nnel work west of Tenth Avenue,
and these lines, together with bench-marks similarly established, were used
in laying out the Terminal Station-West work.

Prior to the commencement of the work, elevations were taken on the surface
at 10-ft. intervals, and elevations of the rock surface were taken on these
points as the rock was uncovered. Cross-sections were made and used in
computing the progress and final estimates.

Very careful records were kept of labor, materials, derrick performances,
steam-shovel performances, quantity of dynamite used, etc., and, in
addition, a diary was kept giving a description of the work and materials
used each day; various tables and diagrams were also prepared.

A daily report was sent to the Chief Office showing the quantities of
excavation removed and concrete built, the force in the field, the plant at
work, etc., during the previous day. At the end of each month a description
of the work done during that month, with quantities, force of men employed,
percentages of work done, etc., was sent to the Chief Office. Two diagrams,
showing cross-sections and contours of the excavation done and the progress
of the concrete walls, were also sent.

COST ACCOUNT.

From the records of labor and material obtained in the field, and from
estimated charges for administration and power, an estimate was made of the
cost to the contractor for doing various classes of work. It was necessary
to estimate the administration and power charges, as the contractor's
organization and power-house were also controlling and supplying power to
the Terminal Station work east of Ninth Avenue and also the work below
sub-grade. The labor and material charges in the field were placed directly
against the class of work on which they were used and the administration
and general charges (which included superintendence, lighting, etc.) were
apportioned to the various classes of work in proportion to the value of
the labor done.

STATISTICS.

The total weight of the structural steel used during the underpinning of
Ninth Avenue was 1,475,000 lb.

The total weight supported during the work under Ninth Avenue was about
5,000 tons.

\U$1\EThe average daily traffic over the Ninth Avenue Elevated Railway was
90,000 passengers, and, during the progress of the excavation and
underpinning, about 100,000,000 passengers were carried over that
structure.

The total excavation was 521,000 cu. yd., of which 87% was solid ro