South Fork and Garden State Offshore Energy 1 (Formerly Skipjack) Offshore Wind Farms, Geotechnical Surveys

Anonymous — Thu, 26 Sep 2019 15:11:23 +0000

South Fork and Garden State Offshore Energy 1 (Formerly Skipjack) Offshore Wind Farms, Geotechnical Surveys Anonymous Thu, 09/26/2019 - 11:11

Challenge

In the emergent offshore wind industry of the U.S., GZA’s client sought to develop two wind farms off the East Coast: South Fork Wind Farm off Martha’s Vineyard in Massachusetts and Garden State Offshore Energy 1 (formerly Skipjack) Wind Farm off Maryland’s eastern shore. Each site was approximately 25 miles offshore, in 75 to 125 feet of water. Few geotechnical firms were capable of performing the complex geotechnical explorations required.

Solution

GZA drew upon its previous experience having successfully performed the geotechnical exploration program for the first U.S. offshore wind farm, Block Island Wind Farm, located off the coast of Rhode Island. GZA designed a program of deep geotechnical borings using wireline technology combined with down-hole geophysical logging executed from a liftboat housing 28 people for 24/7 operations. GZA also performed offshore and on shore geotechnical laboratory testing and managed all logistics including crew vessels and resupply of fuel, water, and food for the liftboat. In addition, drilling operations accommodated marine mammal protected species through use of exclusion zones and drilling shutdowns. Five geotechnical borings were completed at the South Fork site, each to a depth of 215 feet below the sea floor. Seven geotechnical borings were completed at the Skipjack site, each to a depth of 165 feet below the sea floor. Drilling operations were conducted 24 hours a day. The offshore drilling for South Fork was conducted in August 2018, and the drilling for Skipjack was conducted between September and October 2018. This time frame also included some weather down time for Hurricane Florence and Hurricane Michael.

Benefit

GZA delivered a preliminary geotechnical engineering report for each site, which included interpreted soil profiles, scour evaluation, pile and monopile design parameters, pile and monopile axial capacities, p-y, t-z, and q-z curves for the piles, factors of safety for the gravity foundation, and settlement estimates. Under challenging geologic and logistical conditions, the work was conducted safely, expertly, and expeditiously.

Insights

Developed the offshore geotechnical survey and implemented it as Prime Contractor
Deep borings and downhole geophysical logging
Offshore operations logistics
24/7 operations
Geotechnical profiles and design parameter values
Offshore and on shore geotechnical laboratory testing
Preliminary foundation design
Work accommodated protected species

Rhode Island

Energy

Water

Geotechnical Engineering Services

EHS Regulatory Compliance

Block Island Offshore Wind Farm

Anonymous — ��Ϸ��d, 25 Sep 2019 17:28:11 +0000

Block Island Offshore Wind Farm Anonymous ��Ϸ��d, 09/25/2019 - 13:28

Challenge

In 2008, Deepwater Wind entered into an agreement with the State of Rhode Island to develop the first US offshore wind farm. The project consisted of 5 wind turbines located within Rhode Island state waters approximately 3 miles southeast of Block Island, Rhode Island. At this time, Europe had developed many offshore wind farms, predominantly using monopile foundations, which were not manufactured in the US. Given the failure of previous US offshore wind projects, European firms were waiting to see how and if the US offshore wind industry would develop before becoming engaged.

Solution

In 2008, GZA was contracted by Deepwater Wind to provide geotechnical engineering services for the offshore wind farm. The wind turbines were designed with a jacket foundation anchored with steel pipe piles. GZA prepared a geological desktop study and preliminary pile capacity estimates to estimate approximate foundation length and design the depth of the geotechnical explorations.

GZA managed and observed geophysical surveys conducted by Ocean Surveys Inc. (OSI) of Old Saybrook, CT. The geophysical survey consisted of a hydrographic survey, shallow subbottom profile survey, deep subbottom profile survey, side scan sonar survey, and a marine magnetic survey. A turbine layout plan was generated by Deepwater Wind based upon the results of the geophysical survey and recommendations by OSI and GZA.

GZA developed and implemented an offshore geotechnical investigation consisting of 8 borings. Geotechnical explorations were conducted from a lift boat in approximately 75 to 100 feet of water. Borings were drilled by DOSECC Exploration Services LLC using a vessel mounted drill rig, under the direction of GZA. A total of eight geotechnical borings were completed, each to a depth of 225 feet below the seafloor. In addition to coring and sampling, a downhole cone penetrometer (CPT) was pushed at discrete intervals and electronic logging was performed in the borehole to determine in situ properties of the soils.

Off-shore laboratory testing for index and strength properties were performed. On-shore laboratory testing was completed in GZA’s geotechnical laboratory in Hopkinton, Massachusetts consisting of index testing, triaxial strength testing, and consolidation testing.

A geotechnical evaluation and engineering report with interpreted soil profiles was completed. The report included recommended soil parameter values for each turbine location, pile capacity, pile axial and lateral deformation curves, and analysis of pile drivability and constructability issues.

Construction of the project started in 2015 and was completed in 2016. GZA supported the project during construction by providing geotechnical design of the port facility in Providence, Rhode Island which was used for staging and assembly of the wind turbine components. This included evaluation of the stability of the existing seawall, geotechnical investigation of the port facility, bearing capacity evaluation of the staging area, and design of temporary foundations for assembly and staging structures for the tower segments.

Benefit

The success of the Block Island Wind Farm paved the way for additional development of offshore wind along the US Northeast and Mid-Atlantic coast. Projects are being pursued by global developers, engineering firms, manufacturing, and contractors.

Insights

Conducted Geologic Desktop Study
Observed Geophysical Surveys
Developed and Implemented Offshore Geotechnical Program
Oversaw Offshore Drilling Operation
Offshore and On-shore Geotechnical Laboratory Testing Program
Geotechnical Engineering Evaluation and Report Including Pile Capacity.
Provided Geotechnical Engineering of Port Facilities for Staging and Assembly of Wind Turbine Components

Rhode Island

Energy

Geotechnical Engineering Services

Waterfront and Coastal Engineering