What is a Preserver & How Does It Work? with Lance Hoff, P.E. from Momentum Environmental

by | Dec 6, 2023

Episode 018: “The best way to get into what it is and what it does is to talk about the origin story.” Lance Hoff, P.E. created The Preserver over 10 years ago to address the specific issues that his home state of Minnesota found with pretreatment devices in high flow situations. MNDOT was regulated as an MS4 and needed to provide reporting on measurable goals. They started by testing all of the existing infrastructure they had in place. They had a study done at St. Anthony Falls Laboratory at the University of Minnesota. What they found was that the existing units did well at removing sediment at low flows, but did not perform the same at high flows. Trying to find a fix to retrofit the existing equipment was extremely costly. This is how The Preserver was developed, it could be retrofitted into existing sump manholes at a lower cost and worked well at higher flows as a hydrodynamic separator.

The high flow events are not the normal events, but did need to be addressed. “The problem is the high flows, everything scours out. How can we take these sump manholes MN DOT has, and make them work better. They were looking for a product that was retrofittable into sump manholes, and could prevent that scour from happening. They [wanted] to have energy dissipators  to prevent the scour and improve removal efficiency at a fraction of the cost, and you don’t have to place them offline.” Lance breaks down the exact problems The Preserver was designed to address. Lance says “So The Preserver’s a system, it has two components. It has an energy dissipater which goes on the inlet or inlets if you have multiple inlets, and you have a skimmer that goes on the outlet. You’re just trapping any floatable pollutants. Functional wise, it’s got some benefits in that it’s retrofittable and it’s adjustable. But function wise, it’s just skimming off floatable pollutants, trapping anything that floats trash, oils, greases, hydrocarbons, leaves, and helps with organics. Then the dissipator is a perforated sheet, essentially, that has a curved shape and connects at the inlet. So it’s got a bunch of holes in it. Those orifices are what create the energy losses. They also work to control the flow regime and the structure and spread that flow out and makes the sump very quiet.”

Lance and Ty discussed the difficulties for innovative technologies to be recognized and utilized. Everyone knows what they have always done, so that is their first thought when they have a new project. Just because it is what you have always done, doesn’t mean it is the best solution. “So anybody watching this that wants to promote innovation, that’s probably the best way to do it, is keep an eye out for new technologies, especially some of these smaller companies, and help support them and promote those products,” Lance states.  To learn more about The Preserver, visit Momentum’s website: https://thepreserver.com


  • “If I put my spoon in my glass, and I stir it up, stuff drops to the bottom, perfect. That works. If I blast that same cup with the fire hose doesn’t work as well in the big storms.” (10:38 | Ty)
  • “Let’s start doing the math. If we can take half of the sediment before it gets in the pond, and just clean it with a vac truck, it’s way cheaper for us in the long run. We maintain a pond every 60 years, instead, every 30 years, and you run the numbers.” (21:13 | Lance)
  • “ The state just finally made a requirement…what they like about it is even different, because they’re responsible for the waters of the state, and they are just big picture. If you’re pre treating stormwater, everything downstream of it’s working better.” (21:13 | Lance)
  • “ So anybody watching this that wants to promote innovation, that’s probably the best way to do it, is keep an eye out for new technologies, especially some of these smaller companies, and help support them and promote those products..” (29:58 | Lance)

The views expressed are that of the individual and do not represent the opinions of any companies past, present or future.

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