Brief Taliesin Conservation has been instructed by the City and County of Swansea to undertake a desktop assessment/study for an area of land at Maritime Quarter, Swansea, SA1 3SS. The purpose of this study is to initiate a full site investigation as part of a feasibility study and make recommendations on methodology. This report has been prepared exclusively to aid with the evaluation of the potential risks associated with the proposed land. The information contained within this report is based on observations made on site, a review of historical, geological, hydrogeological material and other environmental data obtained for the site. Proposed Development “City and County of Swansea have chosen to enter into a joint agreement with Marriot Hotels to create a new restaurant and ice-cream parlour (with manager’s apartment) on Swansea foreshore, in the position indicated. The site is located between County Hall and the Marriot. The building, which is to share parts of the car park of both of the existing adjacent facilities, is to have a GIA (Gross Internal Area) at ground floor level of approximately 300 square metres. The building is to contain the restaurant, café bar, ice-cream parlour, kitchen, food-stores, etc. At second floor level, there is to be a self-contained manager’s apartment and staff welfare facilities.” Site Description Site Description and Surroundings Site Location Plan Not to scale NB: The proposed area for the site is highlighted in red on the plan above. Continued.../ A description of the site and its surroundings are summarized in Table 1 and a site location plan is included in Fig.1 below. Table 1: Data Information Address The land is located West of the Marriot Hotel, Maritime Quarter, Swansea, SA1 3SS and North of the coastline. Current Site Use The site is currently open land comprising vegetation, trees, and grass Coordinates 51.613264, -3.945464 Site Area 300.00m2 Surrounding Land Use North – Carpark, Iwan Williams Driving School East – Marriot Hotel and carpark, Tawe Basin South - Coastline West – Swansea Central Library and carpark Continued.../ The Topography of the Land The figure above shows the land to be approximately 55ft above sea level. According to Topographic Maps (2019), this is 122ft below the average elevation. Continued.../ Site Walkover A site walkover was undertaken by Owen Towell on the 19th of November 2019. The weather was cold and dry. During the walk over, it was noted that the land has heavy footfall and vehicle traffic nearby. The land protruded from the ground in – what looks to be – man-made mounds (Fig.3 & 4) as a possible means of flood protection. It was also noted that existing services/utilities are located on the site by the presence of manholes. (Fig.5) Continued.../ Continued.../ Site History Historical maps and areal images dating from 1888 have been procured and reviewed. The findings are summarized in the table below. The historical maps are included in the pages to follow. Table 2: Summary of Historical Maps and Images Date On-Site Observations Adjacent Area Observations 1888 – 1913 The Swansea and Mumbles Railway line runs directly through the site with an engine shed located approx. 100m to the West of the site. There is a Sawmill located approx. 150m to the North East of the site. A Gas Works is also located approx. 300m north of the site. 1937 A canister works is located on the site No significant changes are shown on maps. 1945-1946 No significant changes are shown on maps No significant changes are shown on maps 1961 No significant changes are shown on maps The County Goal located approx. 300m North West of the site is now the H.M. Prison. 1991 The railway line and engine shed is no longer visible on maps The Saw Mill is now a residential area and existing Gas Works is now a supermarket. A hotel has been developed within 25m east of the site. NB: Historical maps only offer a brief moment in time and considerations must be taken while attempting to decipher these as it is not clear what has occurred during the intervening years. It is also important to note that industrial uses may not always be recorded. Continued…/ Continued…/ Continued…/ Continued…/ Prior to 1888 (the earliest dated map obtained) the South Dock (East of the site) was constructed in 1859 for the export of coal from Aberdare and commercial shipping ceased in 1971 and is now the Swansea Marina. (Coflein.gov.uk, 2019) The existing railway located north of the site was The Swansea and Mumbles Railway which was incorporated in 1804 to carry coal from the Clyne Valley and limestone from the Mumbles. The line was re-laid in 1855 as an edge railway where steam trains operated from 1876 which were eventually subsided by electric trams in 1929. (Hughes and Reynolds, 1989). During World War II (1st September 1939 – 2nd September 1945) Swansea experienced what is now called The ‘Three Nights’ Blitz’. The Blitz of February 1943 temporarily halted any thinking of post-war development as many areas of the city were destroyed during the onslaught. As you can see from the fig. below, the site location was a direct target of the Luftwaffe and the risk of bombing was extremely high. (Roberts, 2011) Continued…/ It’s also important to note there has been archaeological findings in the proximity of the site. A hoard of Roman treasure was found approx. 