Summary: Better directions: Go N into Richland on GWW, make the hard left onto Aaron at the first light, go W to Beaver Bark Nursery, turn left over the freeway overpass. Turn right. Turn right at Chamna Nature Preserve sign. Park in lot. There is a porta-potty available.
Description: This is a river delta area. Expect it to be mostly flat. It is tackweed-free, scenic, convenient to get to, and has open dryland trails and riverside trails through the trees. It is a great four-season area to ride. Expect to share it with hikers and horseriders. This is the perfect place to bring the GF, kids, or non-bikers to show them that they can have fun on dirt.
Recommended Route: Sunny, hot, dry: Head straight for the river, turn left, start doing loop trails through the trees off to the right on the river side. Some are dead-ends and fishing spots; it's still fun. When you get east to the RR bridge and the osprey pole, you're at the far end of Chamna.
Cool, cloudy, wet: The riverside trails get muddy in wet weather and high water. If there are deer around, the tall grass may have ticks, so check for them on clothing and brush them off. Try the dryland trails through the sagebrush by heading east from the parking lot and wandering through singletrack among the sagebrush for some quick-hands courses and some dirt jumps.
Other recommended trails in the same area: Columbia Point: If you're at Chamna, you can continue off the east end, take the paved bike path under the freeway, then turn right (east) through the trees onto Columbia Point. There's a perimeter trail with river views.
NOTE: Another reviewer mentioned crossing the RR bridge. Bear in mind that its an active railway, and they don't want you trespassing on it.
State Patrol trails: The best in the area. Much fun.
Badger Mountain: The west-face trail is bike-authorized. It is a singletrack shared with hikers, and it is a brutal climb but a fun descent. No jumps or other bike-specific fun. Killer view, though.
Summary: This is an essentially urban trail system found within Richland city limits on City land. Totally legal to ride here. The terrain is flat, and is located on the banks of the Yakima River. While not aerobically challenging the river does offer nice views, wildlife, and trees (which are uncommon in the desert). The trail system has maybe a total of 10 miles if you ride every possible little section. The trails are used a lot by hikers and horses, there are a lot of tie-in between trails so it's easy to get confused. Took me a while to find a good 7-8 mile loop that uses most of the available singletrack. Half the trials are desert terrain and half are wooded. Be careful in spring as the Yakima River floods certain sections. I wouldn't make this trail a separate trip, but if you're in the area and need a quick fix this might be the ticket. Really nice to ride in the summer heat since there is some shade and the trails don't degrade to moondust.
Recommended Route: Tough to describe a good route. I'd recommend going SE out of the parking lot on the singletrack then make your first right and follow the tire tracks. The signage isn't very helpful. Try to find the peninsula trail which can be picturesque, and adds another mile or so.
Directions to trailhead: depending on where you're coming from take Hwy 240 to Aaron Dr. (in Richland) then go south on Jadwin Ave., over the highway and RR tracks, quick right on Carrier Rd., then first right into Chamna (big sign), go to end and park.
Other recommended trails in the same area: State Patrol; Badger Mountain; Finley Hills
Summary: Being a cross country racer and rider for twenty years, finding Chamna Preserve aka Acme Trail, was a very pleasant surprise. If you like downhilling, try State Patrol, which is pretty fun. If you like seeing animals, having nice singletrack with trees, ride here. Great area to build up your stamina and speed for training, fast turning for your handling skills. There are canal drops, dips, off-cambers as well as great straight aways to get to your next section. You can also leave the parking lot, ride along the river, go across the paved trail, and railroad, towards the columbia river, follow the rivers edge, go under the Richland bridge, and stop at Anthonys restaurant for food and beer before heading back. Oh yeah, the night riding on this trail network is awesome!
Recommended Route: From the parking lot, go in three different directions. Go across the bridge to the other side of the river, ride along the canal to find challenging obstacle trails.
Other recommended trails in the same area: State Patrol, Badger Mountain, Finley Hills
Summary: This is one of the few areas in Tri-Cities without goatheads, so it automatically makes the short list of places to ride. That being said, I wouldn't bother going there unless you live close by. If you've gotta drive you may as well go to State Patrol. These trails don't lend themselves all that well to riding, but like the lister said, they do have a few (less than 10) interesting parts. I must disagree, however, a 12 foot downgrade along the bank of a levy doesn't constitute downhill to me, and that's the only thing out there that isn't totally flat.
Recommended Route: I think it's pretty self explanatory since there's so little to ride. Just be careful by the river cause you can end up in a swamp pretty quickly.
Other recommended trails in the same area: State Patrol is the one place in Tri-Cities that is worth riding regularly. It's far better than anything else in the area, and probably one of the best rides on the east side of the state. Check it out.