Monday, August 30, 2021

The west is on fire

They just announced the complete evacuation of the South Lake Tahoe area.

I can't remember this ever happening before.

This is a big deal.

I hope those fire crews can catch a break soon.

Saturday, August 28, 2021

Up, up, and away

Uh oh, this is not good:

  • Millennium Tower Sank More Even After Partial Work Stoppage, Documents Show
    on July 30, the homeowners association board agreed to put a two-to-four-week hold on shaft drilling work, documents show.

    But by that time, 39 shafts had already been installed. Soon, crews refocused on sinking 24-inch diameter piles along Fremont Street.

    But by mid-August, it was apparent from the data that the problem was more complex than fix engineers had hoped. Despite the pause, the building had settled another half inch – possibly due to soil being displaced during installation of the 24-inch piles. That prompted the board to put all pile installation on hold as of Monday.

    Data released by the city on Monday shows the tower is currently leaning 22 inches towards Fremont Street – compared to 17 inches when work began.
  • Millennium Tower's Accelerated Sinking Halts $100 Million Effort to Stop It
    an outside expert, Oakland-based structural engineer David Williams, tells NBC Bay Area that the new data on accelerating sinking is not nothing.

    "The trend is the thing that’s very disturbing, the fact that they have reactivated settlement,” he tells the station, adding that the speed of the new sinking is of special concern."
  • Repairs of Leaning San Francisco Skyscraper on Hold; Engineering Expert Blasts Plan
    Karp says each new piling being driven is causing more issues.

    “You never place piles or piers closer than three pier diameters apart. These are 36 feet [sic; I think the piles are 36 *inches* in diameter] so they should be nine feet apart and they’re, what? — five feet or something. As you do one, you’re disturbing the ground, then you go to the next one you’re disturbing the ground there and you go to the next one until you have a whole zone of disturbance that can’t be fixed,” Karp explained.
  • San Francisco's Millennium Tower fix halted after further sinking observed
    The fix has been likened to putting a bumper jack next to a flat tire, and involves the installation of piles 250 feet deep along the north and west sides of the tower, to be tied beneath the sidewalk to the original foundation.

From last summer, here's a picture and an article with more details on the repair that is being attempted:

  • Reviewers OK Fix for San Francisco's Leaning Millennium Tower
    The structural upgrade is designed to meet the requirements of the voluntary seismic improvements section of the San Francisco Existing Building Code.

    SGH’s Hamburger says his team selected the voluntary seismic upgrade route because it offered the easiest path through the permitting process. “The building code has provisions to allow VSUs without having to bring the building into conformance with the current code,” he says. The primary intent is to arrest settlement, but the 52 piles also will improve seismic performance, he adds.


    The existing mat is supported by 950 14-in.-square precast concrete piles. The aim is to remove 20% of the building weight from the underlying clay strata.

    The load reduction represents “what I could comfortably transfer from the new piles to the existing mat without major modification of the existing mat,” says Hamburger, whose client is Paul Hastings LLP, a lawyer retained by the tower’s developer, Mission Street Development. MSD is part of Millennium Partners.

    The system relies on loading each pile with 400 tons using a permanent hydraulic jack that reacts against a new mat extension. The jacks would be housed in a maintenance access vault above the mat. The scheme calls for a so-called indicator test pile, which is installed to scale.

    The weight loss would result in an almost immediate rebound of about 1 in. of the tower’s north and west sides. That would remove about 25% of the tilt, predicts Hamburger. “Over time, we expect another 25% to 50% of the tilt to come out through continued settlement of the south and east sides,” he says.

    Under the plan, piles would be drilled 4 ft, 9 in. on center under sidewalks—200 ft on the west side and 100 ft on the north side, just outside the tower footprint. The team has applied for an easement to work under the sidewalks, which meet at the block’s northwest corner.

    Piles would extend up through an 8-ft-wide extension of the tower’s 10-ft-thick reinforced concrete mat—4 ft from the old mat. New and old mats would be connected by chipping into the side of the old mat and coupling new and old reinforcing steel.

The plan was to install 52 new piles, and they've drilled the shafts for 39 of them, so they're about 75% done with drilling the shafts.

This troubled construction project is even more troubled now.

Friday, August 13, 2021

Backpacking 2021: Leavitt Meadows Trailhead, Hoover Wilderness

We missed our backpacking trip in 2020, but by Spring of 2021 we were all able to get our vaccinations, and we were raring to go!

Unfortunately, the horrible Dixie Fire had other plans for us, rendering our first planned destination unreachable, unbreathable, and wholly out of consideration for this year's trip. With a week to go before our planned departure, we switched to a second backup plan in Siskiyou county, but the Cronan and River Complex fires had eliminated that possibility as well.

