Engineered Seepage Pit Feasibility Report Requirements

A Feasibility report shall be prepared by a Qualified Professional (QP) or by an individual under the supervision of a QP. The following are considered QP: A California Professional Geologist, a California Certified Engineering Geologist, a California Registered Professional Engineer, California Registered Professional Soil/ Geotechnical Engineer or a California Registered Environmental Health Specialist. 

The following are requirements for an engineered seepage pit. Please address these points in the feasibility report. 

• A log of the soils encountered in 5 ft increments. 
• Description of the soil and soil type listed using California Plumbing Code (type I-IV) 
• Soil boring shall be performed within 35 feet of the proposed seepage pit(s). 
• The location for soil boring shall be selected so as to provide a good representation of the entire leach system. 
• Verification of no adverse geologic conditions (i.e. bedrock, ground water) 12 feet below the bottom of the proposed pit. 
• A site plan shall be included labeling the location of the following:
  • Location of and size of septic tank
  • Location of seepage pits
  • 100% expansion area
  • Location of distribution box
  • Location of residence(s) and number of bedrooms
  • Commercial systems will require a floor plan showing the location of all fixture units along with a drainage fixture unit list
  • Location of water well(s), if any, within 150 feet of septic system
  • Location of any geological features (i.e. large streams, trees, rock outcroppings, rivers, etc.)
  • All setbacks
  • Location of soil borings 
• Diagram of the proposed seepage pit including pit diameter, depth of inlet, and total depth. 
• Location of septic system shall be staked out prior to initial site inspection.  
• Diagram of the proposed septic tank. 
• Absorption capacity shall be calculated based on the quantity of liquid waste discharging and the character and porosity of the surrounding soil using CPC design criteria. 
  • Soil type SHALL NOT be averaged.
  • Total capacity shall be shown in gallons.
  • Show calculations.
• Each report and site plan shall be wet stamped and signed with an original signature by the QP who either performed or supervised the testing.  

NOTES: 

• Seepage pits are not allowed in type 1 or type 5 soil. If either soil type is encountered, it shall not be counted in total absorption capacity. Excessive layers of type 1 or 5 soil will necessitate installation of leach lines.
• Properties with adequate space to install leach lines will not be allowed to install seepage pits. 
• Commercial projects shall size their septic tank based on drainage fixture units or the estimated flow rate, whichever is greater. Provide list of fixtures and their drainage fixture units or show how the estimated flow rate was determined. Show location of fixtures on site plan. 
• Plans are valid one year from the date of approval.