The bridge carrying Tartan Trail Road over San Mateo Creek has been closed since early summer, and if that stretch of town is part of your regular loop, you already know the workaround: Crystal Springs Road to Skyline Boulevard, over to Golf Course Drive, past Hayne Road, and back around to Black Mountain Road to reach the other side. The Town of Hillsborough's own project page has called it a critical access point for a reason. What's less visible from behind the wheel is what it actually took to get a construction crew into that creek bed, and why a single culvert crossing turned into one of the more expensive capital projects the town has taken on this cycle.
This wasn't a case of a road simply wearing out. According to the town's own description of the project, the bridge and roadway were compromised by a combination of erosion, pavement failure, and subsurface issues connected to PG&E's underground conduits running beneath the crossing. That last detail matters more than it sounds. A straightforward pavement failure is something a public works crew can plan around on a normal schedule. A failure tangled up with a utility easement means every design decision has to be coordinated with PG&E before a shovel goes in the ground, which is part of why the town classified this as an emergency repair in the first place rather than a routine resurfacing job.
The Hillsborough City Council awarded the original design-build contract to Power Engineering Construction Company on November 10, 2025. That got permitting and design underway, but it didn't cover the full scope of what the creek crossing needed. On February 9, 2026, the council approved a Phase 2 amendment worth $3.31 million, which brought the total agreement to $3.9 million. Do the subtraction and the original contract comes out to roughly $589,000, meaning the town ended up authorizing more than five times that amount once crews got a real look at what was underneath the road.
That same February meeting wasn't just about Tartan Trail. The council also signed off on an $11.34 million local match commitment for a FEMA Hazard Mitigation Grant tied to the Highline Safety Pipeline Project, and closed out the Macadamia Access Road Repair Project's first phase at just over $1 million. None of these are flashy line items on their own, but stacked together they point to a town spending heavily this budget cycle on infrastructure that residents drive over without a second thought until it fails. A recap of that council meeting shows the items were adopted together on the consent calendar by unanimous voice vote.
Hillsborough's roads were never built for redundancy. They curve through hillside lots and cross a handful of creek beds, and in this particular stretch there's no second bridge to fall back on. The town's official detour runs through five named roads:
Golf Course Drive is exactly what it sounds like, a road that runs along the edge of the town's golf course frontage, which means detour traffic is now sharing pavement with a route that wasn't designed to carry through-traffic volume. It's not a dramatic inconvenience, but it does turn what used to be a short, direct trip along Tartan Trail into a longer loop through streets that were built for local access, not as a substitute arterial.
The town's official language has consistently framed the reopening as targeted for "Winter 2026" rather than committing to a firmer date, and that hedge makes sense given the nature of the work. Construction at a creek crossing depends on water flow, regulatory windows tied to environmental permitting, and weather that can shift a schedule by weeks with a single storm system. As of this fall, the project is still active, which means the crossing will be under construction heading into the rainy season, the exact stretch of the calendar when creek-adjacent work gets hardest to predict. The town has said it will post updates through its current projects page, e-blast notifications, and the electronic message boards posted near the closure itself, so the most reliable read on timing will keep coming from those channels rather than a fixed date anyone can bank on today.
Hillsborough's appeal has always rested partly on its roads being narrow, wooded, and slow, the kind of streets with no sidewalks and no big through-corridors that would ever carry regional traffic. That's by design, and it's part of what makes the town feel the way it does. But the same design that keeps traffic light also means there's very little slack in the system. When one creek crossing fails, there usually isn't a parallel route sitting nearby to absorb the load. The detour becomes the only option, and a repair that would be routine on a grid-pattern street becomes a multi-season, multimillion-dollar undertaking on a town road that maybe a few hundred households use on a given day.
That trade-off isn't a flaw so much as the fine print behind the privacy. A town with this few through-roads gets quiet, low-traffic streets in exchange for having almost no redundancy when infrastructure ages the way infrastructure eventually does. Tartan Trail Road is the current example. It probably won't be the last one this decade, given how much the town is currently spending across its road and utility network at once.
If you're planning around this closure for the rest of the season, the detour through Crystal Springs Road, Skyline Boulevard, Golf Course Drive, Hayne Road, and Black Mountain Road remains the town's official route until further notice.
If you want to talk through how projects like this affect a specific pocket of Hillsborough, whether you're weighing a move within town or just trying to understand a corridor better, the Anagnostou Team has been tracking this one closely and is happy to share what we're hearing as the timeline firms up.
Compass
1377 El Camino Real
Menlo Park CA, 94025
Panos Anagnostou
(650) 918-8210
[email protected]
CA DRE# 5082543