Current through August 31, 2023
01.
General. Section
440 regulates both public and
private municipal wastewater collection pump stations and does not regulate
individual residence pump stations, individual residence grinder pump stations,
or individual residence septic tank effluent pump stations. See Section
441 for regulation of those types
of pump stations. (3-31-22)
a. Flooding.
Wastewater pumping station structures and electrical and mechanical equipment
shall be protected from physical damage by the one hundred (100) year flood.
Wastewater pumping stations shall remain fully operational and accessible
during the twenty-five (25) year flood. Regulations of state and federal
agencies regarding flood plain obstructions shall be considered.
(3-31-22)
b. Accessibility and
Security. The pumping station shall be accessible by maintenance vehicles
during all weather conditions. (3-31-22)
c. Grit. The wet well and pump station piping
shall be designed to avoid operational problems from the accumulation of grit.
(3-31-22)
d. Safety. Provisions
shall be made to consider the protection of maintenance personnel and visitors
from typical and foreseeable hazards in accordance with the engineering
standards of care. See also Subsection
450.07.
(3-31-22)
02.
Design. Design of wastewater pumping stations shall meet the
applicable requirements of Subsections
440.02.a. through 440.02.i.
(3-31-22)
a. Type. Wastewater pumping
stations in general use fall into four types: wet well/dry well, submersible,
suction lift, and screw pump. (3-31-22)
b. Structures. (3-31-22)
i. Separation. Dry wells shall be completely
separated from the wet well. Common walls must be gas tight.
(3-31-22)
ii. Equipment Removal.
Provision shall be made to facilitate removing pumps, motors, and other
mechanical and electrical equipment. Individual pump and motor removal must not
interfere with the continued operation of remaining pumps. (3-31-22)
iii. Access and Safety Landings. (3-31-22)
(1) Access. Suitable means of access for
maintenance personnel wearing self-contained breathing apparatus shall be
provided to dry wells and to wet wells. See also Subsection
450.07. (3-31-22)
(2) Safety Landings. Section
009 provides a reference to
requirements of the Occupational Safety and Health Administration (OSHA),
compliance with which may be required by other law.
(3-31-22)
iv. Buoyancy.
Where high groundwater conditions are anticipated, buoyancy of the wastewater
pumping station structures shall be considered and, if necessary, adequate
provisions shall be made for protection. (3-31-22)
v. Construction Materials. Materials shall be
selected that are appropriate under conditions of exposure to hydrogen sulfide
and other corrosive gases, greases, oils, and other constituents frequently
present in wastewater. This is particularly important in the selection of
metals and paints. (3-31-22)
c. Pumps. (3-31-22)
i. Multiple Units. Multiple pumps shall be
provided. Units shall have capacity such that, with any unit out of service,
the remaining units will have capacity to handle the design peak hourly flow.
(3-31-22)
ii. Protection Against
Clogging. Pumps (except screw pumps) handling separate sanitary wastewater from
thirty (30) inch or larger diameter sewers shall be protected by bar racks.
Appropriate protection from clogging shall also be considered for small pumping
stations. (3-31-22)
iii. Pump
Openings. Pumps handling unscreened raw wastewater shall be capable of passing
spheres of at least three (3) inches in diameter or be a grinder pump.
(3-31-22)
iv. Priming. The pump
shall be placed so that, under normal operating conditions, it will operate
under a positive suction head, except as specified in Subsection
440.03. (3-31-22)
v. Electrical Equipment. Section
009 provides a reference to the
requirements of the National Electrical Code, compliance with which may be
required by other law. (3-31-22)
vi. Intake. Section
008 provides a reference to the
American National Standard Institute/Hydraulic Institute ANSI/HI 9.8, American
National Standard for Centrifugal and Vertical Pump Intake Design.
(3-31-22)
vii. Dry Well Dewatering.
Dry wells shall be equipped with a positive means for dewatering.
(3-31-22)
viii. Pumping Rates. The
pumps and controls of main pumping stations shall be selected to operate with
varying rates. The pump control system design shall take into account, and
minimize as needed, downstream impact of pump discharge hydraulic surges. The
station design capacity shall be based on peak hourly flow as determined in
accordance with Section
411 and shall be adequate to
maintain a velocity in the force main sufficient to avoid solids deposition.
