Who We Are
Founded in 2009, Ramirez, Johnson, and Associates provides engineering solutions with a customized approach that delivers the best value for every project. As a small firm, we can give each client and project the personal attention deserved. Licensed in Colorado and beyond, our engineers, commissioning agents, and designers are ready to take on projects ranging from $1,000 to $100,000,000, including commercial spaces, healthcare facilities, educational facilities, multi-family and high-end custom residential projects. RJA is M/WBE, DBE, SBE, EBE Certified.
Our Partners
Darin Ramirez, PE
Founding Partner
As a founding principal of RJA, Darin provides experience attained since 2004 in the design, construction, and consulting industry. He is involved in all aspects of the firm’s daily operations. As designer, Darin’s passions include collaborating with owners and users to truly understand their needs, and providing design solutions that are efficient and appropriate for each clients. Off the clock, Darin can usually be found chasing his kids, climbing, and skiing in the Rocky Mountains.
Education:
Bachelor of Science, Mechanical Engineering, University of Florida
Affiliations and Registrations:
Professional Engineer: CO, KS, MD, MN, NC, NV, NJ, NM, OH, OK, OR, PA, SC, TN, TX, WA, WY, MT, and UT
Certified Geoexchange Designer
LEED AP
Eric Johnson, CxA
Founding Partner
Eric’s passion for buildings and sustainable design directs the work of the firm and his construction and contracting background provides a practical perspective on each project. With two decades of experience, Eric is involved in either a design or commissioning role on every project and excels at leading talented engineers and designers towards solutions that are in the best interest of the client and the project. As a strong community supporter, Eric’s volunteerism through Junior Achievement helps to provide a positive and lasting impact on young people’s economic and entrepreneurship skills, career choices, and success. During his free time, Eric enjoys skiing, hiking, golfing, and spending time with his family.
Education:
Bachelor of Science, Architectural Engineering, University of Colorado
Affiliations and Registrations:
LEED AP
Certified Commissioning Authority, CxA
Our Engineers
Paul Plewczynski
Electrical
As an electrical designer, Paul has amassed engineering experience in the Denver area since 2007. His background includes roles on the owners’ team as well as on the consulting side of the industry. Paul is responsible for spearheading RJA’s Revit/BIM collaboration with our clients, and he specializes in new and existing projects that require creative power distribution design. Paul enjoys hiking, backpacking, and mountain biking with his wife and three kids.
Education:
Bachelor of Science, Electrical Engineering Technology, MSU Denver
Associates Degree, Computer Aided Drafting, ITT Technical Institute
Affiliations and Registrations:
ICT Design Fundamentals
Scott Zimmerman, PE
Mechanical
Scott is an established mechanical engineer with a wealth of experience spanning the commercial and industrial sectors. Since 2010, he has brought his expertise to a wide range of projects, from telescope observatories and state-of-the-art college sports facilities to mineral processing plants, commercial kitchens, and craft breweries and distilleries. With a mastery of the BIM/VDC design process, Scott is an advocate for leveraging 3D modeling software to bring projects to life with precision and efficiency, always pushing the boundaries of what’s possible in engineering design. In his free time, Scott enjoys four wheeling and exploring Colorado’s backcountry.
Education:
Bachelor of Science, Mechanical Engineering, University of Arizona
Affiliations and Registrations:
Professional Engineer: AZ, CA, CO, IA, ID, and UT
Member ASHRAE, former Chapter President
LEED Green Associate
Judah Katz, CxA
Mechanical
Judah is a talented and detail-oriented individual with over a decade of mechanical and plumbing design experience in the residential, commercial, and light industrial sectors. His project experiences are comprised of a diverse group of industries including educational facilities, restaurants/breweries/bars, retail spaces, institutional housing, and higher education. Technically, Judah is adept in the use of multiple energy modeling, BIM, and design softwares. Judah became a certified Commissioning Agent in 2024. Family, music, and finding ways to enjoy the sun are his choice priorities when not in the office.
Education:
Bachelor of Science, Mechanical Engineering, University of Alabama
Affiliations and Registrations:
Certified Commissioning Authority, CxA
Member ASHRAE
Chris Wood
Mechanical
Chris launched his career in 2012 as a mechanical and plumbing designer, gaining valuable experience in multi-family and light commercial construction. Over the years, he has engineered and managed a wide range of projects, from large-scale 350-unit multi-family buildings to smaller office tenant finishes. Originally from Western New York, Chris moved to Denver in 2009 after graduating from Alfred State College. Outside of work, he enjoys staying active by biking and hiking, and he loves spending quality time with his dog, making the most of Colorado’s outdoor lifestyle.
