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 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.