See Subsection 440.09.
(3-31-22)
d. Controls.
Water level control sensing devices shall be designed to allow for automatic
control of pumps. (3-31-22)
e.
Valves. (3-31-22)
i. Suction Line. Suitable
shutoff valves shall be placed on the suction lines of dry pit pumps.
(3-31-22)
ii. Discharge Line.
Suitable shutoff and check valves shall be placed on the discharge line of each
pump (except on screw pumps). The check valve shall be located between the
shutoff valve and the pump. Check valves shall be suitable for the material
being handled and shall be placed on the horizontal portion of the discharge
piping except for ball checks, which may be placed in the vertical run. Valves
shall be capable of withstanding normal pressure and water hammer. All shutoff
and check valves shall be operable from the floor level and accessible for
maintenance. Outside levers are recommended on swing check valves.
(3-31-22)
f. Wet Wells.
(3-31-22)
i. Section
008 provides a reference to the
American National Standard Institute/Hydraulic Institute ANSI/HI 9.8, American
National Standard for Centrifugal and Vertical Pump Intake Design as a guidance
document. (3-31-22)
ii. Air
Displacement. Covered wet wells shall have provisions for air displacement to
the atmosphere, such as an inverted "j" tube or other means.
(3-31-22)
g. Safety
Ventilation. Adequate ventilation shall be provided for all pump stations
unless access is provided using confined space entry procedures. Where the dry
well is below the ground surface, mechanical ventilation is required. If
screens or mechanical equipment requiring maintenance or inspection are located
in the wet well, permanently installed ventilation is required. There shall be
no interconnection between the wet well and dry well ventilation systems.
Section 008 provides
a reference to guidance documents; see Subsection
008.11. (3-31-22)
h. Flow Measurement. Suitable methods for
measuring wastewater flow shall be addressed at all pumping stations.
(3-31-22)
i. Water Supply. There
shall be no physical connection between any potable water supply and a
wastewater pumping station which, under any conditions, might cause
contamination of the potable water supply. If a potable water supply connection
is made to the station, the connection shall comply with IDAPA 58.01.08, "Idaho
Rules for Public Drinking Water Systems." (3-31-22)
03.
Suction Lift Pump Stations -
Special Considerations. Suction lift pumps shall meet the applicable
requirements of Subsection
440.02. (3-31-22)
a. Pump Priming and Lift Requirements.
Suction lift pumps shall be of the self-priming or vacuumpriming type. Suction
lift pump stations using dynamic suction lifts exceeding the limits outlined in
Subsections 440.03.b. through 440.03.d.
may be approved upon submission of factory certification of pump performance
and detailed calculations indicating satisfactory performance under the
proposed operating conditions. (3-31-22)
b. Self-Priming Pumps. Self-priming pumps
shall be capable of rapid priming and re-priming at the "lead pump on"
elevation. Such self-priming and re-priming shall be accomplished automatically
under design operating conditions. (3-31-22)
c. Vacuum-Priming Pumps. Vacuum-priming pump
stations shall be equipped with dual vacuum pumps capable of automatically and
completely removing air from the suction lift pump. The vacuum pumps shall be
adequately protected from damage due to wastewater. The combined total of
dynamic suction lift at the "pump off" elevation and required net positive
suction head at design operating conditions shall not exceed twenty-two (22)
feet. (3-31-22)
d. Equipment, Wet
Well Access, and Valving Location. The pump equipment compartment shall be
above grade or offset and shall be effectively isolated from the wet well to
prevent a hazardous and corrosive sewer atmosphere from entering the equipment
compartment. Wet well access shall not be through the equipment compartment and
shall be at least twenty-four (24) inches in diameter. Gasketed replacement
plates shall be provided to cover the opening to the wet well for pump units
removed for servicing. Valving shall not be located in the wet well.
(3-31-22)
04.
Submersible Pump Stations - Special Considerations. Submersible
pump stations shall meet the applicable requirements of Subsection
440.02, except as modified in
Subsection 440.04. (3-31-22)
a. Construction. Submersible pumps and motors
shall be designed specifically for raw wastewater use, including totally
submerged operation during a portion of each pumping cycle. An effective method
to detect shaft seal failure or potential seal failure shall be provided.
