Wastewater Treatment & Disposal Solution- Small but Growing Community

[allie075]

Hello everyone:

I work for an approval agency. We have this development comprising 140 single family units. The development was given approval for use of a double compartment septic tank, sand filter trench and chlorine contact chamber (Clayey Soils). One problem is that the lot size is smaller than the proposed lot size which was submitted with the WW system for approval. Space is a problem as well as elevations. The existing drain is too shallow.

The houses are being built by individual home-owners who want to maximise their land space and have began building unique versions of the system...shorter trenches, no lining etc. Of course, there is a health risk involved and the approved system will not work without modification.

So far, the options we have are:
1. Introduce a sump and pump to each lot to discharge disinfected effluent
2. Small bore system with ATU
3. Centralised WW Treatment Facility

The first one is risky because the residents are already complaining about the cost of the chlorine tablets and maintenance is a common problem here.

The second and third are iffy because there are only ten houses built/being built at present. We are not sure when the others will decide to build so flows may be very small for some time.

I'd appreciate your comments/advice.

Thanks much
Allie

 

[ccor]

My guess is you will receive a lot of varying opinions on this, but my two cents: 140 SFUs is too large for the proposed and approved treatment options. There may only be ten homes now, but now is the time to get it right before it is too late. I vote for the centralized WWTP. It will likely provide better overall treatment and receive the maintenance and attention it deserves.

 

[ptmoss]

Without knowing what kind of design criteria you have for the individual units it's kind of hard to surmise whether there would be a long term problem. I personally believe on-site systems are suitable as long as soils and lot sizes are adequate and the systems are designed and installed by experienced people.

That said, your comment that landowners are building "unique versions of the system" leads me to believe this will not work out if it continues in this manner. Who's designing those 'unique versions' and how did lot sizes get smaller than what was originally approved? It sounds like there needs to be some firm regulating of these sites and systems before it gets too far out of control.

Who are the landowners going to come crying to when their systems don't function? Or their drinking water becomes undrinkable (are there also individual wells for drinking water?).

Sounds like the development needs more thought. In lieue of a central system for 140 or so houses, if individual systems don't work then perhaps a series of common systems for groups of ten houses, or whatever, could work? I understand how people like to have flexibility to do what they'd like with their yards and a bunch of small common systems might be another way to achieve this.

However this works, it needs to be dealt with firmly, and sooner rather than later!

 

[Sdave999]

I can think of a "hybrid" system here that may prove to be workable but end up being much more expensive overall... so... I would vote for a centralized system. Find a manufacturer that provides small tankage that is easily expandable. 140 homes, depending on occupancy, will produce 35,000 to 50,000 gallons per day of wastewater.

Start out with 15,000 gpd (40 to 50 homes). Expand as needed as the flow increases.

Check out an outfit called McNeill Company. They have a pretty good extended aeration WWTP in small expandable increments.

 

[dicksewerrat]

I guess you have to go back to the original 'approved' site plans. Enforce them. Then start designing the WWTP.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com