PURPOSE: This rule specifies the minimum standards for the design of lagoons and wastewater irrigation alternatives that are part of wastewater collection and treatment systems. This rule is to be used with rules 10 CSR 20-8.110 through 10 CSR 20-8.210. It does not address all aspects of design, and the design engineer may refer to other appropriate reference materials so long as these minimum standards set forth in this rule are met.

PUBLISHER’S NOTE: The secretary of state has determined that publication of the entire text of the material that is incorporated by reference as a portion of this rule would be unduly cumbersome or expensive. This material as incorporated by reference in this rule shall be maintained by the agency at its headquarters and shall be made available to the public for inspection and copying at no more than the actual cost of reproduction. This note applies only to the reference material. The entire text of the rule is printed here.

1. (1) Applicability. Wastewater systems that utilize lagoons, earthen basins, and wastewater irrigation alternatives shall be designed based on criteria contained in this rule, published standards, applicable federal and state requirements, standard textbooks, current technical literature, and applicable safety standards. In the event of any conflict between the above criteria, the requirement in this rule shall prevail.

   1. (A) This rule shall not apply to treatment units covered in 10 CSR 20-8.300.
   2. (B) This rule shall not apply to treatment units covered in 10 CSR 20-8.500.
   3. (C) This rule shall not apply to lagoons or earthen basins built to contain or control the release of stormwater only that does not come in contact with process waste or process wastewater.
   4. (D) This rule shall not apply to any earthen basin constructed to retain and settle nontoxic, nonmetallic earthen materials such as soil, silt, and rock.

2. (2) Alternative Design. The department may approve an alternative design, after public participation in accordance with 10 CSR 20-6.020, when it determines that the proposed alternative design is as effective or more effective than the requirements of this chapter and when compliance with the design requirements of this chapter would be unfeasible or impractical. The owner of a project proposing an alternative design must provide engineering justification to the department. The justification must—

   1. (A) Be requested in writing;
   2. (B) Be signed, sealed, and dated by a professional engineer licensed in Missouri;
   3. (C) Include an explanation of how compliance with a design requirement of this chapter is unfeasible or impractical; and
   4. (D) Include all pertinent facts, data, reports, and studies certifying the proposed alternative design will result in equivalent or improved effectiveness compared to the minimum design requirement in this chapter.

3. (3) Supplementary Field Data for the Facility Plan. The facility plan shall contain pertinent information on location, geology, soil conditions, area for expansion, and any other factors that will affect the feasibility and acceptability of the proposed project, including the information required per 10 CSR 20-8.110. The following information must be submitted:

   1. (A) Lagoons and spray irrigation fields shall be located where stormwater runoff from the watershed is minimized;

   2. (B) Geohydrologic Evaluation. A geohydrologic evaluation shall be requested from the department’s Missouri Geological Survey on all new lagoons, lagoon major modifications, earthen basins, earthen basin major modifications, new wastewater irrigation sites, and subsurface absorption fields. Supplemental information may be submitted for consideration by the department.

      1. 1. Severe collapse potential. Lagoons and earthen basins

shall not be located in areas with a severe collapse potential rating unless additional information supports an alternative determination by the department for the proposed location;

1. (C) Soils Investigation. Detailed soils investigations and reports shall be submitted for facilities surface irrigating more than twenty-four inches per year (24"/yr) and for all subsurface absorption fields. Soils reports shall comply with 10 CSR 20- 8.110(7);

2. (D) Where geosynthetic liners are used in storage or treatment basins for wastewaters of an industrial nature, the application shall—

   1. 1. Document that the liner or storage structure material is

capable of containing the wastewater for at least twenty (20) years;

1. 2. Specify repair or replacement procedures in the event of

leakage or damage to the seal; and

1. 3. Include an evaluation of secondary containment or

leakage detection and collection devices for corrosive or reactive wastewaters and for toxic materials.

1. (4) Basis of Design.

   1. (A) Area and Loadings for Discharging Lagoons.

      1. 1. Lagoon design for BOD5 loadings shall not exceed thirty-

four pounds per day per acre (34 lbs/day/acre) at the three-foot (3') operating depth in the primary cells.

1. 2. Aerated lagoons. Aeration equipment shall be capable

of—

1. A. Maintaining the design level of dissolved oxygen

within a particular cell with one (1) unit in the cell out of service;

1. B. Maintaining a minimum dissolved oxygen level of

two milligrams per liter (2 mg/L) in the lagoon at all times;

1. C. Delivering one and four-tenths pounds of oxygen per

pound of biochemical oxygen demand removed (1.4 lbs O2/1 lb BOD); and

1. D. Delivering an additional four and sixth-tenths pounds

of oxygen per pound of ammonia nitrogen removal (4.6 lbs O2/1 lb NH3).

