In Missouri, developers of residential housing subdivisions are required to follow strict guidelines for the treatment of wastewater generated by the homes constructed within the subdivision's boundaries. According to the Missouri Clean Water Law, if a subdivision is platted into seven or more lots that are smaller than 40,000 square feet (.92 acres), then the developer must provide that the subdivision will be served by a centralized wastewater treatment and collection system. If the subdivision is platted into seven or fewer lots, then the developer is free to install individual on-site wastewater treatment systems, such as septic tanks.

The Missouri Department of Health and Senior Services ("MDHSS") regulates the installation, maintenance and permitting of on-site wastewater collection systems. However, according to MDHSS regulations, developers of subdivisions must first contact the Missouri Department of Natural Resources ("MDNR") in order to determine whether their subdivision will require a centralized wastewater treatment system before applying for any approvals for permits from the MDHSS for on-site wastewater treatment systems. This safeguard is designed to assist developers in making appropriate planning decisions about which method of wastewater treatment must be provided to their subdivisions, according to Missouri law.

Several methods for the centralized collection and treatment of wastewater are available to residential housing subdivision developers, including but not limited to, wastewater treatment lagoons, connection to existing wastewater treatment systems, individual wastewater treatment plants, and no-discharge/land application systems. Developers should contact an engineer to determine which method of wastewater treatment would be serve their subdivision based on the soil, groundwater, and geologic conditions of the land surrounding the subdivision, and the applicable regulatory standards.

If you are a subdivision developer, consult the DNR's Residential Housing Subdivision Rule, 10 CSR 20-6.030, for all of the regulatory testing, monitoring and permitting requirements for centralized wastewater treatment systems. If your subdivision is exempt from the rule, contact your local county health department official for the regulatory and permitting requirements for on-site wastewater treatment systems.