Updating 89,000 meters across a large service area with extremely variable terrain i isn’t a simple task.

The City of Scottsdale, Arizona’s municipal water utility, Scottsdale Water, is working hard to get its automated metering system program on track for success. The program needs to select meters that work effectively, provide predictable savings and ensure that meter-reading staff can make the transition, says Ken Rock, water distribution manager.

In the desert, water conservation is critical. The city relies on multiple water sources, including 27 groundwater wells and three sources of surface water: the Verde and Salt rivers, and the Central Arizona Project, which diverts water from the Colorado River. The city also injects advanced treated wastewater into recharge wells to bolster groundwater. The city’s 23 golf courses are supplied with raw and recycled water.

Customers depend on more than 2,100 miles of pipe ranging from 6 to 66 inches in diameter. The system is relatively young, with the majority of pipes less than 40 years old.
Transmission mains are most commonly made of steel-reinforced concrete, which holds up against corrosive desert soils. The oldest distribution pipe is cast iron, while newer sections are made of PVC, asbestos cement and ductile iron.

“A lot of pipe went in during the early 2000s, when the city was growing fast,” Rock says. “Bedding issues, not quality of pipe, is probably our biggest source of failures. Ductile is our preferred pipe replacement material. Properly bedded, it has lots of structural integrity. We protect it on the outside with poly bags and keep our Langelier index slightly positive so we don’t have internal corrosion.”

A youthful water system

Rock rates Scottsdale among the top 2 percent of cities for pipe condition. The city fields an active pipe replacement program, allocating $10 to $15 million per year to the most problematic areas, including the oldest cast iron pipes and failed PVC installations. The utility also targets pipes located on easements along the backs of properties.

“Servicing those pipes and meters can range from problematic to nearly impossible,” Rock says. “We move those pipes from back easements to street easements.”

Pipe replacement projects are generally designed or reviewed in-house, but completed by outside contractors. Leak repair is handled by in-house repair crews.

Scottsdale’s size and terrain are another challenge.

“Covering 185 square miles is a lot for a city of 220,000,” Rock says. “Our lowest customer is at 1,188 feet above sea level, while the highest customers are more than half a mile higher. That results in 146 hydraulic grade levels, 18 pressure zones, more than 700 pressure-reducing valves, 48,000 main valves and 11,000 hydrants. Even exercising the valves every three years according to our program is a challenge.”

Automated savings

Automating the meter reading system across the entire city is part of an effort to seek economy while improving function. The utility has considered three types of technology:

• Automated meter reading (AMR) for drive-by reading service — extra costs associated with AMR include a wired register and encoder-receiver-transmitter (ERT). It generally employs the same utility box lid.
• Advanced metering infrastructure (AMI) — information is received at home base, so no meter readers are used. Requires a wired register and a special ERT (also compatible with AMR), towers, software and new plastic box cover.
• Advanced meter analytics (AMA) — requires a wired register, new endpoint and lid. It requires no meter readers, but relies on existing cell towers and requires a subscription contract to transmit information.

Parts of the city were already covered by AMR and AMI technology. The utility also tested AMA.

“The most valuable AMI and AMA systems have two-way communication capability that would let us provide information to customers or allow them to access the information themselves,” Rock says. “Our test of several AMI and AMA systems revealed that they worked effectively, even in areas offering poor cellular coverage. On a cell phone, a text will work even when a call can’t be completed and the meters send out signals like a text. AMI incorporates dedicated repeaters and collectors.  However, the capital and operating costs of AMA are significantly higher than AMI.”

The middle road

Rather than wait for the perfect marriage of price and technology, or replacing all of the meters at once, Scottsdale chose a middle ground. By converting over several years, the program wouldn’t divert capital resources from main replacement.

“We are hoping that during the transition either AMA will become less expensive or AMI might become advanced enough that we could go to two-way customer communication without towers,” Rock says.

The smart meter program began with AMR in the north part of the city, which is home to thousands of thinly-spread, large estates.

