12 May 2003
Including change 1, 19 January 2007
Table 3-6 (Continued)
Special Pier Structures and Appurtenances
NOTES TO TABLE 3-6
Use siphons for carrying sewers under obstructions or waterways.
For siphons: maintain velocity of 3 fps (0.9 m/s). Use no less than two barrels with minimum
pipe size of 6 inches (150 mm). Provide for convenient flushing and maintenance.
Requirements for siphons: use WEF MOP FD-5 for hydraulic design.
Use intercepting sewers where discharge of existing sewers must be brought to a new
Requirements for intercepting sewers: take special care against infiltration due to depth or
proximity of surface water.
Use traps and interceptors on all outlets from subsistence buildings, garages, mechanical shops,
wash pits, and other points where grease or oil can enter the system.
For traps and interceptors: use a displacement velocity of 0.05 fps (0.015 m/s). Grease removal:
in absence of other data use 300 to 400 mg/L. Provide for storage of 1 week's grease production
(1 day if continuous removal is provided). Length = twice depth.
Use terminal cleanouts terminally on all pier collection systems.
Requirements for terminal cleanouts: locate where it will not interfere with other operations on
the pier or other utilities.
Requirements for receiving hose connections: design connections to receive the discharge from
Properly support all sewer pipes, especially pipes located under the pier. See paragraph 2-4.1.3.