Poor soils will result in additional costs for the east frontage road under construction in Ham Lake.
In May the city council approved a supplemental agreement for the project. The agreement calls for a net increase of $63,000.15 in the project’s overall cost.
The frontage road is designed to float over the muck area.
According to David Krugler, senior engineer with RFC Engineering, Inc., the city’s engineering firm, the depths of the muck are beyond 12 feet and an adjacent boring on 153rd Avenue had the muck depth beyond 36 feet.
The depth of the poor soils has caused the roadway to settle. Estimates had the roadway settling some two feet. However, certain locations have settled between three and four feet.
This large amount of settling has caused an increased need for borrow material to keep the road grade at the designed elevation.
The bid called for 31,724 cubic yards of granular borrow to keep the road at grade. However, an additional 4,709 cubic yards of granular borrow is needed, bringing the total amount to 35,451 cubic yards. This is a 15 percent increase.
The supplemental agreement calls for increasing the amount of granular borrow by 6,000 cubic yards to allow extra material that may be placed on the roadway between now and when the class five is placed in June.
This increases the cost by $71,400. The city will only pay for the amount of granular borrow actually used, however, so the $71,400 is the maximum cost. Actual costs may be lower.
“I don’t anticipate that much cost,” said City Engineer Tom Collins at the May 6 council meeting.
The city will save money on the contract, however by using recycled material in the wear course of the bituminous.
By using a different aggregate size and allowing recycled materials, the contract cost will be reduced by $8,399.85, bringing the total contract cost to a $63,000.15 increase.
Kelly Johnson is at firstname.lastname@example.org