Story by Adam GropmanThe noise drifting on the ocean breeze is not the usual sort one hears emanating from the Santa Monica/Venice beach path area on a warm, beautiful day. It is more raucous and hard-charging, almost martial...nearly barbarian. I have to investigate. Atop and around the small, manicured grass-covered hills that lie just east of Ocean Drive, between the tall residential towers and the shorter Sea Colony complex of southwestern Santa Monica, I see a few hundred people- mostly in their 20's and 30's partying their asses off in a brazen, carefree manner usually reserved for university campuses, outdoor music festivals and the former New Orleans.Mush, shopping cart! Mush!I spot lots of zany costumes- many duplicated in groupings of three or four - some haphazardly thrown together, others more intricate and carefully assembled. There are white-capped sailors, long-bearded Old Testament characters, coonskin-hatted Davey Crocketts and human-sized bunny rabbits, among others. Shouts, chants, song, laughter and eager conversation fill the air and the bubbly, boozy vibe is palpable, further evidenced by ubiquitous beer cans in hands and a full size keg in a supermarket shopping cart. In fact, many such carts are interspersed among the revelers. The energy is beyond infectious. It is a pure shot of untroubled, bacchanalian joy- something all too rare here in the City of Angles.This, I soon find out, is Los Angeles' second annual Urban Iditarod, an event that started a few years earlier up in San Francisco and has now spread to several U.S. cities. The idea of the U.I. is to very, very loosely recreate the original Alaskan Iditarod, happening on the same day. In Alaska, a hand full of brave and masochistic souls on wooden sleds race through the stingy, frozen Northern tundra yelling Mush! Mush! to a team of equally brave and masochistic dogs. Here in L.A., creatively costumed teammates push shopping carts from Marina Del Rey to Santa Monica, yelling out whatever pops into their minds and drinking like it's St. Patrick's Day. OK, in general the L.A. version is a lot easier, although it is a hell of a lot more challenging to keep the beer cold. Teams pay $20 each to participate and any leftover money goes to the L.A. Humane Society- maybe to karmically compensate for those poor sled dogs busting their asses up in Alaska. In Alaska it's very dangerous. says Trino, 26, a tall, gregarious software specialist from Culver City wearing an awesome red and blue Underdog costume. You could get frostbite, you could get lost, you could get eaten by your own dogs. Here, we try to emulate the dangers. We've got cops, sprained ankles, skinned knees, alcohol poisoning.