Question: The 2011 USA Sevens competition was held at a football stadium with an elevation how many feet above sea level?

Context paragraphs:
2015 USA Sevens: The 2015 USA Sevens (also sometimes referred to as the 2015 Las Vegas Sevens) is the twelfth edition of the USA Sevens tournament, and the fifth tournament of the 2014–15 Sevens World Series.  The tournament is scheduled for February 13–15, 2015 at Sam Boyd Stadium in Las Vegas, Nevada.

2007 USA Sevens: The 2007 Steinlager USA Sevens was a rugby union sevens tournament held on February 10 and February 11, 2007 in the United States at 44,500 capacity Petco Park in San Diego, California.  It is part of the IRB Sevens World Series.  Although the 2006–07 season is the eighth of the Sevens World Series, this was only the fourth edition of the USA Sevens, which began in 2004 as a part of the 2003-04 series.  This was the first time for the event in San Diego with past editions being held at The Home Depot Center in the Los Angeles suburb of Carson.

2014 USA Sevens: The 2014 USA Sevens (also sometimes referred to as the 2014 Las Vegas Sevens) was the eleventh edition of the USA Sevens tournament, and the fifth tournament of the 2013–14 IRB Sevens World Series.  The tournament was held January 24–26, 2014 at Sam Boyd Stadium in Las Vegas, Nevada.

2010 USA Sevens: The USA Sevens is played annually as part of the IRB Sevens World Series for international rugby sevens.  The 2010 competition, which took place on February 13 and February 14 at Sam Boyd Stadium in Las Vegas, Nevada, was the fourth Cup trophy in the 2009–10 IRB Sevens World Series.  It was the first edition of the USA Sevens to be held in the Las Vegas area; the tournament had been hosted by the Los Angeles suburb of Carson, California from 2004 to 2006 and by San Diego from 2007 to 2009.

Jon Prusmack: Jon Prusmack is a former United States national rugby team player and is currently a sports entrepreneur.  Prusmack is the founder and CEO of United World Sports (UWS), a sports marketing and event company.  UWS owns and operates the annual USA Sevens, an international rugby sevens tournament held every February at Sam Boyd Stadium in Las Vegas.  The USA Sevens is the largest annual rugby sevens tournament in North America.  UWS also owns and operates the annual Collegiate Rugby Championship, a college rugby sevens tournament held every June at PPL Park in Philadelphia.

Sam Boyd Stadium: Sam Boyd Stadium is a football stadium in Whitney, Nevada, United States, an unincorporated community in the Las Vegas Valley.  It honors Sam Boyd (1910–1993), a major figure in the hotel and casino industry in Las Vegas.  The stadium consists of an uncovered horseshoe-shaped single-decked bowl, with temporary seating occasionally erected in the open north end zone.  The field has a conventional north-south orientation and is at an elevation of 1600 ft above sea level.

2011 USA Sevens: The 2011 USA Sevens competition was held on February 12 and February 13 at Sam Boyd Stadium in the Las Vegas, Nevada area.  The USA Sevens is played annually as part of the IRB Sevens World Series for international rugby sevens (seven-a-side version of rugby union).  It was the fourth of eight events in the 2010–11 IRB Sevens World Series.

USA Sevens: The USA Sevens (also sometimes referred to as the Las Vegas Sevens) is a rugby sevens tournament held annually during the second weekend of February in Las Vegas in the United States.  The USA Sevens is the largest annual rugby competition in North America, drawing over 60,000 fans, and is broadcast live in the United States by NBC and NBC Sports.  The USA Sevens was introduced in 2004, and has been held at its current home, Sam Boyd Stadium in Las Vegas every February since 2010.  The USA Sevens tournament features 16 teams representing countries from every continent, including the host, the U.S. national team.

2017 USA Sevens: The 2017 USA Sevens (also sometimes referred to as the 2017 Las Vegas Sevens) was the fourteenth edition of the USA Sevens tournament, and the fifth tournament of the 2016–17 World Rugby Sevens Series.  The tournament was played on 3–5 March 2017 at Sam Boyd Stadium in Las Vegas, Nevada.

2016 USA Sevens: The 2016 USA Sevens (also sometimes referred to as the 2016 Las Vegas Sevens) is the thirteenth edition of the USA Sevens tournament, and the fifth tournament of the 2015–16 World Rugby Sevens Series.  The tournament was played on 4–6 March 2016 at Sam Boyd Stadium in Las Vegas, Nevada.  This was the first time a World Rugby Sevens Series event was contested on artificial turf.

Supporting paragraphs: 2011 USA Sevens Sam Boyd Stadium
Answer: 1600