On March 24, 2014, the twenty-fifth anniversary of the spill, NOAA scientists reported that some species seem to have recovered, with the sea otter the latest creature to return to pre-spill numbers. Scientists who have monitored the spill area for the last 25 years report that concern remains for one of two pods of local orca whales, with fears that one pod may eventually die out. Federal scientists estimate that between 16,000 and 21,000 US gallons (61 to 79 m3) of oil remains on beaches in Prince William Sound and up to 450 miles (725 km) away. Some of the oil does not appear to have biodegraded at all. A USGS scientist who analyses the remaining oil along the coastline states that it remains among rocks and between tide marks. "The oil mixes with seawater and forms an emulsion...Left out, the surface crusts over but the inside still has the consistency of mayonnaise – or mousse." Alaska state senator Berta Gardner is urging Alaskan politicians to demand that the US government force ExxonMobil to pay the final $92 million (£57 million) still owed from the court settlement. The major part of the money would be spent to finish cleaning up oiled beaches and attempting to restore the crippled herring population.