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Riprap is a permanent layer of stones that reduces the speed of runoff. Here, it's slowing runoff flowing through a channel. |
When it rains or when snow melts, soil and vegetation absorb and filter runoff as it flows along the natural contours of the land. However, on a site that's undergoing development and construction, the land has been graded and cleared of vegetation, and the protective topsoil has been removed. When it rains, the runoff flows much more quickly, and the soil absorbs relatively little. As runoff flows down a hillside that has disturbed soil, it takes soil with it, eroding the hillside and transporting that soil to rivers, lakes, streams, and other bodies of water.
To minimize environmental problems, the builder develops and implements a Stormwater Pollution Prevention Plan (SWPPP). A SWPPP specifies the Best Management Practices (BMPs) to be used at the site to control runoff and to prevent or minimize erosion and sedimentation. BMPs that control runoff reduce the amount and speed of runoff flowing through the jobsite or redirect the flow of runoff through or around the site.
Do you know the best practices for implementing runoff controls? Answer the question below to test your BuildIQ and click the Submit button to see if you're right.
Why are geotextiles placed on the ground before riprap is installed?
Do you know the best practices for implementing runoff controls? Answer the question below to test your BuildIQ and click the Submit button to see if you're right.
Why are geotextiles placed on the ground before riprap is installed?
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A. To speed the flow of runoff through the riprap
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A is incorrect. The geotextiles aren't placed to speed the flow of runoff. Geotextiles are placed on the ground to maintain the riprap base and keep the soil underneath the riprap from eroding.
B. To maintain the riprap base and keep the soil underneath it from eroding
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B is correct. Before riprap is installed, geotextiles are placed on the ground to maintain the riprap base and keep the soil underneath the riprap from eroding.
C. To prevent vegetation growth in the area surrounding the riprap
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C is incorrect. The geotextiles aren't placed to prevent vegetation growth. Geotextiles are placed on the ground to maintain the riprap base and keep the soil underneath the riprap from eroding.
