Be Cheap: The costs of using an engineer or design

professional is usually justified by quality of the plans and specifications. The quality of

the plans and specs is measured by the number of change orders and if the final SCADA

system performs as intended. By all means, look for the best value, but always keep

quality just as high on your list.

If you elect to pursue the SCADA project using the EFI delivery method, many of these same

criteria can be used, but keep in mind that although EFIs will have a broad knowledge base, they

will very likely maintain only a few vendor partnerships and those partnership will be much of

their expertise is focused around. This being said, below are some additional values that an EFI

will bring to the SCADA project.

Product Knowledge: You as the owner may already know quite a bit about the equipment

you use, but you haven't had the time to research everything about it. And when you're

adding new types of equipment to your system, you can never be quite sure how your old

and new equipment will work together. You can turn to old equipment vendors for

assistance, but while they can tell you a lot about their own equipment, they likely will

not know how their older equipment may interact with equipment from other

manufacturers. EFIs usually have broad knowledge of different types of equipment used

throughout the industry, and they have deep experience of integrating different equipment

during installation. That experience and expertise is difficult to reproduce or obtain

elsewhere.

Outsourcing Time and Trouble: You may have been given the responsibility for a system

deployment, but that doesn't mean you have the time, the resources, or the staff to

oversee every detail of the project-especially if managing the deployment is an extra job

that's been added to your everyday duties. If this is your situation, you may have a

classic business case where outsourcing the work will get the job done faster, more

38

efficiently, and even less expensively than trying to do the work entirely in-house or with

a traditional design-bid-build method.

Project Management: Deployments often take longer than planned, especially if you're

working with new equipment. There's a lot you have to learn to execute a successful

implementation, and it's easy to make beginner's mistakes that can extend your time and

budget. The project management experience of an EFI provider can be of real value here.

These are companies with years of experience overseeing telemetry deployments, and

they have highly developed systems for ensuring projects are completed on schedule and

as planned.

So, does this added value justify using an EFI provider for your project? Before you decide yes

or no, ask yourself these questions:

1. Does the deployment project require extra training for your installation technicians?

2. Do you have the time to manage the entire project yourself?

3. Do you have the experience to anticipate and prevent problems and delays with your

implementation?

4. If an EFI project delivery cannot meet your schedule or quality requirements, cheaper and

faster is not necessarily better.

5. Do you have an established data management plan, or does this need to be part of the

overall project?

6. Do you have ability to analyze the data acquired by the SCADA system?

7. Do you have a plan or the ability to use the new data in an intelligent manner in order to

perform advanced planning and management in your system?

39

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42

Appendix A - Listing of Water Related Sensor Manufacturers 2012

ABB

Eureka Environmental

Engineering Mena Water

ADS Environmental Service Eutech* Meter Master

Advanced Measurements &

Controls GE METTLER TOLEDO

Anacon Georg Fischer multitrode

Analytical Sensors &

Instruments Ltd

Global Water

Instrumentation, Inc. Oakton Instruments

Analytical Technology Hach OI Analytical

AquaMetrix Hanna Instruments Omega Engineering, Inc.

Arjay Engineering HF Scientific Process Instruments (Pi)

ASA Analytics Honeywell ProViro Instrumentation

Banner Engineering Horiba Real Tech

BeLink Icx Technologies (FLIR) RMS Water Treatment

Cambell Scientific In USA Inc. Rosemount*

Chemical Injection

Technologies, Inc. (Superior) Inficon Scan Measurement Systems

Cole-Parmer Innovative Components Severn Trent Services

Control Micro Systems Innovative Waters Siemens

Datalink Instruments In-Situ Inc Stedham Electronics

DEVAR Inc. Invensys

Stevens Water Monitoring

Systems, Inc

EMEC Liquid Control Systems Itron Thermo Scientific

Emerson ITT Water and Wastewater Vega Controls

Endress + Hauser JMAR Wedgewood Analytical

Entech Design Keco Engineered Controls YSI

Environment SA