Water Protection Program fact sheet
Division of Environmental Quality Acting Director: Steve Feeler

As Missouri State Operating Permit conditions and requirements undergo changes, many treatment facility owners and operators have expressed an interest in the option of reusing treated wastewater through irrigation or land application. This fact sheet lists many commonly asked questions about this option. This list does not answer all potential questions, and it is recommended that the facility contact the Department of Natural Resources Water Protection Program or their local regional office for further information.

Question:  Is no-discharge or irrigation the only option for our treatment facility to meet operating permit requirements?
Answer:  No. The department does not specify the options used to meet operating permit requirements. However, when comparing possible upgrades, an engineering report must evaluate the feasibility of converting to a no-discharge system and eliminating the discharge as one alternative. We recommend that communities and their engineers evaluate multiple options and choose one that will meet all permit requirements in the most practical way for the long term.

Question:  How can we determine if a no-discharge or irrigation system is in the community’s best interest?
Answer:  Prior to any final decision, the community should discuss all possible options with a professional engineer (registered in Missouri). While a no-discharge or irrigation treatment facility has benefits, it may not be the most practical option for all communities. 

Question:  What is the estimated cost of a surface irrigation system?
Answer:  The cost estimates discussed here are from the Water Environment Research Foundation (WERF).   The costs in Table 1 are to be used for general comparison only. These costs reflect the dispersal system itself, and not any other part of the wastewater collection and treatment system, engineering, other professional fees or the cost of land acquisition.

50,000 Gallons per Day or 200 Homes




Relatively flat

Material and Installation

$1,260,000 to $1,890,000

Annual O&M

$21,000 – $31,000

Question:  What is the process to install or upgrade to a no-discharge or irrigation type of treatment facility?
Answer:  First, it is recommended that the permittee contact the department to discuss possible alternatives for upgrading. Then, before construction begins or facility changes are made, the permittee must have an engineer evaluate different options and develop an engineering report (or facility plan, depending on the funding source) that compares the alternatives and provides a recommendation. The report or plan must be submitted to the department for approval. Once the report or plan is approved, the permittee will then have an engineer submit a completed application for a construction permit along with engineering plans, technical specifications, and a summary of design (calculations). These documents must be submitted to the department’s Water Protection Program. After a department review of the design, a construction permit would be issued to the permittee, and then construction may begin. Once construction is complete, the permittee would then have an engineer submit a Statement of Work Completed.

The permittee may qualify for a Small Community Engineering Assistance Program grant. This grant may pay for the original engineering report for qualifying small cities.

Further, the financial burden of any upgrades and replacements can be eased by seeking funding through the department’s Clean Water State Revolving Fund or other funding agencies in the state. Most monies available are low-interest-rate loans. However, there are some grants available. Should it become necessary to obtain additional funding for upgrades and replacements, the community could apply to the department’s State Revolving Fund loan program or to the Missouri Water and Wastewater Review Committee to determine potential funding options from various state and federal agencies. A copy of the Clean Water State Revolving Fund Intended Use Plan and loan application packet is available onlinel. In order to be eligible for funding, contracts for engineering services must be negotiated on the basis of demonstrated competence, qualifications for the type of services required, and at fair and reasonable prices. The procedures and procurement requirements in Sections 8.285-8.291, RSMo apply. For further information concerning financial assistance opportunities for wastewater infrastructure, you may contact the department’s Financial Assistance Center at 573-751- 5723.

Question:  Is engineering or a permit required for all changes to a treatment facility?
Answer:  Any condition or action that would be considered operation and/or maintenance (O&M) may be done without prior engineering or approval, if it is merely repairing or replacing equipment like for like. Work such as repair or replacement of collection lines with similar materials without change in size or location would be considered O&M. For any other changes, the permittee can submit a written request for a permit determination of the proposed activities. The department will evaluate the request and issue a written notice to the facility regarding whether a construction permit would be required. Regardless of whether a construction permit is required, the permittee would need their engineer to design any modifications based on the minimum requirements provided in state law or regulations.

Question:  Will a no-discharge or irrigation facility be required to obtain and keep a valid Missouri State Operating Permit?
Answer:  Any facility that meets the conditions of 10 CSR 20-6 for an operating permit will be required to obtain and maintain a valid Missouri State Operating Permit. There are some exemptions for very small, domestic-wastewater only, no-discharge systems. Please contact the department to discuss whether your system could be exempt from permitting requirements.

Question:  If a facility uses irrigation, is that facility still required to have a certified wastewater operator?
Answer:  If a facility meets the conditions of 10 CSR 20-9, the facility will still be required to have and maintain the services of a certified wastewater operator.

Question:  Is the operational monitoring stated in 10 CSR 20-9 still required for facilities that irrigate?
Answer:  The requirements for operational monitoring found in 10 CSR 20-9 are still applicable to facilities that irrigate, if they meet the minimum requirements. A facility may request a modification of these requirements from the department by submitting a written request. The department will then evaluate the request and issue a written notice to the facility approving, denying, or modifying the operational monitoring requirements. Additional monitoring specific to irrigation facilities may also be included in the operating permit.

Question:  Is soil sampling of the irrigation field required?
Answer:  The operating permit will specify sampling required for compliance with the issued operating permit, which could include soil monitoring or other requirements. Soil sampling is typically required every year or every three years. There are some exemptions for facilities that irrigate at a very low rate.

