About Us

Oakridge Engineering specializes in solid waste, farm sites, and small dams. We are a small specialty engineering firm of about 12 people, including engineers, technicians, inspectors, and administrative staff.

Erik Lietz, PE Founder and Principal

Erik grew up in a small town in northeast Wisconsin, received his bachelor in civil engineering from Michigan Technological University, and has over 20 years of experience in private consulting. He currently is vice president and safety ambassador of the Wisconsin Badger SWANA chapter.


  • Registered Professional Engineer in Wisconsin and Wyoming
  • MSHA Part 46 Annual Refresher
  • Hazardous Waste Operations and Emergency Response 8-Hour Refresher
  • Solid Waste Disposal Facility Manager, WI
  • Hazardous Waste Operations and Emergency Response 24-Hour Training

Registrations Licenses

Our staff hold professional engineer licenses in Arizona, Iowa, Minnesota, New York, Wisconsin, and Wyoming. We are NCEES certified, so we can obtain a professional engineer license easily in almost any state. Staff are also a TSP (technical service providers) with NRCS. We are members of DBA, PDPW, MN Milk, ASCE, ASABE, and SWANA.

Mission Statement Values

Committed to quality, knowledgeable, trusted, and efficient - our goal is to provide what you would want your Engineering Department to be.

History Background

Oakridge Engineering, Inc. purchased Tiry Engineering, Inc. (specializing in agricultural sites and small dams) in July 2017. Tiry Engineering had been founded in April 1994 by Michael J. Tiry. Mike has over 50 years of experience engineering for farmers and is still on staff at Oakridge. Today, Oakridge serves solid waste and municipalities as well as agriculture, water, and commercial clients. A sentence….

Testimonial from Shelly at Monroe County Landfill

“Just wanted to say THANK YOU! Erik, for always giving Monroe County EXCELLENT and above-the-call-of-duty service!

When I realized I was too close-for-comfort in achieving my remaining training credits needed for my WDNR Facility Operator certification renewal, there you were, once again, with a quick answer and solution!

The training you provided was top-notch, your seasoned experiences shared with us very valuable, and the group sharing experiences from the various other landfill attendees also valuable.

I would recommend Oakridge Engineering for all our future training needs!”

Very Sincerely,