Requirements for a Lagoon Septic System

What to watch for when constructing and maintaining your sewage pond

By Glyn Sheridan

Photo by iStockphoto.com

A lagoon septic system replaces a traditional tank-type septic system for residential sewage treatment on farms and in rural areas where the soil is not adequate for lateral drain fields. Also called "sewage ponds," these large, excavated depressions hold wastewater and waste solids in an open-air environment. Because raw sewage accumulates in these ponds, most rural communities regulate the size, shape and location of a lagoon septic system.

Percolation Tests

Percolation tests determine the rate at which the soil absorbs water and when that rate is not sufficient, a lagoon system may be the answer. The presence of clay soil or other high-compaction soil is usually a requirement before a property owner can obtain a permit to dig a lagoon. An inspector may perform or monitor a percolation test before approving the lagoon.

Size of Lagoon

County zoning boards commonly regulate the size of a lagoon and its proximity to a residence or to neighboring property. The number of people who will live in the residence or the number of bedrooms in the home determines the size of the lagoon. Lagoons are often square or rectangular, with a sloped sidewall. The standard slope of the sidewall is 3:1, meaning for every foot from the rim of the lagoon to the middle, the sidewall must slope downward 3 feet.

Installation

A professional excavation company will dig and shape the lagoon in an area where flooding is not a concern. Because a lagoon operates on a gravity-flow design, the pond must sit at a lower elevation than the home it serves. A licensed plumber will calculate the slope of the drainage pipe from the home to the lagoon, burying it beneath the soil.

Maintenance

Heavy foliage is discouraged around and in the lagoon pond because it reduces airflow along the surface of the wastewater. The formation of algae and beneficial bacteria help the waste naturally decompose and evaporate. You may chemically treat the lagoon to raise the oxygen ratio and speed the decomposition process if you notice a strong disagreeable odor, although a slight odor is common with a lagoon septic system.

Precautions

A secure fence with a gate must surround the lagoon to restrict pets and children but allow access for mowing and maintaining the inside bank. Some zoning boards may require an additional septic tank on the drain line ahead of the lagoon to trap waste solids, allowing only the effluent water to fill the lagoon.