Council is planning to take a pro-active approach to the management of Infiltration and Inflow (I&I) within our wastewater network.
Inflow and infiltration refers to rain water and ground water that enters the sewer (wastewater) system.
As part of our Asset Management Plans, Council is setting aside funds to undertake I&I studies, and subsequently target rectifying defects found to reduce the amount of unnecessary stormwater and groundwater the wastewater plants have to treat as well as reducing the amount of rain water and ground water entering the sewer system on private property to limit overflows.
Inflow is stormwater that enters directly into the sewer (wastewater) system. The cause is low gully traps, illegal downpipe connections to the sewer, cracked or damaged pipes.
Infiltration is stormwater that seeps into the ground and enters the sewer system through pipes and connections. The cause is connection defects, cracks and joints in the pipes.
During heavy rain, the sewer network starts to fill with stormwater as a result of inflow and infiltration. Excess water in the sewerage system can cause it to back up and overflow sewage into homes and the environment.
The first area to study is Otane - planned for Mid 2019, click the drop down link below for greater detail.
The following Water NZ guide on Infiltration and Inflow is the best practice guide for controlling I&I : https://www.waternz.org.nz/Folder?Action=View%20File&Folder_id=394&File=II%20Manual%20Volume%202.pdf
A project flyer was delivered to all Otane households in early May 2019.
Council has engaged CCTV Operator - Draincare to undertake the work to CCTV all mains and laterals to understand the additional flows as outlined below.
Works is expected to start Mon 20th May 2019.
The purpose of this program is to manage and reduce inflow and infiltration (I&I) into the wastewater network to assist with compliance with the resource consent, free up capacity in the pipe network and assist with the development of CHBDC’s capital works programmes.
Council is currently finalising the scope of works for the I&I study to be commissioned in Otane.
Shortly home owners will receive a letter outlining the proposed works.
The wastewater network operated by CHBDC for the provision of wastewater services to the residents of Otane consists of the following assets:
7.0 km of gravity wastewater mains
1.9 km of service laterals
270 wastewater connections
83 wastewater manholes
1 wastewater treatment plant
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