By 
Brad Johnson
During the past 60 years, the US Army Corps of Engineers, city and state government spent millions studying ways to protect Lake Kampeska and Watertown from flood waters bringing economic devastation and psychological harm.
Here’s what we got.
There will be no protection from a 1997-level flood for Lake Kampeska or its property owners. Southwest Watertown will get a $26 million levy and river widening system that will protect about 36 blocks.
There is more. The plan actually will damage Lake Kampeska as the corps and city try to use it as a storage reservoir, inviting sedimentation, phosphorous, nitrate and e coli pollution.
The corps unveiled its proposal at a Sept. 17 public meeting in Watertown and set an Oct. 9 deadline for comments about its plan. Comments from Lake Kampeska residents and the Lake Kampeska Water Project District (LKWPD) largely sent a resounding “forget it.”
Simply, if you can’t provide any flood relief to the lake, leave it alone and don’t damage it.
Unfortunately for the city, according to corps documents, the plan is not economically feasible unless Lake Kampeska can be a dumping ground.
The LKWPD not only believes that economic analysis is flawed and also questions the corps’ ability to lower the lake during the fall. The LKWPD’S arguments were outlined in a detailed analysis submitted to the corps this week by RESPEC, an engineering firm with expertise on Big Sioux River flooding.
Disappointingly, it appears there is no similar comments defending the lake from Watertown city staff. The Watertown City Council’s silence indicates acquiescence if not outright support.
In fact, here is what the corps’ report says with comments in parentheses added by me for clarification. “The Non-Federal Sponsor (City of Watertown) supports the TSP (Tentatively Selected Plan) and the proposed implementation plan.”
Either the Corps is misleading everyone, or city staff has committed the city council to sacrificing the lake. Or the city council in an executive session with the corps earlier this year made decisions without public input. Based on more recent skeptical comments from elected city leaders, I’d guess the corps overstated the city’s support.
Here is what the Corps plan entails.
Lake Kampeska would be lowered in the fall to 9.6 inches below its full elevation if it were at that level or above. That would create 3,300 acre-feet of storage. An acre foot is enough water to cover one acre in one foot of water.
In 1997, Lake Kampeska started about 13 inches below full and six days later was about 71 inches over full. About 100,000-acre feet came down the river in that flood.
Artificially lowering the lake also ignores why the diversion structure was built by SD Highway 20 after the 2001 flood. It exists to keep polluted water out of the lake.
Research by the lake district estimated the 1997 flood deposited about 29,000 tons of sediment into the lake. Imagine public reaction if 2,100 dump trucks full of gravel were lined up to empty their load in Lake Kampeska.
After the Corps creates a dumping ground in Lake Kampeska, it then turns to the Big Sioux River.
A levee would start on the river’s left bank near West Kemp Avenue and extend south to just north of U.S. Highway 212. It would avoid the Watertown Iron and Metal facility.
About 4.6 miles of the Big Sioux River starting just north of Fourteenth Avenue Northwest to south of Twentieth Avenue Southeast (the US-212 bypass east of U.S. Highway 81) would be widened.
About 50 feet on each side of the existing channel would be dug out, creating a ditch that history shows almost 65 percent of the time would carry little water. This new system cannot speed water downstream, as that is prohibited by law.
It is simply designed to contain a 100-year flood that that corps’ models show is almost 50 percent bigger than the 1997 flood.
The final decision on this project is years away but chips are now on the table.
