Thursday, June 08, 2006

Uplifting day on Loma Alta

Today Loma Alta was closed to through traffic so a crane crew could set up and hoist replacement utility poles to hard-to-reach locations. The large (160 ton) crane was brought in to reach over neighbors' homes and drop two new utility poles into holes which were prepared in advance by SCE.

The first one was on the north side of the Gooseberry catch basin (south of Loma Alta), a couple hundred feet west of the Stonehill intersection. The other was on the west side of the Gooseberry flood channel, just north of Loma Alta. Both were basically in people's back yards, so lifting the 40 foot poles in from above was the only practical way to get them in.

Once each new pole was secured in it's hole next to the old one, the power lines (which run at the top of the poles) were moved over to it. Then the crane was bridled to the old pole, and the crew chainsawed off the top 8 feet or so. Once the top of the old pole was cut loose, the crane hoisted the piece of scrap back up over the rooftops, leaving the shortened old pole in place until the other utility crews can come out and transfer lower telephone and cable lines to the new pole. Then the old poles can finally be removed altogether.

From what I understand, the crane is called "160 ton" because that is the gross weight of the whole system. I assume this includes the support vehicles, etc., because the three huge counterweights they used, which travel separately on tractor-trailers, weigh 12 tons each. So if there are "only" 36 tons of counterweight, they must be factoring in the whole crane itself plus three or four support vehicles, etc. to get to 160 tons.

The rigger told me that with the jib out and the boom fully extended, the crane was 270 feet tall, but that there were additional inserts which could be installed to bring it to a maximum height of 320 feet. I assume the 50 feet of inserts were somewhere else, as I didn't see it anywhere on the job site.

I seem to recall that the maximum allowed "gross vehicle weight" of a tractor-trailer is 40 tons on major roads (many smaller roads are less). They brought three (large) vehicles (forget about pickup trucks, etc.), so assuming each one vehicle is limited to 40 tons (3 x 40 = 120), one must assume the didn't bring all their toys with them. One of the young guys mentioned their was an additional counterweight that I didn't see anywhere, and the inserts were nowhere around, so there must be one or two more tractor-trailers full of Legos to get them up to a full 160 tons of fun.

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