Baker River limestone and the town of Concrete, Washington

By Dave Tucker      April 6, 2010

"Silo Park" at the intersection of Superior and Hwy 20. The cement storage silos are 90 feet high. Click on any image to enlarge.

The town of Concrete, Washington is well-named. Well, it was. Because of a fortuitous limestone deposit, this small community in the Skagit Valley became a regional center of cement production. Beginning in 1905, portland cement was manufactured in the town from limestone. Cement from the town was used, among many other things, for hydropower dam construction. The nearest dam, Lower Baker is just north of town across a gorge in the Baker River. This dam, completed in 1927,  is operated by Puget Sound Energy. A trio of dams operated by Seattle City Light is further up the Skagit River- Gorge (1924), Diablo (1936), and Ross (1952) Dams. (Ross Dam is in the news these days, due to a rock slide that blocks road access to the dam).

Concrete was formed from the merger of two towns: the charmingly – named Cement City, on the east side of Baker River, had the first cement plant, operated by Washington Portland Cement Co. The Superior Portland Cement Company built a rival plant across the river in the older community of Baker. The towns merged to form Concrete in 1909.

This field trip will visit the abandoned limestone mine near Concrete, which was last operated in 1962. A related field trip to a nearby limestone cave will be posted later.

Getting there: Concrete lies along Washington Route 20, 22.5 miles up the Skagit valley east of Sedro Woolley. There are two sets of cement silos in town, you can’t miss ‘em!

  • Folks traveling from the west: from Highway 20, turn north (left) on Superior Street by the

    Lower Baker Dam rises only 1/2 mile up the Baker River from Concrete.

    unmistakable set of silos. Turn right at the stop sign onto Main Street, and go through town. At the east edge of downtown is a T-intersection by the map mural. Turn left, and cross the bridge over Baker River. At the far end, turn sharp left on the Baker River Road.

  • From the east: reach the east edge of town on Highway 20 and turn north (right) on Everett Avenue just before the eastern set of cement silos. Turn left in one block on E. Main Street, continue beyond the Puget Sound Energy offices and veer right on Baker River Road. Now we are all in the same place, the junction of Baker Dam road and East main. Set odometers to zero if you wish, but not really necessary for this trip.
  • Everyone: Drive up paved, but curvy, Baker River Road. Stop at the overlook (0.2 miles) to look at the Lower Baker Dam. Raised to 293 feet (89 m) in 1927, it was the tallest hydro dam in the world. Stay left at the junction with Lake Shannon Road (0.6 mi). There is a Y at 1 mi. – the left goes to a view of the backside of Lower Baker Dam, and is recommended. Take the right, and you will quickly come to a blue gate. Continue on if the gate is open, if not, park and walk a couple of hundred yards into the abandoned limestone quarry, which is pretty hard to miss and 1.3 miles from where you turned off East Main.

Geology of the limestone quarry

A clip from the geologic map (Tabor and others, 2003). The quarry is at the large blue unit at lower center.

The old quarry is in limestone of the Permian, Carboniferous, and Devonian Chilliwack Group. The Chilliwack is a mishmash of marine rocks, including these limestones, as well as clastic sedimentary and volcanic rocks. The clastic sedimentary rocks are mostly volcaniclastic. All these rocks were accreted to the margin of North America in the Cretaceous. For more information, see Tabor and others (2003). The geologic map is available online, as is the accompanying text description. Limestone is a minor component of the Chilliwack Group- some has been metamorphosed to marble. The outcrop above the dam is one of the largest in the region; other fairly large limestone outcrops are found along the Dock Butte trail near the summit (which is reached by the Blue Lake Trail, above Sulphur and Rocky Creeks). In Whatcom County, limestone is mined north of Kendall on Red Mountain. This rock is commonly used as retaining walls in the area. An abandoned limestone mine is on Black Mountain, also in Whatcom County- you have to bushwhack to get there now.

North - dipping bedding planes at the east edge of the quarry. The wall is nearly 200 feet high.

