Hybrid Pressurized + Traditional Gravity Septic System
The Challenge: A Limiting Layer Below the Site
When digging the test pits on this property in Weld County, they revealed sand and gravel at approximately five feet deep. This is considered a limiting layer, or a soil or groundwater condition that restricts how deep a septic system’s leach field can be installed.
Because the sand and gravel layer was located at five feet, the leach field could not be installed at the depth that would normally allow the system to operate entirely by gravity.
A fully pressurized leach field was another option, but that would require additional components throughout the leach field, including pressurized distribution and flushing assemblies. That would add both installation costs and potential maintenance considerations for these homeowners.
The goal was to find another way to move the effluent (liquid wastewater from the septic tanks) to the leach field while still allowing the individual leach field areas to operate by gravity.
The Solution: A Lift Station With a Shallow Leach Field
The solution was to install a lift station after the septic tanks and use it to move effluent up to the leach field. Rather than placing the leach field deep in the ground, the field was installed at approximately one foot deep. The pump then moves effluent from the tank up to a distribution box positioned above the tank elevation. From there, the system can use gravity to distribute effluent through the leach field.
This approach eliminated the need for a fully pressurized leach field while allowing the system to work around the site’s limiting layer.
It also meant the project could use a smaller pump and reduce costs on the leach field side of the installation.
The Benefits: A Practical Alternative to a Fully Pressurized System
This project shows how site conditions can change the design of a septic system and why the right solution is not always the most complex one.
Even though the limiting layer meant a conventional gravity system was not an option, a fully pressurized leach field was not necessary either. By combining a lift station, a shallow leach field, and a gravity distribution system, we were able to work around the soil conditions while avoiding unnecessary components and the added cost of a fully pressurized field.
This septic system was designed specifically around the conditions of this Pierce property: especially with its cold winter temperatures in mind. The transport line from the pump tank to the distribution box slopes back toward the tank, allowing the water in the line to drain back through a weep hole when the pump shuts off. This helps prevent the line from freezing during cold Northern Colorado winters.
Location:
Pierce, CO
Full Scope of Work: Septic System Design, Septic System Installation, Foundation Excavation & Backfill
Budget:
$30K-33K
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