12 May 2003
Including change 1, 19 January 2007
Odor/Septicity Control. Slope sewer pipes as much as possible to
minimize detention time. Provide aeration in accordance with sound engineering
practices. Holding tanks must be aerated unless detention time is less than 3 hours at
average 24-hour flow. Keep force mains as short as possible and avoid sulfide
generation. Control sulfide generation by using an injection of oxidizing chemicals such
as chlorine, permanganate, or hydrogen peroxide. Consult suppliers of chemicals feed
equipment regarding costs and expected performance. Refer to WEF MOP FD-5,
Gravity Sanitary Sewer Design and Construction, for rational methods to predict sulfide
generation rates and methods of control. Maintain minimum flow velocity of 0.9 m/s (3
ft/s). Provide cleanouts and air relief valves at strategic and accessible locations.
Provide check valves at pump stations.
Structures and Appurtenances. Some sewer structures and
appurtenances have already been defined in Figure 3-11, Figure 3-12, and Figure 3-13.
Additional features are defined in Figure 3-14, and Figure 3-15. Also, see Table 3-6.
Pump Stations. The design of sewage pump stations at waterfront
facilities requires the careful consideration of all associated parameters including the
premium value of real estate. The system must account for all ship flows and the
connection to the station's central sewage distribution system. Careful coordination is
required with the Activity and the cognizant NAVFAC EFD/EFA OR USACE DISTRICT.
It is imperative to provide a properly operational system at minimum construction cost
and operational cost while optimizing the use of waterfront property.
Pipe. A variety of pipe materials may be acceptable to specify and will
vary on a pier-by-pier basis. Consult with the Activity and the cognizant NAVFAC
EFD/EFA OR USACE DISTRICT for the final material selection. In general, PVC pipe
may be used for gravity systems. Ductile iron pipe is preferred for pressurized systems.
However, PVC pipe and HDPE pipe has been specified for pressurized systems at
some pier facilities. Lined ductile iron with mechanical joints should be used for
exposed locations and where high impact resistance is important. Support exposed
pipe in accordance with manufacturer's recommendations. In other exposed locations
where corrosion resistance is a major concern, consider specifying thermoplastic (high
density polyethylene) pressure pipe with butt fusion joints. Plastic piping on pier and
wharf systems should be protected from impact by floating debris and other hazards. In
these cases, consider a specially designed utility trench. For buried lines, apply general
sewer pipe selection guidelines.