A group of skateboarding enthusiasts plans to rebuild Marshfield’s downtown skate park. Chris Cunio, one of the organizers, said the park, installed in the early 2000s, is nearing the end of its life. The goal is to replace it with a “skate plaza,” a more park-like environment with ramps, stairs, curbs, and other elements of a skate park, plus grass, trees, and benches. “It has a much, much higher aesthetic appeal,” he said. The concrete skating surfaces would have a 30-year life. The retail cost for a park that size would be $250,000 to $350,000, but some elements could be built by a contractor at a lower rate, Cunio said. Organizers plan to fund the park through donations and community preservation funds, and the amount to be requested from the town hasn’t been determined. They hope to break ground in the spring of 2014.