2. In excavations for structures, excess excavation in the rock beneath foundations shall be
filled with concrete which shall have a minimum 28-day compressive strength of 3000
psi. Other excess excavation shall be filled with Class B backfill compacted to a
minimum of 92 percent density (ASTM D1557 Method C) as specified under
Section 02300, EARTHWORK.
3. — If the rock below normal depth is shattered due to drilling or blasting operations of
the Contractor, and the Engineer considers such shattered rock to be unfit for
foundations, the shattered rock shall be removed and the excavation shall be
backfilled with concrete as required, except that in pipe trenches crushed stone may be
used for backfill, 1f approved. All such removal and backfilling shall be done by and at
the expense of the Contractor.
D. When directed by the Engineer, the Contractor shall remove all dirt and loose rock from
designated areas and shall clean the surface of the rock thoroughly to determine whether
seams or other defects exist.
E. When concrete 1s to be placed on rock, the rock shall be free of all vegetation, dirt, sand,
clay, boulders, scale, excesstvely cracked rock, loose fragments, water, ice, snow, and other
objectionable substances.
3.03 VIBRATION AND AIR BLAST MONITORING:
A. The Contractor shall measure air blast and vibration levels of blasting operations to assure
compliance with all applicable regulations and local permits.
B. — Records of each day's air blast and vibration measurements shall be submitted to the
Engineer in writing no later than the start of the next day's work. Records shall include, as a
minimum:
Identification of instrument
Name of observer
Name of interpreter
Distance and direction of recording station from the area of detonation
Date and exact time of reading
Type of ground at recording station
Peak particle velocity for all components as well as resultant for all frequencies of
vibrations
Duration of motion with a velocity in excess of one thousandth of an inch per second A
copy of the photographic record of seismograph readings Peak air blast level.
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