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Save Sugar Pine Bridge?

The National Park Service has released its new plan for Yosemite. In 1987, Congress designated the Merced and the Tuolumne as Wild and Scenic Rivers, and now after years of study the park has put together a plan to comply. I’ve been reading through some of the plan, trying to understand the details, but I haven’t made a lot of headway, and the plan is only open for public comment until the 18th. The report is here with links to a summary and information about commenting.

From what I’ve read, a lot of the proposals make sense. For instance, the proposed expansion of Camp 4 is desperately needed. During the high season, people start lining up hours before sunrise and by 6AM there’s a line of people in sleeping bags waiting for the kiosk to open, camping out in hopes of getting a campsite. I don’t even try to get a site any more. So that proposal is easy to support.

Proposed development in the west end of the valley, near El Cap Meadow, is more of a concern. I LOVE El Cap Meadow, in large part because it is one of the less developed parts of the valley. I haven’t read deep enough into the plan to find out the details of what is planned. The Access Fund, a climbing advocacy group, has a form letter that more or less represents my point of view until I get a chance to find out a bit more.

I also wish I knew more about the proposal to remove Sugar Pine bridge, the stone-clad bridge near Curry Village. According to the report, the bridge impedes the river’s flow during high water. You can kind of see in these Library of Congress photos that the abutments are out in the flow of the river.

I wish I was going to have a chance to read more about that before the comment period ends. If anyone know or finds any substantial info, please let me know. Sugar Pine is probably not the single most iconic of the Yosemite bridges, but as a group the stone bridges are quite wonderful. There aren’t a lot of stone bridges in California. It would be shame for it to go.

BGS Quarry Photos

Corncockle Quarry, Lochmaben. Dumfriesshire ‘Close-up view of splitting the sandstone by the ‘chisel wedge’ method. Eleven wedges are seen being forced into the stone to separate a block from the main mass of rock. Three quarrymen in typical working clothes are seen, two holding large sledge or striking hammers used for driving in the wedges. A selection of picks rest on the rock behind.’

A couple of photos in STONEZINE led me to the website of the British Geologic Survey which has some great photos from quarries and other sites of geologic interest. These photos here are all 1930’s era, but to some extent the techniques haven’t changed that much, and pallets of stone still sometimes come marked with the name of the individual who quarried them.

Rubislaw Quarry. Aberdeenshire ‘View at surface, showing dressed and partly dressed building stones. The granite is mainly used for building and monumental work. Two quarrymen prepare a granite block to be split by using the plug and feather method. They are using pneumatic drills to drill short holes around the block into which the plug and feathers are inserted. These are then systematically struck with hammers, causing the block to split. Another quarryman appears to be using a measuring stick against a large block of granite.’

Silver Grey Quarry, Creetown. Kirkcudbrightshire ‘A large granite block being prepared for splitting on the quarry floor by means of ‘plug and feathers’ method. Two quarrymen can be seen inserting the ‘plug and feathers’ into a large granite block. A recently separated block can be seen in the foreground. A series of narrow holes a few inches apart were drilled by a pneumatic drill. Two half cylinders of steel called ‘feathers’ were inserted into all the holes. A steel wedge-shaped ‘plug’ was then inserted. The plugs were then hit in succession with a hammer and a straight split in the granite block would result.’

Silver Grey Quarry, Creetown. Kirkcudbrightshire ‘A large granite block split into two on the quarry floor using the plug and feathers method. Two quarrymen, one wielding a crowbar, displaying recently split large blocks using the ‘plug and feather’ method. A series of narrow holes a few inches apart were drilled by a pneumatic drill. Two half cylinders of steel called ‘feathers’ were inserted into all the holes. A steel wedge-shaped ‘plug’ was then inserted. The plugs were then hit in succession with a hammer and a straight split in the granite block would result.’

Craignair Hill Quarry, Dalbeattie. Kirkcudbrightshire ‘A view of the open kerb-making yard. Two workers can be seen standing at barrels filled with sand on which the stone was dressed. Completed kerbs are seen stacked to the left of the photograph.’

