The Governing Framework

Mississippi regulates individual onsite wastewater under MSDH:

• MSDH Regulation Governing Individual Onsite Wastewater Disposal Systems (IOWDS) — the substantive rule for residential and small-commercial onsite systems.
• MSDH Chapter 5 — Individual Onsite Wastewater Disposal Design Standard — the detailed engineering design document.
• Mississippi Code Title 41 — Public Health. Section 41-67 chapter provides enabling statutory authority.
• Mississippi State Department of Health (MSDH) — develops policy and regulations, provides technical assistance to regional environmentalists.
• Regional environmentalists — MSDH field staff who design, permit, and inspect individual onsite systems across the nine MSDH regions.

Septic Tank Capacity — Bedroom-Based

Mississippi's capacity rule uses the standard bedroom-based approach for dwellings, with sizing tied to the number of bedrooms proposed or anticipated in the residence. Specific capacity table is in the MSDH Chapter 5 design standard. Consult the design standard PDF or your regional environmentalist for the authoritative residential capacity table governing your project.

Setback Distances

MSDH IOWDS rules specify minimum setback distances including:

• 50 feet from any water source or property boundary (baseline)
• Additional setbacks to wells, surface water, structures, and water supply lines specified in Chapter 5

Delta parishes and coastal counties may have additional floodplain-specific setback requirements. Verify with your regional environmentalist.

Permit Process

1. Contact your MSDH regional environmentalist. The nine MSDH regions cover all Mississippi counties.
2. Site evaluation. Regional environmentalist performs soil and site evaluation per Chapter 5 protocols.
3. System design. MSDH staff may design the system directly for simple residential cases, or review designs submitted by the homeowner or installer.
4. Permit issuance. Fees typically $200–$500.
5. Licensed installer construction. Mississippi licenses onsite installers.
6. Final inspection. MSDH regional environmentalist inspects before backfill.

Regional Considerations

• Mississippi Delta (Bolivar, Coahoma, Washington): Flat alluvial land with poorly-drained clay soils and high water tables. Mound systems and pressure dosing are the norm. Conventional trench systems often fail Chapter 5 soil criteria.
• North Central Hills (Lafayette, Yalobusha, Calhoun): Loess and clay soils with moderate percolation. Standard systems typical.
• Piney Woods (Forrest, Jones, Lauderdale): Sandy coastal plain soils with good percolation. Standard systems work well.
• coastal (Hancock, Harrison, Jackson): Hurricane floodplain considerations. Tank anchoring required. Post-Katrina regulatory amendments apply.
• Jackson Metro: Urban/suburban transition from septic to municipal sewer. Remaining septic parcels in rural-perimeter counties (Rankin, Madison, Hinds rural).
• Loess Bluffs (Warren, Claiborne, Jefferson): Deep wind-blown loess, excellent percolation in stable conditions. Some slope stability concerns on bluffs.

Material Approvals

MSDH accepts polyethylene tanks meeting Chapter 5 construction standards. Verify at order:

• IAPMO PS 1 or NSF 46 listing
• Ribbed polyethylene construction
• Hurricane-zone anchoring for coastal counties
• Elevated-riser compatibility for Delta flood zones
• Effluent filter compatibility

Frequently Asked Questions

Who is my "regional environmentalist"?

MSDH operates 9 regional health offices across Mississippi. The regional environmentalist at your region is the MSDH field-staff person who handles septic permits, inspections, and site evaluations. Contact the MSDH On-Site Wastewater Program headquarters or your county health department to identify your regional office.

Does MSDH design the system for me?

For straightforward residential systems, MSDH regional environmentalists often design the system directly at no extra cost. Complex systems, commercial flows, or alternative-technology installations typically require private engineering services.

What about Delta soil conditions?

Mississippi Delta clay soils with high water tables usually fail Chapter 5 site evaluation for conventional systems. Alternative systems — mounds, pressure dosing, aerobic treatment units, or drip dispersal — are the norm. Expect higher system cost and ongoing maintenance obligations.

Are there special coastal requirements?

Yes. Post-Katrina regulatory amendments added hurricane-anchoring and flood-zone elevation requirements for coastal counties. Your regional environmentalist will specify these for your parcel.

Does Mississippi accept polyethylene tanks?

Yes, provided they meet IAPMO/NSF listings and Chapter 5 construction standards. Major OEM tanks are accepted.

Source Citations

• MSDH On-Site Wastewater Program
• MSDH On-Site Wastewater Regulations
• MSDH Chapter 5 Individual Onsite Wastewater Disposal Design Standard (PDF)
• MSDH On-Site Wastewater Resources
• Mississippi IOWDS Rules (Secretary of State PDF)
• Mississippi Code § 41-67-2 Public Health

Agricultural Tank Regulations — MDAC Bureau of Plant Industry

The Mississippi Department of Agriculture and Commerce (MDAC) Bureau of Plant Industry administers pesticide, fertilizer, and feed regulation under:

• Mississippi Administrative Code Title 2 — Agriculture and Commerce, Rules of the Bureau of Plant Industry.
• MDAC Pesticide Program — registration, commercial and private applicator certification, licensing of commercial applicators and consultants, and compliance/enforcement.
• Feed, Fertilizer, Lime, Soil and Plant Amendments (FFLSP) program — product registration, facility registration, inspection and sampling against label guarantees, and penalty assessments.
• Mississippi Code Title 75 — Pesticide Law and Pesticide Application Law, the statutory backbone for MDAC's pesticide rules.

MDAC's rules require registered product labels, licensed applicators, and compliant storage. Specific prescriptive containment geometry isn't published at the level of Kentucky's 302 KAR 31:040, so Mississippi operators should plan to at least meet the federal SPCC floor for oil and the EPA Pesticide Container Containment Rule (40 CFR 165 Subpart E) for repackaging operations. Bulk retail fertilizer sites typically follow industry best practice of 110% containment with an impervious pad.

