Expert evidence presented to the Environment Court of New Zealand regarding resource consent appeals for the Remediation (NZ) Ltd composting facility at Uruti, Taranaki. This case involves complex environmental management issues including land application of organic wastes, wastewater treatment, and contaminated site remediation.
Senior Environmental Scientist at Lowe Environmental Impact with over ten years of specialized experience in organic waste management and land treatment systems.
NZ Society of Soil Science, Water New Zealand, NZ Land Treatment Collective
640 hectares located in rural Taranaki, encompassing headwaters of Haehanga Stream, tributary of Mimitangiatua River
38.7 hectares (6% of property) used for composting, vermicomposting, and wastewater management activities
Approximately 8,000 t/yr for Pad 1 composting, 4,000 t/yr for Pad 2 vermicomposting, plus legacy stockpile exceeding 20,000 tonnes
The facility operates under six resource consents from Taranaki Regional Council. Two critical consents expired in May 2018, leading to renewal applications, a Council hearing, consent decline, and subsequent appeal to the Environment Court.
Main composting operations on 10,420 m² concrete pad with truckwash and collection pond. Material received via weighbridge from State Highway 3.
10,000 m² area for receiving and dewatering paunch material prior to vermicomposting, with wetland treatment system covering 15,000 m².
15,500 m² area containing blended drilling mud stockpile and decommissioned ponds, representing significant contamination challenge.
15.96 hectares available for wastewater irrigation, occupying valley bottom with mix of native and constructed soils.
All operational areas are directly adjacent to the Haehanga Stream and its tributaries, creating potential pathways for contaminant migration to surface water.
Discharge of organic materials onto land within and outside wastewater catchment areas, with evidence of unauthorized placement beyond designated pads.
Discharge of leachate from raw, partially composted, and mature compost to groundwater, eventually reaching surface water as diffuse discharge.
Wastewater seepage from truckwash, settling, and irrigation ponds to groundwater, with losses estimated at 11-110% of the site nitrogen load.
Both "clean" and potentially contaminated stormwater via overland flow to Haehanga Stream, with inadequate separation and treatment.
Wastewater to land by irrigation, with potential for groundwater leaching or surface water overland flow when mitigation strategies fail.
Partially treated wastewater from wetland treatment system to stream tributary, proposed for cessation but lacking detailed retirement plan.
Predicted distribution, transport, and loss of contaminants likely underestimated. Missing data includes seepage and breakout from wastewater catchments, contaminants from stormwater areas containing compost products, and materials from uncontrolled storage areas. Ongoing effects cannot be accurately quantified.
Existing irrigation pond undersized for retention during wet periods. Addition of Pad 2 flows (1,200 m³/year) represents 9% of pond volume, creating risk of overtopping or inappropriate irrigation when soil is saturated, resulting in contaminants entering streams.
Irrigation areas cannot receive additional nutrient loads from Pad 2 without increased leaching to groundwater. Historical applications exceeded 1,000 kg N/ha/yr, compared to National Environmental Standard limit of 190 kg N/ha/yr. Facility unlikely to meet proposed 400 kg N/ha/yr maximum.
No timeline for securing 20,000+ tonne contaminated stockpile. LOSP chemicals detected in irrigation pond demonstrate ongoing risk. Diligent evaluation of remediation options needed urgently, with interim measures to prevent runoff entering wastewater treatment system.
A 2015 BTW groundwater analysis established preliminary understanding of site hydrology but remains unconfirmed. The shallow groundwater table (0.25-1.4 meters below ground) sits in clay soils overlain by porous silty loams, creating direct connectivity with the Haehanga Stream.
Groundwater velocities estimated at 0.23 m/day, though likely underestimated for upper catchment areas with steeper topography and more porous soils. The stream alternates between gaining and losing reaches depending on rainfall and groundwater levels.
Estimated groundwater velocity in lower catchment areas
GND 2188, 2189, 2190 installed but lacking complete construction data
Estimated seepage losses from pond system as percentage of site load
Animal-origin wastes containing potential pathogens deposited at Pad 1. Previous practice of depositing into Pad 3 ponds posed high pathogen transfer risk through irrigation system.
Heat-based pathogen reduction relies on temperature and moisture monitoring. No timeframe set for blending raw materials. Risk of cross-contamination and vector attraction requires better management.
Rainfall on windrows generates high-concentration leachate. Newly blended or turned windows can absorb 700mm rainfall before releasing contaminants to truckwash pond.
Paunch material received to 10,000 m² Pad 2 for dewatering before vermicomposting. Leachate currently transferred to degraded wetland treatment system before discharge to stream tributary. Wetland treatment effectiveness reduced from design levels.
Retirement of Pad 2 portion may create contaminated soil excluded from managed wastewater collection, risking high-nutrient sediment entrainment in "clean" stormwater system.
