Interim Phosphate Delivery Plan Stage 1 Report
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Herefordshire Council Interim Phosphate Delivery Plan Stage 1 – Guidance on calculating phosphate budgets for new developments draining to the River Wye SAC Report for Herefordshire Council Ricardo for Herefordshire Council – ED14585 ED14585 | Issue number 1 | Date 25/03/2021 Ricardo Confidential Herefordshire Council Interim Phosphate Delivery Plan – Stage 1 phosphate budget calculation guidance Ref: ED 14585 | Final Report | Issue number 1 | Date 25/03/2021 Customer: Contact: Herefordshire Council Dr Jenny Mant, Water Team – London Office Customer reference: 13 Eastbourne Terrace, ED14585 London, W2 6AA T: +44 (0) 1235 753 422 E: [email protected] Confidentiality, copyright and reproduction: Author: This report is the Copyright of Herefordshire Dr Gabriel Connor-Streich, Declan Sealy Council and has been prepared by Ricardo Energy Approved by: & Environment, a trading name of Ricardo-AEA Ltd under contract ED14585 dated 12/10/2020. The Dr Jenny Mant contents of this report may not be reproduced, in Signed whole or in part, nor passed to any organisation or person without the specific prior written permission of Herefordshire Council. Ricardo Energy & Environment accepts no liability whatsoever to any third party for any loss or damage arising from any interpretation or use of the information contained in this report, or reliance on any views expressed therein, other than the liability that is agreed in the said contract.” Date: 25/03/2021 Ref: ED14585100 Ricardo is certified to ISO9001, ISO14001, ISO27001 and ISO45001 Ricardo Confidential ii Herefordshire Council Interim Phosphate Delivery Plan – Stage 1 phosphate budget calculation guidance Ref: ED 14585 | Final Report | Issue number 1 | Date 25/03/2021 Executive summary The River Wye Special Area of Conservation (SAC) is a higher-level national network site1 (hereafter national sites) that supports a diverse and rare ecology; however, the ecology of the SAC is under pressure due to phosphorus (P) pollution from point and diffuse sources. Following the Court of Justice of the European Union (CJEU) ruling known as the ‘Dutch Nitrogen Case’2, mitigation to achieve ‘nutrient neutrality’ is required for new developments that would otherwise contribute additional nutrient loads to a European designated site that is close to unfavourable condition or in unfavourable condition due to nutrient pollution. Thus, all new developments that increase wastewater discharges to parts of a SAC that are close to or in unfavourable condition due to nutrient pollution must be able to demonstrate nutrient neutrality in order to be compliant with the ‘Habitats Regulations’ as demonstrated through a Habitats Regulations Assessment (HRA). The first step in demonstrating nutrient neutrality for new developments in the Wye SAC catchment is the production of a phosphate budget. Following advice from Natural England (Natural England, 2020), this report details a methodology for calculating a phosphate budget for new developments, including the rationale behind the values chosen as inputs to the various components of the phosphate budget. The phosphate budget is calculated in four stages as the balance between: 1. The increase in P loading to National sites that result from the increase in wastewater from a new development, which is based on population increase, water use and nutrient concentrations in discharges from wastewater treatment works (WwTW) and package treatment plants. 2. The P export from the past and present land use of the development site. 3. The P export from the future mix of land use on the development site e.g. urban land, greenspace. 4. Calculation of the net change in P loading to a designated site using the outputs from Stages 1-3, i.e. the P budget, which includes the addition of a 20% precautionary buffer. Inputs to the various components of each of these four stages were determined using scientific literature, best practice industry guidelines, secondary data and modelling. Where estimates for an input were subject to uncertainty, the precautionary principle was applied in order to determine a suitable value. The values recommended are in Table 1.1. It should be noted that the Natural England guidance on which this methodology is based only covers nutrient budget calculations for residential developments. Agricultural and industrial development that may subject to an HRA due to increased nutrient loading is subject to ongoing guidance development. The inputs into the Stage 1 phosphate budget calculations incorporate data from the most recent census (2011) on occupancy rates, per person water usage based on industry best practice water efficiency standards that have been adopted in the 2015 Herefordshire Local