Crews are digging up portions of Fourth Street, Second Street and Marquard Avenue as Marin Water's Miracle Mile pipeline replacement project officially entered its first phase of construction on Tuesday, Aug. 4.

The work, confirmed in a City of San Rafael announcement published Tuesday, Aug. 4, replaces more than a mile of cast iron pipe, some installed as early as 1883, with seismically resilient welded steel pipe. The aging mains are leak-prone, according to Marin Water, and serve as a critical supplemental water supply feed to the greater San Rafael area.

For shoppers and business owners along the corridor just west of downtown, the disruptions are real but bounded. Construction runs Monday through Friday, 8 a.m. to 5 p.m. Street parking in active work zones will be restricted during those hours but reopens each evening. Parking lots connected by driveways to Miracle Mile remain accessible throughout, and all businesses and properties stay open during construction.

The bigger inconvenience: water shutoffs. Most customers along the project area will experience at least three planned temporary service interruptions before Phase One wraps up in late August. Marin Water will deliver a door-hanger 48 hours before any major planned shutoff.

Marin Water spokesperson Jessie Underhill told the Marin Independent Journal on July 22 that work would progress in sections along the alignment to limit impacts to any one area at a time.

"Replacing this section of aged water main provides an enormous benefit to the San Rafael area in terms of water system reliability and resiliency," Underhill told the Marin Independent Journal on July 22.

The pipeline project is being sequenced ahead of a separate $4.1 million city project to improve the Second and Fourth Street intersection. City civil engineer Grey Melgard said in July that Marin Water expedited its Phase One work so crews would clear the area before the intersection project begins. The city expects to award a construction contract for those intersection improvements by early September, with that work estimated to last three months.

Phase Two of the pipeline replacement is estimated for 2027 and will extend west along Fourth Street into San Anselmo, where the road becomes Red Hill Avenue. That phase begins after the city's intersection improvements are completed.

In total, Marin Water plans to replace approximately 7,000 feet of pipe across both phases. The total cost of the pipeline project has not been disclosed.