That’s the day that contractor Neumann Brothers Inc., of Des Moines, will start to build scaffolding and bring in trailers for fencing.

Once construction gets underway, a portion of North Seventh Street from Central Avenue south to an alley behind the courthouse will be closed to accommodate construction equipment and materials. Construction for the bid, awarded to Neumann for $6.16 million, is expected to wrap up by the end of the year. There will be no disruption to Central Avenue or any surrounding streets.

“This is a tough project,” said Chad Bunner, principal project manager, before articulating the plan of attack at Tuesday’s pre-construction meeting with county stakeholders. “We’ve got about nine months to rock and roll.”

Scaffolding installation on the clock tower itself will not happen until later in phase two. The building will remain open for county business during the entirety of the construction, including for two potential first-degree murder trials anticipated this year. The scaffolding will encompass the face of the building and bridge around the tower, anchored to the building’s stone joints.

A 3D scan of the tower will help guide the project after scaffolding is installed, before and after the removal of the iconic green-tinted copper sheathing. All copper and wood will be stripped off the tower and stored in two semi-trailers on North Seventh Street.

“Since it’s a big copper job, I’m concerned about theft,” Bunner said.

Supervisors are mulling ideas to save unique pieces of copper for local museums and other fundraising ideas.

Phase two will also replace the skylight, a process anticipated to take six to eight weeks in the summer, during which the roof will be at least partially open. Only temporary rubber will separate business on the third floor from the elements. Flat areas of the roof will be renovated last.

“We’re going to do our best to keep water out during the construction process,” the manager said.

Construction workers are expected to operate from 6 a.m. to 2:30 p.m. most days.

Neumann was awarded the bid for the project in January, even though it came in over $1 million more than previous consulting engineer estimates.

The project was found to have a daunting effect on contractors. Craig German, a structural engineer for Shuck-Britson of Des Moines, said previously that many contractors had no frame of reference for how to go about the project. Many found they did not have enough time to wrap their heads around how large the project would be or to articulate their plans in time to submit a bid.

The restoration has been in the works for well over a year.

A key part of the restoration will include installation of a plastic membrane to act as a water barrier between the copper and wood of the tower, leaving most levels dry. The top level of the tower is open to the air, so that the bell can ring. The water barrier will be designed so that water can flow back outside, preventing rotting of the wooden structure underneath.

Roof construction will replace the fiberglass with glass, significantly increasing the amount of light that comes in and removing the yellow tint from more than 100 years of UV exposure that currently comes from the roof. The new glass will have a longer life span with a better ability to resist impact from ice during the winter.

The project’s blueprints include a partial replacement of the clock tower that will keep the intact pieces of the old green patina sheathing and restore the roof’s skylight. The change may result in a browner clock tower overall, a departure from the green color earned over a century. The sheathing’s extensive weathering over 118 years contributed to the need for action.