Crews Monday determined the extent of the damage caused at the Riverwalk Golf Course in Mission Valley by recent heavy rainfall.Two weeks ago, the course was largely under water, but even after the rainy days subsided, the course is still not completely open.Crews said it's not the fairways and greens that are the problem, but the sand traps on the Presidio Course. Several of them were washed out by the December rain. So while two of Riverwalk's three nine-hole courses are open, the Presidio's nine-hole course remains closed."What we don't want to do is open up the property and have people have a poor experience," said Monica Davis, general manager of Riverwalk. "So the bunkers now are a bit of a challenge."Several of them will have to be totally rebuilt, and Davis said, "New sand, new gravel, new drainage."Players on the Mission and Friars nines said the fairways were still a little wet, but the course is actually playing quite well."Oh, yes," said Howard Kennedy, who plays the course often. "Considering all the rain we've gotten, it's playing good."There was quite a bit of play last week, with people in town for the Holiday Bowl. This week, which has been a traditionally slow week, has been quiet."The course is like a private course," said golfer George Seckington. "Nobody's out here, and we're really enjoying it."On December 22, Riverwalk was flooded and the images were seen across the country."Oh boy," said Davis. "I was thinking this is not the best PR that Riverwalk wants. The best part about it is that everything has drained out."Initial damage estimates were in the range of $20,000. Davis said with the repairs to the sand traps, that figure may go higher.