§ 10-2. Design and construction criteria.

(a)

Developments shall be designed for drainage using Louisiana Department of Transportation and Development published drainage design procedures using the Rational Method for a two-year storm for improvements within the development; a five-year storm for improvements to the existing lateral ditches within a development; and a ten-year storm for improvements to existing major drainage channels within a development. Developers of large developments may in addition to the above be required to submit a drainage impact analysis. If it is found that runoff may increase significantly after construction is complete, runoff detention systems may be required.

(b)

The natural drainage within the subdivision shall be followed in as far as economically feasible. Streets and lots shall be arranged so as to keep artificially relocated drainage canals to a minimum.

(c)

Drainage pipe used shall meet the requirements of ASTM Designation C-76, Class III reinforced concrete pipe with proper pipe joints (per LDOTD Hydraulic Manual) and shall be sized using Manning's roughness coefficient of 0.013 for design. Corrugated Metal Pipe (CMP) and Ribbed Polyvinyl Chloride Culvert Pipe (RPVCCP) shall be allowed where soil resistivity is not unfavorable and based on using the Louisiana Department of Transportation and Development design standards for gages at various fill heights, protective coatings, and Manning's roughness coefficients.

(d)

Open channels shall have side slopes designed for proper stability, both for slope failure and erosion protection purposes. Unlined earthen channels shall be allowed for improvements which meet such design requirements and have 3(H):1(V) or flatter side slopes. Flexible revetment shall be allowed in lieu of concrete lining for channels which meet such design requirements and have 2(H):1(V) or 2.5:1 side slopes. Concrete lined channels shall be required for channels which do not meet such design requirements or where side slopes are steeper than 2:1. Open channels shall be concrete lined where in the collective opinion of the planning commission the aesthetics of the area are of primary concern for a particular development. When concrete lined channels are constructed the bottom of the channel shall have a minimum thickness of six inches, sides shall have a minimum thickness of four inches, and a five-foot collar on each side shall be a minimum thickness of four inches. All such designs shall be certified by a current and duly registered engineer qualified in the State of Louisiana for such engineering practice.

(e)

The following servitude criteria shall be required for each ditch, canal, sewer collection line and storm sewer:

(1)

Minimum servitude, 15 feet.

(2)

Canals with a bottom width of less than six feet, a minimum of five feet from the top of the bank to the property line, on each side.

(3)

Canals with bottom widths of six feet to 15 feet, a minimum of five feet on one side and 15 feet on the other.

(4)

Canals with bottom widths in excess of 15 feet and a top width of less than 40 feet, a minimum of five feet on one side and 25 feet on the other.

(5)

Canals with a top width in excess of 40 feet, 25 feet on both sides.

(6)

Major drainage canals that the subdivider is not required to line (see 10-1(e)), a minimum of 25 feet on each side.

(f)

When a proposed ditch must discharge into a major unlined canal, the subdivider shall be required to enclose the ditch, under the access strip of the major canal, in a metal pipe or concrete culvert. The culvert shall extend four feet into the canal beyond the side slope, and shall discharge into a concrete flume that extends a minimum of five feet into the bottom of the canal. The flume shall be constructed immediately after conduit is installed.

(g)

Unless drainage channels are being dedicated or developed for recreational or other public or private open space use, the subdivider shall construct a five-foot chainlink fence along all lined channels.

(Ord. No. 939, 11-10-97; Ord. No. 1007, 2-14-05)