Education:
Bachelor of Science, Mechanical Engineering Technology, Alfred State College
Theresa Gray, PE
Electrical
Theresa has been a driving force in the electrical and lighting design industry since 2001. Her passion for lighting design and efficient power systems has helped shape countless projects. Theresa continues to push the boundaries of design excellence, and her commitment to the field is further demonstrated by her active involvement in the Illuminating Engineering Society of North America. Her experience and dedication to advancing lighting technology make her a respected leader in the industry.
Education:
Bachelor of Science, Architectural Engineering, University of Colorado, Boulder
Affiliations and Registrations:
Professional Engineer: CO, AZ, MD, WY, WA, UT, TX, MN
IES
LEED AP
Andy Achtermann, PE
Mechanical
Andy’s career as a mechanical engineer began in 2012, and since then, he has amassed experience across a diverse range of building system types. His expertise includes residential, commercial, and industrial sectors, where he has worked on everything from designing systems for restaurants and bars to hotels, multi-family buildings, schools, offices, and even specialized process designs for steam systems and grow facilities. His broad skill set allows him to approach each project with a unique perspective, ensuring that every design is both functional and innovative. In his free time, Andy enjoys traveling, golfing, baking, and brewing beer.
Education:
Bachelor of Science, Architectural Engineering, University of Colorado, Boulder
Affiliations and Registrations:
Professional Engineer: CO, AR, and TX
Member ASHRA
Nora Raine, EIT
Mechanical
Nora’s possesses a solid foundation in Mechanical Engineering, having earned her degree from Iowa State University. With hands-on experience designing innovative mechanical systems in central Iowa, she developed a keen understanding of the field before deciding to embark on the next chapter of her career. In 2021, she made the decision to relocate to Denver, where she joined the RJA team and further honed her skills. Outside of work, Nora enjoys cooking, hiking, and skiing.
Education:
Bachelor of Science, Mechanical Engineer, Iowa State University
Henry Furuta, PE
Mechanical
Henry launched his career in the MEP industry in 2018, bringing his expertise to a diverse range of projects nationwide, from sports stadiums to office tenant improvements. With a passion for 3D modeling, he thrives on bringing designs to life in creative and efficient ways. In his free time, he spends his time playing Ultimate Frisbee, traveling, and flying.
Education:
Bachelor of Science, Mechanical Engineering, University of Texas at Austin
Affiliations and Registrations:
Professional Engineer: CO
Shelly Achtermann
Electrical
With a talent for creating energy-efficient electrical systems, Shelly has been transforming spaces since 2018. She designs power and lighting solutions for a wide range of projects, including multi-family residences, restaurants, schools, and warehouses. Her professional experience shows her commitment to blending creativity with precision, ensuring each design is both functional and sustainable. When she’s not designing, you’ll find her hiking, tending to her garden, playing with her dogs, or caring for her chickens.
Education:
Bachelor of Science, Biological Sciences, Colorado State University
Derek Wetch
Mechanical
With a strong background in the multi-family and restaurant sectors, Derek brings a unique blend of mechanical and plumbing design expertise. His experience as a field engineer, having served as both a Project Engineer and VDC Engineer in Montana, provides him with a comprehensive understanding of the design and construction process. Skilled in Revit and Navisworks, he utilizes these tools throughout every phase of a project.
After earning his master’s degree in Mechanical Engineering from the University of Colorado Boulder in 2023, Derek continues to grow his knowledge and skills. Outside of work and school, he enjoys backpacking, fly-fishing, and backcountry skiing. A native of Arvada, Derek is excited to apply his expertise to help shape Colorado’s future in a sustainable and responsible way.
Education:
Bachelor of Science, Mechanical Engineering, Montana State University Bozeman
Masters of Science, Mechanical Engineering, University of Colorado Boulder
Huseyin Martin Yildiran
Mechanical
Martin is a skilled mechanical and plumbing designer who thrives on helping owners and contractors uncover design efficiencies that drive project success. With a deep understanding of various mechanical systems, he plays a key role in RJA’s commitment to guiding clients through the complexities of the updated Energize Denver requirements. Martin also brings specialized expertise in California Title 24 energy standards, ensuring projects meet rigorous energy efficiency goals. Outside of work, he’s an avid basketball and soccer fan, enjoys playing video games, and loves swimming.
Education:
Bachelor of Science, Mechanical Engineering, University of Sakarya, Turkey
Sammi Reeves
Electrical
Working as an electrical designer since 2017, Sammi relocated to Denver in 2023. Her background includes electrical design, specializing in large-scale commercial and retail spaces. Sammi leads the electrical team in Revit/BIM application, with a strong emphasis in multi-discipline coordination and collaboration. In her free time, she enjoys hiking, reading, and spending time with her dog.
