It was deemed necessary to remove all the rubbish and debris within the
building and from an area measuring 10 feet from the outer walls in
every direction. Plate CXVII shows the extent of this area, and six
sections are shown in plates CXVIII and CXIX, three on east-and-west
lines and three on north-and-south lines. The lines along which these
sections were made are indicated on the plan, plate CXVII. The ground
level was determined by excavation, and is of course only approximate.
The sections show the estimated amount of debris which was to be
removed. Aside from other considerations, it was necessary to uncover
the walls to the ground level in order to do the necessary underpinning.

It was planned to underpin the walls, where erosion at the ground level
had weakened them, with hard-burned brick laid in cement mortar. Plate
CXVII shows in a measure the extent of this erosion. The brick surface
was to be set back an inch or two and faced with that thickness of
cement mortar. Plate CXX shows the south front and plate CXXI the south
and east fronts when the brickwork was completed, but before it was
plastered, and will illustrate what was planned better than can a
description.

This treatment, it was believed, would give a surface capable of
effectually resisting atmospheric influences and the destructive action
of flying sand, and at the same time would not disfigure the ruin by
making the repairs obtrusive.

The broken-out lintels of openings were to be replaced, and the cavities
above them filled in with brick faced with mortar similar to the
underpinning.

The south wall, which was in a dangerous condition, was to be supported
by three internal braces, as shown in the plan, plate CXVII. The longest
brace or beam was necessarily of wood, as the wide range of temperature
in this region, even between day and night, would produce so much
expansion and contraction in an iron rod 60 feet long that without some
compensating device the wall would be rocked on its base and its rapid
destruction necessarily follow.

EXECUTION OF THE WORK

Appended to that portion of the sundry civil appropriation act approved
March. 2, 1889,[1] in which certain expenses of the United States
Geological Survey are provided for, is the following item:

Repair of the ruin of Casa Grande, Arizona: To enable the Secretary
of the Interior to repair and protect the ruin of Casa Grande,
situate in Pinal County, near Florence, Arizona,