Modelling projected nutrient loads in Nutrient Neutrality catchments

Descriptions

The key deliverable for this contract will be: Create a bespoke model for up to 15 catchments that allows the Natural England Nutrient Mitigation Team (NMT) to understand the anticipated phosphorus and nitrogen loading from housing development up to 2030, to include the pre upgrade and in perpetuity figures. This information should be summarised in tabled and mapped formats (GIS), taking the following into consideration: • The backlog in housing development as a result of nutrient neutrality, Local Plan and other housing data (including estimation of windfall) sourced and analysed from the relevant local planning authorities for each catchment; accounting for scale, geographic location and timescales for growth. - Local Plan variability will affect the modelling, it is likely some assumptions will be necessary e.g. to standardise end dates where Local Plan timescales are not consistent across a catchment. - To identify how delays due to non-response from local planning authorities will be overcome. •Generate an annual nutrient loading figure for each year up to and including 2030, to sub-catchment level where appropriate, presented in tabled and mapped formats. •To align with the Natural England Nutrient Budget methodology, including water usage and occupancy rates. •Spatially link Local Plan data with water company data to understand which houses will connect to which WwTWs, specifically noting which developments might occur out of water company boundaries and will need septic tanks/PTPs. •Provide flexibility for the NMT to amend the model inputs to allow for the impacts of legislation, such as measures implemented by water companies to reduce catchment-wide permitting levels as outlined in the Levelling Up and Regeneration Bill. This is to be confirmed at an initial inception meeting. The model should capture both the pre and post-TAL nutrient load for houses projected to be built before 1st April 2030, to include any AMP upgrades. - Where information is unavailable on scheduled water company works, the assumption that 'all treatment works over 2000 PE will be upgraded' should be used. •Provide flexibility in the model for the NMT to amend the inputs to include the impact of implementing potential grey solutions. •To be able to update housing data when necessary - i.e. when new Local Plans are adopted. •To complete a confidence assessment of the model outputs for each catchment based on data used to generate (i.e. confidence in Local Plans). To highlight where the Local Plan system is in reform and the potential uncertainty this may cause. •To align with the Natural England Nutrient Budget methodology, including water usage and occupancy rates. •Model development will occur in close collaboration with Natural England oversight/direction over the modelling.