Design Center mobile

Arbor Lake

Grinnell, Iowa

Stormwater Treatment


Grinnell Department of Public Works


Veenstra & Kim



Technical Description:

  • Product Used:
  • Vortechs® System Model 7000

Grinnell, Iowa, named “one of the best small towns in America,” is home to Arbor Lake, a favorite fishing, boating and picnic spot for locals. In recent years the community noticed that the lake was changing.

The Challenge

Grinnell did not fall under the state’s National Pollution Discharge Elimination System permit program, and at that time, urban runoff flowed into the lake untreated.

“We started seeing signs of pollution damaging the ecosystem and endangering wildlife,” stated Jan Anderson of Grinnell Public Works. “We knew it was time to restore the lake.”

The Solution

It was hometown civic pride that inspired the citizens to restore the beauty of Arbor Lake. When federal grant money became available under the Natural Resources Conservation Service, a civic group applied for and received funding to implement this restoration project.

Forrest Alderidge of Veenstra & Kimm, an engineering firm specializing in municipalities, was brought in to develop a Contech plan. An on-site visit by Alderidge confirmed the pollution — he saw cups and plastic bags floating in the water and high sediment levels. A five-year plan was developed and Phase I of the project was implemented.

Alderidge reviewed several stormwater treatment systems before selecting the Vortechs® System, a hydroynamic separator, as the best method to meet the needs of Grinnell. The system is engineered to remove sediment, trash and free oil and grease from stormwater flows. In addition, unobstructed access to the isolated pollutants make inspection and maintenance of the unit easy.

Rather than redesign the current stormwater drainage system, the Vortechs System was easily installed within the existing storm drain. A segment of 24-inch storm drain was removed and replaced with the Vortechs model 7000. The system treats peak stormwater flows up to 11 cfs to the 15-acre lake. Stormwater flows into the treatment system, entering the patented swirl chamber, where a vortex motion maximizes the settling of contaminated sediments. The water then travels through a series of chambers where baffle walls trap oil, grease and floatables.

The Result

“This has been a very exciting project for the community and our residents will benefit from it for years to come,” said Anderson.

Technical Description:

  • Product Used:
  • Vortechs® System Model 7000

800-338-1122 |


© 2023 Contech Engineered Solutions LLC, a QUIKRETE Company