Marin Water plans to upgrade two seismically vulnerable sections of an aging pipeline that carries untreated water from the Nicasio Reservoir and Kent Lake to the water treatment plant in San Geronimo. Construction is expected to begin in August and will require closing one lane of Sir Francis Drake Boulevard at Lower Peters Dam Road. The deteriorating pipe, northeast of the salmon viewing area in Samuel P. Taylor State Park, is currently supported by concrete trestles located in the creek bed. The section carrying water from Nicasio Reservoir will be hoisted onto a new steel truss, and a new 36-inch pipe will be elevated 2 to 3 feet above the ground on concrete piers about 20 feet outside the creek bank. The second section is near private homes and roads and will be rerouted onto district land, requiring the installation of 1,700 feet of pipe below the boulevard. The board approved the project, which is expected to cost from $3 million to $5 million, and adopted an environmental assessment outlining mitigation measures in December.