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

Chapter 5 Water Infrastructure
Table 5-3
Design Criteria List for a Typical Water Facility Design (Example)
Description Design Criterion/Design Data Comments
General:
Design Flow Rate 19,100 gpm (27.5 mgd) Year 2040 peak flow rate in a 36-inch pipeline
Flow Velocity 6.02 fps Year 2040 peak flow rate in a 36-inch pipeline
Typical Operating Pressure 120-180 psi
Design Working Pressure, Pw 250 psi
Design Transient (Surge)
Pressure, Pt
332 psi Based on 133% of working pressure and
allowable stress of 66.7% of yield stress
Minimum D/t ratio 240
Pipe Materials:
Pipe Type
Lining
Coating
Mortar-Lined and Polyurethane
Coated Welded Steel Pipe,
AWWA C200
Cement Mortar, AWWA C205
Polyurethane Coated, AWWA
C222
Joints Restrained Joint Double lap-welded joint provides thrust
restraint at bends, seal testing, and seismic
restraint. Maximum joint length and resulting
joint location is 60 ft. for steel pipe. Consider
thermal expansion and fittings to allow
movement, specifically with exposed pipe.
Example: pip supported by hangers under
bridges.
Pressure Class 250 psi 40,000 psi yield strength steel
Minimum Slope 0.001
Pipe Buoyancy Safety Factor 1.1
Minimum Cover – Roads 3 ft
Minimum Cover –
4 ft
Non-Roadway
Pipe Loading – Traffic HS-20 AASHTO
Traffic – Trench Condition HS-20 AASHTO “Prism Trench”
design condition assumed
Separation from Utilities 12 inch vertical, 10 ft horizontal See Std Plan 286
Deflection Lag Factor, Dl Minimum 1.25
Construction Tolerance ½-inch from specified line and
grade
Tolerances during tunneling higher as
specified
Steel Deflection Limit 2.25% of Diameter
Bedding Compaction – Non- 90% of Modified Proctor
Roadway
Bedding Compaction – 95% of Modified Proctor
Roadway
Bedding Constant 0.10
Modulus of Soil Reaction (E’) 700 psi See Geotechnical Report
Appurtenances:
Isolation Valves Butterfly Valves, 250 psi rating Located at tie-ins and interties to existing
mains
Blow-offs/drains
6-inch size. Provide at all low
points in pipeline
Used double valves, one for isolation and one
for throttling.
Line Valves
2,000 ft
Combination Air-Vacuum and
Air Release Valves
4-inch size. Provide at all high
points in pipeline
Also located at abrupt downward grade
breaks
SPU Design Standards and Guidelines
5-15