Marin County Fire is planning to conduct a controlled burn in the Mount Tamalpais watershed as early as next week, after wet weather postponed previous attempts to rid the watershed of overgrown vegetation that can fuel wildfires. The burn will eliminate 27 acres of vegetation between Stinson Beach and Mill Valley, creating a firebreak. Chief Todd Overshiner, a spokesman for Marin Fire, said about 25 of the department’s firefighters would participate in the burn, which will last a day or two, followed by several more days of mop-up efforts. The precise timing will be announced in advance through social media and the websites of Marin Fire and Marin Water. The operation had been scheduled for mid-February but was canceled due to wet weather. Controlled burns decrease the likelihood of high-intensity wildfires that can damage water supply infrastructure, threaten neighboring residential communities and degrade forests.