Water Protection Program

fact sheet

Division of Environmental Quality

Director: Kyra Moore

This fact sheet outlines when a multiple family development is required to receive approval for the method of wastewater treatment and how it receives that approval per 10 CSR 20-6.030 Disposal of Wastewater in Residential Housing Developments.

This fact sheet is not intended to explain how a subdivision receives approval from the department for the method of wastewater treatment. A link to the department's fact sheet On-site Wastewater Disposal in a Subdivision - PUB2226.

For the purpose of this rule, each unit of a multiple family development (apartment, hotel room, RV campsite, etc.) is counted as a single family residence. Multiple family developments that discharge less than or equal to 3,000 gallons per day of domestic wastewater into a subsurface soil absorption systems are required to receive approval for the method of wastewater treatment if the development will have seven or more units or for development expansions of three or more units. At minimum, the department would require an engineer’s report as stated in Section (6) of the Residential Housing Rule. That report must follow the criteria set forth in 10 CSR 20-8.020 Design of Small Sewage Works.

If the flows are greater than 3,000 gallons per day for the subsurface soil absorption system or they discharge directly into the environment the developer should contact the department’s regional office for assistance and permitting.

Engineer’s Report
The following is required as the minimum components of an engineer’s report. The department may require more information depending upon geology, soils, landscape position and the complexity of the site conditions that may influence its ability to treat and control the wastewater.

  • Nature of use, such as duplex, quadplex, hotel, motel, recreational development, etc.
  • If the system is to serve a recreational development, the developer must submit a copy of the restrictive covenants prohibiting continuous year round living. The covenants must also prohibit cabins or other structures from being used as year round residences.
  • Documentation of ownership and responsibility. For the purpose of this rule, the owner is defined as the individual or individuals responsible for the continued operation and maintenance activities required to ensure the dependable function and financial responsibility of the entire wastewater treatment system.
  • Description of existing wastewater treatment facilities, if applicable.
  • Description of the method of wastewater treatment, alternatives and why this type of system is proposed as compared to others, which are feasible and practical. The report must discuss the options and the reason for selecting the recommended treatment system. If more than one subsurface soil absorption system for the multiple family development is proposed, documentation should be submitted ensuring they act independently (collection, treatment and dispersal) along with why they are necessary. Please note: The actual system design is not required to be submitted as part of the engineer report. If it is submitted, it will be returned to the applicant.
  • Calculations of the estimated flows using Table 2A-Quanities of Domestic Sewage Flows of 19 CSR 20-3.060 Minimum Construction Standards for On-Site Sewage Disposal Systems.
  • Description of water supply and placement to the wastewater treatment and dispersal area.
  • The report must include a copy of the Geohydrologic Evaluation conducted by the department’s Division of Geology and Land Survey. To receive an evaluation, developers must complete the “Request for Geohydrologic Evaluation of Liquid-Waste Treatment Facility/ Site” form. Visit the department's GeoEdge website to submit your request or view other geohydrologic evaluations. The department does not charge a fee for this service.
  • The report must also include a thorough and systematic soil investigation conducted by a qualified Soil Scientist as defined in 701.040(2)(e) RSMo. Soil observation pits (backhoe or hand dug) must be dug to a depth to reveal the major soil horizons. The number of observation pits should be sufficient to adequately represent the soils and landscapes of the primary and reserve dispersal sites. The documentation of the soil description pits may be supplemented by soil borings to help determine the extent of similar soil properties.

The soils report must contain a topographic map delineating the proposed dispersal areas into the following categories: 0-2%, 3-14%, 15-30% and 31% and greater. Along with a map delineating the depth of the acceptable soils into the following categories: less than 18 inches, 18 to 30 inches and greater than 30 inches over bedrock or a limiting layer.

  • A plat or general layout clearly indicating the following must be submitted
  • The location of the primary and reserve dispersal sites for the subsurface soil absorption system(s)
  • All set-back distances for the primary and reserve dispersal areas
  • Soil observation pit locations
  • Supplemental boring locations
  • Location of all potable water sources
  • Location of existing and proposed structures
  • Locations of existing and proposed easements
  • Location of all natural drainage ways and other cultural features that may affect the design, installation, operation and maintenance of the subsurface soil absorption system
  • Location of all monitoring wells if required; and the location of all known or proposed utilities
  • A copy of a U.S. Geological Survey topographic map with the area of development clearly outlined
  • A copy of a soil map with legend from the U.S. Department of Agriculture County Soil Survey with the area of development clearly outlined
  • Other pertinent information, as determined by the Department

Department Review
To ensure an efficient review and reduce delays, please submit all of the required documentation at one time. A copy of the Request for Approval under 10 CSR 20-6.030 Disposal of Wastewater in Residential Housing Developments - MO 780-1706 form. The Department does not charge a fee to review these submittals.

The developer must comply with all of the conditions written in the Department’s approval letter as well as the Missouri Clean Water Law and its corresponding regulations. The developer must meet these requirements before the sale or lease or start of construction by any developer or other individual. There cannot be any deviation or change that may adversely affect the geohydrologic evaluation, soils, estimated daily flow or the reported water supply for the development without first securing written approval of the proposed changes from the Department.

Approval for the method of wastewater disposal under 10 CSR 20-6.030 should not be considered as approval for the reported potable water supply. It also does not excuse the developer or any other individual from complying with or from liability for violations of the Missouri Clean Water Law and regulations or any other state or local laws.

After the method of wastewater treatment receives written approval, the developer must contact either the Department of Health and Senior Services or local administrative authority, which is commonly the local health department, to receive assistance and information regarding the necessary permits to construct. Approval from the department does not obligate the Department of Health and Senior Services or local administrative authority to approve any particular type of subsurface soil absorption system or that a wastewater system will be approved for the development.

Remember for the purpose of compliance with 10 CRS 20-6.030 each unit is considered equal to a single family residence. The components described above are required as the minimum for an engineer’s report, although more information may be required depending upon the complexity of the site and its ability to treat and control the wastewater.

The Department realizes there is always an infinite number of “What if” questions this and other fact sheets may not be able to answer. If you have any questions concerning your specific project, please contact the department for assistance.

Related Department of Natural Resources Fact Sheets and Other Resources

Nothing in this document may be used to implement any enforcement action or levy any penalty unless promulgated by rule under chapter 536 or authorized by statute.

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