final bid specs 09328.pdf - Freese and Nichols, Inc.

3.00 EXECUTION
3.01 PREPARATION
Clear and grub the area to be excavated prior to the start of excavation.
3.02 EXCAVATION
A. When footing concrete or masonry is to rest upon rock, remove the rock to a depth sufficient
to expose sound rock. Level off or cut the rock to approximate grades, and roughen the area.
When footing concrete or masonry is to rest on an excavated surface other than rock, take
care not to disturb the bottom of the excavation, and do not make final removal of the
foundation material to grade until just before the concrete or masonry is placed.
B. For footings where the soil encountered at established footing grade is an unstable material,
use the following procedure unless other methods are specified: Remove unstable soil.
Carry the excavation at least 1' beyond the horizontal limits of the structure on all sides.
Replace the unstable soil with compacted select fill. Place in uniform layers at a suitable
depth for compaction. Wet each layer if necessary and compact by rolling or tamping to
provide a stable foundation for the structure.
C. When unfeasible to construct a stable footing as outlined above, construct footing by the use
of special materials, such as flexible base, cement stabilized base, cement stabilized backfill,
or other material, as directed by the Engineer.
D. Perform excavation to permit surfaces to be brought to final line and grade within + or - 0.1
foot. Restore over-break at the Contractor's expense. In general, perform excavation in
open-cut from the surface of the ground and at the line and grade indicated.
E. The sides of the excavation, from the bottom of the excavation to the top of the ground shall
be supported in accordance with OSHA requirements. Maintain the supports throughout
construction. Remove supports after the completion of the work.
3.03 DEWATERING OF SITE
Pumping or bailing from the interior of any foundation enclosure shall be done in a manner which
precludes the possibility of movement of water through or alongside any concrete being placed.
No pumping or bailing shall be permitted during the placing of structural concrete, or for a period
of at least twenty-four (24) hours thereafter, unless from a suitable sump separated from the
concrete work by a water-tight wall. Pumping or bailing during placement of seal concrete shall
be only to the extent necessary to maintain a static head of water within a cofferdam. Do not start
pumping or bailing to de-water a sealed cofferdam until the seal has aged at least thirty-six (36)
hours.
3.04 PLACEMENT OF MATERIAL
A. GENERAL
1. Backfill excavated spaces and areas not occupied by the permanent structure, except
that no backfill shall be placed against any structure until the concrete has reached its 28
day compressive strength or seven (7) days whichever is longer. Do not place backfill
adjacent to support walls until the top slab has been in place at least four (4) days.
2. Take care to prevent wedging action when placing backfill around structures. If backfill is
to be placed on two (2) or more sides of the structure or facility, simultaneously place the
backfill on all sides to avoid uneven loading on the structure.
3. Do not permit rollers to operate within 3' of structures.
Structural Excavation and Backfill 31 23 10-3
DPR09328