“There are 209 land features still unoccupied in the South China Sea and we could seize them all. And we could build on them in 18 months.”
The U.S. dispatched freedom-of-navigation patrols to the South China Sea six times since 2011, including three times navigating the waters around the Spratly Islands. But no patrols have gone within 12 nautical miles of the rocks and reefs where China has built its artificial islands since 2012.
Here are highlights, A 28 page report for the US congress "Chinese Land Reclamation in the South China Sea: Implications and Policy Options", by Ben Dolven, Specialist in Asian Affairs, Jennifer K. Elsea Legislative Attorney, Susan V. Lawrence Specialist in Asian Affairs, Ronald O'Rourke Specialist in Naval Affairs, Ian E. Rinehart, Analyst in Asian Affairs June 18, 2015
In a May 30, 2015, speech, Secretary of Defense Ashton Carter said China had created over 2,000 acres (809 hectares) of land in the South China Sea in the past 18 months, “more than all other claimants combined ... and more than in the entire history of the region.” China has also undertaken construction of harbors, radar towers, an airstrip long enough to support most military aircraft, and other facilities. Defense Department officials have also reportedly identified artillery vehicles on at least one of the artificial islands.
Big Dredger that in 193 days built up island volume triple the volume of the Hoover Dam
Chinese reports credit new technology for China’s success in rapidly transforming Chinese-controlled features in the Spratlys. China has deployed a sophisticated new dredger known as the Tianjing, or “Sky Whale,” operated by state-owned Tianjin Dredging Co., Ltd, a unit of China Communications Construction Company, Ltd. According to reports on the website of the vessel’s designer and owner, the Tianjing was designed by Shanghai Jiaotong University and the German engineering firm Vosta LMG and built by China Merchants Heavy Industry Yard in Shenzhen between April 28, 2008 and January 2010. It is now the third largest self-propelled cutter suction dredger in the world, and the largest in Asia, with the ability to dredge to a depth of 30 meters (98 feet) and to move 4,500 cubic meters (159,000 cubic feet) of clay, compacted sand, gravel, and rocks per hour. Because it is self-propelled, it can make its own way to the southern part of the South China Sea, unlike non-self-propelled vessels, which need to be towed. Once in place, the Tianjing can easily shuttle among all the Spratlys reefs that China occupies.
Writing on a popular Chinese news aggregator site, Guancha, commentator Shi Yang reported that the Tianjing spent 193 days moving among five reefs in the Spratly Island group between September 2013 and June 2014. Shi estimated that in that time, the Tianjing blasted more than 10 million cubic meters (13 million cubic yards) of sand and sea water onto the reefs, or the equivalent of three times the volume of concrete used to build the Hoover Dam. “In this reclamation contest involving national will and capacity, where China is coming from behind, the advanced technology and superior products of the industrial departments will undoubtedly be crucial,” Shi wrote.
NBF - China build up its urban areas with a new Los Angeles every year. It would be relatively trivial for China to build 10 to 20 new Dredgers and build up the 209 sites into more artificial islands.
Short of direct U.S. military intervention, it is not clear what the United States can do to directly stop China’s land reclamation activities. U.S. options for responding to those activities thus appear to consist of potential actions for imposing costs on China for continuing those activities. With many of these options, as with current policy, there is a risk that the United States may either provoke strong Chinese reactions or be seen as ineffectual if China does not change course.
There is a 164 page document on Perspectives on the South China Sea Diplomatic, Legal, and Security Dimensions of the Dispute by the Center for Strategic and International Studies (CSIS) 
SOURCES - Newsweek, Chinese Land Reclamation in the South China Sea: Implications and Policy Options, Perspectives on the South China Sea Diplomatic, Legal, and Security Dimensions of the Dispute