Life in the Fast Lane

Crews Have Just 90 Days to Build a N.M. Overpass

By Will Higgins

The $3.8 million Washington Street overpass in northeastern Albuquerque is being replaced, and contractor A.S. Horner has less than three months to complete it from start to finish.

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In late 2006, Albuquerque-based A.S. Horner Inc. was awarded a $3.8 Million contract with NMDOT for the replacement of the Washington Street Overpass. The contract provided for only 90 calendar days to complete the construction.

The original Washington Street overpass was constructed in 1963 as Interstate 40 was being built through the growing Albuquerque Northeast Heights. The original construction provided two lanes and a full shoulder in each direction, conforming to early Interstate construction standards.

During the past decade, the "Big I" and numerous other overpasses and segments of I-40 through Albuquerque were replaced to provide additional lanes as area growth demanded more vehicle capacity.



As with most of these older overpasses, the original Washington Street Overpass design provided for four bridge spans. There was a center pier between eastbound and westbound lanes and two piers near the toe of the slopes at the abutment ends. As traffic increased, these piers prevented the addition of more lanes.


Carl Johnson, A.S. Horner's superintendent on the project, says that unlike some other projects with tight schedules "there are no incentives for early completion. However, there are liquidated damage penalties for late completion." Horner crews started the project on Feb. 12, and are racing toward a May 11 completion date.

"We are working 20-hour days, seven days a week; however, we work 24-hour days when needed," Johnson says. "In order to accomplish this, we have six crews working four-day schedules. There are six foremen and one assistant superintendent, Efren Parra."

As part of the new design by Albuquerque-based HDR Engineering , the bridge clearance will be increased approximately 2-ft in addition to the additional length required by the freeway lanes. The design necessitates the addition of fill materials for both approach embankments.

The abutments are built upon 11, 3-ft-diameter drilled caissons with a structural cap 3-ft below grade. Dywidag anchors are set into these caisson caps. The abutment face and structural support for the beams are double-T walls, supplied by Coreslab Structures Inc. of Albuquerque.

Cast into each of the tee legs are four conduits provided for the installation of the Munich, Germany-based manufacturer DYWIDAG's post-tensioned components that are connected to the anchors. The DYWIDAG system is stressed at 177kps when all are in place. This provides the structural integrity for the retaining wall and load bearing requirements of the abutments.

"The double-T walls have seismic retaining cables as an additional feature new to bridge construction in the state," Johnson says. "This should minimize damage to the structure in the event of an earthquake in the area." A concrete cap is formed and cast on the DT walls.

The non-load bearing sides of each abutment have reinforced earth retaining wall panels manufactured by Vienna, Va.-based Reinforced Earth Co. in an aesthetically-pleasing curve around each abutment end, Johnson says.

The panels are anchored by 2-in. by 17-ft horizontal anchor straps placed in the compacted fill. "The 17-ft length anchor straps are not standard with RECO walls," Johnson says. "However, this is what RECO called for on this project."

The bridge is a two-span design. There is a concrete pier between the interstate eastbound and westbound lanes. "This pier was formed using a Gates 9000# tie system. Horner crews built all forms for the pier and abutments on site," Johnson says.

"Under normal construction schedules, concrete is placed and allowed to gain strength over at least seven days," Johnson says. "Due to the 90-day schedule for this project, much of the substructure concrete needs to have 3,000 psi compressive strength after only three days. To make this happen, a 4,000 psi design mix is being used.

"Pier and abutment caps poured on March 22 were ready for pre-stressed concrete beam placement on March 26 and 27."

Johnson says the pre-stressed concrete beams are 63 in. by 108 ft and each weighs 56 tons. There are seven girders per span. The beams were erected with off-peak schedule closure of traffic lanes below the span.

The concrete bridge deck is 9 in. thick. The bridge railing is cast-in-place concrete, topped with a freeway protective pedestrian fence. Albuquerque-based Lafarge Corp. supplied the concrete, with ACE Rebar handling the reinforcing steel.

Key Players

Owner:
New Mexico Dept. of Transportation

Design:
HDR Engineering

General Contractor:
A.S. Horner Inc.

Subcontractors/Suppliers:
Anderson Drilling; Coreslab Structures; ACE Rebar;
Twin Mountain Construction; Valley Fence Co.; BSN;
Dywidag Systems Intl.; Lafarge Corp.

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