Beds located outside wastewater collection catchments with no observed bunds. Leachate high in ammoniacal nitrogen and organic compounds likely travels to stormwater drainage and Haehanga Stream.
"Trends in ammoniacal nitrogen measured in the Haehanga tributary suggest a discharge to the stream is occurring." - TRC monitoring evidence
No monitoring of vermicompost bed discharge conducted. Not included in site nutrient balance, providing no mechanism to detect and assess effects.
Contaminated drilling mud and unsuitable materials accumulated over time
Timber treatment chemicals including permethrin, tebuconazole, propiconazole detected in irrigation pond
Copper, chromium, arsenic contamination from timber treatment chemicals, baled but not removed
Two ponds filled without NESCS compliance evaluation, approximately 250 m³ excavated material
Ponding observed around stockpile following rainfall, leachate potentially entering irrigation system
Robust characterization completed by PDP, but no remediation timeline established. Material continues posing environmental risk. Urgent evaluation of remediation options needed with interim measures to prevent runoff entering wastewater treatment system.
Collects contaminated stormwater from Pad 1 via sheet flow plus truck washout water. Contains organic compounds, nutrients, pathogens, and solid materials. Requires aeration to avoid odour issues.
Receives transfer from truckwash pond, located on Pad 3. Shares aerator with truckwash pond. Biocides including LOSP chemicals detected, potentially impacting biological treatment processes.
Final treatment stage with approximately one month retention time. System likely undersized for both treatment and storage during wet periods when irrigation cannot occur.
Peak historical nitrogen application rate to irrigation areas
Recent application rates across six of eight irrigation areas
Proposed maximum nitrogen leaching rate unlikely to be achieved
National Environmental Standard for Freshwater limit for comparison
15.96 hectares available for wastewater irrigation using soil moisture-based timing. Cut and carry pasture system removes nutrients when baleage or silage exported from property. Small moveable irrigators replacing travelling irrigators should reduce groundwater losses.
Chloride triggers frequently exceeded. LOSP chemicals from treated sawdust likely accumulated in irrigated soils. Detailed investigation needed across site. No evaluation of long-term impacts on soil and plants for newly identified contaminants.
Seepage and breakout from ponds not fully accounted. Historical concentrations not reflected in loading calculations. Additional nutrients from Pad 2 integration not adequately assessed.
Contaminants from areas containing compost and vermicompost products not evaluated. Inadequate separation between clean and contaminated stormwater systems.
Materials deposited outside designated pads. Contaminated fill used for land development. Approximately 4,400 m² area between Pad 1 and vermicompost beds containing covered mature compost.
Pad 3 stockpile contributions to nutrient balance uncertain without removal or isolation plan. Legacy contamination continuing to impact irrigation pond quality.
Total site nitrogen loss likely underestimated. Effects of discharge inadequately assessed despite activities occurring near surface water paths with reduced attenuation opportunity and short groundwater travel distance.
Generally concur with Gary Bedford and Dr. David Horne's assessments. Strongly agree management plans should be finalized and audited before allowing further waste receipt or continuing operations. Current detail insufficient to conclude effects can be avoided, remedied, or mitigated.
Mr. Irvine's Pad 2 reduction from 1.0 ha to 0.1 ha requires demonstration of feasible layout. Mr. Kay's nitrogen uptake assumptions (15 t/ha) likely unachievable at this location. Ms. Webster's assertion Pad 3 poses no immediate risk disputed given LOSP detection in irrigation pond.
Disagree with Mr. Easton's assertion stormwater is controlled across site. No evaluation of areas, volumes, or contaminants beyond silt provided. No comprehensive site map showing catchments and treatment devices. Contaminants beyond sediment likely discharging to streams.
Disappointing lack of site-specific monitoring data for system operating this long. Pad 2 leachate quality predicted rather than measured. Temperature and moisture data for composting process not reviewed. Pathogen monitoring of products would demonstrate safety.
Proposed activities rely on management plans not submitted for review. Lack of detail regarding future site management creates high uncertainty. No confidence that RNZ can remedy or mitigate effects due to unclear site design and poor operational description.
Contaminant migration pathways not evaluated. Groundwater conceptual site model remains unconfirmed since 2015. Connectivity between shallow groundwater and Haehanga Stream demonstrated but travel times and flow paths uncertain. Impact assessment incomplete.
No limit on material volume allowed on site. History of unauthorized waste deposits. Contaminated sawdust baled but not removed. Comprehensive site characterization needed to determine location, extent, and composition of materials around site.
Pad 3 remediation evaluation needed as matter of urgency. Detailed investigation of LOSP and other contaminants across irrigation areas required. Stormwater Infrastructure Management Plan development essential. NESCS compliance evaluation for pond decommissioning work needed.
"I do not have confidence that RNZ can remedy or mitigate effects due to the site operation on the basis of the evidence provided." - Katie Jane Beecroft, MSc
KATE JANE BEECROFT