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Boulder Cave: An Adventure in Nature

BOULDER CAVE is now OPEN for the 2018 season!

This area is managed by the U.S. Forest Service. The cave attracts in excess of 35 thousand visitors a year!

Plan Your Trip

Day Pass: There is a charge of $5.00 per vehicle, $15.00 per bus, per day for parking, Northwest Forest Day or Annual Pass, Interagency Annual or Military Pass, Interagency Senior or Access Pass, Golden Age or Access Passport card or Every Kid in the Park Pass, can be used in lieu of the payment of $5.00, if passes are properly displayed on hanger located on vehicle rearview mirror and the card holder has identification.Boulder Cave Highway 410

Hours: This day use site is open 8:00 a.m. to 8:00 p.m.; the main access gate is closed at 8:00 p.m. each night.

Activities: Day hiking, nature/outdoor learning

Posted Trail: Those using Boulder Cave Trail and visiting the cave will find updated signs at the trailhead and at the cave.  Please follow posted signs which emphasize staying on the trail and observe the rules.

Pets: Pets are allowed along the trail as long as they are kept on a leash and owners clean up after them.  Pets are not allowed in the cave due to the potential for spreading White-Nose Syndrome disease.

Facilities: 2 (accessible) restrooms, interpretive signage, drinking water, parking, picnic area.

Nature Interpreter: During the summer peak season, an interpreter is on site during weekends  only at Boulder Cave to provide programs associated with the need to protect the declining bat population (dependent on forest budget may or may not have an interpreter at site which varies each year).  Forest Service employees also monitor the use of Boulder Cave, Boulder Cave Trail and the River Walk Trail.

Protect the Bats: Please brush your shoes and scrape them on the Astro Turf before entering the cave to protect the bats from the unwanted spread of White-Nose Syndrome disease. Learn more below.

School Tours: School tours and individual group tours may be arranged by calling Joan St. Hilaire, Wildlife Biologist at (509) 653-1439.

Access: Boulder Cave and Trail #962 leading to Boulder Cave are closed from October 1 through May 31 to all visitor use.  The reason for this closure is for public safety (trail and cave have hazardous ice conditions during the winter), to protect the sensitive Pacific Western big-eared bat species and to discourage vandalism.

Location / Directions

Boulder Cave is located near Milepost Marker 95.43 on State Route 410, approx. 32 miles west of Naches.  There is a sign on the road pointing toward Boulder Cave Day Use Site.

Coming from the east (Yakima/Naches towards Chinook Pass on U.S. Hwy 12, then State Rte. 410).  Just past Cliffdell, turn left at the first road past Whistlin’ Jack Lodge - Forest Service Road #1706 / Swamp Creek.

Coming from the west (Enumclaw) the turn is just before Whistlin’ Jack Lodge.  Turn to the right on Forest Service Road #1706 / Swamp Creek.

After you turn onto FS Road #1706 you will cross a bridge over the river, after you cross the bridge, at the T-junction take a right approximately 1.4 miles, follow the signs and paved road to Boulder Cave.

Boulder Cave Trail

BatsThe Boulder Cave Trail is less than 2 miles long round trip and normally takes about an hour.  The trail gains about 200 feet in elevation and can be slippery in places.  The gravel and dirt trail runs along the edge of a deep ravine, climbing gradually through a forest of Douglas Fir and Ponderosa Pine.  Devil Creek flows through the ravine, framed by trees and several species of broad leafed shrubs.  In autumn, the golden tones of the leaves splash new color across the landscape, contrasting sharply with the evergreen forest.

Approximately 400 feet from the cave, the trail narrows and descends to bring visitors to the entrance.  A strong flashlight is required in the center portion of the cave.  A good pair of walking shoes, layered clothing and some water is also needed.  Once you get to the cave you’ll enjoy the cool treat on a warm summer day. 

All visitors need to wipe off their shoes on the turf mat and use the boot brush before entering the cave and when they leave the cave, in order to reduce the health dangers for the bats that live in the cave.

In the canyon’s cool shadow, notice how the plants differ from those growing on the sunny ridge.  As the cave engulfs you, let some of your other senses explore the darkness.  Feel the moisture in the air.  Listen to the creek.  Lava that once flowed hot is now cold and hard to the touch.  This is a unique cave.  The Boulder Cave trail was built by the Civilian Conservation Corps (CCC) in 1935.  With the voluntary help of a local stone mason, the trail was improved by the Youth conservation Corps (YCC) in 1987.

The Formation of Boulder Cave

Boulder Cave - Chinook PassHow was Boulder Cave created?

Caves are unusual in the northwest and Boulder Cave is the largest, most extensive cave of its kind.  When most people think of caves, a limestone cavern or lava tubes come to mind.  Boulder Cave is unlike any cave you have ever been in before.  It took millions of years of volcanic action to create this landscape and thousands of years for erosion and weathering to shape the features you’ll see on your visit. 

Over thousands of years, lava flows occurred periodically in the Yakima basin and covered deposits of soft, loose rock and soil. The lava cooled, forming hard layers of basalt, and trapping the softer layers of loose sediment between.

Next, water went to work. Water is a patient sculptor, etching it’s signature into the basalt for thousands of years. The water is now carving though soft sedimentary layers of loose rock, soil, and ash deposited between lava flows. The stream is busy cutting out a new cave. This is how Boulder Cave may have looked if you visited Devil’s Creek thousands of years ago.

At Boulder Cave, the water flowing in Devil's Creek eroded a deep channel through the top layer of hard basalt and the softer layer of deposits beneath. When Devil’s Creek met the next layer of hard basalt, the creek stopped its downward action and instead continued to erode the softer deposits horizontally. In time, the horizontal erosion carved a hollow pocket underneath the top layer of basalt.

