Dunedin City Council (website) on Stormwater:
Stormwater is rain or snow runoff that does not soak into the soil.
When an area is developed, stormwater generally increases due to runoff from impermeable surfaces (eg roofs, roads, carparks, or compacted soil). It flows naturally from higher to lower ground, and ultimately discharges into natural watercourses such as wetlands, creeks, rivers or the sea. Land development results in the creation of both private and public stormwater systems, which collect and transfer stormwater to lower ground more efficiently. The public stormwater system is a network of drains, gutters, pipes, mud tanks, detention ponds, stormwater reserves and other associated infrastructure.
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At other threads (here and here), contributor JimmyJones has cited the South Dunedin Integrated Catchment Management Plan (ICMP) to draw attention to the actual or perceived state of the stormwater pipes at South Dunedin. He believes the type of pipeways and the deteriorating condition of the pipes contributed to the June 2015 South Dunedin “flood event”, and will require budgeted upgrade.
But is the South Dunedin ICMP correct about the underground pipes and their condition?
Largely, the ICMP was a desktop assessment carried out by consultants for the Dunedin 3 Waters Strategy. Namely, Opus International Consultants and URS New Zealand (now trading as Aecom) in association with Dunedin City Council.
South Dunedin ICMP – Integrated Catchment Management Plan
● Sth Dunedin ICMP (PDF, 11.1 MB)
● Sth Dunedin Mapbook (PDF, 12.0 MB)
Read more about the 11 ICMPs for Dunedin here.
DCC says ICMPs are used for planning and management of the stormwater system. For each stormwater management area, or catchment, issues are identified and prioritised, and solutions are identified and implemented. The ICMPs are mainly in the metropolitan Dunedin area (including Mosgiel and Port Chalmers). They inform investigation and planning decisions and help focus council priorities for future operational and capital works. Implementing the ICMPs is also a key requirement of DCC consents to discharge stormwater into the coastal marine area. Further information is available on the Stormwater monitoring page, see also the Stormwater responsibilities page.
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The Pipes at South Dunedin
Local water and drainage experts familiar with the stormwater system say:
Received.
Sat, 18 Jun 2016 at 10:52 a.m.
The South Dunedin ICMP report has been read, it’s “ok”. But it’s also described as “…glossy and costly for the consultant(s). Basically, such reports tell the Council stuff they neither read nor understand, but would have mostly been trivial knowledge (where accurate)” to local experts familiar with the design and day-to-day workings of the stormwater system.
“You can believe any part of [the ICMP] or not. It’s a desktop study, which speculates on pipe condition. Robinson and Hendry have read it and obviously don’t agree. Pipes last for an eternity with limited maintenance (other than blockage removal) provided there isn’t ground movement or corrosion (these pipes are concrete).”
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Listener, June 11-17 2016, pp22-29 (not yet available online):
[excerpt —click to enlarge]
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ODT 13.2.16
“Mr Hendry believed South Dunedin’s infrastructure, which he spent six years helping build as a surveyor in the 1960s, would have been good enough to prevent much of the damage had it been properly maintained. […] My view is that these people out here, a lot of them have got nothing. Now they have got a hell of lot less. It’s not fair on them. Nobody’s come out and said ‘we were wrong. Something wasn’t done right’.”
█ Come to the Public Meeting in South Dunedin on Monday evening, hosted by the South Dunedin Action Group.
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Related Posts and Comments:
17.6.16 So we’re going to play it this way #SouthDunedinFlood
● 16.6.16 Public Meeting: South Dunedin Action Group #AllWelcome
10.6.16 “Civic administration” reacts to hard hitting Listener article
● 6.6.16 Listener June 11-17 2016 : Revisiting distress and mismanagement
● 4.6.16 Johnstone review … DCC Infrastructure Services meeting 26.4.16
3.6.16 DCC —godsakes, how did it get to this? #flood #property damage
● 19.5.16 Johnstone review of 2nd DCC report #SouthDunedinFlood
29.4.16 Vandervis emails batch 2 #Dunedin #infrastructure #flood #mudtanks
27.4.16 Vandervis emails batch 1 #Dunedin #infrastructure #flood #mudtanks
27.4.16 DCC meeting and apology NOT Enough— #SouthDunedinFlood
20.4.16 DCC Politics : Release of Infrastructure Report #SouthDunedinFlood
14.4.16 South Dunedin flood risk boosters #ClimateChangeCrap #PissOffPCE
31.3.16 DCC: Infrastructure report 2 pending —Mudtanks & stormwater…
● 8.3.16 Johnstone independent review of DCC report #SouthDunedinFlood
2.3.16 DCC compels extensions on LGOIMA requests #SouthDunedinFlood
26.2.16 Mudtanks and drains + Notice of Public Meeting #SouthDunedinFlood
21.2.16 DCC infrastructure … report (30.11.15) subject to ‘internal review’ only
● 13.2.16 South Dunedin Flood (3 June 2015): Bruce Hendry via ODT
4.2.16 2GP commissioner appears to tell Council outcome… #hazardzones
4.2.16 Level responses to Dunedin mayor’s hippo soup #Jun2015flood
30.1.16 DCC Rates: LOCAL CONTEXT not Stats —Delta and Hippopotamuses
● 25.1.16 DCC: South Dunedin Integrated Catchment Management Plan (ICMP)
19.1.16 Listener 23.1.16 (letter): South Dunedin #Jun2015flood
16.1.16 NZ Listener 16.1.16 (letter): South Dunedin #Jun2015flood
14.1.16 ‘Quaking!’ Dark day$ and tide$ to come #Dunedin #Jun2015flood
10.1.16 Infrastructure ‘open to facile misinterpretation’…. or local ignore
5.1.16 Hammered from all sides #fixit [dunedinflood Jun2015]
24.12.15 Site notice: posts removed
● 3.11.15 South Dunedin Flood | Correspondence & Debriefing Notes released by DCC today #LGOIMA
Downloads:
● Kerr, Elizabeth LGOIMA Correspondence Hendry and Williams 2015
● Kerr, Elizabeth LGOIMA Flood Debrief Notes 2015
█ For more, enter the terms *flood*, *sea level rise*, *stormwater*, *hazard*, *johnstone*, *hendry*, *south dunedin action group*, *debriefing notes* or *listener* in the search box at right.
