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STORMWATER | STANDARD


This component is for projects which have significant impact on stormwater runoff. STD's usually involve projects that either have an individual on-site stormwater management facility for the commercial development or a master stormwater management facility for a subdivision (residential or commercial).

Typically, these projects are required to complete the site plan and subdivision review process.

GENERAL INFORMATION REQUIRED


  1. Administrative
  2. Plan in agreement with any limited use site plan, PUD, DRI or other zoning
  3. Permit plans compatible with approved site plan
  4. Site plan approval conditions met
  5. Authorization for encroachment upon any easement
  6. Legal description provided
  7. Proof of ownership provided
  8. Approved NFI and EIA
  9. Mitigation as required by Matrix
  10. Authorization for encroachment upon adjacent property
  11. All existing and proposed wells, waterlines, sanitary sewers, storm sewers, underground and overhead electric lines shown.
  12. Building and other structural setbacks shown
  13. Zoning and land use of all adjacent properties indicated on a plan.
  14. City connection permit or other approval required
  15. Permit fee calculated correctly
  1. General Site Design
  2. Off-site run off entering property adequately dealt with.
  3. Grade changes do not alter the natural flow of off-site uphill generated runoff, unless controlled.
  4. Inlets on slopes use deflectors to prevent run off bypassing.
  5. Runoff from driveways diverted into drainage system in order to prevent direct discharge into a street.
  6. Adequate end treatment on all pipe ends
  7. Energy dissipator structure at outlet of pipes under a large head and at the end of paved flumes.
  8. County or DOT approval for construction in or connection to right-of-way or drainage system.

STANDARD FORM APPLICATION REQUIREMENTS


  1. General location map
  2. A site plan including:
  3. An overall grading plan; showing existing and proposed contours, and including contours of the areas adjacent to the site;
  4. All improvements proposed, including buildings, pavement, sidewalks and existing pavement and structures shown and labeled;
  5. Minimum finished floor elevations; compliance with flood hazard ordinances
  6. Type(s) of ground cover on previous areas (such as grassed, landscaped, bare, wood), including both before and after development;
  7. Bottom elevations, dimensions and cross sections for detention and retention areas;
  8. Detailed drawings and dimensions for outfall structures from detention facilities, including storm drain inverts and sizes;
  9. Pipe sizes, inverts and inlet types for interior conveyance systems;
  10. Swale locations, dimensions and side slopes, along with specific proposed methods of stabilization;
  11. All wells, drainage easements and areas to remain natural associated with the site, both existing and proposed;
  12. Applicable flood boundaries for sites lying wholly or partially within the twenty-five (25)-year and one-hundred (100)-year flood plains, with cross sections and all other information necessary to show compliance;
  13. Stormwater Technical Support Information
  14. For existing conditions:
  15. Xerox of an SCS soil map with project boundaries.
  16. Aerial photo showing sufficient detail - for projects 15 acres or larger.
  17. A detailed topographic map with pre-development contours. Where necessary, indicate flow directions with small arrows. Indicate sub-basin boundaries.
  18. Boundaries and storage volumes of major surface depressions.
  19. Location and description of site discharge point and path receiving water body.
  20. Details showing calculation of pre-development curve number, time of concentration and associated calculations.
  21. Wet season depth to ground water table for projects located adjacent to the flood plains of closed basins, determine this by field measurements of interpretation of soil profiles.
  22. For closed basins: measured volumetric drawdown rate, or estimate thereof based on wet season water budget analysis.
  23. Peak discharge rate and total runoff volume for storms up to and including the 25-year event (per FDOT critical storm analysis procedure). Open basins: analyze 1, 4, 8 and 24 hour events. Closed basins: analyze 1 hour to 10 day events.
  24. Post Development Hydrologic Conditions:
  25. A detailed post development topo map with: previous, directly connected impervious, and non-directly connected impervious areas delineated. Indicate percent of total area represented by each.
  26. Detailed calculation of post curve number and time of concentration. For larger or steep areas treat DCIA separately.
  27. Choose appropriate hydrograph generation methodology: Dabro, Santa Barbara, SCS unit hydrograph, modified rational, etc. and justify (briefly).
  28. Post development peak run off (inflow to pond) rates and total volumes from all storms specified in pre-development requirements. Use FDOT critical storm methodology. Supply hydrograph for the critical storm.
  29. State - volume relationship for pond.
  30. State - discharge relationship for each separate outfall structure, for the filter, for percolation (if applicable), and for all structures acting in concert.
  31. Post development peak discharge rates from pond and total outflow volumes for all storms specified above. For critical storm, supply complete outflow hydrograph (include stages).
  32. Table comparing pre-development with post development storm conditions that shows post discharge rate less than or equal to pre-development rates.
  33. Show proposed outfall location.
  34. Hydraulic assessment of off site conveyance to handle additional discharge - include calculations and cross-section drawings. Topo map showing necessary off site drainage easements with description and notarized permission to use. Legal descriptions, plats and legal authorization by owner must be submitted prior to final approval.
  35. Details of Pond:
  36. Detailed engineering drawings of stormwater collection structures, stormwater pond, filter, outfall structures and spillways with necessary sizes, elevations and other specifics to understand operation and construction of the stormwater management system.
  37. Show areas to be planted and planting/stabilization details.
  38. Show sediment sump and address maintainability of same.
  39. Provide a pond maintenance prescription.
  40. Show ability to pass peak flow for 100 year - 24 hour storm.
  41. Additional descriptive information presented in a narrative form, including:
  42. Environmental and land use characteristics, including zoning, current and proposed land used, proximity to wetlands, water bodies, watercourses or other sensitive environmental features and natural land cover, including any protected trees located on the site;
  43. An erosion and sediment control plan which utilizes structural and the best management practice appropriate to the site;
  44. A construction schedule setting forth a sequence of development activities, which are limited to the maximum extent feasible of areas disturbed at one time, so as to prevent the occurrence of erosion;
  45. The name, local address and telephone number of an individual who shall be designated stormwater management control officer for the project;
  46. Note on plans that operating permit will be secured and post construction certification provided prior to final inspection;
  47. If the site is to utilize approved off site or regional/multi-state stormwater facilities, evidence of capacity of such facility, demonstrating that there is capacity;
  48. Information regarding any off site impacts anticipated as result of the proposed development and means by which such impacts are to be mitigated; if no off-site impacts are anticipated, then a signed statement to that effect.
  49. Specific signed statement, indicating whether flood plains, wetlands, or protected trees or other environmentally sensitive features exist on the site;

