A Homer-based biologist has determined whatever shells and organic marine debris was attached to the Endeavour-Spirit of Independence in the past did not survive the trip from Singapore to Cook Inlet waters.
In a report made available to the Clarion on Thursday, David Erikson, senior biologist with URS Corporation, determined that based on his inspection of the rig, the time the Endeavour spent in dry dock and out of the water during its about 30-day trip aboard the Kang Sheng Kou was the “dominant factor” in killing the attached marine biota thus “substantially reducing the potential for any non-indigenous or invasive species” to be introduced into Kachemak Bay where the rig is currently.
Alaska Department of Fish and Game officials talked with the rig’s owner, Buccaneer Energy, last week about what organisms might have still been attached to the rig when it was brought north from Singapore after a Homer resident plucked a small shell from one of the rig’s legs during a tour.
The shell that Larry Smith said appeared to be a foreign oyster was “one of thousands” in the area where he found it. The discovery prompted Fish and Game’s invasive species program to offer Buccaneer a survey of any organisms still on the rig. Buccaneer instead hired Erikson to do such a review on Sept. 10 and 11.
It is against the law to “knowingly introduce” an invasive species in Alaska, specifically “fish, invertebrates and amphibians,” said Tammy Davis, a Juneau-based Fish and Game biologist who leads the department’s invasive species program.
In general, jack-up rigs provide “an excellent hard substrate for encrusting marine invertebrates and algae to attach to,” and some marine growth on a rig’s large leg structures is “to be expected,” Erikson wrote in his report. For that reason, rig legs need periodic maintenance and cleaning to reduce the potential of invasive species being introduced into an area.
“From the size of the shells, the attached oyster shells appeared to be from mature specimens at least a couple of years old,” Erikson wrote. “The number of species of oysters or barnacles present on the rig and their age was not determined.”
Erikson wrote that some of the shells might have been from an earlier period in the rig’s history.
Ginny Litchfield, area manager of Fish and Game’s habitat division, said the department has received the report and is reviewing it.
“ADF&G will review all pertinent information prior to determining course of action or possible follow-up,” she wrote in an email.
The first day of Erikson’s survey, he wrote, focused on the rig’s three legs, particularly the portions near the waterline or that were in the water during the period when the rig was cold-stacked. Erikson took photographs and collected samples of shells from the rig’s leg guide slots and on the deck and walkways that had come detached.
The second day of the survey focused on the spud cans — the bottoms of the legs — and the supporting members.
“These areas had not been recently scraped and painted like the rest of the legs and marine growth was evident,” Erikson wrote.
Photos and samples of a film of encrusted marine life on a structural component of the spud can were taken for microscope analysis.
Shells found on the rig were primarily confined within a 4-inch space between the legs and the jacking guide as the jacking movement doesn’t scrape them off, Erikson reported. Most of those shells were covered with a thin coat of gray paint and were determined to be primarily oyster shells and barnacles, he wrote.
None of the shells examined supported any live animals and contained no remnant tissue, Erikson wrote. Some shells had started to deteriorate, he added.
The sampled marine film from the spud can contained no living organisms either. Microscope analysis determined the mat contained dried calcareous tube worm cases, juvenile mussels and a few juvenile clams, Erikson wrote.
Erikson recommended Buccaneer remove loose shell debris from all areas near the rig’s legs, scrape and paint spud cans, supporting structures and catwalks at the same time as other parts of the rig to minimize the risk of invasive species, clean and monitor the 4-inch gap near the jacking guides and clean marine biota from leg structures after the rig has completed drilling each year.
Brian Smith can be reached at email@example.com.