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 rock.

The average drill performance was about 33 lin. ft. per 8-hour shift.

The average number of cubic yards of excavation per drill shift was 13.9.

The average number of feet of drilling per cubic yard of excavation was about 2.4.

The average excavation per pound of dynamite was 2.2 cu. yd.

The average amount of excavation per derrick shift of ten hours, 87% of the excavation being rock, was 50 cu. yd.

The average derrick force per shift, including only foreman and laborers, was 13 men.