Worries about some sonic seafloor mapping in Estero Bay were apparently unfounded as the owner of the Morro Bay Power Plant uneventfully conducted its research over two days — Oct. 26-27 with no discernable adverse effects.
Dynegy, Inc., of Houston Texas, owners of the Morro Bay Power Plant gave notice that it would be conducting underwater testing to map the seafloor surrounding its old oil loading pipeline, that runs underground from the plant’s old tank farm (now removed) out to a former oil tanker mooring, offshore from Morro Strand Beach. The mooring was removed many years ago, and Dynegy needed to map the seafloor to see about removing the actual pipes.
Over time, sand could be expected to pile up and further bury the pipes, or even scour the sand and expose them. The company really didn’t know and needed to map the area to find out.
Tankers used to moor offshore and deliver various fuels — diesel, kerosene, fuel oil — to be burned at the plant. But with the completion of a dedicated gas pipeline to the plant from the Oildale area, PG&E weaned itself off the dirty-burning fuels switching to natural gas exclusively until the plant closed for good in 2013.
Dynegy, the plant’s current owner, conducted underwater sonar mapping with an eye at eventually removing the old loading line. A tank farm both at the plant and on a hillside above Hwy 41 that used to store fuel, have since been removed, leaving just the underground loading line in place from the old fuel system.
Confusion had set in with some in the community when information about the mapping became known, thinking it was the same kind of high-energy seismic testing that had been proposed by PG&E to study offshore earthquake faults for its Diablo Canyon Nuclear Power Plant.
Those potentially devastating tests, though called for by the State, were vehemently opposed by local activists and eventually the plan was scrapped.
Such high-energy sound blasts are harmful to sea life, especially whales, dolphins and seals and sea lions, among numerous other species. The confusion prompted the City to ask Dynegy to clarify what its intentions were with the mapping work.
“Dynegy, Inc., owner of the now-defunct Morro Bay Power Plant, is working to decommission and remove a large pipe that allowed oil tankers to connect to the facility and offload fuel to be used to run the plant. This decommissioning of the offshore tanker berth requires surveying to understand how to best undertake the project.”
The State Lands Commission has been after the plant owners — from PG&E to Duke Energy and now Dynegy — to first decommission the line and now, apparently to remove it.
But there is reason to be skeptical of the plans, as Dynegy is also pursuing a possible wave-energy facility offshore from Morro Bay and has been given the OK to do a test of the technology by the Federal Government.
Running the electrical lines up the old fuel line into the plant and connecting to the power grid through an existing switchyard is one of the aspects of that potential project.
Removing the line could force the company to use the plant’s old outfall canal, the only other underground access to the plant and the power grid.
And complicating this scenario is a developing proposal by Trident Wind, LLC., a Washington State company looking to build a 1,000 megawatt wind farm that would be located some 15 miles offshore from Estero Point (Cayucos), some 20 miles northwest of Morro Bay.
The City and Trident signed a “memorandum of cooperation” Oct. 13, pledging to work together on its project that would produce renewable clean energy. That initial proposal would bring electrical lines to shore through the outfall canal at the base of Morro Rock.
A Trident representative told the Council it would be 10 years or more before it built it’s farm, consisting of hundreds of 30-foot tall, wind turbine buoys anchored to the seafloor, which is nearly a mile deep in the general area being looked at.
Dynegy’s survey used electronic sonar and a fathometer, similar to the devices used by millions of boaters and fisherman all over the world. “This is a routine survey of a type performed offshore California many times each year,” Ninah Rhodes Hartley, who is working on the project for Dynegy, said in a letter to the City. That letter was released to the public by the City to try and ease fears of residents.
The company will use a fathometer to gauge depth and side scan sonar to map the seafloor contours at the offshore berthing site. “Its purpose,” Rhodes Hartley said, “is to simply take a picture of the seafloor and will use an electronically generated sound frequency of 400 kHz (kilohertz).
“This electronic sonar causes no harm to sea life or humans. In contrast, seismic surveys use air guns to produce high decibel explosions [200 to 230 dB sound waves] to study geologic formations under the seafloor. Air guns and side scan sonar are two entirely different things.”
On a chart included in Fugro’s letter, the fathometer is listed to be 190 decibels (dB) at 400 kHz and is “inaudible to sea life.” So while the dB level is louder than any known natural sound, the wavelength is extremely short making it inaudible.
As a contrast the seismic testing that PG&E had proposed but abandoned in the face of opposition, was up to 230 dB, at .2kHz and was intended to penetrate deep into the sea floor to map earthquake faults, and not simply bounce off the ground. Those “air guns” while high energy have long wavelengths, making them audible to and potentially harmful to sea life.
As for the possible future of the approximately 117-acre plant property, City officials have said that the company intends to sell the land in one piece along with all its holdings in California.