Approximately 25,000 years ago, the outer edge of this pocket weakened and collapsed into the hollow below, leaving an archway 350 feet long and 30 feet wide - Boulder Cave!! Today, Devil's Creek still flows through the cave that it created. The formation of Boulder Cave is unusual - most caves are old lava tubes or are formed from groundwater dissolving layers of limestone.

Safety Concerns for Visitors

Not Allowed: 

  • Climbing on rock formations, visitor could fall and cause serious injuries.
  • Swimming or floating through and/or pass the cave, visitor could drown or cause a serious injury.
  • Creating new trails in or around the cave, could cause resource damage to existing vegetation and trees. 
  • Vandalism will not be tolerated.

This is a Federal Forest Service Sites that has historical significance and we want to preserve it for future generations.

Chinook Scenic BywayHiking the River Trail

The River trail runs north of the trailhead. It is a 3/4 mile barrier free paved loop designed to provide easy access to the Naches River for everyone. Users can leisurely admire nature's beauty or fish along the Naches River (see State Fishing Regulations for more specific information). Resting benches and quaint wooden bridges encourage visitors to linger and enjoy the sights and sounds of the out-of-doors.

Along the River Trail

Green ribbons of life: Riparian areas are the vibrant green realms lining a waterway or lake. Logs, rocks, and gravel move in and out, creating a constantly changing landscape. You will find this place always in a flex, one plant battling another for dominance. A healthy riparian area will have plants that provide food, shade, and shelter. For the same reasons we seek these quiet places, so do the animals, birds, and fish.

Bountiful haven: This tranquil creek is unique in several ways. It was man-made rearing ground for juvenile salmon. Fingerlings spend their first year here. Stream-side plants offer shade to cool the water from the sun and food to nurture young fish. Logs in the water provide refuge from predators. The side channel, completed in 1990 was done by the U.S. Forest Service and Trout Unlimited. If you would like to help with such a project, contact a chapter of Trout Unlimited near you to volunteer.

Boulder Cave near NachesBeyond the river’s flow: The plants here have transformed from lush riparian vegetation near the river to drier upland grass and flower meadows. Grassland is an area where water is collected, absorbed, and percolated through the soil and into the watershed below. Abundant grasses hold a watershed together. This will happen in downstream waters also.

River ghost – paths of the past: This was once the bed of the Naches River. You can see dry wash areas and small knolls created by the water’s current. Imagine how the old river threaded its way into pools on this flood plain. A river is alive and ever changing. It’s a restless soul and always searching for a new course to travel.

Boulder Cave Picnic Area

In the 1920s, the Forest Service created Boulder Cave Recreation Area for visitors to discover the natural wonders of the cave for themselves. A picnic area, located near Boulder Cave Trailhead, is enhanced by a group shelter with a large stone fireplace that was built by the CCC in 1935. The shelter can not be reserved, but is available on a first-come, first-served basis. Drinking water is supplied at the picnic area, but not along the Boulder Cave or River Trail. Picnic tables, fire rings, and barrier free toilets are also on site.

Other Area Opportunities

Opportunities for overnight camping along the Naches River are nearby. Sawmill Flat Campground, Halfway Flat Campground and Little Naches Campground are developed sites that are located within five miles of the Boulder Cave Trailhead. Sawmill Flat offers barrier free restrooms and sites suitable for larger recreational vehicles. Food, gas, and lodging are available at Whistlin' Jack's in Cliffdell, two miles from the Boulder Cave Trailhead.

Big-Eared Bat Hibernaculum

Plesa Help SAve Our BatsBOULDER CAVE CLOSED October 1st TO May 1st for protection of the Townsends Big Eared bats.

Learn more and through these PBS shows.

BATS: Boulder Cave is home to the only known population of Pacific Western Big-Eared Bats in this part of Washington State. The Pacific Western Big-Eared Bat is listed as a sensitive species in Washington and Oregon. A small population of 50 bats use Boulder Cave as a hibernaculum’s during the winter. In the 1920s and 1930s, the Boulder Cave bat population numbered in the thousands. These bats have historically used Boulder Cave during the summer, but presently do not. The big-eared bat is extremely intolerable to human disturbance. It appears the heavy human use during the summer has discouraged the big-eared bat's use.

By implementing the following guidelines, you could help encourage the bat to use Boulder Cave again.

  • Please observe the following in the cave:
  • Limit conversation and all noise. Whisper if you must talk.
  • Stay on the trail and don't double back.
  • Use dim flash lights. Keep the beam directed at the trail.
  • Don't build campfires in the cave.

If you see any sick, oddly behaving or dead bats, please report them to the Department of Fish and Wildlife.

Read more tips in "Please Help Save Our Bats".

Thank you for your help!

This highly beneficial species is in rapid decline due to disturbance during hibernation. Bats must survive the winter months on a limited supply of stored fat; any disturbance that may awaken bats will deplete this food supply resulting in their death. Humans within sight or sound of the bats create sufficient disturbance to awaken them.

Our thanks to the Naches Ranger District of the Okanogan and Wenatchee National Forests for providing this information on Boulder Cave.

Open: Boulder Cave Day Use is normally open on Memorial Day weekend and stays open through Labor Day weekend.  Call the Naches Ranger Station office at (509) 653-1401 in early spring and late fall for confirmation that Boulder Cave is already/still open to the public, as open/close dates vary.

Updated May 29, 2018

 
   


Upper Valley Bulletin Board
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