17.10.160 - Drainage and Storm Sewers.

A.

General Requirements. Each Plat shall make adequate provision for storm or flood water runoff in compliance with Title 13 and the Construction Specifications and Standard Drawings. The storm water drainage system shall be separate from and independent of the sanitary sewer system. Storm sewers, where required, shall be designed by the Rational Method or other methods as approved by the City Engineer, and a copy of storm water system design computations shall be submitted along with plans. 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. On-Site storm water detention is required.

B.

Nature of Storm Water Facilities.

1.

Location. Upon the recommendation of the City Engineer, the Planning Commission may require the Applicant 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 Dedicated to the City and constructed in accordance with Title 13 and the Construction Standards and Specifications.

2.

Accessibility to Public Storm Sewers.

a.

Underground storm sewer systems shall be constructed throughout the Subdivision and be conducted to an approved out-fall, maintained by the Owner. Periodic inspection of facilities shall be conducted by the City Engineer over the life of the Development.

b.

If a connection to a public storm sewer will be provided eventually, as determined by the City Engineer and the Planning Commission, the Applicant shall make arrangements for future storm water disposal by a public utility system at the time the Plat receives final approval. Provision for such connection shall be incorporated by inclusion in the performance Guaranty required for the Subdivision Plat.

3.

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 Applicant shall hire a qualified engineer to determine the necessary size of the facility, based on the provisions of the current MS4 permit and Construction Standards and Specifications assuming conditions of maximum potential permitted Development. The City Engineer must review, recommend modifications where applicable, and approve the proposed design prior to Plat approval.

4.

Effect on Downstream Drainage Areas. The City Engineer shall also require the Applicant's qualified engineer to study the effect of each Subdivision on existing downstream drainage facilities outside the Area of the Subdivision. City storm drainage studies together with such other studies as shall be appropriate, shall serve as a guide to any needed improvements required by the Development to City facilities prior to Development approval. No Subdivision shall be approved unless adequate storm/flood water drainage will be provided to an approved drainage watercourse or facility with capacity to serve the anticipated storm water flow.

5.

Areas of Poor Drainage. Whenever a Plat is submitted for an Area that is subject to periodic flooding, the Planning Commission upon recommendation of the City Engineer, may approve such Subdivision provided that the Applicant fills the affected Area of said Subdivision with appropriate structural base materials to an elevation sufficient to place the elevation of Streets and Lots at a minimum of twelve inches (12") above the elevation of the maximum probable 100 year flood event. The Plat of such Subdivision shall provide for an overflow zone along the bank of any stream or watercourse, in a width that is sufficient in a time of high water to contain or move the flood water without damaging improved properties, including City Streets and facilities. No fill shall be placed in the overflow zone nor shall any Structure be erected or placed therein.

6.

Flood Plain Areas. The Planning Commission may, upon recommendation of the City Engineer and 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 flood plain of any river, 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.

C.

Dedication of Drainage Easements.

1.

General Requirements. Where a Subdivision is traversed by a watercourse, drainage way, channel, or stream, the Owner shall Dedicate to the City a storm water easement or drainage Right-of-Way conforming substantially to the lines of such watercourse, and of such width and construction or both as will be adequate for drainage in the 100 year flood event. The existing drainage will be maintained by an open channel with landscaped banks and adequate width for maximum potential volume of flow.

2.

Drainage Easements.

a.

Where topography or other conditions make impractical the inclusion of necessary drainage facilities within road Rights-of-Way, perpetual unobstructed easements at least twenty feet (20') in width for such drainage facilities shall be provided across the platted Property outside the platted road lines and with satisfactory access to the road. Drainage easements shall be indicated on the Plat. Drainage easements shall be carried from the road to a natural watercourse or to other drainage facility.

b.

When a proposed drainage system will carry water across private land outside the Subdivision, appropriate drainage rights must be secured from the affected land Owner and must be indicated on the Plat.

c.

The Applicant shall Dedicate, either in fee simple or by drainage easement, land on both sides of existing watercourses within the Subdivision.

d.

Low-lying lands along watercourses subject to flooding or overflowing during storm periods, whether or not included in Areas for Dedication, shall be preserved, and retained in their natural state as drainage ways.

(Ord. No. 2020-02, § IV(Exh. C), 1-8-2020; Ord. No. 2023-27, § 1(Exh. A), 9-12-2023)