Specifications and details for approved sand aggregate used in alternative drainfield mound and bed systems. The best resource for the exhaustive list is the Florida Department of Environmental Protection.
Reference only: Approved-component lists are sourced from the Florida
Department of Environmental Protection and may not be exhaustive. Always verify with FDEP
before specifying components for permitted work.
Drainfield Sand Profiles
Clay1 model·Very sticky and very plastic when wet. You can roll it into a long, thin ribbon or rope without it breaking. When it dries, it gets hard and can form solid clods.
Silty Clay1 model·Very smooth, very sticky, and highly plastic. Little to no grit. Forms a long, smooth ribbon when pressed out. Dries into hard, dense clods.
Sandy Clay1 model·Sticky and plastic like clay, but still noticeably gritty. When moist it forms a strong ball and a short ribbon. Feels both heavy and abrasive.
Silty Clay Loam1 model·Smooth and slick (no noticeable grit), sticky, and moderately plastic. When moist it forms a ball and a medium ribbon. Dries firm but not as rock-hard as full clay.
Clay Loam1 model·Firm, dense, and moderately sticky when moist. More plastic than loam but less than pure clay. It will form a ribbon, but the ribbon is shorter and breaks sooner than clay.
Sandy Clay Loam1 model·Moderately firm, with both stickiness and grit. When moist it forms a ball and a short ribbon. Grit from sand is obvious, but it still holds shape well.
Silt Loam1 model·Smooth and silky, almost like flour when dry. When moist it feels slick and slightly plastic but not gritty. You can form a weak ball, but it’s easily deformed and smears like paste.
Loam1 model·Balanced feel: not overly gritty, not overly sticky. When moist it forms a ball that holds together but breaks apart with light pressure. Mildly plastic, only slightly sticky.
Very Fine Sandy Loam1 model·Feels smooth with only mild, very fine grit. When moist it forms a ball that holds together better than fine sandy loam but still crumbles under firm pressure.
Very Fine Sand1 model·Feels almost powdery or talc-like at first touch, but still not sticky. Very low cohesion; even moist material does not form a lasting ball.
Sandy Loam1 model·Gritty feel from noticeable sand. When moist it will form a ball, but the ball is weak and crumbles with pressure. Only slightly sticky.
Loamy Sand1 model·Almost all sand with just a little fine material. Clearly gritty. When moist it barely holds together at all; it falls apart with the slightest touch.
Fine Sand1 model·Still gritty, but the grains are smaller and more uniform. When moist you might briefly pinch it into a weak ball, but it immediately falls apart.
Loamy Coarse Sand1 model·Dominantly coarse, gritty sand with just enough finer material to slightly dirty your hand. Practically no cohesion. Won’t hold a shape when squeezed.
How do the different types affect the performance of my system?
The performance of a sand filter or mound system is highly dependent on using the correct sand specification, such as C-33 sand. Using sand with the wrong grain size or too many fine particles can lead to clogging, poor drainage, and premature system failure.
Do I automatically have to have a mound because of bad soils?
The determining factor on whether a mound is required will ultimately be the water table on the property. There are circumstances where soils may lead to a mound, but all things being equal, a subsurface system may be possible if the water table allows. The cost of excavation, when possible, may be prohibitive.
Where can I source the material for my system?
Sand that meets the specific requirements for septic systems, often called filter sand or C-33 sand, can be sourced from local quarries, landscape supply yards, or construction material suppliers. Always ensure the supplier can certify that the sand meets the specifications on your permit.