Scour construction at 119th Street bridge
HELLO JOHNNIE >> When you get a chance, could you please look into the purpose of the construction going on under and adjacent to the North 119th Street bridge over the St. Vrain River? There are a lot of steel pilings and concrete pouring at the crossing, looks like it could be a new irrigation ditch headgate. Keep up the good work with your comprehensive research and detailed reporting. — Dave Z.
HELLO DAVE Z. >> I apologize in advance for an answer that is neither comprehensive nor detailed — and is late.
By the time I headed over to that location to see what you were asking about, there was no sign of construction at the bridge crossing. Hmm. Maybe you were asking about the construction activity at the mine site just southwest of the bridge?
I turned to the Holcim group, to see if your description matched work being done at its mine site. Wyatt Webster, Holcim’s environmental and land manager, replied, saying that no, what you described wasn’t the work at the mine site, but that “scour improvements” at the bridge had been completed less than a week before I made my inquiry.
Just missed it.
I checked the Boulder County website and found that last summer, the county had put out a request for bids for “Scour Improvements at North 119th Street Bridge Over St. Vrain River.” That work was to include “removal of portions of existing riprap and placing new riprap” at the bridge and “temporary creek diversion and access, and temporary erosion control best management practices, to minimize construction impacts to St. Vrain River.”
So, what are “scour improvements”?
According to the US Geological Survey, “Bridge scour, or the process of erosion around a bridge foundation caused by flooding, is the leading cause of bridge failure.” So, the improvements were work to protect from scour. And riprap? That, according to Ayres, a company that provides civil engineering services, “describes a range
of rocky material placed along shorelines, bridge foundations, steep slopes, and other shoreline structures to protect from scour and erosion.” I’m sure, Dave, that you’ve seen that along other waterways around the area.
Thanks for the request, Dave. And thanks to Wyatt Webster for his reply.
DEAR JOHNNIE >> I just read your column about Ninth and Collyer. I have driven that intersection many times. There is one safety fault. There is no sign for westbound drivers on Ninth, so they think they can make a right on red turn onto northbound Collyer. I have had several close calls at that intersection as I was traveling north. — Avoids Main Street
DEAR JOHNNIE >> This intersection also provides an additional issue. Example: I was westbound on Ninth at legal speed but slowing to prepare to turn left on Collyer when suddenly the light changed yellow but too late to stop at the east crosswalk, only a matter of a few feet when the light changed, and by the time I reached the middle of the intersection the light was red forcing me to stop in that one car length left turn lane. That light remained red. Because of that intersection, I did not feel safe sitting for the light to turn green again. The same would no doubt be true for the eastbound Ninth. I think this is staggered lights, and eastbound Ninth was next up. Is there a remedy to look at? — E.E.
DEAR AVOIDS >> I can picture the problem you describe. If you would bring this concern to the city’s attention, you may do so by going to longmontcolorado.gov and searching for “serviceworks.”
DEAR E.E. >> I tried to recreate this scenario, driving westbound through that intersection with the intention to turn left, late in the light cycle. What I experienced, however, was a late left-turn arrow allowing me to proceed southbound on Collyer. You are welcome to share your “stuck in the intersection” concerns at the city website.