76Management of stormwater

76 Management of stormwater

76 Management of stormwater

Stormwater runoff from development is to discharge to a Council drainage system approved by the Council for the purpose and is to have minimal impact on any receiving stormwater infrastructure, watercourse, stream, lagoon, lake, waterway or the like. Water quality control measures are to be provided in accordance with the Northern Beaches Stormwater Management Plan.

In particular, stormwater runoff is to be controlled using on-site stormwater detention in accordance with the Council’s “On-site Stormwater Detention Technical Specification”, except where it is demonstrated that—

• the discharge from the development will not pass through a drainage control structure such as a pipe, culvert, bridge, kerb and gutter or natural drainage system before reaching receiving waters such as the ocean, or

• the design of the stormwater drainage system is in accordance with the Council’s standard specification for engineering works (AUSPEC 1), or

• the additional runoff created by the development will not adversely affect any natural or constructed drainage system either downstream or upstream of the development site, or

• the total post-development impervious area (roof, driveway, paving etc) will be less than 35% of the total site area, or

• the additional impervious surface resulting from the development will not exceed 50m2 in area, or

• the soil conditions are such that stormwater can be retained and disposed of on-site, but only if the case is established by a geotechnical report, or

• the site is within an established 100-year flood plain and the local drainage system is not adversely affected by lesser storm events.

Stormwater detention systems are to be visually unobtrusive and integrated with site landscaping.

Development must drain via gravity to a Council constructed or natural drainage system, unless drainage to such a system is not possible, in which case stormwater may be retained and disposed of on-site, where it can be demonstrated soil conditions so allow.

Development is to have regard to the Council’s natural drainage systems, drainage easements and public drainage systems and be in accordance with the Council’s draft policy “Drainage Easements and Building over Constructed Public Drainage Systems”.

Note—

Copies of the “On-site Stormwater Detention Technical Specification” and “Drainage Easements and Building over Constructed Public Drainage Systems” can be obtained from the Council.