Our team

Our team. Our people.

At OneStone we are a close-knit team who collaborate often, working alongside each other as well as our clients to produce the best solution for each project.

Our team of talented professionals, spanning years of experience on a national and international level, has been brought together by our founder Eelko who has a passion for engaging the logical left-brain with the creative right-brain to analyse and solve complex water engineering challenges.

Eelko Van Der Vaart


Master of Science in Civil Engineering, Delft University, the Netherlands (specialising in Environmental Engineering and Water Management)

Leaving the Netherlands in 2005, where he developed his expertise in water management and control systems, Eelko came to WA where he applied his highly transferable knowledge and design skills to an increasingly diverse range of water management and distribution projects.

In 2010, he established OneStone with the mission to support clients in sustainably managing our state’s most precious resource by employing a creative, integrated approach to water systems design.

Eelko’s passion for water management is born out of his insatiable appetite for analysing complex problems. He loves the dynamic nature of water and the inherent complexities of water systems, which give him the opportunity to combine his scientific knowledge with his creative design and engineering skills.

And when he isn’t working tirelessly to find new and better ways to manage water, you’ll find him indulging in his other water-based passion – surfing at Trigg Beach.

Folkert Drijfhout


Master of Engineering, North West University, South Africa MSc Technology Management, Systems Engineering, University of Pretoria

Folkert joined OneStone in May 2023, bringing with him a wealth of experience as a Lead Mechanical Engineer specialising in machine and water industry design for nearly 12 years. His arrival adds a diverse and invaluable range of experience to our team, encompassing over 20 years of involvement in designing and testing cutting-edge equipment and process systems for defence, nuclear, and water sectors.

Folkert’s extensive background includes notable accomplishments in various areas. He has played a key role in designing water and wastewater treatment plants that incorporate pumps, filtration systems, and chemical dosing. Additionally, he has excelled in conducting comprehensive reviews and optimisations of hydraulic water systems, selecting appropriate pumps, and overseeing multidisciplinary engineering teams throughout studies, detailed designs, and construction projects.

Beyond his professional achievements, Folkert possesses a profound passion for engineering, particularly in the realm of dynamic fluid systems. His unwavering dedication to seeking innovative solutions for complex problems distinguishes him as a forward-thinking engineer who consistently strives to push the boundaries of what is possible.

Outside of work, Folkert maintains an active lifestyle through recreational walking and cycling. He also cherishes spending quality time with his family.

Alex Leeman


Bachelor of Civil and Construction Engineering (Honours), Curtin University

Alex joined the OneStone team in September 2021 after predominantly working within the mining sector for close to 10 years.

He has been involved with many projects in the water industry, such as water systems and transfer infrastructure, dewatering, water resources, flood risk assessments, and environmental management. Alex has field expertise in auditing and commissioning, to properly develop hydraulic models and successfully designing modifications and solutions to engineering issues.

Alex comes from a background as a designer, where he simultaneously obtained his degree in Civil and Construction Engineering at Curtin University. He has a passion for the water industry and enjoys solving challenging technical issues.

When he’s not pursuing his career interests, Alex enjoys spending time with his young family, while honing his barbequing skills.

Felix Nguyen


Master of Professional Engineering (specialising in mechanical), University of WA.

Felix joined OneStone Consulting in November 2020 and since that time has gained experience using hydraulic modelling software for conducting water hammer analysis on water supply pipelines, hydraulic design, and pump station control system analysis.

He is interested in machinery, engineering processes and network systems, material sustainability and fatigue as well as learning and solving problems relating to water systems from a strategic and hydraulic perspective.

In his career so far, Felix has completed several projects including pressure vessels, hydraulic cylinders, gas pipelines also research into the benefits of black soldier fly larvae’s frass in agriculture.

Felix is currently working as a Research Assistant for UWA since April 2021 to develop the process of pelletizing fertilizer pellets from black solder fly larvae frass in modern agriculture.

In his spare time, he enjoys sports especially volleyball and badminton.

Sue Bosotin


Sue joined One Stone Consulting in July 2019 as the company’s Administrator.

With extensive experience in office administration, Sue has gained knowledge across a wide range of industries whilst working in a temp role for a period of 6 years.

Most of her career has been working within the commercial and residential air conditioning industry, where she was responsible for purchasing, quality, sales and administration. Sue was Quality Auditor and formed part of the Quality Team that won The Australian Quality Award in 1994.

Sue enjoys being part of the OneStone team and endeavours to ensure the administration function of OneStone works efficiently and effectively, assisting the team in meeting their objectives.

Outside of work, Sue enjoys spending time with the grandkids which keeps her fit and active.