Cal State Engineering Inc. has over 30 combined years in designing a wide range of septic system types and sizes for both residential and commercial applications.

A typical design process begins with a site/soils investigation with the Engineer, Government Agency and a backhoe to evaluate soil parameters, and determine the septic type.

Upon completion of the soils investigation, the design process continues with a percolation test report and a topographic survey of the parcel, detailing all relevant site information and constraints. The Engineer uses all of the above information to prepare the septic design. The number of bedrooms allowed is confirmed at this stage.

Plans are then submitted to the proper governmental agency for approval.

Site/Soil Investigation

Our engineer's at Cal State Engineering, Inc. are highly trained and experienced in understanding soils for proper soil evaluation. Before any disposal area is determined, our engineers, along with a Government Agency employee and a backhoe operator, undergo a soil investigation.

Understanding the soils at a site allows for the selection of the appropriate methods or technology that needs to be used for proper sewage treatment and disposal. Soils that need to be identified and evaluated to determine the ability of a site to treat and disperse the resultant treated effluent.

Most often this evaluation takes place in what is called a soil profile. A soil profile is a cross-sectional view of the structure that is present in a particular soil. Soil horizons, along with texture, structure, color, general site features, landscape position, vegetation and slope of land are all recorded in soil logs during the soil profiling process and are used to determine the overall design.

After site location is determined, field technicians will go on site for a percolation test. A percolation test determines how fast fluid will drain through soil. This is cricial for every system to determine how effective the soil will be at dispersing the treated effluent.

(Most common)
System Type
Pressure Dosed - Septic tank with internal pump to pressurize and distribute waste water along the disposal field.
Requires more soil than a sand filter system.
Pump adds to the system's complexity.
Good distribution of waste water. Relatively inexpensive.
Requires less soil than standard system.
Standard - Waste water flows from septic tank to disposal field by gravity.
Inexpensive, simple system.
Intermittent Sand Filter - Septic tank with internal pump forces waste water to sand filter bed where it is distributed evenly. Pump in sand filter bed then forces water to shallow disposal trenches.
Requires the least amount of soil of all system types.
Waste water is filtered and "cleaned" by sand filter.
Complex in comparison to other systems.
At-Grade - Septic tank with internal pump forces waste water to distribution bed comprised of pipes resting on a gravel bed. Gravel bed and pipes are covered with a minimum of 12" of soil.
Requires little soil, good distribution.
Requires moderate slope of 25% or less.
Septic System Types
Requires moderate slope.
Requires little soil, good distribution of waste water.
Allows septic systems where not otherwise feasible.
At-Grade with Sand Filter - Septic tank with internal pump sends waste water to sand filter bed. Sand filter pump forces water to distribution bed comprised of pipes resting on a gravel bed. Gravel bed and pipes are covered with a minimum of 12" of soil.
Requires additional maintenance.
Requires less area for construction of system.
Advantex-Textile Filter - Septic tank with internal pump sends waste water through a pre-treatment filter attached to tank, then forces water to disposal trenches.
Several other septic stytems are available for use in the area, but most see little use.
See Operational Guidelines
Requires the most soil of all systems.
Poor waste water distribution.
Septic System Design





JACKSON, CA. 95642

(209) 223-1441(209) 223-5044 FAX


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427 Broadway - Jackson, Ca. 95642 - (209) 223-1441 - ( 209) 223-5044 Fax -

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