Wooden boards and steel I-beams will be the construction materials for a 400-foot-long retaining wall intended to make cycling safer near the intersection of Alpine and Arastradero roads in Portola Valley.
The Town Council, by consensus, chose wood and steel over rock or rock-faced concrete when it met on April 22. A wood wall is "incredibly non-obtrusive" and would be consistent with another retaining wall on Portola Road near the border with Woodside, Councilwoman Ann Wengert said.
Cyclists should benefit. Alpine Road is a popular route, but there are no bike lanes and the road shoulders don't have the consistent width required for formal bike lanes. The shoulder on the north side of the road begins to narrow significantly at Arastradero, to as little as 2 1/2 feet wide at one point, according to a staff report.
This narrow stretch sits next to a hillside that will have to be excavated to widen the shoulder, prompting the need for a retaining wall.
In January 2014, a unanimous council, acting on the recommendation of the town's Bicycle, Pedestrian, Traffic Safety Committee, passed a resolution to seek grant funding from the San Mateo County Transportation Authority for a retaining wall.
The committee applied for and won a $250,000 grant, which includes a $77,100 matching contribution from the town.
The project is expected to cost $230,000, Public Works Director Howard Young told the council. Money left over will go toward widening the shoulder at another pinch point along Portola Road opposite Town Center.
Town staff expect construction on the wall on Alpine Road to start in late summer, if the schedule stays on track, and to take two to three months to build, Mr. Young said.
Wood and steel walls have a lifespan of 50 years, Mr. Young told the council. If they break, just take out the broken piece and insert a new one, he said.