sanitary sewer design

[lpf]

i am currently working on a project which involves the extension of an existing sanitary sewer system into our property to service 4 homes. based on the soil borings that were taken, it is very possible that the proposed sewer main will have to be constructed within, or very,very near the water table. i am looking for information pertaining to the construction techniques used in this type of situation.

 

[rosebud]

Many sewer lines are placed below water table. Ensure that specifications require adequate infiltration, exfiltration or pressure tests. Require rubber collars at the manhole/pipe connection. Check for adequate pipe bedding and haunching for existing soil conditions. As always the ensure quality installation by on site inspection.

 

We are designing a hospital with a population potentially growing 100%. If we design with the projected population, the velocity of current flow is below 2fps. The owner representative would like a system that will service the future population.

What are some of the options to improve the velocity? and options for maintenance?

Also what are good estimates of gpd for beds and out patients.

 

[b]

Typical flows range from 150 to 250 gallons per person per day . A typical value of 175 gallons per person per day. A mean velocity greater than 1.0 fps is generally sufficient to prevent serious deposition of of sewage solids. I am assuming that the system is designed for gravity flow then there are a few options I can suggest to increase the velocity either decrease the pipe diameter or adjust the slope. Since you are designing for the projected population the first option is not feasible. You can work with the slope if possible to increase the velocity but ensure that at future design capacity it does not exceed the maximum allowable velocity. A third option is to install a sewage fflow regulating device which will allow flow at the peak times. Hope that has been of some help.