Jan 20, 2013

Winter Lake Status

I can't explain why, but one of the things we love about our abused and battered little lake is walking on the ice on a moderate winter day. There is something oddly cool about making a lap or two around the island when the sun is out, the lake is frozen solid, and traffic is blasting past us, oblivious of our presence. It's not quiet. It's miles from pastoral, but it is oddly peaceful. A little more snow and the lake would be cross-country ski-able. A little less and, I guess, you could skate it. Before the winter hammer fell on Last Saturday, we were out on the lake enjoying the moderate temperature and windless day.

A few years ago, this was a 3' diameter concrete
culvert. Today, it's packed with freeway sediment.
The lake's level is as low as it has been in years. So low that I was able to take some pretty pointed pictures (say that 3X fast) of the damage MNDOT's past "engineering" has done to our lake. For example, smack in the middle of this shot is what remains of a drainage culvert MNDOT used to drain water (and massive quantities of sediment) from the south-bound I35E Little Canada Road freeway entrance. When we moved to Little Canada in 1997, this drainage culvert was completely exposed and the lake was approximately 4' deep about a canoe paddle's length away from the culvert. That general condition and relative height stayed constant for years (discounting the catastrophic lake level drop when the Watershed District screwed up the water levels at the end of the 1990's) until the freeway redesign a few years ago.

This picture gives some perspective on how large the
sediment "beach" is, at least the above water beach.
For a couple of seasons, all of the freeway entrance ramp drainage was routed through this culvert and over the edge of the ramp's curbs until the drainage culvert was filled with sediment. The rest of the silt and sediment is simply poured off of the ramp into the lake, resulting in a dramatically eroded lake shore and an increasingly steep bank. At one time, this was the deep end of the lake by several feet. There was some source of water movement that always kept the ice either thin or clear about 30' west of this point, but after the freeway redesign the massive influx of sediment filled in that source of current and helped allow the nearly complete coverage of water lilies by making the lake shallow enough for them to take root. The sediment shelf is completely above the water-line right now and anyone can walk out and examine the damage done. You can also see the erosion effect by looking at the freeway fence posts. The concrete post footers are being rapidly exposed as the lake bank vanishes from runoff erosion.

This was my first opportunity to see the Little Canada-funded Gopher Electronics parking lot drainage plan and I'm not particularly impressed. We gave this design a shot on the drainage pipe at the south end of our property about 12 years ago and it worked for a season, but was quickly overwhelmed by the quantity of sediment pouring into the lake from Lake Shore Ave and the sediment "island" has continued to expand since. This design is not a "trap," but is more like a temporary diversion with a little landscaping.

Sediment traps are either holding ponds, like those we see along the eastbound sections of the new I694 design, or complicated concrete affairs that have to be regularly maintained. Any man-made system requires maintenance and that is often the fatal flaw in major construction designs. The designs are fine, but the follow-up is insufficient or non-existent. Supposedly, we have traps like the ones illustrated in the mechanical drawings (on the left) for all of our street drains, but if no one cleans the traps they were one more waste of taxpayer dollars.

It's not like all of this hasn't been reported to the city, county, and state in the past, but if you'd like to see what's really going on with our lake, now is the time to take a walk on the ice. Worst case, the lake is about 4' deep at the deepest spot right now. The water levels are probably 2' below where they were early last spring.

If we get the noise barriers and the construction of those barriers doesn't do more harm than good, the quality-of-life value of our lake could improve dramatically. It would be nice to get some of this street and freeway drainage problem solved at the same time so that the lake just doesn't slowly fill with sediment and become a mosquito breeding ground.