Because of poor soil conditions, costs have increased for installing a walkway near the sewage treatment plant in Windjammer Park.

Oak Harbor City Council approved an increase in the budget by $20,000 last week to cover unexpected extra costs for the promenade.

The council met via teleconference because of pandemic restrictions on public gatherings.

The walkway is being built by PNW Civil, Inc., which estimated the cost of the walkway at $75,791. The cost of the project increased to $95,791.

Construction of the promenade is a contractual obligation the city must fulfill as part of the construction of the sewage treatment plant, according to city officials. It is expected to be about 60 feet long and rise about three feet. It will connect to the Waterfront Trail.

Shortly after construction began on March 16, the poor soil was discovered.

“As soon as the contractor started work, we hit unsuitable soils underneath the foundation,” City Engineer Jim Bridges said. “We had to excavate down six to seven feet to remove those soils and place heavy gravel underneath of it.”

Without the gravel, Bridges said the ramp would quickly deteriorate within a year or two.

“It would look like garbage,” he said. “It would be all cracked up and settling and so we needed to make those adjustments.”

Cost to improve the soil conditions is estimated to be $12,000. The project will also close a four-foot hole in the handrail.