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The BEEMS (British EDF Energy Estuarine and Marine Studies) programme is funded by NNB Generation Company (HPC) Limited. Through this programme, Cefas provide authoritative scientific information on the marine and transitional waters in the vicinity of potential new build nuclear power stations and require the Supplier to deliver the marine sampling, profiling, and laboratory analysis services described in Section 3 below.
3. Contract Duration
The Contract implementation will start as soon as possible following contract award with the initial Contract period of 12 months, with the option to extend by up to 4 further periods of 12-months each.
4. Scope of Requirements
Cefas require the supplier to acquire sediment and water samples along with water column profiles of conductivity, temperature and depth (CTD) and other variables from a suitable vessel for the purpose of physical and chemical monitoring of the marine offshore environment adjacent to the Hinkley Point C new nuclear build power station.
It is anticipated that the required sampling will involve circa 3 days of vessel operations – two days for water sampling and one day for sediment sampling. The requirement includes collection of all samples and field measurements and all laboratory sample analysis, excluding hydrazine analysis which is to be conducted by Cefas laboratory.
General Survey Strategy:
The marine water and sediment sampling survey will be conducted in Bridgwater Bay adjacent to the Hinkley Point C construction site, in summer 2026, with the potential for continued annual sampling for at least 4 years. Water sampling will be carried out over a full tidal cycle at two main locations detailed in the sections below, with a full day dedicated to each location, requiring a minimum of two survey days. Sediment samples will be collected as detailed below and sampling will be conducted on a separate survey day. Suppliers will propose a survey schedule to fulfil the sampling requirements.
The survey schedule will be agreed prior to the survey but should be planned to maximise efficiency. At least one month prior to the first survey start date, the supplier will provide a RAMS including a description of the acquisition, storage and shipping, and laboratory analysis requirements of each of the samples. It is anticipated that this will be informed by the analysing laboratory but must be agreed by the Cefas team prior to the survey.
Water sampling
Water quality samples will be collected repeatedly over a full tidal cycle from a vessel at three stations in the vicinity of the cooling water outfall heads (CWO) and three stations in the vicinity of the fish recovery and return outfall (FRR). The stations are provided in Table 1 and Figure 1.
Target station locations have been selected based on modelling outputs and are aligned with tidal currents. Survey logistics, safety measures or ongoing works may require the precise locations to be amended during final survey planning or during the survey. Final target stations and positioning tolerance will be agreed between the supplier and Cefas before the survey during a kick-off meeting.
Surveys will be conducted annually in the summer to establish a contemporary baseline prior to the station commencing operation. It is anticipated that each survey will consist of two days of water sampling, one day at the CWO stations and a second at the FRR stations.
Water sampling – survey strategy
Water samples will be collected from six sampling locations: three close to the CWO, and three close to the FRR (Table 1). At each of these stations, samples will be taken at the surface and near bottom (nominally 0.5 – 1 m of the bed). A multi-parameter sonde (to continuously record salinity, temperature, dissolved oxygen and pH) will be deployed with a niskin bottle (or similar sampling bottle) at each depth and at each station. The vessel will work at one of the locations per day (FRR or CWO) and acquire multiple samples throughout the tidal cycle. So, for example, day one may look like this:
FRR A – Profile + surface and near bottom samples – transit to;
FRR B – Profile + surface and near bottom samples – transit to;
FRR C – Profile + surface and near bottom samples – transit to FRR A and repeat.
When the samples are processed, logged and stored the vessel will return to FRR A and start sampling again. This process will continue throughout the day with the aim of gathering as many samples as possible (nominally every hour) within one 12-hour period (time spent on site should be maximised by choosing an appropriate harbour to work from).
Hydrazine samples will be analysed by Cefas laboratories and as such, Cefas will provide sampling equipment, including pre-spike sampling contained, and an SOP for collection ahead of the survey. Suppliers should note that hydrazine samples require fixing with hazardous chemical reagents provided (acetone and ethanol spiked with isotopically labelled hydrazine).
There is a requirement for measurements of total residual oxidant (TRO) which must be conducted onboard with a colorimetric method and reagent. A CamLab CW1000 colorimeter or equivalent specification will be used, calibrated with a reference standard each day. The detection limit of the TRO test must be at least 0.02 mg/L. Three replicate measurements of TRO are required from each sample. The supplier will undertake this analysis immediately after taking water samples to avoid degradation.
Sediment Sampling
Sediment will be collected from a vessel at pre-determined (nearfield and control stations) (Table 3 and Figure 2) around the CWO and the FRR outfall. Surveys will be conducted annually to establish a contemporary baseline prior to the operation of the power station. It is anticipated that the sediment sampling will be completed in one day.
Sediment sampling – survey strategy
Sediment samples will be acquired with a Day grab and samples analysed for:
• Trace metals
• Particle Size Analysis (PSA)
• Total Organic Carbon
It is anticipated that sediment will be collected from all 20 stations (Table 3) in one day of survey. Replicate (spare) samples must be acquired at every station (but not analysed unless required). Supplier must obtain a full set of samples (A replicates) from one Day grab, with a second grab deployed at each station to provide a full set of replicate samples (B replicates). The B replicates will be processed and stored appropriately to be analysed only if there is an issue with the replicate A samples.
Table 4 provides a list of all determinands which need to be analysed from sediment. Analysis must be completed by a MMO certified laboratory and meet the minimum reporting requirements for each determinand . Samples will be collected using the correct type of cleaned scoop, decanted into appropriate receptacles and frozen / refrigerated all in line with the laboratory’s requirements (agreed with Cefas prior to the survey).