§ 6.02.11. Stormwater Management

A.

Compliance with Technical Requirements of the Southwest Florida Water Management District (SWFWMD) and Hillsborough County.

The Stormwater Management System shall be designed to comply with the water quality requirements of SWFWMD and with the Hillsborough County Stormwater Management Technical Manual.

B.

Drainage Easements; Use Restrictions and County Maintenance.

1.

Drainage improvements shall be allowed in drainage easements. When public drainage easements are shown on the plat, the plat and affected deeds shall state, "Drainage easements shall not contain permanent improvements, including but not limited to sidewalks, driveways, impervious surfaces, patios, decks, pools, air conditioners, structures, utility sheds, poles, fences, sprinkler systems, trees, shrubs, hedges, and landscaping plants other than grass, except as approved by the County Administrator."

2.

Drainage easements shall be granted to Hillsborough County for all stormwater management facilities to be maintained by Hillsborough County. Off-site drainage easements may be required in cases where the minimum maintenance activities associated with roads and stormwater management facilities to be dedicated to Hillsborough County would not be practical without such easements. For subdivisions which are to be privately maintained, the design and maintenance requirements are the same as those for stormwater management facilities that are to be dedicated to Hillsborough County.

C.

Permanent Improvements in Road Rights-of-Way.

Permanent improvements in road rights-of-way, including but not limited to curb inlets (unless designed for heavy wheel loads), poles, fire hydrants, and trees shall not be located in such a manner as to block access to drainage easements or drainage rights-of-way.

D.

Inverted Crowns.

Streets to be dedicated to Hillsborough County shall not have inverted crowns, unless otherwise authorized by the Administrator.

E.

Developments in Floodplains.

1.

Criteria. The criteria for development in floodplains shall pertain to all floodplains and not be limited to those floodplains identified on FEMA maps. The EOR shall be responsible for determining the on-site 100-year flood elevations if not determined by a FEMA study. The EOR is required to submit a Letter of Map Amendment or Map Revision to FEMA for any changes in flood zone designations as determined by a detailed study of the area.

2.

100-Year Frequency Floodplain. No development (structures or fill) shall be allowed in the conveyance portion of any 100-year frequency floodplain associated with a freshwater stream, channel, lake, or waterway, unless provisions are made to compensate for any reduction in conveyance caused by the development.

3.

100-Year Frequency Floodplain Non-Tidal. No development (structures or fill) shall be allowed in any 100-year frequency non-tidal floodplain, unless provisions are made to compensate for the reduction in storage volume due to the proposed development.

4.

Compensation Storage Volumes. Any compensation storage volumes shall be provided in addition to stormwater detention or retention volumes otherwise required to reduce peak runoff rates from the development.

5.

Earthen Fill. No earthen fill shall be placed within a 100-year floodplain area unless an equal amount of flood storage volume is created by excavation below the 100-year flood elevation and above the seasonal high ground water table elevations, whichever is appropriate.

6.

Exceptions. Exceptions shall be allowed if the floodplain is associated with a landlocked waterbody and is under one ownership.

7.

Encroachment. No encroachment shall be allowed in a regulatory floodway, as designated on the FEMA Floodway Maps, unless approved by FEMA and subsequently accepted by Hillsborough County.

8.

All new development or substantially improved structures within a designated Coastal Barrier Resource System area will not be eligible for Federal flood insurance pursuant to the Coastal Barrier Improvement Act of 1990 (Public Law 101-591).

F.

Enclosed Stormwater Conveyance Systems.

1.

Enclosed stormwater conveyance systems shall be located in drainage easements or road rights-of-way dedicated to Hillsborough County.

2.

For enclosed stormwater conveyance systems not within road rights-of-way, the drainage easement width shall be sufficient to encompass a work trench having 1:1 side slopes (measured from the proposed ground surface to the proposed invert of the enclosed stormwater conveyance system) and a bottom width two feet wider than the total width of the installed conveyance system.

3.

The drainage easement width shall not be less than 20 feet unless otherwise approved by the Administrator.

G.

Canals and Ditches.

Canals and ditches shall have sufficient drainage easement dedicated to Hillsborough County to allow for installation of the canal or ditch including an unobstructed 20-foot wide maintenance area on both sides, measured from the top of the bank, unless otherwise approved by the Administrator.

H.

Stormwater Detention and Retention Ponds.

If the pond is to be maintained by Hillsborough County, sufficient drainage easements shall be dedicated to Hillsborough County to include the area of the pond within the perimeter of the inside top of bank and an unobstructed 20-foot wide maintenance area around the entire perimeter of the inside top of bank. If the maintenance area is on an embankment, the drainage easement shall extend to the external toe of slope of the embankment. Alternatives to the width or extent of the maintenance area shall be approved by the Administrator if it can be demonstrated that proper maintenance practices would not be impaired.

I.

Ingress and Egress.

Sufficient perpetual, legal access shall be conveyed to Hillsborough County to provide ingress to and egress from a drainage easement. This access shall be unobstructed and at least 20 feet in width.

J.

Finished Foundation Elevation.

A Certification of the Finished Foundation Elevation (FFE) shall be provided to the Building Services Division certifying that the FFE conforms to the approved subdivision Lot Grading Plan. This Certification shall be required prior to requesting a framing inspection. requesting a framing inspection.

(Ord. No. 00-21, § 2, 5-18-00; Ord. No. 04-27, § 2, 6-10-04; Ord. No. 06-18, § 2, 8-1-06)