MINNEAPOLIS, MN — Target Field, the Minnesota Twins' new $545 million ballpark, has earned LEED-Silver certification, becoming the second Major League Baseball stadium to pass muster under the standards set by the U.S. Green Building Council.

The council, through its Green Building Certification Institute, conferred the rating on Target Field on Thursday, just in time for the ball club's first home opener at the new stadium on Monday.

The Washington Nationals' ballpark, so far the only other MLB stadium to achieve green building certification, also has LEED-Silver certification, which was awarded in 2008. However, Twins' management emphasizes the teams are not tied: Target Field scored 36 LEED points in acquiring its rating; National Park had 34.

Building the open-air ballpark in Minnesota's historic Warehouse District posed a number of challenges, including its location -- the site sits on a former brownfield -- and securing funding to support the green design and pursuit of LEED certification.

In order to build the park, contaminated soil was treated and replaced. Groundwork included the installation of a giant cistern, which is buried beneath the warning track. Water collected in the cistern will be filtered and used for irrigation and hosing down the seating bowl. The site was a made a hub for public transportation by buses, commuter trains and light rail service.

"Target Field is baseball's most urban ballpark, and the site constraints we faced were actually paramount to achieving LEED certification," said Earl Santee, senior principal at Populous, the design firm that managed the certification process for the ballpark.

"With the addition of new, immediate access to public transportation at the ballpark, we've helped to bridge the site to its urban surroundings as a model for positive growth," Santee said in the team's announcement of its certification.