Let’s take a look at the quarry above Lower Baker Dam. It is a big semicircular bite taken out of the hillside, and measures about 900 feet E-W and 700 N-S. I estimate the walls to be about 200 feet high; I used my buddy Bob Mooers as scale for my initial estimate, and then verified the height on the topographic map. There are plenty of big blocks of limestone lying around in the talus at the base of the high quarry walls. Bedding structure is nicely revealed, especially on the eastern wall. Beds dip 50 degrees to the north, as mapped by Tabor and others (2003). I looked for fossils- crinoids are reported from this quarry. I only found a small bits and pieces. Perhaps you will have better luck. If you find something nice, send a photo via comment! Tabor and others (2003) adopt earlier work to assign a Mississippian (322-347 Ma = early Carboniferous) age to the limestones, based on these crinoid fossils.

The steep, back wall of the quarry has some curious – looking structures. The slabby rock has numerous steep fractures running up and down the cliff that angle

Looking south toward the back wall of the limestone quarry. Plenty of bullet-riddled junk lying around.

obliquely back into the rock, to the east. Looking very carefully at these fractures I saw fine grained, apparently cataclastic (meaning ‘broken up’) layers running along the trend of the fracture. I had to look in a number of places to get a good viewing angle to see that this feature was typical of many of these steep fractures. Further examination convinced me that this whole smoothish rock face is part of a shear (fault) structure, and the fractures are incremental slip surfaces. Subtle slickensides show that movement did occur along these fractures, although the rock tends to weather pretty easily and destroy the slicks. I had to look at a lot of fractures to be convinced this was what I was seeing. Please feel free to discuss via comments.

My finger is on a layer of fault gouge in the curving fracture. Subtle slickensides are on the light colored rock.

From limestone to cement and then to concrete

Ruins between the quarry and the lake.

The other cool thing about this quarry is the ruins. I don’t know what the old concrete (but of COURSE!) structures were for. There is one that looks like it was some sort of an enclosed ramp, and another that might be related to getting product down to the lake for…barge shipment?  To where, when there is such a good road? Research needed into this subject. Anybody? Go to the geology.com webpage to learn the basics of cement production, including the history of ancient cement, and modern portland cement. It is cement you buy to mix with sand or gravel in your wheelbarrow. The finished product is ‘concrete’.

References

Crinoid stem fragment. This is the only recognizable fossil I found. Hope you have better luck!

A fascinating, nearly century – old publication that talks about cement resources in the state is:

Shedd, S., 1913, Cement Materials and Industry in the State of Washington: Washington Geological Survey Bulletin 4

The pamphlet is available on line- use the table of contents (page 5) to find Whatcom or Skagit counties. A description of the quarrying method used at the Lake Shannon quarry is found on page 220 and onward. I believe the quarry and limestone milling methods were changed in the years between publication of this pamphlet (1913) and the end of limestone quarrying here (1962).

Calcite. The intersections of cleavage planes form characteristic 74 degree angles at center. Calcite is the predominant mineral in limestone.

Tabor, R., Haugerud, R., Hildreth, W., and Brown, E., 2003, Geologic map of the Mount Baker 30-by 60-minute quadrangle, Washington: Geologic Investigations Series I-2660. US Geological Survey. The map, cross sections and explanatory pamphlet are available online.

10 Responses

  1. The rock from the quarry was carried by a tramway across the river, over the hill and into town. The quarry and tramway existed before the lake did. The tramway operated till the 1960s or 1970s..

  2. I grew up in Sedro Woolley, and still live neaby. We drive upriver a couple of times a month to sightsee, photograph the area’s beauty, spot eagles, and yes, visit the quarry for fossil hunting. There’s also a great view of Mt. Baker from the quarry.
    When I was a kid we’d go to Concrete and there was so much dust in the air from the cement plant that everything in and near the town was coated in white. A cyclone fence enclosed the cement plant and due to rain there was so much dust build up on it that the fence had almost become a solid sheet, just tiny holes in the fence pattern. Think of peoples’ lungs! When they closed the plant there was a giant cleanup for everyone in town. I’ll bet it still took years for the dust to go away.
    You have to train your eyes a bit to spot the fossils, and learn what sections of the quarry they can be found in most easily. They’re not really great collector specimens, but they are interesting. You find mainly chunks and pieces, no long stems or crinoid ‘flowers’. But still quite interesting.

