(KAIR)--A discovery beneath the surface of a planned street extension in Atchison is adding nearly $56,000 to the cost of construction.

The Atchison City Commission approved a change order totaling $55,917.50 during its November 2 meeting for the First Street extension north of Riley Street.

According to city officials, excavation uncovered a layer of buried concrete, asphalt and brick rubble approximately four to five feet deep. The material is unsuitable as a foundation for the new street and must be removed before construction can continue.

Atchison Public Works and Utilities Director Clinton McNemee told commissioners the discovery was made after contractor Pruett Construction began grading the site.

"When he was doing his grading, he encountered rubble underneath about a foot down, and then about three or four or maybe up to five feet thick of concrete chunks, asphalt chunks, brick," McNemee said. "We went down and looked at it. It is not something that I would recommend trying to build a city street on."

The approved change order calls for removing approximately 1,200 cubic yards of rubble and unsuitable soil and replacing it with fill material that can be compacted and stabilized.

The additional work increases Pruett Construction's original contract of $149,453.40 by $55,917.50, bringing the revised contract total to $205,370.90.

Despite the unexpected expense, city officials say the overall project remains within its approved $250,000 budget, which also includes improvements along Riley Street, including asphalt overlay work and a section of curb and gutter.

The First Street extension project includes grading, stormwater infrastructure, curb and gutter, asphalt paving and sidewalks.

Completion will depend on weather conditions and asphalt availability, with some work potentially extending into the spring.