BEFORE INDEPENDENT HEARING COMMISSIONERS AT TE AWAMUTU. IN THE MATTER of the Resource Management Act 1991

Transcription

1 BEFORE INDEPENDENT HEARING COMMISSIONERS AT TE AWAMUTU IN THE MATTER of the Resource Management Act 1991 AND IN THE MATTER of the hearing of submissions on an applications for resource consent by Fonterra Limited for the manufacturing site at Te Awamutu STATEMENT OF EVIDENCE OF DARYL IRVINE ON BEHALF OF FONTERRA LIMITED (IRRIGATION ASSESSMENT) 7 MARCH 2019 Counsel Instructed B J Matheson Richmond Chambers PO Box 1008 Shortland Street Auckland 1140

2 2 1. INTRODUCTION 1.1 My full name is Daryl Davidson Irvine. I am a Technical Director and Environmental Engineer in the Auckland Office of Pattle Delamore Partners Ltd. 1.2 I hold the degree of Bachelor of Technology (Environmental Engineering), from Massey University and I am a graduate member of Engineering New Zealand 1.3 Over the last 19 years my experience has been in the design, management, and assessment of effects of waste and wastewater, treatment, land treatment and disposal facilities. 1.4 In the course of my work, I have obtained extensive experience in the treatment and disposal of industrial and municipal wastewaters, in particular in land treatment of dairy and meat plant wastewaters and associated solid waste streams. Wastewater and biosolids, land treatment operations and assessments that I have been involved in include: Fonterra Hautapu, Reporoa, Edendale, Te Awamutu, Stirling, and Brightwater sites, Silver Fern Farms Takapau wastewater irrigation, Wallace Corporation wastewater irrigation and Inghams Enterprises (NZ) Limited wastewater irrigation to land. 1.5 I have assisted Fonterra in relation to the Te Awamutu Site since 2015, investigating the options for irrigating wastewater and condensate to land as an alternative option ( ) and then assessing the potential for irrigating condensate to land as an individual waste stream (2018). Scope of Evidence 1.6 My evidence presents the key findings of the investigations into the potential for irrigation of treated wastewater and condensate to land in the Te Awamutu area (PDP 2016) and assessment of potential irrigation of condensates to neighbouring properties (PDP 2018). For both documents I was the lead author. 1.7 This evidence has been prepared as a supplementary document, appended to evidence from Fonterra Limited and other expert witnesses.

3 3 2. SUMMARY OF WASTEWATER IRRIGATION ASSESSMENT 2.1 A desk top assessment of potential irrigation of wastewater and condensate (also referred to as cow water) to land was conducted by PDP, as detailed in the report Te Awamutu Plant Wastewater irrigation Investigation (PDP 2016). 2.2 The assessment considered irrigation of wastewater and condensate (up to 5,500 m 3 /d) with condensate contributing up to 2,000 m 3 /d of the wastewater volume. 2.3 Based on the assumption that wastewater irrigation would be irrigated to third party owned farms, it was anticipated that approximately 55 mm/month to 60 mm/month of the combined wastewaters could potentially be taken by farmers, between November and April, to achieve as close to deficit irrigation rate as possible. This hydraulic loading rate would require a total irrigation area of: (i) Condensate only: 93 ha (ii) Treated process water: 153 ha (iii) Combined wastewaters: 246 ha 2.4 Allowing for up to 300 ha of usable irrigation land, at a utilisation rate of 50%, the total area of combined third party farms required to join the scheme was estimated at 600 ha. 2.5 If irrigation occurred from November to April it was assessed that approximately 7,400 kg TN/yr and 2,700 kg TP/yr could be removed from direct discharge to the Mangapiko Stream. However, if both process water and condensate were irrigated to land, the risk of additional nitrogen leaching to groundwater from irrigated land may increase. This could result in a larger mass load of nitrogen being leached from farm land on an annual basis than is removed from the direct discharge of treated wastewater and condensate (final discharge) to the Mangapiko Stream. While it is unlikely that all of the leached nitrogen would migrate to the Mangapiko Stream, the benefits of removing the nitrogen from the direct discharge to the Mangapiko Stream may be minor.

