Column: Making Waves

Published 12:00 am Friday, June 9, 2006

Poor sediment control means poor water quality

By Cathy Rofshus

Last month’s column introduced five top issues in the Shell Rock River Watershed:

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1. Farm field runoff.

2. Wind erosion.

3. Construction site runoff.

4. Shoreland erosion.

5. Urban storm water runoff.

In May, I explained how erosion from rural areas can hurt water quality and how best management practices can prevent that damage. This month’s focus is construction sites.

Phosphorus is flowing into Fountain Lake with sediment, according to a preliminary analysis of water monitoring&160;from 2005. Phosphorus is the nutrient that fuels algae blooms. This is how sediment &045; dirt &045; hurts Fountain Lake and other local bodies of water:

-&160;Rain carries sediment into storm sewers, which drain into local lakes

-&160;Sediment contaminates streams and lakes by muddying the water and carrying pollutants

-&160;Sedimentation degrades fish and wildlife habitat

-&160;Poor water quality also harms water-based recreation such as swimming and fishing

-&160;Erosion decreases the capacity of drainage systems, meaning higher maintenance costs

Construction sites can be a major source of sediment. The U.S. Environmental Protection Agency estimates that 20 to 150 tons of soil per acre runs off construction sites with rain water.

In fact, more sediment can run off a construction site in one rain event than off a farm field in a decade of rainfall.

The Shell Rock River Watershed District is working with contractors and with farmers to better control sediment. As the conservation technician for the Watershed District, Brett Behnke worked with farmers and ag land owners to put in filter strips and other practices to reduce erosion. Reducing erosion means less sediment washing into local waterways and lakes.

Now as district administrator, Behnke is working with contractors to better control erosion and sediment on construction sites. Once a week, Behnke tours construction sites to see how sediment controls are working. When he sees collapsed silt fences or other problems, he contacts the contractor to resolve the problem.

The district is asking all contractors to effectively control erosion on construction sites &045; of all sizes &045; through proper design, implementation and maintenance. Many times, building professionals associate sediment control with silt fences. Silt fences are just a tool to contain sediment, once erosion has already occurred, and are only effective if set up and maintained properly, especially after rainfall.

While erosion control may cost a little in the short term, it saves water quality, wildlife habitat, and government spending in the long run. Studies have shown that for every $1 not spent on erosion control, $14 to $15 is spent on correcting the impact. Prevention is a sound investment.

Construction companies and developers looking for help with sediment control can ask the following offices:

-&160;The City of Albert Lea Inspection Dept. at 377-4340

-&160;Freeborn County Environmental Services at 377-5186

-&160;Shell Rock River Watershed District at 377-5785

Information is also available at:

-Storm water Management Resource Center &045;

-&160;Minnesota Erosion Control Association &045;

-&160;Pollution Control Agency &045;


Healthy lakes make for a healthy community, both economically and environmentally.

Next month’s column will look at shoreland protection.

Trivia question

The range of phosphorus levels for lakes similar to Fountain Lake in this ecoregion is 65 to 150 ml/100L. What was the average level of phosphorus for Fountain Lake in 2005?

a. 150

b. 185

c. 220

The answer is 185 ml/100L. Thus, Fountain Lake had higher phosphorus levels than similar lakes in this ecoregion.


(Cathy Rofshus is the outreach director for the Shell Rock River Watershed District. She can be reached at 377-5785.)