Getting rid of bulky trash is easy. Do not dump bulky items. And get rid of items that were dumped in alleys and other places by others. Call 311 or call 800-773-2489. The latter number is on each of the blue, black, green garbage bins in case one forgets.Bulky items are picked up following the normal trash truck.
… Or as commenter Hossa stated, use the MyLA311 app. It is that easy.