with sewage shall be constructed of corrosion resistant material.
Enclosure for controls shall be NEMA 250 Type 4.
2.11.3
Pumping Structures
Wetwells [and drywells] shall be sized to permit access to pumps and other
equipment for maintenance. [Drywells shall be provided with sump pumps and
dehumidifiers to protect the equipment against corrosion.] [Pump houses
shall be weatherproof and shall be louvered for ventilation.] Wetwells
shall be sized to handle part or all of short term peak flows and shall
provide for minimum pump run times.
2.12
FLOW METERING AND CONTROL
Provide means for flow metering and control.
2.12.1
Flow Metering
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NOTE: Delete inapplicable flow metering paragraph.
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2.12.1.1
Float Operation
Measurement of wastewater flow shall be accomplished by an outfall weir and
a float operated recorder. The recorder shall be of the electrically
operated circular or strip chart type and shall continuously record the
flow through the plant in L per second gpm. The recorder shall also
produce an electrical signal in proportion to the flow for control of the
chlorinator. A weatherproof enclosure shall be provided for the recorder.
2.12.1.2
Ultrasonic Measuring
Measurement of wastewater flow shall be accomplished by an outfall weir and
an ultrasonic flow meter with digital recorder. Measurement shall be
noncontact, echo-time measuring-type for use with V-notch weir. Unit shall
have reference receivers providing instant compensation in gas medium for
temperature, atmospheric pressure and humidity changes. Enclosure for
transmitter shall be NEMA Class 250, Type 4X and shall include indicator
and recorder. Transmitter shall provide a flow proportional signal if
required.
2.12.2
Flow Control
Adjustable weirs shall be provided at the inlet and outlet of the
chlorination tank for control of wastewater depth in the plant.
2.13
ACCESS WALKWAYS, PLATFORMS, AND HANDRAILS
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NOTE: Include handrails around plant perimeter if
plant is installed with tank walls at or near grade.
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Access walkways and platforms shall be provided for access to all equipment
for operation and maintenance. Walkways and platforms shall be nonslip
open grating fabricated from galvanized steel, factory painted mild steel,
aluminum, or fiberglass. Rigid handrails shall be provided along the sides
of walkways and platforms [and around the perimeter of the entire plant].
SECTION 11390
Page 25
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