If that proves to be the case, the sheen can be expected to eventually disappear. Another possibility is that it is formation oil escaping from the subsurface, using the Macondo well casing as flow conduit, possibly intersecting a naturally occurring fault, and then following that to escape at the surface some distance from the wellhead. If it proves to be oil from the subsurface, then that could indicate the possibility of an indefinite release of oil. The oil slick was comparable in size to naturally occurring oil seeps and was not large enough to pose an immediate threat to wildlife. The fundamental strategies for addressing the spill were containment, dispersal and removal. In summer 2010, approximately 47,000 people and 7,000 vessels were involved in the project. By 3 October 2012, federal response costs amounted to $850 million, mostly reimbursed by BP. , 935 personnel were still involved. By that time cleanup had cost BP over $14 billion. It was estimated with plus-or-minus 10% uncertainty that of oil was released from the well; of oil went into the Gulf. The report led by the Department of the Interior and the NOAA said that "75% [of oil] has been cleaned up by Man or Mother Nature"; however, only about 25% of released oil was collected or removed while about 75% of oil remained in the environment in one form or another. In 2012, Markus Huettel, a benthic ecologist at Florida State University, maintained that while much of BP's oil was degraded or evaporated, at least 60% remains unaccounted for. In May 2010, a local native set up a network for people to volunteer their assistance in cleaning up beaches. Boat captains were given the opportunity to offer the use of their boat to help clean and prevent the oil from further spreading. To assist with the efforts the captains had to register their ships with the Vessels of Opportunity, however an issue arose when more boats registered than actually participated in the clean up efforts - only a third of the registered boats. Many local supporters were disappointed with BP's slow response, prompting the formation of The Florida Key Environmental Coalition. This coalition gained significant influence in the clean up of the oil spill to try and gain some control over the situation. Containment booms stretching over were deployed, either to corral the oil or as barriers to protect marshes, mangroves, shrimp/crab/oyster ranches or other ecologically sensitive areas. Booms extend above and below the water surface and were effective only in relatively calm and slow-moving waters.