(3-31-22)
b. Pump Removal.
Submersible pumps shall be readily removable and replaceable without personnel
entering or dewatering the wet well, or disconnecting any piping in the wet
well. (3-31-22)
c. Electrical
Equipment. Section 009 provides
a reference to the requirements of the National Electrical Code, compliance
with which may be required by other law. (3-31-22)
i. Power Supply and Control Circuitry.
Electrical supply, control, and alarm circuits shall be designed to provide
strain relief and to allow disconnection from outside the wet well. Terminals
and connectors shall be protected from corrosion by location outside the wet
well or through use of watertight seals. (3-31-22)
ii. Controls. The motor control center shall
be located outside the wet well, be readily accessible, and be protected by a
conduit seal or other appropriate measures to prevent the atmosphere of the wet
well from gaining access to the control center. The seal shall be located so
that the motor may be removed and electrically disconnected without disturbing
the seal. When such equipment is exposed to weather, it is recommended that it
meet the requirements of weatherproof equipment NEMA 3R or 4.
(3-31-22)
iii. Power Cord. Pump
motor power cords shall be designed for flexibility and serviceability under
conditions of extra hard usage. Ground fault interruption protection shall be
used to de-energize the circuit in the event of any failure in the electrical
integrity of the cable. Power cord terminal fittings shall be
corrosion-resistant and constructed in a manner to prevent the entry of
moisture into the cable, shall be provided with strain relief appurtenances,
and shall be designed to facilitate field connecting.
(3-31-22)
d. Valves.
Valves required under Subsection
440.02 shall be located in a
separate valve chamber. Provisions shall be made to remove or drain accumulated
water from the valve chamber. The valve chamber may be dewatered to the wet
well through a drain line with a gas and water tight valve. Check valves that
are integral to the pump need not be located in a separate valve chamber
provided that the valve can be removed from the wet well in accordance with
Subsection 440.04. Access shall be provided
in accordance with Subsection
440.02.
(3-31-22)
05.
Screw
Pump Stations - Special Considerations. Screw pump stations shall meet
the applicable requirements of Subsection
440.02. (3-31-22)
a. Covers. Covers or other means of excluding
direct sunlight shall be provided as necessary to eliminate adverse effects
from temperature changes. (3-31-22)
b. Pump Wells. A positive means of isolating
individual screw pump wells shall be provided. (3-31-22)
c. Bearings. Submerged bearings shall be
lubricated by an automated system without pump well dewatering.
(3-31-22)
06.
Alarm
Systems. Alarm systems with a backup power source shall be provided for
pumping stations. The alarm shall be activated in cases of power failure, dry
well sump and wet well high water levels, pump failure, unauthorized entry, or
other cause of pump station malfunction. Pumping station alarms, including
identification of the alarm condition, shall be transmitted to a twenty-four
(24) hour response center. Audio-visual alarm systems may be acceptable in some
cases in lieu of a transmitting system depending upon location, station holding
capacity, and inspection frequency. (3-31-22)
07.
Emergency Operation.
(3-31-22)
a. Objective. The objective of
emergency operation is to prevent the unintended discharge of raw or partially
treated wastewater to any waters or land surface and to protect public health
by preventing back up of wastewater and subsequent discharge to basements,
streets, and other public and private property. (3-31-22)
b. Emergency Pumping Capability. Emergency
pumping capability is required for all new lift stations constructed after
April 15, 2007. Emergency pumping capability is required for all existing lift
stations that undergo a material modification or expansion unless overall
system reliability can be proven adequate to the Department as shown in
Subsections 440.07.b.i. and 440.07.b.ii.
or overflow prevention is provided by adequate emergency storage capacity as
defined in these rules. If required, emergency pumping capability shall be
accomplished by connection of the station to at least two (2) independent
utility substations as determined by and stated in a letter from the
appropriate power provider, by provision of portable or in-place internal
combustion engine equipment which will generate electrical or mechanical
energy, or by the provision of portable pumping equipment. Such emergency
standby systems shall have sufficient capacity to start up and maintain the
total rated running capacity of the station. Regardless of the type of
emergency standby system provided, a portable pump connection to the force main
with rapid connection capabilities and appropriate valving shall be provided
outside the dry well and wet well. (3-31-22)
i. System reliability is considered adequate
if power grid outages average three (3) or less per year based on data for the
three (3) previous years with no more than six (6) outages in a single year.