PERFORMANCE AND DESIGN STANDARDS OF STORMWATER MANAGEMENT SYSTEMS


  1. Peak post development discharge rate does not exceed pre-development rates for all critical duration storms up to and including 25 year storm. (See also Post Development Hydrologic Conditions)
  2. When redevelopment occurs - assume the site is in a natural and undeveloped condition.
  3. Rate control is not necessary if discharge is into offsite stormwater facility or into a waterbody or watercourse of sufficient size with negligible effect.
  4. Design provisions for maintenance:
  5. Adequate easements to accommodate maintenance and inspections.
  6. Design standards and design life - stormwater facilities designed in compliance with policies of local governmental entity with primary jurisdiction.
  7. Minimum 50 year useful life for major structural components.
  8. Ditches - minimum standards:
  9. Side slopes no steeper than 3:1 unless;
  10. Slopes are paved for depths greater than 1' - 2:1 maximum;
  11. 1:1 side slope for depths up to 1'.
  12. Stabilized (V < 2.5 - grassed and mulched; V < 4 - sodded; V < 4 - paved; between 4 and 5.5 feet per sec., ditches may be sodded if lap-staked and joint staggered.)
  13. Alternate stabilization allowed.
  14. Sediment and Erosion Control Plan:
  15. Construction sequence provides for installation of control between disturbed areas and adjacent property, waters bodies, watercourses, inlets, culverts and wetlands.
  16. Clearing allowed for installation of controls (limited to within 5 feet of controls).
  17. Method of control is an allowable method listed under Sec. 10-4.327.
  18. Best management practices indicated for minimized erosion and sediment retained on-site.
  19. Other suitable method approved by director.
  20. Notes on plan concerning maintenance of erosion and sediment controls.