The San Francisco call., 1895-07-16
Character of the Subsoil Suit
able for the Proposed
Structure.
FIND NO CAUSE FOR DELAY
Are of the Opinion That Construc-
ton Can Be Commenced
at Once.

official report by the United States Govern
ment engineer officers, with fourteen in
closures, as to the stability of the site
selected for the erection of the public
building at San Francisco, was to-day re-
ceived at the Treasury Department, and
with Secretary CarlisIe's consent is made
public. II was as follows:
SAN FRANCISCO, Cal, July 8, 1895.
The Honorable Secretary Of the Treasury, Wash
fngton, d. C-SIR: The undersigned, appointed
in accordance with the provisions of the act of
Congress, approved March 2, 1895, to examine
the site for the Postofice and Courthouse
building in San Francisco, have the honor to
render the following report:
Under date of April 3, having received noti-
fcation OF appointment TO perform the duties
assigned to US, we reported to you for instruc-
tions to guide Us in the proposed examinations,
On May 27 instructions were issued from the
acting Secretary of the Treasury and received
by us on June 4. In this letter we were re-
quested ''to examine the nature OF the subsoii
and bed OF the foundation, and TO report to the
department whether the character OF the same
is proper for the contemplated building, and
what would be the cost of making the fou unda-
tion for said building, and whether the con-
Etruction of said building should be proceeded
with on said Site We were further requested
to make a recommendation as 10 the character
of the foundation and present an approximate
estimate of same.
Immediately after the receipt of the above
mentioned letter proposals were invited from
s. NJ. B. Haley, who made the former borings
on the site and the Beal Core Drill Company.
One bid was received, that of Haley. Mr..
Haley proposed to bore the site to depth of
so to 80 feet at the rate of 81 % per foot; be-
yond so feet he was to receive so cents addi-
tional Tor each foot.
Under the former action of the Treasury De-
partment four borings were made at the site.
These borings will be designated A, B. C and
D. Their locations approximate to the four
corners of the building. Awas near the south
west corner and was sunk to a depth of 149
feet. was near the southeast corner, depth
Ill feet. was near the northwest corner,
depth LAT feet. d was near the northeast cor
ner, depth 140 feet. In a general way the bor-
ings at B, C and show that to a depth OF 80
TO 40 feet clean sand of varying colors was
found; thence to depth of 80 feet clay was
found and below that sand of different grades
and colors. In boring A the indications were
not so favorable in the upper strata, as the
sand was found mixed with vegetable matter,
debris, peaty sand, etc. Our boring indicates
like nature of material at same location, ex-
tending through only limited area.
We made eleven additional borings 10 a
depth of SO feet each. Their location is
shown on the foundation plan. They are des-
ignated by numbers. Borings TO d inclusive
show that to a depth OF about So feet clean
sand of varying colors was found, as in the
previous borings; then stratum of black peat
about inches in thickness; then about foot
OF heavy black mud, and below that to so feet
slate-colored clay. Borings z, 8, 8 and 10 were
made at the southwest corner, as at this loca-
ton the nature of the subsoil appears to indi-
cate that some additional precautions should
be taken in preparing the foundation, and the
accompanying diagram shows the locations of
these five borings. No. was in the imme-
diate vicinity of A. Yellow, black and white
sand was found to a depth of d feet; thence
TO 40 feet sand, mud, debris, in general rather
soft material, and below that to so feet sand
and clay. No. s showed the general character
istics of borings l to g. No. 9 showed common
sand to IS feet then foot of soft black mud
and decayed vegetation; then III feet OF black
peaty mud and sand, filed with sticks, roots,
etc.; then good sand for 1917 feet, with few
grass roots at about 29 feet; at forty feet 1
foot rotten wood and soft mud; then black
clay, hard and sticky, 1 foot thick; then slate
colored and yellow sandy clay to sos. Nos
10 and IL had the usual characteristics of the
first borings; that is, sand to 38 and 40 feet,
and clay below to so feet The results of the
Throughout the site the general indications
are of hill sand TO depth of about % feet
below the surface of the ground, and below
that clay. The Coast Survey chart of 1858
shows that the site was a sand lot covered with
brush and small trees. There was no indica-
tion of running water on the lot. It is only in
the northwest corner for a distance of from SO
to so feet along Seventh street and along Mis-
sion that the material is OF such a nature as to
10
foundation. Water was found at a depth of
s.8 to IL feet. The surface OF the ground was
connected by levels with the beach mark
(29.o4) and the level of the water standing in
each well was determined. This latter level
is shown on the plats.
1t may be stated that the material as found
and brought to the surface may not show its
condition in place, as the boring apparatus
necessarily broke up the mass and its mixture
with the water in the well caused it to appear
soft and yielding. 1t may be that in its natural
condition it may stand the same amount of
pressure as in other portions of the site.
To the first inquiry, therefore, whether the
character of the subsoil is proper for the con-
templated building, we are of the opinion that
the building can be safely constructed upon it.
AS to the inquiry whether the construction of
the building should be proceeded with, from an
engineering point OF view we see no reason TO
report otherwise.
1t remains for us to state in a general way
only the character of the foundation and to
present an approximate estimate OF the same.
The foundation should be of concrete. The
depth is given at AZ feet. For the purpose of
spproximating to the cost we have taken that
depth,for the main walls and depth OF 3 feet
for the columns, making the top of said foun-
dAtion two feet wider than the base of the wall.
For length of 60 feet on Mission street and on
Seventh street, where the soft material is
found, the base of the foundation is increased
TO 25 feet. 1t is assumed that the ground can
be drained into the street sewer for depth of
about nine feet. The water that may be found
In the sand to be extracted by pumping will
probably depend upon the season in which the
excavation may be done. 1t is hardly capable
OF estimate, although we insert an item for the
work.
The approximate estimate of the cost of the
foundation is as follows: Excavation of 9528
cubic yards OF material and disposal of same at
90 cents per cubic yard $4764; 1882 cubic
yards OF concrete ct 81 so, $29, 100; pumping
$4,000. Total, $35, ,944. Contingencies, 10 per
cent, S3595. Total, $39, $40 The concrete
proposed consists OF the best Portland cement
with twelve cubic feet of selected sand and
thirty cubic feet of broken stone to the barrel
Very respectfully, your obedient servants,
G. w. MENDELL
Colonel Corps OF Engineers.
W. H. Fl. BENYAURD
Jieufpnant-CnloneI Corne nf Epo;roors