§ 22-48. Lowest floor elevation and lot drainage.

(a)

Purpose and intent. The purpose of this section is to ensure new residential construction and additions to existing residential structures increasing the floor area footprint, provide for drainage of surface water away from structures to protect buildings from flooding and to maintain ground stabilization for supporting foundations.

(b)

Policies and procedures. The county manager or designee is authorized to create policies and procedures for the administration and enforcement of this section in order to clarify the application of its provisions. Such administrative policies and procedures shall be in compliance with this section and shall not have the effect of waiving the requirements specifically provided for herein.

(c)

Site drainage plan required. All building permit applications for new residential buildings, mobile and manufactured home installations, additions to residences and substantial improvements to residential buildings affecting or altering existing drainage patterns shall be accompanied by a site drainage plan meeting the minimum standards established by this section. The site drainage plan must demonstrate that surface water is diverted to the road right-of-way, or to a storm water conveyance or surface water discharge improvement designed and constructed to receive surface water discharge from the lot. The site drainage plan must, at a minimum, contain the following information:

(1)

The site drainage plan must be dimensioned and drawn to scale, and identify the vertical datum used for elevations. The plan must include the location of all proposed and existing improvements on the property and show dimensions from all existing and proposed buildings to property boundary lines. The plan must show the location and elevation of existing and proposed septic tank drain field (if applicable).

(2)

The drainage plan must show centerline elevations of the abutting roadway(s).

(3)

The drainage plan must show the existing and proposed elevations at all lot corners and lot grade elevations sufficient to demonstrate slopes and drainage pattern(s). The plan must identify the centerline location and slope of existing and proposed swales. The minimum allowable slope for the centerline of swales conveying surface water is one percent.

(4)

The drainage plan must clearly indicate the flow direction of proposed surface water drainage and show the discharge location(s) of surface water from the lot.

(5)

The drainage plan must show the location of existing and proposed drainage features including, but not limited to: swales, berms, ditches, ponds, lakes, drainage structures, easements, etc.

(6)

The drainage plan must show the lowest floor elevations of all existing buildings on the property and the lowest floor elevations for proposed buildings enclosed by a solid roof and walls, including garages.

(7)

The drainage plan must include the floor elevation(s) of existing dwellings on abutting properties.

(8)

Properties in a Federal Emergency Management Agency FEMA special flood hazard area or in an approved engineered subdivision shall have all elevations based on a North American Vertical Datum of 1988 (NAVD '88) or National Geodetic Vertical Datum of 1929 (NGVD '29) certified benchmark.

(9)

The drainage plan must identify any specialized drainage improvements to include, but not limited to onsite retention of surface water in lieu of discharge off the lot, use of stem walls, pilings, retaining walls, installation of piping, inlets, terracing, or steeper slopes with low maintenance ground cover vegetation, etc. Such specialized drainage improvements may require design by a professional engineer where topographic conditions exist that warrant professional design.

(d)

Minimum standards for finish floor elevations.

(1)

All new one and two family residential buildings including the installation of manufactured homes, or additions to residences increasing the building footprint, must provide for the lowest floor, including the floor of an attached garage, to be elevated above the street on which the property abuts. Concrete floor slabs on grade shall also have a minimum six-inch clearance between the top floor surface and the adjacent finished grade to protect the floor to wall joint from water intrusion. The floor elevation must be sufficiently high to provide for building foundation drainage as prescribed by the Florida Residential Building Code.

The lowest floor elevation shall be based upon the lot drainage types as follows:

(a)

Type A drainage. The lowest floor elevation for buildings on interior lots designed with type A (rear to front) drainage must be at least 24 inches above the crown elevation of the street on which the property abuts, measured at a point approximate to the center of the lot.

(b)

Type B drainage. The lowest floor elevation for buildings on interior lots designed with type B (split) drainage must be at least 18 inches above the crown elevation of the street on which the property abuts, measured at a point approximate to the center of the lot.

(c)

Type C drainage. The lowest floor elevation for interior lots designed with type C (front to rear) drainage must be sufficiently high to provide for flood protection and drainage of surface water from the lot, and provide for foundation drainage as prescribed by the Florida Residential Building Code.

(d)

Corner lots. The lowest floor elevation for corner lots must be at least 24 inches above the crown elevation of the street on which the property abuts, measured at a point approximate to the center of the lot on the street which the building faces.

