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

1. Corrosion of exposed reinforcing steel and corrosion caused by use of dissimilar
metals, such as stainless steel ladders adjacent to mild steel, either coated or
embedded.
2. Foundation failure due to settlement or leaks causing undermining of the
foundation.
The low alkalinity and pH of cement materials can cause deep cracking on the interior of
the facility and may expose the reinforcing steel to air and moisture, resulting in
corrosion. As reinforcing steel corrodes, the integrity of the structure will weaken and
eventually fail if not repaired.
Cracking in walls roofs and floors, failed expansion joints, failed water stops, are also
common concerns with concrete reservoirs that should be addressed in design.
For concrete reservoirs, the following AWWA standards must be applied:
B. Steel Tanks
D110 – Wire- and Strand-Wound, Circular, Pre-stressed Concrete Water Tanks
D115 – Circular Pre-stressed Concrete Water Tanks With Circumferential
Tendons.
The structural integrity of steel storage tanks is primarily affected by corrosion.
Corrosion can attack specific portions of the tank and cause significant structural
problems.
For steel tanks, the following AWWA standards must be applied:
5.9.2.3 Coatings
D100 – Welded Steel Tanks for Water Storage
D103 – Factory-Coated Bolted Steel Tanks for Water Storage.
For steel tanks, the following AWWA standards must be applied:
5.9.2.4 Liners
D102– Coating Steel Water Storage Tanks
For liners and floating covers in contact with potable water, the following AWWA standards
must be applied:
D130 – Flexible-Membrane Materials for Potable Water Applications.
5.9.2.5 Corrosion Control Systems
If used for steel tanks, the following AWWA standards must be applied:
D104– Automatically Controlled, Impressed-Current Cathodic Protection for the
Interior of Steel Water Tanks.
The design engineer should consult with a corrosion control specialist and evaluate the
following:
Conditions above and below the water level
5-52 SPU Design Standards and Guidelines