RSA Tower – The Advance Package

Dropping Into The Abyss

Sonny Wadsworth’s demo work proceeded without notable incident until he started on the large United Lighting Company showroom, which fronted on Madison Avenue.  The structure came down easily under the onslaught of Sonny’s large D-8 Caterpillar tractor.  The D-8 Cat was pushing debris about on United’s concrete warehouse floor slab when it happened.  Suddenly the machine, driver and all, disappeared into an abyss, emitting a great roar followed by a resounding thud and a cloud of dust.

No one had remembered that Montgomery’s once-beloved Leak-Memory Mortuary had occupied the spot many years before, nor that the embalming room had been in the basement below it.  When a large grocery store (later remodeled into United Lighting) was built on the site, its owners declined either to utilize the basement nor to fill it in. They just formed a slab over it and the void became a Poe-like entombment.  Thus when the Caterpillar broke through, it fell into a sealed aroma of formaldehyde and a ghastly past.  Sonny’s black saucer-eyed driver survived the fall, but he took the rest of the day off to recover from the episode.

Outflanking The Pile Drivers

On heavy construction like the Tower, you never know for sure how deep the pile foundations must go to give the necessary bearing capacity.  Our foundation designs and the contractors’ bids are based on test borings and the opinion (read “guess”) of a geotechnical engineer, but the final depth is adjusted after “test piles” are installed by the contractor with the particular rig he proposes to use.  These are load tested and the actual pile depth to be used is then set based on the test result.  Unit prices are included in the bid to adjust the contract price up or down as needed.

Pile contractors are a sorry lot (akin to well diggers) and feel they have a mandate to bilk owners and architects.  Thus their bids might state $2.00 credit for every foot shallower the piles are drilled, and $12.00 per foot extra for every foot deeper they must go.  PH&J always sets the bid table to thwart this strategy–we demand one single price to go up or down with pile depth, and this inevitably elicits howls of protest from the pile contractors.

Even when faced with a single unit price for pile depth adjustment, many pile contractors still feel compelled to outwit the architect and geotechnical engineer just for the sport of the thing.  These pile subs believe they know more about piles and dirt than anyone, and they try to anticipate if pile depths will be increased or decreased.  It becomes a real game as they use their bid to make a bet on pile depth.

Most of the pile unit prices submitted on the Tower were in the $7.00 to $8.00 per foot range, which was probably a fair price.  One bid was for $12.00, obviously from a piling contractor who thought we would go deeper.  The Barcus bid was for $4.00 per foot, reflecting a strong expectation that the pile depth would be reduced.

It turned out that Barcus, who was awarded the Tower piling contract, was correct.  The test piles showed that we could reduce the pile depth from 60 feet to 50 feet.  Barcus licked his chops in anticipation of making an extra $100,000.00 (that would result from giving back only $4.00 per linear foot for 10-foot of pile depth worth $8.00 plf, as applied to 2200 piles).  But to the contractor’s consternation, our structural engineer, Lynn Blackburn, counseled that we should leave the pile depth as bid.  I agreed with Lynn, more to spite Barcus and not be fleeced, than for any other reason, and when our decision was announced Barcus had a conniption fit.  We were besieged with a blizzard of protest letters from Barcus, but Lynn and I stood our ground.  I still feel good every day, knowing that we have an extra ten feet of depth on those foundations.

This is written several years after L. G. Barcus & Son completed the auger cast piling on the RSA Tower.  I am told that the St. Louis company still brags on its Internet home-page about doing this job in Montgomery, Alabama–so they must have forgiven me.

The Monster Pile Cap

When L. G. Barcus & Sons had completed the 2200 auger cast piles, it was time for Parker Building Company to install the pile caps.  Pile caps are usually 12-foot square chunks of concrete poured as a cap over a cluster of piles.  The building columns are supported by these caps.  Depending on the column structural load, pile caps normally cover as few as two piles, up to as many as 35.

The Tower foundation largely included pile caps which were not all that unusual, but it did include one that was the granddaddy of all pile caps.  This monster was to be 87 feet square x 6 feet deep, and it was so big that the sheer logistics of placing that much concrete in a single pour posed genuine concern.  On our plans it was called the “J-cap”.

The J-cap would take 1682 cubic yards of concrete–that’s 168 transit trucks full.  The pour level of its 7500 square-foot surface had to rise quickly enough that it would set as a structurally monolithic mass.  On the other hand, it must rise sufficiently slow that its lower stratas have obtained an initial set and the fluid mass does not impart an overwhelming force against the side forms.  All of us–but especially the owner’s rep, Ron Blount–worried that Parker Building Company of Opelika did not comprehend the magnitude and difficulty of what he was about to undertake.  For small-town Montgomery, the J-cap was indeed a daunting challenge, but much more so for a con-tractor from even smaller Opelika.

When you visit the Tower and ride an elevator, or visit the restroom on either side of any floor, you should know you are supported by the J-cap.

The big pour took place on Saturday, February 13, 1993.  Arrangements were made with the City to barricade and close Lawrence, McDonough and Monroe Streets, except to construction traffic.  Two separate concrete supply companies were engaged, one to deliver concrete to the Lawrence Street side, and one to deliver to the McDonough side.  Special gravel roads were built to get the transit trucks down into the excavation.  Two giant concrete pumper trucks were leased, and each one had a boom-mounted discharge hose which could reach the center of the cap.  The operation was scheduled to start at 5:00 a.m. and to continue as late as 9:00 p.m. that night.  All that for a single pile cap!  But then, it was the single biggest pour ever attempted in these parts.

As it turned out, the advance preparation almost worked too well.  The pour went so fast with two bulk plants operating that the schedule was exceeded and one plant was shut down early.  Even with that slowdown, the mass stayed so liquid that the 6-foot-high side forms began to fail, and a phalanx of carpenters had to begin frantic shoring operations.

Parker Building managed to finish the J-cap and went on to complete the balance of its work under the advance contract.  Parker’s work was accepted on June 1, 1993, and at 8:00 a.m. on that date Huber, Hunt & Nichols assumed custody of the site and began its portion of the endeavor.

-Charles Humphries (“Peril and Intrigue Within Architecture”)

This is one of many RSA Tower stories. The rest can be found here.

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