Corsehill Quarry, Annan. Dumfriesshire ‘The masons are shown wielding wooden mallets called ‘mells’ and chisels as they work on the stone. On the left are sawn blocks; some show small holes cut in the faces. These holes are used for gripping and handling the blocks with a dog and chain sling as in the centre foreground.’

Craignair Hill Quarry, Dalbeattie. Kirkcudbrightshire ‘Granite sett-making on the yard floor. A sett-maker wielding a hammer at work in front of his hut. On the left are the rough unprocessed blocks while to the right are carefully stacked finished setts. A ‘sett’ is stone roughly squared for paving.’

Craignair Hill Quarry, Dalbeattie. Kirkcudbrightshire ‘Sett-making on the yard floor. Two workers (and a dog!) are seen. One is working on a sett. Note the chisel faced hammer he is using and the very large pile of completed setts piled carefully behind.’

Locharbriggs Quarry. Dumfriesshire ‘A close-up showing the ‘shot-grove’ and chisel wedge method of splitting stone. Widely spaced holes are drilled and filled with black powder; once blown and the blocks dislodged, chisel wedges are driven in along planes of weakness (usually bedding planes) to further work the stone. Note the quarryman wielding the large crowbar.’

Locharbriggs Quarry. Dumfriesshire ‘A close-up showing the ‘shot-grove’ and chisel wedge method of splitting stone. Widely spaced holes are drilled and filled with black powder; once blown and the blocks dislodged, chisel wedges are driven in along planes of weakness (usually bedding planes) to further work the stone. Note the quarryman wielding the large crowbar.’

Rubislaw Quarry. Aberdeenshire ‘General view of floor and west wall of this granite quarry, showing west-south-westerly running joints and material brought down by blasting. Holes, six metres long were drilled using pneumatic drills, black powder was inserted and then blasted. The natural weakness of the joint planes was used in deciding where to drill and blast.’

Middle Harbor Training Wall Memorial

This finger of stone sticking out into the mudflat (click on all of these to see them bigger) is a memorial to one half of the Bay Area’s largest and most ambitious drystone structure. It’s in Oakland’s Middle Harbor Shoreline Park, which is a rather random park, if you’ve never been to it. The park is out in the middle of the port surrounded by industrial activity, there’s a ton of lawn which no one ever uses and in fact the geese have turned into something that no one should ever use, and and there are a bunch of big landscape elements that reference the history of the port: the shade structure in the photo below, a concrete path that marks the footprint of a giant 19,000 square foot building that they took down, and the rock structure that commemorates the port’s north training wall.

The harbor’s north and south training walls were two long jetties designed to ‘train’ the tide. Unlike a typical riprap jetty made of haphazardly dumped piles of rock designed to absorb wave or tidal energy, each rock in the training wall was fitted by stoneworkers to give the wall a smooth face that would accelerate the water instead of slowing it down. Back in the 1800’s, Oakland’s harbor was shallow and it tended to fill with silt; ships could only enter it during high tide. The idea of the training walls was to channel the tide’s energy so that when the tide went out it would also suck all the silt out with it, reducing the need for dredging. The walls were started in 1874 and took twenty years to build, with some impressive stats: 310,000 tons of stone, 500,000 square feet of wall, 20 feet wide at the base, 8 feet wide at the top, 6 feet above the low water point. The north wall was 9500 feet long, the south wall 12,000. Apparently the walls worked; the signage says the port’s activity went up 2000% after they were built.

The south wall is still there, but they took the north wall out in 2001 when they widened the channel so bigger container ships could use it, and they used some of the north wall’s rock to build this memorial. I didn’t do all that good with my photos of it (there’s a better one at Oakland Geology) and I might try again some time when the tide is in or try to find a good place to see the south wall, but, honestly, I think the appeal is more intellectual than aesthetic.

It looks a little better with some sun flare drama. You can see the contrast between the training wall’s fitted stone (above) and the riprap’s rough faces (below).

