Preliminary Phase II Geo-Environmental Assessment Phase 2 – ‘GT20’ (Parcels R1-R4) Delta-Simons Project Number 17-0337.02 Preliminary Phase II Geo-Environmental Assessment Phase 2 – ‘GT20’ (Parcels R1-R4) Presented to Consortium of Taylor Wimpey, Persimmon Homes and Hopkins Homes Issued: October 2017 Delta-Simons Project No. 17-0337.02 Environment | Health & Safety | Sustainability Preliminary Phase II Geo-Environmental Assessment Phase 2 – ‘GT20’ (Parcels R1-R4) Delta-Simons Project Number 17-0337.02 Report Details Client Consortium of Taylor Wimpey, Persimmon Homes and Hopkins Homes Report Title Preliminary Phase II Geo-Environmental Assessment Phase 2 – GT20 (Parcels R1-R4), Land off Salhouse Road, Sprowston, Norwich, Site Address NR13 6LB Project No. 17-0337.02 Report Date October 2017 Delta-Simons Tom Horner ([email protected]) Contact Quality Assurance Issue Issue Technical Status Comments Author Authorised No. Date Review 1 Final 20.10.2017 - Gemma Tatton Tom Horner Dan Webb Consultant Principal Unit Manager About us Delta-Simons is a trusted, multidisciplinary environmental consultancy, focused on delivering the best possible project outcomes for customers. Specialising in Environment, Health & Safety and Sustainability, Delta-Simons provide support and advice within the property development, asset management, corporate and industrial markets. Operating from eight locations - Lincoln, London, Leeds, Manchester, Norwich, Nottingham, Durham and Dublin - we employ over 70 environmental professionals, bringing experience from across the private consultancy and public sector markets. Delta-Simons is proud to be a founder member of the Inogen® Environmental Alliance, enabling us to efficiently deliver customer projects worldwide by calling upon over 4,330 resources in our global network of consultants, each committed to providing superior EH&S and sustainability consulting expertise to our customers. Inogen Environmental Alliance offers its clients more consultants, with more services in more countries than the traditional multinational consultancy. Environment | Health & Safety | Sustainability Preliminary Phase II Geo-Environmental Assessment Phase 2 – ‘GT20’ (Parcels R1-R4) Delta-Simons Project Number 17-0337.02 Executive Summary Brief Delta-Simons Environmental Consultants Limited (‘Delta-Simons’) was instructed by Taylor Wimpey, Persimmon Homes and Hopkins Homes to undertake a Phase II Geo- Environmental Assessment for a parcel of land known as ‘GT20’ (Parcels R1-R4), located off Salhouse Road, Sprowston, Norwich, NR13 6LB (hereafter referred to as the ‘Site’). It is understood that the Site is to be redeveloped for residential use, comprising approximately 460 dwellings, however, at the time of writing, a specific proposed development plan had not been provided to Delta-Simons. The purpose of this assessment is to identify the potential for land contamination issues to be present at the Site in the context of the proposed development, to support the planning application and to provide a geotechnical assessment. Site Setting The Site was historically occupied by agricultural land, with areas of woodland, Round Hill Plantation and Arnup’s Belt, present in the northern and southern areas of the Site respectively. A Polo Ground was also present in the south of the Site from 1919 to circa 1929. The Site is currently utilised for agricultural purposes. Ground The current ground investigation recorded Topsoil underlain by the Sherringham Cliffs Conditions Formation. In the north of the Site, the superficial Happisburgh Glacigenic Formation has been identified overlying the Sherringham Cliffs Formation. Both the Happisburgh Glacigenic Formation and the Sherringham Cliffs Formation comprised alternating layers of cohesive and granular deposits to a maximum proven depth of 10.45 m bgl. Land Human Health Contamination No elevated concentrations of contaminants have been identified compared to their Assessment respective GAC in the context of a residential (with consumption of home grown produce) end use. Controlled Waters Although elevated concentrations of heavy metals including cadmium, chromium, mercury and nickel have been identified within the groundwater across the Site, these are considered to be representative of background concentrations, and therefore, do not pose a significant risk to sensitive receptors. Built Environment Although no significant organic contamination has been identified at the Site, confirmation should be sought from the Local Water Authority as to whether they will require upgraded water supply pipework. Ground Gas Ground gas monitoring data indicates that the Site should be classified as CS2 – Amber 1. This scenario will require the implementation of ground gas protection measures within the proposed development, however, given that elevated concentrations of carbon dioxide and flow rates were only recorded in the south of the Site, it may be possible to ‘zone’ the Site once final development layouts are known and following consultation with the Local Authority. Environment | Health & Safety | Sustainability Preliminary Phase II Geo-Environmental Assessment Phase 2 – ‘GT20’ (Parcels R1-R4) Delta-Simons Project Number 17-0337.02 Geotechnical Shallow strip foundations are considered to be suitable for the proposed development, Assessment founded within the underlying superficial deposits, at a minimum depth of 1.00 m - 1.50 m bgl. Suspended floor slabs are likely to be a requirement to meet ground gas protection guidance in line with the Site’s CS2 – Amber 1 classification, in the south of the Site. It is recommended that a conservative CBR value of 2% should be adopted for the shallow soils, for preliminary pavement design for external areas. It is recommended that plate CBR tests are undertaken at formation level prior to finalising pavement design. Buried concrete may be designed in accordance with DS-2 and AC-2, as per requirements of BRE Special Digest 1:2005 ‘Concrete in aggressive ground’.. Recommendations Based on the findings of this report, the following recommendations are made: ▲ In order to fully characterise the gas regime at the Site, it is recommended that additional ground gas monitoring is undertaken once development layouts have been finalised; ▲ Waste classification has not been undertaken as part of the scope of works, should it be proposed to dispose of materials from the Site, then specific additional investigations may be needed to classify the materials in accordance with current regulatory requirements; ▲ Any topsoil imported onto the Site as part of the development works, or sourced from the Site and re-used, should be tested to confirm suitability, prior to, and once placed, in landscaped / garden areas; ▲ Additional, unidentified localised areas of contamination may exist at the Site and an appropriate ‘hotspot’ protocol should be in place for groundworkers to act upon should such contamination be identified during the construction process; ▲ As with all development sites, groundworkers who are required to perform sub- surface work at the Site should be made aware of the known contaminants in soil and groundwater and the possibility of encountering additional localised low levels of contamination. Therefore, good standards of personal hygiene should be observed and appropriate levels of PPE utilised where necessary; ▲ Suitable dust suppression techniques will need to be implemented by the groundworkers during construction works; and ▲ Confirmation should be sought from the Local Water Authority as to whether they will require upgraded pipework to be installed for new service installations. This is intended as a summary only. Further detail and the limitations of the assessment are provided within the main body of the Report. Environment | Health & Safety | Sustainability Preliminary Phase II Geo-Environmental Assessment Phase 2 – ‘GT20’ (Parcels R1-R4) Delta-Simons Project Number 17-0337.02 Table of Contents 1.0 INTRODUCTION ............................................................................................................................................................... 1 1.1 Appointment ............................................................................................................................................ 1 1.2 Context & Purpose ................................................................................................................................. 1 1.3 Scope of Works ...................................................................................................................................... 1 1.4 Existing Information ................................................................................................................................ 1 1.5 Limitations ............................................................................................................................................... 1 2.0 SITE DETAILS ................................................................................................................................................................... 2 2.1 Site Setting ............................................................................................................................................. 2 2.2 Preliminary Conceptual Site Model ........................................................................................................ 3 3.0 SITE INVESTIGATION ....................................................................................................................................................