In late summer, I would swim and stream-walk a small section of the Raccoon River. While sedimented for decades now, the water was clear in the shallows. For a few years now, the water is pea-green from edge-to-edge. For decades and worse now, this water has strongly contributed to a vast hypoxia zone in the Gulf.

In the 1980s, I wrote about the wisdom of the river, focusing on the Des Moines River as a living, very open metaphor for the essential streaming dynamic of the universe that is within us as well in the streaming of our body metabolism and thought.

Thursday, September 22, 2016

Urban Water Pollution

Urban water pollution is not the primary water pollution in Iowa.  However, mediating urban water pollution will be as difficult as mediating rural water pollution.  In fact, they will be so difficult to really clean up that even a reasonable clean up will not occur without a serious revaluing of water and life in Iowa.

I MOVED INTO MY home on the West side of Des Moines twenty years ago.  it is situated on the ancient upper sandy banks of a washout of the ice-aged Des Moines Lobe.  There was likely a succession of pines chasing the retreat of the ice sheets north.  In more recent centuries, the sandy bank became a white oak savannah.  Today a remnant channel of the ice-aged stream continues to flow, and it is named Walnut Creek.  

Lance Kinseth, Walnut Creek, photo

Walnut Creek runs 97 miles north, draining 62,643 acres that remain perhaps sixty percent rural but hat are gradually becoming more urban.  A few miles south of my house, Walnut Creek empties into the Raccoon River.  One mile downstream on the Raccoon River from where the creek drains into the river is a source of water for the Des Moines Water Works.

Just down the street in front of my house, to the East, a short-length feeder stream (at least visibly above ground) runs into Walnut Creek.  This stream has an slow active flow throughout the year and it is edged by trees and some parkland on both sides.

Both Walnut Creek and this unnamed feeder stream are impacted by pollution.  Walnut Creek has both rural and urban runoff, while the feeder stream is entirely urban pollution.

The emphasis of this blog is upon urban water pollution.  Both these streams gather storm water, and urban hard surface generates 9x more storm runoff than woodland.  

While much emphasis in mediating rural water problems is placed on creating buffer strips, it is quickly apparent that on my little feeder stream even rather dense woodland buffer strips do little to mediate water problems.  [This will also become evident when taking a look at the pond in Greenwood Park a little later in this post.]

What are the urban water pollution elements?

Lawn fertilizers, automobile oil, grease, rubber, heavy metals, break pad dust, sediment from construction, de-icers/road salt, bacteria from animal [pet] waste and from leaking household and city sewage lines, littering, industrial waste/chemical storage, synthetic detergents, fuel storage tanks, poorly discarded hazardous waste, airborne pollutants (acid rain, nitrate and ammonium deposition), fertilizer and pesticides.  Construction sites are estimated to contribute 25 percent of the sediment load in the Walnut Creek watershed.   Construction takes rural land that may absorb pollutants and can affect natural drainage. These pollutants are intensified in rainfall, especially coming off hard surfaces. 

Sanitary sewers, both household and business/industrial and city lines, leak as they age, reflecting infrastructure issues that are not easily addressed in stormwater rules that might apply to construction projects.  And when there are rules, there may not be regular inspection or even application for construction with subsequent violations.  Further, rules and inspection or lack thereof vary across the collection of city boundaries that are superimposed on the watershed.

Buffer strips and bank stabilization and collection areas to reduce flooding are some possibilities, but largely ineffective.  First, they are few and far between, and second, they do not do much.  And they are more costly than one would imagine so that the many other more “squeaky wheel” projects vie for available funding.

How much cost and how effective?

An example of the problems with high cost and limited  effect is illustrated by strong efforts to have a clean pond at Greenwood Park behind the Des Moines Art Center.

The 2-3 acre pond has been plagued for years by silt runoff, invasive plants and nutrient pollution in particular.  
2013:construction of 2 detention ponds above the major pond, $275,000
2014/2015: drained [2014] then dredged from 5 to 15 foot depth [2015], $381,000

Lee Rood, Greenwood Park Pond 2016, Des Moines Register

This pond  was again experiencing significant algal growth.  The hope is that the pond will improve as elements come into balance.  The detention ponds are in a woodland section where one might expect a little more silt retention as well as a wetland effect on reducing pollutants.

In 2016, Greenwood Park pond, clean? 


A similar project is currently in  process in Easter Lake and is anticipated to be underway in the future for a pond in MacRae Park.  While it may be beneficial for future recreation it is not a long-range solution.  Most artificial ponds and lakes in Iowa require dredging in a rather short number of years, and all silt in quite rapidly, even much larger water bodies such as Saylorville Reservoir just to the north of Des Moines and Lake Red Rock to the southeast.

Your 2 Cents Worth [Reader’s submission to Des Moines Register]:

Regarding the algae problems in Greenwood Park Pond, 
it should be a concern for all the residents nearby from 
airborn-causing health problems.  It must be controlled by
aeration.  Use park profits from the golf courses to 

install fountains to circulate the water during the hot season.

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