The Idaho recorder. [volume] (Salmon City, Idaho) 1886-1927, 1917-07-06

"llfIt Llit ibdi 10 VI 10 "a BNNtNN ~ ~
come Of sufficient importance to war
rant highly improved surface, the
maximum grade usually is fixed with
reference to this feature about as fol-
lows:
Per cent.
Coastal plain and prairie reglons....2 to
Average rolling country ........,.....4 TO
Hilly or mountainous regions........6 to
The question of minimum grade is
of importance only as regards the side
bitches. These should have adequate
fall to empty the water that collects
In them ut a sufficiently rapid rate to
prevent damage to the road. Ordlnar-
lily 1t Is desirable to give the side
bitches a fall of about one foot per 100
feet Of length, though somewhat less
fall has proved satisfactory some
times.
Wherever changes in grade occur
the change should be made by means
of Il vertical curve, and not by an
abrupt angle.
Slopes.
The slope at which earth will stand
when faced up in a cut or placed in an
embankment depends % on the char
acter of the earth and (2) on the eli.
mate. In cuts, good quality of nom
shaking clay usually will stand on a
slope of about 45 degrees, or, as slope
is expressed usually, one horizontal to
one vertical, even where fairly deep
freezing occurs, and in some of the
Southern states such material has been
slope of less than one-half to one. On
the other hand, clay that slakes very
easily, may require slope of three to
one, or even four to one, under the most
favorable condition of climate, but
this latter extreme Is very unusual.
The usual slope for clay in cuts is one
to one in warm climates and one and
one-half to one in cold climates.
While in the case of entertainments
clay usually can be deposited on an
initial slope of about one to one, this
steep slope seldom can be maintained
unless the material is of an exceptional
quality and the climate very favorable.
Ordinarily clay entertainments should
have slope of about two to one in
cold climates and at least one and one
half to one in warm climates; and II
the clay be of questionable quality
these values should be increased. En-
bankment slopes require more care In
construction than excavation slopes,
because any fiattening of an embank-
ment slope by the action of weather
after the road is completed Is very
likely to damage the road surface
while the sliding in of excavation
slopes usually does no further damage
| than to obstruct the side bitches,
which can be reOpencd readily.
Sand of average quality usually re-
quires slope of about two to one in
cuts and three to one in embankments,
regardless of climate. Moderately
coarse sand mixed with gravel will
stand on a sleeper slope than finU
sand, because the former Is not moved
so readily by the action of storm wa.
ter.
Solid rock excavation usually can he
/ done on an average slope of about one.
/ fourth to one, except where the rock
/ occurs In slOplng strata separated by
/ slippery clay seams. In the latter case
the average slope may be as much IA
one-half to one or three-fourths to one,
/ The faces of rock cuts usually are not
| dressed down to even an approximate
/ ly smooth slope, as is done In earth
( cuts. In excavating solid rock only
/ such material is moved as Is actually
necessary TO obtain the desired width
at the bottom of the cut or as has been
/ loosened in blasting. The faces should
OF course, be cleared of all material
| which is loose, or which might he
| iooSened subsequently by frost and
slide down upon the road. Stone EN-.
banGments usually will stand on a
/ slope of. about one to one.
In order to prevent damage by wash,
. ing all earth slopes in either excaya.
! ton or emhankment should be prote,t.
/ ed by a growth of grass as soon ms
practicable after they are formed.
/ In many localities where the soil Is
| fertile and good quality Of grass Is
native no seeding OF the slopes is nee
( cSsary. In other cases the soil may no,
possess sufficient fertility to grow
grass even when the slopes are seed
cd, and in which event it ,uay be VERY
desirable To cover the slopes with chi
sod. This latter process usually /;
. very expensive, and should be en-
pIoyed only where ii is known Tim.
thorough seeding and fertllizing wouI,
Iall to secure covering Of sod.
Another precauuon frequently neces
Sary in order to prevent the wnsbIns
away OF excavation slopes Is to inter
cept water from the natural rrorn,
surface which otherwise would flow
down over the excavation slope. Thi,
Is done by means of BERN" ditcI
constructed well back from the ton q
the slope. Figure . illustrates a con
dition which makes a "f,ecp" ditcl
desirable and also shows how sucb
! ditch * constructed.