300m southwest of the site and the remains of a medieval castle is located approx. 700m north of the site. See fig. below. Continued…/ Geology and Mining Geology On review of a borehole survey taken directly in the vicinity of the proposed site (British Geological Survey ID: 370246: BGS Reference: SS69SE345), STRATA SURVEYS Ltd, Cheshire concluded the makeup of the ground as follows: Table 3: Summary of Soil Strata, STRATA SURVEYS Ltd Description of Strata Thickness (m) Made ground consisting of ashes 0.5m Made ground consisting of loose, light grey fine-medium sand 1.00m Made ground consisting of grey sand with layers of soft sandy clay 1.05m Made ground consisting of soft red-brown sand clay with brick shale 0.95m Made ground consisting of dense bricks, ashes, sand, and clay 1.45m Very dense brown sandy gravel with traces of sandy clay 2.05m Very dense brown sand with gravel 0.95m Still grey-brown gravelly boulder clay 3.05m Very stiff grey gravelly boulder clay 7.6m Grey mudstone 12.82m The above report coincides with additional research findings on the makeup of the soil strata which indicate superficial deposits of blown sand, artificial or made ground and parent rock of mudstone. Continued…/ Mining A map dated 1945 (above) states that the proposed site is located on/near exposed coalfields and that concealed coalfields are ‘probably present’. This correlates with more recent records sourced from The Coal Authority which states that the region in which the proposed site is located is rich in coal deposits, particularly surface coal (highlighted in the fig. below). “The online records provided by The Coal Authority are used to prepare plans called “Coal Mining Development Referral Area Plans” for all coalfield Local Planning Authorities, which refine the defined coalfield areas into areas of higher risk (known as the Coal Mining Development Referral Area) and lower risk (known as Standing Advice Area).” (Risk Based Approach to Development Management, n.d.) During the planning process of internal alterations to Meridian Tower, Trawler Road SA1 1JW in 2015 (approx. 150m from the proposed site location), a final delegated report stated the following: Table 4: Summary of Constraints from Alterations to Meridian Tower, 2015 Constraint Type Reference Description Text Mining Area MINE AREA MINEAREA (Pl Consultation Zones) MINING AREA Coal Mining Development Referral Data StAdvice Coal Mining Development Referral Data Standing Advice Meaning that despite the area was a ‘mining area’ the risk of development was low. This was also supported by a direct letter from The Coal Authority during the planning application for the construction of a 3 storey block at Trawler Road, Swansea, SA1 1UP (approx. 300m from the proposed site): Hydrogeology and Flooding On review of online resources, the proposed location of the site shows to be situated directly in the vicinity where surface water flooding is high risk and tidal flooding is probable. Continued…/ This directly coincides with the conclusions made during the planning application for developments to the Meridian Tower, Trawler Road, SA1 1JW in 2015 (approx. 150m from the proposed site location). The final delegated report built for the project stated the following: Table 5: Summary of Constraints from Alterations to Meridian Tower, 2015 Constraint Type Reference Description Date Flooding Floodzone 3 - Tidal - M 0.5% or greater Tidal Flooding May 2013 Flooding Floodzone 2 - Fl & Ti - M Between 1% abd 0.1% Fluvial Flooding or 0.5% and 0.1% Tidal May 2013 Dam Maps - Tan 15 Zone C2 Tan 15 - Flooding 2013 Flood Zone 2 ‘Flood Zone 2’ is defined as land that has been assessed as having between a 1 in 100 and 1 in 1000 annual probability of river flooding (1% - 0.1%) or between a 1 in 200 and 1000 annual probability of sea flooding (0.5% - 0.1%) in any year. (Environmental Agency, 2019) Flood Zone 3 ‘Flood Zone 3’ is defined as land assessed as having a 1 in 100 or greater annual probability of river flooding (>1%), or a 1 in 200 or greater annual probability of flooding from the sea (>0.5%) in any year. (Environmental Agency, 2019) Tan 15 – Zone C2 Planning Policy Wales developed a Technical Advice Note for the Development and Flood Risk (Tan 15). The above report for the development at the Meridian Tower states that based on the Tan 15, the area is classified as a development zone of ‘Zone 2’. Based on Environment Agency extreme flood outline, ‘Zone C2’ is defined as an area which has an equal to or greater than 0.1% (river, tidal or coastal) risk of flooding without significant flood defence infrastructure. NB: For development proposals in Zone C, a flood consequences assessment is required. Zone C1 development can take place subject to a satisfactory assessment. In Zone C2 only less vulnerable forms of development should even be considered. (Planning Policy Wales, 2004) Environmental Review Historic Contaminants During the historic review of the site, it was clear that over the years the site was a heavily industrial area with several different uses – and thus, is classed as a brownfield site (“previously developed land”). The previous developments located in the vicinity of the proposed site may prove to still be contaminating the land: Table 6: Summary of Possible Contaminates Use of Land Location Possible Contaminates Railway Line Directly through the proposed site location • Oil-derived products • heavy metals • Polycyclic aromatic hydrocarbons (chemicals found naturally in coal, and crude oils) • Polychlorinated biphenyl (manmade chemicals widely used in electrical equipment) Engine Shed Approx. 