From the Boulder Daily Camera:
Last summer, as the snow began to melt and ditches began to flow with irrigation water, the people living along Valmont Road east of 75th Street noticed something strange. A large pool of standing water formed to the south of the road, where it stayed — an unwelcome mosquito breeding ground — until winter. At the same time, on the north side of the road, where groundwater had been plentiful, one neighbor’s well went dry and another’s pond evaporated, leaving a mess of dead fish. Now, Valmont’s “new swamp” has returned. Since no one can remember any of these things happening before, neighbors agree something has changed, and the obvious villain is the new Erie Pipeline, laid to the south of the road last spring…
Erie built the $15 million pipeline to bring a reliable supply of Colorado River water to town via the Boulder Reservoir, and town officials aren’t yet ready to take responsibility for the collage of groundwater problems on Valmont Road. Erie spokesman Fred Diehl said the town has met with Boulder County, which has jurisdiction over that area of Valmont Road, and both agree on four points: the water table in that area is quite high; the elevation is quite low; water comes to the surface when the nearby ditch begins to run in the spring; and the ditch is leaky. But as to whether the pipeline exasperated the already-high water table by creating an impermeable barrier — backing up the water on one side and drying out the soils on the other — Diehl would say only that “the town and our engineers are continuing to look into this matter.
Boulder County, while not actually saying Erie is at fault, points to a report on the standing water prepared by Centennial Engineering in Fort Collins, which concludes that “the installation of the water line altered the groundwater flow paths sufficiently that all the water leaking from Green Ditch could not pass the recently installed pipeline.”