Sec. 21A-67. Design control guidelines.
The following guidelines provide a uniform design procedure to control the discharge of stormwater from areas where proposed changes in land use will result in changes in natural flow pattern and are necessary to: (1) clearly delineate the problem of handling runoff in urban areas; (2) define the responsibility any owner has to control the stormwater runoff from his property.
All land developers wishing to develop property in the Town of St. John are required to prepare and submit a master drainage plan for the total development area.
(1) Prepare a topographic contour map, with the drainage area delineated, with plan for draining the total upstream tributary watershed through the proposed development.
(2) Prepare a topographic map with at least one (1) foot contours, with general layout of the proposed inlets and storm sewers for the total development showing all existing drainage structures with size and invert elevations.
(3) Determine the capacity of the downstream open channel, culvert or storm sewer that may be used for an outlet.
(4) Examine the points downstream that may be used as a control to determine the maximum allowable rate of stormwater runoff for the design storm. Existing culverts are not necessarily controls.
(5) Provide a routing path for runoff in the event the drainage facility’s capacity is exceeded. The routing path will become part of a grading plan which will be submitted with detailed plans.
(6) Examine and show the routing of excess stormwater through the site and as it is discharged to off-site lands.
(7) The routing path shall be continuous from one development to the next.
(8) If the decision is made by the Town of St. John, through its Engineer, to handle stormwater runoff by storage and releasing it at a regulated rate to prevent flooding downstream, the storage basin will be located in and become part of the routing path.
(9) Excess stormwater will be kept out of proposed habitable structures.
(10) The master drainage plan shall be approved by the Engineer.