Sea Pen Engineering Prototype
2015 Notes from Brett Geraghty, University of Maryland: As a general note, I added a picture of a proposed location for Lolita’s new pen at the very bottom of the document as well as the link where it was found. This appears to be an ideal location because there is really only 2 sides of walls necessary.
Update 2023: I believe this was the location that Orca Network put forth in their plan.
Lolita’s size
Lolita is around 21 feet long and 7,000 pounds. Back in the 90s, a similar situation happened with Keiko the whale. Keiko was slightly longer than 21 feet, and weighed about 9,600 pounds. The initial estimated capacity of Keiko’s pen size was a little over 3 million gallons, or about 400,000 cubic feet. This was increased due to the pen going in deeper water than initially anticipated. His pen was 250 feet long, 100 feet wide, and 30 feet deep, for a volume of approximately 750,000 cubic feet. Lolita is of a similar length and weighs less, so a pen of this size or maybe even slightly smaller should suffice.
(http://www.orcanetwork.org/captivity/keikostory.html)
(http://community.seattletimes.nwsource.com/archive/?date=19980519&slug=2751600)
What materials should be used?
Then pen used to house Keiko was made of foam-filled polyethylene pipes, which were designed to float on the surface with the currents and also resist the pressure of any ice that might form. A company called Spectra-Net made the netting used to set the perimeter of the pen. The material they chose was graphite and Kevlar for high strength. The issue here is that this is still netting, which can lead to a risk of entanglement. To reduce the risk of entanglement, a closed wall pen would be the best solution. This would be different than Keiko’s pen, which was designed to move. A closed wall pen will certainly need to be anchored to keep it in place, which would drive the cost up as well. The proposed areas where this sea pen would be constructed are salt water. This means that any material used in construction would have to be corrosion resistant. Possible materials for the walls would be stainless steel or plastic. Stainless steel is more expensive and actually can corrode if the saltwater strips the thin passive layer off of the surface, so plastic would be more ideal for this application. Three types of plastics that would hold up in this environment are Polyvinyl Chloride (PVC), Polyethylene Terephthalate (PET), or Isoplast. All three offer resistance to seawater, with Isoplast being the strongest of the three. Isoplast is also more expensive, so a cost/benefit analysis would need to be done to determine if the extra cost would be worth the added longevity of the walls.
How would it be anchored
The construction of the pen would ultimately determine the anchoring necessary. The advantage of a pen with netting is that it would not necessarily need to be anchored. Assuming a net-walled pen is ruled out, new ideas have to be researched for securing the pen to the ocean floor. As suggested above, to avoid entrapment, some sort of solid material possibly with little holes drilled in it will be necessary. ~more information necessary~
