From The Fort Collins Coloradoan (Miles Blumhardt):
Mesmerized by miles of mountainsides of blackened trees and seared soil that hugs the banks of the upper Poudre River, it’s difficult not to reflect on the 2012 High Park Fire and 2013 flood.
You can’t help but wonder, given the steepness of the slopes and the severity of the riverside scar left by the Cameron Peak Fire, if Northern Colorado is poised for a repeat of history regarding the Poudre River.
Come spring, snowmelt, rainfall and potential flash floods are almost certain to wash large amounts of ash from Colorado’s largest wildfire, soil and even entire trees into the river that serves as a source of drinking water to hundreds of thousands of people in Fort Collins and the surrounding area…
A recent Burned Area Emergency Response assessment for the Cameron Peak Fire indicated a 90% to 100% chance that water quality would be impacted by ash- and sediment-laden runoff, nutrient loading and potential debris flows within the first few years following the fire.
And that’s only the half of it.
Fort Collins receives half of its water from the Poudre River and the other half from Horsetooth Reservoir, whose water quality could be impacted by the East Troublesome Fire in Grand County.
An assessment for the East Troublesome Fire estimated 53% of the burn area suffered moderate (48%) or high (5%) soil burn severity compared to 36% — 30% moderate and 6% high — for the Cameron Peak Fire. The Cameron Peak Fire assessment also showed more than half the soil tested to be repellent to water absorption…
By the time the 112-day Cameron Peak Fire’s flames were finally extinguished on Dec. 2, a watershed recovery collaboration of area municipalities, Larimer County, federal and state agencies, water providers and organizations such as the coalition, was already meeting to start planning efforts to address the fire’s impact.
This isn’t the first fire for many of those stakeholders, and lessons learned from the High Park Fire are helping the group quickly prepare for this spring’s impacts.
That being said, the Cameron Peak Fire was more than twice the size of the High Park Fire and paired with the 193,812-acre East Troublesome Fire — the second-largest wildfire in state history — delivered a massive one-two punch to several watersheds, making recovery even more daunting…
Mark Kempton, the city of Fort Collins’ interim deputy director of Water Resources and Treatment, said the city has implemented steps since the High Park Fire to better equip it to handle the after-effects of a major fire.
He said the city has installed warning systems along the Poudre River that alert it several hours ahead of water turbidity issues so workers can turn off the water supply. When the city turns off the Poudre River supply, it can draw on Horsetooth Reservoir water. That was the case for 100 days during the High Park Fire.
The High Park Fire taught recovery leaders to include the use of shredded tree mulch instead of straw mulch to better prevent the mulch from blowing away for soil and slope stabilization. Strategically increasing culvert size also reduced damage to roads.
Kempton said another key component will be workers removing sediment by flushing the water treatment system more often and removing sediment from the river intake system and catch basins.