Horowhenua District Council has been granted a new 25-year consent for discharging treated wastewater on land at The Pot, at the end of Hokio Sands Rd, with strict conditions dealing with the level of nitrate-nitrogen ending up in the Waiwiri Stream and cultural safeguards agreed to with local iwi and hapū.
The council has reached agreements with three hapū of Ngāti Raukawa on conditions as well as with Muaūpoko Tribal Authority and the Maūpoko Lands Trust, satisfying the RMA commissioners demand for dealing with cultural issues arising.
These agreements resulted in being granted a 25-year consents rather than the 15 years the commissioners initially proposed due to "lack of conditions dealing with cultural effects in the original application."
The Pot was established in 1987, and became fully operational in 1991. Treated waste water from the wastewater plant in Levin is pumped to The Pot and is irrigated on land after settling in a pond.
This method has reduced nitrogen discharge into surround groundwater by a third. Solids from the wastewater plant settling ponds have gone to the Levin landfill since 2011.
Levin uses secondary treatment of wastewater. Primary treatment means coarse screening, while secondary treatment involves use of clarifiers, trickling filters, UV light, and tertiary treatment would include nutrient stripping, which is very expensive and redundant because of land based discharge of secondary treated wastewater here, the RMA Hearing Commission's decision said.
The Pot comprises of 110ha of land in four parcels: two owned by Muaūpoko Land Trust (MLT) and two by the council. MLT has signed a 40-year agreement to lease their land to HDC for wastewater disposal.
The Pot's pond is 7ha, where treated waste pumped 7km from the plant to settle and pumps 8000 cubic metres a day with an average dry weather flow of 6400 cubic metres and a maximum inflow of 27,000 cubic metres.
Eighteen per cent of that irrigated water seeps through the base and sides of the pond into surrounding groundwater, expert evidence showed the commissioners.
Their decision describes what is going on at The Pot:
"Irrigation of the remaining 82 per cent goes on 40ha of land. Between 73-91 per cent of the rainfall and the irrigated wastewater is estimated to drain down into the underlying groundwater.
"Four lateral drains capture water that infiltrates to shallow groundwater below the site and discharge into the Waiwiri Stream, which is estimated to be the final receiving environment for about 80 per cent of the treated wastewater that enters the groundwater at The Pot.
"Groundwater also receives this water resulting in a plume that is slowly moving towards the sea under the land below Hokio A Trust land, which is expected to reach the coast in 15 years... making its total travelling time between 40 to 50 years, because of the flat hydraulic gradient of the land the fine-grained sand it travels through."
Consent is now given for continued use of the Pot for the next 25 years but with significant modifications to the existent regime:
For example the land use will increase from 40.5ha to 60ha, and that includes 5ha of pine trees and 10ha of kanuka/manuka trees.
The irrigated area to be increased from 8ha to 20ha, with reduction from 100mm to 20mm in application rate and an increase of irrigation passes each year from 52 to 92 days. The annual application volume is to increase from 1.89 to 2.24 million cubic metres a year. The total mass loading of nitrogen and phosphate discharges to land will increase but the volume per unit will decrease, because a larger area is used.
Also proposed are protection of an existing kanuka stand, rehabilitation of some of the wetter areas to attempt wetland restoration and planting on the north bank of the Waiwiri Stream to better shade the stream to try and inhibit in stream macrophyte growth.
Initially the commissioners considered a council's expert's statement that the "effects of the discharge to land at The Pot were no more than minor effects, "unfounded." Expert advice from various sources swayed them, however.
"We concluded that the discharges from The Pot are having no more than minor effects on the Waiwiri estuary, and are having and will continue to have less than minor effects on open coastal water."
Some of the cultural conditions agreed to with iwi and hapū include: faecal source tracking to be carried out to ensure E.coli bacteria of human origin are not detected in the Waiwiri Stream, MTA and Ngāti Raukawa are invited to prepare a cultural health monitoring protocol and undertake cultural health monitoring, iwi and hapū to be invited to develop wānanga and karakia options to restore cultural connections.
"We are satisfied the relevant tangata whenua groups with customary rights and interest in the area of the application are represented by the three parties who did come to an agreement on conditions with HDC".
Enhancing the mauri of the Waiwiri Stream, ensuring the role of MTA and Ngāti Raukawa haū as kaitiaki is enhanced and that the concept of whanaungatanga is implemented – will "certainly be a challenge for the council to meet," they wrote.
But they are "encouraged by the significant commitment demonstrated by both the applicant and tangata whenua to working together."
They note the only "adverse effects of significant concerns was that elevated levels of in stream nitrate-nitrogen due to The Pot discharges could have toxic effects on fish in the Waiwiri Stream," pointing out that a 95 per cent protection threshold is set for the Waiwiri Stream in the regional council's One Plan.
