It wasn’t California surfin’, dude, but no one seemed to care. Dozens of river surfers in wetsuits and helmets jumped into the waters of South Platte River Run Park Thursday night to ride two man-made wave features. Even though the water flow was half of what it’s supposed to be, enthusiastic whoops of excitement filled the air as the sun set over the water. The $15 million project, which has been in the works for more than four years, opened its initial phase.