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Posted by Elizabeth Kerr
Election Year. This post is offered in the public interest.
What if? Dunedin... 
Copied from another thread:
JimmyJones
2016/06/18 at 6:17 pm
So far the experts that believe that there were no problems with the stormwater pipes are: Neil Johnstone, Bruce Hendry and Darrel Robinson. On this one point, all of them are wrong. I say that the network of South Dunedin stormwater pipes was, and is, substandard and this was a contribution to the 2015 flooding and is a continuing risk for when the next big rain comes. These people have done good work and I have no other criticism.
I believe that the pipes are buggered because the South Dunedin ICMP tells me so and so does the DCC Water And Waste Manager and the DCC CEO.
The ICMP was prepared for the DCC by URS New Zealand Ltd. Each of you will need to judge for yourself if the ICMP is a credible source of information. I have given you some relevant quotes from it on this page (June 17, 2016 at 6:28 pm) or you can read the pdf »HERE«
Most of the time of the DCC Infrastructure Services Committee meeting (ISC) 27/4/16 was spent not discussing the mud-tank cleaning nor the badly designed pump screen, they were talking about the bottlenecks in the pipes and what to do about the areas with low levels of service and about the cost of upgrading the network and why they can’t afford it in a time of “austerity” and why they have no plans to upgrade the bad areas. The point is that Council staff and councillors are convinced that the pipes are buggered. I am with the DCC on this one. Also they were motivated to keep the substandard pipes a secret so that people didn’t discover that they didn’t know what they were doing, so they have nothing to gain from making things up.
Johnstone, Hendry and Robinson tell us that the pipes were upgraded recently (1960~) and so everything should be fine. This claim contradicts the ICMP which tells us that 46% (by length) of South Dunedin stormwater pipes were installed in 1940 and before (Table 4-3). The ICMP is credible because it has detailed information about how old the pipes are and where they are. Some pipes are good, some are not. The net result is a low level of service for the renters and ratepayers of South Dunedin.
From what they have written, Johnstone and Hendry show no sign of being aware of the ICMP and they seem unfamiliar with the content of the ISC meeting. Their claims about the pipes should not be accepted until they have properly assessed the South Dunedin ICMP and the 27/4/15 ISC (YouTube video). Don’t believe me, don’t believe them, decide for yourself.
JimmyJones, how would the two council staff you mention know what condition the South Dunedin pipes are in ? I so rarely see them in mudsuits excavating the underbelly of the catchment’s stormwater system. Surely they aren’t relying on a desktop assessment or have they more current information from contractors Fulton Hogan and City Care than we the public have ?
Or, have the two staff more direct knowledge than ex council staff responsible for designing and installing the current system and its network connections ?
So many questions :)
Received.
Sun, 19 Jun 2016 at 11:42 a.m.
Neil Johnstone replies:
Reliance on a management plan to define the actual condition of underground pipes would be unwise, particularly if the sole determining parameter is pipe age.
For the record though, the ICMP document that the anonymous JJ relies on indeed shows that 46% of South Dunedin’s pipes were installed before 1940 (but none before 1900).
The ICMP also shows (but not referenced by JJ) that 54% of the entire city’s pipes were installed before 1940, including 11% before 1900.
If there were a credible correlation between pipe age and failure, then South Dunedin would have less to be concerned about than much of the rest of the city. It had, of course, much more to worry about than the rest of the city in June 2015. The real reasons for the June 2015 South Dunedin disaster lie elsewhere and are steadily being revealed.
Neil Johnstone: The only reason I mentioned the age of the pipes is because the ICMP (South Dunedin) directly conflicts with what Darrel Robinson said in the NZ Listener. I don’t know exactly how the ICMP performance measures were estimated, but the the age of the pipes will be only one factor. Other factors mentioned in the ICMP are breaks, cracks, under-sized pipes, internal roughness and siltation. I agree that pipe age is not the only factor.