The council wanted stream site 4 to fall below the national bottom line of nitrate toxicity during the first 10 years after the consent comes into effect. Commissioners have added a condition, however, that this cannot fall below Band C for those first 10 years.
They were persuaded by expert advice from Dr De Luca for the applicant and Dr Giles, a s42A reporting officer contracted by the regional council, that in the estuarine sediments all volatile and semi-volatile organic compounds were below detection limits, that nitrogen concentrations were very low and phosphorous concentrations were low. It is unlikely that any faecal contaminants of human origin are present.
"Any discharges attributable to The Pot would be readily diluted in the open coast receiving environment, and no measurable effects on water quality would occur. The experts agreed that effects on shellfish presence or absence, or shellfish health are 'highly unlikely' to result from The Pot discharge.
"When it does the rate of discharge is estimated to be only 250 litres per day per lineal metre of beach, which is miniscule. Such a discharge could not have any discernible effect on the biota of the open coast."
Groundwater quality monitoring indicates that the irrigation of wastewater is very effective at removing E.coli (the indicator organism for bacterial contamination) due to filtration through the sandy strata, they wrote.
"Changes in the irrigation will see a decrease in nitrogen entering the groundwater, but population growth will negate this improvement that in 35 years the nitrate influx will be 6 per cent grater."
Wetlands and permeable reactive barriers are being considered at The Pot. Both can reduce nitrogen influx further.
Effects of what happens at The Pot on the ground below Hokio A trust land adjacent is unknown as trustees refuse to do or allow any monitoring, though the council would like a groundwater monitoring bore to be installed. There is also no evidence presented that the water table below that land has risen.
Discharge to land of treated waste water is by far the best option, the commissioners wrote.
"This 100 per cent land discharge approach creates a lessening of many of the surface water concerns that would otherwise be occurring."
Discharge of treated wastewater from Levin at The Pot is done "in a affordable way."
"There are no other viable options to dispose of Levin's wastewater in an environmentally acceptable way."
The only significant contaminant in groundwater down gradient of The Pot discharge is nitrate-nitrogen and the evidence is that concentrations present will meet NZ drinking water standards. A condition has been put in by the commissioners to ensure that water quality will remain of that standard.
They wrote The Pot meets the purpose of the RMA better than any discharge to water (which may not have been consented), and also meets the tests for being the best practicable option.
Agreements on conditions reached with Ngāti Raukawa's three hapū and MTA also ensure more stringent water quality outcomes that first proposed.
Commissioners note that many submitters wanted wastewater to go elsewhere, but to them the big question remained: to where...?
Alternative options were looked at by the council and they included direct discharge into the ocean, or to fresh water.
Neither of which is culturally or environmentally acceptable, the commissioners wrote.
A third option: discharge to land elsewhere west of Levin is unlikely as there is no such land available.
The RMA hearing committee said discharge inland of Levin would be "unacceptable."
"The land there is much heavier and proportionately less wastewater would soak into the ground, resulting in contamination of surface water bodies and groundwater. Lake Horowhenua would likely be an eventual receiving environment for any such discharge."
Lastly they said they had to take into account the investments made over the years for the existing consent, which includes $18m worth of pipeline. They said they have no doubt the cost of long term development of infrastructure at The Pot and Levin's wastewater plant has run into the millions.
Figures showed recent and projected capital works and improvements at The Pot and the wastewater treatment plant since 2013/14 totalled $4.3m. "These are significant community investments which would have to be at least partially written off should the discharge go to any alternative site."
Wastewater is from domestic sources and not some "kind of thick brown sludge", they wrote. "Toilet waste makes up only a very small proportion of the total flow of wastewater to the wastewater treatment plant."
The only more concentrated human waste entering the plant is from septic tanks, there is also industrial discharges, such as from the Alliance Meat Plant, and a small volume of leachate from the Levin landfill nearby.
Shorter terms do not achievements much, the commissioners wrote. "We have been able to determine accurately the effects of the applicant's discharges at The Pot on the receiving environments. A short term may refine... but would not substantially change any of that assessment.
"A short-term consent would impose substantial additional cost on the applicant, and its ratepayers, for little if any environmental gain. It would likely have resulted in a loss of momentum towards getting any agreements with iwi and hapū.
Strong suggestions from the commissioners made on the final day of hearing on substantial improvement of certain conditions were mostly taken on board by the council, they wrote.
Appeals to this decision are still possible but the commissioners warned that appeals to the Environment Court could take months, even years, during which time the situation as-is will continue.
"Given that the conditions that we have granted consent on are much more robust than those of the existing consents this would be absolutely counter-productive, as this will mean the new consents cannot come into effect immediately, nor indeed perhaps for several years."
Resource consents granted for 25 years: ATH-201820041.00 to store wastewater and the associated discharge of wastewater to land and water; ATH 1998004064.01 to discharge treated wastewater to land and water; and ATH-1998007461.01 to discharge aerosols and odour to air.