DCC borrowing $60 million for “Surface Treatments” from George St. to the Exchange, is being ‘justified’ by underground pipe renewals.

Screen Shot 2020-04-30 at 10.39.59 PM

I am all for spending on needed deferred maintenance of pipes and cables, but the $60 million still planned for Surface Treatments is unjustifiable.

From: Lee Vandervis <lee@vandervision.co.nz>
Date: Wednesday, 29 April 2020 at 10:11 PM
To: <jared.oliver@dcc.govt.nz>
Cc: "Council 2019-2022 (Elected Members)" <council.2019-2022@dcc.govt.nz>, Sue Bidrose <Sue.Bidrose@dcc.govt.nz>, Sandy Graham <Sandy.Graham@dcc.govt.nz>, Simon Drew <Simon.Drew@dcc.govt.nz>
Subject: Discussions with ex DCC water manager Darrel Robison

Hi Jared,

Thank you for your engineering insights into the George st water systems today.

I have had a few discussions with Darrel on the subject recently, as it applies to the George st upgrade proposal.
Darrel was quick to point out that initially doing up the pipe-work while we were at doing up George anyway made some sense, but that this sound argument had lately morphed into ‘we have got to do up the pipe-work now so we should do the George st upgrade while we are at it’.

But to the technical stuff as below, Darrel seems to have a more optimistic view of pipe maintenance needs than I have heard recently. It was interesting to have confirmed that some brick/tile drains built by the Romans are still in use in London!

Looking forward to your further advice, and if it is similar to what Darrel lays out in detail below, including a block-by-block analysis:

From: Darrel Robinson <dlrobinson@xtra.co.nz>
Date: Saturday, 18 April 2020 at 1:45 PM
To: Lee Vandervis <lee@vandervision.co.nz>

Comments of Wastewater, Stormwater and Water Mains in George Street from Octagon to Albany Street

Hi Lee

I have spent a bit of time looking at the DCC Water Services Maps and supplementing / verifying that information from my own recollections.  The maps themselves were put together by a diligent team who had excellent base maps which were created in the 1960’s to start with so I expect them to be extremely reliable.  However not all data would have been available to them and thus there will be some information gaps, particularly on repair data.

The extent of the proposed George Street upgrade I understand to be from the Octagon to Albany Street so will comment on the services on a block by block basis.

An area of significant risk of needing repair are the stormwater and wastewater drains serving individual premises.  These are owned by the properties they serve and thus are not the responsibility of Council.  There is much greater risk of structural failure on one of these drains than of the wastewater / stormwater sewer they connect to.  They may also be older than the sewer connected to as this area was originally served by a combined sewer system (both wastewater and stormwater in the same pipe) and it was only in the 1990’s that separation of these combined sewers was completed.  In the case of George Street, the separation work immediately preceded the George Street upgrade programme those almost 30 years ago.  I know that there is an investigation underway within Council staff about assuming ownership of these sections of private drains (and also watercourses) but am unaware of where that work has got to.  The same issue does not really apply to water services as the service from the main to the property stop cock is part of the Council’s asset and it is only the short (300 mm) section of the service from stopcock to the street boundary that is privately owned.  Given that these services are quite shallow, that does not pose an undue risk.  However the vast majority of water repairs are on water services so I would advocate that the services be replaced as part of any street upgrade.

There will be a number of fire services from water mains and connected to building fire sprinkler systems.  I am pretty sure that those too are owned by the property served. You would need to check on that.

Before a block by block comment, a general comment on the 300 mm water main and the 900 x 600 stormwater sewer running along the George Street centreline.

The 300 mm watermain is of cast iron material and is the City’s first main and dated from the 1860’s and installed as part of the system that followed the construction of the Ross Creek Dam and Reservoir.  It has been very reliable to the best of my knowledge.  When the concept to upgrade George Street along with the replacement of services was first mooted, I thought quite a bit around “if it was my call, would I replace the 300 mm watermain and the 900 x 600 mm stormwater sewer?”  I didn’t reach a firm position and to me, it is a very tough call to make.  To some degree, I guess it comes to the Council’s tolerance of risk which I perceive to be quite low.

Both are old but neither seems to give any significant trouble so it’s quite a big call to make.  The length of street being redeveloped is in the order of 900 metres and at a rate of say $1500 / metre on the stormwater and $1100 / metre on the water, that represents a spend of $2,340,000. To that must be added valves, hydrants, manholes, traffic management, engineering fees, and other sundry items so I would suggest the final figure would approach $3,500,000.  So quite a big spend if it’s not actually necessary.  To me, before making a decision, a robust engineering assessment of condition needs made.  Currently, a lot of emphasis seems to be placed on an asset’s age as an indicator of condition.  Sound engineering judgement has always been a fundamental input to sound asset management practice but it seems that element has been given reduced importance in the modern application of asset management.  Nothing can replace sound engineering judgement.

The 900 x 600 mm stormwater dates from the 1870’s and was part of the original drainage scheme for the Central City.  The sewers are egg shaped (pointed end down) and constructed of brick.  The brick was source from local brickworks and thus were of varying quality.  To counteract wear, the invert of the pipe was a shaped ceramic tile set in to the brickwork.  In most cases, the brickwork has not given rise to much in the way of structural issues; the issues are more cosmetic.  I would have thought by now that any structural issues would have emerged.  TV inspection surveys were done in 1970 and that showed the lines were generally in good condition.  Any that were not in good order were progressively relayed with concrete pipe or lined with plastic liners.  The pipes are hugely oversized so there is no issue relating to capacity.  A further inspection in the 1990’s showed little if any degradation in most lines.  The exception was the line down St Andrew Street and with it being quite shallow and the level of heavy traffic, significant cracking and structural deformation had taken place.  It has since been replaced. There will also be gas pipes in George Street but I doubt if they were still in service.  Those not in service were sold to Telecom so I suspect they are now part of the Chorus asset.

