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Site Planning - Phase I

Homework Problem

Marianne Parsons

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The following investigation is designed as a homework problem that can be used in conjunction with Phase I, Cut and Fill.

Topography

The following topography map was retrieved from City Hall for site development. The map has been marked off into 5 sections (0ft-100ft), horizontally across the site for the cut and fill process. Draw the section cut 25ft by hand (or with Geometer's Sketchpad). Let 1/4" = 10'-0" for the vertical heights of the different elevations (10ft-70ft), and label the line "existing elevation line" as in Phase I. Use the drawing below to get started, and answer the following questions on a separate sheet of paper.

1. How could you project the topography lines down onto your drawing, to represent the appropriate elevation heights for section cut 25ft? (Hint: look at the intersection between the topography lines and the dashed section cuts).

2. How could you represent the height of each of the topography lines on the section elevation?

3. Which horizontal section cut (dashed line) on the topography map looks like it would give us the best representation of the existing site conditions (i.e. which cut will show the most elevation changes)? Why?

4. Describe how the elevations would look if the section cuts were taken perpendicular (or vertically) to the dashed cut lines drawn below. To get an accurate representation of the existing site conditions, do you think 5 cuts vertically across the site would be enough? Why or why not?

Click here to use the GSP file for this problem.

One Correct Student Response

The following represents a sample student response to the questions and drawing given in the homework problem above. Note there are more than one possible correct student answers to each question, and should be discussed as a class.

Question Responses:

1. Use the points of intersection between the dashed cut line and the topography lines. Then, draw lines perpendicular to the cut lines onto the elevation drawing below. These lines represent the points on the elevation that meet each topography line. Then, by determining the height of these points on the elevation, the points can be connected to generate the elevation of the section.

2. Draw the height of each topography line on the section elevation, using the given scale of 1/4" = 10'-0".

3. Section cut line 0ft because it intersects the most topography lines of all the section cuts. Therefore elevation at section 0ft will show the most elevation changes.

4. The section cuts would be shorter, and have different elevations. Most of the elevation cuts would not intersect the highest point on the site, and so most of them would look very flat. I don't think 5 cuts would be enough because the site is too long and 5 cuts would not give an accurate estimate of the existing conditions. More cuts would have to be taken.