Building Over Public Sewers

Acceptable Practice (as at June 2007)

1. We prefer not to have the city's public sewers under buildings because of potential difficulties with maintenance and repairs.

2. However, it is generally preferable to construct buildings over sewers than to divert a sewer around a building using multiple manholes.

3. It is permitted to construct buildings over sewers provided:

   1. there is no reasonable alternative for the property owner,

   2. the existing sewer is not greater than 225 mm diameter,

   3. the length under the building is minimised,

   4. one of the following solutions is used:

      1. the sewer is replaced with a PE pipe of equivalent diameter laid within a PVC sleeve of the next largest size or as specified by the Council to facilitate future size upgrading. A minimum  clearance of 200 mm from foundations to the sewer sleeve shall be maintained.

         The PE shall be PE80B of wall thickness equivalent to SDR17 manufactured in accordance with AS/NZS 4130 'Polyethylene (PE) pipes for pressure applications', notwithstanding that the re-laid pipe may be a gravity pipe. Jointing shall be by butt fusion welding in accordance with the requirements of Council's Construction Standard Specification (CSS).

         The PVC sleeve shall be PVC pipe manufactured in accordance with AS/NZS 1260 ‘PVC-U pipes and fittings for drain, waste and vent application’ and to the pipe stiffness value (SN) required for PVC Waste Pipe as listed on Council's Approved Materials web site (refer to: http://www.ccc.govt.nz/webapps/approvedmaterials/frmAPRSearch.asp#Display

         Jointing shall be with rubber ring joints and pipe laying and backfilling shall follow the requirements of CSS."

         OR

      2. there is still access for repairs or replacement without disturbing the building, e.g. high open foundations on poles or cantilevered, with a minimum of 2 metres vertical clearance from ground level and 1 metre horizontal clearance from the sewer.

   5. the Asset & Network Planning Unit is advised of and approves each proposal.

   6. the property owner:

      1. where the pipeline is covered by an easement, requests a waiver letter from the Asset & Network Planning Unit, seeking permission to encroach upon the sewer easement.

         OR

      2. where the development is part of a subdivision, pays the preparation and legal costs of a waiver to the easement document recording the agreement to build on the easement line.