Korth Engineering, LLC
Consulting Engineering Services
Marlborough, CT


"Septic System
Design Definitions And Process"

septic plot plan

Site Plan

A document prepared by a Professional Engineer or other qualified person providing specific design details for installation and/or repair of a septic system Often there are several design methods which can be utilized and existing systems may qualify for various exemptions. Hence the System Designer has a potentially significant effect on the cost of installation or repair of a septic system. Site plans may include as appropriate, additional factors beyond minimum specifications required by Local and State Health Codes.

Site Conditions

Various site conditions such as soil characteristics, location of on-site buildings, property lines, lot size, watercourses, utility lines and location of any existing or previous septic systems are specifically addressed in various Local and State Regulations. The combination of overall site conditions greatly influences costs for installation and/or repair of a septic system.

back hoe
Soil Testing

Installation details for a septic system such as size, location, depth and configuration are determined by soil testing. Percolation tests and Deep Observation pits are typical methods required by Health Code(s).

Percolation Test

A hand dug hole in the area of the proposed septic system. This hole is initially filled with water (presoak) in an attempt to saturate the soil, allowed to drain away and than refilled. The rate at which the water drops in the hole is measured at intervals over a period of time. The uniform slowest rate of drop of the water level over a measured time interval is used as a basis of design in determining the septic system size.

Deep Observation Pit (s)

Observation pits are dug in the proposed septic area in order to be able to see the various soil layers / characteristics. These holes are dug with a backhoe machine generally to a depth of about 7 ft and observations are made of the soil layers, color and texture and recorded by the sanitarian and/or engineer. Particular attention is given to the depth to ledge rock or ground water since both must be sufficiently separated above ground water or impervious soil and ledge rock.

Septic System Design and Installation Process

A general overall process which requires obtaining various Local and State Permits includes:

  1. Identification of Site Conditions including appropriate Soil Testing and Site Evaluation.
  2. Site Plan preparation and approval by Local and as necessary State Health Departments.
  3. Septic System Installation including necessary oversight.
  4. Permit to Discharge (utilize system) including necessary as-built construction documents.