Septic Design Plans

At WJH, we provide a wide range of services, including plot plans, subdivisions, site plans, surveys, septic design plans, and many others. A septic design plan is prepared when there is no public sewer available to a site. This can limit the size and scope of a project. A commercial building’s size can be constrained based on the availability of a public sewer. If public sewer is available, the size will be determined based on the local zoning ordinances. However, if there is no public sewer available and a septic system is to be constructed, the commercial building’s size will be limited by the septic system design.

When working on our septic design plans, there are many factors that we must take into account. To start, we must have two things: a survey of the site; and a test pit of the soils. A test pit is an excavation dug to visually analyze soil conditions. This analysis is transcribed and recorded in a soil log.

By excavating to a depth of 10 feet or more for the test pit, we discover the many components of the soil and the level that the septic system should be designed at. We take a sample of the soil at the depth where the septic system will be, and here at WJH, we perform in-house permeability tests to see the rate of how fast effluent will move through this soil. This rate will help determine the size the septic system has to be, based on State requirements. Another factor that will help determine the size of the septic system is the projected flow. The State has separate requirements if the project is for a commercial building, a school, or a warehouse, as well. And here at WJH, we have designed systems from ±600 square feet to ±40,000 square feet in size!

After finding the size of the system, WJH has other factors that will influence the design. These factors include, but are not limited to: the depth of the seasonal high water table, determining the size of a septic tank, determining if a pump is needed, and re-grading the site. 

Once a design is completed, WJH will work with the County’s Health Department, the Department of Environmental Protection (DEP), as well as the Town, if required, to achieve an approval.

Contact WJH Engineering today to work with you on your next project!