Best location of sewer lines in a subdivision

[bnard]

I am designing a 10 hectare subdivision and the space is limited. The developer wants to maximize the saleable area he can derived based from the 70 to 30% area distribution of saleable to non-saleable areas. There are no provision of easement at the back of the lot where we usually place the sewer lines. Would anyone advise the best location of sewer lines within the 19m right of way of road considering the other utilities (water system, drainange system and underground electrical lines)? Thanks so much

 

[RDK]

With a 19m ROW you would have say 10m curb to curb. That gives you 4.5 m each side of the curb to property line.

Put the sewer on one side of the street and the water along the other. Run the gas 1 m inside the ROW and the electrical including telephone and cable on an easement 1 m inside the property.

Then push the sewer and water services under the road and you will end up with a road on undisturbed soil and never have to dig up the pavement for line breaks.




Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[TVE]

"Best location for who?" is the question that gets asked around here.

Traditionally here we use a 20.12m (66') R.O.W. which is now becoming a 20.0m R.O.W. as various Municipalities switch their old design standards to metric. Residential roads are generally have an 8.5m clear width which means we try to have a watermain 1.5m from the Property line and a sanitary sewer 4.25m from the Property line on one side of the road and the storm sewer 4.25m from the other property line.

Those locations are being argued about now because someone got the bright idea to "co-ordinate" the locations with all the various utility companies. Unfortunately, the electrical, television and telephone utilities all want secondary corridors in the bouldevards so the sanitary and storm sewers are getting shoved to 1.5m either side of the road centreline. (With all the associated joys of differential settlement and frost heave in the trenches destroying the asphalt pavement.)

Hope that helps..

Dave
Thames Valley Engineering

 

[KRSServices]

Ususlly the development authority will specify where the utility alignments are to be placed, assuming of course that a municipality will assume ownership after the warranty period expires.

Rick, your idea has merit, but does not work so well over the long term because if the contractor uses open cut trenching, and the cuts are deep, there are numerous failure locations and settlements along curbs that are in need of repair about 10 to 15 years later. If the lines are too close too the property lines, it is impossible to effect repairs without encroaching on private property without a working right of way being titles to the municipality. Conversely, anything in a roadway requiring repair gets nasty and the repair is prone to settlement after. That being stated, after experienced both philosophies, I prefer to place the water mains strategically in the road right of way such that there will be uniform disturbance (and blending) of soils. Use of floating MH and valve covers assist in mitigating settlement "bumps" and overall there seems to be less failure of curbing and asphalt over time due to settling.



KRS Services

http://www.krs-services.com

 

[RDK]

Most contractors here will use cages. I always specify and enforce that if the area under the road is to be open excavated that the backfill has to be tamped to natural occurring densities and that this has to be done in 150 mm lifts.

I was involved in a sub division this summer and the entire sewer and water excavations were off the final roadway. The entire road width was placed on virgin soil.

Where we had to cross the road due to the layout, the pipe was pushed. Ducts for the electrical and gas lines were placed at the bottom of the road sub-base and the pit run placed over them.

There are sub divisions now 6 years old that we put in with this method and the road is as smooth as it was the day the asphalt was placed. There are other subdivisions in town where the utility trenches are under the road and these had noticeable settlement within a couple of years. These sub divisions are now 20 years old and have several repairs necessitating cutting the pavement and these repairs also have noticeable settlement.

If the utility lines do require repairs then it will be a lot easier and less disruptive to excavate grass than asphault.


Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[KRSServices]

Rick,

As I previously stated, you are absolutely correct, and with the use of cages it works tremendously well. However, two years ago, a simple little repair on a leaking mainstop clamp proved to be the "service from Hell" in terms of my budget. You see, the main was about 2.0 m off property. Now my crews did not have a cage for repairs, and therefore had to excavate in accordanc ewith WCB. The propoerty just happened to have a beautifully finished brick and stone decorative wall, complete with wrought iron ornates, completely within their property. The leaking clamp caused settlement and surfaced near the cc, which was outside the property line per specifications. The long and short was the wall was damaged both from the leak and excavations and cost us a small fortune to restore, all under the watchful eye of her solicitor. I've had some other costly repairs too close to property lines in well established neighbourhoods.

The moral of the story is that the majority of the main repairs that were similar in nature, if out in the street, would have been far easier to deal with than so close to the property line. I've spec'd both alignments and have had good results, but when longterm maintenance costs and headaches are factored in, I would advise a street alignment over boulevard alignments.

Those are my thoughts, and to be honest, I think it comes down to opinion, because your practices are absolutely correct as well. Have a good weekend, and....GO ESKS GO!

KRS Services

http://www.krs-services.com

 

[RDK]

I see the moral of the story as always have the right tool for the job.

You did not have a cage and that was the right tool for that job.

BTW, Where are the Esk’s going?




Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[KRSServices]

Rick,

To Regina, to bring the Grey Cup back home! If you do not follow the CFL much, please disregard those references.

Regarding the alignments, you are correct, but mot all P.Works departments have cages as they are very expensive or for whatever reason, department heads have not deemed them to be e necessity. In this case, it would not really have heled because the soils were so saturated, the wall "came crumbling down" so to speak with every bucket load of material removed during the initial excavation.

KRS Services

http://www.krs-services.com

 

[RDK]

I know that this is Grey Cup weekend, I just think that the Esk’s are going to come home empty handed. We’ll see tomorrow.

I guess that in addition to a cage you needed some dewatering equipment. I know that most public works departments do not have this equipment but any decent sewer and water contactor would.

They have this equipment because for them time is money. Not like the more make work approach of most governments be it municipal, provincial or federal.

With the proper equipment this or any other type of repair would be relatively simple and inexpensive since there is no road repair and need for compactin or allowing time for settlement to occur.




Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com