Ava Lawrence, EIT
Mechanical
Since graduating from the University of Vermont in 2020, Ava has been making her mark as a mechanical engineer, specializing in designing innovative mechanical and plumbing systems for residential, commercial, and office spaces. After leaving Burlington, VT, she embraced a new chapter in Denver, where she continues to grow both professionally and personally. Outside of her engineering career, Ava enjoys cooking, rock climbing, skiing, and weightlifting.
Education:
Bachelor of Science, Mechanical Engineering, The University of Vermont
Meryem Canoz
Electrical
Meryem’s electrical design experience covers a wide range of projects, including single-family homes, hotels, apartments, restaurants, and office buildings. Her comprehensive knowledge allows her to design electrical systems that meet the unique needs of each project, from residential to commercial spaces. Meryem’s professional interest lies in power distribution systems, where she focuses on optimizing efficiency and safety, and load analyses for complex, mixed-use buildings, ensuring that every system can support the demands of modern infrastructure. In her spare time, Meryem enjoys cooking, reading historical novels, and cycling.
Education:
Bachelor of Science, Electrical & Electronics Engineering, University of Gaziantep, Turkey
Mike Sullivan, EIT
Mechanical/Electrical
Mike has been making waves as an MEP design professional in the Denver area since 2021. Drawing on valuable experience from the contracting sector, he delivers high quality solutions for commercial, residential, and light industrial projects. With expertise in both mechanical/plumbing and electrical engineering, he bridges the gap between trades, ensuring integration and precision in every design.
Outside of his professional life, Mike loves the Colorado mountains, hiking, and fishing.
Education:
Bachelor of Science, Mechanical Engineering, Kennesaw State University
Patrick Murphy, EIT
Mechanical
Since 2019, Patrick has established himself as a talented mechanical designer with a diverse range of project experience, including hospitality, restaurants, and innovative designs for fitness centers and pools across the country.
Outside of his professional life, Patrick is an avid adventurer, having hiked over 400 of Colorado’s 13ers. With a passion for the mountains, he’s set his sights on conquering the remaining 200 peaks. His love for the outdoors continues to inspire his work and fuel his drive to push boundaries—both in the field and on the trails.
Education:
Bachelor of Science, Mechanical Engineering, University of Colorado, Boulder
Quinn Thielmann
Mechanical
Quinn’s journey in mechanical and plumbing design began during his college internships, bringing his experience with him to RJA after graduation from the University of Colorado Boulder. With a background which spans several states and federal projects, Quinn has become a skilled expert in MEP design. Originally from Overland Park, Kansas, he loves the great outdoors— among his favorite activites are rock climbing, disk golf, and fishing. When he’s not adventuring outdoors, Quinn is always up for a friendly competition, especially if it involves a board game with family and friends.
Education:
Bachelor of Science, Mechanical Engineering, University of Colorado, Boulder
Zoe Mencke
Electrical Intern
Zoe blends the artistry of theatrical lighting design with the precision of architectural lighting design, bringing creativity and technical expertise to each project. Outside of work, she has a passion for the arts and enjoys attending a wide variety of theatrical productions. During her free time, Zoe loves traveling to new destinations, hiking , and playing video games.
Education:
Bachelor of Arts, Theatrical Design, University of Northern Colorado Masters, Architectural Lighting Design, Politecnico di Milano
Jessie Thomas
Business Manager
With over a decade of experience in business management and accounting in the legal, conservation, textile, and veterinary industries, Jessie excels at navigating complex financial landscapes and improving operational efficiency. Specializing in budgeting, financial forecasting, and strategic planning, she adapts her expertise to drive growth and sustainability. Now focusing on engineering, Jessie combines technical insights with business acumen to optimize processes and foster innovation.
In her free time, Jessie loves floating the river in Golden, CO, snowboarding, reading books by the fireplace, and spending time with her family; husband Jordan, Pomeranian Geddy, and Conures Guinness and Gemma.
Education:
Bachelor of Science, Psychology, University of Central Florida
See What We’ve Been Working On
View some of the engineering projects our team has designed locally, in the state of Colorado, and across the country. We’ve created solutions for commercial, retail, food service, multi-family housing, healthcare, renovation, hospitality, government, industrial, laboratory, and tenant finish projects.
Contact Our Denver Team
We consider projects of all sizes across the state of Colorado and beyond. Talk to our team to see if RJA is right for your next engineering project.
OUR CERTIFICATIONS
- Professional Engineering
- MBE, DBE, SBE, EBE
- Member of the AABC Commissioning Group
- CXA Certified Commissioning Agents
- Certifiably Green Denver
OFFICES & CONTACT