Marine environmental survey and sediment chemistry assessment of Victoria Harbour, Hartlepool

Marine Environmental Surveys

Carcinus was commissioned to design and implement a multidisciplinary marine ecological survey of the approach channel and turning basin of Victoria Harbour, Hartlepool. The purpose of the study was to inform an Environmental Impact Assessment (EIA), with respect to predicted impacts of the proposed dredging and construction operations associated with scheme.

A detailed scope of works was reviewed by Carcinus and agreed with the Marine Management Organisation (MMO) (with input from Natural England) as the appropriate authority. Marine environmental surveys and a sediment chemistry assessment needed to be undertaken within a challenging timeframe to meet the project programme. Marine ecological elements were to inform a baseline ecological characterisation of the area and an assessment of potential impacts on ecological receptors. Sediment chemistry samples were to be obtained, analysed and interpreted to support a marine licence application in relation to the marine disposal of dredge spoil.

A single survey vessel was mobilised to undertake all sampling operations consecutively to meet the project timeframes and to maximise cost savings for our client. The dedicated multidisciplinary coastal survey vessel, ‘Humber Guardian’ was chartered and served as the platform for all marine survey deliverables described below. Samples were obtained from pre-defined locations, with positional accuracy achieved through the use of differential Global Navigation Satellite System (dGNSS) with offsets applied for equipment deployment locations and layback.

Benthic Ecology & Sediment Chemistry Analysis

Seabed sediment samples were collected from stations positioned throughout the survey area to allow characterisation of the benthic community and substrates across a range of water depths and seabed habitats. The survey comprised of grab sampling for benthic infauna, Particle Size Distribution (PSD) and sediment contaminants using a scientific grade, 0.1 m² stainless steel Day Grab. Benthic faunal samples were sieved and preserved on deck for later macroinvertebrate analysis at a taxonomic laboratory participating in the NMBAQC scheme. In addition, for each sample, a detailed record was made of sediment characteristics, conspicuous species and redox conditions along with high-resolution photographs.

Fish Ecology and Epibenthic Ecology

Epifauna and juvenile fish samples were collected by our specialist marine ecologists using a Cefas specification scientific 2 m beam trawl. Transects were run within the approach channel and processed, in full, onboard using the wet lab facilities. Details of the fish species present and their age structure were recorded to provide an understanding of fish populations and community structure. Later analysis revealed the area was mainly inhabited by juvenile flatfish such as plaice and dab. The survey also revealed an epibenthic invertebrate community that was suited to soft sediment environments and typical of the study area.

Drop-Down Video (DDV) Survey

Seabed video and still images were acquired to characterise areas of rocky outcrop. Using the STR SeaSpyder Drop-Down Video (DDV) system our ecologists recorded continuous video and took high-resolution still imagery of the seabed along five transects. The DDV system was deployed and towed along each predetermined transect, just above the seabed to avoid damage to the habitats present. Real time monitoring of a live video feed was undertaken by the onboard marine ecologists. All data was georeferenced with positional offsets and videos overlay applied. On completion of each of transect, quality assurance checks were made to validate the data obtained.

Marine Environmental Consultancy

Data were analysed using a multivariate statistical package to investigate relationships, similarities and differences, community structure and relationships. Sediment chemistry results were reviewed and compared against Cefas Action levels.

Fish ecology and epifauna assemblage was analysed by our marine consultants and abundance and distribution within the study area described. All video data and still images were analysed by our marine ecologists using in-house Carcinus image analysis methods to identify and enumerate species present, to inform the determination of biotopes and to provide qualitative assessments of the habitats and epibenthic communities present.

Findings from the multidisciplinary marine environmental survey were detailed within a comprehensive technical report. Our marine environmental consultants provided advice and guidance to the client throughout the lifespan of the project to facilitate delivery and input into the EIA within the desired timeframe.