There are extensive ducts for phone and electricity cables.  In the case of phone ducts, they are massive – probably 6 pipes high by 6 pipes wide so they do take up a lot of space.  I recall they were laid near the western kerb.

So now to comments block by block.

Octagon to Moray Place.

  • Water.

There are 3 water mains in this block

  • 300 mm dia cast Iron main dating from 1860’s on eastern side of carriageway – no known faults or repairs.
  • 50 mm dia rider main in western footpath – no repairs recorded. As this main is so small, replacement is recommended if it is not in polyethylene pipe.
  • 100 mm main in eastern footpath (cast iron) constructed 1939 in eastern footpath – 2 repairs recorded, I at Bath Street and the other at the Octagon.
  • 900 x 600 mm brick egg shaped stormwater sewer laid in 1874 – thought to be in reasonable condition and no knowledge of faults. The backup fibre optic cable from the Civic Centre computer system to the Civil Defence basement is attached inside this pipe from opposite the Civic Centre George Street entrance and heads south.
  • 150 dia stormwater lines laid as part of the George Street upgrades of 30 years ago. These are shallow and will be in good condition.
  • Wastewater
  • The only waste water service in this block is a short 150 dia concrete line serving the Civic Centre and runs from Moray Place to the Civic Centre northern boundary. It was laid in 1982 and will be in good condition.

Moray Place to St Andrew Street

  • Water

Again 3 mains in this block.

  • 300 mm dia cast Iron main dating from 1860’s on eastern side of carriageway – 1 repair in the St Andrew Street intersection recorded. I am also aware of anecdotal evidence of a repair outside the Westpac Bank.
  • 100 /150 mm main in western footpath. The cast iron section running north from Moray Place dates from 1938 and there are no repairs recorded.  The 150 mm section near St Andrew Street is in asbestos cement pipe (laid 1966) again has no repairs recorded but should be replaced as asbestos cement pipe is now recognizes as having a much shorter life than other materials.
  • 100 mm main in the eastern footpath is in cast iron pipe, dates from 1938 and repairs are recorded near Blacket Lane and 2 repairs near Moray Place.
  • Stormwater
  • 900 x 600 mm brick egg shaped stormwater sewer laid in 1874 – thought to be in reasonable condition and no knowledge of faults.
  • 150 dia stormwater lines laid as part of the George Street upgrades of 30 years ago. These are shallow and will be in good condition.
  • There is a 150 mm concrete wastewater sewer for most of the block and joining the St Andrew Street system. The sewer dates from 1989 and is most likely to be in excellent condition.

St Andrew Street to Hanover Street.

  • 300 mm dia cast Iron main dating from 1867 on eastern side of carriageway. No repairs recorded
  • 150 mm asbestos cement / 100 mm cast iron in western footpath. The asbestos cement main was laid in 1966 and should be replaced.  The 100 mm cast iron section was laid in 1939 and there are 2 repairs recorded.
  • 100 mm cast iron main in eastern footpath (1938) and 2 repairs are recorded at the St Andrew Street intersection.
  • 900 x 600 mm brick egg shaped stormwater sewer laid in 1874 – thought to be in reasonable condition and no knowledge of faults.
  • Numerous short sections of 150 mm PVC pipe laid in 1990 as part of the George Street Upgrade. They are shallow and should be in excellent condition.
  • 150 mm PVC wastewater sewer in the carriageway laid in 1988. Should be in excellent condition.

Hanover Street to Frederick Street.

  • 100 mm cast iron (1939) in western footpath. 3 repairs recorded.
  • 300 mm dia cast Iron main dating from 1867 on eastern side of carriageway. No repairs recorded.
  • 100 mm cast iron main in eastern footpath. Laid 1939 and 7 repairs are recorded.
  • 900 x 600 mm brick egg shaped stormwater sewer laid in 1874 – thought to be in reasonable condition and no knowledge of faults.
  • 750 mm concrete pressure stormwater sewer in carriageway laid 1928. No knowledge of any issues with this sewer.
  • 150 mm PVC stormwater sewers on both sides of road laid in 1990. These are shallow and should be in excellent condition.
  • 150 and 225 mm pipes, mainly ceramic, laid in 1988 and should be in excellent condition.
  • Also there is an old (1915) 100 mm wastewater sewer crossing part of the carriageway near London Street. Given its age and being only 100 mm, it should be renewed in 150 dia pipe.  Not a big job.

Frederick Street to Albany Street.

  • Water
  • 300 mm dia cast Iron main dating from 1867 on eastern side of carriageway. No repairs recorded.
  • 100 mm cast iron main in eastern footpath. Laid 1939 and 1 repair recorded.
  • Stormwater
  • 900 x 600 mm brick egg shaped stormwater sewer laid in 1874 – thought to be in reasonable condition and no knowledge of faults.
  • 150 mm pipes from 3 lanes on east side. All are 1990’s and thus should be in excellent condition.
  • 225 mm concrete pipes laid 1996. Should be in excellent condition.
  • 150 mm pipes from 3 lanes on east side. All are 1990’s and thus should be in excellent condition.

I hope this information is of use to you.  After you have had a read, perhaps you could give me a call with any questions.

Best wishes

Darrel.

 

This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s