By Melissa Nann Burke and Jeff Montgomery

The News Journal

WILMINGTON – A Wilmington contractor said Wednesday his company previously placed mounds of dirt alongside I-495 that now are part of a state investigation into how support piers on a span over the Christina River shifted, forcing officials to close the bridge for emergency work.

"Only thing I can tell you right now is I feel very badly about what happened to the bridge. I have absolutely no idea what happened," Jim Thomas, the owner of Keogh Contracting Co., said by phone Wednesday.

"I'm going to cooperate 100 percent with DelDOT, and I have been since Monday when I found out about this."

Engineers for the Delaware Department of Transportation believe the mounds of dirt set alongside the leaning piers could have had a role in compacting soft soils beneath the surface. Another possibility, DelDOT says, is corrosion of the steel piling, which reaches 140 to 160 feet below the surface to anchor in bedrock.

"It's too early to tell if it's a factor," Transportation Secretary Shailen Bhatt said of the dirt mounds. "Most of the folks who took a look at this say that something of that mass, of that height and weight, could certainly have an effect on compression. That's why we want to get the dirt out of there."

DelDOT is in the early phases of determining what caused the subsurface shifting of four pairs of 50-foot-tall bridge supports, called piers.

The worst pier is 4 percent out of vertical alignment. The concrete footing upon which the piers sit, as well as the bridge deck, have also shifted. With the increased load, the structure can support its own weight but not traffic.

Bhatt said DelDOT will take action if it determines that someone is responsible, but Thomas has been responsive since officials contacted him Monday about removing the stories-high piles of dirt — part of which sit within the state's right-of-way. The agency will soon send reinforcements to speed up the process, Bhatt said.

"It would be very premature for us to assign any kind of blame right now. He has been cooperative. When we called him and asked him to come down and move his dirt, and he did that," Bhatt said.

Thomas would not comment Wednesday on the purpose of the dirt pile or how long it's been on site.

"I haven't had any contact with DelDOT today, and I'm really not in a position to talk about that. I'd be guessing. I just can't talk right now," Thomas said.

Transportation officials closed I-495 in both directions Monday evening at the bridge between Terminal Avenue and 12th Street. They expect it to remain closed for several weeks until the structure can be shored up and leveled. The affected segment of I-495 carries an average 90,000 vehicles a day, according to state estimates.

According to county records, the property along the southeast side of the bridge is owned by the DuPont Co. Port Contractors Inc. President Michael Evanko said his company leases the tract from DuPont, but has an agreement with Keogh for it to use the land for storage.

Evanko said he couldn't provide any information about the dirt, referring questions to Thomas. However, Port Contractors is allowing Keogh to temporarily relocate the dirt at its industrial yard next door on Christiana Avenue, Evanko said.

Dump trucks continued transporting load after load of the dirt from next to the bridge to the yard Wednesday.

A check of multiple years of aerial images of Delaware, distributed through the state's Geospatial Data Exchange, show little stockpiling of material around or under the bridge in past years through 2012, although some piles appear adjacent to the span.

An image of the site for 2013 clearly shows large volumes of material along and under the edge of the northbound approach span's right side — the side to which the piers are leaning.

DelDOT and builders around the world sometimes use piled soils to "pre-load" or "pre-consolidate" soft or unstable ground prior to construction of roadways or other projects. Time and weight relentlessly pack soil particles and other underground materials downward and squash away water, providing a more reliable base.

But the same process generates changes and forces in other directions as well, potentially affecting the ground or structures nearby.

"It's a perfectly good, common-sensical assumption" that piles near the I-495 approach spans created a problem, said C. David Jamison, a retired DelDOT engineer now in private practice. "Once you start loading up soil that's not stable in one direction, you create vertical loads and horizontal loads and it makes sense that something is going to have to give."

"In this case, it's scary. Usually when stuff settles, it takes a while," Jamison added. "This sounds very fast to me."

Murad Abu-Farsakh, who holds a doctorate in geotechnical engineering from Louisiana State University and teaches there, said soil stockpiling near major bridge structures should not be taken lightly and results are difficult to predict.

"It can't be answered quickly. It takes calculations. If there are existing pilings, this might cause problems," Abu-Farsakh said.

Although pre-loading was used successfully in the building the Del. 1 toll road in the 1990s, a similar effort went awry during construction of an earlier design for the Indian River Inlet Bridge, resulting in abandonment of an initial plan and a more-than $20 million DelDOT lawsuit against contractors, settled late last year for $5.25 million.

"You couldn't just look at it and say whether the effect is going to be significant or not significant," Abu-Farsakh said. "You need to know about the subsurface conditions, how much has been added, and how close it is to the piles. It can have a significant effect on the surrounding environment."

Tilt sensors placed on the leaning bridge piers have detected negligible movement within the first 36 hours of monitoring – less than 0.02 degrees, Bhatt said. Engineers are focusing on learning more about what's happening beneath the surface, officials said.

The last bridge inspection in October 2012 found no signs of leaning piers or other deficiencies.

The structure received a sufficiency rating of 82 out of 100 — a score designed to gauge the importance of replacing the span. A bridge scoring less than 50 can be eligible for federal dollars to help fund replacement.

New Castle County records show that the DuPont Co. owns triangular-shaped parcels of land on either side of the approach span between the Christina River and Christiana Avenue.

Alma Properties LLC owns land adjacent to both of DuPont's, and along the south side of Christiana Avenue in the area of 495. Its holdings include property used by Port Contractors just west of I-495 near the Christina's southern banks, and by Peninsula Compost LLC, which in turn has as one of its partners Port Contractors.

DuPont spokesman Terry Gooding confirmed Wednesday that DuPont's property had been leased out and then made available by the lease-holder to Keogh, and referred questions to Thomas. Alma officials did not return calls. Port Contractors Inc. is a family-founded material- and cargo-handling business and contractor that operates in multiple locations with its base in Wilmington.

Its Wilmington ventures have included a range of activities along Christiana Avenue near the I-495 bridge, including handling of petroleum coke from the Delaware City Refinery, as well as an interest in an industrial scale composting plant nearby.

Google removed the bridge from its mapping application Wednesday, which may have helped route through-travelers around the closure, Bhatt noted.

To ease traffic congestion, DelDOT has adjusted signal timings at intersections, tweaked detour signs and is setting up a temporary signal at the Terminal Avenue exit of I-495, where northbound traffic is forced to exit.

Southbound motorists are urged to detour via I-95, although local traffic can access the highway to 12th Street.

Contact Melissa Nann Burke at (302) 324-2329, mburke@delawareonline.com or on Twitter @nannburke. Contact Jeff Montgomery at (302) 463-3344 or jmontgomery@delawareonline.com.

