/ OSTDS Feasibility · Miami-Dade County
Septic Feasibility in Miami-Dade
If a parcel has no sanitary sewer at the street, four county requirements decide whether it can be developed as intended. All four are desktop tests. A PE-led feasibility screen answers them while an inspection period is still open, not after closing.
Conventional septic is not an option here
Most budgets for a Miami-Dade lot with no sewer at the street assume a tank and a drainfield. That system cannot be permitted for new construction. Four requirements decide the parcel, and all four can be tested from a desk.
Type 1 systems are prohibited for new construction and complete replacement
Only Type 2 secondary, Type 3 advanced secondary or nutrient, or Type 4 nutrient treatment systems are permitted. What gets installed is a treatment system with an operating obligation, not a tank and a field.
Local overlay - Miami-Dade County Code Sec. 24-42.7(2).
36 inches of separation to the wet-season high water table
Measured from the bottom of the drainfield, against 24 inches under the state rule, and demonstrated by surveyed elevation on a cross-section.
Local overlay - Sec. 24-42.7, compared against state rule F.A.C. 62-6.006.
100 feet to surface water and to potable wells
The state minimum is 75 feet. Miami-Dade also requires 50 feet to the property line where the site is served by a well. Canal-side and waterfront parcels that look adequate on a survey fail here.
Local overlay - Sec. 24-42.7.
15,000 square feet minimum land area for a single-family residence
On public water; 20,000 square feet for a duplex, and 20,328 and 29,040 square feet respectively on a private well. Other uses are generally limited by gallons per day per unsubmerged acre.
Local overlay - Sec. 24-43.1(5).
Why the county is stricter than the state
F.A.C. Chapter 62-6, Table III classifies oolitic limestone, fractured rock, gravel, and coarse sand with a high water table as severely limited to unsuitable for a standard drainfield. That is the Miami Limestone the county is built on, and it lies over the Biscayne Aquifer - a designated sole-source aquifer. State rule - F.A.C. Chapter 62-6, Table III.
Rapid infiltration is not treatment. Ground that takes water fastest is the ground that treats it least. The EPA onsite wastewater manual reports that pathogen retention and die-off occur largely within the first two to three feet of unsaturated soil. That is why an extra foot of elevation, rather than better equipment, is usually what decides a Miami-Dade parcel. National reference - U.S. EPA, EPA/625/R-00/008.
Two things that surface after closing
Sewer availability may already have decided it
Connection to public sanitary sewer is mandatory where an approved gravity sewer or force main is available and operative in an abutting right-of-way or easement, or where sewer is within the feasible distance computed under Sec. 24-43.4 on total building area.
Cost of missing it: a septic budget on such a parcel is not the cheaper option. Local overlay - Sec. 24-43.1(7) and Sec. 24-43.4.
The parcel is measured twice, on two different numbers
The Chapter 24 feasible-distance and lot-loading calculation uses gross roofed area - every level, covered patios, closets, elevator areas, garages. That is a different and larger number than the net building area used for F.A.C. 62-6 sizing.
Cost of missing it: using one number twice is a common reason a package comes back. Local overlay - Chapter 24; state rule - F.A.C. 62-6.
There is also no default relief. Miami-Dade does not accept F.A.C. 62-6 drainfield-size or setback reductions by default; an alternative must be specifically allowed and demonstrated, signed and sealed, to give equal or better pollutant reduction. Local overlay - Chapter 24.
What the feasibility screen delivers
A desktop review of one specific parcel against the requirements above, delivered as a dated PDF built to be finished inside a normal inspection period and read by a lender, a partner, or a seller's agent.
Sewer availability and feasible distance
Written utility and agency evidence on whether an onsite system is even the applicable path, rather than an assumption from the listing.
Land area and loading
The Chapter 24 minimum land area and loading test, run on gross roofed area for the intended use.
Separation screening
Wet-season high water table against the 36-inch separation requirement, using the survey and available elevation data.
Setback and reserve-area fit
Whether the 100-foot setbacks and the property-line setback leave a buildable area with a reserve area still available.
Likely required treatment type
Which permitted treatment class the parcel and use point toward, so the budget reflects a treatment system rather than a tank.
A red, yellow or green finding
With the specific evidence still required to close it out, so the next step is obvious either way.
How a screen runs
- Send the folio number and address, intended use with unit and bedroom count, the survey and any elevation data, the site plan or intended footprint with gross roofed area, and your decision date.
- Scope review and a fixed fee, in writing, before any work starts.