Overall, though I said it was random, the park is also pretty cool. The ships and cranes and machinery right next to the park are all impressive. There’s also a habitat planting with some natives struggling against weeds and a path out to a great view of the Bay Bridge and the city. The water area of the middle harbor is being converted into a mudflat, slowly getting filled with the silt from dredging of the channel. It’s a good place to see water birds.

And the park is a great place to see the sunset. Information and a map of the park is here, a historic photo with the training walls visible on the left side is here.

Barker Dam

My last post on Joshua Tree is from Barker Dam, aka Big Horn Dam. The park is a desert, but it received more rainfall a hundred years ago and homesteaders tried raising cattle there. A couple of ranchers in the area made a seasonal reservoir, first a rancher named Barker in the early 1900’s, then William Keys fifty years later. Personally, I thought it was a little weird to see this empty reservoir and rather jury-rigged dam in the middle of the desert. Keys was the kind of guy who would kill someone in a dispute and then make a stone marker to commemorate/brag about it afterwards, and some of that shows in the design and craftsmanship of the dam. But the birds seem to like it and the visuals are interesting and it’s a stone structure on the national register of historic places, so here it is.

The reservoir was done in a couple of phases; the bottom nine feet are faced with rock and the upper six feet of concrete were added by Keys in 1950. He made a sign in a smear of concrete to commemorate/brag about this too.

The concrete had rock dumped in between the forms to save money. You can actually make a pretty nice wall this way if you place the rock a little more carefully and scrub more concrete off the faces off after you take away the forms.

Behind the dam there’s an interesting pattern of bathtub rings. Apparently the reservoir still fills to the top, flooding twenty acres during the wettest time of year.

There’s a second, lower dam below the main one, full of cattails living off the seepage.

And a cattle trough below the second dam. All in all, a funky little area.

Altun Ha Mayan Ruins

Altun Ha

Hmmm, I meant to post this sooner. Our Belize vacation already feels like it was a long time ago. As I mentioned just after we got back, we spent most of our Belize vacation on a small island, hanging out, sometimes snorkeling but mostly just sitting in a hammock. At the end of our trip we did one true sightseeing thing, we went to the Mayan ruins of Altun Ha.

Anita and I have both been to Mayan ruins before, but not for about ten years. Altun Ha is a good one. The entire site is about 25 square miles, mostly focused around two main plazas that are cleared and excavated, with pyramids as tall as the trees. The name means Stone Water or Rockstone Pond, named for the limestone wells. It was settled around 250 BC, with the first buildings going up around 100 AD. The population got up to 10,000 people at it height; it was abandoned around the 10th century. Now there’s just forest around it and it would be hard to imagine a lot of people ever living there if it weren’t for the big stone pyramids.

The Other, Adjacent Plaza

Mayan ruins are great, and I of course was interested in the stonework. Each building was built over about a one hundred year period, sometimes directly on top of previous buildings. During the Mayan times the stone would have also been covered with stucco and painted.

More detail photos than anyone really needs to see are below. (more…)

Stern Grove

Stern Grove

View from the Stage, click to enlarge

‘I wanted it to have the feeling of being in one of the great Greek amphitheaters,’ Lawrence Halprin

Last month I went to Stern Grove and took some photos. I’d been there during concerts, but I wanted to check it out without all the crowds. It didn’t disappoint. It’s a great space, with awesome stonework, and worth visiting even when there isn’t a concert happening. I wasn’t expecting to see anyone there, but an impressive number of people passed through the space, even though it was a rainy Sunday morning. I’d always thought of it as a theatre, but it actually works quite nicely as a park, too.

View from the West

The Grove has been a park and concert space since the 1930’s, but the stonework is all from about 5 years ago when Lawrence Halprin led a big renovation. Before the renovation it was just a natural amphitheater, and everyone would slowly slide downhill while they listened to music. Halprin terraced the slope and turned it into a proper Greek theater. My impression of him was that he tended to just make things up, but the design at the Grove is actually quite true to the style of the Greeks, with appropriate stonework and other detailing. Even the plan, which is rather free-form, is in keeping with the old Greeks’ appreciation for natural topography. One theater in particular, Thorikos, has a plan that reminds me of Stern Grove. (more…)

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