An adequate storm drainage system shall be constructed for each proposed subdivision or development. The storm drainage system shall consist of a system of underground conduits, which provide adequate inlets for all surface runoff and a separate storm drainage connection for each individual residential, commercial or industrial unit.
(a) The sizes of storm drainage conduits shall be computed by the rational method. All computations shall be submitted for review and approval. The computations shall be based on a five year frequency rain and that the maximum allowable time of concentration of initial inlet shall be 20 minutes.
(b) All public storm conduits shall be a minimum of 12 inches in diameter and constructed at such a gradient as to maintain a minimum velocity of flow of two feet per second when flowing at 50% of capacity.
(c) All storm sewer conduits constructed within or outside the limits of the right-of-way, shall be constructed of reinforced concrete pipe meeting the ASTM, Int’l, specification C-76 and all joints shall be sealed with an approved field-applied bituminous pipe joint compound, or Polyvinyl Chloride (PVC) minimum SDR35, or Polyethylene Pipe ASTM D-3350; sizes and materials shall be determined by the City Engineer.
(d) All service connections to public storm conduits shall be six inches in diameter or larger and shall extend from the main conduit to the limits of the right-of-way or utility easement. Downspouts and footer drains of structures shall not be connected to the curb, or directly to a storm sewer.
(e) Unless otherwise specifically authorized by the City Engineer, the minimum depth of the invert of the storm service connection at the right-of-way line shall be six feet below the established centerline grade of the pavement.
(f) In general, storm manholes shall be precast type and they shall be constructed at all change of alignment and grade of the conduit, and at maximum intervals of 300 feet.
(g) The inlets shall be grate type and the slots shall run parallel to the direction of the flow and be at least 12 inches long and the area of the opening shall be at least 50% of the area of the grate.
(h) All areas which contribute or may contribute storm water, either in conduits or by overland flow, to the proposed storm drainage system shall be considered in the determination of the size of the proposed storm conduits.
(i) Where natural drainage channels intersect any right-of-way, the applicant shall construct satisfactory bridges and/or culverts, unless the applicant has submitted, and Council has accepted, a petition described in Section 1137.10 for the construction of such improvements. The culverts shall extend across the entire right-of-way width of the proposed street. The cover over the culvert and its capacity shall be determined by the City Engineer. The minimum diameter of a culvert pipe shall be 18 inches, and headwalls are required at each end of the culvert.
(Ord. 16-19. Passed 9-16-19.)