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