Project SHEET Baydaratskaya Bay, Pipeline crossing

INTRODUCTION features The Baydaratskaya Bay Project is located in the Client Yamalgas invest () Kara Sea in the North of Russia. The Kara Sea is bordered on its western side by Novaya Zemlya Period July - November 2008 and on the east by the North Siberian Coast. Location Baydaratskaya Bay, Kara Sea, Baydaratskaya Bay is located in the south of the Russian Federation Kara Sea between the Ural Coast and the . Yamalgasinvest (Gazprom) is planning Main Contractor Mezhregiontrubo provo destroy (MRTS) the construction of four pipelines and two cable crossings at Baydaratskaya Bay for the exploitation of the Bovanenkova and Harasawejskoje gas field on the Yamal Peninsula. The pipeline trajectory continues to Uktha an important industrial city in the Komi Republic of North Western Russia. The gas mainline system Bovanenkova-Uktha is part of the Yamal- gas mainline projected for natural gas supply to the gas-transport network of Central Russia an d further on to Western Europe.

Mezhregiontruboprovods troy (MRTS) was awarded the works as the main contractor for the A installation of 2 pipelines (main and reserve) with an outside diameter of 1,219 mm. The de sign A location map capacity of these two subsea pipeline s is 68.5 B Work in progress billion m3 per year. The overall scope covered the C Due to its northern location the area is characterized by a dredging of a 40 km long trench from 7 km severe arctic climate allowing operations only to take place from July until October offshore from the Yamal Coast to 21 km offshore from the Ural Coast.

ABOUT BOSKALIS OFFSHORE Boskalis Offshore (BO) was subcontracted by mining, offshore supply and support services and decommissioning services. MRTS to execute the trenching works for the first Boskalis provides clients with tailored, project-specific solutions for above pipeline crossing. Boskalis Offshore brings dredge related offshore services . together the offshore skills, resources and experience of Royal Boskalis Westminster. The ARCTIC CLIMATE group's offshore capabilities include seabed Due to its northern location the area is characterized by a severe arctic rectification works for pipeline/cable and platform climate allowing operations only to take place from July until October. During installation, construction of pipeline shore the remaining part of the year the temperatures drop drastically and sea ice approaches and landfalls, offshore mineral covers the Kara Sea. In addition the remoteness of the area demands an

B C 01 — 2012 The information contained in this data sheet is for guidance purposes only and may be subject to changes. © Boskalis. All rights reserved. vessel to perform thetrenchingoperationsatgreat vessel toperform Dynamic position/dynamictrackingenabledthe extremely coldconditions. dredger hasbeenadaptedforoperatingunder Because ofpreviousoperationsinthearcticthis was mobilizedforthedredgingoperations. The largetrailingsuctionhopperdredger‘Oranje’ TRENCHING OPERATIONS its deepestpoint. variedbetween9and23mat pipeline trajectory possible danger. Thewaterdepthalongthe sufficiently deepundertheseabedtoavoidany 1.5 m(includingcoatings)hadtobeburied pipeline whichhadadiameterofapproximately indepthbetween0.2and1.0m.The varying showed scarsintheseabedcausedbyseaice ofthepipelinetrajectory performed Surveys was toprotectthepipelinefromseaice. thepipelineunderseabed objective ofburying between3and3.5m.Primary depth varying between thetoelinesof8m,1:2slopesanda The trenchwasdesignedtohaveabottomwidth TRENCH DESIGN lacking andnofacilitiesareavailable. extensive preparationsinceinfra-structureis D E Pipeline crossing Ba 2008 aspertherequirementsofClient. The workintheseasonof2008wassuccessfullycompletedearlyNovember load. whilst navigatingoverthepipelinetrenchatslowspeedwhiledischarging origin alseabedlevelwasbackfilledinonelayer.Theselayerswerecreated uptothe level of0.5mabovethetoppipeline.Theremainingpart level. Backfillingofanentiresectionwasrealizedinlayers0.5muptoa the sand-watermixtureuntilaheapwascreateduptooriginalseabed abovetherequiredlocationanddischarged the vesselremainedstationary pipeline. Duringthefirststageofbackfilling(fixingpositionpipeline) the laidpipelineensuringasafedistancebetweendragheadand heightabovethetopof suction pipe.Thepipewaskeptatacertain Backfilling wasrealizedbydischargingthedredgedmaterialthrough was fixed.Onceacompletesectionfixedbackfillingcommenced. 200or500mtoensurethatthepositionoflaidpipeline backfilled every the UralCoast.Priortobackfillinganentiresectionspecificlocationswere for backfillingwasobtainedbydredgingatadesignatedborrowareanear sections wherepipelayinghadbeencompletedbyMRTS. Suitablematerial ofthe Upon completionofthetrenchingoperationsbackfillingwasperformed BACKFILLING OPERATIONS the vesselwasequippedwithdragheadsclayvisors. and inordertoachievethemostoptimalproductionthesesoilconditions installed onthevessel.Soilconditionsvariedbetweenmediumtohardclay hopper dredgerherself.Forthatpurposemulti-beamtransducerswere bythetrailingsuction wereperformed accuracy .Hydrographicsurveys F E D F ydaratska Working inseaice great accuracy thetrenchingoperationsat perform dynamic trackingenabledthevesselto Work inprogress.Dynamic positionand facilities areavailable since infrastructureislackingandno demands anextensivepreparation The remotenessofthearea y a B y, Russia www.boskalis.com [email protected] F +317869555 T +317869000 The Netherlands 3350 AAPapendrecht PO Box43 Royal BoskalisWestminster N.V.