Tampa is the anchor of the Tampa Bay metro area and the largest city in Hillsborough County, a region experiencing some of the fastest population growth in the United States. While the City of Tampa and its immediate suburbs are served by municipal sewer, vast stretches of unincorporated Hillsborough County — including growing communities in Riverview, Ruskin, Lithia, and Wimauma — depend on onsite septic systems. Hillsborough County has more than 100,000 permitted OSTDS installations. Tampa's unique challenge is the intersection of rapid suburban sprawl, a persistently high water table driven by the Floridan aquifer system, and the state's BMAP nitrogen-reduction mandates tied to Tampa Bay restoration. Homeowners and builders alike must navigate stricter standards than almost anywhere else in Florida, making professional septic expertise essential.
Soil Conditions
Tampa's soils are dominated by Myakka fine sand and Immokalee fine sand — USDA Spodosols with a spodic horizon (hardpan) of cemented organic matter and iron 18-36 inches below grade. The surface horizon is low-organic, highly permeable fine sand (percolation rates of 2-6 inches per hour), but the spodic hardpan severely restricts vertical drainage. Flatwoods soils classified as Poorly Drained and Very Poorly Drained cover much of Hillsborough County, requiring engineered drain field solutions in most new installations.
Hillsborough County soils are primarily Myakka and Immokalee series fine sands — classic Florida Flatwoods Spodosols formed under slash pine and saw palmetto. The sand surface absorbs water rapidly, but the spodic horizon (a cemented Bh or Bs layer) acts as an aquitard that perches the water table seasonally at or near the surface. Site evaluators must probe to at least 48 inches to locate the spodic layer depth and assess whether adequate unsaturated fill material can be placed above it. Many lots require raised or mound systems using clean fill sand to achieve the 24-inch separation from the seasonal high water table. Coastal and near-bay properties may also encounter sulfidic materials and high-salinity groundwater, requiring specialized design.
Water Table: Seasonal water table ranges from 0-12 inches below grade during the wet season (June-September) and 12-24 inches during the dry season. The shallow Floridan aquifer and flat topography mean saturation is nearly continuous in low-lying areas. Florida Department of Health requires a minimum 24-inch separation between the bottom of the drain field and the seasonal high water table.
Local Regulations
Chapter 62-6, F.A.C. govern all OSTDS in Hillsborough County. The Tampa Bay BMAP (Basin Management Action Plan), jointly enforced by FDEP and the Southwest Florida Water Management District (SWFWMD), requires nitrogen-reducing septic upgrades for properties within the BMAP zone — a mandate affecting tens of thousands of existing systems on a phased compliance timeline. New construction in BMAP zones must install Advanced Wastewater Treatment (AWT) systems or connect to sewer where available. Hillsborough County also participates in the state's Septic Tank Upgrade Incentive program, which offers rebates of up to $5,000 for qualifying low-income households.
Hillsborough County Environmental Health (Florida Department of Health - Hillsborough) issues all onsite sewage treatment and disposal system (OSTDS) permits. Applications require a site evaluation by a licensed inspector, soil profile evaluation to 6 feet, and a completed FDOH Form 4015. Permit fees are $325 for new systems and $175 for repairs. Properties within the Tampa Bay Basin Area-wide Management Plan (BMAP) zone must meet enhanced nitrogen reduction standards — many existing systems require upgrade to nitrogen-reducing units by state-mandated deadlines. Licensed contractors must pull installation permits and pass final inspection before system activation.