EPCOR: water supply and treatment in a semi desert

EPCOR: water supply and treatment in a semi desert

EPCOR is proving a flexible and reliable provider of water services to the people of Arizona: we look at a few of the more imaginative projects currentl...

EPCOR is no newcomer to providing reliable utilities. It traces its heritage back to 1891 when it was established as an electrical power generator and distributor at Edmonton, Alberta – and the City of Edmonton still owns all of the company’s shares. And it was as long ago as 1913 that it built its first water treatment plant at Rossdale. In 2016, EPCOR celebrated 125 years of providing water and wastewater services to some 1.9m people across the Canadian provinces of Alberta, British Columbia and Saskatchewan, and the U.S. states of Arizona, New Mexico and Texas.

EPCOR’s first foray into the USA was in 2011 when it acquired Chaparral City Water Company in Fountain Hills, Arizona, followed in 2012 by the acquisition of Arizona American Water and New Mexico American Water, wholly owned subsidiaries of American Water Works Company Inc. Since then it has been building out its facilities and acquiring additional small water and natural gas businesses in Arizona, New Mexico and Texas as opportunities arise, says Engineering Director Andrew Brown. Brown joined EPCOR in 2013, bringing with him 25-plus years of water service experience from the City of Phoenix.

Though arid in parts, and threatened by climate change-induced drought, Arizona has a variety of water sources, chief among them the 336-mile long Central Arizona Project (CAP), which diverts water from the Colorado River. Other sources include the Salt River Project canal system and groundwater wells tapping into underground aquifers.

Population demands and nature’s challenges

Brown and his team are responsible for delivering a large annual capital improvement program, one of which is the project to expand the White Tanks Regional Treatment Facility (White Tanks), built in 2009 to treat water from the CAP and supply it to consumers. This project provides a good illustration of the challenges faced by EPCOR in the State, and the best practices it is employing to meet them. White Tanks was originally designed to treat 20mn gallons of water per day (MGD) with a firm capacity of 13.4 MGD. The total capacity will be increased to 33 MGD as part of this project, he explains. “In recent years our peak demand in the summer has been pushing 19 MGD. The capacity was stressed so we had to expand.”

A further challenge was that a number of events, including heavy rain events and storm runoff in the summer, can result in a surge of particles and mud to the CAP, which disrupts the plant’s treatment ability because of the time it takes for this turbidity to settle out. When these water quality ‘excursions’ happen, they can last for up to three weeks. Excursions don’t happen every year, but Brown and his team looked for a way to solve this problem at the same time as expanding the overall capacity of the plant. “We did something unique!” he says. “Besides taking the White Tanks Regional Treatment Facility from 20 to 33 MGD we knew we needed more enhanced treatment technology to address the excursion events and build resiliency in the treatment process.”

The solution ultimately chosen was ‘ballasted flocculation’, which will provide more efficient and effective removal of particulate matter from the water. Conventional flocculation/sedimentation methods were dismissed due to both size and cost constraints. The ballasted flocculation system chosen for the White Tanks was a CoMag system from Evoqua Water Technologies. This uses an inert iron ore by-product called magnetite that attracts the particles and settles them as much as 30 times faster than conventional treatments. Once it has done that, the magnetite can be recovered and reused.

Partnership in projects

Though magnetite flocculation had been used before in the USA for wastewater, the $28.7mn White Tanks Regional Treatment Facility 2019 Expansion and Process Upgrade was the first in the country to use the CoMag system on the water supply end. It’s a pioneering project for EPCOR, the design team from Water Works Engineers and the contractor Archer Western, all of whom have worked together before.

The project was won by Archer Western in a competitive tender; work started late in 2017 and is on schedule to be completed with new treatment systems online by March 2019. “We are also constructing a 20mn gallon raw water reservoir where initial settling takes place,” explains Brown. “That’s a lot of additional capacity at that point: then we added some drying beds for the sludge that is removed. Electrical improvements, more back up power generators, enhanced chemical facilities – and of course the CoMag plant – are the most important areas of work currently.” The annual shutdown of the plant – typically between late November and early February to coincide with a CAP canal maintenance shutdown – will provide the opportunity to complete the expansion and connect it to the existing system.

At the other end of the water cycle, EPCOR is building a brand new wastewater facility in Phoenix’s West Valley, close to the Luke Air Force Base. It’s of interest because of the phased way in which it is being introduced – there’s both industrial and residential development along the Route 303 corridor that circles the city. “We started by building a small pumping station for the initial flows, and at present we are pumping that wastewater into trucks and hauling it over to another of our facilities nearby for treatment.” The first phase of the 150,000 gpd treatment facility has just been completed, he explains, but is not being put into service until flows from the mushrooming housing development in the area are enough to make it efficient to start up and operate – most likely early in 2019.

Eventually that facility could grow to its master-planned capacity of 8 MGD, he envisages. Close proximity to an airfield comes with other challenges. Clearly the height of any construction has to be limited, however that’s not too much of a burden for a sewage plant. A bigger headache is the need to keep everything covered. Open water attracts birds: birds and low-flying aircraft represent a mutual threat!

Local and appropriate

As Arizona’s cities expand, EPCOR will continue to provide localized solutions. “When you have lots of small developments and they are not contiguous then it can make sense to have localized treatment,” says Brown. This is good news for EPCOR and its partners. It happens that both the projects we have discussed so far have been delivered by the design/construction teams of Water Works Engineers and Archer Western Contractors (Walsh Group), however, EPCOR works with many local consultants and contractors.

Not everyone is blessed with a surface water supply. Many communities still rely exclusively on wells, but climate change is drying the wells up so in some areas around Phoenix people have come to rely some or all of the time on water brought to them by trucks. Around the Anthem community in the northern portion of the Greater Phoenix metropolitan area this service was indirectly provided by a local municipality but was withdrawn in 2017. EPCOR’s response was to build a water hauling station – to the great relief of these 1,500 residents when it opened in July 2018.

The Desert Hills New River Water Station is a location where water haulers can purchase potable water that meets all Federal and State drinking water standards. It’s open seven days a week during daylight hours and has two filling points that can feed trucks at a rate of about 425 gallons per minute. “This is a standalone part of our business,” says Brown. “We can’t charge our existing customers, so we make a charge to the water haulers to cover the cost of the facility.” The water hauling facility illustrates some highly relevant points – among them the alarming scarcity of water resources in Arizona, the diversity of consumers’ circumstances – and the alacrity and flexibility with which EPCOR looks for appropriate solutions.

Andrew Brown