Where does the St. Vrain Greenway actually end right now? If you have pedaled or walked it more than a few times this year, you already know the honest answer is "it depends which direction you're headed and what week it is." The trail that most Longmont residents think of as a finished, decades-old amenity is, at this exact moment, an active construction site on one end and a stalled, unfunded gap on the other.
That matters more this week than most. Overnight work on Colorado Highway 119 on August 9 and 10 will shift traffic into a new configuration built specifically to support the pedestrian underpass that eventually reconnects the trail's eastern half. If you're planning a Sunday or Monday evening ride near Sandstone Ranch, the ground under you is about to change.
This Weekend's Overnight Work Is Part of a Longer Story
The City of Longmont has scheduled overnight construction on the night of Sunday, August 9, and again Monday, August 10, 2026, from 6 p.m. to 7 a.m., on Highway 119 between County Road 5 and County Road 7. Crews will stripe the roadway and shift westbound traffic Sunday night, then shift eastbound traffic Monday night, with the new pattern locked in by 7 a.m. Tuesday, August 11. The work is described by the city as moving the highway into "Phase 2" of construction for the St. Vrain Greenway's pedestrian underpass, the tunnel that will eventually let trail users pass safely beneath the highway instead of crossing at grade.
This isn't a new disruption appearing out of nowhere. CBS Colorado reported that the broader lane shift on 119 began back on March 23, 2026, with construction crews working Monday through Friday, 7 a.m. to 5 p.m., the speed limit dropped to 45 mph, and the configuration expected to hold through late August. This weekend's overnight work is the next step inside a setup that has already been in place for months and is close to its own end date, not a fresh detour with no finish line. If your commute or your evening ride already routes around the reduced-speed stretch near the highway, that adjustment continues for a few more weeks. What's new right now is the tunnel work happening under it.
Why This Particular Phase Matters More Than the Last Ten
Here's the part that surprised me the most in digging through the project records: most of the greenway's regular users assume the trail has been essentially complete for years. It has not been, and the current construction is one of only two remaining pieces standing between "mostly done" and "actually done."
The greenway's original master plan dates to 1992, calling for seven miles of trail corridor from North 75th Street to County Line Road. An east corridor update followed in July 2001, extending the vision further toward Weld County. Then, in September 2013, Longmont experienced what the city itself calls the most devastating flash flood in its history, and the greenway took the brunt of it. Some sections have been rebuilt since through the Resilient St. Vrain project, but the flood also had a lasting effect on funding priorities that most casual users never hear about.
The phase currently under construction, called Phase 13, will extend the trail more than two miles northeast from Sandstone Ranch Nature Area to the existing trail network at St. Vrain State Park. It includes two new pedestrian bridges over St. Vrain Creek. According to the engineering firm Otak, which has led design work across multiple phases of the greenway, the corridor's pedestrian structures include spans as long as 140 feet and 240 feet, built to cross a genuine 100-year floodplain rather than a decorative creek. Once this segment and its underpass are finished, expected by spring 2027, the trail will connect onward to the Weld Legacy Trail east of I-25 in Firestone, which itself is part of the statewide Colorado Front Range Trail, a corridor planned to eventually run from Wyoming to New Mexico. A local walking loop becomes, quite literally, a fragment of a border-to-border trail system.
Two Unfinished Ends of the Same Trail
The eastern extension gets the funding and the construction crews. The western side tells a different story, and comparing them side by side shows how uneven the greenway's completion really is.
| Phase 13 (East, active) | Phase 12 (West, stalled) | |
|---|---|---|
| Status | Under construction | Not yet funded |
| Started | January 5, 2026 | No start date set |
| Expected finish | Spring 2027 | Undetermined |
| Connects to | Sandstone Ranch to St. Vrain State Park, eventually Weld Legacy Trail in Firestone | Golden Ponds to Airport Road, eventually toward Lyons |
| Funding source | Partial funding from a DRCOG Multimodal Options Funds Transportation Improvement Program grant | Original funding reallocated to 2013 flood repairs, restoration date undetermined |
That western gap, running from Golden Ponds Nature Area out to Airport Road toward the Town of Lyons, was originally planned under a 2004 St. Vrain Trail Master Plan. Its construction money got redirected to flood recovery more than a decade ago and has not been restored. So while the eastern end is weeks away from a completed underpass, the western end has been sitting in planning limbo since 2013 flood repairs took priority. Both halves are technically part of the same "finished" trail most people picture when they think of the St. Vrain Greenway.
Getting Around It If You're Already Out There
For anyone actually on the trail this month rather than reading about it, here's what's changed on the ground near Sandstone Ranch:
- A portion of the Sandstone Ranch Parking Area near the Visitors Center has been closed for the duration of the project since December 23, 2025. The Visitors Center itself and the trails remain accessible, and additional parking is available at the Visitors Center and at the Sandstone Soccer Complex.
- Since January 26, 2026, the dirt trail connecting the Sandstone Ranch Parking Area near the Visitors Center to Sandstone Drive has been intermittently closed during active work hours, so if you normally cut through on that unpaved link, check posted signage before you commit to it.
- During the overnight work this weekend specifically, the city is directing visitors to use the Sandstone Ranch Parking Area or the soccer field lots, both of which stay open and connected to the greenway.
None of this affects the paved main trail west of Sandstone Ranch. If your usual route is Golden Ponds to Roger's Grove to Izaak Walton Park, you won't notice a thing.
The Mile Most Dog Walkers Don't Realize Is Off Limits
While we're on the subject of things regulars think they know about this trail: the stretch of greenway east of County Line Road, roughly the final mile before Sandstone Ranch, has a standing city ordinance banning dogs, leashed or unleashed. It's easy to miss because it's not marked as construction related and it's been in place separately from anything happening this year. The city cites protection of wildlife habitat as the reason, and the habitat in question is not abstract. Otak's design documentation for the corridor notes the presence of nesting bald eagles and other sensitive habitat that shaped how the trail was routed in the first place. If your regular loop includes the dog and you haven't been turning around at County Line Road, you've likely been walking a stretch you're not supposed to be on with a leash.
What's Still Completely Normal
Here's what hasn't changed, because the construction headlines can make the whole ten-plus mile corridor sound like a mess. It isn't. The stretch through the heart of Longmont, past The Cheese Importer and Left Hand Brewing Company's microbrewery, remains fully open and is arguably the most scenic and social portion of the entire trail. Golden Ponds, Roger's Grove, and Izaak Walton Park all sit well west of the construction zone and see no disruption. Golden Ponds in particular draws regular sightings of great blue herons, wood ducks, and Canada geese, so it's worth the slower pace even on a day when you're not looking for wildlife. The Sandstone Ranch homestead, built in the 1880s by a Gold Rush-era pioneer and often overlooked by people who've lived here for years, is still standing at the trail's eastern edge, unaffected by the work happening a short distance beyond it near the highway.
The greenway most people know and use daily is intact. What's changing is the small, specific piece that finally closes a gap the city has been planning to close since before some of its current users were born.
If you're the kind of person who tracks these details because you actually live your life on this trail, you already understand what it means when a place keeps evolving instead of sitting still. That's part of what makes Longmont worth paying attention to, whether you're watching a bridge go up over St. Vrain Creek or watching what's happening two blocks over from a house you've had your eye on. If you ever want a local read on either, Jane Kraemer is always happy to talk through what's changing in this town and what it might mean for you.
