A wooden staircase built by a Minnesota Department of Transportation contractor after the collapse of the Interstate 35W bridge in Minneapolis cost taxpayers more then $157,400, according to agency records.

The staircase -- reportedly built to federal safety standards -- was needed to provide access for emergency workers as they walked to and from the MnDOT command post located at the top of a steep hill, the agency said.

The staircase was built with 120 steps -- a cost of about $1,311 per step. Of the total cost, $149,000 covered carpentry materials and labor expense. Most of the labor charges went to pay overtime for a 15-worker crew, according to invoices submitted to MnDOT.

A review of invoices and receipts shows that the contractor charged for the most basic of tools that even a small-scale firm typically would already own.

The contractor was Graham Penn-Co Construction Inc. of Eagan, part of Graham Group Ltd., based in Calgary.

The company was reimbursed for buying such new equipment as two long-handled shovels, two automatic nail guns costing $459 each, two sledgehammers, a pickax, a post-hole digger, a rake, a chainsaw and a reciprocating saw, invoices show. The company spent $95 to buy a 10-gallon water cooler and also charged the state $20 for a cup-holder and $7 for paper cups, according to invoices.

Dave Lenss, the company's project manager, said the costs were justified given what MnDOT was asking them to do.

"We were asked by MnDOT to get this job done as quickly as possible and do whatever it takes," he said. "It was faster to go out and buy some of the equipment than to go back and get tools that were at other job sites.

"MnDOT never questioned what we were doing and watched us along the way," Lenss said.

His company was hired by Carl Bolander & Sons Inc., the St. Paul firm hired on an emergency, no-compete basis for debris removal at the site. A spokesperson for Bolander referred inquiries about the cost of the staircase project to MnDOT.

The staircase was built between Aug. 9 and 12. Of the 520 hours of labor charged for the work over those three days, nearly half were charged as overtime, according to Graham Penn-Co's invoice for the period through Aug. 31. Wages totaled $47,582, including a $10,615 "markup" by the company, according to the invoice.

The company identified two of the crew as superintendents and three others as foremen, according to the invoice.

Lucy Kender, a MnDOT spokeswoman, said the overtime expense was justified because the state and federal recovery effort was underway 24 hours per day for the first 20 days.

"If overtime was required because of the need for safety, we agreed to pay the extra cost," Kender said. She said the staircase was built to standards required by the federal Occupational Safety and Health Administration.

Building the staircase was part of an overall safety program at the bridge site to ensure that workers would not be hurt, Kender said. There were 117,000 hours worked throughout the recovery and debris-removal operations without any serious accidents or injuries, she said.

"OSHA tells us this is truly remarkable for an operation of this type," Kender said.

Several weeks ago, workers tore out sections of the stairway that were reportedly in the way of construction for the new bridge. Kender said it is "unclear" whether the remaining stairway will be used again.

tkennedy@startribune.com • 612-673-4213 pmcenroe@startribune.com • 612-673-1745