1. (B) Area and Loadings for Wastewater Irrigation Storage Basins. Treatment prior to surface irrigation shall provide performance equivalent to that obtained from a primary wastewater lagoon cell designed and constructed in accordance with section (5) of this rule, except that the lagoon depth may be increased to include wastewater storage in addition to the primary volume.

1. (5) Lagoon and Earthen Basin Construction Details.

   1. (A) Embankments and Berms.

      1. 1. Berms shall be constructed of relatively impervious

material and compacted to at least ninety-five percent (95%) maximum dry density test method to form a stable structure.

1. 2. The minimum berm width shall be eight feet (8') to

permit access of maintenance vehicles.

1. 3. Minimum freeboard shall be two feet (2').

2. 4. An emergency spillway shall be provided that—

   1. A. Prevents the overtopping and cutting of berms;
   2. B. Is compacted and vegetated or otherwise constructed

to prevent erosion; and

1. C. Has the ability for a representative sample to be

collected, if discharging.

1. (B) Lagoon and Earthen Basin Bottom. Soil shall be compacted with the moisture content between two percent (2%) below and four percent (4%) above the optimum water content and compacted to at least ninety-five percent (95%) maximum dry density test method.

2. (C) Lagoon and Earthen Basin Seal.

   1. 1. The lagoon or earthen basin shall be sealed to ensure

that seepage loss is as low as possible and has a design permeability not exceeding 1.0 x 10-7 cm/sec.

1. 2. Soil seals. The minimum thickness of the compacted clay

liner must be twelve inches (12"). For permeability coefficients greater than 1.0 × 10-7 cm/sec or for design average operating depths over five feet (5'), such as an aerated lagoon system, the following formula shall be used to determine minimum seal thickness, Equation 200-1: Equation 200-1 H × K t = ______________________ 5.4 × 10-7 cm/sec where: K = the permeability coefficient of the soil in question; H = the design average operating depth of water in the lagoon or earthen basin, excluding the inner berm depth; and t = the thickness of the soil seal.

1. 3. Synthetic liners. Synthetic seals thickness may vary

due to liner material, but the liner thickness shall be no less than two-hundredths inch (.02") or twenty (20) mil and be the appropriate material to perform under existing conditions.

1. 4. Seep collars shall be provided on drainpipes where they

pass through the lagoon or earthen basin seal.

1. (D) Influent Lines.

   1. 1. Unlined corrugated metal pipe shall not be used due to

corrosion problems.

1. 2. A manhole shall be installed with its invert at least six

inches (6") above the maximum operating level of the lagoon or earthen basin, prior to the entrance into the primary cell, to provide sufficient hydraulic head without surcharging the manhole. For manhole installation, follow the provisions listed in 10 CSR 20-8.120(4).

1. 3. The influent line(s) shall be located along the bottom of

the lagoon or earthen basin so that the top of the pipe is just below the average elevation of the lagoon or earthen basin seal; however, there shall be an adequate seal below the pipe.

1. (6) Covers for Lagoon Retrofits.

   1. (A) Lagoon covers shall be constructed with a minimum thickness of two-thousandths inch (.002"), two (2) mil, or meet the manufacturer’s recommendations, and be ultravioletand weather-resistant.
   2. (B) Trial seams shall be used to verify acceptable installation techniques.
   3. (C) The cover shall include a stormwater removal system that conveys collected precipitation to sumps or includes drainage areas in the membrane within the acceptable leakage rate to allow stormwater to drain into the lagoon.

2. (7) Surface Irrigation of Wastewater.

   1. (A) Site Considerations. For site considerations, follow the provision in section (3) of this rule.

   2. (B) Wetted Application Area. The wetted application area is the land area that is normally wetted by wastewater application. The wetted application area must be—

      1. 1. Located outside of flood-prone areas having a flood

frequency greater than once every ten (10) years;

1. 2. Established—

   1. A. At least one hundred fifty feet (150') from existing

dwellings or public use areas, excluding roads or highways;

1. B. At least fifty feet (50') inside the property line;
2. C. At least three hundred feet (300') from any sinkhole,

losing stream, or other structure or physiographic feature that may provide direct connection between the ground water table and the surface;

1. D. At least three hundred feet (300') from any existing

potable water supply well not located on the property. Adequate protection shall be provided for wells located on the application site;

1. E. One hundred feet (100') to wetlands, ponds, and

gaining streams (classified or unclassified; perennial or intermittent); and

1. F. If an established vegetated buffer or the wastewater

is disinfected, the setbacks established in subsections (A)–(E) of this section may be decreased if the applicant demonstrates the risk is mitigated; and

1. 3. Fenced, or if not fenced, provide in the construction

permit application or the facility plan, the—

1. A. Method of disinfection being utilized;
2. B. Suitable barriers in place; or
3. C. Details on how public access is limited and not

expected to be present.

