In general, the construction inspection
requirements for retaining walls are similar to those for other concrete
structures. In some cases, state
agencies may have inspector checklists for this type of construction. Here below is a summary of typical
construction inspection requirements for retaining walls.
CONTRACTOR
SET UP
1. Review
plans and specifications
2. Review
the contractor’s schedule
3. Review
test results and certifications for preapproved materials, e.g., cement, coarse
and fine aggregate.
4. Confirm
that the contractor’s stockpile and staging area are consistent with locations
shown on the plans
5. Discuss
anticipated ground conditions and potential problems with the contractor
6. Review
the contractor’s survey results against the plans
EXCAVATION
1. Verify
that excavation slopes and/or structural excavation support is consistent with
the plans
2. Confirm
that limits of any required excavations are within right-of-way limits shown on
plans
3. Confirm
that all unsuitable materials, e.g., sod, snow, frost, topsoil, soft/muddy soil
are removed to the limits and depths shown on the plans and that the excavation
is backfilled with granular material and properly compacted
4. Confirm
that leveling and proof-rolling of the foundation area is consistent with
requirements of the specifications
5. Confirm
that the contractor’s excavation operations do not result in significant water
ponding
6. Confirm
that existing drainage features, utilities, and other features are protected
7. Identify
areas not shown on the plans where unsuitable material exists and notify the
engineer
FOOTING
1. Approve
condition of footing foundation soil/rock before concrete is poured
2. Confirm
reinforcement strength, size, and type consistent with the specifications
3. Confirm
the consistency of the contractor’s outline of the footing (footing size and
bottom of footing depth) with the plans
4. Confirm
the location and spacing of reinforcing steel consistent with the plans
5. Confirm
water/cement ratio and concrete mix design consistent with the specifications
6. Record
concrete volumes poured for the footing
7. Confirm
appropriate concrete curing times and methods as provided in the specifications
8. Confirm
that concrete is not placed on ice, snow, or otherwise unsuitable ground
9. Confirm
that concrete is being placed in continuous horizontal layers and that the time
10. between
successive layers is consistent with the specifications
STEM
1. Confirm
the placement of weep hole inserts (number, elevation, and specific locations)
with the plans if weep holes are used,
2. Confirm
that concrete is poured in section lengths consistent with the specifications
3. Record
concrete volumes used to form the stem
4. Confirm
that all wall face depressions, air pockets, gaps, rough spots, etc. are
repaired
5. Confirm
that storage of reinforcing bars is consistent with the specifications,
e.g.-use of platform or supports.
6. Perform
preliminary check of condition of epoxy-coated reinforcing bars
7. Confirm
that forms are clean and appropriately braced during concrete pour operations
8. Confirm
that all reinforcing bars are held securely in place and are being rigidly
supported at the face of forms and in the bottom of wall footings
9. Confirm
that construction joints are being made only at locations shown on the plans or
otherwise at locations approved by the engineer
DRAINAGE
SYSTEMS AND BACKFILL
1. Confirm
that installation of the drainage system is consistent with the specifications
and plans
2. Confirm
that the backfill material being used is approved by the engineer
3. Confirm
that placement of the backfill is performed in lifts consistent with the
specifications
4. Confirm
that minimum concrete strength is achieved before backfill is placed and
compacted against back of wall
5. Confirm
that the backfill placement method used by the contractor does not cause damage
to drainage material or drain pipes
6. Confirm
that earth cover over drainage pipes is sufficient to prevent damage from heavy
equipment. The minimum cover based on
ground pressure from equipment should be provided in the specifications.
7. Perform
required backfill density tests at the frequencies specified, especially for
areas that are compacted with lightweight equipment, e.g., areas just behind
the wall.
8. Check
that the drainage backfill just behind weep holes is the correct gradation and
that it is properly installed
POST
INSTALLATION
Verify
pay quantities
Note:
Throughout the project, check submittals for completeness before transmitting
them to the engineer.
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