The ICMP says this: “The current level of service for the network in this catchment varies across the catchment, but is approximately equivalent to a 1 in 2 yr ARI rainfall event”. It is quite detailed and it mentions a number of locations affected by hydraulic bottlenecks. The W&W Manager reports that there are ongoing problems which result in complaints from the public. She is aware that South Dunedin suffers from low levels of service (ISC 27/4/16) – she quantifies this as a one in two year capability and sometimes as a one in three-year capability.
If you disagree with the ICMP (2011) and the W&W Manager (2016) then I would like you to give better reasons, with quantified estimates of the performance. I can think of two good reasons why the performance would have decreased since 1960 – because of more hard surfaces the effective catchment area has increased with no corresponding upgrade of the network, and the DCC traditionally under-funds depreciation which will in time be guaranteed to result in low levels of service.
You are quoted as saying “pipes don’t work that well when they’re blocked at both ends, even when they’re brand new“, but they also don’t work when they are also blocked in the middle. Because parts of the system are relatively new, should not lead you to believe that the overall performance is satisfactory – see ICMP fig. 4-14 for where the old pipes are and fig. 4-17 for locations of reported flooding (up to 2011). Some evidence of the constraint of the pipe network can be see from the DCC November report, where before the screen became blocked, the pump flow did not reach its full capacity – even though the pipes were fully surcharged. For your information, I have no qualifications or experience in this area.
While I don’t understand underground hydraulics, ‘undersized pipes’ is dilly. How can you put in the Wrong Sized Pipes if your profession is Pipe Installer?
Conjecture is a smoking pipe. –Big Chief
Received.
Sunday, 19 June 2016 at 10:52 p.m.
Neil Johnstone:
I have read Jimmy Jones’ lengthy contributions of the last day or so. I can certainly support, even without knowing his true identity, his ultimate conclusion that he indeed has no qualifications or experience in the area. My final advice is that “Jimmy” should front at tomorrow’s meeting and engage the experts in person, and in full public view.
Neil Johnstone: your work has been very helpful and I agree with you on everything except this one point. I have pursued this point because the DCC is likely to continue the freeze on stormwater improvements if they believe that the citizens are unaware of the buggered pipes or don’t believe there is a problem. The DCC has admitted this is a problem – something they normally try to avoid. The people of The Flat deserve a 1 in 10-year rain event capability and dry floors with a 1 in 50-year event as exists in most first-world cities. This should be the goal of the SDAG.
My old desk
does an arabesque
on the Catchment Management Plan
You better check
the joints and nicks
on my integrated desk
Having revisited the ICMP Three Waters Report, I come irrevocably to the conclusion that the report is an unabridged ‘consultants’ assessment obviously commissioned by the DCC. Zone by zone it is repetitious and reiterates the ‘mantra’ of the DCC (compare with DCC referencing to the June 2015 South Dunedin Flood).
It makes disputable claims, not by lay people, but disputable by the likes of experts Neil Johnstone and former city surveyor engineer Bruce Hendry who was directly involved in the 1960s upgrade of the South Dunedin stormwater system.
The consultant’s report was strong on recommendations for mitigation, including the accommodating of the contentious ‘Climate Change’ which in itself is based on no empirical data or evidence in itself. This all brings the opportunity of further work in developing design and execution of recommended upgrades, whether needed or not.
All this reinforces my long held contention that the city badly needs to revert to installing its own engineering department headed by an accredited Chief Engineer and staff capable of designing, executing and maintaining the city’s infrastructure.
I don’t recall in former times public scandals (yes, that is what it is) of amateurish administration of outside contractors failing to carry out basic preventative maintenance of simple tasks like cleaning of mudtanks and inlet pump screens. Basically incompetence by bureaucracy, costing many innocent citizens untold costs and anguish.
A general note:
The following documents (strategy and management plans) predate the 3 June 2015 South Dunedin flood event.
The Three Waters Strategy (aka Three Waters Strategic Direction Statement) was approved by Council on 01 February 2010. Link
“The 3 Waters Strategic Direction Statement is intended to provide a generalised set of priorities and approaches for use in all areas of water, wastewater and stormwater management undertaken by the Dunedin City Council.”
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The ICMP Summary Report is not dated. [Opus, URS, DCC]
Executive summary (PDF, 2.8 MB)
The South Dunedin Integrated Catchment Management Plan 2010-2060
Contract No. 2993 Dunedin 3 Waters Strategy is dated 23 November 2011. [Opus, URS, DCC] (PDF, 11.1 MB)
The Other 3 Waters, by the people who did “Twin Rivers”, Banks Peninsula.
The First Water
Waitaki. Geographical boundary. Saved from canalling. Fellahin upset.
The Second Water
Taieri. Volatile, but enough about her. A remarkable rain stays on the plain. Leveed State Highway called ‘Flood Free’.
Third Water
Mataura. Maligned, sylvan waterway, called ” Up The Mataura”. May now be The Clutha. Blamed for everything to do with St Clair beach, some distance NE up the Coast.