§ 33-6.26. Low impact development.

(a)

Purpose. Jefferson Parish promotes the general welfare through sustainable, low impact development which reduces the long-term capital and operational costs of public facilities and minimizes adverse effects on the environment, public works infrastructure, and public health. Managing stormwater with low impact development (LID) techniques provides an approach to development and redevelopment that works with nature and can achieve the following benefits and purposes:

(1)

Reduce flooding, runoff, subsidence, stormwater runoff volume, peak discharge rates, sewer overflows, and the costs of stormwater and sewer treatment;

(2)

Mimic a site's predevelopment hydrology by infiltrating, filtering, storing, evaporating, and detaining stormwater runoff;

(3)

Add green space by preserving and re-creating natural landscape features including existing tree vegetation;

(4)

Use plants and soil to absorb, slow, filter, and cleanse runoff near the source;

(5)

Promote low maintenance landscaping that reduces the use of herbicides, fertilizers, and pesticides;

(6)

Minimize imperviousness to create functional and appealing site drainage;

(7)

Treat stormwater as a resource rather than a waste product and help meet National Pollutant Discharge Elimination System (NPDES) requirements;

(8)

Reduce the heat island effect and mitigate the effects of development and the built environment;

(9)

Protect natural drainage features and emulate the functions of natural systems to increase recharge and reintegrate rainfall into the water cycle and watershed; and

(10)

Reduce energy and water use.

(b)

Applicability. The applicant for any site plan review required in Chapter 33 or Chapter 40 of this Code may use LID best management practices (BMPs) to meet or exceed the requirements for stormwater management in Article 7 of this UDC and for landscaping, buffering, screening, and tree preservation requirements of this Code.

(c)

Best management practices (BMPs). An application for low impact development shall demonstrate the use of BMPs, including, but not limited to, the techniques described in "Bayou Land RC&D Stormwater BMP Guidance Tool," to meet stormwater management requirements. Jefferson Parish recognizes that in most cases, BMPs, or nonstructural practices, will need to be combined with engineered or structural approaches to meet requirements. BMPs may be placed in the public right-of-way upon approval of the parish engineering director, provided that the perpetual maintenance of the BMPs is borne exclusively by the property owner.

(d)

Standards. An application for low impact development shall, in addition to all other applicable requirements, achieve the following standards, as applicable: for new developments, retain and filter the first one and one-quarter (1.25) inch rainfall event through the utilization of BMPs; or, for redevelopment, either filter the first one and one-quarter (1.25) inch rainfall event through the utilization of BMPs, reduce existing imperviousness by fifty (50) percent, or a combination of the two. These minimum standards should be achieved through the following approaches:

(1)

Utilize BMPs appropriate to the scale and type of development and specific location, and design them for effective and efficient long-term maintenance;

(2)

Consider the variation of conditions from one location to another, adjusting to the predevelopment green-to-grey continuum, existing engineered elements, character of the soil, topography, or site geometry, intensity of development, and other factors;

(3)

Minimize the need for grading and use creative grading techniques to manage stormwater runoff and encourage more filtration;

(4)

Reduce the amount of impervious surface and disconnect impervious surfaces by directing runoff from rooftops, sidewalks, driveways, or parking lots to landscaped areas or porous pavement;

(5)

Scrutinize setbacks, parking spaces, travel aisles, driveways, and sidewalks or walkways to see if any of these elements can be reduced in scale;

(6)

Choose native plants that are easy to maintain, adapted to the local climate and soil conditions, and possess the ability to intercept and hold rainwater and decrease water flow velocity; and

(7)

Maximize natural lands or existing vegetation set aside for conservation or preservation and protect them from clearing, grading, and other construction-related impacts.

(e)

Ministerial exceptions. Jefferson Parish encourages property owners and developers to apply low impact development techniques based on good land use planning and environmentally sound land use strategies. The parish finds that flexibility in site design practices can promote low impact development while maintaining the safety, health, and welfare of the public. To achieve the purposes of this section, for any application for low impact development that demonstrates full compliance with the standards set forth above, the planning director may approve any or all of the following ministerial exceptions:

(1)

Dimensional requirements.

a.

Decrease in minimum setback or increase in maximum setback, but no greater than fifty (50) percent of the required minimum or maximum setback, as long as:

1.

The total required landscaped and buffer area for a site is not reduced;

2.

The required buffer between a commercial district and a residential district is not reduced; and

3.

The amount of the decrease or increase is the minimum amount needed to enhance or extend BMP on the site or in public right-of-way adjacent to or in the same block as the property; and

b.

