Sanitary sewer design
Sanitary sewer design
(OP)
I'm currently working on a design for a sanitary sewer. The neighborhood currently utilizes septic tanks, drainage fields. I'm concerned with the lack of flow in the sewers since very few homes will be connected. I realize I need to increase slope but then my manholes/pipe will become excessively deep. For instance, I will have a 200' run of 8 inch pvc with only one home connection. Also, I noticed the standard tip of designing for minimum velocity of 2 ft/sec @ half-full. The pipe will never come close to half-full. I would appreciate any advice.





RE: Sanitary sewer design
RE: Sanitary sewer design
RE: Sanitary sewer design
You have the right answer, flushing the lines. Now the question is what is the easiest and cheapest way to do it. I think if it were my design, I would design flushing manholes at stratigic locations to acconplish main cleaning. The designs I have done in the past all worked well and as flows pick up via connections, they are easily decommissioned.
Good luck in that political world you are in there!!!
BobPE
RE: Sanitary sewer design
RE: Sanitary sewer design
This also makes you look at each line more often and finding other types of problems before they become crises.
RE: Sanitary sewer design
small diameter pressure sewer mains
http://www.epa.gov/ORD/NRMRL/Pubs/1991/625191024front.pdf.pdf
RE: Sanitary sewer design
RE: Sanitary sewer design
It sounds as though you are trying to design the serives for acreages or similar. One consideration in your design is the connection (and cost) of the private system to the public line. I might suggest that a tank and pump out system might be better served, but I guarantee that the municipality will be in for some costly maintenance headaches if it intends on owning the systems on private lands. If gravity flow, the lines have to be deep enough to protect from freezing (if applicable) or at least enough to provide 1% or 2% grade for drainage. If the residence is set back far enough or it is an older home, additional costs to modify and connect to the system will be becessary.
If the manholes are going to be excessively deep, will the proposed system be able to tie into the existing system without need of a lift station?
As an aside, regarding the bylaws, or statutes, how is the cost of this collection system being distributed? Are the majority of owners in favour or a handfull? Is the municipality borrowing to put the system in, and if so, is the municipality intending on recovery via a frontage bylaw or specified area? I ask because in some cases, a project such as this can easily be scuttled if there are sufficient objections raised by the ratepayers.
KRS Services
www.krs-services.com
RE: Sanitary sewer design
As far as funding, the homeowner will be responsible for tie-in to the main, and I believe we have received a grant from the state to install the mains. Being an staff engineer in the public works department, I'm not totally exposed to the financial workings of the municipality.
RE: Sanitary sewer design