(e)

On properties where topographic conditions make compliance with the minimum lowest floor elevation standards contained herein impractical, such as irregularly shaped lots, tracts, or parcels, flag stem lots, unusually large properties, roads with inverted crown or similar conditions, a lower elevation may be approved by the county manager or designee where sufficient evidence is provided to ensure said lower floor elevation will provide for flood protection and drainage of surface water from the lot. In all cases the floor elevation design must provide grading for building foundation drainage as prescribed by the Florida Building Code.

(2)

All habitable structures located in a Federal Emergency Management Agency (FEMA) designated special flood hazard area shall have the lowest floor, including the floor of an attached garage and all appurtenant building equipment, elevated a minimum of 12 inches above the 100-year base flood elevation. All structures shall comply with all the standards set in chapter 62, article XI.

For properties within special flood hazard areas adjacent to FEMA defined regulatory floodways, the lowest finished floor of all new construction and substantial improvements of non-residential and residential structures, including attached garages and basements if applicable, shall be elevated at least 12 inches above the floodway encroachment elevation for that regulatory floodway as established by FEMA and defined in the FEMA flood insurance study for the county.

(3)

All rental and condominium association manufactured home parks with a county approved site plan having lowest floor elevations established shall comply with the county approved site plan provided they meet the current standards set in chapter 62, article XI and Federal Emergency Management Agency designated special flood hazard areas.

(4)

In approved engineered subdivisions, the lowest floor elevation shall not be less than the designed floor elevation as depicted on the approved subdivision construction plans. Lower floor elevations shall require site specific engineered design.

(f)

Alternative designs and methods. Alternate lot drainage designs utilizing alternate construction methods that are at least equivalent in effectiveness and performance to the minimum standards of this section may be permitted subject to the approval of the county manager or designee. The following performance standards must be considered in approval of alternate lot drainage or floor elevation design or method:

(1)

Alternate site drainage plans shall be designed by a professional engineer licensed in the state when site conditions exist that require specialized drainage design to protect buildings from flood. Such specialized design may include, but is not limited to: design of onsite retention of surface water in lieu of discharge of surface water off the lot, the use of stem walls, pilings, retaining walls, and pumped on-site sewage systems with elevated drain fields, installation of piping, inlets, and terracing, steeper slopes with low maintenance ground cover vegetation.

(2)

All structures located in a Federal Emergency Management Agency (FEMA) designated special flood hazard area shall have the lowest floor elevated a minimum of 12 inches above the 100-year base flood elevation.

(3)

If the alternate design relies on percolation of surface water, then the design must include evaluation of geotechnical soils investigation, water table, and soil percolation characteristics.

(g)

Foundation survey required. A foundation survey prepared by a state professional land surveyor must be submitted to the county for review after placement or construction of the building concrete floor slab on grade or floor at ground level. The foundation survey must show the floor elevation(s) and setback dimensions from the building to property lines. Inspections for construction above or beyond the floor will not be performed until the county reviews said foundation survey for compliance with the approved site drainage plan and county regulations and approves and releases the construction to continue.

(h)

Final survey required. A final as-built survey prepared by a state professional land surveyor must be submitted and approved by the county prior to the issuance of a certificate of occupancy. The final survey must include elevations sufficient to demonstrate compliance with the approved site drainage plan and the lot grading and finished floor elevation standards contained herein and provide at a minimum topographic elevations at each lot corner, elevations along each property line at 25-foot intervals, and elevations of swales or berms on the lot at 25-foot intervals.

(i)

FEMA elevation certificate. A FEMA elevation certificate prepared by [a] state land surveyor must be submitted prior to issuance of a certificate of occupancy for structures located in a Federal Emergency Management Agency (FEMA) designated special flood hazard area.

(j)

Certificate of occupancy. The issuance of a certificate of occupancy shall not be construed as a warranty of the drainage system. Deviation or modification of the drainage system after issuance of the certificate of occupancy or failure to maintain the drainage system that results in the intrusion of water on adjacent properties shall be the responsibility of the property owner.

(Code 1979, § 6-1.1(b); Ord. No. 95-52, § 1, 10-24-95; Ord. No. 2000-27, § 1, 5-2-00; Ord. No. 02-09A, § 2, 2-26-02; Ord. No. 2003-42, § 1, 8-26-03; Ord. No. 2015-06, § 2, 3-31-15)

Editor's note

Ord. No. 2015-06, § 2, adopted March 31, 2015, amended the title of § 22-48 to read as set out herein. Previously § 22-48 was titled floor elevation to be above grade of adjacent thoroughfare.