Plan and the phosphate concentration in the treated wastewater from the development. The latter input is determined by the type of treatment applied to wastewater at the receiving treatment works, with guidance also provided for new developments that will be served by package treatment plants. The Stage 2 phosphate budget calculations account for the phosphate load from the current land use on the development site. This phosphate load is offset against the new phosphate load from the development. Phosphate export coefficients are provided for greenfield and urban land based on values determined through literature review and secondary data. For agricultural land, Farmscoper3 modelling was used to determine phosphate export coefficients for the 9 farm types detailed in Natural England’s (Natural England, 2020) advice. Sensitivity testing of the Farmscoper model was used to determine suitably precautionary values for agricultural phosphate export, with these values taking 1 Prior to Brexit these sites were part of the Natura 2000 network and generally referred to as “European designated sites”. 2 Joined Cases C-293/17 and C-294/17 Coöperatie Mobilisation for the Environment UA and Others v College van gedeputeerde staten van Limburg and Other 3 Farmscoper Version 4 produced by ADAS and available to download from: https://www.adas.uk/Service/farmscoper, accessed on: 18/01/2021 Ricardo Confidential iii Herefordshire Council Interim Phosphate Delivery Plan – Stage 1 phosphate budget calculation guidance Ref: ED 14585 | Final Report | Issue number 1 | Date 25/03/2021 account of emerging research highlighting long-term issues related to legacy phosphate leaching from post-agricultural soils. Stage 3 of the phosphate budget calculations accounts for the phosphate export from the mix of urban and greenspace land uses on the post-development site. These inputs use the urban land use and greenspace phosphate export coefficients determined in Stage 2 of this methodology. The difference between the new phosphate load from a development (Stages 1 and 3) and the phosphate load from previous land use on the development site (Stage 2) results in the net change in phosphate loading to the River Wye SAC (Stage 4). There are uncertainties inherent in all of the inputs used in Stages 1-3 of the phosphate budget calculation methodology. This uncertainty is recognised by Natural England through the addition of a 20% precautionary buffer to the net change in phosphate loading calculated in Stage 4. If the final output from the phosphate budget calculations results in additional phosphate loading to the areas of the River Wye SAC that in unfavourable condition or close to being in unfavourable condition, the additional phosphate load will need to be mitigated so as to reduce phosphate to at least the pre-existing load, thus achieving nutrient neutrality. Table 1.1: Summary of key values advised for phosphorus budget calculations Stage Value type Component Value Units Occupancy rate 2.3 Persons/dwelling 1 Population Water usage 120 Litres/day Agricultural phosphorus Variable – dependant on combinations of rainfall, 2 kg P/ha/year export soil drainage and farm type coefficients Greenspace 0.02 Urban land Variable Non- Woodland 0.02 agricultural 2 & 3 kg P/ha/year export Shrub 0.02 coefficients Water 0.00 Community food growing Variable Ricardo Confidential iv Herefordshire Council Interim Phosphate Delivery Plan – Stage 1 phosphate budget calculation guidance Ref: ED 14585 | Final Report | Issue number 1 | Date 25/03/2021 Table of Contents Executive summary ................................................................................................. iii Table of Contents ..................................................................................................... v Table of Figures....................................................................................................... vi Table of Tables ........................................................................................................ vi Glossary ................................................................................................................... vi 1 Introduction ........................................................................................................ 1 1.1 Purpose of the report .............................................................................................................. 1 2 Background to Nutrient Neutrality and the River Wye Catchment ................ 2 2.1 The Dutch Nitrogen Cases ...................................................................................................... 2 2.2 River Wye SAC and Phosphorous Pollution ........................................................................... 3 2.3 The River Wye Nutrient Management Plan (NNP) and