If you looped the Lakeside Nature Trail anytime in the past few weeks, you noticed it before you could name it. The tower that has watched over the reservoir since the late 1920s looks wrong now, shorter, capped with scaffolding instead of the little roofline that's shown up in a thousand family photos. Dog walkers stop mid-stride to point. Runners slow down at the dam crossing. Something that has looked the same for nearly a century changed, and it changed fast.
Here's what most people circling the lake this month don't realize: the argument over whether this would happen was settled back in November 2024. What you're watching now isn't a live debate playing out in real time. It's construction crews finishing a decision the state already made.
The 97-year-old miscalculation you're looking at
The tower wasn't built too tall by accident of neglect. It was built too tall because the plan changed underneath it. When construction on the dam began in 1927, engineers were working toward a structure roughly 33 feet taller than what actually got built. The dam height came down during construction, but the tower had already gone up to serve the taller version. The result is a spillway tower that has spent nearly a century sized for a dam that never existed.
That mismatch didn't matter much until 2017, when the Oroville Dam crisis in Northern California pushed the state's Division of Safety of Dams to tighten seismic standards across the board. Once DSOD reevaluated Lafayette's tower under the new rules, it rated the reservoir "Fair" rather than the "Satisfactory" score nearly every other EBMUD dam carries, specifically because of the tower and the conduits beneath it. State flood maps built from that review show a tower failure could send water into parts of Lafayette and Walnut Creek, an area that includes a K-8 school, the Lafayette Police Department, and the Lafayette BART station.
That's the safety case. It's also the reason EBMUD says shortening the tower by 40 feet, rather than leaving it at its current height, is the only design DSOD would approve.
The part of the story most visitors missed
Here's what makes this different from a typical infrastructure project: Lafayette didn't just accept the plan. A group of local residents who happen to be professional structural engineers and architects formed a volunteer Citizen's Technical Advisory Committee and spent more than two years building an alternative case, arguing the tower could be retrofitted at its existing height without the seismic tradeoff EBMUD described. The City Council backed them. In 2023 and again in 2024, the city formally asked EBMUD to pause and reconsider.
EBMUD reviewed the committee's proposals and rejected them. When the city escalated the disagreement directly to the state, DSOD responded in November 2024 that the shortening design as proposed already satisfied its seismic concerns, and it declined to order a third-party peer review. That letter is the actual turning point. Everything visible at the reservoir since, the netting that went up around the tower in February, the barge and crane that arrived in July, the roofline coming down piece by piece, is the execution of a decision that was locked in nearly two years before most casual visitors noticed anything different.
Crews began the visible demolition on July 10, 2026, cutting away roughly a dozen concrete rings from the tower stem, each about three feet tall. EBMUD's own construction updates had the tower on pace to reach its new, shortened height by August 21, which means if you're reading this in the days around that date, the height change is likely already finished. The work that continues after that point shifts to something less dramatic: building a new floor and structural supports inside the shortened tower ahead of installing a new operating house on top.
What's actually different on your lap around the lake
The politics are settled, but the practical question for anyone who uses this park weekly is simpler: what changes for you between now and next year? The answer is narrower than four years of contentious meetings might suggest.
| Still available now | Affected through the project |
|---|---|
| Both loop trails: paved 2.7-mile Lakeside Nature Trail and unpaved 4.7-mile Rim Trail | A segment of the Walter Costa Trail that runs through the adjacent Water Treatment Plant property, closed for a separate concurrent EBMUD upgrade |
| Fishing and hiking on a first-come basis | Picnic site reservations, paused February through July 2026 while equipment staged near the shoreline |
| First-come picnic tables and grills | Occasional 10 to 15-minute pedestrian delays where crews cross the Lakeside Trail with equipment |
| Weekend recreation generally | Some parking spaces, used intermittently for staging |
EBMUD structured the schedule so that active tower work happens on weekdays, which is why weekend traffic around the loop has stayed close to normal even during the loudest phase of demolition. No trucks route through downtown Lafayette either. Debris comes off the site by way of the Acalanes Road onramp to Highway 24, a detail EBMUD built in specifically to keep heavy equipment out of the Mt. Diablo Boulevard corridor.
The reservoir itself never needed to be drained for any of this. That's worth sitting with if you assumed a project this disruptive to the skyline would also mean months of closed gates. It hasn't.
What EBMUD is keeping, and what it's building new
The agency has tried to preserve some continuity with the original structure, not just the schedule. A window dating to the late 1920s was salvaged from the tower before demolition. The new metal operating house going on top is designed to echo the shape of the one it replaces, so the silhouette from across the water should read as familiar even at the shorter height. EBMUD has also said it's exploring ways to turn salvaged pieces of the old tower into a commemorative token for the public, though the details of that plan haven't been finalized.
There's also an environmental layer to the work that doesn't show up in the visible construction but shapes the calendar. A biological monitor has been on-site every workday from May through October, watching for nesting birds, bats, bumblebees, and species like the California red-legged frog and the western pond turtle. EBMUD says the swallows that return to the tower every year will still have a structure to come back to once the work wraps.
What the loop looks like by fall
The new operating house is targeted for completion by November 2026. After that, the seasonal environmental work window closes for the year, and crews pause the underwater portion of the project, the slide gates and electric motor operators still to be installed at the base of the tower, until the next permitted window opens in spring 2027. EBMUD's full timeline has the tower back in complete operational service by fall 2027, more than a year from now.
None of that has stopped the calendar that actually brings people to this park. The Lafayette Res Run for Education, the loop race that's been a fixture on Mt. Diablo Boulevard and around the reservoir for years, is still scheduled for October 26, 2026, running its usual 5K, 10K, and 2-mile courses around the same water the construction crews have been working beside all summer.
The tower will keep changing shape for another year. The reason it's changing was decided long before this summer, and the way most people actually use this park, the dog walks, the weekend loops, the fishing mornings, has stayed close to what it always was.
If you're weighing a move to Lafayette or already calling it home and want a clearer read on what's happening in the neighborhoods around it, Julie Whitmer can walk you through what's changing block by block, reservoir included.