Oil & Gas Produced Water — State Oil and Gas Board

The Mississippi State Oil and Gas Board has exclusive jurisdiction over oil-field exploration and production waste, including produced water and brine, under Mississippi Code Title 53, Chapter 1 and related chapters. Key elements:

• Title 26 Part 2 (MS Admin Code) — Statewide Rules and Regulations of the State Oil and Gas Board.
• 26 Miss. Code. R. 2-1.45 — Pollution of Air, Fresh Waters and Soils Prohibited. Requires operators to prevent seepage, overflow, and damage to topsoil or surface waters.
• Noncommercial disposal of oil-field E&P wastes by injection is permitted only into sub-surface strata with a total dissolved solids content above 10,000 ppm that are void of oil and gas. Each noncommercial disposal arrangement is case-by-case subject to Supervisor authorization.
• MDEQ coordination — State Oil and Gas Board rules on waste disposal are subject to Mississippi Commission on Environmental Quality approval.

Operators running frac tanks, brine tanks, and tank batteries in the Mississippi Salt Basin and the Smackover Trend must comply with OGB containment, reporting, and disposal authorization requirements. Polyethylene specification should account for specific gravity and chemistry of the local produced water, which can exceed 100,000 ppm TDS in some Smackover wells.

Septic System Sizing Deep Dive

Mississippi State Department of Health (MSDH) regulates onsite wastewater under the Individual Onsite Wastewater Disposal System (IOWDS) rules, with design-flow tables referenced in MS Admin Code Title 15 Part 20 and the Mississippi Code Title 41, Chapter 67. Key design parameters typically applied on the ground:

• Minimum tank: 1,000 gallons for typical residential systems.
• Design flow: Calculated on a bedroom basis for dwellings and a peak-fixture basis for non-dwellings.
• Setbacks: Typical minimums include 50 feet from wells and surface water, 10 feet from property lines, and additional distances for commercial-scale systems. Specific Table setbacks should be confirmed with MSDH before design.
• Inspections: MSDH environmental health district offices perform pre-cover inspections; certified installers are required.

Coastal counties (Hancock, Harrison, Jackson) face high-water-table challenges and may require mound systems or alternative technologies. Delta counties with heavy clay often need pressure distribution. Upland pine-belt parcels generally support conventional trench systems.

Chemical Storage Secondary Containment & Spill Reporting

Federal SPCC (40 CFR 112) applies at 1,320 gallons aggregate aboveground oil. Mississippi spill reporting layers on:

• Miss. Code Ann. §§ 49-17-17(i) and 49-17-401 — statutory authority for MDEQ release reporting.
• 11 Miss. Admin. Code Pt. 5, Ch. 2 — UST rules. A spill or overfill that releases more than 25 gallons of product from a UST system must be reported to MDEQ, typically within 24 hours. Smaller releases must be contained and cleaned up; if cleanup can't be completed within 24 hours, MDEQ must be notified.
• Hazardous substance RQ releases must be reported immediately to the National Response Center (1-800-424-8802) in addition to MDEQ.
• MDEQ 24-hour emergency line for spill notification is published on the MDEQ Report a Release page.

Operators specifying polyethylene chemical tanks must design secondary containment to hold at least 110% of the largest tank volume, use impervious flooring, and document SPCC compliance. Consult MDEQ directly for current fee schedules and any state-specific reportable-quantity adjustments.

Permit Pathways at a Glance

• Residential septic: MSDH district environmental health.
• Commercial pesticide/fertilizer retail: MDAC Bureau of Plant Industry registration and applicator licensing.
• Oil & gas produced water storage & disposal: State Oil and Gas Board permitting; Class II UIC authorization.
• Petroleum UST: MDEQ registration under 11 Miss. Admin. Code Pt. 5.
• SPCC > 1,320 gal oil: Federal SPCC plan; MDEQ spill reporting.

Fees and timelines are agency-specific. Contact MDAC, MDEQ, or the State Oil and Gas Board directly for current numbers.

More Mississippi FAQs

Are coastal parcels in Harrison and Jackson counties harder to permit?

Yes. Saltwater intrusion, shallow groundwater, and post-Katrina building-elevation standards all compound the IOWDS design. Plan on elevated tank risers, pressure distribution, and potentially advanced treatment. Budget 30–60% premium over a typical pine-belt installation.

My farm is in the Delta and holds 8,000 gallons of liquid fertilizer seasonally. What applies?

Above 1,320 gallons aggregate you're a federal SPCC facility if that product is classified as oil (some specialty liquid ag products qualify). Even where SPCC doesn't apply, MDAC rules for the retail/commercial site and MDEQ spill reporting still apply. Build containment to 110% of the largest tank and maintain a site plan.

Can I store produced water in a poly frac tank on my Smackover well pad?

Yes, subject to State Oil and Gas Board approval and assuming the polyethylene chemistry holds up to the brine. Smackover brines in southwest Mississippi run extremely high TDS; many operators use fiberglass or steel with chemical resistant liners for long-duration storage. For short-term holding a properly-specified XLPE tank may be acceptable — verify with the manufacturer.

What are the rules for non-residential IOWDS (restaurants, truck stops)?

MSDH treats non-dwellings under engineered-design rules. Peak daily flow and peak-hour surge drive tank and field sizing. A licensed engineer typically prepares the design.

Is there a state-funded cleanup program?

The Groundwater Protection Trust Fund covers eligible petroleum UST releases. Non-petroleum chemical releases are owner liability with no state reimbursement.