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Keep soil on developments, out of Walnut Creek

Sep 20, 2016

The Register's editorial | Original Article

{Damaged erosion-control socks can't keep soil from washing off this Waukee housing development. The stormwater drain is filled with soil.(Photo: The Register)}

Construction crews are moving a lot of earth as development booms in Des Moines’ far western suburbs. But where is the soil going?

Unfortunately, too much of it ends up in Walnut Creek. The last thing we need is Iowa’s most precious resource going down the drain.

Agriculture is the largest source of Iowa’s water problems, but not the sole source. Cities and suburbs must do more to prevent erosion, flooding, nutrient runoff and other problems plaguing the state’s lakes and streams. Fortunately, many cities will be asked to take an important first step in coming weeks.

“If we’re going to ask people in agriculture to consider these practices, then we should be willing to do so as residents,” said Darren Fife, a member of the Walnut Creek Watershed Coalition, one of the groups supporting a multi-governmental plan to protect the 53,000-acre watershed.

Walnut Creek is unique in Iowa because a series of challenges flow into its banks. Its headwaters begin in the farmland of rural Dallas County. Then the creek and its tributaries flow through rapidly developing suburban landscapes and highly populated urban areas before the creek dumps into the Raccoon River — and into Des Moines’ drinking water supply.

The creek and its neighbors feel the effects: High nitrate concentrations from fertilizer runoff. Large amounts of e. coli bacteria from pet waste and other sources. Increasing flooding as rainfall flows quickly off parking lots and new developments. Large amounts of sediment in the water from erosion.

Construction sites contribute as much as 25 percent of the sediment load in the watershed, and more in urban areas, according to a study by the Des Moines Metropolitan Planning Organization and other groups. It’s easy to see why.

An editorial writer visited construction sites this month near Alice’s Road in Waukee, where new apartments, housing developments and commercial buildings are popping up. Fortunately, many sites were using silt gates, large erosion-control socks, drain covers and other ways to keep soil out of drains and ditches — as they are legally required to do.

Such practices, however, were inconsistent. Some streets were lined with a layer of dirt that had washed off construction sites after a recent rain. In one housing development near Grant Ragan Elementary, equipment had crushed the socks and a stormwater drain was so full of soil that plants were growing out of it.

Members of the watershed coalition have noted such practices and worse — including mountains of soil that sit near open drains, awaiting the next rain.

Cities must do more to enforce stormwater rules. “We inspect, but not frequently enough,” West Des Moines City Manager Tom Hadden told the editorial board early this year. He’s one of the local officials supporting the Walnut Creek Management Authority’s Watershed Master Plan.

The voluntary plan outlines approaches to improve water quality, habitat, recreation and public health. It calls for such practices as widening buffer strips along streams, stabilizing creek banks, enforcing stormwater rules on building sites and restricting construction in 100-year flood plains.

Last week, Clive became the first community to approve the plan. Clive residents have felt some of the watershed’s problems: frequent flooding, stream banks eroding in their backyards, and lakes filling with silt.

Other communities could face worse problems if action isn’t taken. Residents should urge their representatives to support the master plan when it comes before city councils in Dallas Center, Des Moines, Grimes, Johnston, Urbandale, Waukee, West Des Moines and Windsor Heights.

Creeks know no boundaries. If one city rejects the plan, Walnut Creek — and all of us in its watershed — suffer.

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"Covered erosion and necessary practices very well."


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