Design an open-cut detention basin for the developed tract shown in Figure 15-23 to result in zero increase in peak runoff for the 100-year storm. Computations are to be done by NRCS Method by...

Design an open-cut detention basin for the developed tract shown in Figure 15-23 to result in zero increase in peak runoff for the 100-year storm.

Computations are to be done by NRCS Method by computer or by hand. ­Locate the basin on site south of the parking area and discharge at one of the on-site streams. Make all slopes 3 horizontal to 1 vertical. Use the following assumptions:

1. Project location: near St. Paul, Minnesota

2. Hydrologic soil group B

3. Predevelopment soil cover on site: wooded, good condition

4. Postdevelopment soil cover on site:

  Impervious

  Lawns, good condition

 Woods, fair condition