3.1.4
Grade Tolerances
The grading tolerance shall be within 50 mm 2 inches from the prescribed
elevations, with no abrupt variations that would cause unacceptable
projections of individual blocks.
3.1.5
Subgrade Surface Tolerances
The subgrade shall be maintained in a smooth condition between installation
of the geotextile and the blocks. Windrows, stones, clods of cohesive
soil, and irregularities shall be raked smooth. Ruts, rills and gullies
resulting from traffic, precipitation runoff, groundwater seepage, etc.
shall be corrected prior to installation of blocks.
3.2
GEOTEXTILE INSTALLATION
3.2.1
General
The geotextile shall be laid flat and smooth so that it is in direct
contact with the subgrade. The geotextile shall be free of tension, folds,
and wrinkles. The number of seams and overlaps shall be minimized by
selective orientation of geotextile panels, within the limitations of
maintaining a consistent pattern. Geotextile shall be placed immediately
prior to block installation, if necessary to limit damage to the geotextile
from equipment or repeated pedestrian traffic and limit disturbance of the
subgrade from precipitation or runoff.
3.2.2
Geotextile Seams
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NOTE: Sewn, welded or glued seams are desirable for
shoreline protection (or where flow reversal
occurs). Substitute the following for sewn seams:
Seams shall be continuously sewn at the locations
shown on the drawings. The minimum distance from
the geotextile edge to the stitch line nearest to
that edge shall be 75 mm (3 inches). Seam strength
shall meet the minimum requirements specified in
AASHTO M288 for a class 2 geotextile. Quality
assurance samples shall be taken at the request of
the Contracting Officer. The thread at the end of
each seam run shall be tied off to prevent
unraveling. Seams shall be on the top side of the
geotextile to allow inspection. Skipped stitches or
discontinuities shall be sewn with an extra line of
stitching with a minimum of 450 mm (18 inches) of
overlap.
Pins/staples may not be desirable where filtration
is critical.
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Seams shall be overlapped a minimum of 450 mm 18 inches. Seams on slopes
and butt end seams shall be shingled so that runoff and channel flow passes
over the fabric. Geotextile panels shall be secured before block placement
by adequate sandbags, spare blocks, or pins/staples.
SECTION 02382
Page 17
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