(A)   Drainage map. The project engineer shall include in the construction plans a master drainage map showing all existing and proposed features. The map is to be prepared on a 24-inch by 36-inch sheet on a scale not to exceed one inch equals 200 feet. Listed below are the features that are to be included on the drainage map. (As a minimum, the city requires the same amount of information as required by the St. Johns River Water Management District.)
      (1)   Drainage bounds: Both pre-development and post-development drainage basin boundaries are to be delineated on the drainage plan. This includes any off-site areas contributing stormwater runoff to the development in the pre-development and post-development conditions.
      (2)   Topographic information: A topographic map of the development delineating one foot contour intervals must be included on the drainage plan. The pre-development contour lines should be shown as dashed lines and the post-development contour lines should be shown as continuous lines.
      (3)   All wetlands must be shown on the drainage plan. A line 25 feet upland of the normal high water and/or the wet land vegetative line, whichever applies, must be staked in the field and shown on the plans. The city requires this 25 feet as a buffer to the wetland areas. All lands below the elevation of either of the two above described lines shall be dedicated as environmental/conservation easements. Additionally, the development of the subject property shall comply with the following provisions:
         (a)   Run-off. All new development, redevelopment of existing lots, additions to existing structures and the construction of accessory structures shall provide on-site stormwater retention, per code.
         (b)   During construction of all new development, redevelopment of existing lots, additions to existing structures and the construction of accessory structures, the owner of the property shall install shall install silt fence and/or any other means of erosion control approved by the city to prevent the run-off of sediments.
         (c)   During construction, at least once a week, the city shall inspect the construction site and the silt/erosion control measures to ensure that such measures are in place and functioning as required by the permit. If such measures are found to be operating at less than optimal level, the city shall require the contractor and/or owner of the property to take such actions as are necessary to return the silt control measures back to optimal efficiency. If such measures are not taken in what the city determines to be a timely manner, the city may issue a "Stop Work Order" for the subject property.
         (d)   All permits for work on lots shall be accompanied by a survey that clearly shows the type and location of all soils, the location of all wetlands, the 100-year flood elevation, if applicable, and the mean high water elevation.
         (e)   Wetlands shall be delineated by a professional biologist, ecologist or other consultant, approved by the city.
         (f)   Except as permitted by the St. Johns River Water Management District and/or the Florida Department of Environmental Protection, existing wetlands shall not be removed, reduced in size by mowing and/or other mechanical means, impacted and/or degraded by chemical application.
         (g)   Except as permitted by the St. Johns River Water Management District and/or the Florida Department of Environmental Protection, the construction of docks, as permitted in § 154.12, shall not encroach into, remove and/or impact existing wetlands.
         (h)   Except as permitted by the City Engineer, the maximum slope of any lot for new development and/or redevelopment shall not exceed 4 to 1.
         (i)   At the time of permitting, the plans shall be checked to ensure that the proposed development complies with the maximum allowable grades.
         (j)   Prior to the approval of the certificate of occupancy (CO), staff shall verify that the grades of the property do or do not comply with grades shown on the approved plans.
      (4)   High water data on all existing water bodies and wetlands must be shown on the drainage plan. This includes the 10, 25 and 100-year flood elevations. Also, the source or sources of these elevations must be shown.
      (5)   Notes pertaining to existing standing water, areas of heavy seepage, high ground water table, or springs must be shown.
      (6)   Any existing drainage features, either upstream or downstream from the development, which will be impacted by the development, must be shown.
      (7)   Subdivision layouts with horizontal and vertical controls must be shown.
      (8)   All proposed drainage facilities (including: swales, inlets, pipes, manholes, retention ponds, detention ponds, outfall structures, filtration systems, and the like) must be shown.
      (9)   All drainage easements and ingress/egress areas for maintaining the drainage system must be shown.
      (10)   Description of the pre-development ground cover and land use must be noted on the drainage plans or in the drainage calculations which must accompany the plan.
      (11)   Lines delineating areas of different soil types must be shown and, each area must be labeled with its appropriate Soil Conservation Services soil-type name. This information can be included in or accompany the soils report from the geotechnical engineer.
      (12)   A recent aerial of the site depicting the predevelopment condition must be submitted with the drainage-plans.
      (13)   Drainage details. The drainage details to be shown in the drainage plans include, but are not limited to, the following:
         (a)   Cross sections of all retention/detention ponds showing the 10, 25 and 100 year flood elevations.
         (b)   Typical swale, ditch, or canal cross-sections.
         (c)   Drainage right-of-ways and easements.
         (d)   Outfall structure details.
         (e)   Typical inlet types and details.
         (f)   Oil skimmer details
         (g)   Mitered end details.
         (h)   Erosion control details.
   (B)   Subsoil investigation. A subsoil report shall be prepared by a Geotechnical Engineer registered in the State of Florida. The contents of this subsoil report will be in accordance with design criteria, division (D), and as a minimum will include, but not be limited to, soil borings which indicate American Association of State Highway and Transportation Official's soil classifications, gradation, determination of existing (24-hour test), and wet season water table, field-determined vertical and horizontal soils permeability rates, soils porosity values, and the depth of the relative impermeable soil layer for determining the duration of the vertical infiltration. A minimum of two borings will be taken in each retention/detention pond.
   (C)   Stormwater calculations-hydrological. Stormwater calculations must be submitted with the drainage plans. These calculations must be in accordance with § 3. Hydrologic Design Criteria, and should include as a minimum the same degree of detail as required by the St. Johns River Water Management District.
      (1)   The calculations should include enough information to verify the functionality of the proposed drainage system. This information includes hydrograph tabulations and stormwater routing tabulations for both the pre-development and post-development conditions, and all the information necessary to generate these tabulations.
   (D)   Stormwater calculations-hydraulic. All calculations necessary to show that the storm sewers, swales, and other hydraulic structures function correctly during the design storms must be included with the stormwater calculations. These calculations should be in accordance with § 4, Hydraulic Design Criteria.
      (1)   The storm sewer tabulations to be shown on the plans or in the calculations include, but are not limited to, the following:
         (a)   Location and type of structures.
         (b)   Type, size, and length of storm sewer pipe.
         (c)   Drainage basin areas contributing to each structure.
         (d)   Runoff coefficients.
         (e)   Time of concentration of each sub-basin.
         (f)   Arrows delineating stormwater flow directions to structures and in pipes.
         (g)   Hydraulic gradients.
         (h)   Estimated receiving water elevations with sources of information.
         (i)   Outlet velocities.
(Ord. 632, passed 2-4-93; Am. Ord. 1282, passed 3-6-08) Penalty, see § 154.04