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

Chapter 5 Water Infrastructure
5.9.2 Water Storage Facility Structures
The following are the primary structural functions of a water storage facility:
Remain as water tight as achievable for the design seismic, geotechnical, and
thermal conditions over its design life
Survive the design seismic event so that its operational purpose (fill, storage, and
draw of potable water) is maintained
Maintain the sanitary integrity of the tank so that its water quality is not
compromised.
The following are general design requirements for structural and material design elements of
storage facilities to meet the above requirements. All elements must be evaluated and
addressed to establish the basis of design for every new or refurbished storage facility.
5.9.2.1 Geotechnical and Seismic Requirements
The following are SPU standards:
1. A geotechnical study must be performed before design of any new or structurally
refurbished storage facility. Soils and groundwater characteristics for each site are
unique, so the geotechnical study must be tailored accordingly.
2. The methods, findings, and recommendations of the geotechnical study must be
documented in a geotechnical report.
3. The structural design requirements of storage facilities must address specific seismic
criteria for Essential Structures per the Seattle Building Code (SBC) and AWWA D-
100.
The following are guidelines for the geotechnical report:
Identification of previous geotechnical work for the storage facility site and the key
observations and conclusions from the previous work.
A detailed description of subsurface soils and groundwater conditions.
Identification and descriptions of known geologic hazards, including seismic, steep
slopes and landslides, erosion, and contaminated soils hazards
Identification of locations for additional field explorations/borings, if needed.
Conclusions and recommendations for design, including geologic hazards, seismic
criteria (e.g. probabilities of peak ground acceleration), excavation and shoring,
dewatering, foundation and backfill requirements, erosion and sedimentation
control measures, and hazardous materials.
5.9.2.2 Structural Materials
A. Concrete Reservoirs
Two primary issues for concrete storage reservoirs must be addressed in design:
SPU Design Standards and Guidelines
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