The Cleaning Of A Landmark


by Anne Dolan

Workers have nearly finished vacuuming 36 years of dirt off 
the bottom of Lake LaVerne. The job will take about a month 
and will leave the lake cleaner and deeper. The lake last was 
dredged in 1959 and years of sediment accumulation have left 
it just 2 to 3 feet deep in many spots and 5 feet at its 
deepest point. The dredging is expected to double those 
levels and restore the lake to long-ago depths.

American Underwater Contractors, Cedar Rapids and St. Louis, 
is doing the work. A floating dredge essentially vacuums 
water and sediment from the lake as an auger-like instrument 
attached to the dredge loosens soil at the bottom of the 
lake. A shoreline pump sends the mixture into an 8-inch 
aluminum pipe laid in an enclosed portion of College Creek 
that runs under Campustown and across the ISU Arboretum 
southwest of campus. Through this pipeline the water mixture 
is pumped upstream 5,400 feet to a 9-foot deep sediment pond 
off State Avenue constructed for this project in late May.

The sediment pond is engineered so that water filters through 
the sediments to an underground tiling system. From there, a 
second pipeline carries the clean water back into College 
Creek, where it flows naturally back to the vicinity of Lake 
LaVerne.

Back at Lake LaVerne, a temporary 6-foot dam across College 
Creek collects the recycled water and a second offshore pump 
carries the clean water through a pipe back into the lake.

When the dredging is complete, the water level in the lake 
will be lowered temporarily to a level of about 4 feet to 
allow crews to reroute several storm sewers that currently 
empty into the west and north sides of the lake. The north 
shore will be given a flatter grade and rocks will be brought 
in to keep the new shoreline intact. A well was installed 
near the southwest corner of the lake to supply fresh water 
to replace water lost through evaporation.

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contact:  Anne Dolan, Internal Communications, (515) 294-7065
updated:  7-28-95