Updated on DrainWise project

Larry Foster

COLUMN

There are no official council meetings on this week, but there is a citizenship ceremony at the Cosmopolitan Club on Wednesday at 10am. This is a chance to welcome new residents who have applied for citizenship to our special piece of paradise.

At our Assets and Infrastructure meeting last week we had a presentation and update of the DrainWise project. We heard that two of the council’s technicians are working on property inspections in Kaiti, which is the priority area because it has the highest inflow and infiltration rate of stormwater getting into the wastewater network in the city. It is followed closely by Whataupoko.

The inspections include: Inspecting sewer laterals with closed-circuit television (CCTV); smoke-testing for illegal stormwater connections into the wastewater network; identification of on-site stormwater issues; and height and condition assessment of gully traps.

The recent introduction of in-field mobile devices has resulted in huge productivity gains, avoiding the need to come back to the office and manually load each inspection.

Over the last year more than 700 properties have been inspected.

Two more technicians have been employed on a six-month contract to inspect and, where possible, repair any leaking or faulty gully traps. In a three-week period 160 gully traps have been water tested and 90 sealed and repaired.

The property inspections identify faults which lead to a series of notices requesting property owners to fix. The most common is downpipes going directly into the wastewater system, which are required to be removed immediately. Another common problem is gully traps being too low and allowing flood water to enter after heavy downpours.

A series of recent wet weather events have also highlighted the possible existence of some constraints within the wastewater network that could be affecting its performance. As part of the investigations, the Eastern Interceptor — which conveys the main flows from Kaiti, Whataupoko and Mangapapa to the wastewater treatment plant — was inspected near Hirini Street. A large “fatberg” was identified that blocked off about 35 percent of the pipe diameter leading into the siphon across Gladstone Road Bridge.

The interceptor from The Rivers to Peel Street Bridge via Reads Quay was jet cleaned and found to contain a considerable amount of debris that could not be removed. As a result, tenders have been called for cleaning the 3.38km long Eastern Interceptor. When cleaned it will greatly enhance performance and assist in reducing network-related overflows.

A recent inspection of a residential sewer main has also highlighted the ongoing issue of fat build-up. We were shown photos of the inside of pipes that were very clogged with large amounts of fat; even pipes which were totally blocked.

The ongoing message is please do not pour fat down your sink, it will block your wastewater system and also get into our community’s system causing serious problems and costs.

We also heard of the commitment our staff have in trying to prevent the wastewater overflows into our rivers. Whenever there is the likelihood of an extreme weather event, no matter what time of day or night, a certain procedure will kick in. Up to 10 people from the council and Fulton Hogan will be closely monitoring water levels and clearing any excess water from our pipe network in anticipation of a deluge. All our pump stations are computerised, so staff know when the network is at total capacity, and only then is the call made to open the scours into our rivers. It is definitely the last resort. And it is good to see progress being made.

There are no official council meetings on this week, but there is a citizenship ceremony at the Cosmopolitan Club on Wednesday at 10am. This is a chance to welcome new residents who have applied for citizenship to our special piece of paradise.

At our Assets and Infrastructure meeting last week we had a presentation and update of the DrainWise project. We heard that two of the council’s technicians are working on property inspections in Kaiti, which is the priority area because it has the highest inflow and infiltration rate of stormwater getting into the wastewater network in the city. It is followed closely by Whataupoko.

The inspections include: Inspecting sewer laterals with closed-circuit television (CCTV); smoke-testing for illegal stormwater connections into the wastewater network; identification of on-site stormwater issues; and height and condition assessment of gully traps.

The recent introduction of in-field mobile devices has resulted in huge productivity gains, avoiding the need to come back to the office and manually load each inspection.

Over the last year more than 700 properties have been inspected.

Two more technicians have been employed on a six-month contract to inspect and, where possible, repair any leaking or faulty gully traps. In a three-week period 160 gully traps have been water tested and 90 sealed and repaired.

The property inspections identify faults which lead to a series of notices requesting property owners to fix. The most common is downpipes going directly into the wastewater system, which are required to be removed immediately. Another common problem is gully traps being too low and allowing flood water to enter after heavy downpours.

A series of recent wet weather events have also highlighted the possible existence of some constraints within the wastewater network that could be affecting its performance. As part of the investigations, the Eastern Interceptor — which conveys the main flows from Kaiti, Whataupoko and Mangapapa to the wastewater treatment plant — was inspected near Hirini Street. A large “fatberg” was identified that blocked off about 35 percent of the pipe diameter leading into the siphon across Gladstone Road Bridge.

The interceptor from The Rivers to Peel Street Bridge via Reads Quay was jet cleaned and found to contain a considerable amount of debris that could not be removed. As a result, tenders have been called for cleaning the 3.38km long Eastern Interceptor. When cleaned it will greatly enhance performance and assist in reducing network-related overflows.

A recent inspection of a residential sewer main has also highlighted the ongoing issue of fat build-up. We were shown photos of the inside of pipes that were very clogged with large amounts of fat; even pipes which were totally blocked.

The ongoing message is please do not pour fat down your sink, it will block your wastewater system and also get into our community’s system causing serious problems and costs.

We also heard of the commitment our staff have in trying to prevent the wastewater overflows into our rivers. Whenever there is the likelihood of an extreme weather event, no matter what time of day or night, a certain procedure will kick in. Up to 10 people from the council and Fulton Hogan will be closely monitoring water levels and clearing any excess water from our pipe network in anticipation of a deluge. All our pump stations are computerised, so staff know when the network is at total capacity, and only then is the call made to open the scours into our rivers. It is definitely the last resort. And it is good to see progress being made.

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