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The Larimer County Engineering Department will be replacing a series of seven (7) culverts in lower Rist Canyon where Rist Creek crosses CR 52E (Rist Canyon Road) beginning November 15, 2012 . Two (the most eastern ones) of the seven are expected to be installed before the end of the year, with the remaining 5 in the spring. Because a detour for complete roadway closure is very lengthy for citizens, staff is anticipating that one lane of traffic will be maintained throughout the construction. The estimated $1,680,000 cost for the 7 culverts was approved by the Board of County Commissioners out of general fund reserves for High Park Fire recovery efforts.

 

The project is necessary due to the High Park Fire, the largest recorded fire in the northern foothills of Larimer County, burning more than 87,000 acres in June 2012. The fire significantly altered the landscape and ground conditions, creating unprotected earth and making some of the soil water repellent. These changed conditions are causing a dramatic increase in rainfall runoff, along with soil and debris flowing down creeks in even minor rain events. Analysis shows that the anticipated post-fire stormwater discharge in lower Rist Creek will be between 2.5 to more than 5 times larger than the pre-fire flows for a similar rain event. There is significant concern that these large volumes of water, coupled with soil and debris will overwhelm and plug existing culverts of Rist Creek under CR 52E, causing flooding, roadway overtopping, erosion, and potentially washing out of large sections of road. The increased risk to the road will remain for years while the re-vegetation and re-growth of the area slowly occurs. 

 

The new concrete box culverts will be several times larger than the existing culverts. They are sized to accommodate as large a volume of water as possible given the road geometrics. Because some heavier rain events will still overwhelm the new culverts, the roadway will be rebuilt at the crossings to allow overtopping while minimizing the potential of roadway washout. 

 

Design and construction are occurring as quickly as possible in order to have the new crossings in place before spring run-off and summer thunderstorms. Larimer County asks for your patience and understanding at times when there may be delays moving through the area. 

 

As details become available and construction nears, coordination will occur with emergency service responders and other key roadway users such as the postal service and Poudre School District. Maps and updated information, such as specific construction dates, will be posted, as it becomes available, on the High Park Long-Term Recovery web site at  larimer.org/highparkfire. If you have additional questions please contact Assistant County Engineer Rusty McDaniel at 970.498.5730 or by email at rmcdaniel@larimer.org.