Question:  Is effluent and irrigation water sampling required? Will parameter limits be set for effluent/irrigation water?
Answer:  In properly operated facilities, irrigation of all wastewater makes the facility a no-discharge system. It is designed to be operated so that there is no discharge of effluent water to the receiving stream, except in the event of catastrophic or chronic rainfall events. In the event that a discharge does take place, the department may require sampling and place effluent monitoring and limits in the operating permit. Actual irrigation water may also be required to be periodically monitored for items such as nitrogen and phosphorus. Any sampling requirements or limits would be contained in the operating permit.

Question:  Will the facility still be required to submit discharge monitoring reports or other records?
Answer:  The facility will still be required to submit reports and records as required in the operating permit. An additional separate annual report for the irrigation aspects of the facility may also be required. These requirements will be listed in the operating permit.

Question:  Is overhead or pivot irrigation the only option for irrigation systems?
Answer:  No. The department does not specify the method of irrigation. Rather, the performance standard is no-discharge operation of the facility. Some options include, but are not limited to, center-pivot irrigation, traveling gun irrigation, irrigation via low-impact sprinkler head, and subsurface drip irrigation.

Question:  How much irrigation water can be applied to a specific site?
Answer:  Irrigation amounts are dependent on the specific conditions of a particular irrigation site. Items that could affect this are soil conditions and soil makeup, the topography of the site, and agricultural practices used. Each site would be reviewed by the engineer and appropriate application rates determined. For more information, contact the department’s Water Protection Program.

Question:  Are buffer distances required on irrigation sites?
Answer:  Required buffer distances are 300 feet from a drinking water well, sinkhole, or losing stream; 150 feet from existing dwellings or public use areas; and 50 feet inside the property line and from streams. These distances or additional criteria may be added or modified, on a case-by-case basis.

Question:  How many acres will a facility need for irrigation?
Answer:  The typical irrigation rates in Missouri are 0.5 inch per hour, 1 inch per day, 3 inches per week, and 24 inches per year. This amounts to approximately 652,000 gallons per acre per year. Irrigation is typically limited to 100 days during the calendar year, during the daytime only. This irrigation rate may be raised or lowered depending on specific conditions of the irrigation site, including topography, soil limitations, and the need for any buffer distances. Actual acreage needs would be determined by the engineers during the design phase.

Question:  Will we have to build a lagoon storage cell or basin?
Answer:  Additional storage is dependent on current storage available in the existing system. Since wastewater is not allowed to be irrigated during frozen, snow-covered, or saturated soil conditions, wastewater must be stored during these times (for example, when wastewater is generated during the winter). In Missouri, typically 60-120 days of storage volume are required for the dry-weather flows plus additional storage for the 1-in-10-year, 365-day rainfall minus evaporation. For seasonal facilities (not generating wastewater during the winter), typically a minimum of 45 days storage is required for pretreatment of wastewater to reduce odors, etc.

Question:  Will the department require us to purchase the irrigation land?
Answer:  A facility may obtain the needed land for irrigation application through common options such as purchase, leasing, or rental. The department does not require the purchase of land for irrigation. However, experience has shown that ownership of the property provides the facility with the ability to land apply when needed.  Depending on the agreement with the landowner, this option may not be available for leased or rented property. Therefore, the department does recommend that a community consider purchasing property. If a long-term agreement is proposed, the department may require that the permittee provide assurances that wastewater will be irrigated when required (for example, by obtaining additional land, possibly from multiple landowners).

Question:  What are the uses of the irrigation property? Can row crops be planted? Can we sublease to a third party?
Answer:  Row crops, pasture, and hay crop are just some of the options for land used for irrigation. There may be specific agricultural stipulations not already required by current design guides that could be applicable. These should be investigated with the appropriate regulatory authority. A community may sublease the property to another party. It is important that the facility’s governing body understand that they are still responsible for meeting the conditions of the operating permit. In general, if wastewater is applied to a public-use area, the wastewater must be disinfected first. In addition, wastewater should not be applied to land within 30 days of grazing by livestock (or 14 days for dairy cattle).

Question:  What are the penalties for the community if we are unable to operate the facility as a no-discharge system?
Answer:  Like any wastewater treatment system, the installation and operation of a no-discharge, irrigation system is a serious commitment for the community involved. Any facility seeking to operate a no-discharge, irrigation system must evaluate the immediate benefit against the long-term obligations. The inability to operate the facility in accordance with its design can endanger public health, can negatively impact the quality of the waters of the State of Missouri, and can be a violation of the conditions of the issued Missouri State Operating Permit as well as state and federal clean water laws. Violation of the clean water laws can carry penalties for communities and individuals.

However, if a permittee is faced with effluent limits that are more protective than their current treatment facility can meet, eliminating the discharge can be a way to meet these effluent limits. The community should have an engineer evaluate the costs versus the benefits of each upgrade alternative, including the initial (capital) costs, the long-term (annual operating) costs, the periodic replacement costs (e.g. for equipment that fails), the difference in costs for a certified operator, the salvage value of any land purchased, and possibly even the profit from selling any hay crops grown each year. The department recommends no-discharge systems wherever they are feasible.

See the following fact sheets:

*Soil treatment area for surface land application can vary greatly in Missouri and is calculated using standards set forth by the Missouri Clean Water Law and its regulations.

Users should not rely solely on this document when making treatment technology decisions; it is important to consult with a professional engineer experienced in selecting a treatment technology including a no-discharge option.

These cost are taken from the WERF Fact Sheet D4 for Decentralized Wastewater Systems, Performance & Cost of Decentralized Unit Processes, Dispersal Series.  The actual cost can vary significantly depending upon local economic factors. WERF included 20 percent for overhead and profit for the contractor. Cost given within the WERF Fact Sheets reflect 2009 dollars.