- Utility and agency evidence obtained in writing - not assumed from a listing, a survey note, or a contractor's assurance.
- Dated PDF with the four tests, the finding, and the evidence still needed.
- On a green or yellow finding, the design engagement picks up from the same evidence rather than starting over.
Free: run the four tests yourself first
Two dated PDFs, no email required. The brief explains the requirements and why they exist; the worksheet is what you fill in on a specific parcel. Every statement in both is cited and tagged by authority layer.
- Type 1 Is Dead — the four requirements, the reason they exist, the two traps above, and five questions to answer before an inspection period closes, in four pages · Download the PDF
- Parcel Screening Worksheet — three printable pages: five gates with write-in fields, the state design-flow table, an evidence log, and a meets / does not meet / not yet verified decision on each gate · Download the PDF
- More free Miami-Dade references - plan-review checklists by discipline, the NEC and IMC glossaries, and the ventilation fundamentals guide - are on the resources page.
County and state requirements cited on this page were verified on 30 August 2026 and are re-verified before use after 28 November 2026. Requirements change; confirm the current text of Miami-Dade County Code Chapter 24, F.A.C. Chapter 62-6, and the applicable agency's current guidance for your parcel.
Common questions
Can a conventional septic system still be installed in Miami-Dade?
Not for new construction or complete replacement. Miami-Dade County Code Sec. 24-42.7(2) permits only Type 2 secondary, Type 3 advanced secondary or nutrient, or Type 4 nutrient treatment systems. Repairs, modifications and partial replacements are treated differently. Confirm the current code text and the county's current guidance for your specific parcel and scope of work.
How much separation to groundwater does the county require?
36 inches from the bottom of the drainfield to the wet-season high water table, shown by surveyed elevation on a cross-section. The state rule, F.A.C. 62-6.006, sets 24 inches. One foot of elevation frequently decides whether a lot works without imported fill or a mound system.
What is the minimum lot size for a septic system in Miami-Dade?
Miami-Dade County Code Sec. 24-43.1(5) sets a minimum land area of 15,000 square feet for a single-family residence and 20,000 square feet for a duplex on public water, and 20,328 and 29,040 square feet respectively where the site is served by a private well. Other uses are generally limited by a gallons-per-day per-acre loading limit instead.
The lot is on a canal. Does that change the answer?
Often, yes. Miami-Dade requires 100 feet to surface water and to potable wells, where the state minimum is 75 feet, plus 50 feet to the property line where the site is served by a well. Small, canal-side and waterfront parcels that look adequate on a survey routinely fail on setback fit and reserve area.
Sewer runs a few streets away. Does that matter?
It can decide the question before any septic design begins. Connection to public sanitary sewer is mandatory where an approved gravity sewer or force main is available and operative in an abutting right-of-way or easement, or where sewer is within the feasible distance computed under Sec. 24-43.4 on total building area. Where that applies, an onsite system is not the cheaper option.
Why is Miami-Dade stricter than the rest of Florida?
Because of what is under the lot. F.A.C. Chapter 62-6, Table III classifies oolitic limestone, fractured rock, gravel and coarse sand with a high water table as severely limited to unsuitable for a standard drainfield. That is the Miami Limestone the county is built on, and it lies over the Biscayne Aquifer, a designated sole-source aquifer. Ground that takes water fastest treats it least.
What does a feasibility screen cost?
Fixed fee, quoted after a short scope review. That is the standard basis for every Masterbuild engagement. The screen is deliberately priced and scoped to be an easy decision next to a full design cycle on a parcel that cannot support the intended use.
Is a feasibility screen a county determination?
No. It is an engineering opinion on the evidence available at the time, with utility and agency evidence obtained in writing rather than assumed. It is not an agency determination and it does not establish that a permit will be issued. A favorable finding is a decision to proceed to design.
Scope boundary. A feasibility screen is an engineering opinion on the evidence available at the time. It is not an agency determination, it is not a permit, and it does not establish that a permit will be issued. A favorable finding is a decision to proceed to design.
Requirements vary by parcel and change over time. Nothing on this page is a project-specific engineering conclusion for your property.
Send the folio number and your decision date
A feasibility screen starts with a specific parcel. Include the folio number and property address, the intended use with unit and bedroom count, the survey and any elevation data you have, the site plan or intended footprint with gross roofed area, and the date you have to decide by. Fixed fee, quoted after a short scope review.
Send parcel background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. A feasibility screen is an engineering opinion on the evidence available at the time. It is not an agency determination and it does not establish that a permit will be issued.