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10 TWENTY-EIGHTH ASSUAL REPORT

An investigation of the feasibility of raising the Lower San Fernando
Dam was made in great detail, including thorough testing to determine
the condition of the present fill. This was done by means of test pits,
shafts, auger holes and rotary core drill holes on cross-sections of the
dam at right angles at its axis and about 500 feet apart. The drill holes
along the axis of the dam, into bedrock through the center hydraulic
core, showed the latter to be tight and plastic. Borrow pits to secure
earthfill material were explored by test pits and borings, and sufficient
material of good quality was found within 2000 feet of the dam.
The proposed improvement consists of raising the crest of the dam
from elevation 1130 feet (capacity 14,700 acre feet) to elevation 1142
feet (capacity 18,900 acre feet), reinforcing the downstream toe, con-
structing a new and larger spillway, and making other incidental better-
ments to bring the storage up to the level originally contemplated for
this site. Preliminary estimates were approved by the Board of Engi-
neers, and final designs then prepared and submitted to the State Engi-
neer. A tentative approval of these plans has been obtained, subject to
certain slight revisions and alterations. Construction work on this project
is now well under way.
Topographically, the Chatsworth Reservoir offers greater possibility
for economical additional storage than any other of the City's reservoirs,
. or than any of the proposed new reservoir sites, mentioned above, within
reasonable distance of the City. Unfortunately, however, the geological
features of this site are not particularly favorable. The hills near the
lower end of the valley, where the dams must be located, contain appreci-
able deposits of a very light, chalky material, and the valley floors are
somewhat soft and unstable. Numerous plans for the enlargement of
this reservoir have been prepared, up to a capacity of 63,000 acre feet,
and many test borings made, to determine the suitability of foundation
conditions in various possible dam sites. Extensive testing has also been
done to secure data as to the availability and suitability of local mate-
rials for use in construction of an earth fill dam.
Preliminary plans for enlarging this reservoir have been considered
by the Board of Engineers and definite recommendations have been made
as to the safe limit of dam height, capacity, and other design features,
and that further tests be made to establish more certainly the character
of the foundation material. Tentative plans confirming to the findings
of the Board have been made, and the additional testing is now under way.
Preliminary plans and comparative estimates have been prepared for
securing additional storage capacity of 2000 to 5000 acre feet at Upper
San Fernando Reservoir. The cost was found to be relatively high, how-
ever, so this construction has been indefinitely postponed.
Office studies have been made, in greater or less detail, of sources
of additional water supply for the city, to supplement the present flow
available from the Owens Valley Aqueduct, the Los Angeles River and
the numerous wells. Reports were prepared based on proposals which
involve diversions from Mono Basin, Walker River Basin, South Fork of
Kern River, Mojave River, and Little Rock Creek. Detailed investigations
are being continued as to the possibilities of the Mono Basin supply, to
serve as a reserve until the Colorado River Aqueduct project can be com-
pleted.
Owens River Aqueduct Division'
J. E. PHILLIPS, Engineer
WATER SUPPLY
The expected break in the continued drouth of the past several years
has again failed to materialize. Early season snow surveys in the Sierra
Nevada Mountains during the past winter, indicated that we might have
at least a normal year. Later surveys, however, revealed that, while the
snow coverage was good, the snow was of very low water content. Also,