Clean Water Services CEO Diane Taniguchi-Dennis: 2019 WF&M Award Winner

If you’re looking for a public utility leader who’s respected by her peers for her leadership style, passion about water and engagement across the industry to effect change in water resources management, Diane Taniguchi-Dennis checks all the boxes.

As chief executive officer of Clean Water Services serving Oregon’s second-largest county, Taniguchi-Dennis embodies the modern utility executive. Her education and background in both environmental engineering and business management reflect the utility’s approach of combining science and nature to enhance Oregon’s Tualatin River Watershed.

“She’s a very visionary thinker about the potential utilities have for contributing to the environment as a whole,” says Pat Sinicropi, executive director at the WateReuse Association, for which Taniguchi-Dennis is treasurer and a member of the board of directors. “She likes to think outside the box but at the same time understands the practical realities.”

Clean Water Services is renowned for its achievements in resource recovery and serves about 600,000 residents in the urbanized portions of the Tualatin River Watershed, which stretches from small cities near the foothills of the Oregon Coast Range to the suburbs on the west edge of Portland.

Among its many accolades, Clean Water Services in 2016 was among 61 public and private utilities to be honored by the inaugural Utility of the Future program — an effort led by the National Association of Clean Water Agencies (NACWA), the Water Environment Federation (WEF), the Water Environment & Reuse Foundation (now Water Research Foundation) and the WateReuse Association — to recognize exceptional performance and innovation. In 2019, the utility was once again recognized as a Utility of the Future and was inaugurated into the Leading Utilities of the World network, which represents the gold standard of utility innovation and performance.

As the utility prepares to celebrate its 50th anniversary in 2020, it continues to receive accolades from across the industry for initiatives that express its underlying one water philosophy. At the heart of the mission is Taniguchi-Dennis, who in 2018 was named the first woman CEO of the organization after serving as deputy general manager.

“My favorite part is the creativity and the innovation, and knowing we can make a difference for the Tualatin River Watershed,” she says. For her leadership both at Clean Water Services and across the industry, Taniguchi-Dennis has been voted this year’s Water Finance & Management Award winner.

A Connection to Water

Growing up in Hawaii, Taniguchi-Dennis says she’s always felt a connection to water and the environment.

“In Hawaii, there’s this kind of deep commitment to land, air, water and family. I deeply understood the importance of water to life and public health,” she says, noting that water supply challenges existed in Maui when she was growing up due to economic expansion and population growth on the island.

Her interest in the environment continued when she earned her bachelor’s in civil and environmental engineering from Cornell University in New York. At Cornell, she met her husband, Clay, a native of Oregon. Later, after moving with him to the Pacific Northwest, she earned her MBA from Willamette University in Salem, Oregon.

“The whole understanding of water and community was really honed into me as a student,” she recalls. “There was also a lot of conversation about sustainability and understanding of urban development and the need for manufacturing and industry to be in harmony with nature. I think that’s always been the underpinning of who I am today.”

Taniguchi-Dennis began her career in the consulting world where she spent seven years working on design for water and wastewater treatment facilities and learning about the emerging technologies used in the process. In 1989 she moved to the municipal side, first joining the City of Salem and a decade later the City of Albany, Oregon. She gained progressive experience in all technical areas of public works infrastructure and public service delivery, culminating with eight years of service as the City of Albany’s public works director.

“I learned a lot about how different kinds of public improvements need to interface with the community,” she says of her time working in the two cities. “It’s all about managing these services within the context of what the community desires for livability.”

Clean Water Services

Taniguchi-Dennis joined Clean Water Services in 2011 and was named CEO in 2018 after the retirement of longtime general manager Bill Gaffi. Since being named CEO, Taniguchi-Dennis has not only enhanced her reputation as an advocate in the water sector, but as a well-versed organizational executive.