(3-31-22)
ii. Outage duration
averages less than four (4) hours based on data for the three (3) previous
years, with not more than one (1) outage during the three (3) previous year
period exceeding eight (8) hours. Power loss for at least thirty (30) minutes
qualifies as an outage. (3-31-22)
c. Equipment Requirements. (3-31-22)
i. General. The following general
requirements shall apply to all internal combustion engines used to drive
auxiliary pumps, service pumps through special drives, or electrical generating
equipment: (3-31-22)
(1) Engine Protection.
The engine must be protected from operating conditions that would result in
damage to equipment. Unless continuous manual supervision is planned,
protective equipment shall be capable of shutting down the engine and
activating an alarm on site and as provided in Subsection
440.06. Protective equipment
shall monitor for conditions of low oil pressure and overheating, except that
oil pressure monitoring will not be required for engines with splash
lubrication. (3-31-22)
(2) Size.
The engine shall have adequate rated power to start and continuously operate
under all connected loads. (3-31-22)
(3) Fuel Type. Reliability and ease of
starting, especially during cold weather conditions, shall be addressed in the
selection of the type of fuel. (3-31-22)
(4) Fuel Storage. Fuel storage and piping
facilities if provided shall be constructed in accordance with applicable state
and federal regulations. (3-31-22)
(5) Engine Ventilation. The engine shall have
adequate ventilation of fuel vapors and exhaust gases. (3-31-22)
(6) Routine Start-up. All emergency equipment
shall be provided with instructions indicating the need for regular starting
and running of such units at full loads. (3-31-22)
(7) Protection of Equipment. Emergency
equipment shall be protected from damage at the restoration of regular
electrical power. (3-31-22)
ii. Engine-Driven Pumping Equipment. Where
permanently-installed or portable engine-driven pumps are used, the following
requirements in addition to general requirements shall apply. (3-31-22)
(1) Pumping Capacity. Engine-driven pumps
shall meet the design pumping requirements unless storage capacity is available
for flows in excess of pump capacity. Pumps shall be designed for anticipated
operating conditions, including suction lift if applicable. (3-31-22)
(2) Operation. The engine and pump shall be
equipped to provide automatic start-up and operation of pumping equipment
unless manual start-up and operation is justified. Provisions shall also be
made for manual startup. Where manual start-up and operation is justified,
storage capacity and alarm system must meet the requirements of Subsection
440.07.c.ii(3).
(3-31-22)
(3) Portable Pumping
Equipment. Where part or all of the engine-driven pumping equipment is
portable, adequate emergency storage capacity with alarm system shall be
provided to allow time for detection of pump station failure and transportation
and hookup of the portable equipment. (3-31-22)
iii. Engine-Driven Generating Equipment.
Where permanently-installed or portable engine-driven generating equipment is
used, the following requirements shall apply in addition to the general
requirements of Subsection
440.07. (3-31-22)
(1) Generating Capacity. (3-31-22)
(a) Generating unit size shall be adequate to
provide power for pump motor starting current and for lighting, ventilation,
and other auxiliary equipment necessary for safety and proper operation of the
lift station. (3-31-22)
(b) The
operation of only one pump during periods of auxiliary power supply must be
justified. Such justification may be made on the basis of the design peak
hourly flows relative to single-pump capacity, anticipated length of power
outage, and storage capacity. (3-31-22)
(c) Manual or special sequencing controls
shall be provided to start pump motors unless the generating equipment has
capacity to start all pumps simultaneously with auxiliary equipment operating.
(3-31-22)
(2) Operation.
Provisions shall be made for automatic and manual startup and load transfer
unless only manual start-up and operation is justified. Automatic transfer
switches shall be UL listed and meet NEC requirements. The generator must be
protected from operating conditions that would result in damage to equipment.
Provisions shall be made to allow the engine to start and stabilize at
operating speed before assuming the load. Where manual start-up and transfer is
justified, storage capacity and alarm system must meet the requirements of
Subsection 440.07.c.iii.(3).
