2013 Water System Plan, Volume II - Seattle City Clerk's Office - City ...

5.9.1.4 Operations and Maintenance (O&M) Requirements
A. Routine Operations
At a minimum, each water storage facility must follow water supply and quality goals for
operational procedures common to all facilities as shown on Table 5-10.
Table 5-10 Sample Requirements for Routine Operation of Water Storage Facilities
Parameter Requirement Comments
Pressure Maintenance to
Zone(s) Served:
Minimum
Drawdown and Filling
Water Age
(turnover rate)
Operational Volume
Sample Collection
Supervisory Control and
Monitoring
B. Emergency Operations
30 psi Maintain 30 psi under peak hourly
demand conditions
Maintain 20 psi under fire flow
conditions
20 psi
Typical draw between 8AM and
5PM
Typical fill between 8PM and
5AM
Draw and fill cycles for some storage
facilities may vary from this objective to
meet other requirements.
Note: These times are a starting point.
Drawdown occurs during day and fill
overnight as a general rule
3 – 5 days Longer water ages may be acceptable for
some storage facilities based on chlorine
residual data, water mixing systems and
ease of chemical injection
As required to meet seasonal
demands, pressure
requirements, and water age
targets
Easily accessible sample port
enclosed in cabinet
Water elevation
Overflow indication
Inlet and outlet metering
Operational volumes will vary seasonally
for many of the storage facilities
Sampling may be required at different
elevations within the tank
The following are minimum design requirements for operation of water storage facilities
under emergency conditions that can result in loss of power or a water quality condition
that could be harmful to health:
Maintain at least one storage cell on-line if facility has two or more storage cells.
If the facility is a single cell, maintain at least 50% of the volume online
Fill all storage cells
Draw from at least one storage cell to meet emergency demands for at least (as
required) hours
Hydraulically isolate all storage cells from the supply and distribution system
Complete drain-down of a storage cell as specified in the basis of design
Inject a solution of treatment chemical
Collect a water quality sample from an easily accessible collection point
5-50 SPU Design Standards and Guidelines