“We’re so fortunate to have Diane leading the organization,” says Kathryn Harrington, chair of the board of commissioners in Washington County, which also serves as the board for Clean Water Services. “She is passionate about clean water and I just think so highly of her and her ability to transcend various stakeholder groups. At the same time, she can keep up with the best of them from not only a financial side but a business strategic standpoint, as well. That’s an incredibly powerful combination in one person.”

Staff join Taniguchi-Dennis at a budget committee presentation in May 2019.

Clean Water Services is a county service district that provides sanitary sewer and stormwater management services to people, businesses and industries in 12 cities, the heavily populated urbanized portions of unincorporated Washington County, and small portions of nearby Clackamas and Multnomah counties that fall within the Tualatin River Watershed. The utility treats about 65 million gallons of wastewater each day. It maintains a network of more than 800 miles of sewer pipes and 42 pump stations that route used water to its four resource recovery facilities — Durham, Rock Creek, Hillsboro and Forest Grove/Fernhill. The cleaned water is returned to the Tualatin River to be reused as source water. The organization also maintains 670 miles of gray and green stormwater management infrastructure, including storm sewers, open ditches, detention ponds and water quality facilities.

“Our core business is continually evolving,” says Taniguchi-Dennis. In addition to providing the traditional collection services and treating wastewater, the larger goal is ensuring the sustainability of the Tualatin River Watershed. With residents, businesses, recreational activities and wildlife habitats all prevalent in the Tualatin Basin, water is tied to everything.

“I’ve always been interested in the interface of the natural system with the urban water system,” she says of viewing the operation in a one water context. “Water is the source of life, a renewable resource that has the power to bring people and nature together. All water moves through a cycle of use and reuse in watersheds throughout the world. We speak of used water, stormwater, tap water and reuse water – but it’s really one water, cycling through the continuous and renewable water loop that supports our ecosystem, economy and community.”

The approach dates to 2004 when Clean Water Services secured the nation’s first integrated municipal watershed-based permit that essentially blends its NPDES and MS4 permits together as one. Going beyond pollution control, the new permit helped the organization recognize the complex interrelationships between water quality, water supply and wildlife habitats and helped streamline water quality programs under a new framework.


Victoria Lowe, former member of the Forest Grove City Council, joined Taniguchi-Dennis for a tour of construction at the Fernhill Natural Treatment System in 2012.

One example of Clean Water Services’ experiments in this area is its Fernhill Natural Treatment System. Fernhill is a 700-acre facility designed to demonstrate water reuse from the perspective of ecological restoration. Secondary effluent from the utility’s Forest Grove treatment plant runs through 90 acres of the wetlands, which acts as a natural treatment system, as a way to control nutrient levels and reduce thermal requirements in the effluent before it’s returned the Tualatin River. Fernhill also includes a healing water garden, created in collaboration with Hoichi Kurisu, a renowned, Portland-based Japanese landscape architect.

“Nobody ever thinks it’s part of a wastewater treatment facility,” jokes Taniguchi-Dennis, who was involved in a similar effort aimed at treating water and reducing pollutants called Talking Water Gardens while at the City of Albany. “Not only does it make economic sense, it makes ecological sense,” she says, adding that the healing garden connects to the notion of ohana, or family, that she was raised with – the understanding that all people and creatures on the Earth are family to care for.

Resource Recovery

At Clean Water Services’ four treatment facilities, the focus is firmly on resource recovery. The utility’s plants incorporate reuse capabilities, as well as energy recovery. The utility generates 40 percent of its own energy and annually recovers 755 tons of phosphorous for use as commercial and residential fertilizer, produces 11,000 dry tons of biosolids for agricultural land application and operates the state’s largest water reuse program. Currently, its Rock Creek facility is looking into the production of compressed natural gas.

In 2009, Clean Water Services’ Durham facility became the first in the United States to operate a commercial nutrient recovery facility. This process uses a struvite recovery system from Ostara Nutrient Recovery Technologies. The technology simplifies the treatment process by directly removing phosphorus and ammonia from wastewater. More traditional methods involve sending water through multiple cycles, which can increase operating costs and capacity. In 2012, a second Ostara system opened at Clean Water Services’ Rock Creek facility.

