Retaining Wall Drainage in Gosford and across the Central Coast

Two separate things sit behind a retaining wall: the water it has to move, and whatever Council's buried pipes are doing nearby. A wall's drainage must never redirect water or sediment onto a neighbour's land, and it must never obstruct an overland flow path. Building near a Council sewer or water main carries its own clearances and its own fee.

Call (02) 4326 8289

What retaining wall drainage in Gosford and across the Central Coast actually involves

Any retaining wall or unsupported earthworks must be designed so surface water is not redirected onto adjoining land. Council's floodplain chapter says overland flow paths must not be obstructed by retaining walls. Where a property is burdened by a stormwater, water or sewer easement, Council will generally not allow excavation or filling inside it.

Near a Council sewer or water main

Backyard sewer mains can be as shallow as 450 mm, so ask Council for the depth and location before you dig. Keep at least 1.5 m clearance to the centre of a sewer manhole or lamphole, and do not build within 3 m of a water main without Council's approval. A wall within a sewer main's zone of influence must be certified by a practising engineer as self-supporting. Where Council needs to check your plans against its pipes, its fee for that assessment is A$178.14, with no GST. The clearances are from Council's June 2014 guide for the former Gosford City Council; the fee is from its 2026-27 schedule.

A black corrugated drainage pipe laid in gravel along the foot of a block retaining wall, with a bank of soil above it — retaining wall drainage, Gosford and the Central Coast. Illustrative example.

Before you dig, and a tree in the way

Lodge a free Before You Dig Australia enquiry before any digging. Before removing or pruning a tree to build or replace a wall, check with Council whether you need approval: its fee for a Vegetation Works Permit on private land is A$245 for two trees or fewer, plus A$129.50 for each extra tree, excluding GST, and Council defines a tree as 3 m or more high, or with a trunk 75 mm or more thick measured 1.4 m above the ground. The main page has the licence and approval lines.

Photograph where water leaves the site before the wall goes in: it is the line a neighbour's complaint will be measured against.

A grey drainage pipe coming out of a rendered retaining wall and dripping onto a grated drain pit set in paving — retaining wall drainage, Gosford and the Central Coast. Illustrative example.

Retaining wall costs and rules check