The bathymetric survey at the proposed survey area for pipeline launching in Al Ghubrah IWP Plant was conducted by Nusail Engineering Consultancy, Sultanate of Oman. The site is approximately 20 km west of Muscat City on the coast of the Sea of Oman, occupying an area of approximately 8.4 hectares. The contract was awarded by Oman Power and Water Procurement Co. (SAOC) for the Independent Water Project in Al Ghubrah, Muscat.

Scope of the Survey

The survey aimed to provide supporting data for the bathymetric survey and seabed survey conducted by Nusail Engineering Consultancy. The marine survey covered the epibenthic biodiversity of the sub-tidal zone in the vicinity of the GPDP plant within the 4 km² site. The survey also included logging of temperature, spot measurements of physical seawater quality parameters, a marine baseline study of sediments and seawater quality, and videography.

Bathymetric & Topography Survey

The survey covered an area 2 km in width along the shoreline and 2 km into the sea, with a minimum line spacing of 20 m, totaling around 4 km². During the survey, a water level recorder was installed, and the state of the sea was described. The depth data collected was reduced to the local vertical level using water level variations registered with the recorder.

Equipments of the Study

• Odum Hydrotrac Echo Sounder
• Transducer
• Valeport Tide Gauge
• Sokkia RTK GPS
• Sokkia Total Station and Bar Plate
• Valeport Midas CTD+
• Video Ray Pro III XE GTO ROV System
• Water Sampler/Sediment Sampler
• Video Ray Pro III Integrated Control Unit
• Video Ray Pro III Spares Kit
• Video Ray Tether Cable, Neutral 75m
• Video Ray Tether Cable, Positive 40m
• Ocean tools VO-5 Video Overlay (3 Ch)
• 14" Composite Video Monitor
• Pioneer DVD Recorder

Bathymetry Survey Procedure

Phase and speed settings ensured the best possible record unobstructed by annotation and converted the antenna position into local UTM projection coordinates. Positions were entered into the navigation system and displayed onto the helmsman’s display. Underwater photography and video recording methods were used for underwater observations of the epifauna, with ROV Video also employed for the visual survey.

Seabed Photos

The course of each transect was plotted using a Global Positioning System (GPS). Images were captured, with locations noted at initial points, when habitats or particular features were observed, and at one-minute intervals. Digital transect records were included by the contractor as DVDs attached to the report.

Result

An Odom Hydrotrac single frequency (200 kHz) single beam echo sounder was utilized to acquire bathymetry data. As a result of the ‘bar check’ results, a velocity of 1540 m/s was used as the velocity of sound in water during data acquisition. The bathymetry data were processed using HydroPro Software. The seabed was predominantly a featureless sandy bottom dominated by polychaete and mollusc communities, with no evidence of rocky patches. Interesting new records of an octocoral, octopus, and nudibranchs were reported, warranting further investigation. The overall conclusion from the monitoring studies is that ongoing discharges from the existing plant adversely impact bottom communities, but the replacement of the MSF/Power plant units with the SWRO plant should improve conditions.