1. (C) Preapplication Treatment. At a minimum, treatment prior to irrigation shall provide performance equivalent to that obtained from a primary wastewater lagoon cell designed and constructed in accordance with sections (4) and (5) of this rule, except that the lagoon depth may be increased to include wastewater storage in addition to the primary volume.

   1. 1. The size of storage basins shall be based on the design

wastewater flows and net rainfall minus evaporation expected for a one (1) in ten (10) year frequency for the storage period selected and shall meet the minimum storage days listed below.

1. A. Seventy-five (75) days for facilities located in Barry,

Barton, Bollinger, Butler, Cape Girardeau, Carter, Christian, Dade, Dent, Douglas, Dunklin, Greene, Howell, Iron, Jasper, Lawrence, Madison, McDonald, Mississippi, New Madrid, Newton, Oregon, Ozark, Pemiscot, Perry, Reynolds, Ripley, Scott, Shannon, Stoddard, Stone, Taney, Texas, Wayne, Webster, and Wright counties.

1. B. Ninety (90) days for facilities located in Bates, Benton,

Camden, Cedar, Cole, Crawford, Dallas, Franklin, Gasconade, Henry, Hickory, Jefferson, Laclede, Maries, Miller, Moniteau, Morgan, Osage, Phelps, Polk, Pulaski, St. Charles, St. Clair, St. Francois, St. Louis, St. Louis City, Ste. Genevieve, Vernon, and Washington counties.

1. C. One hundred five (105) days for facilities located

in Audrain, Boone, Callaway, Carroll, Cass, Chariton, Clay, Cooper, Howard, Jackson, Johnson, Lafayette, Lincoln, Monroe, Montgomery, Pettis, Pike, Platte, Ralls, Randolph, Ray, Saline, and Warren counties.

1. D. One hundred twenty (120) days for facilities located

in Adair, Andrew, Atchison, Buchanan, Caldwell, Clark, Clinton, Daviess, DeKalb, Gentry, Grundy, Harrison, Holt, Knox, Lewis, Linn, Livingston, Macon, Marion, Mercer, Nodaway, Putnam, Schuyler, Scotland, Shelby, Sullivan, and Worth counties.

1. E. Seasonal facilities. For facilities that operate and

generate flows only from April through October season, a minimum storage capacity of forty-five (45) days shall be provided. For facilities that operate or generate flows only from November through March, the minimum storage listed in subsections (A)–(D) of this section is required.

1. (D) Application Rates and Soils Information. The application rates for each individual site shall be based on topography, soils, geology, hydrology, weather, agricultural practice, adjacent land use, and application method. Application of wastewater shall not be allowed during periods of ground frost, frozen soil, saturated conditions, or precipitation events. In design of the application rates, the following shall apply:

   1. 1. Do not exceed the hourly application rate at the design

sustained permeability rate except for short periods when initial soil moisture is significantly below field capacity. Do not exceed an hourly rate of one-half (½) the design sustained permeability for slopes exceeding ten percent (10%);

1. 2. Base the daily and weekly application rates on soil

moisture holding capacity, antecedent rainfall, and depth to the most restrictive soil permeability.

1. A. For facilities applying at twenty-four inches per year

(24"/yr), the application rate cannot exceed one inch (1") per day and three inches (3") per week.

1. B. For facilities applying above twenty-four inches per

year (24"/yr), the application rate cannot exceed the values determined in the soils report and loading design. Follow the provisions in 10 CSR 20-8.110(7), Soils Reports, for additional information; and

1. 3. Design the maximum annual application rate not

to exceed ten percent (10%) of the design sustained soil permeability rate for the number of days per year when soils are not frozen.

1. (E) The applicant shall defer the grazing of animals or harvesting of forage crops, as listed below, following wastewater irrigation, depending upon ambient air temperature and sunlight conditions:

   1. 1. Fourteen (14) days from grazing or forage harvesting

during the period from May 1 to October 31 of each year; and

1. 2. Thirty (30) days from grazing or forage harvesting

during the period from November 1 to April 30 of each year.

1. (F) Public Access Areas. Wastewater shall be disinfected prior to irrigation (not storage) in accordance with 10 CSR 20-8.190.

   1. 1. The wastewater shall contain as few of the indicator

organisms as possible and in no case contain more than one hundred twenty-six (126) Escherichia coliform colony forming units per one hundred milliliters (126 cfu/100 ml);

1. 2. The public shall not be allowed into an area when

irrigation is being conducted.

1. 3. For golf courses utilizing wastewater, all piping and

sprinklers associated with the distribution or transmission of wastewater shall be color-coded and labeled or tagged to warn against the consumptive use of contents.

1. (G) Alarm System. An automatic notification alarm system shall be installed on the pressure monitoring system, on each pivot and pump system, and be capable of notifying an on-call operator when a fault occurs in the system.

