Page 308 - Moving the Earth_ The Workbook of Excavation

LANDSCAPING AND AGRICULTURAL GRADING

7.2 THE WORK

Grading is also affected by the extent and type of basement excavation. A deep, full basement
produces large quantities of fill, while digging for footings and a floor slab may yield little or
none. When the building is to have a basement, is to sit low, and is to be built on a plot having a
good grade, it will probably be economical to haul away all dirt not required for backfill around
the foundation.
Desired depth of the foundation below ground line may be obtained by digging full depth and
removing spoil; by putting the basement floor at the original surface and filling; or by an inter-
mediate method. In general, the most economical way is to cut just enough to provide the necessary
amount of fill to build the ground up to the building.

Rock and Water. The presence of rock or water near the surface may make a plot a poor invest-
ment, and in any case is important in deciding whether to have a basement, and the depth to place
its floor.
5
Shallow rock can be found with a probe made of 4 or 5 feet of ⁄ 16 -inch stainless steel rod, with a
sharp point at one end and a handle at the other. This can be pushed down into any but the hardest soils.
However, it will not tell whether resistance is a cobble or ledge. A long sharp crowbar or prybar
can be sunk by repeated dropping and turning. If it is stopped by an obstruction, lack of vibration as
it strikes indicates a small stone; vibration only near the hole, a boulder; and a general jarring, a for-
mation of bedrock.
Vegetation will tell a lot about water conditions. Bush willows and bog or bunch grass must
have it wet in spring at least. Such water-loving plants on a flat indicate swampy conditions. On a
slope they show a spring or seepage, and may warn of ledge rock as well.
If rock or a high water table is found on the site or surface drainage is poor, it is often good
practice to reduce the depth of excavation and truck in fill.
No fill should interfere with drainage from adjoining property. If the land must be raised,
drains must be placed under or around any dam that is formed.
A septic field on low or impervious ground may have to be placed in a filter bed (pervious fill)
which may be quite costly.

Hill or Valley. A hilltop is almost always well drained, so that the wet basement difficulties dis-
cussed in Chap. 5 will not arise. On the other hand, it is much more likely to have rock close to
the surface, so that the expense of basement digging may be three to six times greater than for dirt
excavation.
Ground drainage can be too good. A person wanting to enjoy lawns and gardens will have dif-
ficulty with them in dry weather if they are on a heap of sand or gravel. Topsoil is likely to be
poor, thin, and stony.
Building on low ground risks water trouble in the basement, if any, and the possibility of serious
flooding from streams or drains. It limits view to the immediate surroundings, provides a higher
average temperature but increases danger of frost damage (cold air flows downhill), reduces
effect of cooling breezes in the summer and even more cooling gales in the winter, and usually
provides rich and moist soil for lawn and garden.
If at all damp, a low site is dangerous to the health of arthritis and asthma victims.
Slopes may offer any combination of features of high and low land. Special factors to consider
are that if the land slopes down to the south, it will be warm (or hot), and, down to the north, it will
be cold in the northern hemisphere.
View. A building on high ground may be largely deprived of the enjoyment of a fine view by
being set too low or too far back from a slope, or by careless grading or planting.
A common error is to build or fail to remove a high spot which, although lower than the house,
blocks the view of nearby down slopes and hollows. See Fig. 7.1.
There is often much conflict between trees and view, which must be decided on a basis of indi-
vidual preference. In general, ordinary young trees may be quite readily sacrificed while old trees
or fine specimens of younger ones should be preserved if possible. Drastic pruning will often
serve the same purpose as removal.