The Bunker Hill Bridge cast a long shadow over the sea of slate gray concrete bowls and ramps, the whine of traffic competing with the constant whirl of BMX and skate wheels on concrete. It was music to Vivi Angelino’s ears.

Trotting down the hill from one of the viewing areas, she scooped up a discarded napkin that had blown from the refreshment stand and popped it into the trash. Charles River Skate Park was her baby, and even the smallest piece of trash marred its perfection.

Switching her board from one hand to the other, she paused at the bottom of the half-pipe to watch as some kid attempted a five-forty McTwist. A thrum of empathetic exhilaration pulsed through her as the skater sailed into the air and spun gracefully into the move.

Vivi had yet to land the five-forty, but when she did it would be here, at the Boston park she’d spent every spare minute raising money and corralling support to build.

The McTwister wiped out right in front of her with a slam and a loud “Sonofabitch!”

Vivi walked over to help the kid up, offering knuckles to the failed skater. “You’ll get it.”

“Damn right I will,” he said, popping up even though his butt had to burn. “The McTwist is better than sex.”

“I wouldn’t know,” she said, half to herself as she checked out the top of the ramp. “Haven’t tried it yet.”

The cement reflected silver white in the rare winter sunshine, a gift on a Sunday in February, when the weather gods usually tortured Boston with snow.

The pipe was crowded, so she decided to cruise the park some more and give herse...