1. (8) Subsurface Absorption Systems.

   1. (A) Site Restrictions.

      1. 1. Subsurface systems shall—

         1. A. Exclude unstabilized fill and soils that have been

highly compacted and/or disturbed, such as old road beds, foundations, or similar things;

1. B. Provide adequate surface drainage where slopes are

less than two percent (2%);

1. C. Provide surface and subsurface water diversion where

necessary, such as a curtain or perimeter drain; and

1. D. Have a ten-foot (10') buffer from the property line.
2. 2. The vertical separation between the bottom of the drip

lines and/or the trench and a limiting layer, including but not limited to bedrock, restrictive horizon, or seasonal high water table, shall be no less than—

1. A. Twenty-four inches (24"); or
2. B. Twelve inches (12") for systems dispersing secondary

or higher quality effluent; or

1. C. Forty-eight inches (48") where karst features are

present.

1. (B) Preliminary treatment. Subsurface systems shall be, at a minimum, preceded by preliminary treatment. For design of a secondary treatment system, follow the provisions in 10 CSR 20-8.180 or section (4) of this rule.
2. (C) Loading rates shall not exceed the values assigned by the site and soil evaluation.

1. (9) Low Pressure Pipe (LPP) Subsurface Systems.

   1. (A) Design.

      1. 1. The LPP system shall be sized in accordance with the

following equations, Equation 200-2 and Equation 200-3: Equation 200-2 Q A = ______ LTAR and Equation 200-3 A L = ______ 5 ft where: A = Minimum LPP soil treatment area (square feet (sq.ft)) L = Minimum total length of LPP trench (ft) Q = Maximum daily wastewater flow (gallons per day (gpd)) LTAR = Long term acceptance rate (gpd/sq.ft). This is the lowest reported LPP soil loading rate between the soil surface and at least twelve inches (12") below the specified LPP trench bottom, or as approved by the Missouri Department of Natural Resources (department).

1. 2. All network piping and low pressure distribution piping

and fittings with polyvinyl chloride (PVC) shall meet ASTM Standard D 1785 Standard Specification for Poly(Vinyl Chloride) (PVC) Plastic Pipe, Schedules 40, 80, or 120 as approved and published August 1, 2015, or equivalent rated to meet or exceed ASTM D2466 Standard Specification for Poly(Vinyl Chloride) (PVC) Plastic Drain, Waste, and Vent Pipe and Fittings as approved and published August 1, 2017. These standards are incorporated by reference into this rule, as published by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. This rule does not incorporate any subsequent amendments or additions.

1. 3. Manifold design shall address freeze protection while

assuring uniform distribution and to minimize drain down of laterals into other laterals at a lower elevation between dosing events.

1. (B) Dosage. The dosing frequency shall be based on the soils report and the dosing volume in zoned systems.

2. (C) Orifices and Orifice Shielding.

   1. 1. The orifice number and spacing shall be designed to

provide a distribution of no more than six (6) square feet per orifice with an orifice size of not less than one-eighth (1/8) inch.

1. 2. The distal pressure shall be designed and maintained at

the end of each lateral to be no less than two feet (2 ft) (0.87 psi) when using three-sixteenth inch (3/16") or larger diameter orifices, and no less than five feet (5 ft) (2.18 psi) when using orifices smaller than three-sixteenth inch (3/16").

1. (10) Drip Dispersal Subsurface Systems.

   1. (A) Design.

      1. 1. The location and size of the drains and buffers must

be factored into the total area required for the drip dispersal system.

1. 2. The drip dispersal system shall be sized with the

minimum soil treatment area and total length, in accordance with the following equations, Equation 200-4 and Equation 200-5: Equation 200-4 Q A = ______ HLR Equation 200-5 A L = _____ 2 feet Where: A = Minimum soil treatment area (square feet (sq. ft)) Q = Maximum daily wastewater flow (gallons per day (gpd)) HLR = Maximum hydraulic loading rate determined in the soils report (gpd/sq.ft) L = Minimum total length of drip dispersal lines (ft)

1. (B) Lines.

   1. 1. The drip dispersal lines shall be placed at a minimum

depth of six inches (6") below the surface.

1. 2. Emitters and drip dispersal lines shall be placed at a

minimum on a two-foot (2') spacing to achieve even distribution of the wastewater and maximum utilization of the soil.

AUTHORITY: section 644.026, RSMo 2016.* Original rule filed Aug. 10, 1978, effective March 11, 1979. Amended: Filed June 15, 2018, effective Feb. 28, 2019. Amended: Filed June 14, 2024, effective Jan. 30, 2025. *Original authority: 644.026, RSMo 1972, amended 1973, 1987, 1993, 1995, 2000, 2012, 2014.