Reject the Plan
"Sand" is a considerable portion of the solid or absorbent materials
dropped during low or slow flow in and out City lakes. The sand carried
into Lake Hiawatha has several sources but much of it was spread on City
streets along with chemicals to melt ice. The chemicals are persistent:
they reform or dry into solids some times. The more street wash, the more
chemicals and solids are carried along in creek or sewer to the Lake.
Other crap (literally and figuratively) is also carried along, held in the
Lake below the weir-top level and concentrated as the water evaporates.
The water flow is seriously polluted including chemicals, toxins,
biological matter, and too often contaminated illegally, and the government
give more lip service to preventing it than policy or budget or attention.
In this debate, let's change "sand" to *solids and adsorbents* [that take
up space in the Lake increasing local flooding and carrying *various
pollutants and microbes *that make the lake water unhealthy for swimming]
are dropped into the Lake.
Ed 10 of 10, Adam 1 debate point.
'Weirs" are a kind of dam to control flow; direct or limit the rate or
volume. The adjustable weir top directs flow into the next reach of
Minnehaha Creek. There is limited storage volume in that reach, as the
next control --under the road near Minnehaha Park --is set to limit flow
(rates) over the Falls to slow the erosion and collapse of the Falls (which
has been moving slowly upstream for centuries).
Here's how it works: The weir top (called the *invert elevation* is the
lowest point of the land surrounding Lake Hiawatha. So unless the Lake is
being filled more rapidly than the outflow, the top of the water is
controlled to the invert elevation and in low flow, drops further due to
evaporation. In late Summer without a storm, Lake Hiawatha *would be higher
than it would have been that day and year if the invert had not been
raised.*
Ed 6, Adam 4
"Depth" The storage or volume below the invert elevation is more
complicated than either Ed or Adam seem to realize. The basin's geometry is
hard to measure. The surface area of the Lake at the invert elevation is
known, but the depth contours are not visible and may not be scanned (like
a depth finder) accurately because the density of the water, mud, golf
balls, tires, fish and sand is being measured not the water depth or the
actual bottom of the Lake.
"Volume" is better than "depth." But, yes, the actual liquid water that can
be held in the Lake depends on what else is sunk, floating or suspended in
the basin --and if if anything is blocking leaks. There is a big, porous
limestone plateau under Minneapolis that has pockets, streams and lakes
Rest of post
--ground water. These are fed by lakes and rivers miles away and nearby.
Used as wells, ground water is removed faster than it is replaced by
intermittent flows and seeps. There is no evidence that the "water table"
is involved in basement flooding. There is evidence that ground water is
depleted (sink holes).
Ed 1, Adam 2.
Lake Recreation. Water quality determines this, not volume, The golf course
"surface water" pumped into the Lake is less polluted than the Creek water
and far cleaner than storm sewer water.
Ed 10, Adam 4
Flooding: If the pumped water is added to Lake Hiawatha in flood stage
(water is over-flowing the banks of the Creek or the Lake) it has the same
effect as more rain or ice melt in the Lake. But it isn't pumped, I
understand, unless the Lake Level is below the invert elevation and the
pumping then only increases humidity --not flooding even in a summer
thunderstorm aftermath.
Ed 4, Adam 0.
*Debate won by Ed, 31 to 11. *
Jim Spensley (Former MCWD Manager and President)
Note: I was the most-downstream Manager and I asked permit seekers to
convert *cubic-feet per minute *flow rate increases into *basements full
per hour *using the average size Minneapolis basement area times 6 feet
depth.
On Tue, Mar 2, 2021 at 11:33 AM Ed Felien <<email obscured>>
wrote:
> Adam, please help me understand. How do I misunderstand the weirs and the
> sand in Lake Hiawatha?
> Hasn't the weir at the exit of Lake Hiawatha into Minnehaha Creek raised
> the water level of the Lake?
> Hasn't the dumping of sand by the City flowed that has flowed into Lake
> Hiawatha through the storm sewer system seriously reduced the depth of the
> lake? And hasn't that negatively affected the water quality making it
> unfit for swimming?
>
>
> Ed Felien
>
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> ________________________________
> From: Minneapolis Issues Forum <mpls@forums.e-democracy.org> on behalf of
> Adam Miller <<email obscured>>
> Sent: Tuesday, March 2, 2021 7:13 AM
> To: mpls@forums.e-democracy.org <mpls@forums.e-democracy.org>
> Subject: Re: [Mpls] Reject the Plan
>
> The pumping is something like 90% surface water off the golf course and
> the proposal has always been to keeping doing the pumping needed to keep
> basements dry.
>
> It would be helpful if people would stop repeating misinformation
> (including Ed’s misunderstandings of the weir(s) and sand).
>
> Adam Miller
> Hale, Minneapolis
> About/contact Adam Miller: http://forums.e-democracy.org/p/adammiller
>
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> Ed Felien
> Powderhorn, Minneapolis
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