Kūmānu (formerly Nelmac) and the Nelson City Council network. Sewer and stormwater monitoring with HiLo since 2019.
The deployment in numbers
Kūmānu is the operations and maintenance contractor for Nelson City Council’s three waters network. Its wastewater and stormwater team needed a more reliable way to find where stormwater was entering the sewer (inflow and infiltration), one that did not depend on staff being at the right manhole at the right moment during a storm.
“The original way was that we’d have to go out in the rain event, start popping sewer manholes and look at where flows had increased compared to normal,” says Adam, who leads Kūmānu’s inflow and infiltration (I&I) work. “Timing a rain event and actually getting the staff out there to go and manually look was a real chore.”
Kūmānu had trialled radar level monitoring before it came across HiLo. The unit it tested worked, but the price meant only a handful could ever be deployed, which is not enough to characterise a catchment. “HiLo was substantially more economical,” Adam says, “and produced a good quality and reasonably priced product to enable us to get more out there.”
The first deployment covered a catchment with around eight monitors, placed branch by branch where the team suspected inflow. That gave them a continuous level record across a whole catchment, through multiple rain events, without sending staff out to inspect.
Level responses during rain were large enough that word moved through the council, and requests started arriving from other parts of the city. “It just sort of ballooned after that, really.” Kūmānu now runs close to 100 HiLo monitors on the I&I programme, with a further 30 to 40 across stormwater projects.
Continuous data surfaced problems the team had no way of seeing before, and the more it gathered, the more it could identify and resolve.
“We’ve actually increased man hours, because we’re just finding more and more issues,” Adam says. “We have had to take on another staff member to help out.”
The workflow is straightforward. Monitors go into a catchment and stay for several rain events. If the water level response is significant, the team escalates investigation to CCTV pipe inspection, looking for damaged pipe, leaking joints or laterals, and signs of groundwater finding its way into the sewer. Options to remediate are lining the pipe, dig and repair, or replacement. If the I&I response during rain is minimal, that part of the network moves down the list for I&I investigation.
“If there’s a big response, we’ll prioritise it and start looking a bit harder for the sources,” he says. “The more we look, the more we find, and now we’ve got actual data rather than just looking down a manhole and estimating an increased response.”
Kūmānu reviews the full fleet of level sensors roughly every second day, and unusual levels trigger a service request. “It’s usually indicating a blockage, the drainage team can investigate and clear the blockage with a pipe jet cleaner if required.” The same monitors give live assurance during construction: when sewer flows were recently diverted for an upgrade to a major main, the team monitored the receiving sewer main levels closely for capacity issues or overflows.
NCC began monitoring tide gate performance along the Maitai River and found several were not sealing properly, which opened up a chain of cause and effect the team could not have traced without data. Where a tide gate doesn’t seal adequately, tidal water travels up the stormwater pipe, and where that pipe is compromised, seawater leaks out into the ground and can migrate into the sewer if the pipe isn’t fully sealed. After a new modern one-way valve was fitted to a large diameter stormwater pipe, level data and saltwater testing together confirmed the seawater path had closed significantly. The council’s CBD saltwater I&I reduction programme, which uses level sensors to look for tidal influence, has contributed to an improvement in salinity infiltration that is measurable at the treatment plant.
“When you start getting data, you start having a deeper understanding of what’s happening in the network,” Adam says.
As the rollout grew, Kūmānu needed to assess parts of the sewer network where gas testing was returning readings of potentially explosive gases. The LS1-R units in the ground at that stage were not certified for explosive atmospheres, so placing any battery-powered device into those manholes raised a health and safety question.
The council ran its own process and moved to requiring intrinsically safe units where gas was likely present in the network, based on various studies. A map was produced of Nelson on a traffic light basis: red zones around industry required mandatory intrinsically safe devices, while green zones, generally located in residential areas, are low risk, although gas detection at the time of install is still required.
HiLo’s IECEx certified monitors were developed in time to meet the requirement. “The evolution of the intrinsically safe model was a game changer, we were going to have to potentially start trying to source explosive rated sensors, and HiLo came to the party on that as well,” Adam says. With the certified units now at the same price point, NCC fits them across the network as standard, commissioning from the surface with a bracket so nobody enters a manhole.
Through the programme’s growth, Adam and the team at Kūmānu have relied on HiLo’s ongoing support. “I found the HiLo team really good to work with, and good at supporting us the whole time,” Adam says. “I can pretty much just call up and get an answer to my question, or someone will go away and come back to me. They’ve been really good at adapting and changing their software to get the required results.”
Kūmānu has since introduced other organisations to HiLo. “We’ve recommended HiLo to quite a few places now, and everyone seems to be pretty happy. As far as value goes, it’s pretty hard to beat HiLo from what we can tell.”
Nelson is not a Tier 1 metropolitan utility, and Kūmānu did not begin with a network-wide rollout or a large capital line. It began with eight monitors in one catchment and let the findings justify the next step. Any council under pressure on overflows and ageing pipes can work the same way: select a problem catchment, monitor it across a few rain events, and use what comes back to decide where the money goes.
Kūmānu runs more than 130 HiLo radar level monitors across the Nelson sewer and stormwater network, and now standardises on the LS1-R Plus. The LS1-R Plus is IECEx certified (Ex ia IIB T4 Ga) for explosive atmospheres, rated IP68, and built around 60GHz pulsed radar with HiLo ADA™ (Adaptive Detection Algorithms), the intelligence layer that interprets the radar signal and adapts to conditions inside each manhole to identify the true liquid surface. Monitors are commissioned from the surface via the HiLo mobile app and report to HiLo Live. HiLo is NZ owned, designed and engineered.
When you start getting data, you start having a deeper understanding of what’s happening in the network.
IECEx certified, IP68 radar level monitor for sewer manholes, stormwater and surface water networks.
View the product →Talk to the HiLo team about monitoring a catchment across a few rain events and using the data to decide where to investigate.