Addendum to Regional Water Supply Facilities Plan Final Report (April 2011) Page: 5-2

                                
APRIL 2011

provide protection and reliability against
interruption in the raw water supply to
the WTP which could result from
planned or unplanned outages of the raw
water   diversion  and   conveyance
facilities; reduce fluctuations in the raw
water quality entering the WTP caused
by rapid changes in raw water turbidity
that can occur during rainfall events, and
provide flow equalization.
Floodwater Detention Basin
As part of the overall project, a FWDB
was proposed at each location to store
floodwater.  Floodwater within the
FWDB can be used to supplement the
base flow water for water supply
purpose during drought season. Also,
the FWDB provides flood protection
downstream along the ditch by reducing
flood water flow rates.
At SITE I, the proposed FWDB has a
total capacity of 616 acre-feet with a
surface area of 88 acres. A diversion
channel of 4,800 feet was proposed to
convey floodwater to the basin.
At SITE II, an FWDB of 797 acre-feet
was proposed with a surface area of 145
acres. A diversion channel of 200 feet
was proposed to convey floodwater to
the basin by gravity. The function and
operation of the proposed at this site are
the same as the SITE I.
At SITE III, a FWDB of 625 acre-feet
with a surface area of 124 acres was
proposed. The function and operation of
the proposed at this site are the same as
the SITE I and SITE II.
Flow diagrams and design data for the
intake facilities are illustrated in Figures
5-1, 5-2, and 5-3 respectively for SITE I,

SITE II, and SITE III. Figure 5-4 shows
the dimensions of the RWSB, and Figure
5-4 shows the layout for pump station II.
Operating Strategy of
RWSB and FWDB
The proposed RWSB can selectively
withdraw raw water from the drainage
ditch or from the proposed FWDB when
floodwater is available in the basin.
Water within   the  FWDB    can   be
regulated to flow to the RWSB by
gravity when the water level in the
detention basin is higher than the water
level in the RWSB, or flow to the wet
well by gravity and pumped to the
RWSB when the water level in the
FWDB is lower than the water level in
the RWSB. Screening will be required
at the discharge to the wet well and
RWSB from FWDB.
Water Quality Monitoring
System
A water quality monitoring system
should be installed at the diversion site
on the ditch to monitor the water quality
conditions within the ditch in order to
optimize treatment operations.

REGIONAL WATER SUPPLY FACILITIES PLAN

5-2