Senior Mechanical Engineer - Wastewater
Parsons
Fountain Valley, CA · Posted August 18, 2026
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Pay compared with the market
This listing does not state pay. Across 80 open senior mechanical engineer listings that state pay, the middle half runs $150,000 to $173,000 and the median is $164,000.
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AI use among mechanical engineers is little observed so far. Measured exposure for mechanical engineers: 8% (little observed).
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Parsons has filed 5 layoff notices in the last twelve months, covering 94 workers, most recently October 2026. These are public filings with state labor departments, and an open role can sit alongside them. See the filings
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About the job
In a world of possibilities, pursue one with endless opportunities. Imagine Next!
At Parsons, you can imagine a career where you thrive, work with exceptional people, and be yourself. Guided by our leadership vision of valuing people, embracing agility, and fostering growth, we cultivate an innovative culture that empowers you to achieve your full potential. Unleash your talent and redefine what’s possible.
Job Description:
Join Our Team: Principal Mechanical Engineer – Water Group Location: Pasadena, CA (with initial assignment in Orange County, CA)
Are you a seasoned Mechanical Engineer passionate about creating solutions that improve communities? Parsons’ Water Group in Pasadena, CA, is seeking a dynamic Principal Mechanical Engineer to lead and innovate in the design of cutting-edge wastewater treatment facilities. Join an established engineering team that values collaboration, creativity, and technical excellence.
This role offers an exciting opportunity to contribute directly to impactful infrastructure projects while working in Orange County, CA, during the initial assignment phase.
Why Join Parsons?
Make an Impact: Be at the forefront of designing essential wastewater treatment systems that enhance environmental sustainability and community well-being.
Grow with Us: Lead a team of skilled engineers and designers, guiding technical excellence and driving professional growth within the team.
Engage in Innovation: Use the latest tools and technologies to create efficient, state-of-the-art designs.
Your Key Responsibilities
As a Principal Mechanical Engineer, you’ll:
Design Excellence: Develop detailed designs for mechanical piping systems, reclaimed water systems, lift stations, and wastewater treatment facilities.
Create and review technical specifications, detailed drawings, and scopes of work.
Perform quality assurance and control (QA/QC) reviews for comprehensive, multi-discipline design projects.
Project Leadership: Lead project teams on medium to large-scale projects, ensuring designs meet client expectations and compliance standards.
Mentor and guide engineers and designers to achieve technical and professional growth.
Construction Support: Address engineering bid questions, respond to contractor inquiries, and verify equipment compliance with design specifications.
Support site investigations and develop operation and maintenance (O&M) plans, including on-site training for personnel.
Technical Expertise: Conduct hydraulic calculations, system head curves, and pump and motor sizing.
Oversee the design of processes such as headworks, aeration basins, disinfection systems, anaerobic digestion, and more.
Ensure designs align with industry standards, including ASME, ASTM, ANSI, NFPA, and OSHA.
What You’ll Bring to the Team
Required Skills:
Proven leadership and ability to perform in a lead capacity.
Expertise in wastewater treatment system design, including piping layouts, chemical storage systems, HVAC, and pumping systems.
Proficiency in engineering software and tools, including AutoCAD and Revit.
Strong communication skills, both written and oral.
Working knowledge of safety standards, including Cal OSHA regulations.
Bachelor’s degree in Mechanical Engineering.
Licensed Mechanical Engineer (PE) in the State of California.
Minimum of 10 years of experience in wastewater treatment or similar industrial facility design.
Desired Skills:
Familiarity with interdisciplinary design processes.
Advanced knowledge of mechanical engineering codes and standards.
Proactive problem-solving skills and a self-starter attitude.
What We Offer
Competitive salary and benefits package.
Opportunities to work on meaningful, high-impact projects.
A supportive and inclusive team environment where innovation thrives.
Take the next step in your career and make a difference with Parsons. Apply today to become part of a team that’s shaping the future of water infrastructure.
Security Clearance Requirement: None
This position is part of our Critical Infrastructure team.
For more than 80 years, our experts have designed and delivered the critical infrastructure that connects and protects communities around the world. We work in collaborative teams, both within the company and with our partners and customers, to plan, design, build, and modernize infrastructure. We take special pride in projects and solutions that improve communities as well as people’s quality of life by promoting economic growth, enhancing mobility, and increasing sustainability and resiliency. Powered by our people, we provide the imagination necessary to support our customers’ visions—and to help them see what's next!
Salary Range: $103,500.00 - $181,100.00
We value our employees and want our employees to take care of their overall wellbeing, which is why we offer best-in-class benefits such as medical, dental, vision, paid time off, Employee Stock Ownership Plan (ESOP), 401(k), life insurance, flexible work schedules, and holidays to fit your busy lifestyle!
Parsons is an equal opportunity employer, and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, national origin, disability, veteran status or any other protected status.
We truly invest and care about our employee’s wellbeing and provide endless growth opportunities as the sky is the limit, so aim for the stars! Imagine next and join the Parsons quest—APPLY TODAY!
Parsons is aware of fraudulent recruitment practices. To learn more about recruitment fraud and how to report it, please refer to https://www.parsons.com/fraudulent-recruitment/ .