4 4 2.6 The assessment found that if only process wastewater is to be irrigated, a net reduction in nitrogen discharged to the water (surfacewater and groundwater) could be maintained, with approximately half the nitrogen removed from the Mangapiko Stream estimated to leach to ground water. However, the potential effects of sodium loading may be compounded without the dilution effects of the condensate. In addition, the heat load on the Mangapiko Stream would remain. 2.7 A fatal flaw assessment was conducted, assessing soil types and property sizes (>50ha) within a 6 km radius of the Te Awamutu plant, which identified 67 properties of potential irrigation, predominantly to the north west and north east or the plant. A multi criteria assessment was then conducted, which was weighted based on: land area, distance from plant, topography, proximity to other potential irrigation sites, and distance from developed area. From the multi criteria assessment, 9 preferred sites were identified (8 dairy farm operations and the race course), to the north and north west of the plant, which could form part of an overall irrigation scheme. 2.8 Based on hydraulic load alone (as the nutrient content of the wastewater is low), it was estimated that irrigation of the wastewater could improve the annual profit for farmers by approximately $2,000 to $2,500 per hectare (based on a milk solids rate of $5.97 per kg). 2.9 Based on a 300ha, pod style irrigation system, the estimated costs for developing an irrigation system to manage all three waste streams from November to April are were estimated at a capital cost of $5.9M - $6.8M (+/- 30% and excluding GST) for off farm costs, and $2.7M - $3.5M (+/- 30% and excluding GST) for on farm cost (based on 2016 rates). 3. SUMMARY OF CONDENSATE IRRIGATION FEASIBILITY ASSESSMENT 3.1 During 2018, Fonterra engaged PDP to conduct an assessment of the potential for irrigation of condensate from the Te Awamutu Plant to the neighbouring Venn property and the Te Awamutu Race Course, to assess the potential for removing condensate from the Mangapiko Stream during low flow conditions. Details of the assessment are outlined in the technical memorandum titled

5 5 Te Awamutu Plant Condensate Management, Condensate Feasibility Assessment (PDP 2018). 3.2 In order to identify the potential frequency of required irrigation of condensate to land, to minimise heat load on the Mangapiko Stream during low flow conditions, it was essential to identify the low flow rates and frequencies in the Mangapiko Stream. There is limited knowledge of the low flow conditions in the Mangapiko Stream, with only a few years of data manually recorded from the stream level gauge adjacent to the Te Awamutu Plant. A regression analysis was therefore conducted, between the known data points and the Puniu River WRC flow monitoring site. The correlation between the data points was poor, but there appeared to be a slight correlation at flows below 16 m 3 /s in the Puniu River. While the data is coarse and limited by the accuracy of the Mangapiko Stream flow gauge, the estimated 7 day mean annual low flow (MALF) in the Mangapiko Stream was 202 L/s in the Mangapiko Stream, which is in keeping with information provided by Magg (Magg GR 1990) indicating a 1 in 10 year low flow of 230 L/s (at Race Course Rd), providing reasonable closeness of low flow conditions. 3.3 Based on the catchment flow regression, low flow conditions (<500 L/s) can be expected on average to be approximately 50% of days during March (as the month with the highest frequency of low flow conditions). However, during dry years, as experienced in 2008, it can be expected that low flow conditions could occur for 100% of days for January to March. 3.4 To assess the potential temperature impacts of discharges of condensate on the Mangapiko Stream, an energy balance was conducted for varying upstream temperatures, varying condensate discharge rates and the existing condensate temperature (45 C) and the potential future condensate temperature (35 C). Based on the energy balance (see the appended Table 1), it was concluded that if the upstream water temperature is greater than 24 C and all condensate is discharged to the stream, then it could be expected that the downstream temperature will be increased above 25 C, even if additional condensate cooling technologies are implemented to cool the condensate to 35 C prior to discharge. This indicated that an alternative condensate management would be required to maintain temperatures below 25 C during low flow conditions, for all or partial condensate flows during low flow conditions. If the volume of

