contours (for instance, halfway between 103 and 104). The spot elevations at the top and bottom of the curbs for the four contours shown in the figure are summarized as follows: Table 13.1 Relation of Spot Elevations along a Curb to Contours
D 103
Top of Curb Elevation
Bottom of Curb Elevation
103.5’
103.0’
C 104
104.0’
103.5’
C 105
105.0’
104.5’
C 106
106.0’
105.5’
Curb, slope, spot elevation, and contour line mark-ups have been added to the photograph in Figure 13.11 to facilitate visualizing a parking lot as it would be drawn in a site-grading plan. A 2 percent cross slope was created with the contours (Item A).
105
C
104
D
102
B
C
C
106
105 CB 103.5
34 33 32
A 103
104
Crown
Figure 13.11 Parking lot with crown shown in photograph with diagram to right
The photographs in Figure 13.11 show how water flow is directed in a parking lot using contours and spot elevations. The contours shown in Figure 13.12 have been drawn to create a valley down the center of the drive with surface water sheet flowing at a 1 percent slope. The valley solution concentrates water down the center of the drive lane, reducing water in the parking spaces so that people stepping out of their vehicles
Detailed Grading with Slopes, Contours, and Spot Elevations
221