ITT for provision of mudflat monitoring surveys at Hinkley Point C

Descriptions

The BEEMS (British EDF 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 a competent Supplier to deliver the element described below.

Cefas require services to conduct intertidal mudflat monitoring surveys for the Hinkley Point C (HPC) Nuclear New Build project to meet regulatory environmental monitoring requirements. The ongoing mudflat monitoring programme focuses on a bivalve species, the Baltic tellin, Macoma balthica. This species is a key component of the Hinkley Point mudflat community and was identified, during the HPC environmental impact assessment process, as potentially sensitive to localised seawater temperature increases brought about by the cooling water discharges from HPC. As such, biological samples and physical measurements are collected every year. The monitoring programme is focussed on mudflat intertidal areas around Bridgwater Bay and at a reference site in Wick St. Lawrence, located to the north of the bay.

The Contract implementation is expected to start mid-February 2026 and the initial Contract period will end 31 December 2028, with the option to extend by 2 further periods of 12 months each to maximum end date of 31 December 2030.

Scope of Requirements:

Biological samples are collected at all the sampling stations in high shore and low shore and require the following:

a) Six replicate macrofauna samples are collected using a 0.01 m² corer to a depth of 15 cm. Each sample is placed in a sealed plastic bag and transported via private courier to a third-party laboratory for macrofauna analysis. The courier service, arranged by the Supplier, ensures delivery to the Cefas appointed UK based laboratory within 24 hours of collection. Alternative approaches to this analysis method are welcomed and should be outlined within your proposal. (Figure 2)

b) Some mud is then shovelled into a 1 mm mesh sieve and sieved on site to collect up to 75 Macoma balthica individuals by hand using tweezers for population dynamic analysis. Samples are stored in a plastic ziplock bags (Figure 3). If only small individuals are found, an additional 10 - 15 larger individual (>1 cm width) must be collected for the condition index measurements and placed in a separate ziplock bag for a condition assessment. Samples are stored in a fridge or in cool box to keep individuals alive for processing at the end of the sampling day. These are then sent to the Lowestoft Cefas Laboratory.

c) Sediment samples are collected using a 50 ml plastic syringe with a truncated tip to sample the first 2 cm of sediment as a core (five replicate). Four of the five samples (for pigment and nutrient analysis) are pooled together in a plastic ziplock bag to account for small scale variability and one sample is stored in a pot for Particle Size Analysis. Samples are stored in dry ice for the duration of the survey. These are then sent to the Lowestoft Cefas Laboratory.

Physical measurements are carried out at the low shore stations only and require the following:

a) Temperature and pressure sensors (Star-Oddi's Data Storage Tag DST centi-TD) are deployed on metal stakes (Figure 4) at the five low shore stations on stakes (see Figure 1). The sensors, which remain in situ, record temperature continuously and data need to be uploaded on a quarterly basis.

Biological samples must be collected twice a year during spring tide windows in February and in August. Physical measurement surveys must be carried out four times a year, in February, May, August and November. Note that the biological and physical measurements in February and August are completed during the same survey.