    • Thank you for your comment, Dale. I really appreciate local insights about the old cement quarry and refining days. I grew up in Tacoma and Steilacoom, didn’t come up to the NW corner of the state until 1971 (so, I’ll never be a ‘local’). I remember Concrete, Sedro-Woolley adn all the valley towns in the days before the North Cross State Highway (i.e. Highway 20). Imagine: paved streets in Concrete now!
      Dave

  3. I can remember going through Concrete back in the 60’s on our way camping at Marblemount,I do remember the tram running and coming off the north hill down to the town area,or where they dumped the stuff,yeah the town was white alright!,kinda a year roun’ snow sorta,ha,ha!,you can still see the area up on that hill where the tram was and came over,although its grown up alot,I think it closed down in the late 60’s,to early 70’s,we still camp up river,and I go up often to pick up logs off small homeowner jobs,my Dad helped build Ross dam after WW 2,and he ended up retiring at Marblemount,my mothers family the Clarks,homesteaded up there around 1902-3

  4. Major construction project at Lower Baker Dam has at least temporarily closed access to quarry and possibly Lake Shannon boat launch. I’ll update when access reopens.

  5. Construction at the Lake Shannon dam has slowed and moved away from boat launch and quarry areas. I launched from the boat ramp last weekend (Feb. 9-10, 2013) and had no problems. The following Monday went back for hiking exploration and a helicopter temporarily tied up the boat launch area but everything removed by end of day. Newly improved gravel boat ramp went all the way down to the water. Lake Shannon is near maximum seasonal draw-down and quite dramatic. Quarry had limited construction traffic on Monday. Heavy equipment traffic by blue gate (see directions in the article above) but possible alternative approach to quarries is: continue on main Lake Shannon Road (see above directions). In less than 1-1/4 mile from this intersection (drive past little Lake Everett) pull off and park at an old blocked gate on left (downhill side of road). Follow wet abandoned road down less than 1/4 mile and 200 ft of elevation; pass under power lines and into larger upper quarry.

  6. The answer to the question of why an aerial tram for limestone delivery if good roads were present is explained by the sequence of events. Originally a railroad spectacularly hung from a cliff wall crossing the Baker River Gorge to the east side of what eventually became Lake Shannon. Limestone was processed at the quarry and hauled into the town of Concrete via the railroad. Before the construction of the Lower Baker Dam (impounding Lake Shannon) cut and topped this railroad the tram was built to deliver crushed limestone in aerial carts to town, bringing it down just east of the silos on the east side of town, east of the river. Nearby logging railroads were replaced by an expanding truck road system which eventually included the quarry. For those who enjoy relics and ruins: the remnants of the original railroad are still visible during the seasonal draw-down of Lake Shannon. Last weekend (February 9-10, 2013) they were visible from five to 15 feet above the current lake level depending on their original grade and distance from the dam.

  7. The buildings located below the upper quarry were for crushing and grating the raw limestone. Please be aware that these old concrete structures are extremely dangerous and should be viewed from a safe distance and not entered. The large multistory building was where the dynamited limestone was trucked in and dropped through the floor. Various crushers below reduced the large rubble to a uniform finer size. When the railroad originally ran; the limestone was dropped out the bottom of the building directly downhill to a loading area (still visible during winter lake draw-down). Later a bucket conveyor was installed to lift the crushed limestone to the top of this large building then deposited it into the long ramp structure which is merely an enclosed conveyor belt. This long conveyor lifted the fine crushed limestone even higher before dropping it into a funnel shaped hopper where it could be loaded into the aerial trams which circled the bottom of this “funnel.” A short distance from the open end of the tram building just above the lake shore is the first tower that supported the tram system. If you look across Lake Shannon a little upstream of the dam you may be able to see a second tower hidden in the foliage on the far hill. Connecting these three locations will allow you to project a pretty accurate line of the aerial tram. What is most unusual is that all of the structures were built almost entirely of concrete; the almost unlimited and probably most economic material on hand for this particular operation. Unfortunately, age and exposure has weakened much of the remaining structures making it dangerous to be near them. Best and easiest to view them from a safe distance.

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