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case study feature seven lakesSeven Lakes, Nova Scotia, Canada


Create a sustainable development served by a central sewer system while preserving the natural environment.


The Penney Group chose the ALL-TERRAIN SEWER pressure sewer system from E/One to serve the development. 

After spending almost six years to consolidate separate parcels into a contiguous 634-acre tract of mature forest touching seven different lakes -- and another four negotiating a development agreement with the regional government -- Penney Group embarked on a unique challenge: creating an open space conservation community restricted to only 634 moderately sized and priced residences while leaving 60 percent of the pristine landscape undisturbed.

Houses at Seven Lakes are clustered together in "little villages" surrounding nature preserves with each homesite measuring one-quarter to three-quarters of an acre. Eventually, seven clusters (totaling 634 residences) of single family homes, duplexes and four-plexes will be linked by trails for walking, hiking and biking.

Septic systems and gravity sewer systems were also considered for wastewater disposal, but The Penney Group ultimately chose pressure sewer for several reasons:

  1. First, Canadians are used to central sewer systems, and the idea of maintaining a septic tank was not appealing.
  2. Home sites at Seven Lakes are of modest size with lots of trees, and septic systems often result in expansive lawns.
  3. Constructing a gravity sewer system would have likely required removing acres of trees, and one of the goals of the project was to conserve as many trees as possible to keep a natural environment.

Photos and video courtesy and copyright of The Penney Group and Seven Lakes Development. Used with permission.


Terrain was also not conducive to septic or gravity sewer systems: the area has a lot of bedrock, and frost heave is also a concern. Septic systems are often not a good choice for lake communities because of soil conditions. Gravity sewer systems would require many manholes and several pump stations. The pressure sewer mains follow of the contour of the land, are located just below frost depth (approximately 5.5 ft), and can be insulated during installation if needed. 

Related Articles

Subterranean Secrets — Using grinder pumps and pressure sewers to keep home prices affordable, excavation minimal, and sewage manageable. Green Builder magazine, Sept/Oct 2017

Pressure Sewer System Key to Nova Scotia Home Builder's Conservation Philosophy — Developing a new community when septic tanks and gravity sewer systems were not possible Environmental Science & Engineering, June 2018

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