Project Snapshot

Interestingly, Clean Water Services was formed nearly 50 years ago by vote after water quality and flow issues in the region became a problem. When the organization was established (it was known as the Unified Sewerage Agency from 1970-2001), one of the state’s requirements was for the utility to secure an additional water supply so the Tualatin River could maintain in-stream flow.

Since the 1970s, that flow has come from Hagg Lake, created by the building of Scoggins Dam to aid agricultural irrigation, provide drinking water supply and flow augmentation. Clean Water Services also participates in the Barney Reservoir Joint Ownership Commission. Between Hagg Lake and Barney Reservoir, Clean Water Services now controls nearly a quarter of the stored water in the Tualatin River Watershed. The utility is currently working with the Bureau of Reclamation on the Tualatin Basin Joint Project, which Taniguchi-Dennis describes as a unique example of a clean water entity going beyond traditional collection and treatment and investing in upgrades for dam safety and water supply. It’s an effort that’s been ongoing for 25 years.

In another recent project, Clean Water Services replaced the Upper Tualatin Interceptor, which was installed in 1974. The interceptor serves the cities of Beaverton, King City, Tualatin, Tigard and Sherwood, and directs flows into the Clean Water Services’ Durham facility. The utility took an innovative approach with design-builder Mortenson Construction and engineer Kennedy Jenks. Part of that innovation was the use of microtunneling to complete the 470-foot long tunnel for the new interceptor. The microtunneling was performed by Brownsville, Wisconsin-based contractor Michels, and included a tight, U-shaped vertical curve under the Tualatin River.

The new siphon is a gravity-based system installed under the Tualatin River. The siphon was fitted with seismically resilient HDPE carrier pipe that is better suited for the corrosive environment within the pipeline. The siphon’s concrete casing pipe was specially designed for the project and constructed in Malaysia to meet the project’s specifications.

Advocacy and Pure Water Brew

Leadership positions at water utilities require the boss to wear many hats and shoulder responsibility for matters concerning public health. But there are many who go beyond that charge. Many are involved in industry organizations and participate in the national conversation about the future of water management and environmental policy. Taniguchi-Dennis is not only one of those people, she’s usually in high demand. Her extracurricular activities include serving on the board of directors at NACWA, the WateReuse Association and the Water Research Foundation.

“I’ve always appreciated her vision and her focus on the art of possible, as opposed to impossible,” says Cindy Wallis-Lage, president of Black & Veatch’s global water business and a fellow member of the board of directors at the Water Research Foundation. “I think that’s why she gets pulled into a variety of roles. Diane is so grounded and is always focused on what can be done and how to keep making a difference. She always feels like there’s more that she can do. I think that’s very motivating for her staff.”

In addition to leading her staff at Clean Water Services, Taniguchi-Dennis takes pride in her role to be an advocate for water resources management, new technologies and approaches. One of those is in the area of water reuse, exemplified in the creation of the Pure Water Brew competition.

In 2014, Clean Water Services partnered with the Oregon Brew Crew to pilot the first Pure Water Brew challenge. The project proved that home brewers could make beer with highly purified water drawn from a reach of the Tualatin River that was 30 percent effluent. The novel approach to start a public conversation about recycled water worked so well that the logical next step was to purify 100 percent effluent for a limited batch of beer, which Clean Water Services did in 2015 after securing regulatory approval.

Although Clean Water Services is not a drinking water utility and does not distribute potable water, Taniguchi-Dennis says it helped launch the effort as part of a long-term sustainable water initiative for the region. Fitting for Oregon, a noted craft beer hub, the initiative involves changing the regulations in the state, which currently does not allow direct-potable reuse for producing drinking water.

