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A radio repeater is air-lifted to Cat Mountain in a Pima County. Repeaters include the pole, enclosure, solar panel, regulator, battery, cabling, and antenna. Photo: Richard Sloan.
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    Identifying alarm conditionsWastewater plant operators are notified of a blockage after seven consecutive violations sound. Source: Richard Sloan

In addition to the hardware costs above, plan on:

  • Internal and external development costs (engineering, programming, etc.)
  • Budgeting long term for repair/ replacement cost of components
  • Budgeting and training for on-call personnel to screen alarms prior to dispatching field crews
  • Funding and training a dedicated crew to maintain components.

With an initial cost of $350,000 ($100,000 from the capital and operations and maintenance budgets funds the system's annual operation), the system's total cost is expected to top out at $1.2 million.

Remote conversations

Hardware and software work together to gather and transmit data.

Because Pima County's Wastewater Management Department is one-third of the way through its program to implement systemwide remote monitoring, it's continually installing new equipment. To ensure resident buy-in, the department notifies home owners of when they'll be on their property and how the system works.

The remote equipment is solar-powered and communicates via unlicensed 900 MHz spread spectrum radios. Fast Ethernet TCP/IP maximizes bandwidth and enhances security over the communication link.

The only remote equipment that can't be easily shown to residents is the actual metering equipment, which is placed in the sewer pipe below grade. Radio repeaters are needed whenever the distance between radios exceeds 25 miles or line-of-sight requirements between them are interrupted. In large metropolitan areas with many buildings, you may not be able to use this system with the 900 MHz radio since line-of-sight may be limited.

By the time its system is fully installed, Pima County could have more than 100 monitoring locations, though that target number will increase as its population continues to grow.

— Sloan is a licensed chemical engineer based in Oro Valley, Ariz.