Increase or decrease in the maximum gross floor area of a building by up to twenty-five (25) percent where a zoning district provides a maximum or minimum gross floor area.

(2)

Parking requirements.

a.

Reduce the total parking requirement by up to twenty-five (25) percent, as an approximation of the floor area occupied by circulation and mechanical systems;

b.

Allow off-site parking to meet up to one hundred (100) percent of the required off-street parking, as long as the off-site site has parking in excess of its required parking and the amount of required parking spaces being reduced on-site is equal to the amount of excess spaces being provided off-site. The off-site site must be located within six hundred (600) feet measured along and following a reasonable and safe walking route from the nearest main entrance of the building or use to the off-site parking area; may be on land separated by a public right-of-way, except roads classified on the Jefferson Parish Thoroughfare Plan as interstates, freeways, or major arterials; and, shall be on land with a zoning district listed in section 40-661(3) for non-residential uses in non-residential districts. All other requirements for a recorded parking agreement shall apply; and

c.

Allow shared parking between two (2) or more non-residential uses in the development, or between non-residential uses in the development and off-site non-residential uses, whose peak parking demands occur at different times. The applicant shall demonstrate, through peak use analysis approved by the parish traffic engineer, that the number of parking spaces provided will satisfy the minimum off-street parking requirement for all uses. An applicant may use the latest peak demand analysis published by the Institute of Traffic Engineers (ITE) or other source acceptable to the parish traffic engineer. The off-site site must comply with the provisions for an off-site site listed in subsection b above. All other requirements for a recorded parking agreement of section 33-3.56.4(c), Shared parking, shall apply.

(3)

Landscaping requirements.

a.

Substitute native grasses or other plant materials where shrubs are required, and waive the requirement that they create a continuous opaque barrier, if the grasses or other plant materials are integral and necessary to the functioning of a proposed BMP;

b.

Waive the requirements for interior parking lot landscaping that specify location and minimum widths of islands, peninsulas, endcaps, and planting strips, provided that the minimum square footage of landscaped area and quantity of landscape materials required is still provided on the site, if the alternative interior parking lot landscaping layout is necessary for the proper functioning of the site's overall stormwater management system;

c.

Waive the requirement that sod be installed in all areas that are not plantings beds, provided that an alternative is proposed that positively contributes to the site's overall stormwater management system;

d.

Waive the requirement for species diversity, if the applicant can demonstrate that meeting the diversity requirement would be impracticable given the necessary design standards and constraints of the proposed stormwater management system;

e.

Waive the requirement for mulch, provided that an alternative is proposed that positively contributes to the site's overall stormwater management system; and

f.

Reduce or eliminate the requirement to irrigate the site, provided that the proposed BMPs provide the same function.

(f)

Stormwater management plan. An application for low impact development shall include a stormwater management plan that integrates BMPs with other required plans for site, landscaping, construction, and engineering. A pre-application conference, coordinated by the planning department with appropriate parish staff, is required. In addition to standard information required on plans, the stormwater management plan shall include the following information:

(1)

Narrative description of stormwater management plan, including a description of proposed series of stormwater BMPs;

(2)

Existing site conditions, including a description and topographic map of land cover, contours, description and map of soil types, and estimated stormwater pollutant load;

(3)

All storm drainage systems, including existing and proposed drain lines, culverts, catch basins, headwalls, hydrants, manholes, and temporary and permanent stormwater BMPs;

(4)

All required hydraulic and hydrologic calculations and specifications used in the design and construction of the permanent stormwater BMPs. Safeguards to prevent short-circuiting of permanent stormwater BMPs shall be designed into the system. Capacities of BMPs shall show surface and sub-surface volumes (in aggregate, chambers, cisterns, etc.) in gallons;

(5)

A plan showing site sub-catchment areas, all BMP areas and capacities, stormwater runoff treatment train of BMPs in which runoff is directed before leaving the site (surface or sub-surface), and final contours;

(6)

Description of the receiving stream, canal, pipe, culvert, ditch or other drainage structure into which the runoff from the property flows;

(7)

Name of entity responsible for maintenance of BMPs; and

(8)

Plan shall be stamped and signed by appropriate qualified professional.

(g)

Maintenance. A maintenance plan is required in order to ensure the long-term effectiveness of all BMPs. The maintenance plan shall be prepared in accordance with a template approved by the planning director and shall be recorded with the parish clerk of court.

(Ord. No. 25405 , § 36, 8-9-17)