“It’s all about focusing on the quality of the water, not where it comes from,” she explains. “At first it was ‘no way, no how’ can you do this. We then demonstrated downstream of our outfall that we could take water from the river that is 30 percent effluent by volume, and there are no regulations on doing so as long as the water meets potable requirements.”

Since 2014, several organizations around the globe have created their own Pure Water Brew competitions, and the Pure Water Brewing Alliance was formed in response to the interest. The concept of using treated wastewater to brew beer has been featured at the WEFTEC show in various forms over the past five years. With this momentum, Clean Water Services has taken the conversation on the road with the Pure Water Wagon – a mobile showcase of water purification technology that is changing how people nationwide think about water.

“We really wanted to share with the rest of the industry how we did it and to capture people’s interest in water reuse,” Taniguchi-Dennis says. “We helped stimulate what I would say is a nationwide and a global movement to demonstrate and educate our communities about water reuse.”

Clean Water Services recently gained approval from Oregon DEQ to provide high purity water to commercial breweries, hoping to reach a broader audience and continue the reuse water conversation.

At a recent board meeting, CWS staff and board celebrated the organization’s designation as a Water Resources Utility of the Future. Taniguchi-Dennis is in the center, holding the award. Board Chair Kathryn Harrington is to her left.

Outlook at Clean Water Services

For all the work underway at Clean Water Services, Taniguchi-Dennis recognizes that the industry as a whole is in a state of change. She notes that workforce development challenges exist at her utility as they do elsewhere, but is encouraged by the diverse opportunities offered at an organization like Clean Water Services from operators and mechanics to electricians, instrument technicians and more.

“When I think of Diane and all our interactions over the years, the word prescience comes to the forefront,” says Jim Horne, manager of the sustainable utilities program at the EPA’s Office of Wastewater Management. “The essence of prescience is the ability to predict the future before it actually happens — in other words, foresight. Diane’s broad understanding of the challenges facing her own organization, and the water sector as whole is truly remarkable. This combined with an understanding of the practical realities facing a utility executive every day, truly make her a water leader of the future.”

Taniguchi-Dennis also points to the incorporation of new technology as a major theme across the water sector in recent years, noting the impact artificial intelligence and automation are having on utility operations. She says while current industry challenges like PFAS/PFOA and water contaminants will test the capabilities of technology, she’s confident Clean Water Services will stay ahead of the game.

“We couldn’t do what we do without the great Board we have,” she says. “They push us on entrepreneurship and innovation and they’re very supportive about investing in the technology that’s needed to be effective.

“I couldn’t do what I do without the really talented team I have at Clean Water Services and their dedication to public service and the environment.”

About the WF&M Award

The Water Finance & Management Award was created in 2012 to recognize leaders in the water/wastewater/stormwater utility sector who are driving innovation and who have had a lasting and meaningful impact within their utility/field. Nominations are submitted and voted on by WF&M’s editorial advisory board. The winner is chosen by vote, based on innovation, as well as the economic, social and environmental benefits that have occurred as a result of the individual’s leadership, contributions and lasting impact.

 Past Water Finance & Management Award Recipients

2018 – Karen Pallansch, CEO, Alexandria Renew Enterprises
2017 – George Hawkins, CEO, Moonshot LLC (fmr. CEO & GM, DC Water)
2016 – Kim Colson, Director, North Carolina Division of Water Infrastructure
2015 – Julius Ciaccia, Roetzel Consulting Solutions (fmr. CEO, Northeast Ohio Regional Sewer District)
2014 – Ben Grumbles, Secretary of the Environment, State of Maryland
2013 – Kevin Shafer, Executive Director, Milwaukee Metropolitan Sewerage District
2012 – Steve Allbee, Office of Water, U.S. EPA (retired)

Andrew Farr is the managing editor of Water Finance & Management, published by Benjamin Media in Cleveland, Ohio. He has covered the water sector in North America for eight years and also covers the North American trenchless construction industry for sister publications Trenchless Technology and NASTT’s Trenchless Today.

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