Palo Alto is set to launch today, Monday, the next phase of the San Antonio Road construction project, an effort that includes widening a section of the road, replacing street trees and repaving the busy street at the city's southern border with Mountain View.

The work is the second phase of a multi-year project aimed at repairing aged infrastructure along the busy street at Palo Alto's southern border and improving median islands and sidewalks. Construction began last fall.

The second phase of the project includes widening San Antonio to create a new left-turn lane at Middlefield Road. The city also plans to repave the street between Middlefield and U.S. Highway 101 and install new trees and a new irrigation system and install video detection for traffic signals.

The work will result in some lane closures, though Palo Alto city officials plan to keep all traffic lanes open during the busiest commute hours. According to the city's announcement, all lanes will be open until 9 a.m. and after 4 p.m. to minimize disruption. On-street parking will not be allowed in the construction area, according to a flier from the Palo Alto Public Works Department.

The project includes removing 101 trees, more than half of which are stone pines, and planting 120 new trees of different varieties. The pines have already been removed and the replacement trees will be planted once the paving is completed.

The stage of construction that will begin next week will focus on widening San Antonio and creating the new left-turn lane at Middlefield Road.

Officials had determined after consulting with arborists that the pines are "at the end of their useful lifecycle and require significant ongoing maintenance, including branch removal, surface road grinding and extensive sidewalk and road repair," according to a report from the Public Works Department.