“That area was one of the catalysts for establishing the program,” Rock says. “It’s too far to walk between houses, but even with a jeep it involved nothing but getting in and out of the vehicle to walk to the meter. The area is very hilly, so you would need a lot of transmitter-receivers to provide connectivity. But the homeowner’s associations won’t allow for any towers, including streetlights and traffic lights. When we had to put up a pump station, we had to camouflage the communication tower as a Saguaro cactus. That cuts out AMI, so we decided to convert the north part of the city to drive-by AMR.”

In the southern part of the city, where houses are closer together, the potential savings for AMR and AMI were narrower.

“But these systems can be competitive with walking,” Rock says. “We tested a couple of AMR and AMI systems and ended up going with one that could be switched to either system using the same ERT. The important calculation is to amortize the cost of the meter over the service lifetime of the ERT. New ERT batteries are good for 20 years, and our research indicated that we could count on our Badger meters for at least 15 years because of their durability and accuracy over time, even with high-volume users. We married new ERTs to new meters to reduce service replacement costs by creating a system where we would replace both units simultaneously, making automated reading the competitive choice.”

A gradual retrofit

Additionally, all existing meters three years or younger will be retrofitted with an ERT. The city’s oldest meters, dating back to before 2000, will be gradually replaced by new meters paired with new ERTs.

“Under this plan, by 2023 the entire city will be covered by some sort of automated metering system,” Rock says. “By then, our oldest smart meter installations will be 15 years old, and ready for replacement. This will maintain a relatively smooth staff workload and budget outlay.”

The utility also considered the impact of AMS on its current meter readers. Over the seven-year conversion period, some staff members would leave through attrition.

“That also gives the remaining employees the option to achieve the certification necessary to join the growing team that performs repairs, installations and replacements of meters and ERTs,” says Rock. “Until we get all of the AMS completed we’ll still need meter readers to run routes and make customer service visits. Even with a full two-way Customer Information System, you never eliminate the need for customer service and meter component maintenance.”

Recent data concerning low water levels in Lake Mead on the Colorado River suggest water restrictions could affect Scottsdale at some future date.

“Arizona has secondary priority for water from the Colorado River, so we’d feel a shortage first,” Rock says. “If that happened, a more comprehensive CIS informed by daily meter information would be a tremendous advantage for the utility and customers who could actively monitor water use and be alerted within 24 hours of a leak. Savings in operating costs are what lead most utilities to go to smart meters, but I think that the new driver could be to optimize water consumption, and giving customers the controls and knowledge to do that for themselves.”

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Keeping the critters out

Meter readers opening a utility box in Scottsdale, Arizona, can face a host of surprises native to the Sonoran desert — rattlesnakes, tarantulas, scorpions and centipedes looking for relief from the sun. Antelope squirrels also chew on wire insulation, and dig through the earthen floors, heaping dirt on top of meters.

“Rattlesnakes get in through the same holes made by the squirrels,” says Ken Rock, water distribution manager, City of Scottsdale Water Resources. “Some meter readers wear rattlesnake guards on their lower legs, but they typically open and close the box lid before a coiled rattlesnake can strike.”

Reading up to 400 meters per day, meter readers must often clear squirrel backfill. However, scuffing away dirt scratches meter lenses, making them harder to read.
The city reckons that the cost of slower reads, meter servicing and damage in 5,000 affected boxes was adding up to about $17,000 a year.

Field personnel were empowered to develop their own solution to the problem and devised the “critter barrier” made of steel window screens. “They cut the screen with scissors and mold the screens to fit under the meters,” says Rock. “They then tape the screen to the walls of the interior or exterior of the box.”

The department improved on the design with the addition of Soiltac by Soilworks, a nontoxic polymer that solidifies dirt so that squirrels are discouraged from digging. Meters found filled with dirt are emptied using a vacuum truck. Soiltac is applied and the screens are added in about 15 minutes at a material cost of about $3 per box.

“Our people still find it easy to break the Soiltac with tools for meter work or replacement,” says Rock.