100m West of the site • Oil-derived products • heavy metals • Polycyclic aromatic hydrocarbons (chemicals found naturally in coal, and crude oils) • Polychlorinated biphenyl (manmade chemicals widely used in electrical equipment) Canister Works Located directly on the site • Oil-derived products • heavy metals • Polycyclic aromatic hydrocarbons (chemicals found naturally in coal, and crude oils) • Polychlorinated biphenyl (manmade chemicals widely used in electrical equipment) Saw Mill Approx. 150m North East of the site • Polychlorinated phenols (preservatives) • Polychlorinated dibenzofurans (Organic compounds) Gas Works Approx. 300m North of the site • Oil-derived products • heavy metals • Polycyclic aromatic hydrocarbons (chemicals found naturally in coal, and crude oils) • Polychlorinated biphenyl (manmade chemicals widely used in electrical equipment) Continued…/ Current Emissions Having researched the ground records of the site in question, the National Atmospheric Emissions Inventory has already identified the following contaminates at high levels: Table 7: Summary of Constraints Found at Site (NAE) Contaminate Units Kg/1x1km Arsenic 0.342225 kg 1 x 1km Cadmium 0.047561 kg 1 x 1km Chromium 0.916639 kg 1x1km Carbon dioxide as carbon 3295.167480 t 1x1km Copper 12.156734 kg 1x1km Lead 2.149844 kg 1x1km Nickel 1.170992 kg 1x1km Vanadium 11.898720 kg 1x1km Zinc 11.749370 kg 1x1km All of the above contaminated could be naturally occurring, or as a result of contamination and could be in the form of solids or gas. Continued…/ According to Public Health England, there is also the potential of coming into contact with radon while excavating the land. (Please see fig. below) As shown in the map fig. above, the maximum radon potential in the area in which the proposed site is located is between 1 – 3% meaning that care should be taken while excavating. (UKRadon.org, 2019) Conclusion and Recommendations Table 8: Summary of Conclusions and Recommendations Section Conclusion Recommendation Site Walkover • Manholes present • No utilities map available online • The site is easily accessible • Gain access to existing utility plans from the relevant sources i.e. Welsh Water etc. • Services engineer on-site during the investigation to locate buried utilities using surveying tools and detecting devices as well as reading/interpreting plans. • Mark the services found and confirm their status. NB: The above should be undertaken under the guidance of The Health and Safety Executive – Avoiding danger from underground services (HSG47, 2014) and should comply with BSI PAS 128:2014 – The Robust Specification for Underground Utility Detection, Verification, and Location. Site History • Potential of Medieval hoards • Potential of Roman hoards • Possibility of unexploded ordinates. • Archaeologists to be present during site investigation and excavation. • Should the contractor come into contact with anything of interest to the Archaeologist, work must stop and further investigation is required. NB: All of the above should be undertaken, ensuring compliance with the CIfA Regulations, standards and guidelines. Geology and Mining • Surface coal probable • Made up ground • Sand and silt • Further investigation required by a competent and licensed contractor (see investigation recommendations below) NB: The above should be undertaking in compliance with BS 5930:2015 – Code of practice for ground investigations • A Coal Authority report must be obtained • The probability of shallow coal workings affecting surface stability should be established in conjunction with the Coal Authority Report • An engineer with suitable experience and qualifications should address any potential of mine working or mine entries in the proposed site location. NB: The above should be undertaken in accordance with CIRIA SP 31: Construction Over Abandoned Mine Workings. Hydrogeology and flooding • Potential of surface, and tidal flooding • Allowances for sustainable flood and coastal erosional risk measures must be in place to allow for: rises in drainage charges, and protected water supplies. NB: The above must comply with The Flood and Water Management Ace (2010) • Soakaway tests should be undertaken to determine the infiltration rate of the ground. Environmental • High probability of existing contaminates. • Radon likely present in the ground. • An environmental engineer is recommended to be on-site during site investigation, excavation and construction. • Due to the possible contaminates of the land, capping