(3-31-22)
(3) Portable Generating
Equipment. Where portable generating equipment and manual transfer is provided,
adequate emergency storage capacity with alarm system shall be provided to
allow time for detection of pump station failure and transportation and
connection of generating equipment. Special electrical connections and double
throw switches shall be provided for connecting portable generating equipment.
Manual transfer switches shall be UL listed and meet NEC requirements.
(3-31-22)
iv. Independent
Utility Substations. Where independent substations are used for emergency
power, each separate substation and its associated transmission lines shall be
capable of starting and operating the pump station at its rated capacity.
(3-31-22)
08.
Instructions and Equipment. Wastewater pumping stations and
portable equipment shall be supplied with a complete set of operational
instructions, including emergency procedures, maintenance schedules, tools, and
such spare parts as may be necessary. (3-31-22)
09.
Operation and Maintenance.
(3-31-22)
a. An operation and maintenance
manual shall be submitted to and approved by the Department as required by
Section 425.
Adherence to the terms of this approved manual shall be required. The owner
shall be responsible for maintaining the wastewater facility in a manner that
assures its designed operation. (3-31-22)
b. For private municipal wastewater
collection pump stations, documents that detail the technical, managerial, and
financial capabilities of the private entity to properly operate and maintain
said pump station for the long term shall be submitted to the Department for
approval prior to operation. (3-31-22)
10.
Force Mains. (3-31-22)
a. Velocity and Diameter. At design pumping
rates, a cleansing velocity of at least two (2) feet per second shall be
maintained. (3-31-22)
b. Air and
Vacuum Relief Valve. An air relief valve shall be placed at high points in the
force main to prevent air locking. The force main configuration and head
conditions shall be evaluated as to the need for and placement of vacuum relief
valves. (3-31-22)
c. Termination.
The force mains from other than individual grinder pump stations shall enter a
receiving manhole. Corrosion protection for the receiving manhole shall be
provided. Control of odors at such discharge points shall be evaluated.
(3-31-22)
d. Pipe and Design
Pressure. Pipe and joints shall be equal to water main strength materials
suitable for design conditions. The force main, reaction blocking, thrust
restraint, and station piping shall be designed to withstand water hammer
pressures and associated cyclic reversal of stresses that are expected with the
cycling of wastewater lift stations. The use of surge valves, surge tanks, or
other suitable means to protect the force main against severe pressure changes
shall be evaluated. (3-31-22)
e.
Special Construction. Force main construction near streams or water works
structures and at water main crossings shall meet applicable provisions of
Section 430.
(3-31-22)
f. Design Friction
Losses. (3-31-22)
i. Friction Coefficient.
Friction losses through force mains shall be based on the Hazen and Williams
formula or other acceptable methods. When the Hazen and Williams formula is
used, the friction losses for varying values of "C" shall be evaluated for
different types and ages of pipe. (3-31-22)
ii. Maximum Power Requirements. When
initially installed, force mains will have a significantly higher "C" factor.
The effect of the higher "C" factor shall be considered in calculating maximum
power requirements and duty cycle time to prevent damage to the motor. The
effects of higher discharge rates on selected pumps and downstream facilities
shall also be considered. (3-31-22)
g. Identification. Where force mains are
constructed of material which might cause the force main to be confused with
potable water mains, the force main shall be appropriately identified using
trench tape saying "raw sewage," "biohazard," or other appropriate wording.
(3-31-22)
h. Leakage Testing.
Leakage tests shall be specified including testing methods and leakage limits.
Testing shall conform with Sections
401.3.6 and
505.3.3 of the "Idaho Standards
for Public Works Construction," incorporated by reference into these rules at
Section 004.
(3-31-22)
i. Thrust Blocking or
Restraint. Thrust blocking or restraint shall conform with Sections
401.3.4 of the "Idaho Standards
for Public Works Construction," incorporated by reference into these rules at
Section 004, or
specific calculations reviewed and approved by the Department.
(3-31-22)
j. Maintenance
Considerations. Isolation valves shall be used if force mains connect into a
common force main. (3-31-22)
k.
Cover. Force mains shall be covered with sufficient earth or other insulation
to prevent freezing or other physical damage. (3-31-22)