6 6 discharge condensate is decreased to below 20% (at 45 C) then the temperature may be maintained below 25 C. If the condensate temperature is cooled to 35 C prior to discharge then approximately 50% of the condensate could be discharged to the Mangapiko Stream under low flow conditions (~230 L/s). 3.5 Fonterra had identified two potential condensate irrigation properties to the north of the Te Awamutu Plant being the Venn Property and the Te Awamutu Race Course (subject to further consultation), with an assessed combined potential irrigation area of 71.5 ha. Based on the assessed available irrigation land it was concluded that this property only has sufficient capacity to irrigate between 65% and 81% of the daily condensate volumes between January and March. On average, this would be sufficient to manage condensate volumes during low flow conditions (provided that condensate temperatures are cooled to below 35 C prior to discharge). 3.6 During a summer elevated rainfall event, there may be a period where irrigation is not viable but stream conditions do not allow discharge of condensate. This could be in the order of 10 days where either storage is required or there is an acceptance of a short term increase in stream temperature. 3.7 The estimated capital costs for installing a pump station and irrigation system on the Venn Property and Race Course were $3.30M plus GST (+50%/-30% contingency), excluding installation of a storage lagoon facility. 3.8 Fonterra confirmed the outcome of consultation with the Racing Club, which concluded that given the likely move towards a centralised Waikato racing hub the Te Awamutu race course will be sold for residential development. 3.9 Due to the uncertainties around the consentable thermal load on the Mangapiko Stream during summer months and the uncertainty around the ongoing availability of the Race Course for condensate irrigation, a full condensate irrigation system was also assessed, incorporating irrigation of farms identified in the initial irrigation assessment (PDP, 2016). With an allowance of up to 35 mm/month of irrigation capacity between January and March, approximately 177 ha of irrigable area would be required.

7 Estimated capital costs for installing a pump station and a 177 ha condensate irrigation system on Farms 2 and 8 are $7.62M plus GST (+50%/-30% contingency) Based on the estimated low flow condition frequency in the Mangapiko Stream and the assessed irrigation capacity, it was concluded that irrigation to land is a feasible option, however, to avoid the need for storage of condensate during summer time elevated rainfall events, there would need to be an acceptance from WRC of short term increases in temperature in the stream while land is not available for irrigation Following the assessment of a full scale condensate irrigation system (PDP 2018) I utilised a generic dairy farm nutrient model, utilising Overseer (Version 6.3.1), to assess the potential increase in nitrogen leaching associated with the condensate irrigation system, during periods of temperature limiting conditions in the Mangapiko Stream. Assumptions utilised in the model include a stocking rate of 3.3 Friesian cows per hectare, well drained allophanic soils, and an annual nitrogen fertiliser loading rate of 150 kg N/ha/yr. The model indicated that irrigation of condensate between November and March (at 35 mm/month) would increase nitrogen leaching by approximately 2 kg TN/ha/yr (354 kg TN/yr for a 177 ha irrigation system). If condensate irrigation also included October then nitrogen leaching would increase by approximately 5 kg TN/ha/yr (885 kg TN/yr for a 177 ha irrigation system), above a nonirrigated system If the irrigation option is to be investigated further, the assessment identified that land owners would need to be consulted to identify the actual available land for irrigation and soil investigations conducted to confirm the soil distribution utilised in this assessment. It was also recommended that a more accurate, continuous flow gauging system be installed along with temperature monitoring, to obtain a larger data set, prior to irrigation detailed design and installation. Daryl Irvine 7 March 2019

8 8 Table 1: Calculated Temperature Increase in Mangapiko Stream (based on 24 C upstream temperature) Condensate 45 C % condensate discharged 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Stream Flow (L/s) Condensate 35 C: % condensate discharged 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Stream flow (L/s)