155 Sheridan St., Portland
Developers of a 19-unit residential condominium at 155 Sheridan St. in Portland's Munjoy Hill neighborhood hope to avoid a loud and lengthy construction process by using an innovative "soil nail" system, instead of pile driving, to stabilize the building on the steep property below Fort Sumner Park. (Portland Phoenix/Colin Ellis)
advertisementSmiley face

Developers of a 19-unit condominium building planned on Munjoy Hill hope to eliminate several months of noisy, earth-shaking work by avoiding one of the most disruptive phases of construction: pile driving.

The building planned at 155 Sheridan St. by Sumner Heights Realty sits just below Fort Sumner Park. It has been permitted by the Portland Planning Department, but still has a few more steps to go before construction begins. Mark Robinson, a spokesperson for Sumner Heights, said planners will have to send the updated proposal to the Parks Commission, which will eventually send it to the City Council.

He said the unique aspect of the project is the desire to replace pile driving – where support beams are hammered deep into the ground vertically to stabilize the hillside building – with horizontal “soil nails.”

Some soil nails have already been placed into the property the company owns, but additional nails will need to be inserted under Fort Sumner Park, which is owned by the city. Robinson said use of the nails will not affect the park or any future construction planned by the city, although it does require approval before work can begin.

“It’s a close neighborhood, it’s a narrow street, there are some condos directly across from the construction site,” Robinson said. “The idea was (using soil nails) costs more, but why not gain a few months by not having to do pile driving?”

Soil nails are a construction technique developed for use with unstable natural soil slopes. The long, slender, reinforcing rods are inserted into pre-drilled holes in the slope. Robinson said soil nails are not a new technique, and their installation is much faster and quieter than pile driving.

“In evaluating the site further and looking at the closeness of the neighborhood and wanting to help out the neighbors, that’s what propelled the construction team to use the nails,” he said.

James Rather, development review manager in the Planning Department, said the request to use soil nails came after the project had received final Planning Board approval, when the developer discovered the slope below the North Street park would need reinforcement.

Rather said pile driving would only involve property owned by Sheridan Heights, and would not need additional approval. But the use of soil nails will require the additional OK to encroach beneath city property.

“The city isn’t obligated to give them this approval,” he said, adding that he anticipates the request will get to the Parks Commission by early February.

If approval is granted, Robinson said installation of the soil nails would only take about three weeks. If the proposal is rejected, he said, pile driving would be expected to last for several months.

Sumner Heights will contain 19 one- and two-bedroom condos, with prices starting at $699,000. Robinson said construction is expected to last 14-18 months.

Video: The Sumner Heights Realty proposal