With barely 72 hours left, we frantically searched for an alternate plan, but finding a place free of smoke and yet with permits available for last minute hikers such as ourselves was quite challenging. Finally, just as we were ready to give up, we came across a viable possibility, which was to hike up into the upper Walker River watershed in the Hoover Wilderness. Permits were available, and although there was considerable smoke in the area from the Tiltill fire, the forecast was for the winds to shift and blow the smoke elsewhere.

It was time to go, so we got up and went.

Leavitt Meadows is an enormous High Sierra meadow, stretching for several miles along the upper reaches of the Walker River. The Walker River, in turn, is one of the great rivers of the Eastern Sierras, and is well-known as one of the great fishing rivers of the Western United States.

We weren't planning on doing any fishing, but it's always a joy to hike along and camp near the great rivers of the Sierra Nevada, and the approach via Leavitt Meadows was particularly appealing as you can get several miles away from any roads or buildings just by walking the trail along the meadow. This is a very pleasant experience as you can put a lot of distance behind you with relatively little elevation gain.

Above the river we stopped for lunch at lovely Lane Lake, small but ever so picturesque.

About 1.5 miles beyond Lane Lake, we were able to make our way off the main trail and found a lovely campsite near a beautiful forty foot waterfall on Walker River. Although this has been an extremely dry year, and the river was very low, the falls were still running and very wonderful to view.

I had recently invested in a Supai backpacker's boat, and Lane Lake proved to be the perfect venue for an afternoon of High Sierra boating.

The Walker River watershed in this area is dotted with many other lakes, as well as various tributaries of the river, which has its headwaters near Forsyth Peak in Yosemite National Park. Trips both short and long are easy to fashion in this area, and we certainly enjoyed ourselves.

Because this area is so accessible and quite popular, we saw a lot of other hikers (and not a lot of other wildlife), but the watershed is large and there are plenty of secluded areas where peaceful and quiet campsites can be found.

Given the way the trip had nearly ended before it even began, we all agreed that the trip wildly exceeded our expectations, and it was certainly great to be able to go back into the wilderness again with old friends.

Thursday, August 5, 2021

Shape: a very short review

Jordan Ellenberg is probably the foremost writer in the micro-niche of what I'd call "layman's mathematics books," a speciality that is perfect for people like me (math nut since I was knee-high to a grasshopper, but have very little involvement with real mathematics nowadays).

Ellenberg's latest book is Shape: The Hidden Geometry of Information, Biology, Strategy, Democracy, and Everything Else.

It is, like all of Ellenberg's other work, simultaneously rigorous, educational, entertaining, and approachable, which is quite a hard combination to achieve.

Shape is a serious book, 500 pages of meaty material, and you aren't likely to race through it. You'll either find it fascinating, in which case you'll be stopping every few pages to let what he says settle into your mind, or you'll decide after a few dozen pages that it's not the book for you, in which case that's that.

I enjoy Ellenberg's work, and I hope he continues to write many more such.

Monday, August 2, 2021

Klara and the Sun: a very short review

I must first admit that I had not heard of Kazuo Ishiguro before I happened to pick up Klara and the Sun; clearly I've been missing out on the work of one of the great writers of our time.

I loved this book.

I read it very fast, as it is both extremely compelling yet also quite approachable. And, as I read it, I kept having different reactions.

At first I thought: "oh, this is clever! What an interesting idea!" About a quarter of the way through the book, I thought: "I think this would have made a fine short story, but I think he's exhausted everything he came here to say."

But as I continued reading, I found that on the contrary, he had much more to say.

Klara and the Sun is, I believe, deliberately intended to be both thought-provoking and disturbing.

It is also rather topical, which makes me wonder a bit how well it will age: will it still be relevant 75 years from now? Ishiguro takes on topics such as: the ethics of artificial intelligence; the ethics of genetic editing; equity of access to health care; equity of access to education; the increasing isolation and remoteness brought upon us by technology; job displacement by technology; and much more.

It's also quite clearly drawn from the last 18 months of global shelter-in-place, as one of the main characters is a young child, confined to her home, without playmates, being educated by remote professors over video hookups, sufficiently withdrawn that her family takes her to "interaction parties" where she can (with adult supervision) learn how to interact with other home-sheltered peers.

Other aspects of the book are more universal and timeless, such as the sub-plots involving the invocation of prayer and the search for a greater power in the presence of hopelessness and pain, and the observations about human relationships and how they change as we age.

I think that many different people will find many different things to say about Klara and the Sun. For me, I think I will stop with these two observations:

  1. All along, even while I was thinking to myself that this book, so easy to read and be fascinated by, was shallow and superficial, I kept abruptly realizing, time and again, how much deeper and richer it was than I had given it credit for ("Beach reading" this is not).
  2. Disturbing though the book is, literally from start to finish, I can't help but feel that Ishiguro, overall, means the book to be hopeful. I think he wants us to realize that we can in fact influence how it turns out; we don't just need to let the future happen to us without thinking about it.