The true Democrat. [volume] (Bayou Sara [La.]) 1892-1928, 1912-05-04
CAUSE OF "SAND BoiLs."

Sand boilS' or "blOW-OutS' are
said to be the cause of the most de-
structiVe creVasses that have occur
red. These phenomena of the floods
have rarely been encountered along
the levee-protected fronts of the
lands bordering the Mississippi river
below the mouth of Red river. The
most Of them have been visible above
Vicksburg, or the confluence Of the
Yazoo with the Mississippi river.
AS the most recent illustration on
this subject, the Salem crevasse of
East Carroll parish, with it's result
ant complete or partial overflow of
eight Louisiana parishes, lying be-
tween the Arkansas line and the low
er end of Red river, was caused by
a "sandboip' some distance behind
the base of the broken levee. The
leVee to all appearance at the point
of breakage, was in good condition
with its broad crown several feet
above the highest possible point of
the approaching rise, when suddenly,
behind the landWard edge of it's base,
a boring torrent of muddy water
burst above ground, and a hundred
feet of the great embankment sud
denly collapsed, Disappeared" or
caved in.
This result would apparently signi-
fly the existence of a strata or bed of
quicksand below the base of the le-
wee. That sub-strata, becoming sat
urated and semi-fluid, was forced out
inward by the enormous hydrostatic
pressure of the external flood. Such
seems to have been the origin of
numbers Of the most noted creVasS-
es that have flooded the lands of
the Yazoo Valley in Mississippi and
those between the Arkansas and the
Red rivers on the western side of the
Mississippi river. Why "sandboils"
should have been responsible for so
many creVasses along the Mississip.
pi river above the mouth of the Red,
and for none, so far as known, he
low, it is apparently due to the fol
lowing causes:
In building up it's bordering lands
the ancient, unleveed Mississippi,
coming down with a great slope and
swifter current above the point OF
its later junction with the Red and
Atchafalaya rivers, deposited most OF
it's coarser or sander silt on it's an,
nually overflowed banks above Red
river. 1t left a minimum of finer
| clay deposits in those upper bends
where the current was rapid. Below
the present mouth of Red river with
a considerably lessened slope to the
sea, and a consequently slackened
current, there was a far greater pro
portion of finer tenacious clay de
posts mixed with a finer silt in its
annual contribution to its overflowed
borderlands. The presence of this
greater proportion of impenetrable
clay prevented the infiltration of wa
ter in the soil subsequently destined
to become the basis of our modern
levees.
Accepting this theory to be true
it would seem that, like the scriptu,
raj building of a house upon sands
it might in future, be considered un'
wise to build some of the most i'm
portant links in the long and suppos
eddy strong chain of our lower Mis-
sissippi levee-system ON foundation
of quicksand ever liable to be made
semiliquid through the infiltration OF
water subject to the tremendous by
drostatic pressure of twenty'foot
outside flood altitude.
And right here is where the nation
al government should take strong
er hand in the construction of our le
wees. Regardless of first cost, rather
than that the leveeS should be bas'
ed upon a "sand foundation" the
surface soil which now supports then
should be excavated until a firm
foundation is reached, just as it is
for the construction for building fol
human occupancy and human occupa
tons.
Surface soil called upon to support
levees in such dangerous districts
should, before a levee contract was
given out be subjected to propel
chemical analysis to determine if i
develop the quick-sand tendency pro
duced by water infiltration under
| heavy hydrostatic nressure. And i