CLEARWATERS: Telemetering in New York

The New York City collection system consists of fourteen water pollution treatment plants and ninety pumping stations located in five boroughs. The City's average dry weather flow is 1.27 billion gal/day. Any failure in a pumping station causes sewage to back up, potentially floods neighborhood basements and streets, and may generate bypasses. For that reason, NYCDEP makes every effort to keep all pumping stations in good working condition all the time. Telemetry is an excellent way to provide the collection operators with continuous monitoring for all the pumping stations.

See a map showing the pumping stations and POTWs throughout New York City (new window opens).

What is telemetry?

Telemetry is a network of hardware that, when interconnected (by radio, dial-up telephone lines, or any other communication medium), forms a system that allows an operator to receive alarms from any field device, directly connect to any field location, and review historical data for the various signals that are brought into the system.

Since September 1998, all eighty-nine pumping stations in New York City can be monitored using desk-top computers. Operators, supervisors, and managers can call any pumping station and see what is going on in that station. If an alarm condition arises in any pumping station, the computerized controller in that station will call and post an alarm notice to the crew quarters of the involved collection facilities. The system allows an operator to:

Components

The NYCDEP pumping station Telemetering System consists of a network of hardware that is interconnected by ordinary dial-up telephone lines.

VAX computer

A VAX computer is the heart of the Pumping Station Telemetering System. This computer system consist of redundant Microvax 4000/60 mini-computers manufactured by the Digital Equipment Corporation, connected to thirty-six voice-grade dial-up telephone modems. The VAX Computer also archives all data collected by the system. The thirty-six telephone modems that are connected to the VAX are its link with the outside world. Through these lines, remotely located personal computers running special software can dial-up, connect to the VAX and access its information. Remote Terminal Units (RTUs) located in each of the ninety pumping stations can also access the VAX by telephone lines to transfer real-time or historical data.

Work station computers

Operators around the City use twelve computers to access the system. Each location is supplied with a color printer to print alarms and reports. Each computer and printer communicates independently with the VAX. This allows an operator to turn off the computer when not in use, leaving only the printer turned on. If an alarm is generated during this time, the printer will be called by the VAX, and an alarm message will be printed.

Remote terminal unit

Each pumping station is equipped with a small computer, referred to as an RTU. Each RTU is hard-wired to various devices in the pumping station. This microprocessor-based RTU communicates by a dial-up telephone line to the VAX. The RTU automatically dials the host computer every 24 hr to download historical data. The RTU also dials the host computer whenever an alarm occurs.

Points to be monitored

Monitoring devices

To gather the data that is necessary to permit operators to make intelligent decisions, several devices are used to sense, collect, and transmit information:

Pressure transducer This device measures force main pressure and transmits the reading to the RTU. When high pressure is found, the RTU will dial the host computer system, and an alarm will register at the appropriate crew headquarters.

Current transducer measures pump motor current and transmits the reading to the RTU. When it senses high current, the RTU dials the host computer system and registers an alarm.

Differential pressure transmitter also measures level in the wetwell and transmits the reading to the RTU where a bubbler-type level-control system is installed. When the wetwell is high or low, the RTU dials the host computer system, and an alarm is registered at the appropriate crew quarters.

Ultrasonic level transmitter measures level in the wetwell and transmits the reading to the RTU. When the wetwell is high or low the RTU dials the host computer system, and an alarm is registered at the appropriate crew quarters.

Feeder power monitor monitors the incoming power to the pumping station and communicates to the RTU. If the power fails, the battery-backed RTU dials the host computer system, and an alarm is registered at the appropriate crew quarters.

Relay and limit switches monitor the run status of pumps and the position of the sluice gates and valves.

Level switches send an alarm to the RTU if flooding occurs in the pumping station dry well.

Pressure switches measures pressure in the potable water supply line.

Vandal alarm switch sends an alarm to the RTU should a break-in to the station occur. The RTU dials the host computer system.

Upgrading the system

In the next upgrade to this project, which is currently in the registration process, control may be added to the monitoring capabilities. State-of-the-art technology is making control more and more reliable. More points can be added to those currently monitored. Other locations maintained by the same operator group (regulators) may be included. Faster telecommunication media will be employed to augment the dial-up telephone lines.

Results

This great tool—telemetry—is being successfully used by the collection facilities. From the computers in the crew quarters, operators monitor what is happening at any pumping station. When operators received an alarm, they can check it, and mobilize forces more effectively to respond to the problem. The telemetry system is saving time, resources, and money.

The response time to the dry weather bypass events had been reduced dramatically. For fiscal year 2000 the total dry weather bypass from all eighty-nine stations was 0.0056% of the total dry weather flow treated by the New York City treatment plants (see table).

Summary: fiscal year bypass comparison

Fiscal year	Events	Total Bypass (million gal)	Duration (hr)
1991	41	68.93	829.44
1992	44	59.27	948.05
1993	48	43.92	3976.05
1994	65	33.66	2070.95
1995	44	62.53	423.07
1996	52	35.20	412.00
1997	40	40.00	986.00
1998	30	22.87	844.11
1999	11	8.22	65.54
2000	26	25.74	72.57

Every time a pumping station failure or partial failure is avoided, a number of New York City residents and or streets are saved from being flooded by wastewater. Keeping ninety pumping stations under continuous surveillance in a city as large as New York is a formidable task. Not only do crews have to perform the surveillance every day but they also must respond to problems promptly as they arise. Having a telemetry system helps automate the surveillance part of the crews' work and has helped to make a substantial reduction in the volume of wastewater bypassed.
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Stella Rozelman, PE (phone 718-595-4864) and Shawky Aziz, PE are with Collection Facilities Planning, Analysis and Engineering in the Bureau of Wastewater Treatment, New York City Department of Environmental Protection.