5.04.07 SUBDIVISION DESIGN STANDARDS: DRAINAGE AND STORM

A. General Requirements: Planning & Zoning shall not approve or recommend for approval any subdivision application which does not make adequate provision for storm or flood water runoff channels or catch basins. The storm water drainage system shall be separate and independent of the sanitary waste system. Storm drains, where required, shall be designed by the Rational Method, or other methods as approved by a qualified engineer, and a copy of design computations shall be submitted along with plans. Inlets shall be provided so that surface water is not carried across or around any intersection, nor for a distance of more than six hundred feet (600’) in the gutter. When calculations indicate that curb capacities are exceeded at a point, catch basins shall be used to intercept flow at that point. Surface water drainage patterns shall be shown for each and every lot and block. B. Location: The applicant/developer may be required by the Land Use Authority, upon the recommendation of a qualified engineer, to carry away by pipe or open channel any spring or surface water that may exist either previously to, or as a result of the subdivision. Such drainage facilities shall be located in the road right-of-way where feasible, or in perpetual unobstructed easements of appropriate width, and shall be constructed in accordance with the construction standards and specifications. C. Accommodation of Upstream Drainage Areas: A culvert or other drainage facility shall in each case be large enough to accommodate potential runoff from its entire upstream drainage area, whether inside or outside the subdivision. The developer shall hire a qualified engineer licensed in the State of Utah to determine the necessary size of the facility, based on the provisions of the construction standards and specifications assuming conditions of maximum potential watershed development permitted by this Code and the General or Master Plan. A qualified Engineer must review and approve the design. D. Effect on Downstream Drainage Areas: The Town’s qualified Engineer may require the developer's qualified Engineer to study the effect of each subdivision on existing downstream drainage facilities outside the area of the subdivision. Town storm drainage studies together with such other studies as shall be appropriate, shall serve as a guide to needed improvements. Where it is anticipated that the additional runoff incident to the development of the subdivision will overload an existing downstream drainage facility, the Land Use Authority may withhold approval of the subdivision until provision has been made for the improvement of said potential condition in such sum as the Land Use Authority and Town Engineer shall determine. No subdivision shall be approved unless adequate drainage will be provided to an approved drainage watercourse or facility. E. Areas of Poor Drainage: Whenever a plat is submitted for an area which is subject to flooding, the Land Use Authority, may approve such subdivision provided that the applicant fills the affected area of said subdivision to an elevation sufficient to place the elevation of streets and lots at a minimum of twelve (12) inches above the elevation of the maximum probable flood, as determined by a qualified engineer. The plat of such subdivision shall provide for an overflow zone along the bank of any stream or watercourse, in a width which shall be sufficient in time of high water to contain or move the water, and no fill shall be placed in the overflow zone nor shall any structure be erected or placed therein. The boundaries of the overflow zone shall be subject to approval by a qualified engineer. Development in areas of extremely poor drainage will not be allowed. F. Flood Plain Areas: The Land Use Authority may, when it deems it necessary for the health, safety, or welfare of the present and future population of the area and necessary to the conservation of water, drainage, and sanitary facilities, prohibit the subdivision of any portion of the property which lies within the floodplain of any stream or drainage course. These flood plain areas should be preserved from any and all destruction or damage resulting from clearing, grading, or dumping of earth, waste material, or stumps, except at the discretion of the Land Use Authority.