RTD was looking to solve a serious FasTracks conflict with freight trains on its Adams County line when ordinary citizens chimed in with a suggestion.

Why not run new tracks to the east of the Commerce City industrial area? That way, the future commuter rail line would better serve the commercial and residential part of town.

Now it appears this idea could potentially serve Commerce City better than other potential track locations, as well as save RTD money on the North Metro transit corridor.

RTD didn't take the names of the people who came up with the suggestion at the Feb. 27 station-planning meeting in Commerce City, said Manolo Gonzales-Estay, the North Metro public involvement coordinator.

But planners conducting the environmental impact study for the $437.7 million, 18-mile rail line through Commerce City, Northglenn and Thornton have added two variations of the suggested alignment to the official map.

They've determined it's the least expensive way to get around the heavy industrial area near the Suncor Refinery, Metro Wastewater treatment plant, Interstate 270, Sand Creek and the busy mainline crossings of the Union Pacific and the Burlington Northern- Santa Fe railroads.

The dilemma began with the railroads. The North Metro commuter rail line has long been planned to use the UP tracks heading north. But there is a famously busy and congested location called Sand Creek Junction.

That railroad convergence is a diagonal crossing of the UP and BNSF mainlines and is located right over the point where Sand Creek flows underneath the tracks and I-270 flies overhead. Neither railroad wants the hassle of RTD commuter trains competing for space, and insisted that RTD build a fourth-level overpass that would take FasTracks trains over the freeway. That requires an expensive bridge and retaining wall of a mile and a half, or longer.

RTD began looking at a "cross-country" bypass to the west, laying new tracks between the refinery and treatment plant. It would be less expensive then the original plan, but it took FasTracks service farther from Commerce City and also required bridges and walls.

The citizen-inspired alternative to the east would use existing spur tracks to bypass Sand Creek Junction to the east, closer to the core of Commerce City.

Sean Lehocky, a project engineer for Commerce City, said it would have to be looked at closely to determine impacts and potential, but the city likes the idea of having this other option.

RTD doesn't have hard cost estimates yet, but it knows this new alternative would be the least expensive of all the possibilities, said Bob Boot, a senior FasTracks planner. That's because a lot of it would be at grade with fewer bridges and walls.

flynnk@RockyMountainNews.com or 303-892-5247