Well, its been a while since I posted on this thread, but the road has collapsed once again. This was not beaver related this time.
This time, the road collapsed after a second pipe replacement was done only a few years after I started this thread in 2016. The 2016 corrugated metal pipe shown in the pictures with my old dog Murphy peering into the pipe, was installed and then disintegrated in an extraordinarily short period of time. The fairly new failed metal pipes were replaced with high density polyethylene about two or three years ago. Over the last few days the road collapsed around the pipes. Our adopted Springer Paisley led us right to the spot today.
I lived here 41 years and this is about third or 4th time fourth time the crossing has failed. The primary problem is that there has never been a proper concrete headwall constructed on the upstream and downstream sides of the road at the stream crossing. The water manages to find its way between the pipes and around the pipes and flushes all of the fill material away. The road collapses when that happens. Simple.
Another problem could be that the pipes are undersized. It seems that the size of the pipes used has always been 48 inch dia. but maybe that's just because the road cannot be easily raised to traverse over larger pipes or additional pipes. The watershed area leading to this crossing is about 19 square miles. The last time the USGS had a metering station in place was just downstream from the crossing and historic data shows a peak flow occurred in 2007 of 180 cubic feet per second. That's a lot of water. You can't guess at what size pipe or how many pipes you may need to handle those types of flows.
Yet another problem is the materials used in the past to retain the side slopes of the road have been logs scavenged from the surrounding area. Mostly pine, as can be seen in my 2016 photos. I have watched over the years repeated attempts to drive pipes and posts in to retain the trees. That doesn't work very well either.
The current polyethylene pipes are actually intact beacause the water bypassed both pipes by finding soft spots in the multiple layers of fill material that have been placed. In the pictures that I am attaching you’ll see multiple layers of fill material an remnants of a sheet pile anchor rod.
The State and our Forest Fire Service really need to work to find enough money somewhere to do the job right, because this will never stop happening. Fixing the current problem by adding more fill and staking some pine logs on the banks of a road that is intended to support the wheel load of a forest fire vehicle is senseless and dangerous for the firefighters
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