Foxton Wastewater Treatment Plant Prioritisation of Land for Wastewater Land Treatment (LEI, 2014:A2)
Total Page:16
File Type:pdf, Size:1020Kb
Foxton Wastewater Treatment Plant Prioritisation of Land for Wastewater Land Treatment (LEI, 2014:A2) Prepared for Horowhenua District Council Prepared by November 2014 Foxton Wastewater Treatment Plant Prioritisation of Land for Wastewater Land Treatment (LEI, 2014:A2) Horowhenua District Council This report has been prepared for the Horowhenua District Council by Lowe Environmental Impact (LEI). No liability is accepted by this company or any employee or sub-consultant of this company with respect to its use by any other parties. Quality Assurance Statement Task Responsibility Signature Project Manager: Hamish Lowe Prepared by: Katie Beecroft, Sian Cass, Phil Lake Reviewed by: Hamish Lowe Approved for Issue by: Hamish Lowe Status: Final Prepared by : Lowe Environmental Impact Ref: Foxton_WWTP -A2_Land_Prioritisation - P O Box 4467 FINAL.docx Palmerston North 4442 Job No.: 10 172 | T | [+64] 6 359 3099 | E | [email protected] Date: November 201 4 | W| www.lei.co.nz TABLE OF CONTENTS TABLE OF CONTENTS ........................................................................................ 2 1 EXECUTIVE SUMMARY ............................................................................ 1 2 INTRODUCTION ...................................................................................... 3 2.1 Purpose .................................................................................................................. 3 2.2 Background ............................................................................................................. 3 2.3 Scope ..................................................................................................................... 3 3 DESIGN PARAMETERS FOR WASTEWATER DISCHARGES ...................... 4 3.1 General ................................................................................................................... 4 3.2 Resource Assessment ............................................................................................... 4 3.3 Land Application Area for Assessment Purposes .......................................................... 4 4 LAND APPLICATION ASSESSMENT METHODOLOGY ............................... 5 4.1 Process Overview ..................................................................................................... 5 4.2 Parameters .............................................................................................................. 5 4.3 Development of Zones ............................................................................................. 6 4.4 Aggregation of Rating Results ................................................................................... 8 5 ASSESSMENT PARAMETERS .................................................................... 9 5.1 General ................................................................................................................... 9 5.2 Land Use Attributes .................................................................................................. 9 5.3 Soil Attributes .......................................................................................................... 9 5.4 Hydrological and Hydrological Attributes .................................................................. 10 5.5 Summary .............................................................................................................. 12 6 PARAMETER ASSESSMENT .................................................................... 13 6.1 General ................................................................................................................. 13 6.2 Nutrient Uptake Potential ........................................................................................ 13 6.3 Soil Drainage and Permeability ................................................................................ 13 6.4 Soil Depth to Restrictive Layer ................................................................................ 13 6.5 Soil Slope and Stability ........................................................................................... 14 6.6 Mounding Risk ....................................................................................................... 14 6.7 Flood Return Interval ............................................................................................. 14 6.8 Rating Summary .................................................................................................... 14 7 ASSESSMENT SUMMARY ....................................................................... 15 8 FOXTON ................................................................................................. 16 8.1 General ................................................................................................................. 16 8.2 Land Near Foxton WWTP ........................................................................................ 16 8.3 Land for Further Investigation ................................................................................. 16 9 CONCLUSIONS AND RECOMMENDATIONS ........................................... 17 9.1 Assessment Conclusions ......................................................................................... 17 9.2 Recommendations ................................................................................................. 17 10 REFERENCES ......................................................................................... 18 11 APPENDICES.......................................................................................... 19 1 EXECUTIVE SUMMARY Horowhenua District Council (HDC) operates the Foxton wastewater treatment plant (FWWTP). The FWWTP currently discharges its treated effluent to Foxton Loop, a former meander of the Manawatu River, and requires resource consents to replace the existing discharge consents. In 2012, HDC examined potential land treatment options for the wastewater discharges from each of the district’s municipal WWTPs. Lowe Environmental Impact (LEI) were engaged to identify a prioritised list of land treatment and potential storage areas for the general areas of Levin, Shannon, Foxton and Foxton Beach; this resulted in a report (LEI 2012) containing maps showing the land treatment suitability of the land within a 10 km radius of each Horowhenua township. As part of the re-consenting process for the FWWTP, this report presents the land prioritisation details relevant to the FWWTP from that report, and includes a more focussed desk top assessment of land within a 5 km radius of FWWTP. The process undertaken to determine the ability of areas around Foxton to receive wastewater is summarised as follows: The parameters selected for assessment of land application sites in the Foxton area are given below. The parameters are all weighted equally and include: • Land use; o Nutrient uptake. • Soil attributes; o Soil drainage and permeability. o Depth to restrictive layer. o Slope and stability. • Hydrological and hydrogeological attributes; | Horowhenua District Council – Foxton WWTP Land Prioritisation for Wastewater Treatment | P a g e | 1 | o Mounding risk. o Flood return interval. This desktop assessment method has been used as a first step in the design process for a wastewater application to land scheme(s). Additional stages are required to supply detail about preferred land areas and project engineering considerations, such as reticulation routes and costs. The additional information contains a level of detail which is not considered feasible or appropriate for a desktop assessment of regional suitability for land application of wastewater. Recommendations are given below for the progression of additional work to determine an appropriate location and application regime. The investigation undertaken as part of this report concluded that, in general, there is suitable land available for the establishment of a land treatment system for the Foxton discharges. Extensive areas of land in the vicinity of Foxton and Foxton Beach indicate that pursuing land within the Zone A areas should be the first choice for HDC, subject to consideration of the impact of groundwater levels on land application feasibility. This report provides a large scale view of land treatment suitability near Foxton and Foxton Beach. The next step in selecting land to pursue for the development of a land treatment system is to limit the land areas examined. In selecting the areas for further investigation, information from the preceding reports (land assimilative capacity, discharge scenarios) should be incorporated. Within the selected areas the following should be considered: • Land parcel sizes and ownership; • The impact of shallow groundwater limitations; • Special use considerations i.e. known heritage sites; and • Approximate reticulation routes. From the completion of this stage the project moves from a desktop investigative approach to incorporation of design and cost elements. It is recommended that stakeholders are consulted, in particular Horizons, to enable the approach taken to date to be discussed and in-principle agreement with the approach to be sought. Based on the outcomes of this report it is recommended that land adjacent to the FWWTP be examined. Land directly south of the Manawatu River mouth and north to north-east of Foxton should also be examined further. | Horowhenua District Council – Foxton WWTP Land Prioritisation for Wastewater Treatment | P a g e | 2 | 2 INTRODUCTION 2.1 Purpose The purpose of this report is to: • Identify locations