where additional gravel can be placed without the particles extending more
than 1/2 their volume above the water surface. The support gravel shall be
backwashed after it has been placed, in accordance with AWWA B100.
3.7
FILTER MEDIA INSTALLATION
**************************************************************************
NOTE: Media installation may be performed by the
manufacturer supplying the filter system for package
treatment systems. This paragraph should be used
only when the media will be installed in the field.
Delete the freeboard requirement for filtration
systems which do not require bed expansion during
**************************************************************************
Media shall be installed under the supervision of the filter equipment
supplier. Before installing the filter media, the Contractor shall check
all piping connections and ensure filter components are in good condition
and proper position. Media shall be placed to the depths [required by the
manufacturer] [as follows:
Media Type
Layer Thickness
__________
_______________
Sand
[_____]
Anthracite
[_____]
[_____]
[_____]]
A minimum freeboard of [_____] shall be left between the top of the media
and the top of the tank.
3.7.1
Media Layers
Each layer of media shall be completed before the next layer above is
started. Each layer of media shall be deposited so as not to disturb the
level surface of the layer below. Any media which is made dirty before or
after placement shall be removed and replaced.
3.7.2
Cleaning of Media
The filter media shall be backwashed, scraped, and skimmed in accordance
with AWWA B100 to remove excess fine material upon completion of placement
of each layer. The number of washes, the wash rate and duration of wash
required to achieve the specified gradation for each layer shall be in
accordance with the recommendations of the filter media supplier.
3.8
IDENTIFICATION SYSTEMS
3.8.1
Identification Tags
**************************************************************************
NOTE: Delete when identification tags are not
considered necessary on small projects.
**************************************************************************
Identification tags made of brass, engraved laminated plastic, or engraved
anodized aluminum, indicating service and valve number shall be installed
on valves, except those valves installed on supplies at plumbing fixtures.
SECTION 11393
Page 37
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