Specifications

Section 6 The Selected Alternative Plan
EAA Storage Reservoirs Revised Draft PIR and EIS February 2006
6-25
providing power for the lights, controls for the pumps, ventilation fans,
trash rake, etc. The emergency generator will not be sized to handle the
load for the electric motor pump drives.
10. Controls systems for the engine/motor pump drives. These systems shall
be as described in the Electrical Design section below.
11. During the detailed design, the designer shall coordinate with local and
state authorities to ensure that the various permits (air, fuel, etc.) are all
adequately addressed.
6.4.3.2.3 Pump Intake and Discharge Design
The larger pumps for the medium-sized pumping stations may be designed with
Formed Suction Intakes (FSI) and may include siphon discharges. A
representative example section of a pumping station with an FSI and a siphon
discharge is shown on Appendix A Plate M-7. FSIs have been shown to be more
efficient than typical suction bell intakes, but the design decision on whether to
use them will be based on comparing potential efficiency savings with increased
construction costs over the life of the project.
In order to reduce the engine size and horsepower (and fuel) required to
overcome the head on the large pumps, siphoning discharge systems may be
used. If a siphon discharge system is used, priming would be accomplished by
means of a station vacuum system; however, with the impeller submerged as
shown and depending on the characteristics of the equipment offered, the
pumping systems should be capable of being self-priming in an emergency.
During self-priming, the engine pump drives may be subjected to momentary
overload. Again, the design decision on whether to use siphon discharges for the
larger pumps in the medium-sized pumping stations will be based on comparing
potential savings on the cost of the diesel engine pump drives and the lower fuel
requirements with the increased construction costs over the life-cycle of the
pumping station. Note that if the siphon discharge is used, each pump discharge
tube will be provided with twin vertical-lift type backflow gates, as shown on
Appendix A, Plate M-7, with relief flaps located at the siphon terminus. The
gates are needed to prevent the possibility of reverse siphoning and backflow due
to incomplete breaking of the prime during pump shut-down. Each gate will be
raised and lowered by a single screw-stem with a Limitorque-type electric motor
operator controlled from within the station.
For discharge pipes that will be below high water levels, a second means of
preventing backflow will also be incorporated. The discharge pipes will have
their upper invert elevation (summit) above the high water level on the
discharge side. The siphon would then self-break.