layers will likely be required for the proposed development. • Should radon be present during excavation, it’s recommended that either a Radon sump or positive pressure system installed prior to the construction to avoid the probability of seepages post-construction. NB: The design of the building should comply with BS 8485:2015 – The code of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings. Ground Investigation Method We recommend that vertical boreholes are undertaken in clusters over the footprint of the proposed building and are done in compliance with Construction (Design & Management) Regulations 2007/ Borehole Sites, Operations Regulations 1995, GSHVBS Vertical Borehole Standards and BS 5930:2015 – Code of practice for ground investigations. Should the layout of the structure not be established while the site investigation is conducted, then it’s recommended that uniformly spaced grid boreholes are undertaken. Eurocode 7 specifications state that the spacing for exploration stations creating a grid ranges from 20-40m and should be positioned close to the suggested foundation. “(a) The minimum number of boreholes to be carried out should be 1 per 300 m2 of the area of project site, 2 per block of building and not less than 3 per site. The borehole spacing should be between 10m to 30m apart.” (Building and Construction Authority, 2016) We recommend that the number of boreholes carried out is in accordance with Building and Construction Authority requirements and a minimum of 3no boreholes across the footprint of the site is required. Following the review of the existing borehole data taken from the site, it would be reasonable to conclude that bedrock is at a depth of approx. 22m. We, therefore, recommend that the appropriate plant is used to accommodate the assumed depth – this being an Open Hollow Stem Auger. The reasoning for this is that it is compatible with non-cohesive, softer sediments such as sand and gravel deposits. The Open Hollow Stem Auger can also drill below water tables, and following the review of the hydrology and flooding data, we feel this is necessary. The depth of which the borehole is required is also possible with this rig and has the capacity to case the borehole sampling as it proceeds. Continued…/ Foundation Type Due to the presumed depth of parent rock, and the poor ground bearing capacity of the strata above, we recommend that end baring piles should be the method of choice. Silts and sands are prone to settlement, therefore bedrock must be met to ensure an equally distributed load - thus minimizing the risk of future complications. We recommend that the method of piling should be by way of replacement, Continuous Flight Auger (CFA), cast in situ concrete with reinforced concrete link beams between pile caps. This method is suitable in weaker soils and is economical and fast in installation. Concrete should be poured utilizing a tremie pipe from the bottom upwards to avoid cavities/air bubbles, thus minimising the probability of failure. Steel caging is then lowered into the concrete as reinforcement, extruded at the top of the pile where caps and beams are connected and installed. Continuous Flight Augers are the quietest and least disruptive form of piling as the method is rotary as opposed to percussion - which is relevant considering the site location. The Welsh Government has declared this area to be a ‘quiet area’ and any construction works should comply with Local Authority rules and regulations relating to permissible noise levels as recommended in BS 5228-1:2009, Code of practice for noise and vibration control on construction and open sites, the Control of Noise at Work Regulations 2005 and the Control of Vibration at Work regulations 2005. There are also several tall buildings adjacent to the site which could be affected by heavy vibrations caused by percussion. Continued…/ As the proposed site is located near the coast, the permeability of the concrete must be considered to protect the steel reinforcement inside. Steel will corrode rapidly when exposed to the combination of moisture, oxygen and sodium chloride (seawater) and therefore must be protected with a coat of red oxide. We also recommend lowering the permeability of the concrete by substituting between 25-65% slag cement for Portland cement. (Slag Cement Association, 2019) Design, layout, construction, monitoring and maintenance of pile foundations should be compliant with BS 8004:2015 – Code of practice for foundations. We recommend that an experienced structural engineer is involved during the design stage to carry out calculations of load-bearing capacities to accurately design the proposed layout and pile spacing. The plant used for the ground investigation boreholes would also facilitate the foundation piling method with additional attachments - therefore plant can remain on-site following investigation until required, thus minimizing costs and environmental impact. Sketches NB: The proposed pile sketches below are indicative and should be accurately re-designed by a structural engineer once the footprint and ground makeup are confirmed. DRAWINGS ARE NOT TO SCALE. Continued…/