Roads & Sidewalks

Stormwater is the runoff from rain, which is ordinarily absorbed by plants and soils, but hard surfaces such as pavement, driveways, pool decks, and building roofs, can prevent this runoff from being properly absorbed into the ground. This kind of excess runoff is bad for our community and the environment. Stormwater can pick up all sorts of pollutants before eventually finding its way back to lakes, streams, rivers, and bays. Stormwater can also cause high water flow during heavy rainfalls, which can result in flooding on roads and properties.

A storm drainage system is a network of constructed inlets, underground pipes, ditches, drainage channels, and other structures that carry and temporarily hold stormwater before it ends up in streams and waterways. The network consists of both public and private systems.

Water runoff does not follow neighborhood boundaries. Stormwater must be managed for the common good across the whole community. The County's responsibility and challenge is to repair and maintain existing public stormwater facilities and address the long list of needed capital improvement projects.

Hillsborough County is bound by law to proactively keep stormwater pollution from entering creeks, streams, rivers, and bays, as well as clean up those waterways within County limits. Historically, the stormwater program has been funded partially by an annual Stormwater Management Assessment and partially by the general Ad Valorem Property Tax. Without a single dedicated source of funding for the entire program, meeting these important community needs will continue to compete for funding with public safety and other critical local government services.

Impervious surfaces are areas of a property that are covered by buildings, driveways, parking areas, and other hard surfaces that prevent runoff from being absorbed into the soil.

Building footprints were determined by using the building Total Gross Area for each property, as recorded by the Hillsborough County Property Appraiser.

• How to find your property's total gross area.

The current assessment structure more equitably separates most residential properties into tiers based on different sizes of impervious area (roofed, paved, or similar surface). Based on the impact to the stormwater system, properties with less impervious area, pay less and properties with more impervious area pay more.

• Most single-family residential properties are placed into a tier based on their total gross area building footprint, provided by the Property Appraiser. This approach avoids having to individually calculate the impervious area for more than 220,000 residential properties, which would be impractical.
• Properties with exceptionally small building footprint areas, such as condominium units, townhomes, and mobile homes are billed flat rates.
• Non-residential properties and very large single-family properties are billed per square foot of impervious area.

The current assessment structure will utilize an “Equivalent Residential Unit”, or ERU, as the basis for most assessments. The average single-family residence in the County includes 4,267 square feet of impervious surface (roofed, paved, or similar surface), which equals one ERU.

The 2024 assessment for one ERU is $91.56

Assessments for specific parcels are based on either an assigned ERU or the actual impervious square footage, as shown in the chart below:

Calendar Year 2024

Questions regarding the assessment can be addressed with Hillsborough County Public Works at (813) 635-5400.