Page 320 - Moving the Earth_ The Workbook of Excavation

LANDSCAPING AND AGRICULTURAL GRADING

7.14 THE WORK

Sidehills. A long driveway of the farm or estate type may have to cross a hill slope. It is notched
into it in the same way as a pioneer road. However, since it is a permanent improvement which
should have a pleasant appearance, special procedures are followed.
Such a drive serves not only as an automobile route but also as a drainageway. Unless diversion
ditches are made above it, whatever water flows down the slope will land in the driveway cut, and flow
down it or across it. Unless an ample channel is provided, the drive may often resemble a streambed.
A driveway crossing a hillside below a long slope should be 14 to 16 feet in width, including
drive, shoulder, and gutter, but not the slopes. The gutter should be at least 3 feet wide and deep
enough to carry all the water. It can be relieved at frequent intervals by diagonal cross drains to
the lower slope. The drive cross-section may be crowned or sloped oppositely to the hill, but
should never slope with it. See Figs. 7.8 and 8.1.
The cheapest gutter is sod, and it may hold on quite steep slopes if well established. Temporary
diversion ditches can be made with a plow to keep much of the water off until it is well estab-
lished. Stone, concrete, and blacktop are water-resistant, but are subject to frost heaving unless on
a stone or gravel base.
The slopes of the cut and fill should be topsoiled and seeded. They are often too steep for mowing.
Garage Level. Driveways offer minimum trouble in use and maintenance if they are nearly
level. Unnecessary expense and inconvenience may be caused by placing the garage so that grades
are created or exaggerated.
If the driveway is long, the garage should be at about the grade of the ground around its
entrance after landscaping. If the drive is short, the garage should be at about street level.
It is unusual for a garage to be higher than the grade around it, but it is very common practice to
place it under the building at basement level. In this case the driveway often must enter through a deep
cut bordered by steep slopes or retaining walls, and usually descends more or less steeply as well.
A descending drive must level off several feet outside of the doors, and must not do it so
abruptly as to cause a car’s bumpers to scrape when entering or leaving. Extra width is needed
between walls. One or more grating drains should be provided outside the doors, with plenty of
capacity. Drainage from a long drive or from the lawn should be diverted to other drains or channels.
Failure to observe both of these precautions may result in a flooded garage or basement. It is also
necessary to keep the area clear of leaves and trash that might block the drain.
If the drive is short, its slope will be determined by the difference in level between the garage and
the street. Driveways as steep as 30 percent grade are in use, but they are both difficult and dangerous.
Any steep drive requires care in designing the vertical curves at each end so that the center of
the car will not scrape on a convex curve, nor its bumpers hit on a concave one. There should be
a parking place which is moderately level if possible.
In climates where freezing weather occurs, steep grades may become dangerous or impassable.
Also, drifting snow may entirely fill a cut to a low garage, from which it will probably have to be
dug or blown rather than plowed.

FIGURE 7.8 Hill slope driveway section.