For decades, petroleum and arsenic seeped into the groundwater aquifer below a Union Pacific Railroad rail yard a stone’s throw from Fremont Boulevard. Today, after the city of Las Vegas leveraged millions in Environmental Protection Agency funding and private capital, the city and federal agency say it’s one of the nation’s biggest environmental success stories, where a so-called polluted “brownfield” became a community asset — Symphony Park. Kurt Goebel, senior vice president, principal geologist and environmental division manager at the firm Converse Consultants, said he has worked on the project with the city for years. During a Nevada Brownfields Conference tour of sites across the Las Vegas Valley on Wednesday, Goebel said Symphony Park’s transformation shows what is possible when local governments, nonprofits, tribes or developers make use of federal dollars to clean up brownfields. “Symphony Park really is the ‘Cinderella’ story of brownfields,” Goebel said. “It started with a vision.…